If the aviation industry is going to meet the formidable fuel-efficiency goals laid out in the European Commission’s “Flightpath 2050,” a lot of progress needs to be made.The successful test flight of PC-Aero’s single seat Elektra One in 2011 proved that electric power is a potential solution.
But a concept presented by research institution Bauhaus Luftfahrt at this week’s ILA Berlin Air Show makes that vision of air travel more relevant, efficient, and downright cool.
The recently unveiled Ce-Liner is a fully electric commercial passenger plane that would carry nearly 200 travellers between continents and over oceans. To develop it, Bauhaus Luftfahrt is using a variety of new technologies.
The distinctive “C-wing” improves aerodynamic efficiency and makes the goal of powering transatlantic flights with electricity more viable. The research institution predicts that battery technology will advance enough by 2030 to allow a flight range of nearly 700 miles. That will jump to 1,000 miles by 2035, and to 1,600 miles by 2040.
In addition to emissions-free flight (provided the electricity is produced from renewable resources), the Ce-Liner will have a half hour airport turnaround time, easily reversible motors for better speed control, and seat design that gives passengers more room when the plane is not full.
More importantly, electric flight could transform aviation. Airlines, no longer hostage to rising oil prices, would be freed from the need to pack flights and reduce service to produce profits. Electricity would actually make air travel pleasant, especially since there’s no headache-inducing jet engine noise.
To find out just how Bauhaus Luftfahrt plans to get the Ce-Liner built and into the skies in the next few decades, we spoke with Dr. Askin T. Isikveren, the head of the research institution’s Visionary Aircraft Concepts program.
Here’s what he told us.
Q: How does the C-Wing impact flight in terms of aerodynamics and efficiency?
A: The C-Wing concept, originated by [Ilan] Kroo of Stanford University and [John H.] McMasters of Boeing/University of Washington, focuses on reducing a significant amount of the drag attributed to aircraft lift – much in the same way winglets reduce drag on commercial transports and business jets. The difference here is we combine the traditional horizontal tail (usually a separate smaller wing at the back-end of the aircraft) with the main wing in such a manner that it can further enhance the benefits given by winglets. Think of it as a “winglet-let”. Our predictions indicate a total drag reduction of up to 11 per cent compared to projected improvements in conventional, separate wing-horizontal tail designs.
Q: What makes the Ce-Liner’s motors capable of producing enough power for a large aircraft?
A: We utilise so-called High Temperature Super-conducting electric motors. These are very much in the experimental phase – currently a good measure of test-rig laboratory work is being performed in the US. These motors are well suited to aerospace application because they are expected to exhibit very good power-to-weight ratios. The Silent Advanced Fans utilising Electrical power (SAFE) propulsion devices of the Ce-Liner need a total of around 59,800 hp in order to take off.
By shrouding the SAFE fan blades, we project very quiet levels of community and cabin noise and yet still produce a high level of efficiency for the aircraft during operation. One additional benefit of utilising electric motors for propulsion is to generate reverse thrust (slow down the aircraft during, for example, landing) simply changing the direction of rotation achieves this. Today, kerosene-based engines require dedicated equipment for such a function, which increases weight and cost.
Q: What other design differences are there between the Ce-Liner and current, conventional passenger jets?
A: Bauhaus has also focused on the cabin. We propose a centre-fuselage boarding and de-boarding. Our novel Sideward Foldable Seat allows passengers to board and de-board quickly. In addition, when the cabin is not full (average US DOT numbers indicate cabins are not 100 per cent full), by having the Sideward Foldable Seats collapsed when passengers do not require them, the cabin will have a feeling of more space in its surroundings, therefore affording more comfort.
To make sure the aircraft is ready for departure from the gate within 30 minutes, we have designed specially modified industry-standard LD-3 cargo containers (called Charge Carrying Containers, or 3Cs) to house the advanced lithium ion batteries. In this way, the aircraft can be turned around quickly without having to wait for them to be recharged (which takes up to two hours) – the procedure will be to load and unload these 3Cs when the aircraft is at the gate.
Q: What is the most difficult design challenge facing the Ce-Liner?
A: The most difficult challenge is to reduce the weight of the Universally-Electric Systems Architecture necessary for the Ce-Liner. Although we at BHL have set relatively aggressive weight targets for the electrical system components, the aircraft still ends up being heavier than, say, a future aircraft that operates with kerosene alone. This tends to penalise the performance of the aircraft, e.g. diminish range capability.
By communicating the outcomes of our research work, we look towards collaborating with the wider academic community and industry to assist us in addressing this problem. It should be highlighted that our investigations have shown, even with this high weight penalty, the Universally-Electric Systems Architecture alone produces up to 10 per cent better vehicle efficiency compared to future kerosene based designs. Such an outcome is due to the inherently more efficient components and sub-systems associated with electrical based solutions. This is good news when one considers the potential when utilising energy, whatever it might be, for future applications in aerospace.
Q: How much is the design and construction of the Ce-Liner expected to cost?
A: We have not as yet conducted a full product development cost prediction for Ce-Liner. Seeing that many of the component technologies that constitute the Universally-Electric Systems Architecture are in the experimental phase nowadays, the target we have set is moderately higher than the cost one normally associates with advanced, kerosene-based narrow-body aircraft.
Q: What is the estimated sale price?
A: Our market value and subsequent aircraft list price modelling does not capture the effect of how zero-emissions capability would influence price. This is currently too difficult to predict. Based on a method generally accepted by the aviation community using range capability, passenger accommodation, and other cabin and performance attributes, we have projected a list price of $39.6 million.
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