Post VI – Geothermal Energy

Harvesting the toots of the Earth.

Er, fruits, that is.

Geothermal technology works by taking advantage of the heat trapped in the Earth’s core. By drilling deep into the Earth, this trapped heat can rise to the surface and be used similar to how steam engines work. Basically the heat (or sometimes superheated liquid) creates steam, which is used to spin a turbine which in turn activates a generator, similar to the principles of solar and wind energy.

—> A nifty video on the process.

Unfortunately, as is the tiring custom with all alternative energies, the resistance to geothermal technology is a result of the hefty investment.. Drilling costs alone make up 50% of the investment.

Usually geothermal technology is only useful in areas where there are ‘hotspots’, or weaknesses in the crust that allow heat to pass through. But the U.S. is host to a decent number of potential hotspots. The following map provides temperatures of the U.S.’s layers at a depth of 6km:

However, like solar and wind energy, geothermal energy can be utilized on an individual basis. According to Renewable Energies, LLC,

Below the frost line – usually about six feet deep – the earth is a constant temperature of about 50 degrees Fahrenheit all year long. During the winter, a heat pump absorbs heat from the ground and uses it to warm the air in your home or business. In the warmer summer months, the processed is reversed, taking heat from your home or business, transferring it back into the ground.

Geothermal energy is used for a wide variety of purposes. A 2005 report:

While geothermal is hot and all, there are reports that heat pumps used on an individual basis, while money-saving, also produces 1.5 times as much carbon dioxide as a conventional gas furnace. In terms of geothermal plants, however,

Modelling calculations are presented for two hypothetical geothermal plants (based on real-world examples) which show that gas discharge rates (tonnes of CO² / MWe.s) are between 0.5 and 50% of emission rates from fossil-fuelled power plants.

What’s even better is that the CO2 generated by geothermal plants could possibly be put to good use and be kept out of the atmosphere. According to a November 2009 Technology Review article,

Carbon dioxide that’s cycled through hot regions kilometers underground can efficiently bring heat to the surface, where it can be used to generate electricity. The likelihood is that the process would leave lots of carbon dioxide underground, and thus out of the atmosphere, according to Symyx project leader and materials scientist Miroslav Petro. “You’re sequestering CO₂ and at the same time generating power from it.”

That’s neato and all, but there’s still another big catch. The process of harvesting heat from the Earth’s core is potentially damaging to the landscape (since those deep layers are basically being fractured), and in terms of subterranean layers the damage may be irreversible. Drilling might also contaminate local water sources.

And that’s not all. The process of finding suitable spots for plants involves a land survey which is, again, costly but also time-consuming. Additionally hotspots are often located next to volcanoes, which are not the most suitable spot for any installation. As well, a site might unexpectedly stop producing steam for an unknown length of time.

So, while geothermal is a neat alternative to fossil fuels, it is unfortunately fraught with a lot of issues, not least among them is cost.

Geothermal plant at the southern end of the Salton Sea in Cali.

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