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Date: Around 1993

Einstein's photo electric equation K=hv-eV gives the maximum kinetic energy of electrons emitted from a metal if incident em radiation of frequency v exceeds the potential barrier eV. For a given frequency above the emission threshold, the number of electrons emitted increases with the intensity of the light source. Since electric current is the rate of electron flow in a conductor, and power = current times voltage drop, then would not more intense light increase the power of photo-voltaic cells? Would the use of concentrators such as Fresnell lenses and parabolic mirrors be a cost- effective method of increasing the power of photo-cells?

You are quite right. Concentrators will certainly increase the power from the photo-cells. But cost effectiveness is rather more complicated. How does the cost of the concentrator compare to the cost of additional photo-cells? Does the concentrator need to track the source (sun)? This would be an additional cost. Some concentrators are unfocused and do not require close tracking. Another concern is whether the increased intensity at the photo- cell might overheat the device. All of these concerns affect the cost-effectiveness.


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