Thread: Solar power
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Old 03-29-2019, 11:54 PM   #1 (permalink)
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Solar power

Mainly photo electric but thermal solar is alright too.

To get it started how about the myth of:
"A solar panel will never make more energy than it took to create it".
Fine, but I don't believe it. So a 220 watt panel could produce 1kwh per day for at least 20 years. That adds up to something like 7 megawatt hours. I dont think a little 220w panel takes any where near 7 megawatt hours.
My prediction is it takes way less than 1 mega watt hours.

I searched around some didn't find real clear guidance but I found something saying it take about 40kwh to make a 200 to 250 watt panel. That sounds pretty fantastic. I would like it to be true but find it hard to believe.

I found a 240w mono panel on ebay that measures 65x39 inches.

We will say worst case scenario no green washing. Panels made from all new materials.

The most energy intense part of the solar panel is probably the glass it's the bulk of the mass and energy intensive to produce. So start there. After looking around for a while I found some info on glass saying that it takes around 5 to 10 kwh per Kg of glass from new materials. Complex shapes take the most energy. Flat glass takes a lot less.
Even though a large portion of glass is recycled (more than a third) it all started as sand.

We will say the panel has 1/8 inch thick glass where I am you want at least eighth inch thick glass because of hail, and we want them to last 25 to 30 years right?. So 65 x 39 x 0.125 is 161 cubic inches or about 30lb or 13kg depending on if you self identify as imperial or metric.
The 240w panel on ebay weighs 42lb. I suspect most of its mass is glass. 30 of 42lb seems plausible.

So 13kg of flat glass lets say it takes 5kwh per kg. That's a lot more than 40kwh. But no where near 7Mwh.
Just the glass can we say it's 65kwh?

Next the aluminum frame.
Ok aluminum is insane I was way off when I thought the glass was the most energy intense part of the solar panel. 72 kwh per kg to make virgin aluminum.
Can someone help me figure out how much aluminum is in a typical 200 to 250 watt panel? I'm coming up empty.
I'm thinking its only 2 or 3 kg.

I haven't even tried to figure out how much it takes to make the cells. The process that makes mono cells is very weird and very energy intensive. Google it.

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