AA Carbon battery.The world's all-vanadium redox flow battery VRB technology development

　　Development status of all-vanadium redox flow battery VRB technology in the world. Some energy generation systems, such as wind power generation, solar energy, etc., are affected by natural conditions such as climate change and wind strength, and their electrical energy output is characterized by instability and intermittentness. The large changes in mechanical power will cause fluctuations in the active and reactive power output of the generator, which will also degrade the power quality of the power grid and cause a waste of electrical energy. At present, a new international wind power storage technology, the all-vanadium redox flow battery (Vanadium Redox Battery, VRB), has entered the practical stage. Through efficient conversion and storage of energy, it ensures stable electric power output and improves the security and reliability of the power grid.

　　The development status and shortcomings of VRB technology in my country

　　At present, many research institutions such as the Chinese Academy of Engineering Physics, the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences, and Tsinghua University have carried out a series of related research on all-vanadium redox flow batteries and achieved certain results. In 1995, the Institute of Electronic Engineering of the China Academy of Engineering Physics was the first to conduct research on VRB batteries in China and successfully developed a 500W, 1kW prototype. It has patents such as electrolyte solution preparation and conductive plastic molding. In March 2006, the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences successfully developed a 10kW test stack and passed the acceptance of the National Ministry of Science and Technology, marking a phased progress in my country's all-vanadium redox flow battery system. Tsinghua University utilizes nearly two decades of research experience and technology accumulation in the preparation of membrane separation functional materials, membrane process and equipment design, as well as rich theoretical research results in the thermodynamics of electrolyte solutions, physical chemistry of functional membrane materials, and mass transfer in chemical processes. He has achieved research results in stack flow channel design, stack sealing structure, and locking methods, and has applied for 3 patents. And successfully developed an all-vanadium redox flow battery testing platform. Compared with foreign countries, the research on all-vanadium flow batteries in my country is still in its infancy in terms of key materials for flow batteries, including ion exchange membranes, electrode materials, high-concentration electrolytes, and engineering amplification technology. Active efforts are needed to strive for progress in recent years. Make breakthrough progress. All-vanadium flow batteries have good application prospects in the power supply of large power companies, remote areas and medium-sized power users, and ordinary residential users. Its technical characteristics of high efficiency and energy saving have long-term implications for the development of new energy in my country. Impact.

　　VRB technology principles and development

　　The principle of the all-vanadium redox flow battery (VRB) was first proposed in 1984 by researchers such as Maria Skyllas-Kazacos of the University of New South Wales. Afterwards, through technology transfer and development, it has been intensively studied in Australia, Japan and Canada. At present, the all-vanadium redox flow battery technology developed by Canada's VRBpowerSystems and Japan's Sumitomo Electric has entered the practical stage. The following is an introduction to the technical principles and characteristics of all-vanadium redox flow batteries based on the latest VRB Energy Storage System (VRB-ESS) energy storage system of Canada-based VRBpowerSystems. The VRB-ESS energy storage system is an energy storage system developed by VRBpowerSystems based on the all-vanadium redox flow battery technology proposed by researchers at the University of New South Wales. It converts chemical energy and electrical energy into each other. Chemical energy is stored in vanadium ions of different stages. The electrolyte solution is vanadium ion sulfuric acid electrolyte. The electrolyte flows from two independent plastic storage tanks into two half-battery units through a pump, using a proton exchange membrane (pEM) As the separator of the battery pack, the electrolyte solution flows in parallel across the electrode surface and electrochemical reactions occur, collecting and conducting current through the dual electrode plates. This reaction process can be reversed to charge, discharge and recharge the battery.

