Geothermal Energy

I don't know much about this so it might be better to get an expert opinion, but I did see and hear about such systems in operation in Iceland. I believe they drilled a deep bore hole and pumped water down them, which turned to steam and was forced to the surface by the pressure much like a geyser. The part I am not positive about was if they were pumping water down, or if they just got steam out of the holes naturally. I know around the power plant, the ground was steaming naturally but that doesn't mean much other than they didn't have to drill that deep.

Geothermal plants are located where heat is already near the surface. A feed well and an injection well are drilled, and away we go. Because it is rare to find water hot enough to use directly in a steam turbine (not to mention the mineral content) a binary system is normally used. In a binary system, a working fluid (usually pentane or butane) is used to transfer the heat from the water to the turbine. It's really a pretty simple process, though the devil is truly in the details. Biggest problem is corrosion caused by hot, oxygenated mineral water. Does that answer your initial questions?

Yes it does,

It gets me a little closer to the process that current technology is using, the binary system, pentane/butane being used as a working fluid gives me some more research to do.

I imagined that the source of energy was limitless, but it appears that some thinking is that geothermal plants take more energy out then nature can put back.

Makes me wonder what type of technologies need to be developed over the next 20 years to start feeding large ammounts of electricty into the grid from geothermal plants.

Thanks for that

Well, all of nature is a big heat engine, and entropy is the ultimate enemy. Although billed as a renewable resource, it is true that any energy taken from geothermal sources is gone forever, but the same subsurface water can be pumped to the surface and send back for reheating over and over again. I have no data on geothermal sources "playing out", but it seems to be a non issue so far. Let me know if you find out differently.

Nevada (where I'm at) considers themselves a leader in geothermal power generation. Their website is here. Good luck on your research.

This map, http://www.smu.edu/geothermal/2004NAMap/Geothermal_MapNA_7x10in.gif, has some interesting information about this subject. The writing's a bit small, but you can just about make out some of the useful facts. If you right click/Save picture As... you can zoom it with something like MS Office Picture Manager & read it quite easily.

There's a plot of temperature vs. depth for a well in Kansas, and it gets up to 29°C at 500m (not really very deep!).

In 1964 I visited Klamath falls, Oregon. Actually I was visiting my fiance and soon to be bride. While there I was introduced to geothermal energy being used to heat homes and streets. If there was a problem in the winter with freezing streets they piped it with geothermal energy. We haven't been there recently but it would be a good place to start.

Go to Nevada Power's site. They do what you looking for.