Micro-scale ORC-based combined heat and power system using a novel scroll expander
Micro-combined heat and power generation (micro-CHP) based on the organic Rankine cycle (ORC) is a flexible technology that allows saving the environment and promoting the economic growth. However, ORC expanders employed recently suffer from key problems including excessive fluid leakage, thermal losses and low isentropic efficiency, and no commercial micro-scale expanders are available in the market and applicable for ORC applications. The possibility of driving a micro-CHP system by solar thermal energy, biomass combustion, waste heat or other clean energy sources allows attaining diversity and security in energy supply as well as decreasing pollutants and gas emissions. In the current work, a solar- biomass-driven micro-CHP system based on the ORC technology is theoretically and experimentally investigated to provide the thermal and electrical needs for residential applications. The micro-CHP system employs an innovative micro-expander utilizing an environmentally friendly working fluid. A numerical model was developed using the Engineering Equation Solver (EES) software to simulate the thermal and electrical performance of the overall CHP system. A parametric study was conducted to investigate the effect of different operational parameters on the CHP system performance. In addition, an experimental set-up was built to test micro-scale ORC-CHP system performance under different conditions using hydrofluoroether (HFE)-7100 fluid. The maximum electric power generated by the expander was in the range of 500 W under a pressure differential of 4.5 bars. The expander isentropic efficiency has exceeded 80% at its peak operating conditions with no working fluid leakage.