Tuesday, November 24, 2009

Fuel cells for aircraft in the news again

Back in July I wrote about the Antares DLR-H2, the first manned fuel-cell-powered aircraft, under development in Germany. Now comes news of two developments in the USA, both concerned with powering small unmanned aerial vehicles (UAV's).

The US Naval Research Laboratory has just achieved a milestone by flying a fuel-cell-powered UAV for more than 24 hours. In a news release, the USNRL reported:

The Naval Research Laboratory's Ion Tiger, a hydrogen-powered fuel cell unmanned air vehicle (UAV), has flown 26 hours and 1 minute carrying a 5-pound payload, setting another unofficial flight endurance record for a fuel-cell powered flight. The test flight took place on November 16th through 17th.

The electric fuel cell propulsion system onboard the Ion Tiger has the low noise and signature of a battery-powered UAV, while taking advantage of hydrogen, a high-energy fuel. Fuel cells create an electrical current when they convert hydrogen and oxygen into water and heat. The 550 Watt (0.75 horsepower) fuel cell onboard the Ion Tiger has about four times the efficiency of a comparable internal combustion engine and the system provides seven times the energy in the equivalent weight of batteries. The Ion Tiger weighs approximately 37 pounds and carries a 4- to 5-pound payload.

. . .

NRL has now demonstrated that PEM fuel cell technology can meet or surpass the performance of traditional power systems, providing reliable, quiet operation and extremely high efficiency. Next steps will focus on increasing the power of the fuel cell to 1.5 kW, or 2 HP, to enable tactical flights and extending flight times to 3 days while powering tactical payloads.

There's more at the link. Here's a video from earlier this year showing testing of the Ion Tiger.

It's also reported that United Technologies has applied fuel cell technology to a helicopter UAV. From UT's press release:

United Technologies Research Center (UTRC), the central research and innovation arm of United Technologies Corporation (NYSE:UTX), achieved first flight of a hydrogen/air fuel cell-powered rotorcraft. The successful technology demonstration was accomplished using a remote-controlled electric helicopter model modified to incorporate a custom Proton Exchange Membrane (PEM) fuel cell power plant.

"Achieving vertical flight represents a key milestone in fuel cell-powered flight as the power density requirements are much greater than for fixed wing aircraft," said Dr. David Parekh, Vice President, Research, and UTRC Director. "In addition, this environmentally friendly power system produces zero pollution, zero emissions of greenhouse gases and operates with very low noise."

The pioneering flight using a high power-density PEM fuel cell took place on Oct. 11, 2009, at 10:30 a.m., on the East Hartford campus of UTRC. The remote-controlled helicopter originally designed to run on batteries had a rotor diameter of 2 meters and a takeoff weight of 10 kg. The duration of the fuel cell powered flight was approximately 20 minutes. The team plans to demonstrate longer flight durations in the future.

Again, there's more at the link. Here's a video of the helicopter UAV during its test flight.

If such fuel cells can be further developed, they'll provide a major increase in capability to UAV's. They typically are far more 'energy-dense' than the equivalent weight of an internal combustion engine plus fuel, or a battery pack, so UAV's using them can carry a more power-hungry payload, or fly further or faster or higher, or a combination of these advantages.

If the German tests of a manned aircraft with fuel cell propulsion also prove successful, and their technology can be 'mated' with that under development here, we may see light general-aviation aircraft powered by fuel cells before long. Given restrictions on the refining of high-octane aviation gasoline, plus its relatively high cost, that might be a blessing for this sector.



reflectoscope said...

Hydrogen is questionable for use in military hardware which must be storeable and deployable; how big is a usable hydrogen generator?

Also, the suggestion that it is clean ignores the energy which must be consumed to isolate and compress it.

If methanol fuel cells can be made to work, that is a must more practical proposition. Methanol is corrosive, but it is nothing which cannot be managed with appropriate materials.

The fact that it is already widely available and simple to store and transport makes it a much more obvious choice for things like UAVs and portable generators for those with boots on the ground.

One other advantage to methanol is that a UAV using it for fuel could be refueled mid-air using current technology. (The KC-135Q had a separate storage system for the JP-7 for the SR-71, for example)

As it is, using hydrogen in fuel cells seems like a neat trick, and it might work for really high value applications like miniature UAVs and perhaps guided weapons, but I think methanol is the future.


Mario in PY said...

OK, so the system itself may be zero emission.

But, what about the production process of the system?