Thursday, January 29, 2009

Solar vs Coal, Land Area Comparison.

Thirty-eight years of Kentucky strip mining have, at one time or another, destroyed 1.5 Million Acres (6,070,284,633 m2) of land, and torn down 470 Mountains.

Let's roughly compare the land impact of Coal to the potential land impact of Solar, with this 1.5 Million Acres as a basis.

First, let's see how much Energy could be produced by all the Coal that was mined in Kentucky in 2007*. Answer: 553 Billion kWh.

Per Salon, 158 Million Tons of Coal were produced in Kentucky 2007. I know from previous calculations that a very efficient coal plant can produce around 3.5 MWh/Ton, so burning the entire 158 Million Tons of coal produced in Kentucky in 2007 gives, 158 Million Tons * 3.5 MWh/Ton = 553 Million MWh, or 553 Billion kWh.

Now lets look at how much Solar Energy is available to an equivalent area of Kentucky. Answer: 10,000 Billion kWh.

Take a look at the US Insolation Map and note that the State of Kentucky is almost entirely bright yellow. Look at the legend, and note the value of 4.5-5.0 kWh/m2/day for this color. This is the Average amount of Solar Energy striking a 1 m2 panel on some single Day of the year (Averaged over the whole Year). Let's take the low estimate, and get the total Solar Energy incoming onto a 1 m2 panel, over an entire year, by multiplying 4.5 kWh/m2/day * 365 days = 1642.5 kWh/m2**. Multiplying this by 6.07 * 109 m2 gives us the total Solar Energy Striking the mined area of Kentucky in 2007, or 10 * 1012 kWh, or 10,000 Billion kWh.

So, how much of this Energy could actually be converted to Electricity using modern Solar Panels? Answer: 1,600 Billion kWh.

Of course, Photovoltaic Panels don't convert all of the Energy Striking them into Electricity. At this time, it would be fair to use 16% as a rough Average Conversion Efficiency***. So, if you were to cover that 1.5 Million Acres with Solar Panels, and each panel was 16% efficient at converting that light to Energy, that installation would produce 10,000 Billion kWh * .16 = 1,600 Billion kWh of electricity.

The Conclusion?

If you covered the 1.5 Million Acre area of Kentucky that has been affected by Strip Mining and Mountaintop Removal with Solar Panels like those commonly manufactured today, then you would produce 2.9 times the energy every year from that Installation than you would from mining the coal. In addition, unlike in coal mining, where once you've mined out an area, you have to move on to another, in the case of Solar, the Installation would produce Energy Year after Year from the same pieces of land. If you just wanted to produce the same amount of Energy as the 2007 Coal Production, you would only have to set up solar panels on 517 Thousand Acres of land. Of course, the Installation doesn't have to be all in one place, the Panels could be distributed among small Installations all across the State (2% of the total land area of Kentucky).

Note that this post does not attempt to address price. Those calculations are elsewhere, and ongoing. However, just in terms of land use, it becomes clear that the energy content of Coal could, in fact, be replaced by an Installation of Solar, while distrupting a Third of the land area of ongoing Coal Mining Operations.

Also note that this does not address the availability of Solar Panels. This will be addressed incrementally by a growing industry.

* Depends on numerous factors, including Coal Chemistry, and Power Plant Design. The values that I used assume very high Energy Content Coal, and highly efficient, state of the art, Power Plants.

** Note that this isn't quite correct, as the Insolation values on the map are not based on a panel laying flat on the ground, but are based on a panel tilted to the South. Within the scope of these calculations, though, this should be negligible.

*** Expect Conversion Efficiencies of low cost Crystalline Silicon Solar Panels to increase significantly within the next 3 years.

1.5 Million Acres = 6,070,284,633 m2
Kentucky total area = 104 658 829 550 m2 = 40409 mile2

For more information on "Insolation," see "A Note on Units of Energy and Insolation".

This article is followed by, which estimates the Solar Output of 1.5 Million Acres of Kentucky Land, using real Land Use data from Sunpower Corporation.

Related Posts by Categories

Widget by Hoctro | Jack Book


Anonymous said...


One thing I'd like to add is the fact that you are dealing with a one time expense that when amortized over 30 year (life of panel) there are significant other savings. Coal production over 30 years is a continual expense with mining.

Kubrat said...

If you look at the study did
Solar Energy Land Area Efficiency or How Much Acres per MW, kWp per Acre
on the land use efficiency of modern solar photovoltaic parks you can easily assume 0.2MW per acre. For 1,500 million acres that is 300MW. That's the size of a small nuclear reactor. That, in Kentucky, will probably give you about 360 GWh of electricity per year (at about 1,200 nominal insolation hours per year). At $0.10 per kWh, conditionally, that's electricity worth $36 million annually.

As the other commenter mentioned - there is a one time cost associated with it and no pollution, no poisonous gases.

D Pickard said...


I think you're off by a bit. 1,500,000 Acres * .2 MW/Acre = 300,000MW. Thats 300 nuclear plants.

Anonymous said...

I see the points and the math is thier but this math is done on the bases that the state of Kentucky never suffers from cloudy days when the panels are producing OkWh, the same goes for night and any other type of weather realted event. Dont get me worng I love the idea of solar but it needs to be looked at as a way of provding a suplemental electricty and not as away to remove coal.

D Pickard said...

Actually, the Insolation does account for typical weather as well as day / night. That's why the Insolation rate is around 20%, because it's only generating power about 20% of the 24 hour day on average.

Anonymous said...

I guess none of you ever plan to live in Kentucky therefore covering that hovel of a place and all of its mountains with black (hot in the sun) panels is of little consequence. The area impacted that you discuss is continually reclaimed therefore only a fraction of the total area mentioned is disturbed at any one time.
I've been wondering about the other 84% of the energy not converted to power in a solar panel.
It seems that under natural conditions a tan desert (like those here in Nevada) would reflect much of the sun's enegy back out into space, but since the solar panel is nearly black won't is cause much of that potentially reflected energy to be converted directly to heat much like asphalt? The 84% that is.