Feasibility analysis of an indirect heat pump assisted solar domestic hot water system

Abstract

It is well understood that a typical solar domestic hot water system can greatly reduce a building’s reliance on electrical consumption. The system may be further improved by including a heat pump as part of the design. In theory, a heat pump would result in colder fluid temperatures entering the collector thereby resulting in higher collector efficiencies and longer operation periods.One Indirect-style Solar Assisted Heat Pump (i-SAHP) design was modeled using the TRNSYS software and compared to a traditional solar domestic hot water (SDHW) system and an electric domestic hot water (DHW) system. All of the systems had the same load profile and delivered domestic hot water at a constant temperature. This insured that each system delivered the same amount of energy for the entire modeling period thereby creating a common basis for comparison. It is important to note that each system considered in this study was used for domestic water heating only. It was found that the electrical consumption and operating cost were the lowest with the i-SAHP system. Other i-SAHP configurations need to be modeled to determine which configurations work best under the local design constraints. Further, the incremental cost of the i-SAHP needs to be determined in order to estimate realistic payback periods and to gauge economic feasibility.This work was done as a preliminary stage and was meant to roughly gauge the feasibility of the specific i-SAHP system in the study. Therefore, generic inputs were consistently used with all of the TRNSYS components and the trends of the results were considered more important than the actual numerical values obtained.