Page - 130 - in Clean Water Using Solar and Wind - Outside the Power Grid

130 Clean Water Using Solar and Wind: Outside the Power Grid The battery can serve as a rechargeable battery, where an electric power source drives regeneration of the fuel. One of the biggest advantages of flow batteries is that they can be almost instantly recharged by replacing the electrolyte liquid. The energy capacity is a function of the amount of liquid electrolyte and the power a function of the surface area of the electrodes. The fundamental difference between conventional batteries and flow batteries is that energy is stored as the electrode material in conventional batteries but as the electrolyte in flow batteries. A wide range of chemistries and electrolytes have been tried for flow batteries. Vanadium is increasingly being embraced by battery manufacturers as a core material in the production of batteries to be used in both small-scale and large-scale applications. The electrolyte is composed of vanadium salts in sulphuric acid. Vanadium redox-flow batteries (VFBs) have started to grow in influence as energy companies look to improve energy storage. During a VFB battery charge, V 3+ ions are converted to V 2+ ions at the negative electrode through the acceptance of electrons. Meanwhile, at the positive electrode, V 4+ ions are converted to V 5+ ions through the release of electrons. Both of these reactions absorb the electrical energy put into the system and store it chemically. During discharge, the reactions run in the opposite direction, resulting in the release of the chemical energy as electrical energy. Due to their superior performance and gradual price reduction lithium batteries have until now been the preferred technology. However, the demand for flow batteries has increased rapidly over the last couple of years. The flow batteries have low variable costs (USD/kWh) and use a wide state of charge (SoC) range. On the other hand, efficiency is lower than for the lithium batteries and fixed costs (USD/kW) are higher. Activities in flow batteries in China illustrates the growing interest in using flow batteries for energy storage. Two recently announced projects in Hubei and Dalian are sized at 100 MW/500 MWh and 200 MW/800 MWh respectively. The Chinese government is aiming for a long-term strategy to push energy storage to integrate renewable energy. 10.4 BATTERY PARAMETERS A battery can be characterised not only by its energy capacity but also by its discharge rate. Both these parameters are crucial for a storage battery used in renewable energy systems. Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user