untraditional sources heating solar energy sources 29 unconventional energy sources 22 thermal pumps 18 biomass 10 geothermal energy sources 9 air-conditioning 8 more ... solar cells 6 heating 5 biofuels 4 low energy buildings 4 thermal collectors 4 bioenergetics 3 pellets 3 solar power stations 3 building equipments 3 heat-generating plants 3 heat storage 2 cooling 2 urban economics 2 power stations 2 energy sources 2 power engineering 2 energy 2 photovoltaic cells 2 solid fuel boilers 2 towns 2 heat recuperation 2 simulation and modelling 2 solid fuels heating 2 less ...