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Using underground energy storage is the main way of international energy reserves
2023/6/20
Underground energy storage, also known as deep underground energy storage or deep earth energy storage, refers to the use of deep salt caverns, mining areas, abandoned pits and other deep underground space to store energy or energy materials such as oil, natural gas, hydrogen and carbon dioxide in the deep underground strata. The use of deep underground space for large-scale energy reserves is the main way of international energy reserves, which is of great significance to ensure national energy security, strategic material security and the realization of the "double carbon" goal.
"Deep underground energy storage is an important direction for the development of future energy reserves, and it is the only way to solve the traditional strategic oil reserves, natural gas peaking security, sustainable supply of renewable energy and the future large-scale and efficient use of hydrogen energy." Recently, the 748th Colloquium of the Xiangshan Scientific Conference was held in Beijing, and the executive chairman of the conference, Yang Chunhe, a member of the Chinese Academy of Engineering and a researcher of Wuhan Institute of Geotechnics, Chinese Academy of Sciences, said at the conference that "vigorous development of deep-ground energy storage is the key to achieving carbon neutrality and transformation and upgrading of energy structure in China."
In this Xiangshan Science Conference, a number of academicians, experts and scholars focused on the core difficulties in the field of underground energy storage, sorted out the core scientific issues and major technical bottlenecks to be focused on for energy storage in deep underground space, formed a corresponding technology roadmap, and laid the foundation for the industrial development of underground energy storage in the future.
What exactly is underground energy storage? Why should we promote the industrial development of underground energy storage? What are the technical difficulties of underground energy storage?
Unveiling the "veil" of underground energy storage
The executive chairman of the conference, academician of the Chinese Academy of Engineering, President of Shandong University Li Jucai introduced, underground energy storage is also known as deep underground energy storage or deep ground energy storage, refers to the use of deep salt caverns, mining areas, abandoned pits and other deep underground space, the oil, natural gas, hydrogen and carbon dioxide and other energy or energy materials stored in the deep strata.
The use of deep underground space for large-scale energy reserves is the main way of international energy reserves, which is of great significance to ensure national energy security, strategic material security and the realization of the "double carbon" goal.
Take oil as an example, the current oil storage methods mainly include surface storage tanks, salt caverns and hard rock cavern storage, of which the use of salt caverns for crude oil storage is the main way adopted by many countries in the world.
Yang Chunhe introduced, in the United States, a number of strategic oil reserves built in the 1970s and 1980s, a total of more than 60 salt caverns, oil storage capacity of more than 700 million barrels. These oil reserves not only ensure the energy security of the United States, but also establish the dominant position of the United States in the international oil pricing.
Germany's oil reserves mainly include crude oil, gasoline, diesel, heavy oil, etc., among which crude oil is mainly stored in underground salt caverns. In addition to being used as a strategic reserve, Germany's oil reserves will also provide storage services for customers by using the remaining storage capacity according to the changes of oil prices in the international market. France, on the other hand, established a petroleum reserve system by law as early as 1925, and its petroleum reserves consist of one underground salt cavern reservoir and above-ground reservoirs throughout the country.
Why do countries choose salt caverns for underground storage? Salt rock is an ideal geological body for large-scale energy storage because of its physical stability, low permeability, self-healing damage, solubility in water, and wide distribution. The use of salt formations for energy storage is a priority development direction for the implementation of large-scale energy reserves in China in the future.
China's salt mine geological conditions are complex, so the first choice to carry out the construction of salt cavern storage in Jintan salt mine in Jiangsu Province, where geological conditions are relatively simple and superior, based on independent research and development, overcoming difficulties such as insoluble interlayer and geological non-homogeneity, breaking through a series of technical bottlenecks and achieving great success, initially building China's first technical standard system for salt cavern storage, forming China's salt cavern storage construction "Jintan model". This model provides important reference and engineering demonstration for salt cavern storage site construction, cavity building destination layer preference, cavity building method and gas injection and brine discharge process improvement, etc.
