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In article , "Joel Kolstad"
writes: Watson A.Name "Watt Sun - the Dark Remover" wrote: Also the currewnt outputdepends somewhat on the latitude you're at. You won't get all that current at the arctic circle. He might actually have a better chance there during the periods when the sun never sets than at, e.g., the equator... solar cells are noticably more efficient when they're keep cold, which is typically a lot earier to do in the arctic than at the equator! Ahem, Joel, consider the location of "the land of the midnight sun..." :-) Ackshully, based on a little bit of experience on Solar One, the first (of two) experimental 50 MWe solar plant in Barstow, CA, (in the middle desert of California with not much else), sunlight has a considerable variance in energy over the course of a day. A combined buck-boost switching power supply would be a consideration for reliable solar cell charging of a secondary battery during daylight. There are several different ICs just for the purpose of wide-voltage-range inputs from National, Linear, and Maxim along with application notes from all three. Roy Lewallen hit the subject nail on the head in saying, correctly, that solar cells behave more as constant-current sources than constant-voltage (as batteries are) sources. Those who care to test that will find out from connecting a fixed resistor to solar cell outputs and measuring the voltage during the course of daylight, especially the differences between clear and cloudy skies. Solar One was a boiler system, over 500 independent mirrors were used as a giant reflector array to focus sunlight on a central boiler made from the same stainless-steel-like tubing used in rocket engine bell structures. Rocketdyne Division of Rockwell International was the subcontractor to MacDonnell-Douglas that made the boiler and the underground steam-heat storage system of Solar One. The peak daylight energy was in excess of 100 MWe equivalent but the extra heat had to be stored overnight for the steam-turbine-powered generators to run 24/7. Rocketdyne, now purchased by Boeing, made the Space Shuttle Main Engines. Rocket engine bells are made from tubing to circulate fuel before entering combustion. That pre-warms the fuel as well as cooling down the tail of the engine's output. Not exactly what a QRP operator would need... :-) Len Anderson retired (from regular hours) electronic engineer person |
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