From devices to home appliances and soon even entire cities, everything around us is getting smarter. 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 Professor Seung-Jung Lee, along with 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 fibers that can also act as a triboelectric nanogenerator (TENG)— a type of mechanical energy harvester to be featured in zero energy buildings.
What are zero energy buildings?
A zero energy building (ZEB) produces enough renewable energy to meet its own annual energy consumption requirements, thereby reducing the use of non-renewable energy in the building sector. ZEBs use all cost-effective measures to reduce energy usage through energy efficiency and include renewable energy systems that produce enough energy to meet remaining energy needs. There are a number of long-term advantages of moving toward zero energy buildings, including lower environmental impacts, lower operating and maintenance costs, better resiliency to power outages and natural disasters, and improved energy security.
In practice, actual projects seeking to verify zero energy should work to ensure no harm is done in the process of achieving zero energy performance across other, non-energy-related considerations, such as water protection, optimized comfort for low-load buildings, and comprehensive indoor air quality. While these considerations don’t affect the definition of zero energy, it is important that in practice a design team ensures that other important building considerations and values are not sacrificed in pursuit of zero energy.
What does the new material do?
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 fibers 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.
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 (triboelectric nanogenerator) can harvest energy from these sources via contact electrification— a process where electricity is generated as a result of interactions between two materials.
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. This material could be used to build zero energy buildings that can harvest energy from human motion in their floors and wind and raindrops hitting them.