A team of researchers from the United States has created a better energy storage solution than batteries: cement.
This special material can overcome the limitations of other renewable energy sources, shaping the prospect of a future where our offices, roads, and homes play a significant role in a world powered by clean energy.
Renewable energy sources promise unlimited power supplied by the sun, wind, and water. However, the sun doesn't shine all the time, the wind doesn't blow constantly, and water isn't always abundant. These energy sources are intermittent, and in our increasingly energy-starved world, this is a major problem.
Therefore, we need batteries. However, batteries rely on precious materials like lithium, which are hard to source and do not meet the demand created by the global effort to decarbonize energy and transportation systems.
There are 101 lithium mines worldwide, and economic analysts are pessimistic about the capacity of these extraction units to meet global demand, reports the BBC.
According to environmental specialists, lithium extraction consumes a lot of energy and water, reducing the benefits of transitioning to renewable energy sources.
The lithium extraction process can sometimes lead to the leakage of toxic substances into local water sources.
Despite recent discoveries of lithium reserves, the limited supply of this material, excessive dependence on only a few mines worldwide, and the environmental impact have prompted the search for alternative materials for batteries.
And here come Damian Stefaniuk and his colleagues from the Massachusetts Institute of Technology (MIT) in the United States with a solution. They have created an energy storage unit, a supercapacitor, using three inexpensive basic materials: water, cement, and a substance similar to soot, called carbon black - a powder composed of fine particles of amorphous carbon, obtained by depositing the smoke resulting from incomplete combustion of natural gases or hydrocarbon-based raw materials, such as coal tar.
What is a supercapacitor and what can it do
Supercapacitors are highly efficient in energy storage but differ from batteries in several respects.
They can store energy much faster than a lithium-ion battery and do not have the same level of performance degradation. However, they lose power more quickly, making them less useful in devices like mobile phones, laptops, or electric cars that require a constant energy supply over a long period.
Stefaniuk says that carbon and cement supercapacitors could make a significant contribution to global efforts to decarbonize the economy.
"If the technology can be expanded, then it can solve an important problem - storing renewable energy," he says.
Researchers from MIT and the Wyss Institute for Biologically Inspired Engineering at Harvard University are considering several applications for their supercapacitors.
One could be creating roads that store solar energy and then releasing it to wirelessly recharge electric cars as they drive. The rapid release of energy from the carbon-cement supercapacitor would allow vehicles to get a quick boost to their batteries.
Another application could be building foundations or structural elements for houses and other buildings: "Having walls, foundations, or columns that are useful not only in supporting a structure but also in the fact that energy is stored inside them," explains Stefaniuk.
Projects like low-emission cement and concrete that stores energy outline a future where our offices, roads, and homes play a significant role in a world powered by clean energy.
However, research is still in its early stages.
Currently, the cement supercapacitor can store just under 300 watt-hours per cubic meter. Enough to power a 10-watt LED bulb for 30 hours.
The output power may seem low compared to conventional batteries, but a foundation of 30-40 cubic meters of concrete could be enough to meet the daily energy needs of a residential home. "Given the widespread use of concrete globally, this material has the potential to be extremely competitive and useful in energy storage," says Stefaniuk.
MIT researchers have scaled up the prototype, reaching a 12V supercapacitor. Stefaniuk has also managed to use larger versions of it to power a portable gaming console.
The team is now aiming to build larger versions, including one up to 45 cubic meters that could store approximately 10 kWh of energy needed to power a home for a day.
How does a supercapacitor work
The supercapacitor operates thanks to an unusual property of carbon black, a material with high conductivity. When carbon black is combined with cement powder and water, it creates a kind of concrete full of networks of conductive material, taking a form resembling tiny, branched roots.
Capacitors consist of two conductive plates with a membrane between them. In this case, both plates are made of cement with carbon black, soaked in an electrolyte salt called potassium chloride.
When an electric current is applied to the plates soaked in potassium chloride, the positively charged plates accumulate negatively charged ions from the potassium chloride. And because the membrane prevents the exchange of charged ions between the plates, the separation of electric charges generates an electric field.
Since supercapacitors can accumulate large amounts of charge very quickly, they could be useful in storing excess energy produced by intermittent renewable sources like wind and solar. This would relieve pressure on the grid during times when the wind isn't blowing and the sun isn't shining.
"A simple example would be an off-grid house powered by solar panels: using solar energy during the day and the energy stored in the foundation during the night," explains Stefaniuk.
Disadvantages of supercapacitors
Supercapacitors are not perfect. They discharge quickly and are not ideal for a constant current output required to power a home throughout the day.
Stefaniuk and his colleagues are working on a solution that would allow them to adjust the carbon-cement version by adjusting the mixture, but they will only reveal the details once they complete the tests and publish a paper.
There may be other challenges to overcome - adding more carbon black allows the resulting supercapacitor to store more energy but weakens the concrete slightly. Researchers say that any use that has a structural role and energy storage should find an optimal mix of carbon black.
Although carbon-cement supercapacitors could help reduce our dependence on lithium, they have their own environmental impact. Cement production is responsible for 5-8% of global human activity carbon dioxide emissions, and the carbon cement required for supercapacitors should be freshly manufactured rather than adapted into existing structures.
Nevertheless, it seems to be a promising innovation, believes Michael Short, head of the Center for Sustainable Engineering at Teesside University in the UK. However, more research will be needed to transition this innovation from the lab to the real world.
And here's some more good news: there might already be a way to overcome the issue of environmentally harmful cement. Short and his colleagues at Teesside University are already working on low-emission cement obtained from by-products of the steel and chemical industries.
T.D.