Compressed Air Energy Storage (CAES) - Pneumatic energy storage. How does a pneumatic energy accumulator work? Energy capacity of chemical accumulators

A reservoir of air or other gas connected to a duct and equipped with a safety valve regulated to a specified pressure. A pneumatic accumulator is a necessary element of sand blowing and sand-shooting machines for the manufacture of... ... Metallurgical dictionary

pneumatic accumulator- pneumatinis akumuliatorius statusas T sritis Energetika apibrėžtis Suslėgtų dujų arba oro energijos kaupiklis. atitikmenys: engl. pneumatic accumulator vok. Druckluftspeicher, m rus. pneumatic accumulator, m; pneumatic accumulator, m pranc.… … Aiškinamasis šiluminės ir branduolinės technikos terminų žodynas

PNEUMATIC ACCUMULATOR- a tank with air (or other gas), connected to the air duct and equipped with a safety device. valve, which is regulated to a given maximum pressure. Used in complex pneumatic applications. networks for equalizing operating pressure, on wind-electric... ... Big Encyclopedic Polytechnic Dictionary

Battery (disambiguation)- Battery (lat. accumulator collector, from lat. accumulo collect, accumulate) a device for storing energy for the purpose of its subsequent use. Car battery is a rechargeable battery used in a car... ... Wikipedia

Battery- This term has other meanings, see Battery (meanings). Battery (lat. accumulator collector, from lat. accumulo collect, accumulate) a device for storing energy for the purpose of its subsequent use, ... ... Wikipedia

BATTERY- (from Latin accumulator collector) a device for storing energy for the purpose of its subsequent use. 1) An electric battery converts electrical energy into chemical energy and, as needed, provides the reverse conversion;... ... Big Encyclopedic Dictionary

BATTERY Modern encyclopedia

Battery- (from the Latin accumulator collector), a device for storing energy for the purpose of its subsequent use. 1) Electric battery galvanic cell reusable; converts electrical energy into chemical energy and... Illustrated Encyclopedic Dictionary

battery- A; m. A device for storing energy for the purpose of its subsequent use. Thermal, electrical a. Charge a. ◁ Rechargeable, oh, oh. A. tank. And the battery. * * * battery (from Latin accumulator collector), a device for storing... ... encyclopedic Dictionary

Battery- (lat. accumulator collector, from accumulo collect, accumulate) a device for storing energy for the purpose of its subsequent use. Depending on the type of accumulated energy, A. are distinguished: electrical, hydraulic, thermal,... ... Great Soviet Encyclopedia

The simplest such battery is a regular one. gas cylinder, into which at the moment of peak electricity generation the compressor pumps air under high pressure. When energy production drops or, conversely, its consumption increases sharply, the valve opens and the escaping compressed air spins the generator turbine. The efficiency of such an installation turns out to be relatively small, but given the fact that often at peak production energy simply goes to waste, heating the surrounding space, even this addition should not be neglected.

How can you increase the efficiency and reduce the relative cost of such a system? In a setup called Compressed Air Energy Storage (CAES), first built by the US in 1991 in McIntosh, Alabama. A natural underground salt cave is used as a reservoir. The layer of salt does not allow air to pass through, even under high pressure- small grains, salt dust seals the smallest cracks that may appear in the thickness of the formation. Air into the cave with a volume of 538 thousand cubic meters. pumped by a compressor to a pressure of 77 atmospheres. When power consumption on the grid increases unexpectedly, air escapes and releases power into the system. The time for emptying the tank to a lower operating pressure of 46 atm is 26 hours, during which the station produces 110 MW of power.

How to increase the efficiency of the system? Compressed air does not spin the impeller on its own, but is mixed with natural gas and supplied to the gas turbine. Most of The power of a gas turbine (up to two-thirds) is usually spent on driving the compressor, which pumps air into it - this is where we get significant savings. Additionally, before entering the turbine, the air is heated in the heat exchanger (recuperator) with combustion products, which also adds efficiency.

In total, being equal to a traditional gas turbine, this scheme provides a reduction in gas consumption by 60...70%, quick start from a cold state (several minutes) and Good work at low loads. The Mcntosh station took 30 months to build and cost $65 million (even despite the presence of a natural salt cave).

