air turbine expander .
Can you imagine that the air that is everywhere around us can both store energy and generate electricity?
In Changzhou, Jiangsu, there is such a power station that uses air to store energy and generate electricity - the 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 power generation project in China to utilize salt cavern resources. Because the salt cave, the "container" that holds compressed air, is located nearly a kilometer underground, it is also known as the "air power bank" hidden underground.
is a national experimental demonstration project in the field of air energy storage. Its successful commissioning marks the qualitative leap of my country's compressed air energy storage technology from theoretical experiments to engineering applications. It can be called a milestone in the development of my country's new compressed air energy storage technology . . Academician of the Chinese Academy of Sciences Lu Qiang said that salt cavern "non-supplementary combustion" compressed air energy storage technology is one of the important supporting technologies for realizing large-scale consumption of new energy and building new power systems. It is important for promoting the upgrading of my country's energy structure and Ensuring the sustainable development of the energy and power industry is of great significance.
So, how much electricity can this "air power bank" hidden underground store, and how does it charge and discharge? How is "non-supplementary combustion" achieved? The reporter recently interviewed the comrades responsible for the project.
A new safe and environmentally friendly energy storage method
Compressed air energy storage during low electricity consumption, releasing power generation during peak hours
html At 9:57 on June 24, in the centralized control room of the Jintan Salt Cave Compressed Air Energy Storage Power Station, the phone rang. Deng Jianjun, the shift supervisor who was on duty, received an instruction from the dispatching office of State Grid Jiangsu Electric Power Company, requiring Unit 1 of the power station to "connect to the grid on time at 10:17 for peak regulation."For a while, the relevant staff in the centralized control room became busy.
starts the warm pipe operation to preheat the heat exchanger ; opens the control valve at the wellhead of the gas storage salt cavern, and air with a pressure close to 140 atmospheres rushes out from the salt cavern thousands of meters underground, driving the air turbine to expand. The machine rushed... At 10:17, the generator set was integrated into the Wujia substation power grid on time and started generating electricity.
More than 10 minutes later, the generator set reached full load operation.
...
At 3 pm, the generator set was decommissioned. This round of power generation operation is completed. When electricity consumption is low,
uses low-peak electricity or renewable energy curtailment to compress air into and stores it in underground salt caves; when electricity consumption peaks, it releases high-pressure air to drive the generator set to generate electricity to ensure electricity demand. Changing the "instant-to-use" status quo of traditional electricity, cutting peaks and filling valleys, ensuring that valley power is not wasted and peak power is blessed, is exactly the function of the Jintan Salt Cave Compressed Air Energy Storage Power Station as a "power bank".
In recent years, with the large-scale development of wind, solar and other new energy sources, my country's clean energy installed capacity 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 renewable energy power generation capacity reached 1.1 billion kilowatts. Among them, conventional hydropower is 360 million kilowatts, pumped hydropower is 40 million kilowatts, and the installed capacity of new energy power generation such as wind power, photovoltaic power generation, and biomass power generation has exceeded 700 million kilowatts.
However, new energy power generation such as wind and solar power needs to "depend on the weather" and is greatly affected by the environment. Taking wind power as an example, more power is generated when the wind is strong, and less power is generated when the wind is low. When the electricity load is small at night, the amount of electricity generated may be large, causing a lot of the electricity generated not to be connected to the Internet. On the contrary, during the peak electricity consumption period during the day, the amount of electricity generated 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 water 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 battery , lithium battery, etc.
reporter learned that different energy storage technologies have their own advantages and disadvantages.Pumped storage power generation has high efficiency and large scale, but requires abundant water resources and is greatly affected by geographical environment; flywheel energy storage technology is suitable for small-scale energy storage such as rail transit; while battery energy storage has fast energy conversion speed, but The lifespan is limited, the cost is high, and there are also follow-up processing problems.
"The most mature application currently is pumped hydro 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 hydro storage at present. Comparable large-scale energy storage technology, "In contrast, compressed air energy storage is large-scale, safe, environmentally friendly, and small in footprint. It is a new trend in the development of large-scale energy storage."
