Untapped Clean Energy

Container ships that draw power from the air, rather than fossil fuels? Processes that could enable aircraft to run on hydrogen? Reactions that turn waste into biofuel? WPI researchers have some interesting ideas on how to use their technological expertise to find viable pathways for people to run their homes, cars, and businesses while not exhausting the Earth’s resources.

Behind the work is the urgent need to lower emissions from fossil fuels and remove carbon dioxide, or CO₂, from the atmosphere. The Earth just recorded its warmest year on record, with the European Union’s climate monitor reporting that the world’s average temperature in 2023 was up more than 2.7 degrees Fahrenheit since the start of the industrial age. The annual United Nations climate conference in 2023 included a stark message to nations: Speed up the transition to clean renewable energy.

Michael Timko, William B. Smith Professor of Chemical Engineering and leader of the university’s Energy Research Group, says the problems of energy and sustainability are both scientific and social, which requires a multifaceted search for solutions.

“WPI researchers are tackling multiple aspects of the problem by focusing broadly on processes, materials, and modeling aimed at reducing the production of carbon dioxide,” Timko says. “The research also acknowledges the importance of finding solutions that will benefit people in their communities. Climate change is a global problem, but solutions will need to make sense for communities as they deal with solid waste, water needs, infrastructure, jobs, energy costs, and clean air. “

Carbon is everywhere, and that’s generally OK. Carbon is, after all, the fourth most abundant element in the universe–stored in the Earth’s sediments and critical to the molecules that form living beings.

CO₂ is everywhere, too. People and animals exhale carbon dioxide when they breathe. Plants absorb CO₂ from the atmosphere and then release it when they decay. CO₂ in the atmosphere produces a natural greenhouse effect that keeps Earth cozy for plants and living beings.

Yet the growth of CO₂ emissions from human activities–burning carbon-rich fossil fuels to generate energy–is supercharging the greenhouse effect and climate change. Alternative energy sources offer cleaner options, but they also present challenges. Solar and wind power are carbon-free, but they only generate power when the sun shines and breezes blow. Batteries are needed to make the most of intermittent energy sources by storing the power for later use.

At their simplest, batteries store and convert chemical energy into electrical energy. Some materials used in those chemistries are rare, including lithium. Another rare mineral critical to many batteries, cobalt, has been mined in countries such as the Congo in ways linked to environmental damage and human rights abuses.

But Wang also is examining another element for batteries: sodium. His lab has worked on processes using magnesium, a mineral that is abundant in the earth and in oceans, to improve the activity and structural integrity of sodium-ion batteries that might be useful for storing energy.

“There is only so much lithium in the earth, and demand for lithium is driving up the price of batteries,” Wang says. “Sodium-ion batteries may never be as small and fast-charging as lithium-ion batteries, but they might be functional and affordable alternatives to lithium-ion batteries in low-end vehicles or renewable energy installations. Going forward, it will be critical to develop batteries without depending entirely on lithium.”

Some of Adam Clayton Powell IV’s research also is aimed at non-lithium technologies. Powell, an associate professor in the Department of Mechanical and Materials Engineering, has led work on a molten salt metal-air battery that might have the potential to power the massive container ships that transport the world’s traded goods across oceans.

Unlike conventional batteries that rely on metallic electrodes, metal-air batteries draw oxygen from the atmosphere to interact with a metallic electrode and produce the chemical reaction that converts into electrical energy. Magnesium makes a good candidate metal due to its abundance in sea water, where it is second only to sodium. It also has a higher energy density than sodium or lithium in a metal-air battery. 

The battery is designed so that ions move through a watery electrolyte solution that, unlike materials in flammable lithium-ion batteries, would resist catching fire. Teng says the new battery chemistry could lead to devices that could store large amounts of energy generated by renewable sources, including the wind and sun.

“Technology engineering for industry has often focused on making things that are bigger, faster, stronger,” Teng says. “In the 21^st century, technology will also need to be environmentally responsible. That’s why it will be important to not just optimize existing battery chemistries, but to invent entirely new chemistries that are more sustainable.”

WPI researchers are also working to develop new materials that could enable hydrogen production and storage. Hydrogen represents a promising energy source because it is the most abundant element in the universe and, when burned, emits only water. Yet a critical barrier exists: Most hydrogen production currently requires the burning of fossil fuels.

Yu Zhong, associate professor in the Department of Mechanical and Materials Engineering, is researching chromium-resistant air electrode material in solid oxide electrolysis cells (SOECs) that would split water into hydrogen and oxygen. The project, with $1.25 million in funding from the Department of Energy, ultimately seeks a way to produce hydrogen using electricity generated by renewable energy sources such as solar and wind power.  Zhong’s lab is developing computational models for new materials and collaborating with researchers at West Virginia University on experimental work.

“Current methods of generating hydrogen are not sustainable, especially for the levels of hydrogen needed to meet the energy demands of heavy industry,” Zhong says. “By linking renewable energy sources, such as wind and solar power, to installations of SOECs, it should be possible to produce hydrogen with much less fossil fuel.”