In addition to the project in Alabama, in 1978 in Huntorf, the Germans launched a 290 MW storage facility (2 hours of operation) in two salt caves at a depth of 600...800 m with a pressure range of 50...70 atmospheres. The storage facility originally served as a hot reserve for industry in northwest Germany and is now used to smooth out peaks in wind farm output.

In Soviet times, it was planned to build a 1050 MW pneumatic battery in Donbass, but alas, like many projects of those years, everything remained on paper.

Well, a video from the project developers.

Ecology of knowledge. Science and technology: In the context of the active development of new technologies in the energy sector, electricity storage devices are a well-known trend. This is a high-quality solution to the problem of power outages or complete lack of energy.

There is a question: “Which energy storage method is preferable in a given situation?”. For example, what method of energy storage should I choose for a private house or cottage equipped with a solar or wind installation? Obviously, in this case no one will build a large pumped storage station, but it is possible to install a large tank, raising it to a height of 10 meters. But will such an installation be sufficient to maintain a constant power supply in the absence of sun?

To answer the questions that arise, it is necessary to develop some criteria for evaluating batteries that will allow us to obtain objective assessments. And to do this, you need to consider various drive parameters that allow you to obtain numerical estimates.

Capacity or accumulated charge?

When talking or writing about car batteries, they often mention a value called the battery capacity and expressed in ampere-hours (for small batteries - in milliamp-hours). But, strictly speaking, the ampere-hour is not a unit of capacity. In electrical theory, capacitance is measured in farads. And ampere-hour is a unit of measurement of charge! That is, the accumulated charge should be considered (and called so) as a characteristic of the battery.

In physics, charge is measured in coulombs. A coulomb is the amount of charge passed through a conductor at a current of 1 ampere in one second. Since 1 C/s is equal to 1 A, then, by converting hours to seconds, we find that one ampere-hour will be equal to 3600 C.

It should be noted that even from the definition of a coulomb it is clear that the charge characterizes a certain process, namely the process of current passing through a conductor. The same thing even follows from the name of another quantity: one ampere-hour is when a current of one ampere flows through a conductor for an hour.

At first glance, it may seem that there is some kind of inconsistency here. After all, if we are talking about energy conservation, then the energy accumulated in any battery should be measured in joules, since the joule in physics is the unit of energy measurement. But let's remember that current in a conductor occurs only when there is a potential difference at the ends of the conductor, that is, voltage is applied to the conductor. If the voltage at the battery terminals is 1 volt and a charge of one ampere-hour flows through the conductor, we find that the battery has delivered 1 V · 1 Ah = 1 Wh of energy.

Thus, in relation to batteries, it is more correct to talk about accumulated energy (stored energy) or accumulated (stored) charge. Nevertheless, since the term “battery capacity” is widespread and somehow more familiar, we will use it, but with some clarification, namely, we will talk about energy capacity.

Energy capacity - the energy given off by a fully charged battery when discharged to the lowest permissible value.

Using this concept, we will try to approximately calculate and compare the energy capacity various types energy storage devices.

Energy capacity of chemical batteries

Fully charged electric battery with a declared capacity (charge) of 1 Ah, it is theoretically capable of providing a current of 1 ampere for one hour (or, for example, 10 A for 0.1 hour, or 0.1 A for 10 hours). But too much battery discharge current leads to less efficient power delivery, which non-linearly reduces the time it operates with such current and can lead to overheating. In practice, battery capacity is calculated based on a 20-hour discharge cycle to the final voltage. For car batteries, it is 10.8 V. For example, the inscription on the battery label “55 Ah” means that it is capable of delivering a current of 2.75 amperes for 20 hours, and the voltage at the terminals will not drop below 10.8 IN.

Battery manufacturers often indicate technical specifications of their products, the stored energy in Wh (Wh), and not the stored charge in mAh (mAh), which, generally speaking, is not correct. Calculating the stored energy from the stored charge is not easy in the general case: integration is required instantaneous power, issued by the battery for the entire time of its discharge. If greater accuracy is not needed, instead of integration, you can use the average values ​​of voltage and current consumption and use the formula:

1 Wh = 1 V 1 Ah.

That is, the stored energy (in Wh) is approximately equal to the product of the stored charge (in Ah) and the average voltage (in Volts): E = q · U. For example, if the capacity (in the usual sense) of a 12-volt battery is stated to be 60 Ah, then the stored energy, that is, its energy capacity, will be 720 W hours.

