By AnneMarie Hunter
Two pencils + a 9-volt battery + water = hydrogen
The equation to produce hydrogen gas is relatively simple. The process to produce liquid hydrogen is not. Though it has the potential to be a vital green energy source, production of liquid hydrogen has long proved elusive for researchers and energy innovators.
“One kilogram of liquid hydrogen has the same energy as a gallon of gasoline but is much more efficient than burning gasoline,” said Dr. Jacob Leachman, associate professor in the Washington State University School of Mechanical & Materials Engineering. “It’s environmentally friendly, green energy. Water is its byproduct which falls out of the sky as rain.”
For decades, Leachman has been committed to developing a process to convert hydrogen gas into liquid hydrogen. In 2010, he founded the Hydrogen Properties for Energy Research (HYPER) Laboratory on the WSU Pullman campus with a mission to bring this vision into reality. With the assistance of donor funding, Leachman and his HYPER team have been originating concepts for a hydrogen conversion process.
One of the key challenges to achieving this goal has consistently been temperature requirements. Liquid hydrogen is actually cryogenic hydrogen. In order for hydrogen gas to become liquid, it must be cooled to a cryogenic temperature below -420 degrees Fahrenheit.
From the development of equipment that will liquefy the hydrogen, to exploring materials that will safely store the liquid hydrogen, the process to realize Leachman’s goal has been exponentially complex and multifaceted.
In April, Leachman and a team of innovative graduate and undergraduate students advanced their cutting-edge project one monumental step closer to reality. After nearly two years of laser-focused design and development, this pioneering group completed the build of a Mobile Hydrogen Generation Unit (MHGU, pronounced magoo) – also known as a deployable hydrogen liquefier.
A SCIENTIFIC ACHIEVEMENT OF A LIFETIME
“With over 6,000 parts, this liquefier is the most incredible achievement I’ve seen by engineering students in my lifetime,” Leachman said. “Each student delivered something key and critical to the project.”
Funded by the United States Army, the liquefier will be tested later this year with the intent to provide cryogenic hydrogen fuel for army drones. An initial proposal for the MHGU was submitted to the army in June of 2018 and approved in January of 2019.
From that point, the MHGU team started to form at the HYPER Lab, which happens to be the sole cryogenic hydrogen research laboratory in the US. Sean Dimmer joined the MHGU group in early 2019 as the CAD and plumbing team lead.
“My work involved putting together diagrams for the fluid systems, generating concepts and designs for subsystems and determining locations for equipment, so maintenance, access, and clearance requirements were met,” said Sean, who was awarded his Bachelor of Science in mechanical engineering in the fall of 2020. “From there, the team and I merged with the controls and electrical team as ‘the BUILD squad’ to put it all together.”
The hydrogen liquefier’s sophisticated computer mechanisms were all built into an unassuming, 8-by-8 tan cube of a mil-spec shipping container.
“The challenge was fitting all 6,000 components into the container, while managing the heat loads and hydrogen safety standards,” Leachman said. “One of our goals was to design it like computer architecture. Students Sean, Hannah, and Andy created an amazing CAD model of the liquefier with weight, mass, and dimensions for all 6,000 parts to verify they would work together in the box.”
In fact, all of the students who collaborated on this project forged uncharted terrain throughout this groundbreaking undertaking.
MHGU CHALLENGES AND VICTORIES
“Building the MHGU was like solving one giant jigsaw puzzle,” said Hannah Gardner, a mechanical engineering student who has been awarded numerous scholarships, including the Regents Scholars Award and the Voiland College of Engineering and Architecture Dean’s Scholarship. “Learning how to pioneer a new technology in a developing field is hard to do. This project’s goals were unique and we had many problems to solve.”
Like Sean, Hannah worked with the CAD and Plumbing Team and on the BUILD Squad.
“Throughout this project,” Hannah said, “we had two major constraints: the size of the container, and the hydrogen safety rules we had to abide by. We had huge pieces of equipment we needed to fit in MHGU, and safety rules to follow which dictated certain locations of equipment and additional other safety measures.”
The MHGU’s challenges were not limited to these constraints.
“The biggest recurring issues for this project were extended lead times from slowed supply chains due to the COVID-19 pandemic,” said Sean. “Three-week quotes were extended to five weeks, to seven, and so on. I realized that for many of our components, we had no idea when they were going to show up.”
Regardless of obstacles, the resilient MHGU team persevered, achieved, and transformed the MHGU dream into reality.
“The most inspiring aspect of this project was the team that I got to work with,” Hannah said. “We had a constant flow of ideas and positivity, and even when we got sent back to the drawing board, we were never defeated. I feel that I left this project as a better person, team member, and engineer after working with them.”
In mid-April, after more than two years of work, MHGU was completed and a two-ton crane was used to lift the equipment cages into the container. This summer, the MHGU team will travel with the liquefier to Oregon’s Pendleton Field and the John C. Stennis Space Center in Mississippi for testing.
“I don’t think the magnitude or scale of what we were doing quite set in for me until we lifted the equipment cages into the container,” Sean said. “Seeing MHGU with all the equipment loaded in, after working on the CAD assembly for months, blew my mind. It looked like a photorealistic rendering of what had been designed.”
Hannah’s experience mirrored Sean’s.
“The most inspiring moment was when I saw the MHGU being pulled out of our indoor lab site onto a trailer and moved to our outdoor testing location,” she said. “Everything that we’d been doing was preparing for this moment. As I saw it roll away, I knew what we were doing was going to work.”
Prior to MHGU, both Hannah and Sean were committed to the field of green energy exploration. After working on this project, their goals were solidified.
“This project cemented my interest in working in the hydrogen industry with the goal of contributing to the widespread adoption of hydrogen fuel infrastructure and technology,” Sean said. “I learned so much at the HYPER lab and on this project that I can’t really picture myself working in any other field!
“I have a deep passion for clean energy due to its ability to lower carbon emissions and help the environment,” she said. “I hope one day to continue pursuing projects that will benefit the environment.”
Learn more about the MHGU and outcomes of the drone tests later this summer in the second article of this two-part series.
LIQUID HYDROGEN: THE PROCESS
Hydrogen gas is the most abundant element in the universe. A hydrogen molecule is composed of two hydrogen atoms each with a proton and one electron. It is the lightest element known to mankind and also takes up a tremendous quantity of space. Because of its abundance on earth and ability to carry energy, hydrogen has the potential to be a clean, green global energy transmission system.
In order for hydrogen gas to be transformed into a green fuel, it can be converted into a more dense substance – liquid hydrogen. Hydrogen becomes liquid when it is cooled to a temperature of -420 degrees F, which is a realm of temperature known as ‘cryogenics.’ In this new, dense form, hydrogen is referred to as liquid hydrogen.
The recently completed hydrogen liquefier designed and built by the HYPER Laboratory team at WSU streamlines this process. Initially, purified water is split into hydrogen and oxygen in an electrolyzer. The hydrogen is then scrubbed free of water and transferred into a small hydrogen liquefier or cryogenic cooler referred to as a dewar.
The HYPER Lab’s dewar is made of stainless steel alloy #316 which will not become brittle from the extreme temperatures or the hydrogen gas. Once converted, the liquid hydrogen remains in the hydrogen tank until it is needed as fuel. At that time, the storage container doors are opened and a transfer line is connected between the tank and the vehicle being fueled, such as a drone. The flow of liquid hydrogen is then initiated from the tank to the vehicle.