Evaluation of Two Ground Source Heat Pump Systems in Nearly Zero Energy Buildings

Abstract

In the future, most buildings will be nearly Zero Energy Buildings (nZEBs). Heat pumps are frequently used as heating system in Swedish single family buildings, but in most cases they are used in buildings with higher heating demand than the nZEBs of tomorrow. In this study, operation parameters such as heating water and brine temperatures were analyzed in real operation in two different nZEBs. The results show that the measured supply temperatures coincide in some cases well with what is described in the standard developed to be harmonized with the ecodesign and energy labelling regulations—EN14825, but in some cases they were higher. However, the brine temperatures were often considerably higher than the test conditions described in EN14825. The results also show how interconnection of a tank affects the operating parameters of a heat pump system. Another finding was that in order to reach the highest overall energy performance the heat pump and the heating system must be optimized together and not separately, which often is the case today.