Guest essay by Chris Yakymyshyn
Vermonter Bill McKibben was recently quoted in Salon Magazine:
“The roof of my house is covered in solar panels. When I’m home, I’m a pretty green fellow. But I know that that’s not actually going to solve the problem.”
This is a very interesting comment. He had solar panels installed on his home, even though he knew it would not ‘solve’ the CO2 problem.
One goal of installing solar PV is to reduce CO2 emissions associated with generating electricity. Ideally, this would be achieved at a cost that is less than the social costs of CO2 emissions, estimated by the EPA to be somewhere between $12 and $117 per ton in 2015. To minimize the cost of avoided CO2 emissions, ideally a residential solar PV system replaces utility energy that is supplied by burning coal, since coal produces the highest CO2 emissions per kilowatt-hour. Likewise, adding solar panels in a location that already receives 100% carbon-free electricity will result in an infinite cost per ton of avoided CO2, since no CO2 emissions will be avoided. The reality at your wall outlet will lie somewhere between these two limits.
I decided to calculate how much it costs to reduce one ton of CO2 emissions by installing a residential solar PV system in Vermont. I then repeated the calculation in every other U.S. state and Canadian province or territory. This estimate assumes that electricity generated within a state, territory or province is consumed there, and that electricity imports constitute a small percentage of total electricity consumed within that state, province or territory.
The first step is to figure out roughly what percentage of today’s wall-plug power is provided by coal, natural gas, nuclear, wind, solar, hydro, geothermal, biomass, etc. The Energy Information Agency (EIA) tabulates, by year and by state, the total amount of electrical energy (in Megawatt Hours, or MWhr) delivered by each type of generating source. For the most recent year available (2011) in each state, the utility and IPP (Independent Power Producer) electrical energy generated by CO2 emitters (coal, natural gas, petroleum liquids) and non-CO2 emitters (nuclear, wind, solar, hydroelectric, geothermal and biomass) was extracted, with the assumption that biomass was carbon neutral. The ratio of fossil fuel to total electrical energy produced was then calculated for each state in 2011. The results ranged from 0.14% fossil electricity in Vermont, to 98.7% fossil electricity in Delaware.
The same tabulation was performed for Canadian provinces and territories using 2011 data from Statistics Canada. In Canada the results covered the entire range, from essentially 0% fossil electricity in Prince Edward Island up to 100% fossil electricity in Nunavut.
Next, the CO2 emissions per MWhr were calculated using the following emissions estimates: 1.4 tons/MWhr for coal, 1.0 tons/MWhr for fossil liquids, and 0.47 tons/MWhr for natural gas. The total CO2 emissions were estimated by multiplying the energy in MWhr produced from each source, by the CO2 emissions per MWhr for each source. The resulting CO2 emissions in 2011 ranged from <0.001 million tons CO2 in Prince Edward Island, 0.008 million tons in Vermont, up to 279 million tons in Texas.
The average CO2 emissions associated with electricity generation in each state, province or territory in 2011 was then calculated by dividing the total CO2 emissions by the total amount of energy generated. The resulting averages ranged from <0.001 tons CO2 per MWhr in Prince Edward Island, 0.001 tons CO2 per MWhr in Vermont, 0.567 tons CO2 per MWhr in Nevada, to 1.36 tons CO2 per MWhr (almost 100% coal) in West Virginia.
The amount of solar energy generated by a solar PV residential system was next estimated. The annual averaged hours per day of full sun for a South-facing fixed solar array tilted at latitude was extracted from the National Renewable Energy Labs (NREL) Renewable Resource Data Center. The values ranged from a low of 2.5 hrs/day in Yukon Territory up to 6.5 hrs/day in Nevada and Arizona. Assuming a 10 kW(AC) system with a 20 year service life and no aging, the total energy delivered by the rooftop solar PV system was estimated in Nevada to be (6.5 hrs/day)*(365 days/yr)*(20 yrs)*(10 kW(AC)*(0.001 MWhr/kWhr) = 475 MWhr of electricity. All of the generated electricity was assumed to be used somewhere in Nevada. This calculation was repeated for every state, province and territory.
