Geothermal's Geographical Limitations

My previous posts have focused on solar power; a widely available, under-utilised resource with small geographical limitations but supply constrained by hours of sunlight. In stark contrast, geothermal energy has large geographical limitations, far smaller availability but continuous accessibility. Therefore, I wanted to focus on this resource in my next few posts to see how feasible large scale deployment is.

Geothermal energy is the utilisation of the Earth's internal heat energy in order to produce electricity for anthropogenic use. This internal heat can either come from radioactive decay within the Earth's crust, or from the energy resulting from the Earth's formation.

In some areas, natural water sources are heated by the transfer of this thermal energy below the Earth's surface. In areas with very hot subsurface rock, but limited natural groundwater sources, water can be actively pumped below the surface and then returned to a power station. In both cases, the hot water can be captured and the release of steam is used to drive turbines, which produce electricity for commercial use.

The Workings of a Geothermal Power Station
Source: bbc.co.uk

Iceland is well known for its abundant geothermal resources which are available due to the country's geographical location on the Mid-Atlantic Ridge. It is one of the most active tectonic locations on Earth due to the spreading of the North American and Eurasian plates on which it sits. These plates are currently moving apart at a rate of circa 2cm a year.

Ragnarsson (2013) outlined the nations significant use of renewables, with 87% of energy in 2013 provided by their own clean resources; 69.2% of this being geothermal energy and 17.6% coming from hydropower. The research outlines the transition to renewable energy that took place in the 1970's after the huge global increase in oil prices; today, 90% of the nations heating is provided by geothermal resources.

The United States is also produces a large amount of geothermal energy, however it is small in comparison to their total energy consumption. The Western United States have a large amount of geothermal energy, with a significant hotspot being Yellowstone National Park; much of this energy is currently under-utilised.

Geothermal Power Station, Iceland
Source: ITProPortal

At present, around 20 countries use geothermal energy, with availability largely confined to areas of tectonic activity. Many areas aren't exposed to enough geothermal energy to make use of it on a commercial scale, however, the majority of nations with significant geothermal potential are currently under-utilising this resource. An MIT study (2006), stated that the United States has the potential to produce 100,000 MW of geothermal energy over a 50 year period. Other areas that also have huge potential include East Africa, Indonesia and Japan, with the latter holding the third greatest geothermal potential in the world.

Iceland meets a huge proportion of energy demand with this resource and many other counties have the potential to duplicate this model. Harnessing geothermal energy would allow for faster economic growth of poorer areas such as Indonesia and East Africa and it would allow for significant development using a clean, efficient and relatively cheap resource.