EDLC (ultracapacitors) - device, types, application
Currently, they are widely used devices that consume high power for a short period of time, for example: electronic locks, relays, motors, pulse emitters. It is not always possible for them to use a battery as a buffer source of energy. Difficulties may arise with the formation of powerful short-term currents. For such situations, they began to use ionistors or supercapacitors, which can be installed instead of the battery or in combination with it. A technology based on the use of the effect of the formation of a double electric layer is used to manufacture these elements. This compares favorably with batteries and accumulators.
Industrial EDLCs appeared not so long ago, but both domestic and foreign manufacturers are already engaged in mass production.
What are ultracapacitors
Energy-intensive systems place high demands on power supplies. Various modern equipment requires the accumulation and supply of a certain energy. To solve this problem, use batteries or ultracapacitors connected to the battery. In the latter version, EDLC (molecular energy storage devices) play the role of insurance against voltage drop. Ultracapacitors are characterized by a low energy density and high power, which ensures efficient discharge to the load. When you turn on the device in parallel with the battery, the pulse load on it is reduced, which allows to extend the service life.
Ultracapacitors are electrochemical capacitors with high power densities. They have better technical characteristics than batteries. These elements charge and discharge faster.
In the future, the developers plan to completely replace the batteries with these devices. They can become alternative power sources in various fields, for example, in the production of automobiles. Ultracapacitors are used in wind power structures and solar panels. Such devices are a combination of a standard capacitor and a battery.
One of the differences between EDLC and conventional capacitors is the presence of a double electric layer, which allows you to accumulate a significant amount of energy. The design combines such characteristics as the speed of charging and discharging the capacitor and the battery capacity. Such devices differ from conventional capacitors in the absence of a conventional dielectric between the electrodes.
EDLC differ in the following characteristics:
1. Internal resistance (measured in milliOhms).
2. The maximum current. (A).
3. Rated voltage (V).
4. Power consumption(F).
5. Self-discharge parameters.
Activated carbon or carbon on a foam basis is used as electrodes in the device. These components are placed in an electrolyte. The separator is designed to protect the device from short circuit electrodes. In modern devices, an electrolyte based on an acid or a crystalline alkali solution is not used, since these components have a high level of toxicity.
The internal cavities of the structure contain an electrolyte that stores electrical energy when interacting with the plates.
The first electrochemical EDLC (molecular energy stores) were developed more than 50 years ago. They were made on the basis of porous carbon electrodes. They are currently used in some electrical appliances.
Compared with lithium-ion batteries, modern EDLC are characterized by a large resource and a high discharge rate.
When using EDLC, a more economical mode of operation can be achieved by accumulating excess energy.
Between the plates of the structure is not a standard dielectric layer, but a thicker layer, which allows a thin gap. At the same time, the device provides the ability to produce electricity in large volumes. A ultracapacitor accumulates and consumes charges faster than alternatives. A double dielectric layer increases the area of the electrodes. This improves electrical performance.
Differences between ultracapacitors and batteries
Ultracapacitors are often used instead of batteries. Standard capacitors can store a small amount of electricity. Ultracapacitors can accumulate charges thousands, millions and billions of times more. Similar devices work faster than batteries. This is due to the fact that the ultracapacitor creates statistical charges on solids, and the batteries depend on slow-moving chemical reactions.
Batteries are characterized by a higher energy density, and EDLC have a higher power density. Ultracapacitors are able to function at low voltages, and to get more voltage, they need to be connected in series. This option is necessary for more powerful equipment.
The technology of EDLC can find application in energy and instrument engineering. One application is for use in wind turbines. Such devices help smooth out intermittent wind power.
Portable electronic devices use various types of power supplies. In devices such as tablets, smartphones and laptops, specific energy consumption is important. The higher this indicator, the higher the capacity of the device with the same physical parameters.
Installation of a device with a more significant specific energy consumption will increase the operating time of mobile equipment without increasing its parameters. Therefore, smartphones often use polymer batteries, which are leaders in small-sized rechargeable power supplies.
Rechargeable batteries have a limited resource. With intensive use, the resource of the device is a critical factor that shortens the life cycle of the equipment. Therefore, more promising devices include EDLC. They are an ideal energy storage device.
The EDLC is similar to an electrolytic capacitor, but with the same dimensions it has a large capacity. Such devices can accumulate a large amount of energy in a short period of time, which will reduce the charging time to a minimum value. Ultracapacitors can withstand tens of thousands of cycles without visible degradation.
Due to the low toxicity of materials for the manufacture of EDLC, they are easier to dispose of than similar options. But due to the high self-discharge current, these devices are not suitable for very long-term storage of electricity. EDLC are great for wireless peripherals. Here, such properties as efficiency and high charge speed manifest themselves.
A wireless device with an EDLC requires daily recharging. But this procedure will take several minutes.
Ultracapacitors are of the following types:
1. Pseudo-capacitors are equipped with solid electrodes. Capacitance depends not only on electrostatic processes, but also on Faraday reactions with the movement of charges.
2. Hybrids are an adapter between the battery and the capacitor. They are able to accumulate and give charge in a double electric layer. The electrodes are made of various materials, and the accumulation of charges is produced by different mechanisms. Redox reactions increase the specific capacity of the mechanism.
3. Two-layer ultracapacitors consist of porous electrodes separated by a separator. The electric charge in such devices is determined by the capacity of the double electric layer. The electrolyte is a connecting conductor with ionic conductivity.
Ultracapacitors come in many shapes and sizes. The main purpose of such devices is to duplicate the main source when the voltage drops.
