As IoT technology advances, the question of how to power these devices, especially in locations where reliable electrical sources are scarce, poses a significant challenge.
Researchers at the University of Utah’s College of Engineering have developed a new form of battery that could help solve this dilemma. The solution, which is in the proof-of-concept stage, comes in the form of a pyroelectrochemical cell (PEC).
The integrated device, developed by associate professors of mechanical engineering Roseanne Warren and Shad Roundy, collects thermal energy from the environment and converts it into stored electrochemical energy. This essentially creates a supercapacitor or battery, which could be ideal for IoT and sensor applications.
Low energy levels
The device works by charging with changes in ambient temperature, whether it is in a vehicle, an aircraft or even underground in an agricultural environment.
“We’re talking about very low levels of energy harvesting,” Warren said, “but the ability to have sensors that can be distributed and don’t need to be charged in the field is the key benefit. We investigated its basic physics and discovered that it can generate a charge when its temperature rises or falls.”
Although solar cells can provide an alternative energy source for IoT devices, the practical aspects often pose problems. “In many environments you encounter two problems,” says Roundy. “One is that it gets dirty over time. Solar cells must be kept clean. In these types of applications they become dirty and their strength decreases. And then there are a lot of applications where you simply don’t have sunlight available. For example, we are working on soil sensors that we place just below the top layer of the soil. You don’t get any sunlight.”
With the use of a pyroelectric composite material made of porous polyvinylidene fluoride (PVDF) and barium titanate nanoparticles as a separator in an electrochemical cell, the electrical properties of the device change as it is heated or cooled. This action changes the polarization of the pyroelectric separator. This shift in temperature in turn creates an electric field within the cell, which moves ions and allows the cell to store energy.
Despite only producing 100 microjoules per square centimeter from a single heating/cooling cycle, this could be sufficient for the needs of some IoT applications.
The study, funded by the National Science Foundation, is featured on the cover of the March 21 edition of the journal Energy and environmental sciencespublished by the Royal Society of Chemistry.