Potter Drilling, which is partly funded by Google.org, is developing a novel drill which uses heat, rather than abrasion, to break through rock.

Rocks do not expand uniformly when they get hot. This creates stress between the grains of the mineral sand that causes them to break apart. According to Jared Potter, chief executive of Potter Drilling, "The key is to heat it very quickly".

The idea was developed in the 1950s using hot air, effectively fired from a jet engine, to split rocks. But this only worked close to the surface in applications such as quarrying. The Potter drill uses super-heated water rather than air and is expected to work at great depths.

In a traditional drilling rig, most of the energy is wasted in friction and other inefficiencies. Drill bits wear out frequently  - in certain types of rock, it may only be possible to drill for 30 metres before they need to be replaced. Jared Potter explained that "Our technology doesn’t have a bit, can drill continuously and we can drill 3-5 times faster than they can. .. And we’re not taking the bit in and out of the hole. Our energy is right at the rock face."

In the past 18 months, the company has drilled test holes of 2.5 to 10 centimetres in diameter through hard rocks. In August this year, the company will, for the first time, drill a 10 centimetre hole to a depth of 300 metres. Jared Potter said that "A realistic target for this type of intermediate development would be 5 kilometres. Eventually our goal is to be able to drill to 10km."

The Massachusetts Institute of Technology has estimated that tapping just 2% of the potential of enhanced geothermal ("hot rock") energy between 3 and 10 kilometres below the surface of the continental USA could supply more than 2,500 times the country’s total annual energy use.

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Enhanced or "hot rock" geothermal power production usually works by pumping water into fissures in hot rocks deep underground, A shaft is drilled into the fissures and some ot the resulting super-heated water comes to the surface where it is used to drive a turbine.

One problem with this technique is the amount of water needed since much of it remains underground.

In 2000, a Los Alamos National Laboratory physicist, Donald Brown, proposed replacing water with supercritical carbon dioxide, a pressurized form that is part gas, part liquid. Subsequent modelling at the Lawrence Berkeley laboratory has shown that using carbon dioxide would produce 50% more heat than using water because the carbon dioxide will flow more freely than water through cracks in the rock.

As well as being more efficient, using carbon dioxide would sequester much of the gas.

A Salt Lake City-based geothermal developer, GreenFire Energy, has now announced plans to build a two-megawatt carbon dioxide-based demonstration plant near the Arizona-New Mexico border. The company proposes to commence drilling in 2010 and says that the location could yield enough heat to generate up to 800 megawatts of power and, in the process, could absorb much of the carbon dioxide generated by the six large coal-fired power plants in the region.

(Adapted from sources including Technology Review)

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The US Department of Energy is beginning a program to demonatrate a way in which the oil  industry can produce useful power from waste heat.

When drilling oil and gas wells and on exploration drilling rigs, fluids are used to provide pressure, to keep the drill bit cool and clean and to carry the drill cuttings out of the bore hole. Because these wells are often deep the fluids are hot when they reach the surface. In the average US oil well, ten times as much hot fluid is produced as oil.

The Department of Energy intends to demonstrate how the waste heat in this fluid can be used to generate electricity.

Because the use of the waste heat produces no new carbon emissions, it effectively lowers the carbon cost of the extracted oil.

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Engineers from the University of Oviedo in Spain have published research which shows that mine shafts on the point of being closed down could be used to provide significant amounts of geothermal energy.

The engineers have developed a method which makes it possible to estimate the amount of heat that a tunnel could potentially provide.

According to Rafael Rodríguez, from the Oviedo Higher Technical School of Mining Engineering, "one way of making use of low-intensity geothermal energy is to convert mine shafts into geothermal boilers, which could provide heating and hot water for people living nearby".

The study, published in the Renewable Energy Journal, gave as an example the geothermal energy potential of a two-kilometre-long mine shaft, in which the temperature of the rocks 500 metres below the surface is around 30º C. It found that water could be forced in through tubes at 7º C and return at 12º C, a big enough heat gain to be of benefit to towns located above the mines.

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Scientists at the US Department of Energy’s Pacific Northwest National Laboratory have developed a new method for capturing significantly more heat from low-temperature geothermal resources. A technical and economic analysis conducted by the Massachusetts Institute of Technology has estimated that enhanced geothermal systems could provide 10 percent of the United States’ overall electrical generating capacity by 2050.

