Electric aircraft are aircraft that use electricity as their main source of power to fly. They are seen as a potential solution to reduce the environmental impact of aviation, as they produce zero emissions and less noise than conventional aircraft. However, electric aircraft also face many technical, economic, and regulatory challenges that need to be overcome before they can become a reality. In this article, we will explore the following aspects of electric aircraft:
1.Definition of electric aircraft: What are electric aircraft and how do they work?
2. Environmental benefits of electric aircraft: How can electric aircraft contribute to reducing carbon emissions?
3. Cost and efficiency: How do electric aircraft compare to conventional aircraft in terms of cost and efficiency?
4. Technical challenges: What are the technical challenges that need to be solved to make electric aircraft feasible?
5. Safety and regulations: What are the legal and regulatory issues associated with electric aircraft?
6. Future use cases: How can electric aircraft change the aviation industry in the future?
7. Current innovations: What are some of the current innovations in the field of electric aircraft?
1. Definition of electric aircraft
Electric aircraft are aircraft that use electricity as their main source of power to fly. Electricity can be generated by different methods, such as batteries, fuel cells, solar panels, or hybrid systems that combine electricity with other fuels. Electric aircraft usually have electric motors that drive propellers or turbines, which provide thrust and lift. Electric aircraft can be classified into different types, depending on the amount of electricity they use and the way they store it. Some examples are:
- All-electric aircraft: These are aircraft that use only electricity to fly, without any other fuel. They rely on batteries or fuel cells to store electricity onboard. They have the advantage of producing zero emissions and less noise, but they also have the disadvantage of having limited range and endurance, due to the weight and capacity of the batteries or fuel cells. An example of an all-electric aircraft is the [Lange E1 Antares], a self-launching glider that has been in production since 2006.
- Hybrid-electric aircraft: These are aircraft that use a combination of electricity and other fuels, such as jet fuel or sustainable aviation fuels, to fly. They use electric motors to supplement or replace the conventional engines, which can improve the fuel efficiency and reduce the emissions. They have the advantage of having longer range and endurance than all-electric aircraft, but they also have the disadvantage of still producing some emissions and noise. An example of a hybrid-electric aircraft is the [E-Fan X], a demonstrator project by Airbus, Rolls-Royce, and Siemens, that aims to test a hybrid-electric propulsion system on a regional jet.
-Solar-electric aircraft: These are aircraft that use solar panels to generate electricity from sunlight, which can be used to power the electric motors or to charge the batteries or fuel cells. They have the advantage of being able to fly for long periods of time without refueling, as long as there is enough sunlight, but they also have the disadvantage of being vulnerable to weather conditions and having low performance and payload. An example of a solar-electric aircraft is the [Solar Impulse 2], a single-seater aircraft that completed a circumnavigation of the Earth using only solar power in 2016.
2. Environmental benefits of electric aircraft
One of the main motivations for developing electric aircraft is to reduce the environmental impact of aviation, which accounts for about 2.4% of the global CO2 emissions from fossil fuels, and has other effects such as NOx, contrails, and noise pollution. Electric aircraft can offer the following environmental benefits:
- Zero emissions: Electric aircraft that use only electricity to fly, such as all-electric or solar-electric aircraft, do not produce any emissions during flight, which can help mitigate the climate change caused by greenhouse gases. However, this also depends on the source of the electricity, which may have emissions associated with its production and distribution. Therefore, it is important to use renewable or low-carbon sources of electricity, such as wind, solar, hydro, or nuclear, to power the electric aircraft.
- Less noise: Electric aircraft that use electric motors to drive propellers or turbines, instead of conventional engines, produce less noise during flight, which can improve the quality of life of the people living near airports or under flight paths. Electric motors are quieter than combustion engines, and propellers or turbines can be designed to reduce the noise level. For example, the [E-Fan], a two-seater all-electric aircraft developed by Airbus, has a noise level of 65 decibels, which is comparable to a car, while a typical jet aircraft has a noise level of 140 decibels, which is comparable to a gunshot.
