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Solar payback
By brkwind2, Section Solar Posted on Sat Mar 28, 2009 at 04:33:53 AM MST
Someone should have told me

http://www.otherpower.com/otherpower_solar_new.html
A while back I put forward the theory that solar panels won't produce enough electricity to make up for what it took energy wise to make them. My post got buried because the mod said we don't want to discourage anybody. True, however I wish someone had pointed me to this link earlier. I might have bought solar panels sooner than I did. I couldn't resist so did it anyway. Glad I ran accross this info. in the link. Now I feel better. Hopefully this will help dispell that myth & others will be encourged to try out a few panels.

Solar payback | 15 comments (15 topical)

Re: Solar payback (3.00 / 0) (#1)
by wooferhound on Sat Mar 28, 2009 at 01:38:10 AM MST

I have 80 watts of panels or about 6 amps charging to the battery. Using the power efficiently running 12 volt items, it seems that I get unlimited power with a 225 amphour battery. It's a really big battery for the size of the panels that I'm using. If I plan on cloudy days by watching the Weather Channel, I can get 10 days of power, But then it takes 4 days of full Sun to fully recharge my battery while still minimizing my loads.

It really is Fun . . .
http://www.fieldlines.com/story/2009/3/18/232910/066

W o o f -={(

Re: Solar payback (3.00 / 0) (#2)
by bzrqmy on Sat Mar 28, 2009 at 04:41:02 PM MST

Woof,

What do you really get out of those HF panels? Best I can get is about 30 Watts. I have checked to see if one is dead, but all three appear to be working. On a good day, I can get just over 2 amps into my bank.

[ Parent ]

Re: Solar payback (3.00 / 0) (#7)
by s4w2099 on Mon Mar 30, 2009 at 11:18:05 AM MST

I have a few also. I have noticed they like to be VERY cold. When they are hot they become complete garbage as sometimes their voltage goes down to ~14 or so volts per panel. Also they like to be pointed to the sun very accurately.

[ Parent ]

Re: Solar payback (3.00 / 0) (#3)
by dnix71 on Sat Mar 28, 2009 at 07:14:44 PM MST

HF panels work well in cold weather. They were probably rated for 70F or so.
If you get 30 watts out then you've done well.

Re: Solar payback (3.00 / 0) (#4)
by Ungrounded Lightning Rod on Sun Mar 29, 2009 at 01:17:13 AM MST

There's more to it than that, as well. Comparing the energy used to make the panels vs. the energy delivered and complaining if the latter is less (even if it were, which it isn't) is bogus. The target is to deliver a certain amount of electrical power to a particular site. To make an apples-to-apples comparison you have to compare the energy cost of doing that with solar panels to what it replaces - grid power.

The energy cost of delivering grid power includes cutting trees and processing them into poles. Smelting, forming, manufacturing, and delivering generators, transformers, wires, insulators, electrical boxes, a meter, switches and breakers, etc. Clearing (and using indefinitely) land for the run of poles. Transporting the workers and equipment to and from the construction site and running the equipment while there. And so on.

Then there's the ongoing energy cost of generating and transporting the power to be delivered. You typically start with fuel and burn it in a big stationary heat engine, paying the carnot cycle penalty - plus more because no heat engine is perfect. Then you transport the power, losing it to resistance in the wires, hysteresis and eddy currents in the transformers, corona and insulator arcing, etc.

THAT'S what you have to beat when you consider the energy cost of your solar instalation. Even including the energy that goes into building the inverter and batteries and installing the array it's a slam-dunk.

Can you IMAGINE the same fools who started the "energy breakeven" meme demanding the power grid be shut down because it consumes more energy than it delivers? B-) (I can. They ARE scientifically-illiteratre eco-wackos.)

Now if somebody were silly enough to try to build photovoltaic solar panels using ONLY energy from other photovoltaic solar panels (not even solar concentrators for raw heat but getting that fromn solar-powered resistive heaters), comparing manufacturing energy input to delivered energy would make sense.

Re: Solar payback (3.00 / 0) (#5)
by TomW on Sun Mar 29, 2009 at 07:16:56 AM MST

ULR;

Nicely stated.

It is about time to put that old wives tale [solar panels taking more energy to make than they ever produce] to rest. It simply is NOT TRUE.

Just the facts, please.

Tom

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it

[ Parent ]

Re: Solar payback (3.00 / 0) (#8)
by imsmooth on Mon Mar 30, 2009 at 11:54:03 AM MST

I agree. One also has to consider that solar produces no carbon emissions compared with fossil fuels. This may not seem significant now, but if the bulk of our energy was derived in this manner, multiplied by 100's of thousands of people, one would see an enviromental impact, for which there is no price tag.
Jonathan
[ Parent ]

Re: Solar payback (3.00 / 0) (#9)
by brkwind2 on Mon Mar 30, 2009 at 03:48:47 PM MST

Thanks, those are some good points. People need jobs too so even if it was break even as far as what energy went into them as opposed to what came out of the solar panel, it would be better to have someone working on solar than on a coal fired plant. I heard that theory about solar not being practical a long time ago & just accepted it. Maybe it was true in the begginning & not so much now.
Shine on.
Happy trails
"I get along with all people despite their shortcomings of race, religion or orientation. So long as they recognize my superiority we'll get along fine." "O
[ Parent ]

Re: Solar payback (3.00 / 0) (#10)
by Ungrounded Lightning Rod on Mon Mar 30, 2009 at 09:06:33 PM MST

Not being "practical" is a whole different can of worms.