The cost of the residential solar PV system was needed next. A recent article at Solar Panels Review gave 2013 price estimates for a contractor-installed system using several panel choices. The average unsubsidized cost was $5.57/Watt AC, or $55,700 for a 10 kWAC system. This unsubsidized cost is assumed to be the same everywhere.
The cost of CO2 emissions avoided using residential solar PV can now be estimated. The cost per ton CO2 avoided is given by the solar PV system cost divided by the total CO2 tonnage avoided over the 20-year life of the system. For example, using the previous estimates for Nevada, the avoided CO2 emissions cost is given by ($55,700)/(475 MWhr*0.567 tons CO2 per MWhr) = $207/ton CO2. This calculation was repeated for every state, province and territory and, as shown in Figure 1, plotted versus the fraction of generation that is free of CO2 emissions.
First, notice that the vertical axis is a logarithmic scale, ranging from $1/ton CO2 (well above the 5 cents/ton that traders at the now-defunct Chicago Climate Exchange determined was an appropriate price), up to $10,000,000 per ton CO2. Several horizontal lines indicate the California carbon exchange price of about $12/ton CO2 and one EPA estimate of around $60/ton CO2. A vertical line marks one widely discussed goal of 80% CO2-free electricity generation.
Note how the use of residential solar rapidly escalates the cost of avoiding CO2 emissions as the power grid moves towards a ‘low-carb’ diet. Also note that even in ‘high-carb’ states at the left side of the graph, residential solar PV is an expensive way to avoid CO2 emissions associated with electricity generation, never breaking below $100/ton CO2. Substituting DOE’s 2020 SunShot goal of $1.50/Watt installed cost for a residential system shifts the curve down, but retains the highly coveted hockey stick shape J.
So, Bill McKibben’s solar panels in Vermont are indeed avoiding CO2 emissions in Vermont (one of the data points at the far right side of Figure 1), at a cost of around $155,000 per ton CO2. This is equivalent to paying a carbon tax of $2.00 for one teaspoon of gasoline.
Figure 1- Semi-log graph showing the cost of avoiding one ton of CO2 emissions using residential solar PV, province or territory, as a function of the carbon content at the wall outlet. Several U.S. states and Canadian provinces are indicated. The two horizontal lines represent two official estimates of the social cost of carbon dioxide emissions.
References-
Salon magazine article-
http://www.salon.com/2013/09/15/bill_mckibben_being_green_wont_solve_the_problem/
Solar insolation data from NREL-
http://rredc.nrel.gov/solar/old_data/nsrdb/1961-1990/redbook/sum2/state.html
Electricity production in the U.S.-
http://www.eia.gov/electricity/data/state/
Electricity production in Canada-
Solar PV system costs-
http://solar-panels-review.toptenreviews.com/
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Anyone who buys solar panels and installs them in vermont for CO2 avoidance purposes ends up with a net negative as it is doubtful that the power generated by the panels over their lifetime exceeds the cost of energy to produce, transport, and install them.
Even in southern CA that factor is only about 3-5x.
Did you account for the fact that solar panels do produce some electricity? The way I would approach the calculation is to first find out how much (unsubsidized) solar costs above and beyond what you pay at present. Surely it’s that additional cost that is what you are paying to reduce CO2? Does it make much difference?
It would appear the external cost of CO2 on agriculture negative, so to charge a tax for CO2 emissions seems a little backward. I’m wondering when we can start taxing everyone else for the $3,500 Billion we’ve improved agriculture so far…
Yep, waiting for my “Big Oil” check.
http://www.co2science.org/education/reports/co2benefits/MonetaryBenefitsofRisingCO2onGlobalFoodProduction.pdf
There are other ways of using solar energy to generate electricity though… http://www.climal.com/solar-power.php
From, http://www.climal.com/solar-power.php
“but are not very effective on overcast days. “
Isn’t that always the bottom line on solar?? So, you always have to have an equal amount of backup solar generation, and it always has to be on, so it is always running at idle. So you have to double up all of your power generation, and yet somehow, solar is more cost effective. By definition, if you only have the backup solution you only have to pay for a single solution. And thus, since it will be used 100% of the time, it is cost effective to make it as efficient as possible.
