08.03.2020
How to make one solid piece from kitchen salt, is it possible? How to store energy. Molten salt, compressed air and super flywheel Reaction of water and molten salt
The power industry is one of the few areas in which there is no large-scale storage of manufactured "products". Industrial storage of energy and the production of various types of storage devices is the next step in the large electric power industry. Now this task is especially acute - together with the rapid development of renewable energy sources. Despite the indisputable advantages of renewable energy sources, one important issue remains that must be resolved before massively introducing and using alternative energy sources. Although wind and solar energy is environmentally friendly, its generation is "intermittent" and requires energy storage for later use. For many countries, a particularly urgent task would be to obtain technologies for seasonal energy storage - due to large fluctuations in its consumption. The publication Ars Technica has prepared a list of the best energy storage technologies, we will tell you about some of them.
Hydroaccumulators
The oldest, most established and widespread technology for storing energy in large volumes. The principle of operation of the accumulator is as follows: there are two water tanks - one 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 hydro generator installed there, the water turns a turbine and generates electricity.
In the future, Germany plans to use old coal mines to create hydraulic accumulators, and German researchers are working to create giant concrete spheres for hydronegration placed on the ocean floor. In Russia, there is the Zagorskaya GAES located on the Kunya River near the village of Bogorodskoye in the Sergiev Posad District of the Moscow Region. The Zagorskaya PSPP is an important infrastructural element of the power system of the center; it participates in automatic regulation of frequency and power flows, as well as covering daily peak loads.
As Igor Ryapin, head of the department of the Association of Communities of Energy Consumers, within the framework of the New Energy conference: Internet of Energy, organized by the Energy Center of the Skolkovo Business School, said the installed capacity of all hydroaccumulators in the world is about 140 GW, to the advantages of this technology include a large number of cycles and a long service life, efficiency of the order of 75-85%. However, the installation of accumulators requires special geographic conditions and is expensive.
Compressed air energy storage
This method of storing energy is similar in principle to hydroelectric generation - however, instead of water, air is forced into the tanks. With the help of a motor (electric or otherwise), air is pumped into the accumulator. To obtain energy, compressed air is released and rotates the turbine.
The disadvantage of this kind of storage is low efficiency due to the fact that part of the energy is converted into a thermal form during gas compression. The efficiency is not more than 55%, for rational use the storage device requires a lot of cheap electricity, therefore, 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, which is why it is placed in solar thermal installations, where hundreds of heliostats (large mirrors centered on the sun) collect the heat of the sunlight and heat the liquid inside - in the form of molten salt. Then it is sent to the reservoir, then, by means of a steam generator, it drives the turbine into rotation, so electricity is generated. One of the advantages is that the molten salt operates at high temperatures - over 500 degrees Celsius, which contributes to the efficient operation of the steam turbine.
This technology helps to extend working hours, or to heat the premises and provide electricity in the evening.
Similar technologies are used in the Mohammed Ibn Rashid Al Maktoum Solar Park, the world's largest network of solar power plants, united in a single space in Dubai.
Flow-through 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 operate 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 plus is so far the only battery technology with long-term energy output - more than 4 hours. Among the disadvantages are bulkiness and lack of recycling technology, which is a common problem for all batteries.
German power plant EWE plans to build the world's largest 700 MWh flow battery in Germany, in caves where natural gas used to be stored, according to Clean Technica.
Traditional batteries
These are batteries similar to those found in laptops and smartphones, only of 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 regions. Thermal storages allow to freeze the water stored in cisterns during the night, during the day the ice melts and cools the house, without the use of the usual expensive air conditioner and unnecessary energy consumption.
Ice Energy, a California company, has developed several similar projects. Their idea is that ice is produced only during off-peak power loads, and then, instead of using additional electricity, ice is used to cool the premises.
Ice Energy is partnering with Australian firms looking to bring ice battery technology to the market. In Austria, because of the active sun, the use of solar panels is developed. The combination of sun and ice will increase the overall energy efficiency and sustainability of homes.
Flywheel
A super flywheel is an inertial storage device. The kinetic energy of motion stored in it can be converted into electricity using a dynamo. When there is a need for electricity, the structure generates electrical energy by decelerating the flywheel.
To grow a salt crystal, you will need:
1) - salt.
It should be as clean as possible. Sea salt is best suited, since there is a lot of debris in an ordinary cookery that is invisible to the eyes.
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 filtration.
3) - glasswarein which the crystal will be grown.
The main requirements for it: it must also be perfectly clean, no foreign objects, even insignificant specks should not 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 is almost certainly a suitable one that could not get through the hole in the salt shaker. You need to choose a transparent crystal closer to a parallelepiped in shape.
5) - wand: plastic or wooden ceramic, or a spoon made of the same materials.
One of these items will be required to mix the solution. It would probably be superfluous to remind you that after each use, they must be washed and dried.
6) - varnish.
Varnish is required to protect the finished crystal, because without protection in dry air it will crumble, and in wet air it will creep into a shapeless mass.
7) - gauze or filter paper.
Crystal growing process.
