**Applications**

[19] Bestrin R, Vermeulen AG. Mathematical modeling and analysis of vapour compres

[20] García-Vallardes O, Pérez-Segarra CD, Rigola J. Numerical simulation of double-pipe condensers and evaporators. International Journal of Refrigeration. 2004;**27**:656-670 [21] Xu B, Yebi A, Onori S, Filipi Z, Liu X, Shutty J. Power maximization of a heavy duty diesel organic Rankine cycle waste heat recovery system utilizing mechanically coupled and fully electrified turbine expanders. In: Proceedings of the ASME 2016 Internal

[22] Invernizzi C, Iora P, Silva P. Bottoming micro-Rankine cycles for micro-gas turbines.

[23] Weiss HH, Boshwirth L. A simple but efficient equipment for experimental determi

[24] Feru E, Willems F, de Jager B, Steinbuch M. Modeling and control of a parallel waste heat recovery system for Euro-VI heavy-duty diesel engines. Energies, vol. 7, pp. 6571-

[25] Moran MJ, Shapiro HN. Fundamentals of Engineering Thermodynamics. 5th ed.,

[26] Mollaei Barzi Y, Assadi M, Parham K. A waste heat recovery system development and analysis using ORC for the energy efficiency improvement in aluminum electrolysis

[27] Elmqvist H, Mattsson SE. An introduction to the physical modeling language Modelica. In: Proceedings of the 9th European Simulation Symposium, ESS'97; October 19-23,

[29] Cennerilli S, Sciubba E. Application of the CAMEL process simulator to the dynamic simulation of gas turbines. Energy Conversion and Management. 2007;**48**:2792-2801 [30] Cennerilli S, Fiorini P, Sciubba E. Application of the Camel process simulator to the dynamic simulation of gas turbines. In: ECOS 2006 Proceedings; Vol. 1; 2006. pp. 355-363

[31] Traverso A. TRANSEO: A new simulation tool for transient analysis of innovative energy systems [PhD thesis]. Italy: TPG-DiMSET, University of Genova; 2004

2

nation of valve loss coefficient under compressible and steady flow conditions. In:

Combustion Fall Technical Conference; Greenville, SC, USA; 2016. p. 11

International Compressor Engineering Conference; 1982. pp. 69-76

: John Wiley & Sons, Inc; 2006

cells. International Journal of Energy Research. 2017:1-13

[28] Pfafferott T, Schmitz G. Modeling and transient simulation of CO

with Modelica. International Journal of Refrigeration. 2004;**27**:42-52

Applied Thermal Energy. 2007;**27**:100-110

August 2003

124 Organic Rankine Cycle Technology for Heat Recovery

6592, 2014

Chichester

, England

1997; Passau, Germany; 1997

sion system. International Report. Eindhoven, Netherlands: University of Technology;

**Chapter 7**

**Provisional chapter**

**The Development and Application of Organic Rankine**

**The Development and Application of Organic Rankine**

The development of engine waste heat recovery (WHR) technologies attracts ever increasing interests due to the rising strict policy requirements and environmental concerns. Organic Rankine Cycle (ORC) can convert low medium grade heat into electrical or mechanical power and has been widely recognized as the most promising heat-driven technologies. A typical internal combustion engine (ICE) converts around 30% of the overall fuel energy into effective mechanical power and the rest of fuel energy is dumped through the engine exhaust system and cooling system. Integrating a well-designed ORC system to ICE can effectively improve the overall energy efficiency and reduce emissions with around 2–5 years payback period through fuel saving. This book chapter is meant to provide an overview of the technical development and application of ORC technology to recover wasted thermal energy from the ICE with a particular focus on vehicle applications. **Keywords:** internal combustion engine, vehicle application, organic Rankine cycle,

Over the last century, the internal combustion engine (ICE) as one of the main power sources has been widely adopted in the vehicle and marine propulsion systems such as automobiles, trains, trucks, boats, and ships. The increasing concerns on the environmental problems caused by burning fossil fuels promote the technology development of more efficient, more compact, and more cost-effective ICE, which can potentially improve the overall energy efficiency, reduce the emissions and generate more effective engine shaft power by burning fossil

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.78401

**Cycle for Vehicle Waste Heat Recovery**

**Cycle for Vehicle Waste Heat Recovery**

Yiji Lu, Anthony Paul Roskilly and Xiaoli Yu

Yiji Lu, Anthony Paul Roskilly and Xiaoli Yu

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.78401

engine waste heat recovery

**Abstract**

**1. Introduction**

#### **The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery**

DOI: 10.5772/intechopen.78401

Yiji Lu, Anthony Paul Roskilly and Xiaoli Yu Yiji Lu, Anthony Paul Roskilly and Xiaoli Yu

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.78401

#### **Abstract**

The development of engine waste heat recovery (WHR) technologies attracts ever increasing interests due to the rising strict policy requirements and environmental concerns. Organic Rankine Cycle (ORC) can convert low medium grade heat into electrical or mechanical power and has been widely recognized as the most promising heat-driven technologies. A typical internal combustion engine (ICE) converts around 30% of the overall fuel energy into effective mechanical power and the rest of fuel energy is dumped through the engine exhaust system and cooling system. Integrating a well-designed ORC system to ICE can effectively improve the overall energy efficiency and reduce emissions with around 2–5 years payback period through fuel saving. This book chapter is meant to provide an overview of the technical development and application of ORC technology to recover wasted thermal energy from the ICE with a particular focus on vehicle applications.

**Keywords:** internal combustion engine, vehicle application, organic Rankine cycle, engine waste heat recovery

## **1. Introduction**

Over the last century, the internal combustion engine (ICE) as one of the main power sources has been widely adopted in the vehicle and marine propulsion systems such as automobiles, trains, trucks, boats, and ships. The increasing concerns on the environmental problems caused by burning fossil fuels promote the technology development of more efficient, more compact, and more cost-effective ICE, which can potentially improve the overall energy efficiency, reduce the emissions and generate more effective engine shaft power by burning fossil

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

fuels [1]. Moreover, the increasingly strict emission legislations are focusing on the nitrogen oxides (NOx), particulate matter (PM), carbon monoxide (CO), and hydrocarbon (HC).

the commercial ORC system for vehicle application is still not available from the market. One of the possible reasons is the concern on the substantial capital cost due to the complexity of the

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery

http://dx.doi.org/10.5772/intechopen.78401

129

The application of steam Rankine cycle for vehicle waste hear recovery has been reported by BMW in 2005 [15], who later announced the proposed system can achieve 15% improvement for engine performance [16, 17]. **Figure 1** is the schematic diagram of the BMW turbosteamer concept, who converts both engine coolant and exhaust energy into engine mechanical power. The system adopts two-stage turbine machines, which is similar as large-scale stationary

In 2008, Honda has reported the project exploring the application of steam Rankine cycle for engine exhaust heat recovery as illustrated in **Figure 2** [18]. The system adopts an axial piston swash plate type expander as the expansion machine under the controlled steam operational conditions ranging from 400 to 500°C at the pressure ranging from 7 to 9 MPa in order to optimize the Rankine cycle performance in engine transient driving conditions. The expander was directly connected to an electric generator producing electricity to recharge the battery pack. The maximum thermal efficiency of the system is 13% at 23 kW and the maximum power from the expander is 32 kW. Results are shown in 62 miles/h constant speed driving tests; the overall thermal efficiency can be improved by 3.8%. However, Honda announced the system

will not be considered for production unless higher efficiencies can be achieved [18].

**Figure 1.** Schematic diagram of BMW-Turbosteamer concept [16].

system and complicated control strategies required for vehicle application.

**1.2. Representative prototypes developed by vehicle manufactures**

power generation system.

Engine manufacturers have developed and adopted the technologies such as turbocharging, variable valve timing [2], Miller timing strategies [3], advanced injection strategies, and engine friction reduction technologies in order to improve the system thermal efficiency. However, adopting the stated technologies the ICE is still difficult to convert more than 40% of the fuel energy into effective mechanical power [4, 5]. And there is around 60–70% of fuel energy is wasted from the exhaust system and cooling system of ICE [4, 5]. Other approaches such as burning alternative fuels [6] and the development of hybrid pneumatic system [7] to recover the engine kinetic energy were also considered. Recent research attentions are focusing on the development of engine bottoming technologies such as advanced after treatment systems or engine waste heat recovery (WHR) technologies [8]. The Organic Rankine Cycle (ORC) is one of the most promising heat-driven technologies converting heat into mechanical power or electricity [9, 10]. ORC system can recover various heat sources such as biomass combustion heat, solar energy, geothermal heat, and industry wasted heat and heat from Internal Combustion Engine (ICE) [9]. Adopting ORC technology for engine waste heat recovery can effectively improve the overall system efficiency and reduce the emissions. A well-designed ORC system can potentially achieve around 2–5 years payback period through fuel saving [4, 5, 10]. However, Velez et al. [10] pointed out the market available ORC system with the power ranges of 0.2–2 MWe under the cost around 1and 4 × 103 € /kWe, and lower powers are in pre-commercial status because of the relatively long payback period using small-scale ORC system. The technical development, main research barriers, and potential solutions of the technology are summarized in this chapter, which aims to have an overview of the ORC technology and promote its applications.

#### **1.1. Emerging applications of the technology for vehicles**

The applications and extensively research interests of waste heat recovery technologies started in the 1970s during the oil crisis [11]. The first application of ORC for engine waste heat recovery was reported by Patel and Dovle in 1976 [12]. The research project conducted by Mack Trucks and the Thermo Electron Corporation was sponsored by US Department of Energy (DOE). The first prototype ORC machine was installed on a Mack 676 diesel engine to recover the exhaust waste heat. The system adopted Fluorinol-50 as the ORC working fluid and a three-stage axial flow turbine expander. The mechanical power of the expander was transferred to the power take-off device coupled with a speed reduction gearbox. They demonstrated the technical feasibility of the system and its economic interests. The optimal performance of the system could achieve a 13% increase in maximum power with around 15% reduction of fuel consumption. Follow on progress reported by Pate et al. [13] announced a 1 year test program of an ORC bottoming system coupled on a Mack diesel engine in 1979 and they declared a plan of expanding the ORC system on 10 trucks in 1981–1982. In 1983, the research group reported the testing results of the program [14], which demonstrated 12.5% improvement of the average fuel consumption on high-way vehicle fuel economy tests. However, no follow on progress for the expanding plan can be found from the literature. The ORC systems developed nowadays can achieve much higher efficiency because of the broad choice of advanced working fluids and the development of system components, such as expansion devices and heat exchangers. However, the commercial ORC system for vehicle application is still not available from the market. One of the possible reasons is the concern on the substantial capital cost due to the complexity of the system and complicated control strategies required for vehicle application.

#### **1.2. Representative prototypes developed by vehicle manufactures**

fuels [1]. Moreover, the increasingly strict emission legislations are focusing on the nitrogen oxides (NOx), particulate matter (PM), carbon monoxide (CO), and hydrocarbon (HC).

Engine manufacturers have developed and adopted the technologies such as turbocharging, variable valve timing [2], Miller timing strategies [3], advanced injection strategies, and engine friction reduction technologies in order to improve the system thermal efficiency. However, adopting the stated technologies the ICE is still difficult to convert more than 40% of the fuel energy into effective mechanical power [4, 5]. And there is around 60–70% of fuel energy is wasted from the exhaust system and cooling system of ICE [4, 5]. Other approaches such as burning alternative fuels [6] and the development of hybrid pneumatic system [7] to recover the engine kinetic energy were also considered. Recent research attentions are focusing on the development of engine bottoming technologies such as advanced after treatment systems or engine waste heat recovery (WHR) technologies [8]. The Organic Rankine Cycle (ORC) is one of the most promising heat-driven technologies converting heat into mechanical power or electricity [9, 10]. ORC system can recover various heat sources such as biomass combustion heat, solar energy, geothermal heat, and industry wasted heat and heat from Internal Combustion Engine (ICE) [9]. Adopting ORC technology for engine waste heat recovery can effectively improve the overall system efficiency and reduce the emissions. A well-designed ORC system can potentially achieve around 2–5 years payback period through fuel saving [4, 5, 10]. However, Velez et al. [10] pointed out the market available ORC system with the power ranges of 0.2–2 MWe under the cost around 1and 4 × 103 € /kWe, and lower powers are in pre-commercial status because of the relatively long payback period using small-scale ORC system. The technical development, main research barriers, and potential solutions of the technology are summarized in this chapter,

which aims to have an overview of the ORC technology and promote its applications.

