Solar-powered airplane to reach the stratosphere


From pv magazine France

Swiss start-up SolarXplorers is currently developing the world's first PV-powered stratospheric plane, at the Payerne military airfield in Switzerland.

Called Solarstratos, the aircraft measures 8.5m in length and 24.8m in wingspan and has a total weight of 450kg. It is covered with 22m2 of solar panels totaling 5 kW that will power an electric motor connected to lithium-ion batteries to ensure its operation.

To reach the announced 25,000m altitude, the aircraft is powered by a three-bladed propeller and a 2×19 kW double electric motor which is entirely powered by solar energy. The PV system is based on solar cells with an efficiency of between 22 and 24%. The photovoltaic cells were integrated directly into the wings by the Swiss Center for Electronics and Microtechnology (CSEM), a scientific partner of the project.

The cells were deployed in series or in parallel, to ensure their electrical insulation. This, according to the airplane developers, makes them more resistant to external factors such as humidity, rain, snow or corrosion, and even mechanical shocks.

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The solar cells power the device's lithium-ion batteries, which have a total capacity of 14 kWh, expandable to 21 kWh.

To limit the weight of the aircraft, the aircraft is not pressurized and the pilot must be equipped with a spacesuit specially designed for the project, and which also operates on solar energy. It was the Russian space supplier Zvezda which developed the technology for this suit, which combines several innovations to regulate temperature and pressure, and to protect the pilot from solar exposure.

The fuselage and wings are constructed of carbon fiber with a large wingspan that allows the aircraft to fly at reduced speed. “SolarStratos will stay in the stratosphere for a while, consuming nothing other than unlimited solar energy and, above all, totally clean,” said Philippe Pilloud, who is in charge of operations and flight safety. “This is Icarus' dream, but in this case the sun will be an ally and no longer an enemy.”

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