Shulou(Shulou.com)11/24 Report--

In 2022, energy storage has become one of the most popular tracks, and the research on the technical direction is an important link in the research of energy storage industry. The newly launched "Industrial Insight" column focuses on various sub-areas and analyzes the frontiers of the development of various industries. This week launched a series of energy storage, this article is mechanical energy storage research, inventory of mechanical energy storage of several technical paths and development challenges and other issues. You are welcome to forward and read.

01. Pumped storage has been widely used since the middle of the 20th century. it is the earliest large-capacity energy storage technology, and it has become the most widely used energy storage technology in the world. Globally, pumped storage accounts for 94% of the total energy storage scale; domestically, pumped energy storage accounts for 89.3% of the total energy storage scale.

The working principle of pumped storage is to use water as energy storage medium to realize the storage and release of electric energy, and its underlying technology is through the mutual transformation of electric energy and water potential energy. Specifically, during the operation of the pumped storage power station, when the electricity consumption is low, the water is pumped into the reservoir for storage through the excess electricity in the power grid, and the electric energy is converted into the potential energy of the water; when the electricity consumption is large, the stored water is released, and the water current pushes the turbine to generate electricity, converting the potential energy of the water into electricity.

At present, there are two types of pumped storage, one is pure pumped storage, the other is hybrid pumped storage. The former is only used for energy storage and is most widely used in China, while the latter can be used not only as energy storage, but also as a conventional hydropower station.

There are many reasons why pumped storage is most widely used, first, the technology is mature and it has been commercialized since the 1960s; secondly, the cost is relatively low, although the initial construction cost is high, the service life of pumped storage power station is longer, at least more than 50 years, the diluted cost is still low, and the average unit installed investment is 6136 yuan per kilowatt. Thirdly, it is rich in development resources, and the pumped storage power station can not only be built along the river, but also can be pumped storage off the river to increase exploitable resources and reduce costs; finally, the safety is high, unlike electrochemical energy storage, which is prone to accidents. Pumped storage uses water as energy storage medium, the safety is extremely high.

In addition, pumped storage also has many advantages, such as long energy storage cycle, long safe operation cycle, good stability and so on. This makes pumped storage by far the most widely used method of energy storage, with about 616000 sites worldwide, including existing reservoirs, according to public data.

Based on the advantages of pumped storage and the actual market demand of pumped storage, pumped storage ushered in opportunities for the development of the industry. In September last year, the National Energy Administration issued the medium-and long-term Development Plan of pumped Storage (2021-2035), which pointed out that by 2030, the total scale of pumped storage production will double that of the 14th five-year Plan, reaching about 120 million kilowatts. By rough calculation, it is expected to nearly triple in the next 10 years.

02, flywheel energy storage "play an auxiliary"

Flywheel energy storage uses high-speed rotating rotor in low friction environment to store energy. its working principle is to use electric energy to accelerate the flywheel and convert electrical energy into mechanical energy for storage. When electricity is needed, the flywheel drives the generator set and converts mechanical energy into electricity.

The advantage of this method of energy storage is obvious, because it is the transformation of electric energy and mechanical energy, and it is relatively less polluting. In addition, the flywheel energy storage energy density is relatively high, and the start-up speed is relatively fast, which is very practical for some specific scenarios, such as a sudden power outage in the data center. In order to avoid data loss, the energy storage system needs to respond quickly and start quickly.

However, the flywheel energy storage shortcomings are also very prominent, flywheel energy storage can only power for more than ten seconds at a time, the time is relatively short, in most cases will not be used independently, need to be used in conjunction with other energy storage systems. Therefore, the installed capacity of flywheel energy storage is not high, and its market share is not high. By the end of 2021, the cumulative installed capacity of flywheel energy storage in China is 0.01GW.

At present, there are flywheel energy storage projects in Chengde City, Changzhi City, Shanxi Province, Taiyuan City and other areas. For example, 30MW flywheel energy storage project is built in Changzhi City, Shanxi Province, which is the only project that uses flywheel energy storage technology alone to achieve FM auxiliary services. Yuncheng City, Shanxi Province has built 50MW / 100 "Lithium Iron Phosphate + Flywheel Energy Storage" independent energy storage project of peak regulation and frequency modulation. 50MW Mei Fang Gujiao shared Energy Storage demonstration Station has been built in Taiyuan City, Shanxi Province.

