The aviation industry is undergoing a revolutionary transformation as it seeks to reduce its carbon footprint and embrace more sustainable technologies. Electric, hybrid, and hydrogen-powered aircraft are the three leading types of powertrains in this evolution.
Each of these technologies offers unique advantages and challenges, but they all share a common goal: to make air travel cleaner and more efficient.
Let's explore these innovative approaches to flight and see how they're shaping the future of aviation.
The Electric Revolution in Aviation
Electric aircraft represent a significant leap forward in aviation technology. These planes rely entirely on battery-powered electric motors for propulsion, offering several advantages
- Zero direct emissions: Electric aircraft produce no carbon emissions during flight.
- Reduced noise pollution: Electric motors are significantly quieter than traditional jet engines.
- Lower operating costs: Electric motors require less maintenance with fewer moving parts.
- Energy efficiency: Electric motors convert a higher percentage of energy into thrust compared to combustion engines.
Here's how electric aircraft work:
- Energy Storage: High-capacity lithium-ion batteries store electrical energy.
- Electric Motors: These convert electrical energy into mechanical energy. They typically use permanent magnet synchronous motors (PMSM) or axial flux motors for their high power-to-weight ratio.
- Power Electronics: Inverters convert DC power from batteries to AC power for the motors, controlling speed and torque.
- Propellers or Ducted Fans: These are directly driven by the electric motors, providing thrust.
Electric Vertical Takeoff and Landing (eVTOL) aircraft are at the forefront of this technology. These nimble aircraft can take off and land vertically like helicopters, making them ideal for short-range urban air mobility solutions. Key features of eVTOLs include:
- Distributed electric propulsion: Multiple smaller motors provide redundancy and enhanced maneuverability.
- Tilt-rotor or tilt-wing designs: Allow for efficient vertical takeoff and horizontal cruise.
- Advanced flight control systems: Enable precise control in urban environments.
Companies like Joby Aviation, Lilium, and Archer are pioneering eVTOL technology, aiming to revolutionize city transportation. Joby's S4, for instance, promises a range of 150 miles and a top speed of 200 mph while carrying four passengers and a pilot. It uses six tilting electric motors that point upward for vertical takeoff and landing and tilt horizontally for forward flight.
For larger electric aircraft, companies like Heart Aerospace are developing the
ES-19, a 19-seat electric plane designed for regional flights up to 250 miles. These aircraft use wing-mounted electric motors driving propellers, typically in the megawatt range, to provide sufficient thrust for takeoff and cruise.
Electric motors' efficiency is a key advantage. They can convert over 85% of electrical energy into mechanical energy, compared to around 40% for combustion engines. This high efficiency helps maximize the limited energy available from current battery technology.
However, the main challenge for electric aircraft is range limitation due to current battery technology. Lithium-ion batteries have an energy density of about 200-300 Wh/kg, significantly lower than jet fuel's 12,000 Wh/kg. This makes them best suited for short-haul flights and urban air mobility applications.
Hybrid Aircraft: Bridging the Gap
Hybrid electric aircraft combine traditional combustion engines with electric propulsion systems. This approach offers several benefits:
- Extended range: The combustion engine can take over when battery power is depleted.
- Flexibility: Electric power can be used for takeoff and landing, reducing noise in urban areas.
- Reduced emissions: Hybrid systems can significantly lower overall emissions than conventional aircraft.
- Operational versatility: Some hybrid aircraft can operate from existing airports without requiring new infrastructure.
There are three main configurations for hybrid aircraft:
- Partial Hybrid: Electric motors assist the main engine during high-power phases.
- The combustion engine provides primary propulsion.
- Electric motors provide additional power during takeoff and climbing.
- Series Hybrid: The combustion engine acts solely as a generator.
- The engine is not mechanically connected to the propeller.
- It powers a generator, which produces electricity for the electric motor and battery.
- The electric motor alone drives the propeller.
- Parallel Hybrid: Both the combustion engine and electric motor can drive the propeller.
- The combustion engine is connected to a generator, producing electricity.
- This electricity powers the electric motor and charges the battery.
- Either or both power sources can drive the propeller, allowing for flexible operation.
Heart Aerospace is developing hybrid-electric regional aircraft that promise to make short to medium-haul flights more sustainable. Their ES-30 aircraft uses a series hybrid system with two turbo generators that can run on sustainable aviation fuel. It aims to carry 30 passengers up to 250 miles using electric and sustainable aviation fuel power. It can fly 125 miles in full-electric mode, extending the range to 250 miles when using the sustainable fuel reserve.
Ampaire, another key player, has successfully test-flown its Electric EEL, a six-seat aircraft converted from a Cessna 337 Skymaster. Similar designs in the works are projected to have up to 30% fuel savings. The electric motors in hybrid aircraft are similar to those in fully electric planes but are often smaller. They work in tandem with the combustion engine, allowing for:
- Electric-only operation during takeoff and landing, improving energy efficiency and reducing noise in urban areas.
- Combustion engine operation during cruise for extended range.
- Peak power sharing between electric and combustion systems for maximum efficiency.
Hybrid technology is seen as a crucial stepping stone towards fully electric aviation. It allows for the gradual electrification of flight while overcoming current battery limitations.
