The use of metal powders to power external combustion engines could offer a viable alternative to the use of fossil fuels, according to researchers at Canada’s McGill University in Montréal, Québec. In a study published in the journal Applied Energy, the energy and power densities of the proposed metal fuelled zero carbon heat engines are predicted to be close to current fossil fuelled internal combustion engines, making them an attractive technology for a future low carbon society.
“Technologies to generate clean electricity – primarily solar and wind power – are being developed rapidly; but we can’t use that electricity for many of the things that oil and gas are used for today, such as transportation and global energy trade,” states the lead author of the study, Professor Jeffrey Bergthorson, a mechanical engineering professor and Associate Director of the Trottier Institute for Sustainability in Engineering and Design at McGill University.
When burned, metal powders react with air to form stable, nontoxic solid-oxide products that can be collected relatively easily for recycling, unlike the CO2 emissions from burning fossil fuels that escape into the atmosphere, state the researchers. Iron powder could be the primary candidate for this purpose, according to the study, as it is readily recyclable with well-established technologies and some novel techniques can avoid the carbon dioxide emissions associated with traditional iron production using coal.
“Biofuels can be part of the solution, but won’t be able to satisfy all the demand; hydrogen requires big, heavy fuel tanks and is explosive, and batteries are too bulky and don’t store enough energy for many applications,” stated Bergthorson. “Using metal powders as recyclable fuels that store clean primary energy for later use is a very promising alternative solution.”
Unlike the internal-combustion engines used in gasoline-powered cars, external-combustion engines use heat from an outside source to drive an engine. External-combustion engines, modern versions of coal fired steam locomotives, are widely used to generate power from nuclear, coal or biomass fuels in power stations.
While laboratory work at McGill and elsewhere has shown that the use of metal fuels with heat engines is technically feasible, no one has yet demonstrated the idea in practice. The next step toward turning the laboratory findings into usable technology, therefore, will be “to build a prototype burner and couple it to a heat engine,” added Bergthorson.