Scott Barnett Researches Fuel Cells to Make Fossil Fuels More Efficient
The future of energy could lie in harnessing the energy of solar and wind to power our homes and reduce CO2 emissions. But technology has not yet reached the point where we can rely solely on renewable energy — the vast majority of our energy still comes from fossil fuels.
So how can we make those fossil fuels more efficient and better for the environment now? One answer is fuel cells — specifically, solid oxide fuel cells (SOFCs), which use an electrochemical conversion device to produce electricity directly from the fuel. Research happening at the McCormick School of Engineering at Northwestern University aims to better understand just how these fuel cells work — and to find better materials to create them.
Fuel cells work by using two electrodes and an electrolyte to exploit the reaction between oxygen and hydrogen. By combining hydrogen from a fossil fuel directly with oxygen (instead of burning it, like in a coal power plant) we can harness the electricity from the reaction with an efficiency of 40 to 60 percent, compared to less than 30 percent for conventional power plants. The result is a highly efficient, low-emission energy source.
So why aren't fuel cells used more often? NASA has used them on its space shuttles, and Google uses fuel cells to power part of their private headquarters. But cells are still relatively high-cost and can't yet be used directly with fossil fuels — they work best with hydrogen, which is found in most fossil fuels but needs to be processed out. Some also question fuel cells durability and lifespan, and whether the cost can be reduced enough for broad commercial markets.
Scott Barnett, professor of materials science and engineering, is working on two SOFC research projects — both funded by the National Science Foundation through the American Reinvestment and Recovery Act — that will address these challenges. Barnett is an expert in SOFCs — he's been working in the field for more than 20 years — and says fuel cells are currently the best bet for producing greener energy.
"The technology has come a long way," he says. "Fossil fuels like coal are going to be in use for a long time to come, until renewable energy sources take over, and SOFCs provide a means for using them more efficiently and reducing our production of CO2."
Over the last five years, Barnett and his research group have been using a Focused Ion Beam Scanning Electron Microscope to peer inside SOFCs to see just how they work. Barnett's team, working with Peter Voorhees, Frank C. Engelhart Professor of Materials Science and Engineering, spent several years trying to figure out the process for imaging the fuel cells — no one had ever done it before — and process works similar to an MRI: the microscope produces 3D images that show the insides of fuel cells. These images show both the electrochemical processes and how the fuel cells degrade over time.
"Being able to accurately measure these structures is useful in figuring out how they actually work," Barnett says. "We're trying to get a handle on how fuel cells degrade over time, and we can do that with this technique. That will allow manufacturers to make better fuel cells in the future."
Barnett is also researching how to use fuel cells for energy storage. Solar and wind power are intermittent — solar power is produced only during the day, for example, and yet we still need electricity during the night. By running solar or wind-produced energy backwards through a fuel cell, you could use it to make fuels like hydrogen or natural gas, and store that fuel until you need it.
"We've started publishing papers on this, and we're getting good results," Barnett says. "It looks very feasible."
Part of Barnett's research projects include looking for new materials to use in fuel cells. Right now, fuel cells run best on hydrogen, but that hydrogen has to be processed out of fuel. Fuel cannot be used directly with fuel cells because, as is the case with natural gas, the methane deposits carbon on the nickel that is used as a key material in the fuel cell. Natural gas also contains impurities like sulfur, which glom onto the nickel and render it inoperable.
"We're trying to find alternative materials to nickel to overcome these problems," Barnett says.
To conduct this research, Barnett uses a cadre of both graduate and undergraduate students in his lab.
"It's fun to have undergraduates around," he says. "A lot of them do meaningful research and are getting their names on publications. We invest a little time initially, and pretty soon they are giving back."