The applications and extensively research interests of waste heat recovery technologies started in the 1970s during the oil crisis [11]. The first application of ORC for engine waste heat recovery was reported by Patel and Dovle in 1976 [12]. The research project conducted by Mack Trucks and the Thermo Electron Corporation was sponsored by US Department of Energy (DOE). The first prototype ORC machine was installed on a Mack 676 diesel engine to recover the exhaust waste heat. The system adopted Fluorinol-50 as the ORC working fluid and a three-stage axial flow turbine expander. The mechanical power of the expander was transferred to the power take-off device coupled with a speed reduction gearbox. They demonstrated the technical feasibility of the system and its economic interests. The optimal performance of the system could achieve a 13% increase in maximum power with around 15% reduction of fuel consumption. Follow on progress reported by Pate et al. [13] announced a 1 year test program of an ORC bottoming system coupled on a Mack diesel engine in 1979 and they declared a plan of expanding the ORC system on 10 trucks in 1981–1982. In 1983, the research group reported the testing results of the program [14], which demonstrated 12.5% improvement of the average fuel consumption on high-way vehicle fuel economy tests. However, no follow on progress for the expanding plan can be found from the literature. The ORC systems developed nowadays can achieve much higher efficiency because of the broad choice of advanced working fluids and the development of system components, such as expansion devices and heat exchangers. However,

**1.1. Emerging applications of the technology for vehicles**

128 Organic Rankine Cycle Technology for Heat Recovery

The application of steam Rankine cycle for vehicle waste hear recovery has been reported by BMW in 2005 [15], who later announced the proposed system can achieve 15% improvement for engine performance [16, 17]. **Figure 1** is the schematic diagram of the BMW turbosteamer concept, who converts both engine coolant and exhaust energy into engine mechanical power. The system adopts two-stage turbine machines, which is similar as large-scale stationary power generation system.

In 2008, Honda has reported the project exploring the application of steam Rankine cycle for engine exhaust heat recovery as illustrated in **Figure 2** [18]. The system adopts an axial piston swash plate type expander as the expansion machine under the controlled steam operational conditions ranging from 400 to 500°C at the pressure ranging from 7 to 9 MPa in order to optimize the Rankine cycle performance in engine transient driving conditions. The expander was directly connected to an electric generator producing electricity to recharge the battery pack. The maximum thermal efficiency of the system is 13% at 23 kW and the maximum power from the expander is 32 kW. Results are shown in 62 miles/h constant speed driving tests; the overall thermal efficiency can be improved by 3.8%. However, Honda announced the system will not be considered for production unless higher efficiencies can be achieved [18].

**Figure 1.** Schematic diagram of BMW-Turbosteamer concept [16].

The heat sources from the engine are usually calculated under engine steady state points from either experimental tests or simulation results. Although it is theoretically feasible and potentially worthwhile to recover the heat from charger air cooler and engine lube oil as reported in the literature [23], the practical applications of ORC system for engine waste heat recovery are mainly focusing on the exhaust energy and engine coolant energy. These two heat sources contain the majority of wasted heat energy from the engine. The maximizing utilization of these two heat sources can benefit for the overall vehicle thermal management and improve

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery

http://dx.doi.org/10.5772/intechopen.78401

131

Rather than the engine used in stationary power generation system, who usually operated under fixed rotational speed for an electrical generation [24], the engine used for vehicle application operates under variable speed and torque conditions. Therefore, the full engine operational map analysis method is popularly used to evaluate the heat sources from the engine for vehicle application. For example, Zhang et al. [25] used similar analysis methods and conducted the analysis of a 105 kW light-duty diesel engine. In order to conduct the parametric performance study of engine waste heat recovery system, the following four parameters are critical to being identified: the temperature and mass flow rate of exhaust and coolant energy under variable engine operational conditions. Another alternative method to evaluate the recoverable waste heat from the engine coolant and exhaust energy was introduced by Ringler et al. [17], who pointed out that the ratio of the recoverable heat from the coolant and exhaust energy of ICE ranges from 1.5 to 0.5. The results from the reported work also supported the conclusion [26–28]. Similar analysis method to evaluate the recoverable coolant and exhaust energy from a single

cylinder engine was used and reported by Lu et al. as illustrated in **Figure 3** [30].

**Figure 3.** Recoverable coolant and exhaust energy from a single cylinder ICE [29].

the cooling circuit impact.

**Figure 2.** Layout of the Honda Rankine cycle prototype [18].

Cummins has conducted a project funded by U.S. Department of Energy to study an advanced engine waste heat recovery system using ORC technology since 2005 [19]. Cummins announced the developed ORC system can potentially improve the engine total efficiency by 5–8% [19]. The company further developed the waste heat recovery system and integrated with other advanced engine technologies aiming to boost the heavy-duty diesel engine to as high as 55% efficiency as reported in 2013 [20].

## **2. Organic Rankine cycle (OCR) for vehicle waste heat recovery (WHR)**

#### **2.1. Heat sources from ICEs**

The designed temperature difference between evaporation and condensation temperature determines the overall efficiency of a typical ORC. For on-road vehicle application, the condensation temperature is controlled by the radiator and the capability of engine radiator determines the lowest condensation temperature. Therefore, the majority studies of Waste Heat Recovery (WHR) from ICE focus on the engine exhaust energy [21], because the exhaust temperature of ICE is various from 200 to 700°C, which is much higher than the coolant temperature ranging from 80 to 100°C [4, 5]. The other two heat sources are the charge air (50–70°C) and engine oil (80–120°C) [22]. The maximum ratio of utilization the fuel energy converting into engine brake power for propulsion is about 40–45%. The rest of fuel energy is dumped through engine exhaust, wasted because of friction losses and heat transfer loses. It is, therefore, necessary to study the heat sources from ICE to design and evaluate an ORC system for engine waste heat recovery.

The heat sources from the engine are usually calculated under engine steady state points from either experimental tests or simulation results. Although it is theoretically feasible and potentially worthwhile to recover the heat from charger air cooler and engine lube oil as reported in the literature [23], the practical applications of ORC system for engine waste heat recovery are mainly focusing on the exhaust energy and engine coolant energy. These two heat sources contain the majority of wasted heat energy from the engine. The maximizing utilization of these two heat sources can benefit for the overall vehicle thermal management and improve the cooling circuit impact.

Rather than the engine used in stationary power generation system, who usually operated under fixed rotational speed for an electrical generation [24], the engine used for vehicle application operates under variable speed and torque conditions. Therefore, the full engine operational map analysis method is popularly used to evaluate the heat sources from the engine for vehicle application. For example, Zhang et al. [25] used similar analysis methods and conducted the analysis of a 105 kW light-duty diesel engine. In order to conduct the parametric performance study of engine waste heat recovery system, the following four parameters are critical to being identified: the temperature and mass flow rate of exhaust and coolant energy under variable engine operational conditions. Another alternative method to evaluate the recoverable waste heat from the engine coolant and exhaust energy was introduced by Ringler et al. [17], who pointed out that the ratio of the recoverable heat from the coolant and exhaust energy of ICE ranges from 1.5 to 0.5. The results from the reported work also supported the conclusion [26–28]. Similar analysis method to evaluate the recoverable coolant and exhaust energy from a single cylinder engine was used and reported by Lu et al. as illustrated in **Figure 3** [30].

**Figure 3.** Recoverable coolant and exhaust energy from a single cylinder ICE [29].

Cummins has conducted a project funded by U.S. Department of Energy to study an advanced engine waste heat recovery system using ORC technology since 2005 [19]. Cummins announced the developed ORC system can potentially improve the engine total efficiency by 5–8% [19]. The company further developed the waste heat recovery system and integrated with other advanced engine technologies aiming to boost the heavy-duty diesel engine to as

The designed temperature difference between evaporation and condensation temperature determines the overall efficiency of a typical ORC. For on-road vehicle application, the condensation temperature is controlled by the radiator and the capability of engine radiator determines the lowest condensation temperature. Therefore, the majority studies of Waste Heat Recovery (WHR) from ICE focus on the engine exhaust energy [21], because the exhaust temperature of ICE is various from 200 to 700°C, which is much higher than the coolant temperature ranging from 80 to 100°C [4, 5]. The other two heat sources are the charge air (50–70°C) and engine oil (80–120°C) [22]. The maximum ratio of utilization the fuel energy converting into engine brake power for propulsion is about 40–45%. The rest of fuel energy is dumped through engine exhaust, wasted because of friction losses and heat transfer loses. It is, therefore, necessary to study the heat sources from ICE to design and evaluate an ORC

**2. Organic Rankine cycle (OCR) for vehicle waste heat recovery**

high as 55% efficiency as reported in 2013 [20].

**Figure 2.** Layout of the Honda Rankine cycle prototype [18].

130 Organic Rankine Cycle Technology for Heat Recovery

**(WHR)**

**2.1. Heat sources from ICEs**

system for engine waste heat recovery.

## **2.2. Working principle of Rankine-based power generation systems**

#### *2.2.1. Rankine cycle*

Steam Rankine cycle has been widely employed in large-scale power plants in the industry. This technology has been recognized as the most popular energy conversion systems, which mainly consists of four components, a pump, an evaporator, a turbine, and a condenser shown in **Figure 4**. The working principle of steam Rankine cycle can be described as follows. The liquid-phase water is first compressed to high-pressure state and flows into the evaporator, where the heat is provided from the heat sources to change the water from the liquid phase into the gas phase. The high-temperature and high-pressure steam then flow through an expansion machine where the power can be retrieved or converted into electricity. In the final step, the condenser rejects the heat from the expander steam and condenses the steam into the liquid phase.

Rankine cycle applies water as the working fluid, which has the advantages of high specific heat capacity, broad ranges of working conditions, non-toxic, and safe to use and environmentally friendly. However, steam Rankine system requires very high driven temperature in order to keep the steam in the gas phase at the exit of the expander. Because the exiting of liquid phase of fluid requires being prevented otherwise the blades of the turbine will be gradually damaged resulting in the reduction of lifetime and decrease of the expander efficiency [31].

in **Figure 5**. The wet fluids such as R717 have a negative slope of the vapor saturation curve. On the other hand, the dry fluids have a positive slope. The isentropic fluids have a vertical

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery

http://dx.doi.org/10.5772/intechopen.78401

133

A wrong choice of working fluid could lead to a low-efficient and expensive plant of ORC system. Tchanche et al. [37] assessed the thermodynamic and environmental properties of 20 different fluids for solar Organic Rankine Cycle by comparing the system efficiency, irreversibility, flow rate, pressure ratio, toxicity, flammability, ozone depletion potential (ODP), and global warming potential (GWP). The influence of fluid properties on an ORC and a supercritical Rankine cycle with 35 different working fluids was assessed by Chen et al. [36] considering the latent heat, density, specific heat, and the effectiveness of superheating. An exergy-based study of fluid selection for geothermal generated ORC system was conducted by Heberle et al. [38]. The exergy analysis indicated in a series circuit, working fluids with high critical temperatures such as isopentane are more favorable to be used. The working fluids with low critical temperatures, such as R227ea, are favored in parallel circuits and power generation under the heat source temperature below 450 K. The author investigated a small-scale solar-powered regenerative ORC system using six different refrigerants. The first and second law analysis suggested that R600 and R600a have the best performance under the temperature ranges from 70to 120°C [31]. Wang et al. [33] report a study to compare the performance of 10 kW net power output ORC system using different working fluids for engine exhaust heat recovery. Results indicate R11, R141b, R113, and R123 manifest slightly higher thermodynamic performances than other working fluids [33]. The system performance study of a geothermal ORC system using 31 pure working fluids has been conducted by Saleh et al. [34]. The maximum thermal efficiency is 0.13 with n-butane as working fluid under 120°C heat source temperature [34]. There is no working fluid can be recognized as the best to be used in any ORC systems. The section of optimal working fluid needs to consider the system thermodynamic performance, the economics of the system, designed system parameters such as maximum and minimum

temperature and pressure conditions, environmental, and safety aspects.

slope of the vapor saturation curve such as R134a.

**Figure 5.** Three types of ORC working fluids: dry, isentropic, and wet.

#### *2.2.2. Organic Rankine cycle (OCR)*

As mentioned before, steam Rankine cycle requires very high heat source temperature. The Organic Rankine Cycles have been widely investigated since the 1880s. Instead of using water in Rankine cycle, the Organic Rankine Cycles employ organic working fluids such as refrigerants and hydrocarbons to recover the low-grade heat from biomass power plant, geothermal power and solar ponds [32]. The selection of working fluid plays a key role in ORC performance [33–36].

The working fluids used in Organic Rankine Cycle can be classified as wet, dry and isentropic types, who have different slopes of the vapor saturation curves in the *T-s* diagram as shown

**Figure 4.** Schematic diagram of steam Rankine cycle.

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery http://dx.doi.org/10.5772/intechopen.78401 133

**Figure 5.** Three types of ORC working fluids: dry, isentropic, and wet.

**2.2. Working principle of Rankine-based power generation systems**

Steam Rankine cycle has been widely employed in large-scale power plants in the industry. This technology has been recognized as the most popular energy conversion systems, which mainly consists of four components, a pump, an evaporator, a turbine, and a condenser shown in **Figure 4**. The working principle of steam Rankine cycle can be described as follows. The liquid-phase water is first compressed to high-pressure state and flows into the evaporator, where the heat is provided from the heat sources to change the water from the liquid phase into the gas phase. The high-temperature and high-pressure steam then flow through an expansion machine where the power can be retrieved or converted into electricity. In the final step, the condenser

rejects the heat from the expander steam and condenses the steam into the liquid phase.

Rankine cycle applies water as the working fluid, which has the advantages of high specific heat capacity, broad ranges of working conditions, non-toxic, and safe to use and environmentally friendly. However, steam Rankine system requires very high driven temperature in order to keep the steam in the gas phase at the exit of the expander. Because the exiting of liquid phase of fluid requires being prevented otherwise the blades of the turbine will be gradually damaged resulting in the reduction of lifetime and decrease of the expander efficiency [31].

