The term “geothermal” means “Earth heat” or “heat of the Earth.”. The heat flowing from the Earth’s interior is estimated to be equivalent to 44.2 terawatts-thermal (TWth) of power (Pollack et al.1993)—more than twice the amount needed to supply total global primary energy consumption in 2015 (Energy Information Administration [EIA] 2017a). So, why isn’t this renewable energy source more widely deployed?
In times of climate change this type of sustainable energy source is vital for all humankind. Due to the location of Iceland in the Mid-Atlantic Ridge, a very active volcanic zone that powers the geothermal system we have extensive access to geothermal resources. But this energy source certainly is also accessible in other countries. The other counties which already have deployed geothermal for long time is USA, New Zealand, Indonesia, Turkey, Italy and Kenya.
Geothermal energy is thermal energy which is generated and stored within the Earth. To harness the geothermal power, we need to drill geothermal wells deep into underground reservoirs, to get access to the steam and hot water there. In very basic terms, then the geothermal gradient highlights the increase in temperature per 100 m of depth – around 2-3 degrees Celsius. You might assume that the temperature will reach around 60° C (140¨F) at the depth of 2000 meters and around 90° C (194° F) at 3000-meter depth. This temperature trend continues a few thousand meters deeper. However, this is very different depending on where you are in the world. Iceland for example, which is located in between the two tectonic plates (North American and Eurasian), the heat of the earth can be found closer to the surface, and volcanic activity is common. This means we have an abundance of high temperature areas which can be found in a few places in Iceland, meaning that the temperature gradient is many times the average value.
Geothermal energy can be harnessed for both direct use and electricity generation. Commercial electricity generation mainly uses steam from high temperature fields above 200° C (392°F), but generation of electricity using lower temperature from 120° C (248° F) is also possible using different technology. The high-pressure steam coming out of the deep wells, is used to drive turbines connected to electricity generators.
Geothermal has numerous other benefits other than electricity generation. The usage of lower temperatures around 100° C (212° F) and lower we categorize as „Direct use“ The direct use takes various forms, such as to heating up our houses (district heating), to heat up our swimming pools. It is also being used in aquaculture, in horticulture and food processing as well as production of cosmetics in the famous geothermal spa Blue Lagoon. In Iceland we even use the surplus water to melt snow of sidewalks and car parking spots.
Geothermal has benefited humankind since the earliest dates, such as for bathing in hot springs, cooking in hot springs. In Iceland, we have historic evidence that our ancestor used the geothermal resources for bathing in the 13th Century.
Geothermal energy is the most reliable form of renewable energy. It is the only renewable energy source that can provide baseload power to the grid 24/7, complementing the insecure supply of solar and wind energy.
If you are interested in more knowledge about geothermal, then book some of our tours marked “geothermal”. Our Guide have decades of experience in the geothermal sector and will be able to give you excellent guidance in this field.