Their technique uses the rapid expansion and contraction capabilities of a new liquid, called a biphasic fluid, developed by the research team. To improve efficiency, the scientists have added nanostructured metal-organic heat carriers, which boost the power generation capacity to near that of a conventional steam cycle.

The researchers expect to have a functioning prototype generating electricity by the end of the year.

Ironically, development of the technique came out of research aimed at finding nanomaterials for capturing carbon dioxide from buring fossil fuels.

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The World Wildlife Fund and the Australian Geothermal Energy Association have produced a report on Australia’s geothermal energy potential.

The main findings of the report are:

• By 2050 geothermal energy could reduce Australia’s emissions by avoiding approximately 25% of today’s electricity generation emissions.
• Over 17,000 Australians could be employed in the geothermal energy industry by 2050
• Jobs from coal, oil and gas (and their associated service and support industries) are readily transferrable to the geothermal industry, thanks to similarities between drilling technologies.
• Baseload emission-free energy resources like geothermal need targeted support today so so that their development is fast and seamless

Paul Toni, WWF Program Leader for Sustainable Development commented that “When it comes to geothermal energy, we truly are the lucky country. The energy stored in hot rocks near the Earth’s surface in Australia is a thousand fold what we use each and every year.”

The full report, titled "Power to Change: Australia’s Geothermal Future" can be downloaded here.

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Raser Technologies has begun delivering 10 megawatts of clean electricity to Anaheim, California, from its first low-temperature, binary geothermal plant located in Beaver County, Utah.  The plant’s power source is underground brine which is at a temperature of just 126ºC  Geothermal plants typically need temperatures over 180ºC to operate effectively.

In a binary cycle closed loop geothermal plant, hot brine is pulled from the earth and passed through a large tank that contains an evaporator. The heat from the brine causes a low-boiling-point fluid in the evaporator to flash into vapor. The vaporized fluid, which is now at high pressure, is fed into a high efficiency turbine, which drives a generator. With most of the energy removed from the vapor as it drives the turbine, the fluid is exhausted into a condenser heat exchanger. The exchanger removes any remaining heat and a small pump takes it back to the evaporator. The process is the reverse of a refrigeration cycle.

Traditionally, the lead time on a geothermal plant is three to five years, but the Raser plant has been powered up in just five months. To help meet such rapid construction schedules, the plant uses off-the-shelf modular components, taken from the air conditioning industry, which are essentially running in reverse.

The concept of running a refrigeration cycle in reverse to generate power is not new. However, until now, it has never been seriously pursued. The power generation modules used by Raser Technologies are modified version Carrier Industrial Chillers. By keeping as many components the same as possible, costs can be substantially reduced by taking advantage of Carrier’s mass production line. In fact, a Carrier refrigeration mechanic couldn’t tell the difference between the turbine/generator assembly and a Carrier compressor/motor.

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General Electric and Google have announced that they will collaborate to develop smart-grid technologies with a particular focus on plug-in hybrid vehicles and enhanced, "hot rock" geothermal systems.

Smart-grid technology lets utilities more efficiently manage electricity on the grid while smart meters and displays in homes and businesses allow consumers better understand and control home energy use.

The deal combines each company’s strengths: GE will make the hardware — from turbines to metering switches, and Google will make the software.

For example, electric cars will require more power generation capacity, which GE will provide, and the intelligence needed by the grid to tap the electricity stored in charged car batteries when they’re parked at night would come from Google.

In the geothermal area, Google will create visualization software while GE will work on power conversion technology. Google recently invested in a number of enhanced geothermal projects, while GE does not yet have a large investment this area.

GE, however, does have a large investment in wind energy, expecting revenues of more than $7 billion from wind power this year. Google will work on software to manage the grid so that power generated from wind, wherever it may be blowing at a particular time, will be available where it is most needed.

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Google is investing $US10.5 million in three research projects on the potential of using geothermal energy from deeply buried hot rocks to produce electricity.

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A survey released by the Geothermal Energy Association shows a 20% increase since January of this year in the number of new geothermal power projects under development in the United States. The report identified 103 projects underway. When developed, these projects could provide nearly 4,000 MW of new electric power, enough electricity to meet the needs of roughly 4 million homes.

According to Karl Gawell, GEA’s Executive Director, “These new projects will result in the infusion of roughly $15 billion in capital investment in the western states and will create 7,000 permanent jobs and more than 25,000 person-years of construction and manufacturing employment.”

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