Grid Storage Possible with New Fuel Cell

Thursday, February 13, 2014 @ 09:02 AM gHale

The ability to keep costs down and achieve high-cycle efficiency comprise two benefits Harvard scientist are hoping to achieve with a new fuel cell/battery hybrid for bulk energy storage in renewable power systems.

The beauty of this flow battery is the lack of metals in the system — the key to its low cost and high efficiency.

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In a flow battery, two tanks store electrolytes away from the electrodes — one tank for each of the ions reacting at the electrodes. When electricity is required, electrolytes flow into a chamber containing the electrodes.

Storage capacity is in proportion to tank size — separate from power-generating capability, which the electrode area sets within the reaction chamber.

The Harvard team, sponsored by the U.S. Department of Energy grid-scale battery program, has developed a quinone-bromide chemistry based around a particular quinone screened from 10,000 candidate quinones.

Metals comprise the active components of electrolytes in most flow batteries, the team said. Fuel cells use platinum. The most commercially advanced flow-battery technology now in development uses vanadium, but the cost per kWh is high. Fuel cells use platinum, a precious metal electrocatalyst. But the quinone cell matches the performance of vanadium flow batteries with less expensive chemicals, the scientists said.

Organic molecules offer a whole new range of possibilities. “Some of them will be terrible and some will be really good, said Harvard chemist Professor Roy Gordon. “With these quinones, we have the first ones that look really good.”

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