Potential for reliance on solar water heating throughout the summer in northern cloudy climates

In latitudes between 50° and 60° north domestic hot water is frequently provided by the house's central heating boiler. These are run for short periods in the summer just to provide hot water, this tends to be inefficient. In places with a constant solar climate it should be possible to rely on solar energy to provide domestic hot water, however many northern cities have a large daily variation in solar radiation. The potential of solar water heaters to meet the hot water demand of a household throughout the summer period in a wide range of cities was investigated. Hourly solar irradiation and air temperature values for a typical year are used to calculate the efficiency of a commercially available solar panel and estimate the energy collected each hour. The hot water is stored with daily extraction varied to correspond to different levels of occupants. The heat loss from the store is also calculated and used to find the optimum area of solar collector for a given store size. It was found that it should be possible to provide domestic hot water by solar panels for the period when space heating is not required in all location considered.