　　The VRB-ESS system includes two electrolyte storage tanks with vanadium ions in different oxidation states, namely the positive V(IV)/V(V) and negative V(II)/V(III) redox electrode pairs. The electrolyte is circulated between the storage tank and the stack by a pump. The stack consists of multiple cells, each with two half-cell sections separated by a proton exchange membrane. In a half-cell, electrochemical reactions take place on carbon plate electrodes, producing current to charge and discharge the battery. VRB-ESS system technical advantages VRB-ESS energy storage system has many technical advantages in design and construction, operation and maintenance, system performance, etc.:

　　1. Design and construction

　　(a) Use rapid design and construction, including environmental permitting, typically 6-8 months.

　　(b) The existing system can be quickly upgraded by simply increasing the electrolyte capacity to increase the storage capacity and achieve low cost; and the output power can be increased by increasing the number of stacks. 2. Operation and maintenance

　　(a) The operating temperature is low and the impact of changes in ambient temperature is small.

　　(b) The SCADA interface of the data collection and monitoring system supports Internet connection or dial-up connection. The Modbus bus interface supports interconnection with other auxiliary systems.

　　(c) Power control adopts advanced multi-quadrant current control technology, allowing output power phase control, voltage drift compensation, low harmonic distortion, reaction current compensation (pFC), and instantaneous high load capacity, increasing the performance stability of the system. And has multi-layer, encrypted control pLC.

　　(d) Low-cost maintenance. VRB-ESS system maintenance cost is $0.008/kWh. 3. System performance (a) Long battery life. Both the positive and negative electrode reactions of the battery are completed in the liquid phase. The charge and discharge process only changes the state of vanadium ions in the solution. No external ions participate in the electrochemical reaction. Repeated charge and discharge will not cause the battery capacity to decrease. The VRB-ESS system can charge and discharge more than 10,000 times. times (20%-80%SOC).

　　(b) The system is highly efficient. Since the active materials in the positive and negative half-cell electrolytes are stored in different storage tanks, self-discharge consumption during the electrolyte storage process is completely avoided. System circulation efficiency can reach 65-75%.

　　(c) The theoretical charging and discharging speed ratio is 1:1 (actually 1.8:1), allowing charging during off-peak hours and discharging during peak hours, turning unstable power input into continuous, safe and reliable power output, and improving the security of the power grid. and reliability, it is an ideal energy storage system in the field of wind power generation. VRB-ESS system application case VRBpowerSystems applies the VRB-ESS energy storage system to Australia's KingIsland wind power generation system to provide stable and reliable power transmission. KingIsland is located in the South Strait of Australia and has abundant wind resources. It originally used four 1500kW diesel generator sets, and later added three 250kW and two 850kW wind turbine sets. However, the output power of wind turbines is not stable continuously, so the VRB-ESS energy storage system is used to solve this problem. The VRB-ESS energy storage system is used to stabilize short-term power transmission changes and load changes in wind power generation, provide frequency and voltage control, implement system "load transfer", and optimize the operating performance of diesel engines and wind power generation hybrid systems. The application of the VRB-ESS system reduces the operating load of the diesel generator set, thereby reducing the cost of fuel and the exhaust gas pollution emitted by the diesel unit. At the same time, it also provides stable power supply for industrial and civil needs in the KingIsland area. Basic parameters of the VRB-ESS energy storage system: Energy storage capacity: 1100kWh Continuous transmission power: 200kW (4 hours) Peak maximum output power: 400kW (10 seconds), 300kW (5 minutes) Table 1: Economic and environmental benefits

　　Benefit Project Benefit Quantity Benefit Annual revenue Reduce hot standby 8 hours/day Save fuel 440L/day $91,500 Improve operating efficiency 25L/hour Low fuel consumption Save fuel 440L/day $83,200 Capture overflow wind 1100kWh/day Save fuel 260L/day $51,200 Reduce maintenance costs Reduce unit operating hours by 12 per day, extend maintenance cycle by $23,000, total $248,900 (cost recovery in 3.5 years), reduce emissions by 4,000,000kg/yrCO299,000kg/yrNOx75,000kg/yr unburned hydrocarbons

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