Hydrogen: The Long-Range Solution
Hydrogen-powered aircraft represent perhaps the most exciting frontier in sustainable aviation, especially for long-range flights. These aircraft can use hydrogen in two ways:
- Hydrogen Fuel Cells:
- Hydrogen is stored in cryogenic tanks at -253°C.
- It's fed into a fuel cell, where it reacts with oxygen from the air.
- This electrochemical reaction produces electricity, with water as the only byproduct.
- The electricity powers electric motors, which drive propellers or fans.
- These systems are highly efficient and produce zero emissions.
- Direct Hydrogen Combustion:
- Liquid hydrogen is burned directly in modified jet engines or gas turbines.
- The engines require significant modifications to handle hydrogen's different combustion properties.
The advantages of hydrogen power are significant:
- Long-range capability: Hydrogen has a higher energy density than batteries, allowing longer flights.
- Zero emissions: When used in fuel cells, the only byproduct is water vapor.
- Rapid refueling: Hydrogen tanks can be refilled much faster than batteries can be recharged.
- Potential for carbon-neutral operation: Hydrogen can be a truly zero-emission fuel if produced using renewable energy.
Several major players are investing heavily in hydrogen aviation technology:
- Airbus: The aerospace giant is developing the ZEROe concept to introduce the world's first zero-emission commercial aircraft by 2035. They're exploring three concept designs:
- A turboprop design for short-haul flights.
- A turbofan design for longer-range flights.
- A "blended-wing body" design for maximum efficiency. Airbus is developing a 1.2MW fuel cell engine for smaller aircraft and hydrogen-burning gas turbine engines for larger aircraft.
- ZeroAvia: This startup has already conducted test flights of hydrogen fuel cell aircraft and aims to have commercial operations by 2025. Their initial
focus is on 9-19-seat aircraft for short-haul flights, with plans to scale up to larger aircraft capable of flying up to 500 miles by 2027. Their testbed aircraft, a modified Dornier 228, uses a 600kW fuel cell powertrain on one side, demonstrating how hydrogen fuel cells can power existing aircraft designs with minimal modifications to the airframe. - Universal Hydrogen: Working on hydrogen propulsion systems and innovative fuel delivery solutions for airports. Their approach includes developing modular hydrogen capsules that can be easily transported and loaded onto aircraft, potentially solving the infrastructure challenge.
- H2Fly: H2Fly, a German company and Joby Subsidiary, has successfully flown the HY4, a four-seat hydrogen fuel cell aircraft. They're now working on a 40-seat regional airliner with a range of up to 1,000 miles.
The electric motors used in hydrogen fuel cell aircraft are similar to those in battery-electric planes. However, they benefit from hydrogen's higher energy density, allowing for sustainable, longer-range flights. Hydrogen combustion engines, while not using electric motors for primary propulsion, still incorporate them for auxiliary power and engine starting. These motors must be highly reliable and capable of operating in extreme temperatures.
Technical challenges for hydrogen-powered flight include:
- Fuel storage: Liquid hydrogen must be stored at -253°C, requiring advanced cryogenic tanks (which Airbus is working on building).
- Fuel system design: New fuel delivery systems must be developed to handle hydrogen's unique properties.
- Engine modifications: Existing jet engines need significant modifications to burn hydrogen efficiently.
Despite these challenges, hydrogen shows immense promise for decarbonizing long-haul flights, which account for most aviation emissions. The technology is advancing rapidly, with companies like Fabrum and FKN Aerospace working on lightweight composite LH2 tanks and Rolls-Royce partnering with easyJet to test hydrogen combustion engines.
Powering the Future: Carpenter Electrification's Role
At the heart of all these innovative aircraft designs lies a critical component: high-performance electric motors. This is where Carpenter Electrification comes into play. Our industry-leading soft magnetic materials are essential for creating
the powerful, efficient, and lightweight electric motors that these aircraft require.
Our Hiperco® and Hypocore® alloys offer:
- Higher power and torque density, allowing for smaller, lighter motors.
- Improved transient response for better performance.
- Lower operating temperatures, reducing thermal stress.
- Enhanced reliability for direct-drive applications.
These advantages translate directly into benefits for electric aircraft:
- Lighter motors mean reduced overall aircraft weight.
- Higher efficiency leads to extended range and endurance.
- Improved reliability ensures safer operations.
Our expertise extends beyond just materials. We offer full-service support from concept to production, including prototyping, design optimization, and supply chain management. This comprehensive approach ensures that aircraft manufacturers achieve the best possible performance from their electric propulsion systems.
A Cleaner Sky Ahead
The future of aviation is undoubtedly electric, whether powered by batteries, hybrid systems, or hydrogen fuel cells. Each of these technologies has its place in the evolving landscape of air travel, from short-hop urban air taxis to long-haul international flights.
As the industry continues to innovate and overcome challenges, one thing is clear: high-performance electric motors will be at the core of this revolution. Carpenter Electrification is proud to be at the forefront of this transformation, providing the materials and expertise needed to make sustainable aviation a reality.
Are you developing the next generation of electric aircraft? Reach out to our team at Carpenter Electrification to learn how our advanced materials and manufacturing capabilities can help you achieve your goals in sustainable aviation.