Underground is the ideal place for energy storage
Why should energy be "hidden" underground? Is it because the surface equipment can not meet the demand for energy reserves? In fact, the advantage of underground energy storage is precisely the word "underground".
Of course, to understand the necessity and importance of underground energy storage, we must first understand China's current energy structure and energy storage status.
Since 2017, China's policy to promote low-carbon reform of the energy system has gradually increased, and has initially formed a comprehensive development of coal, electricity, oil, natural gas, new energy supply system. In recent years, the status of coal as the mainstay of China's energy consumption has remained unchanged, but its share in energy consumption has shown a trend of decreasing year by year. The proportion of clean energy consisting of natural gas and non-fossil energy sources has increased significantly, from 17.9% in 2015 to 25.9% in 2022. Among them, the proportion of non-fossil energy such as wind, light energy and geothermal increases from 11% in 2015 to 17.5% in 2022.
Yang Chunhe said that accelerating the use of non-fossil clean energy is a major trend in global energy development, and is also a priority direction for China's energy development. However, because wind and solar energy and other typical regional and not continuous and stable supply, to the stable operation of the power grid has brought certain challenges, restricting the rapid development of renewable clean energy. For many years, China has been the phenomenon of abandoned wind and abandoned light.
How to improve the efficiency of renewable energy use, the abandoned electricity storage? To this end, scientists have thought of many ways, including pumped storage, piezogas storage, liquid flow battery energy storage, etc.. However, whether it is pressurized gas storage or liquid flow battery energy storage, all need a large storage space, with the advantages of large volume, can withstand high pressure and other advantages of the deep underground space has become the ideal place for energy storage.
At present, there are reports on the use of deep salt mining areas to carry out liquid flow battery energy storage experiments, which provide ideas for using liquid flow batteries for large-scale energy storage.
Of course, for the storage needs of hydrogen, oil, natural gas and other energy sources, the vast deep underground is also "not to be denied".
Yang Chunhe introduced that hydrogen energy is an effective way to solve the sustainable development of energy, with the advantages of wide source, high calorific value, no pollution, and rich application scenarios. The molecular weight of hydrogen is smaller than that of natural gas, which means that more space is needed for storing hydrogen and the storage space needs to be better sealed. Therefore, deep subsurface salt caverns provide a good environment for large-scale hydrogen energy storage.
In addition, using deep underground space to store oil can avoid the disadvantages of using ground storage tanks for oil storage such as poor economy, low safety and large floor space, and further guarantee the safe supply of oil; accelerating the construction of underground gas storage can also ensure the stable supply of natural gas for long-distance pipelines and avoid the occurrence of large-scale "gas shortage".
Crack the problem of energy storage with technological innovation
Underground energy storage has obvious advantages, so it becomes very important to promote underground energy storage technology innovation.
Over the years, China has conducted in-depth research in deep underground space energy storage, and has accumulated rich practical experience, but there are still some problems to be solved in the site selection, construction and storage of energy storage. For example, the mechanism of multi-scale interaction between deep ground energy storage medium and surrounding rock body is not clear, the mechanism of spatial and temporal evolution of seepage disaster in deep ground energy storage is not clear, the long-term stability of deep ground energy storage and the mechanism of library group interaction need to carry out targeted research, and the multi-scale permeability testing technology of low permeability surrounding rock body needs to be developed.
Yang Chunhe added that in order to use Chinese stratified salt rocks for large-scale energy reserves, it is urgent to solve the key theoretical research difficulties such as multi-scale progressive damage under multi-field coupling conditions of low-permeability media, leakage catastrophe and long-term functional deterioration of energy storage reservoirs; at the same time, it is necessary to carry out a series of key technology research such as multi-scale permeability testing of stratified salt rocks, intelligent construction of energy storage reservoirs and long-term functional guarantee, so as to provide theoretical and technical guarantee for the implementation of large-scale energy reserves in China. Theoretical and technical guarantee for the implementation of large-scale energy reserves in China.
