If a new technology pans out, the fading notion that hydrogen will someday supplant fossil fuels may be on the verge of a comeback.
There was a time in the early 90's when the fuel cell was touted as the clean energy technology of the future. The only byproduct was water and it also packed a whole lot more energy than electric car batteries. For instance, nine pounds of the stuff was enough to enable a vehicle to go 150 miles. However, methods to generate hydrogen were in and of themselves energy intensive. And ultimately, the concept of needing energy to produce energy was problematic enough to make it a dealbreaker for many green investors.
But now researchers at Penn state have demonstrated an innovative "self-powered" process of producing hydrogen that, if scalable, can revive interest in fuel cell technology.
What enables the technique to work is the clever integration of bacteria, seawater and fresh water. In 2009, researchers discovered that special bacteria called microbial electrolysis cells can break down matter in wastewater to release hydrogen, though it still needed a slight jolt of electricity to get the process going.
They eventually turned to a separate process known as reverse-electrodialysis or RED, which is similar to desalination, except run in reverse. The logic goes something like this: extracting the salt from seawater requires quite a bit of energy, so bringing the two back together would release energy that can be used to give the little bugs a kick start.
"If you think about desalinating water, it takes energy, Bruce E. Logan, a professor of environmental engineering, told the BBC. "If you have a freshwater and saltwater interface, that can add energy. We realized that just a little bit of that energy could make this process go on its own."
Logan's cells were between 58 and 64 percent efficient and produced between 0.8 to 1.6 cubic meters of hydrogen for every cubic meter of liquid run through the cell each day. The researchers estimated that only about 1 percent of the energy produced in the cell was needed to pump water through the system.
The findings were published in this week's issue of the Proceedings of the National Academy of Sciences.
So far, this approach has only been demonstrated successfully in the lab. To scale up this technology, the researchers proposed running seawater and river water through a stack of alternating cathode and anode exchange membranes.
"This system could produce hydrogen anyplace that there is wastewater near sea water. It uses no grid electricity and is completely carbon neutral," Logan said. "It is an inexhaustible source of energy."
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