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Ongoing volcanic activity in many parts of the world suggests a potential abundance of geothermal energy. There are locations where geothermal energy produces steam that directly and indirectly drives turbines and electrical generation equipment. The Top Energy group in New Zealand flows geothermal steam through heat exchangers to vaporize pentane that drives the turbines. The Raser group has developed a heat exchange technology to convert geothermal heat at near the boiling point of water to electric power. There is an evolving technology that shows the potential to convert even lower-grade geothermal energy into electric power.
Research undertaken by Dr. Jorg Schlaich in Germany revolves around using a physically very large technology that will operate at relatively low efficiency while being able to convert renewable thermal energy to electric power at very competitive cost per megawatt. His research forms the basis in the development of solar towers, a scale model prototype of which is being demonstrated as proof of concept near Seville in the south of Spain. That research and its proof of concept indicates that it may be adapted to generate large amounts of electric power from low-grade geothermal energy where the temperature levels are well below that of the boiling point of water.
Much of that low-grade geothermal energy can be found at deep in the earth in the permeable and porous rock of exhausted natural gas wells and exhausted oil wells. The rock temperature at the bottom of these wells can vary between 50 degrees C and 120 degrees C (120 degrees F to 248 degrees F) and that heat is accessible because in many parts of the world water is pumped into the wells to displace the residual oil or gas. The water becomes the medium by which to transfer heat to the surface using wells that had originally been drilled to extract gas or oil. The cooled water may then be returned to the deep porous rock via other nearby wells.
The Green Tower Group of Germany and South Africa as well as the Enviromission group of Australia and the United States propose to operate their solar towers 24 hours per day. They intend to do so by storing some daytime thermal energy in tanks and troughs of water. To access geothermal energy, the center of the tower would be built directly above a deep-drilled well of an exhausted deposit of natural gas. The air intake skirt of the tower would extend to include the return well located some 2 miles or 3 kilometers away. The water reservoir in the porous rock could be several thousand meters below ground surface.
Geothermally heated water at 60 degrees C to 80 degrees C would be pumped up one well and flow through a spiral pipe placed on the ground under the intake skirt before being flowed into the return well. The water would have over 845 times the density and over 4-times the specific heat of the intake air flowing under the skirt and toward the tower. The spiral pipe would heat the air current at a comparable rate of effectiveness as a cross-flow heat exchanger and becomes the trigger that sustains the air current in the tower.
The geothermal heat under the tower and its intake skirt would serve a similar purpose as the control valve at a hydroelectric dam, the trigger of a thyristor or the button of an aerosol can that requires very little energy to initiate the movement of a vast amount of energy. There would be much latent heat on the ground and on large bodies of water for several kilometers surrounding the air intake of the tower skirt. The tower would become the conduit through which air currents carry low-grade thermal energy to higher altitude.
Outside of tropical regions solar towers may operate on solar energy during summer and on other sources of renewable thermal energy during cooler weather, thereby improving the tower's cost competitiveness per unit output. During winter air at 10 degrees C or 50 degrees F could flow into the intake skirt and cool the water in spiral heater pipe from 80 degrees C or 176 degrees F down to 20 degrees C or 68 degrees F. The temperature or the air approaching the turbines built into the base of the tower could rise to over 40 degrees C or 104 degrees F.
Heating the air inside the tower would increase both the updraft and the air velocity through the turbines. Tower technology would allow greater extraction of thermal energy from saturated geothermal steam that is slightly above the boiling point of water. All of the latent heat of condensation would be transferred to the incoming air as the steam in the pipe system cools and is transformed into liquid water. A geothermal tower could operate on geothermal steam for the first several years after which it may then operate on low-grade geothermal energy for the next several decades.
The depth and extent of the porous rock in the earth below the tower could determine as to whether to extract only geothermal energy or whether to use the porous rock as a means of seasonal thermal storage. During summer heat from concentrated solar thermal energy or from large-scale air conditioning systems may be pumped into the porous rock using water pipe systems. This option would be viable if insufficient heat from molten magma deep in the earth is transferred into the porous rock during summer when the tower operates mainly on solar energy.
