Will airplanes and renewable energy ever get to co-exist?

“What about airplanes?”

That’s one of the most common questions I get when people start talking with me about renewable energy. It’s like asking Henry Ford “Hey, Henry, when’s that Model A going to be able to run 200 miles an hour for about three hours at Talladega?”

The answer: Not immediately, but a Ford that’s a direct descendant of the Model A will be able to do that. It’s not like asking when a Ford car will be able to land on the moon.

Switching to renewable energy will be possible without discontinuing large-scale aircraft. Renewable fuel flight won’t force international travel back onto luxury liners. Using renewable fuel for planes won’t require planes with lead-acid batteries that can only fly 20 miles at a time.

It also won’t require that airlines start every flight by winding up several VERY LARGE rubber bands, brought to you by the people at ACME who have been addressing Wile E. Coyote’s roadrunner-hunting equipment needs since the 1940s.

Some work is underway on battery-powered planes. Lithium-ion batteries, which use lightweight lithium rather than heavy lead, have been used to power small planes for several years. Early last year, the AutoFlight eVTOL successfully completed a test flight of 155 miles at about 200 mph.

As with small electric cars, small electric planes will eventually be introduced on a small scale. We can expect that they’ll gradually increase their market share as mass production lowers their price, making their advantageous maintenance and fuel costs more and more relevant.

Big planes, for the foreseeable future, will require liquid fuels, which contain a lot of energy per pound. There are several options available to synthesize liquid airplane fuels.

An alternative that’s already been used, and proven in some specific large-scale market circumstances, is the Fischer-Tropsch (FT) chemical synthesis process. This process is used to convert a mixture of carbon monoxide and hydrogen into liquid fuels. A few years ago, the U.S. Air Force proved that it works in today’s airplanes, by doing several test flights of F-16s powered with a completely synthetic FT fuel.

FT requires significant electric energy. However, as discussed in this space before, the cost of electricity generated by solar and wind systems is still falling, and the costs of energy storage systems that can make intermittent solar and wind available 24 hours a day are also falling. Putting renewable energy systems directly beside a FT synthesis plant could provide cheap energy without the costs and losses associated with transmitting the energy over long distances.

Carbon monoxide and hydrogen can come from gasification of otherwise-landfilled organic wastes, or from plants grown specifically for fuel. Considerable attention is going into the question of how to grow fuel precursors using non-food crops on marginal lands. Switchgrass, for instance, grows very quickly and can be planted in locations unsuitable for food crop production, such as sandy soils or, conceivably, even freeway medians.

And there’s yet another option: Production of biofuels, like ethanol, is also a proven technological concept. The same ideas as for gasification feedstocks are being investigated to avoid competition with food crops. One can realistically envision a future in which the cost of a FT fuel or biofuel will be competitive with the cost of a fuel derived through the distillation and transportation of conventional crude oil.