As the search for new, affordable, and renewable energy sources progresses, electricity is turning up all over the place. Have you ever considered that the power of your steps or the make-up of your flooring could create electricity? Triboelectric flooring can do just that. Triboelectric technology harnesses triboelectricity, which is produced when materials experience friction and is also the cause of static electricity. When this technology is used in wood flooring (more details on how that happens below), we can generate electricity to use in our homes by simply walking around inside of them. The innovative wood flooring that the researchers at The University of Wisconsin-Madison are developing can be used to power a building’s lights and other low-electricity appliances. Xudong Wang, an Associate Professor of Materials Science and Engineering who is working on the flooring, says that based on lab results, the electricity-generating materials of the flooring can work for millions of cycles without problems. More extensive, real world tests are coming soon. Wang is pictured below.
Flooring that Creates Energy
To search for untapped energy in the world around us is a process that is often referred to as roadside energy harvesting. Many believe that harnessing the energy in our movements and physical environment will be a powerful, growing branch of the evolving and increasingly necessary field of eco-friendly energy. Wang explains that,
“We’ve been working a lot on harvesting energy from human activities. One way is to build something to put on people, and another way is to build something that has constant access to people. The ground is the most-used place.”
This is far from the first product to develop in the world of energy-producing flooring; another common type of energy harnessed in this field is called piezoelectricity. Piezoelectricity, or the piezoelectric effect, occurs when materials that are vibrated are able to create an AC (alternating current) voltage or when materials vibrate when an AC voltage is applied, or sometimes even both of these. For example, quartz is considered piezoelectric because when a quartz crystal is arranged between two metal plates that vibrate, it creates AC voltage. Some microphones and alarms rely on the piezoelectric effect and sometimes flooring does too, as in the case of Elizabeth Redmond’s POWERLeap piezoelectric tiles in sidewalks. These tiles harvest and store piezoelectric electricity for lighting and low-energy use appliances, much like the new wood flooring from UW-Madison that harnesses triboelectricity.
The wood flooring coming out of UW-Madison is harvesting and storing a type of renewable energy called triboelectricity. In these floors, the energy-producing layers are flexible, transparent, and have less than one millimeter of thickness. They are made up of types of wood pulp that contains cellulose nanofibers. In the flooring, these nanofibers are also paired with fluorinated ethylene propylene within recycled-cardboard fiberboard. Some of the nanofibers can be treated to produce an electric charge so that the layers have different charges. When people walk across the floor and create friction between the layers, a charged layer of nanofibers rubs against an untreated layer of nanofibers. The layers have what Wang describes as different electron affinity and so electrons begin to move between the two layers. This creates a charge imbalance and when the electrons try to return to right this imbalance, they pass through a circuit and this process creates the triboelectric energy. The flooring can produce up to 30 V and ~90 μA when walked over.
Triboelectric Flooring Benefits and What’s Next
With this powerful single layer, the floor will be harnessing the energy of steps to run appliances such as lights or battery chargers. Also, multiple layers can be included to increase the potential energy output to the home or other building. These types of nanofibers have also already been used in designing more environmentally friendly batteries.
The wonderful thing about discovering this process in wood pulp is that wood pulp is a byproduct of many industries and is fairly affordable, meaning that these very high functioning floors might not end up costing much more that typical new wood flooring. Another benefit of this type of energy is that it is not weather or season-dependent like solar or wind power. Will Cushman of UW–Madison News explains that, “while there are existing similar materials for harnessing footstep energy, they’re costly, non-recyclable, and impractical at a large scale.” Buildings that install these floors will have an amazing mechanical industry source literally underfoot. The study abstract says that,
“this development shows great promises in creating large-scale and environmentally sustainable triboelectric board for flooring, packaging and supporting infrastructures.”
Wang and his team are still optimizing this flooring and are hoping to try out an educational prototype in a high-traffic area on campus soon. High foot traffic is an ideal condition in which to test and show off the flooring’s triboelectric potential. More details of the flooring research can be read in the September of 2016 publication of the study in the journal Nano Energy. Along with Wang, the other authors are Yanhao Yu, Zhiyong Cai, and Alberto Hernandez. The Forest Products Laboratory and National Science Foundation funded this story and The Wisconsin Alumni Research Foundation owns the patent for this triboelectric flooring technology. I, for one, will be following its evolution with great interest and would love to one day walk over and use the energy produced by this type of flooring.