Alan Belcher says

Essentially a low-temperature Brayton cycle system, it uses air as the thermal transport medium. Heat would be extracted at well head via a liquid/gas heat exchanger to heat pressurized air at constant pressure. In a typical open cycle system, the compressor draws in air at atmospheric pressure, discharging same via an intercooler to the high pressure area. An expander section draws air from this section, reducing the pressure back to atmospheric in the process.

Operating temperature would be in the range of 54.5 degrees C (130 degrees F) to 149 degrees C (300 degrees F).

The novel aspect in this system is that both the compressor and the expander are positive displacement machines based on manometric technology. “Sealing” is achieved entirely by hydrostatics thus eliminating any internal frictional components. Mechanical efficiency is extremely high – possibly in the order of 96% -- which results in a correspondingly high thermal efficiency of about 27.4 % for a simple cycle machine (no regeneration).

Rotational velocities are limited by a maximum peripheral velocity, resulting in low r.p.m. at extremely high torque. Consequently it is quite impractical to derive mechanical energy directly and, for electric power generation, an additional stage is required. The normal power output of a manometric engine is a high pressure source of water or air. For electric power generation this fed a conventional off-the-shelf hydropower turbine/generator set. The net efficiency at the electrical output must therefore be reduced to approximately 90%.

Ernest Siddall says

Ernest Siddall April 14

david hawk says

The environmental community was partially successful (economic times did the rest) in pushing the major and large independent oil compainies out of the geothermal exploratory picture over the last 25 years. Those companies understood risk, how to measure it, and how to accept it. They had access to capital and they were not afraid to drill a dry hole. There are only a few companies left along with a few individuals who are willing to risk it all.

Those indiviudals who "want" geothermal developed for the most part, have no skin in the game. They are willing to tell us how it can be done and even must be done but they are not putting any personal wealth at risk. We need to listen to the remaining developers and they must realize the value they receive for their electric production must fall within reasonable guidelines similar to the avoided cost of the utility to which it will be sold. After the risk dollars, a significant amount of capital is required prior to the first turn of the generator. That said, geothermal no longer has to compete with lower cost hydro or coal. It may come into its own right now if anyone is left who will advance the capital.

David H. Hawk Energy Analysis and Answers

Richard Vesel says

Federal and local governments are trying to spend huge amounts of money on CCS demonstration power plants right now. For example, the State of New York wants to devote millions to one of these bogus "clean coal" projects:

http://www.state.ny.us/governor/press/press_0610081.html

http://www.praxair.com/praxair.nsf/0/73500C7E5C3A94D4852574650052EEB8?OpenDocument

The overall investment in this one project was to be $45M for a 15MW power plant.

Binary cycle equipment could be bought and installed, for the an equivalent capacity, for less money. New York could be demonstrating a 21st century technology power plant, rather than a 19th century one with a fancy bandaid applied to it. All this in or near an area with known geothermal resources already available. For a slightly larger investment, a larger combined flash/binary plant could be built, of perhaps 40-50MW, and it could be designed as a "standard plant" from which multiple copies could be located around the region, for hundreds of MW of clean environmentally benign generation.

Repeat this scenario in dozens to hundreds of locations around the world ... sinking money into CCS is going to be a dry hole, and the same investment in geothermal will pay off for decades to come.

I have personally written to parties involved to try to get them to look forward, and to separate themselves from the coal lobby so that they can do the right thing with their investments in power generation. More voices added to this would be helpful.

Two companies have binary cycle equipment already available: United Technologies PureCycle(TM) - PureCycle 200, and Calnetix Power Solutions' WHG100. These systems can work in parallel and cascaded/serial systems, at 8-10% thermal-to-electric conversion efficiency.

Regards, RWVesel

David Walters says

1. Money. 2. If you find hot rocks, and not a steam reservoir, which is what California' geo plants are mostly, there is NO guarantee that if you inject water, you can get stream out *at pressure*. 3. Basically you have to sitting almost on top of a volcano to find this kind of steam or exploit it. 4. You have to have a hazardous waste permit and disposal plan. "But I thought this was clean energy". Then you thought wrong. You need to steam cleaners to clean the steam of a variety of waste products, mostly sulpher and heavy metals. It can and is done, much of it recycled, but it costs money. 5. Reservoir steam can decay over time, thus a falling rate of profit for investments made.

Just some things to think about but it is WHY there is not massive geothermal generation out there.

David

Mathew Hoole says

My understanding of geothermal is that at the moment it can't generate enough power to be competitive with hydro or a coal plant? Is this a fair statement?

If so, but what about the potential for geothermal. All the soundbites and other marketing aside, does it have potential? Is it just a case of digging deeper to generate more energy?

Comments appreciated.

Cheers

Roger Arnold says

There are partial exceptions, of course. In areas where magma intrudes close to the surface, the heat flow is high enough that the reservoir the geothermal well is drawing from will remain hot indefinitely (on a human timescale). Prime geothermal locations are those where the magma intrusion is close to porous rock that hosts an aquifer. But the number of such locations is limited, and the best are already tapped. They tend to make themselves somewhat obvious, with subtle clues like hot springs, geysers, and, uh, volcanos.

Fred Linn says

This is not true. There are two sources of heat in the interior of the earth.

The first is radioactive decay. As radioactive isotopes decay, they give off energy which is trapped in the earth's interior and builds up. This energy is sufficient to melt rock and drive convection currents that drive tectonic plate movements--basically thin cool crusts on top of a thick soup of slowly boiling magma(molten rock) which carries the heat toward the surface.

The other source of heat is electrical induction. As the earth moves around the sun, the core of the earth which is primarily molten iron passes through magnectic fields created by the sun and a sea of magnetically and electrically charged ions streamiing into space from the sun. This heats the core by electrical induction in the same way that wires passing through a magnetic field in a generator induces current flow. The resulting flow of electrons through the molten iron core heats the interior of the earth by electrical resistance, the same way that a space heater makes heat by passing electrons through a wire with electrical resistance.