Hot Rocks

[Torsten]

We focus a lot on harnessing the energy from the sun, yet we actually have quite a bit of energy in the earth that we could use - if we could get to it.

In Australia we have hot rocks at a depth of up to 5km that can be harnessed for power generation. A recent survey estimates that at least 20% of australia's electricity demand could be met via this method. The process is simple. Somewhere deep down is a geological feature that is either hot from the crust still cooling or from an ongoing radioactive decay. Two holes are drilled some distance apart. water is forced down one hole and pumped back up the other hole after passing through the hot rock. The hot water is then used to run turbines for electricty generation. The same water is used again and again.

Pilot projects in australia have received little or no governmental funding and yet they have gone ahead for most of this decade. The biggest draw back is probably that the power is generated in very remote areas of western Qld and northern SA and hence needs major infrastructure to be brought to the cities.

New Scientist has just run a feature on Hot Rocks so I thought I'd draw everyone's attention to this energy source.

What gets me though is why countries that have much easier access to lava flows don't harness this and become net exporters of liquid fuels. eg, it would not be difficult to use the heat from thermal springs to make hydrogen that can then be shipped anywhere.

[nabraxas]

New Scientist has just run a feature on Hot Rocks

:

// Who needs coal when you can mine Earth's deep heat?

SURROUNDED on all sides by desert, over 1000 kilometres from the nearest city, lies the tiny town of Innamincka, South Australia.

Innamincka has a permanent population of just 12, but each year up to 50,000 tourists swell their numbers, keen to experience the Australian outback, if not its lack of creature comforts. To keep these visitors cool, the tiny town runs up diesel bills of roughly $250,000 each year.

Come next January, however, the town could be powered for free, with electricity generated from heat mined from subterranean "hot rocks".

Conventional geothermal power taps hot water rising naturally to the surface from shallow beds of volcanic rock. By contrast, hot rock, or engineered geothermal systems, depend on heating water by circulating it through rock as far down as 5 kilometres, that has been shattered to make it porous. Neither type of geothermal power emits much in the way of greenhouse gases, but while volcanic rocks are rare, EGS can harvest heat from common types of hot subterranean rock, raising the possibility of a continuous, affordable, green power supply anywhere on Earth.

"There is an enormous amount of energy in the Earth's upper crust," says Ingvar Fridleifsson, director of the United Nations University Geothermal Training Programme in Reykjavik, Iceland, and author of a 2008 report on geothermal energy for a meeting of the Intergovernmental Panel on Climate Change. "If EGS can be proved economical on a commercial scale, its development potential will be limitless in many countries." A recent study led by the Massachusetts Institute of Technology suggested that for a government investment of $1 billion dollars EGS could provide more than 100 gigawatts of affordable electricity in the US by 2050 - 6 per cent of its current needs.

After decades of development, heat mining is now at a pivotal point. The first 1.5-megawatt power station at Europe's experimental EGS plant in Soultz, France, will soon begin operating continuously, and a second 3-MW EGS power station in Landau, Germany, is already selling electricity, albeit heavily subsidised. Meanwhile, the US Department of Energy has announced plans to fund research geared towards commercialising EGS, raising hopes that the US will again become a major player in hot-rock technology after first proving the concept in the 1970s at Fenton Hill, New Mexico.

However, while these plants have proved the technology works, they have yet to show that it is cost-effective, and this is where Innamincka comes in. The town sits on a 1000-square-kilometre slab of granite that reaches a depth of 10 kilometres. This slab is heated by naturally occurring radioactive elements, and covered by four kilometres of insulating sediment - the gas-rich Cooper Basin - on top of which sits the town. It is the biggest, shallowest, and at up to 290 °C, the hottest, non-volcanic rock formation in the world. This makes it an ideal place to try producing electricity from EGS, as the heat reserve in the granite is large enough to allow developers to rapidly build up to commercial-scale operation.

Also in the site's favour is Australia's pro-mining mindset. Government and private investors are ploughing money into EGS, comfortable with the high upfront costs for exploration and development, and the idea that wealth can be dug out of the ground. A total of 33 companies are exploring EGS in every state in Australia. One of these, Brisbane-based Geodynamics, has sole exploration rights to the granite beneath Innamincka.

