Peltier cells and their solar electric applications.

System · June 2008

I had a question for you guys I've been meaning to ask.

My thought was to place many peltiers on a heatsink to be placed on the backside (shady side) of some form of heat trapping device. This device could be an aluminum plate or heatsink painted black and inside of a box with a clear cover to let in the sun. The idea is to trap heat. The sun would heat the plate inside the box and it's only way out would be to transfer through the peltiers to the other, much cooler, heatsink outside the box behind it. I have no idea what the tempature differential would be across the cell but perhapse it would be enough to produce a usable amount of electrical power. Maybe more power could be made using the heat from the sun then could be made with a solar electric panel.

Peltiers are fun to play with. I hooked 2 of them together and took a lighter to one cell and could feel the heat comming off the other. I was suprised at how hot it was getting. Kinda weird to imagine the flame "traveling through a wire" to the other side. I know they draw quite a bit of current to function. This means they generate alot of current. Could be a good thing. I smell a boost converter.

To go on even further with this idea, you could use liquid cooling waterblocks, used for computer CPUs, and a small pump to circulate water into an underground radiator such as a coil of copper tubing. The gain in efficiency could be enough to power the pump and still produce enough additional efficiency to justify the complexity.

Has anyone tried this? What do you guys think?

mike95490 · June 2008

Re: Peltier cells and their solar electric applications.

It takes a LOT of heat differential, and a LOT of cells, to get something useful. Solar PV is actually more efficient. If you make solar heat blocks, you need a heat sink, and the cold side needs to be next to the hot side, with the module in the middle, the junctions need hot & cold to work, and they produce electricity. The power needed to run a cooling pump, is more than the array can generally produce. If you could float an array in a lake, that's a start.

niel · June 2008

Re: Peltier cells and their solar electric applications.

i am in total agreement with mike on this as they need a large differential and many peltiers to produce a modest amount of power. i had the thought of a small supplemental power source in the winter by tapping the furnace's output in the chimney waste heat and piped to the outside through the peltiers. this may help with some of the losses experienced with less sun being available in the winter.

BB. · June 2008

Re: Peltier cells and their solar electric applications.

Here is a thread on Peltier cells here:

http://forum.solar-electric.com/showthread.php?t=1677

-Bill

Roderick · June 2008

Re: Peltier cells and their solar electric applications.

From the Wikipedia article on Peltier that I read, my impression was that they are inefficient as coolers, being only 10% or so the efficiency of a regular compression-driven refrigerator. Their main uses are for cases where the cooling must fit in a very small space (CPU cooler, for example), or high reliability at the cost of efficiency is needed (cooling satellite electronics). They also have application where fairly low temperature is needed. Peltier coolers seem to be rated for about a 70 degree C differential across their surfaces, or maybe 110 C when stacked.

My impression is that Peltiers are similarly inefficient at converting a temperature differential into power.

On the topic of solar applications, I had dreams of building a Peltier water condenser for a cabin on a lava flow. It's illegal to use groundwater in Ocean View, Hawaii, and the only alternatives are catching rainwater, or paying a truck to deliver water. But I was thinking, for a vacation cabin, one could condense their own water out of the humid air for 330 days a year, and fill a tank. Even if it's only a gallon or two a day, that would be enough to supply a few weeks' vacation visit. The condenser would run off solar panels, of course, and when visiting for vacation, one would switch the electricity over to power the laptop, radio, or whatever. The reason for using Peltier in the condenser was to get extreme unattended reliability. I scrapped the idea when I found out how cheap and efficient commercial dehumidifiers are. Someone could let an off-the-shelf dehumidfier generate water for the away time, and if when they come back to the cabin, the water tank is empty, they could always call the water truck.

mike95490 · June 2008