In the early morning, deep in the Dabie Mountains, the reservoir of the State Grid Anhui Jinzhai Pumped Storage Power Station rippled with waves and water surged. As the water level of the reservoir gradually rises, the power station units quietly wait for the arrival of the peak electricity consumption, storing energy and waiting to be released.

'If four units are fully pumped, they can fill the upper reservoir in six hours and charge more than 7 million kilowatt hours of electricity into the 'super power bank' of Jinzhai Power Station.' Zhu Anping, Chairman of State Grid Anhui Jinzhai Pumped Storage Co., Ltd., introduced that during peak electricity consumption, the power station will start the units according to the grid dispatch instructions, discharge water from the upper reservoir to the lower reservoir for power generation, ensuring power supply and maintaining grid balance.

Storing electricity during low electricity consumption periods and releasing it during high electricity consumption peaks - a large number of energy storage projects that resemble 'super power banks' are avoiding the 'busy and uneven' power system through peak shaving and valley filling, ensuring the safe and stable operation of the power system, and supporting the large-scale development of clean energy.

Energy storage, as a key link in energy conversion, is an important part of building a new energy system. How does State Grid of China promote the development of energy storage industry? What technical challenges have been overcome? What application scenarios have been expanded? Let's go take a look together——

Scale expansion

A Hundred Flowers Bloom in Energy Storage Technology

At present, energy storage mainly includes two types: pumped storage and new energy storage. Among them, pumped storage is currently the most mature and cost-effective energy storage technology, suitable for large-scale development and construction. New energy storage refers to various energy storage technologies that use electricity as the main output form, in addition to pumped storage, including lithium-ion batteries, compressed air energy storage, mechanical energy storage, etc.

'The new type of energy storage has fast response speed, high regulation accuracy, flexible layout, and short construction period, but is constrained by factors such as cost and safety.' Huidong, Chief Technical Expert of China Electric Power Research Institute, introduced that pumped storage has advantages such as large capacity, high reliability, good economy, and mature application technology. It plays an important role in ensuring the safety of the large power grid and promoting the consumption of new energy, but is also limited by factors such as high site selection conditions and long construction period.

Different energy storage technology routes have both advantages and disadvantages, but they do not affect their diversity. With the proposal of the 'dual carbon' goal, China's energy storage industry has entered a period of rapid development, becoming an important support for building a new power system and building a new energy system.

Not long ago, deep in the mountains of Chengde City, Hebei Province, Unit 6 of State Grid Hebei Fengning Pumped Storage Power Station was officially put into operation for power generation. It is reported that the power station has set four 'world firsts' in terms of installed capacity, energy storage capacity, underground plant scale, and underground cavern group scale, setting multiple records in the development history of pumped storage in China and creating miracles in pumped storage construction.

The underground factory building, which is over 400 meters long, 25 meters wide, and over 50 meters high, is built above six two-way waterways. In the center of the factory building, 12 generator units are arranged in a straight line and connected to the underground water supply system. 'When pumping water, the water pump is driven by electricity, and when generating electricity, the potential energy drives the turbine to generate electricity. One unit has both pumping and power generation functions. The unit can transform from full load pumping to full load power generation within 5 minutes.' said Wu Peizhi, Deputy General Manager of State Grid Hebei Fengning Pumped Storage Co., Ltd. In December 2021, the first batch of units in the power station were put into operation and connected to the Zhangbei flexible DC grid, reducing the volatility of new energy power generation at the source. This not only pioneered the development of pumped storage, but also provided a valuable 'Chinese solution' for solving the large-scale development and utilization of new energy. As of now, Fengning Power Station has cumulatively put 10 units into operation, with an installed capacity of 3 million kilowatts.

Zhang Xueqing, Director of the Infrastructure Department of State Grid Xinyuan Group, introduced that China's pumped storage energy has reached international advanced or leading levels in reservoir anti-seepage, high head pressure pipelines, and complex geological underground cavern groups. Units are developing towards large capacity, high head, high speed, and variable speed. According to data provided by the China Electricity Council, as of the end of 2022, the total installed capacity of pumped storage in China reached 45.79 million kilowatts, more than 2.2 times that of the end of 2012, ranking first in the world.

