4.1.1. P-V-T diagram calculation with equations of state

To describe the P-V-T diagram behavior, it is necessary to use precise equations of state (EOS) with specific parameters for pure substances. In the case of carbon dioxide, the equations of Bender [19] and Span and Wagner [37] are the most used. The Bender equation is presented below, where the parameters were determined from experimental PVT data of carbon dioxide. Table 1 shows the parameters of the Bender equation.

Table 1. Bender equation constants for CO2 [19].

$$P = \frac{T}{V} \left[ R + \frac{B}{V} + \frac{C}{V^2} + \frac{D}{V^3} + \frac{E}{V^4} + \frac{F}{V^5} + \left( G + \frac{H}{V^2} \right) \frac{1}{V^2} \exp\{-a\_{20} / \ \slash\!V^2\} \right] \tag{1}$$

where

4. High-pressure carbon dioxide properties

critical CO2. ( ) 50C, ( ) 60C, and ( ) 70C isotherms [17].

150 bar 190 bar

220 bar

of the item 2.2 for the isotherms T1 > T2 > T3 > T4 > T5.

4.1.1. P-V-T diagram calculation with equations of state

Table 1 shows the parameters of the Bender equation.

calculated by volumetric properties (P-V-T) using equation of state.

The influence of the density in the solvation power by the tunable operating conditions (P, T) is

LABP 700 800 900

Figure 8. Total anthocyanins compounds content in lyophilized açaí berry pulp before and after extraction with super-

 **Density (Kg/m3**

**)**

 **CO2**

220 bar

270 bar

320 bar

350 bar

420 bar

490 bar

Above the critical point, the supercritical extraction process can operate over a wide range of operating conditions (P, T) and the simplest density behavior can be obtained through an isotherm, being possible to select a wide range of operating pressures, as shown in Figure 3

The density is defined by the inverse of specific volume, and for practical purpose, could be

To describe the P-V-T diagram behavior, it is necessary to use precise equations of state (EOS) with specific parameters for pure substances. In the case of carbon dioxide, the equations of Bender [19] and Span and Wagner [37] are the most used. The Bender equation is presented below, where the parameters were determined from experimental PVT data of carbon dioxide.

the most important thermodynamic effect in the high-pressure fluid processes.

4.1. Thermodynamic properties

0

20

40

60

80

100

**Anthocyanins Content (mg/100g)**

120

140

160

180

220 Carbon Dioxide Chemistry, Capture and Oil Recovery

$$B = a\_1 - \frac{a\_2}{T} - \frac{a\_3}{T^2} - \frac{a\_4}{T^3} - \frac{a\_5}{T^4} \tag{2}$$

$$C = a\_6 + \frac{a\_7}{T} + \frac{a\_8}{T^2} \tag{3}$$

$$D = a\_{\phi} + \frac{a\_{10}}{T} \tag{4}$$

$$E = a\_{11} + \frac{a\_{12}}{T} \tag{5}$$

$$F = \frac{a\_{1\frac{\nu}{\nu}}}{T} \tag{6}$$

$$G = \frac{a\_{14}}{T^3} + \frac{a\_{15}}{T^4} + \frac{a\_{16}}{T^9} \tag{7}$$

$$H = \frac{a\_{1\overline{\gamma}}}{T^3} + \frac{a\_{1\overline{\mathfrak{s}}}}{T^4} + \frac{a\_{1\overline{\mathfrak{s}}}}{T^5} \tag{8}$$

$$a\_{20} \approx V\_C^2 \tag{9}$$

Figure 9 shows the calculation with Bender equation [19] of state for the P-V-T diagram isotherms and saturation curve, including an isotherm close to the critical temperature of the carbon dioxide. The calculations were performed using a Microsoft Excel spreadsheet. The equation presents accuracy in calculations when compared to data taken from IUPAC International Thermodynamic Table.

Figure 9. P-V-T diagram of carbon dioxide calculated with Bender EOS and compared to IUPAC data (symbols).

However, for applications of supercritical technology, it is necessary to calculate other thermodynamic properties. The thermodynamic properties of the pure solvent (density, enthalpy, and entropy) and the thermodynamic properties of the solute/solvent mixture, among which the equilibrium compositions, enthalpies, and mixing entropies, must be calculated in the operating conditions throughout the process. The cubic equation of state, also called Van der Waals type equation, represents an alternative, since the Bender-type equation described above is complex. In these cases, the cubic equations of state of Peng-Robinson (PR) [38] and Soave Redlich-Kwong (SRK) [39] are presented as the most commonly applied options in process simulations (Table 2). These equations of state use various thermodynamic properties and the following physical properties of the pure substance: critical pressure, critical temperature, and the acentric factor, which are tabulated, in the case of carbon dioxide.

Table 3 shows the calculated values of the carbon dioxide densities for some isotherms above the critical point using the equations of Peng-Robinson [38] and Soave-Redlich-Kwong [39]. The computational package PE 2000 developed by Pfohl et al. [40] was used for calculations. The results are compared to data taken from IUPAC International Thermodynamic Table and from NIST Chemistry Webbook (NIST Standard Reference Database). The Peng-Robinson equation of state presented the best results for the carbon dioxide density calculation in the conditions of pressure and temperature of Table 3 when compared with different databases.

Figure 10 shows the calculation with Peng-Robinson [38] equation of state for P-V-T diagram isotherms and saturation curve, including an isotherm close to the critical temperature of the carbon dioxide. The Peng-Robinson equation of state was able to describe all the phases of the carbon dioxide P-V-T diagram for the isotherms studied when compared to data taken from

Pressure (bar) Temperature (C/K) CO2 density (kg/m3

 36.85/310 617.3 563.0 683.4 686.5 847.8 763.8 855.5 857.0 941.1 846.6 921.5 922.7 46.85/320 418.1 390.6 444.6 449.4 781.5 707.9 801.5 803.1 845.3 763.8 848.0 849.5 893.0 805.9 882.4 883.7 963.2 868.2 933.2 934.4 66.85/340 260.5 246.2 258.1 258.6 643.2 589.3 678.7 680.5 731.7 666.7 751.9 753.3 794.4 721.8 800.6 801.8 882.9 799.6 866.7 867.9

)

PR SRK NIST IUPAC

Carbon Dioxide Use in High-Pressure Extraction Processes

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223

IUPAC International Thermodynamic Table.

Table 3. Carbon dioxide density calculated with different equations of state.

Cubic equations

Table 2. Cubic equations of state.

Table 2. Cubic equations of state.

