How to halve the electricity consumption for a household dishwasher

In the household appliance industry, heat pump systems have been used for a long time in refrigerators and freezers to cool food, and the industry has driven the development of small, high-quality, low-price heat pump components. The low price of good quality heat pump components, along with an increased willingness by customers to pay extra for lower electricity consumption and environmental impact, have made it possible to introduce heat pump systems in other household appliances, with the expressed purpose of reducing electricity consumption. Heat pump tumble dryers have been on the market since 2000 and dominate the market today. A heat pump dishwasher was introduced on the market in 2014 and a heat pump washing machine in 2016. The purpose of adding a heat pump system in these three products was to decrease electricity consumption. Papers I and II used a methodology where transient simulation models were developed and used to increase knowledge about how to decrease electricity consumption for a tumble dryer (I) and a dishwasher (II) by adding a heat pump system. Simulations in Paper I showed that a 50% larger compressor in a heat pump tumble dryer decreases the drying time by 14% without using more electricity. This satisfies the consumer requirement for a shorter drying time without increasing energy use. Papers II, III and V showed that a lower electricity consumption and lower global warming potential together with an energy-efficient drying method, with no humid air going into the kitchen, give a heat pump dishwasher competitive advantages compared to any conventional dishwasher currently on the market. Using simulations, this dissertation concludes that a commercial heat pump dishwasher, using R600a as a refrigerant, will reduce electricity consumption and TEWI by 50% compared to the conventional dishwasher. Paper IV shows the possibility to use a low cost expansion device as a capillary tube in the heat pump dishwasher without increasing electricity consumption. This result increases the possibility of the heat pump dishwasher becoming more common in the future. The challenge for the manufacturer is to develop and produce a highquality heat pump dishwasher with low electricity consumption, predict future willingness to pay for it, and launch it on the market at the right moment with the right promotion in order to succeed.