A Hybrid Solar-Biomass ORC-Based CHP System Using a Novel Scroll Expander

Micro Combined heat and power generation (Micro-CHP) based on the organic Rankine cycle (ORC) presents a flexible and reliable technology that can help in saving the environment, achieving energy security and flourishing the economic growth especially if it is driven by a renewable energy resource. However, the majority of ORC expanders employed recently suffer from key problems including excessive working fluid leakage, thermal losses and low isentropic efficiency, with no commercial micro-scale scroll expanders available in the market and applicable for ORC applications. In this study, a hybrid solar-biomass driven micro-CHP system based on the organic Rankine cycle technology is theoretically and experimentally investigated to provide the thermal needs and part of the electrical demands for a residential application. The micro-CHP system employs a new type micro-expander with environmentally friendly working fluid. A Numerical model was developed using the Engineering Equation Solver (EES) software to simulate the thermodynamic behaviour of the ORC unit predicting the thermal and electrical performance of the overall CHP system. In addition, an experimental setup was built to test the whole ORC-CHP system performance under different operational conditions using HFE-7100 fluid. The maximum electric power generated by the expander was in the range of 500 W at a pressure differential of about 4.5 bars. The expander isentropic efficiency has attained more than 80% at its peak operating conditions with no fluid leakage observed.