However, for applications of supercritical technology, it is necessary to calculate other thermodynamic properties. The thermodynamic properties of the pure solvent (density, enthalpy, and entropy) and the thermodynamic properties of the solute/solvent mixture, among which the equilibrium compositions, enthalpies, and mixing entropies, must be calculated in the operating conditions throughout the process. The cubic equation of state, also called Van der Waals type equation, represents an alternative, since the Bender-type equation described above is complex. In these cases, the cubic equations of state of Peng-Robinson (PR) [38] and Soave Redlich-Kwong (SRK) [39] are presented as the most commonly applied options in process simulations (Table 2). These equations of state use various thermodynamic properties and the following physical properties of the pure substance: critical pressure, critical temperature, and

Figure 9. P-V-T diagram of carbon dioxide calculated with Bender EOS and compared to IUPAC data (symbols).

**Specific Volume (cm3**

100 1000 10000

**/mol)**

 SAT T=250 K T=310 K T=410 K T=510 K T=610 K Bender

Table 3 shows the calculated values of the carbon dioxide densities for some isotherms above the critical point using the equations of Peng-Robinson [38] and Soave-Redlich-Kwong [39]. The computational package PE 2000 developed by Pfohl et al. [40] was used for calculations. The results are compared to data taken from IUPAC International Thermodynamic Table and from NIST Chemistry Webbook (NIST Standard Reference Database). The Peng-Robinson equation of state presented the best results for the carbon dioxide density calculation in the conditions

the acentric factor, which are tabulated, in the case of carbon dioxide.

0

100

200

**Pressure (bar)**

300

400

222 Carbon Dioxide Chemistry, Capture and Oil Recovery

of pressure and temperature of Table 3 when compared with different databases.

Table 3. Carbon dioxide density calculated with different equations of state.

Figure 10 shows the calculation with Peng-Robinson [38] equation of state for P-V-T diagram isotherms and saturation curve, including an isotherm close to the critical temperature of the carbon dioxide. The Peng-Robinson equation of state was able to describe all the phases of the carbon dioxide P-V-T diagram for the isotherms studied when compared to data taken from IUPAC International Thermodynamic Table.

Under supercritical conditions, the thermal conductivity is influenced by both temperature and pressure and at constant pressure this property increases with increasing temperature, and on the other hand, at constant temperature, the thermal conductivity increases with pressure [42]. Carbon dioxide and other supercritical solvents have low viscosity and high diffusivity values. The viscosity and thermal conductivity of gases and liquids differ by one to two orders of magnitude, and the diffusivity values of gases and liquids differ by four orders of magnitude [41]. In the supercritical state, the substances have intermediate characteristics between the properties of a gas and a liquid, which contributes to more favorable hydrodynamic properties than the liquids, with diffusion coefficients close to those of a gas, which provides a fast and efficient mass transfer. Another feature of the supercritical fluid includes its low viscosity, which facilitates the penetration of the fluids into a solid matrix. Therefore, high diffusivity and low viscosity lead to a faster extraction time providing a dissolving power so that the

Carbon Dioxide Use in High-Pressure Extraction Processes

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225

Table 4 shows that supercritical fluids are characterized by transport properties (viscosity and diffusivity) between gases and liquids. The viscosity of a supercritical fluid is smaller than the viscosity of a gas and the diffusivity of the liquid is greater than the diffusivity of a supercritical fluid. In summary, the scheme of Figure 11 shows the basic properties of supercritical

Viscosity Pa s 105 104 to 105 103

Unit Gas SCF Liquid

/s 101 103 to 104 106

carbon dioxide, which become fundamental in high pressures extraction processes.

supercritical fluid is considered a solvent.

Table 4. Order of magnitude of transport properties.

Diffusivity cm2

Figure 11. Carbon dioxide properties.

Figure 10. PVT diagram of carbon dioxide calculated with Peng-Robinson EOS and compared to IUPAC data (symbols).

From a process point of view, the accuracy of the cubic equations of state was good, considering that the operating conditions commonly applied in CO2 extraction at high pressures are close to the values of temperature and pressure used in Table 3.

## 4.2. Other high-pressure carbon dioxide properties

The application of the high-pressure fluid extraction technologies in both laboratory and industrial scales requires not only the knowledge of the physical and thermodynamic properties of the solvent, but also requires the understanding of thermal and transport properties behavior. Among them, the most commonly cited are viscosity, diffusivity, thermal conductivity, and dielectric constant.

The dielectric constant describes the ability of a solvent to be polarized. The dielectric constant value is associated with the ability to dissolve electrolytes or polar compounds. The dielectric constant increases with temperature for most substances [41]. The dielectric constant of supercritical carbon dioxide with approximate value of a hydrocarbon alone does not characterize it as an important solvent; it only identifies it as a non-polar substance. Its solvation power is mainly related to the considerable increase of its density in the supercritical region with the properties as viscosity and diffusivity complementing the characteristics that makes supercritical carbon dioxide a differentiated solvent.

Under supercritical conditions, the thermal conductivity is influenced by both temperature and pressure and at constant pressure this property increases with increasing temperature, and on the other hand, at constant temperature, the thermal conductivity increases with pressure [42].

Carbon dioxide and other supercritical solvents have low viscosity and high diffusivity values. The viscosity and thermal conductivity of gases and liquids differ by one to two orders of magnitude, and the diffusivity values of gases and liquids differ by four orders of magnitude [41].

In the supercritical state, the substances have intermediate characteristics between the properties of a gas and a liquid, which contributes to more favorable hydrodynamic properties than the liquids, with diffusion coefficients close to those of a gas, which provides a fast and efficient mass transfer. Another feature of the supercritical fluid includes its low viscosity, which facilitates the penetration of the fluids into a solid matrix. Therefore, high diffusivity and low viscosity lead to a faster extraction time providing a dissolving power so that the supercritical fluid is considered a solvent.

Table 4 shows that supercritical fluids are characterized by transport properties (viscosity and diffusivity) between gases and liquids. The viscosity of a supercritical fluid is smaller than the viscosity of a gas and the diffusivity of the liquid is greater than the diffusivity of a supercritical fluid. In summary, the scheme of Figure 11 shows the basic properties of supercritical carbon dioxide, which become fundamental in high pressures extraction processes.

Table 4. Order of magnitude of transport properties.

From a process point of view, the accuracy of the cubic equations of state was good, considering that the operating conditions commonly applied in CO2 extraction at high pressures are

Figure 10. PVT diagram of carbon dioxide calculated with Peng-Robinson EOS and compared to IUPAC data (symbols).

