Increasing solar gains by using hot water to heat dishwashers and washing machines

Document identifier:
Access full text here:10.1016/j.applthermaleng.2006.05.027
Keyword: Engineering and Technology, Civil Engineering, Teknik och teknologier, Samhällsbyggnadsteknik, Dishwasher; Clothes washer; Washing machine; Domestic appliances; Solar heating system; Solar combisystem; Solar hot water system; SDHW; System design.
Publication year: 2007
Relevant Sustainable Development Goals (SDGs):
SDG 7 Affordable and clean energy
The SDG label(s) above have been assigned by


70 to 90% of the electric energy used by dishwashers and washing machines heats the water, the crockery, the laundry and the machine and could just as well be replaced by heating energy from solar collectors, district heating or a boiler. A dishwasher and a washing machine equipped with a heat exchanger and heated by a hot water circulation circuit instead of electricity (heat-fed machines) have been simulated together with solar heating systems for single-family houses in two different climates (Stockholm, Sweden and Miami, USA). The simulations show that a major part of the increased heat load due to heat-fed machines can be covered by solar heat both in hot and cold climates if the collector area is compensated for the larger heat load to give the same marginal contribution. Using ordinary machines connected to the hot water pipe (hot water-fed machines) and using only cold water for the rinses in the washing machine gives almost the same solar contribution; however considerably lower electrical energy savings are achieved. The simulations also indicate that improvements in the system design of a combisystem (increased stratification in the store) are more advantageous if heat-fed machines are connected to the store. Thus, using heat-fed machines also encourages the use of more advanced solar combisystems.


Tomas Persson

Högskolan Dalarna; Miljöteknik
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Mats Rönnelid

Högskolan Dalarna; Miljöteknik
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