According to foreign aviation media flightglobal on April 19, the U.S. Naval Research Laboratory (NRL) conducted a test flight of a hybrid tiger UAV in November 2020, with a flight time of more than 24 hours.

The electric drone is powered by hydrogen fuel cells and solar panels on its wings, and uses energy harvesting technologies, such as flying with hot updraft, the laboratory said on April 14. The demonstration was conducted at the Aberdeen Proving Ground (APG) in Maryland.

Richard Stroman, a mechanical engineer in the Chemistry Department of the Naval Research Laboratory, said: "the flight was actually a performance test in the worst case: the temperature dropped below 0 ℃, the wind speed reached 20 knots (37 km / h), and there was relatively little solar energy near the winter solstice on December 21. Still, the hybrid tiger is doing well.

According to reports, as the UAV performs well in harsh conditions, engineers at the Naval Research Laboratory expect it to be able to fly for more than two consecutive days in better weather and sunlight. The lab plans to have such a demonstration later this spring.

The hybrid tiger is powered by a high-pressure hydrogen fuel tank and fuel cell system at night and by efficient photovoltaic solar panels during the day.

The NRL said the project's researchers are also developing energy aware power management algorithms that can change operating modes and generate navigation strategies based on weather forecasts and locally observed energy harvesting opportunities, such as using updraft to increase flight altitude. "Hybrid tiger" combines a variety of power sources and different advantages to achieve the ultimate endurance.

An algorithm developed by the Institute allows a similar unmanned glider to fly 61.3 meters (113 kilometers) in 4.5 hours, during which only thermal updraft is used to periodically raise altitude, the report said.

In addition, because hydrogen fuel can be produced by electrolyzing water from solar panels, NRL believes that this technology is a way out of the aviation fuel supply chain. "Using hydrogen can not only extend the endurance, it can also produce fuel locally," strohman said.