Is water the fuel of the future?
Space rockets may one day be fueled by tap water instead of gas tanks, thanks to research from the University of Tennessee and Oak Ridge National Laboratory.
The Department of Energy recently awarded a team of researchers from UT and ORNL a $2 million grant to decrease the cost to produce hydrogen fuel cells. The DOE also granted a separate $1.5 million to a UT-led team for research on more efficient fuel cells. These research efforts could help make hydrogen viable as fuel storage and limit environmental damage from burning fossil fuels.
Feng Zhang, UT associate professor in aerospace engineering and member of NanoHELP, is leading the first project to reduce the cost produce fuel cells. Matthew Mench, the department head for Mechanical, Aerospace, and Biomedical Engineering at UT, is also on the team.
The second project is led by Thomas Zawodzinski, the Governor’s Chair for Electrical Energy Conversion and Storage at UT and ORNL. He is researching methods to make hydrogen fuel cells more efficient.
“Whether it’s nuclear plants, solar cell plants, hydrogen batteries can take electricity from many sources,” Zhang said. “It can solve all problems for energy.”
Hydrogen fuel cells may fuel the future
Both teams are looking for ways to improve the way hydrogen is split from oxygen in water in hydrogen batteries. This is typically done through a process called electrolysis.
During this process, water is essentially zapped with electricity to separate its atoms. And when hydrogen is removed from oxygen, it can be used to create electricity.
When hydrogen is not connected to another atom, its electron can be pulled and passed through a circuit. That circuit can then be used to energize lights, engines, cars, rockets or entire cities. After the electron passes through the circuit, it is reunited with its hydrogen atom. That atom is then reunited with oxygen, producing water. That water is then recycled and its molecules are split again, continuing the cycle and preserving energy.
Although it is an environmentally friendly way to preserve electricity, hydrogen fuel cells need an initial charge of electricity before they can work.
Even though water is the final product of the whole process, recycling that water can be inefficient. As a result, the cost of hydrogen fuel cells could exceed the costs of natural gas.
“It has long been a goal to make a regenerative fuel cell, a single device that functions as both a fuel cell and an electrolyzer,” Zawodzinski said. Such a fuel cell would only need a small initial charge before it can continue to produce electricity.
Yet regenerative devices have also been inefficient in the past.
An attempt at regenerative batteries
Zawodzinski is developing a fuel cell which produces hydrogen peroxide as waste, instead of water. While not as clean, hydrogen peroxide can be easily stored and has less of an environmental impact than fossil fuels. And by using hydrogen peroxide, fuel cells can be far more efficient.
And since his battery will be more efficient, it will require less starting electricity to pull hydrogen electrons. That means the battery’s initial charge can pull electricity from renewable solar or wind sources and store it for longer.
“The hydrogen can then be used to power fuel cells, provide a stream of hydrogen and oxygen for another process such as combustion,” Dr. Mench said. “In effect, they are energy storage devices like batteries. The main limitation in the past for these has been cost.”
Finding cheaper and better ways to separate hydrogen from oxygen has been a primary concern. Materials capable of doing so can be expensive and can be too thick to maintain the water’s purity, making energy storage inefficient.
Electrolysis for cheap
Zhang’s team found a way to make a super-thin electrode that can efficiently separate hydrogen and oxygen. This material can improve the purity of water, which can lead to more hydrogen being pulled, which is then used to maintain electricity in a fuel cell. Since the new material is so thin, it is also cheaper.
“It reduces the thickness, volume and weight of fuel cells,” Dr. Zhang said. “In space exploration, they need oxygen and hydrogen. This makes transport easier, since it has less weight and volume.”
Zhang and his team are continuing to develop the new material. He said he is getting input from different companies, and is continuing to demonstrate the material’s potential in labs.
“We are trying to illustrate its performance to open more opportunities for the future,” Zhang said.
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