Nature gave man a variety of energy sources: the sun, wind, rivers and others. The disadvantage of these free energy generators is the lack of stability. Therefore, during periods of excess energy, it is stored in storage devices and spent during periods of temporary recession. Energy storage devices are characterized by the following parameters:
- amount of stored energy;
- speed of its accumulation and returns;
- specific gravity;
- energy storage time;
- reliability;
- manufacturing and maintenance cost and others.
There are many ways to organize drives. One of the most convenient is the classification according to the type of energy used in the storage device, and according to the method of its accumulation and return. Energy storage devices are divided into the following main types:
- mechanical;
- thermal;
- electric;
- chemical.
Accumulation of potential energy
The essence of these devices is straightforward. When a load is lifted, potential energy is accumulated; when lowered, it performs useful work. Design features depend on the type of cargo. It can be solid, liquid orloose substance. As a rule, the designs of devices of this type are extremely simple, hence the high reliability and long service life. The storage time of the stored energy depends on the durability of the materials and can reach millennia. Unfortunately, such devices have low specific energy consumption.
Mechanical storage of kinetic energy
In these devices, energy is stored in the movement of a body. Usually this is an oscillatory or translational movement.
Kinetic energy in oscillatory systems is concentrated in the reciprocating motion of the body. Energy is supplied and consumed in portions, in time with the movement of the body. The mechanism is quite complex and capricious in setting. Widely used in mechanical watches. The amount of stored energy is usually small and is only suitable for the operation of the device itself.
Gyroscope powered storage devices
The store of kinetic energy is concentrated in a rotating flywheel. The specific energy of a flywheel significantly exceeds the energy of a similar static load. It is possible to receive or output significant power in a short period of time. The energy storage time is short, and for most designs is limited to a few hours. Modern technologies make it possible to bring the energy storage time to several months. Flywheels are very sensitive to shock. The energy of the device is in direct proportion to the speed of its rotation. Therefore, in the process of accumulation and return of energy, a change in the speed of rotation of the flywheel occurs. And for a load likeas a rule, a constant, low rotational speed is required.
More promising devices are superflywheels. They are made from steel tape, synthetic fiber or wire. The design may be dense or have empty space. If there is free space, the coils of the tape move to the periphery of rotation, the moment of inertia of the flywheel changes, part of the energy is stored in the deformed spring. In such devices, the rotation speed is more stable than in solid structures, and their energy consumption is much higher. They are also safer.
Modern super flywheels are made from Kevlar fiber. They rotate in a vacuum chamber on a magnetic suspension. Able to store energy for several months.
Mechanical storage using elastic forces
This type of device is capable of storing a huge specific energy. Of the mechanical drives, it has the highest energy intensity for devices with dimensions of several centimeters. Large flywheels with very high rotational speeds have a much higher energy capacity, but they are very vulnerable to external influences and have a shorter energy storage time.
Spring energy mechanical storage
Capable of delivering the highest mechanical power of any energy storage class. It is limited only by the tensile strength of the spring. The energy in a compressed spring can be stored for several decades. However, due to constant deformation, fatigue accumulates in the metal, and the spring capacitydecreases. At the same time, high-quality steel springs, under proper operating conditions, can work for hundreds of years without appreciable loss of capacity.
Spring functions can be performed by any elastic elements. Rubber bands, for example, are dozens of times superior to steel products in terms of stored energy per unit mass. But the service life of rubber due to chemical aging is only a few years.
Mechanical storage devices using the energy of compressed gases
In this type of device, energy is stored by compressing the gas. In the presence of an excess of energy, the gas is pumped under pressure into the cylinder using a compressor. As needed, compressed gas is used to turn a turbine or electric generator. At low capacities, it is advisable to use a piston motor instead of a turbine. Gas in a vessel under pressure of hundreds of atmospheres has a high specific energy density for several years, and with high-quality fittings - for decades.
Heat energy storage
Most of the territory of our country is located in the northern regions, so a significant part of the energy is forced to be spent for heating. In this regard, it is necessary to regularly solve the problem of keeping heat in the drive and extracting it from there if necessary.
In most cases, it is not possible to achieve a high density of stored thermal energy and any significant periods of its conservation. Existing effective devices indue to some of its features and high price are not suitable for wide application.
Storage due to heat capacity
This is one of the most ancient ways. It is based on the principle of accumulation of thermal energy when a substance is heated and heat transfer when it is cooled. The design of such drives is extremely simple. It can be a piece of any solid substance or a closed container with a liquid coolant. Thermal energy accumulators have a very long service life, an almost unlimited number of cycles of accumulation and release of energy. But the storage time does not exceed several days.
Electrical energy storage
Electric energy is the most convenient form of it in the modern world. That is why electric storage devices are widely used and most developed. Unfortunately, the specific capacity of cheap devices is small, and devices with a high specific capacity are too expensive and short-lived. Electric energy storage devices are capacitors, ionistors, batteries.
