Energy performance of direct-expansion solar heat pump integrated with thermal network

Abstract

Direct-expansion solar-assisted heat pumps (DX-SAHP) are increasingly used in heating applications owing to their high efficiency. In this study, the energy performance of a DX-SAHP for a distributed thermal prosumer in a thermal network was investigated. A thermal network for supplying hot water, established in the eco-friendly energy town of Jincheon, was selected as the test site, and a daycare center was selected as the pilot building. A control logic for serving produced thermal energy to the thermal network was developed as an operation of thermal prosumer. Experiments were conducted during the cooling and heating seasons, and the results of three operation cases showed that the proposed prosumer operation can transfer the thermal energy within the thermal network. The daily load of domestic hot water was approximately 50–100 kWh, and the daily coefficient of performance of the DX-SAHP ranged from 2.0 to 5.0. The coefficient of performance of the DX-SAHP was found to be strongly dependent on the outdoor air temperature, solar irradiation, and outlet water temperature. During the operation, the DX-SAHP contributed to achieving over 66% savings in the operating energy compared with a conventional electric heater.

Keywords

• Direct-expansion solar heat pump
• Decentralized thermal prosumer
• Coefficient of performance
• Experimental analysis