As mentioned before, steam Rankine cycle requires very high heat source temperature. The Organic Rankine Cycles have been widely investigated since the 1880s. Instead of using water in Rankine cycle, the Organic Rankine Cycles employ organic working fluids such as refrigerants and hydrocarbons to recover the low-grade heat from biomass power plant, geothermal power and solar ponds [32]. The selection of working fluid plays a key role in ORC perfor-

The working fluids used in Organic Rankine Cycle can be classified as wet, dry and isentropic types, who have different slopes of the vapor saturation curves in the *T-s* diagram as shown

*2.2.1. Rankine cycle*

132 Organic Rankine Cycle Technology for Heat Recovery

*2.2.2. Organic Rankine cycle (OCR)*

**Figure 4.** Schematic diagram of steam Rankine cycle.

mance [33–36].

in **Figure 5**. The wet fluids such as R717 have a negative slope of the vapor saturation curve. On the other hand, the dry fluids have a positive slope. The isentropic fluids have a vertical slope of the vapor saturation curve such as R134a.

A wrong choice of working fluid could lead to a low-efficient and expensive plant of ORC system. Tchanche et al. [37] assessed the thermodynamic and environmental properties of 20 different fluids for solar Organic Rankine Cycle by comparing the system efficiency, irreversibility, flow rate, pressure ratio, toxicity, flammability, ozone depletion potential (ODP), and global warming potential (GWP). The influence of fluid properties on an ORC and a supercritical Rankine cycle with 35 different working fluids was assessed by Chen et al. [36] considering the latent heat, density, specific heat, and the effectiveness of superheating. An exergy-based study of fluid selection for geothermal generated ORC system was conducted by Heberle et al. [38]. The exergy analysis indicated in a series circuit, working fluids with high critical temperatures such as isopentane are more favorable to be used. The working fluids with low critical temperatures, such as R227ea, are favored in parallel circuits and power generation under the heat source temperature below 450 K. The author investigated a small-scale solar-powered regenerative ORC system using six different refrigerants. The first and second law analysis suggested that R600 and R600a have the best performance under the temperature ranges from 70to 120°C [31]. Wang et al. [33] report a study to compare the performance of 10 kW net power output ORC system using different working fluids for engine exhaust heat recovery. Results indicate R11, R141b, R113, and R123 manifest slightly higher thermodynamic performances than other working fluids [33]. The system performance study of a geothermal ORC system using 31 pure working fluids has been conducted by Saleh et al. [34]. The maximum thermal efficiency is 0.13 with n-butane as working fluid under 120°C heat source temperature [34]. There is no working fluid can be recognized as the best to be used in any ORC systems. The section of optimal working fluid needs to consider the system thermodynamic performance, the economics of the system, designed system parameters such as maximum and minimum temperature and pressure conditions, environmental, and safety aspects.

#### **2.3. Expander candidates**

The expansion machines can be divided into two types: turbine machine using the kinetic energy of the working fluid to drive the expander and positive displace expander producing power by changing the volume of working chamber.

was directly connected to a high-speed generator to produce electricity and results indicated the maximum cycle efficiency, the isentropic turbine efficiency, and electricity power obtained from the testing rig is 5.22%, 78.7%, and 32.7 kW, respectively [42]. Pei et al. [47, 48] carried out an experimental investigation on a 1–2 kW ORC system using a special designed and constructed radial flow turbine. The reported study achieves the isentropic efficiency of the radial flow turbine at 65–68% with the rotational speed around 20,000–40,000 using R123 as the organic working fluid in the ORC system [46, 47]. Compared with positive displacement expander, turbines are easier to be designed with relatively less required parts. A single stage turbine only requires two bearings to be mounted to the generator on the shaft. Furthermore, there is no contact seal existing in the turbines, which means no lubrication oil is necessary to be adapted to the system. The application of turbine for small-scale application is still not successful because the turbine is designed under rather low-expansion ratios and high-volume flows. The rotational speed of conventional turbines ranges from 10,000 to 100, 000 rpm because of the physical design of this type of expansion machine, which results to a limited or hard sourcing of proper generator for electricity production. One of the solutions to adapt the turbine machine directly with the generator is to use a high-speed generator, which will lead to high initial cost and increase the overall cost of electricity generation system. The other method to obtain the mechanical work from the turbine and convert it into electricity is by using gear. This method can effectively solve the high initial cost of the system but will require larger space for the turbine unit and reduce the efficiency of the turbine machine due to mechanical losses in the gear. Furthermore, the availability of small-scale turbine machine is still limited. The currently used radial flow turbines in small-scale power generation system are either from specially designed by the researcher or

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery

http://dx.doi.org/10.5772/intechopen.78401

135

modified from a conventional turbine from an automotive turbocharger.

Different from the working principle turbine machines, positive displacement expanders use the expansion power by changing the volume inside the expansion chambers, which can also be named volumetric expanders. The most commonly used positive displacement expanders include piston type expander, screw expander, and scroll expander and vane expander. The positive displacement expanders can be classified into two types reciprocating piston expanders and rotary expanders. Screw expander, scroll expander, and vane expander are three main

The piston type of machines attracts extensive intentions since it was invented and has been widely applied in different areas to meet various requirements such as the most commonly used as an Internal Combustion Engine. In the past 30 years, piston expander has been adopted and developed as the expander into steam Rankine system integrating with the internal combustion engine to recover the exhaust energy [4]. The piston type of expander can be designed and constructed with one valve version and two valve version in order to allow the expansion process starting and ending inside the piston volume chamber. The working principle of these two types of reciprocating piston expanders is illustrated in **Figure 7**. Piston type of expansion machine requires precisely controlled methods for the intake and exhaust valves, which will result to the requirement of a complex control system although this type of expander can potentially reach very high-expansion efficiency [50]. Moreover, piston

*2.3.2. Positive displacement expanders*

types of rotary expanders.

#### *2.3.1. Turbines*

Turbines have been widely applied as the expansion machine to replace the piston type of expander in steam Rankine cycle since the nineteenth century and have been acknowledged as the optimal expander for large-scale power plants. It consumes the internal energy of vapor into kinetic energy, which results the velocity of the flow are relatively high but the pressure and forces between the supply and exhaust point are rather small [39]. The mechanical power is then been obtained from the shaft of the turbine by turning the rotor blades when the highvelocity fluid passes through the turbine. There are mainly two types of turbines: axial flow turbines and radial flow turbines [40]. The axial flow turbines are driven by the flow in the parallel direction to the shaft, while the radial flow turbines are rotated by the flow traveling through the hub to the tipoff the turbine as indicated in **Figure 6**. However, the application of turbines for small-scale power generation system has not been widely accepted as the best expansion machine, especially in the power plants lower than 100 kW. Radial flow turbines are one of the exceptions, which have been recently used for small-scale application in Organic Rankine Cycle (ORC) [42–47]. Kang reports the design and experimental investigation of an ORC using R245fa as the working fluid and radial flow turbine as the expansion machine [42]. The radial turbine

**Figure 6.** Working principle of turbine machines. (a) Axial flow turbine and (b) radial flow turbine [41].

was directly connected to a high-speed generator to produce electricity and results indicated the maximum cycle efficiency, the isentropic turbine efficiency, and electricity power obtained from the testing rig is 5.22%, 78.7%, and 32.7 kW, respectively [42]. Pei et al. [47, 48] carried out an experimental investigation on a 1–2 kW ORC system using a special designed and constructed radial flow turbine. The reported study achieves the isentropic efficiency of the radial flow turbine at 65–68% with the rotational speed around 20,000–40,000 using R123 as the organic working fluid in the ORC system [46, 47]. Compared with positive displacement expander, turbines are easier to be designed with relatively less required parts. A single stage turbine only requires two bearings to be mounted to the generator on the shaft. Furthermore, there is no contact seal existing in the turbines, which means no lubrication oil is necessary to be adapted to the system. The application of turbine for small-scale application is still not successful because the turbine is designed under rather low-expansion ratios and high-volume flows. The rotational speed of conventional turbines ranges from 10,000 to 100, 000 rpm because of the physical design of this type of expansion machine, which results to a limited or hard sourcing of proper generator for electricity production. One of the solutions to adapt the turbine machine directly with the generator is to use a high-speed generator, which will lead to high initial cost and increase the overall cost of electricity generation system. The other method to obtain the mechanical work from the turbine and convert it into electricity is by using gear. This method can effectively solve the high initial cost of the system but will require larger space for the turbine unit and reduce the efficiency of the turbine machine due to mechanical losses in the gear. Furthermore, the availability of small-scale turbine machine is still limited. The currently used radial flow turbines in small-scale power generation system are either from specially designed by the researcher or modified from a conventional turbine from an automotive turbocharger.

#### *2.3.2. Positive displacement expanders*

**Figure 6.** Working principle of turbine machines. (a) Axial flow turbine and (b) radial flow turbine [41].

The expansion machines can be divided into two types: turbine machine using the kinetic energy of the working fluid to drive the expander and positive displace expander producing

Turbines have been widely applied as the expansion machine to replace the piston type of expander in steam Rankine cycle since the nineteenth century and have been acknowledged as the optimal expander for large-scale power plants. It consumes the internal energy of vapor into kinetic energy, which results the velocity of the flow are relatively high but the pressure and forces between the supply and exhaust point are rather small [39]. The mechanical power is then been obtained from the shaft of the turbine by turning the rotor blades when the highvelocity fluid passes through the turbine. There are mainly two types of turbines: axial flow turbines and radial flow turbines [40]. The axial flow turbines are driven by the flow in the parallel direction to the shaft, while the radial flow turbines are rotated by the flow traveling through the hub to the tipoff the turbine as indicated in **Figure 6**. However, the application of turbines for small-scale power generation system has not been widely accepted as the best expansion machine, especially in the power plants lower than 100 kW. Radial flow turbines are one of the exceptions, which have been recently used for small-scale application in Organic Rankine Cycle (ORC) [42–47]. Kang reports the design and experimental investigation of an ORC using R245fa as the working fluid and radial flow turbine as the expansion machine [42]. The radial turbine

**2.3. Expander candidates**

134 Organic Rankine Cycle Technology for Heat Recovery

*2.3.1. Turbines*

power by changing the volume of working chamber.

Different from the working principle turbine machines, positive displacement expanders use the expansion power by changing the volume inside the expansion chambers, which can also be named volumetric expanders. The most commonly used positive displacement expanders include piston type expander, screw expander, and scroll expander and vane expander. The positive displacement expanders can be classified into two types reciprocating piston expanders and rotary expanders. Screw expander, scroll expander, and vane expander are three main types of rotary expanders.

The piston type of machines attracts extensive intentions since it was invented and has been widely applied in different areas to meet various requirements such as the most commonly used as an Internal Combustion Engine. In the past 30 years, piston expander has been adopted and developed as the expander into steam Rankine system integrating with the internal combustion engine to recover the exhaust energy [4]. The piston type of expander can be designed and constructed with one valve version and two valve version in order to allow the expansion process starting and ending inside the piston volume chamber. The working principle of these two types of reciprocating piston expanders is illustrated in **Figure 7**. Piston type of expansion machine requires precisely controlled methods for the intake and exhaust valves, which will result to the requirement of a complex control system although this type of expander can potentially reach very high-expansion efficiency [50]. Moreover, piston

no commercially available product under the power output lower than 10 kW from the market as reported by Ian et al. [55]. Because small size of screw expander needs extremely precise machining requirements to make the rotors and internal leakages of small size screw expander

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery

http://dx.doi.org/10.5772/intechopen.78401

137

Scroll type of machine was first developed by a French inventor in 1905 and then the scroll machine starts to attract attention to be applied in Air condition system as a compressor to produce refrigeration since the mid of 1980s [57]. The most of the available scroll expanders from the market are modified from scroll compressor by swapping the inlet and outlet ports to change the device working mode from compressor to the expander. Scroll device is relatively simple equipment, which mainly includes two scrolls. The scroll expander has the advantages of little vibration, low-noise, a limited number of moving parts, broad availability, high-reliability and low initial cost [58, 59]. Scroll device has two scrolls and one of the scrolls is fixed on the shell, which is called situational scroll, while the other scroll orbiting eccentrically without rotating is named orbiting scroll. During the expansion process, high-pressure vapor enters and expands centrally of two scrolls pushing the orbiting scroll to start orbit as illustrated in **Figure 9**. The mechanical work can be continually obtained from the orbiting scroll through the shaft. Likewise the other positive displacement expanders, scroll expander has a fixed built-in expansion ratio. The optimal performance of scroll expander can be obtained when the specific volume ratio of the designed system equal to the built-in expansion ratio. Quoilin et al. pointed out the losses appearing when scroll type of expansion machine is working under and over expansion processes [9]. For example, 1 kW

are relatively higher than that of the large-scale device [51, 56].

**Figure 9.** Expansion process of the scroll device under different crank angles [60].

**Figure 7.** Working principle of reciprocating piston expander. (a) Single valve piston expander and (b) two valve piston expander [49].

expander requires a lot of bearings, a great number of moving parts, and balancing setting up, which results in a relatively complex and costly system.

