Performance of two domestic solar water heaters with drain water heat recovery units: Simulation and experimental investigation

This paper presents an investigation on the performances of drain water heat recovery (DWHR) system and two solar domestic water heaters (SDWH). The DWHR units and water heater systems were recently installed side-by-side at the Archetype Sustainable Twin Houses at Kortright Center, Vaughan, Ontario. The first SDWH system in House A consists of a flat plate solar thermal collector in conjunction with a gas boiler and a DWHR unit. The second SDHW system in House B consists of an evacuated tube solar collector, an electric tank, and a DWHR unit. The extrapolated results based on the experimental study showed that the DWHR unit is capable of an annual heat recovery of 789 kWh and an overall effectiveness of about 50%. The flat plate and evacuated tubes collectors based SDWH systems produce an annual thermal energy output of 2038 kWh and 1383 kWh, respectively.