According to Reza Kholghy, a professor of aerospace and mechanical engineering and lead researcher in Carleton University's Energy and Particle Technology Laboratory, using metals, particularly aluminium, as a fuel source for energy storage and release could significantly decrease gas emissions and other pollutants associated with burning fossil fuels.
Each year, the amount of carbon dioxide (CO2) released into the atmosphere exceeds what the Earth's natural processes can eliminate. CO2 emissions, which come from burning fossil fuels for energy, significantly contribute to global warming. Mines, mills, power plants, and factories are the main sources of these emissions, with the industrial sector being Canada's largest producer of greenhouse gases.
Kholghy specifically mentioned: "Metals, when oxidised with another substance like water or oxygen, can generate power. We have been working with a reactor that has shown us just how multi-faceted this power can be."
To produce and store hydrogen fuel, the lab's industrial partner GH Power Inc built a reactor that burns metals. This power plant has been named a zero-discharge facility because it produces no harmful pollutants, and everything it creates is useful. Kholghy was consulted by GH Power Inc. in 2020 to provide input for the reactor's future.
"It ended up being the perfect match. My background is energy conversion and particle technology, and I always was looking for directions on carbon-free energy conversion," Kholghy praised the collaboration.
Under his guidance, the company constructed a test-sized reactor in Kholghy's laboratory, about the size of a soccer ball. The Carleton team has adjusted the reactor's construction and perfected the metal properties required to extract high-grade heat, carbon-free hydrogen that can be utilised to generate electricity, and other valuable materials, such as metal oxides.
The process is quite straightforward. First, the metal of choice, mainly aluminium, is shredded to reduce size. Then, it is mixed with oxygen or water in a specific ratio to initiate a reaction. The metal mixture is then poured into the reactor's opening and ignited after a few minutes, triggering the reaction.
This combustion produces various substances, including high-grade heat, which can be collected from the reactor's walls when aluminium is mixed with water. Solid alumina (aluminium oxide) powder is obtained from a tray below, and the most significant outcome is the hydrogen gas, which exits the reactor from the top.
"Everything this reactor creates is useful," Kholghy went on to give a detailed analysis.
"The alumina the reactor produces can either be recycled back into the aluminium metal to go through another cycle of energy storage, or it can be used in making highly valuable products like LEDs and batteries. The hydrogen gas it releases can generate electricity in fuel cells or even in gas turbine engines, and when burned, it only produces power and water. There's no pollution," he added.
Although hydrogen gas is a carbon-free and easily produced renewable energy source, it is yet to be used on a large scale due to difficulties in storing and transporting it. However, Kholghy's reactor has removed this barrier by generating hydrogen on the spot, eliminating the need for transportation. The reactor uses a self-sustained process for generating hydrogen, allowing it to be used on-demand and off-grid, making it useful in remote communities that rely on diesel fuel for power.
"By creating hydrogen fuel immediately and removing the need to store and transport it, our reactor is not only making renewable energy accessible but also viable long-term," Kholghy asserted.
After the reactor is optimised, only metals need to be transported as they are simple to move compared to hydrogen.
"Metals can be stored for long periods of time without any loss in energy," Kholghy exclaimed.
"This means we can produce metals at one point and then send them to a different location or trade them across the globe. Canada also produces aluminium with one of the lowest carbon footprints in the world, making this abundant resource a pathway to carbon-free energy storage, production and trade," he also added.
Kholghy's lab comprises seven graduate students and two postdoctoral fellow scientists who have been invaluable in pushing this work along. Additionally, fellow mechanical engineering researchers Metin Yaras and Rong Liu are collaborating and providing guidance on managing significant amounts of heat and material selection and assessment, respectively. If their research is successful, Kholghy hopes to introduce this pollution-free energy production method across all Canadian sectors.
"I believe this work is one big step towards the road to net zero and will drastically help with clean economic growth for Canada," Kholghy concluded.
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