Anyone who has been in the Midwest is bound to run across a wind farm sooner rather than later – that's how prevalent wind energy is in the area nowadays. However, the wind energy sector has run into a roadblock. It needs to find an affordable yet effective way to store electricity produced during off-peak hours.
"We get a lot of wind at night, more than at daytime, but demand for electricity is lower at night, so, they're dumping it or they lock up turbines – we're wasting electricity," explained Trung Van Nguyen, the leader of the University of Kansas (KU) research team.
According to Nguyen, wind farm owners could store power generated throughout the night and sell it during the day, when it's in demand. A high-capacity energy storage device would give them the incentive to keep their wind turbines running 24 hours a day, which maximizes their investment. (Related: New “smart blade” technology will make wind turbines even more efficient.)
The original concept for the hydrogen-bromine battery dates back to the 1960s. Nguyen and his team started working on their version in 2010.
Their prototype energy storage device is roughly the size of a truck. It could store excess energy from wind farms during the evening and do the same for solar farms during the day, ensuring it is never without work.
According to Nguyen, their design could be scaled up to handle the immense energy needs produced by commercial wind farms. He envisions a single battery will have the storage capacity for one megawatt-hour of electricity.
He personally helped develop the hydrogen-bromine battery's electrode, which needed a large surface area for maximum efficiency. Earlier attempts stacked paper-carbon electrodes on top of each other to attain the needed electrical output. The use of multiple layers resulted in bulky electrodes that cost more and suffered from high resistance.
Learning from those earlier designs, the KU team chose to grow carbon nanotubes right on top of a porous material. This technique massively increased the surface area while keeping the electrode within a reasonable size.
The biggest drawback of a hydrogen-bromine battery is its use of its namesake gas. Bromine has been compared to chlorine gas in terms of corrosive effects.
Because of its potentially deadly contents, such batteries must be kept far from populated areas. They need to be stored underground in tightly-sealed conditions to minimize the chance of leakage.
While it cannot be installed in commercial or residential areas, the energy storage system is viable for renewable energy facilities. Solar farms and wind farms are usually constructed in remote locations with plenty of room to safely bury the batteries.
Bromine's corrosive property also has a complex development of a catalyst that increases the performance of the battery. In addition to having higher output and resistance, the catalyst must be able to withstand corrosion.
Nguyen feels his latest candidate shows much promise. The new catalyst uses rhodium sulfide, which is highly resistant to corrosion, and testing showed it could increase the rate of hydrogen reaction.
Once the corrosion-related kinks have been ironed out, the KU team believes their hydrogen-bromine battery could make renewable energy even more attractive to investors, who are usually hesitant to commit to projects with daunting start-up costs.
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