**Specific Volume (cm3**

100 1000 10000

**/mol)**

 SAT T = 220 K T = 250 K T = 310 K T = 410 K T = 510 K T = 610 K Peng-Robinson

The application of the high-pressure fluid extraction technologies in both laboratory and industrial scales requires not only the knowledge of the physical and thermodynamic properties of the solvent, but also requires the understanding of thermal and transport properties behavior. Among them, the most commonly cited are viscosity, diffusivity, thermal conductiv-

The dielectric constant describes the ability of a solvent to be polarized. The dielectric constant value is associated with the ability to dissolve electrolytes or polar compounds. The dielectric constant increases with temperature for most substances [41]. The dielectric constant of supercritical carbon dioxide with approximate value of a hydrocarbon alone does not characterize it as an important solvent; it only identifies it as a non-polar substance. Its solvation power is mainly related to the considerable increase of its density in the supercritical region with the properties as viscosity and diffusivity complementing the characteristics that makes supercrit-

close to the values of temperature and pressure used in Table 3.

4.2. Other high-pressure carbon dioxide properties

ical carbon dioxide a differentiated solvent.

ity, and dielectric constant.

0

100

200

**Pressure (bar)**

300

400

224 Carbon Dioxide Chemistry, Capture and Oil Recovery

Figure 11. Carbon dioxide properties.


**5. Strategies to overcome crop yield reduction**

Climate smart agriculture (CSA) is now widely accepted as the best approach for addressing the effects of climate change in agriculture. It is defined as agriculture that sustainably increases productivity, resilience (adaptation), reduces/removes greenhouse gases (mitigation), and enhances the achievement of national food security and development goals. CSA promotes the transformation of agricultural systems and requires the transformation of agricultural policies to increase food production, to enhance food security, to ensure that food is affordable (low inputcost) while ensuring sustainable natural resource management and resilience to a changing climate.

#### **5.1 Management of the environment**

Climate influences all components of crop production including crop area and crop intensity. Weather forecasting and crop yield prediction or simulations are relevant tools that provide a warning to farmers in preparation of the upcoming season. From the simulation results, farmers can change the crop planting date, use appropriate genotypes, adjust the fertilization and the irrigation cycles to obtain reasonable yields, thus reducing the risk of unexpected events [51]. Several studies have been successfully conducted in crop yield simulation models and were reviewed by Tandzi and Mutengwa [51]. In a general view, the reduction of chemicals' usage such as fertilizers and pesticides, associated with the improvement of crop input use efficiency will minimize greenhouse gases emissions while protecting the environment. It has been reported that any programs that are working to minimize the adverse impact of climate change on food crops production should first consider the type of crop grown, the production area as well as the geographical and climatic conditions [15]. The knowledge of appropriate planting methods is important because climate events influence the selection of planting method and thus yield even though the total planted area remains unchanged [52]. There is a possibility of producing more yields in sustainable agriculture while generating less environmental pressure (**Figure 3**).

#### **5.2 Management of agricultural inputs**

Improvement of irrigation performance and water management are critical to ensure the availability of water both for food production and for competing human and environmental needs. To improve crop productivity and sustainability, it is very important to evaluate the effects of human activities in soil fertility through the use of appropriate agricultural systems such as tillage, use of recommended rates and types of fertilizer, incorporation of farmyard manure and/or crop residues into the soil (increase supply of N, P, K and other nutrients) and avoid sewage sludge irrigation. The application of these inputs improves physical properties of soil or soil organic matter in the long term and ensures sustainable agriculture. Shang et al. [28] found that high crop yields and low production variability can be achieved by increasing integrated soil fertility quality index in intensive cropping systems.

Climate-smart agriculture is the best way to lower the negative impact of climatic variations on crop adaptation. The type of inputs utilized during production combined with adapted high-yielding genotypes will determine the quality and quantity of harvest products to obtain (**Figure 4**). In addition, cover crops provide weed and pathogen control, decreased soil erosion, reduced loss of soil nitrogen, phosphorus and carbon. On the other hand, plant-beneficial microbes provided disease control and phosphorus availability [53]. The application of integrated pests and diseases management in farmers' fields will consistently reduce yield loss. Alternative agricultural practices such as organic production is promoted as being environmentally friendly with reduce agricultural impacts on water quality. Several countries have introduced organic farming practices to produce good quality food. The application of compost with chemical fertilizers not only results in high yields but also improves soil organic matter accumulation and soil fertility. In addition, the application of chicken manure compost enhanced soil quality and increased the accumulation of soil organic matter, available phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) content in Botswana [54]. Microbial fertilizers are distinctly environment-friendly, non-bulky, cost-effective and play a significant role in plant nutrition [55]. Policymakers in different countries should formulate policy on sustainable fertilizer and pesticide management in crop production with

**17**

**Figure 4.**

**Figure 3.**

and fertilizer application).

*Nutrient budgets between inputs and outputs [28, 56, 57].*

different placement methods to reduce the overuse of those chemicals while preserving the environment. Guan et al. [58] identified RCF3, a KH domain-containing RNA-binding protein localized in the nucleus, as an upstream negative regulator of thermo-tolerance by modulating the expression of genes encoding heat-shock proteins (HSPs) in Arabidopsis. In South Africa, the maintenance of yield quality and quantity under actual prevailing environmental conditions have been largely achieved through the change in water and fertilizer management as well as new crop management practices (such as appropriate use of rotation system, lower seeding

*Strategy of moving towards higher crop productivity and less environmental impacts [28].*

*Factors Affecting Yield of Crops*

*DOI: http://dx.doi.org/10.5772/intechopen.90672*

*Factors Affecting Yield of Crops DOI: http://dx.doi.org/10.5772/intechopen.90672*

#### **Figure 3.**

*Agronomy - Climate Change and Food Security*

**5.1 Management of the environment**

environmental pressure (**Figure 3**).

**5.2 Management of agricultural inputs**

Climate influences all components of crop production including crop area and crop intensity. Weather forecasting and crop yield prediction or simulations are relevant tools that provide a warning to farmers in preparation of the upcoming season. From the simulation results, farmers can change the crop planting date, use appropriate genotypes, adjust the fertilization and the irrigation cycles to obtain reasonable yields, thus reducing the risk of unexpected events [51]. Several studies have been successfully conducted in crop yield simulation models and were reviewed by Tandzi and Mutengwa [51]. In a general view, the reduction of chemicals' usage such as fertilizers and pesticides, associated with the improvement of crop input use efficiency will minimize greenhouse gases emissions while protecting the environment. It has been reported that any programs that are working to minimize the adverse impact of climate change on food crops production should first consider the type of crop grown, the production area as well as the geographical and climatic conditions [15]. The knowledge of appropriate planting methods is important because climate events influence the selection of planting method and thus yield even though the total planted area remains unchanged [52]. There is a possibility of producing more yields in sustainable agriculture while generating less

