Innovative design and performance analysis of a Static Shaft Wankel Expander for Micro-Scale Organic Rankine Cycles

Micro-scale Organic Rankine Cycles (mORC) hold significant potential for utilizing low-grade heat sources, such as solar energy, geothermal energy, and industrial waste heat. However, the development of efficient, cost-effective expanders remains a challenge. This study introduces a novel Static Shaft Wankel Expander (SSWE) designed and manufactured without valves, allowing the rotating rotor to directly control inlet and exhaust port timing, thereby simplifying construction and reducing costs. We performed a three-dimensional Computational Fluid Dynamics (CFD) simulation to analyse the SSWE’s flow characteristics and thermodynamic performance, achieving up to 84 % isentropic efficiency and generating 874 W of power. Validation through experimental testing, using refrigerant R245fa, showed a deviation of only 4.5 % from the CFD results. The experimental results indicated that the mORC with the SSWE produced 834 W at 94 °C with an isentropic efficiency of 81 %. The study highlights the SSWE as a promising candidate for mORC applications, offering low cost, simplified design, and competitive efficiency. This approach contributes to the advancement of sustainable energy systems, supporting the economic feasibility and broader adoption of mORC technologies.