Who's Online

We have 806 guests online


1027 readings
Written by Joan Russow
Tuesday, 07 January 2014 05:37

By Matt Whitney




You only have to see the steam billowing from Iceland's naturally heated 'Blue Lagoon' to realise the potential geothermal energy has to provide more than enough heat in even the coldest of places.

The 'Land of Fire and Ice' sits atop a plume of magma that lends itself perfectly to the exploitation of geothermal heat. This rather neglected renewable energy source has huge potential, and not just in Iceland. New technologies and growing demand makes geothermal power a possibility all across the world. At the moment, only 5% of global production potential is realised and the sector is growing by 10% each year.

How it works

Generally speaking, the deeper you dig into the Earth, the warmer it gets. In its most simple form, geothermal power systems converts subterranean heat into electricity by boiling water to generate steam, which can then be used to power turbines. In normal conditions, the temperature gradient of Earth is not high enough to yield hot enough temperatures, thereby limiting geothermal energy to areas where magma wells up near the surface (at volcanoes, tectonic boundaries and hotspots, for example).

Simple schematic of an Enhanced
Geothermal System. Source
Technological advances during the 20th Century means that geothermal energy can now be used in areas that do not have such near-surface magma upwelling. 'Enhanced Geothermal Systems', for example, uses the same technology as fracking, whereby water is injected at high pressures into rock deep underground to force open fractures and effectively create new aquifers. These fractures expose the injected water to high temperatures that can then be pumped back out and used for electricity generation. Contrary to fracking, which uses water laced with toxic chemicals, the process is not deemed to be environmentally damaging.

Geothermal energy is also widely used for smaller-scale heating purposes through 'Geothermal Heat Pumps'. These systems do not exploit heat from Earth's interior but instead take advantage of the insulating properties of the ground, which is typically warmer than air in the winter and cooler in the summer. Heat pumps simply transfer subterranean heat into the cool air above in winter and do the opposite in summer, allowing simple heating and cooling systems for domestic use virtually world-wide.

Where it's used
Electricity has been generated using heat from the Earth's interior since northern Italy successfully powered 5 lightbulbs from natural steam vents in 1904. Over a century later, industrial scale geothermal plants are operating in 24 countries and generate over 10,000 MW of electricity each year.

The Nesjavellir geothermal power
plant in Iceland
The world leaders - with nearly 30% of the global share - is the United States. In 2010 the US had a capacity of about 3090 MW, equivalent to the annual power requirements of about 2.2 million people. Whilst this is an impressive amount of generation, it doesn't even represent half a percent of the nation's total electricity production. However, like with many other renewable technologies, this number is growing with the US reportedly having 175 geothermal projects in development as of early 2013, representing a potential 5.5 GW of power.

Unsurprisingly, Iceland leads the way in per capita geothermal power. About 25% of the nation's annual electricity supply and nearly 90% of heating and hot water is provided by geothermal energy. As well as being ideally placed for geothermal power, the oceanic climate of Iceland means the country has plenty of rivers to provide hydropower, which makes up the majority of its remaining energy needs.

Perhaps more surprising is the dominance of geothermal power in the Philippines and Indonesia, representing the second and third biggest geothermal electricity producers respectively. Owing to its volcanic geology, Indonesia has 40% of the world's potential geothermal capacity and it already generates 3.7% of the country's electricity demand. The government targets growth and hopes to produce more than 9,000 MW by 2025, equivalent to 5% of the country's electricity demand.

Top 10 geothermal electricity producers (Source)
The Untapped Potential

With the impressive capabilities of drilling and water-injection technology - mostly developed in the oil and gas industry - geothermal energy has become more accessible than ever. On average, temperature will increase about 25°C per kilometre of depth and the oil industry has the capability to drill up to at least 12 kilometres, which would provide temperatures more than high enough for geothermal applications.

The red regions on the map show where this temperature gradient is steeper - i.e. it is hotter nearer the surface than the average area - making these areas suitable for relatively cheap and accessible geothermal heat. However, a significant development has been the ability to derive geothermal energy from even the most tectonically stable areas. The UK, for example, is estimated to have potential for 9.5 GW of electricity generation, the equivalent of 9 nuclear power stations and 20% of the country's current annual electricity consumption. Many other European countries also have pilot projects, potentially exposing geothermal power to many more countries than shown on the map.
Perhaps the greatest advantage of geothermal energy, however, is its scaleability. Geothermal energy can be employed both at an individual and industrial level. Heat pumps are widely used in domestic settings in at least 78 countries and represents the largest and fastest growing use of geothermal heating, providing space heating for millions of people who would otherwise rely on fossil fuels. For electricity generation, the consistent energy supply of geothermal systems give them a large advantage over other renewable technologies such as wind or solar that cannot operate 24 hours a day.

The increasing potential for geothermal extraction is, in part, due to advances in technology developed for the fossil fuel industry. To take such technology and apply it to a limitless, clean and widespread energy source is a sign of our increasing environmental awareness and faith in renewable energy. Whilst it may only a small proportion of the global energy mix at present, geothermal power looks likely to become an important player in the future. 

For news and updates, follow @ClimateReach on Twitter
Last Updated on Tuesday, 07 January 2014 05:53

Latest News