Energy capacity of gravitational energy storage devices

In any physics textbook you can read that the work A done by some force F when lifting a body of mass m to a height h is calculated by the formula A = m · g · h, where g is the acceleration of gravity. This formula takes place in the case when the body moves slowly and friction forces can be neglected. Working against gravity does not depend on how we lift the body: vertically (like a weight on a watch), along an inclined plane (like when pulling a sled up a mountain) or in any other way.

In all cases, work A = m · g · h. When lowering the body to its original level, the force of gravity will produce the same work as was expended by the force F to lift the body. This means that when lifting a body, we have stored up work equal to m · g · h, i.e. the raised body has energy equal to the product of the force of gravity acting on this body and the height to which it is raised. This energy does not depend on the path along which the rise took place, but is determined only by the position of the body (the height to which it is raised or the difference in heights between the initial and final position of the body) and is called potential energy.

Using this formula, let us estimate the energy capacity of a mass of water pumped into a tank with a capacity of 1000 liters, raised 10 meters above ground level (or the level of a hydrogenerator turbine). Let us assume that the tank has the shape of a cube with an edge length of 1 m. Then, according to the formula in Landsberg’s textbook, A = 1000 kg · (9.8 m/s2) · 10.5 m = 102900 kg · m2/s2. But 1 kg m2/s2 is equal to 1 joule, and when converted to watt hours, we get only 28.583 watt hours. That is, to obtain an energy capacity equal to the capacity of a conventional electric battery of 720 watt-hours, you need to increase the volume of water in the tank by 25.2 times.

The tank will need to have a rib length of approximately 3 meters. At the same time, its energy capacity will be equal to 845 watt-hours. This is more than the capacity of one battery, but the installation volume is significantly larger than the size of a conventional lead-zinc car battery. This comparison suggests that it makes sense to consider not the stored energy in a certain system - energy in itself, but in relation to the mass or volume of the system in question.

Specific energy capacity

So we came to the conclusion that it is advisable to correlate the energy capacity with the mass or volume of the storage device, or the carrier itself, for example, water poured into a tank. Two indicators of this kind can be considered.

We will refer to the mass specific energy capacity as the energy capacity of a storage device divided by the mass of this storage device.

Volumetric specific energy capacity will be the energy capacity of a storage device divided by the volume of this storage device.

Example. The lead-acid battery Panasonic LC-X1265P, designed for 12 volts, has a charge of 65 ampere-hours, weighs 20 kg. and dimensions (LxWxH) 350 · 166 · 175 mm. Its service life at t = 20 C is 10 years. Thus, its mass specific energy intensity will be 65 · 12 / 20 = 39 watt-hours per kilogram, and its volumetric specific energy intensity will be 65 · 12 / (3.5 · 1.66 · 1.75) = 76.7 watt-hours per cubic decimeter or 0.0767 kWh per cubic meter.

For discussed in previous section of a gravitational energy storage device based on a water tank with a volume of 1000 liters, the specific mass energy intensity will be only 28.583 watt-hours/1000 kg = 0.0286 Wh/kg, which is 1363 times less than the mass energy intensity of a lead-zinc battery. And although the service life gravitational storage may turn out to be significantly larger, yet from a practical point of view, a tank seems less attractive than a battery.

Let's look at a few more examples of energy storage devices and evaluate their specific energy intensity.

Energy capacity of the heat accumulator

Heat capacity is the amount of heat absorbed by a body when it is heated by 1 °C. Depending on which quantitative unit the heat capacity belongs to, mass, volumetric and molar heat capacity are distinguished.

Mass specific heat capacity, also simply called specific heat capacity, is the amount of heat that must be added to a unit mass of a substance to heat it by a unit temperature. In SI it is measured in joules divided by kilograms per kelvin (J kg−1 K−1).