Screw expander is composed of two meshing helical rotors a male and a female rotor, which requires at least four bearings for the two rotors as shown in **Figure 8**. This type of expansion machine has been widely applied in steam Rankine cycle plants for geothermal waste heat recovery system [52]. Lubrication oil is commonly used in the screw machine to seal the expanded working fluid inside the expansion chamber, which can effectively reduce the internal leakage losses during the expansion process. Screw expander has a relatively high rotational speed in positive displacement expanders and the rotation speed of this machine can reach as high as 6000 rpm [52]. The electricity production from screw expander, therefore, requires a specially designed high-speed generator or adding a gearbox to convert the mechanical power from the screw machine into electricity. This type of expansion devices has the advantages such as medium internal frictions, medium leakage losses, low vibration noise, wide ranges of power output, and long lifetime. The power produced from this expansion machine as reported by previous researchers ranging from 1.5 kW to 1 MW with the expansion ratio of 2–8 [53]. Leibowitz et al. developed an ORC power generation system using screw expander in a demonstration unit to cost-effectively recover the waste heat into power. Results indicated that screw expander is a good candidate expansion machine for the ORC system with the power output at 20 kW with installation cost in the range of \$1500 –\$2000/kWe [54]. However, there is

**Figure 8.** Working principle of screw expander [51].

no commercially available product under the power output lower than 10 kW from the market as reported by Ian et al. [55]. Because small size of screw expander needs extremely precise machining requirements to make the rotors and internal leakages of small size screw expander are relatively higher than that of the large-scale device [51, 56].

Scroll type of machine was first developed by a French inventor in 1905 and then the scroll machine starts to attract attention to be applied in Air condition system as a compressor to produce refrigeration since the mid of 1980s [57]. The most of the available scroll expanders from the market are modified from scroll compressor by swapping the inlet and outlet ports to change the device working mode from compressor to the expander. Scroll device is relatively simple equipment, which mainly includes two scrolls. The scroll expander has the advantages of little vibration, low-noise, a limited number of moving parts, broad availability, high-reliability and low initial cost [58, 59]. Scroll device has two scrolls and one of the scrolls is fixed on the shell, which is called situational scroll, while the other scroll orbiting eccentrically without rotating is named orbiting scroll. During the expansion process, high-pressure vapor enters and expands centrally of two scrolls pushing the orbiting scroll to start orbit as illustrated in **Figure 9**. The mechanical work can be continually obtained from the orbiting scroll through the shaft. Likewise the other positive displacement expanders, scroll expander has a fixed built-in expansion ratio. The optimal performance of scroll expander can be obtained when the specific volume ratio of the designed system equal to the built-in expansion ratio. Quoilin et al. pointed out the losses appearing when scroll type of expansion machine is working under and over expansion processes [9]. For example, 1 kW

**Figure 9.** Expansion process of the scroll device under different crank angles [60].

**Figure 8.** Working principle of screw expander [51].

expander requires a lot of bearings, a great number of moving parts, and balancing setting

**Figure 7.** Working principle of reciprocating piston expander. (a) Single valve piston expander and (b) two valve piston

Screw expander is composed of two meshing helical rotors a male and a female rotor, which requires at least four bearings for the two rotors as shown in **Figure 8**. This type of expansion machine has been widely applied in steam Rankine cycle plants for geothermal waste heat recovery system [52]. Lubrication oil is commonly used in the screw machine to seal the expanded working fluid inside the expansion chamber, which can effectively reduce the internal leakage losses during the expansion process. Screw expander has a relatively high rotational speed in positive displacement expanders and the rotation speed of this machine can reach as high as 6000 rpm [52]. The electricity production from screw expander, therefore, requires a specially designed high-speed generator or adding a gearbox to convert the mechanical power from the screw machine into electricity. This type of expansion devices has the advantages such as medium internal frictions, medium leakage losses, low vibration noise, wide ranges of power output, and long lifetime. The power produced from this expansion machine as reported by previous researchers ranging from 1.5 kW to 1 MW with the expansion ratio of 2–8 [53]. Leibowitz et al. developed an ORC power generation system using screw expander in a demonstration unit to cost-effectively recover the waste heat into power. Results indicated that screw expander is a good candidate expansion machine for the ORC system with the power output at 20 kW with installation cost in the range of \$1500 –\$2000/kWe [54]. However, there is

up, which results in a relatively complex and costly system.

expander [49].

136 Organic Rankine Cycle Technology for Heat Recovery

oil-free scroll expander was used in an ORC system to recover the exhaust gas heat from a 30 kW gas turbine as reported by June et al. [61]. The ORC system used a zeotropic mixture with 48.5% R245fa and 51.5% R365mfc as the working fluid and the experimental results indicated the overall efficiency of the ORC system was about 3.9% [61]. The scroll expander was operated in the over-expansion region, which can therefore only achieve the efficiency of 28.4% under the tested condition. The overall ORC efficiency can be much higher than 3.9% if the expansion machine has been operated within the optimal conditions [61]. A prototype of ORC system using an open-drive oil-free scroll expander with R123 as the working fluid was experimentally investigated by Lemort et al. [62]. Results indicated the maximum isentropic efficiency of the scroll expander could be as high as 68% [62]. Muhammad et al. [63] reported the experimental study of a small-scale ORC system recovering the heat from hot steam. An oil-free scroll expander was used in the system to produce electrical power. Results show the maximum electrical power from the system was 1.016 kW when the system thermal efficiency was 5.64% and the isentropic efficiency of the expander was 58.3% [63]. During the experiment, the maximum ORC thermal efficiency was achieved at 5.75% and the scroll expander achieved the maximum isentropic efficiency as high as 77.74% [63]. A hermetic type refrigerant scroll compressor with built-in volume ratio at 3.24 was modified as an expander and used in an ORC system as reported by Yang et al. [64]. The experimental results indicated the maximum shaft power was 2.64 kW when the ORC thermal efficiency was 5.92% [64]. The majority of scroll expanders available from the market are modified from scroll compressors, which are not designed to be used for expansion applications. A separate lubrication system is normally required to lubricate the contact seals of two scrolls and reduce the radial leakage. The other function of the oil is to seal the working fluid inside the expansion chambers during the expansion process to prevent and reduce the flank leakage of the scroll type machine.

**2.4. Cycle investigations**

(BSFC) can be reduced by a maximum of 5.0% [24].

**Figure 10.** Working principle of vane-type expander [56].

Due to the limited space, the demand of high-power to weight ratio for ORC system and complicated control strategies for vehicle application, the ORC systems are still under technical development and testing stages. The current commercialization status of ORC technology for engine waste heat recovery is mainly for stationary power generation applications because of their desirable stable operating profiles [11]. A representative study on ORC system recovering exhaust energy from a stationary compressed natural gas (CNG) engine was reported by Song et al. [24]. The results showed the electric efficiency of the CNG engine could be potentially improved by a maximum 6.0% and the overall engine brake specific fuel consumption

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery

http://dx.doi.org/10.5772/intechopen.78401

139

The two primary heat sources from ICE systems are engine cooling system and exhaust gases, which almost contain 60–70% of the fuel energy. Engine coolant energy is normally recognized as a heat source that is not worth to recover because the coolant temperature is about 80–100°C. However, the coolant energy contains about 30% of the fuel energy. The effective utilization of engine coolant energy for ORC waste heat recovery of the ICE could potentially improve the overall system efficiency and reduce the pay-back period of the overall cost with a properly designed system [9, 10]. A typical single-loop ORC system recovering both engine coolant and exhaust energy can be shown in **Figure 11**. A recuperator can be used to recover unused heat at the exit of expansion machine to preheat the working. The coolant energy can either be used as preheating source or main heat source for ORC systems. Only part of the coolant energy can be recovered if it was used as preheating source. For example, a study conducted by Yu et al. [69] investigated the potential of using engine coolant energy as ORC preheating source. The simulation results indicated there is around 75% exhaust heat and 9.5% coolant energy can be recovered from a diesel engine [69]. Tian et al. [70] deeply investigated the effects of fluids and parameters of the ORC system for engine exhaust heat recovery. The performance ORC system using 20 working fluids (boiling point range from −51.6 to 32.05°C) was studied to evaluate the

Vane expanders have the advantages of simple construction, easy manufacture, low-cost, self-start under load and smooth torque production [35, 65]. The expansion process happens between the cylinder wall and the sliding vanes. When the high-pressure working fluid flows into the inlet port and fills chamber A, the spinning power from the rotor can be gathered as illustrated in **Figure 10**. The pressure differences among the chambers resulted by expansion process driver the rotor. Qiu et al. [56, 66] investigated a vane expander in a biomass fire CHP system with ORC and achieved the isentropic efficiency of 54.5% at the speed of 824 RPM (mechanical work of 1.552 kW). The electricity generated by the vane expander was 792 W, which lighted seventeen 50 W bulbs. The efficiencies of several vane expanders using different working fluids at different working temperatures and pressures were summarized by Aoun [67]. Results showed that the maximum efficiency of 80% was achieved by a vane expander using R-11 at 800 RPM. The rotational speed of vane type of expanders is relatively lower than other expansion machines with commonly from 1500 to 3000 rpm, which can be directly installed to the generator without requiring of gear box [35]. However, the average isentropic efficiency of vane expanders is with the range of 15–55%, which is not that competitive compared with other volumetric expansion machines, as reported by Muhammad et al. [53]. Moreover, this type of expander requires a lubrication system to lubricate the contact surface of the rotor and vane. The existing of lubricate oil will contaminate the working fluid and flow back to the system.

**Figure 10.** Working principle of vane-type expander [56].

#### **2.4. Cycle investigations**

oil-free scroll expander was used in an ORC system to recover the exhaust gas heat from a 30 kW gas turbine as reported by June et al. [61]. The ORC system used a zeotropic mixture with 48.5% R245fa and 51.5% R365mfc as the working fluid and the experimental results indicated the overall efficiency of the ORC system was about 3.9% [61]. The scroll expander was operated in the over-expansion region, which can therefore only achieve the efficiency of 28.4% under the tested condition. The overall ORC efficiency can be much higher than 3.9% if the expansion machine has been operated within the optimal conditions [61]. A prototype of ORC system using an open-drive oil-free scroll expander with R123 as the working fluid was experimentally investigated by Lemort et al. [62]. Results indicated the maximum isentropic efficiency of the scroll expander could be as high as 68% [62]. Muhammad et al. [63] reported the experimental study of a small-scale ORC system recovering the heat from hot steam. An oil-free scroll expander was used in the system to produce electrical power. Results show the maximum electrical power from the system was 1.016 kW when the system thermal efficiency was 5.64% and the isentropic efficiency of the expander was 58.3% [63]. During the experiment, the maximum ORC thermal efficiency was achieved at 5.75% and the scroll expander achieved the maximum isentropic efficiency as high as 77.74% [63]. A hermetic type refrigerant scroll compressor with built-in volume ratio at 3.24 was modified as an expander and used in an ORC system as reported by Yang et al. [64]. The experimental results indicated the maximum shaft power was 2.64 kW when the ORC thermal efficiency was 5.92% [64]. The majority of scroll expanders available from the market are modified from scroll compressors, which are not designed to be used for expansion applications. A separate lubrication system is normally required to lubricate the contact seals of two scrolls and reduce the radial leakage. The other function of the oil is to seal the working fluid inside the expansion chambers during the expansion process to prevent and reduce the flank leakage of the scroll type machine.

138 Organic Rankine Cycle Technology for Heat Recovery

Vane expanders have the advantages of simple construction, easy manufacture, low-cost, self-start under load and smooth torque production [35, 65]. The expansion process happens between the cylinder wall and the sliding vanes. When the high-pressure working fluid flows into the inlet port and fills chamber A, the spinning power from the rotor can be gathered as illustrated in **Figure 10**. The pressure differences among the chambers resulted by expansion process driver the rotor. Qiu et al. [56, 66] investigated a vane expander in a biomass fire CHP system with ORC and achieved the isentropic efficiency of 54.5% at the speed of 824 RPM (mechanical work of 1.552 kW). The electricity generated by the vane expander was 792 W, which lighted seventeen 50 W bulbs. The efficiencies of several vane expanders using different working fluids at different working temperatures and pressures were summarized by Aoun [67]. Results showed that the maximum efficiency of 80% was achieved by a vane expander using R-11 at 800 RPM. The rotational speed of vane type of expanders is relatively lower than other expansion machines with commonly from 1500 to 3000 rpm, which can be directly installed to the generator without requiring of gear box [35]. However, the average isentropic efficiency of vane expanders is with the range of 15–55%, which is not that competitive compared with other volumetric expansion machines, as reported by Muhammad et al. [53]. Moreover, this type of expander requires a lubrication system to lubricate the contact surface of the rotor and vane. The existing of lubricate oil will contaminate the working fluid

and flow back to the system.

Due to the limited space, the demand of high-power to weight ratio for ORC system and complicated control strategies for vehicle application, the ORC systems are still under technical development and testing stages. The current commercialization status of ORC technology for engine waste heat recovery is mainly for stationary power generation applications because of their desirable stable operating profiles [11]. A representative study on ORC system recovering exhaust energy from a stationary compressed natural gas (CNG) engine was reported by Song et al. [24]. The results showed the electric efficiency of the CNG engine could be potentially improved by a maximum 6.0% and the overall engine brake specific fuel consumption (BSFC) can be reduced by a maximum of 5.0% [24].

