Smart cities that champion sustainable net-zero energy consumption are no longer an all-new concept. However, achieving this state seems plausible only in the distant future for the building sector.
Now university researchers have developed a novel cement-based composite that can generate and store energy induced via contact between materials. This material could be used to build buildings that can harvest energy from human motion in their floors and wind and raindrops hitting them.
Everything around us is getting smarter, from devices to home appliances and eventually entire cities. The concept of a smart city, which involves energy-efficient ecosystems that can reduce carbon emissions, save energy, and provide better lives, are no longer a thing of the distant future. However, it’s worth noting that since the building sector alone is single-handedly responsible for 40% of the entire modern world’s power consumption, buildings need to be able to offset this energy consumption.
The solution to this problem may be closer than you might think. In a recent study published in Nano Energy, researchers from Incheon National University (INU), including Prof. Seung-Jung Lee, and researchers from Kyung Hee University and Korea University, addressed this issue by developing an all-new structural material that can make construction more eco-friendly.
The team developed a cement-based conductive composite (CBC) with carbon fibres that can also act as a triboelectric nanogenerator (TENG)— a type of mechanical energy harvester. This paper was available online on 3 August 2021 and was published in Volume 89, Part A of the journal Nano Energy in November 2021.
“We wanted to develop a structural energy material that could be used to build net-zero energy structures (NZES) that use and produce their own electricity. Since cement is an indispensable construction material, we decided to use it with conductive fillers as the core conductive element for our CBC-TENG system,” explains Lee. The concrete exteriors of buildings are often exposed to external mechanical energy sources such as ocean waves, movement of objects, wind on the walls, and raindrops on the roofs. Cement-based TENGs can harvest energy from these sources via contact electrification— a process where electricity is generated as a result of interactions between two materials.
The team designed a lab-scale NZES and a CBC-based capacitor using the developed material to test its energy harvesting and storage abilities. The results indicated that at a 1% volume of conductive carbon fibres in a cement mixture, the CBC mixture exhibits optimal electrical properties while retaining the superior mechanical properties of cement. The researchers’ electrical measurements confirmed that CBC-TENG could be safely used as a building material as the current generated by it was much lower than the maximum allowable current for the human body.
Apart from energy storage and harvesting, the material could also be used to design self-sensing systems that monitor the structural health and predict the remaining service life of concrete structures without any external power. “Our ultimate goal was to develop materials that made the lives of people better and did not need any extra energy to save the planet. And we expect that the findings from this study can be used to expand the applicability of CBC as an all-in-one energy material for net-zero energy structures,” concludes Lee.
