Long term energy storage has great advantages and potential
- Long term energy storage requirements
- Current status of long term energy storage applications
- Long term energy storage technology
The speed of new energy grid connection is accelerating, and the construction of long term energy storage is the general trend. In recent years, the penetration rate of renewable energy has continued to increase, and the penetration rate of new energy has increased rapidly, superimposed on the instability of its output, which has pushed up the market demand for energy storage.
There are various time scale requirements for energy storage applications in power systems. Long term energy storage (generally refers to more than 4h) has become an important direction of energy storage development and has many advantages in the power system.
Overally speaking, long term energy storage has the potential to improve new energy consumption capacity and replace traditional power generation methods. It can provide sufficient flexible resources for the power grid, effectively reduce power grid operating costs, and have stronger peak-valley arbitrage and market profitability.
Long term energy storage requirements
The increase in the penetration rate of renewable energy
The data shows that in 2021, China will add 54.88GW of photovoltaic installed capacity, and the cumulative photovoltaic installed capacity will exceed 305GW. Thus, the development of photovoltaic cell is rapid and there appear lots of photovoltaic cell manufacturers.
You can click our article of top 10 photovoltaic cell manufacturers in China and have a look. In 2021, China will add 47.5GW of wind power installed capacity, and the cumulative installed wind power capacity will be about 330GW.
Among them, the newly installed capacity of wind power and photovoltaics exceeded 100 million kilowatts for the first time, and the installed capacity of new energy power generation is expected to maintain rapid growth.
Long term energy storage has many advantages
Long term energy storage has the potential to improve new energy consumption capacity and replace traditional power generation methods. At present, among the new electrochemical energy storage projects put into operation in China, the installed capacity on the new energy power generation side is the largest, exceeding 580MW in 2020, of which short-term energy storage within 4 hours is the main one.
Because the high output time of wind power and photovoltaic power generation does not strictly correspond to the peak period of user demand, and short-term energy storage does not have the power generation and consumption capacity of several hours or even days, which affects the stability of the power system. At present, renewable energy + long term energy storage has become one of the important solutions to consume renewable energy and replace traditional thermal power plants.
Current status of long term energy storage applications
Selection of the definition standard of long term energy storage
Long term energy storage is currently in the early stages of development, and the definition of the duration of energy storage has not yet been unified, but some experts define it as an energy storage system that can realize cross-day, cross-month, and even cross-season charge-discharge cycles.
The long term energy storage market is hot
Governments of many countries represented by the United States have begun to increase policy support for long term energy storage, and the world’s long term energy storage market is hot. Since 2018, the U.S. Department of Energy has continuously invested in the research and development of long term energy storage technology, with the goal of reducing the cost of energy storage to less than 5 cents per kilowatt-hour by 2030.
As one of the most active regions for long term energy storage, California has issued a tender to purchase a 50MW/4GWh 8-hour long term energy storage system in 2020, and plans to provide US$380 million to further support long term storage in the 2022-2023 budget. can be deployed.
China establishes a long term energy storage development trend
China has increased policy support in the field of long term energy storage. In response to new energy consumption and system peak regulation, China will promote the demonstration of large-capacity, medium and long term energy storage technologies.
At the same time, China has also deployed various types of long term energy storage technologies such as all-vanadium flow batteries, iron-chromium flow batteries, compressed air energy storage, molten salt heat storage, and hydrogen energy storage.
Long term energy storage technology
Pumped storage is the most mature long-term energy storage technology with the largest installed capacity. Its main advantages are reflected in the large energy storage capacity, mature technology, high operating efficiency, long operating life, low maintenance costs, etc., but it has high requirements on geographical resources and a relatively long construction period.
The general energy storage time of a pumped storage power station is 4-10 hours, and the single-unit capacity is 300,000-400,000 kilowatts, which fully meets the long-term energy storage needs.