To create hybrid devices, cathodes of a special kind are used. They are made from graphene of the hyperoxidized type. Graphene is a two-dimensional carbon modification in which atoms are placed in a single layer. This component is characterized by high chemical resistance.
The principle of operation of the EDLC is similar to a conventional capacitor. But these devices differ in the materials used. The plates are made of porous material, which is an excellent conductor. This allows you to increase the capacity of the device. An electrolyte is used as a dielectric, which reduces the distance between the plates and increase the capacity.
In the ultracapacitor, the charge accumulates as a result of the formation of a double electric layer on the electrode during the adsorption of ions from electrolytes.
The principle of operation is the expansion of the potential difference to current outputs. In this case, negative ions are created at the cathode, and positive ions are created at the anode. The separator passes electrolyte ions and prevents a short circuit between the electrodes. Electricity is stored in a static way. In the process of charge-discharge there are no reactions of the electrochemical type.
Ultracapacitors are able to accumulate a large amount of energy in a short period of time, which reduces the time for recharging devices.
Modern ion batteries can give off only 60% of the energy spent on charging them. For ultracapacitors, this indicator exceeds 90%. Another important advantage is the large resource. In many types of batteries, a decrease in capacity occurs after several hundreds of discharge-discharge cycles. And EDLC withstand up to a million cycles without breaking.
Unit cell designs allow you to create modules of various sizes and any voltage. Devices can be made with cooling of various types - air, water and natural.
Advantages and disadvantages
You should choose ultracapacitors for the following benefits:
1. Charge and discharge quickly. They can be used when it is not possible to put the battery due to prolonged recharging.
2. EDLC have a large number of charge-discharge cycles compared to other equipment.
3. For recharging, special devices are not required, which facilitates maintenance.
4. Devices are lighter than batteries and are smaller.
5. Extensive operating temperature range from -45 to 70 °C.
6. Longer life compared to rechargeable batteries.
7. High capacitance and efficiency of discharge cycles.
8. Ecological cleanliness, durability and reliability.
9. Excellent power density.
10. Allowed full discharge.
Some disadvantages cause difficulties with the operation:
1. Costly items.
2. Low characteristics of rated voltage. To deal with the problem requires a series connection of several elements.
3. If the temperature is not observed, the device may break quickly.
The device must be protected against short circuit, as this may cause a rise in temperature. As a result, the element will need a replacement.
The unique characteristics of EDLC find application in various fields of technology.
Ultracapacitors are used in the following variants of technology:
1. Public transport. In electric buses, instead of batteries, EDLC are installed. They are charged during the boarding and boarding of passengers. Such vehicles are able to go around traffic jams and breaks in contact lines.
2. Electric cars. One of the problems with such vehicles is the long charging time. The ultracapacitor allows charging at short stops.
3. Бытовая электроника. Устройства применяются в фотовспышках и другом оборудовании. Они обеспечивают быструю подзарядку.
4. Non-polar capacitors are used in wind turbines and acid batteries.
5. EDLC are used in damping systems of energy loads, as well as in equipment for starting electric motors.
6. Ultracapacitors are needed in complexes in which critical loads are provided. For mobile towers, hospital facilities and port equipment.
7. The devices are used for backup power sources of a PC, as well as in microprocessors and mobile phones.
To improve the operation of the car radio, you can purchase and put an EDLC. It allows you to smooth out voltage fluctuations during ignition on. In some countries, buses without traction batteries are used, and all work is carried out by ionizers.
In the course of the tests, it was found that such devices are superior to lead-acid batteries in wind turbines. Ultracapacitors are in demand in uninterruptible power systems, in which it is necessary to ensure fast power transmission.
There are approximately 66 of the largest manufacturers of EDLC in the world.
Prospects for use
EDLC are becoming more perfect every year. An important parameter to which scientists pay special attention is the increase in specific capacity. After some time, it is planned to replace the batteries with such devices. Such elements allow you to replace batteries in various technical fields. Experts have high hopes for the development of graphene devices. The use of innovative material will help in the near future to create products with high rates of stored specific energy.
The EDLC of the new sample is several times superior to alternative options. These elements are based on a porous structure. Graphene is used, on which ruthenium particles are distributed. The advantage of graphene foam is its ability to retain particles of transition metal oxides. Such ultracapacitors operate on an aqueous electrolyte, which allows for safe operation.
In the future, new items will be used in the manufacture of personal electric vehicles. Devices based on graphene foam can be recharged up to 8,000 times without deterioration in quality.
In the field of automobile construction, the development of alternative types of fuel and high-energy energy storage devices is underway. Similar devices can be used for freight transport, electric cars and trains.
In the automotive industry, ultracapacitor batteries find the following applications:
1. The starter is connected in parallel with the starter batteries. It is used to increase the operational life and improve the starting characteristics of the engine.
2. For stable power supply of high-power speakers in the car.
3. Buffer batteries are suitable for use in hybrid vehicles. They are characterized by small capacity and significant power output.
4. Traction batteries are relevant when used as the main power source.
Ultracapacitors have many advantages over batteries in the automotive industry. They withstand voltage surges perfectly. Devices are characterized by ease, so you can install a large number of them.
For the microelectronics industry, new technologies are being developed for the production of compact ultracapacitors. In the manufacture of electrodes, special methods of deposition of a special carbon film on a thin substrate of silicon dioxide are used.
The use of ultracapacitors allows the implementation of environmental energy saving technologies. In the future, it is planned to expand the scope of application of such devices for the automotive, mobile, and communications industries.