adminFLOW BATTERY
Flow battery store energy in liquid electrolytes held in external tanks. The electrolytes are pumped through the system allowing the battery to be charged and discharged, thus enabling the decoupling of power and energy storage.
There are several types of flow batteries and they are; vanadium redox (VRFB), zinc bromide (ZnBrFB), iron chromium (FeCrFB), organic redox (ORFB), polysulphide bromide (PSBrFB) and cerium zinc flow batteries.
Vanadium redox (VRFB) flow battery uses vanadium ions in two different oxidation states to store energy. Vanadium redox flow batteries have a high efficiency, long life span and are flexible in their operation.
Zinc bromine flow batteries zinc and bromine ions to store energy. Zinc bromine flow batteries have a high energy density and are relatively low cost to operate but has a lower efficiency compared to vanadium redox flow batteries.
Iron chromium flow batteries uses iron and chromium ions to store energy. Iron chromium flow batteries are low cost to operate with a long life span but with lower efficiency compared to vanadium flow batteries
Organic redox flow batteries use organic molecules (e.g. Quinones) dissolved in water instead of metals to store energy. Organic electrolytes are based on quinones, which are commonly used as dyes. They are abundant in nature and are potentially low cost in operatation.
Polysulphide bromide (PSB) flow batteries uses two salt solution electrolytes; sodium bromide and sodium polysulfide ions to store energy. Polysulfide bromide flow batteries are efficient in operation and most importantly they use inexpensive and abundantly available electrolytes.
Cerium zinc flow batteries uses zinc and cerium ions to store energy. Cerium zinc flow batteries are moderate in cost of operation but possess a high energy density.
The advantages of flow batteries are; flow batteries can easily be scaled up or down to suit various applications. Flow batteries can store energy for extended periods, making them suitable for grid scale energy storage and long duration of operation. Flow batteries have high round trip efficiency (up to 90%) and can maintain efficiency over many charge and discharge cycles. Flow batteries can be designed to meet specific application requirements such as power and energy ratings. Flow batteries have low self-discharge rate making them suitable for long term energy storage.
The disadvantages of flow batteries are; flow batteries are more expensive than other energy storage technologies such as lithium ion batteries. Flow batteries require complex systems, including pumps, valves and control systems, which can increase maintenance cost, flow batteries have limited life span typically ranging from 5 to 15 years. Some flow batteries chemistries such as vanadium can be expensive and may have supply chain limitations.
Flow batteries find applications in the following: grid scale energy storage where they are used to provide long duration energy storage and grid stability; Renewable energy integration, where they are used to integrate renewable energy sources such as solar and wind power into the grid; Micro grid applications, where they are used to provide energy storage and grid stability; Remote area power source where they can be used to provide energy storage and power.
The future of flow batteries depends on the advances and development of the following technologies: the cost of flow batteries is projected to decrease drastically in the future, making them more competitive with other storage technologies; flow batteries efficiency is expected to increase with some prototypes achieving efficiencies of up to 95%; standardization of flow battery systems and components are expected to increase in the future making it easier and cheaper to provide and deploy flow batteries.; researchers are exploring new chemistries for flow batteries such as zinc air and iron air, which could offer improved performance and cost advantages; solid state electrodes are being developed for flow batteries, which could improve the efficiency and lifespan of flow batteries; advanced materials and new membrane technologies such as graphene and Nano materials are being developed to be used in flow batteries which could improve performance and reduce costs; also hybrid flow batteries that combine different chemistries or technologies are being developed, which could offer improved performance and cost advantages over other batteries; generally, flow batteries are expected to become widely adopted for grid scale energy storage and long duration applications such as renewable energy integration and micro grid energy integration thereby enhancing grid stability.
SOURCES:
- Flow batteries: A review of the current status and future directions by Z. Yang, J. Zhang, M.C.W Yang and J.P Zhang.
- Energy storage: A new era of flow batteries by R.C Tennant, A.J Winn and J.W Hall.
- Flow batteries for energy storage: Design, principles and applications by H.S Park, J.H Kim and Y.J Kim.
- Advanced energy storage systems: Flow batteries and other technologies by S.S Rao, S.K Srivastava and A.K Singh.
- Sustainable energy: Choosing the right energy storage solution by J. Kleinschmidt, S. Lim and A.W Weigel
