Rust never sleeps, Neil Young famously observed. Now a team of researchers based at the University of Calgary has discovered that rust, along with a few other choice ingredients, may be the key to turning sporadic sources of renewable energy into a round-the-clock power supply.
Reporting in Friday's edition of the journal Science, the team has developed a type of cheap chemical catalyst – a material that can speed up the breakdown of water to produce hydrogen gas. The hydrogen represents stored energy that can be converted back to electricity when needed.
If it can be made to operate at a commercial scale, the new catalyst would offer a way to capture excess energy from solar panels and wind turbines for later use and make renewable energy a more practical proposition for consumers.
"That would make us a lot less reliant on carbon emitting fuels because we could run our houses almost entirely on renewable energy," said Simon Trudel, a chemist who is part of the Calgary team.
The classic challenge for renewable energy is that available supply does not always correlate with demand. The wind may be blowing at 2 a.m., but there is little need for the energy generated at that moment – hence the interest in catalysts that can facilitate renewable energy storage and smooth out the supply problem.
Catalysts that can do this are typically made with rare metals such as iridium and rubidium which are prohibitively expensive for commercial purposes. The Calgary team found they could replace such pricey ingredients with iron oxide – rust – among other materials, to create an effective electrolyzer that can be applied onto a surface in the form of an amorphous film.
"We're able to get a performance that matches or even exceeds that of more expensive metals," said Curtis Berlinguette, a chemist and director of the university's Centre for Advanced Solar Materials.
The scientists have launched a spinoff company to develop the material for commercial use. They envision household storage units that can soak up extra energy from renewable sources such as wind and solar at times when that energy isn't being used.
In addition to being relatively cheap, the catalyst is non-toxic and operates under conditions that make it suitable for a home appliance.
"Because this is done in air, and at room temperature, it's a very nice and scalable method," said Dr. Trudel, who together with Dr. Berlinguette hit upon an approach to creating the catalyst three years ago during an impromptu pub night discussion.
Outside experts caution that the amorphous material produced by the Calgary team has a way to go to prove itself. In addition to low cost, the material must be chemically durable for long term use and efficient at converting electrical energy in hydrogen.
"Efficiency is very important," said Chris Ainscough, a senior engineer at the National Renewable Energy Laboratory in Golden, Colorado. Because hydrogen production must be paired with a fuel cell that can turn the energy back into electricity, there is a loss of efficiency at both stages of the round trip cycle.
Last year, the US Department of Energy set a target efficiency for electrolyzers at 82 per cent. Rodney Smith, a postdoctoral fellow at the Calgary lab and lead author on the Science paper, said the group had measured the efficiency of its material at between 85 and 90 per cent at low output but noted, "As with all systems, efficiency will decrease as we increase the output rate."
Dr. Smith said the next phase of the work would involve building a complete system around the new material.
"The work has promise to provide a lower cost solution," said Jack Brouwer, Associate Director of the National Fuel Cell Research Centre at the University of California, Irvine, who was not involved in the research.
The notion of hydrogen as an alternative fuel has a history of passing in and out of fashion. One barrier is the effort needed to drive the complex chemical reaction that ultimately splits hydrogen off from water.
"Nature works against us," said Dr. Brouwer. Under normal conditions at Earth's surface, "the natural state that hydrogen wants to be in is in the form water."
Nevertheless, he added, when there is an available supply of electricity that would otherwise be wasted, hydrogen offers an energy storage medium with many advantages. "In context, this type of technology makes perfect sense," Dr. Brouwer said.
Dr. Berlinguette noted that the catalyst work is an example of the kind of basic science that could use more support in Canada. Following the release of its 2013 budget the federal government has been criticized for emphasizing a more short-term and targeted approach to research with industrial partners.
"This is not a project that would have been sponsored by any company," said Dr. Berlinguette, "Even though that's where the funding has shifted to in Canada."