Low-grade geothermal energy could become available from closely spaced test wells that may be uncapped. Modern drilling technology may be used to drill an interconnecting lateral well at great depth through which water may flow between pair of wells that are located near a river or ocean. The difference in temperature to between the surface water and the deep water may energize a closed cycle heat engine that operates on a refrigerant such as ammonia or R138a as the working fluid. Such technology would be comparable to ocean thermal energy conversion technology.
An abundance of capped deep test wells exist worldwide and offer the opportunity to access geothermal energy at low cost. Most were drilled into the earth during an earlier period of oil exploration. Other similar deep wells were drilled into productive deposits of oil and natural gas that have since become exhausted. These wells also hold potential to provide abundant low-grade geothermal energy.
Solar towers, vortex engines and geothermal towers only need heat the air at the base of the towers to a few degrees above the prevailing ambient to generate a convection current of air that will flow up the tower. Despite low thermal efficiency, large towers can be designed to operate on a combination of geothermal and solar heat to improve the cost competitive per unit of power output against other renewable thermal technologies.
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There is an existing system that is already in use for low-quality geothermal-to-electricity energy conversion: United Technologies, parent company of Carrier Corp. (of air conditioning fame) has a system called PureCycle 200. They have used standard large scale air conditioning equipment, essentially running "backwards", to generate 100-200kw per system. From the description above, it seems that a lot less infrastructure, and thus capex, is required to put in a small scale plant.
I am H>S.Sharma,FAO(UNO) Consultant Ex.In India there are large no of sites where Geothermal Energy could be effectively utilised,but have not been done due tp lack of information -H.S.Sharma M-09873020599 Sites are located at :-Chintapurni(Near Pathankot) in Himchal pradesh wher huge quntity is burning as aflame for thousands of years 2.Sohna 60 Km from Delhi whwere water at 80C is coming out for thouasnds of years 3.Munger in Bihar(Near Dumka large amount of hot water at high temperature flows ) hot water is flowing for thousands of years If any body interested i acn give more details-H.S.Sharma
KENNY MAGERS 1.21.09
Yes I agree that there is a system that is known about that has the output of a steam power plant from nature's combinations of 8. Geothermal is really a result of solar heat, and natural wind on the surfuss. RENEWABLE THERMAL WIND POWER THE ENERGY POWER SOURCE has 5 differant size structure from 10-20 homes to a large city, and beyond. This systems can be built over a closed steam plant using all the infurastructures thus costing less and doesn't need to rely on the wind or solar to keep running after start up. Thinking for some is hard to think outside the box of normal thought process. This is not new technologies it's been around over 40 years, It's the combinations of it's internal thermal rescources that make the world's first natural base power plant utility and water systems from 1 structure. The facts of smaller structures can be built where needed no battery storage ! ON DEMAND POWER ! Get the facts email@example.com
Jerry Watson 1.21.09
Kenny: Geothermal energy is not a result of solar energy or surface wind. The source of geothermal heat is the radioactive decay of isotopes in the liquid outer core and solid inner core of the earth. I believe the current scientific consensus is the molten iron and nickel outer core would have solidified millions of years ago was it not for the radioactive decay of uranium, thorium, and potassium so geothermal energy is more correctly classified as nuclear energy. Solar and wind effect thin layer at the surface that acts like a capacitor in that its heat capacitance acts to produce temperatures approximating the average temperature of the air above. Using these near surface temps to do work or increase efficiency is often labeled as geothermal, but since it is not geothermic in nature, I feel it is a misnomer.
Jerry Toman 1.22.09
Harry: The Vortex Engine is an excellent choice for combining geothermal and other surface heat sources with atmospheric sources (Convective Available Potential Energy) that may be strong during some months of the year, yet weak during others. In no case, however would an Atmospheric Vortex Engine need a tall and expensive tower in order to function effectively, as would be required by a solar tower (e.g. Enviromission). The comparison between the two can be found at:
At least this article indicates an awakening to the idea that the earth's surface is not the most efficient place to reject heat involved in the production of work using the Carnot cycle.
There are sources of warm surface sea water in places with a dearth of other types of resources (Gaza in SE Mediterranean) which could be transformed by these technologies. From the cheap electricity which could be produced, they could become world manufacturing capitals, due to their otherwise geographically advantageous locations. The Great Lakes are another great seasonal location. Even in January, the water temperature of Lake Michigan near Chicago is 30 C greater than the air temperature. Via water-air heat exchange inside a Vortex Engine, great quantities of electricity could be harvested from a convergence zone produced by creating a massive (rotating) updraft of buoyant air.
