Electric power industry is one of the few areas in which there is no large-scale storage of produced “products”. Industrial energy storage and production of various types of storage devices is the next step in the large electric power industry. Now this task is especially acute - along with the rapid development of renewable energy sources. Despite the undeniable advantages of renewable energy sources, there remains one important question, which must be resolved before the widespread introduction and use of alternative energy sources. Although wind and solar energy are environmentally friendly, their generation is intermittent and requires energy storage for later use. For many countries, a particularly urgent task would be to obtain seasonal energy storage technologies - due to large fluctuations in energy consumption. Ars Technica has prepared a list of the best energy storage technologies, and we will talk about some of them.

Hydraulic accumulators

The oldest, most mature and widespread technology for storing energy in large volumes. The principle of operation of the hydraulic accumulator is as follows: there are two water tanks - one is located above the other. When the demand for electricity is low, the energy is used to pump water into the upper reservoir. During peak hours of electricity consumption, water is drained down to a hydrogenerator installed there, the water spins a turbine and generates electricity.

In the future, Germany plans to use old coal mines to create pumped storage tanks, and German researchers are working on creating giant concrete hydrostorage spheres placed on the ocean floor. In Russia there is the Zagorskaya PSPP, located on the Kunya River near the village of Bogorodskoye in the Sergiev Posad district of the Moscow region. Zagorskaya PSPP is an important infrastructural element of the center's energy system, participating in the automatic regulation of frequency and power flows, as well as covering daily peak loads.

As Igor Ryapin, head of the department of the Association "Community of Energy Consumers" said at the conference "New Energy": Internet of Energy, organized by the Energy Center of the Skolkovo Business School, the installed capacity of all hydraulic accumulators in the world is about 140 GW, to the advantages of this technology relate a large number of cycles and long operating life, efficiency is about 75-85%. However, the installation of hydraulic accumulators requires special geographical conditions and is expensive.

Compressed air energy storage devices

This method of energy storage is similar in principle to hydrogeneration - however, instead of water, air is pumped into the reservoirs. Using a motor (electric or other), air is pumped into the storage tank. To generate energy, compressed air is released and rotates the turbine.

The disadvantage of this type of storage device is low efficiency due to the fact that part of the energy during gas compression is converted into thermal form. The efficiency is no more than 55%; for rational use, the drive requires a lot of cheap electricity, so at the moment the technology is used mainly for experimental purposes, the total installed capacity in the world does not exceed 400 MW.

Molten salt for solar energy storage

Molten salt retains heat for a long time, so it is placed in solar thermal plants where hundreds of heliostats (large mirrors concentrated on the sun) collect the heat sunlight and heat the liquid inside - in the form of molten salt. Then it is sent to the reservoir, then, through a steam generator, it rotates the turbine, which generates electricity. One of the advantages is that molten salt operates at a high temperature - more than 500 degrees Celsius, which contributes to efficient work steam turbine.

This technology helps extend working hours, or heat rooms and provide electricity in the evening.

Similar technologies are used in the Mohammed bin Rashid Al Maktoum Solar Park - the world's largest network of solar power plants, united in a single space in Dubai.

Flow redox systems

Flow batteries are a huge container of electrolyte that is passed through a membrane and creates an electrical charge. The electrolyte can be vanadium, as well as solutions of zinc, chlorine or salt water. They are reliable, easy to use, and have a long service life.

There are no commercial projects yet, the total installed capacity is 320 MW, mainly within the framework of research projects. The main advantage is that it is so far the only battery technology with long-term energy output - more than 4 hours. Disadvantages include bulkiness and lack of recycling technology, which is a common problem with all batteries.

German power plant EWE plans to build the world's largest 700 MWh flow battery in Germany in caves where natural gas was previously stored, Clean Technica reports.

Traditional batteries

These are batteries similar to those that power laptops and smartphones, but in industrial size. Tesla supplies such batteries for wind and solar power plants, and Daimler uses old car batteries for this.

Thermal storage

A modern home needs to be cooled - especially in hot climates. Thermal storage facilities allow water stored in tanks to be frozen overnight; during the day, the ice melts and cools the house, without the usual expensive air conditioning and unnecessary energy costs.

The California company Ice Energy has developed several similar projects. Their idea is that ice is produced only during off-peak power grid periods, and then, instead of wasting additional electricity, the ice is used to cool rooms.

