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Siemens and partners build first aircraft with series hybrid electric drive

Siemens Drive Technologies Division supplied the integrated drive train for the first series-hybrid electric aircraft. Source: Siemens. Click to enlarge.

Siemens, Diamond Aircraft and EADS have built an aircraft equipped with a series hybrid electric drive system. The partners are presenting the two-seater motor glider DA36 E-Star at the Paris Air Show Le Bourget 2011 (until 26 June) in daily flight shows. The aircraft was built to test the hybrid electric drive concept.

The technology, which is intended for later use also in large-scale aircraft, will cut fuel consumption and emissions by 25%, compared to today’s most efficient aircraft drives, according to Siemens.

Based on Diamond Aircraft’s HK36 Super Dimona, the E-Star’s propeller is powered by a 70 kW electric motor from Siemens. Electricity is supplied by a small Wankel engine from Austro Engine with a generator that functions solely as a power source. A Siemens converter supplies the electric motor with power from the battery and the generator.

Fuel consumption is low since the combustion engine always runs with a constant low output of 30 kW. A battery system from EADS provides the increased power required during takeoff and climb. The battery is recharged during the cruising phase. The plane is able to start noiseless with the electric drive and can fly over long distances. During test flights, it was airborne for about two hours.

The next development step will be to further optimize the entire drive train. Siemens researchers are currently working on a new electric motor that is expected to be five times lighter than conventional drives. In two years, another aircraft is expected to be equipped with an ultra-light electric drive.

Siemens’ Drive Technologies Division has already used integrated drive trains in other applications like marine drives. The know how gained in these areas has now been applied in the aviation industry as well. Combined with the corresponding product portfolio, the components of the drive train can be optimally adjusted to one another.



Another validation(besides the Audi A1 E-tron) of the constant rpm Wankel as a electric generator for an electric drive motor.


GM got no guts making series hybrid drivertrain for Chevy Volt. Let's hope Audi A1 E-tron will be real thing.


"Siemens researchers are currently working on a new electric motor that is expected to be five times lighter than conventional drives."

80% reduction in weight would be quite impressive!

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That’s right. It is more evidence the Wankel engine is scheduled for a huge comeback this time as the motor of choice for genset applications when low weight and high energy density is required. However, the Wankel engine is not very durable so for commercial vehicles the diesel engine is still superior as a genset engine for plug-in vehicles.

Note also that Siemens believes they are on track to increase the energy density of their 70kW electric motor by no less that 500%! Hopefully Siemens can do it without also increasing its price so that their new motor can be used for mainstream electric vehicles as well.

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Darius you can be certain that GM is working on a better drive train for the Volt. When GM developed the Volt they took the best engine they had in-house in order to get the Volt developed as fast as possible so that it could be launched ultimo 2010 and ahead of all the competition. It takes years to develop a new engine and even more when the engine is a Wankel engine that GM’s engineers have no previous experience with. I will not be surprised to see GM market a new Volt version based on a Wankel engine genset before 2015. And GM will also drop the complexity and high costs of the current Volt design with a direct engine drive when at high speeds.

The auto industry is characterized by long-product cycles about 6 years for engines. So don’t expect the Wankel engine to be in the first iteration of plug-in cars. It will come in the second or the third development cycle 6 or 12 years from now.


Direct e-motor drive, with electrically coupled ICE (Wankle?) generator, requires a powerful e-motor to offer performances comparable to current ICE vehicles.

The new Siemens e-motors (and equivalent) with higher power density may offer a good possibility. Coupled with super-caps it would have higher all around performances.


Brush less DC in-wheel motors have been built with very high power density of 4.8Kw/Kg. If Siemens could do 5 times better, a 100 Kw motor would weight only 4.16 Kg. It would be ideal as in-wheel motor/generator for PHEVs and BEVs.

The Wankel engine has a power density of 1.5Kw/Kg. A 45 Kw unit could be as light as 30 Kg.

The power to weight problem is still with e-energy storage (super-caps and/or batteries) with energy density of only 30 Wh/Kg to 25 Wh/Kg.


Correction: Last line should read....30 Wh/Kg to 250 Wh/Kg respectively.


I would drive the engine through the motor. You have both for take off and climbing, then you have the motor for emergency landings.


One alternative would be high power density e-motors ( 2 or even 4 for ultra quick start and hill climbing... available now) together with very quick charge/discharge, high energy density batteries (probably not available before 2016+) and a very light weight, very high power to weight, operating at best efficiency range.


Add a generator and a motor and batteries ?

To an airplane?

There is no regen for city driving.

Aircraft ICEs do not spend that much time at low power.
They run near max for takeoff, climb and cruise (cruise is at altitude where max power is lower and, again close to required power).
So it makes no sense to charge the batteries during the descent to help the TKO, CMB and CRU on the NEXT flight.

Just so you can run the engine is it's sweet spot?
That is highly overrated.

Makes sense - MAYBE - in a motor glider - but not too many of those in revenue service.


In the not too distant future, many modern ultra light aircraft will be equipped with very high power density e-motors fed from ultra high energy density storage units. Ultra high efficiency (55+%) flexible solar panels integrated into the body will supply a high percentage of the power required to keep the plane flying. Many of those light planes will be capable of 24/7 flights on solar power alone.

Combo aircraft with various hybrid combinations are possible and will be flying by 2020/2030.


If I had a small plane, I would like to have an engine driving through a clutch to a motor driving a propeller. I have more power for take off and climbing. If I have a fuel, ignition or engine problem, I can disengage the clutch and land on motor power.


Note that this application is on a motorglider, which has relatively low power demand. There may be some opportunity for regeneration during descent and landing, but the high power dissipation is very demanding on batteries and capture efficiency is likely to be low. Dynamic braking is a possibility, dumping power to resistors as a replacement for wing flaps as drag devices.

I think the turbo Scuderi split cycle has more potential for conventional aircraft than this electric scheme.

Thomas Pedersen


I would be worried that regeneration (with the prop) would de-stabilize the air craft. Adding resistance to the front end just does not seem like a good idea...

Btw, the propeller on this air craft is fixed (judging by the photo), so the possibility is not even there.


The button at the bottom says "comments" not argue nor criticize.


Props are widely used as drag devices; crank a constant-speed prop to max RPM and its drag goes up as it windmills the engine.
(This is a serious problem for engine-out operation in twins if the dead engine's prop can't be feathered.)

Most motorgliders have props which can be feathered for power-off operation. Changing the stops to allow for something close to flat pitch for braking would be a minor change.


The cost of a variable pitch prop, if needed only for regenerative braking does not seem sensible.

Cruising all the way to the destination and then diving out of the sky at low prop pitch will recover little of the trip energy required.

Just allow a high speed/low power descent for the last segment.

Hybrid cars have an advantage IN-THE-CITY where there are lots of stops and have few or no advavtages intercity.

This is a mis-application.

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