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Registered Member #175
Joined: Tue Feb 14 2006, 09:32PM
Location: Sudbury, ON
Posts: 111
Yeah, solar cells are going to give more bang for your buck as solar cells than LEDs will. The LEDs probably benefit from having the clear dome on them-- focus sunlight onto the die. Focused solar-cells heat up and degrade faster, though, is my understanding. But one can always connive some cooling arrangement.
Most alcohol burner flames I've seen have been blue, but I suppose your mileage may vary... Modern Mechanix has the Soviet kerosene lamp thermocouple here:
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
He probably meant infrared light, that would make more sense.
I have managed to get more than 2mA from a LED, a very high power density considering the very small size of the chip. Silicon semiconductors does not do very well in high temperature and they degrade much faster at elevated temperatures. Specially designed semiconductors can do very well at high temperatures.
Avalanche, did it take more power to run the fan than what you got out of the Peltier?
I have seen people getting 10W out of single peltiers when used on wood stoves. There are still people that live places where it is not possible to get electricity and where it is not enough sunlight to use solar power. Wind power would work but a peltier is much cheaper when you only need to power a radio and charge some small batteries. If the peltier elements were cheap enough it should be possible to get 500W or more out of a wood stove.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
Actually, if Emcore (or any of the other solar companies for that matter) has anything to do with it, solar power is going to be made by a triple junction (or once we can make them, 4 5 6 junction cells) solar cells, which are essentially several cells made of different materials (Si GaAs, Ge, etc) stacked on top of each other. The top cell absorbs from 400nm+ the middle from 600-400nm, and the bottom on anything up to 600nm (very roughly) . These cells produce about 30% sun->electricity efficiency, and we are planned to be up to 50% in the next few years.
Of course these cells cost $$$$$ to make, so we are running them at about 1000x concentration. Cooling really isn't that big of of problem, since the overall assembly doesn't get more than 1sun worth of energy, so we just use have the cells bolted to an Al block painted black.
We have complete modules ready to be bolted down to a concrete pad for sale if you are interested. Or you can buy just a piece of solar cell soldered to a copper block ready for your own concentrator. We are actually working with a bank to allow us to give you a panel, and then you pay it back by selling electricity back into the grid
Registered Member #1056
Joined: Thu Oct 11 2007, 11:15PM
Location: CT, USA
Posts: 27
Bjørn Bæverfjord wrote ...
He probably meant infrared light, that would make more sense.
I have managed to get more than 2mA from a LED, a very high power density considering the very small size of the chip. Silicon semiconductors does not do very well in high temperature and they degrade much faster at elevated temperatures. Specially designed semiconductors can do very well at high temperatures.
Avalanche, did it take more power to run the fan than what you got out of the Peltier?
I have seen people getting 10W out of single peltiers when used on wood stoves. There are still people that live places where it is not possible to get electricity and where it is not enough sunlight to use solar power. Wind power would work but a peltier is much cheaper when you only need to power a radio and charge some small batteries. If the peltier elements were cheap enough it should be possible to get 500W or more out of a wood stove.
Wouldnt it just be easier to boil water to turn to steam to run a generator?
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
Wouldnt it just be easier to boil water to turn to steam to run a generator?
No, not on a small scale. Everything that has to do with water and steam is a huge pain to get working reliably and safely. On a small scale it would be a more expensive too. A large part of the reason is that there are no small small mass produced generators. Just try e-bay for a small steam engine and see what the prices are. And they are mostly not up to continious use.
In theory a steam engine is far more efficient, it is not very hard to reach 50% efficiency even for a small one. You just can't buy one for $30 like a peltier, probably not even for $3000.
Registered Member #103
Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845
wrote ...
Crap, I kinda figured that it wasnt practical. Oh well, I guess theres always generators.
Don't rule out the peltiers yet, I was just demonstrating that it can work to generate usable power - but to make it worthwhile it would need to be a lot more thought out than my crappy attempt above. Like I said if I 'cooked' the peltier, I got a much larger output for the short duration that the large temperature differential could be maintained, but the fan couldn't keep up (eventually the output would drop to what it was before - similar overall temperature differential, but with the whole thing just 'hotter'. Hope this makes sense!
A better approach might have been for me to mount the thing sideways, so the hot air rising out of the lamp didn't directly heat the top heatsink! Also a much larger top heatsink would have helped.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
I mounted the peltier almost vertical with a small heatsink on the hot side and a large heatsink on the cold side. It worked fairly well. It is all about maintaining as large a temperature differential as possible.
It is a significant problem to regulate the temperature accurately. If it gets too hot the solder melts, not hot enough and the efficiency suffers badly.
Registered Member #1056
Joined: Thu Oct 11 2007, 11:15PM
Location: CT, USA
Posts: 27
After looking on google using the right terms, seems Im not the only one who had the same idea..However, There was one article I came across that Solar cells would start to be used in the IR range, ie, heat.
Hmm, Technically, If I got a solar cell, and used red filim on it, I could <theoretically> generate power from heat. But from what Ive heard, solar cells dont like Too much Heat. Ive heard that they best perform at 70C (or was it 70F?)
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Power Generation Idea
