Store electricity in gas, green and low-carbon, Jintan salt cavern compressed air energy storage power station in Changzhou, Jiangsu——

Enabling underground salt caverns to facilitate efficient energy utilization (Economic Focus · First-line look at energy storage ②)

  core reading

  The air is compressed and stored underground when electricity consumption is low, and the air is released during peak electricity consumption, which can generate 60,000 kilowatt-hours of electricity per hour.

In Jintan District, Changzhou, Jiangsu, relying on "non-supplementary combustion" technology, the Jintan salt cavern compressed air energy storage power station can save 30,000 tons of standard coal throughout the year, reduce carbon dioxide emissions by more than 60,000 tons, and provide ±60,000 tons for Jiangsu Power Grid Kilowatt peak shaving capability.

  It seems not uncommon to use batteries to store energy and use water reservoirs to generate electricity, but did you know that the invisible and intangible air around us also has the same function?

At the foot of Maoshan Mountain in Jintan District, Changzhou City, Jiangsu Province, there is a large-scale "charging treasure" transformed from salt caverns - Jintan salt cavern compressed air energy storage power station.

As a national experimental demonstration project in the field of air energy storage, on May 26, 2022, this "non-supplementary combustion" compressed air energy storage power station was officially put into operation.

  How does compressed air achieve energy storage and discharge?

How to play value?

What are the development prospects?

The reporter takes you to reveal the secret together.

  How effective is energy storage?

  Can generate 60,000 kWh per hour

  "Ding Lingling——" At 8:56 on January 28, a telephone rang in the centralized control room of the Jintan salt cavern compressed air energy storage power station.

Yuan Ercong, the shift leader, answered the phone, and the other end of the phone was an instruction from the dispatching center of the State Grid Jiangsu Electric Power Company: Unit 1 of the power station was required to be connected to the grid for peak regulation at 9:32 on time.

At this time, however, there is no electricity in the power station – it is stored in the air and the heat storage medium in two other forms of energy.

  "At about 21 o'clock the day before, it was the low power consumption period, and the grid had surplus power, so we started to charge the 'power bank'." Han Yuefeng, director of the General Affairs Department of China Salt Huaneng Energy Storage Technology Co., Ltd., introduced that this process is like giving Balloon pumping - the huge salt cavern at a depth of more than 900 meters underground is a "balloon", and the air compressor driven by electricity is a "pump", which compresses the air at 1 standard atmosphere into high-pressure air at 140 standard atmospheres.

  In the process of compressing the air, the temperature of the air will increase to more than 300 degrees Celsius.

In order to ensure the safety of the system operation, it is necessary to cool the high-temperature and high-pressure air to the normal temperature and high-pressure air of about 40 degrees Celsius.

The heat is not wasted, but is "taken" by the heat exchanger and stored in the heat transfer oil, which is stored in a large high-temperature heat transfer oil tank on the ground.

In this way, after "charging" at night, the electrical energy is converted into air potential energy and heat energy.

  After receiving the dispatch call, the staff in the central control room immediately got busy.

What they have to do is to "recombine" the potential energy of the air with the thermal energy and convert it back into electrical energy, which can be used by residents during the peak period of electricity consumption.

  At the site where various pipelines are distributed vertically and horizontally, workers first preheat the heat exchanger, and then open the salt cavern wellhead control valve.

In an instant, high-pressure gas with a pressure of nearly 140 standard atmospheres rushed out from the salt cavern deep in the ground, and was heated to more than 300 degrees Celsius by heat transfer oil in the heat exchanger, turning into high-temperature and high-pressure air, driving the air turbo expander to rotate, passing through The bearing drives the generator to rotate—electricity, "reborn" from the air again.

  At 9:32, the No. 1 generating set of the power station was connected to the grid on time and started to generate electricity; 10 minutes later, the generating set reached the full-load operation state of 60 MW; at 14:30, the generating set was disconnected, and the power generation operation was successfully completed.

  "When the power consumption is low, the air is compressed and stored in the underground salt cavern, and the cycle of one charge is 8 hours; when the power consumption is peak, the high-pressure air is released, which can generate 60,000 kWh per hour, and can continuously generate power for 5 hours. , and the power generation capacity can reach 300,000 kwh." Han Yuefeng introduced.

  What are the innovations?

  Using "non-supplementary combustion" technology, power conversion is more environmentally friendly

  The Jintan Salt Cavern Compressed Air Energy Storage Power Station jointly built by China Salt Group, China Huaneng Group and Tsinghua University can provide ±60,000 kilowatts of peak-shaving capacity for Jiangsu Power Grid.

Soon after the power station was put into operation, Jiangsu ushered in a hot summer.

The power station responded to about 40 peak-shaving orders between July and August, among which in August it responded for 23 consecutive days, and even switched flexibly and responded multiple times within one day, contributing to the peak-to-summer power supply.

