While viable solar power is still a long way off for commercial airliners, alternative fuels research continues

Weighing in at a feather-light 1,600kg, the world has a new aviation first. After 26 continuous hours in the air, the 63.4m-wide Solar Impulse HB-SIA recently entered the record books having completed the longest solar-powered flight.

But, a dose of reality. The sun might be the most potent source of energy on the planet, but understanding how to harness it for mass aviation remains light years away.

The Airbus 380 weighs 200 times more than the Solar Impulse HB-SIA. At present, the pioneering plane’s electric engines produce a similar horsepower to that of a small motorcycle. Multiply that ten-fold and it would still be a challenge to get a passenger plane out of the hanger, let alone into the air.

“Given the amount of thrust from a solar panel system it seems – at least in the short or medium term – that light aircraft will be as far as this technology can realistically go. If people want to keep flying, we need to keep innovating,” warns Iain Watt, principal sustainability adviser and head of the climate programme at UK sustainability charity Forum for the Future.

That is not to pooh-pooh alternatives altogether. Serious experimentation in the use of biofuels is happening in the aviation industry. Last year, a Japan Airlines 747 took off from Tokyo under the propulsion of a biofuel mix based on camelina and jatropha oilseed plants. Virgin Atlantic and Air New Zealand have used coconut extract to achieve similar results.

Emma Harvey, head of sustainable business at Virgin Atlantic, echoes the confidence of the industry in predicting a “breakthrough” on biofuels in coming years. “Biofuels are likely to be phased in over time, as a ‘drop-in’ fuel with the regular fuel mix, with volumes increasing as the right fuels become more readily available,” she says.

Biofuels are no panacea, however. Issues still abound. For a start, fossil fuel comprises a substantial portion of their content (50% in the case of certified hydrogenated biofuel-based jet fuels).

Direct and indirect land use are major public concerns as well. As a result, biofuels can only hope to comprise 10% of total aviation fuel come 2050, the UK Committee on Climate Change (CCC) concludes.

The algae option

Other low-carbon solutions could still present themselves. Earlier this year, for example, French engineers put an all-electric aerobatic plane in the air – fuelled, in part, by algae. But don’t hold your breath. Most of the probable solutions are “on the table now” or at least in the research and development stage, according to Ben Combes, senior aviation analyst at the CCC.

Whatever the renewable technologies may be, the future of low-carbon commercial aviation lies with the airlines themselves.

At a company level, Etihad and Qatar Airways both announced substantial investments in biofuel research earlier this year. The Sustainable Aviation Fuel Users Group and the Aviation Global Deal are taking similar steps at an industry level.

Yet the focus of most airlines’ climate change strategies lies elsewhere. Fleet fuel-efficiency leads the way. Cuts in unnecessary air time, reductions in onboard weight and carbon offsetting follow close behind. A handful of more progressive airlines, such as Air France-KLM, have even discussed switching short-haul passengers onto high-speed rail.

But none suggests replacing the combustion engine. For now, at least.

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