Thursday, December 06, 2007

Green Vocab WotD #001: Cogeneration

My, aren't I being optimistic by numbering this one 001 and though I expect 998 more of them! I'm hoping to bring a little more information into my blog here as well as keep myself "in the know." No use talking about stuff I know very little about, eh?


From Wiki:

Cogeneration (also combined heat and power, CHP) is the use of a heat engine or a power station to simultaneously generate both electricity and useful heat.

Hence, COgeneration. It goes on...
Conventional power plants emit the heat created as a byproduct of electricity generation into the environment through cooling towers, as flue gas, or by other means. CHP or a bottoming cycle captures the byproduct heat for domestic or industrial heating purposes, either very close to the plant, or —especially in Scandinavia and eastern Europe—for distribution through pipes to heat local housing.

This goes back to the LED lights I put on my X-mas tree. I told you that there is no hear coming off of them and that is where the energy savings is. In this case, the "byproduct of electricity generation" is heat and there is nothing to do about that (for now). So, there is waste energy. Remember, heat = light = electricity = radiation = energy. They are in different forms but it's all, thermodynamically, the same thing. We could theoretically power our own biological processes with electricity... in fact some of them are (nervous system, anyone?)

Cogeneration is another example of "Big Picture" thinking. Someone realized, decades after the discovery, that, hey, energy is energy. Waste heat (like your car engine) is wasted energy from gasoline. Get rid of the waste heat and you use less gasoline, plain and simple. In the case that you can't get rid of the heat (like your car engine), use it somehow.
In the United States, Con Edison produces 30 billion pounds of steam each year through its seven cogeneration plants (which boil water to 1,000°F/538°C) before pumping it to 100,000 buildings in Manhattan—the biggest commercial steam system in the world.

Cities are disgusting, pollution-soaked, dangerous clusters of wasteful humans... for now. They are also beautiful in their design and complexity and a great place to start using green technology. I find cities fascinating and will likely never live outside of one. Despite the destruction and waste that goes into maintaining them, it is better, in my opinion, than sprawl. Working to make NY, LA, Seattle, etc. cleaner will always trickle down to other locations.

Where was I going with that? Oh yeah... that kind of heating couldn't really happen in Spokane or Poway or any other small city. The electricity generation has to be massive and the populated areas have to be nearby. Look forward to systems like this pervading the nation.
Byproduct heat at moderate temperatures (212-356°F/100-180°C) can also be used in absorption chillers for cooling. A plant producing electricity, heat and cold is sometimes called trigeneration or more generally: polygeneration plant.

Heat used for cooling?! That's witchcraft!!! Not really... refrigerant like what is in your car/home AC is simply moved and vaporized using heat. Refrigerant cools things down by evaporating, like how your hand gets cold when you spill rubbing alcohol on it. It's all thermodynamics!
Cogeneration is a thermodynamically efficient use of fuel. In separate production of electricity some energy must be rejected as waste heat, but in cogeneration this thermal energy is put to good use.

Amen to that!

Hopefully we all learned something... I know I did :)

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