7 energy storage methods for data center including lithium ion batteries

Energy storage technology-one of the necessary options for new data center

The new data center focuses on supporting the digital transformation, intelligent upgrading and integrated innovation of the economy and society. Guided by the application needs of 5G, industrial Internet, cloud computing and artificial intelligence, it gathers multiple data resources and applies green and low-carbon technologies. As a high energy carrying data center industry, it has become an inevitable trend for new data centers to use renewable energy.

Energy storage, as a technical direction that can well solve the shortcomings of poor stability of renewable energy, has received extensive attention from IDC industry. The stored energy can be used as emergency energy, or it can be stored when the grid load is low, and output energy when the grid load is high.

It can be used to cut the peak and fill the valley, reduce the fluctuation of the grid, and reduce the operating cost of the data center. Energy storage technology has become one of the necessary options for building new data centers.

Current energy storage technologies and their advantages and disadvantages

Can energy storage be combined with IDC industry to give birth to a new operation mode of “energy storage + IDC”? Energy storage technology plays a key role. Lithium ion battery is one of the most common energy storage technologies. It is widely used in portable power station, powerwall, home battery backup and so on. The following will introduce other current energy storage technologies, as well as the advantages and disadvantages of various energy storage technologies.

Pumped storage

The energy storage technology uses water as the energy storage medium to realize the storage and management of electric energy through the mutual conversion of electric energy and potential energy. During the period of low power load, water is transported to high-lying places and stored in reservoirs. At the peak of power load, the potential energy of water flowing down from high places is converted into electrical energy for power generation.

Pumped storage is a large-scale energy storage mode with the most mature technology, the best economy and the most large-scale development conditions at the present stage. It is a green, low-carbon, clean and flexible regulated power source for the power system. At present, Fengning pumped storage power station in Hebei Province of China is the largest pumped storage power station in the world, with a planned installed capacity of 3600MW.

However, pumped storage is greatly limited by geographical conditions, and the energy storage density is low. At the same time, due to the need to build corresponding infrastructure such as dams and reservoirs, the construction period is long and the investment amount is large.

Compressed air energy storage

This energy storage technology will use electric energy to compress air and store it in the gas storage chamber (salt cavern) during the low load period of the power grid. In the peak load of the power grid, the stored air is released to drive the steam turbine to generate electricity. Its essential principle is similar to that of pumped storage.

The forms of compressed air energy storage mainly include: traditional compressed air energy storage system, compressed air energy storage system with heat storage device, and liquid gas compression energy storage system.Pumped energy storage and compressed air energy storage have relatively high technical maturity, large storage capacity, long storage time, low overall project cost, and relatively low “threshold” for application.

Not long ago, the world’s first 300MW level non afterburning compressed air energy storage demonstration project invested by the main body of China energy construction started in Hubei Province. After the project is completed, it will achieve three world firsts in “single machine power, energy storage scale and conversion efficiency” in the field of non afterburning compressed air energy storage.

However, as far as the existing technology is concerned, compressed air energy storage generally has disadvantages such as large-scale occupation of energy storage room, long construction period, and low conversion efficiency (generally 60% ~ 63%).

Gravity energy storage

The energy storage technology is to use renewable energy to pull up heavy objects through machinery such as guide wheels to store energy mechanically during the low load period of the power grid. In the peak load of the power grid, the potential energy is generated when the heavy object falls is used to convert the potential energy into electrical energy for energy storage.

Gravity energy storage has the characteristics of low construction cost, high comprehensive conversion efficiency, high safety and long service life. However, gravity energy storage is still in its infancy. Under the background of the existing technology, its small energy storage capacity and high operation and maintenance cost are the main reasons for its failure to become a mainstream energy storage mode.

Molten salt energy storage

This energy storage technology uses the ionic melt formed by the melting of inorganic salts at high temperatures to store the energy such as solar photoheat, geothermal heat, waste heat, low-grade waste heat, and electricity during the low load period of the power grid in the form of thermal energy, and releases the thermal energy during the peak load period of the power grid to generate electricity.

Molten salt energy storage has high relative energy storage density, high stability, long service life and low construction cost. At the end of 2021, Malta, a long-term thermal storage technology company in the United States, and NB Power, a Canadian energy company, announced that they had signed a cooperation agreement.

The two sides will jointly build a 1000mwh long-term thermal storage project in New Brunswick, Canada, which is expected to be put into operation in 2024. After completion, the project will become the largest long-term heat storage project in the world. At present, the main disadvantages of molten salt energy storage are low thermal conductivity, low specific heat capacity, strong corrosion and poor safety.

Vanadium battery energy storage

Vanadium battery energy storage is also called all vanadium flow battery energy storage. This battery is a redox battery in which the active material is in a circulating liquid state. Similar to the energy storage mode of the above energy storage technology, vanadium batteries can be charged during the valley period of the power grid and discharged during the peak period of the power grid.

Vanadium battery has high conversion rate (about 75%), high safety, long service life and high power. At present, Dalian, China has built an all vanadium flow battery energy storage project with a capacity of 100MW and 400mwh. However, the disadvantage of all vanadium flow battery is also obvious, and its storage capacity per unit volume is low.

Flywheel energy storage

Flywheel energy storage is an energy storage method that uses a motor to drive the flywheel to rotate at high speed and then drives a generator to generate electricity when necessary. Flywheel energy storage has the characteristics of long service life, high conversion efficiency (up to 90%), fast response speed (millisecond level), small footprint and high safety.

However, the power output time of flywheel energy storage is extremely short, only lasting for more than ten seconds to a few minutes, and the cost is expensive and the operation and maintenance cost is high. Therefore, for the data center, the flywheel energy storage effect can be achieved by using UPS power supply, and the overall cost is much lower.

Electrochemical energy storage

Electrochemical energy storage is an energy storage method that stores electric energy through a battery and releases it when needed. Its principle is similar to that of a power bank. The existing electrochemical energy storage mainly includes lead-acid batteries, lead-carbon batteries, lithium batteries and nickel cadmium batteries.

Electrochemical energy storage technology is relatively mature at present, but the service life of lead-acid batteries and the amount of energy stored per unit volume determine that they can only be used as emergency power supply in data centers, not as large-scale and long-term energy storage in data centers.

Based on the analysis of existing technology and raw materials, lithium iron phosphate battery is the preferred battery for large-scale and long-term energy storage in data centers.

Conclusion

As a high energy carrying industry, even if the carbon emission reduction can be achieved through the reduction and efficiency improvement of equipment, 100% renewable energy power supply is undoubtedly one of the best ways to achieve true carbon neutrality. And energy storage can solve the problem of unstable power supply of renewable energy.

There are many energy storage BMS companies in China. The combination of large-scale long-term energy storage and 100% renewable energy will become one of the best operation modes of data centers in the future. Although lithium iron phosphate battery energy storage promotes the carbon neutralization process of data centers, there are still many problems in the application process, and the new mode of energy storage + IDC is still in the trial stage.