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Jüngste Posts

Iceland's Earth power

Nachricht hinterlassen von Sarina Ritorto Tuesday, 20th September 2016

Hi. I was recently in Iceland, where I saw they generate all their electricity from just hot water from under the ground. How does that work, and how do these power plants compare in output to conventional plants, like coal or nuclear?

Nachricht hinterlassen von Andrew Bone Tuesday, 20th September 2016

Thank you for your question. Yes, geothermal energy is a realistic alternative to dirty fossil fuel for generating electricity. Unfortunately, there are not many places around the world with such large geothermal resources such as Iceland enjoys: the USA, China, the Philippines, Mexico, Japan, New Zealand and Italy are some of the other major exploiters of geothermal energy.

Electricity is made by a generator: this is basically a large number of powerful magnets and a moving coil (or you can have a static coil and moving magnets - your choice). When a coil moves relative to a magnetic field, there is a force, called the electromotive force, on all the electrons in the wire of the coil. These get 'pushed' down the wire, and that is electrical current.

To turn the shaft the coil is on, any form of energy can be used: fossil fuel evaporates water, which drives through a turbine (a complex set of fans on a shaft), to turn the rotor of the electrical generator. In a hydropower plant, water rushes out of a pipe at the base of a dam, and drives the turbine by physical pressure.

There needs to be a temperature differential in order for the water to have the energy to turn to steam and drive the generator shaft. By passing cool water through hot rocks beneath the Earth's surface, the expansion to steam loads it with sufficient kinetic energy to generate electricity, just like steam from a fossil fuel boiler. But in the case of geothermal energy, there are no carbon dioxide, sulphur dioxide or nitrous oxide emssions, all of which are seriously bad news for the environment.

Nachricht hinterlassen von Andrew Bone Tuesday, 20th September 2016

The Nesjavellir power station in the southwest of Iceland is its largest geothermal plant, and has an electrical power output of 300 MW (300 million watts). It produces this from 1800 litres per second of hot water passing through its turbines.  

By comparison, a typical coal power station produces 400 - 600 MW, and a nuclear station as much as 1000 MW. In addition, the efficiency of the geothermal plant is much higher than fossil fuel stations, and its price for the consumer is very competitive.

Although 11 gigawatts (about the output of 15 nuclear power stations or 20-25 coal stations) of electricity is generated around the world by geothermal plants, the majority (70%) of geothermally produced hot water is used more directly, such as for heating and in industry.

Nachricht hinterlassen von Andrew Bone Tuesday, 20th September 2016

The price of geothermal power, like all renewable energies, is falling as it becomes more widely used, and technology improves. There would be enough geothermal energy to satisfy all human energy needs, but the restrictions of price and ease of extraction limit the degree to which it is currently exploited.

In the USA, some estimates suggest geothermal will be the cheapest electricty source by 2020, beating coal and oil. For example, the Lazard Investment Bank (New York) in their 2015 report on comparative energy prices, positions geothermal very favourably against fossil fuels: $82-117 for a MWh (a million watts of power for one hour, or if you prefer one watt for a million hours...) for geothermal, compared to $212-281 for a diesel engine, and $65-150 for a coal-power station, $97-136 for nuclear, and $32-77 for wind energy.

As you can see, the myth that renewable energy will always be economically unviable compared to fossil fuel has well and truly been blown away. The future is under our feet and blowing in the wind...

Nachricht hinterlassen von Sarina Ritorto Tuesday, 20th September 2016

Is the production of geothermal energy possible in Switzerland?

Nachricht hinterlassen von Andrew Bone Thursday, 22nd September 2016

Switzerland is not very active seismically, let alone volcanically, so has no truly naturally accessible geothermal sites. However, there have been attempts at high-pressure stimulation. This involves injecting water at high pressure into rock, to cause fracturing, which would allow injection/retrieval of water through hot rocks.

I was actually involved in such a project in Basel in 2006, which was stopped after the stimulation caused a minor earthquake due to induced seismicity. There was some property damage, but nobody was hurt. The incident was caused by contraction of the well rock after the hot water or steam was extracted. Another project in Sankt Gallen also met a similar fate.

Germany has only 0.04% of its electricity generated by geothermal power, so it too has few resources.

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