Low-Grade Heat-Driven Adsorption Heat Pumps
Innovative thermally driven rapid thermal swing adsorption (RTSA) heat pumps use abundant lowest-grade waste or renewable heat and benign working fluids to provide heating and cooling with high efficiency. Adoption of adsorption heat pumps was slowed by inefficient adsorbents and heat exchangers that result in large system volumes and capital cost. This paper shows how RTSA heat pumps may be improved via novel higher performance materials and shaping methods in terms of performance, sustainability, and cost. Low thermal and mass transport resistance and high-capacity adsorbent coatings on heat exchanger fins are studied with a novel temperature jump system (TJS). Using these results adsorption heat pump operation was calculated indicating that low thermal and mass transport resistances allow faster cycles and a larger active-todead- mass ratio. The concept is demonstrated for 10 kW cooling systems in scenarios with applications for datacenters and compressors. The TJS extension model is applied to two case studies: (1) In datacenters, waste heat as low as 45°C from graphics processor units (GPUs) is converted into cooling to reduce the electrical energy demand. (2) 75-90°C heat from compressors that is converted into suction gas cooling to improve compression efficiency. The case studies show that our new industrial heat pump driven with 200 kW heat provides cooling with a COPth close to 1. Leveraging high specific cooling power and a reduction in electrical energy consumption for cooling by > 95%.