Investigation and performance study of a dual-source chemisorption power generation cycle using scroll expander

Development of novel heat recovery system attracts ever increasing attentions to convert wasted heat into useful energies. This paper reports the study of a novel dual-source chemisorption power generation cycle using scroll expander to recover dual heat sources. The proposed chemisorption power generation system contains four adsorption beds and two expansion machines for simultaneously and continuously producing electricity by recovering dual-source low grade heat energy such as solar energy and industrial waste heat into electricity. The system performance using nine Metal Chlorides-Ammonia working pairs are studied to identify the suitable operational conditions of the system using scroll expander for power generation. Results indicate that SrCl2 as the LTS can achieve the highest thermal efficiency of the bottom part (LTS-exp2-HTS) ranging from 11% to 7%. MnCl2-SrCl2 is suitable to be used under the first heat source temperature ranging from 200 to 250 °C and second heat source temperature about 100 °C with the overall thermal efficiency around 10%. The average specific energy of the system under the suggested working conditions can be as high as 102 kJ/kg(salts) in the upper cycle and 82 kJ/kg(salts) in the bottom cycle. The dynamic system performance evaluation is conducted by using the integrated adsorption mathematical model and scroll expander simulation model. Results shows that for a system using 25.2 kg MnCl2 and 18.12 kg SrCl2, the average electricity under the first heat source temperature at 220 °C is about 300 W within 30 min of upper cycle time. And the bottom cycle can produce average 500 W electricity within 22.5 min of bottom cycle time under the second heat source temperature at 160 °C.