3. Cost and efficiency
Another factor that influences the development of electric aircraft is the cost and efficiency of the technology, which affects the economic viability and competitiveness of the electric aircraft. Electric aircraft can have the following advantages and disadvantages in terms of cost and efficiency:
- Lower operating costs: Electric aircraft that use electricity to fly, instead of jet fuel or sustainable aviation fuels, can have lower operating costs, as electricity is cheaper and more abundant than fossil fuels. According to a study by the University of Illinois, the operating cost of an all-electric aircraft can be 40% lower than that of a conventional aircraft, while the operating cost of a hybrid-electric aircraft can be 30% lower. However, this also depends on the price and availability of electricity, which may vary depending on the location and time of the flight.
- Higher capital costs: Electric aircraft that use batteries or fuel cells to store electricity onboard, instead of jet fuel tanks, can have higher capital costs, as batteries or fuel cells are more expensive and heavier than fuel tanks. According to the same study, the capital cost of an all-electric aircraft can be 60% higher than that of a conventional aircraft, while the capital cost of a hybrid-electric aircraft can be 20% higher. However, this may change in the future, as the technology improves and the prices decrease. For example, the price of lithium-ion batteries, which are commonly used in electric vehicles and aircraft, has dropped by 87% between 2010 and 2019.
- Lower performance and payload: Electric aircraft that use batteries or fuel cells to store electricity onboard, instead of jet fuel tanks, can have lower performance and payload, as batteries or fuel cells have lower energy density and specific energy than jet fuel. This means that electric aircraft can carry less weight and fly shorter distances than conventional aircraft, which limits their applications and markets. For example, the [Pipistrel Alpha Electro], a two-seater all-electric aircraft, has a maximum takeoff weight of 550 kg and a range of 130 km, while the [Cessna 172 Skyhawk], a four-seater conventional aircraft, has a maximum takeoff weight of 1,100 kg and a range of 1,200 km.
4. Technical challenges
One of the main obstacles for the development of electric aircraft is the technical challenges that need to be solved to make electric aircraft feasible and reliable. Some of the technical challenges are:
- Battery and fuel cell technology: The current battery and fuel cell technology is not mature enough to meet the requirements of electric aircraft, such as high energy density, specific energy, power density, specific power, safety, durability, and recyclability. Batteries and fuel cells need to be improved in terms of capacity, weight, cost, charging time, lifespan, and environmental impact, to enable electric aircraft to fly longer, faster, and safer. For example, the [Velis Electro], the first type certified all-electric aircraft, has a battery capacity of 24.8 kWh and a flight time of 50 minutes, while the [Tesla Model 3], a popular electric car, has a battery capacity of 75 kWh and a driving range of 568 km.
- Electric motor and power electronics technology: The electric motor and power electronics technology is also not advanced enough to meet the demands of electric aircraft, such as high efficiency, power, torque, speed, reliability, and cooling. Electric motors and power electronics need to be optimized in terms of size, weight, cost, performance, and integration, to enable electric aircraft to have more thrust and lift, and less drag and heat. For example, the [MagniX Magni500], an electric motor for electric aircraft, has a power of 560 kW and a weight of 135 kg, while the [Rolls-Royce Trent XWB], a jet engine for conventional aircraft, has a power of 84,000 kW and a weight of 7,000 kg.
- System integration and optimization: The system integration and optimization of electric aircraft is also a complex and challenging task, as it involves the coordination and interaction of different components, such as the battery, fuel cell, electric motor, power electronics, propeller, turbine, wing, fuselage, etc. The system integration and optimization aims to achieve the best performance, efficiency, reliability, and safety of the electric aircraft, while satisfying the design constraints and requirements. Some of the methods and tools that can be used for system integration and optimization are:
-Multidisciplinary design analysis and optimization (MDAO): This is a method that integrates different disciplines, such as aerodynamics, structures, propulsion, systems, etc., into a single framework, and uses optimization algorithms to find the optimal design variables that maximize or minimize a certain objective function, such as fuel consumption, emissions, noise, etc. MDAO can help to explore the design space and trade-offs of electric aircraft, and to evaluate the impact of different technologies and architectures on the overall performance and cost. For example, ² presents an MDAO framework that integrates aircraft and subsystem sizing tools for hybrid-electric commuter and regional aircraft.
