Geothermal energy – why so little attention? PDF Print E-mail
Thursday, 27 August 2009 07:34

geothermal3_optThe future could see power stations requiring no fuel and releasing virtually no greenhouse gases into the atmosphere

ikola Tesla, the man who invented the alternating current systems that powered the world, was appalled at the idea of using coal and oil to generate electricity. “That’s like living on capital,” he said. 

Tesla’s answer was to use hydroelectric power and then geothermal power. The challenge, as he saw it, was to find an economic way to drill holes deep into the crust of the Earth to tap the unlimited heat seeping up from the Earth’s molten core.

He understood that temperatures increase by between 2.5° and 3° C for every 100 metres of depth from sea level so at, say, 10 000m, the rocks would be about 300° C and capable of producing a continuous supply of steam.

At the time, the technology to drill these deep wells did not exist, but there were a number of ‘hot spots’ where volcanic action brought some of the heat close to the surface in hotwater springs and geysers.

One of them was in Italy, where they have now been using geothermal energy to produce electricity for about 100 years.

Iceland obtains all its power and heating from geothermal energy, while New Zealand and California have had small geothermal power stations in operation for about
50 years.

Kenya has a small industry, but a series of new geothermal projects is planned in the Rift Valley to provide a quarter of the country’s electricity by 2017. The proven potential is 7 000MW, roughly equivalent to four Koeberg nuclear power stations.

In Indonesia and the Philippines, the oil company Chevron has developed enough geothermal electricity to power seven million homes.

The present generation of geothermal plants tap into aquifers heated by volcanic action. This water is under great pressure and heated to a few hundred degrees Celsius.

When it escapes to the surface, it becomes super-heated steam to drive turbines and generators in the conventional manner.

Where there are no hot aquifers, the plan is to use enhanced geothermal energy. This involves drilling down into the hot rocks and introducing water from the surface to produce the steam. When the resulting steam has passed through the turbines, it is condensed and reintroduced through an adjacent well.

The existing geothermal energy projects are found in the hot spots near the boundaries of the Earth’s tectonic plates, but the Icelanders – the leading exploiters of geothermal energy – say, like Tesla, that it is simply a matter of drilling holes deep enough to reach the heat.

In 2006 a Massachusetts Institute of Technology (MIT) study estimated that an investment of only US$1 billion in research and development over 15 years would pave the way for 100 billion watts of generating capacity in the United States by 2050. That is equivalent to 55 Koebergs.

The MIT study went on to say that geothermal heat had the potential to supply all of the world’s energy for a few thousand years!

A billion dollars sounds a large sum, but the required investment seems trivial when compared to the sums the US government has used to bail out ailing companies and banks. And it is also small in comparison to the funds sunk into nuclear research.

So we could have clean power stations that require no fuel and release virtually no greenhouse gases into the atmosphere. And there would be no radioactive wastes about which to worry!

In the long run, geothermal energy would have to compete with nuclear power and sunlight converted into electricity by photovoltaic cells. These PV panels are expected to improve dramatically over the next two decades as a result of developments in nanotechnology, but even the existing silicon panels can be made more productive by using mirrors to reflect more sunlight onto them.

With more sunlight comes more power and since mirrors are much cheaper than PV panels, the costs go down.

At present, geothermal wells are seldom more than 3 000 metres deep, but if the technology is to be more generally exploited, the wells will have to be three times as deep. This is already technically possible, with oil companies drilling down to depths of 11km and 12km.

In South Africa, we have working gold mines as deep as 3.7km, and the Anglo American company is planning a new mine (Western Ultra Deep) that will be 5km deep or 3 000m below sea level.

One of the greatest problems it will encounter is heat from geothermal energy, and massive cooling plants will be required to reduce temperatures.

The existing gold mines use cooling plants on a large scale and the mining industry has a long history of fighting against geothermal heat, but not of using it. Is it too fanciful to suggest that one day we may start drilling down to the hot rocks from the depths of a worked out mine and build an enhanced geothermal power station underground?

Given South Africa’s unchallenged expertise in deep-level mining and the geological knowledge accumulated over a century of prospecting for minerals, it is surprising that we have given geothermal energy so little attention.

It is also surprising that the National Energy Regulator omitted geothermal energy from the schedule of tariffs for electricity from renewable resources. That may have encouraged entrepreneurs to explore for hot spots near some of our hotwater springs.

We may be missing a great opportunity, but geothermal electricity will come and it will probably be supplied by the oil industry – when it is ready to do so. The oilmen know that the days of their black gold are nearing an end and they are feeling the pressure from the green lobby. But they also know that they are in the best position to provide the clean energy the world needs.

Over the last 150 years, they have drilled many thousands of holes into the crust of the Earth in just about every part of the world, and the accumulated knowledge means that not only do they know how to drill very deep holes, but they also know where to drill them.

And all that basic research is paid for.

For the present, however, they have oil to sell and they are doing very nicely.

What far-sighted governments around the world should do, is push the oil industry into accelerated research and development of geothermal power. The industry has the funds and it is the best way for the oilmen to stay in the energy business when the new generation of electric cars takes to the streets.

It is ironic to think that our salvation may lie with the industry responsible for much of the worst pollution, but it will not be the first time that oilmen have prevented an ecological disaster. A century and a half ago, whales were being hunted to extinction because they were the main source of lamp oil. They were saved by the paraffin lamp and oil industry.

Tony Robinson

Media consultant and researcher for the Cape Chamber of Commerce
 

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