Volumetric heat capacity is the amount of heat that must be supplied to a unit volume of a substance to heat it per unit temperature. In SI it is measured in joules per cubic meter per kelvin (J m−3 K−1).

Molar heat capacity is the amount of heat that must be supplied to 1 mole of a substance to heat it per unit temperature. In SI it is measured in joules per mole per kelvin (J/(mol K)).

A mole is a unit of measurement for the amount of a substance in the International System of Units. A mole is the amount of substance in a system containing the same amount structural elements, how many atoms are there in carbon-12 weighing 0.012 kg.

The specific heat capacity is affected by the temperature of the substance and other thermodynamic parameters. For example, measuring the specific heat capacity of water will give different results at 20 °C and 60 °C. In addition, specific heat capacity depends on how the thermodynamic parameters of the substance (pressure, volume, etc.) are allowed to change; for example, the specific heat capacity at constant pressure (CP) and at constant volume (CV) are generally different.

Transfer of matter from one state of aggregation to another is accompanied by an abrupt change in heat capacity at a specific temperature point of transformation for each substance - the melting point (transition solid into liquid), boiling point (transition of liquid into gas) and, accordingly, temperatures of reverse transformations: freezing and condensation.

The specific heat capacities of many substances are given in reference books, usually for a process at constant pressure. For example, specific heat capacity liquid water at normal conditions- 4200 J/(kg K); ice - 2100 J/(kg K).

Based on the data presented, you can try to estimate the heat capacity of a water heat accumulator (abstract). Let's assume that the mass of water in it is 1000 kg (liters). We heat it to 80 °C and let it give off heat until it cools down to 30 °C. If you don’t bother with the fact that the heat capacity is different at different temperatures, we can assume that the heat accumulator will release 4200 * 1000 * 50 J of heat. That is, the energy capacity of such a heat accumulator is 210 megajoules or 58.333 kilowatt-hours of energy.

If we compare this value with the energy charge of a conventional car battery (720 watt-hours), we see that the energy capacity of the thermal accumulator in question is equal to the energy capacity of approximately 810 electric batteries.

The specific mass energy intensity of such a heat accumulator (even without taking into account the mass of the vessel in which the heated water will actually be stored and the mass of thermal insulation) will be 58.3 kWh/1000 kg = 58.3 Wh/kg. This already turns out to be more than the mass energy intensity of a lead-zinc battery, equal, as calculated above, to 39 Wh/kg.

According to rough estimates, the heat accumulator is comparable to a conventional one car battery and by volumetric specific energy capacity, since a kilogram of water is a decimeter of volume, therefore its volumetric specific energy capacity is also equal to 76.7 Wh/kg, which exactly coincides with the volumetric specific heat capacity of a lead-acid battery. True, in the calculation for the heat accumulator we took into account only the volume of water, although it would also be necessary to take into account the volume of the tank and thermal insulation. But in any case, the loss will not be as great as for a gravity storage device.

Other types of energy storage devices

The article “Review of energy storage devices (accumulators)” provides calculations of the specific energy intensity of some more energy storage devices. Let's borrow some examples from there

Capacitor storage

With a capacitor capacity of 1 F and a voltage of 250 V, the stored energy will be: E = CU2 /2 = 1 ∙ 2502 /2 = 31.25 kJ ~ 8.69 W h. If you use electrolytic capacitors, their weight can be 120 kg. The specific energy of the storage device is 0.26 kJ/kg or 0.072 W/kg. During operation, the drive can provide a load of no more than 9 W for an hour. Life time Electrolytic capacitors can last up to 20 years. In terms of energy density, ionistors are close to chemical batteries. Advantages: the accumulated energy can be used within a short period of time.

Gravity drive type accumulators

First, we lift a body weighing 2000 kg to a height of 5 m. Then the body is lowered under the influence of gravity, rotating the electric generator. E = mgh ~ 2000 ∙ 10 ∙ 5 = 100 kJ ~ 27.8 W h. Specific energy capacity 0.0138 W h/kg. During operation, the drive can provide a load of no more than 28 W for an hour. The service life of the drive can be 20 years or more.

Advantages: the accumulated energy can be used within a short period of time.

