Today, there are already ultralight aircraft powered by batteries,
Spirit of Innovation
Spirit of Innovation is an Electroflight designed propulsion system that they engineered and built into an airframe to set air speed records. Badged as the Rolls-Royce Spirit of Innovation.
- 345 mph – 3 kilometres
- 331 mph – 15 kilometres
- 202 seconds – 3000 metre climb
Rolls-Royce ‘spirit of innovation’ is officially the world’s fastest all-electric aircraft.
but what about commercial airplanes?
Let’s demonstrate it on an example. I will use a 19-seat Dornier 228 as the example, it has a standard fuel capacity of 2390 L (~1900 kg) of fuel which is 22944 kWh of energy. The Dornier 228 consumes ~200 kg of fuel per hour which is 2.4 MWh of energy per hour.
The most energy-dense battery available is the CATL Qilin battery, it can achieve a specific gravimetric energy of up to 255 Wh/kg. Let’s assume that we will install this battery pack in the airplane and its weight is equal to the weight of the fully refueled tanks of Dornier 228 (~1900 kg). The 1900 kg CATL Qilin battery pack can hold 484 kWh of energy and let’s suppose that its usable capacity is 460 kWh.
Let’s suppose that the turboprop propulsion system is ~30% efficient and the battery electric propulsion system is ~80% efficient. During one hour of flight, the turboprop converts 2.4 MWh of fuel’s chemical energy into 720 kWh of mechanical energy. The electric propulsion system can convert 460 kWh of energy into 368 kWh of mechanical energy. It means that the battery pack with a capacity of 460 kWh can power the Dornier 228 for almost 31 minutes (368 / 720 x 60).
Battery-powered airplanes face a challenge in terms of their landing weight, which remains the same as their take-off weight. This is due to the fact that they don’t consume fuel during flight. Consequently, the landing gear needs to be robust and substantial (heavy) to handle this constant weight.
This very short analysis is greatly simplified because significantly more energy is consumed during the start of the aircraft than during the flight itself and the flight with takeoff would certainly take less than 30 minutes.
The calculation is quite basic, but it gives us an idea of the potential of battery-powered aviation right now. Perhaps by utilizing superlight materials and enhancing its aerodynamics, a plane could stay airborne for approximately 45 minutes. However, it appears improbable that it would be able to fly for around 2 hours or more, right? 😊
- With the batteries we currently have, a small passenger airplane can only stay airborne for a brief period of time.🤔
- The only option is to wait for batteries that are more energy-dense to provide us with the necessary energy for longer flights.
- I think that one day such energy-dense batteries will be developed, but I don’t know when. I still can’t see the light at the end of the tunnel 😏
See also: Aerospace Battery Systems, Aviation Battery Systems, Battery Pack Sizing
You assume here that we should re-engine existing aircraft, and of course we then get a short range. By designing from scratch and optimising around a battery powertrain, we get a far better result. (e.g. 35% AUM as battery, high aspect ratio, laminar flow wings) With 300Wh/kg at the pack level (available now) an eCTOL aircraft with 6 passengers can fly 400km, plus reserves. This is the best place to start with low certification costs and ready markets. As density improves, so of course do size and range.
This is great, can you walk us through a 300Wh/kg pack as the highest we have seen so far is 260Wh/kg with the WeLion cells integrated into a pack in the NIO ES6 150kWh, a pack at 300Wh/kg is an interesting item in it’s own right.
Magnix (https://www.magnix.aero/batteries) say they can deliver their Samson 300….
Standard reserve flight times are normally 30 minutes. Meaning that the range of this hypothetical Dornier aircraft is exactly zero.