The thermal springs of Larderello
People have used water heated by nature since ancient times.
But the first industrial geothermal station in the world was set up in the Italian town of Larderello in 1904. The steam formed from thermal waters at the Italian resort was the first to provide electricity for four light bulbs. A few years later, in 1911, a power station was built here – and it is still in operation today.
Over the course of the 20th century, geothermal power stations were built in other countries – in the United States, Japan, New Zealand, Mexico. In 1965, a station was built in the Soviet Union – the first binary cycle station using as its energy source both thermal water and steam.
Types of geothermal stations
The International Energy Agency outlines five types of sources of geothermal energy – dry steam, wet steam (hot water+steam) geothermal baths (hot water or steam + water) dry, hot rock formations, heated magma and magma.
The most popular method of producing power – is using steam to turn generator turbines. The only difference is the way in which you produce the steam – by burning coal or gas or by means of water heated in the Earth’s core.
There are three ways to make electricity through geothermal energy. One is the direct method of using dry steam. The steam comes from wells straight into the turbine. This is the oldest method, in addition to being the simplest and least expensive. But it can only be used in specific places, where appropriate sources of steam with the required temperature can be found.
An indirect method of using water if the most widespread type. Here, hot water from the core is subjected to high pressure and is transformed in part into steam and the steam turns the turbine. After its use, the steam is pumped out into the well or is used to heat buildings.
Binary cycle stations allow no liquids into the turbine in theory. Thermal water in the heat exchanger heats a second liquid – freon for instance – which has a lower boiling point, is transformed into steam and turns the turbine. This is a closed system – the liquid condenses and once again returns to the heat exchanger. And it allows for thermal water to be used at a lower temperature.
There is also petrothermal energy — based on using differences in temperature on the Earth’s surface. The means here is hot stones. Two wells are drilled, and water is pumped out of one of them, it is then heated and comes out through the second well in the form of steam.
The technology of extraction of heat from the Earth – known as hot dry rock – is used in more than 60 countries. The first time the petrothermal circulating system was used to extract heat from porous rock for heat occurred in Paris in 1963. Australia is the leader in use of petrothermal circulating systems — hot, dry rocks are placed about 3.5-4.5 km below the surface. The potential for petrothermal energy in Russia is estimated at 3,500 trillion tonnes of fuel equivalent – but its extraction and production are, at the moment, considered unfeasible.
Steam from the Earth
Iceland is the traditional country for geothermal energy. And for good reason. Almost all homes in the country of geysers are heated with contributions from geothermal heat and green sources cover all energy needs, including thermal power stations.
But altogether 27 countries produce geothermal electricity. In 2019, 72 % of installed capacity of geothermal power throughout the planet originated in six countries: the United States, Indonesia, the Philippines, Turkey, Mexico and New Zealand.
The United States is the biggest producer and the biggest geothermal electricity complex – “Geyser” – is in California. In 2020, 93 geothermal power stations were operating in seven states in the United States, in seven states. They generated about 17 billion KWh, or 0.4 % of the power produced in the United States. And more than 70 % of all geothermal installations are in California and a further 20 % in Nevada.
And most of the system of centralised geothermal water supply benefits from the support of governments at different levels – critically important for its development.
From 2016 to the beginning of 2020, the capacity of geothermal energy in the United States rose from 3.627 GW to 3.673 GW—the country brought on stream seven new geothermal power stations and took out of service 11 older facilities. The United States has 23 geothermal systems with centralised heat supply. The oldest was set up in 1892.
Beginning in 2020, nine new agreements on purchasing geothermal energy were signed, including a plan to build the first two geothermal power stations in California over the next 10 years.
The U.S. government is relying on the development of the sector and is putting up for auction new sites for development. For instance, the Bureau of Land Management in October is putting up for auction 32 sites in Nevada for developing geothermal energy. The next auction of geothermal sites is set for autumn 2022. Sites are put up for lease for 10 years with an option for expanding.
The second largest producer of geothermal energy is Indonesia – it accounts for about 5 % of total energy production.
Of interest is the fact that a country like Kenya, which holds down eighth place as a producer but accounts for 40 % of power used in their country. That makes Kenya, in theory, a “geothermal country”.