Much of the research into energy and sustainability at WPI has been funded by state and federal agencies, but corporate partnerships and philanthropy are playing a role, too.

Andrew Teixeira, associate professor in the Department of Chemical Engineering, focuses on micro-reaction engineering, and his work is core to WPI’s research collaboration with Honeywell Aerospace. While Honeywell has created its hydrogen fuel cell technology toward the electrification of the aviation industry, WPI’s researchers are engineering and modeling new solid hydrogen storage materials and reactors that safely power them. The research is aimed at examining how hydrogen fuel cells could power aircraft and reduce the carbon footprint of passenger travel, cargo airplanes, and unmanned aerial vehicles. Aviation accounted for 2 percent of global energy-related CO₂ emissions in 2022, according to the International Energy Agency.

Pratap Rao, associate professor in the Department of Mechanical and Materials Engineering, is using a $70,000 one-year seed grant from the Gapontsev Family Collaborative Venture Fund to develop a fiber-optic probe that could help researchers explore a process to break apart methane into hydrogen gas and a solid carbon material known as carbon nanotubes. His collaborators on the project are Teixeira and Ceren Yilmaz Akkaya, postdoctoral fellow, and Yuxiang Liu, associate professor, both from the Department of Mechanical and Materials Engineering.

The research arises from interest in improving ways of generating hydrogen for fuel. The process, known as methane pyrolysis, involves heating methane gas in the absence of oxygen to break the gas down into hydrogen and solid carbon, and typically requires high temperatures and a lot of energy. Adding a nickel catalyst to the process reduces the temperature and energy consumption, Rao says, and directs most of the solid carbon to form carbon nanotubes. However, a fraction of the solid carbon produced by the process remains on the nickel catalyst surface and ultimately deactivates the catalyst and shuts down the reaction. The Raman spectroscopy probe that Rao’s team is developing will allow researchers to better monitor this deactivation and ultimately understand how it can be prevented.

“This is an important technical challenge with a potentially large impact, because hydrogen is a carbon-free fuel,” Rao says. “In addition, carbon nanotubes are a useful material that could be attractive in a number of industries. This one-year project to develop a new probe could open up a number of opportunities for research.”

Where others see waste, Michael Timko sees material that could become something better.

His lab has combined used cooking oil, water, and a catalyst called ZSM-5 in a heated, pressurized container to form industrial chemicals known as one-ring aromatics. Add pigments, and you’ve got paint. Another project has involved working with researchers around the world on a process to grind up bamboo, a fast-growing plant, and treat it with an enzyme to produce ethanol fuel for cars and trucks. Both projects aim to reduce the use of fossil fuels.

To address the amount of plastic trash floating in oceans, Timko’s lab has studied the feasibility of installing reactors aboard ships to convert marine plastics into fuel. The researchers concluded that ships could potentially self-power cleanups of debris such as the Great Pacific Garbage Patch by using a hydrothermal liquefaction process to produce fuel.

Teixeira is working with Timko on a separate $2 million project funded by the Department of Energy and the Massachusetts Clean Energy Center to engineer the optimal feedstock for a waste-to-biofuel process. The researchers are working with Idaho National Laboratory and RAPID Institute to examine feedstocks, the raw ingredients of the recipe, at the molecular level and using machine learning, a form of artificial intelligence, to determine the best feedstock attributes.

“We want to know what happens when we blend waste streams such as food waste and woody biomass, or maybe store waste for a period of time under acidic conditions before pressure cooking it in a hydrothermal reactor to extract fuel,” Teixeira says. “We are also studying the cost and carbon footprint of turning waste into fuel, and whether the high temperatures and pressures of the hydrothermal liquefaction process might destroy PFAS, the ‘forever chemicals’ in consumer products that have been linked to health risks.”

An obvious thread running through many of the energy sustainability projects at WPI is collaboration, whether with academic or corporate partners.

Chemical Engineering Professor N. Aaron Deskins, whose research focuses on molecular modeling to address energy and environmental problems, has collaborated widely with WPI researchers, including with Teng on electrocatalysis and with Timko on a biochar that might be useful in filtering heavy metals from drinking water. Deskins also has worked with physics Associate Professor Lyubov Titova on MXenes, a class of inorganic compounds that form molecular sheets with many potential applications, including as battery electrodes.

“This field of research is at the core of what we as humans need to do to survive on this planet without destroying it,” Deskins says. “Computational modeling is valuable in advancing scientific discovery since we can model and screen hundreds of materials in a short time. But it’s also critical that we collaborate to validate in the laboratory what we predict in the computer.”

Collaboration matters, Timko says, because much work remains to be done to steer humanity to a better, cleaner future. WPI students and alumni, their families and friends, public and private research funders, and many others can play a role, he says.

“There’s nothing new about environmental concerns,” Timko says. “During the last 20 years, though, we realized we’re actually in a crisis situation. We cannot leave these problems to future generations and hope that they’ll invent miraculous technologies or find cheaper solutions. Countries and individuals are already spending billions upon billions of dollars to respond to disasters caused by climate change, provide clean water to people, and stabilize regions. We need everyone to get involved in this challenge.”