I was reading an article recently about mountaintop removal (MTR) coal mining and got to thinking.

How many square miles have been cleared in Kentucky for MTR?

And, if we covered all that space with photovoltaic (PV) solar panels, how much electricity in kilowatt-hours (kWh) would be produced?

Would it be enough to match the electricity consumed in Kentucky each year?

What about MTR in the U.S. as a whole?

If we covered all the square miles that have been cleared for MTR in the U.S. with PV solar panels, what percentage of the national annual kWh consumption could be provided?

I decided to crunch the numbers and what I discovered was quite intriguing.

According to the website of Appalachian Voices (a nonprofit committed to protecting the land, air and water of the central and southern Appalachian region), 574,000 acres (897 square miles) of land in Kentucky have been surface mined for coal and more than 293 mountains have been severely impacted or destroyed by MTR coal mining.

Meanwhile, the total electricity consumption in Kentucky (residential, commercial, and industrial) in 2005 was 89,351,000,000 kWh, according to the Department of Energy.

The following projection is based on experience from PV solar installations already in place here in Kentucky and from the fact that we get four and a half hours of sunlight per day on average, accounting for clouds. To produce that much electricity in one year from PV solar panels in this region, around 190 square miles of land would need to be covered by a 69.1 GW (gigawatt) solar array. And 897 square miles of land has been has been flattened by MTR. Therefore, if we merely put PV solar panels on one-fifth of this already cleared land, we would supply ALL of the electricity needs for the entire Commonwealth of Kentucky!

If we covered the entire 897 square miles of cleared MTR space in Kentucky, we could supply nearly 10% of the electricity needs of the entire U.S.!

Additionally, according to Appalachian Voices, a total of 1,160,000 acres (1,813 square miles) of land has been surface mined for coal in the central and southern Appalachian region.

The United States consumed a total of 3.873 trillion kWh of electricity in 2008.

To produce that much electricity in one year from PV solar panels in this region, 8,225 square miles of land would need to be covered. Accordingly, roughly 22% of the electricity consumed in America could be provided by PV solar panels if the 1,813 square miles of land cleared by MTR in Appalachia were covered.

At this point, you're probably asking yourself: that's great, but how much would it cost? And, what about energystorageso we can use that electricity at night?

I'll admit that projecting the costs for a solar array of this size is an exercise in pure conjecture, but I'll do my best.

Currently, large-scale, megawatt-level PV solar panel arrays cost around $3 per watt to install without tax subsidies. A GW-scale solar array might start to approach the $2 per watt installed cost level in the not so distant future. Using this metric, it would cost about $138 billion to install the 69.1 GW solar array required to build the capacity capable of producing 100% of the electricity consumed in Kentucky per year. If the solar panels have the industry standard 25-year warranty, the cost of daytime electricity comes to 6.2 cents per kWh. That's cheaper than what consumers in Kentucky pay for electricity right now (e.g., LG&E residential customers pay 7.9 cents/kWh).

The sun doesn’t shine at night, and shines only intermittently during the day. As such, solar systems would have to be supplemented with storage, gas turbines or other technologies. The price of renewable power, thus, would invariably be higher in the initial years. (Editor's note: The environmental remediation costs typically associated with MTR would also be hundreds of millions of dollars less for a solar farm too.)

There are many options coming online now for grid-level energy storage, including, but not limited to: pumped hydro, compressed air energy storage (CAES), sodium-sulfur batteries, lead acid batteries, nickel-cadmium batteries, flywheels, and lithium-ion batteries.

Empty, abandoned coal mines in Germany are being looked at as potential sites for pumped hydro energy storage for renewable energy systems -- something I would assume we have plenty of in Kentucky.

Adding energy storage could cost as little as $1 per watt to the solar array in an ideal situation, such as compressed air at a geological site. The current price is higher for most technologies, but storage is an industry is just starting: price declines are inevitable. This would increase the cost of the array for Kentucky to $207 billion with an electricity cost of around 9.3 cents per kWh. That price per kWh is a little above what LG&E customers are paying right now, but will soon be on par with current rates, as LG&E recently requested the Kentucky Public Service Commission to allow rates to increase by 19 percent over the next five years.

Again, the cost projection is all conjecture and does not include grid transmission and maintenance. But it's a start.

This sounds like a lot of money until you consider that, according to a study by the Environmental Law Institute, the fossil fuel industry in the U.S. received $72 billion in subsidies from 2002 to 2008. Imagine using that money to fund a GW solar project in Kentucky!

And here's some proof that solar does work here.

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Dan Hoffman is the president of RegenEn Solar, an installer in Louisville, Kentucky.