Ice Energy is collaborating with Australian firms that are looking to bring ice battery technology to the market. In Australia, due to the active sun, the use of solar panels is developed. The combination of sun and ice will increase the overall energy efficiency and environmental friendliness of homes.

Flywheel

The superflywheel is an inertial accumulator. The kinetic energy of motion stored in it can be converted into electricity using a dynamo. When the need for electricity arises, the structure generates electrical energy by slowing down the flywheel.

Individual salts can serve as electrolytes in the production of metals by electrolysis of molten salts, but usually, based on the desire to have an electrolyte that is relatively fusible, has a favorable density, characterized by a fairly low viscosity and high electrical conductivity, a relatively high surface tension, as well as low volatility and the ability to degree to dissolve metals, in the practice of modern metallurgy, molten electrolytes that are more complex in composition are used, which are systems of several (two to four) components.
From this point of view, the physicochemical properties of individual molten salts, especially systems (mixtures) of molten salts, are very important.
Quite a large amount of experimental material accumulated in this area shows that the physicochemical properties of molten salts are in a certain connection with each other and depend on the structure of these salts both in the solid and in the molten state. The latter is determined by such factors as the size and relative amount of cations and anions in the crystal lattice of the salt, the nature of the connection between them, polarization and the tendency of the corresponding ions to form complexes in melts.
In table 1 compares the melting points, boiling points, molar volumes (at the melting point) and equivalent electrical conductivity of some molten chlorides, arranged in accordance with the groups of the table of the periodic law of elements by D.I. Mendeleev.

