Scientists have succeeded in generating electricity from latent heat more efficiently than in previous attempts. This heat is the energy of when a substance transits from the solid, liquid or gaseous state, to another state.
The achievement is the work of the team of Hongyao Zhou, from the University of Tokyo in Japan.
This breakthrough will fuel the practical use of thermocells, devices that use changes in temperature to create electricity, known as thermoelectric conversion. Since all materials are capable of undergoing phase transitions under the right circumstances, this research supports the idea that a wide range of materials have the potential for thermoelectric conversion. Latent heat that was previously wasted could be used in the not too distant future for devices to generate their own power while cooling, thus reducing their reliance on other energy sources.
Zhou and his colleagues created their own heat cell using a hydrogel (a water-rich polymeric material) called PNIPAM, which they modified with a compound of the type known as viologen. This modified hydrogel contained a polymer capable of reacting to temperature change, in this case being soluble in cold water but insoluble in hot water. With this thermocell, they were able to use the tiny amount of energy from the latent heat generated by the phase transition (between soluble and insoluble) to generate electricity.
The performance of a thermocell is evaluated based on the electrical voltage that can be generated from a small temperature difference, which is called the Seebeck coefficient. The higher the Seebeck coefficient, the more electrical energy can be extracted. The Seebeck coefficient of thermocells using organic compounds is typically less than 1 microvolt (one millionth of a volt) per kelvin of temperature, but in this test they exceeded 2 microvolts per kelvin.
Currently, electrochemical refrigeration is not widely used or commercialized due to its poor performance compared to other options such as electrical refrigeration. However, the new research could be a first step on a path to change this situation. (Image: 2023 Yamada. CC BY)
The researchers hope that this work will be the first step in a series of advances that will culminate in a level of progress sufficient to see this technology find practical applications in various fields.
Zhou and his colleagues report the technical details of their achievement in the academic journal Advanced Materials, under the title “Direct conversion of phase-transition entropy into electrochemical thermopower and Peltier effect.” (Fountain: NCYT by Amazings)