"Deep underground energy storage is an important direction for the development of future energy reserves, and it is the only way to solve the traditional strategic oil reserves, natural gas peaking security, sustainable supply of renewable energy and the future large-scale and efficient use of hydrogen energy." Recently, the 748th Colloquium of the Xiangshan Scientific Conference was held in Beijing, and the executive chairman of the conference, Yang Chunhe, a member of the Chinese Academy of Engineering and a researcher of Wuhan Institute of Geotechnics, Chinese Academy of Sciences, said at the conference that "vigorous development of deep-ground energy storage is the key to achieving carbon neutrality and transformation and upgrading of energy structure in China."
In this Xiangshan Science Conference, a number of academicians, experts and scholars focused on the core difficulties in the field of underground energy storage, sorted out the core scientific issues and major technical bottlenecks to be focused on for energy storage in deep underground space, formed a corresponding technology roadmap, and laid the foundation for the industrial development of underground energy storage in the future.
What exactly is underground energy storage? Why should we promote the industrial development of underground energy storage? What are the technical difficulties of underground energy storage?
Unveiling the "veil" of underground energy storage
The executive chairman of the conference, academician of the Chinese Academy of Engineering, President of Shandong University Li Jucai introduced, underground energy storage is also known as deep underground energy storage or deep ground energy storage, refers to the use of deep salt caverns, mining areas, abandoned pits and other deep underground space, the oil, natural gas, hydrogen and carbon dioxide and other energy or energy materials stored in the deep strata.
The use of deep underground space for large-scale energy reserves is the main way of international energy reserves, which is of great significance to ensure national energy security, strategic material security and the realization of the "double carbon" goal.
Take oil as an example, the current oil storage methods mainly include surface storage tanks, salt caverns and hard rock cavern storage, of which the use of salt caverns for crude oil storage is the main way adopted by many countries in the world.
Yang Chunhe introduced, in the United States, a number of strategic oil reserves built in the 1970s and 1980s, a total of more than 60 salt caverns, oil storage capacity of more than 700 million barrels. These oil reserves not only ensure the energy security of the United States, but also establish the dominant position of the United States in the international oil pricing.
Germany's oil reserves mainly include crude oil, gasoline, diesel, heavy oil, etc., among which crude oil is mainly stored in underground salt caverns. In addition to being used as a strategic reserve, Germany's oil reserves will also provide storage services for customers by using the remaining storage capacity according to the changes of oil prices in the international market. France, on the other hand, established a petroleum reserve system by law as early as 1925, and its petroleum reserves consist of one underground salt cavern reservoir and above-ground reservoirs throughout the country.
Why do countries choose salt caverns for underground storage? Salt rock is an ideal geological body for large-scale energy storage because of its physical stability, low permeability, self-healing damage, solubility in water, and wide distribution. The use of salt formations for energy storage is a priority development direction for the implementation of large-scale energy reserves in China in the future.
China's salt mine geological conditions are complex, so the first choice to carry out the construction of salt cavern storage in Jintan salt mine in Jiangsu Province, where geological conditions are relatively simple and superior, based on independent research and development, overcoming difficulties such as insoluble interlayer and geological non-homogeneity, breaking through a series of technical bottlenecks and achieving great success, initially building China's first technical standard system for salt cavern storage, forming China's salt cavern storage construction "Jintan model". This model provides important reference and engineering demonstration for salt cavern storage site construction, cavity building destination layer preference, cavity building method and gas injection and brine discharge process improvement, etc.
Underground is the ideal place for energy storage
Why should energy be "hidden" underground? Is it because the surface equipment can not meet the demand for energy reserves? In fact, the advantage of underground energy storage is precisely the word "underground".
Of course, to understand the necessity and importance of underground energy storage, we must first understand China's current energy structure and energy storage status.
