Parameter study of four different instantaneous water heaters in a solar assisted multi-family-house with TRNSYS

摘要

The use of instantaneous water heaters avoids heating of the complete storage to 60 °C, which is necessary to fulfill hygienic requirements. This allows temperature sensitive renewable heat supply systems, like solar thermal or heat pumps, to decarbonize the heat demand in bivalent systems Technical properties of the instantaneous water heater (IWH), like the specific heat transfer rate UA and switching time of the return flow diverter, have been derived from a market survey and lab tests A suitable setting/choice of these properties can increase the solar thermal yield, improve the temperature stratification and may reduce the maximum required temperature in the upper part of the storage. This allows a solar thermal collector to substitute more fossil fuels and to reduce more effectively CO_2-emissions. A parametric study with a DHW supply system of a multi-family house with 8 apartments reveals that the CO_2-savings by solar thermal heat are highly sensitive to these technical properties. They range from (35 % up to 46 %).