Conceptual Designing of aircraft provides a major role in designing of aircraft. Let's consider the weight estimation in it. For electric aircrafts its fuel variation is " zero ". Hence W|f is noted as zero. But as the battery power\charge is lowered there's must be a variation in it !! How to determine it ? Also how to calculate it ? . Explain it for academic purposes . ( When I refer some books I got the term BMF- Battery Mass Fraction , It denoted for weight of fuel, How it works )
In the conceptual design of aircraft, weight estimation plays a critical role, particularly concerning fuel and power sources. In traditional aircraft powered by combustion engines, fuel consumption leads to a significant weight variation during flight. However, in electric aircraft, where batteries serve as the primary power source, there's no direct fuel consumption leading to weight variation during flight. Instead, the weight of the batteries remains constant throughout the flight since there's no consumption akin to traditional fuel. For hybrid aircraft, this changes, see here: https://brelje.net/blog/deriving-modified-breguet-range-equation-hybrid-turboelectric-aircraft/
To adapt liquid fuel calculations for estimating the weight of electric aircraft, begin with the motor power requirements. Assuming that only the fuel type changes, we would need to determine the battery weight necessary to support the motor's power requirements. Today's batteries are in the range of 150-170 watts per kilogram, including their physical and thermal protection. Once you have determined the wattage requirements for the airframe based on the liquid fuel calculations, you can convert that into the corresponding battery weight.
Considering the transition from liquid fuel to electric power in aircraft, particularly helicopters, it's crucial to account for changes in airframe weight due to the reduced number of mechanical parts, such as rotors, and the added weight from increased wiring and motor controllers. Additionally, the weight of the motors themselves will also vary.
Replace batteries for fuel cells as electrical current source and you will have fuel mass variation even larger than for hybrid electric powered aircraft.