Improvement of irrigation performance and water management are critical to ensure the availability of water both for food production and for competing human and environmental needs. To improve crop productivity and sustainability, it is very important to evaluate the effects of human activities in soil fertility through the use of appropriate agricultural systems such as tillage, use of recommended rates and types of fertilizer, incorporation of farmyard manure and/or crop residues into the soil (increase supply of N, P, K and other nutrients) and avoid sewage sludge irrigation. The application of these inputs improves physical properties of soil or soil organic matter in the long term and ensures sustainable agriculture. Shang et al. [28] found that high crop yields and low production variability can be achieved by increasing integrated soil fertility quality index in intensive cropping systems. Climate-smart agriculture is the best way to lower the negative impact of climatic variations on crop adaptation. The type of inputs utilized during production combined with adapted high-yielding genotypes will determine the quality and quantity of harvest products to obtain (**Figure 4**). In addition, cover crops provide weed and pathogen control, decreased soil erosion, reduced loss of soil nitrogen, phosphorus and carbon. On the other hand, plant-beneficial microbes provided disease control and phosphorus availability [53]. The application of integrated pests and diseases management in farmers' fields will consistently reduce yield loss. Alternative agricultural practices such as organic production is promoted as being environmentally friendly with reduce agricultural impacts on water quality. Several countries have introduced organic farming practices to produce good quality food. The application of compost with chemical fertilizers not only results in high yields but also improves soil organic matter accumulation and soil fertility. In addition, the application of chicken manure compost enhanced soil quality and increased the accumulation of soil organic matter, available phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) content in Botswana [54]. Microbial fertilizers are distinctly environment-friendly, non-bulky, cost-effective and play a significant role in plant nutrition [55]. Policymakers in different countries should formulate policy on sustainable fertilizer and pesticide management in crop production with

**16**

*Strategy of moving towards higher crop productivity and less environmental impacts [28].*

#### **Figure 4.**

*Nutrient budgets between inputs and outputs [28, 56, 57].*

different placement methods to reduce the overuse of those chemicals while preserving the environment. Guan et al. [58] identified RCF3, a KH domain-containing RNA-binding protein localized in the nucleus, as an upstream negative regulator of thermo-tolerance by modulating the expression of genes encoding heat-shock proteins (HSPs) in Arabidopsis. In South Africa, the maintenance of yield quality and quantity under actual prevailing environmental conditions have been largely achieved through the change in water and fertilizer management as well as new crop management practices (such as appropriate use of rotation system, lower seeding and fertilizer application).

#### **5.3 Development of new adapted crop genotypes**

Breeding is routinely conducted to increase levels of durable resistance to specific pests, diseases and different abiotic stresses using conventional crop improvement methods. However, there is now an increased use of modern biotechnology techniques such as marker-assisted selection, and transgenic approaches that involve genetic modification and high-throughput sequencing of both plant and pathogenic micro- organisms. Attempts have also been made to utilize transgenic technologies to build intrinsic tolerance mechanisms by the plants through alteration of functional genes [16]. Sustainable technologies like classical breeding approaches and integrated farming principles are also being considered to develop crops adaptation and/or enhance the adaptive mechanisms.

Under stress conditions, crop plants have evolved a set of perception and signal mechanisms to respond or adapt to adverse environmental conditions via regulation, transcription, gene expression, protein translation, modification, degradation, and metabolic regulation [17]. For example, strong associations were observed between the Na+ content and some metabolites, including several sugars, suggesting that metabolic regulation is important for plant responses to salinity stress [59]. It has been demonstrated that manipulation of auxin biosynthesis pathway may improve crop plants tolerance to drought [60]. Physiological plant responses of crops to drought and heat stresses involve mechanisms to prevent membrane, regulate photosynthesis, respiration, and transpiration. For instance, developing crop genotypes with improved water used efficiency is one of the solutions to overcome drought stress. The most promising traits that might enhance crop flooding tolerance and facilitate longitudinal oxygen transport to sustain root aeration and water absorption in anaerobic soils, are anatomical adaptations such as formation of aerenchyma, a barrier against radial oxygen loss, and the growth of adventitious roots [39, 42]. The CBF/DREB1 genes are thought to be activators that integrate several components of the cold acclimation response by which plants increase their tolerance to low temperatures after exposure to non-freezing conditions. The DREB1/CBF genes have been successfully used to improve abiotic stress tolerance in a number of different crop plants [25].

The combination of genomics approaches such as marker-assisted selection (MAS) and genome wide associated studies (GWAS) can be efficiently used to develop biotic and abiotic stress tolerant cultivars (**Figure 5**). Future bio-computational integration of multiple omics and meta-omics with innovative research tools (reference genomes, proteomes, metabolomes with comprehensive annotations and structure–function relationships) will improve the understanding of the complexity of plant stress physiology [43] which will gather the development of the highyielding and most adapted crop cultivars.

In definitive, there is a need to improve research activities into water quality and water use efficiency, nutrient and soil conservation technologies and techniques, climate-resistant crops and livestock, as well as agricultural productivity in line with the national development policy of each country, to promote the development of climate-smart agriculture which lower agricultural emissions and boosts agricultural production.

#### **5.4 Climate: smart agriculture and food security**

One of the most difficult and important tasks is to ensure the protection of the planet from the degradation through sustainable consumption and production, sustainable management of natural resources and urgent action to take towards climate change at national, regional and global level. Climate change is one of the leading

**19**

climate.

**Figure 5.**

*crop genotype [13].*

**6. Conclusion and recommendations**

*Factors Affecting Yield of Crops*

*DOI: http://dx.doi.org/10.5772/intechopen.90672*

risks affecting the four dimensions of food security which are food availability, food accessibility, food utilization and food system stability [61]. Climate-smart agriculture (CSM) is an approach for transforming and reorienting agricultural systems to support food security under the new realities of climate change [62]. It promotes multidisciplinary actions to be taken by farmers, researchers, private sectors, civil society and policymakers towards climate-resilient pathways. In addition, CSM is based on three principles which are production (sustainable increase of the level of agricultural production and income), adaptation (development of resilient production systems adapted to climate change) and mitigation (reduction or elimination of greenhouse gas emission where possible) [63]. It is therefore a response to the challenges faced to satisfy the food needs of an increasing population in a changing

*Different steps of applying combined biotechnological tools in the breeding for biotic and abiotic stress tolerant*

Climate smart agriculture sustainably increased crop yields while facilitating achievement of adaptation and mitigation goals in crop production. The development of new climate resilient crop tolerant and adapted to biotic and abiotic stresses will require the propagation of novel cultural methods, the implementation of various cropping schemes, and the combination of different conventional and non-conventional approaches. The development of integrated soil-crop system management and integrated diseases and pests' management with existing crop varieties and the increase of new improved and adapted high-yielding varieties under water and nutrient limited environment should be the new target for the coming generations. The application of genetically engineered crop plants by the introduction and/or overexpression of selected genes seem to be a viable option to hasten the breeding of improved adapted and high-yielding crop genotypes. Trans and interdisciplinary

**Figure 5.**

*Agronomy - Climate Change and Food Security*

a number of different crop plants [25].

yielding and most adapted crop cultivars.

