Electricity hidden deep underground is becoming a clean resource bonanza in the eyes of tech giants and chaebol.

Recently, Google signed an agreement with NV Energy, a subsidiary of Warren Buffett's Empire, to purchase 115 megawatts of renewable energy from a geothermal facility operated by Fervo Energy to power its data center in Nevada.

Renewable wind or solar farms not only power tens of thousands of homes, but a large portion also contributes to data centers operated around the world by tech giants like Google, Meta, X, and Amazon.

The giants' exploration of clean electricity has extended from the surface to the ground. Buffett began focusing on geothermal energy a few years ago. 4% of Berkshire Hathaway Energy's renewable power generation capacity in 2023 already comes from geothermal energy; in order to fulfill its commitment to reduce emissions, Google's focus on geothermal energy began in 2021.

How many environmental benefits can geothermal power generation bring? What is the current state of development of this kind of sustainable clean electricity in China, which has about the same reserves of geothermal resources as the United States?

Low cost, low carbon emissions

Geothermal power generation is a new type of power generation technology that uses underground hot water and steam as a power source. Its basic principle is similar to thermal power generation, but the difference is that this power generation method is sustainable.

According to estimates by the Geothermal Energy Association, the global geothermal energy currently uses only 6.9% of the total potential, while the Intergovernmental Panel on Climate Change estimates that the global geothermal potential is between 35 gigawatts and 2 terawatts because the heat it extracts only accounts for a small portion of the Earth's internal thermal energy.

This type of power generation also has significant economic and environmental benefits. On the one hand, compared with other types of energy storage methods, geothermal energy storage has the advantage of low cost.

An analysis of the economic benefits of the Dutch deep aquifer energy storage system found that when 75℃ hot water is injected into a large-scale deep aquifer energy storage system, the cost price of extracting heat per gigabyte is only 3.5 euros. If the hot water temperature is further raised, the energy storage will drop further. Similarly, another study predicted the leveled energy cost of the deep aquifer energy storage system in the Netherlands through a leveled energy cost calculation model for deep aquifer energy storage systems in the Netherlands, which is approximately 2.76 euros per gigajoule thermal energy, while the equalized energy cost of natural gas reached more than 10 euros during the same period.

On the other hand, from the perspective of energy saving and emission reduction, the contribution of geothermal energy storage technology in reducing carbon dioxide emissions is considerable. According to a study in the Swedish region, using a combination of a deep aquifer energy storage system and a solar heating system, the carbon dioxide emission reduction reached 2,654 tons by 16 GW hours compared to the existing energy supply system.

Evaluation results of deep aquifer energy storage systems in the Netherlands show that using deep aquifer energy storage will save 83% of fossil fuels and reduce carbon dioxide emissions by 31,000 tons.

According to the report of the Intergovernmental Panel on Climate Change, the average greenhouse gas emissions from geothermal power plants are about 45 grams of carbon dioxide per kilowatt-hour, less than 5% of the emissions from traditional coal-fired power plants.

However, an expert from China University of Petroleum's School of Carbon Neutrality Future Technology said that geothermal energy storage technology may also cause other environmental problems during operation. This effect mainly comes from geothermal energy storage methods, which mainly use aquifer-type geothermal energy storage. In particular, in shallow technology, the ground fluid carries harmful substances such as heavy metals and harmful microorganisms into the groundwater system during fluid recharging and heating. At the same time, harmful substances in underground aquifers are brought into the shallow surface water system during the geothermal process, causing pollution to drinking water sources.

China's conundrum

In order to promote the development and utilization of geothermal energy resources, many countries such as Greece, Indonesia, and Peru have set geothermal development goals.

In 2021, various departments such as China's National Development and Reform Commission, the National Energy Administration, and the Ministry of Finance also jointly issued “Certain Opinions on Promoting the Development and Utilization of Geothermal Energy”, which proposes that by 2025, a number of geothermal power demonstration projects will be built in regions with good resource conditions, and the installed capacity of geothermal power generation will double that of 2020; by 2035, the installed capacity of geothermal energy power generation will double that of 2025.

In fact, the practice of geothermal power generation in China began in 1970, and the commissioning of the Fengshun Geothermal Power Plant in Guangdong made China the eighth country in the world to successfully use geothermal heat for power generation. Since then, small medium- and low-temperature geothermal power plants have been built one after another in Huailai in Hebei and Yichun in Jiangxi. As early as 1977, China's first megawatt high-temperature geothermal power plant successfully generated electricity in Yangbajing, Tibet.

However, after a period of operation, most geothermal power plants were shut down due to problems such as poor efficiency and economic benefits; since then, the development of China's geothermal power generation industry has almost stagnated, and there has been no significant increase in the installed capacity of geothermal power generation. Deep geothermal power generation in China is still in the exploration stage. Only a small number of test units are in operation, and large-scale power generation has not been achieved.

China is rich in geothermal resources reserves, and the distribution of geothermal resources shows a trend of increasing geothermal resources and rising temperatures from central to eastern and southwestern regions. According to the “13th Five-Year Plan” for the Development and Utilization of Geothermal Energy, China's shallow geothermal energy resources are equivalent to 700 million tons of standard coal; the amount of hydrothermal geothermal energy resources is equivalent to 1.25 trillion tons of standard coal, and the annual extractable amount is equivalent to 1.9 billion tons of standard coal; and the amount of dry-hot rock geothermal energy buried at a depth of 3,000 to 10,000 meters is equivalent to 856 trillion tons of standard coal.

However, a report from the Institute of Geology and Geophysics of the Chinese Academy of Sciences also shows that currently the geothermal resources that can be explored in China are mainly medium to low temperature geothermal heat. This is one of the reasons why China's geothermal resource reserves are comparable to those of the United States, but the installed capacity of power generation is far different.

By the end of 2020, China's installed capacity of geothermal power generation was 44.56 megawatts, which is a big gap with the target of adding 500 megawatts of geothermal power generation capacity planned in the “13th Five-Year Plan”; the installed capacity of geothermal power generation dropped from 8th place in the late 1970s to nearly 20th place at present. The installed capacity of geothermal power generation is less than 1% of the world, and development is clearly lagging behind foreign countries.

“The development of geothermal resources in China has a complex geological background, unclear resource enrichment mechanisms, large depth of burial, complex engineering geological conditions, and difficult development technology, which limits the development and utilization of geothermal resources to a certain extent. Due to huge investment in early exploration and technology, the benefits of geothermal power plants have yet to be assessed. Due to technical problems, profits are not high, and economic efficiency also limits further development.” A researcher at the Institute mentioned above explained it this way.

Currently, there are 30 geothermal power generation countries in the world, with an installed geothermal power generation capacity of 15.95 gigawatts, an increase of about 27% compared to 2015. The top five countries are the United States, Indonesia, the Philippines, Turkey and Kenya. According to the International Energy Agency (IEA), global direct installed geothermal capacity will reach 650 gigawatts by 2040.

Direct utilization is mainly concentrated in the European region. Countries such as France, Germany, Hungary and other countries use geothermal resources with a temperature higher than 100℃ for heating. Currently, French geothermal direct uses an installed capacity of 524 megawatts, Germany 460 megawatts, and Hungary 319 megawatts. According to Rystad Energy's forecast, due to the energy crisis, EU countries will drill about 1,100 geothermal wells for district heating by 2030.