If a new low-carbon aviation fuel uses more energy to produce than the resulting amount of energy it makes available to power an aircraft, that’s unsustainable. Aerospace engineers in The Grainger College of Engineering, University of Illinois Urbana-Champaign, are working with Boeing to develop novel and truly renewable energy solutions for the future of aviation from well to wake—that is, from processing raw materials into fuel and developing the best tank/storage solution, all the way to measuring the emissions in the wake of an aircraft.

“The first part of this work is to document the full lifecycle of various fuel options,” said Matthew Clarke. “Well-to-tank asks what methods are available to create these fuels and how much emissions those methods create. From there, we will model power and propulsion systems. Phil Ansell leads this first half of the project.”

Clarke said Boeing is actively exploring different technologies to improve the efficiency of their aircraft fleet. Recognizing that there are emissions associated with sustainable aircraft fuel made from renewable biomass and waste resources, Boeing approached U of I to examine other fuel options and is providing funding to help Illinois engineers study the options and suggest solutions.

“I’ll be looking at the next phase, which is tank-to-wake,” Clarke said. “Our primary objective is to develop higher fidelity models of the full propulsion architecture, which allow us to capture the impacts of burning various lengths of hydrocarbon chain molecules. In so doing, can investigate the impact on overall aircraft performance and quantify the emissions associated with each respective energy carrier pathway.”

He said they’ll study electricity for charging batteries, hydrogen, methane, ethane, propane, and synthetic kerosene.

“Boeing is also, of course, interested in how the aircraft will perform with a new type of fuel, but this is not just about aircraft performance. It’s about creating a sustainable ecosystem,” he said. “Do we have enough crops and water? How would biomass fuel affect food insecurity? What emissions are created when you create more propane, the most widely used hydrocarbon? And if we produce more propane for aircraft, how much will that increase the emissions from propane production?”

Clarke said he, Phil Ansell and his postdoctoral fellow are becoming chemical experts.

“We’ve had to learn about how propane burns. How much energy is produced when propane is burned during an aircraft’s flight? It’s important to know the difference when you burn a gallon of propane versus a gallon of jet fuel because it will influence the size of the tank that’s needed.”

Clarke said his part of the project is to develop the subsystems—better aircraft engines, battery models, motors, and how they are affected when burning a particular fuel. Last year, he was named one of Forbes' 30 under 30 for the program he developed called RCAIDE to develop the subsystems.

“Because we already have an validated code that is extensively used for these types of trade studies, we’re not starting from scratch. Our focus will be on integrated higher-accuracy computational models to delve further into the nuances of developing a clean sheet design vs. retrofitting an existing fleet with advanced technology. In fact, Boeing has used some of our tools before in prior projects with other institutions. They have confidence in our current tools. It’s one of the reasons why they came to us.”

Clarke said the final task of the project is integration. He and Ansell will combine their work, integrating everything they learned for advanced sustainable aircraft design. Clarke and Ansell will ultimately optimize what they have learned to explore new aircraft.

“We’ll know the options for energy pathways and the emissions that will be created. Now, we can explore the design so we can advise Boeing on the type of aircraft they could consider creating in 2030 that will have a long-lasting impact.

“We may say we want to use a propane pathway to the aircraft, but it’s not pure propane. It may have many other species included in the final jet fuel. I’ll use Phil’s data to simulate that on an aircraft, taking the problem all the way from well to wake.”

Boeing also wants these findings to inform their new cascade tool—a prediction model Boeing uses to answer the question: If you explore different energy pathways, what will emissions look like in 2050?

“We’ll give Boeing direction in terms of how to develop their next generation of aircraft—what it should be so the entire community benefits. Because models aren’t always accurate, we’ll create data to aid in CASCADE’s predictions for actual trajectories on flight operations over the entire world, for example to learn how it will impact emissions.”