According to the prediction of many institutions, flywheel energy storage has obvious advantages in improving power grid stability, security and flexibility. In the next few years, with the continuous expansion of the energy storage market, the installed capacity of flywheel energy storage will continue to grow, and it is expected to reach 88.9MW by 2026.

03. Compressed air energy storage will usher in an inflection point

The working principle of compressed air energy storage is to use electric energy to compress air into salt caves, metal mines, oil and gas wells, coal mines or pressure vessels. When electricity is needed, compressed air is released to promote the air turbine expander to generate electricity.

The compressed air energy storage has obvious advantages, the service life of the energy storage equipment is relatively long, and it is not easy to be damaged, but the disadvantage is also very prominent. The investment cost of compressed air energy storage is relatively high, and it is greatly affected by geological conditions, so it has higher requirements for the construction environment.

On May 26 this year, China's first national demonstration project of compressed air energy storage was officially put into operation. It was Jintan Salt Cave compressed Air Energy Storage Power Station in Jiangsu Province, jointly built by China Huaneng, China Salt Group, Tsinghua University, three-dimensional Chemical Industry and other units. After a total of 12 years of research and development and construction, the first phase of energy storage installed 60MW, long-term planning 1000MW.

At present, among the compressed air energy storage projects that have landed, there are relatively many projects built in Qinghai Province. for example, the new liquid compressed air energy storage demonstration project, the compressed air energy storage demonstration project using the existing mine transformation (oil and gas well), the compressed air energy storage demonstration project using the transformed coal mine (metal mine), the new gas tank advanced compressed air energy storage demonstration project, etc., in addition, Datong City has built 50MW Datong Kai Yungang mine field compressed air energy storage project, Linyi City has built Guohua Lanling compressed air energy storage power station demonstration project.

According to the statistics of Zhongguancun Energy Storage Industry Technology Alliance, by the end of 2021, the cumulative installed capacity of compressed air energy storage in China is 0.18GW.

04. Gravity energy storage is expected to make up.

The medium of gravity energy storage is mainly water and solid matter, and its working principle is to rise and fall the energy storage medium through the height drop, so as to realize the charge and discharge of the energy storage system. Specifically, the medium is lifted to a high place by electric power to increase its gravity potential energy to complete energy storage. When electricity is needed, the falling medium uses gravity potential energy to convert kinetic energy into electric energy.

According to its working principle, it can be seen that gravity energy storage solid materials need substances with high energy density, such as metal, cement, sand and gravel, etc., in various links of storage and power generation, because they do not involve chemical reactions, so the overall operation is relatively safe. it also has little impact on the natural environment.

Moreover, gravity energy storage has no great restriction on site selection, has strong adaptability to the environment, and its application is very flexible. In addition, such as metal, cement, sand and other substances, in the use of relatively small loss, can be used for a long time, generally can be recycled for decades.

Before 2019, gravity energy storage is mostly technical. For example, the industry has successively put forward a variety of technical routes based on pumped energy storage, structure height difference, mountain drop, underground shaft and so on. At present, there are mainly four technical routes. They are piston gravity energy storage, suspended gravity energy storage, concrete block energy storage tower, mountain gravity energy storage.

By July 2020, the Swiss 5MW Business demonstration Unit (CDU) using EV1 technology will be connected to the grid and landed on the ground, making gravity energy storage enter a new experimental stage. Since 2022, gravity energy storage has been commercialized gradually, EV and Gravitricity gravity energy storage projects have taken the lead in application, and 100MWh gravity energy storage demonstration project has been built in Rudong, Jiangsu Province.

It is worth noting that the power generation efficiency of gravity energy storage is as high as 80%, which is much higher than 70% of pumped energy storage, and can effectively play a supplementary function in the future.

This article comes from the official account of Wechat: new Research (ID:chuxinyanjiu), author: Feifei, Editor: Tang Shi

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