Geothermal

Geothermal energy is produced from the internal heat of the earth.

The Philippines, in at least one respect, is ahead of its time. Around 25% of its electricity is generated from underground heat produced by geysers. It’s free, inexhaustible and available day & night.

Jefferson Tester, a researcher at the Massachusetts Institute of Technology (MIT), says the earth’s depths are hot everywhere. If there is no natural volcanism to bring the heat to the surface then his answer is to create controlled, artificial volcanism – “Engineered Geothermal System” (EGS). Instead of relying on hot springs, you make your own.

In principle it’s easy to make your own – you drill 2 parallel holes in the ground a few hundred metres apart, continue to drill until the rock is hot enough (approximately 200 degrees Centigrade), then pump cold water down one hole and wait for it to come up the other at a suitably elevated temperature. The superheated water turns to steam which powers a generator.

Dr Tester believes this geothermal power source is neglected because it’s invisible. Everyone feels the wind and the sun but only miners feel the heat from the interior of the earth. Therefore, no one thinks of drilling for it.

Dr Tester opines that spending $1billion on demonstration projects over the next 15 years would change all that. Such projects would provide enough information to allow 100 gigawatts worth of EGSs to be created in America by 2050 at a commercially acceptable price.

Much more than this can be done though. The heat under the USA is equivalent to 2000 years worth of the country’s current energy consumption, according to a report Dr Tester and his colleagues published a few years ago. Similar assessment of Europe’s heat resources from the earth suggest they could generate as much electricity as all of the continent’s nuclear power stations produce now.

EGS, however, is not as easy as it sounds. Before the term ‘EGS’ was coined, the field was known as hot-dry-rock geothermal energy, & this name encapsulates the problem precisely. A century’s worth of data collected by oil companies suggests that impermeable rocks, i.e. granite, are most effective reservoirs of heat. Dryness increases their heat capacity. To get the heat out of them though, you have to make them permeable; which is the E in EGS.

Some of Dr Tester’s $1billion would be spent on working out how to drill cheaply & effectively through this sort of rock – something oil companies don’t do as impermeable rocks do not contain petroleum. A lot of $ would go on finding ways to force open fissures in the granite to let water flow from the injection hole to the exit hole.

The Cooper Basin in South Australia has the hottest non-volcanic rocks of any known place in the world & Australia leads the world in exploiting subterranean heat. There are currently 7 firms that are snooping around in the area.

One of them recently completed what it claims is a commercial-scale well. The turbines too will soon turn in France on an experimental non-commercial project.

If it can work, EGS has got the lot – no unsightly turbines, no need to cover square kms of land with mirrors, & it’s always on.

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