In table 1 it can be seen that alkali metal chlorides belonging to group I and alkaline earth metal chlorides (group II) are characterized by high temperatures melting and boiling, high electrical conductivity and smaller polar volumes compared to chlorides belonging to subsequent groups.
This is due to the fact that in the solid state these salts have ionic crystal lattices, the interaction forces between the ions in which are very significant. For this reason, it is very difficult to destroy such lattices, which is why chlorides of alkali and alkaline earth metals have high melting and boiling points. The smaller molar volume of chlorides of alkali and alkaline earth metals also results from the presence of a large proportion of strong ionic bonds in the crystals of these salts. The ionic structure of the melts of the salts under consideration also determines their high electrical conductivity.
According to the views of A.Ya. Frenkel, the electrical conductivity of molten salts is determined by the transfer of current, mainly by small-sized mobile cations, and the viscous properties are due to more bulky anions. Hence the decrease in electrical conductivity from LiCl to CsCl as the radius of the cation increases (from 0.78 A for Li+ to 1.65 A for Cs+) and, accordingly, its mobility decreases.
Some chlorides of groups II and III (such as MgCl2, ScCl2, УСl3 and LaCl3) are characterized by reduced electrical conductivity in the molten state, but at the same time quite high melting and boiling points. The latter indicates a significant proportion of ionic bonds in the crystal lattices of these salts. Ho in melts noticeably interact with simple ions to form larger and less mobile complex ions, which reduces the electrical conductivity and increases the viscosity of the melts of these salts.
Strong polarization of the chlorine anion by small Be2+ and Al3+ cations leads to a sharp reduction in the fraction of ionic bonds in these salts and to an increase in the fraction of molecular bonds. This reduces the strength of the crystal lattices of BeCl2 and AlCl3, due to which these chlorides are characterized by low melting and boiling points, large molar volumes and very low electrical conductivity values. The latter is apparently due to the fact that (under the influence of the strong polarizing effect of Be2+ and Al3+) strong complexation occurs in molten beryllium and aluminum chlorides with the formation of bulky complex ions in them.
The chloride salts of elements of group IV, as well as the first element of group III, boron, which have purely molecular lattices with weak residual bonds between molecules, are characterized by very low melting temperatures (the values ​​of which are often below zero) and boiling. There are no ions in the melt of such salts, and they, like crystals, are built from neutral molecules (although there may be ionic bonds within the latter). Hence the large molar volumes of these salts at the melting point and the lack of electrical conductivity of the corresponding melts.
Fluorides of metals of groups I, II and III are characterized, as a rule, elevated temperatures melting and boiling compared to the corresponding chlorides. This is due to the smaller radius of the F+ anion (1.33 A) compared to the radius of the Cl+ anion (1.81 A) and, accordingly, the lower tendency of fluorine ions to polarize, and consequently, the formation of strong ionic crystal lattices by these fluorides.
The fusibility diagrams (phase diagrams) of salt systems are of great importance for choosing favorable electrolysis conditions. Thus, in the case of using molten salts as electrolytes in the electrolytic production of metals, it is usually first of all necessary to have relatively low-melting salt alloys that provide sufficient low temperature electrolysis and less electrical energy consumption to maintain the electrolyte in a molten state.
However, at certain ratios of components in salt systems, chemical compounds can arise with elevated melting points, but possessing other favorable properties (for example, the ability to more easily dissolve oxides in the molten state than individual molten salts, etc.).
Research shows that when we are dealing with systems of two or more salts (or salts and oxides), interactions can occur between the components of these systems, leading (depending on the strength of such interaction) to the formation of eutectics, recorded on the fusibility diagrams, or regions of solid solutions, or incongruently (with decomposition), or congruently (without decomposition) melting chemical compounds. The greater orderliness of the structure of matter at the corresponding points in the composition of the system, due to these interactions, is preserved to one degree or another in the melt, i.e., above the liquidus line.
Therefore, systems (mixtures) of molten salts are often more complex in their structure than individual molten salts, and in the general case, the structural components of mixtures of molten salts can simultaneously be simple ions, complex ions and even neutral molecules, especially when in the crystal lattices of the corresponding salts there is a certain amount of molecular bonding.
As an example, let us consider the effect of alkali metal cations on the fusibility of the MeCl-MgCl2 system (where Me is an alkali metal, Fig. 1), characterized by liquidus lines in the corresponding phase diagrams. It can be seen from the figure that as the radius of the alkali metal chloride cation increases from Li+ to Cs+ (respectively from 0.78 A to 1.65 A), the fusibility diagram becomes increasingly more complex: in the LiC-MgCl2 system, the components form solid solutions; in the NaCl-MgCl2 system there is a eutectic minimum; in the KCl-MgCl2 system in the solid phase, one congruently melting compound KCl*MgCl2 and, possibly, one incongruently melting compound 2КCl*MgCl2 are formed; in the RbCl-MgCl2 system, the fusibility diagram already has two maxima, corresponding to the formation of two congruently melting compounds; RbCl*MgCl2 and 2RbCl*MgCla; finally, in the CsCl-MgClg system, three congruently melting chemical compounds are formed; CsCl*MgCl2, 2CsCl*MgCl2 and SCsCl*MgCl2, as well as one incongruently melting compound CsCl*SMgCl2. In the LiCl-MgCb system, Li and Mg ions interact with chlorine ions to approximately the same extent, and therefore the corresponding melts are close in structure to the simplest solutions, due to which the Fusibility diagram of this system is characterized by the presence of solid solutions in it. In the NaCi-MgCl2 system, due to the increase in the radius of the sodium cation, there is a slight weakening of the bond between the sodium and chlorine ions and, accordingly, an increase in the interaction between the Mg2+ and Cl- ions, but this does not, however, lead to the appearance of complex ions in the melt. The resulting somewhat greater ordering of the melt causes the appearance of eutectic in the fusibility diagram of the NaCl-MgCl2 system. The increasing weakening of the bond between the K+ and Cl- ions due to the even larger radius of the potassium cation causes such an increase in the interaction between the ions and Cl-, which leads, as the KCl-MgCl2 fusibility diagram shows, to the formation of a stable chemical compound KMgCl3, and in the melt - to the appearance of the corresponding complex anions (MgCl3-). A further increase in the radii of Rb+ (1.49 A) ​​and Cs+ (1.65 A) causes an even greater weakening of the bond between the Rb and Cl- ions, on the one hand, and the Cs+ and Cl- ions, on the other hand, leading to a further complication of the diagram fusibility of the RbCl-MgCb system in comparison with the fusibility diagram of the KCl - MgCb system and, to an even greater extent, to the complication of the fusibility diagram of the CsCl-MgCl2 system.

