When he began his graduate studies, Hamza Alnawafah joined UWM’s Industrial Assessment Center as an energy engineer. Through Wisconsin’s only U.S. Department of Energy funded center, teams of engineering students consult with industries to find ways to save companies money using energy-efficiency strategies. While assessing a wastewater treatment plant Alnawafah hatched an idea.
Wastewater treatment, an operation that exists in every community, is an energy-intensive process, he said. But because there’s also widespread inefficiency, he saw an opportunity to create a single platform that could produce more than one resource while also contributing to energy sustainability.
He based the work on creating “green” hydrogen.
Hydrogen isn’t naturally available as a fuel. It must be produced, using water and electricity in a process called electrolysis which splits water molecules into hydrogen and oxygen. For hydrogen production to be green however, the electricity used would have to come from a renewable source, driving up the cost. The highly flammable gas is also difficult to store and transport.
Solving these obstacles could pay off handsomely. Once produced, hydrogen is three times more efficient than fossil fuels and burning it gives off only water vapor.
Closed-loop system could offset electricity purchased from the grid
Alnawafah, a doctoral student in mechanical engineering, proposes using gray water at treatment plants and electricity from solar cells to produce green hydrogen on site. He then uses the two resulting elements – hydrogen and oxygen – in a “closed loop” where the hydrogen heats the plant and oxygen improves the efficiency of the water treatment. Nothing goes to waste.
“Wastewater treatment plants take in gray water – why not instead use that in electrolysis?” Alnawafah said.
By optimizing the processes, he believes his closed-loop system could mean that treatment plants could make and use green hydrogen to offset much of the electricity they currently buy from the grid.
“Our technology can be used in many different processes to arrive at several outcomes,” said Ryo Amano, professor of mechanical engineering and Alnawafah’s advisor. “It provides extra power and additional energy sources for utility operations.” It’s the only research into green hydrogen at UWM that he’s aware of, Amano said.
“A few employees from local companies came to see the lab because there isn’t anywhere else where the system concept can be displayed in a real environment,” he said. “In addition, Hamza has successfully demonstrated a 15% increase in energy efficiency at one Wisconsin wastewater treatment facilities.”
More avenues for optimizing
The researchers said their technology aims to make hydrogen a viable secondary source of energy at certain locations. The key to adopting green hydrogen, is controlling costs by optimizing its production.
Warmer water temperature in electrolysis and boosting the pressure of the hydrogen produced make a difference in the amount of hydrogen that can be produced, Alnawafah found. In fact, it’s the pressure and the flow rate that determines how much hydrogen you produce with a set amount of energy.
A unique aspect of the work is the researchers’ recognition that oxygen is not simply a by-product, but a valuable resource. Oxygen is pumped into the plant’s aeration tanks – the tanks that combine water and oxygen to accelerate the breakdown of organic material that is then removed from wastewater.
Air is currently used for this, but air contains only 21% oxygen. Alnawafah’s system would collect and immediately use 100% oxygen. He is now testing a hypothesis that pure oxygen will decrease the amount of time that the oxygen takes to accomplish its task.
The researchers cite hospital complexes, which also use oxygen as a raw material, as another example of how the technology could be used.
“With this project, we are showing how it could be done,” he said. “It won’t be as cheap as using natural gas, which creates carbon emissions, but by building in efficiencies for certain large-capacity needs, we give it a place in the overall energy equation.”