**5.4 Climate: smart agriculture and food security**

between the Na+

**5.3 Development of new adapted crop genotypes**

crops adaptation and/or enhance the adaptive mechanisms.

Breeding is routinely conducted to increase levels of durable resistance to specific pests, diseases and different abiotic stresses using conventional crop improvement methods. However, there is now an increased use of modern biotechnology techniques such as marker-assisted selection, and transgenic approaches that involve genetic modification and high-throughput sequencing of both plant and pathogenic micro- organisms. Attempts have also been made to utilize transgenic technologies to build intrinsic tolerance mechanisms by the plants through alteration of functional genes [16]. Sustainable technologies like classical breeding approaches and integrated farming principles are also being considered to develop

Under stress conditions, crop plants have evolved a set of perception and signal mechanisms to respond or adapt to adverse environmental conditions via regulation, transcription, gene expression, protein translation, modification, degradation, and metabolic regulation [17]. For example, strong associations were observed

that metabolic regulation is important for plant responses to salinity stress [59]. It has been demonstrated that manipulation of auxin biosynthesis pathway may improve crop plants tolerance to drought [60]. Physiological plant responses of crops to drought and heat stresses involve mechanisms to prevent membrane, regulate photosynthesis, respiration, and transpiration. For instance, developing crop genotypes with improved water used efficiency is one of the solutions to overcome drought stress. The most promising traits that might enhance crop flooding tolerance and facilitate longitudinal oxygen transport to sustain root aeration and water absorption in anaerobic soils, are anatomical adaptations such as formation of aerenchyma, a barrier against radial oxygen loss, and the growth of adventitious roots [39, 42]. The CBF/DREB1 genes are thought to be activators that integrate several components of the cold acclimation response by which plants increase their tolerance to low temperatures after exposure to non-freezing conditions. The DREB1/CBF genes have been successfully used to improve abiotic stress tolerance in

The combination of genomics approaches such as marker-assisted selection (MAS) and genome wide associated studies (GWAS) can be efficiently used to develop biotic and abiotic stress tolerant cultivars (**Figure 5**). Future bio-computational integration of multiple omics and meta-omics with innovative research tools (reference genomes, proteomes, metabolomes with comprehensive annotations and structure–function relationships) will improve the understanding of the complexity of plant stress physiology [43] which will gather the development of the high-

In definitive, there is a need to improve research activities into water quality and water use efficiency, nutrient and soil conservation technologies and techniques, climate-resistant crops and livestock, as well as agricultural productivity in line with the national development policy of each country, to promote the development of climate-smart agriculture which lower agricultural emissions and boosts agricul-

One of the most difficult and important tasks is to ensure the protection of the planet from the degradation through sustainable consumption and production, sustainable management of natural resources and urgent action to take towards climate change at national, regional and global level. Climate change is one of the leading

content and some metabolites, including several sugars, suggesting

**18**

tural production.

*Different steps of applying combined biotechnological tools in the breeding for biotic and abiotic stress tolerant crop genotype [13].*

risks affecting the four dimensions of food security which are food availability, food accessibility, food utilization and food system stability [61]. Climate-smart agriculture (CSM) is an approach for transforming and reorienting agricultural systems to support food security under the new realities of climate change [62]. It promotes multidisciplinary actions to be taken by farmers, researchers, private sectors, civil society and policymakers towards climate-resilient pathways. In addition, CSM is based on three principles which are production (sustainable increase of the level of agricultural production and income), adaptation (development of resilient production systems adapted to climate change) and mitigation (reduction or elimination of greenhouse gas emission where possible) [63]. It is therefore a response to the challenges faced to satisfy the food needs of an increasing population in a changing climate.


**Abstract**

Global health initiatives have expanded over the last 25 years and are no longer based solely on improving public health issues like clean water and childhood vaccination programs. Global healthcare assistance has grown into programs that provide specialty services and education today. Cardiovascular diseases are causing more deaths today in low and middle-income countries today as infectious diseases cease to be the number one cause of mortality in many of these countries. Growth in cardiovascular assistance has been substantial during the last 25 years and especially in the area of pediatric cardiac care. We discuss the ethical issues that can be found when visitors assist countries with different cultural values. The success of program development depends on navigating the ethical issues such that all stakeholders are satisfied with the project and the end result. The foundation of program development should be based upon medical ethics that are sensitive to cultural differences so that a capable sustainable program is developed upon completion.

**Keywords:** Ethics, short term global surgery programs, cardiac surgery, humanitarian assistance

#### **1. Introduction**

Global health programs have substantially increased in number and sophistication over the last 25 years. No longer do we see only primary care programs from upper-income countries (UIC) visiting lower and middle-income countries (LMIC). Today we have specialty global health care initiatives that include pediatrics, pediatric general and cardiac surgery, orthopedic and neurological surgery. Internal medicine programs specifically for endocrine and oncology, as well as singular issues with women's health. The increase in global health initiatives has sparked a discussion in the overall purpose and ethics of these efforts. The altruistic nature of these efforts cannot be overstated, but with the health care deficits in LMIC it is vitally important to consider building capacity at the local level and not fostering a dependency on the visiting team for a higher level of healthcare that is intermittent at best. Cardiovascular diseases are the number one cause of mortality world-wide [1]. However, there are deficiencies in cardiac care in almost 90% of the world, almost all in LMIC [2]. The result is that patients in these areas are poorly served and a significant healthcare in-equality continues to exist. The need to expand cardiac care to these parts of the world must be balanced with a beneficent approach to this problem since there are several ethical issues in providing medical

education, training, experience and optimal patient care which can be violated without adequate thought, preparation, and execution. Moreover, legal issues with the importation of medicines, supplies, equipment, and licensure must be considered on a country-by-country basis. Critics of surgical development assistance in general and cardiac specifically abound, some with relevant points. It is incumbent of those assisting to do so within the scope of ethical standards both from the visiting team's country and the country receiving assistance if success is to be assured.


**1. Introduction**

The consumption of sprouts, common in Asia, has been growing in western countries in the last decade once they were found to possess a broad spectrum of biologically active properties such as antioxidant, anti-inflammatory, allelopathic, and viewed as a valuable dietary supplement [1–4]. *Medicago sativa L* and *Trifolium pratense* sprouts are commonly consumed worldwide. They belong to the *Fabaceae* family, generally known by their commonly edible seeds [4–6].

