Supercapacitors will usher in great development due to new energy vehicles

  "Super Capacitor" will become another important power system after the recommended directory relay power battery. In 2017, there are 6 companies in the 1-4 batch recommendation catalogue, and 13 passenger cars are equipped with super capacitors, including Zhengzhou Yutong and Zhongtong Bus. Xiamen Golden Brigade and other leaders, and what is the relationship between supercapacitors and new energy vehicles?

What is a supercapacitor

Supercapacitor structure diagram

An electrochemical device through the electrolyte to the polarization of super capacitor energy storage (Supercapacitors, ultracapacitor), is from the 1970s and eighties developed. It is different from the traditional chemical power source. It is a power source with special performance between the traditional capacitor and the battery. It mainly relies on the electric double layer and the redox tantalum capacitor to store electric energy. However, there is no chemical reaction in the process of energy storage. This energy storage process is reversible, and it is precisely because this supercapacitor can be repeatedly charged and discharged hundreds of thousands of times. The basic principle is the same as other types of electric double layer capacitors, which use an electric double layer structure composed of activated carbon porous electrodes and electrolytes to obtain an extremely large capacity.

The outstanding advantages are high power density, short charge and discharge time, long cycle life and wide operating temperature range. It is the largest capacity among the electric double layer capacitors that have been put into mass production in the world.

Application of New Energy Bus

New energy buses are the mainstay of public transportation. In the field of new energy buses, supercapacitors are most widely used in urban hybrid bus braking energy recovery systems. The brake energy recovery system consisting of supercapacitor modules is capable of absorbing and storing all the kinetic energy generated by the vehicle during braking, releasing these energy when the passenger car starts or accelerates, thereby saving fuel consumption and reducing emissions.

Wang Binggang, head of the supervision and consulting expert group of the National 863 Program “Energy Saving and New Energy Vehicles”, said that the supercapacitor has high power density and fast charging and discharging characteristics. As a technical route of hybrid buses, supercapacitors are very suitable. Demonstration operation of city buses.

From the development of the whole technology system, the energy storage device has a game of energy density and power density. Generally, the energy density characteristics are good, and the power density characteristics are worse. Conventional lithium batteries have good energy and poor power, which are suitable for long-term output. The super capacitors have good power and are suitable for short-time high-power output.

In addition, the application range of supercapacitor is wide. Taking digital equipment as an example, people in the open air environment below -10 °C in the northeast region find that the mobile phone is quickly out of power, which is determined by the temperature characteristics of the battery, but the resistance of the super capacitor. The low temperature performance is very good.

At the beginning of 2016, when the state applied ternary lithium batteries to public transportation, the safety issue was specifically clarified. In terms of electrochemical system, there is no active metal ion inside the supercapacitor product, and the heat permeability is good. The safety performance from thermal runaway, puncture and combustion is relatively high, and it is suitable in the field of public transportation.

It is worth noting that the life of super capacitors is long, and the life of household car batteries is generally around two or three years. Super capacitors do not have this problem, and even exceed the life of the car. It is understood that Yutong Bus's first batch of new energy buses using super capacitor system in 2009 will complete its eight-year operational mission by the end of 2016.

Seeking development

The development of supercapacitors has been shrouded in the shadow of batteries (mainly nickel-metal hydride batteries, lithium batteries). The development of nickel-metal hydride batteries and lithium batteries is greatly facilitated by the huge amount of financial support from the government and large investors, and it is easier to focus on the world. In contrast, supercapacitors are difficult to get strong financial support, and technological progress and development are subject to a large degree of constraints. In addition, the high cost of supercapacitors and the low energy density are in sharp contrast with lithium batteries, which makes it cold in many fields, and is always replaced by batteries in practical applications. However, once the breakthrough in the technology of supercapacitors, it will have a great impetus to the development of the new energy industry.

At the same time, fortunately, in December 2016, the "China Super Capacitor Industry Alliance" jointly sponsored by more than 50 units in China's super capacitor field was formally established. It is understood that China Super Capacitor Industry Alliance will provide a common platform for all government departments, enterprises, universities and scientific research units dedicated to supercapacitors and related power sources to support the development of China's super capacitor industry. development of.

Supercapacitor advantages and disadvantages

Advantages: (1) The charging speed is fast, and the charging can reach more than 95% of its rated capacity in 10 seconds to 10 minutes;

(2) The cycle life is long, the frequency of deep charge and discharge cycles can reach 10,000 to 500,000 times, and there is no “memory effect”;

(3) The high current discharge capacity is super strong, the energy conversion efficiency is high, the process loss is small, and the high current energy cycle efficiency is ≥90%;

(4) High power density, up to 300W/KG~5000W/KG, equivalent to 5~10 times of battery;

(5) There is no pollution in the composition, production, use, storage and dismantling of raw materials, which is an ideal green power source;

(6) The charging and discharging circuit is simple, no charging circuit like rechargeable battery is needed, and the safety factor is high, and maintenance is free for long-term use;

(7) Good ultra-low temperature characteristics, the temperature range is wide -40 ° C ~ +70 ° C;

(8) Easy to detect, the remaining power can be read directly;

(9) The capacity range is usually 0.1F–1000F.

Disadvantages: (1) If used improperly, it will cause electrolyte leakage and other phenomena;

(2) Compared with aluminum electrolytic capacitors, it has a large internal resistance and thus cannot be used in an AC circuit;

Development and opportunity

At present, domestic supercapacitor manufacturers have a high concentration. Some manufacturers face the current situation of incomplete development of supercapacitor technology, do not dare to invest easily, adopt a wait-and-see strategy, and expect the market to have an example of getting involved in this field and succeeding. Other manufacturers are convinced that as long as the production cost of supercapacitors is greatly reduced, it can be quickly popularized only by its current fast charge and discharge characteristics.

In the automotive industry, with the strict control of carbon emissions and the rapid advancement of carbon credit policy, the application of intelligent start-stop control system provides a broad stage for supercapacitors, especially in plug-in hybrid vehicles .

Due to the frequent starting and stopping of electric vehicles, the discharge process of the battery varies greatly. During normal driving, the average power drawn by the electric vehicle from the battery is quite low, and the peaks during acceleration and climbing are quite high. Under the existing electric vehicle battery technology, the battery must balance the specific energy and specific power and the specific power and cycle life, and it is difficult to pursue high specific energy, high specific power and long in a set of energy systems. life. In order to resolve the contradiction between the driving range of electric vehicles and the acceleration of climbing performance, two energy systems can be considered, in which the main energy source improves the optimal driving range, while the auxiliary energy provides short-term time during acceleration and climbing. Auxiliary power. The energy of the auxiliary energy system can directly take the independent energy, and can also recover the renewable kinetic energy when the electric vehicle brakes or downhill, and use the super capacitor as the auxiliary energy. In the short term, the extremely low specific energy of the supercapacitor makes it impossible to use it alone as an electric vehicle energy system, but it has significant advantages as an auxiliary energy source. The best combination for use on electric vehicles is the battery-supercapacitor hybrid energy system, which separates the specific energy and specific power requirements of the battery. The supercapacitor has load balancing effect, and the discharge current of the battery is reduced. The available energy and service life of the battery are significantly improved; compared with the battery, the super capacitor can quickly and efficiently absorb the regenerative kinetic energy generated by the electric vehicle brake. The early and balanced performance of the supercapacitor and the energy recovery make the vehicle's driving range greatly improved. However, the system should comprehensively control and optimize the matching of the battery, super capacitor, motor and power inverter. The design and application of the power converter and its controller fully consider the matching between the motor and the super capacitor.

Judging from the current products of various manufacturers, supercapacitor enterprises are at the forefront of transformation and development. Although they have an irreplaceable position in wind power, they lack enterprise support in the new energy industry, and in the future, with the continuous subdivision of the market, industry technology With the continuous maturity, under the pressure of double integration and emissions, the application of supercapacitors will usher in a new explosion in the market.

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