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From a global perspective, with the increasing proportion of intermittent energy installations such as solar and wind power, the demand for large-scale long-term energy storage in the power system is becoming more and more urgent.
In this article, long duration energy storage will be introduced from definition, features, technologies to the future development.
What is long duration energy storage
Compared to short-term energy storage, long duration energy storage can achieve cross day, cross month, long-term energy storage can even cross season charging and discharging cycles, with more obvious advantages in improving the capacity of new energy generation and consumption, enhancing the flexibility of the power grid, and is considered a key link in building a new type of power system.
Long duration energy storage technology can be specifically divided into the following types.
Medium to long duration energy storage mainly refers to energy storage systems that operate continuously for 4-10 hours at rated power Long term energy storage mainly refers to an energy storage system that operates continuously for 10 hours to 1 week at rated power.
Ultra long duration energy storage mainly refers to energy storage systems that operate continuously for more than one week at rated power.
Advantages of long duration energy storage
Relieve intermittent issues with wind and solar energy
With the gradual increase in the proportion of new energy, uncertainties such as user load, wind power generation, and photovoltaic power generation have intensified the fluctuation of net load in the power system. Therefore, long duration energy storage should have the advantage of frequency regulation.
Enhance the stability of the power grid
Enhancing the consumption capacity of new energy. Renewable energy generation has intermittent characteristics, with main generation periods and peak electricity consumption periods being misaligned, resulting in a supply-demand gap.
The higher the penetration rate of renewable energy generation, the longer the required energy storage time. Therefore, as the penetration rate of renewable energy increases year by year, the demand for balancing the load of the power system increases. Long duration energy storage can regulate the fluctuations of new energy generation in a longer time dimension, avoid grid congestion, and increase the capacity for clean energy consumption.
Strong emergency recovery capability
There are more and more extreme weather events, and long duration energy storage can improve the resilience of local and regional power supply. At the same time, frequent natural disasters and energy supply shortages can lead to rising electricity prices and increased grid operating costs. Long duration energy storage to ensure power supply can reduce social electricity costs.
Why is long duration energy storage so important
By introducing more advanced long duration energy storage technology, it is possible to achieve longer storage and release of electrical energy, making the energy storage system more flexible in scheduling under different electricity price periods.
In addition, continuously promoting research on long durationenergy storage technology can help drive technological innovation, improve the energy density and cycle life of energy storage systems, reduce system costs, thereby enhancing the commercial competitiveness of long duration energy storage systems and promoting their widespread application in the time of use electricity price market.
Currently, the rapid growth of wind and photovoltaic power generation projects in China still brings a certain degree of wind and solar power curtailment and electricity consumption issues. Therefore, experts generally believe that the long-term demand for energy storage still exists and may shift more towards the grid side and user side.
On the user side, energy storage systems are regarded as a flexible and adjustable load resource that not only actively participates in the electricity market, but also ensures the safety and stability of the power grid. The economic benefits of user side distributed energy storage systems are directly affected by electricity market pricing policies and system functional requirements.
In fact, the development of long duration energy storage has become a global consensus. For example, the case of California in the United States shows that due to the large amount of excess electricity generated by photovoltaic power generation during lunchtime, it needs to be stored until the evening peak period for use, and a 4-hour energy storage system can meet 80% of peak valley regulation needs.
Similarly, with the increasing proportion of new energy connected to the grid in Europe, the demand for flexible regulation capabilities in the power system continues to rise, further highlighting the importance of long duration energy storage. Since 2022, large-scale energy storage projects in Europe have gradually extended their distribution and storage time to adapt to changes in grid regulation needs.
Types of long duration energy storage technologies
At present, mainstream long duration energy storage technologies can be divided into four main lines: physical energy storage, chemical energy storage, thermal energy storage, and hydrogen energy storage.
Physical energy storage includes Gravity Storage Compressed Air and Energy Storage (CAES).
Electrochemical energy storage includes Iron Air Battery, Zinc based Battery and Flow Battery.
Physical energy storage has the advantages of lifespan and cost, while electrochemical energy storage has the advantages of high energy conversion efficiency and short construction period.
Chemical energy storage includes Hydrogen Storage and Methanation.
