The world's first "non-supplementary combustion" compressed air energy storage power station is put into operation
The "air charging treasure" hidden in the ground
Our reporter Wang Zhen
Can you imagine that the ubiquitous air around us can not only store energy, but also generate electricity?
In Changzhou, Jiangsu, there is such a power station that uses air for energy storage and power generation - Jintan Salt Cave Compressed Air Energy Storage Power Station.
Recently, the power station was officially put into operation.
This is the world's first "non-supplementary combustion" compressed air energy storage power station, and the first domestic power generation project utilizing salt cavern resources.
Because the "container" that holds compressed air - the salt cavern is located nearly a thousand meters underground, it is also known as the "air charging treasure" hidden underground.
As a national experimental demonstration project in the field of air energy storage, its successful production marks a qualitative leap in my country's compressed air energy storage technology from theoretical experiments to engineering applications, and can be regarded as a milestone in the development of new energy storage technologies in my country.
Lu Qiang, an academician of the Chinese Academy of Sciences, said that the "non-supplementary combustion" compressed air energy storage technology of salt caverns is one of the important supporting technologies for realizing large-scale consumption of new energy and building a new power system. Sustainable development is of great significance.
So, how much electricity can this "air charging treasure" hidden in the ground be stored, and how is it charged and discharged?
How is "non-supplementary combustion" achieved?
The reporter recently interviewed the responsible comrades of the project.
A new way of safe and environmentally friendly energy storage
Compressed air energy storage at low electricity consumption and power generation at peak
At 9:57 on June 24, the phone rang in the centralized control room of the Jintan Salt Cave Compressed Air Energy Storage Power Station.
Deng Jianjun, the on-duty supervisor on duty, received an order from the State Grid Jiangsu Electric Power Company Dispatching Office, requiring Unit 1 of the power station to "connect to the grid on time for peak regulation at 10:17".
For a time, the relevant staff in the centralized control room were busy.
Start the pipe-warming operation to preheat the heat exchanger; open the control valve at the wellhead of the gas storage salt cavern, and the air with a pressure of nearly 140 atmospheres rushes out from the salt cavern at a depth of 1,000 meters underground, driving the air turboexpander to rush and rotate At 10:17, the generator set was merged into the power grid of the docking home substation on time and started to generate electricity.
After more than 10 minutes, the generator set reached full load operation.
...
At 3:00 pm, the generator set was de-loaded.
This round of power generation work has been completed.
When electricity consumption is low, use low-valley electricity or renewable energy to compress the air and store it in the underground salt cave; when electricity consumption peaks, release high-pressure air to drive the generator set to generate electricity to ensure electricity demand.
Changing the status quo of traditional electricity "as soon as it is used", cutting peaks and filling valleys, ensuring that valley electricity is not wasted, and peak electricity is blessed, is exactly the function of Jintan Salt Cave Compressed Air Energy Storage Power Station as a "charging treasure".
In recent years, with the large-scale development of new energy sources such as wind and light, the installed capacity of clean energy in my country has increased rapidly.
According to the latest news from the National Energy Administration, as of the end of May this year, my country's total installed capacity of renewable energy power generation reached 1.1 billion kilowatts.
Among them, conventional hydropower 360 million kilowatts, pumped storage 040 million kilowatts, wind power, photovoltaic power generation, biomass power generation and other new energy power generation installed capacity exceeded 700 million kilowatts.
However, wind, light and other new energy power generation needs to "see the sky to eat", which is greatly affected by the environment.
Take wind power as an example, when the wind is strong, more power is generated, and when the wind is small, less power is generated.
When the electricity load is small at night, the power generation may be large, resulting in a lot of outgoing electricity that cannot be connected to the Internet; on the contrary, during the peak electricity consumption period during the day, the power generation may be less, resulting in insufficient electricity.
This brings hidden dangers to the safe and stable operation of the power grid.
In this context, the construction of large-scale energy storage facilities is particularly urgent.
The existing energy storage technologies can be roughly divided into two categories: one is physical energy storage, such as pumped hydro energy storage, compressed air energy storage, flywheel energy storage, etc.; the other is chemical energy storage, which mainly includes various batteries , such as lead-acid batteries, lithium batteries, etc.
The reporter learned that different energy storage technologies have their own advantages and disadvantages.
Pumped storage has high power generation efficiency and large scale, but requires abundant water resources and is greatly affected by the geographical environment; flywheel energy storage technology is suitable for small-scale energy storage such as rail transit; while battery energy storage has a fast energy conversion speed, but The lifespan is limited, the cost is high, and there are follow-up issues.
