Achieving total domestic hot water production with renewable energy

Various means of producing domestic hot water (DHW) with renewable energy in zero net energy homes (ZNEH) are examined for two climates (Montréal and Los Angeles). Four alternatives are examined: (i) a regular electric hot water tank; (ii) the desuperheater of a ground-source heat pump (GSHP) with electric backup; (iii) thermal solar collectors with electric backup; and (iv) a heat pump water heater (HPWH) indirectly coupled to a space conditioning GSHP. Results show that heating DHW with thermal solar collectors with an electric backup (which is either provided by the photovoltaic (PV) panels or the grid in a ZNEH) is the best solution for a ZNEH. The second part of this paper focuses on determining what should be the respective areas of the thermal solar collectors and PV array to obtain the least expensive solution to achieve total DHW production with renewable energy.