Aviation
Connor Dolan
By Quailan Homann
Global aviation accounts for 2% of all human-induced carbon emissions, and passenger numbers are expected to double over the next 18 years. The aviation industry has a distinct lack of all-electric planes due to difficulties of technology substitution and scaling. Direct electricity is applicable to power a propeller, but it cannot be substituted for a jet engine which requires combustion-produced thrust. Powering a propeller plane with a battery introduces problems as well. The common adversary to flight, weight, is exacerbated when scaling batteries to power larger aircraft. Battery size is directly proportional to the amount of power that needs to be drawn from it. Current energy density puts a theoretical battery powering a 787 Dreamliner at a weight of 4.5 million pounds, according to Aerospace Engineering Professor Richard Anderson, director of Embry-Riddle Aeronautical University’s flight research center. These issues have placed aviation in the aptly named “hard-to-decarbonize” category.
In response, the aviation industry is looking into hydrogen fuel cells as a replacement to conventional aircraft propulsion systems. Fuel cells would provide zero-emission travel, with the only byproducts being heat and water. Hydrogen provides an advantage over batteries as it is significantly lighter, making it a realistic option for flight. Recent developments within fuel cell and hydrogen aviation is bringing the industry closer to achieving carbon-free transportation.
NASA
NASA has a history with fuel cell technology, and it is continuing the progress with the development of CHEETA – the Center for Cryogenic High-Efficiency Electrical Technologies for Aircraft. NASA will be providing researchers at the University of Illinois with $6 million dollars over three years to develop a fully electric aircraft using a liquid hydrogen fuel cell propulsion system. Since the hydrogen will be stored at extremely cold temperatures in order to remain liquid, the low temperature can be used for superconducting energy transmission and motor systems, which reduces electrical resistance to practically zero, resulting in an overall efficiency increase.
Artist rendition of an aircraft using CHEETA systems. Source: University of Illinois at Urbana-Champaign Department of Aerospace Engineering
Alaka’i
The advent of ridesharing apps was substantially disruptive to the vehicle-for-hire industry. Alaka’i intends to revolutionize commuting by taking it to the skies. Founded in 2006 by top-level NASA, Raytheon, and Beechcraft employees, FCHEA member company Alaka’i Technologies aims to cut travel times and carbon emissions with its liquid hydrogen fuel cell air-taxi: the “Skai”. Alaka’i has set its sights on providing an aircraft capable of four-hour flight times and a 400-mile range for urban and regional trips. The Skai’s vertical takeoff and landing would deliver “point-to-any point” transportation, allowing access to hard-to-reach areas. The 1,000 lb. payload would allow for cargo transportation. Skai is currently undergoing testing and certification, but Alaka’i estimates that it will receive FAA approval as soon as 2020.
Side image of Alaka’i’s Skai air taxi. Source: Alaka’i
ZeroAvia
California-based ZeroAvia seeks to tackle growing transportation carbon emissions head on with a zero-emission fuel cell airplane. The company’s current small-cabin aircraft targets 300 to 500 mile short-haul trips. According to ZeroAvia, the fuel cell powertrain has 75% lower fuel and maintenance costs, reducing total trip costs by 50% compared to conventional propeller aircraft. Most recently, the company received a GBP 2.7 million (approximately $3.3 million) grant from the United Kingdom to develop the Hyflyer project. The project is expected to utilize a Piper M-class six-seater aircraft with a hydrogen powertrain to fly 250 – 300 nautical miles. FCHEA member Intelligent Energy is assisting on the project by optimizing its evaporative cooling fuel cell technology. The Hyflyer project is another step in ZeroAvia’s goal of providing commercial operators and manufacturers with a 500 mile, 10 – 20 seat plane by 2022.
ZeroAvia fuel cell plane using Piper matrix. Source: ZeroAvia
HY4
In September 2016, the DLR Institute of Engineering Thermodynamics, a German aerospace research group, debuted the HY4, a fuel cell plane. HY4 is currently being developed as a four-seat passenger aircraft for regional transport. To produce the aircraft, DLR partnered with H2Fly, Pipistrel, the University of Ulm, Stuttgart Airport, and FCHEA member Hydrogenics. Currently, the aircraft has a range between 750 and 1,500 kilometers (approximately 466 to 932 miles), depending on speed, altitude, and load. The 80-kilowatt motor can get the plane to a maximum of 200 kilometers per hour (approximately 124 mph).
HY4 fuel cell aircraft taking off. Source: HY4
HES Energy Systems
In 2018, Singapore-based HES Energy Systems began development of the Element One fuel cell passenger aircraft. The four-seater plane can fly for 500 km (310 miles) using compressed hydrogen, or 5,000 km (3,100 miles) using liquid hydrogen. HES will be using existing hydrogen technology from its drone systems to outfit the Element One. As a result, the refueling times will be no more than 10 minutes, due to an automated nacelle swap system. HES has a goal of providing a working prototype before 2025.
Digital rendering of HES concept Element One fuel cell aircraft. Source: HES
Fuel cells provide an excellent opportunity for the aviation industry to decarbonize. As technology develops further, planes will scale up to larger sizes and will be able to replace current models. FCHEA will provide updates as hydrogen and fuel cells become more prevalent within the aviation industry.