At the same time, positive progress has been made in the construction of demonstration projects, exploration of business models, and construction of policy systems for new energy storage, with the market application scale steadily expanding.

On the Zhangbei grassland, the National Wind and Solar Energy Storage and Transmission Demonstration Project is the world's largest new energy demonstration power station project that integrates wind power generation, photovoltaic power generation, energy storage systems, and intelligent transmission. Based on this demonstration project, State Grid of China has successfully completed the first large-scale new energy system grid performance test at home and abroad. Here, infinite 'wind and light' are transformed into green electricity, continuously outputting outward. This project helps all venues of the Beijing Winter Olympics achieve 100% green electricity supply, and 'the wind of Zhangbei lights up the lights of Beijing' has become a shining business card for the green Winter Olympics.

According to Liu Yafang, Deputy Director of the Energy Conservation and Technology Equipment Department of the National Energy Administration, as of the end of 2022, the installed capacity of new energy storage projects in operation nationwide has reached 8.7 million kilowatts, with an average energy storage time of about 2.1 hours, an increase of over 110% compared to the end of 2021.

Lu Gang, Director of the Energy Strategy and Planning Research Institute of State Grid Energy Research Institute, pointed out that we are currently in a critical period of green and low-carbon energy transformation and development. As a new energy storage method, 'super power banks' are of great significance in meeting the regulatory needs of the power system, ensuring power system safety, promoting large-scale development and consumption of new energy sources.

Overcoming Difficulties

Realize multiple technological breakthroughs

We often compare pumped storage power stations to a 'super power bank', but it is not easy to successfully install this 'super power bank' in the mountains and rivers. In addition to construction difficulties, the overall commissioning of the unit also faces various challenges. For many energy storage project builders, going to the factory, coordinating, monitoring progress, and solving difficult problems have become commonplace.

Recently, amidst cheers from staff, the No. 3 main transformer of the State Grid Tianchi Pumped Storage Power Station in Nanzhao County, Nanyang City, Henan Province, was successfully put into operation. The author has learned that the main transformer of Tianchi Pumped Storage Power Station is located in an underground power plant. Due to the heaviest transportation of a single transformer, high installation process requirements, and significant space limitations during installation, it is considered one of the most technically challenging equipment for the installation of mechanical and electrical equipment in the entire underground power plant.

'The impact test plan for the No. 3 main transformer must be strictly implemented,' said Xu Zhizhuang, the special person in charge of the operation and maintenance department of the State Grid Tianchi Pumped Storage Power Station. Before the impact of the No. 3 main transformer transmission, the Tianchi Power Station strictly implemented the second level risk control measures for the transmission impact test operation. Participants from all parties were selected to configure personnel according to the test plan, and the central control room personnel were assigned to summarize information and dispatch on-site. Debugging personnel were dispatched to command on-site, ensuring that personnel in each area coordinated and cooperated well in equipment inspection, protection testing, status inspection, and other aspects. After a continuous 120 minute impact test, the performance of the differential protection of the No. 3 main transformer in avoiding excitation inrush current was finally verified.

Compared to the construction of pumped storage power stations, builders of new energy storage projects focus more on technological innovation breakthroughs.

At the first megawatt level hydrogen comprehensive utilization demonstration station in Lu'an City, Anhui Province, there are proton exchange membrane pure water hydrogen production equipment that continuously produce hydrogen from a positive source and transport it through pipelines to advanced hydrogen fuel cells for power generation and utilization.

'The difficulties in research and development, design, and other aspects once put our research at a standstill,' said Teng Yue, the technical director of State Grid Anhui Electric Hydrogen Comprehensive Utilization Demonstration Station. Fortunately, these difficulties have been solved through technological innovation. 'We have pioneered the core equipment technology for high-power and low-energy hydrogen to electricity conversion, developed safety warning and protection technology for the entire station, achieved early warning and accident prevention of hydrogen leakage, and also pioneered the full chain technology integration and full power operation of megawatt level 'hydrogen production hydrogen storage hydrogen power generation' for the first time in China.'

