From Waste to Resource: A Techno-Economic Evaluation of a CO2 Heat Pump and ORC Combined System With Photovoltaic Integration and Thermal Storage

The escalating global energy demand has resulted in a corresponding increase in greenhouse gas emissions. Multiple energy sources of various quality levels and forms must be developed to reduce emissions. One promising approach involves utilizing low-grade heat sources such as industrial process heat. This work investigates a novel combined heating and power approach through a comprehensive techno-economic analysis of a hybrid system that combines a CO2 heat pump (HP) and an organic Rankine cycle (ORC) for utilizing low-grade waste heat. The HP is powered by photovoltaics (PV), enabling sustainable heat extraction from low-grade sources, and is further integrated with thermal energy storage (TES) for demand management. The system primarily aims to supply district heating, but it seamlessly transitions to an ORC-based power generation mode in scenarios with reduced district heating demand. The integration of PV, HP, ORC, and TES allows for the efficient utilization of diverse low-grade heat sources, with adaptability to various operational strategies and applications contingent upon demand and supply dynamics. The study’s techno-economic and parametric analysis explores component and system-level performance, with Miami, FL, serving as a case study. Lastly, multiple operational scenarios and trade-offs are presented based on heating demand, power generation requirement, and resource availability.