A 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 is no longer able to dissolve, the solution is poured into another clean dish so that no sediment from the first container gets into it. To ensure better cleanliness can be poured through a funnel with 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 there.
Place the container in a dark, cool place and be patient - the visible process will begin in a couple of days, but it will take several weeks to grow a large crystal.
As the crystal grows, the liquid will naturally decrease, and therefore, approximately 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 influences, significant temperature fluctuations must 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. The dried crystal is coated with a colorless varnish to give strength, for which you can use both household and manicure.
And finally, fly in the ointment.
The crystal grown in this way cannot be used to make a full-fledged salt lamp, since a special natural mineral is used there - halite, which contains many natural minerals.
But even from what you have obtained, it is 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, powered by a battery.
The main idea of \u200b\u200bthe entire project is to ensure the continuity of the supply of energy generated by alternative sources, primarily wind and sun.
The Alphabet holding, of which Google is a part, has an “X” division that deals with projects that look like pure fantasy. One of such projects is just about to be implemented. It is called Project Malta, and Bill Gates is going to take part in it. True, not directly, but through its Breakthrough Energy Ventures fund. It is planned to allocate about $ 1 billion.
It is not yet clear when exactly the funding will be allocated, but the intentions of all partners are more than serious. The idea of \u200b\u200ban energy storage facility, part of which is a reservoir of molten salt, and part of which is a cooled coolant, belongs to scientist Robert Laughlin. He is a professor of physics and applied physics at Stanford University, Laughlin received the Nobel Prize in Physics in 1998.
The main idea of \u200b\u200bthe entire project is to ensure the continuity of the supply of energy generated by alternative sources, primarily wind and sun. Yes, of course, there are various kinds of battery systems that allow you to store energy during the day and give it away at night or during periods of time that are problematic for alternative sources (cloudiness, calm, etc.). But they can store a relatively small amount of energy. If we talk about the scale of a city, region or country, then there are no such battery systems.
But they can be created using Laughlin's idea. It includes the following structural elements:
- A green energy source, such as a wind or solar power plant, which transfers energy to storage.
- Further, the electric energy drives the heat pump, the electricity is converted into heat, and two regions are formed - hot and cooled.
- Heat is stored in the form of molten salt; in addition, there is a “cold reservoir”, which is a highly cooled heat carrier (as an example).
- When energy is required, the "heat engine" (a system that can be called an anti-heat pump) starts and electricity is generated again.
- The required amount of energy is sent to the general network.
The technology patent has already been obtained by Laughlin, so now it is only a matter of technology and funding. The project itself can be implemented, for example, in California. Here, about 300,000 kWh of energy generated by wind and solar power plants were "lost". The fact is that so much of it was produced that it was not possible to save the entire volume. And this is enough to supply more than 10,000 households with energy.
The situation is similar in Germany, where in 2015 4% of "wind" electricity was lost. In China, this figure has generally exceeded 17%.
Unfortunately, representatives of "X" do not say anything about the possible cost of the project. It may well be that, subject to proper implementation, an energy storage with salt and chilled liquid will cost less than traditional lithium batteries. Nevertheless, now the cost of lithium-ion batteries is falling, and the cost of "dirty" energy is kept at about the same level. So if the proponents of the Malta project want to compete with traditional solutions, they need to achieve a significant reduction in the cost of a kilowatt in their system.
Be that as it may, the implementation of the project is just around the corner, so that soon we will be able to find out all the necessary details. published If you have any questions on this topic, ask them to the specialists and readers of our project.
Individual salts can serve as electrolytes in the production of metals by electrolysis of molten salts, but usually, based on the desire to have a relatively low-melting electrolyte, with a favorable density, characterized by a sufficiently low viscosity and high electrical conductivity, a relatively high surface tension, as well as low volatility and ability to the degree to dissolve metals, in the practice of modern metallurgy, molten electrolytes of more complex 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.
A fairly large amount of experimental material accumulated in this area shows that the physicochemical properties of molten salts are in a certain relationship with each other and depend on the structure of these salts, both in solid and 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 bond between them, polarization and the tendency of the corresponding ions to complex formation in melts.
Table 1 compares the melting points, boiling points, molar volumes (at the melting point) and the equivalent electrical conductivity of some molten chlorides located in accordance with the groups of the table of the periodic law of elements of D.I. Mendeleev.
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 melting and boiling points, high electrical conductivity and lower 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 forces of interaction between the ions in which are very significant. For this reason, it is very difficult to destroy such lattices; therefore, chlorides of alkali and alkaline earth metals have high melting and boiling points. A 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 beliefs of A.Ya. Frenkel, the electrical conductivity of molten salts is determined by the transfer of current, mainly by small mobile cations, and the viscous properties are due to the bulkier 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, a decrease in its mobility.
Some chlorides of groups II and III (such as MgCl2, ScCl2, USl3 and LaCl3) are characterized by low electrical conductivity in the molten state, but at the same time, rather high melting and boiling points. The latter indicates a significant fraction of ionic bonds in the crystal lattices of these salts. Ho in melts, simple ions interact noticeably with the formation of larger and less mobile complex ions, which reduces the electrical conductivity and increases the viscosity of the melts of these salts.
