Monday, April 21, 2008

Flow Cells for Home Energy Use

Flow cell batteries represent a technology that is more often touted as a utility load-leveling tool. But a home-scale version of a flow cell battery is being sent to Beijing for the 2008 Summer Olympics, as part of the Zero Net Energy Future House USA display.
... the cell's design is different than a traditional battery, with fluid charged with electrolytes flowing past its cell membranes, said Kevin Dennis, vice president of sales and marketing for ZBB.

"There are a couple of advantages (with this design)," he said. "Once the cell is charged, you can turn it off. A battery is always on." ZBB's fuel cells are designed for large energy efficient homes, commercial and industrial properties and power relay stations. When they're not in use, ZBB Energy's fuel cells discharge at a much slower rate than batteries, Dennis said. The fuel cells are rechargeable, and can be recharged many more times than rechargeable batteries. "We design fuel cells like this on the order of 20 to 30 years," he said. "You will have to replace the (cell) membrane in about 10 years. The cycles are on the order of thousands."

The ZESS 50 is ZBB Energy's 50 kWh energy storage module. ZBB Energy also makes the ZESS 500, which can store up to 500 k Wh. ZBB Energy has piloted its fuel cells for the past four years, Dennis said, and began production earlier this year. The company, which has 38 employees, manufactures the fuel cells from its 72,000 square foot facility in Menomonee Falls.

The Future House USA will be part of the Future House Village, a neighborhood of eco-friendly demonstration homes created by teams from Canada, China, Germany, Japan, South Korea, Spain, Sweden and the United States. The high-visibility program is designed to promote energy-saving strategies and construction that will have a minimal impact on the global environment. __Source
The term "fuel cell" is a misnomer for this technology. The proper term is Zinc-Bromine "redox flow cell (PDF)." Presumably, the company uses the term "fuel cell" in its press releases due to greater public familiarity with the term (if not the underlying concept).

Matsushita in Japan produces a true home fuel cell, which will be placed outside some Japanese homes starting next year.

It is highly likely that both home fuel cells and home flow cells will enjoy much higher rates of utilisation within the next ten years, than most energy analysts anticipate. The main technological obstacle to greater utilisation of redox flow-cells is the low energy density. For that reason, it is likely that the larger uses of the technology will be for utility and industrial scale power backup and load leveling. Eventually, flow cells should move downscale to commercial buildings, hotels, apartments and condominiums, and single family residences.

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