The first geothermal plant in Russia was the Pauzhetskaya station in 1966 on the Kamchatka peninsula, built in 1966. At its launch, the station’s capacity was 5 MW – by 2011 it had risen to 12MW.
The largest power station was brought on stream in 2002 – Mutnovskaya, also on Kamchatka, with a capacity of 50 MW. Verkhne (Upper) Mutnovskaya geothermal power station has an installed capacity of 23 MW and was brought on stream in 1999 – the two stations work in tandem. The Mendeleyevskaya station on Iturup in the Kurile Islands was launched in 2002 with a capacity of 3.6 MW.
Another geothermal station is planned for Iturup – Okeanskaya-2 at a cost of 2 billion roubles ($27.5 million) and a capacity of 5 MW with the possibility of boosting that figure to 15 MW. Iturup is also the site of the Okeanskaya station featuring two installations with a capacity of 1.8 MW each but the facility was taken out of service after a fire in 2013.
Overall, although geothermal stations are important for energy supplies on Kamchatka, their share of the national energy balance is minuscule. Whereas world-wide geothermal capacity totals 13.3 GW, in Russia, the total stands at only 74 MW. Russia, however, has considerable geothermal resources – the most promising regions are the Kuriles, western Siberia and the North Caucasus.
Cheap to run and green all around
The chief advantage of geothermal is its environment-friendly nature.
Energy is produced without burning fossil fuels and emissions of carbon dioxide into the atmosphere are estimated at 45 kg per KWh of energy produced.
Geothermal stations produce only one-sixth the volume of CO2 emissions produced by gas-fired stations and a minimum of nitrous oxide or sulfur-containing gases. Emissions of greenhouse gases are one-quarter the volume of solar-powered stations.
Modern binary cycle stations and closed system produce no emissions at all. Geothermal power stations on average use less water over the course of their working life than traditional stations.
And geothermal steam is practically an inexhaustible source of energy. It continues to act for as long as the Earth exists – temperatures at the Earth’s core are about 6000 C and the rate of cooling is 300-500 C over a billion years. They are in no way influenced by weather conditions – by availability of sunlight or wind – and they can be sited in hard-to-reach areas. Geothermal energy is available around the clock, every day of the year.
Geothermal stations need limited space—on average they occupy 400 sq.m. per 1.1 GW of power produced while solar stations need 3 sq. km. Construction of a geothermal station has a minimal effect on the nature around it. They are small – all that is required on the surface is a machine room with a turbine and a generator.
But the main advantage is surely inexpensive operating costs. Geothermal stations can potentially provide from 0.0035 to 2 Tw of energy, have low day-to-day costs with expenditure limited to servicing.
Expensive construction and toxic water
The liquid used in operations at geothermal stations can be dangerous.
Underground water and steam are not necessarily mineral water – they may contain gases, heavy metals like lead, cadmium, arsenic or ammnak. There may be problems disposing of water or dangerous substances and leaks are possible.
Extracting water from different layers could result in surface shifting, deformation of those layers or earthquakes. But it should not be forgotten that the majority of geothermal stations are located in remote areas.
The costs of maintaining a geothermal station are low but serious investments are required for their construction, mainly in exploration and drilling of geothermal energy resources and also the heating systems and cooling and other equipment. Expenditure on construction of geothermal systems depends on the location of water and its composition, the construction itself, the vital creation of closed systems and water treatment. Operating costs total about 2800 per Kw of installed capacity, compared to $1,000 for thermal stations.
But stations depend on the availability of thermal water and that can imply problems with siting the station and energy transmission.
According to analysts Rystad, the global capacity of geothermal power stations will rise from 16 GW at the end of 2020 to 24 GW in 2025 – if $25 billion is investment in the projects. In 2010-2020, $40 billion was invested in new geothermal projects.
Some experts believe that geothermal energy can develop at a rate of 2 % growth a year and production of power from geothermal energy will rise from 16 billion KWh in 2019 to 52.2 KWh in 2050.
For the moment, the potential of geothermal energy remains undiscovered. But undoubtedly, the ever-quickening energy transition will provide an impulse for the development of this energy sector and prompt more and more new players to pay due attention to it.