Due to the increase in the use of sprouts in the human diet, there has been an expansion in the scientific literature regarding their phytochemical contents and biological proprieties. Nutritional properties of *Fabaceae* have been investigated in numerous studies [1,7].

The most interesting secondary metabolite classes found in *Medicago species* are the triterpene saponins and the polyphenolic compounds. The extraction, profiling, and identification of *M. sativa* saponins were extensively studied [8–11]. In contrast to the saponins, *Medicago* polyphenols are less genus-specific and generally encountered in many legumes. Nonetheless, alfalfa contains specific potentially valuable flavonoids with phyto-estrogenic abilities, which makes it particularly interesting for chemical characterization and pharmacological studies [12].

Red clover (*Trifolium pratense* L) sprouts are recognised as a source of phytoestrogens with high biological activity and as a dietary supplement reducing menopausal symptoms [13,14]. However, most studies focused only on certain classes of phenolic compounds such as isoflavones compounds with phytoestrogenic activity and their glycosides [13,15,16]. Among them, other polyphenolic compounds were identified by high-performance liquid chromatography HPLC in *Trifolium pratense L*.: glycitein, pratensein, pseudobaptigenin, and prunetin [16]. The comprehensive profile of phenolic compounds in aerial parts of *Trifolium pratense L*. extracts was obtained by the HPLC-tandem mass spectrometry HPLC-MS/MS technique [17,18].

Fewer reports have developed methods for qualitative and/or quantitative analysis of polyphenols in alfalfa. Flavonoids content in alfalfa was analysed in aerial parts [19,20] or in commercial sprouts by HPLC [5,6]. Ferulic acid, luteolin, myricetin, and *p*-cumaric acid were quantified in alfalfa sprouts by Oh and Rajashekar (2009) [1] using an HPLC system. However, due to the limitation of applied instrument methods, only high-level components were studied in previous studies. Moreover, a comprehensive overview of the polyphenols content variation in red clover and alfalfa during germination has not yet been reported.

High resolution mass spectrometry (HRMS), which is able to provide the accurate mass of unknown compounds, has become an important tool for characterizing chemical components in a natural product [21,22]. In the present work, we describe a comparative study conducted on alfalfa and red clover seeds and sprouts during different germination stages. Extensive characterisation of polyphenolic compounds was done by quantitative and qualitative analysis performed using ultra high-performance liquid chromatography-Q Exactive hybrid quadrupole-orbitrap high resolution accurate mass spectrometry (UHPLC-Q-Orbitrap HRMS). Thus, 29 compounds were tentatively identified without a reference standard, based on their retention times, mass spectra in a full scan mode (MS), and fragmentation patterns observed in MS-MS mass spectra. A number of 30 major compounds were unambiguously identified and quantified by comparing with reference standards.

A fully non-targeted approach of data acquisition with and without fragmentation in one single run was developed. A full scan acquisition event without fragmentation at 70,000 full width at half-maximum FWHM of resolving power was followed by five consecutive fragmentation events at a resolving power of 35,000 FWHM (variable data independent acquisition, *v*DIA) where all ions from the full scan range are fragmented. Data Independent Acquisition is an advanced option to perform untargeted fragmentation, where the entire full scan mass range is segmented in a number of subsequent fixed m/z precursor ion ranges, which are fragmented subsequently. Thus, the fragment can be restricted to the masses in a certain fragmentation event. Zomer and Mol (2015) [23] and Elmiger (2018) [24] used this approach in the analyses of small molecules as pesticides and drugs. Compared to all-ion fragmentation, vDIA can improve selectivity because product ions result from a smaller range of precursor ions [23,24].

The data obtained were subjected to statistical processing using multivariate analysis (PCA) and hierarchical clustering analysis (HCA). The present study results could represent a novel opportunity for food science and health promotion so that only certain classes of phenolic compounds in alfalfa and red clover plants/sprouts were described in previous works [13,15,18,19]. Based on our knowledge, this is the first comparison study on the chemical profile of polyphenolic compounds in sprouts of red clover and alfalfa in different germination stages.


**5. Summary and conclusions**

This chapter provides an overview of passive, active, and creative energy technologies that are particularly important for realizing ZEB in buildings commonly used in Japan.

The main knowledge obtained in this chapter is summarized as follows:

To actually realize ZEB, it is important to consider the following steps: (i) reduce energy demand through passive technology, (ii) use energy without waste through active technology for the demand that is absolutely necessary, and (iii) provide energy through energy creation technology.

Moreover, in the operational phase of a building, it is also important to have energy management technology to determine where energy waste is occurring and how to efficiently operate the facilities. This energy management technology will help reduce energy consumption on an ongoing basis.


**6. Conclusion**

Two categories of change detection techniques (Lu et al., 2004) were considered in this chapter, all of them including classification methods: Post-classification comparison and strategy with GIS.

The strategy with GIS isolated the poligon corresponding to the "Potential area for agriculture", then, the interference between some pair of classes was eliminated, by instance, wetlands and rice crops. The post-classification comparison allowed a rapid approach about the region with minor accuracy (preliminary results). Definition of the method used depends on the ratio between cost and efficiency according to the designed objectives.

Errors associated to classification methods are mainly due to the spectral answer, by undefinition of classes or occurrence of pixels of transition, because the errors derived from digitalization were insignificant. Atmospheric conditions and the regional topography also influence the process of classification.

Land cover changes in a dynamic way, sometimes with significant transformation rates of one class to another, as the discussed cases confirm. Truth of field appears as an optimal method to improve results, but the cost of process, in time, financial and human resources is incremented.


**4. Discussion**

In this pilot clinical trial, we evaluated the safety and tolerability of oral THC:CBD combination and CBD-only capsules over a 12 week period in PLWH on effective ART. Overall, the capsules were safe and well-tolerated, with AEs mostly mild to moderate in severity. Most participants completed the full 12 weeks of treatment. Importantly, even at the highest dose, capsules did not negatively affect immunological (CD4 and CD8 T cells counts) or virological (HIV viral load) parameters associated with HIV infection.

Highly purified THC:CBD combination and CBD-only capsules demonstrated acceptable safety and tolerability profiles in clinical trials for persons with epilepsy, chronic pain, and symptoms associated with multiple sclerosis and cancers [40,45–56]. In these trials, the common cannabinoid-related AEs were mostly somnolence, diarrhea, abdominal pain, fatigue, nausea, dry mouth, or dizziness, which occurred mainly during the up-titration and were considered mild or moderate in severity and resolved without discontinuation of the cannabinoid [40,45–56]. Similar to these studies, our participants also experienced somnolence and diarrhea as common AEs regardless of study arm. Abdominal pain, fatigue,

nausea, dry mouth or dizziness were also reported, but less frequently. All these AEs were mild or moderate in severity and none resulted in treatment discontinuation.

