Store energy bags
The problem of the accumulation and conservation of energy is old, but scientists are not tired of working in this direction, because the topic is very promising. The owners of android phones joke that a person who can offer a battery for their devices, holding a charge for at least a week, very quickly will be included in the famous Forbes list. But their problems are incomparable with the scale of the complexities of power systems, which have extremely uneven energy consumption schedules and need powerful energy storages to compensate for peaks. For these purposes, there are already solutions, but research continues.
Design engineer Maxim de Jong tests the CAES five-meter energy store during initial tests at Thin Red Line Aerospace in Canada.
Lithium is insanely expensive and not too durable. Pumped storage power plants (PSPPs) are not always convenient and require large one-time capex, although their idea can be used in other areas. Let me remind you that it consists in the fact that in moments of low energy consumption (for example, at night), the installation stores in some form (in the case of the PSPP - pumps water into the upper basin) a part of the excess energy of the power system, and during periods of maximum energy consumption (for example, morning and vespers peaks), returns to the grid (at the HPSP this is done by dumping the raised water into the lower pool through energy generating turbines).
There is the idea of ​​accumulating energy with compressed air. Some kind of air storage is needed. With the accumulation of energy, it is fed to the electric motor, which drives the compressor. Compressed air is cooled and stored at a pressure of 60-70 atmospheres. If necessary, spend the stored energy, the air is extracted from the drive, heats up, and then enters a special gas turbine, where the energy of compressed and heated air rotates the steps of the turbine, the shaft of which is connected to an electric generator that produces electricity in the power system.
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The concept is not new, the storage of compressed air in an underground cave was patented back in 1948, and the first plant with compressed air energy storage (CAES) with a capacity of 290 MW has been working at the Huntorf power plant in Germany since 1978. At the Massachusetts Institute of Technology (USA), we tried to do something similar with hollow concrete balls, but they were susceptible to chemical degradation and did not tolerate tensile loads.
Another CAES unit with a capacity of 110 MW has also been operating in McIntosh, Alabama, since 1991. But, in spite of ambitions and claims that these are “green” solutions, in these projects at present the energy of hydrocarbon fuels is used as part of the technological process. During the air compression stage, a large amount of energy is lost in the form of heat. This lost energy must be compensated for compressed air before the expansion stage in the gas turbine, for this purpose hydrocarbon fuel is used, with which the air temperature is raised. This means that the plants have far from one hundred percent efficiency.
There is a promising direction for increasing the effectiveness of CAES. It consists in retaining and preserving the heat released during the operation of the compressor at the stage of compression and cooling of the air, followed by its reuse in the return heating of cold air (the so-called recuperation). However, this option CAES has significant technical difficulties, especially in the direction of creating a system of long-term heat preservation. In the case of solving these problems, AA-CAES (Advanced Adiabatic-CAES) can pave the way for large-scale energy storage systems, the problem was raised by researchers around the world.
Researchers from the University of Nottingham (UK), under the guidance of Professor Seamus Garvey, proposed a new idea that is more profitable than previously considered. They test Energy Bag - a huge inflatable bag, anchored at a shallow depth near the Orkney Islands (Scotland). Underwater bags are an interesting option, because the sea acts as a pressure vessel, and the energy accumulation density of a pneumatic accumulator increases in direct proportion to pressure. There is no cost for the full infrastructure, only the construction materials needed to keep the bag at the bottom. You do not need a meter of sushi. Regardless of whether the container is full or empty, the pressure remains the same, and this facilitates the operation of equipment on the surface of the sea.
“The reasons for which we do not store compressed air in tanks under pressure on the surface is mainly the cost of such a solution,” explains the professor. “CAES can potentially become the cheapest energy storage system for capital costs per kWh, which ranges from 1 to 10 euros. At PSPPs, such specific capital costs are usually more than 50 euro / kWh, and electrochemical batteries - up to 500 euro / kWh. The use of surface ships to store high-pressure air in a CAES system usually leads to costs comparable to the use of electrochemical batteries.
In the Garvey solution, heat is accumulated by a special vault, which has 9 layers. Three outer layers mainly consist of sea water, they are suitable for temperatures up to 100 ° C. Three more layers contain a coolant of mineral oils in the porous layer of crushed rocks and can be used for temperatures up to 250 ° C. Three inner layers use molten salt as a heat carrier and can serve up to 450 ° C.
Such a system of heat accumulation makes it possible to ensure an efficiency of 75–85% - while the highest achievement is the Energy Bag. However, unlike conventional batteries, there is no self-discharge effect: the pneumatic shut-off valve does not consume energy. And when the accumulated need to remove, you only need to open the valve, and the water itself will displace air from a six-meter depth.
Air storages for this experiment are designed and made by the Canadian company Thin Red Line, which also manufactures fabrics for the aerospace industry. They are made of butyl rubber, and the outer layer of polyester reinforced fabric. Special coated steel or aramid belts provide the necessary structural strength. The balls themselves can be small, and a couple of tens of meters.
The Energy Bag developers consider the project to be quite suitable for small and medium-sized businesses: at a cost, such a system is supposedly much cheaper than an emergency diesel generator running during a blackout and dramatically increasing the cost of electricity (diesel fuel!). Deployment of such facilities is advisable in coastal areas.
At a depth of 600 meters, where they are being tested, the largest 20-meter Energy Bag accumulates 70 MWh of energy, which is equivalent to a 300-ton lithium battery worth tens of millions of dollars. One bag is already enough to compensate for the uneven operation of even the most powerful windmill, and a standard wind turbine will pump the required amount of air in just 14 hours. But the uneven flow of wind energy is one of the problems that significantly complicates the design and operation of a wind power plant.
