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How to save energy: the most popular technologies

How to save energy: the most popular technologies
27 May 2021

Historically, most of the electricity produced in the world is consumed immediately after generation. Or it is not consumed and is simply wasted, writes ArsTechnica.

Climate change has affected the interest of governments in renewable energy sources. And "green" energy is different, it is not always able to produce energy exactly at the time when it is needed. How can such a flaw be corrected? As research in the field of energy storage increasingly attracts the attention of scientists, building energy storage facilities for solar or wind power plants is beginning to make more and more sense.

It should be noted that energy storage is not something completely new. Today, there are many energy storage technologies, and their use depends on what resources are available from the local electricity producer. Energy companies invest in technologies that are locally justified, whether it's a pumped storage plant, compressed air, or lithium-ion batteries.

Many new energy storage projects are based on technologies that have been around for decades. To better understand the future of energy storage, we have collected some of the most efficient energy storage in the world.

Hydraulic storage station

energy storage, which operates on the principle of a hydroelectric power plant, is perhaps one of the oldest forms of energy-saving energy systems. It is able to compensate for the lack of megawatts of electricity during peak hours. The technology is quite simple: the system has a lower water tank, from which water is pumped to the upper one, which is topographically higher. When there is no need for electricity (for example, at night), you use the excess energy to pump water to the upper tank (in fact, to charge the battery). When the demand for electricity is high, the water from this reservoir is drained through the turbines of the electric generators down to the lower reservoir. Then the cycle repeats.

This method of energy storage is quite popular, although outdated from many points of view. For example, Germany is considering using old coal mines to build hydraulic storage stations, and some German researchers are working on building giant concrete spheres that can store energy after they are placed on the ocean floor.

Energy storage facilities based on compressed air

Compressed air energy storage (CAES) is similar in many ways to a hydraulic storage station, but instead of water, the electricity producer pumps compressed air into a special tank during a period of low demand. When electricity is needed, the compressed air is released from the reservoir and turns the turbine of the electric generator.

Since the air is heated during compression, this heat must be removed before it is injected into the high-pressure tank. But during decompression, the air will be very cool, so it needs to be heated again. For this purpose, either an additional gas heater or other technologies are used.

Although schemes for storing energy in compressed air tanks have been discussed for the past few decades, the construction costs and complexity of the storage facilities themselves have prevented the creation of many such facilities. Today, there are only a few really working systems and a slightly larger number of test complexes. For example, the Canadian company Hydrostor is working on creating powerful compressed air systems in Ontario and Aruba.

Thermal storage of molten salt

Molten salt can retain heat for a long time, and this property is used in solar power plants, where hundreds of large mirrors focus the sun's rays to generate energy. In some power plants, the sun's rays are directed to a large central thermal tower, in which the working fluid quickly heats up and boils. There is another technology where the working fluid is heated in pipes that pass in front of parabolic mirrors. Either way, this heat can be used immediately to start a steam turbine, or direct solar energy to heat the salt. Molten salt is able to retain heat for several hours. This helps solar power plants increase their operating time and generate electricity even in the evening.

Technologies for heat storage using molten salt have clear prospects. Researchers are working on improving molten salt tanks for various purposes, and more recently SolarReserve announced plans to build a solar thermal plant in Chile that will operate 24 hours a day thanks to a huge molten salt storage tank.

Some companies are looking for ways to store the energy of molten salt without the need for solar.