A key observation from this study is the potential risk for transaminitis and hepatotoxicity, particularly for high doses of CBD (800 mg per day) in PLWH. In our study, two participants experienced an abnormal rise in their ALT serum levels above the upper limit of the normal range during the up-titration of CBD from dose 400 to 800 mg. Transient CBD-related elevations of ALT and AST are commonly reported in clinical studies [40,46–48,50,54,56]. Transient transaminase abnormalities do not seem to be of critical long-term clinical significance for the liver as they tend to normalize following dose reduction or treatment discontinuation [57,58]. On the other hand, the second participant who experienced abnormally high elevated transaminases was a 62 years old white man with underling fatty liver disease with elevated levels of transaminases (ALT and AST) and blood glucose before the initiation of CBD treatment, along with alcohol binging which was not openly disclosed to the study team. This participant presented a significant and persistent rise of ALT, AST, ALP and total bilirubin, with an increase in blood glucose levels. In that case, the persistency of the transaminitis, even after treatment discontinuation, prompted us to conduct further liver examinations which revealed a pancreatic adenocarcinoma. The underlying pathological state of this participant with several serious comorbidities and pre-existing elevated transaminases would have facilitated the marked rise of transaminases during the up-titration as shown in another clinical trial where participants having elevated baseline serum ALT had 3 fold greater incidence of significant ALT elevations compared to those starting CBD with normal level of ALT [56]. The likely involvement of high doses of CBD in the aggravation of the pathological state of the participant cannot be excluded [56]. Together, these findings suggest that HIV physicians should consider screening PLWH with risk factors for hepatic steatosis with transient elastography (Fibroscan®, Echosens, Paris, France) before initiating cannabinoid-based medicines given the high number of baseline comorbidities and risks for chronic liver disease in this specific population [59]. Study teams should follow liver enzymes closely to detect any subtle rises in transaminases which may suggest an undiagnosed steatohepatitis. Following the SAE in the later patient, we reduced the maximum dose of CBD to 400 mg po daily in the CBD-only arm. As CBD oils are available for purchase without prescription in Canada and some other jurisdictions, PLWH who use these products should be counselled about their potential hepatotoxicity.

Although two participants in our study had worsened blood glucose control, in one case this was the same participant with the SAE, suggesting that this could have been induced by binge drinking. In the other participant, although less probable, a potential drug interaction between cannabinoid treatment and one of the other medications taken by the participant could not be entirely excluded. Cannabinoids can alter hepatic metabolism of other drugs, making them ineffective or toxic [60,61]. The roles of cannabinoids in glucose metabolism and diabetes have been documented, though mostly in in vitro and animal studies, and suggest beneficial, rather than deleterious effects on diabetic parameters [62–69]. Similarly, observational studies in individuals using cannabis more often suggest a protective effect of cannabis use against metabolic syndrome and diabetes mellitus [70–72]. In another pilot clinical trial assessing the effect of cannabinoids on glycemic parameters in diabetic individuals, although CBD failed to directly improve diabetes parameters, it did not worsen glucose levels [73]. The findings from these other studies suggest that the uncontrolled blood glucose levels observed in two participants in our trial are unlikely due to a direct effect of cannabinoids, but rather to a combination of factors including comorbidities, alcohol consumption and polypharmacy.

Improvement in quality of life and mood are primary reasons why many PLWH use cannabis [74], although cannabinoids did not impact on quality of life or on mood scores throughout the study. However, most participants had good quality of life and mood scores at baseline, perhaps making it difficult to observe significant improvements. Future studies may wish to enroll individuals with poor or moderate mood or quality of life scores at baseline in order to appreciate whether any improvement occurs with treatment. Other studies have shown that cannabis in PLWH [12] or individuals with chronic pain [59] was associated with a marked improvement in quality of life [12,59].


By comparing the obtained spectral characteristics in both analyzed electrode systems and for the same supply voltage level, significant differences in their shapes and spectral ranges can be observed. For the needle–needle electrode system, the spectral range is mainly in visible light, and a small extent in the near-infrared and ultraviolet range. In turn, the spectra obtained for the surface discharge system contained a higher proportion of ultraviolet radiation. This showed the potential possibility of using optical spectra analysis for the recognition of single-source forms of electrical By comparing the obtained spectral characteristics in both analyzed electrode systems and for the same supply voltage level, significant differences in their shapes and spectral ranges can be observed. For the needle–needle electrode system, the spectral range is mainly in visible light, and a small extent in the near-infrared and ultraviolet range. In turn, the spectra obtained for the surface discharge system contained a higher proportion of ultraviolet radiation. This showed the potential possibility of using optical spectra analysis for the recognition of single-source forms of electrical discharges.

#### discharges. **4. Optical Radiation Energy**

**4. Optical Radiation Energy**  Based on the obtained characteristics of spectral distributions and using the quantum description where optical radiation is described as a photon stream, the share of emitted energy can Based on the obtained characteristics of spectral distributions and using the quantum description where optical radiation is described as a photon stream, the share of emitted energy can be estimated. Each wavelength of emitted radiation corresponds to a specific photon energy which can be determined from the relation:

$$E = n \cdot h \cdot \upsilon \tag{1}$$

where: *E*—total energy of the photon stream (J), *n*—number of photons counted (-), *h*—Planck constant 6.626 × 10−34 (J·s), and υ—wave frequency (1/s).

The frequency of the waveform is expressed by the formula:

$$\nu = \frac{c}{\lambda} \tag{2}$$

where: υ—wave frequency (1/s); *c*—phase speed of the wave, speed of light in vacuum 2.998 × 108 (m/s); and λ—wavelength (nm).

Table 2 presents examples of the calculated energy values of optical radiation emitted by electric discharges generated in the tested electrode systems. In order to better present the determined total energy values, the physical unit of energy description in the form of electronvolts (eV) was used. They were calculated from a simple relationship resulting from the definition of eV, where 1 J ≈ 6.241509126(38) × 1018 eV. The calculated energy was not the total energy radiated by electrical discharges. The presented values were estimated based on the registered optical radiation by the spectrophotometer. This stage of research does not include an attempt to prepare energy balance, but only presents the possibility of applying energy distribution analysis to recognize the form of electrical discharges.

**Table 2.** Examples of optical radiation energy values.

#### *Analysis of the Variability of Optical Energy Shares in the UV–VIS–NIR Range*

The analysis of optical radiation variability in the UV–VIS–NIR range was carried out using traditional statistical methods. The main aim of the variability analysis was to determine the share of the energy of optical radiation, in particular spectral ranges for recorded optical spectra emitted by electric discharges generated in the analyzed electrode configurations. The results of the variability analysis are presented in Table 3. The results presented in Table 3 were determined on the basis of 10 registered characteristics for each variant of the measuring system.

