Paper Conference

Proceedings of eSim 2020: 11th Conference of IBPSA-Canada


A novel approach for assessing Solar Assisted Heat Pump (SAHP) system incorporation in domestic hot water heating applications

Heba Teamah 1, Marilyn Lightstone 2
1 McMaster University, Canada
2 McMaster University, Canada

Abstract: The integration of a heat pump into a solar domestic hot water system has been reported as a promising approach for enhancing overall system performance. The benefits arise from a reduction in solar collector heat losses and/or an increase in the heat pump coefficient of performance which increases the “free energy” captured by the heat pump. In northern climates, which typically use covered or insulated solar collectors, careful design of the solar assisted heat pump system (SAHP) is required in order for the system to benefit from the “free energy” associated with the heat pump. This paper presents a comparison of predicted annual system performance for conventional solar domestic hot water (SDHW) systems, series SAHP systems, and parallel SAHP systems. The modelling is performed using the TRNSYS simulation environment using weather for Toronto, Canada. The system performance criterion is the free energy ratio (FER). It quantifies the contribution of free resources (solar and air energy if present) to meet the load. The results highlight that the role of the heat pump in a series-arrangement is to lower collector heat losses, rather than to transfer energy from the ambient air. This is a result of the collector insulation which impedes heat exchange with the environment. This is in contrast with standard heat pump design which requires enhanced heat exchange of the evaporator fluid with the environment to capture the free energy. As a result of this paradox, only marginal increases in system performance are obtained with the series SAHP configuration in comparison to a conventional SDHW system. Moreover, simulations show that parallel integration of heat pumps into a solar domestic hot water system results in a substantial increase in the FER in comparison to both conventional SDHW and series-based SAHP systems. .