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article imageSolar power is key to extended drone flights

By Tim Sandle     May 18, 2017 in Science
As with many things battery powered drones have a finite time to function after which the power runs out. One means to make longer flights possible is with the application of solar power. This has been looked at by the Naval Research Laboratory.
As part of a new project, researchers are developing what they’re terming “autonomous cooperative soaring of unmanned aerial vehicles.” Essentially this is about enabling long endurance flights of unmanned drones which draw upon the power of the Sun. This involves the use of solar photovoltaics.
Solar photovoltaics describe a power system that supplies usable solar power via photovoltaics (the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect). A photovoltaic effect is where voltage or electric current is created in a material upon exposure to light and is a physical and chemical property.
Solar photovoltaic panel functions to absorb and convert sunlight into electricity. The system also requires a solar inverter to change the electric current. The basic function of the system is to convert light directly into electricity; unlike other solar-based systems there is no concentration of power or generation of solar thermal energy used for heating.
The new project is called the Solar Photovoltaic and Autonomous Soaring Base Program and it is being run by the U.S. Marine Corps' Expeditionary Energy Office. The aim is to produce drone aircraft for surveillance and reconnaissance missions.
To date trials have been successful, according to navy aerospace engineer Dr. Dan Edwards. The aircraft have flown for ten hours based on a combination of solar photovoltaics and autonomous soaring (that is gliding).
With the aircraft, which are coded PV-SBXC, the photovoltaic array has been located in the center wing panel. Also equipped into the aircraft is a power management and distribution system, which functions to convert the power from the solar arrays into direct current. The current powers the electric motor needed propulsion. When the craft is gliding the power is used to recharge the battery.
An added sophisticated is the PV-SBXC software. This contains an algorithm designed to assess local vertical winds around the aircraft. This triggers whether the motor operates or whether the craft moves through autonomous soaring. This is a little like when a bird flaps its wings or glides through the air.
Going forwards testing will look into improving solar cell efficiency and solar-recharging, to make the craft more efficient and in an attempt to increase the distance traveled.
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