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Hydrothermal is no walk in the park. First, the superheated liquid itself can be quite acidic, requiring pretty expensive stainless steel (or better) for piping. Plus, it’s super hot (duh) so it’s even more corrosive. Not cheap to build, but of course it has to be compared to the alternatives.

Second, the fluid brought up to the surface can release a lot of sulfuric gases (sulfur dioxide, hydrogen sulfide)
These have to be treated in some way. In the Iceland situation where they are actually drilling into a volcano, there could be a lot of dissolved gases in the water. At The Geysers, there is apparently a rock cap which allows the setup to use said rock as a barrier between the reaction (below) and the heating reservoir, so there aren’t many (or any) dissolved gases in the water.

Third, after the super hot water has done its work, it has to be pumped back underground. = more power thrown into the mix.

Google “The Geysers” for info about a pretty successful power plant in CA which generates (they say) about 725 MW, which is serious cheese, that’s roughly the amount of a full size nuke or coal plant.

I’m not an expert in this area; the propaganda from Calpine, the operator of the power plant up there, looks pretty good. If this could be done in more places, I can hardly see any objection to the idea of hydrothermal.

Not necessarily hydrothermal, but rather the broader potential, geothermal.

Within five miles below where you or I are standing right now is virtually an infinite supply of geothermal energy, 450 deg heat, in either dry or "wet" form.

The relative efficiency (entropy loss) with which an energy source can be utilized is a function of its gradient, and the 400 deg delT/30,000 ft of a say normal oil well is not at this time as efficient as just sucking up the oil (chemical energy) itself.

But the dryrock efficiency can be utilized, through "binary" plants and its efficiency enhanced. There is I think an MIT group working on the scenario's, but there is in general (politically) a lack of purpose. It's just that we have technically-challenged, arrogant Senators, and now President, who only think as far as their next media appearance, and the control over others it presents to them.

But there is plenty of energy available, in many forms; it's just that others will develop it before the cabal of lawyers in the US (re politicians) even allow it to be thought about in this increasingly sad and misled nation.

I believe the anthropogenic global warming threat is the most sinister scam ever coordinated on the US, and world's, citizens.

Johnny Suntrade

The Suntrade Institute

So of all the renewable sources the being pushed, why is hydrothermal seem to be so minimized in this country?

Like all "clean energy" schemes, after the romance of getting something for nothing rubs off, there is always a lot of expensive, difficult, and sometimes dangerous engineering needed to get to a level of commercial production from the clean source (which may or may not prove as "clean" as the promoters claim!)

Iceland sits on the "Mid Atlantic Rift". The tectonic plates are pulling apart as Europe and Africa move further and further away from the Americas. They are sitting on the edge of a plate at it's thinnest point, so they have a relatively easy job in tapping the heat in the magma beneath their feet. The plate is much thicker as you move toward the center and thicker still as you move toward the "subduction" zone (the "ring of fire" that surrounds the Pacific Ocean) where you have the North American plate sliding up and over the Pacific plate.

There are localized "hot spots" which allow magma to rise closer to the surface. The Hawaiian Islands and Yellowstone National Park are such but ordinarily the thickness of the plate is such as to make recovery of usable geothermal heat very difficult if not impossible. There are geothermal wells in California, however they are not reliable as continuous sources of power. When you begin to extract steam from a well you are "emptying the tea kettle" and the water table drops. If you withdraw steam at a rate grater then the water can percolate into the hot zone the output drops steadily. It then becomes necessary to let the field sit idle as the water table rises back toward its normal level.

Another problem is the quality of the steam recovered. Most thermal (steam) power plants run a closed cycle with the water used to make steam being purified, deionized, filtered and treated to be as near pure H₂O as is humanly possible to make it. This is done to prevent mineral deposits from forming in the boiler. It is also done to minimize corrosion which in a coal fired plant is a good idea, but in a nuclear fueled plant is absolutely essential (changing out a heat exchanger requires you to work inside the containment vessel, a "hot zone" of a different sort.)

Using steam from a geothermal source is not quite as easy as it seems because the steam is carrying a lot besides H₂O. It is not at all unusual to find hydrogen sulfide gas dissolved as well as all sorts of minerals. This precludes its use to directly drive a power plant. It is necessary to pass the raw steam through a heat exchanger containing the pure water required for proper operation of the plant. This has two major drawbacks, one being the corrosion and plugging of the HE making it a high maintaince item. The other being a loss of efficiency. By using the geothermal steam to heat process water it will produce steam at a lower temperature then the geo-source steam. It's in the nature of thermodynamics that the heat exchanger can never be 100% efficient. You can't really change the temperature of the geothermal source without drilling deeper into the crust. That is basically what the Icelanders are doing. They don't really need to go very deep compared to where most of us live.

The thermal efficiency of any heat engine (internal combustion, external combustion, solar, nuclear or what ever you can dream up) is limited by the ratio of the absolute temperatures of the "working fluid" measured at it's highest and lowest point during the cycle. In a steam plant that would be the temperature of the steam leaving the superheater and the condensate in the "still well" prior to re-injection back into the preheater. All heat engines MUST reject heat back to the environment because it (heat) becomes unavailable to do more work at the low temperature of the cycle. Keeping in mind that the "absolute temperature" of the condensate may be over 500°R. That limits real world thermal efficiencies (at least on the surface of the planet) to high 30s to low 40s.

Regards,
GtG

PS I wonder what the Icelanders would do if their bore hole became another volcano? Giving new meaning to the phrase "Aw $#!^"