Compressed air energy storage is A new energy storage technology. This technology was mentioned many times in the "Implementation Plan for New Energy Storage Development during the 14th Five-Year Plan" released by the National Development and Reform Commission and the National Energy Administration in February this year.
Jiangsu Jintan Salt Cave Compressed Air Energy Storage Power Station Project is a national experimental demonstration project in the field of air energy storage in my country. It is jointly developed by China Huaneng Group , China Salt Group and Tsinghua University project team. China Huaneng Group The Jiangsu company is responsible for construction, commissioning and operation and maintenance. The first phase of the project has an installed power generation capacity of 60 MW and an energy storage capacity of 300,000 kWh. The annual power generation is expected to be approximately 100 million kWh.
"can provide the Jiangsu power grid with a peak shaving capacity of ±60,000 kilowatts." Lin Tong told reporters that for Jiangsu, which has a large peak-valley difference in the power grid, such a "power bank" is undoubtedly a "timely rain".
Thousand-year-old salt caves turned into "gas storage tanks"
5 hours of power generation can meet the daily electricity needs of 60,000 people
Located in Maoba Well, about one kilometer northeast of the Jintan Salt Cave Compressed Air Energy Storage Power Station, this power station is The core part - salt cave.
"This is a place where compressed air is stored, which is equivalent to a pumped water storage reservoir." Lin Tong said that there are many gas storage devices, such as pressure vessels , pipeline steel , etc. "Using salt cave resources to store This is the first time in China that gas-fired power generation has been achieved. "
Salt caverns are mines left after underground salt layers are mined. They are well sealed and most of them are idle. They are suitable for storing important strategic materials such as oil and natural gas. It is also an ideal place to store high-pressure air. Compared with the storage method of new steel tanks and other pressure vessels, the use of salt caverns can significantly reduce the cost of raw materials, land, etc.
"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, more than 4,000 megawatts of compressed air energy storage power stations can be built. These salt caverns are mostly distributed 800 meters underground. to 1,000 meters, with strong pressure resistance," Lin Yinghu, deputy director of the energy storage project department of Jinling Power Plant of Huaneng Jiangsu Company, told reporters. However, this does not mean that all salt caverns can be used as compressed air storage devices. They also need to meet appropriate volume and geology. Conditions such as stability and appropriate distance.
The Maobajing salt cavern used in the Jintan Salt Cave Compressed Air Energy Storage Power Station Project is located about 1,000 meters underground. The pear-shaped cavity has a maximum diameter of about 80 meters, a height of more than 100 meters, and a volume of more than 220,000 cubic meters, equivalent to 105 Standard swimming pool. Moreover, the salt cave wall is smooth and the overall shape is relatively stable. The air seal test can fully meet the requirements of air energy storage and can withstand up to 200 standard atmospheric pressures.
However, the original diameter of the salt cave is small and cannot bear the high-flow and high-speed air transport. The researchers decided to transform it: they blocked an old well and re-drilled two large-diameter wells. However, since this was the first time that a large-diameter salt well was drilled in China, it was very difficult and the entire construction took nearly two years.
"If the salt cave is compared to an oversized balloon with a fixed volume, then the process of energy storage is the process of blowing up the balloon." Lin Tong gave an analogy to reporters. He told reporters that the project conquered the world's highest parameter centrifugal compressor , which is a key device for "blowing". Through this device, air of 1 standard atmosphere can be compressed into 140 standard atmospheres. High-pressure air is stored in the "balloon"; when power consumption peaks, the high-pressure air is released to drive the air turbine expander to rotate the "windmill" to drive the generator to generate electricity.
"We usually start energy storage at 11 o'clock and 12 o'clock in the evening when the electricity consumption is low. By the next morning, an energy storage cycle is 8 hours." Lin Yinghu told reporters that during the peak period of electricity consumption, full load power generation can be achieved in one hour. It can generate 60,000 kilowatt-hours of electricity, which can be generated continuously for 5 hours. “That is 300,000 kilowatt-hours of electricity, which is equivalent to the electricity consumption of 60,000 residents for a day.”
