$3 million ONR-funded research aims to combat climate change by decarbonizing naval fleet 

The U.S. Department of Defense (DOD) annually emits more than 55 million metric tons of carbon dioxide. This amount accounts for approximately 80% of the U.S. government’s carbon dioxide emissions. If the DOD was a sovereign nation, it would be the 56th largest greenhouse gas emitter, surpassing countries like Switzerland, Denmark and Peru.

This past January, President Joe Biden signed an executive order that placed the climate crisis at the forefront of foreign policy and national security planning. It included reducing defense-related carbon dioxide emissions to assist the U.S. Navy’s future investment in hybrid designs with alternative fuels. A collaboration of four departments from the College of Engineering and Computing recently began research that aims to develop, assess and simulate alternative fuels for decarbonization while maintaining or improving performance and combat readiness.

Department of Chemical Engineering Professor Bill Mustain will lead the $3 million Office of Naval Research (ONR) funded project. The co-principal investigators are Jochen Lauterbach, James Ritter and Sirivatch Shimpalee (chemical engineering); Frederick Dryer, Tanvir Farouk, Kevin Huang and Sang Hee Won (mechanical engineering); Roger Dougal (electrical engineering); and Nathan Huynh (civil and environmental engineering).  

Ten years ago, I would have never thought that I would work with a large team and make a significant impact.

- Bill Mustain

The project’s origin began this past February at the McNair Center when ONR officials held a briefing on the progress of existing programs. 

“As a part of that visit, I gave a presentation about our energy capabilities and energy-related research,” Mustain says. “At that end of that talk, they were very impressed by the capabilities at USC, which led them to talk about other problems they are trying to solve, including carbon dioxide emissions. They left us with the challenge to find pathways to better understand and help to solve the problem.” 

After that visit, groups of faculty met over two-and-a-half days to determine a plausible approach. “We worked together to figure out the gaps in knowledge and set a strong pathway forward. It was one of the most motivating and satisfying collaborative experiences I have had in my career,” Mustain says. 

The research began in September and is divided into four thrusts. Dougal’s work on the program will determine how changing from the current JP-8 (jet fuel) to an alternative fuel will affect physical conditions and the design and performance of individual vessels. For example, how would the storage and steerage power flow change to accommodate a new fuel? Huynh will work with Dougal by conducting simulated logistical fuel train scenarios. 

“Additional equipment will be needed to store, process or consume the alternative fuels. The efficiencies of engines will change with the fuel composition or fuel blend, and thus the amount of power available for ship propulsion or for operation of mission systems will vary,” Dougal says. “We will study these things by building component and system models of ships using our S3D software for analysis of power and energy flows.”

Seawater electrolysis to produce hydrogen is a key component of the program since it can be used either directly or to make other zero-carbon fuels. Regardless of the alternative fuel used, seawater electrolysis must be created from a source that is renewable, abundant and available to the Navy. Mustain will work with Shimpalee and two subcontractors from Georgia Tech and the University of Connecticut to combine electricity and seawater for making hydrogen. 

“We've already submitted a patent disclosure for a new design of a reactor that tries to overcome some of the energy problems with seawater electrolysis. The first step is to deionize the seawater before doing the electrolysis, which is very energy consuming. We've tried to come up with a way that could eliminate the first step and passively generate freshwater to electrolyze,” Mustain says.

Lauterbach and Ritter will work on two different designs for ammonia synthesis reactors, which is the largest-scale chemical process regarding energy consumption. Ammonia is currently made from the Haber-Bosh process, which is a reaction between nitrogen and hydrogen from steam reforming. But the single pass efficiency rate is only between 25% to 35%.

“Ammonia, although a carbon-free energy carrier, needs hydrogen for its production. But most of this hydrogen comes from natural gas or coal, releasing carbon in the production process. Ammonia synthesis also occurs with high pressures and temperatures, making it a very energy-intensive process,” Lauterbach says. “We are developing new catalysts and reactor concepts that allow ammonia production under milder conditions so that we can utilize hydrogen from water splitting with excess renewable energy.”

Won will lead the final thrust, alongside Farouk and Dyer. The trio will determine how to use an alternative fuel most effectively and investigate the impacts of ammonia and its blend with jet fuel on various combustion behaviors. Using ammonia to power a diesel engine is a technical challenge, and Won’s group will attempt to overcome required ignition timing issues. Huang’s expertise in solid oxide fuel cells will help determine if blends of ammonia and hydrogen can be used to enable jet fuel operation without encountering significant sulfur issues. 

“Ammonia combustion is very unique compared to JP-8 combustion in terms of its oxidation characteristics and pollutant emission, so it’s critical to understand the fundamental aspects and characteristics for ammonia and its mixtures with JP-8,” Won says. “A model gas turbine combustor will be developed to evaluate and identify fuel injection strategies for future technology development.”

Mustain’s idea of a successful outcome will be one where each fundamental activity completes a technical feasibility assessment to determine the possibilities, such as knowing if there is a problem with ammonia in diesel and whether an alternative fuel can be implemented. 

“I hope that some of the things we're doing will transition off this project. Then we will have new questions and decide what to push forward,” Mustain says. “As long as one of the technologies that we develop works and the team continues to operate cohesively, the project is a success.”

Mustain is excited to perform research that would completely change how the Navy operates. He also hopes this project could be a model for large research collaborations at the University of South Carolina. 

“Ten years ago, I would have never thought that I would work with a large team and make a significant impact,” Mustain says. “Our team is acting as a hub for other projects, and I think this has set in motion a subset of 10 to 15 faculty in the college that will now work together on various projects. We have a very strong set of people who are very confident in their ability to work together to make real change for the Navy and other sponsors.”