Uninterruptible power supply for a city? It takes a huge battery
How big a battery is required to supply one million watts for eight hours (or 8 million watts for 1 hour)? The use of a Vanadium Redox Battery system allows this to be done in a reasonable space. According to information supplied by VRB Power Systems, Vancouver BC, liquid storage of 400,000 liters of electrolyte is required. Then an additional 10 to 15% area of space is required to hold the battery cell stacks and the power conversion system to convert from DC power to AC power. The system is based on energy storage in two different electrolyte solutions which are made up of dilute sulphuric acid and emulsified vanadium particles. The particles are stored in two tanks, one for the positive electrolyte, and one for the negative electrolyte. The two liquids are pumped to opposite sides of half-cells separated by a membrane. In large installations, the cell stacks are rated at 50 kW each. Based on the direction of current flow, the cells either produce power, or use applied power to recharge the electrolytes.
An agreement was signed in March 2001 licensing the Vancouver company to use the Vanadium Redox Battery Technology owned by Pinnacle VRB Limited of Australia within Canada, the United States, including Hawaii and Alaska, Central and South America and the Caribbean. These VRB Power Systems can be used to provide emergency power for cellular telephone towers, to provide storage of excess energy generated at windmill farms when high wind conditions exist, and to level out peaks of energy demand and supply for utilities. They offer a reasonably low initial system cost, almost negligible maintenance cost, and they have the lowest ecological impact of all energy storage technologies.