Don Hirschberg 1.24.09
"the water temperature of Lake Michigan near Chicago is 30 C" even in January.
Not so. Take it from one who has been in Lake Michigan many times I have never known the water temp to be anywhere near as high as 30 C even in late summer, let alone January.
Which brings to mind a true story. It goes back many years. Every year some people in Gary (Indiana, not Illinois) would row out in the lake to fill jugs at a certain spot with lake water. When asked why they responded that where they took the water was the last place to freeze. They wanted that water for their car radiators. A perfect example of the scientific method.
Don Hirschberg 1.24.09
Jerry, I miss-read you. Sorry. But I don't agree that the lake water is 30 C above January air temps. Off the top of my head I'd say water at about 40 F and air at about 25 F or something like 8-10 C delta.
Jerry Toman 1.24.09
Don--your temperature data are correct, and you are also right about the delta in January being about 10 C. In the last quarter of the year, however I believe the actual temperature difference between the day/nignt average air, and the surface water temperature to be in the 12-15 C range (midlake at Illinois-Wisconsin line).
However, this temperature difference represents only the "sensible" temperature differences. When the air is humidified by lake water, much of this condenses in the 2-5 km altitude range releasing additional heat which can amplify the temperature difference between the rising stream and its surroundings to as much as double the original value at the surface. It was this potential that I was trying to convey, but should have been more precise in the description of my methods.
Glad someone was paying attention, however.
Don Hirschberg 1.24.09
Contrite about my earlier misreading I sought and found the actual temperatures for Chicago and Lake Michigan water - actually very easily.
Average air temperatures are 32 F high and 18 F low in January, for an average of 25 F. (I guessed that one on the head.) At 1900 CST (as if that makes a difference) the lake water was 33 F extending for some miles out from shore to a high of 42 F vic the center.
I can recall seeing the lake frozen beyond sight. I thought that was normal. I also remember crossing the lake on a ferry (carrying freight trains, cars and passengers) and crushing a path through ice for many miles. The sound was impressive.
I don't know what kind of temperature differences a Vortex engine needs to be viable. But I doubt whether "average temperatures" are what we are after. Because a river has an average depth of three feet doesn't mean I can wade across.
Thanks for responding
Jerry Toman 1.25.09
Thanks for your personal anecdotes and experiences in this very interesting area of our country. I am convinced that there is much untapped energy in the region which could be the key to "sustainable redevelopment".
I made my comments initially for the month of January, perhaps somewhat carelessly because this happens to be the month we're in now. In my response to you, I backtracked a bit, indicating the potential for the AVE (from lake water) would be greatest in the fourth quarter of the year. By the time January rolls around, the AVE potential would have weakened considerably, at least during the day, and the need for some other source as a "fill-in" would be required, perhaps extending through most of the first quarter of the year. Beyond the vernal equinox, CAPE itself fills the air, and the AVE would not need any lake water to operate (see FAQs or go to http://tornadochasers.org for a "CAPE Class" ).
The "fill-in" electricity supplier would not necessarily require many more stand-by turbines and generators and electrical connections, since the exhaust stream from an inexpensive "peaking" gas turbine unit based on natural gas could simply send its second stage heat to the AVE instead of to a new steam turbine, with only a moderate loss in efficiency.
Alternatively, if horizontal winds are strong, the AVE itself could lperhaps be designed to capture the energy of this flow, or, at the very least, be supplemented with energy from a conventional wind farm.
As with any "renewable" energy source, the potential ebbs and flows. However, the AVE energy output would not only most consistently be in phase with people's needs, but its output would be rather more predictable than say wind power alone would be.
In any event, the purpose of my posting is not just to engage in rhetoric, but to demonstrate real possibilities in the hope that some "decision makers", be they commercial or governmental, take the time to inquire directly to the owners about them. They can be reached at http://vortexengine.ca
If I'm not mistaken, I believe some type of presentation to a group could be arranged, either in person or remotely.
Jerry Toman 1.28.09
The correct reference (for those of you interested in understanding the Convect Available Potential Energy in the atmosphere) should have been http://tornadochaser.net (not tornadochaser.org)