Energy benefit of organic Rankine cycle in high-rise apartment building served by centralized liquid desiccant and evaporative cooling-assisted ventilation system

Building heating, ventilating, and air-conditioning systems have high impacts on the energy and environmental performance of residential buildings. To reduce the energy consumption of the building for sustainable buildings and cities, this research proposed the organic Rankine cycle (ORC) applied to a centralized liquid desiccant (LD) and evaporative cooling-assisted ventilation system serving an apartment building and evaluated the energy impact of the proposed system via detailed energy simulations. As a small combined heat and power application in residential buildings, the ORC produces heat and power that are consumed by the proposed system and the building. A conventional decentralized energy recovery ventilator powered by the existing power grid was selected as a reference system. The combination of the ORC, LD, and evaporative cooling-assisted ventilation system allows decoupling of the sensible and latent cooling and offers energy benefits by reclaiming heat from the ORC compared with the reference system owing to the parallel system of energy consumption. Energy simulations were conducted for one floor of a 30-story apartment building. The proposed system exhibited 28% annual primary energy savings and provided a 54% higher annual average coefficient of performance compared with the reference system, although the proposed system consumed more fan and pump energy. The majority of the operating energy savings of the proposed system were achieved by reclaiming the waste heat from the ORC condenser.