Pipistrel hybrid goes through the first integrated systems test. I wouldn’t have run it at full power two meters away from the garage door but that’s just me
Amazing. Pipistrel are really taking the lead in GA it seems.
I have done the math a couple of times on hybrid propulsion. Makes sense to me.
In this case my guess is that:
The 200 KW (150 KW ICE + 50 KW Electrical) is available for 5 minutes and then it drops down to 150 (ICE)
In cruise 150 KW is fine, and one can allocate a small percentage to re-charging the batteries.
Some more can be done on descent.
In case of an engine failure upon take-off, 50KW opens up a lot of options instead of a straight ahead crash!
And in cruise, one could count on 25 KW for 10 minutes while descending.
Twin engines, but in-line, no loss of control due to asymetry.
From a total mass perspective, the electric motor replaces a starter and flywheel, it becomes the generator when not in use.
And for high altitude operations, one could add an electrically powered supercharger, eliminating the heat issues associated with turbocharging…
All powertrain components were developed by Siemens
I thought Siemens got pissed at Pipistrel over the Channel flight (Pipistrel vs. Airbus eFan), which Colomban settled for them (we have a proverb in Poland: where two are fighting, the third one benefits). Wonder if this means Siemens found Pipistrel to be in a better position to actually achieve something here than Airbus. Hey, more power to them!
BTW, the “hybrid” here means “series hybrid” where the ICE acts only as a electric generator, the propulsion is always provided by the electric engine.
More info on the powerplant is here
Edited to add that the news item about Pipistrel is here
It would be nice to get the papers/slides/videos from these talks from http://www.dlr.de/tt/en/desktopdefault.aspx/tabid-9610/
14:40 Serial Hybrid Propulsion System Architecture, Certificability and Associated Safety Implications, by Heintje Wyczisk, Siemens AG
15:10 Integration Challenges, Cooling and Structural Requirements for Hybrid Powertrain Installations on an GA Airframe, by PIPISTREL d.o.o. Ajdovščina1
Looking at this http://www.hypstair.eu/wp-content/uploads/2013/12/poster_siemens_profile.jpg
and reading here http://www.hypstair.eu/most-powerful-hybrid-electric-powertrain-powers-up/ that
“The drive motor, delivering 200 kW take off power and 150 kW continuous, and the generator, delivering 100 kW feature a power density exceeding 5 kW/kg”,
I got this:
1) 5kW/kg = 40kg for what, just the motor? Motor + generator? Motor + generator + inverters + controllers?
2) I read 200kW as take off power for short time before the motor overheats, 150kW as climb power until the batteries run dry (but with no worries about overheating the motor), and 100kW as the cruise power that can be supplied via the generator from the ICE while there is fuel in the tanks (you would want to cruise at less, say 80kW, to recharge the batteries – or perhaps recharge them during the descent?).
3) Soo, it looks like you need about 100kW ICE engine … any lightweight efficient ones around?
4) 3min at 100kW + 12min@50kW = 15kWh, that would be 50-100kg of batteries, I guess…
5) where do you put the ICE? Right behind the electrical stuff, I guess – loong nose.
Overall, this seems to be a system that adds at least 150-200kg (and who knows how much $$$) to an airplane that cruises on 100kW, so that you can takeoff with 200kW and climb with 150kW. The added benefit is less worry (once all the electrical gremlins are worked out, the electric motor should be very reliable) of sudded engine stop – if ICE stops, you still have your batteries to find nice place to land (won’t help you over North Atlantic, though).
Quoting from the article “breakthrough in emission-free propulsion in aviation”. What is emission-free about this power plant? Even the electricity for the electrical motor is generated by the combustion engine.
Marketing bullshit, of course.
With an oversized battery, you can do your circuits and short leisure flights/hamburger runs on pure battery power, and use the ICE only for longer cross-country flights. Might be more convenient/faster as well – no engine warmups, quick check and go… perhaps more likely to actually go flying.
Hmm, not a healthy regime for that ICE – only occasional running.
Trying to come up with other advantages (no problem ciming up with disadvantages :-) ) .
1) propeller strikes should be less of a problem, with ICE decoupled, and the electric motor much more resistant to shock loads
2) no power pulses to the propeller, can be made lighter, and the ICE does not need to worry about power pulses, just optimize for efficiency at one power setting
Hybrid does not work for any application where there is high power operation for extended periods.
Typical GA cruise is 65% to 75% of max power.
It might work in a “motor glider” type of aircraft, which might stay up on say 30% of max power, flying close to Vbg which is anyway the “best MPG” speed (assuming powerplant efficiency is linear with the power output; not the case with IC engines).
Unless you come up with some other source of electricity, but an ICE ain’t it, in this context. Nuke powered gliders, eh? ;-)
One could look at the generator as a complicated variation on a gearbox, but I’m sceptical about the efficiency.
It is a chicken&egg problem – the ICE engines don’t like being run at 30%, so the airplanes are designed to be flown at 65-75% power.
Diesels are a bit better in this regard, and are often run at lower % (55).
Motorgliders are somewhat slower and give choppier ride, their main problem is often anemic takeoff and climb performance – electric boost can help with that significantly.
Anyway, hybrid makes sense only if you design the aircraft from scratch around that.
And the benefits will not be the classical speed/useful load ones, but less tangible ones (less worry about engine failure, ability to very quickly climb to safe altitude/ through an icing layer).
Peter wrote:
Typical GA cruise is 65% to 75% of max power.
And that’s the point. The rest isn’t. An aero engine will run efficiently at that exact power setting and corresponding RPM. If the aircraft is used as a super tanker, running at one power setting for days and weeks, none of this matters or course. With a hybrid the engine can run at best efficiency – allways, all the way from start of taxi to stop. A turbine will have much higher benefit, but the benefit will be large also for a piston. In addition, the max power is not limited to “100%”, it can be 150 – 200 or more. It will be able to go straight up, and straight down also.