Reporters learned that the Jintan Salt Cave Compressed Air Energy Storage Power Station Phase II Project The scale is planned to be 400 MW, and the scale of the third phase project is expected to reach more than 1,000 MW. Judging from the total amount of salt cavern gas storage owned by Jintan, the energy storage capacity will be more than 60 times that of today in the future.
Some experts said that underground salt caverns have the natural advantages of large size, good sealing 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 storage. In the future, other underground spaces such as abandoned mine tunnels and artificial underground gas storages will also be viable options for underground gas storages.
For the first time in the world, zero-carbon power generation from compressed air has been achieved.
The power conversion efficiency has been increased to more than 60%, with no combustion and no emissions in the entire process.
In fact, although it is the first time in China to use salt caverns to store energy for power generation, it has precedents in the world. The special feature of Jintan Salt Cave Compressed Air Energy Storage Power Station lies in the application of “non-supplementary combustion” technology.
What is "non-supplementary combustion" technology? That is, the compressed air power generation process does not rely on the combustion of external energy sources such as coal and natural gas.
It is understood that after the high-pressure air in the salt cave is released, it needs to be heated and expanded to generate greater thrust and maintain the circulation of the system. The salt cavern compressed air energy storage power stations currently in operation around the world require burning coal or natural gas to heat the air. This process is called "supplementary combustion" and will inevitably produce pollutant emissions.
The Jintan Salt Cave Compressed Air Energy Storage Power Station does not rely on external energy at all. It 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 and becomes a natural "booster". The entire process of energy storage and power generation is a physical process, so there is no combustion or emissions.
It is understood that the salt cavern compressed air energy storage systems currently in operation internationally are of the supplementary combustion type. Excluding the fossil fuel part, their electrical energy conversion efficiency is only about 20%. In other words, if 100 kilowatt-hours of electricity are used to store energy, only 20 kilowatt-hours of electricity will eventually be generated. The Jintan Salt Cave Compressed Air Energy Storage Project adopts "non-supplementary combustion" technology, which can increase the power conversion efficiency to more than 60%, achieving zero-carbon compressed air power generation for the first time in the world.
"'Non-afterburning' technology has no precedent in the world. We have overcome the design, manufacturing and engineering application problems of a series of key equipment such as compressor ." Lin Tong said that there is no technical solution at home and abroad for reference. We can only start from scratch and explore step by step.
On one side of the power station, seven huge tanks are very conspicuous, where the heat energy generated during air compression is stored. Between the two large factories, densely packed pipes criss-cross, including the hairpin heat exchanger, a key facility for realizing "non-post-firing" technology.
"When I got this drawing, I was shocked. Various intricate pipelines involve various professions, including fire water pipelines, circulating water pipelines, closed cold water pipelines, hot oil pipelines, cold oil pipelines, and cable trenches for cables... It forms a form equivalent to a five- or six-story overpass, and the direction, purpose, burial depth, and diameter of each pipe are different." Lin Yinghu recalled the scene when he first arrived at the project, from equipment design and development to heat exchange media. The solution to the stuck neck problem is still incredible every step of the way.
In the power plant building, there is a big white thing called an air turbine expander. "With a length of 9 meters, a height of 4 meters and a weight of over 160 tons, it is currently the largest 'non-afterburning' air turbine equipment in the world." Mentioning this, Lin Tong is very proud. This device is equivalent to an engine and is the "power source" for power generation. "Before power generation, the air turbine expander begins 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 thermal oil tank were released at the same time, the power station began to generate electricity.
From project germination and implementation planning to taking shape and formal 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 a.m. on September 30, 2021. "In the centralized control room, there was thunderous applause, which lasted for a long time."
Now, it has formed a "power station" with completely independent intellectual property rights. Non-supplementary combustion compressed air energy storage technology system, the core equipment has been 100% localized, applied for more than 100 patents, and released the first domestic compressed air energy storage power station KKS coding standard... It can be said that the project is a new power system The construction provides technical support and basic equipment to help achieve the goal of " carbon peaking , carbon neutral ". The reporter learned that currently, the construction work of the second phase of the Jintan salt cavern compressed air energy storage project is being stepped up.
Source: China Discipline Inspection and Supervision News
