When the HYPER lab was founded in 2010, our inaugural project here in the heartland of the aerospace industry, was to build the first liquid hydrogen fueled drone by a university team. Genii, short for the Latin Pondus Hydrogenii (a.k.a. ph, the hydrogen potential) was designed for a 1 kW proton exchange membrane fuel cell and lithium ion batteries. Here’s a flight overview video:
Our reasons for aerospace as a founding lab focus are clear:
- Washington State is the #1 aerospace state in the US.
- Aerospace is one of the most challenging sectors to decarborize (as described in this 2020 McKinsey report).
- The weight and power curves of hydrogen fuel technologies shown in the preceding section are close to ideal for typical aircraft.
- The solid state drive train of hydrogen fuel cell technologies is more reliable, quieter, has lower thermal signature, and higher excess power available for instruments than other technologies.
- The logistics of hydrogen fuel allow for production on the deck of aircraft carriers or in other remote locations as long as water and electricity are available.
The first thing you should know is that the idea of using hydrogen for aircraft is not new. In the aftermath of World War II, liquid hydrogen was viewed as the highest performing promise land of fuel for the airspace military theatre. Project Suntan is a great read from the NASA history archives as one of the first to develop a liquid hydrogen fueled aircraft. Long story short, hydrogen had superior performance as a fuel compared to JP-1 however the logistics of producing the fuel around the world forced the SR-71 to pivot to JP-1 instead of liquid hydrogen. The liquid hydrogen team then took their research experience to NASA where they developed the RL-10 and RL-25 rocket motors for the Saturn 5, Centaur, and Shuttle. “Taming Liquid Hydrogen: The Centaur Upper Stage Rocket 1958-2002” is a comprehensive history.
The National AeroSpace Plane (NASP) project in the 1980’s sought to develop an advanced aerospace vehicle to operate on liquid or slush hydrogen fuel but was cancelled after successful ground test technology demonstrations and a shift in administration.
In 2000, the European Union commissioned the Cryoplane project to convert a conventional passenger aircraft over to liquid hydrogen fuel ran through conventional turbofan engines. However the volume requirements for liquid hydrogen storage compared to kerosene (~4:1 ratio) consumed a substantial percentage of the fuselage. It became clear that non-traditional passenger plane geometries would be required to give hydrogen an advantage.
In the mid 2000’s two major shifts began to occur: 1. robotic aircraft (a.k.a. drones) began to emerge as a way to flight test new technologies, and 2. hydrogen fuel cell technology began to reduce dramatically in price and weight. Boeing’s PhantomEye and AeroVironment’s Global Observer chose internal combustion engines for their High-Altitude-Long-Endurance (HALE) concept vehicles. The Navy’s Ion Tiger project was one of the first to demonstrate liquid hydrogen with a fuel cell. It was inspiration from these three vehicles, and the associated difficulties faced, that motivated us to develop Genii.
The Genii project eventually grew into a Washington State supported project with Boeing’s subsidiary Insitu, and then into a project supported by the US Army. What we (WSU) has demonstrated through this effort is a 3D printed liquid hydrogen tank that removes many of the logistical difficulties of preparing hydrogen fuel for use in a fuel cell. We’ve also constructed small modular hydrogen liquefier systems for producing liquid hydrogen fuel in the field and transferred to the aircraft. One of our recent tests at our new outdoor liquid hydrogen test facility is described here.
Now in 2020, with a pandemic hammering the aviation industry and presenting an opportunity for pivot, hydrogen is in the spotlight as an upcoming aviation fuel. In late September and early October Airbus announced the ZEROe hydrogen aircraft project to develop the world’s first hydrogen powered passenger aircraft by 2030. This comprehensive approach considers a complete changeover of material handling equipment at airports to running on hydrogen in addition to the aircrafts themselves. Given the success of hydrogen fuel-cell forklifts as material handling equipment, luggage totes are likely to see similar success trends. The premium value of airport real-estate and fast recharging time of hydrogen vehicles (40x faster than 120 kV battery electric ‘superchargers’) will be particularly advantageous for airports.
A key challenge for Airbus to overcome includes speeding the refueling times of liquid hydrogen aircraft. Due to the super-insulation construction of liquid hydrogen tanks a considerable length of time is required to reach thermal equilibrium. Our 3D printed tank technology (link below) is once concept for solving this issue.
Another key challenge is local production of liquid hydrogen fuel. Smaller, more modular, hydrogen liquefiers with significantly higher efficiencies are needed to advance this area.