The geothermal resources of the earth are clean and plentiful. Unlike most other renewable energy resources, geothermal energy is available throughout the year, has an inherent storage capability and is independent of weather conditions.
This storage capability makes it an ideal stabilizing energy, which can compensate for the fluctuating nature of other forms of renewables, originating from the sun or the wind. Underground thermal energy storage systems store energy by pumping heat into an underground space. Thermal energy can be stored in boreholes, aquifers and caverns or pits. The storage medium is water but can also be molten salts, soil and rocks. Boreholes are man-made vertical heat exchangers that work to transfer heat between the energy carrier and the ground layers.
Geothermal energy resources differ from one geographic location to another, depending on depth, temperature and pressure, abundance of ground water and underground chemical composition.
State of play
As highlighted in the most recent REN 21 report, Turkey and Indonesia remained in the lead for new geothermal installations in 2019, followed closely by Kenya. Other countries that added new geothermal power plants in 2019 (or added capacity at existing facilities) were Costa Rica, Japan, Mexico, the United States and Germany.
The top 10 countries with the largest stock of geothermal power capacity at the end of 2019 were the United States, Indonesia, the Philippines, Turkey, New Zealand, Mexico, Kenya, Italy, Iceland and Japan. Several amongst them see geothermal electrical energy as one of the ways to meet their renewable energies target, in an attempt to align with the Paris Agreement on Climate Change. For instance, the Indonesian government’s target for 23% renewables in the energy mix by 2025 assumes an installed geothermal power capacity of 7 GW (7% of the energy mix).
IEC Standard for steam turbines
For the geothermal industry to continue expanding everywhere around the world, the technology used must meet proper safety and performance benchmarks. IEC International Standards ensure that systems and devices employed are tested and meet the appropriate standards of quality and efficiency. IEC Technical Committee 5 develops specifications and standards for the rating and testing of steam turbines. In 2020, it released the second edition of a key standard specifying the requirements for steam turbines: IEC 60045-1, which now includes automation safety specifications. The standard can be used for geothermal steam turbines but also for turbines employed in concentrated solar power plants, another form of renewable energy.
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