Characterizing the performance of a passive solar house with hydronic floor energy capture system – Heating season experiments

Abstract

Large south-facing window areas can significantly reduce space heating demands – the dominant energy demand in houses in cool and cold climates – by increasing passive solar gains. However, due to the risks of overheating in highly glazed spaces, reduced window areas or passive cooling strategies which sacrifice some of the available solar resource are often implemented. Active cooling strategies that can put excess passive solar gains towards useful means have not been widely considered. An energy capture system consisting of hydronic floors coupled to a water-water heat pump and energy stores has been conceived to enable larger south-facing window areas to permit greater passive solar gains. By capturing excess passive solar gains that occur at certain times, the system can protect against overheating and make use of the captured and stored energy to provide hot water heating and future space heating demands. A prototype of the concept has been designed and implemented at a full-scale experimental facility in Ottawa, Canada. Measurements were taken during two sunny and cool days in February to assess the design and operation of the system. These results show that the system can prevent overheating even when passive solar gains exceeded 10 kW (greater than the house’s peak heating load) and has the ability to capture and store these solar gains to heat domestic hot water and provide space heating at night. The results also revealed opportunities for improving the design and operation of the system.