Natural ester

**Type of Liquid**

**Table 3.** *Cont*. NIR 1.70 0.08 0.29 17.06 1.41 < Xtyp < 1.99

**needle–needle system**

**2**

*Energies* **2020**, *13*, x FOR PEER REVIEW 7 of 10

**Table 3.** Comparison of the share of optical radiation emitted by electric discharges.

**Variance Standard**

**Deviation**

UV 0.70 0.01 0.06 8.57 0.64 < Xtyp < 0.76 VIS 97.60 0.62 0.79 0.81 96.81 < Xtyp < 98.39

**Coefficient of Variation**

 **s Vs Xtyp**

**Range of Typical Values of Radiation Energy Share**

Figures 6–8 present the percentage share of energy in optical radiation ranges emitted by electrical discharges generated on the system of needle–needle electrodes and surface discharge systems in the insulating liquids adopted for testing. The UV radiation was less than 1% of the total energy radiation and poorly detectable in all tested insulating liquids. However, it was different in the case of electrical discharges generated in a surface discharge system, where the proportion of ultraviolet radiation was much higher. Figures 6–8 present the percentage share of energy in optical radiation ranges emitted by electrical discharges generated on the system of needle–needle electrodes and surface discharge systems in the insulating liquids adopted for testing. The UV radiation was less than 1% of the total energy radiation and poorly detectable in all tested insulating liquids. However, it was different in the case of electrical discharges generated in a surface discharge system, where the proportion of ultraviolet radiation was much higher.

**Figure 6.** Percentage of optical radiation energy for electrical discharges generated in natural ester, Midel 1204, on electrode systems: needle–needle (**a**) and for surface discharges (**b**). **Figure 6.** Percentage of optical radiation energy for electrical discharges generated in natural ester, Midel 1204, on electrode systems: needle–needle (**a**) and for surface discharges (**b**). *Energies* **2020**, *13*, x FOR PEER REVIEW 8 of 10

**Figure 7.** Percentage of optical radiation energy for electrical discharges generated in natural ester, Midel 7131, on electrode systems: needle–needle (**a**) and for surface discharges (**b**). **Figure 7.** Percentage of optical radiation energy for electrical discharges generated in natural ester, Midel 7131, on electrode systems: needle–needle (**a**) and for surface discharges (**b**).

**Average Energy (%Ec)**

**Range of Optical Radiation**

(**a**) (**b**) **Figure 8.** Percentage of optical radiation energy for electrical discharges generated in mineral oil,

This is probably due to various energy transformations accompanying the phenomenon of electrical discharges, which occurs in the used electrode systems. In the electrode system of the needle–needle type, electric discharges mostly occur in the form of a spark, while in the system for surface discharges, the phenomena occur continuously. Radiation in the ultraviolet range, in the case

The spectral distribution of the optical radiation emitted by electrical discharges in insulating liquids differed according to the electrode geometry. Needle–needle electrodes had < 1% UV radiation in all analyzed cases. In contrast, surface discharges had 7% or more UV radiation, depending on the type of electrical insulating liquid. This result might allow identification of the discharge type from the radiation spectrum and might be incorporated in expert diagnostic systems used in various technical areas. The results also justify further research, in terms of the applicability of the proposed indicator, for recognizing forms of electrical discharges in high-voltage insulation

**Funding:** This research was co-funded by the National Science Centre, Poland (NCN) as a part of the Preludium

**Conflicts of Interest:** The author declares no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to

Orlen Trafo EN, on electrode systems: needle–needle (**a**) and for surface discharges (**b**).

of discharges in the needle–needle system, is short-lived and effectively suppressed.

**5. Conclusions**

systems.

publish the results.

Research Project No. 2017/25/N/ST8/00590.

(**a**) (**b)**

**Figure 7.** Percentage of optical radiation energy for electrical discharges generated in natural ester,

*Energies* **2020**, *13*, x FOR PEER REVIEW 8 of 10

**Figure 8.** Percentage of optical radiation energy for electrical discharges generated in mineral oil, Orlen Trafo EN, on electrode systems: needle–needle (**a**) and for surface discharges (**b**). **Figure 8.** Percentage of optical radiation energy for electrical discharges generated in mineral oil, OrlenTrafo EN, on electrode systems: needle–needle (**a**) and for surface discharges (**b**).

This is probably due to various energy transformations accompanying the phenomenon of electrical discharges, which occurs in the used electrode systems. In the electrode system of the needle–needle type, electric discharges mostly occur in the form of a spark, while in the system for surface discharges, the phenomena occur continuously. Radiation in the ultraviolet range, in the case of discharges in the needle–needle system, is short-lived and effectively suppressed. This is probably due to various energy transformations accompanying the phenomenon of electrical discharges, which occurs in the used electrode systems. In the electrode system of the needle–needle type, electric discharges mostly occur in the form of a spark, while in the system for surface discharges, the phenomena occur continuously. Radiation in the ultraviolet range, in the case of discharges in the needle–needle system, is short-lived and effectively suppressed.

#### **5. Conclusions 5. Conclusions**

The spectral distribution of the optical radiation emitted by electrical discharges in insulating liquids differed according to the electrode geometry. Needle–needle electrodes had < 1% UV radiation in all analyzed cases. In contrast, surface discharges had 7% or more UV radiation, depending on the type of electrical insulating liquid. This result might allow identification of the discharge type from the radiation spectrum and might be incorporated in expert diagnostic systems used in various technical areas. The results also justify further research, in terms of the applicability of the proposed indicator, for recognizing forms of electrical discharges in high-voltage insulation The spectral distribution of the optical radiation emitted by electrical discharges in insulating liquids differed according to the electrode geometry. Needle–needle electrodes had < 1% UV radiation in all analyzed cases. In contrast, surface discharges had 7% or more UV radiation, depending on the type of electrical insulating liquid. This result might allow identification of the discharge type from the radiation spectrum and might be incorporated in expert diagnostic systems used in various technical areas. The results also justify further research, in terms of the applicability of the proposed indicator, for recognizing forms of electrical discharges in high-voltage insulation systems.

systems. **Funding:** This research was co-funded by the National Science Centre, Poland (NCN) as a part of the Preludium Research Project No. 2017/25/N/ST8/00590.

**Funding:** This research was co-funded by the National Science Centre, Poland (NCN) as a part of the Preludium Research Project No. 2017/25/N/ST8/00590. **Conflicts of Interest:** The author declares no conflict of interest. The funders had no role in the design of the **Conflicts of Interest:** The author declares no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to

#### publish the results. **References**

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