The two primary heat sources from ICE systems are engine cooling system and exhaust gases, which almost contain 60–70% of the fuel energy. Engine coolant energy is normally recognized as a heat source that is not worth to recover because the coolant temperature is about 80–100°C. However, the coolant energy contains about 30% of the fuel energy. The effective utilization of engine coolant energy for ORC waste heat recovery of the ICE could potentially improve the overall system efficiency and reduce the pay-back period of the overall cost with a properly designed system [9, 10]. A typical single-loop ORC system recovering both engine coolant and exhaust energy can be shown in **Figure 11**. A recuperator can be used to recover unused heat at the exit of expansion machine to preheat the working. The coolant energy can either be used as preheating source or main heat source for ORC systems. Only part of the coolant energy can be recovered if it was used as preheating source. For example, a study conducted by Yu et al. [69] investigated the potential of using engine coolant energy as ORC preheating source. The simulation results indicated there is around 75% exhaust heat and 9.5% coolant energy can be recovered from a diesel engine [69]. Tian et al. [70] deeply investigated the effects of fluids and parameters of the ORC system for engine exhaust heat recovery. The performance ORC system using 20 working fluids (boiling point range from −51.6 to 32.05°C) was studied to evaluate the

was reported by Shu et al. [74], who investigated the influence of using different working fluids. The high-temperature loop adopted water to recovery the exhaust energy and six working fluids have been selected for the low-temperature [74]. The dual-loop ORC system can achieve the maximum overall exergy efficiency as high as 55.05% using R1234yf as working fluid [74]. The dual-loop ORC requires two sets of ORC system components and advanced controlling strategies to balance the different heat sources, which will increase the capital cost

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery

http://dx.doi.org/10.5772/intechopen.78401

141

The power output from the ORC system can be either mechanical or electrical. As introduced in the previous section, the expansion machines can be divided into two types turbine machine using the kinetic energy of the working fluid to drive the expander and positively displace expander producing power by changing the volume of working chamber. When the mechanical configuration is used, the expander shaft is connected to the engine drive belt or a gear. Alternatively, an alternator is used to convert the mechanical work from the ORC expander to electricity. The generated electricity can be used to power the vehicle battery or supply auxiliary utilities. One of the main drawbacks of the solution is the efficiency of avail-

The designed evaporation and condensation temperature determines the overall efficiency of ORC system. A higher temperature difference between evaporation and condensation can result in a higher overall ORC efficiency. The engine front radiator is therefore required to reject high-load of heat in order to maintain the low condensation temperature. The limited space for vehicle application restricts the size of engine cooling system. An electrically driven cooling fan is generally not recommended to achieve low condensation temperature because

Another main technical constraint is the dynamic/transient heat sources. In order to maintain the ORC system within the optimal operating region, the control of pump speed, and expander speed are required. Therefore, the complex control strategies are critical to being

of the system and result in high payback period.

**Figure 12.** Dual-loop ORC system (a) schematic diagram and (b) *T-s* diagram [26, 75].

able vehicle alternators, which is around 50–60% [5, 9].

it would sharply reduce the overall system performance.

**2.5. Technical barriers**

**Figure 11.** Single-loop ORC for engine coolant and exhaust recovery [68].

cycle parameters such as the overall thermal efficiency, expansion ratio, effective power output and electricity production cost [70]. R141b, R123, and R245fa were identified as the optimal working fluids. The highest thermal efficiency of these three working fluids ranges from 16.6% to 13.3% with the electricity production cost various from 0.30 to 0.35 €/kWh [70]. A simulation study of an ORC system for diesel engine exhaust heat recovery was reported by Zhao et al. [71]. Results indicated the BSFC reduction and the overall thermal efficiency of the engine integrated with ORC unit is 3.61 g/(kWh)–0.66% [71]. Shu et al. [72] recommended to use alkane-based working fluids for diesel engine exhaust heat recovery from the technical and economic point of view [72].

Another potential approach for engine coolant and exhaust recovery is using dual-loop ORC, which adopts two separately ORC systems to regenerate multi-heat sources from ICE [28, 73, 74]. The schematic system diagram and *T-s* diagram of dual loop ORC system can be found in **Figure 12**. Wang et al. [28, 73] conducted the study on a dual loop ORC to evaluate the performance of a gasoline engine and a light-duty diesel engine. The dual loop ORC system contains a high-temperature loop recovering engine exhaust heat and a low-temperature loop for coolant heat recovery. The proposed concept has the potential to comprehensively reuse all the recoverable heat from engine coolant and exhaust sources [73]. The investigations of using dual loop ORC system were also conducted on a selected gasoline engine and a diesel engine. For the selected gasoline engine, the results showed the dual loop ORC system can effectively improve the overall system efficiency by 3–6% throughout the engine operating region [73]. When the system was used on a light-duty diesel engine, the evaluation results indicated the thermal efficiency can be improved by 8% compared to that of the original engine [28]. At the engine rated power condition, the power output of the combined system can be improved by 26.63% [28]. Further study of the dual-loop ORC for engine coolant and exhaust recovery The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery http://dx.doi.org/10.5772/intechopen.78401 141

**Figure 12.** Dual-loop ORC system (a) schematic diagram and (b) *T-s* diagram [26, 75].

was reported by Shu et al. [74], who investigated the influence of using different working fluids. The high-temperature loop adopted water to recovery the exhaust energy and six working fluids have been selected for the low-temperature [74]. The dual-loop ORC system can achieve the maximum overall exergy efficiency as high as 55.05% using R1234yf as working fluid [74]. The dual-loop ORC requires two sets of ORC system components and advanced controlling strategies to balance the different heat sources, which will increase the capital cost of the system and result in high payback period.

#### **2.5. Technical barriers**

cycle parameters such as the overall thermal efficiency, expansion ratio, effective power output and electricity production cost [70]. R141b, R123, and R245fa were identified as the optimal working fluids. The highest thermal efficiency of these three working fluids ranges from 16.6% to 13.3% with the electricity production cost various from 0.30 to 0.35 €/kWh [70]. A simulation study of an ORC system for diesel engine exhaust heat recovery was reported by Zhao et al. [71]. Results indicated the BSFC reduction and the overall thermal efficiency of the engine integrated with ORC unit is 3.61 g/(kWh)–0.66% [71]. Shu et al. [72] recommended to use alkane-based working fluids for diesel engine exhaust heat recovery from the technical and economic point of view [72]. Another potential approach for engine coolant and exhaust recovery is using dual-loop ORC, which adopts two separately ORC systems to regenerate multi-heat sources from ICE [28, 73, 74]. The schematic system diagram and *T-s* diagram of dual loop ORC system can be found in **Figure 12**. Wang et al. [28, 73] conducted the study on a dual loop ORC to evaluate the performance of a gasoline engine and a light-duty diesel engine. The dual loop ORC system contains a high-temperature loop recovering engine exhaust heat and a low-temperature loop for coolant heat recovery. The proposed concept has the potential to comprehensively reuse all the recoverable heat from engine coolant and exhaust sources [73]. The investigations of using dual loop ORC system were also conducted on a selected gasoline engine and a diesel engine. For the selected gasoline engine, the results showed the dual loop ORC system can effectively improve the overall system efficiency by 3–6% throughout the engine operating region [73]. When the system was used on a light-duty diesel engine, the evaluation results indicated the thermal efficiency can be improved by 8% compared to that of the original engine [28]. At the engine rated power condition, the power output of the combined system can be improved by 26.63% [28]. Further study of the dual-loop ORC for engine coolant and exhaust recovery

**Figure 11.** Single-loop ORC for engine coolant and exhaust recovery [68].

140 Organic Rankine Cycle Technology for Heat Recovery

The power output from the ORC system can be either mechanical or electrical. As introduced in the previous section, the expansion machines can be divided into two types turbine machine using the kinetic energy of the working fluid to drive the expander and positively displace expander producing power by changing the volume of working chamber. When the mechanical configuration is used, the expander shaft is connected to the engine drive belt or a gear. Alternatively, an alternator is used to convert the mechanical work from the ORC expander to electricity. The generated electricity can be used to power the vehicle battery or supply auxiliary utilities. One of the main drawbacks of the solution is the efficiency of available vehicle alternators, which is around 50–60% [5, 9].

The designed evaporation and condensation temperature determines the overall efficiency of ORC system. A higher temperature difference between evaporation and condensation can result in a higher overall ORC efficiency. The engine front radiator is therefore required to reject high-load of heat in order to maintain the low condensation temperature. The limited space for vehicle application restricts the size of engine cooling system. An electrically driven cooling fan is generally not recommended to achieve low condensation temperature because it would sharply reduce the overall system performance.

Another main technical constraint is the dynamic/transient heat sources. In order to maintain the ORC system within the optimal operating region, the control of pump speed, and expander speed are required. Therefore, the complex control strategies are critical to being developed or advanced ORC systems should be investigated. Using variable speed pump, adding control valves and integrating thermal energy storage system to manage fluctuation waste heat are some common strategies as reported by Manuel et al. [76].

**References**

Energy. 2018;**221**:67-74

2015;**8**:1152-1167

2013;**22**:168-186

Applied Thermal Engineering. 2018;**137**:710-720

engines—A review. Applied Energy. 2017;**185**:300-319

butyrate and ethanol blends. Applied Energy. 2017;**195**:693-701

and Sustainable Energy Reviews. 2011;**15**:3963-3979

[15] Hanlon M. BMW unveils the turbosteamer concept. 2005

Cycle System: SAE Technical Paper; 1976

[1] Lu Y, Roskilly AP, Yu X, Jiang L, Chen L. Technical feasibility study of scroll-type rotary gasoline engine: A compact and efficient small-scale Humphrey cycle engine. Applied

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery

http://dx.doi.org/10.5772/intechopen.78401

143

[2] Li Q, Liu J, Fu J, Zhou X, Liao C. Comparative study on the pumping losses between continuous variable valve lift (CVVL) engine and variable valve timing (VVT) engine.

[3] Zhao J. Research and application of over-expansion cycle (Atkinson and Miller)

[4] Wang T, Zhang Y, Peng Z, Shu G. A review of researches on thermal exhaust heat recovery with Rankine cycle. Renewable and Sustainable Energy Reviews. 2011;**15**:2862-2871 [5] Sprouse C III, Depcik C. Review of organic Rankine cycles for internal combustion engine exhaust waste heat recovery. Applied Thermal Engineering. 2013;**51**:711-722 [6] Chen L, Zhang Z, Lu Y, Zhang C, Zhang X, Zhang C, et al. Experimental study of the gaseous and particulate matter emissions from a gas turbine combustor burning butyl

[7] Fang Y, Lu Y, Yu X, Roskilly AP. Experimental study of a pneumatic engine with heat supply to improve the overall performance. Applied Thermal Engineering. 2018;**134**:78-85 [8] Johnson TV. Reviewof vehicular emissions trends. SAE International Journal of Engines.

[9] Quoilin S, Broek MVD, Declaye S, Dewallef P, Lemort V. Techno-economic survey of organic Rankine cycle (ORC) systems. Renewable and Sustainable Energy Reviews.

[10] Vélez F, Segovia JJ, Martín MC, Antolín G, Chejne F, Quijano A. A technical, economical and market review of organic Rankine cycles for the conversion of low-grade heat for power generation. Renewable and Sustainable Energy Reviews. 2012;**16**:4175-4189 [11] Tchanche BF, Lambrinos G, Frangoudakis A, Papadakis G. Low-grade heat conversion into power using organic Rankine cycles—A review of various applications. Renewable

[12] Patel PS, Doyle EF. Compounding the Truck Diesel Engine with an Organic Rankine-

[13] Doyle E, DiNanno L, Kramer S. Installation of a diesel-organic Rankine compound

[14] DiBella FA, DiNanno LR, Koplow MD. Laboratory and on-highway testing of diesel organic Rankine compound long-haul vehicle engine. SAE International. 1983

engine in a class 8 truck for a single-vehicle test. SAE Technical Paper. 1979

## **3. Conclusions**

Vehicle waste heat recovery technologies are currently under enormous interests for the purpose of reducing emissions and improving overall efficiency. Organic Rankine Cycle is one of the best solutions to recover engine waste heat into mechanical or electrical power. Key conclusions of this chapter can be summarized as follows.

It is critical to characterize the recoverable heat from the engine before designing the ORC system. A broad range of working fluids are available to be selected but there is no working fluid can be recognized as the best to be used in any ORC systems. A high-efficiency alternator to be coupled with ORC expander is in high-demand in order to promote the application of electrical version engine waste heat recovery system. For vehicle application, a compact system is desirable because of the limitation of space. A well-designed engine thermal management system should be considered. The transient heat source performance is the major technical obstacle to use ORC system for engine waste heat recovery and it can be expected either advanced control strategies or thermal energy storage technology should be used to solve the problem and promote the practical application of the ORC system for the vehicle.

