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Re: E-M:/ Power from Not-So-Hot Geothermal

Enviro-Mich message from Rane Curl <ranecurl@engin.umich.edu>

On Mon, 25 Sep 2006, Brad van Guilder wrote:

The article describes how the system makes use of hydrofluorocarbon (HFCs) refrigerants which is vaporized to drive turbines. HFCs are the less destructive substitute for ozone depleting CFCs. However, HFCs are extremely potent greenhouse gases - 1,000 to 10,000 times worse that Carbon Dioxide and their use should not be encouraged. Energy conservation and discouraging increases in demand for energy should be our first task.

The point is well taken, but it is not necessary to use HFCs for the cited low-temperature turbine projects. Other refrigerants, such as ammonia, would serve. CFCs, HCFCs and HFCs just get thought of first because of their stability, relative nontoxicity, and established use in refrigeration. The main problem with the low-temperature turbine idea is the poor efficiency, which lowers the power produced for the capital investment required.

--Rane L Curl

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