December 20, 2019, ©. Leeham News: We continue our series why e in ePlane shall stand for environment and not electric.
If our target is to lower the environmental footprint from air transport we must have a target that focuses just that, lowering the CO2 load from our airliners. Electric or Hybrid-electric aircraft are not the most efficient way to achieve this. There are better ways to this target.
We increase the CO2 content in our atmosphere when we burn fossil fuel. With present technology fully electric aircraft other than UAMs, light sport aircraft or short-haul air taxis are not feasible.
Anyone who says it is have not done even the most basic checks with realistic system assumptions and an aircraft performance model. And it won’t be feasible for at least another decade (if not two).
And hybrids won’t be much better. The initial hybrid-electric aircraft will have a shorter range and burn more CO2 generating fuel than today’s airliners. I realized this when I started modeling the possible hybrid concepts two years ago, in preparation for my first article series on the subject.
Since then I have talked and listened to every expert on the subject, and my view hasn’t changed. In anything, I see a longer route to a worthwhile hybrid today than I did then.
You can do a hybrid aircraft that can fly airliner routes. Different to full electric aircraft it’s possible. It’s just not a smart way to do it.
After spending a lot of money you will get it to fly with some payload and range. After spending even more money and time you will get it certified for carrying passengers. But it will be a long route there.
And no-one has been able to explain the real point in a hybrid propulsion system for aircraft. You have the gas turbine already, why not bolt the propeller or fan to it and be done?
And don’t come with a story the gas turbine can get more efficient if we have a hybrid concept. Marginally yes, but this gain is consumed before we are past the generator. We will analyze the other claimed gains in later Corners. To summarize, they don’t change anything.
The complexity of a hybrid brings us problems but little else. You now shall convince the FAA/EASA/etc. it’s safe to have 3kV electrics routed through the aircraft pumping 15,000 Amps of current to generate the 50 MegaWatts of power the propulsor fans need to get an A320 sized aircraft into the air.
Nothing bad will happen. Not in normal operation and not if there is a major upset/runway excursion/crash or system/isolation failure. It will work with total safety at up to 41,000ft and with all possible cosmic effects on its control electronics, creating no hazard for at least the next 2,000 flights until major maintenance can have a look if something has happened. And so on.
Realize we have NO experience of the tensions and currents involved, including flying with these types of Volts and Amps, at the altitudes and atmospheres (wet, humid) involved. The military are in this bracket when they do experimental airborne death lasers. But our safety-oriented civil air transport has no experience of such challenges.
And you have the same gas turbine generating the propulsive power to drive these 50 MegaWatts to get the aircraft to take off and later 15 MegaWatts to cruise. Only now through a heavy, complicated and risky hybrid chain instead of directly to the fan. Your gains from the hybrid chain will not compensate for the added weight, complexity and risk.
No-one who has real expert knowledge of all parts of the chain has so far been able to explain to me how we will gain in fuel consumption and by it CO2 emissions with this technology.
The route described above spends our invest money and burns the time we don’t have. Instead, we should focus on more productive options to get the job done. I will give examples of such options below and in the coming Corners.
The options are more straight forward and attainable than the electric/hybrid investments and will achieve several times more over the next decade than all these projects combined.
We start with the one which needs no new technology and no big investments, just the will for change:
With a focus on reducing the fuel consumed per transported passenger-km the most obvious advancement would be an improved air traffic system. We are today flying inefficient routes rooted in historical incomplete knowledge of where our airliners are in the air. And we fly a lot of these routes every day, Figure 1.
The present air traffic routing and separation technology necessitate separating principles that fly the aircraft on routes that are up to 10% longer than necessary. With every aircraft in US-controlled airspace having ADS-B from January 1st, 2020 (which tells every aircraft and air traffic control where everyone is all the time) flights can be completed more efficiently once this technology is embraced and used. And an ADS-B mandate like the US can be applied worldwide today. It’s just to decide.
For this global change, the technology is there. The production lines for the equipment are up to speed and all aircraft OEMs have developed the mod kits (they need it for the US market). And the software changes for the ATC systems have been trialed over the last five years. Yet progress is tepid. This is shameful.
The state in the US won’t give the FAA the money to get the NEXTGEN system ready soon and the air traffic controller unions in Europe block SESAR, the European effort, as they want to stay with the old. It’s more inefficient and keeps more controllers on the state’s payroll.
It’s a low hanging fruit that can reduce our emissions the same amount as upgrading all our 20,000 airliners flying our airspaces every day to a newer generation aircraft. It would with one feasible, realistic and badly needed change significantly lower our CO2 emissions from air transport. Yet it’s not done.
NexGen is debated ad nauseam in the US and the European equivalent, SESAR, is going nowhere. Our politicians pay lip service by allocating research funds to environmental projects with electric and other buzz words, yet they don’t do what they have control over. Order our airspace providers (they are all state organizations) to settle with the air traffic controllers on how we can get the new more efficient airspace done. Any delay is blocking a real chance to reduce CO2 emissions and do it now.
Instead, the policymakers prefer to believe in the dreams of e as electric to fix the problem. Then they don’t have to do anything or spend any money with their airspace providers. New technology will save them from having to do what can be done now.
In the next Corner, we will list more nearby options to reduce our CO2 emissions.