Flow Batteries To Be Used In Grid System

The conventional batteries used in inverters and other applications have solid electrodes of carbon materials to conduct the flow of ions. These batteries have been used extensively in each and every sector but the problem with these batteries is that it cannot handle large fluctuations under the operating conditions. To do away with these difficulties, flow batteries were invented. Now what are flow batteries? These are the batteries which have flowing electrolytes functioning as electrodes instead of solid ones as in normal batteries.

Today’s era is an era of the non conventional energy resources as an alternative to the exhaustible resources has to be used now. Hence, the numbers of solar and tidal power plants are increasing day by day. Now obviously, they cannot provide energy all day round as no solar energy is available after the sunset.  As these sources of power are available for specified amount of time, the grid has to be activated and deactivated daily. Consequently we are going to need better batteries for this purpose. The best suiting technology for this is the flow batteries. Though this technology is 30 years old, it has not yet been used for the grid system.

This battery uses two electrolytes as electrodes which react with each other when pumped through a cell stack. The battery comprises of two large electrolyte tanks and a cell stack. As the electrolyte flows through the porous membrane in each cell, the ions and electrons flow in forward of reverse direction thus charging or discharging a battery. To recharge the battery we simply have to put in new electrolyte. The energy storage capacity of the battery can be increased by increasing the size of the tank. These batteries are already used in factories and other installations for backup power.

The manufacturers are pumping millions of dollars in a venture to design flow batteries which can be used in a grid. $31 million have been poured in the Recovery Act fund by The U.S Department of Energy (DoE) in order to start five utility scale projects. The Zinc bromine flow battery can store one kilowatt for less than $500. This amount is one third as compared to lithium ion batteries and about a third quarter as compared to th sodium sulphur battery. Craig Horne, CEO of flow-battery start-up EnerVault, in Sunnyvale says that their architecture makes them practically safe to use. The advantage with this system is that you can have a megawatts of energy stored in the electrolyte tanks but only a small amont of it is taken in the stack. Moreover, the supply to the tanks can be shut off as per the requirement.

The Vanadium and the zinc bromine batteries are most widely used and popularly known. Vanadium batteries have been mostly used in Japan by Sumitomo electric industries to reduce the peak loads and to store the wind energy. “Premium Power”  will be testing seven 2.8 MWh installations for three years under the DoE. Many other grid- flow batteries will be in the market in 5 years. Newer chemistry are being worked upon by the start-ups such as Primus Power, EnerVault, and Deeya Energy.