The situation is similar in the MeF-AlF3 systems, where in the case of the LiF - AlF3 system, the fusibility diagram indicates one congruently melting chemical compound SLiF-AlFs, and the fusibility diagram of the NaF-AIF3 system indicates one congruently and one incongruently melting chemical compound; respectively 3NaF*AlFa and 5NaF*AlF3. Due to the fact that the formation in the salt phase during crystallization of one or another chemical compound is reflected in the structure of this melt (greater order associated with the appearance of complex ions), this causes a corresponding change, in addition to fusibility, and other physicochemical properties that change sharply (not subject to the additivity rule) for the compositions of mixtures of molten salts corresponding to the formation of chemical compounds according to the fusibility diagram.
Therefore, there is a correspondence between the composition-property diagrams in salt systems, which is expressed in the fact that where a chemical compound is noted on the fusibility diagram of the system, the melt corresponding to it in composition is characterized by a maximum crystallization temperature, a maximum density, a maximum viscosity, a minimum electrical conductivity and a minimum elasticity pair.
Such a correspondence in the change in the physicochemical properties of mixtures of molten salts in places corresponding to the formation of chemical compounds recorded on the fusibility diagrams is not, however, associated with the appearance of neutral molecules of these compounds in the melt, as was previously believed, but is due to the greater ordering of the structure of the corresponding melt, greater packing density. Hence the sharp increase in the crystallization temperature and density of such a melt. The presence in such a melt in the greatest number large complex ions (corresponding to the formation of certain chemical compounds in the solid phase) also leads to a sharp increase in the viscosity of the melt due to the appearance of bulky complex anions in it and to a decrease in the electrical conductivity of the melt due to a reduction in the number of current carriers (due to the combination of simple ions into complex ones).
In Fig. 2, as an example, a comparison is made of the composition-property diagram of melts of the NaF-AlF3 and Na3AlF6-Al2O3 systems, where in the first case the fusibility diagram is characterized by the presence of a chemical compound, and in the second - eutectic. In accordance with this, on the curves of changes in the physicochemical properties of melts depending on the composition, in the first case there are extrema (maxima and minima), and in the second, the corresponding curves change monotonically.

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To grow a salt crystal you will need:

1) - salt.

It should be as clean as possible. Sea salt is best, since regular table salt contains a lot of debris that is invisible to the eye.

2) - water.

The ideal option would be to use distilled water, or at least boiled water, purifying it as much as possible from impurities by filtering.

3) - glassware, in which the crystal will be grown.

The main requirements for it: it must also be perfectly clean; no foreign objects, even minor specks, should be present inside it throughout the entire process, since they can provoke the growth of other crystals to the detriment of the main one.

4) - salt crystal.

It can be “obtained” from a pack of salt or in an empty salt shaker. There at the bottom there will almost certainly be a suitable one that could not fit through the hole in the salt shaker. You need to choose a transparent crystal with a shape closer to a parallelepiped.

5) - wand: plastic or wooden ceramic, or a spoon made of the same materials.

One of these items will be needed to mix the solution. It would probably be unnecessary to remind you that after each use, they must be washed and dried.

6) - varnish.

Varnish will be needed to protect the finished crystal, because without protection it will crumble in dry air, and in humid air it will spread into a shapeless mass.

7) - gauze or filter paper.

The process of growing a crystal.

The container with prepared water is placed in warm water(approximately 50-60 degrees), salt is gradually poured into it, with constant stirring. When the salt can no longer dissolve, the solution is poured into another clean container so that no sediment from the first container gets into it. To ensure better purity, you can pour through a funnel with a filter.

Now, the previously “mined” crystal on a string is dipped into this solution so that it does not touch the bottom and walls of the vessel.

Then cover the dishes with a lid or something else, but so that foreign objects and dust do not get in there.

Place the container in a dark, cool place and be patient - the visible process will begin in a couple of days, but growing a large crystal will take several weeks.

As the crystal grows, the liquid will naturally decrease, and therefore, approximately once every ten days, it will be necessary to add a fresh solution prepared in accordance with the above conditions.

During all additional operations, frequent movements, strong mechanical stress, and significant temperature fluctuations should not be allowed.

When the crystal reaches the desired size, it is removed from the solution. This must be done very carefully, because at this stage it is still very fragile. The removed crystal is dried from water using napkins. To add strength, the dried crystal is coated with colorless varnish, which can be used for both household and manicure purposes.

And finally, a fly in the ointment.

A crystal grown in this way cannot be used to make a full-fledged salt lamp, since it uses a special natural mineral - halite, which contains many natural minerals.

But from what you got, it’s quite possible to make some kind of craft, for example, a miniature model of the same salt lamp, by inserting a small LED into the crystal, powering it from a battery.