- Modeling and simulation: This is a tool that uses mathematical models and numerical methods to represent and analyze the behavior and performance of the electric aircraft and its components under different scenarios and conditions. Modeling and simulation can help to validate and verify the design and operation of electric aircraft, and to identify and solve potential issues and risks. For example, ³ presents a modeling and simulation approach for the power management of a serial hybrid-electric propulsion system of a propeller aircraft.
-Testing and experimentation: This is a tool that uses physical models and prototypes to measure and evaluate the characteristics and performance of the electric aircraft and its components in real or simulated environments. Testing and experimentation can help to demonstrate and validate the feasibility and reliability of electric aircraft, and to collect data and feedback for further improvement and optimization. For example, presents a testing and experimentation platform for the system integration of a hybrid-electric distributed propulsion system for a light aircraft.
5. Safety and regulations
Another aspect that affects the development and deployment of electric aircraft is the safety and regulatory framework that governs the aviation industry. Electric aircraft need to comply with the existing standards and regulations that ensure the safety and security of the passengers, crew, and the public, as well as the environmental and social responsibility of the operators and manufacturers. Some of the safety and regulatory issues that need to be addressed are:
- Certification: Electric aircraft need to obtain the necessary certification from the relevant authorities, such as the European Union Aviation Safety Agency (EASA) or the Federal Aviation Administration (FAA), before they can enter into service. The certification process involves the verification and validation of the design, performance, and operation of the electric aircraft, as well as the demonstration of compliance with the applicable requirements and specifications. The certification process can be challenging and time-consuming, as electric aircraft may introduce new technologies and concepts that are not covered by the existing regulations, or may require modifications or exemptions from the existing regulations. For example, the [Velis Electro], the first type certified all-electric aircraft, took about three years to complete the certification process, which involved close cooperation between the manufacturer (Pipistrel) and EASA.
- Airworthiness: Electric aircraft need to maintain the required level of airworthiness, which is the measure of the suitability of an aircraft to operate safely in the air. Airworthiness depends on the condition and performance of the aircraft and its components, as well as the maintenance and inspection procedures that ensure the aircraft is fit for flight. Airworthiness can be affected by various factors, such as the aging and degradation of the batteries or fuel cells, the reliability and availability of the electric motors and power electronics, the compatibility and interoperability of the different systems and subsystems, the environmental and operational conditions, etc. Airworthiness can be ensured by following the appropriate standards and guidelines, such as the EASA CS-E ⁷ or the FAA AC 33.28-1 ⁸, which provide the criteria and methods for the certification and airworthiness of electric propulsion systems and components.
- Training and licensing: Electric aircraft need to be operated by qualified and competent pilots and crew, who have the necessary knowledge and skills to handle the electric aircraft safely and efficiently. Training and licensing are the processes that ensure the pilots and crew meet the minimum standards of proficiency and competence, as well as the specific requirements of the electric aircraft. Training and licensing can be different for electric aircraft than for conventional aircraft, as electric aircraft may have different characteristics and features, such as the battery or fuel cell management, the electric motor control, the power management, the emergency procedures, etc. Training and licensing can be provided by the authorized organizations, such as the flight schools or the operators, in accordance with the relevant regulations, such as the EASA Part-FCL ⁹ or the FAA Part 61 , which specify the requirements and conditions for the training and licensing of pilots and crew.
