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Solar energy projects?

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Solar energy projects?

Postby loraksus » Oct 1st, 2008, 9:40 pm

So I have these big magnifying glasses (plastic fresnel lenses). By big I mean about 1 meter squared.
When focused, they have a lot of potential - and are a bit dangerous - I've melted pennies, burned my shoe, nuked my eyes (before I bought welding goggles), etc, etc. I saw an estimate somewhere that the Sun during summer noon puts out about 1700 watts per square meter, and these lenses can focus that down into about 3 cm squared.
I also have a few large glass lenses which can be used to further focus the beam (and not melt). And some mirrors, etc.

Anyways, I lack motivation in doing something with them. If anyone is interested and wants to do some sort of project, let me know.
It would be cool to get several of these lenses together and combine the output onto 1 point, but I haven't been able to find anything reflective enough that doesn't melt.
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Re: Solar energy projects?

Postby NoOne » Oct 1st, 2008, 10:03 pm

i have been kicking around a few ideas for sometime. mostly heat generation in winter.
those lenses are very interesting. what did they come from. some kind lighting fixture / unit?
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Re: Solar energy projects?

Postby loraksus » Oct 1st, 2008, 11:00 pm

NoOne wrote:i have been kicking around a few ideas for sometime. mostly heat generation in winter.
those lenses are very interesting. what did they come from. some kind lighting fixture / unit?


From rear projection TVs. Plenty of people wanting to get rid of theirs now and get a plasma or something. Fairly simple to extract the fresnel lenses (and the mirrors too - some mirrors are mylar stretched over a frame, some are really high quality glass)
I have something like 20 panels and I have a source for more.
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Re: Solar energy projects?

Postby NoOne » Oct 2nd, 2008, 12:25 am

I know the type of tv you mean. I have removed some of the lenses (3 barrel crt type) from RGB projectors. used to work on them way back when.
also had a 8" glass lens from a overhead projector from the 1950's. the lens alone weighed a good ten pounds (glass). liked to pull it out (the lens) when we went camping or at a BBQ. always surprised the kids and some adults on how fast you can heat up water in a metal. cup with sun.
my ideas revolve on heat collection/storage from the sun. trying to heat a wall of black fire brick as a storage device for overnight heating. focusing the sun would work better but could not get around the cost of lenses.

your source floods my mind with new ideas. like a solar light bulb went on....



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Re: Solar energy projects?

Postby BoB76 » Oct 2nd, 2008, 12:48 am

Have you guys looked into getting solar panels and some batteries?
You can't fix stupid........BUT you can dress them up and over pay them to teach your kids!
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Re: Solar energy projects?

Postby NoOne » Oct 2nd, 2008, 1:02 am

BoB76 wrote:Have you guys looked into getting solar panels and some batteries?


great idea for electricity but not for heat. i am working on a winter greenhouse for year round veggies.
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Re: Solar energy projects?

Postby BoB76 » Oct 2nd, 2008, 1:09 am

Can't you convert solar energy into power so that you can turn on a heater? I learned that in Grade 2 or 3 if I remember correctly.

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Re: Solar energy projects?

Postby NoOne » Oct 2nd, 2008, 2:24 am

BoB76 wrote:Can't you convert solar energy into power so that you can turn on a heater? I learned that in Grade 2 or 3 if I remember correctly.


efficiently, no

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Re: Solar energy projects?

Postby loraksus » Oct 2nd, 2008, 11:31 am

NoOne wrote:
BoB76 wrote:Can't you convert solar energy into power so that you can turn on a heater? I learned that in Grade 2 or 3 if I remember correctly.

efficiently, no
NoOne


IIRC, the conversion from solar to electricity stored in batteries w/ solar panels eats something like 92% of the input. Efficiency the other way isn't a problem ;)

For something like a greenhouse, I think a relatively small amount of water should work, especially if you insulate the storage tanks to stop loss to the ground, etc. I'm not sure what size you're thinking of, but I'm wondering if it would scale - have a few drums of water being heated during the day, possibly some sort of heat release system (tubing?) at night?

On a side note, I have roughly 100 pounds of lithium ion laptop batteries. Plenty of storage potential there ;)
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Re: Solar energy projects?

Postby Born_again » Oct 2nd, 2008, 12:47 pm

A European manufacturer(backed by a university) has now cracked the 37% efficiency level for a solar cell. This has been reported within the last week, but I can't find the article again. I'll try and dig it out.
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Re: Solar energy projects?

Postby Born_again » Oct 2nd, 2008, 1:08 pm

A solar cell developed by Boeing-Spectrolab has achieved a world-record conversion efficiency of 40.7%.

The 37% efficient cells are now in production and are economically viable, if memory serves.
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Re: Solar energy projects?

Postby loraksus » Oct 2nd, 2008, 1:11 pm

Born_again wrote:A European manufacturer(backed by a university) has now cracked the 37% efficiency level for a solar cell. This has been reported within the last week, but I can't find the article again. I'll try and dig it out.


I was also talking about losses due to the voltage regulator, the charging system, etc, but yes, they are getting much better nowadays ;)
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Re: Solar energy projects?

Postby NoOne » Oct 2nd, 2008, 1:32 pm

a report i have on a test greenhouse in Manitoba reported that they achieved a internal temp of +27 C with an outside temp of -29 C using only passive solar heating an earthen wall. i am looking at a similar design, maybe 20' by 30'.

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Re: Solar energy projects?

Postby loraksus » Oct 3rd, 2008, 5:37 pm

Found this today. Will probably have to wait until next year, but I think I'm going to try it. I got a few mylar blankets a while ago from... somewhere for about a buck each.
http://www.homegrownevolution.com/2008/ ... rator.html
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Re: Solar energy projects?

Postby NoOne » Oct 3rd, 2008, 9:36 pm

loraksus wrote:Found this today. Will probably have to wait until next year, but I think I'm going to try it. I got a few mylar blankets a while ago from... somewhere for about a buck each.
http://www.homegrownevolution.com/2008/ ... rator.html


i might follow you on this one. the wife is into canning and pickling so this would be my secret side project. seems pretty straight forward. can see it being able to dry a lot with a tall tower.
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