  In addition, in recent years, with the accelerated development of new energy sources such as wind and light, the total installed capacity of renewable energy power generation in Jiangsu has reached 53.5494 million kilowatts.

However, new energy power generation is highly volatile. In Jiangsu, a large industrial province, the peak-to-valley difference in power generation is as high as 50%, which brings hidden dangers to the safe and stable operation of the power grid. It is especially necessary to build large-scale energy storage facilities.

  "At present, there are two kinds of energy storage methods, physical energy storage and chemical energy storage. The former includes pumped water storage, compressed air energy storage, flywheel energy storage, etc., and the latter includes various battery energy storage." Jintan Salt Cavern Compressed Air Energy Storage Mei Shengwei, the chief scientist of the power station project and a professor of the Department of Electrical Engineering of Tsinghua University, told reporters that the compressed air energy storage power station has a large scale, fast construction, safety and environmental protection, and is one of the important development directions of new energy storage.

  Of course, the construction of a compressed air energy storage power station also needs the support of rich salt cavern resources and mature cavity building experience, which puts forward certain requirements for the construction environment.

Salt caverns, the cavities left after underground salt deposits are mined, are well-sealed and mostly unused, making them ideal places to store high-pressure air.

"Jintan has about 10 million cubic meters of salt cavern resources." Xu Zijun, director of the salt mine of China Salt Jintan Company, introduced that the Maobajing salt cavern used by the Jintan salt cavern compressed air energy storage power station has a volume of about 220,000 cubic meters. Withstand 200 standard atmospheres.

  The use of salt caverns for energy storage and power generation is not without precedent in other countries, but the adoption of "non-supplementary combustion" technology is the first in China.

"After the high-pressure air in the salt cavern is released, it needs to be heated and expanded to generate greater thrust. Power plants that have been put into operation abroad have been heated by burning natural gas, and the 'supplementary combustion' process will generate carbon emissions." Mei Shengwei, Jintan The project stores the heat energy generated in the process of compressing air, and releases the heat energy when generating electricity, increasing the power conversion efficiency to more than 60%.

According to estimates, the project can save 30,000 tons of standard coal and reduce carbon dioxide emissions by over 60,000 tons throughout the year.

  What is the room for development?

  The construction cost will be greatly reduced as the technology continues to mature

  The reporter saw that there is still a large area of ​​construction land near the Jintan salt cavern compressed air energy storage power station.

It is understood that the scale of the second phase of the Jintan salt cavern compressed air energy storage project is planned to be 400 MW, and the scale of the third phase is expected to be 1,000 MW.

  "Salt cavern compressed air energy storage is a comprehensive energy system." Mei Shengwei believes that the future industrialization and commercialization of salt cavern compressed air energy storage depends on two aspects - reducing construction costs and improving power conversion efficiency. It is technological innovation.

  "For example, the development of key equipment such as high-flow high-temperature compressors, high-power heat exchange equipment, and turbo expanders needs to start from scratch, and develop while researching and developing with the technical staff of the manufacturer." Mei Shengwei told reporters that from project approval to formal Putting into operation, the Jintan Salt Cavern Compressed Air Energy Storage Power Station has gone through 10 years of research and development and two years of construction.

During this process, 100% localization of key equipment has been achieved, and more than 100 patents have been applied for.

"The current construction cost is about 7,000 yuan/kW, but as the technology continues to mature, the future construction cost will be greatly reduced."

  Mei Shengwei introduced that in terms of improving efficiency, the R&D team is trying a "two-pronged approach": First, the current heat storage technology uses heat transfer oil, which belongs to medium-temperature heat storage. If molten salt is used to realize high-temperature heat storage in the future, the power conversion efficiency is expected to increase from 60%. Increase to 70%; Second, salt cavern gas storage belongs to constant volume gas storage, and the pressure keeps changing during the charging and discharging process, which affects the operating efficiency of the equipment. The constant pressure gas storage technology under development will realize constant pressure charging and deflation, Further improve the power conversion efficiency of the system.

  Another support for scale development is the electricity price policy.

The National Development and Reform Commission and the National Energy Administration jointly issued the "Notice on Further Promoting the Participation of New Energy Storage in the Power Market and Dispatch Operation", which stipulates the participation of new energy storage in the power market and dispatch operation from the aspects of electricity price, transaction and dispatch mechanism. .

"At present, the power price policy of the power station is still under study, and the competent authorities at all levels are also very supportive of the project." Mei Shengwei told reporters that the 8 compressed air energy storage power stations with a total of 1350 MW participated by Tsinghua University will be launched within two years. Built and put into use.

"I believe that with the continuous optimization of construction costs and conversion efficiency, as well as the continuous improvement of the price system, more institutions and places will participate in the construction of compressed air energy storage power stations, creating more favorable conditions for the high-quality development of new energy .”

  Our reporter Yao Xueqing

  (People's Daily)