Flywheel

The energy stored in the flywheel can be found using the formula E = 0.5 J w2, where J is the moment of inertia of the rotating body. For a cylinder of radius R and height H:

J = 0.5 p r R4 H

where r is the density of the material from which the cylinder is made.

Limit linear speed at the periphery of the flywheel Vmax (approximately 200 m/s for steel).

Vmax = wmax R or wmax = Vmax /R

Then Emax = 0.5 J w2max = 0.25 p r R2 H V2max = 0.25 M V2max

The specific energy will be: Emax /M = 0.25 V2max

For a steel cylindrical flywheel, the maximum specific energy content is approximately 10 kJ/kg. For a flywheel weighing 100 kg (R = 0.2 m, H = 0.1 m), the maximum accumulated energy can be 0.25 ∙ 3.14 ∙ 8000 ∙ 0.22 ∙ 0.1 ∙ 2002 ~ 1 MJ ~ 0.278 kW h. During operation, the drive can provide a load of no more than 280 W for an hour. The service life of the flywheel can be 20 years or more. Advantages: the accumulated energy can be used for a short period of time, the performance can be significantly improved.

Super flywheel

The super flywheel, unlike conventional flywheels, is capable of design features theoretically store up to 500 Wh per kilogram of weight. However, for some reason the development of superflywheels stopped.

Pneumatic accumulator

Air under a pressure of 50 atmospheres is pumped into a steel tank with a capacity of 1 m3. To withstand this pressure, the walls of the tank must be approximately 5 mm thick. Compressed air is used to do the work. In an isothermal process, the work A performed by an ideal gas during expansion into the atmosphere is determined by the formula:

A = (M / m) ∙ R ∙ T ∙ ln (V2 / V1)

where M is gas mass, m - molar mass gas, R - universal gas constant, T - absolute temperature, V1 - initial volume of gas, V2 - final volume of gas. Taking into account the equation of state for an ideal gas (P1 ∙ V1 = P2 ∙ V2) for this implementation of the storage device V2 / V1 = 50, R = 8.31 J/(mol deg), T = 293 0K, M / m ~ 50: 0.0224 ~ 2232, gas work during expansion 2232 ∙ 8.31 ∙ 293 ∙ ln 50 ~ 20 MJ ~ 5.56 kW · hour per cycle. The mass of the drive is approximately 250 kg. The specific energy will be 80 kJ/kg. During operation, the pneumatic storage device can provide a load of no more than 5.5 kW for an hour. The service life of a pneumatic accumulator can be 20 years or more.

Advantages: the storage tank can be located underground, standard gas cylinders in the required quantity with the appropriate equipment can be used as a reservoir, when using a wind engine, the latter can directly drive the compressor pump, there is enough a large number of devices that directly use energy compressed air.

Comparison table of some energy storage devices

Let us summarize all the above values ​​of energy storage parameters into a summary table. But first, let us note that specific energy intensity allows us to compare storage devices with conventional fuel.

The main characteristic of fuel is its heat of combustion, i.e. the amount of heat released during complete combustion. A distinction is made between specific heat of combustion (MJ/kg) and volumetric heat (MJ/m3). Converting MJ to kWh we get:

As we can see, the specific energy intensity of fuel significantly exceeds the energy intensity of energy storage devices. Because as backup source energies are often used diesel generators, we will include in the final table the energy intensity of diesel fuel, which is equal to 42624 kJ/kg or 11.84 kW-hours/kg. And let’s add natural gas and hydrogen for comparison, since the latter can also serve as the basis for creating energy storage devices.

The specific mass energy content of bottled gas (propane-butane) is 36 mJ/kg. or 10 kWh/kg, and for hydrogen - 33.58 kWh/kg.

As a result, we obtain the following table with the parameters of the considered energy storage devices (the last two rows in this table were added for comparison with traditional energy carriers):

The figures given in this table are very approximate; the calculations do not take into account many factors, for example, the coefficient useful action that generator that uses stored energy, volumes and weights necessary equipment and so on. However, these figures allow, in my opinion, to give an initial assessment of the potential energy intensity various types energy storage devices.