Since 2017, China's policy to promote low-carbon reform of the energy system has gradually increased, and has initially formed a comprehensive development of coal, electricity, oil, natural gas, new energy supply system. In recent years, the status of coal as the mainstay of China's energy consumption has remained unchanged, but its share in energy consumption has shown a trend of decreasing year by year. The proportion of clean energy consisting of natural gas and non-fossil energy sources has increased significantly, from 17.9% in 2015 to 25.9% in 2022. Among them, the proportion of non-fossil energy such as wind, light energy and geothermal increases from 11% in 2015 to 17.5% in 2022.
Yang Chunhe said that accelerating the use of non-fossil clean energy is a major trend in global energy development, and is also a priority direction for China's energy development. However, because wind and solar energy and other typical regional and not continuous and stable supply, to the stable operation of the power grid has brought certain challenges, restricting the rapid development of renewable clean energy. For many years, China has been the phenomenon of abandoned wind and abandoned light.
How to improve the efficiency of renewable energy use, the abandoned electricity storage? To this end, scientists have thought of many ways, including pumped storage, piezogas storage, liquid flow battery energy storage, etc.. However, whether it is pressurized gas storage or liquid flow battery energy storage, all need a large storage space, with the advantages of large volume, can withstand high pressure and other advantages of the deep underground space has become the ideal place for energy storage.
At present, there are reports on the use of deep salt mining areas to carry out liquid flow battery energy storage experiments, which provide ideas for using liquid flow batteries for large-scale energy storage.
Of course, for the storage needs of hydrogen, oil, natural gas and other energy sources, the vast deep underground is also "not to be denied".
Yang Chunhe introduced that hydrogen energy is an effective way to solve the sustainable development of energy, with the advantages of wide source, high calorific value, no pollution, and rich application scenarios. The molecular weight of hydrogen is smaller than that of natural gas, which means that more space is needed for storing hydrogen and the storage space needs to be better sealed. Therefore, deep subsurface salt caverns provide a good environment for large-scale hydrogen energy storage.
In addition, using deep underground space to store oil can avoid the disadvantages of using ground storage tanks for oil storage such as poor economy, low safety and large floor space, and further guarantee the safe supply of oil; accelerating the construction of underground gas storage can also ensure the stable supply of natural gas for long-distance pipelines and avoid the occurrence of large-scale "gas shortage".
Crack the problem of energy storage with technological innovation
Underground energy storage has obvious advantages, so it becomes very important to promote underground energy storage technology innovation.
Over the years, China has conducted in-depth research in deep underground space energy storage, and has accumulated rich practical experience, but there are still some problems to be solved in the site selection, construction and storage of energy storage. For example, the mechanism of multi-scale interaction between deep ground energy storage medium and surrounding rock body is not clear, the mechanism of spatial and temporal evolution of seepage disaster in deep ground energy storage is not clear, the long-term stability of deep ground energy storage and the mechanism of library group interaction need to carry out targeted research, and the multi-scale permeability testing technology of low permeability surrounding rock body needs to be developed.
Yang Chunhe added that in order to use Chinese stratified salt rocks for large-scale energy reserves, it is urgent to solve the key theoretical research difficulties such as multi-scale progressive damage under multi-field coupling conditions of low-permeability media, leakage catastrophe and long-term functional deterioration of energy storage reservoirs; at the same time, it is necessary to carry out a series of key technology research such as multi-scale permeability testing of stratified salt rocks, intelligent construction of energy storage reservoirs and long-term functional guarantee, so as to provide theoretical and technical guarantee for the implementation of large-scale energy reserves in China. Theoretical and technical guarantee for the implementation of large-scale energy reserves in China.
In this Xiangshan Science Conference, Li Yang, academician of Chinese Academy of Engineering, Sun Huanquan, academician of Chinese Academy of Engineering, Zhao Wenzhi, academician of Chinese Academy of Engineering and Li Gensheng, academician of Chinese Academy of Engineering, and other experts expressed their opinions and suggestions on the construction of energy storage reservoirs, safe operation and maintenance, and key technologies of CO2 geological storage, sorted out existing problems and challenges, and proposed targeted countermeasures, and jointly drew the underground The technical roadmap of underground energy storage was drawn up.
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