Energy and exergy analysis of a ground source heat pump system for a public building in Wuhan, China under different control strategies

Abstract

This paper presents the energy and exergy studies of a ground source heat pump (GSHP) system for a public building in Wuhan, China under five different control strategies to improve the system performance. Original system was under manual operation with constant frequency heat pump, constant speed circulation pumps, and constant water flow rate. The five control strategies were: 1) Automatic ON/OFF control based on Building Load Ratio (BLR); 2) Optimum circulation flow rate control; 3) Optimum ON/OFF control with variable speed heat pump units; 4) Variable flow control by adjusting valve position; 5) Variable flow control by variable speed pumps. The results of the system exergy efficiency, exergy loss, COP, and energy consumption under different operation scenarios are presented. By comparing original operation with the best case (scenario five), it is found that during cooling and heating season, the system exergy efficiency was improved from 9.0% to 10.4% and from 6.1% to 6.9%; exergy loss dropped by 31% and 51%; COP increased from 3.2 to 3.7 and from 2.7 to 3.8; and energy consumption was reduced by 37% and 60%, respectively.