Here is a good one from todays Telegraph on a design concept for a 'zero emissions' plane. Is this zero-emissions prototype plane the future of flight? -Telegraph Instead of using fossil fuels, the plane would be powered by six hydrogen engines and would feature solar panels on the wings and a wind turbine on board that would generate energy in-flight; new materials such as ultra-light graphene would be used in its construction, alongside titanium, and aluminium alloys. Anyone got any others they can share ?
Well it would actually generate electricity, but no i dont believe its a good idea. O.k i'll give you illiterate.
It doesn't need to generate enough power to fly, but if it helps power the systems without burning additional fuel to generate it then surely its useful...
I recall reading that some airliners are fitted with a small 'wind turbine' which can be deployed in an emergency to provide essential electrical power for some of the instruments in the eventuality of a complete power failure. Ram air turbine - Wikipedia, the free encyclopedia
I understand the RAT for emergency, but surely any wind turbine is additional weight and any electricity it generates will be countered as additional drag on the aircraft? Unless its part of an overall more complex scheme and only used occasionally I can't see it being a particularity good idea. Might come into its own when they are wanting to shed energy, like losing height from cruise to approach, that's the only time I could see it as handy and even then generators are bloody heavy.
The article suggests that hydrogen powered engines could be used to get to altitude then use the wind turbine to power the superconducting electric engines for the rest of the flight, even storing excess electricity in a battery to be dumped via a specially designed truck once they have landed.
It seems that after reading the website the telegraph haven't quite got it right, its not a 'wind turbine' at all. The hydrogen power units generate electricity, the planes engines would be electric and one or more could be switched over from providing drive to being driven by the airflow once the aircraft is at cruising altitude. Like regenerative braking on a hybrid / electric car. The increase in drag would be negligible as there is nothing extra in the airflow. Seems like a fairly sensible idea to me.
Just as well you are a civil engineer Attila So you put a device into the airstream to extract energy that you then use to push you forwards, whilst saving energy
It can't be like regenerative braking, because that would imply that the aircraft would have to be slowing down all the time....?
The device is already in the airstream, its an engine! Cruising at altitude requires far less power than take off, that's why current aircraft throttle back when cruising. It makes sense to turn the engines that are not needed off to save power. However those engines are still in the airflow, the turbofans will be spinning due to the air passing through them and they will be generating drag. This is wasted energy, if even some of that can be recovered then it makes sense. It's not a perpetual motion system, it will never generate enough power to drive the aircraft forward but powering the lights in the cabin etc is easily doable. Regenerative braking was an example of using a vehicles motion to generate power, i'm not suggesting that they deploy an airbrake to power the plane forwards, merely harnessing wasted energy to improve efficiency.
Agreed, but that is not what they are suggesting. From "his website" The AWWA·QG “Progress Eagle” could be equipped with “big” electric superconductive engines, with the same thrust like a powerful fuel turbofan engine. Six engines, one of which is a mixed engine (wind generator/electric engine); the airplane could generate all the necessary energy to feed its superconductive engines (only will need “external” Hydrogen fuel to start –engines & TLMA system- and in specifics moments in the fly); and for the principal systems and subsystems. At the same time it could generate an extra energy that could be storage in the down side of the plane (on the airplane’s cargo bay) to be collected with special electrical storage trucks in the airports, to use after in the same airport or for industries, homes or other electric vehicles.
I'm still struggling a bit, if you use the motor (I assume that's what it is) to act as a generator it will probably have a pretty bad efficiency. I know sod all about super conductive motors but conventional electrical machines are designed as one or the other, although they can do both. Unless the aircraft is in a phase of the flight where there is excess energy that requires to be bled off, then deploying it as generator just makes no sense to me. The minute it is acting like a generator, will it not create more drag as load increases? i.e. the thing becomes harder to turn in proportion to the load it is required to generate. This would then have to compensated for by the engine/motor. Then there is the inefficiencies of both engine and generator, which means you need more power to fly at the same speed than if you just let it windmill, the load there would be simply bearing losses etc: Not to mention the extra weight and complexity of the systems. Maybe I'm missing summit here but I just cannot see how it makes sense, unless you are deliberately trying to shed energy, which is the case in regenerative systems on wheeled vehicles. I'm willing to be enlightened by those with a better understanding
loosely on topic - I just tried in vain to find a link to an engine design that was said to replace the internal combustion chamber with a few improvements (from memory). I don't believe hard copies going into any detail were ever made public but they were enough to dupe Noel Edmonds (yes - he of 'Deal or no Deal') into investing vast sums of money in an effort to secure the design rights. Can anyone remember more or even find a link? Could be 30 years ago or more.
