Hydrogen fuel cells power UAV by jsl16547


									Hydrogen fuel cells power UAV

Researchers at Georgia Institute of Tech-                     Advances and advantages                   power smaller, slower vehicles such as
nology have conducted successful test                  Parekh wanted to develop a vehicle that          UAVs and provide a low-cost alternative to
flights of a hydrogen-powered unmanned                 would both advance fuel cell technology          satellites. These unmanned aircraft could
aircraft believed to be the largest to fly on          and galvanize industry interest. While the       also track hurricanes, patrol borders, and
a proton exchange membrane fuel cell us-               automotive field has made strides with           conduct general reconnaissance.
ing compressed hydrogen.                               fuel cells, the aerospace industry, apart              Tom Bradley, who developed the fuel
     The fuel cell system that powers the              from spacecraft applications, has done lit-      cell propulsion system, is a doctoral stu-
22-ft-wingspan aircraft generates only                 tle to leverage fuel cell technology for         dent in Georgia Tech’s School of Mechan-
500 W. “That raises a lot of eyebrows,”                aerospace uses, he notes.                        ical Engineering. He says that fuel-cell-
says Adam Broughton, a research engi-                       “A fuel cell aircraft is more com-          powered UAVs have several advantages
neer working on the project in Georgia                 pelling than just a lab demonstration or         over conventional types. For starters, fuel
Tech’s Aerospace Systems Design Labora-                even a fuel cell system powering a house,”       cells emit no pollution and, unlike con-
tory (ASDL). “Five hundred watts is plenty             Parekh explains. “It is also more demand-        ventional UAVs, do not require separate
of power for a light bulb, but not for the             ing. With an airplane, you really push the       generators to produce electricity for oper-
propulsion system of an aircraft this size.”           limits for durability, robustness, power         ating electronic components. Another plus
In fact, 500 W represents about 1/100th                density, and efficiency.”                        is that fuel cells operate at near-ambient
of the power generated by a hybrid auto-                    Fuel cells, which create an electrical      temperatures, emitting less of a heat sig-
mobile such as a Toyota Prius.                         current when they convert hydrogen and           nature. UAVs powered by such cells would
     A collaboration between ASDL and                  oxygen into water, are attractive as energy      thus be stealthier than conventionally
Georgia Tech Research Institute (GTRI),                sources because their high energy density        powered craft, he says.
the project is spearheaded by David Pa-                translates into longer endurance.
rekh, deputy director of GTRI and founder                   Though they do not produce enough                     Spreading the word
of Georgia Tech’s Center for Innovative                power for the propulsion systems of com-         A few other research groups have also
Fuel Cell and Battery Technologies.                    mercial passenger aircraft, fuel cells could     demonstrated hydrogen-powered UAVs,
                                                                                                        but these aircraft were either very small or
                                                                                                        used liquid hydrogen. “Compressed hy-
Georgia Tech’s fuel cell aircraft flies above the track at Atlanta Dragway. The unmanned vehicle flew   drogen, which is what the automotive in-
for up to a minute at a time during the test flights.
                                                                                                        dustry is using, is cheaper and easier to
                                                                                                        work with,” says Bradley, “so our research
                                                                                                        will be easier to commercialize.”
                                                                                                              Unlike the smaller UAVs, which had
                                                                                                        no landing gear and had to be launched
                                                                                                        by hand, Georgia Tech’s demonstrator ve-
                                                                                                        hicle operates like a full-sized aircraft, re-
                                                                                                        quiring no auxiliary batteries or boosters
                                                                                                        for takeoff.
                                                                                                              Little information has been released
                                                                                                        about other hydrogen-powered UAVs. By
                                                                                                        contrast, outreach is an important part of
                                                                                                        Georgia Tech’s project. “We are laying the
                                                                                                        groundwork in design development that
                                                                                                        others can use to develop hydrogen-pow-
                                                                                                        ered aircraft,” explains Dimitri Mavris,
                                                                                                        ASDL director and Boeing professor in
                                                                                                        advanced aerospace systems analysis in
                                                                                                        Georgia Tech’s School of Aerospace Engi-

neering. “By documenting the technical
challenges we have encountered—as well
as our solutions—we provide a baseline
for others to follow,” he points out.
     The researchers hope to see many
other aircraft take to the skies on power
from fuel cells.
     “As significant as it is, we are not
merely developing a one-of-a-kind air-
plane,” adds Parekh. “We are working to
define a systems engineering approach for
fuel-cell-powered flight. We are seeking to
blaze a trail that others can follow.”
     The researchers presented papers
about the fuel cell project earlier this year
at meetings held by the American Society
of Mechanical Engineers and the AIAA.                 Thomas Bradley and Reid Thomas go through the procedure of starting up the Georgia Tech fuel cell
The project is supported with internal                aircraft during a test flight at the Atlanta Dragway. All photos by Gary Meek.
funding from GTRI along with grants
from NASA and the National Science                      signed much of the aircraft. Moffitt is a          a rear-mounted propeller, and an in-
Foundation.                                             doctoral student in Georgia Tech’s School          verted-V-shaped tail.
                                                        of Aerospace Engineering.                              •Miniaturization. The fuselage mea-
            Design challenges                                  To construct the fuel cell power plant,     sured 45 in. long with a maximum width
“Hydrogen power requires a drastically                  researchers bought a commercial fuel cell          of 9.75 in. and maximum height of 7.25
different approach to aircraft design com-              stack and modified it extensively, adding          in. Finding components small enough to
pared to conventional planes powered by                 systems for hydrogen delivery and refuel-          fit in this space required some ingenuity.
fossil fuels,” notes Blake Moffitt, who de-             ing, thermal management, and air man-              The team used a pump from a liquid-
                                                                        agement. They also built           cooled computer and a hydrogen tank de-
Thomas Bradley, David Parekh, Parker Parrish, and Adam Broughton        control systems that handle        signed for a paintball gun.
remove the hydrogen tank from the fuel cell aircraft to refill it       data acquisition and allow
for flight.                                                             information to be transmit-                        Test flights
                                                                        ted during flight.                 In June, researchers tested the vehicle at
                                                                              The work involved a          the Atlanta Dragway in Commerce, Ga.
                                                                        number of aircraft design          Hot, humid, windy weather made testing
                                                                        challenges. These included:        conditions less than ideal and reduced
                                                                           •Slim performance mar-          thrust. Nevertheless, the team was able to
                                                                        gins. Researchers developed        conduct four flights, with the aircraft trav-
                                                                        innovative computer tools          eling between 2.5 and 3.7 m above the
                                                                        to analyze performance.            ground for up to a minute at a time.
                                                                        These tools enabled them                 “Especially important, the data gen-
                                                                        to optimize the propulsion         erated during these flights validated our
                                                                        system and aircraft design.        design methodologies,” says Moffitt. “The
                                                                           •Weight management.             data also indicated the aircraft is capable
                                                                        Creative ways of trimming          of longer, higher performance flights.”
                                                                        pounds were found, includ-               The research team plans to continue
                                                                        ing use of carbon foam for         testing and refining the aircraft, making it
                                                                        the power plant’s radiator.        more reliable and robust. Ultimately they
                                                                           •Reducing drag. The re-         plan to design and build a UAV capable of
                                                                        search team achieved drag          a transatlantic flight—something Parekh
                                                                        reduction by using long,           believes will be possible within the next
                                                                        slender wings (spanning 22         five years.               Edward D. Flinn
                                                                        ft), a streamlined fuselage,                              edflinn@pipeline.com

                                                                                                             AEROSPACE AMERICA/NOVEMBER 2006          29

To top