Energy benefits of organic Rankine cycle in a liquid desiccant and evaporative cooling-assisted air conditioning system

Abstract

This study evaluated the effect of an organic Rankine cycle (ORC), powered by various renewable heat sources, on enhancing the primary energy benefits in a liquid desiccant (LD) and indirect and direct outdoor evaporative cooling-assisted air system (LD-IDECOAS). Combining an LD-assisted air conditioning system with the ORC, which uses renewable or waste heat sources, may be beneficial in terms of energy saving and environment efficiency. However, only a few studies have addressed the benefits of integrating the ORC with this air conditioning system as the heat source for the ORC. A solar thermal system, district heat source, and conventional boiler were used respectively in a 2-kW ORC which was integrated with the LD-IDECOAS to establish three system cases, and a comparative investigation was conducted. The power and heat generated by the ORC are supplied to the LD-IDECOAS to satisfy the power and solution heating demands, respectively. By performing a detailed energy simulation, the primary energy consumption in each ORC-integrated case was calculated during the cooling season and compared with that of a conventional LD-IDECOAS driven by grid power and a gas boiler. The results revealed that three ORC-integrated system cases consumed additional electric power compared with the base case (21.6% more electric power consumed in case 1 and 20.0% more electric power consumed in cases 2 and 3). Additional heat input to the ORC evaporator was also required, however, the ORC-integrated LD-IDECOAS powered by a solar thermal system (case 1) and district heat source (case 2), which are renewable energy sources, achieved a primary energy saving of 15.7% and 35.4%, respectively, compared with the base case. In conclusion, the district heat source was more feasible than the other heat sources considered in this study, achieving the best primary energy saving (35.4%) and CO2 emission reduction (23.9%).