And as always, I’ve got to throw a bone at Thorium based liquid sodium reactors. Where it has been estimated that it we could get all the money wasted on wind and solar back, we could have replaced the baseload of coal plants with Throrium nuclear plants. But, then again, that would have not made the special interests group who donate a lot of money to political funds the billions of dollars they have enjoyed making.
great job. bravo.
I think the only useful solar power is when used for heating hot water. Last I calculated it was about a 10 year pay off period (for 38 degrees south) and from then on increasing returns as electricity costs continue to go up. Evacuated tube systems keep efficiency to end of life as it’s cheap and easy to replace any cracked or discoloured tubes.
Overall a much better return than shares!
Building a gas pipeline to displace all the oil used for heating in those frigid winters would make a real difference. “Biomass”, which means woodstoves, is only remotely sustainable because Vermont is mostly forested and has a tiny population.
The reason the electricity supply is nearly CO2-free is because most of it comes from nuclear, and most of the rest from hydro, plus a little wind.
Firemen are not fond of solar panels. They make fighting a fire in the building that has them more dangerous. They are slippery especially when wet!
Tax of $2/teaspoon? Please Sir, can I have some more?
A “key word and tricky phrase” emerges in your excellent article. Thank you!
Now, we need electricity 24 hours per day, and cannot store electricity with anything except “magic” right now. No, there are NO pumped storage sites “allowable” for use right now. NONE. Even NY’s small ” artificial pond” just north of Niagara Falls – essential in maintaining the waterflow over the Falls as a tourist destination for all time – was bitterly protested for years as early as the 1970’s!
Notice that “6.5 hours per day” is for TWO BEST SOLAR SITES in the country Nevada and Arizona
So, assuming 100% efficient storage of some kind, you need 4x (four times!) the “noon” amount of solar panels to create the power you need all day and all night: Realistically, there are losses from the panels to the storage device, within the storage device from electric power to stored energy, from the storage device back to electric power, and then from that electric power supply back to the grid. So, you need to install 5x your “average” noon electric bill just to create enough power to run your average electric load for ONE DAY for ONE HOUSE.
However, bad weather comes frequently, and lasts several days each event.
Assume you need a 3 day electric supply to make up for just two days of cloudy days, rainy days, storms, dust, haze, or snow cover. If so, you need 15x the area of solar panels that you need for your “average” electric load at noon. …
Sometimes things just don’t work the way they are supposed to. The State of Washington is well to the right on the curve in Figure 1 but low in the bend. But there are 2 Washingtons. One is the dry side, the other the wet side. This week, and for several weeks, there is a high pressure ridge (see story at link below), causing a foggy marine layer west of the Cascades and dead-calm everywhere. This will be a really bad week for both solar and wind power in this region.
Full disclosure, Me: all electric and 100% hydro.
http://www.komonews.com/weather/blogs/scott/Northwest-to-be-hit-by-virtual-anti-wind-storm-228533431.html
Solar thermal is about 4x more efficient than PV.
Most households use hot water. Why the obsession with PV?
Just like wind turbines, solar panels degrade as they age and so their capacity factor falls with time. How many will last 20 years. In the less-than-sunny south of the UK, the initial capacity factor of solar farms is around the 10% figure. For roof-mounted solar panels it is around the 6% figure.
Interesting $/ton CO2 numbers, but wait – there’s more:
I have just retired to Florida, and am installing a $36,000 10KW solar system sized to eliminate my $3,000/year electrical bill from Florida Power & Light. Why would I invest in something having a 12 year payback?
Well, I say $36,000, but I get a $2,000 rebate from the HW manufacturer, $20,000 (yep, $20k) from FPL (actually, their rate payers…), and a $10,800 federal tax credit – net installation cost to me after 90 days of filing forms & having stuff inspected is $3,200.
