Non-PV Solar Power

Step 6 Notes

From my setup, my highest recorded voltage is exactly 2.7v. The internal resistance of the Peltier is ~3 ohms because at 7.5v input it draws ~2.5A. This means I could get 2.7/3 = .9A out, and 2.7*0.9 = 2.43W.
So, now I will figure out the cost for the average person to build it.
Heatsink = $5
Peltier = $5
Lens = $5
Fan = $5

Optional:
Solar Cells = $3

Total: $20-25

This is equal to right around $10/W, which is on par with the cost of commercial solar panels. Pretty good for an untested experiment. However, some disadvantages of this are:
-My enclosure is too flimsy to be held vertical so it can harvest power at the middle of the day
- Needs to be well aimed to be effective
-Large
-Less efficient than PV

Yeah, this technology probably isn't ready for prime time. But it is interesting and very fun/cheap to make.

One thing you might be wondering, is why is the power output so low?
Well, first of all, the wattage of a Peltier is not the power it will output. It is the power it will draw at it's rated voltage. Another thing, Peltiers are not designed to generate electricity. They are optimized to pump heat. To really take advantage of the energy available, you will want to get a Seebeck unit. These are the same thing, but optimized to generate. With a seebeck unit, power output would go up by many times. Same with price.
So, I will continue working to improve the output. There are a lot of things I can and will be trying. Make this project your own!

Here are ideas I had:

Use something like the LM2623, LM2371, Mintyboost circuit, or LVBoost to get this up to 5v to charge/power USB devices and Li batteries. You probably will have to parallel a couple of whatever you use to get full output and decent efficiency.

Use one of the projector-TV fresnels and focus it onto a 3-by-3 grid of Peltiers. Put them in series and no inefficient boost converter needed.

Build a solar tracker to harness the output all day.

Get sheet aluminum about 10" by 10", put peltier+heatsink in center, paint other side black, insulate it and put plexiglas over it and it will be a lot like PV.

Comments

[dlginstructables]

Nice job - I've been thinking of heating a peltier element with my solar oven to generate a little electricity, but haven't tried it yet.

[mankysteve]

Thermal electric have been around for ages in fact before photovoltaic there not as efficient as photovoltaic other wise every one wud be using these rather photovoltaic cells. Nice project though.

[AQUARIUMWAREHOUSE]

I am trying to add images.....so far it's been two minutes loading....How long is "this may take a while"???? Hmm, 20 minutes so far, maybe it is my computer or firewall?

[AQUARIUMWAREHOUSE]

2 years ago, I bought my 7th grade son 10 40 or 50 watt thermoelectric chips off ebay to use in his science fair project  and a 5watt solar panel. We were going to make portable or camping generators.  TE chips would be attached to a chunk of old aluminumg griddle, heated with a tin-can "refuge biogasifier stove", make E and cook at the same time.  He also made a Parabolic reflector from a $store mirror and mylar (not tested, but looks cool), and the cardboard packing box of the PV was wrapped inside with Mylar as a perfect concentrator with carrying case for travel.  That worked "good".  ATTACH THE TE CHIsP TO THE BACKS OF PV PANELS, use the mirrors or your fresnel lenses, and cooling PV panels is good for their performance and longevity.  Bill Thomas, Olympia, WA.

[BPHuntley]

Would blackening the "hot" side of the Peltier with a process such as anodizing or an ammonia reaction be better than painting, to avoid the insulating effect?

[bananafred]

Yes it probably would, but that sounds pretty complicated and might have bad side effects. I think the insulating effect of the paint is minimal compared to the heat gains it gives.

[robmeofmyboredom]

I cant believe you even got the fan moving! one observation ive made about pelts is that you really need a good heatsink. i think if you could make a heatsink submerged in water and getting the unit isolated from hot air then maybe output could increase as the difference will be higher. cool project nice work.

[mpikas]

A water submerged heatshink is very effective, but you'll always get some evaporation and most of these elemements are not sealed to deal with water getting into them.  I've gotten away with making the heat sink with a big flat area with a seal which prevented the water from even getting to the other side of the water tank.

[MoleMans]

Great work. There's nothing new under the sun, most people just think and never do. Do you happen to know what kind of temperatures you were getting? I have been playing around with a similar set up and trying to get it to track. I'll post my progress when I get something that works (crosses fingers). It still seems like there are inherent efficiency issues with peltiers, but every little bit counts.

[bananafred]

Yeah... I never tried recording the temperature. I suppose a meat thermometer might work for the hot side.

[aldefork]

Great project, I always thought this could work and you did it. Two suggestions for improvement:
i) Peltiers work by utilising temperature differential which means this would work better in winter or with improved cooling.
ii) paint it black to absorb heat - silver reflects!
Great project, good luck.

[mpikas]

Yes, in theory black absorbs and radiates infrared better than lighter colors, but in practice, you're not only dealing with infrared but convection also, and second, with paint you're putting an insulating coating on it and it hurts as much as the color helps.

You might be able to get around this by choosing materials that are actually the color you need, annodizing black, or by looking into coatings specifically designed for heat exchangers (there are specific radiator paints... I'm not sure if they're actually any better).

Otherwise you're probably hurting more than helping with the black paint.

[brokengun]

I think your estimate for commercial photovoltaic panels is a bit high. Perhaps once they are all installed and stuff that is what it figures out to be, but just looking on harbor freight they are quite a bit cheaper than that.