Exergy analysis and operational efficiency of a horizontal ground-source heat pump system operated in a low-energy test house under simulated occupancy conditions

This paper presents data, analyses, measures of performance, and conclusions for a ground-source heat pump (GSHP) providing space conditioning to a 345 m2 house whose envelope is made of structural insulated panels. The entire house thermal load with RSI-3.7 (RUS-21) walls, triple-pane windows (U-factor of 1.64 W m−2 K (0.29 Btu h−1 ft−2 °F−1)) and solar heat gain coefficient of 0.25, a roof assembly with overall thermal resistance of about RSI-8.8 (RUS-50), and low leakage rates of 0.74 ACH at 50 Pa, was satisfied with a 2.16 ton (7.56 kW) GSHP unit. Coefficient of performance is calculated on the basis of the total power input (including duct, ground loop, and control power losses). Exergy analysis provides a true measure of how closely actual performance approaches the ideal, and it unequivocally identifies, better than energy analysis does, the sources and causes of lost work — the root cause of system inefficiencies and wasted energy.