Amazing things around: Metal Instead of Gasoline?
Have you ever imagined that your car could move without gasoline in its tanks or that you could do without recharging its batteries? Those are not empty dreams! A car could work on metal. Or, rather, it will be able to in the future when scientists succeed in creating a suitable external combustion engine. Mikhail Vlaskin, laboratory director at the Joint Institute for High Temperatures of the Russian Academy of Sciences, told the Global Energy Association about these plans. In 2009, he became the winner of the Global Energy Association Youth program.
To start with, we are talking about energy production through the decomposition (oxidation) of a metal, in particular aluminium, to provide non-stationary consumers with it: these are cars, trains, and sea transport. That is those very consumers who now use petroleum products and who travel. They are part of the city traffic, which means that they make a significant contribution to environmental pollution.
“As a result, we get huge emissions of greenhouse gases and sulfur oxides. To get rid of those, we can replace the gasoline in these cars with aluminium fuel, as the conventional fuel is now replaced by electricity in electric vehicles ,”Vlaskin said.
Actually, he does not consider electric vehicles to be the absolute solution to environmental issues. After all, they use rechargeable batteries, which, in addition to being very expensive, also pose a problem due to the presence of a limit on their specific characteristics, and their disposal is a complex and expensive process.
The scientist said that there was a linear relationship between the reduction of harmful emissions into the atmosphere and cutting the numbers of cars with internal combustion engines. “If you reduce the number of such cars by 10%, emissions will decrease by 10% in turn”, he said.
What is the process of aluminium decomposition, or aluminium combustion, as it is termed in the scientific community? It should be noted straight away that this issue has not yet been solved by science. During combustion, aluminium is coated with an oxide film, and facilitation of the energy release process still poses a problem.
One of the possible oxidising agents is water. “We have found that if aluminium is placed into steam at a temperature of 250 to 400 degrees Celsius, then it burns, and the oxide film is not a problem in this case. We get metal decomposition with heat release, complete oxidation,” said Vlaskin.
In simple terms, it takes about 10 kg of aluminium to replace 10 litres of gasoline of medium octane grade. “In energy intensity, one litre of gasoline is approximately equal to one kilogram of aluminium. But aluminium, due to its much higher density, takes up significantly less space,” the scientist said.
From the technological point of view, the process of “refuelling” a car with an external combustion engine working on aluminium looks like this.
A car arrives at a gas station, loads aluminium into one tank, and unloads aluminium oxide powder from another tank. Aluminium is brought to a gas station by an aluminium carrier. With the same aluminium carrier, aluminium oxide is taken from the gas station and transported to a smeltery. “That is, we have a closed-loop cycle here. Aluminium is easy to store as metal, we don’t have to worry about spills,” Vlaskin noted.
As for the propulsion system, it is still in the making. “We already have a similar power plant that generates energy from aluminium, but it needs a fuel cell. What we need is an external combustion engine. At the dawn of the automotive industry, there were steam engines, electric cars, and internal combustion engines. The steam engine is also an external combustion engine of sorts,” said Vlaskin. He is confident that sooner or later such an engine will be available, especially since not only Russia is working on it, but also the Netherlands, Canada and other countries.
Such engines will be employed not only in cars but also in trucks, on sea ships and rail vehicles.
Metals used for fuel will not lead to the emission of greenhouse gases by such power plants. However, to obtain metal, the electric power will be consumed. “If this power is generated by nuclear power plants, hydroelectric power stations or from renewable energy sources, then the entire cycle of using metal for fuel will not lead to emissions of harmful substances”, the scientist cites the main argument in favour of using metals for fuel.
According to him, using alternative fuels is a more expensive pleasure than a hydrocarbon. “The question here is how our society is going to change and what its priorities will be,” Vlaskin emphasised.
As for the stocks of aluminium and whether they will be sufficient to provide car engines and other vehicles with this metal in the future, we have the following picture. “Look, about 4.5 billion tons of oil are consumed today per year, with 65% of that oil is used for the production of motor fuels. The proven reserves of bauxite (raw materials for aluminium) are estimated at 80 billion tons. 4 kilograms of bauxite can yield 2 kg of aluminium oxide, and those in turn yield 1 kg of aluminium. So we are talking about some 20 billion tons,” Vlaskin added. He immediately reminded that the aluminium oxide spent in external combustion engines will be processed into aluminium over and over again.
How high will be the price of aluminium fuel, and in the future, the price of the fuel made from other metals, such as iron, calcium, sodium, potassium, magnesium? In fact, one shouldn’t be apprehensive about prohibitively high prices, Vlaskin says. “In Europe, one litre of gasoline costs about $2 today, due to taxes. The cost of 1 kg of aluminium around the world is also about $2 at present. And as I have already said, their energy intensity is the same. Therefore, if such power plants were available in Europe, they would already be quite competitive,” he said.
“Yes, in general, metals used for fuel are still more expensive than gasoline. But it’s today. What will happen tomorrow? One has to pay more for environmentally friendly products,” the Russian scientist says.
At the same time, Full member of the Russian Academy of Sciences, Professor Dmitry Markovich, at the request of the Global Energy Association to comment on this idea, noted that the proposal to replace gasoline with aluminium has both certain advantages and some limitations, and only the first steps have been taken in this direction.
"It always happens. In this case, it is very important to correctly define the niche for use. Of course, in order to make this technology real and economically competitive it is necessary to go a long way: to find the optimal design of the external combustion engine, to solve problems associated with the initial start-up, and with the industry of regeneration of metal aluminium from oxide, etc. But, as history shows, all such problems can be solved,” Markovich said.
According to him, the presented concept of external combustion engine on aluminium has prospects in terms of replacing hydrocarbon fuel and its high-temperature combustion in transport systems. First of all, it is important to improve local ecology in megalopolises, where a significant part of polluting components are generated by cars.
"Emissions that poison people in cities - nitrogen oxides, sulphur, under-oxidized carbon in the form of either soot or CO, those are the things we need to fight with. In this sense, such sources are in line with the electric sources, or with power plants on fuel cells, where the fuel is the same aluminium, but it is directly oxidized, without hydrogen phase (we’ve been studying such sources in our Institute of Thermophysics SB RAS), as well as some others,” Markovich noted.
The scientist believes that one of the main tasks of the future energy sector is to accumulate energy from various sources. "In this sense, both hydrogen and aluminium (with further use either directly or through the generation of hydrogen) are, of course, the energy carriers of the future,” Markovich said.