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HMV 1120 19th Apr 2007 5:01 pm

I've gone green!
Okay, so it's not quite radio related, but it is electrical. Meet the worlds most in-efficent solar cell! Maximum output acheived so far is a whopping 0.94 Volts, DC.

This slightly unusual project has been 'stewing' for a little while, and yesterday finally got put together. The 'cell' is contained in an old lemonade bottle, with the top removed. Inside are two metal plates, one of copper and one of copper oxide. In between is electrolyte, water saturated with dissolved salt.

Now, apparently I am 'gifted and talented' at science. This doesn't really have any practical upshot, except that I get to use the science labs for an hour after school on a wednesday - but with supervision. We can do pretty much what we like, so long as it doesn't involve making lethal weapons or consists of a danger to life. To get a sheet of copper oxide, a sheet of pure copper was heated until cherry-red by a bunson burner. This is then allowed to cool, and the diffrent rates of cooling and contraction between the red and black copper oxides result in hot black copper pieces pinging several feet. Very entertaining to watch!
Now, there is some reason why this 'cell' produces power when exposed to sunlight, but i seriously can't remember. I also suspect that having the two diffrent metals in a salt water solution is creating a simple battery, as the voltage doesn't drop below 0.1V, even at night.

Anyway, to actually power anything off it, you'd probably need a window four miles long filled with them. I don't think its the answer to global warming just yet. But if you can think of something for it to power, drop us a line!

Sam 19th Apr 2007 8:27 pm

Re: I've gone green!
Congratulations. It is good that your Science Teacher allows you to play like this. Fortunately my Chemstry and Physics teachers would allow side-line experiments to go on at the end of the lessons with left over stuff or other things found in the cupboards. I learnt nearly as much in Chemistry doing this as we had to work out what may happen before we mixed the two things together! What year are you in? From what I remember GCSE Science could seem a bit dull at times, but A-Level stuff got interesting!

Try powering an LED. It may not light, but at least you will have tried! You can light them with a lemon, copper, and zinc, which I don't remember giving much oomph!

Keep up the experimenting. Unfortunately mine has lapsed :(.


JoshWard 19th Apr 2007 8:29 pm

Re: I've gone green!
Veyr interesting, If we used the labs at my school all the gangs would be waiting outside to beat us up afterwards... That's what things are like here :( . Still, nice to know other people can experiment happily :)

evingar 19th Apr 2007 8:52 pm

Re: I've gone green!
Great to see this type of thing, we also had some enlightened teachers that enouraged this at school - Time becomes an issue later on though, like Sam mine has largely laspsed :(


Veyr interesting, If we used the labs at my school all the gangs would be waiting outside to beat us up afterwards.
This is so depressing Josh, no wonder we have lost our engineering and science base ! >(( >(( :wall:

JoshWard 19th Apr 2007 9:10 pm

Re: I've gone green!
It's not that bad really yet but it's only a matter of time. I doubt we'd be able to use our labs for anything as the teachers aren't the most helpful at my school but it may change one day.

Paul Stenning 19th Apr 2007 9:55 pm

Re: I've gone green!

Originally Posted by Sam (Post 112822)
Try powering an LED. It may not light, but at least you will have tried! You can light them with a lemon, copper, and zinc, which I don't remember giving much oomph!

Two cells in series should give enough voltage for an LED.

muttley 19th Apr 2007 11:29 pm

Re: I've gone green!
Well done for trying! I am a science teacher and would like to get my students to try these things but all they are interested in is the van der Graff generator and any chemistry experiments that go "bang!". I am going to run a "gifted and talented" club from September.

Today I was teaching year 7 (11-12 year olds) about cells and batteries. i demonstrated by showing an old vidor portable radio and connected 10 9V batteries in series for the HT battery and it worked! they were amazed at the 50 year old radio and asked several questions about how the valves worked and why it needed such a high voltage. I hope I got 1 or 2 interested!


HMV 1120 20th Apr 2007 4:03 pm

Re: I've gone green!
Thanks for the response! I am 15, hence in year 10, with GCSE's underway. These tend to take up a lot of time, so I don't always have clear evenings to fiddle with the radio sets, but once they are out the way I plan to get hold of another 'project' to celebrate! I did find yesterday a 1930's battery portable radio set in a 'junk' shop. Built into a black leather suitcase. Its a bit pricey at the moment, so i'll keep an eye on it untill he decides to have a clear out... :D

Oh, and those wires in the corner of the shot - they're feedlines to various valve sets.

daviddeakin 27th Apr 2007 1:53 pm

Re: I've gone green!
You can get very low voltage capacitors in the range of several FARADS quite cheaply. Get one charging for a few days non-stop with your solar cell and you should find some amusing uses for it! A single-use, mini-welder if nothing else!

dave walsh 27th Apr 2007 3:42 pm

Re: I've gone green!
Maybe someone can put this up for HMV. Yesterday's Technology Guardian has an article on sugar powered batteries with a photo that reminded me of his laboratory endeavours. It's a biofuel cell that uses enzymes to get energy from sugar oxidisation. About .75v per cell apparently. Dave

HMV 1120 27th Apr 2007 7:48 pm

Re: I've gone green!
David - thanks! I'll look out for some and see what I can come up with. Another thought I had - would it be possible to use a simple Crystal Radio to trickle charge a small rechargable battery? Can this be done?

Dave - thanks for the comment. I'll ask my gran (Who reads gaurdian) To save me the paper out of the recycling bin. Thankyou!

Alf 28th Apr 2007 3:06 am

Re: I've gone green!
An interesting theory, I've heard of this before, or rather a similar idea. Some years ago, I read that a market garden, not sure where it was, was using power from a local tv or radio transmitter, which was located close by. An apparatus similar to a crystal set was designed, the audio/video content filtered out, the resulting dc voltage being used to power other appliances.

In practice, I think the Crystal Radio trickle charge could work, it'd only charge the battery with micro-amps though. Long time to charge up. :)

HMV 1120 28th Apr 2007 9:41 am

Re: I've gone green!
Perhaps I should build a tiny rechargable battery to go along the cell... Or perhaps I'd get more efficency from copper and zinc and half a lemon^^

The fun part is that it actually works rather than how well it works. That can be worked on.

adibrook 25th May 2007 11:05 pm

Re: I've gone green!
Wow, i did science at school once. I also did electronics. I remember i came up with a real complicated circuit, but got a bad mark because i forgot to write about the enviromental impacts of my circuit, and about my ''research''.

I also liked building stuff like this. I allways wanted to make a solar powered radio control boat. But never worked out somehow.

I remember in physics when i argued with the teacher alot over thigns which were incorrect, but taught to us anyway to simplify our education. I cant remember what it was now. G is DEFINETLY not 10 tho...its 9.8?

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