The aviation industry is constantly striving to find more sustainable solutions, just like other industries transitioning to renewable energy sources. However, one significant hurdle remains: energy storage. Despite advancements in renewable energy production, the technology required for widespread adoption in every industry has not kept up. This is particularly evident in the aviation and aerospace sector, where kerosene is still the primary fuel source for planes, despite the availability of cheaper electricity from the grid.
The main challenge lies in the energy density of storage methods. Energy density refers to the amount of energy that can be harnessed from a specific weight of an energy source. Currently, the energy density of jet fuel (kerosene) is about 43 MJ/kg, while the best lithium-ion batteries can only achieve around 1 MJ/kg. In other words, battery energy is over 40 times heavier than jet fuel.
This weight difference poses a significant problem for airplanes. As the weight of a plane increases, more power is required to generate lift. To accommodate this increased power demand, more batteries are needed, which further increases the weight of the plane. This creates a catch-22 situation in aircraft design.
In order to understand the power requirements and energy supply of a battery-powered plane, let’s take a closer look at the Airbus A320 and a small personal aircraft like a Cessna. The power needed for lift is determined by the mass of the plane, the force of gravity, and the change in velocity (∆vz) of the air that the plane pushes downward.
The lift provided by an airplane is equal to the rate at which it delivers downward momentum to the displaced air. This means that the force of gravity on the plane must be equal in magnitude to the downward velocity of the deflected air, multiplied by the rate at which air gets deflected. The mass of air affected by the plane is determined by the volume of the cylinder it sweeps out per unit time, multiplied by the density of air.
To calculate the power required for lift, we need to consider the area of air affected by the plane as it flies at cruising speed. This area changes with the relative velocity of the plane and the surrounding air. At cruising speed, the plane dissipates vortices that have roughly the radius of the length of the plane’s wings. Approximating this circle as a square, the relevant area becomes L squared at cruising speed.
With these equations, we can determine the power requirements for lift, which depend on variables such as the mass of the plane, gravity, and delta V. As the plane flies faster, the power drawn by the engine actually decreases, but this equation does not consider drag. To reach the total power requirements for flight, we need to double the power needed for lift to account for drag, as the total power needed is minimized when lift and drag forces are equal.
Calculating the real-world consequences of converting an Airbus A320 or a Cessna to battery power reveals some challenges. For a Cessna, the battery weight required is around 100 kilograms, whereas for an Airbus A320, it would be approximately 31 tonnes. These figures represent the power the plane needs at any given moment, but what we are interested in is the weight of batteries required to match the typical range of these planes.
Considering the energy capacity required for a trip, we can estimate that a Cessna would need about 500 kilograms of batteries, while an A320 would require approximately 260,000 kilograms – four times the weight of an empty plane. These calculations demonstrate the significant impact that battery weight has on the range of electric planes.
While small electric aircraft have made strides in the market, adapting larger commercial airliners to electric engines is not currently feasible. The energy storage density of batteries remains a significant obstacle. However, researchers are exploring alternative energy storage mediums, such as hydrogen, to overcome these challenges.
In conclusion, electric planes still face significant hurdles due to the energy density limitations of current battery technology. While smaller aircraft can benefit from electric engines, commercial airliners would require substantial battery weights, drastically reducing their range. Until a more energy-dense storage medium is developed, electric planes are unlikely to become a reality in the aviation industry.
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FAQs
Q: Why can’t electric planes use the same batteries as electric cars?
A: Electric planes require much higher energy densities than electric cars due to the weight limitations of aircraft. While electric car batteries have made great strides, they are still not sufficient for powering commercial aircraft.
Q: Are there any alternative energy storage solutions being explored for electric planes?
A: Yes, researchers are exploring the use of hydrogen as an energy storage medium for electric planes. Hydrogen has a higher energy density compared to current lithium-ion batteries, which could potentially overcome the weight limitations.
Q: Are there any small electric aircraft currently available in the market?
A: Yes, there are small electric aircraft, such as the Alpha Electro, that have been introduced in recent years. These aircraft are designed for short-range flights and have been optimized for electric power.
Conclusion
While the aviation industry is actively seeking sustainable solutions, the transition to electric planes still faces significant challenges. The energy density limitations of current batteries make it difficult to achieve the necessary power-to-weight ratio for commercial airliners. However, advancements in battery technology and the exploration of alternative energy storage options, such as hydrogen, provide hope for a future where electric planes could become a reality.
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