## **Acknowledgements**

The authors would like to thank the supports from EPSRC through (EP/P001173/1)-Centre for Energy Systems Integration, (EP/K503885/1) toward the project- Study of engine waste heat technologies, from NSFC-RS Joint Project under the grant number No.<PHONE_NUMBER> and IE/151256. The support from Cao Guang Biao High Tech Talent Fund, Zhejiang University is also highly acknowledged.

## **Author details**

Yiji Lu1,2\*, Anthony Paul Roskilly1,2 and Xiaoli Yu1

\*Address all correspondence to<EMAIL_ADDRESS>
1 Department of Energy Engineering, Zhejiang University, Hangzhou, China

2 Sir Joseph Swan Centre for Energy Research, Newcastle University, Newcastle, United Kingdom

## **References**

developed or advanced ORC systems should be investigated. Using variable speed pump, adding control valves and integrating thermal energy storage system to manage fluctuation

Vehicle waste heat recovery technologies are currently under enormous interests for the purpose of reducing emissions and improving overall efficiency. Organic Rankine Cycle is one of the best solutions to recover engine waste heat into mechanical or electrical power. Key

It is critical to characterize the recoverable heat from the engine before designing the ORC system. A broad range of working fluids are available to be selected but there is no working fluid can be recognized as the best to be used in any ORC systems. A high-efficiency alternator to be coupled with ORC expander is in high-demand in order to promote the application of electrical version engine waste heat recovery system. For vehicle application, a compact system is desirable because of the limitation of space. A well-designed engine thermal management system should be considered. The transient heat source performance is the major technical obstacle to use ORC system for engine waste heat recovery and it can be expected either advanced control strategies or thermal energy storage technology should be used to solve the problem and promote the practical application of the ORC

The authors would like to thank the supports from EPSRC through (EP/P001173/1)-Centre for Energy Systems Integration, (EP/K503885/1) toward the project- Study of engine waste heat technologies, from NSFC-RS Joint Project under the grant number No.<PHONE_NUMBER> and IE/151256. The support from Cao Guang Biao High Tech Talent Fund, Zhejiang University is

waste heat are some common strategies as reported by Manuel et al. [76].

conclusions of this chapter can be summarized as follows.

**3. Conclusions**

142 Organic Rankine Cycle Technology for Heat Recovery

system for the vehicle.

**Acknowledgements**

also highly acknowledged.

Yiji Lu1,2\*, Anthony Paul Roskilly1,2 and Xiaoli Yu1

\*Address all correspondence to<EMAIL_ADDRESS>
1 Department of Energy Engineering, Zhejiang University, Hangzhou, China

2 Sir Joseph Swan Centre for Energy Research, Newcastle University, Newcastle,

**Author details**

United Kingdom

[16] Obieglo A, Ringler J, Seifert M, Hall W. Future efficient dynamics with heat recovery. In: Presentation at US Department of Energy Directions in Engine Efficiency and Emissions Research (DEER) Conference; Dearborn, Michigan. 2009

[30] Lu Y, Roskilly AP, Yu X, Tang K, Jiang L, Smallbone A, et al. Parametric study for small scale engine coolant and exhaust heat recovery system using different organic Rankine

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery

http://dx.doi.org/10.5772/intechopen.78401

145

[31] Lu Y, Wang L, Tian G, Roskilly AP. Study on a Small Scale Solar Powered Organic Rankine Cycle Utilizing Scroll Expander. In: International Conference on Applied Energy; July

[32] Hung TC, Shai TY, Wang SK. A review of organic rankine cycles (ORCs) for the recovery

[33] Wang EH, Zhang HG, Fan BY, Ouyang MG, Zhao Y, Mu QH. Study of working fluid selection of organic Rankine cycle (ORC) for engine waste heat recovery. Energy.

[34] Saleh B, Koglbauer G, Wendland M, Fischer J. Working fluids for low-temperature

[35] Bao J, Zhao L. A review of working fluid and expander selections for organic Rankine

[36] Chen H, Goswami DY, Stefanakos EK. A review of thermodynamic cycles and working fluids for the conversion of low-grade heat. Renewable and Sustainable Energy Reviews.

[37] Tchanche BF, Papadakis G, Lambrinos G, Frangoudakis A. Fluid selection for a lowtemperature solar organic Rankine cycle. Applied Thermal Engineering. 2009;**29**:2468-2476

[38] Heberle F, Brüggemann D. Exergy based fluid selection for a geothermal organic Rankine cycle for combined heat and power generation. Applied Thermal Engineering.

[39] Weiß AP. Volumetric expander versus turbine-which is the better choice for small ORC plants? In: 3rd International Seminar on ORC Power Systems; Brussels, Belgium. 2015 [40] Barber-nichols. Turbines. Available from: http://www.barber-nichols.com/products/tur-

[41] Technology B. Microturbines and Micro Gas Turbines. Available from: http://wwwgas-

[42] Kang SH. Design and experimental study of ORC (organic Rankine cycle) and radial

[43] Yamamoto T, Furuhata T, Arai N, Mori K. Design and testing of the organic Rankine

[44] Nguyen VM, Doherty PS, Riffat SB.Development of a prototype low-temperature Rankine cycle electricity generation system. Applied Thermal Engineering. 2001;**21**:169-181 [45] Yagoub W, Doherty P, Riffat SB. Solar energy-gas driven micro-CHP system for an office

[46] Pei G, Li J, Li Y, Wang D, Ji J. Construction and dynamic test of a small-scale organic

turbineworldcouk/microturbineguidehtml [Accessed: 02-05-2018]

turbine using R245fa working fluid. Energy. 2012;**41**:514-524

building. Applied Thermal Engineering. 2006;**26**:1604-1610

cycle. Renewable and Sustainable Energy Reviews. 2013;**24**:325-342

cycle layouts. Applied Thermal Engineering. 2017;**127**:1252-1266

of low-grade waste heat. Energy. 1997;**22**:661-667

organic Rankine cycles. Energy. 2007;**32**:1210-1221

5-8, 2012; Suzhou, China

2011;**36**:3406-3418

2010;**14**:3059-3067

2010;**30**:1326-1332

bines [Accessed: 26-08-2012]

cycle. Energy. 2001;**26**:239-251

rankine cycle. Energy. 2011;**36**:3215-3223

[30] Lu Y, Roskilly AP, Yu X, Tang K, Jiang L, Smallbone A, et al. Parametric study for small scale engine coolant and exhaust heat recovery system using different organic Rankine cycle layouts. Applied Thermal Engineering. 2017;**127**:1252-1266

[16] Obieglo A, Ringler J, Seifert M, Hall W. Future efficient dynamics with heat recovery. In: Presentation at US Department of Energy Directions in Engine Efficiency and Emissions

[17] Ringler J, Seifert M, Guyotot V, Hübner W. Rankine cycle for waste heat recovery of IC

[18] Rosebro J. Honda Researching Advanced Hybrid Drive with Rankine Cycle Co-Generation.

[19] Nelson C. Exhaust energy recovery. In: Diesel Engine-Efficiency and Emissions Research

[20] Koeberlein D. Cummins SuperTruck Program Technology and System Level Demonstration of Highly Efficient and Clean, Diesel Powered Class 8 Trucks. presentation at

[21] Liu JP, Fu JQ, Ren CQ, Wang LJ, Xu ZX, Deng BL. Comparison and analysis of engine exhaust gas energy recovery potential through various bottom cycles. Applied Thermal

[22] Lion S, Michos CN, Vlaskos I, Rouaud C, Taccani R. A review of waste heat recovery and organic Rankine cycles (ORC) in on-off highway vehicle heavy duty diesel engine

[23] Hountalas DT, Mavropoulos GC, Katsanos C, Knecht W. Improvement of bottoming cycle efficiency and heat rejection for HD truck applications by utilization of EGR and

[24] Song S, Zhang H, Lou Z, Yang F, Yang K, Wang H, et al. Performance analysis of exhaust waste heat recovery system for stationary CNG engine based on organic Rankine cycle.

[25] Zhang HG, Wang EH, Fan BY. A performance analysis of a novel system of a dual loop bottoming organic Rankine cycle (ORC) with a light-duty diesel engine. Applied Energy.

[26] Song J, C-w G. Parametric analysis of a dual loop organic Rankine cycle (ORC) system for engine waste heat recovery. Energy Conversion and Management. 2015;**105**:

[27] Lu Y, Wang Y, Dong C, Wang L, Roskilly AP. Design and assessment on a novel integrated system for power and refrigeration using waste heat from diesel engine. Applied

[28] Wang EH, Zhang HG, Fan BY, Ouyang MG, Yang FY, Yang K, et al. Parametric analysis of a dual-loop ORC system for waste heat recovery of a diesel engine. Applied Thermal

[29] Lu Y, Roskilly AP, Smallbone A, Yu X, Wang Y. Design and parametric study of an organic Rankine cycle using a scroll expander for engine waste heat recovery. Energy

applications. Renewable and Sustainable Energy Reviews. 2017;**79**:691-708

CAC heat. Energy Conversion and Management. 2012;**53**:19-32

Research (DEER) Conference; Dearborn, Michigan. 2009

(DEER) Conference. Dearborn, MI. August 2008

US Department of Energy Merit Review. 2013

Applied Thermal Engineering. 2015;**76**:301-309

Thermal Engineering. 2015;**91**:591-599

Engineering. 2014;**67**:168-178

Procedia. 2017;**105C**:1421-1426

GreenCar Congress. 2008

144 Organic Rankine Cycle Technology for Heat Recovery

Engineering. 2013;**50**:1219-1234

2013;**102**:1504-1513

995-1005

engines. SAE International Journal of Engines. 2009;**2**(1):67-76

[47] Li J, Pei G, Li Y, Wang D, Ji J. Energetic and exergetic investigation of an organic Rankine cycle at different heat source temperatures. Energy. 2012;**38**:85-95

[63] Muhammad U, Imran M, Lee DH, PBS. Design and experimental investigation of a 1 kW organic Rankine cycle system using R245fa as working fluid for low-grade waste heat

The Development and Application of Organic Rankine Cycle for Vehicle Waste Heat Recovery

http://dx.doi.org/10.5772/intechopen.78401

147

[65] Yang B, Peng X, He Z, Guo B, Xing Z. Experimental investigation on the internal working process of a CO2 rotary vane expander. Applied Thermal Engineering. 2009;**29**:2289-2296

[66] Qiu G, Shao Y, Li J, Liu H, Riffat SB. Experimental investigation of a biomass-fired ORC-

[67] Aoun B. Micro combined heat and power operating on renewable energy for residential building, [PhD thesis], https://pastel.archives-ouvertes.fr/pastel-00005092. École

[68] Lu Y, Roskilly AP, Jiang L, Chen L, Yu X. Analysis of a 1 kW organic Rankine cycle using a scroll expander for engine coolant and exhaust heat recovery. Frontiers in Energy.

[69] Yu G, Shu G, Tian H, Wei H, Liu L. Simulation and thermodynamic analysis of a bottoming organic Rankine cycle(ORC) of diesel engine (DE). Energy. 2013;**51**:281-290

[70] Tian H, Shu G, Wei H, Liang X, Liu L. Fluids and parameters optimization for the organic Rankine cycles (ORCs) used inexhaust heat recovery of internal combustion

[71] Zhao M, Wei M, Song P, Liu Z, Tian G. Performance evaluation of a diesel engine inte-

[72] Shu G, Li X, Tian H, Liang X, Wei H, Wang X. Alkanes as working fluids for hightemperature exhaust heat recovery of diesel engine using organic Rankine cycle. Applied

[73] Wang EH, Zhang HG, Zhao Y, Fan BY, Wu YT, Mu QH. Performance analysis of a novel system combining a dual loop organic Rankine cycle (ORC) with a gasoline engine.

[74] Shu G, Liu L, Tian H, Wei H, Yu G. Parametric and working fluid analysis of a dual-loop organic Rankine cycle (DORC) used in engine waste heat recovery. Applied Energy.

[75] Chen T, Zhuge W, Zhang Y, Zhang L. A novel cascade organic Rankine cycle (ORC) system for waste heat recovery of truck diesel engines. Energy Conversion and

[76] Jiménez-Arreola M, Pili R, Dal Magro F, Wieland C, Rajoo S, Romagnoli A. Thermal power fluctuations in waste heat to power systems: An overview on the challenges and

current solutions. Applied Thermal Engineering. 2018;**134**:576-584

grated with ORC system. Applied Thermal Engineering. 2017;**115**:221-228

recovery from steam. Energy Conversion and Management. 2015;**103**:1089-1100 [64] Yang S-C, Hung T-C, Feng Y-Q, Wu C-J, Wong K-W, Huang K-C. Experimental investigation on a 3 kW organic Rankine cycle for low-grade waste heat under different opera-

tion parameters. Applied Thermal Engineering. 2017;**113**:756-764

based micro-CHP for domestic applications. Fuel. 2012;**96**:374-382

Nationale Supérieure des Mines de Paris. 2008

engine (ICE). Energy. 2012;**47**:125-136

Energy. 2014;**119**:204-217

Energy. 2012;**43**:385-395

Management. 2017;**138**:210-223

2014;**113**:1188-1198

2017;**11**:527-534

[63] Muhammad U, Imran M, Lee DH, PBS. Design and experimental investigation of a 1 kW organic Rankine cycle system using R245fa as working fluid for low-grade waste heat recovery from steam. Energy Conversion and Management. 2015;**103**:1089-1100

[47] Li J, Pei G, Li Y, Wang D, Ji J. Energetic and exergetic investigation of an organic Rankine

[48] Pei G, Li YZ, Li j, Ji J. A High-Speed Micro Turbine for Organic Rankine Cycle. World

[49] Zhang X, Xu Y, Xu J, Xue H, Chen H. Study of a single-valve reciprocating expander.

