Long-term energy storage has received financial and policy support in many European and American countries.

In November 2022, the U.S. Department of Energy announced that it will provide at least USD 350 million in financial support for long-duration energy storage projects, and zero-carbon and low-cost long-duration energy storage technologies with charge-discharge cycles of more than 10 hours are expected to be funded. The European Commission also issued a statement at the beginning of 2023, stating that it will provide up to 470 million euros in financial support to 78 potential startups, including long-term energy storage startups.

The scale of China's long-term energy storage market is also growing rapidly, and the scale of energy storage power stations based on compressed air energy storage and liquid flow energy storage technologies has reached the 100 MW level. In October 2022, the first national-level large-scale chemical energy storage demonstration project, the flow battery energy storage peak-shaving power station, was officially connected to the grid for power generation in Dalian. In the same year, the world's largest new compressed air energy storage power station was connected to the grid for power generation in Zhangjiakou.

Energy storage technology is mainly divided into physical energy storage, electrochemical energy storage, thermal energy storage and chemical energy storage. At present, the most widely used pumped storage technology in the world is physical energy storage. However, due to the difficulty in site selection and the long construction period, it is difficult to meet the peak-shaving demand of renewable energy power only by pumped storage.

Electrochemical energy storage is the fastest growing new energy storage technology in the world in recent years.

According to data from the Advanced Industry Research Institute (GGII), China's energy storage lithium battery shipments will reach 130GWh in 2022, a year-on-year growth rate of 170%. The explosive growth of new energy vehicles has driven the rapid progress of lithium-ion battery technology, while the explosion of energy storage demand has accelerated industrial fission.

Compared with the power field, the operation of energy storage equipment in the power system is more complicated. For example, in a power supply system dominated by solar energy, if the energy storage power station can only discharge for a short time, users will still face the risk of power outages in the second half of the night; long-term power supply pressure.

In the context of current electrification of transportation, it is difficult to meet the needs of future power systems for large-capacity and long-term energy storage only by relying on lithium battery technology. Liquid flow batteries, thermal energy storage technology, compressed air, hydrogen ammonia energy storage, etc. have great potential in "long-term energy storage", and there is a lot of attention at home and abroad.

The U.S. Department of Energy announced the "Long-duration Energy Storage Research" plan in 2021, aiming to reduce the cost of energy storage systems with a duration of more than 10 hours by more than 90% within 10 years. European countries such as Denmark and Germany also have long-term deployments in the field of inter-seasonal heat storage.

On the whole, "long-term energy storage" will further heat up in 2023.

flow battery

Liquid flow batteries have always been considered as a promising long-term energy storage technology, and there are several liquid flow solutions on the electrochemical energy storage track alongside lithium batteries.

After decades of rapid development, flow battery technology has fully blossomed. According to the different electrolyte solutions, various subdivisions such as all-vanadium, zinc-iron, zinc-bromine, and all-iron have emerged, showing the scene of a hundred schools of thought in the field of energy storage. At present, flow batteries receiving attention include zinc batteries and vanadium batteries.

The all-vanadium redox flow battery is currently the most mature flow battery technology. It has the characteristics of high energy efficiency, long cycle life, and high power density. It is suitable for large and medium-sized energy storage scenarios. However, for all-vanadium redox flow batteries, the cost of vanadium electrolyte accounts for about 60% of the battery cost, which greatly increases the initial investment threshold. In contrast, zinc-based flow batteries have received increasing attention due to their low-cost electrolytes.

Overseas, European and American battery start-up companies such as Zinc8, Primus, and Invinity focus on zinc flow batteries; ESS, Avalon, and Sumitomo Electric mainly focus on vanadium flow batteries. In China, Weijing Energy Storage mainly focuses on zinc flow batteries; Shanghai Electric, Dalian Rongke, and Hunan Yinfeng mainly focus on vanadium flow batteries.

compressed air

Compressed air energy storage technology is divided into underground compressed air energy storage technology and liquid air energy storage technology.

Underground air compression uses the underground space as a giant storage tank, uses excess electrical energy to pump compressed air into the underground space, and releases the compressed air when needed to allow the power generation facility to regenerate electricity.

According to the pressure parameters of the ground system at the present stage, salt cavern compressed air energy storage energy is generally buried at a depth of 500-1100m. Salt caverns can be used in places with salt caverns, and artificial caves are relied on in places without salt caverns, with small geological restrictions.

In 2022, two salt cavern air compression projects will be connected to the grid for power generation. On September 30, the national test and demonstration project of salt cavern compressed air energy storage in Jintan, Jiangsu Province was successfully connected to the grid. Applications have made significant progress.

On October 8 of the same year, the first phase of the 10-megawatt (MW) demonstration power station of Yanchuang Advanced Compressed Air Energy Storage Peak Shaving Power Station in Feicheng, Shandong Province successfully passed the acceptance inspection and was officially connected to the grid for power generation. This marks that the world's first salt cavern advanced compressed air energy storage power station has entered the formal commercial operation state.

In addition, there are also large-scale air compression energy storage projects in Bijie, Guizhou, and Zhangjiakou, Hebei, which will be connected to the grid for power generation in 2021.

In addition, many overseas companies are exploring underground air compression solutions that break through geographical restrictions. Canadian energy storage developer Hydrostor has adopted a different approach: pumping compressed air into existing caves (such as abandoned mines) and maintaining it with water Constant pressure, its goal is to free compressed air energy storage technology from being restricted by geological conditions, and at the same time use equipment from other mature industries to minimize technical risks.

Liquid air energy storage compresses air and stores it in pressurized storage tanks, with air compression equipment and generators sourced from established supply chains in established industries. This innovative energy storage technology can be used in grid-scale energy storage systems. After 15 years of development and improvement, British energy storage developer HighviewPower is committed to transforming its liquid air energy storage pilot project into a large-scale commercial energy storage facility.

thermal energy storage

Thermal energy storage technology uses heat storage materials as the medium to store solar energy in the form of heat and release it when needed.

Heat storage technology is mainly used in the storage and utilization of low-temperature heat sources such as heating, hot water, and ice storage. In recent years, with the development and application of solar thermal power generation and industrial waste heat recovery technology, the demand for medium and high temperature heat storage continues to grow.

At present, the installed capacity of my country's photothermal power generation projects has reached 538 megawatts. Nitrate materials are generally used as heat storage media. The working temperature range in the molten state is 290-560 degrees Celsius, and the energy storage time of up to 10 hours can be achieved.

Not long ago, the new heat storage technology designed by the Madrid Polytechnic University team uses silicon alloy materials, and its advantages in material cost, heat storage temperature, and energy storage time have attracted market attention.

Silicon is the second most abundant element in the earth's crust, and the cost per ton of silica sand is only 30-50 US dollars, which is 1/10 of molten salt materials. In addition, the heat storage temperature difference of silica sand particles is much higher than that of molten salt, and the maximum operating temperature can reach more than 1000 degrees Celsius. The higher operating temperature also helps to improve the overall energy efficiency of the solar thermal power generation system.