Smith Electric Company

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?"

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.

Shortest Day of the Year

Well, yesterday was the shortest day of the year here in the Northern Hemisphere.

I haven't seen the numbers from yesterday's production, but we've been getting 9-12 kWh out of the solar panels on a sunny day in December.  Compare that to the record of 42 kWh on a sunny day in June, and you can see what a difference the lower angle of sunshine and shorter days has on the system.

Of course, we aren't using the air conditioning at the moment either, so our usage is down.  We are using lights for longer hours in the evening and even morning now.

So now we turn back to longer days.  Our "net producer" months are predicted to be April, May and a bit of June.

Here Come the Fuzz

Yesterday afternoon, I had a DirecTV installer working at my house on cable issues.  He was parked out front.  About mid-afternoon, a police car starts cruising around the neighborhood.  The car came to a stop right next to my installer, and the officer inside started talking to my installer.  I saw all of this from the window.

So, I high-tailed it outside to see what was up.  When I got within ear-shot, my installer said, "Here's the guy you need to talk to."  (Gulp.)

So the officer says, "Are those solar panels on your roof?"

(Whew!)

I proceeded to explain a bit about them and their costs.  It turns out that the officer lives a few blocks from me, has been considering panels, and recently noticed mine.  He had questions about costs and who installed it.  I gave him the name of my solar installer and the address for this website.

So, for Officer Jones (his real name - might be Corporal or Sergeant, I wasn't paying attention), here are your links.

The panels were installed by Jersey Solar, LLC (website).  The total cost was $52,000 but the state rebate pays about 70%, so my cost was about $16,000.  Click the Major Event Entries link to the left for an index to articles and pictures of the whole process.  If you need anything else, please feel free to e-mail me at the link on the left.

Renewable Energy Feasibility - NJ

The New Jersey Board of Public Utilities commissioned a study to determine whether or not it would be feasible to require that 20% of NJ's energy needs be met by renewables by 2020.  They received the results last week.  (Press Release)

The study results show that increasing the requirement to 20% by 2020 would only result in a 3.7% increase in electric rates - which is negigible over the 16 year period.  It's important to note that this scenario assumes significant cost-reducing technology changes for wind and PV (solar) production.  The report leans heavily on wind-generated power including off-shore wind installations in it's estimates.

Interestingly, the report promises 11,700 jobs related solely to the production and installation of solar and wind technology in NJ.  The report also points to reduction in natural gas prices as a result as demand for natural gas in utility production of electricity declines.  And of course there are the health benefits of reducing polluting methods of producing electricity.

I have to admit - I'm a little skeptical of the results.  For one thing, they base their estimates on the best case scenario - that we would have significant cost reduction for wind and PV power in the 20 years.  However, I'm strongly in favor of anything that makes NJ cleaner and less dependent on fossil fuels.