Capacitors
This is the most massive type of energy storage. Capacitors are capable of operating at temperatures from -50 to +150 degrees. The number of energy accumulation-return cycles is tens of billions per second. By connecting several capacitors in parallel, you can easily obtain the required capacitance. In addition, there are variable capacitors. Changing the capacitance of such capacitors can be done mechanically or electrically or by temperature. Most often, variable capacitors can be found inoscillatory circuits.
Capacitors are divided into two classes - polar and non-polar. The service life of polar (electrolytic) is shorter than non-polar, they are more dependent on external conditions, but at the same time they have a greater specific capacity.
As energy storage capacitors are not very successful devices. They have a low capacity and an insignificant specific density of stored energy, and its storage time is calculated in seconds, minutes, rarely hours. Capacitors have found application mainly in electronics and power electrical engineering.
The calculation of the capacitor, as a rule, does not cause difficulties. All the necessary information on different types of capacitors is presented in technical manuals.
Ionistors
These devices occupy an intermediate position between polar capacitors and batteries. They are sometimes referred to as "supercapacitors". Accordingly, they have a huge number of charge-discharge stages, the capacity is greater than that of capacitors, but slightly less than that of small batteries. The energy storage time is up to several weeks. Ionistors are very sensitive to temperature.
Power batteries
Electrochemical batteries are used if you need to store a lot of energy. Lead-acid devices are best suited for this purpose. They were invented about 150 years ago. And since then, nothing fundamentally new has been introduced into the battery device. Many specialized models have appeared, the quality of components has increased significantly,battery reliability. It is noteworthy that the device of a battery created by different manufacturers differs only in minor details for different purposes.
Electrochemical batteries are divided into traction and starting. Traction are used in electric transport, uninterruptible power supplies, power tools. Such batteries are characterized by a long uniform discharge and its large depth. Starter batteries can deliver high current in a short amount of time, but deep discharge is unacceptable for them.
Electrochemical batteries have a limited number of charge-discharge cycles, on average from 250 to 2000. Even if not used, they fail after a few years. Electrochemical batteries are temperature sensitive, require long charging times, and require strict maintenance.
The device needs to be recharged periodically. The charge of the battery installed on the vehicle is carried out in motion from the generator. In winter, this is not enough, a cold battery does not accept a charge well, and the consumption of electricity to start the engine increases. Therefore, it is necessary to additionally charge the battery in a warm room with a special charger. One of the significant disadvantages of lead-acid devices is their heavy weight.
Batteries for low power devices
If mobile devices with low weight are required, then choose the following types of batteries: nickel-cadmium,lithium-ion, metal-hybrid, polymer-ion. They have a higher specific capacity, but the price is much higher. They are used in mobile phones, laptops, cameras, camcorders and other small devices. Different types of batteries differ in their parameters: the number of charge cycles, shelf life, capacity, size, etc.
High power lithium-ion batteries are used in electric vehicles and hybrid vehicles. They are light weight, high specific capacity and high reliability. At the same time, lithium-ion batteries are very flammable. Ignition can occur from a short circuit, mechanical deformation or destruction of the case, violations of the charge or discharge modes of the battery. Putting out a fire is quite difficult due to the high activity of lithium.
Batteries are the backbone of many appliances. For example, an energy storage device for a phone is a compact external battery placed in a durable, waterproof case. It allows you to charge or power your cell phone. Powerful mobile energy storage devices are capable of charging any digital devices, even laptops. In such devices, as a rule, high-capacity lithium-ion batteries are installed. Energy storage for the home is also not complete without batteries. But these are much more complex devices. In addition to the battery, they include a charger, a control system, and an inverter. The devices can operate both from a fixed network and from other sources. The output power is 5 kW on average.
Driveschemical energy
Distinguish between "fuel" and "non-fuel" types of drives. They require special technologies and often bulky high-tech equipment. The processes used make it possible to obtain energy in different forms. Thermochemical reactions can take place at both low and high temperatures. Components for high-temperature reactions are introduced only when it is necessary to obtain energy. Before that, they are stored separately, in different places. Components for low temperature reactions are usually in the same container.
Energy storage by running fuel
This method includes two completely independent stages: the accumulation of energy ("charging") and its use ("discharging"). Traditional fuel, as a rule, has a large specific energy capacity, the possibility of long-term storage, and ease of use. But life does not stand still. The introduction of new technologies places increased demands on fuel. The task is solved by improving existing and creating new, high-energy fuels.
The wide introduction of new samples is hindered by insufficient development of technological processes, high fire and explosion hazards in work, the need for highly qualified personnel, and the high cost of technology.
Fuelless chemical energy storage
In this type of storage, energy is stored by converting some chemicals into others. For example, slaked lime, when heated, goes into a quicklime state. When discharging, the stored energyreleased as heat and gas. This is exactly what happens when lime is slaked with water. In order for the reaction to start, it is usually enough to combine the components. In essence, this is a kind of thermochemical reaction, only it proceeds at a temperature of hundreds and thousands of degrees. Therefore, the equipment used is much more complex and expensive.
