Solar assisted heat pump system for multifamily buildings: Towards a seasonal performance factor of 5? Numerical sensitivity analysis based on a monitored case study

Abstract

The present work analyses the potential of a combined solar thermal and heat pump (HP) system on new and existing multifamily buildings. The study uses numerical simulation as a complement to a monitored case study. After a description of the case study and a summary of the monitoring results, we present the numerical model developed for this study. Simulation results are validated with the monitored values, at component and system level, in terms of monthly profiles and yearly integrals. On this basis, we carry out an extensive sensitivity analysis concerning the principal sizing parameters of the system. Finally, we investigate the sensitivity of the system to space heating (SH) and domestic hot water (DHW) demands, in particular concerning the applicability of the analysed system in the case of building retrofit. For Geneva's weather conditions, a sizing factor of 3 m 2 solar collector per kW of HP capacity is a good compromise between system size and system performance, resulting in a system seasonal performance factor (SPF sys) between 3.1 and 4.1, depending on the SH distribution temperature. The associated electricity consumption (ranging from 12 kWh/m 2 for a new low-energy building, up to 45 kWh/m 2 for a non-retrofitted building) strongly depends on the heat demand. Such is also the case for the collector area (from 0.08 m 2 per m 2 heated area for a new low-energy building, up to 0.20 for a non-retrofitted building). Finally, a SPF sys of 5 could potentially be achieved, but only in newly constructed buildings with a high efficient envelope, a low SH distribution temperature, and with a collector area of at least 0.20-0.25 m 2 per m 2 heated area. However, the related investment may not be worthwhile, given the rather small associated electricity saving, not to mention that such a collector area would not fit on buildings with more than 4 storeys.

Performance of a demonstration solar PVT assisted heat pump system with cold buffer storage and domestic hot water storage tanks

“…Del Amo et al [21] reported measurements from an energy system in a building in Zaragoza with PVT collector and validated a simulation model with the measured data. Fraga et al [22] did a study on SAHP in a multifamily building, developed a numerical model of the system and conducted a sensitivity analysis for sizing the system. Dupeyrat et al [23] characterized a prototype PVT collector and simulated the performance of a solar hot water system and concluded that the combined PVT panel had advantages over separated PV and solar thermal collectors.…”

Heat pump systems for multifamily buildings: Potential and constraints of several heat sources for diverse building demands

“…Within this context, a recent study concerns a long term in-situ monitoring of a combined parallel/series air + solar HP system implemented on a MFB with very low heat demand situated in Geneva (Fraga et al, 2015), which resulted in a SPFsys of 2.9. In addition, a numerical study allowed to quantify the optimization potential of the specific system, to investigate the sensitivity to SH and DHW demands, in particular concerning the applicability of the concept in the case of building retrofit, as well as to define design guidelines for such systems (Fraga et al, 2017).…”

Contributions Of Heat Pumps To Demand Response: A Case Study Of A Plus-Energy Dwelling

“…This study also tested different preheating times, taking into account the outdoor temperature and achieving cost savings of 16-19 %. The work presented in [18] also analyses the potential of a heat pump system, but in this case coupled with solar thermal energy on multifamily buildings. They concluded that the related investment may not be worthwhile, given the rather small associated electricity savings.…”