Residential solar water heating - measurement and verification case studies

Abstract: South Africa is currently experiencing an electricity crisis. This, combined with the high levels of solar irradiation as well as the power utility’s need to reduce the country’s peak demand through DSM (Demand Side Management), has promoted the installation of solar water heaters (SWHs) in homes across the country. This paper presents three case studies which were M&V’d according to the IPMVP (International Performance Measurement & Verification Protocol). The methodology used does not require baseline measurements since the baseline is calculated from continuous measurements of thermal energy delivered by the newly installed SWHs and estimation of standing losses of the replaced electric water heater (EWH). This allows the homeowner to go ahead with the installation of the SWH without waiting for M&V to establish a baseline for the EWH which is being replaced. This method is preferred by homeowners and the DSM utility alike, since the installation of the SWH is not delayed by M&V. A measurement system including an electric power meter, inlet and outlet water temperature probes, ambient temperature probe, flow meter and GSM modem were developed to measure the service level and performance of the SWH. This measurement system along with a method for modelling the usage of an EWH are crucial to the M&V methodology employed. This paper describes the type of systems investigated, the M&V metering, M&V methodology, and the payback period of each system. The sensitivity of the savings with respect to EWH standing losses is investigated. This case study provides valuable information for those interested in studying or performing M&V on SWHs