Now, the station has broken through more than 20 technological bottlenecks, with an annual hydrogen production capacity of over 700000 standard cubic meters and hydrogen power generation of over 700000 kilowatt hours. The hydrogen produced can be applied in fields such as hydrogen fuel cell vehicles, hydrogen energy steelmaking, and green hydrogen chemical industry, truly writing the 'zero carbon cycle' on the land of Jianghuai.

The 2023 China New Energy Storage Development Report shows that new energy storage is still in its early stages of development, and there are still many technical challenges to be solved in core materials, system integration, scheduling and application, safety protection, and other aspects. In the future, we should fully mobilize the enthusiasm of all parties, increase innovation in new energy storage technologies, and promote industrial upgrading by creating a batch of original technologies.

Free charging and discharging

Meet diverse application scenarios

Due to its functional features such as peak shaving and valley filling, frequency modulation and phase modulation, and flexible charging and discharging, energy storage projects are also regarded as 'stabilizers' and 'regulators' for the safe operation of the power grid, and are put into use in various application scenarios.

In the Electrical Industrial Products City of Xinba Town, Yangzhong City, Jiangsu Province, State Grid Zhenjiang Power Supply Company has put into operation a microgrid with optical storage, charging, and direct flexibility. 'Charging a car with electricity generated by rooftop photovoltaic panels takes twice as long as using grid power,' said Mr. Wang, a citizen, on May 16th, while charging his electric car with a microgrid.

It is understood that microgrids are distributed flexibly and applied efficiently. Compared to the traditional form of unidirectional energy reception in the power grid, it can not only be self-sufficient and achieve the spontaneous self use of photovoltaic power in the region, but also flexibly adjust the operating mode according to the external environment, allowing for flexible interconnection of DC power to adjacent substations, and switching between 'interconnection' and 'islanding' modes.

'The electricity generated by photovoltaic power generation is stored in energy storage devices, which can charge electric vehicles or be transmitted to adjacent lines nearby. In the event of a nearby line failure, it can also bear the load of the faulty line and provide power to users.' Bao Lei, Deputy General Manager of State Grid Zhenjiang Yangzhong Power Supply Company, introduced. According to calculations, through flexible switching, the overall energy efficiency within the microgrid can be improved by more than 6%, saving 3.62 tons of carbon dioxide emissions annually.

This is just one of the various application scenarios for energy storage. Under the booming trend of the new energy industry, the development potential of the energy storage industry is enormous. It is not only conducive to stimulating new momentum for high-quality economic development, but also of great significance for promoting comprehensive green transformation of economic and social development.

Shengtong Technology Group, located in Changsha, Hunan Province, is a leading global manufacturer of aluminum foil and aluminum film panels. As a prominent contributor to energy conservation and emission reduction in China, the company has built an integrated light storage and charging project in its own park and existing parking spaces, with a total energy storage capacity of 16.5 megawatts/40 megawatt hours. The project was put into operation and connected to the grid in October last year. The first day's power generation was 34000 kilowatt hours, with two charging and two discharging of energy storage. It can provide up to about 80000 kilowatt hours of staggered electricity per day. The person in charge of Shengtong Group stated, 'After the construction of the photovoltaic energy storage project, the company's energy consumption costs have been greatly reduced, and it is expected to save the company over 3.6 million yuan in expenses annually in the future.'

It is reported that in order to do a good job in grid connection of energy storage projects, State Grid Hunan Electric Power actively connects with the project construction and development entities to ensure early grid connection and production. It is expected that by the end of June, Hunan will add various new energy storage installations of 1000 megawatts, effectively ensuring the smooth operation of the Hunan power grid this summer.

Industry insiders point out that from the perspective of the power system, energy storage applications can be divided into three major scenarios: power side energy storage, grid side energy storage, and user side energy storage.

Teng Yue introduced that energy storage on the power side is mainly configured on the power side, which can be matched with new energy sources such as wind and light, promoting efficient grid connection and consumption of new energy; Energy storage on the power grid side, distributed at key nodes of the power grid, can provide various services such as peak shaving and frequency regulation, and enhance the system's ability to withstand emergencies and recover from faults; User side energy storage is installed at the user load end, which can enhance the user's flexible adjustment ability.

