A key technology that could enable an electric jet may be just three or four years away, Tesla CEO Elon Musk claimed Monday – and Tesla could be set to reveal some more advancements in the space soon.
Responding to a Twitter thread about the potential for an electric jet, Musk stated that the futuristic zero-emissions jet would require a battery pack with a density of 400 watt-hours per kilogram. This battery would also need to be produced in volume, rather than just an experiment in a lab. Musk claimed in his Twitter post that this breakthrough is “probably 3 to 4 years” from reality.
The news comes as Tesla announced plans for its upcoming Battery Day. The event will happen immediately after its annual shareholder meeting on September 22 at 1:30 p.m. Pacific time. Electrek noted Monday that the main event motif bears resemblance to silicon nanowires, an exotic battery technology that could electrify aviation.
In 2008 Musk noted that “an electric plane gets more feasible as battery energy improves,” and four years later he said he had a design in mind for years. Musk even mentioned the idea during his cameo in the 2010 film Iron Man 2. In a 2016 interview, Musk said the jet would take off and land vertically.
So where is it? The main obstacle is battery density, or how much energy each kilogram of battery can hold. That’s important for flight, as a plane needs to overcome the force of gravity to lift off in the first place. Musk explained in September 2018 that the energy used for cruise speed is actually quite low, and the plane can depend on gravitational potential energy for the landing phase, so it doesn’t need a big bank of reserve energy to return. It’s the initial takeoff phase that’s tricky, and that’s where density is key.
Current electric car batteries are around 250 watt-hours per kilogram, Musk claimed in 2018. Sam Korus, an analyst at ARK Invest, wrote on Twitter that removing 150 kg (330 pounds) from a Tesla Model 3 would add just 15 miles to the car’s range between battery charges. For the electric jet, though, increases in battery density could make the vehicle dramatically more useful.
Battery Day could be a step toward that reality. Korus shared a post that showed battery-technology firm Amprius is located near Tesla’s facilities in Fremont. Amprius claims to be able to reach past that 400 watt-hours per kilogram mark, with its 100 percent silicon nanowire batteries – the same technology speculated to be the backdrop for Tesla’s Battery Day webpage.