The word "concrete" traces its origins back to the Latin verb concrescere, which means to clot, condense, or solidify. Today, the term refers to a ubiquitous building material known for its ability to form a rigid, inert solid. Over time, scientists have added functional enhancements to concrete—such as photocatalyzing ingredients to reduce smog—that make it a multipurpose material. But most surprising perhaps is a collection of recent technologies that enable concrete to generate and store energy.
One example is Dyscrete, a prefabricated concrete panel coated with organic dye-sensitized solar cells (DYSC). Functioning like the chlorophyll in plants, these dyes generate electricity via electrochemical reactions that occur when illuminated. According to Berlin-based manufacturer BlingCrete, “Until now, the possibility of combining DYSC cells with construction materials such as concrete has been overlooked.” Preliminary prototypes consisted of a single layer of organic dyes, which were difficult to manufacture and lacked sufficient durability. BlingCrete then devised a multilayer encapsulation process that resulted in a more robust surface. “By adjusting the dye and electrolyte components, the layer system can be tuned to specific wavebands of light, including the very edges of the visible spectrum,” claims the manufacturer. Furthermore, Dyscrete is inexpensive to produce, suggesting the possibility of rapid adoption in construction.
In a similar endeavor, Swiss building material manufacturer LafargeHolcim and German solar energy equipment company Heliatek recently joined forces to create an architectural concrete panel façade system with the potential to double the power harvesting capability of traditional roof-based solar technologies. Strips of flexible thin film composed of carbon nanoparticles deposited onto a PET substrate form the surface of ultra-high performing concrete panels. According to a LaFargeHolcim press release, if the new technology were to comprise 60 percent of a 10-story commercial structure's façade, it would fulfill 30 percent of the building’s energy needs. “With this Ductal/HeliaFilm solution, building owners and developers as well as architects and engineers will be able to mitigate the energy costs of a building while enjoying the many benefits of a very light, low maintenance and long-lasting cladding solution,” said Gérard Kuperfarb, group head of growth and innovation at the company in the release. Unveiled at the French construction expo Batimat last November, the photovoltaic façade system is currently under development.
Concrete roofs are also getting a power update. Researchers at ETH Zurich have developed an ultra-thin shell, self-supporting concrete structure with multiple layers of functionality. Created for the ETH NEST HiLo project—a research facility focused on lightweight and adaptive construction—the structure offers thermal regulation, insulation, waterproofing, and power generation supplied via an ultra-thin concrete shell with a thickness ranging between 1 and 2 inches along the edges that is topped with strips of thin film photovoltaics.
Concrete has also been coaxed to produce electricity from mechanical pressure. British industrial engineer Laurence Kemball-Cook developed a concrete paver called Pavegen that utilizes piezoelectric technology to convert applied mechanical stress from footfalls into an electrical charge. The pavers incorporate recycled tire rubber as the energy-capturing surface, which rests above a recycled polymer concrete base. The electricity produced can be readily utilized for functions like nighttime illumination. “Ten slabs around a streetlight would power it all night long from the energy generated during the day,” Kemball-Cook told Scientific American in a 2011 article. “You can get 20 or 30 seconds of light from a small light fitting from one footstep.” Pavegen pavers are also supplied with footfall sensors that enable the tracking of pedestrian activity for security or consumer behavior purposes, and were recently installed on London's Bird Street.
Renewable energy technologies greatly benefit from the ability to store electricity for future use, thus overcoming the inherent variability of the energy source. Scientists at Lancaster University have created a new cement that performs this function. The potassium-geopolymetric (KGP) composite is a cementitious mixture made with fly ash, a byproduct of coal combustion. The intrinsic chemical composition of KGP enables electricity to be stored via the diffusion of potassium ions within the cement matrix. This inexpensive approach is favorable to that of typical smart cements that utilize expensive ingredients such as carbon nanotubes and graphene. According to the Lancaster University researchers, KGP is even less expensive than Portland cement, making it readily scalable to buildings as well as large infrastructure projects. “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 lead research engineer Mohamed Saafi in a press release. Not only can KGP-based concrete harvest 200 to 500 watts per square meter, but it also can supply building owners with real-time information about the material’s structural health.
With these innovations, concrete is transforming from an inert, static substance into a dynamic material with energy-generation and storage capabilities. Given the quantity of cementitious products used globally, these newfound capacities make “power concrete” a compelling contender in the renewable energy arena. In fact, the material may outperform traditional solar cells environmentally, considering that conventional polysilicon processing involves significant amounts of energy, emissions, and toxic chemicals. Production volume is another distinguishing factor: About 7 million metric tons of silicon are produced annually, compared with more than 9 billion metric tons of concrete—more than a thousand-fold difference. Thus, although electricity-harvesting concrete technologies are still largely under development, the argument for its potential is strong. Perhaps one day, power concrete may be the norm rather than the exception in concrete construction.
