The energy from solar, geothermal, and/or wind is not free, except to sunbathers and rattlesnakes. The initial costs of converting this energy into electricity is very expensive, and the on going maintenance is also expensive. Someone has to pay the bill, and you environmental extremists are fine with that, as long is it is not you...
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So you build an array of parabolic mirrors [in contrast to mining trucks, fuel, explosives, transportation, refining, waste mitigation, environmental damage] that concentrate the sun on a hermetically-sealed oil filled tube that circulates 300 C fluid past common heat exchangers to boil water to run turbines [like all conventional power plants do] and somehow that free sunshine on that fixed system already installed is "too expensive to harvest"?
If you have the sun shining down on your parabolic tandem cogeneration array to any given power plant already in existence, a simple and cheap adjunct to install rapidly anywhere, let's say for 200 days a year average, somehow were' supposed to believe that producing energy from that plant on any given year will be more expensive using free energy 200 days a year than having to purchase refined coal or oil for those 200 days to burn instead?
Don't become a used car salesman anytime soon. You'll starve to death.
For more on how 'expensive, difficult and time consuming' installing tandem cogeneration with solar thermal can be, view the video in the link below: