Solar PV Energy Payback Discussion
I posted an entry below about the shortest day of the year. In the comments, a reader John Pickens responded with comments about the belief that my system will never produce enough energy to repay the energy used to create the components (panels, etc). I believe that he is incorrect.
UPDATED 12/29/2004 4:47pm EST
Below is the discussion (click the link to continue reading):
John’s response to my entry was:
You polluter, you!
Your solar array, positioned as it is in a too-north latitude, will NEVER EVER produce more energy than it took to produce.
You are WASTING ENERGY!
The thermodynamics are just not there.
Sorry, you might as well get an SUV, you’re wasting your time.
My reply was:
I challenge this.
I know how much energy is being produced. What energy was required to produce my equipment? The entire equipment list is included in my site.
Remember, I’ve got at least 25 years warranty, and probably longer life.
Oh, and I *do* drive an SUV – though I’m looking to replace it with a hybrid SUV next year.
Mark
p.s. And if that’s the case, why are all of the greens in Germany (a higher latitude last time I checked) going solar?
John’s reply to this:
Mark,
You said your installation cost around $52,000.
For Crystalline or Polycrytalline PV arrays, the energy of production is roughly equal to 50% of the commodity cost.
Since the bulk of the energy used is in furnaces to melt and purify the silicon, and these furnaces are fired with electricy resistive elements, then the vast majority of the energy utilized was electric.
So, we are talking about approximately $26,000 worth of electricity. If we use the price of electricity for 2002, data available shows an average price of $0.08 per kWh (kilowatt hour).
Your array utilized $26,000 / $0.08 = 325,000 kWh of electricity.
If we assume that your array has a 28 year lifespan (25 year plus 3 year grace) we get an annual breakeven production requirement of:
325,000kWh / 28 = 11,600 kWh /year.
11,600 kWh /year / 365 days per year = 32 kWh per DAY AVERAGE!
Based upon what I’m seeing on your site (40kWh/very sunny June day), I don’t think you are even going to come CLOSE!
Read it and weep, you energy-waster you….
Now, do you want to hear the truth about hybrid cars before you waste your
time there as well?????
By the way, this analysis of energy cost is skewed towards your benefit.
In actuality, the PV materials used in this country are typically made in parts of the US which utilize very cheap hydroelectric power. Since the producers are using electricity which they negotiate very effectively for,
their average electricty costs are more like 2 to 6 cents per kWh.
Now, you may say, great! We used hydropower to make this array!
Non-polluting! YAY!
Not so fast, to take hydropower, and use it to make PV arrays which are used in areas of the country (Southern CA, AZ, NM, TX, Parts of CO) where energy breakeven is likely, you are doing an environmentally good thing.
To waste this energy in New Jersey, where you will be lucky to get HALF your energy back, is a great big WASTE!!!!
quote: “p.s. And if that’s the case, why are all of the greens in Germany (a higher latitude last time I checked) going solar?”
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Because they are just as ignorant of thermodynamics as you are.
They probably also get distorted “feel good” government subsidies just like you got.
The hybrid car discussion is off-topic for this discussion (and for that matter, this site).
My reply:
The $52,000 cost includes all costs – installation, labor, and the inverters plus the electrical equipment (disconnect boxes, etc.).
The panels are available for about $800/panel commercially. There are 39 of them. That’s $31,200.
1/2 of that is $15,600. That’s 195 MWh.
195,000 / 28 = 6964 kWh/year
That’s 19 kWh per day – which works out to be about the average that we get.
That assumes the 50% figure that you note below. You might want to look at this page:
http://www.otherpower.com/otherpower_solar_new.html
According to that, energy payback time is only 3.3 years for standard modules.
Also, this page: http://www.nrel.gov/ncpv/hotline/09_00_siemens.html
(Siemens Solar is now Shell Solar)
Mark
An additional reply that I would like to add is that we are hardly ignorant of thermodynamics. My wife is a Mechanical Engineer with her NJ State Professional Engineer’s License.
Mr. Pickens in his last e-mail wanted me to post my reply before he answered it.
I invite continued conversation on this issue from Mr. Pickens and others. However, I will not condone insults. Let’s keep this on a mature level.
John’s latest:
Mark,
First, I challenge your estimate of 19kWh per day average power output for your system. Based upon your peak figure of 42kWh in June, and December values around 10kWh, your sunny day average power output is 26kWh.
However, New Jersey experiences many cloudy days which will dramatically lower that average. I would bet you average closer to 12 to 16kWh per day.
Do you have daily data to document this?
Second, how can you exclude infrastructure and installation in your
estimates? After all, these are power expenditures which would not be
undertaken if not for your system. When you make the claim that you are
producing a net surfeit of power with your system, all inputs into the
system must be taken into account.
Third, I used to work for Solarex Corporation, now a subsidiary of BP
Solar. My team produced the first large area amorphous silicon
photovoltaic array able to produce more than 10% sunlight to energy
conversion, as documented by the Solar Energy Research Institute back in
the 1980’s. I know of which I speak. Amorphous Silicon uses far less
energy to produce than the crystalline arrays you have, but unfortunately,
are lower in energy output, and therefore require an even greater surface
area to install.
As it happens, I do have daily readings from the inverters.
The two inverters together have produced 3464 kWh since June 14 (as of yesterday). That’s over the course of 196 days. That produces an average daily production of 17.67 kWh. Of course, this is from June to December – a full year should change the result.
So, that comes up as an annual production of about 6450 kWh. That meets our pre-installation estimates.
I see that you have experience in the industry. However, I have trouble reconciling your claim that my panels required 325,000 kWh to create them with industry data that panels being manufactured now have an energy payback of 3 years.
A study by Utrecht University in 2000 showed that with a medium-high level of irradiation, the payback for present-day roof-top installations is 2.5-3 years. Energy Pay-Back Time and CO2 emissions of PV Systems Holland is at a higher latitude as New Jersey, and if anything has wetter weather. Even if we assume 1/2 the sunlight, we’re looking at a 6-year energy payback.
Do you have any information supporting your contention that the manufacture of my panels took that much energy?
By the way, 0.08/kWh is about right for NJ. I pay a little more because I use Green Mountain energy rather than PSE&G.
Comments
3 Comments on Solar PV Energy Payback Discussion
-
j.pickens on
Wed, 29th Dec 2004 1:46 pm
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AA OLAYEMI on
Mon, 11th Apr 2005 12:43 pm
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Clee on
Thu, 16th Nov 2006 7:04 pm
Mark,
First, I challenge your estimate of 19kWh per day average power output for your system. Based upon your peak figure of 42kWh in June, and December values around 10kWh, your sunny day average power output is 26kWh. However, New Jersey experiences many cloudy days which will dramatically lower that average. I would bet you average closer to 12 to 16kWh per day.
Do you have daily data to document this?
Second, how can you exclude infrastructure and installation in your estimates? After all, these are power expenditures which would not be undertaken if not for your system. When you make the claim that you are producing a net surfeit of power with your system, all inputs into the system must be taken into account.
Third, I used to work for Solarex Corporation, now a subsidiary of BP Solar. My team produced the first large area amorphous silicon photovoltaic array able to produce more than 10% sunlight to energy conversion, as documented by the Solar Energy Research Institute back in the 1980’s. I know of which I speak. Amorphous Silicon uses far less energy to produce than the crystalline arrays you have, but unfortunately, are lower in energy output, and therefore require an even greater surface area to install.
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I saw your blog mentioned in the comments section of
http://thefraserdomain.typepad.com/energy/2006/11/net_metering_fr.html
Here are a couple more studies showing how PV pays for itself in terms of energy in about 3 years. That gives you a good margin of error even at northern latitudes and with your panels pointing east instead of south.
The first study is the one referenced by your otherpower.com link, which might not take into account installation energy.
http://www.homepower.com/files/pvpayback.pdf
The second study takes into account the energy to extract and transport the raw materials, manufacture the panels, install and maintain the entire system, decommissioning and waste disposal. That seems pretty comprehensive to me.
http://www.ecw.org/prod/210-1.pdf
j.pickens seems to be using ancient data from the 1980s. Solar panels have increased in efficiency and decreased in price/watts since then. I’d rather trust the data from this century.
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