"We are predicting a resource potential of 5 to 10 GW in this one slab of granite - 20 per cent of Australia's electricity requirements - based on its geology, temperature, and our estimates of how efficiently we can extract the heat," says Doone Wyborn, Geodynamics's chief scientist and executive director.

The only drawback is that the slab is 500 kilometres from the national electricity grid. Building the power line to the grid will add to initial start-up costs, but Geodynamics is happy to provide Innamincka with free electricity to prove the technology works.

Since 2003 Geodynamics engineers have drilled two 4-kilometre-deep wells, dubbed the Habanero wells after a particularly hot chilli. They have also forced water at high pressure down the injection well and through the rock to expand natural fractures, converting it into a porous, underground heat-exchanger. Earlier this year, they ran tests which showed that water could be circulated down the injection well, through the rock and up the production well at speeds that would make it possible to extract enough heat at the surface to run a power station. This is crucial, as if the flow is too slow it risks becoming uneconomic; too fast and it becomes unsustainable, with heat being extracted more rapidly than it can be replenished by conduction from adjacent rocks.

This week Geodynamics plans to inject a dye into the system and then monitor its concentration at the production well for two months. The dye will "smear out" as the water passes through the cracks, telling engineers the size of the underground network. This data will be used with temperature recordings to calculate how much heat can be mined from the two wells. If all goes to plan, Geodynamics will be able to "declare the reserve", meaning the company will release an audited statement of how much energy it can reasonably expect to extract from its wells. The company hopes to declare up to 10 MW, or enough electricity for a town of 10,000.

By January 2009, it plans to have a 1-MW demonstration plant in place to power Innamincka. Three years after that, Geodynamics hopes to go commercial, initially with nine wells and a 50-MW power plant at the site, expanding tenfold by 2016. "The whole world is waiting to see what happens. They are very brave to go in on such a scale," says Fridleifsson.

Whatever the outcome, experts agree that it will take more than one successful demonstration of commercial-scale EGS for the technology to go mainstream. "To bring the risk down so that banks will invest, we're going to need three to five demonstrations, at different locations, running for at least five years," says MIT's Jefferson Tester.

Those sites will inevitably be less favourable than the Cooper Basin area, requiring heat to be mined from rocks that are cooler, deeper and liable to fracture less favourably. But Tester, Wyborn and others are confident it can be done, with a little help from spiralling oil and gas costs. Besides making alternative energy sources like EGS appear cheaper in comparison, the ever-more desperate search for fossil fuels is spurring the development of faster, cheaper ways to drill very deep wells into very hot rocks, just the sort of technology that is needed to ensure that EGS becomes economically viable.

Australian exploration companies are taking a gamble on that happening. According to government figures, they forecast spending $800 million dollars between 2002 and 2013 on geothermal exploration.

As for Innamincka, it won't be getting free power in perpetuity. Ten or so years after its installation, the demonstration plant will be shut down, and the town's electricity meters will start spinning.

Rachel Nowak, Melbourne

© New Scientist 19 July 2008

Pump up the heating

Of all the ways to harness the Earth's heat, growth in only one is exponential: geothermal heat-pump systems. Rather than produce electricity for heating and cooling, these systems simply exchange heat between the ground and a building, taking advantage of the Earth's capacity to store huge amounts of heat.

Heat-pump systems have been installed in over 33 countries, with capacity greatest in the US and Sweden. China is catching up fast, however. The amount of space it heats with pumps almost quadrupled between 2004 and 2007 to 30 million square kilometres, according to a report at a renewable energy meeting in Lübeck, Germany, in January. The units typically comprise two loops of plastic piping. One loop circulates water through the building, while the other circulates water through the ground, allowing it to reach ambient ground temperatures of 5 to 30 °C.

The pump, which replaces the building's furnace or boiler, transfers heat from the ground loop to the building loop, raising its temperature to the 38 °C or more needed for heating. The cooled water then goes back to the ground to pick up more heat. In the summer the process is reversed for cooling.

For every unit of electricity put in to circulate the fluids and operate the heat pump, you get three to four units of heating or cooling from nature for free. Greenhouse gas emissions are 30 to 50 per cent lower than fossil-fuel-fired heating systems.

© New Scientist 19 July 2008

[Legba]

http://www.news.com.au/story

Hot rocks power 'within four years'

By Cathy Alexander

August 20, 2008 04:21pm

HOT rocks electricity is touted as the latest solution to climate change - and Australia could have its first super-hot power plant within four years.

