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Replacing Coal With Clean Energy — Let Me Count the Ways

Coal-fired power plants provide about 45 percent of U.S. electricity. To increase the percentage of electricity coming from clean energy sources, America will likely have to move away from coal. Credit: Cathy Haglund/flickr.

As I recently pointed out, Americans consume immense quantities of electricity each year. Depending on where you live, it might come from a coal or a gas-fired power plant, a nuclear plant, a hydroelectric dam, wind turbines or even solar panels. I must admit, though, that I have no idea where my electricity comes from (other than out of the wall). But since I live in central New Jersey, my electricity probably comes from both coal, gas, and nuclear power plants.

For the country overall, the relative proportions of each type of electricity have stayed constant for about the past 15 years:

  • Coal and natural gas produce 70 percent of our electricity
  • Nuclear power generates about 20 percent
  • Renewable sources (like wind and hydropower) provide about 10 percent.

Now, it looks like those proportions could be about to change.

During the 2011 State of the Union address, President Obama announced a new U.S. energy target: produce 80 percent of electricity from clean energy sources by 2035. Burning coal and natural gas to generate electricity releases billions of tons of heat-trapping carbon dioxide (CO2) gas into the atmosphere, so switching to more “clean” energy sources would help curb a lot of America’s greenhouse gas emissions, which are partly responsible for warming the climate.

So where is all this “clean energy” going to come from? To start with, Obama’s plan counts natural gas as “clean,” since even though it produces CO2, the emissions for each kilowatt hour (kWh) generated are only half as much as you get with coal. If we left all current gas-burning plants in place but didn’t build any new ones, hitting the 80 percent target would mean about two-thirds of the country’s coal power would need to be replaced. That's not a simple task, because coal alone provides close to half of America's electricity.

Ignoring the costs, here are some of the ways the U.S. could replace enough coal power to meet an 80 percent clean energy sources target by 2035. 

To replace a portion of coal power and get 80 percent of electricity from clean sources by 2035, the U.S. could build 243 new dams the size of Hoover Dam (10 new dams each year). Credit: Josh Kenzer/flickr.

  • We could build 243 hydroelectric dams that have Hoover Dam's generating capacity (that’s 10 new dams a year, on average). Mind you, that means we would also need 243 mighty rivers like the Colorado that don’t already have dams on them. There aren't enough rivers left in the U.S. to support that number of large dams, and smaller dams alone can't generate enough electricity to replace coal power plants. 
  • We could build 194,900 wind turbines, each having 2 megawatts (MW) of capacity (a typical size). That would mean building more than 8,000 new turbines each year, or 22 turbines a day, every day, for 24 years. Even if this is doable, we’d also have to overhaul the U.S. electrical grid, and add a way to store electricity, in order to safely and reliably use the intermittent flow of electricity that comes from wind turbines.  
  • We could build 64 new nuclear power plants the size of New York’s Indian Point power station. Since the Fukushima disaster in Japan last spring, however, that kind of construction rate, with nearly four nuclear plants being built each year, no longer seems realistic. And keep in mind, the U.S. hasn't built a new nuclear plant in over 20 years. 
  • We could build 10,200 solar energy farms — but each one would have to be the size of Nevada’s Copper Mountain solar array, which is currently the country’s largest. The amount of space needed for this number of solar panels: an area about three times the size of Delaware.
  • Or, we could keep using coal-fired power plants as long as they are outfitted to capture and store the CO2 exhaust instead of releasing it into the atmosphere — a technology called CCS, or carbon capture and sequestration. But using CCS makes a plant less efficient in generating electricity, so not only would every existing coal plant in the country need to be outfitted with CCS, but we would have to build 133 new plants that would also be equipped with CCS technology. At the moment, the U.S. doesn’t yet have a single coal-fired plant operating with CCS.
  • We could all improve our energy efficiency, but switching light bulbs won’t be enough to meet Obama's target. Even if everyone in the U.S. changed all their incandescent bulbs to compact fluorescent lights, it would still only save about one percent of the total electricity needed to meet the 80 percent target.

All these options still involve getting about 20 percent of U.S. electricity from natural gas, which produces greenhouse gas emissions. And right now, all of the clean energy sources mentioned here are considerably more expensive than coal.

It’s pretty clear that not one of these options, on its own, is very practical — so as President Obama rightly pointed out during the State of the Union, getting rid of most U.S. coal-powered electricity will take a mixture of all the above.

If we're to successfully meet the 2035 goal, though, it's time to get cracking.

« Charged


By Kim Hedberg (BOULDER, CO 80303)
on July 27th, 2011

According to Jacobson at Stanford, we could do 100% for the whole world by 2050:

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By JIm
on July 27th, 2011


I question your math regarding the amount of area we need to power the nation’s grid in solar, let’s say photovoltaic.

Take the Agua Caliente solar plant east of Yuma, Arizona for example. It covers 2,400 acres (a bit less than four square miles), and will produce about 290 megawatts and supply about 100,000 U.S. homes.

