According to the Energy Performance of Buildings Directive, a significant share of the energy consumption of nearly zero energy buildings is covered from renewable energy. Biomass is considered as one of the most important renewable sources. It is promising since most of the Member states apply very low primary energy conversion factors for it. Nevertheless, the primary energy need is not as favourable as the conversion factors suggest, due to the efficiency of the biomass boilers for all over the year which depends on the changing load. Heating systems supplied with biomass boilers need buffer storage tanks which further decrease the efficiency of the system.
The nearly zero energy buildings, especially those of residential use exhibit more stable load due to the lower heat loss and the overwhelming share of the net energy need of domestic hot water supply.
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