24 June 2014

EFFICIENCIES OF DOMESTIC HOT WATER PRODUCTION


Due to a strict governmental policy on energy performance for new domestic
buildings and the inherent better insulation and parallel the higher comfort demands for domestic hot water (DHW) by the end use, the energy use for DHW is becoming dominant in the overall energy use of the house. The combination of space heating and DHW in one heat generator like a high efficiency
condensing gas boiler for which the capacity is chosen on the instantaneous demand for high comfort DHW (being 32kW), is no longer the obvious solution as the peak demand for space
heating decreases to 4kW and lower. Low capacity systems combined with water storage tanks for DHW get more interesting. In a study done by the authors for the Netherlands Enterprise Agency (RVO) eleven individual concepts and eight collective systems providing domestic hot water have been
compared on the aspect of system losses and primary energy use in the complete chain from the generation system to the individual end user down to the level of kitchen and bath room.
Systems are both based on fossil fuels and renewables. The results show best case efficiencies of each system where heat pumps as well as solar thermal systems have the highest performances, under certain boundary conditions, on system efficiency. Further
recommendations are made to increase the efficiency.