Another thermoelectric solar cell

[Ruud]

Earlier this year I tried to use a solar box cooker as a seebeck generator. That didn't quite work out. Okay, it totally failed. User DaveW suggested I'd use a solar concentrator instead.

Last week I aimed a solar concentrator at the same peltier I used for the previous experiment. Here's the story and some pictures.

These are the copper plates that hold the peltier. The cold side has larger holes, so the bolts from the hot side will not be in direct contact with the cold side

A piece of CPU heat sink. This would later prove to be insufficient.

This plywood disk is supposed to limit the heat that is radiated from the hot plate to the cold one.

Three more pictures of the uhm, thingy. I tested this over a spirit flame. Turned out that the cooling sucked. The heat sink became really hot and power output was near zero.

Damn, I damaged the Peltier. Hope that won't mess up the results too much.

I added four bolts with some rings, nuts and aluminum tube as extra heat sinks. They worked really great. The hot side would be really really hot while the cold side could still be touched.

Testing the solar cell. The concentrator is a 75cm diameter satellite dish with 145 50x50 mm mirrors. The peltier was hooked up to a small electro motor with fan, to provide some extra cooling. In the video it looks as if it is rotating very slowly to the left, where it's actually spinning really fast to the right. Power output was about 0,12 watt. Still not very useful, but at least it was a 1600% improvement over the SBC version.

Testing the concentrator. The sunlight instantly burns a large hole in a cardboard box.

As soon as I find an affordable peltier with some more power, I'll give it another go.

[dinges]

As a fellow Dutchman, I'll grab the opportunity & be the first to respond

Interesting experiment. Am not surprized at the outcome, limited power, but you've definitely thought some things over. BTW, that parabolic antenna has an area of about .7-.8 m^2; at an insolation of, say, 1000W/m^2, you are concentrating about 700W (perhaps more like 500W in this season) at the focal point... 0.12W electrical output is little, when you look at it that way. All the rest ís 'waste' heat.

However, such a parabole WILL be useful for future experiments. Boiling water, for example. I wouldn't put a PV panel in it, it may put out a lot of power but only very briefly

I still hope to scrounge a parabolic antenna some day. I intend to cover it with reflective mylar strips, glued on and weatherprotected by epoxy (if the epoxy doesn't dissolve the mylar). Glueing on dozens of tiny mirrors (where you got these, BTW? Cut yourself?) is not my idea of fun. And looks a bit, ehm, 'homemade'

I doubt another Peltier would improve matters much though. They have notoriously low efficiency, even more so when driven backwards (as an electricity generator).

Try putting a kettle of water in the focal point. It should boil soon enough, with about 700W of energy heating it up. I suppose I don't have to warn you to NEVER put one's head in the focal point, let alone your eye.

It's an interesting story to read by all accounts! Backed up by actual measurements.

[Norm]

Make a hot air engine with the focal point on the

hot side hooked up to a good small stepper motor

 as a generator and note how much more output

you'll get....your project shows that a peltier

is probably the wrong way to go to make any

meaningful electricity....but interesting...

nonetheless...really like your concentrator....

just slightly out of the focal point would make

some toast rather efficiently and quickly!

              ( :>) Norm

[wooferhound]

It might be better to use Thermopiles which are groups of thermocouples in a single package. I had thought of trying your exact idea using a thermocouple and did a little bit of research . . .

http://www.thermonamic.com/Pspec.html

http://www.varmaraf.is/engl/prod.htm

http://www.powerchips.gi/

http://www.dts-generator.com/

http://www.hi-z.com/

http://www.remote-site.com/thermo.html

and for dinges.

do a search on Mirror Tiles

lots of sizes available

http://www.google.com/search?q=mirror+tiles&sourceid=mozilla-search&start=0&start=0&
ie=utf-8&oe=utf-8&client=firefox-a&rls=org.mozilla:en-US:official

[ghurd]

Some Peltiers are designed to generate power instead of move heat.

It's a huge jump in efficiency (25% increase over the standard type?), but still really bad.  And they are not available surplus, so they were Crazy Expensive.

G-

[powerbuoy]

I also recommend to try a stirling engine ... a couple good books on the low temp stirling were written by James Senft .

