Imagine a kerosene lamp that continued to shine after the fuel was spent, or an electric stove that could remain hot during a power outage.
Materials scientists at Harvard have demonstrated an equivalent feat in clean energy generation with a solid-oxide fuel cell (SOFC) that converts hydrogen into electricity but can also store electrochemical energy like a battery.
This fuel cell can continue to produce power for a short time after its fuel has run out.
“This thin-film SOFC takes advantage of recent advances in low-temperature operation to incorporate a new and more versatile material,” says principal investigator Shriram Ramanathan, who is an associate professor of materials science at the Harvard School of Engineering and Applied Sciences (SEAS).
“Vanadium oxide (VOx) at the anode behaves as a multifunctional material, allowing the fuel cell to both generate and store energy.”
The finding will apparently be most important for small-scale, portable energy applications, where a very compact and lightweight power supply is essential and the fuel supply may be interrupted.
Unmanned aerial vehicles, for instance, would really benefit from this, according to Quentin Van Overmeere, a post-doctoral member of the SEAS team.
When it’s impossible to refuel in the field, he reckons an extra boost of stored energy could extend such a device’s lifespan significantly.
The team has typically worked on thin-film SOFCs that use platinum for the electrodes (the two poles are known as the anode and the cathode). But when a platinum-anode SOFC runs out of fuel, it can continue to generate power for only about 15 seconds before the electrochemical reaction peters out.
The new SOFC uses a bi-layer of platinum and VOx for the anode, which allows the cell to continue operating without fuel for up to 14 times as long (3 minutes, 30 seconds).
This early result is only a “proof of concept”, and the team predicts that future improvements to the composition of the VOx-platinum anode will further extend the cell’s lifespan.
Ramanathan and his colleagues estimate that a more advanced fuel cell of this type, capable of producing power without fuel for a longer period of time, will be available for applications testing such as in micro-air vehicles within a couple of years.