As might be expected, the demographic that can pay $36,000 and wait 90 days to collect $32,800 in rebates/credits tends to skew “upscale”. Oh yea, and the value of my house goes up almost the full $36,000 which (by law) does not increase my taxable property value. Go figure.
Living in Washington state across the river from Oregon I watch the energy use evey day. Wind has been flat lined for the last week. It is the green line at the bottom. Solar entering the grid is not even tracked.
http://transmission.bpa.gov/Business/Operations/Wind/baltwg.aspx
Largely because of the feed-in tariff, the solar panels on my house in Chico, California, have reduced my electric bill by roughly 60 percent, for a 1.4kW system, on a 2,800-sq ft single-level, well-insulated house. But that savings is due to the feed-in tariff because there is enough sunshine here even in the wintertime for the panels to produce enough electricity for the meter to run backwards much of the time.
Rooftop solar doesn’t have the habitat destruction issues that large arrays have, but it is being subsidized by other ratepayers and by the taxpayers. You are forced to chose between accepting that or having a humongously larger electric bill – not a very comforting choice..
“””””…..Viktor says:
October 21, 2013 at 7:46 pm
There are other ways of using solar energy to generate electricity though… http://www.climal.com/solar-power.php……””””””
Why do people keep bothering us with these rubbish articles they giggle up on the web.
Why don’t YOU calculate the Watts of solar electricity per square meter OF THE LAND taken up by a reflecting mirror solar furnace power station. You can get more electricity for the space, by riding your gymnasium bicycle turning an alternator.
http://www.theguardian.com/environment/2013/oct/21/uk-nuclear-power-plant-contract-deal-no-deal
Antony Froggatt, from the Chatham House thinktank, said EDF’s costs projection had already increased markedly. “In 2006, its submission to the government’s energy review stated [the type of reactor to be used, a European pressurised water reactor] would cost £28.80 per megawatt-hour in 2013 values,” he said. “This more than threefold increase [to £92.50], over eight years, puts the cost of nuclear electricity at about double the current market rate – higher than that produced by both gas and coal-fired power stations, and more costly than many renewable energy options.”
@Greg. higher than that produced by both gas and coal-fired power stations, and more costly than many renewable energy options.”
Yes, but more reliable and improves energy security, another country cannot turn off the tap, or stop coal shipments, etc. And it provides 24 hr electricity unlike many renewables.
But for me the real issue here is why did the UK, a once world leader in designing, building and running nuclear power stations, allow that technological base and industry to die. Short sighted.
All the 50 & 35 watt, 240 volts, halogen downlighters in my house have been replaced with 4 watt & 7 watt LEDs, a total of 37 luminaires. At a cost of nearly £400-00!!! Has my bill decreased? Not really, because the electricity consumed does not exceed expensive units I have to pay for as part of the “green” surcharges……………………… Granted that the LEDs will probably last 20 years, but will there be electricity then? Plus, all the heat that was generated by the halogens has to be supplied by the central heating…… that requires electricity to power the pump.
Thank goodness we installed a Rumford open fire & have access to free wood. Candles are useful as well. The best part of the equation is the insulation. That really does give the best financial return. Way better than PV.
The UK lost bits lead in nuclear technology because for much of the time the government in power had fellow travellers who equated nuclear power with nuclear weapons.
Solar panels do not look like a good long term investment at all.
http://theresilientearth.com/?q=content/solar-power-failing-world-wide
@ur momisugly RACookPE1978
I don’t think off-grid was proposed. Grid-intertie obviously negates your spurious “15x the area of solar panels that you need for your “average” electric load at noon.”.
All one need do, if they wish to use solar PV (and save/make the most money), is size the system to provide the KWh consumed yearly plus whatever overage the utility allows (many limit the system size allowed to net meter). Sizing the system is old-hat to installers across the country from Baltimore to San Diego.
When the panels produce more electricity than needed — the meter runs backward. It is quite simple.
FYI panels are available for well under $1/watt http://www.sunelec.com
And, of course, what makes it ludicrously worse is that the Social Cost of CO2 emissions is actually negative.