Big battery stores wind power
A flowing chemical electrode lets a durable battery store up to 50 kWh in a self contained unit. Unlike more traditional batteries, the ZESS (zinc energy storage system) is based on fuel-cell ideas and combines aspects from both battery and fuel-cell technologies. When mounted with other modules, most any capacity is possible. The battery represents a clean, green, environmentally friendly and cost-efficient alternative energy storage, says developer ZBB Energy Corp., Milwaukee, Wisc.
The firm says the units are scalable and mobile. Each 50 kWh battery module is composed of three cell stacks, each with 60 cells in a series. Users can charge the battery from a variety of power sources at different charge rates and it can fully discharge repeatedly without damage. Modules are self-contained, and a control system takes care of energy storage and safety functions.
The ZBB battery is often referred to as a Regenerative Fuel Cell (RFC). The company says its design relies on a flowing electrolyte and has these features:
• Chemical reactions take place in the cell stack and excess electrolyte is stored in external tanks.
• The predominantly aqueous electrolyte is composed of zinc bromide salt dissolved in water.
• During charge, metallic zinc is plated from the electrolyte solution onto the negative electrode surfaces in the cell stacks.
• Bromide is converted to bromine at the positive electrode surface of the cell stack and is immediately stored as a safe, chemically complex organic phase in the electrolyte tank.
• Each cell stack has 60 bi-polar electrodes between a pair of anode and cathode-end blocks.
• It operates quietly and at ambient temperature.
Unlike most batteries, ZESS electrodes don’t take part in the chemical reactions. They are substrates for the reactions. That means no loss of performance from repeated cycling that causes electrode material deterioration When the ZESS discharges, the metallic zinc plated on the negative electrodes dissolves in the electrolyte and is available for plating at the next charge cycle. In the fully discharged state, it can be left indefinitely.
In one application, a ZESS 500 storage battery will store the power generated by an 850 kW wind turbine that already provides half of the Dundalk Institute of Technology’s Centre for Renewable Energy project. The addition of the energy storage system will maximize the viability of onsite wind energy. This the first installation of a ZESS 500 in a wind application will let the campus operate independently of the electrical grid.
Filed Under: Energy storage, Turbines