April 10, 2020, ©. Leeham News: We have since December 13, discussed why e in ePlane should not stand for electric and covered a lot of areas explaining why electric aircraft or hybrids are not the best way to environmentally friendly air transport.
We now recap what we learned and then wrap the series.
Figure 1. The Gartner hype cycle. Source: Wikipedia.
The subject to discuss
In the first Friday Corner on December 13 I wrote;
“The electric aircraft hype comes from the fact it works for cars. Applying electric propulsion to aviation is seen as the most promising way to get us to an air transport system that has a lower environmental footprint. On a number of Fridays, I will argue why it doesn’t.”
The electric route is “a route with high technical hurdles, and it involves a lot of unknown unknowns on the risk side. We are still at the first peak in the Gartner hype curve (Figure 1) and we need to pass the trough of disillusionment before we make real progress. There are lower hanging fruits in the tree, but the electric hype stops us from seeing them and from directing our efforts more intelligently.”
The high hanging fruit
We summarize our insights by listing the highest hanging fruit first and then work our way to the lower levels in the tree:
- The highest hanging fruit is the 100% battery-based electric aircraft. Only teams with no experience in developing air transport aircraft are still pretending this is a viable technology. They embarked on almost a mission impossible as it needs a certifiable battery system that has 10 times (this is 1000%!) higher energy density than the best research individual cells of today. It will not be achieved this side of 2040. Structural batteries might help but bring their own problems.
- The next level down goes to the electric hybrids. It’s once again the batteries that drag them down. It doesn’t matter if it’s a parallel or serial hybrid. The first that happens, we lose 10% in efficiency just because the battery’s weight stays fixed during the mission. A hybrid propulsion system has yet to prove it can achieve any improvement over what already know technologies delivers.
- The third branch from the top holds the different aerodynamic wonders that electric technologies shall enable. We proved they are better realized with existing technologies, present for decades. Yet we have no implementations. Could it be because they don’t work?
- To the high hanging fruit, we must add hydrogen-fueled aircraft. Here the technology holds promise; we just have a long way to go to explore and mature it. We need an environmentally correct ecosystem with production, distribution, and in-plane storage. The process of driving fuel cells with hydrogen still needs development, but the burning of hydrogen in a gas turbine combustion chamber works, it predates the use of jet fuel in gas turbines.
The above list is the highest hanging fruit, yet this is where the attention is. This is consistent with Gartner curve observations from other industries. The exiting stuff catches the imagination, then reality catches up.
In five years the hype media will explain why electric and electric hybrid airliners don’t work and what to do now.
In next week’s Corner, we summarize the low hanging fruit.