Solar Radiant Floor and Sub-Surface Ground Heat Exchanger Thermal Storage System: Feasibility and Performance Assessment
Abstract
Solar seasonal thermal energy storage (SSTES) has long been studied and implemented as a viable means of satisfying the thermal demands of both commercial and residential buildings. This paper introduces an SSTES system with the flexibility to direct thermal energy between a solar collector array, a hydronic radiant floor space heater, and/or a sub-surface ground heat exchanger storage medium, depending on the demands on and resources within the system. This SSTES system was modeled in TRNSYS, and the results demonstrated that the system balanced thermal storage charging and discharging over the year quite well, achieving a very high solar fraction (0.96). The SSTES system was then compared to five alternate space heating systems using conventional technologies such as boilers, air source heat pumps, and ground source heat pumps; while the COP of the SSTES system far exceeded the COP of any of the alternate conventional systems, the temperature control of the space was overall tighter for the conventional systems. Parametric studies of insulation thickness over the storage volume and solar collector array type were performed to assess the impact of these variables on system performance. Results demonstrated that both adequate insulation and quality solar collectors with some thermal loss protection (either via glazing or evacuated tubes) are necessary components of a high performance SSTES system.