Many a bad story starts with an empty gas tank and the only sign of humanity being a mysterious house or hotel. This same scenario can happen with non-gasoline powered vehicles too, like unmanned aerial vehicles powered by fuel cells. These UAVs often have to be designed to be as light as possible, so just adding more fuel reserves is not a viable option because of the added weight. Fortunately though, researchers at Harvard School of Engineering and Applied Sciences have created a fuel cell which also acts as a battery and can provide power after the fuel has run out.
The key to this new thin film solid-oxide fuel cell (SOFC) is the addition of a layer of vanadium oxide (VOx) at the anode. Typically the researchers work with SOFCs that only use platinum at the electrodes, and these can produce power for 15 seconds after running out of fuel, but the addition of the VOx layer let it last for 210 seconds, some fourteen times longer. The researchers believe this is because of one of three effects occurring within the VOx layer, but are not certain about which it specifically is.
At just three and a half minutes of battery life, this is only a proof-of-concept design at the moment, but the researchers are confident they can improve this greatly. In just two years they expect to have a device ready for application testing, such as micro-air vehicles.