TechnologyThe ZBB Zinc Energy Storage System (ZESS) is a proprietary and patented regenerative energy storage system based on zinc/bromide technology, which is very different in concept and design from more traditional methods of energy storage such as the lead/acid battery. The ZESS technology is based on the reaction between two commonly available chemicals, zinc and bromide. The ZESS consists of a zinc negative electrode and a bromide positive electrode separated by a microporous separator. An aqueous solution of zinc/bromide is circulated through the two compartments of the cell from two separate reservoirs. The electrolyte stream in contact with the positive electrode contains bromide which is maintained at the desired concentration by equilibrating with a bromide storage medium (Figure 1.). The bromide storage medium is immiscible with an aqueous solution containing zinc bromide. All battery components are made from a bromide inert plastic (Figure 2.).
Figure 1: The Flowing Electrolyte System
Figure 2: Battery Stack Assembly
Unlike the lead acid and most other batteries, the ZESS uses electrodes that cannot and do not take part in the reactions but merely serve as substrates for the reactions. There is therefore no loss of performance, unlike most rechargeable batteries, from repeated cycling causing electrode material deterioration. During the charge cycle metallic zinc is plated from the electrolyte solution onto the negative electrode surfaces in the cell stacks. Bromide is then converted to Bromine at the positive electrode surface of the cell stack and is immediately stored as a safe chemically complexed organic phase in the electrolyte tank. When the ZESS discharges, the metallic zinc plated on the negative electrode dissolves in the electrolyte and is available to be plated again at the next charge cycle. In the fully discharged state the ZESS can be left indefinitely.
The ZESS offers 2 to 3 times the energy density (75 to 85 watt-hours per kilogram) with associated size and weight savings over present lead/acid batteries. The power characteristics of the ZESS can be modified, for selected applications. Therefore, the ZESS has operational capabilities which make it extremely useful as a multi-purpose energy storage option.
Product Design
The ZESS technology is composed of a module or a series of modules for increased power. The ZESS 50 holds 50 kWh, which would roughly power a home for two days, and includes three cell stacks, each containing 60 cells. The module dimensions are 4’ x 4’ x 6.5’, weighing 3,200 pounds. The ZESS 500 fully charges in 4.5 hours and has continuous power of 250 kilowatts (kW), sustainable for two hours, with 200% peaking capability. The ZESS 500 holds 500 kWh, which is actually ten of the ZESS 50s strung together, and is used for commercial or utility applications. Exhibit 4 shows the ZESS 50 and ZESS 500. These storage devices can be located anywhere in ambient temperatures and transported to support the need of renewable energy to mitigate utility congestion. The “Turnkey” capabilities are beneficial based on the ease of simply plugging the batteries into the grid or other alternative source. Furthermore, these products are predominantly manufactured with recyclable plastics, allowing for low production costs and economical mass production.
Exhibit 4: ZESS 500 Storage System
Product Functionality
The ZESS systems store energy from a number of sources and are highly compatible with global renewable energy markets: wind, solar, hydroelectric, biofuels, ocean power, and biomass.
The ZESS 500 is easily transported on a 20-foot trailer and weighs approximately 30,000 pounds. The modular design aims to increase or decrease power needed by either adding or subtracting modules in the string, which is a valuable feature. Other products do not provide these transportable designs and modular capabilities for the added flexible benefits.
|
