Experimental performance of a full-scale solar thermal system designed to meet residential heating demands with passive solar energy

Abstract

This article presents the results of a 250 day study into a novel mechanical system (called PiSCES) that increases the proportion of residential heating demands that can be met with passive solar energy. PiSCES uses hydronic floor cooling to capture excess solar gains to avoid overheating in highly glazed spaces and this extracted energy is transferred to thermal energy storage (TES) systems via a heat pump. The stored energy can then be used to supply active space heating (SH) and domestic hot water (DHW) heating demands as needed. In the current experiment, active cooling removed 54% of the passive solar gains entering the test house and, of the gains left in the conditioned spaces, 93% were able to offset active heating demands without causing overheating. The excess daytime solar gains collected by PiSCES were used towards active heating demands and resulted in modest solar fractions between 51%–54% for SH and between 30%–39% for DHW demands. The utilization of passive solar gains towards heating demands was increased from 49% to around 70% with the addition of PiSCES to manage and distribute the incoming gains. Although PiSCES, as it is currently configured, was not seen to be a net energy benefit for the test house (the system consumed more electrical energy to operate than the solar energy it was able to resupply), it is suspected that improved TES efficiency, increased TES capacity, and a modified heat pump design could significantly improve performance in future studies.