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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.

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