Power electronics explained How much power does an eVTOL actually need?

Related Vendors

Volocopter GmbH

FAULHABER Drive Systems

Wuxi InfiMotion Technology Co., Ltd.

Batteries are everywhere in our everyday life. However, with batteries having larger and larger capacities, one often doesn't even know how high the energy consumption actually is anymore. With a diesel vehicle, most people can tell how far they can go with 5 liters (1.32 gallon) of diesel, but what about other vehicles?

Let's take a look at aviation. After the eVOTL (electric Vertical Take-Off and Landing aircraft) manufacturer Volocopter from Bruchsal had received all necessary approval conditions to carry out flights with passengers at the 2024 Paris Olympics, the city of Paris now describes the project as an "ecological absurdity for ultra-rich people". But let's take a closer look.

Weight

The Volocopter 2X is a complete new development and thus replaces the prototype with the designation VC200. The empty weight of the vehicle is 290 kg. The maximum take-off weight is 450 kg. This leaves 160 kg of payload. This is enough for two passengers that the Volocopter can transport. The total weight of the batteries is between 90 and 135 kg, depending on the exact battery design.

Electric drives

The engines are 18 BLDC motors, which provide lift up to 2,000 meters (1.24 miles)  and accelerate the Volocopter up to 102 km/h (63.38 mph).

Redundancy

Both the battery and the drives are redundantly designed. Some of the 18 BLDC motors can fail before the eVOTL can no longer function independently. With Distributed Electric Propulsion (DEP), the remaining motors take up the work and ensure a safe landing. There is also a substitute for the batteries. A total of nine independent batteries are installed, which also ensure a safe landing.

Performance

Each of the motors delivers 3.9 kW. In total, this leads to 70.2 kW. The exact power of the battery is unfortunately not known. However, it varies depending on the equipment and allows a range of 27 km (16.78 miles).

Energy demand

The energy demand for vertical flight, i.e., for takeoff and landing, is higher than for horizontal flight. Here, the aircraft must overcome its own weight. Typical energy requirements for vertical flight can range between 1 and 3 kWh per minute, depending on the size and weight of the eVTOL.

In horizontal flight, the energy requirement is usually much lower, as the aircraft is supported by the lift, which comes from the shape of the aircraft. The energy efficiency can range between 150 and 300 Wh per flight kilometer, depending on the aerodynamics and the speed of the eVTOL.

Example calculation

To perform the calculation, some parameters need to be defined and assumed.

• Vertical takeoff and landing time: 5 minutes (2.5 minutes each for takeoff and landing)

• Energy consumption during vertical flight: 3 kWh per minute

• Energy consumption during horizontal flight: 0.3 kWh per kilometer

• Flight speed: 70 km/h (for an average calculation—43.50 mph)

Calculation:

• Energy consumption for vertical flight:

• Takeoff: 2.5 minutes * 3 kWh/Minute = 7.5 kWh

• Landing: 2.5 minutes * 3 kWh/Minute = 7.5 kWh

• Total for vertical flight: 7.5 kWh + 7.5 kWh = 15 kWh

Energy demand for horizontal flight:

• Distance: 25 km (15.53 miles)

• Energy consumption: 25 km * 0.3 kWh/km = 7.5 kWh

Total energy consumption:

• Vertical flight: 15 kWh

• Horizontal flight: 7.5 kWh

• Total: 15 kWh + 7.5 kWh = 22.5 kWh

A typical car requires about 15-25 kWh/km. So an eVOTL already uses almost four times as much energy. However, of course, one must also see the advantages in speed. Especially for rescue operations, this could be of great interest, as the maintenance is obviously much lower than would be the case with a helicopter. (mr)