Even a miniature stirling that can be bought as a kit will probably give you more then .12 watts if coupled with your concentrator.

Powerbuoy

[powerbuoy]

Please follow this link

http://www.bekkoame.ne.jp/~khirata/

maybe you'll decide to build and try one ...

Powerbuoy

[coldspot]

Very nice work !

I now, (thanks to you, lol), have plan

number, (somewhere around millions), to build.

I'd think a solar still would be easy using a

solar concentrator.

Water made potable easly and quickly!

Thanks

PS: knowing me, like I do! LOL

I'll add a steam turbine with a stepper just to

do things the hard way like I do. Hey, this power could run the pumping for the water into and out of the whole system,..........

Off I go again...

[Ruud]

Thanks for your comments. I realize Peltiers have a lousy efficiency, but I really don't care much about efficiency. It's purely a dollars to watts matter. If I can get a peltier to deliver the same amount of watts as a PV cell for less money, then it doesn't matter that efficiency is low. It's not like anyone will charge me for the amount of wasted sunlight.

As for the dish, I know it looks ugly, but for now it was the easiest way of making a concentrator. I cut the tiles myself from larger mirrors. Each tile has a magnet glued to it, so I can vary the number of mirrors used.

[Frank Lussier]

Hi Ruud

Love your project, you need sommeting like this

image 1

image 2

I've been working on this project for the past 3 week it's for hot water heating, and the results are phenominal. I heated a bucket of water ( 5 gallons or 20litre) in less than 1H to 100.9F and the water i used was freezing cold,(i did not have a totally sunny day to work with - it was cloudy on and off) the receiver gets close to 1200F - i should get the correct temperature in a week or two when i receive my temperature controller from ebay ($25.00 USD) I used Mylar and super 77 from 3M (glue) to glue the Mylar(don't look at the wrinkles - it was done during a windy day with my 13yr old son - not easy..My son Eric was an incredible helper..i could not of done this without him..thanks buddy!).  p.s. the website is not totally updated but it should be up to date by next week.  You will see when i put a piece of wood infront of the receiver it burst on fire in 4 seconds...pretty awesome power.

You can look at my site

junkyardsolar.com

Frank

[dinges]

Ah. So, glueing the Mylar does work! Interesting. I had never seen this done before, I think I thought up of the glueing Mylar on myself. Still. Good to see that it has been already done and works. Looks very nice too. You didn't protect the Mylar with an additional coating of epoxy or something, to make it better weatherproof?

Just had a look at your website. I love it. Guess that 10ft parabolic antenna is a grown-ups looking-glass for igniting things...

a 10ft parabolic dish... I want one too... I'm wondering... I've got access to a 7.5m parabol dish, steerable (old German Würzburg Riese Radar set, ex WWII). 44m^2 area, at 1000W/m^2 equals 44kW. I'd better go buy some extra rolls of Mylar

[Frank Lussier]

i didn't protect the mylar because it's just a test - and it's amazing that it works!  and hopefully it will last.  I will mostlikely put epoxy or something to weatherproof it.  The dish was free - someone absolutely wanted it out of their yard - all i had to do was take it apart and drive home with it..that was a sight..(quite redneck)  my wife is not too impressed as now i have two huge dishes ( a couple more are coming....now that's redneck) no offence to anyone..

my next task is to run the plumbing.  The receiver is a car heater core radiator.  It is made out of aluminium.  The way i was pumping water it was enough to cool the car heater core down.  You should see the smoke coming out of it before i get the pump going lol...

Do not use pyrex cooking dish to put infront of the receiver...believe me doesn't work...it makes a huge bang when it explodes and hits the dish!!! there was glass everywhere...ofcourse the cats and dog have to investigate so i had to run out before them and pick it all up...thinking up of a good excuse to tell the wife about her dish lol...  

next step - radiator made out of metal

im happy you like my site...it's a work in progess and i love it - my wife came up with the name junkyard solar - she says it reflects our backyard and this project cost me under $300.00 CND.  pretty good for free hot water!!

Frank

[Ruud]

Wow, that dish looks great Frank. Unfortunately I have no room for such a monster.