6. Future use cases
Electric aircraft have the potential to revolutionize the aviation industry and create new opportunities and markets for the transportation of people and goods. Electric aircraft can offer the following advantages and benefits for the future use cases:
- Urban air mobility (UAM): Electric aircraft can enable the development of urban air mobility, which is the concept of using the airspace above urban areas to provide fast and convenient transportation services, such as air taxis, air shuttles, air ambulances, etc. Electric aircraft can be suitable for urban air mobility, as they can reduce the noise and emissions that affect the urban environment, as well as the cost and complexity that affect the urban infrastructure. Electric aircraft can also leverage the advances in autonomous and digital technologies, such as artificial intelligence, machine learning, blockchain, etc., to enhance the safety, efficiency, and integration of the urban air mobility system. For example, the [Volocopter], a two-seater electric vertical take-off and landing (eVTOL) aircraft, is designed to provide on-demand urban air taxi services, and has performed several test flights in various cities around the world.
- Regional air transport (RAT): Electric aircraft can also enable the development of regional air transport, which is the concept of using the airspace between small and medium-sized cities or towns to provide affordable and accessible transportation services, such as air commuting, air tourism, air cargo, etc. Electric aircraft can be suitable for regional air transport, as they can reduce the fuel consumption and emissions that affect the regional climate, as well as the operating costs and maintenance that affect the regional economy. Electric aircraft can also leverage the advances in hybrid and distributed technologies, such as hybrid-electric propulsion, distributed electric propulsion, etc., to enhance the performance, flexibility, and scalability of the regional air transport system. For example, the [Eviation Alice], a nine-seater all-electric aircraft, is designed to provide low-cost and zero-emission regional air transport services, and has received several orders from various operators around the world.
7. Current innovations
Electric aircraft are the result of the continuous innovation and research in the field of electric propulsion and aviation. There are many ongoing projects and initiatives that aim to develop and demonstrate the feasibility and viability of electric aircraft, as well as to address the challenges and barriers that hinder their progress. Some of the current innovations in the field of electric aircraft are:
- NASA X-57 Maxwell: This is a project by the National Aeronautics and Space Administration (NASA) that aims to develop and test a four-seater all-electric aircraft, based on the Tecnam P2006T twin-engine light aircraft, that uses 14 electric motors and propellers distributed along the wing to increase the lift and efficiency. The project also aims to establish new standards and methods for the certification and operation of electric aircraft, as well as to collect and share the data and knowledge with the industry and the public. The project is expected to complete the first flight test by 2022.
- H3PS: This is a project by the Clean Sky 2 Joint Undertaking, a public-private partnership between the European Commission and the European aeronautics industry, that aims to develop and test a two-seater hybrid-electric aircraft, based on the Tecnam P2010 four-seater light aircraft, that uses a combination of a piston engine and an electric motor to power the propeller. The project also aims to demonstrate the benefits and potential of hybrid-electric propulsion for small aircraft, such as lower emissions, noise, and fuel consumption, as well as higher performance and reliability. The project is expected to complete the first flight test by 2021.
- EcoPulse: This is a project by the CORAC (Conseil pour la recherche aéronautique civile), a French council for civil aeronautical research, that aims to develop and test a six-seater hybrid-electric aircraft, based on the Daher TBM 900 single-engine turboprop aircraft, that uses a combination of a turboprop engine and six electric motors distributed along the wing to power the propellers. The project also aims to demonstrate the benefits and potential of distributed electric propulsion for medium-sized aircraft, such as lower emissions, noise, and drag, as well as higher efficiency and stability. The project is expected to complete the first flight test by 2022.
Conclusion
Electric aircraft are the future of aviation, as they offer the possibility of reducing the environmental and social impact of aviation, as well as creating new opportunities and markets for the transportation of people and goods. However, electric aircraft also face many challenges and barriers that need to be overcome, such as the technical, economic, and regulatory issues that affect the feasibility and viability of electric aircraft. Therefore, it is important to foster the innovation and collaboration among the stakeholders, such as the manufacturers, operators, regulators, researchers, and the public, to accelerate the development and deployment of electric aircraft, and to achieve the vision of a green and sustainable aviation.