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78

W

hen carefully

designed, solar

electrically powered

fixed-wing UAVs have

a far greater flight

endurance than purely electrically or

even gasoline-powered aerial vehicles,

and that begins to open doors both for

UAV projects and the solar technology

itself. Given the right environmental

conditions, a solar-powered UAV stores

excess solar energy gathered during

the day in its batteries, which can then

power the aircraft through the night and,

potentially, subsequent day-night cycles.

Long-endurance capability, especially

in the extreme cases of continuous multi-

day flight or even perpetual endurance,

is particularly interesting for applications

such as large-scale mapping,

observation or telecoms relay. It can

also be applied to search and rescue

(SAR) missions, industrial or agricultural

inspection, meteorological surveys,

border patrol and more.

Recently, interest in using large-scale

(wingspan greater than 20 m), solar-

powered high-altitude long-endurance

UAVs as atmospheric satellites, and

stationary/loitering platforms for telecoms

relay, has developed. Notable examples

here are the Aquilla and Zephyr craft, the

latter of which has already demonstrated

a continuous flight of 14 days. By

contrast, smaller scale solar-powered

UAVs are designed mostly for low-

altitude, long-endurance applications.

Although faced with more challenging

meteorological phenomena in the lower

atmosphere – clouds, rain, wind gusts or

thermals – low-altitude UAVs can deliver

higher resolution imaging thanks to

reduced cloud obstruction, are lower in

complexity and cost and are simpler to

handle. These traits are highly beneficial

for first-aid SAR scenarios as well as

other inspection tasks.

Fly longer and carry more – that’s

what every UAV customer wants. As the

uses for small, electric, commercial UAVs

expand, the demand for them to stay aloft

longer and carry heavier, more powerful

payloads increases constantly. Right

now though there are few alternatives

for extending electric UAV endurance

other than adding batteries, improving

the effciency of the electrical systems

or redesigning the UAV to be more

aerodynamic. The frst option tends to

add signifcant weight and takes up a lot

June/July 2016 |

Unmanned Systems Technology

A solar-powered version of the Puma AE (All Environment), a UAV designed

for land-based and maritime operations (Courtesy of Alta Devices)