Concrete Batteries: Cementing a New Foundation for Energy Storage?May 28, 2021 by Jake Hertz
In a newly published paper, researchers from Chalmers University describe how they were able to turn cement into a medium for electrical energy storage.
One of the biggest challenges for mass integration of renewable energy sources (solar in particular) is distribution and storage.
Conventional lithium battery storage solutions are currently limited by capacity and cost––a problem that has prompted researchers to look at new forms of energy storage that may better suit our modern-day infrastructure.
A general depiction of a battery energy storage system with Li-ion batteries. Image used courtesy of Innolia Energy
Recently, with the growing movement towards greener energy solutions, the need for storage has become a pressing necessity. Advocacy groups like the Solar Energy Industries Association (SEIA) are launching a new network called the "Storage Advocacy Network." With this initiative, the hope is to spur more research and development of solar energy storage.
Earlier this month, before the launch of this new network initiative, researchers from Chalmers University announced their research describing an entirely new method for energy storage which, interestingly, is made out of cement.
This article will look at the need for storage to support renewable energy, the researchers’ approach, and how it works.
Why Solar Needs Storage
The need for storage in solar is primarily because solar arrays provide an unpredictable and non-constant power output.
A solar panel’s output varies significantly throughout a 24-hour period, where things like cloud coverage and time of the season will directly affect output. Beyond this, if the assumption that the average summer day has sunlight for 14 hours, that means that there are 10 hours every day where solar panels produce no power. Outputs in winter and northern locations can vary even more drastically.
A high-level example of a solar power system. Renewable energy largely needs storage solutions to accompany them. Image used courtesy of EnergySage
The result is that a solar panel alone cannot feasibly support a building.
One prevalent approach to fix this is to have a home powered by solar when it can and powered by the standard grid when it cannot. While this approach may work, it fails to entirely sever ties with non-renewable energy, which ultimately defeats the purpose of solar.
The other approach is to store any excess energy on-site; that way, when power demand exceeds the solar output, there can be access to reserved energy. This approach is entirely self-sustaining but is limited by the cost and capacity of current Li-on storage solutions.
Research from Chalmers
With the need for energy storage growing, many companies and researchers focus on battery energy storage systems (BESS).
As the researchers at Chalmers University see it, the solution is to find new forms of energy storage, particularly ones that can be built into our current infrastructure. This idea led them down a path that eventually resulted in creating a new type of battery, one which is made out of cement.
The schematic and layout of the researcher’s most successful battery attempt. Image used courtesy of Zhang et al
Previous research has shown that concrete can obtain stable and good electrical conductivity by adding electrically conductive components. The researchers at Chalmers built off of this understanding, exploiting these properties to make a rechargeable battery.
A cement battery showing a potential difference across its terminals. Image used courtesy of Zhang et al
The researcher's battery resembles a standard battery with an anode, cathode, and electrolyte separator. The anode layer, in their most successful iteration, consisted of a cement-based, iron-coated carbon-fiber mesh, while the cathode was a cement-based nickel-coated carbon fiber mesh.
The researchers added ion exchange resin to a cement mortar for a separator, increasing the ionic conductivity while also providing high electrical resistivity.
The project proved to be a huge success, with the researchers creating the world's first rechargeable cement battery. The experiments show that the battery had an average energy density of 7 Wh per square meter during six charges/discharge cycles – a number that is up to 10x better than previous attempts at cement batteries.
While this storage capacity is still significantly lower than most lithium-ion solutions, it prevails in the considerable volume of energy storage a building can provide.
In a house where the entire thing is made of energy-storing cement, the whole surface volume of the building material is essentially a battery, meaning that overall, this technology could provide more than enough storage.
Further, a cement battery makes solar energy storage more economical. Instead of separately paying for the building's materials and energy storage, this technology combines both in one, saving money overall.
While the technology still has a long way to go, it's possible that homes can become energy storage units sometime in the future, enabling a fully solar-powered future.