P. Langlois' analyzes on "flying shuttles":
Electric flying shuttles, a convergence of technologies
Written by Pierre Langlois
The 23 / 01 / 2017
There are at least four different technologies, other than battery chemistry, which should reach maturity within ten years and facilitate the advent of electric flying shuttles. A paradigm shift on the horizon.
Robotic driving
Already, autonomous electric cars are a reality. The improvement of sensors (radars, lidars, sonars, digital cameras), the very significant reduction in their cost, the constant increase in the computing power of processors, the precision of GPS and the connectivity between vehicles are at the origin of the rapid development of robotic driving.
As road regulations allow it, more and more segments of driving will integrate robotization. At first, highway driving and parking, then more complex urban driving.
This same robotic driving will obviously apply to electric flying shuttles (NVE), and to reassure several readers, so that NVE becomes a reality, it will not be a question of authorizing total freedom in the movements of these aircraft and to produce a cacophony above our heads. It is certain that we will create traffic corridors, much like virtual aerial highways. There will be no intersection of the trajectories because the displacements in different directions will be done at different heights in the sky. And the NVEs will talk to each other to avoid potential collisions.
Furthermore, to limit the number of NVEs in the sky, it will be important to focus on public transportation for these aircraft, which also makes economic sense, since these NVEs will not be given and that we would be better off using them for more than an hour a day.
Ultra light and ultra efficient range extenders
Currently, the company Ehang is developing an NVE that can transport two passengers and fly at 100 km / h for around twenty minutes on a full charge of its battery. And, as we saw in my last post, for rapid intercity transport, we would need NVEs capable of reaching 150 km / h for an hour.
It would therefore quadruple the energy density of the batteries if you fill up every 100 km, by recharging or exchanging the battery in specially designed helipads. This recharging would be done during a stop of approximately 5 minutes to raise or lower passengers.
A decrease of a factor of 2 in the weight of the batteries seems achievable within ten years, but a factor of 4 could take 20 years. Never mind, we can always add an ultra light and ultra efficient range extender that uses advanced biofuel (next section).
Such a range extender is currently in development by the company Liquid Piston, and I mentioned it recently in my post of December 19, 2016. Much lighter than a traditional thermal engine, the rotary engines of this company are 30% more efficient than a diesel engine!
Advanced biodiesel that emits significantly less GHG
The Finnish company Neste has developed a synthetic diesel fuel made from vegetable oils, very similar to petroleum diesel. This new advanced biodiesel can mix in all proportions with petroleum diesel, up to 100% biodiesel, and presents no problem in very cold weather, which is not the case with traditional biodiesel. In addition, no modification should be made to the engines of the vehicles. This is called a drop-in biofuel in English literature. Finally, this advanced biofuel from Neste burns cleaner and allows greenhouse gases (GHGs) to be reduced by up to 90%, according to a recent article by Green Car Congress.
In addition, in the electronic magazine Les Affaires, François Normand told us, on January 17, 2017, of a $ 1 billion project to establish a biorefinery in La Tuque, Quebec, in 2023. It would produce advanced biodiesel from forest residues, with the Neste process, which is a partner. A non-profit organization, Bioenergy La Tuque (BELT) was set up to pilot this project.
Instead of using vegetable oil from oleaginous plants or recycled vegetable oils (food industry), we would produce bio-oil using a portable pyrolytic reactor which would be moved over the countless kilometers of roads wood of the region (the city of La Tuque is as big as Belgium). It is the bio-oil that would be sent to the biorefinery, thereby greatly reducing the costs of biomass collection. They are in preliminary studies which should lead to a pilot biorefinery possibly if the preliminary results are conclusive. Then, we would build a commercial factory in La Tuque, for 2023 if all goes well.
New ultra-resistant and ultra-light materials
If we manage to reduce the weight of the structure of the NVE, it is the equivalent of reducing the weight of the batteries. However, MIT researchers have just announced the discovery of a new graphene material structured in a three-dimensional network, which is 20 times lighter than steel and 10 times more resistant! If we manage to produce it on a large scale at a competitive price, it is a real revolution on the horizon, especially for aeronautics.
What MIT researchers knew at the outset was the importance of the shape of materials to increase their mechanical resistance, in addition to their intrinsic resistance of course. For example, a sheet of paper offering very little structural resistance, sees this resistance increase a lot if you roll it. Similarly, a flat steel sheet is much less resistant than a corrugated sheet. They therefore looked for 3D shapes offering the greatest resistance. To help them in this process, the researchers produced several plastic shapes using a 3D printer and tested their resistance. The illustration below shows one of the most promising forms they have tested.
Conclusion
In summary, the use of a range extender 30% more efficient than a diesel engine, which would consume advanced biodiesel emitting much less GHG (over its life cycle), for 30% to 50% of the kilometers ( the rest of the mileage would be electric), is a solution that would make NVE functional with only a reduction by a factor of two in the weight of current Li-ion batteries, within 10 to 15 years. Especially if you use ultra-light and ultra-resistant materials.
We should also not forget that we are targeting rapid intercity public transportation and that the fact of consuming a little advanced biofuel for part of the kilometers offers a perfectly acceptable transitional alternative. Besides a range extender offers redundancy for the electricity source, which increases safety.