Monday, December 27, 2010

The gift of power

Power to the people!

No, wait.

Free power!  Yeah, that's the ticket.

Clean, free power from the sun!

Well, no, not quite.

First: clean.  Manufacturing silicon from silicon dioxide (quartz) consumes about 12 megawatt hours per ton of raw silicon produced.  Yeah, that's *mega*watt hours.  Then, the raw silicon must be refined to get rid of impurities - an exotic chemical process followed in the end with an energy-intensive electrolytic process for recovering the metallic silicon.  In all, about 200 megawatt hours is consumed in the production of a ton of silicon solar cells.  That's a lot of power - power which must be generated somewhere.

Next: free.  In the recent past, solar panels have sold for about $10/watt - that is, a panel with a rated capacity of 100 watts (in the tropics, at noon) would cost about $1000.  That's hardly free power.  If you work out the numbers, at our local power cost of $0.08/kwh, that 100 watt panel would be paid off in 85 years.

But something has been happening in the solar cell marketplace recently.  Solar panels can now be found for under $2/watt (17 year payback), and the bare cells are available for amazingly low prices.  And so just before Christmas, I bought a kilowatt's worth of solar cells and paid an amazing $350 for them - that's $0.35/watt - a payback period of only 3 years.  Those are numbers I can live with!

An early Christmas present!
The actual purchase was 250 cells, each of which is 6" x 6", and will deliver 8 amps at 0.5 - 0.6 volts.  They arrived in 4 boxes and were well protected with packing materials.

Here are a couple of the cells, showing front and back.  They are incredibly thin and fragile.  That ton of silicon mentioned above made a *lot* of these cells.

Now to actually construct the panels in a way that will last, the challenge will be to keep the cost from climbing back to that $2/watt for which commercial panels can be had.

Stay tuned.
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12 comments:

Everyone's Travel Club said...

Where did you get them? Online retailer? New?

Thanks!
-Paul

John Sipkens said...

So Why is the government giving tax credits to go solar?

Erick said...

Excited to see updates on this project. I will be going solar on Windsong, great to hear the prices are quite reasonable these days.

bob said...

Paul -

I bought them on eBay. Yes, they are new (they are so fragile that there is no way they could have been removed from anything). Of course, the lot that I bought is gone, but there are more.

bob

bob said...

John -

I don't know.

I doubt that the credits would apply to a DIY panel anyway.

bob

bob said...

Erick -

I have even seen panels for under $2/watt. Watch eBay...

bob

Drew Frye said...

I will be watching and waiting! I like the idea of creating a custom shape, as well.

If it were me, I would consider making up one 6x6 test frame (any voltage--it's just a test) and leaving it outside, connected to a minor load for 3 months, just to test my methods.

Good luck!

SV Estrellita 5.10b said...

WOW!

audeojude said...

I have purchased two 205 watt solar panels and a 60 amp MPPT charger for Valkyr. I think I paid 1.70 a watt from http://sunelec.com

Wow.. I just checked the website to make sure of my web address and they have some 80 to 100 watt high voltage panels for as low as 1.19 per watt. You would have to use a MPPT controller capable of handling the voltage but it will give you really great efficiencies on charging.

bob said...

Wow. :^( Now I have an even lower target to shoot for with my homebuilt panel. $1.19/watt is going to be hard to hit, when the Sylgard 184 costs about $45 for enough to do approx 100 watt panel... that's $0.45/watt for Sylgard, and $0.35/watt for the solar cells. The Sylgard is actually more than the cells!

audeojude said...

I'm now wondering if it would be worth while to pick up the other solar panels I was wanting to get.. only problem is that the ones I already have are 24 VOC and these are 70+VOC to 124VOC models. Which would mean I would have to purchase a second MPPT controller.. so 250 to 600 more dollars for that.

lol.. its always a compromise in design.

audeojude said...

Your a brave soul Bob... I have seen the cells like you got.. and thought about doing that. It actually looks like fun if you had the time to mess with it.
however I really like the factory sealed panels... Especially for a boat environment.
scott

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