Federal Resources Minister Martin Ferguson today launched the government's $50 million hot rocks fund, first announced two months ago.

Hot rocks technology - also called geothermal - works by pumping water deep below the earth's surface, to areas which generate plenty of heat.

The water converts to steam and shoots back up to the surface, where it is used to make electricity. The technology generates very few greenhouse gas emissions.

Mr Ferguson said hot rocks technology had "truly staggering'' potential for Australia as the world faced up to climate change.

"Geothermal energy provides clean base-load power and is potentially a very important contributor to Australia's energy mix,'' he said as he launched the fund in Melbourne today.

"We could now see Australia's first commercially viable geothermal power plants in place within four to five years.''

Mr Ferguson said just one per cent of Australia's geothermal energy would provide enough electricity to meet the country's power needs - 26,000 times over.

He said the $50 million fund would be carved up into grants of up to $7 million, to go towards the high cost of drilling deep wells, and to finance companies wanting to prove-up the technology.

Funding guidelines were released today.

The government did not provide money for renewable energy in this year's budget, sparking an outcry.

In June, Mr Ferguson backflipped and announced $50 million would go towards geothermal.

The money is the first to come out of the government's $500 million renewable energy fund.

Mr Ferguson said Australia's epicentre of geothermal activity was in South Australia's Cooper Basin, but there was potential in every state.

He noted there were challenges in commercialising geothermal energy.

Many resources are a long way from markets, which creates a transmission problem.

[Statakak]

Yep, Geothermal dose have great potential in Australia.

The Innamincka example sounds promising.

The two greatest problems I've heard of concerning Geothermal is;

1. Setting up the infrastructure to bring power from these remote locations, and the power loss during transition across long distances.

Which could easily be overcome with a bit of funding for these projects.

2. I've heard (no references sorry) that quite a large amount of water is required to run the electricity turbines as there is substantial losses in the rocks and as steam. And most hot rock locations in Australia are are in water deficient arias. (Please correct me if I'm wrong - I hate the idea of posting dubious info on important issues - but I think it's pretty right)

This would not be the case for heating of buildings, probably much more water efficient.

Probably why people in places that have lava flows don't do Geothermal may be that drilling deep bore holes and fracturing the rock could result in the creation of anthropomorphic volcanos, or or an unstoppable hot mud flow like like was created in Indonesia (last year I think) which slowly (over a month or two I think) consumed an entire town!

Iceland would be a good candidate for this though because it is the only place in the world where a mid ocean spreading zone (Zone where tectonic plates pull apart allowing the magma underneath to rise up solidifying, creating new crustal material (to compensate for that which is being subducted at plate margins) rises above the ocean surface.

This type of bassalt flow is the least explosive type of volcanic erruption and is under the least pressure (compared to normal volcanoes) and so would have the least technical problems, although they do still have the issue of earthquakes.

Great to hear that the government is putting some funds towards Geothermal development.

It gets frustrating how much our country resists supporting alternative energy development, especially with the potential sources Australia has.

[occidentalis]

The two greatest problems I've heard of concerning Geothermal is;

1. Setting up the infrastructure to bring power from these remote locations, and the power loss during transition across long distances.

Which could easily be overcome with a bit of funding for these projects.

2. I've heard (no references sorry) that quite a large amount of water is required to run the electricity turbines as there is substantial losses in the rocks and as steam. And most hot rock locations in Australia are are in water deficient arias. (Please correct me if I'm wrong - I hate the idea of posting dubious info on important issues - but I think it's pretty right)

This would not be the case for heating of buildings, probably much more water efficient.

I guess the water issue would be a problem here too, but wouldn't a solution to the first problem be to generate hydrogen gas on site and transport that in tankers to the cities?

no problems with power loss due to resistance there.

[Chiral]

To quote RockHammer ....Probably why people in places that have lava flows don't do Geothermal may be that drilling deep bore holes and fracturing the rock could result in the creation of anthropomorphic volcanos, or or an unstoppable hot mud flow like like was created in Indonesia (last year I think) which slowly (over a month or two I think) consumed an entire town!

This is my big concern..when ever we start drilling and cracking into earth...man it cant be good...there is a great big ball of free energy in the sky every day...at some point we will crack open our brains and work out how to use its energy the RIGHT way.

H.