And, as follows from the table above, the most effective look The storage device is represented by a cylinder with hydrogen. If “free” (excess) energy from renewable sources is used to produce hydrogen, then the hydrogen storage device may turn out to be the most promising.

Hydrogen can be used as fuel in a conventional internal combustion engine, which will rotate an electric generator, or in hydrogen fuel cells that directly produce electricity. The question of which method is more profitable requires separate consideration. Well, safety issues in the production and use of hydrogen can make adjustments when considering the feasibility of using one or another type of energy storage device. published

Join us on

The chain of the technological cycle of electricity production necessarily includes such a link as a storage device (battery). IN traditional ways In electricity generation, energy reserves are accumulated in a preliminary, “non-electric” form, and this link, the energy storage unit, is located directly in front of the electric generator.

The reservoir of the hydroelectric power station is designed to accumulate potential energy river water in the gravitational field of the Earth, raising it to a certain height with the help of a dam. Thermal power plant accumulates in its storage facilities the reserves of solid or liquid fuel necessary for uninterrupted operation, or supplies it via pipeline natural gas, the calorific value of which guarantees the required energy supply. The reactor rods of nuclear power plants represent a supply of nuclear fuel that has a certain resource of nuclear energy available for use.

Constant power mode is available for all listed types of power generators. The amount of energy produced is regulated by within wide limits depending on the level of immediate energy consumption. Alternative sources (wind, tidal, geothermal, solar energy) cannot provide guaranteed constant power generator at the required this moment level. The storage device, therefore, is not so much a storage of resources as a damping device, making energy consumption less dependent on fluctuations in source power. The energy of the source is accumulated in the storage device, and later consumed, as needed, in the form electrical energy. Moreover, its price largely depends on the cost of the drive.

A characteristic feature of the storage device in alternative energy sources is that the energy accumulated in it can be spent on other purposes. For example, with their help, strong and super-strong magnetic fields can be generated.

The units of energy measurement accepted in physics and energy and the relationships between them: 1 kWh, or 1000 W 3600 s - the same as 3.6 MJ. Accordingly, 1 MJ is equivalent to 1/3.6 kWh, or 0.278 kWh

Some common energy storage devices:

Let's make a reservation right away: this review is not full classification storage devices used in the energy sector, in addition to those discussed here, there are thermal, spring, induction, and various other types of energy storage devices.

1. Capacitor type storage

The energy stored by a 1 F capacitor at a voltage of 220 V is: E = CU2 /2 = 1 2202 /2 kJ = 24 200 J = 0.0242 MJ ~ 6.73 Wh. The weight of one such electrolytic capacitor can reach 120 kg. Per unit mass specific energy turns out to be equal to just over 0.2 kJ/kg. Hourly operation of the drive is possible with a load within 7 W. Electrolytic capacitors can last up to 20 years. Ionistors (supercapacitors) have a high energy and power density (about 13 Wh/l = 46.8 kJ/l and up to 6 kW/l, respectively), with a resource of about 1 million recharging cycles. The undeniable advantage of a capacitor storage device is the ability to use the accumulated energy in a short period of time.

2. Gravity type storage devices

Energy storage devices of the pile driver type store energy when lifting a pile driver weighing 2 tons or more to a height of about 4 m. The movement of the moving part of the pile driver releases the potential energy of the body, imparting it to the electric generator. The amount of energy produced E = mgh in the ideal case (without taking into account friction losses) will be ~ 2000 10 4 kJ = 80 kJ ~ 22.24 Wh. The specific energy per unit mass of a copra woman turns out to be equal to 0.04 kJ/kg. Within an hour, the drive is capable of providing a load of up to 22 W. Expected service life mechanical design exceeds 20 years. The energy accumulated by a body in a gravitational field can also be spent in a short period of time, which is an advantage of this option.

The hydraulic accumulator uses the energy of water (weighing about 8-10 tons) pumped from a well into the tank of a water tower. In reverse motion, under the influence of gravity, the water rotates the turbine of the electric generator. A conventional vacuum pump can easily pump water to a height of up to 10 m. The stored energy is E = mgh ~ 10000 8 10 J = 0.8 MJ = 0.223 kW hour. The specific energy per unit mass turns out to be equal to 0.08 kJ/kg. The load provided by the drive for an hour is within 225 W. The drive can last 20 years or longer. The wind engine can directly drive the pump (without converting energy into electricity, which is associated with certain losses); the water in the tower tank can, if necessary, be used for other needs.

