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Why aren't we harnessing waste heat?

Nathan W. Armes/Sipa Press/NEWSCOM/file

(Read caption) A power plant typically uses one-third of the energy produced by burning coal to produce electricity. The other two-thirds is wasted.

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For decades, Tom Casten of Recycled Energy Development  has preached the gospel of saving money, resources and the planet by simply not wasting heat.

The typical power plant uses only one-third of the energy produced by burning fuel (usually coal) to generate electricity. The remaining two-thirds of that energy escapes as waste heat. Mr. Casten says that we easily could — and should — harness this heat to warm water or even cool buildings. (You can cool with a heat source by using an absorption chiller.)

By harnessing waste heat, the same fuel would do twice the work. We'd have doubled efficiency.

The simultaneous production of heat and electricity is called cogeneration.

Electrical generation is not the only heat-wasting culprit. Various industries — the production of metals, glass, and silicon, among other things — release waste heat as a byproduct. In these cases, heat could turn turbines and generate electricity.

Indeed, Casten estimates that industrial waste heat alone could supply about 200,000 megawatts of electricity in the US. That's 20 percent of the US's electricity needs, or 95 nuclear power plants not built.

In other words, we could burn fewer fossil fuels, spend less money, and fight global warming simply by harnessing the heat now flowing out of the country's collective flues and smokestacks.

So why don't we?

In a word, outdated laws. The near monopoly on electrical transmission by utility companies doesn't help either. In most states, for example, it's illegal for all but a utility to erect electrical transmission lines across a public thoroughfare. So if you generate electricity with the heat coming out your smokestack, you can't get it anywhere. There goes the incentive to do something with the waste heat.

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