Sunday, January 17, 2010

Cogeneration

When most of us think of energy efficiency we probably think of buying an Energy Star appliance or replacing incandescent light bulbs with compact fluorescents. While those efforts do save a few kilowatt hours used in our homes and businesses, large amounts of energy are saved or gained with industrial cogeneration. Cogeneration involves capturing heat wasted by industrial processes to make surplus electricity. By putting that waste heat to work, plants can double their efficiencies. And the energy savings can really add up.

A prime example is outlined in the new book $20 Per Gallon, by Christopher Steiner. West Virginia Alloy’s silicon plant uses 135 megawatts to bake quartz in its 6,000 degree Fahrenheit furnaces. That’s enough electricity to power 120,000 homes. This year, the plant will debut a retrofit to capture the waste heat currently being vented to the atmosphere. For $75 million, a giant vacuum system will duct off the 1,400 degree exhaust to make steam that will produce around 50 megawatts of free electricity. Efficiencies at the plant will double. To make that amount of electricity it would take $300 million worth of large wind turbines. So it’s relatively cheap. Plus, WVA stands to save tens of millions of dollars per year in electricity costs, making it the lowest cost silicon supplier in the world.

Another way to go about cogeneration is how United States Gypsum is reconfiguring several of its drywall plants. Typically they dry the wet gypsum slurry in 700-degree natural gas-heated ovens and use electricity from the grid for other applications in the plant. When retrofitted, they will burn natural gas turbines to make electricity for the plant and use the 900-degree exhaust to bake the sheetrock. Again, efficiencies double and USG saves tens of millions of dollars in energy costs annually. This type of cogeneration could also be used to power and heat entire city blocks in densely-populated urban centers.

The Department of Energy estimates 135,000 megawatts of cogeneration opportunities exist in the U.S. Since efficiencies typically double, there would effectively be 67,000 megawatts generated for free. By the way, that’s the equivalent of $3.75 trillion worth of solar panels! Cogeneration has more bang-for-your-buck efficiency than any other green technology and will certainly be a part of our energy future.

~Mark Bremer, Green Explored Contributor

9 comments:

  1. Mark good post A megawatt of solar cost about $5 million to install. 135,000 megawatts would be 675 billion dollars. Please check your math here. No doubt that cogen is the way to go.

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  2. Mark I had an added thought about the cost of PV system. As PV is only available 25$ of the time while the sun is shining one might need 4 times as much capacity around the world to displace the power from the coal or natural gas generation station In that case the investment would have to be 2.7 trillion dollars. I like your blog. Keep them coming

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  3. NY state is trying to install 100 Mw of solar for $600 million, so my number was a bit high. It would be more like $3.24 trillion here. For West Virginia, I'm not sure...

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  4. Yeah 100 mw at 600 million $ is 6 million $ per MW so my figure is closer to the amount. Still very expensive and cogen is a better option.

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