High-Performance Heat-Powered Heat Pumps

This paper introduces a zero-carbon heating solution called High-Performance Heat-Powered Heat Pumps (HP3), which combine the best attributes of hydrogen boilers and electric heat pumps. HP3 systems allow us to continue using the existing gas infrastructure, offer higher efficiencies than hydrogen boilers, and avoid overwhelming the electricity grid. An HP3 blends a heat engine and a heat pump into a single, fully integrated system sharing a common working fluid. This differentiates HP3 systems from gas-engine-driven heat pumps (GEHP), where the integration between subsystems is limited to a mechanical shaft. A parametric analysis of a propane-based system is presented. The heat engine section has two main design variables: the working fluid’s temperature (Tmax) and pressure (Phigh) after collecting high-grade heat from hydrogen combustion. Typical GEHPs achieve CoPs of around 1.8. The HP3 concept achieves a CoP of 2.59 considering a Tmax of 650 °C, Phigh of 250 bar, and an ambient temperature of −9 °C. The paper presents a model for the expander’s efficiency, which indicates that increasing the system’s output makes it possible to achieve a higher expansion efficiency with a lower rotational speed. Results show that HP3 is a promising concept for larger applications such as commercial buildings or district heating systems.