Techno-economic analysis of converting low-grade heat into electricity and hydrogen

Abstract

Low-grade heat recovery has received increasing attention as an essential contributor to improving overall energy utilization efficiency and facilitating the carbon neutrality commitment. Here, we developed a techno-economic analysis model of converting low-grade heat into electricity and hydrogen via the osmotic heat engine (OHE) and power-to-gas facility to alleviate the dilemma of lacking practical application scenarios of waste heat. The contribution margin is optimized in real time by either sending the electricity generated by the OHE into the electrolyzer for hydrogen production or selling it at market price in Wuhan, China, thus to identify the economically viable OHE costs under different conditions. Results show that the allowed heat engine cost is significantly impacted by the capacity factor, lifetime and discount rate. The effect of the capacity size of power-to-gas facility on allowed heat engine cost strongly depends on the hydrogen price. The allowed OHE cost increases with the elevating waste heat temperature for each heat transfer scenario. The hybrid energy system can be economically competitive compared with current mature technologies when the waste heat temperature is higher than 68 ℃ and 105 ℃ for fluid and air as heat transfer fluid, respectively. The economically viable heat engine cost is expected to gradually decline from 50,043 ¥/kW to 18,741 ¥/kW within next 15 years. Incentive policy would boost the economic viability of converting low-grade heat into electricity and hydrogen.