Feasibility study of a localized residential grey water energy-recovery system

In order to improve the overall efficiency of building energy usage, a grey water energy-recovery system, which adopted a multiple-function heat pump system, was proposed for domestic water heating, and space heating and cooling of buildings. A numerical model has been developed for investigation of annual energy and water consumptions of the proposed system and the conventional building energy system with gas furnace space heating, package air-conditioning, and electricity water heater for hot water heating. Based on a case study of a typical residential house with four family members and three bedrooms in New York, NY, results show that the overall source energy consumption with the proposed system decreases 33.9% for space heating and cooling and hot water heating, and also the potable water consumption reduces 27.2% compared with those of the conventional system. An extended study with fourteen other cities was performed in various climate zones in the U.S. Among these 15 cities, the savings in source energy and potable water consumption have ranges of 17%–57.9% and 15%–34.1%, respectively. The results also show the proposed system can provide substantial energy and potable water savings, particularly with moderate outdoor temperature.