[50] Zhang B, Peng X, He Z, Xing Z, Shu P. Development of a double acting free piston expander for power recovery in transcritical CO2 cycle. Applied Thermal Engineering.

[51] Xia G-D, Zhang Y-Q, Wu Y-T, Ma C-F, Ji W-N, Liu S-W, et al. Experimental study on the performance of single-screw expander with different inlet vapor dryness. Applied

[52] Tang H, Wu H, Wang X, Xing Z. Performance study of a twin-screw expander used in a geothermal organic Rankine cycle power generator. Energy. 2015;**90**(Part 1):631-642 [53] Imran M, Usman M, Park B-S, Lee D-H. Volumetric expanders for low grade heat and waste heat recovery applications. Renewable and Sustainable Energy Reviews.

[54] Leibowitz H, Smith K, Stosic N. Cost effective small scale ORC systems for power recovery from low grade heat sources. In: ASME 2006 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineer. Chicago, Illinois,

[55] Smith IK, Stosic N, Kovacevic A. Screw expanders increase output and decrease the cost of geothermal binary power plant systems. In: Transactions of Geothermal Resource

[56] Qiu G, Liu H, Riffat S. Expanders for micro-CHP systems with organic Rankine cycle.

[57] Carrier Corporation Syracuse NY. Scroll compressor, High efficiency compression for

[58] Scroll-compressor. Available from: http://en.wikipedia.org/wiki/Scroll\_compressor

[59] Guangbin L, Yuanyang Z, Liansheng L, Pengcheng S. Simulation and experiment research on wide ranging working process of scroll expander driven by compressed air.

[60] Lu Y, Roskilly AP, Tang K, Wang Y, Jiang L, Yuan Y, et al. Investigation and performance study of a dual-source chemisorption power generation cycle using scroll expander.

[61] Jung H-C, Taylor L, Krumdieck S. An experimental and modelling study of a 1kW organic Rankine cycle unit with mixture working fluid. Energy. 2015;**81**:601-614 [62] Lemort V, Quoilin S, Cuevas C, Lebrun J. Testing and modeling a scroll expander integrated into an organic Rankine cycle. Applied Thermal Engineering. 2009;**29**:3094-3102

cycle at different heat source temperatures. Energy. 2012;**38**:85-95

Journal of the Energy Institute. 2016;**89**(3):400-413

2007;**27**:1629-1636

146 Organic Rankine Cycle Technology for Heat Recovery

2016;**57**:1090-1109

USA. 2006:521-527

Council. Reno, NV; 2005

[Accessed: 20-11-2011]

Applied Thermal Engineering. 2011;**31**:3301-3307

Applied Thermal Engineering. 2010;**30**:2073-2079

Applied Energy. 2017;**204**:979-993

commercial and industrial applications. October 2004

Thermal Engineering. 2015;**87**:34-40

Society of Sustainable Energy Technologies (WSSET)-Newsletter. 2009

**Chapter 8**

**Provisional chapter**

**Organic Rankine Cycle for Recovery of Liquefied**

**Organic Rankine Cycle for Recovery of Liquefied**

DOI: 10.5772/intechopen.77990

Natural gas (NG) is an environment-friendly energy source. NG is of gas state in the environmental condition and it is liquefied to LNG at temperature of about −162°C for transportation and storage. Electric energy of 292–958 kWh is consumed when one ton of LNG is produced. Before being used, LNG must be regasified to NG again at the receiving site, and this process will release a great deal of energy, which is called cold energy. It's very important to recovery LNG cold energy, which is clean and of high quality. Power generation is a conventional and effective way to utilize LNG cold energy. For the low efficiency of the traditional power generation system with liquefied natural gas (LNG) cold energy utilization, by improving the heat transfer characteristic between the working fluid and LNG, this chapter has proposed a conception of multi-stage condensation Rankine cycle system. Furthermore, the performance of power generation systems will be enhanced with two aspects: improvement of system configuration and optimiza-

**Keywords:** organic Rankine cycle, LNG cold energy, two-stage condensation Rankine

Energy shortage and environmental pollution are two major themes in today's world [1]. More and more attentions are paid to Natural gas (NG) because it is clean and has high calorific value [2, 3], and it is widely consumed all over the world [4]. NG is of gas state in the environmental condition and it is liquefied to LNG at temperature of about −162°C for transportation and storage [5]. Electric energy of 292–958 kWh is consumed when one ton of LNG

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

**Natural Gas (LNG) Cold Energy**

**Natural Gas (LNG) Cold Energy**

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.77990

Junjiang Bao

Junjiang Bao

**Abstract**

tion of working fluids.

**1. Introduction**

cycle, zeotropic mixture, system configuration

#### **Organic Rankine Cycle for Recovery of Liquefied Natural Gas (LNG) Cold Energy Organic Rankine Cycle for Recovery of Liquefied Natural Gas (LNG) Cold Energy**

DOI: 10.5772/intechopen.77990

#### Junjiang Bao Junjiang Bao

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.77990

#### **Abstract**

Natural gas (NG) is an environment-friendly energy source. NG is of gas state in the environmental condition and it is liquefied to LNG at temperature of about −162°C for transportation and storage. Electric energy of 292–958 kWh is consumed when one ton of LNG is produced. Before being used, LNG must be regasified to NG again at the receiving site, and this process will release a great deal of energy, which is called cold energy. It's very important to recovery LNG cold energy, which is clean and of high quality. Power generation is a conventional and effective way to utilize LNG cold energy. For the low efficiency of the traditional power generation system with liquefied natural gas (LNG) cold energy utilization, by improving the heat transfer characteristic between the working fluid and LNG, this chapter has proposed a conception of multi-stage condensation Rankine cycle system. Furthermore, the performance of power generation systems will be enhanced with two aspects: improvement of system configuration and optimization of working fluids.

**Keywords:** organic Rankine cycle, LNG cold energy, two-stage condensation Rankine cycle, zeotropic mixture, system configuration

## **1. Introduction**

Energy shortage and environmental pollution are two major themes in today's world [1]. More and more attentions are paid to Natural gas (NG) because it is clean and has high calorific value [2, 3], and it is widely consumed all over the world [4]. NG is of gas state in the environmental condition and it is liquefied to LNG at temperature of about −162°C for transportation and storage [5]. Electric energy of 292–958 kWh is consumed when one ton of LNG

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

is produced [6]. Before being used, LNG must be regasified to NG again at the receiving site, and this process will release a great deal of energy, which is called cold energy [7]. It is very important to recovery LNG cold energy which is clean and of high quality. Usually LNG is heated by sea water or air, so that LNG cold energy is wasted and the sea near the regasification site also is affected [8]. Therefore, the recovery of the LNG cold energy a dual purpose [8].

In this chapter, the performance of power generation systems by LNG cold energy will be enhanced with two aspects: improvement of system configuration and optimization of working fluids. Firstly, the two-stage condensation Rankine cycle is introduced. Based on this, the effect of stage number of condensation process is discussed. Then, the influence of the arrangements for compression process and expansion process is studied. Regarding to the optimization of working fluids, pure working fluids are firstly compared, and then zeotropic mixtures are optimized. Finally, a simultaneous approach to optimize the component and

Organic Rankine Cycle for Recovery of Liquefied Natural Gas (LNG) Cold Energy

http://dx.doi.org/10.5772/intechopen.77990

151

As shown in **Figure 1**, the TCRC system consists of an evaporator, two turbines, two condensers, a mixer, a splitter and two feed pumps. After heated in the evaporator by sea water, working fluid is evaporated to vapor and is divided into two streams in the splitter. The two streams flow into different turbines respectively and are expanded to two different condensation pressures. These two streams transferred heat energy to LNG in two different condensers and cooled to liquid. The two streams are pressurized by two different pumps and mixed in the mixer. The converged stream enters the evaporator again and the new cycle recommences. Except for absorbing the condensation heat from working fluids in two condensers, LNG is further heated to the scheduled temperature in the reheater with sea water. T-s diagram of the TCRC system is plotted in **Figure 2**, and the labeled state points in **Figure 2** is the same as

In order to determine whether the new proposed cycle has a better performance, the novel

system is compared with the conventional methods under the same conditions.

composition of zeotropic mixture is put forward.

**2. Improvement of system configuration**

**2.1. Two-stage condensation Rankine cycle (TCRC)**

that in **Figure 1**.

**Figure 1.** Schematic diagram of the TCRC system.

One of effective ways to utilize LNG cold energy is power generation [9]. The traditional cycles include direct expansion cycle (DE), organic Rankine cycle (ORC) and combined cycle (CC) [10]. Although the simplicity for direct expansion cycle, it has limited applications with low efficiency and high operation pressure. Organic Rankine cycle and combined cycle are more popular and relatively mature. Osaka Gas Company in Japan built ORC and CC system using propane in 1979 and 1982, and the power output reached 1450 and 6000 kW, respectively [11]. Due to the importance of system parameters on the performance of power generation system, many researches are carried out. With seawater as heat source and LNG as heat sink, Kim et al. [12] found that there is an optimum condenser outlet temperature for ORC system. Heat source inlet temperature, evaporation pressure and condensation temperature are studied by Wang et al. [13] to achieve high exergy efficiency of ORC recovering LNG cold energy. With the heat integration of LNG at vaporization pressure of 70 bar, Koku et al. [14] obtained a thermal efficiency of 6% for the combined cycle with propane as working fluid.

Improvement of system structure and proper working fluid selection are two effective way to enhance the system performance. For system structure, the combinations of simple Rankine cycle in series or parallel is often considered by Zhang et al. [7] and García et al. [15] and they found that they were indeed more efficient. Cascaded Rankine cycles are also common improvement and are proved to be superior to simple Rankine cycles by Li et al. [16], Choi et al. [17], Cao et al. [18], and Wang et al. [19]. By combining the Rankine cycle and refrigeration cycle, the study of Zhang et al. [20] showed that both electricity and refrigeration can be produced simultaneously. Mosaffa et al. [21] compared four different cycles, and pointed out that different system structure is best when the objective function changes.

Selection of working fluids is also critical for the performance and economy of system except for cycle structure. By using eight kinds of working fluids, Zhang et al. [7] found n-pentane has the best system performance. A comparative study by Sung et al. [22] showed that R123 were the optimal working fluids for a dual-loop cycle with LNG cold energy as heat sink. Considering ethane, ethene, carbon dioxide, R134a, R143a and propene, Ferreira et al. [23] concluded that ethene and ethane had higher system efficiency. Zeotropic mixtures are also considered in power generation system for recovery of LNG cold energy. Ammonia-water mixture is used by Wang et al. [24], and they found there was an optimal mass fraction at which work output was largest. With R601-R23-R14 ternary mixture as the working fluid, Lee et al. [25] found that the exergy loss of ORC using mixture is lower than that of pure fluids. Kim et al. [26] selected R14-propane mixture as the working fluids for the first stage of a cascaded system and ethane-n-pentane mixture for the other two stages. Modi and Haglind [27] thought that zeotropic mixture is the development direction of working fluids with its higher thermodynamic performance.

In this chapter, the performance of power generation systems by LNG cold energy will be enhanced with two aspects: improvement of system configuration and optimization of working fluids. Firstly, the two-stage condensation Rankine cycle is introduced. Based on this, the effect of stage number of condensation process is discussed. Then, the influence of the arrangements for compression process and expansion process is studied. Regarding to the optimization of working fluids, pure working fluids are firstly compared, and then zeotropic mixtures are optimized. Finally, a simultaneous approach to optimize the component and composition of zeotropic mixture is put forward.

## **2. Improvement of system configuration**

is produced [6]. Before being used, LNG must be regasified to NG again at the receiving site, and this process will release a great deal of energy, which is called cold energy [7]. It is very important to recovery LNG cold energy which is clean and of high quality. Usually LNG is heated by sea water or air, so that LNG cold energy is wasted and the sea near the regasification site also is affected [8]. Therefore, the recovery of the LNG cold energy a dual purpose [8]. One of effective ways to utilize LNG cold energy is power generation [9]. The traditional cycles include direct expansion cycle (DE), organic Rankine cycle (ORC) and combined cycle (CC) [10]. Although the simplicity for direct expansion cycle, it has limited applications with low efficiency and high operation pressure. Organic Rankine cycle and combined cycle are more popular and relatively mature. Osaka Gas Company in Japan built ORC and CC system using propane in 1979 and 1982, and the power output reached 1450 and 6000 kW, respectively [11]. Due to the importance of system parameters on the performance of power generation system, many researches are carried out. With seawater as heat source and LNG as heat sink, Kim et al. [12] found that there is an optimum condenser outlet temperature for ORC system. Heat source inlet temperature, evaporation pressure and condensation temperature are studied by Wang et al. [13] to achieve high exergy efficiency of ORC recovering LNG cold energy. With the heat integration of LNG at vaporization pressure of 70 bar, Koku et al. [14] obtained a thermal efficiency of 6% for the combined cycle with propane as working fluid.

