Energy right under our feet

geothermalWe’re sitting on a treasure chest of energy. It won’t be cheap to get at it, but the Earth’s heat could serve most of our needs into the far future. More than 95% of the planet’s mass is very hot – much of it around 1000 deg C on average. This is the heat left over from formation of the planet out of the space dust that was pulled together by gravity to form a molten blob of rock 4.5 billion years ago. The Earth’s crust has cooled allowing us to live on it, but at depths ranging from just a few metres to 5-50km, the rocks remain superheated.
We can’t go on polluting the air and ruining the land with coal-fired generators. Gas, petroleum and other fossil fuels are ultimately just as bad for global warming. Why spend a fortune on dangerous nuclear energy? Windfarms and solar sources are not yet efficient enough to produce sufficient renewable energy to replace fossil fuels. We need a major alternative. The solution is right under our feet.
To get at this energy and use it, various technologies have been tried and many new innovations are under way.

  • To turn it into useful energy we can use water in a closed system, or flux, sending cool water down and getting steam back up to run our turbines. There are also other practical solutions.
  • One is to store the summer’s heat just under the ground near our homes and industries, and tap into the heat reservoir in winter.
  • Another method is to draw on the moderately heated rocks some 4-5km down, which may reach temperatures of 60+ deg C. Bringing water at this temperature to the surface we can heat up refrigerant fluids that boil at less than 50Deg C, turning in steam that can power devices.
  • Biomass too is a source of geothermal energy. Landfills produce heat and methane gas which can be tapped off.
  • More innovations are in the pipeline. Researchers have realised that geothermal energy can the source of inexhaustible energy with very low emissions with little industrial plant required.

Some countries like Iceland, Norway, the United States and New Zealand already use significant amounts of geothermal energy from hot springs at the surface. The challenge for South Africa is to get at heat sources very deep down. There are few tectonic fissures – that is, volcanic ruptures – in the huge rock plates that sit upon the Southern African subcontinent.

But what we do have is the mining technology and the deep mine shafts that allow us to get at this heat. We can also adapt oil drilling technologies to reach the deeps and install the piping needed for circular flows of water.

No energy source is without problems and geothermal is no exception. Radiation in the deep earth is a factor to contend wit. Insulating us from its effects should prove less of a problem than the far larger doses of radiation to which we may be exposed by nuclear accidents on the surface.

The release of smelly hydrogen sulphide gas from deep down would not only be unpleasant; it would add to global warming. There are ways to keep these emissions to a minimum, preventing large-scale leaks into the atmosphere.

Earthquakes may be induced by disrupting the rocks below us. Residents of the Witwatersrand are used to earth tremors caused by gold mining, and there is little reason to believe that geothermal installations would cause anything worse.

For more on geothermal energy see:

http://m.engineeringnews.co.za/article/south-africas-geothermal-prospects-2010-10-15

http://alive2green.com/energyefficiency/sas-geothermal-potential-being-ignored/

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