1, super capacitor energy storage
According to the theory of electrochemical electric double layer, it is also called electric double layer capacitor. The distance between the two charge layers is very small (generally less than 0.5 mm). The special electrode structure increases the electrode surface area by 10,000 times, and the capacitance is extremely large.
The development of super capacitor energy storage has a history of more than 50 years, and the technology has made rapid progress in the past two decades. Compared with traditional capacitors, its capacitance has been greatly increased, reaching the order of several thousand farads, and its specific power density can reach ten times that of traditional capacitors.
Supercapacitor energy storage directly stores electric energy in the electric field, with no energy form conversion and fast charging and discharging time, which is suitable for improving power quality. Because of its low energy density, it is suitable to be used in combination with other energy storage devices.
2. Superconducting energy storage
Superconducting energy storage system consists of a coil made of superconducting material, a power conditioning system (PCS) and a cryogenic refrigeration system.
Energy is stored in the magnetic field in the form of DC current circulating in the superconducting coil.
Superconducting energy storage is suitable for improving power quality, increasing system damping and improving system stability, especially for suppressing low-frequency power oscillation.
However, due to its high cost and complex maintenance, although there are commercial low-temperature and high-temperature superconducting energy storage products, they are rarely used in the power grid, and most of them are experimental. The application of SMES in power system depends on the development of superconducting technology (especially the development of materials, low cost, refrigeration, power electronics and other technologies).
3. Lead acid battery
Lead-acid battery is one of the most widely used batteries in the world. The anode (PbO2) and cathode (Pb) in lead-acid battery are immersed in electrolyte (dilute sulfuric acid), and a potential of 2V will be generated between the two electrodes, which is the principle of lead-acid battery.
Lead-acid batteries are often used as emergency power supply or standby power supply for power systems. In the past, most independent photovoltaic power generation systems were equipped with such batteries. At present, it is gradually replaced by other batteries (such as lithium-ion batteries).
4. Lithium-ion battery
Lithium-ion battery is actually a lithium-ion concentrated battery, and the anode and cathode are composed of two different lithium-ion intercalation compounds.
When charging, Li+ comes out from the positive electrode and is embedded into the negative electrode through the electrolyte. At this time, the negative electrode is in a lithium-rich state and the positive electrode is in a lithium-poor state. On the contrary, Li+ is deintercalated from the negative electrode and inserted into the positive electrode through the electrolyte, and the positive electrode is in a lithium-rich state and the negative electrode is in a lithium-poor state.
Lithium-ion battery has almost become the most widely used battery in the world because of its application in electric vehicles, computers, mobile phones and other portable mobile devices.
The high energy density and power density of lithium-ion batteries are the main reasons why they can be widely used and concerned.
Its technology has developed rapidly. In recent years, due to large-scale production and application in many occasions, its price has dropped rapidly, so it has been used more and more in power system.
Lithium-ion battery technology is still developing, and the current research focus is to further improve its service life and safety, reduce costs and develop new anode and cathode materials.
5, sodium sulfur battery
The anode of sodium-sulfur battery is composed of liquid sulfur, the cathode is composed of liquid sodium, and there is a β aluminum tube made of ceramic material in the middle. The working temperature of the battery should be kept above 300℃, so that the electrode is in a molten state.
NGK Corporation of Japan is the only manufacturer in the world that can manufacture high-performance sodium-sulfur batteries. At present, 50kW modules are used, and a MW-class large-capacity battery module can be composed of several 50kW modules.
Japan, Germany, France, the United States and other places have built more than 200 such energy storage power stations, which are mainly used for load balancing, peak shifting and valley filling, improving power quality and renewable energy generation, and the battery price is still high.
6, all vanadium flow battery
In a flow battery, energy is stored in an electroactive substance dissolved in a liquid electrolyte, and the liquid electrolyte is stored in a tank outside the battery. Electrolyte stored in the tank is pumped into the battery stack by a pump, and electrical energy is converted into chemical energy or chemical energy into electrical energy through electrodes and thin films.
There are many systems of flow battery, among which vanadium flow battery (VRFB) is the most concerned.
This battery technology was first invented by the University of New South Wales in Australia, and later it was transferred to VRB in Canada.
After 20 10, it was acquired by China Puneng Company, and the products of China Puneng Company have been applied in some pilot projects at home and abroad.
The power and energy of the battery are irrelevant, and the stored energy depends on the size of the energy storage tank, so it can store energy for several hours to several days, and the capacity can also reach MW level, which is suitable for application in power systems.
Advantages and disadvantages of energy storage:
Among all kinds of energy storage systems, lithium-ion battery energy storage is a mature energy storage method at present. Lithium ion secondary battery with olivine lithium iron phosphate as active material has many advantages, such as high energy density, low manufacturing cost and long service life. With the development of electric vehicle industry, the estimation of state of charge, battery integration technology and management system related to lithium iron phosphate battery have been widely and deeply studied. However, most of these studies are carried out under the use environment, operating conditions and conditions of electric vehicles, and their research results and conclusions are not completely applicable to the power grid energy storage system characterized by large-scale energy input/output.
Definition of energy storage:
Broadly speaking, energy storage is energy storage, which refers to the cyclic process of storing one energy form in the same form, or converting it into another energy form through a certain medium or equipment, and releasing it in a specific energy form according to the needs of future applications.
In a narrow sense, for the storage of electric energy, energy storage refers to a series of technologies and measures that use chemical or physical methods to store the generated energy and release it when necessary.
Comparison of advantages and disadvantages of nine energy storage battery technologies;
First, lead-acid batteries
Main advantages:
1, the raw materials are easily available and the price is relatively low;
2. Good high rate discharge performance;
3. Good temperature performance, which can work at -40~+60℃;
4. Suitable for floating charge, long service life and no memory effect;
5. Waste batteries are easy to recycle, which is beneficial to environmental protection.
Main disadvantages:
1, the specific energy is low, generally 30 ~ 40Wh/kg；;
2, the service life is not as good as that of Cd/Ni battery;
3, the manufacturing process is easy to pollute the environment, and must be equipped with three wastes treatment equipment.
Second, Ni-MH battery
Main advantages:
1. Compared with lead-acid battery, the energy density is greatly improved, with the weight energy density of 65Wh/kg and the volume energy density of 200 wh/L;
2, the power density is high, and it can be charged and discharged with large current;
3. Good low-temperature discharge characteristics;
4. Cycle life (increased to 1000 times);
5, environmental protection and no pollution;
6. The technology is more mature than lithium-ion batteries.
Main disadvantages:
1, normal working temperature range-15~40℃, poor high temperature performance;
2. The working voltage is low, and the working voltage range is1.0 ~1.4v;
3. The price is more expensive than lead-acid battery and nickel-hydrogen battery, but the performance is worse than lithium-ion battery.
Three. Lithium-ion batteries
Main advantages:
1, high specific energy;
2, the voltage platform is high;
3, good cycle performance;
4. No memory effect;
5, environmental protection, no pollution; At present, it is one of the most potential power batteries for electric vehicles.
Fourth, supercapacitors.
Main advantages:
1, high power density;
2. The charging time is short.
Main disadvantages: the energy density is low, only 1- 10Wh/kg, and the cruising range of supercapacitors is too short to be used as the mainstream power supply for electric vehicles.
Verb (abbreviation of verb) fuel cell
Main advantages:
1, high specific energy and long automobile mileage;
2, the power density is high, and it can be charged and discharged with large current;
3, environmental protection, no pollution.
Main disadvantages:
1, the system is complex and the technology maturity is poor;
2. The construction of hydrogen supply system lags behind;
3. There is a high demand for sulfur dioxide in the air. Due to the serious air pollution in China, the life of fuel cell vehicles in China is very short.
Six, sodium sulfur battery
Advantages:
1, high specific energy (theoretical 760 wh/kg; Actual 390 wh/kg);
2. High power (discharge current density can reach 200 ~ 300ma/cm2);
3, fast charging speed (30min full);
4. Long service life (15 years; Or 2,500 to 4,500 times);
5, pollution-free, recyclable (the recovery rate of Na and S is close to100%); 6, no self-discharge phenomenon, high energy conversion rate;
Insufficient:
1, the working temperature is high, its working temperature is 300~350 degrees, and the battery needs some heating and insulation when working, so it starts slowly;
2, the price is expensive, 10000 yuan/degree;
3. Poor security.
Seven, flow battery (vanadium battery)
Advantages:
1, safe deep discharge;
2, large scale, unlimited storage tank size;
3. It has a large charge and discharge rate;
4. Long service life and high reliability;
5, no emission and low noise;
6, fast charge and discharge switching, only 0.02 seconds;
7. Site selection is not restricted by region.
Disadvantages:
1, cross contamination of positive and negative electrolytes;
2. Some use expensive ion exchange membranes;
3. The two solutions are large in volume and low in specific energy;
4. The energy conversion efficiency is not high.
Eight, lithium air battery
Fatal defect: Lithium oxide (Li2O), the product of solid-state reaction, will accumulate on the positive electrode, which will hinder the contact between electrolyte and air, thus leading to the stop of discharge. Scientists believe that the performance of lithium-air battery is 10 times that of lithium-ion battery, and it can provide the same energy as gasoline. Lithium-air batteries absorb oxygen from the air to charge, so they can be smaller and lighter. Many laboratories around the world are studying this technology, but if there is no major breakthrough, it may take 10 years to realize commercialization.
9. Lithium-sulfur battery (Lithium-sulfur battery is a large-capacity energy storage system with great development prospect)
Advantages:
1, the energy density is high, and the theoretical energy density can reach 2600 wh/kg;
2, the cost of raw materials is low;
3. Less energy consumption;
4. Low toxicity.