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Current photovoltaic cells are fairly inefficient, maximum efficiency is at about 25% with the rest lost as heat. (I know some recent news has researchers playing with gallium nitride and such, and maybe getting closer to 50 -70%, but they're not just around the corner...) Why not stack the electric
solar cells onto a solar heat collector to scavenge the heat? In small sq footage areas (townhouse roofs, condos, etc) one of these combo cells could make solar a good supplemental heat/electrical source.
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Why not? I've often wondered this myself. [+] |
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There has been some research done on this, with improved efficiency figures. I think the problem is the tradeoff between the PV and thermal outputs and the capital cost when this kind of thing goes to market... bear in mind that a current 'hot water only' system takes 6-8 years to pay for itself, and PV cells are £5 per coffee mat with an output (at midday in July/August) of 1000W/m2 * 0.1m *0.1m * 0.2eff = 2W, so £2.50 for a watt before the clouds come! You need about 4m2 of thermal panels for reasonable hot water performance... that comes to £2,000 before the fitting costs! |
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So the customer pays £5,000 instead of £2,500 for an increace from 60% to 65% system efficiency (the thermal side takes a bit of a knock from the solar panels)! |
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The idea is good, and has been tried, but the market just isn't ready, maybe when GaAs cells are half that price, it'll be reasonable. |
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I thought electrons / photons loved the cold to do their tricks . The obvious goal would be to lose the heat not select fot it . |
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The drying of green lumber might be a good application for both solar technologies in hybrid or side by side. If dried too quickly the wood cracks. If too slow you lose time in getting to market. |
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The electric part could manage fans, doors, humidity, and phone for help when in need. The heat part could help accelerate things when advisable. |
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Robots to paint the barns black and clean the glass of the collectors might be another plus. |
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