Solar proponents love to boast that just a few hundred square kilometers' worth of photovoltaic solar panels installed in Southwestern deserts could power the United States.
Their schemes come with a caveat, of course: without backup power plants or expensive investments in giant batteries, flywheels, or other energy-storage systems, this solar-power supply would fluctuate wildly with each passing cloud (not to mention with the sun's daily rise and fall and seasonal ebbs and flows). Solar-power startup
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Ausra
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Fernando 
Sergio Ferreira
Hans De Keulenaer