So, as the inventors say, the system will soon find itself and as a niche application to the windmills, next to which there is plenty of extra peak generation and the necessary depths.
And in conclusion a short video:
Sources:
One , two , three
Design engineer Maxim de Jong tests the CAES five-meter energy store during initial tests at Thin Red Line Aerospace in Canada.
Lithium is insanely expensive and not too durable. Pumped storage power plants (PSPPs) are not always convenient and require large one-time capex, although their idea can be used in other areas. Let me remind you that it consists in the fact that in moments of low energy consumption (for example, at night), the installation stores in some form (in the case of the PSPP - pumps water into the upper basin) a part of the excess energy of the power system, and during periods of maximum energy consumption (for example, morning and vespers peaks), returns to the grid (at the HPSP this is done by dumping the raised water into the lower pool through energy generating turbines).
There is the idea of ​​accumulating energy with compressed air. Some kind of air storage is needed. With the accumulation of energy, it is fed to the electric motor, which drives the compressor. Compressed air is cooled and stored at a pressure of 60-70 atmospheres. If necessary, spend the stored energy, the air is extracted from the drive, heats up, and then enters a special gas turbine, where the energy of compressed and heated air rotates the steps of the turbine, the shaft of which is connected to an electric generator that produces electricity in the power system.
')
The concept is not new, the storage of compressed air in an underground cave was patented back in 1948, and the first plant with compressed air energy storage (CAES) with a capacity of 290 MW has been working at the Huntorf power plant in Germany since 1978. At the Massachusetts Institute of Technology (USA), we tried to do something similar with hollow concrete balls, but they were susceptible to chemical degradation and did not tolerate tensile loads.
Another CAES unit with a capacity of 110 MW has also been operating in McIntosh, Alabama, since 1991. But, in spite of ambitions and claims that these are “green” solutions, in these projects at present the energy of hydrocarbon fuels is used as part of the technological process. During the air compression stage, a large amount of energy is lost in the form of heat. This lost energy must be compensated for compressed air before the expansion stage in the gas turbine, for this purpose hydrocarbon fuel is used, with which the air temperature is raised. This means that the plants have far from one hundred percent efficiency.
There is a promising direction for increasing the effectiveness of CAES. It consists in retaining and preserving the heat released during the operation of the compressor at the stage of compression and cooling of the air, followed by its reuse in the return heating of cold air (the so-called recuperation). However, this option CAES has significant technical difficulties, especially in the direction of creating a system of long-term heat preservation. In the case of solving these problems, AA-CAES (Advanced Adiabatic-CAES) can pave the way for large-scale energy storage systems, the problem was raised by researchers around the world.
Researchers from the University of Nottingham (UK), under the guidance of Professor Seamus Garvey, proposed a new idea that is more profitable than previously considered. They test Energy Bag - a huge inflatable bag, anchored at a shallow depth near the Orkney Islands (Scotland). Underwater bags are an interesting option, because the sea acts as a pressure vessel, and the energy accumulation density of a pneumatic accumulator increases in direct proportion to pressure. There is no cost for the full infrastructure, only the construction materials needed to keep the bag at the bottom. You do not need a meter of sushi. Regardless of whether the container is full or empty, the pressure remains the same, and this facilitates the operation of equipment on the surface of the sea.
“The reasons for which we do not store compressed air in tanks under pressure on the surface is mainly the cost of such a solution,” explains the professor. “CAES can potentially become the cheapest energy storage system for capital costs per kWh, which ranges from 1 to 10 euros. At PSPPs, such specific capital costs are usually more than 50 euro / kWh, and electrochemical batteries - up to 500 euro / kWh. The use of surface ships to store high-pressure air in a CAES system usually leads to costs comparable to the use of electrochemical batteries.
In the Garvey solution, heat is accumulated by a special vault, which has 9 layers. Three outer layers mainly consist of sea water, they are suitable for temperatures up to 100 ° C. Three more layers contain a coolant of mineral oils in the porous layer of crushed rocks and can be used for temperatures up to 250 ° C. Three inner layers use molten salt as a heat carrier and can serve up to 450 ° C.
Such a system of heat accumulation makes it possible to ensure an efficiency of 75–85% - while the highest achievement is the Energy Bag. However, unlike conventional batteries, there is no self-discharge effect: the pneumatic shut-off valve does not consume energy. And when the accumulated need to remove, you only need to open the valve, and the water itself will displace air from a six-meter depth.
Air storages for this experiment are designed and made by the Canadian company Thin Red Line, which also manufactures fabrics for the aerospace industry. They are made of butyl rubber, and the outer layer of polyester reinforced fabric. Special coated steel or aramid belts provide the necessary structural strength. The balls themselves can be small, and a couple of tens of meters.
The Energy Bag developers consider the project to be quite suitable for small and medium-sized businesses: at a cost, such a system is supposedly much cheaper than an emergency diesel generator running during a blackout and dramatically increasing the cost of electricity (diesel fuel!). Deployment of such facilities is advisable in coastal areas.
At a depth of 600 meters, where they are being tested, the largest 20-meter Energy Bag accumulates 70 MWh of energy, which is equivalent to a 300-ton lithium battery worth tens of millions of dollars. One bag is already enough to compensate for the uneven operation of even the most powerful windmill, and a standard wind turbine will pump the required amount of air in just 14 hours. But the uneven flow of wind energy is one of the problems that significantly complicates the design and operation of a wind power plant.
So, as the inventors say, the system will soon find itself and as a niche application to the windmills, next to which there is plenty of extra peak generation and the necessary depths.
And in conclusion a short video:
Sources:
One , two , three
Source: https://habr.com/ru/post/142784/
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