You need to compare the cost of getting your power from the grid with the cost of getting it from the panels.

If it weren't for governmental distortions of the market you could do it like this:

- Size the array (and aux equipment) to handle your expected load.
- Price it.
- Price a mortgage to pay for it (as an upgrade to your property), paid off over the expected lifteime.
- Add to the mortgage the average price for maintenance (big ticket item: Saving up to pay for periodically replacing the storage batteries.)
- Compare the monthly mortgage payments to paying for grid power.

If the (hypothetical) mortgage comes in cheaper than the grid, you're past financial breakeven. (You can probably actually GET the mortgage if you want - or at least a home-improvement loan at a somewhat higher rate - redo the calculations. But you'll probably be ahead to invest your money in the array than to deposit it in a CD or play the investment market.)

For locations where the grid is already installed the grid generally comes out cheaper for a household load. Solar comes in ahead when you're doing new construction in a rural area and you have to include many kilobux for running the poles and installing the transformer for your hookup. (You ammortize that similarly, or subtract it from the price of the solar installation before computing the mortgage as above.) Solar also comes out ahead of running wires for some small loads even in urban areas. (Yard lights, road signs, emergency telephones, billboards, ...) For suburban areas with good light, solar panels at a dollar a watt would likely beat the grid for houses as well.

But nowadays you also have tax credits for the cost of the installation (if doing it with a contractor to qualify doesn't cost enough to eat it all), the opportunity to sell renewable generation credits to utilities and the like (which can be far more than the cost of the electricity in some cases). These can move financial break-even in a lot. Also: You can sometimes sell your surplus to the grid - and can usually bank it with "annual averaged net metering" for use in dimmer and/or more power hungry seasons. Finally, in places (like California) where your monthly power bill is on a sliding scale, you might use a grid-tied solar system to replace the extra-pricey "over baseline usage" kilowatthours, for another kaCHING into the pocketbook.

[ Parent ]

Re: Solar payback (3.00 / 0) (#15)
by Striider on Thu Apr 02, 2009 at 08:21:44 PM MST

To me, I have to think of the money I have spent building the system versus how much time it took me to make that money. For me, it was a no brainer, since the environmental considerations are not really a huge consideration in my opinion. These panels were already made for SOMEONE SOMEWHERE, and me purchasing them or not didn't cause any more trees or silicon bushes (joke) to die. Perhaps this is an irresponsible way to look at it, but truth be told - someone would have bought them. Also in the interest of preserving the planet, I bought a USED forklift battery - thereby saving even more green things.

My goal was to create useable amounts of power in the middle of nowhere. I am 3 miles minimum from the nearest power pole, so I didn't even bother doing the math.
I overbuilt my system for future needs, and will continue to enjoy it guilt-free for as long as possible.

There IS something magical about watching that MPPT controller pump amperage from "nowhere" into that battery, I must say! And not having to turn on my generator, even to use the shop-vac is pretty sweet indeed.
Eric
[ Parent ]

Re: Solar payback (3.00 / 0) (#6)
by Stonebrain on Sun Mar 29, 2009 at 04:30:15 PM MST

I'm one of those who is aware thar RE is not free and has negative environmental effects too.
So i suppose to be considered as a 'ecowaco' or even an old wive.
I like facts though,that's why ULR's comment makes sense to me.If you compare two energie resources,you have to compare a complete evaluation of both.And solar might come out better then I thought.

For me RE is just a hobby,not a religion.
I don't believe turning off the light for two hours will have much positive impact on eath's future.
But waisting RE energy because it's free,as some proposed as alternative too the 2 hours without light thing,also seems quite stupid to me.

Anyway,what's wrong with older women.And what's wrong with being polite?

cheers,
stonebrain

Re: Solar payback (3.00 / 0) (#11)
by Capt Slog on Tue Mar 31, 2009 at 03:04:52 AM MST

Just my 2p worth....

Why should a solar panel be "energy neutral"? It's just a tool or device. We don't apply this regime to everything we manufacture and use, only it seems to things which can be used for political leverage.

.
"Slowly changing the world, one watt at a time!"

Re: Solar payback (2.00 / 1) (#12)
by DamonHD on Tue Mar 31, 2009 at 06:35:56 AM MST

For those of us explicitly wanting to reduce carbon footprint, rightly or wrongly, ... a good EROEI is important.

Rgds

Damon
"Once you have licked the windows of freedom your tongue gets stuck."
[ Parent ]

Re: Solar payback (3.00 / 0) (#13)
by Capt Slog on Wed Apr 01, 2009 at 03:26:31 AM MST

Sure I understand the reasons, but you never hear anyone saying what their PC (for instance) took to make in terms of energy, or how much energy they expect it to MAKE in its lifetime :-)

.
"Slowly changing the world, one watt at a time!"
[ Parent ]

Re: Solar payback (3.00 / 0) (#14)
by DamonHD on Wed Apr 01, 2009 at 06:41:19 AM MST

Well, I do think about embedded energy now whenever replacing something! B^>

Rgds

Damon
"Once you have licked the windows of freedom your tongue gets stuck."
[ Parent ]

Solar payback | 15 comments (15 topical)

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