Strong polarization by small-sized cations Be2 + and Al3 + of the chlorine anion leads to a sharp decrease 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. The latter is apparently due to the fact that (under the influence of the strong polarizing action of Be2 + and Al3 +), strong complexation occurs in molten beryllium and aluminum chlorides with the formation of bulky complex ions in them.
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 (values \u200b\u200bof which often lie below zero) and boiling points. There are no ions in the melt of such salts, and they, like crystals, are built of neutral molecules (although there can be ionic bonds inside the latter). Hence - the large molar volumes of these salts at the melting temperature and the absence of electrical conductivity of the corresponding melts.
Fluorides of metals of groups I, II and III are characterized, as a rule, by increased melting and boiling points in comparison with 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.
Melting diagrams (phase diagrams) of salt systems are of great importance for the selection of favorable electrolysis conditions. Thus, in the case of using molten salts as electrolytes in the electrolytic production of metals, it is usually necessary first of all to have relatively low-melting salt alloys that provide a sufficiently low electrolysis temperature and less consumption of electrical energy to maintain the electrolyte in a molten state.
However, at certain ratios of components in salt systems, chemical compounds with elevated melting points can arise, but with other favorable properties (for example, the ability to dissolve oxides in a molten state more easily than individual molten salts, etc.).
Studies show that when we deal with systems of two or more salts (or salts and oxides), interactions between the components of these systems can occur, leading (depending on the strength of such interaction) to the formation of eutectics or areas of solid solutions, or incongruently (with decomposition), or congruently (without decomposition) of melting chemical compounds. The high orderliness of the structure of matter at the corresponding points of the composition of the system, due to these interactions, persists 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 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 bond.
As an example, consider the effect of alkali metal cations on the fusibility of the MeCl-MgCl2 system (where Me is an alkali metal in Fig. 1), which is 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 + (from 0.78 A to 1.65 A, respectively), the fusion diagram becomes more and more complex: in the LiC-MgCl2 system, the components form solid solutions; there is a eutectic minimum in the NaCl-MgCl2 system; in the KCl-MgCl2 system in the solid phase, one congruently melting compound KCl * MgCl2 and, possibly, one incongruently melting compound 2KCl * MgCl2 are formed; in the RbCl-MgCl2 system, there are already two maxima on the melting diagram, which correspond to the formation of two congruently melting compounds; RbCl * MgCl2 and 2RbCl * MgCla; finally, three congruently melting chemical compounds are formed in the CsCl-MgClg system; 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 approximately to the same extent with chlorine ions, 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 an increase in the radius of the sodium cation, there is a slight weakening of the bond between sodium and chlorine ions and, accordingly, an increase in the interaction between Mg2 + and Cl- ions, but not leading, however, to the appearance of complex ions in the melt. The resulting somewhat higher ordering of the melt causes the appearance of a eutectic on the melting diagram of the NaCl-MgCl2 system. The increasing weakening of the bond between the K + and C1- 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 fusion 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 Rb + (1.49 A) \u200b\u200band 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 melting diagram shows one congruently melting chemical compound SLiF-AlFs, and the melting diagram of the NaF-AIF3 system is one congruent and one incongruently melting chemical compound; 3NaF * AlFa and 5NaF * AlF3, respectively. Due to the fact that the formation in the salt phase during crystallization of one or another chemical compound is also reflected in the structure of this melt (greater ordering associated with the appearance of complex ions), this causes a corresponding change, in addition to fusibility, and other physicochemical properties, which change dramatically (not obeying the rule of additivity) for the compositions of mixtures of molten salts corresponding to the formation of chemical compounds according to the melting 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 melting diagram of the system, the melt corresponding to it in composition is characterized by a maximum crystallization temperature, maximum density, maximum viscosity, minimum electrical conductivity and minimum elasticity couple.
Such a correspondence in the change in the physicochemical properties of mixtures of molten salts in the places corresponding to the formation of chemical compounds recorded on the melting diagrams, however, is not associated with the appearance of neutral molecules of these compounds in the melt, as was assumed earlier, but is due to the higher ordering of the structure of the corresponding melt. higher packing density. Hence - a sharp increase in the crystallization temperature and density of such a melt. The presence in such a melt in the greatest amount of large complex ions (corresponding to the formation of certain chemical compounds in the solid phase) also leads to a sharp increase in the melt viscosity due to the appearance of bulky complex anions in it and to a decrease in the electrical conductivity of the melt due to a decrease in the number of current carriers (due to the combination simple ions into complex).
In fig. 2, as an example, a comparison of the composition - property diagram of the melts of the NaF-AlF3 and Na3AlF6-Al2O3 systems is made, where in the first case, the fusibility diagram is characterized by the presence of a chemical compound, and in the second, by a eutectic. In accordance with this, the curves of the change in the physicochemical properties of the melts, depending on the composition, in the first case have extrema (maxima and minima), and in the second, the corresponding curves change monotonically.
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