Chemisorption power generation driven by low grade heat – Theoretical analysis and comparison with pumpless ORC

Sorption cycles have been extensively developed for waste heat recovery to deliver cooling, heating, and electricity. Chemisorption cycles using metallic salts as sorbents and ammonia as working fluid have been explored in this work for the maximum potential of pure power generation. In order to get better understanding and more insights, resorption power generation cycle (RPGC) has been theoretically investigated and compared with pumpless organic Rankine cycle (PORC). The PORC operates without a liquid pump in conventional ORC and shares the similar configuration with RPGC. Three different organic fluids (pentane, R123 and R245fa) used in PORCs and four different reactant salts (manganese chloride, strontium chloride, barium chloride and sodium bromide) used in RPGCs have been analysed and evaluated in terms of the power generation capacity, thermal efficiency and energy density under the conditions of heat source temperature from 60 °C to 180 °C and heat sink temperature at 30 °C. The PORCs have higher thermal efficiency of work output for most cases in the studied scenarios, while RPGCs are evidently superior on energy density, at least as twice large as that of the PORCs studied. RPGC and PORC both have intermittent and dynamic operation, and the former one has the potential to have multiple energy productions or perform as energy storage.