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Solar Power and Deserts
tara_li
I see from time to time discussion of solar power plants being set up in the desert, and how the sun's energy can be tapped in this or that manner.  One of the most recent I saw involved huge greenhouses heating up air, and letting it rise through towers to drive turbines.  And that's all well and good, I think.

But what about using the power of the absence of the Sun?

Deserts are odd places - during the day, they get insanely hot.  But at night, the lack of humidity and cloud cover results in something most people don't think of in connection with deserts - COLD.  Enough cold that the Egyptians used to use it to make ice all throughout the year.

Generating power is about connecting two areas of different energy levels - such as high/low (hydroelectric generation) and hot/cold (the above mentioned stacks connecting hot air from greenhouses to the cold upper atmosphere).  Is there some way we can connect the hot daytime to the cold nighttime, and use that for generating power?  There should be, I'm sure.  I'm just not certain what it is...

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it's called a thermal pile. You open shutters to sunlight during the day to make a bed of black rocks get hot. Then at night, you close the shutters and move air over the rocks to warm a cold room.

To make electricty from thermal differentials directly is woefully innefficient. Look up "Peltier Junctions". To get any appreciable current you must have at least 200degrees difference between hot and cold side. This is how our RPGs in deep space probes work (plutonium oxide on the hotside, frigid space for the coldside.) You won't get such temperature differentials here.

What you could do however is have the sun heat up black pipes and circulate that into a hot-brine tank, getting it hotter and hotter. Then that hot brine at night can be used to power a Sterling engine, which gets about 30% efficiency converting temperature differentials to mechanical (and electrical) power. But the Sterling engine has moving parts.

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