Instead of adding batteries to buildings in order to turn them into virtual power plants, what if we could use the building itself to store electricity? That is the thinking behind research at the University of Lancaster in the UK that has come up with a “smart cement” that is able to cost effectively store solar generated electricity for use whenever it may be needed.
Made from flyash and chemical solutions, the novel potassium-geopolymetric (KGP) composites are cheaper than Ordinary Portland Cement, which is currently the most widely used construction material. They are easy to produce and, because conductivity is achieved by potassium ions hopping through the crystalline structure, it does not need any complex or expensive additives.
The research team, lead by Professor Mohamed Saafi, created KGP composites by relying on the diffusion of potassium ions within the structure to store electrical energy and to sense mechanical stresses. When fully optimised, KGP “smart cement” mixtures could have the potential to store and discharge as much as 200 and 500 watts per square metre.
“We have shown for the first time that KGP cement mixtures can be used to store and deliver electrical energy without the need for expensive or hazardous additives,” said Professor Saafi in a recent interview.
If, for example, the exterior of a house were built using KGP and connected to a power source such as solar panels, would easily be able to store power during the day when unoccupied and then discharge its power during the evening hours when the occupiers are home. Interior partition walls within a home could be used instead or in addition in order to create excess power, which could then be sold back to the grid.
It’s not just homes that could benefit from the new material - just consider all the ways we currently use cement. Lamp posts made of smart cement, for example, could be used to take street lighting entirely off-grid. A typical lamp post uses 700 watts each night, meaning a 6-metre tall lamp post made using KGP would hold enough renewable energy to power itself throughout the evening. KGP pavement or curb-stones could store energy to power smart street sensors monitoring traffic, drainage and pollution, creating new possibilities for street level internet of things in smart cities.
“These cost-effective mixtures could be used as integral parts of buildings and other infrastructure as a cheap way to store and deliver renewable energy, powering street lighting, traffic lights and electric vehicle charging points,” added Professor Saafi.
A plethora of large structures like bridges, tunnels, parking lots and flyovers could made with KGP could also be utilized to create massive stores of energy in order to balance the grid in our increasingly power hungry cities. This would no doubt be welcomed by utilities who could manage these new energy deposits to quickly respond to electricity demands without the need for additional generation.
Then consider buildings, structures which could utilize both huge amounts of cement and huge amounts of energy storage. Currently stationary battery systems installed in or around buildings are allowing those facilities to accumulate rooftop solar power in order to release it during the night. Buildings built with KGP could accumulate excess stored energy to be sold to neighbors or back to the grid, essentially transforming buildings into profitable virtual power plants but without the space or financial investment usually associated with energy storage.
KGP is not just a cement with energy storage abilities, however. Another key benefit is that the mixture is structurally “self-sensing”. Changes in mechanical stress, caused by things such as cracks, alters the mechanism of ion hopping through the structure and therefore the material’s conductivity. These changes mean the structural health of buildings can be monitored automatically, by measuring conductivity, without the need for additional sensors.
Currently the structural health of buildings, bridges and other construction is monitored with routine visual checks based on historical data and some external sensor technology. Structures that include sections made from KGP at critical stress points would provide accurate instantaneous alerts when structural defects, such as cracking, occur.
“These cost-effective mixtures could be used as integral parts of buildings and other infrastructure as a cheap way to store and deliver renewable energy, powering street lighting, traffic lights and electric vehicle charging points,” said Professor Saafi, of Lancaster University’s Engineering Department. “In addition, the concrete’s smart properties makes it useful to be used as sensors to monitor the structural health of buildings, bridges and roads.”
The research is outlined in the paper ‘Inherently multifunctional geopolymetric cementitious composite as electrical energy storage and self-sensing structural material’ to be published in the journal ‘Composite Structures’. in October 1st, 2018. The researchers are now doing in-depth studies to optimise the performance of KGP mixtures and they are also looking at 3D-printing as a way to use the cement to create different architectural shapes.
If developed further, it is not inconceivable that we could see a future where all homes are built with KGP or other smart materials that can store electricity. Indeed, as Professor Saafi points out, even existing buildings could have KGP panels retro-fitted to provide foundational, cosmetic, energy storing and structural health monitoring purposes - and we can be sure that our cities are becoming intelligent when even the cement is getting smart!