Will Stay in Oahu Until April as Long Flight Saw Battery Damage
The historic ’round-the-world journey of the 100% sun-powered battery electric Solar Impulse 2 airplane has been delayed at least until April – the aircraft’s lithium polymer batteries suffered “irreversible damage” from overheating during this month’s five-day flight from Japan to Hawaii (F&F, July 7), the Solar Impulse team said this morning.
“During the first ascent on day one of the flight from Nagoya to Hawaii, the battery temperature increased due to a high climb rate and an over insulation of the gondolas,” says a release. “There was no way to decrease the temperature for the remaining duration as each daily cycle requires an ascent to 28,000 feet and descent for optimal energy management.
‘Not a Technical Failure or a Weakness in the Technology’
“Overall the airplane performed very well during the flight,” the team said.
“The damage to the batteries is not a technical failure or a weakness in the technology but rather an evaluation error in terms of the profile of the mission and the cooling design specifications of the batteries. The temperature of the batteries in a quick ascent/descent in tropical climates was not properly anticipated.”
The damage will require repairs expected take several months. “In parallel, the Solar Impulse engineering team will be studying various options for better cooling and heating processes for very long flights.”
State of Hawaii Support
The Solar Impulse team says that the University of Hawaii, with the support of the Department of Transportation, will host the airplane in its hangar at Kalaeloa airport. Post-maintenance check flights will start in 2016 to test the new battery heating and cooling systems.
The round-the-world mission is to resume in early April from Hawaii to the U.S. West Coast. From there Solar Impulse is to fly to New York before making the Atlantic crossing to Europe and returning the point of departure in Abu Dhabi.
Kokam for Lithium Polymer Cells, ABB for Electrical Systems
“Setbacks are part of the challenges of a project which is pushing technological boundaries to the limits,” the team says. “Solar Impulse will try to complete the first ever round-the-world solar flight in 2016 and this delay will in no way influence the overall objectives of this pioneering endeavor.”
Solar Impulse carries 633 kilograms (nearly 1,396 pounds) of lithium polymer batteries, accounting for just over or just over a quarter of the aircraft’s overall weight. They are low-oxidation cells invented by Kokam, a Solar Impulse spokeswoman told F&F today: “It’s a new technology,” she said, “and the best battery for the project thanks to the weight, efficiency and lifespan ratio.”
ABB is the Solar Impulse partner for electrical systems.
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Source: Solar Impulse with Fleets & Fuels follow-up