Vanadium flow batteries are an ideal technology route for high-power, high-capacity, and long-term energy storage, and are expected to become an important way of large and medium-sized energy storage in the future.
1. Analysis of Advantages and Disadvantages of Vanadium Batteries
All vanadium flow battery is a liquid redox renewable battery that uses metal vanadium ions as the active substance. The positive and negative active substances of all vanadium flow batteries are stored in separate electrolyte storage tanks. When charging and discharging the battery, the positive and negative electrolytes undergo redox reactions on both sides of the ion exchange membrane. At the same time, through the action of an external pump, the electrolyte in the storage tank is continuously fed into the positive and negative chambers to maintain ion concentration and achieve charging and discharging of the battery.
Schematic diagram of vanadium battery operation
Advantages:
By increasing the quantity and area of electricity, power can be effectively increased, and by increasing the volume of electrolyte, the capacity of vanadium flow batteries can be increased. Therefore, vanadium flow batteries can achieve high operating power and capacity. Unlike lithium batteries that use non-aqueous electrolytes, vanadium flow batteries use vanadium ion aqueous solutions as the electrolyte, greatly reducing the possibility of overheating, combustion, and explosion, and providing better safety. In addition, due to the fact that the positive and negative active substances in vanadium flow batteries only exist in the positive and negative electrolytes, unlike other batteries, which undergo changes in the electrical structure during charging and discharging (resulting in capacity decay), the battery has a long service life.
Disadvantages:
The mass and volume of vanadium flow batteries are large, so their specific energy and specific power are much lower than other battery systems, making them unsuitable for scenarios such as electric vehicles. Compared to lithium batteries, vanadium flow batteries have a major disadvantage in terms of cost, mainly from the electrolyte and battery stack. Reducing the cost of both is an industry consensus. In addition, vanadium flow batteries have strict environmental temperature requirements. The pentavalent vanadium in the positive * electrolyte is prone to precipitation and blockage of the flow channel at high temperatures (above 45 ℃), and the electrolyte solidifies at low temperatures (below the freezing point of the electrolyte). Therefore, the general operating temperature is required to be between 0~45 ℃, which limits the application of vanadium flow batteries.
Comparison of initial construction costs of different energy storage systems (yuan/kWh)
2. Investment cost analysis of all vanadium liquid flow energy storage
Initial investment cost analysis
The initial investment cost of an all vanadium flow battery energy storage system continuously decreases with the increase of energy storage time.
According to Zhang Huamin's analysis in the article "Technical Progress of All Vanadium Flow Batteries, Price Analysis and Prospects of Different Energy Storage Duration Systems", taking the megawatt level all vanadium flow battery energy storage system as an example, when the price of V ₂ O Å is 100000 yuan/ton, the price of electrolyte used in vanadium flow batteries is about 1500 yuan/kWh, and the market price of battery energy storage systems other than electrolytes is 6000 yuan/kW.
When the energy storage duration is 1 hour, the initial investment cost of the energy storage system is 7500 yuan/kWh. However, when the energy storage duration is extended to 4 hours, the price excluding the electrolyte is allocated to 1500 yuan/kWh. At this time, the total price of the all vanadium flow battery energy storage system is 3000 yuan/kWh. Therefore, the longer the working time of the all vanadium flow battery energy storage system, the cheaper the price per kWh.
Initial investment cost of all vanadium flow battery energy storage systems with different energy storage durations (unit: yuan/kWh)
Full Life Cycle Cost Analysis
The full life cycle cost of vanadium flow batteries is lower.
Due to the renewable and recyclable use of electrolyte in all vanadium flow batteries, their residual value is very high. Taking the vanadium flow battery energy storage system with a storage time of 4 hours as an example, the estimated residual value of scrap metal is 300 yuan/kW, equivalent to 75 yuan/kWh, and the residual value of electrolyte is about 70% of the original value, which is 1050 yuan/kWh. The total residual value is 1125 yuan/kWh, and the actual cost is 1875 yuan/kWh.
For a system with a storage time of 10 hours, the residual value of scrap metal is equivalent to 30 yuan/kWh, with a total residual value of 1080 yuan/kWh, and the actual cost is only 1020 yuan/kWh.
Therefore, for all vanadium flow battery energy storage systems, the longer the energy storage time, the lower the full life cycle cost.
Life cycle cost estimation of all vanadium flow battery energy storage systems with energy storage durations of 4 hours and 10 hours, respectively
Vanadium flow batteries are one of the promising development directions for large-scale long-term energy storage. Suitable for long-term and large-scale energy storage forms mainly include pumped storage, compressed air energy storage, and vanadium flow batteries.
Comparison of the characteristics of three long-term energy storage technologies
Pumped storage, as a mature and stable energy storage technology, is a key form of energy storage investment and construction in China. The main limitations of pumped storage are the high requirements for project construction site selection and the long construction period. Compressed air energy storage is also a mature technology, but the energy conversion efficiency of the system is low and the project location is also limited.
Compared with these two energy storage technologies, vanadium flow battery has a lower energy storage limit than pumped storage, but it has advantages such as high system safety, short project construction cycle, and flexible site selection. With technological progress, the economic advantages of vanadium flow battery will gradually strengthen, and it is expected to become one of the important technical routes for large-scale long-term energy storage in the future.