Thermal energy storage has Molten Salt Storage.
Taking into account five factors - technological maturity, energy efficiency, regulation scale, response time, and construction conditions.
Pumped storage is currently the most technologically mature, energy-efficient, and regulated long duration energy storage, but it is easily limited by construction conditions.
The energy conversion efficiency of photothermal and hydrogen energy storage is relatively low, around 50%, and hydrogen energy storage technology is not yet mature.
Flow batteries and compressed air technology are relatively mature and have the basic conditions for large-scale development.
The application of lithium battery hybrid with other technological routes has emerged one after another, and various new energy storage technologies complement each other to meet the demands of diverse scenarios.
In the long run, with the diversification of energy storage application scenarios and the maturity of various new energy storage technologies, hybrid energy storage combination applications will become the development direction under the comprehensive consideration of economy and applicability.
Market and policy support for long duration energy storage
Global consulting firm McKinsey predicts that the potential market space for long duration energy storage will experience significant growth starting from 2025, with a global cumulative installed capacity of 30-40 GW and a cumulative investment of approximately $50 billion.
Faced with the promising long duration energy storage market, mainstream technologies are accelerating their layout.
The new long duration energy storage technology has made rapid breakthroughs. On the one hand, the market has added mainstream electrochemical energy storage to accelerate technological iteration. Manufacturers have successively launched 500Ah+, 600Ah+, and even 1000Ah+long-term energy storage cells.
In December 2024, EVE launched the industry's first mass-produced 628Ah ultra large capacity battery cell in Hubei Province, China, and announced the launch of a new 60GWh super energy storage plant. The energy storage cells of this factory are mainly used for large-scale energy storage projects such as wind and solar power distribution and shared energy storage for 4 hours or more.
On the other hand, new technologies such as compressed air energy storage, flow battery energy storage, and molten salt energy storage are accelerating their rise.
China's 1.5MW, 10MW, and 100MW compressed gas energy storage projects have been put into operation one after another and their scale continues to "upgrade". The world's first 300MW level compressed gas energy storage power station is fully connected to the grid. The promotion and application of vanadium flow battery energy storage technology have made significant progress, achieving widespread application on the power generation side, transmission and distribution side, and user side.
The thermal storage technology has achieved the commissioning of the world's first electric thermal molten salt energy storage test station and a 660MW coal-fired power unit coupled with steam molten salt thermal storage peak shaving and frequency regulation project. 100MW and medium to long duration energy storage have become the norm for new construction projects.
Overall, there are various routes for new long duration energy storage technologies, but apart from the commercialization of lithium-ion batteries, other technologies are still in the early stages of commercial application or experimental exploration.
Future of long duration energy storage
The rapid increase in the penetration rate of new energy, coupled with the instability of its output, further increases the demand for energy storage. Long term energy storage can increase the flexibility of the power system, that is, storing electricity when there is an excess supply and releasing it when needed, in order to alleviate supply-demand contradictions and regulate supply and demand fluctuations.
The United States expects to deploy 274GW of cross day long duration energy storage and 186GW of multi day/weekly long duration energy storage by 2050, while Australia expects the proportion of multi day/seasonal energy storage in the national electricity market to reach around 60% by 2050. The United States, the European Union, Australia and other countries or regions have identified long-term energy storage as a key industry for future development, and have introduced a series of policies to encourage local long-term energy storage development.
At present, China's long-duration energy storage is in the early stage of development, and the technology and business model are not yet mature.
The Zhongguancun Energy Storage Industry Technology Alliance in China suggests developing a roadmap for long duration energy storage technology, promoting the research and development of new long-term energy storage technologies, advancing the construction of pilot demonstration projects, promoting the commercialization of long-term energy storage, strengthening the protection of intellectual property rights, accelerating the construction of a standard system, and improving the policy mechanism guarantee system to increase support for long duration energy storage.
Conclusion
Long duration energy storage technology was born with the goal of serving the transformation of the power system, and its market prospects and development speed are mainly influenced by the path and pace of power system transformation and development. Long duration energy storage is an inevitable choice in the era of carbon neutrality. The larger the proportion of renewable energy in the future, the greater the necessity and urgency of building long duration energy storage.
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