Seems the airline industry is beginning to discover the benefits of hybrid technology. The recent airshow in Paris included an A320 modified to use electricity to power the wheels, so that it could taxi without using jet fuel. Just as with cars, the system saves gas and reduces emissions. Here's an article with more details.
Seems a bit odd that having enough heavy batteries on board just to taxi, maybe 1/2 a mile is worth it when you consider you then have to fly thousands of miles with those depleted batteries and carry extra fuel for that extra weight. Yes, you save the idling of the jets while you taxi...but you do need to run the jets to warm them up for some amount of time prior to takeoff anyway. Mike
This system will also allow jets to be moved to the commence takeoff position prior to the lifting of curfew at airports which are within populated locations. It also likely means that batteries are getting light enough, with a high enough energy density to make this concept feasible. It is also an indication of which direction aircraft manufacturers believe fuel prices are heading.
This system will also allow jets to be moved to the commence takeoff position prior to the lifting of curfew at airports which are within populated locations. It also likely means that batteries are getting light enough, with a high enough energy density to make this concept feasible. It is also an indication of which direction aircraft manufacturers believe fuel prices are heading.
Not batteries, the Aux Power Unit provides enough power. The only extra weight is one very heavily geared, electric motor with amazing torque and power cables. It has to have enough power to overcome the 'set' of the tires when plane is at rest. Once moving, no problem. The APU burns a fraction of the fuel as the aircraft engines yet still has enough power to handle lights, electronics, and ground air conditioning. Once the plane is rolling, the drag falls off rapidly and the APU can go back to cooling the cabin. Heck it might even justify a larger APU just for this ground handling role. The potential fuel savings is more than enough to justify application of this technology and even retro-fitting to the aircraft fleet. Bob Wilson
If I were given the task, I would size the capacitor bank to provide enough energy to match the APU power, in effect 2x APU, for as long as it takes to get a fully loaded plane to reach taxi speed. However, a capacitor bank would not be a trivial design challenge and becomes 'dead weight' once the plane begins takeoff. So then we have this problem of fuel burn associated with the weight of the capacitor bank and its complexity and maintenance. In the KISS principle, I would look at: What is the taxi way speed requirement for fully loaded plane? How long does APU assigned this task take to get plane moving? Trade-study larger APU to meet taxi requirement second APU to meet taxi requirement capacitor bank battery bank To get a rough idea, not including the tire rolling drag: KE = 0.5*m*(v**2) :: the kinetic energym - mass (kg)v - velocity (m/sec) I would lean towards a more powerful APU since it can probably fit in the same place and similar weight. There might be a small loss of efficiency when not being used to taxi the airplane but compared to the energy loss of running a main engine, this is 'leakage.' Bob Wilson
