Fresnel lenses can indeed be manufactured in large sizes and cheaply. The tradeoff problem is that solar concentrators have to be sun trackers to some degree, and that requires structure and mechanism of some kind, which is expensive. Also, the collectors have to be kept clean or lose effciency. Therefore, one solution is to increase the efficiency of the PV device so that fewer are made, or make it so cheap it can be used as building wrap. The former is costly, the latter inefficient. I have seen designs for afocal solar concentrators , but they are cup-like and keeping them free of dust and debris might be a problem.
Jones' thought of using a collector array to cool a working fluid by dumping its heat into space on a cloudess night is clever, and does not require focusing as the heat sink is diffuse. However, if Fresnel lenses are used, the plastic must be quite transparent in the IR region where the radiation will occur. Mike Carrell
