[Bernard Marx]

Last I heard, the technology was at the point where they were trying to heat the water in an enclosed system (pipes carrying the water round-trip) to avoid the problem of corrosion and mineral build-up, which can be substantial.

I've visited a couple of hydrothermal pilot plants that were set up in the 70s-80s and those problems seemed insurmountable. Corrosion ate up metal as fast as it could be replaced and minerals continually blocked pipes and valves. This would be the best possible source of energy IMO if it can be perfected. Does anyone know how they're getting around those problems in Iceland?

[thackney]

Probably in similiar ways to the methods used in the US.

Geothermal Energy Association
http://www.geo-energy.org/information/plants.asp

[jwparkerjr]

Seems like these problems would not be a consideration if they used a heat exchanger system where the water, or some other fluid, was circulated through the hot areas to pick up the heat but never actually came in contact with whatever is down there.

I can see where pumping water down there and then collecting the steam, along with all the contaminants, would foul pipes and valves. But a sealed system would not seem to me to have that drawback.

[MeanWestTexan]

"Does anyone know how they're getting around those problems in Iceland?"

The hot water bubbles to the surface. They don't have to go get it.