3. Flywheel based storage

The kinetic energy of a rotating flywheel is determined as follows: E = J w2/2, J means the intrinsic moment of inertia of the metal cylinder (since it rotates around the axis of symmetry), w is the angular velocity of rotation.

With radius R and height H, the cylinder has a moment of inertia:

J = M R^2 /2 = pi * p R^4 H/2

where p is the density of the metal - the material of the cylinder, the product pi* R^2 H is its volume.

The maximum possible linear speed of points on the surface of the cylinder Vmax (is about 200 m/s for a steel flywheel).

Vmax = wmax*R, whence wmax = Vmax/R

Maximum possible rotation energy Emax = J wmax^2/2 = 0.25 pi*p R2^2 H V2max = 0.25 M Vmax^2

The energy per unit mass is: Emax/M = 0.25 Vmax^2

The specific energy if the cylindrical flywheel is made of steel will be about 10 kJ/kg. A flywheel weighing 200 kg (with linear dimensions H = 0.2 m, R = 0.2 m) stores energy Emax = 0.25 pi 8000 0.22 0.2 2002 ~ 2 MJ ~ 0.556 kWh. The maximum load provided by the flywheel storage device for an hour does not exceed 560 W . The flywheel may well last 20 years or more. Advantages: rapid release of accumulated energy, the possibility of significantly improving characteristics by selecting the material and changing geometric characteristics flywheel.

4. Storage in the form of a chemical battery(lead acid)

A classic rechargeable battery, having a capacity of 190 Ah at an output voltage of 12 V and 50% discharge, is capable of delivering a current of about 10 A for 9 hours. The energy released will be 10 A 12 V 9 h = 1.08 kWh, or approximately 3.9 MJ per cycle. Taking the mass of the battery equal to 65 kg, we have a specific energy of 60 kJ/kg. The maximum load that the battery can provide for an hour does not exceed 1080 W. Guarantee period The service life for a high-quality battery is within 3 - 5 years, depending on the intensity of use. It is possible to directly receive electricity from the battery with an output current reaching thousands of amperes, with an output voltage of 12 V, corresponding to the automotive standard. Many devices designed for a constant voltage of 12 V are compatible with the battery; 12/220 V converters of varying output power are available.

5. Pneumatic type storage

Air pumped into a steel tank with a volume of 1 cubic meter to a pressure of 40 atmospheres performs work under conditions of isothermal expansion. The work A performed by an ideal gas under conditions T=const is determined according to the formula:

A = (M / mu) R T ln (V2 / V1)

Here M is the mass of the gas, mu is the mass of 1 mole of the same gas, R = 8.31 J/(mol K), T is the temperature calculated on the absolute Kelvin scale, V1 and V2 are the initial and final volume occupied by the gas (at this V2 / V1 = 40 when expanded to atmospheric pressure inside the tank). For isothermal expansion, the Boyle-Marriott law is valid: P1V1 = P2 V2. Let's take T = 298 0K (250C) For air M / mu ~ 40: 0.0224 = 1785.6 moles of substance, gas does work A = 1785.6 8.31 298 ln 50 ~ 16 MJ ~ 4.45 kWh per cycle. The walls of the tank, designed for a pressure of 40-50 atmospheres, must have a thickness of at least 5 mm, and therefore the mass of the storage device will be about 250 kg. Stored data pneumatic storage the specific energy will be equal to 64 kJ/kg. The maximum power provided by the pneumatic accumulator during an hour of operation will be 4.5 kW. Guaranteed lifespan, like most performance-based drives mechanical work their structural parts are from 20 years. Advantages of this type of storage: the possibility of locating the tank underground; the reservoir can be a standard gas cylinder using appropriate equipment; the wind motor is capable of directly transmitting movement to the compressor pump. In addition, many devices directly use the stored energy of compressed air in a tank.

We present the parameters of the considered types of energy storage devices in a summary table: