As an important material basis for human survival and development, energy is a strategic resource related to the national economy and people's livelihood. With the rapid development of our society and economy, the demand for energy is increasing day by day. The massive consumption of fossil energy has caused serious environmental pollution, and severe haze weather occurs frequently, which seriously affects people's health and living environment.
Recently, the state has put forward the strategic thinking of promoting energy consumption revolution, energy supply revolution, energy technology revolution, and energy system revolution. Vigorously promoting the strategic adjustment of the energy structure, improving the utilization efficiency of fossil energy, and popularizing the application of renewable energy are the inevitable choices to achieve sustainable social and economic development in my country, and also to solve my country's energy security and environmental pollution, implement energy conservation and emission reduction, and improve the greenness of the whole society. The strategic needs of the national policy of low carbonization level.
However, renewable energy power generation such as wind energy and solar energy has the characteristics of discontinuity, instability and uncontrollability. Large-scale integration into the power grid will have a serious impact on the safe and stable operation of the power grid, resulting in a large number of abandoned wind and light.
However, large-scale energy storage technology can effectively solve the problems of randomness, intermittency and volatility of renewable energy power generation, realize smooth power output and track planned power generation, thereby improving the grid's ability to absorb renewable energy power generation and solving the problem of wind curtailment. , Abandoned light problem. At the same time, it will also play an important role in grid leveling and peak regulation.
In order to meet the needs of different application fields, a variety of energy storage technologies have been researched and developed in the industry, and various energy storage technologies and their applicable scopes have been explored. These energy storage technologies have their own characteristics and applicable fields. Generally speaking, renewable energy power generation systems such as wind energy and solar energy have higher requirements on the power and reversible storage capacity of energy storage technology. Pumped water storage technology, flow battery technology, lithium-ion battery technology, super lead-acid battery technology, etc. have good application prospects in the field of large-scale energy storage technology.
Eight technical advantages
Compared with other large-scale energy storage technologies, all-vanadium flow battery technology has many advantages.
First, the all-vanadium redox flow battery energy storage system is safe and reliable in operation, can be recycled, and has a small environmental load in the life cycle and is environmentally friendly. The energy storage medium of the all-vanadium redox flow battery energy storage system is an electrolyte aqueous solution, which has high safety.
Second, the output power and energy storage capacity of the all-vanadium redox flow battery energy storage system are independent of each other, and the design and placement are flexible. The output power is determined by the size and quantity of the stack, while the energy storage capacity is determined by the concentration and volume of vanadium ions in the electrolyte solution. The output power of the all-vanadium redox flow battery system is in the range of hundreds of kilowatts to hundreds of megawatts, and the energy storage capacity is in the range of hundreds of kilowatt hours to hundreds of megawatt hours.
Third, the working principle of the all-vanadium redox flow battery is to realize the storage and release of electric energy through the change of the valence state of vanadium ions in the electrolyte. The reversibility of the reaction is good, there is no phase change, the electrolyte flows continuously in the electrodes inside the battery, and the charge-discharge state switching response is rapid. The number of charge and discharge cycles is more than 15,000 times, and the service life is 15 to 20 years. The life cycle is cost-effective.
Fourth, the positive and negative electrolyte solutions in the all-vanadium redox flow battery are of the same element, and the electrolyte solution can be used repeatedly through online regeneration. The stack and battery energy storage system are mainly composed of carbon materials, plastics and metal materials. When the all-vanadium redox flow battery system is discarded, the metal materials can be used continuously, and the carbon materials and plastics can be used as fuels. Therefore, the environmental load of the all-vanadium redox flow battery system in the whole life cycle is small and the environment is very friendly.
Fifth, the price is cheap. In recent years, with the continuous progress of all-vanadium redox flow battery material technology and battery structure design and manufacturing technology, the battery performance has been continuously improved, the energy efficiency of the stack can be maintained above 80%, and the working current density has increased from the original 60-80mA/c increased to 150mA/c. The power density of the battery is doubled, and under this condition, the cost is greatly reduced. Although the research and development cycle is very short and the state's investment is very low, the 1MW/5MW scale of the all-vanadium redox flow battery energy storage system has dropped from 7,000 yuan/kWh in 2013 to 3,500 yuan/kWh in 2016. Moreover, the number of charge and discharge cycles is more than 16,000 times, so the cost of its life cycle is very low.
Sixth, the all-vanadium flow battery energy storage system adopts a modular design, which is convenient for system integration and scale expansion. The all-vanadium redox flow battery stack is formed by stacking a plurality of single cells in a filter press method. The rated output power of a single stack of all-vanadium redox flow batteries is generally between 20 kW and 40 kW; the all-vanadium redox flow battery energy storage system is usually composed of multiple unit energy storage system modules, and the rated output power of the unit energy storage system modules is generally between 100 kW and 300 kW. Compared with other types of batteries, the rated output power of the all-vanadium flow battery stack and battery cell energy storage system module is large, which is convenient for the integration and scale expansion of the all-vanadium flow battery energy storage system.
Seventh, it has strong overload capacity and deep discharge capacity. When the all-vanadium redox flow battery energy storage system is running, the electrolyte solution is circulated in the stack by the circulating pump, and the influence of the diffusion of active substances in the electrolyte solution is small; moreover, the electrode reactivity is high, and the activation polarization is small. Therefore, the all-vanadium redox flow battery energy storage system has a good overload capacity. Moreover, the all-vanadium redox flow battery has no memory effect and has a good deep discharge capability.
Eighth, the energy density of flow batteries is relatively low, and all-vanadium flow batteries are more suitable for stationary large-scale energy storage power stations.
Industrial application is optimistic
The concept of flow battery was proposed by LHThaller (NASA Lewis Research Center, Cleveland, United States) in 1974. This type of battery undergoes a reversible redox reaction (that is, a reversible change in valence state) on the electrode through the active material in the positive and negative electrolyte solutions. ) to realize the mutual conversion of electrical energy and chemical energy.
During charging, the positive electrode undergoes an oxidation reaction, and the valence state of the active material increases; the negative electrode undergoes a reduction reaction, and the valence state of the active material decreases; the discharge process is the opposite.
The positive and negative electrolyte solutions of the flow battery are stored in external storage tanks, and are transported to the inside of the battery through pumps and pipelines for reaction. In theory, different redox stacks can form a variety of flow batteries.
The all-vanadium redox flow battery uses vanadium ions in different valence states as active materials, and realizes the mutual conversion of chemical energy and electrical energy through the change of the valence state of vanadium ions.
Large-scale battery energy storage technology needs to meet some basic requirements, namely, high safety; high cost performance in the life cycle; good economy; low environmental load in the life cycle and environmental friendliness, etc.
In contrast, among many energy storage technologies, flow battery energy storage technology has the advantages of high energy conversion efficiency, large storage capacity, free site selection, deep discharge, safety and environmental protection, etc., and has become a large-scale and efficient energy storage technology. One of the preferred technologies. Among many flow batteries, the all-vanadium flow battery energy storage technology is the most industrialized flow battery energy storage technology.