The use of wirelessly connected devices is expanding and they are being utilized for various applications, including monitoring machinery condition and remote sensing in agricultural settings. These applications have the potential to improve efficiency, but the challenge lies in powering these devices in areas where reliable electrical sources are not available. Research has identified a potential solution in the form of a new type of battery. Systems known as the “Int rnrn
The “Internet of Things” (IoT) has the potential to greatly enhance the efficiency and safety of equipment.
However, there are challenges hindering the implementation of IoT in many applications. One such challenge is how to power these devices in situations where reliable electrical sources are not readily available.
Researchers from the University of Utah’s College of Engineering have proposed a potential solution in the form of a new type of battery called a pyroelectrochemical cell (PEC).
This device was created and tested in the research labs of Roseanne Warren and Shad Roundy, both associate professors of mechanical engineering.
The senior author of a new study introduced an idea for an integrated device that can collect ambient thermal energy and convert it into stored electrochemical energy in the form of a supercapacitor or battery. This technology has potential applications for the Internet of things and distributed sensors. The main advantage is the ability to have sensors that can be distributed and do not require recharging in the field. Even though the device harvests very low levels of energy, it has the capability to generate a charge with an increase in temperature.The study, published in the journal Energy & Environmental Science, explores a new type of energy-harvesting device that can recharge based on temperature changes in its environment. This device, known as a pyroelectric energy converter (PEC), can be charged by differences in temperature within various surroundings, such as inside vehicles, aircraft, or even underground in agricultural settings. The PEC has the potential to power sensors for IoT applications that are difficult to recharge otherwise. While solar cells may be effective in some scenarios, the PEC offers an alternative method for harnessing environmental temperature fluctuations for energy.”In certain environments, there are two issues that arise,” explained Roundy. “One problem is the accumulation of dirt over time, which affects the performance of solar cells. It’s crucial to keep the cells clean in these scenarios. Additionally, there are many applications where sunlight is not available. For instance, we develop soil sensors that are placed just below the surface of the soil, where there is no sunlight.”
The PEC utilizes a pyroelectric composite material as the separator in an electrochemical cell. This material is made up of porous polyvinylidene fluoride (PVDF) and barium titanate nanoparticles, which have electrical properties.
The properties of the pyroelectric separator change as it is heated or cooled, causing the polarization to decrease or increase.
Fluctuations in temperature generate an electric field within the cell, moving ions and allowing the cell to store energy.
Lead author Tim Kowalchik, a graduate student in Warren’s lab, explained, “It stores electricity in what’s called an electric double layer, which stores the charge in positive and negative layers of ions. This is a glorified capacitor. When you heat and cool the system and you’re storing electrochemical energy, you’re changing the amount of positive or negative ions that are in those layers.”
The latest research evaluated the laboratory’s hypothesis on the cell’s functioning. “We had a predicted model of function that included what we called an ‘orientation effect’ in the paper,” Kowalchik said. “If we change the reverse the orientation of separator in the cell, it should drive ions the other way. This is a change we can make to the system that will show a different result that we can gather.” The team’s experiments were designed to verify their predictions, including the orientation effect and the effects of heating versus cooling.
“By applying heat in one way, we should see a reaction. Alternatively, if we first cool it, we should also see a reaction, but it will manifest differently,” explained Kowalchik. “Using a process called amperometry, we were able to apply a voltage and maintain a constant voltage while measuring the current. If there is no change, the energy input into the system remains constant; any change in current indicates a change in energy.”
The cell responded as predicted by the team, but the next question is whether it can function outside of a laboratory setting. Warren is now focused on addressing this question, with one of her students working on circuit modeling to develop a cell.
and optimize its function.”
Warren stated, “Now we begin altering various parameters. How can we enhance the energy harvesting and storage, as well as the combination of the two? Following that, we will conduct a real-world field demonstration.”
According to the study, the cell was capable of generating up to 100 microjoules per square centimeter from a single heating/cooling cycle. While this may not seem like much energy, it is sufficient for IoT purposes.
“For instance, you may want to monitor the condition of your car, machines, plants, soil, and other similar items. These types of sensors are typically quite in demand.”Roundy mentioned that these sensors have a lower power compared to smartwatches or phones because they don’t have a display and are not transmitting a lot of data. The sensors only give periodic updates and operate independently without an interface or a screen.
The research, titled “Direct Conversion of Thermal Energy to Stored Electrochemical Energy via a Self-Charging Pyroelectrochemical Cell,” was funded by the National Science Foundation. Fariha Khan and Danielle Horlacher also contributed to the study. Horlacher, an undergraduate art student, has been working on scientific illustrations for Warren’s group and created the…The image displayed on the cover of the journal is shown above.
Journal Reference:
Tim Kowalchik, Fariha Khan, Danielle Horlacher, Shad Roundy, Roseanne Warren. Direct conversion of thermal energy to stored electrochemical energy via a self-charging pyroelectrochemical cell. Energy & Environmental Science, 2024; 17 (6): 2117 DOI: 10.1039/D3EE03497F (link: http://dx.doi.org/10.1039/D3EE03497F)