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oil pan 4 03-29-2019 11:54 PM

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.

RedDevil 03-30-2019 04:11 AM

Some analysis and adjacent stuff. I haven't read all.

Off hand it wouldn't cost more energy to produce a panel than you could buy for the price of the panel. Though subsidies could play a part there are also profits, wages, taxes and equipment costs. Net energy needed should be less than the cost stands for.

aerohead 03-30-2019 01:42 PM

Manufacturing $$$$$$$$$$$
I peeked over at GOOGLE and saw a number of solar societies and associations which may be able to provide some of this data.I'll look when I can.I'm very interested myself.
I suspect that the US Commerce Dept. also knows,to the penny,what manufacturers pay for facilities,administration,materials,labor,energy,c apital,fixed-costs,marketing, and each phase of fabrication etc..

oil pan 4 03-30-2019 02:06 PM

That guy in NH is assuming an average amount of CO2 per unit of cost. That maybe gives you an idea of how much plant food is produced when building a panel. I want an actual number in KwH. The energy that made the aluminum portion of the panel is likely the biggest energy hog but aluminum smelting is usually done with very cheap nearly carbon free electricity most of the time. The glass portions energy is usually made with very cheap natural gas.
So the unit cost per CO2 only works with maybe like an entire industrial sector, not individual products.

I already figured out how much energy it takes to make glass and aluminum.
It's pretty easy to figure out precisely how much glass they use per panel. The Aluminum is more of a smash and weigh it kind of thing. Just need to know how much they use with out smashing one of my panels.

The exact unit cost is a trade secret in some manufacturing industries. One is tires, only the top 5 or 10 people in the company know exactly what it costs to make the tires.

For the cost of a panel I could buy around 1 mega watt hours of propane or like 6 mega watt hours of bagged high grade anthracite coal.
Problem is I don't have an efficient way to turn coal or propane into electricity.

My main motivations for solar panels are to actually be able to own some of my own power generation and profit.
Like all these people who bought into solar and are looking at like 9 to 20 year pay backs, haha suckers.
I'm looking at like a 2.5 to 4 year pay back. Used panels from AZ, constructing my own racking system, laying conduit, doing every bit of wiring that I'm allowed to do my self.
I would like to keep installing solar until it's no longer profitable.
I'm thinking that means up to a 12kw single phase 240v system.
Beyond that I would have to get my 3 phase 480v transformer hooked back up. Then I would be good for like another 50kw.

oil pan 4 03-30-2019 05:24 PM

Alright I found extrusion specs for a 130mph rated panel frame.
The thin cross section is equal to a 100x1mm flat aluminum strip and a second heavier part would make a 13.6x2mm flat bit.
So the cross section is 127 square mm. That would be like a solid 11.2mm square rod running around the panel, just to give you an idea what that aluminum would look like all compacted together.

So a 250 watt panel would have about 6 liner meters of edges to protect.
That's 762 cc of aluminum.
The density of aluminum is 2.7 g/cm.
That equals 2,050g.
I believe I said that I thought a 250w panel had 2 to 3 kg of aluminum in the frame.

So let's say a 250w panel has a frame weighing 2kg.

Now we can say a 250 watt panel takes about 300kwh to make the glass and aluminum. I still think that's pretty good and is no where near what the panel will make over its life time.

That leaves the solar cells. It looks like mono are very energy intensive but CdTe thin film use a lot less energy to make.
Apparently thin film is where it's at for utility installs, residential installs tend to use mono.

I have almost unlimited space so I don't have to use high $ mono when I install panels.

jjackstone 03-31-2019 12:04 AM

I've read a bit about this issue. Generally the non-return on energy is just another fossil fuel ruse to try to keep people from buying solar. From what I can gather there was a time when it may have cost nearly as much energy to build a panel or module as it ever returned. However in the last ten years with the increase in panel efficiencies, improved manufacturing methods and higher volume the energy costs have decreased dramatically.
Here's a link to more recent data that suggests an energy payback of one to four years.


The graph is on that page too.


sendler 03-31-2019 06:59 AM

One further consideration to keep in mind 2-3 decades down the road, can solar panels (and giant wind turbines) be mined, refined, manufactured, and installed, without fossil fuels? Which they are currently completely reliant on every step of the way.

oil pan 4 03-31-2019 07:48 AM

The amount of energy that it takes to make glass and aluminum hasn't changed much. That part of the solar panel isn't going to change, where you are basically making an aluminum framed window that doesn't open.
It doesn't appear that solar panels will beget solar panels aany time in the foreseeable future and when they do it sure as heck will cost a lot more than one fiat greenback per watt.

California98Civic 03-31-2019 10:41 AM

Several years ago I volunteered with a nonprofit in Los Angeles that installed solar panels on low-income homeowners' roofs. It was part of a state project in distributed solar power generation. I worked on three or four installs, most of them single day some of them today projects.

It seemed to me as if the primary costs, in retail terms not ROI calculations, were the labor and extra fees that install companies add on to the costs for their own profit. The install itself is not very complicated: anchoring the rails for mounting the panels properly and securing the panels and inverter modules to the rails. Both grounding and wiring was taken care easily through Plug and Play Type connectors. It somewhat more complicated and a bit more necessary to get a professional electrician once you want a tie into the grid. The overall simplicity of the install was improving during the two summers and which I volunteered. it's possible that it's even simpler now.

It's just not that hard. Your expectation of a return on investment within a handful of years seems entirely reasonable given that you're going to do almost all the work yourself, especially if you are buying second-hand panels.

Why a 50 kilowatt hour setup? I mean, one way to drive up your costs would certainly be to overbuild and therefore buy too much hardware that you don't really need. I would imagine 50 kwh is maybe because of the electric vehicles you're planning?

oil pan 4 03-31-2019 11:50 AM

The local electric coop limits residential peak grid feed back to about 12kw. I can install more than 12kw of panels if some face east and west but I would rather not.
To install more capacity I would have to go with a 480v setup. No one has done this on the coop so there is no president. So I have no idea how much it would cost. If they hook the transformers back up and don't charge any money good, because I already have a 480v 3 phase transformers on a pole and wires ran to a pump house at aren't being used.

But when I drop down to getting paid generation rate the pay back goes out to at least 10 years. I would probably have to put them on single axis trackers.
I sent my single axis tracker design to my mechanical engineer and he says it looks good, too over built in his opinion. But the trackers are designed to survive a tornado. The panels will be shredded, just add new panels.

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