Different energy storage technologies are suitable for different application scenarios due to their different performance characteristics. Huang Bibin, Deputy Director of the New Energy and Statistics Research Institute of State Grid Energy Research Institute, analyzed that pumped storage power stations have strong capacity efficiency and large single station scale, making them suitable for large-scale and system level applications on the grid side; The new energy storage single station can be large or small in size, has strong environmental adaptability, and can be flexibly deployed in various application scenarios such as power supply, power grid, and user side, which can serve as a beneficial incremental supplement to pumped storage.

Experts predict that, based on traditional application scenarios, integrated water, wind, and solar energy storage, as well as integrated wind and solar energy storage, will continue to emerge in the future. Energy storage projects will play a prominent role in the development of large-scale new energy bases such as the Southwest Hydroelectric Base, and the construction and application of small and medium-sized energy storage projects will be more widespread. The application pattern of energy storage with multiple types and scenarios will gradually emerge.

Significant benefits

Benefiting the people in a better life

In addition to promoting the green and low-carbon transformation of energy, many energy storage projects do not forget to prioritize ecological integration into construction, and ecological benefits have become an important core embedded in the construction process.

At the construction site of State Grid Zhejiang Ninghai Pumped Storage Power Station, the greenery is abundant within sight. 'Greening is one of the most important tasks for us to build a 'super power bank',' Xia Wanqiu, Deputy Director of the Engineering Department of State Grid Zhejiang Ninghai Pumped Storage Co., Ltd., pointed to the surrounding mountains one after another. 'There are broad-leaved grass, tall fescue, purple clover over there, as well as thorny locust, multi flowered magnolia, and cherries.'

According to on-site staff, most of the excavated rock surfaces during construction have a slope of nearly 90 degrees. When returning to green, they need to hang like Spider Man to nail wire mesh on the rocks and spray special formula concrete over and over again, which can not only fix plant seeds but also further protect the soil, slope, and sand. Since the start of the project in 2018, construction has been carried out while greening has occurred, with a greening area exceeding 250000 square meters.

The construction of the 'Super Power Bank' not only brings about the revival of green mountains and clear waters, but also benefits residents' lives through measures such as demolition and resettlement, improving infrastructure, and maximizing economic and social benefits, driving investment and related industry development.

The clear rural paths, beautiful green belts, and rows of two-story buildings... Walking into Liuchi Village, Jiankou Township, Luoning County, Luoyang City, Henan Province, the villages and towns under the blue sky and white clouds appear particularly beautiful. However, the once swimming pool village is hidden deep in Xiong'er Mountain, with only a narrow path leading to the outside world for many years.

With the construction of the State Grid Henan Luoning Pumped Storage Power Station, the villagers of Yongchi Village have undergone immigration and relocation. In the construction of the project, the power station construction party took the initiative to build peripheral extension roads, absorb employment from the villagers of Xichi Village, and strive to provide more benefits for the relocated population.

'The pumped storage power station project has brought earth shaking changes to our village. Not only have every household moved into new houses, but the village has also built clinics, making it more convenient for the elderly to seek medical treatment.' Ji Junwei, Secretary of the Party Branch of Xichi Village, introduced that the village has now become a model for new rural construction and rural revitalization in Luoning County.

Accelerating the development of pumped storage and new energy storage is an urgent need for building a new energy system, an important support for ensuring the safety and stability of the power system, and an important guarantee for the large-scale development of new energy. State Grid Corporation of China stated that it will adhere to the concept of open development, strengthen cooperation with all sectors of society, accelerate the construction of pumped storage power stations, and strive to achieve a pumped storage installed capacity of 50 million kilowatts and 100 million kilowatts in the company's operating area by 2025 and 2030, respectively; Supporting the large-scale application of new energy storage, it is expected that the installed capacity of new energy storage in the company's operating area will reach 100 million kilowatts by 2030. (Liu Leyi and Wang Shengying)

Source: Overseas Edition of People's Daily