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| 04/12/17

Electric aircraft overcoming battery conundrum

TCE

A United States company has revealed plans to develop hybrid-electric aircraft for regional passenger flights by the early 2020s, aiming to lower both the cost and carbon footprint of local air travel.

Backed by Boeing and JetBlue Technology Ventures, Washington startup Zunum Aero plans to build its first prototype in the next two years, develop short-haul passenger aircraft by the early 2020s and eventually move to a completely electric fleet.

Aircraft emissions are the fastest growing source of greenhouse gas emissions, currently about five percent of total emissions and projected to increase to about 22 percent by the middle of the century. Yet air travel is one of the most challenging sectors to decarbonize, mainly due to the difficulty of replacing energy-dense aircraft fuel with heavy batteries.

However recent advances in car battery technology, coupled with plummeting battery costs, means Zunum’s directors are confident of finding the right design among the 30 battery manufacturers they are monitoring.

The challenges are still considerable however. While aviation fuel has an energy density of just under 43 million Joules per kilogram, some of the best batteries on the market today, such as those powering Tesla’s Model S, fall a little shy of a million joules per kilogram. This means that electric planes would need to hold a much greater mass of batteries to complete the same flights as their fossil-fuel powered counterparts. In order to compensate for this, Zunum Aero’s electric-hybrids will use both fuel sources, first drawing power from a battery and then using jet fuel only if the battery’s charge is insufficient for the journey.

If the prototype works, there will be significant gains for both passengers’ wallets and carbon reductions. Owing to the amount of fuel burned while taking-off, short-haul flights use disproportionately more jet fuel than longer flights, and also produce 40% of emissions. Therefore, slashing jet fuel usage would not only cut emissions for short haul trips but also cut operating costs by 40 percent to 80 percent, the company claims.

In addition, if the company succeeds in its plan to provide service to the majority of smaller airports, this may further reduce emissions by decreasing the amount of ground transportation that passengers need to use. Historically, the movement to consolidate passengers to larger airport hubs has meant that more passengers are required to travel longer distances via land to catch their flights. The company says that of the 13,500 plus private airports in the US, 140 large airport hubs take 97% of all air traffic. Because ground transportation tends to be less energy efficient and produce greater emissions per kilometre travelled than air travel including short-haul flights, the expansion of localized air travel options through hybrid craft would be impactful.

Coupled with the eventual decarbonisation of the power grid, electric flights could support a pathway to potentially achieving zero-emissions air travel.

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Electric planes need huge - and heavy - batteries to fly like their fossil-powered counterparts

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