Now…there are approximately 100,000,000 homes in the U.S., so 290,000 megawatts are needed to push our homes’ electric needs, or 1,000 times what Agua Caliente will produce, or a bit less than 4,000 square miles.

You say that “We could build 10,200 solar energy farms ”” but each one would have to be the size of Nevada’s Copper Mountain solar array, which is currently the country’s largest. The amount of space needed for this number of solar panels: an area about three times the size of Delaware.”

Again…if we built 1,000 or so 290-megawatt plants (like Agua Caliente Solar Plant) we would reach our residential goal…and be at about two times the area of Delaware.

I believe that you are over estimating the area needed by ten. Perhaps you added one too many zeros? Or, perhaps the power plant you sited is much small than Agua Caliente, or those currently being built?

Now…I did not include what non-residential electricity needs, but it can’t be ten times greater than residential…can it?

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By Jim
on July 27th, 2011

Okay…Copper Mountain Solar Array, although currently the largest on-line solar plant at 55 megawatts, will soon be dwarfed by those now under construction.

Imperial Valley, for example, will be over ten times what Copper Mountain currently produces.

Just keeping myself on my toes Alyson wink

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By Jim
on July 27th, 2011

A list of Large Solar Plants currently in the works just in California.

Imperial Valley is just over 700 megawatts…or almost 13 times larger than the largest on-line solar plant sited above.

Arizona has:

Abengoa plant just west of Gila Bend, Arizona (ca. 300 mW).
Sempra power plant northeast of Gila Bend, Arizona (ca. 80 mW).
Agua Caliente Solar east of Yuma, Arizona (north of Dateland, Arizona actually) (ca. 290 mW).
Mesquite Solar Power Plant just southwest of the Palo Verde Nuclear Power Plant (ca. 700 mW)
Arlington Valley Solar Energy and Arlington Valley Solar Energy II both south of the Palo Verde Nuclear Power Plant (together around 500 mW).
And many others in Arizona.

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By Alyson (Climate Central)
on July 28th, 2011


Thanks for pointing out the size of the Agua Caliente Solar Project, which will be a larger solar farm than Copper Mountain (in both size and generating capacity). However, when I calculate the “number of Agua Caliente’s” needed to reach the 80% target, I still get to an area considerably larger than 2 times the size of Delaware.

I believe part of the problem is that the Agua Caliente website says the project will power an average of 100,000 homes, as you mentioned. But according to this Pacific Gas and Electric Company letter (, the project is expected to generate an average 688 GWh of electricity each year, which is closer to about 60,000 average American homes. So, the “number of Agua Calientes” or the area needed, is larger than what you calculate.

That being said, my calculations only took into account the current technology available, and I expect that in the coming decades solar technology will become both more efficient and more affordable. It could be that by 2035, the photovoltaic technology available will allow solar power to offer a more significant contribution to America’s electricity needs.

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By Michael
on July 28th, 2011

Why are American so obsessed with lighting when it come to energy efficiency - figures of 10-15% of power consumption? Its heating and cooling which are the big power users which can be more efficient without being uncomfortable for humans (insulation, effective gathering or deflection of solar radiation/heat) or more effectively used by industry without much cost.

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By coal newsletters (Brisbane)
on August 4th, 2011

The use of sophisticated software systems for coal mining (thermal coal, steam coal and metallurgical coal) that is mostly burnt for power generation and steel production and adds to the greenhouse effect is valid for western countries who may allocate resources and funds to alternative and more greener sources of power. Some of the alternatives may be “safer” than the traditional mines. Unfortunately, coal reports and coal statistics show developing economies are more likely to increase their use of thermal coal & metallurgical coal in coming years because of its affordability and to meet increasing demands for electricity and steel. Whether they will embrace and utilise sophisticated software systems that no doubt add to the cost of production is yet to be seen. Cherry of

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By A
on March 23rd, 2012

Coal Power: Expensive or Worth it?

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By Jan Freed (los angeles)
on March 25th, 2012

Area of Delaware: 2,500 sq. miles

Area of Mojave Desert: 25,000 sq. miles.

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By Jan Freed (los angeles)
on March 25th, 2012

Some perspective on the statement: “We could build 194,900 wind turbines, each having 2 megawatts (MW) of capacity (a typical size).”

WWII cost the U.S. about $3.5 trillion in today’s dollars (about what we will have spent for the war in Iraq)

A 2MW Wind turbine costs $3.5 million.

So we could build 1 million wind turbines for the same price (and no one need be killed or maimed).  In other words we could increase our production even fivefold for the same cost. Or,  match 80% reduction targets for 1/5 the cost of WW2.

The loss of life and cost of climate change will be far greater than the cost of any war.

Compare the cost of ocean warming and acidification alone, estimated at $2 Trillion/year.

Ocean change is yet only a part of other costly changes, such as impact of agriculture, heat waves, droughts, floods storms, disease, dislocation ”“ basically the entire biosphere at risk.

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