Compressed air energy storage
Pumped storage is the most mature long term energy storage technology with the largest installed capacity. Its main advantages are reflected in large energy storage capacity, mature technology, high operating efficiency, long operating life, and low maintenance costs, but it has high requirements on geographical resource conditions and a relatively long construction period.
The general energy storage time of a pumped storage power station is 4-10 hours, and the single-unit capacity is 300,000-400,000 kilowatts, which fully meets the long term energy storage needs.
Molten salt energy storage
Compressed air energy storage mainly realizes energy storage through the mutual conversion between the internal energy of air and electrical energy. Its main advantages are reflected in large energy storage capacity, long energy storage period, high system efficiency, long operating life, and relatively small investment. China regards 100-megawatt compressed air energy storage technology as one of the key directions for new energy storage core technology and equipment research.
All vanadium redox flow battery
Molten salt energy storage realizes the storage of thermal energy by heating molten salt, and uses the high temperature and high pressure steam generated by heat exchange of high temperature molten salt to drive the steam turbine to generate electricity during power supply.
Molten salt is a molten liquid of inorganic salt, which forms an ionic solution after melting at high temperature. Generally, it has the advantages of high heat storage density, stable exothermic conditions, and low price.
In practical applications, four methods of trough type, tower type, linear Fresnel type and dish type are generally used to condense light and heat the working medium to realize the conversion of light energy to heat energy. The thermal storage power of molten salt thermal storage can reach the level of 100 megawatts, and achieve a thermal storage capacity of more than ten hours a day, with a service life of more than 30 years.
Gravity energy storage
The all-vanadium redox flow battery mainly realizes the energy storage and release through the change of the valence state of vanadium ions. The electrolyte is an aqueous solution, so it is safer and more scalable.
The reaction process only involves the change of the valence state of vanadium ions. The electrolyte can be recycled and regenerated, and the number of cycles can reach more than 15,000 times, and the service life can be as long as 20 years.
At the same time, China’s vanadium reserves and production ranks first in the world, and the resources required for the development of vanadium battery is independently controllable. Its shortcomings are mainly reflected in the higher initial installation cost, lower energy density and conversion efficiency than lithium batteries, and the cost of the stack can be solved by increasing the power density of the battery, increasing the effective use area of key materials, and reducing material costs.
Hydrogen energy storage
According to the different implementation locations of gravity energy storage, it can be divided into building energy storage, ocean energy storage, mountain energy storage, mine energy storage, etc. The energy storage tower structure is proposed by Energy Vault, which mainly uses cranes to stack concrete blocks into a tower structure to achieve energy storage and energy release.
Undersea energy storage was proposed by German researchers, using the static pressure difference of seawater to realize the effective use of ocean space through the pump-turbine. Piston water pump is proposed by Gravity Power and other companies. It uses the gravitational potential energy of the piston to form water pressure in the sealed channel to realize energy storage, which is suitable for urban medium and small power energy storage.
The energy storage of slope locomotives and slope cable cars using the mountain drop is mainly realized by lifting/dropping heavy objects by cables, which is more stable than the tower energy storage structure. The underground shaft energy storage mainly realizes charging and discharging by repeatedly lifting and lowering the drilling rig, which can more effectively utilize the resources of the abandoned mine.
Hydrogen energy storage
In terms of hydrogen storage, the development of the vehicle-mounted hydrogen storage industry is relatively mature, and the large-capacity hydrogen storage industry has a bright future. Among the existing hydrogen storage technologies, high-pressure gaseous hydrogen storage technology is relatively mature, and liquid hydrogen storage and solid hydrogen storage are still in the stage of demonstration and application.
Companies such as Jingcheng Co., Ltd., Yapp Co., Ltd., Sinoma Technology, and Guofu Hydrogen Energy all have layouts in hydrogen storage bottles, and related technologies have been used in the hydrogen energy vehicle industry. Due to the low hydrogen storage density in the high-pressure gaseous hydrogen storage technology, there are certain safety issues for the large-scale hydrogen storage demand in the hydrogen power generation scenario.