Have you ever been relaxing in a hot spring, feeling the bubbling water tickling your body, the delicate steaming water caressing your face, and wondering how is that possible to have a near boiling water coming form the ground?
It turns out you are sitting right now on a gigantic magma jaccuzzi. Our beautiful earth is not only a blue planet but a very active machinery, boiling in the inside giving us one of the best exploitable resources.
RENEWABLE ENERGY POST TWO: THE EARTH
Geothermal energy comes from the left over heat from the formation of Earth, and the radioactive decay of potassium, thorium and uranium in Earth’s mantle and crust. The radioactive decay involves the disintegration of those natural radioactive elements which is comparable as freeing in a closed room an army of Taz, the Tasmanian devil, and their torpedo would create an enormous energy radiation. The geothermal heat produced in the core of the Earth is actually hotter than the surface of the sun. We have an increase of 3.3°C every 100m to a maximum of about 140°C 4000 m deeper. We are squeezed between two powerful forces, the sun and the steaming bowel of the earth.
So how the energy from the underground manages to warm our hot springs on the surface?
The water is heated when it comes into contact with rocks that have been heated by the magma underneath the surface, which makes springs more common in specific areas. Although geothermal energy is present every where on Earth by conduction of the heat, it is more accessible in volcanic zones, through different mechanisms around the world.
The volcanic activities in New Zealand, Alaska or Japan are due to the movement of one tectonic plate moving underneath another one, which creates volcanoes. In Iceland, however, the tectonic plates pulling away from each other lead the magma to rise to the surface. The mantle material can rise beneath the crust creating hot spots such as in Hawaii or Yellowstone National park.
For hundred of years, only the energy that made its way to the surface with hot springs or heated pools could be used by humans, mainly for bathing or cooking as shown in the picture below taken in New Zealand.
The drilling capabilities developed during the last century enabling us to harvest this abundant energy for human energy needs. The penetration capability to reach deep underground reservoir allowed the creation of geothermal power plants found nowadays in 24 different countries. Resources with temperatures above 150°C are usually used for electric power, where vapour-dominated (drysteam) or fluid systems (flash and binary cycles) turns a turbines-generator set to produce electricity.
Resources below 150°C are used in direct heating/cooling systems and heat pumps. Geothermal heats pumps are fast growing application of renewable energy, based on the constant ground or groundwater temperature in the range of 4° to 30°C available anywhere. Direct use is available for swimming pools, fish ponds, greenhouses, industrial and and process heat for agricultural products (drying of forest products, food and minerals industries).
It is estimated that 8.3% of the total world electricity could be produced by geothermal resources, supplying 17% of the world population. 39 countries could actually produce 100% of their electricity by using this energy.
This renewable energy has advantages and limitations:
– No pollution even though power plant can release polluting gases, it can be re-injected into drill holes and thus not released into the environment.
– Reduces CO2 emissions by reducing the use of fossil fuel.
– Initial costs is quite steep however it generally involves low running costs since it saves 80% over fossil fuel.
– Geothermal heat pumps systems use 25 to 50% less electricity as conventional heating/cooling systems, with long durability.
– Sustainable and renewable energy. The use-mode defines the renewability of the source: geothermal reservoirs can be naturally replenished if not overexploited, assuring the support of the present generation without compromising the needs of future generations.
– Great potential, our worldwide consumption of 15 terawatts is little compared to the energy stored in the Earth. Global market is at about 13.3 GW across 24 countries and planned estimation expect to reach 18.4 GW by 2021, 32 GW in 2030s. We are using only 6-7% of the total global potential based on geologic knowledge and technology. There are vast unused resources that could provide caseload renewable energy.
A feel-good story from the land of Fire and Ice
Near the Arctic Circle, between Greenland and north Europe lies the land of the extremes where glaciers stand along side volcanoes and waterfalls near geysers.
Iceland is not only spectacular for its breathtaking landscapes but also for its inspirational transition from fossil fuel to almost 100% of renewable energies in 40 years. The transition did not start from an environmental action, but it followed the 1970s worldwide oil crisis. Iceland could not sustain the oil price fluctuation so it became economically more viable for the country to rely on local energies sources.
The island is a very active volcanic zone that powers it geothermal systems, and the glaciers covering 11% of the land contribute to the hydropower resources. The city of Reykjavik, also called the renewable energy mecca, is the largest geothermal district heating system in the world producing 95% of heating and 99% of electricity for the city houses and businesses. The only polluting factors in the country is the dependance on fossil fuel for cars, however Reykjavik aims to be completely fossil fuel free by 2050. The geothermal energy is also widely used to melt snow off sidewalks, heat swimming pools, power greenhouse cultivation, geothermal spa and industrial production.
The Iceland transition might seem exceptional but such changes don’t rely only on the availability to the resources. This case story shows that the cohesion between the government, municipalities and the public is substantial to enable such projects. Factors such as costs, investments, production efficiency and the politic in place can be important challenges in many countries trying to use their untapped resources, but solutions are available and the Iceland case could be extrapolated to other destinations.
Do you know which country keep breaking world record for wind power generation????
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All illustrations and photos are from the author of this blog.
Cleveland, C., & Morris, C. (2013). Handbook of energy (1st ed.). Burlington: Elsevier Science.
Lund, J., W. (1998). Geothermal Energy. Encyclopedia Britannica. https://www.britannica.com/science/geothermal-energy