Geothermia - Our forgotten champion

Geothermal Energy is perhaps one of the less know (or at least not as evident) energy sources we have available, this is because it is acquired exploiting Earth's inner heat. It is a rather recent way of supporting ecology.

Geothermal energy source

There's several factors that source geothermal energy, being some of them the geothermal gradient and the radiogenic heat. The term geothermic comes from Greek; "Geo", Earth and "Thermos", heat.

Just like when exploiting any natural resource, it has a series of advantages and disadvantages:

Advantages:

-It can prevent the exterior energy dependency.

-The residues are minimal, edging the "non-contaminant".

-It saves a LOT of money in the energy/$ trade rate.

-Silent, they produce no noise (anyone with an windmill knows what I'm talking about).

-There's more available energy to exploit at geothermal locations than the sum of carbon, oil, natural gas and uranium available on earth.

-It is not a speculative good, like oil is.

-The plants use much less ground than the traditional power plants.

-Carbon dioxide emissions are relatively smaller than the one produced by the burning of fuels.

Disadvantages:

-Potential emissions of sulfuric acid, not easily detected and lethal.

-It can accidentally contaminate water given the arsenic and ammonia involved in the process. (just remember what happens when an oil duct/ship breaks).

-It produces thermal contamination.

-Of course, ruins the landscape (as anything we build!).

-You cannot transport it (yet, you can transport the energy produced).

-It is restrained to be extracted at certain locations.

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Geothermal fields are classified according to the temperature of their waters:

-The high temperature fields present in the active zones of the Earth's crust can have from 150°C to 400°C waters (sometimes even spiking to 550°C!). That produces vapor and with a turbine can produce electricity.

-The mild temperature fields range from 70°C to 150°C. It can still be used to produce electricity, but at a lower pace and efficiency.

-Low temperature fields are present at all the sedimentary basins. With a temperature of around 60°C, ideal for vacational complexes and home heating.

-Very low temperature fields cover from 25°C to 50°C and are used exclusivelly for domestic and agricultural purposes.

Of course geothermal facilities' locations are very arbitrary, since to produce electricity at an acceptable rate we need ~120°C of water temperature, while anything lower than that can only heat up houses (still, cheaper than with "conventional methods".

Converting the energy

The conversion process is based on two pipelines introduced into a perforation of the ground, they are kept in a closed circuit directly connected to the heat source. In one of the tubes cold water is injected from the surface; once it reaches the bottom, it heats up and rises back to the surface in the other tube that is connected to a turbine and a generator. Once the water cools down, it is sent back to heat up, repeating the cycle.

New Zealand, the forefront

New Zealand is perhaps the expert in this kind of resource. Considering their volcanic topography, that makes it ideal for it. They placed the second geothermal electric plant of the world (the first one was at Italy).

They are pioneers on this research branch and the development of technologies to exploit that energy more efficiently. New Zealand is over the edges of 2 tectonic plates (or lithospheric plates, if you want to sound "scientificish") that are pressing against each other: there volcanoes and earthquakes sprout like children in a candy giveaway, a perfect ground where to harvest Geothermal energy.

This is still an early technology. But, as we all know, the Earth core has an abundant heat ready for us to be harvested. Perhaps, in a not so distant future we will be able to dig VERY deep holes.

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