Building integrated solar thermal facade
lightfarm is a new method for utilizing building facade and rooftop in order to collect and concentrate light rays which then is used for heating and power generation by hcpv photovoltaic cells.
in this project, instead of using conventional photovoltaic of 12% to 19% efficiency, the sunlight would be concentrated by building façade using the thin plastic fresnel lenses accompanied by a glass protection, and then a few sq. centimeters of hcpv would generate electricity for the household with record breaking efficiency of 40% .
while photovoltaic cells would provide electricity with an efficiency of 40%, the formerly 60% waste of energy is transmitted to heat-sinks for water and space heating purposes.
Two variations:
circular fresnel lenses have a higher rate of concentration from 500 to 1000 sun and they are suitable for hcpv solar cells, while linear fresnel lenses concentrate sunlight around 10 to 30 times of intensity of sunlight and it is suitable for using lcpv cells.