"The most mature application at present is the pumped storage technology." Lin Tong, deputy general manager of Huaneng Jinling Power Plant and general manager of China Salt Huaneng Energy Storage Technology Co., Ltd., told reporters that compressed air energy storage can be said to be the only one that can compete with pumped storage at present. Comparable large-scale energy storage technology, "In contrast, compressed air energy storage has a large scale, is safe and environmentally friendly, and occupies a small area. It is a new trend in the development of large-scale energy storage."
Compressed air energy storage is a new energy storage technology.
In February this year, the National Development and Reform Commission and the National Energy Administration issued the "14th Five-Year Plan" New Energy Storage Development Implementation Plan, which has repeatedly mentioned this technology.
The Jiangsu Jintan Salt Cave Compressed Air Energy Storage Power Station Project is a national pilot and demonstration project in the field of air energy storage in my country. It is jointly developed by a tripartite project team of China Huaneng Group, China Salt Group and Tsinghua University. Operation and maintenance, the first phase of the project has an installed power generation capacity of 60 megawatts, an energy storage capacity of 300,000 kWh, and an estimated annual power generation of about 100 million kWh.
"It can provide a peak shaving capacity of ±60,000 kilowatts for Jiangsu Power Grid." Lin Tong told reporters that such a "charging treasure" is undoubtedly a "timely rain" for Jiangsu, which has a large peak-to-valley difference in the power grid.
Millennium salt cave turned into "gas storage tank"
5 hours of power generation can meet the daily electricity demand of 60,000 people
In Maobajing, about one kilometer northeast of Jintan Salt Cave Compressed Air Energy Storage Power Station, is the core part of this power station - salt cavern.
"This is a place to store compressed air, which is equivalent to a reservoir for pumped storage." Lin Tong said that there are many gas storage devices, such as pressure vessels, pipeline steel, etc. "Using salt cavern resources to store gas for power generation, which is in This is the first time in the country.”
Salt caverns, that is, the mines left after the underground salt layers are mined, are well sealed and mostly idle. They are suitable for storing important strategic materials such as oil and natural gas, and are also ideal for storing high-pressure air.
Compared with the storage methods of pressure vessels such as new steel tanks, the use of salt caverns can significantly reduce the cost of raw materials and land use.
"my country is rich in salt cavern resources. At present, Jintan alone has about 10 million cubic meters of underground salt cavern resources. In theory, a compressed air energy storage power station of more than 4,000 megawatts can be built. These salt caverns are mostly distributed between 800 meters and 1,000 meters underground. It has strong compressive capacity." Lin Yinghu, deputy director of the energy storage project department of Jinling Power Plant of Huaneng Jiangsu Company, told reporters, but this does not mean that all salt caverns can be used as compressed air storage devices, but also need to meet the requirements of appropriate volume, geological stability, distance suitable conditions.
The Maobajing salt cave used in the Jintan Salt Cave compressed air energy storage power station project is located about 1,000 meters underground. The maximum diameter of the pear-shaped cavity is about 80 meters, the height exceeds 100 meters, and the volume exceeds 220,000 cubic meters, which is equivalent to 105 standards. swimming pool.
In addition, the wall of the salt cavern is smooth and the overall shape is relatively stable. The air tightness test can fully meet the requirements of air energy storage, and can withstand a maximum of 200 standard atmospheres.
However, the original diameter of the salt cavern is small, and it cannot bear the high-flow, high-speed airflow transportation.
The researchers decided to transform it: the original old well was plugged, and two large-diameter wells were re-drilled.
However, since it was the first time to drill a large-diameter salt well in China, it was very difficult, and the entire construction took nearly two years.
"If the salt cavern is compared to an oversized balloon with a fixed volume, then the process of storing energy is the process of blowing the balloon." Lin Tong gave reporters an analogy.
He told reporters that the project has conquered the centrifugal compressor with the highest parameters in the world, which is the key device for "blowing air". Through this device, air at 1 standard atmosphere can be compressed into high-pressure air at 140 standard atmospheres. , which is stored in the "balloon"; when the power consumption peaks, the high-pressure air is released to drive the air turboexpander, so that the "windmill" rotates, thereby driving the generator to generate electricity.
"We usually start energy storage at 11 o'clock and 12 o'clock in the evening during the low electricity consumption period. By the next morning, an energy storage cycle is 8 hours." Lin Yinghu told reporters that during peak electricity consumption, full-load power generation can be generated in one hour. 60,000 kWh of electricity can be continuously generated for 5 hours, "that is, 300,000 kWh of electricity, which is equivalent to the electricity consumption of 60,000 residents in a day."
The reporter learned that the scale of the second phase of the Jintan Salt Cave Compressed Air Energy Storage Power Station is planned to be 400 megawatts, and the scale of the third phase of the project is expected to reach more than 1,000 megawatts.