Improvement of system structure and proper working fluid selection are two effective way to enhance the system performance. For system structure, the combinations of simple Rankine cycle in series or parallel is often considered by Zhang et al. [7] and García et al. [15] and they found that they were indeed more efficient. Cascaded Rankine cycles are also common improvement and are proved to be superior to simple Rankine cycles by Li et al. [16], Choi et al. [17], Cao et al. [18], and Wang et al. [19]. By combining the Rankine cycle and refrigeration cycle, the study of Zhang et al. [20] showed that both electricity and refrigeration can be produced simultaneously. Mosaffa et al. [21] compared four different cycles, and pointed out

Selection of working fluids is also critical for the performance and economy of system except for cycle structure. By using eight kinds of working fluids, Zhang et al. [7] found n-pentane has the best system performance. A comparative study by Sung et al. [22] showed that R123 were the optimal working fluids for a dual-loop cycle with LNG cold energy as heat sink. Considering ethane, ethene, carbon dioxide, R134a, R143a and propene, Ferreira et al. [23] concluded that ethene and ethane had higher system efficiency. Zeotropic mixtures are also considered in power generation system for recovery of LNG cold energy. Ammonia-water mixture is used by Wang et al. [24], and they found there was an optimal mass fraction at which work output was largest. With R601-R23-R14 ternary mixture as the working fluid, Lee et al. [25] found that the exergy loss of ORC using mixture is lower than that of pure fluids. Kim et al. [26] selected R14-propane mixture as the working fluids for the first stage of a cascaded system and ethane-n-pentane mixture for the other two stages. Modi and Haglind [27] thought that zeotropic mixture is the development direction of working fluids with its

that different system structure is best when the objective function changes.

higher thermodynamic performance.

150 Organic Rankine Cycle Technology for Heat Recovery

#### **2.1. Two-stage condensation Rankine cycle (TCRC)**

As shown in **Figure 1**, the TCRC system consists of an evaporator, two turbines, two condensers, a mixer, a splitter and two feed pumps. After heated in the evaporator by sea water, working fluid is evaporated to vapor and is divided into two streams in the splitter. The two streams flow into different turbines respectively and are expanded to two different condensation pressures. These two streams transferred heat energy to LNG in two different condensers and cooled to liquid. The two streams are pressurized by two different pumps and mixed in the mixer. The converged stream enters the evaporator again and the new cycle recommences. Except for absorbing the condensation heat from working fluids in two condensers, LNG is further heated to the scheduled temperature in the reheater with sea water. T-s diagram of the TCRC system is plotted in **Figure 2**, and the labeled state points in **Figure 2** is the same as that in **Figure 1**.

In order to determine whether the new proposed cycle has a better performance, the novel system is compared with the conventional methods under the same conditions.

**Figure 1.** Schematic diagram of the TCRC system.

**Figure 2.** T-s diagram of the TCRC system.

Net power output, thermal efficiency and exergy efficiency of TCRC system is compared with the traditional cycles (DEC, ORC and CC), as shown in **Figure 3**. It should be pointed out that four systems all used propane as working fluid. From **Figure 3**, it can be found that the performance of proposed system is remarkably superior to the traditional power generation cycles. Combined cycle has the highest net power output, thermal efficiency and exergy efficiency among the traditional systems. However, compared with CC system, TCRC system has a 45.27%, 42.91% and 52.31% increase respectively, in term of net power output, thermal efficiency and exergy efficiency.

**2.2. Effects of stage number of condensation process**

**Figure 4.** Heat transfer characteristics between working fluid and LNG: (a) ORC and (b) TCRC.

stages of condensation process should be chosen?

tion expansion cycle (DC) is also considered.

expansion.

In the previous section, it has been proved that two-stage condensation process has the potential to improve the performance of power generation systems by LNG cold energy. If the number of condensation stage is increased, the performance of power generation systems should be better at the cost of greater initial investment with more equipment. How many

Organic Rankine Cycle for Recovery of Liquefied Natural Gas (LNG) Cold Energy

http://dx.doi.org/10.5772/intechopen.77990

153

**Figure 5** shows the schematic of six different cycles from single-stage to three-stage condensation Rankine cycle with or without direction expansion. To take a comparison object, direc-

**Figure 5.** Schematic of single-stage, two-stage and three-stage condensation Rankine cycles with or without direction

In order to explain the reason why TCRC system could have a better performance than the traditional cycle, the heat transfer curves between working fluid and LNG of ORC and TCRC systems are plotted in **Figure 4**. It can be seen from **Figure 4** that heat transfer irreversibility of ORC system is larger than that of TCRC system. The main reason is that compared with ORC system, the condensation process of TCRC system is two-stage, which could lower the heat transfer irreversibility of the condenser.

**Figure 3.** System performance of the four power generation methods: (a) net power output, (b) thermal efficiency, and (c) exergy efficiency.

**Figure 4.** Heat transfer characteristics between working fluid and LNG: (a) ORC and (b) TCRC.

#### **2.2. Effects of stage number of condensation process**

Net power output, thermal efficiency and exergy efficiency of TCRC system is compared with the traditional cycles (DEC, ORC and CC), as shown in **Figure 3**. It should be pointed out that four systems all used propane as working fluid. From **Figure 3**, it can be found that the performance of proposed system is remarkably superior to the traditional power generation cycles. Combined cycle has the highest net power output, thermal efficiency and exergy efficiency among the traditional systems. However, compared with CC system, TCRC system has a 45.27%, 42.91% and 52.31% increase respectively, in term of net power output, thermal

In order to explain the reason why TCRC system could have a better performance than the traditional cycle, the heat transfer curves between working fluid and LNG of ORC and TCRC systems are plotted in **Figure 4**. It can be seen from **Figure 4** that heat transfer irreversibility of ORC system is larger than that of TCRC system. The main reason is that compared with ORC system, the condensation process of TCRC system is two-stage, which could lower the heat

**Figure 3.** System performance of the four power generation methods: (a) net power output, (b) thermal efficiency, and

efficiency and exergy efficiency.

**Figure 2.** T-s diagram of the TCRC system.

152 Organic Rankine Cycle Technology for Heat Recovery

transfer irreversibility of the condenser.

(c) exergy efficiency.

In the previous section, it has been proved that two-stage condensation process has the potential to improve the performance of power generation systems by LNG cold energy. If the number of condensation stage is increased, the performance of power generation systems should be better at the cost of greater initial investment with more equipment. How many stages of condensation process should be chosen?

**Figure 5** shows the schematic of six different cycles from single-stage to three-stage condensation Rankine cycle with or without direction expansion. To take a comparison object, direction expansion cycle (DC) is also considered.

**Figure 5.** Schematic of single-stage, two-stage and three-stage condensation Rankine cycles with or without direction expansion.

Net power output of system:

$$\mathbf{W}\_{\text{net}} = \sum \mathbf{W}\_{\text{tra},l} - \sum \mathbf{W}\_{p,l} \tag{1}$$

The electricity production cost (EPC) can be expressed as:

$$EPC = \frac{3600 \text{ C}\_{\text{total}}}{W\_{\text{net}}} \tag{2}$$

The electricity prices of literatures are different, such as 0.04, 0.061, 0.1, 0.123 and 0.18\$/kWh [28]. DC and CC systems should be selected at the LNG vaporization pressure less than 30 bar if the electricity price is 0.04\$/kWh. No system is profitable at the LNG vaporization pressure of 70 bar. The CC systems are suitable at all the LNG vaporization pressure when the electricity price is 0.061\$/kWh. At the LNG vaporization pressure less than 30 bar, it should be considered DE system. Seven cycles could be profitable if electricity price is larger than 0.1\$/kWh.

Organic Rankine Cycle for Recovery of Liquefied Natural Gas (LNG) Cold Energy

http://dx.doi.org/10.5772/intechopen.77990

155

The capacity of power generation can be weight by net power output, and whether cycle is profitable could evaluated by EPC. But the maximum profitability of the system is determined by both the net power output and EPC, which be reflected by annual net income. The electricity price of 0.123 \$/kWh is taken as the referenced electricity price. It can be seen from **Figure 8** that the annual net income of the 3CC system is largest, while the least is the DC cycle. The annual net income of the Rankine cycles is lower than that of the combined cycles at the same stage number of the condensation process. When the stage number of the condensation process increases, both the annual net income of the Rankine cycle and the combined

**2.3. Influence of the arrangements for compression process and expansion process**

In the field of utilizing LNG cold energy by ORC (organic Rankine cycle), most studies focus on how to reduce the irreversible loss of the heat exchange process but pay little attention to the arrangements for compression and expansion process. The compression and expansion process, as the parts of the cycle that consumes and products energy, affect the cycle performance as well due to that their different arrangements make the efficiency of the component different. The structures of four different two-stage condensation Rankine cycles are shown in **Figure 9**. There are two types of arrangements for the pumps in the compression process.

cycle systems goes up, but their increase rates decrease.

**Figure 7.** The minimum EPC of seven systems at different LNG vapor pressures.

The annual total net income (ATNI) of the system can be defined as:

*ATNI* = 7300(*EP* − *EPC*) *Wnet* (3)

where EP is electricity price.

From **Figure 6** it can be seen that the net power output of the 3CC is the largest and the DE is the least at any LNG vaporization pressure. When stage number of condensation process increases, the net power output of Rankine cycles and combined cycles both increases. The performance of combined cycles is better than that of Rankine cycles at the same stage number of condensation process.

**Figure 7** shows the minimum EPC of seven different cycles at different LNG vaporization pressures. The EPC of the Rankine cycle is larger than that of the combined system at the same stage number of condensation process. The EPC of combined cycle is the least at the LNG vaporization pressure less than 30 bar. With the increase of the stage number of condensation process, EPC of combined cycles and Rankine cycles augments, but its increase rate decreases. When the LNG vaporization pressure increases, the difference of EPC between combined cycles and Rankine cycles at the same stage number of condensation process tends to zero.

**Figure 6.** The maximum net power output at different LNG vaporization pressures.

**Figure 7.** The minimum EPC of seven systems at different LNG vapor pressures.

Net power output of system:

154 Organic Rankine Cycle Technology for Heat Recovery

where EP is electricity price.

ber of condensation process.

The electricity production cost (EPC) can be expressed as:

The annual total net income (ATNI) of the system can be defined as:

**Figure 6.** The maximum net power output at different LNG vaporization pressures.

*EPC* <sup>=</sup> <sup>3600</sup> *<sup>C</sup>* \_\_\_\_\_\_\_*total*

*Wnet* = ∑*Wtur*,*<sup>j</sup>* − ∑*Wp*,*<sup>l</sup>* (1)

*ATNI* = 7300(*EP* − *EPC*) *Wnet* (3)

From **Figure 6** it can be seen that the net power output of the 3CC is the largest and the DE is the least at any LNG vaporization pressure. When stage number of condensation process increases, the net power output of Rankine cycles and combined cycles both increases. The performance of combined cycles is better than that of Rankine cycles at the same stage num-

**Figure 7** shows the minimum EPC of seven different cycles at different LNG vaporization pressures. The EPC of the Rankine cycle is larger than that of the combined system at the same stage number of condensation process. The EPC of combined cycle is the least at the LNG vaporization pressure less than 30 bar. With the increase of the stage number of condensation process, EPC of combined cycles and Rankine cycles augments, but its increase rate decreases. When the LNG vaporization pressure increases, the difference of EPC between combined cycles and Rankine cycles at the same stage number of condensation process tends to zero.

*Wnet*

(2)

The electricity prices of literatures are different, such as 0.04, 0.061, 0.1, 0.123 and 0.18\$/kWh [28]. DC and CC systems should be selected at the LNG vaporization pressure less than 30 bar if the electricity price is 0.04\$/kWh. No system is profitable at the LNG vaporization pressure of 70 bar. The CC systems are suitable at all the LNG vaporization pressure when the electricity price is 0.061\$/kWh. At the LNG vaporization pressure less than 30 bar, it should be considered DE system. Seven cycles could be profitable if electricity price is larger than 0.1\$/kWh.

The capacity of power generation can be weight by net power output, and whether cycle is profitable could evaluated by EPC. But the maximum profitability of the system is determined by both the net power output and EPC, which be reflected by annual net income. The electricity price of 0.123 \$/kWh is taken as the referenced electricity price. It can be seen from **Figure 8** that the annual net income of the 3CC system is largest, while the least is the DC cycle. The annual net income of the Rankine cycles is lower than that of the combined cycles at the same stage number of the condensation process. When the stage number of the condensation process increases, both the annual net income of the Rankine cycle and the combined cycle systems goes up, but their increase rates decrease.

#### **2.3. Influence of the arrangements for compression process and expansion process**

In the field of utilizing LNG cold energy by ORC (organic Rankine cycle), most studies focus on how to reduce the irreversible loss of the heat exchange process but pay little attention to the arrangements for compression and expansion process. The compression and expansion process, as the parts of the cycle that consumes and products energy, affect the cycle performance as well due to that their different arrangements make the efficiency of the component different.