The Pros and Cons of Geothermal Energy

On this blog we’ve covered many forms of renewable energy, but, as far as I can recall, we haven’t mentioned geothermal energy before.  Until today that is. I found a press release from the University of Missouri saying that they developed a geothermal energy system to keep animals on turkey farms warm and cut expensive heating bills during autumn and winter. Just in between Thanksgiving and Christmas, it seemed an excellent time to start divulging a bit on geothermal energy and what it’s all about.

Geo means earth, thermal means heat. So earth-heat.  Below the crust of the earth, the top layer of the mantle, is a hot liquid rock called magma. The crust of the earth floats on this liquid magma mantle. When magma breaks through the surface of the earth in a volcano, it is called lava as you probably know. The centre of the Earth is very hot, temperatures are around 6000 degree Celsius. Even a few kilometres down, the temperature can be over 250 degree Celsius if the Earth’s crust is thin. In general, the temperature rises one degree Celsius for every 30 – 50 metres that you go down, but this does vary depending on location.

Deep under the surface, water sometimes makes its way close to the hot rock and turns into boiling hot water or into steam. The hot water can reach temperatures of more than 150 degree Celsius. It doesn’t turn into steam because it is not in contact with the air.  Geothermal energy uses the escaping heat from the Earth’s core as a means to heat water and produce electricity. By drilling deep into the Earth’s interior, we find temperatures suitably high to produce electricity.

So there is a lot of heat inside the earth, it’s virtually unlimited. That makes it a potential attractive source of energy. Geothermal energy is sustainable, cleaner than fossil fuels and no fuel is used to generate the power.  It has almost no environmental impact when using geothermal heat from nuclear decay. In Japan, the Fukushima disaster paved the way for new geothermal plants. Japan is one of the countries that have huge subterranean reserves of volcanic water. Their geothermal capacity, once tapped in,  could reach 24m kilowatts – the third biggest in the world after the US and Indonesia. According to an article in the Guardian earlier this year, the UK could meet a fifth of its power needs by exploiting geothermal power.

Since ancient times, people having been using this source of energy for taking baths, heating homes, preparing food and today this is also used for the  direct heating of homes and offices.  The initial investment for this direct use of heat might be quite steep but in the long run it will save costs. Also, the cost of the land to build a geothermal power plant on, is less expensive than setting up a nuclear, coal or oil plant.

So geothermal energy has a lot going for it.  Then why is it  not more commonly used? One reason has to do with the depth of drilling into the earth. There is a likelihood of recurring earthquakes in areas where hot water of steam is transported from the ground. In Basel, Switzerland an operation was suspended because of 10,000 seismic events in six days. although the earthquakes are usually not very powerful, they can still cause damage to buildings and the surrounding area. In some cases, harmful gases can escape during the process from deep within the earth, through holes drilled by the constructors.  The released gases include  mercury, boron, arsenic and antimony. We are not talking about large amounts here, but  the gases usually prove to be very difficult to dispose of safely.

Geothermal energy is not available everywhere on the planet. It is only suitable for regions which have hot rocks below the earth and can produce steam over a long period of time. And some of these areas are high up in the mountains or a next to volcanoes, which makes it difficult or, in the latter case,  unwise to set up plants.  There is a chance that locations, if not properly researched run out of steam. Although temporarily, this will be a huge financial loss for companies that have to stop drilling.   Drilling is expensive, it accounts for over half the costs and drilling costs  increase exponentially with depth. Another disadvantage is that geothermal energy cannot be transported over vast distances,  it can only be used to generate electricity for surrounding areas. Power plants can also use the steam to produce heat, but only on a localized basis.


The two geothermal units, recently installed by the University of Missouri at the test farm in the state overcome those obstacles.  The  pipes are buried horizontally instead of vertically as in a traditional geothermal unit which requires deeper – and more  expensive – drilling.  Digging shallower holes makes the system a lot cheaper. The heating isn’t transported but used merely  for the purpose of heating the farm. In the United States tax credits  are available for home and commercial building owners who install geothermal heating and cooling. The credit offers a one time tax credit of 30% of the total investment for homeowners who install residential ground loop or ground water geothermal heat pumps. But also a credit of 10% of the total investment, with no maximum available for a commercial system installation, like on the Missouri turkey farm.

The United States, which began the development of utility-scale geothermal energy in the 1960s, remains the world leader with approximately 3,187 MW of installed capacity. Geothermal energy is the fourth largest source of renewable electricity in the nation, after hydroelectricity, biomass, and wind power.




One thought on “The Pros and Cons of Geothermal Energy

  1. I suggest making a clearer distinction between direct geothermal for energy production and geothermal for heat exchange using a heat pump. The former is a net energy producer (as in utility power plant) and the latter is a net energy consumer (though with greater efficiency and less emissions than conventional combustion heating). Again the former requires high temperature geologic activity near the earths surface (rock or steam ~> 120 deg C) while the latter only requires efficient thermal coupling to local near surface temperatures (10 to 30 deg C). Thus the potential for small scale geothermal heating is very wide spread while the potential for central station geothermal power plants is geographically limited.

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