Judging from the total amount of salt cavern gas storage owned by Jintan, the energy storage capacity in the future will be more than 60 times that of the current one.
Some experts said that underground salt caverns have the natural advantages of large volume, good airtightness and high stability, which can provide excellent gas storage conditions for compressed air energy storage, and are the first choice for compressed air energy storage underground gas storages.
In the future, other underground spaces such as abandoned mine caves and artificial underground gas storages are also viable options for underground gas storages.
World's first zero-carbon power generation from compressed air
The power conversion efficiency is increased to more than 60%, and the whole process has no combustion and no emissions
In fact, although the use of salt caverns for energy storage and power generation is the first time in China, there is a precedent in the world.
The special feature of Jintan Salt Cave Compressed Air Energy Storage Power Station is the application of "non-supplementary combustion" technology.
What is "non-supplementary combustion" technology?
That is, in the process of compressed air power generation, it does not rely on external energy combustion such as coal and natural gas.
It is understood that after the high-pressure air of the salt cavern is released, it needs to be heated and expanded to generate greater thrust and maintain the circulation of the system.
At present, the salt cavern compressed air energy storage power stations that have been put into operation in the world all need to burn coal or natural gas to heat the air. This process is called "supplementary combustion", which inevitably produces pollutant emissions.
The Jintan Salt Cave Compressed Air Energy Storage Power Station does not rely on external energy at all, and uses its own "internal circulation" to store a large amount of thermal energy generated during the compressed air process.
When generating electricity, the stored heat energy is released to become a natural "booster".
The entire process of energy storage and power generation is a physical process, so there is no combustion or emission.
It is understood that the salt cavern compressed air energy storage systems currently in operation internationally are all of the supplementary combustion type, removing the fossil fuel part, and their power conversion efficiency is only about 20%.
In other words, using 100 kWh of electricity to store energy can only produce 20 kWh of electricity in the end.
After adopting the "non-supplementary combustion" technology, the Jintan Salt Cave Compressed Air Energy Storage Project can increase the power conversion efficiency to more than 60%, achieving zero-carbon compressed air power generation for the first time in the world.
"The 'non-supplementary combustion' technology has no precedent in the world. We have overcome the design, manufacture and engineering application of a series of key equipment such as compressors." Lin Tong said that there is no technical solution for reference at home and abroad, only from the Start from scratch and explore step by step.
On the side of the power station, seven huge tanks are very conspicuous, and the heat energy generated when the air is compressed is stored here.
In the middle of the two large workshops, dense pipelines criss-cross, and the key facility to realize the "non-supplementary combustion" technology - the hairpin heat exchanger is among them.
"When I got this drawing, I was shocked. All kinds of intricate pipelines involved various professions, fire water pipelines, circulating water pipelines, closed cold water pipelines, hot oil pipelines, cold oil pipelines, cable trenches for cables... formed It has a form equivalent to a five- or six-story overpass, and each pipeline has different directions, uses, buried depths, and diameters.” Lin Yinghu recalled the scene when he first arrived at the project, from equipment design and development, to heat exchange media and other cards. The solution to the neck problem still feels incredible every step of the way.
In the power plant building, there is a white "big guy" called an air turboexpander.
"It is 9 meters long, 4 meters high, and weighs over 160 tons. It is the largest 'non-supplementary combustion' air turbine equipment in the world." Lintong is very proud of this.
This device is equivalent to an engine, which is the "power source" for power generation. "Before power generation, the air turboexpander starts to warm up and speed up, and then the high-pressure low-temperature air stored in the salt cavern and the thermal energy stored in the heat transfer oil tank. were released at the same time, and the power station began to generate electricity.
From the germination of the project, the implementation of the planning to the initial shape and the official production, the Jintan Salt Cave Compressed Air Energy Storage Power Station project team has experienced ups and downs: nearly ten years of research and development, and two years of construction.
Lin Tong still remembers the scene when the power station sent out the first kilowatt-hour of electricity at 10:00 on September 30, 2021. "In the centralized control room, there was thunderous applause, and it lasted for a long time."
Today, a "non-supplementary combustion" compressed air energy storage technology system with completely independent intellectual property rights has been formed, the core equipment has achieved 100% localization, more than 100 patents have been applied, and the first domestic compressed air energy storage power station KKS code category has been released. Standard... It can be said that the project provides technical support and basic equipment for the construction of a new power system, helping to achieve the goal of "carbon peaking and carbon neutrality".
The reporter learned that at present, the construction of the second phase of the Jintan salt cavern compressed air energy storage project is being accelerated.