<\/noscript> <\/p>\nExperimental thermocell setup. Electrochemical refrigeration is currently not generally used or commercialized due to its low performance compared with other options, such as electrical refrigeration. However, this research may change that. Image credit: Yamada<\/p>\n<\/div>\n
The team created their own thermocell using a hydrogel \u2014 a water-rich polymer material \u2014 called PNIPAM, which they modified with a compound called viologen. This modified hydrogel contained a thermo-responsive polymer, meaning that the polymer reacted to temperature change, in this case being soluble in cool water but insoluble in hot water.<\/p>\n
With this thermocell, they were successfully able to use the very small amount of latent heat energy generated by the phase transition \u2014 between soluble and insoluble \u2014 to create electricity.<\/p>\n
\u201cFor the first time, we\u2019ve confirmed that latent heat has the potential to be used for thermoelectric conversion,\u201d said Professor Teppei Yamada from the Department of Chemistry at the University of Tokyo\u2019s Graduate School of Science.<\/p>\n
\u201cWe believe we can use various kinds of materials for thermocells. Every substance in the world can phase transition under the right conditions: for example, cream into ice-cream, sand into glass, water into steam, etc. With this method, in principle, it is possible to extract electrical energy from even the slightest temperature difference, greatly increasing the number of situations in which thermoelectric conversion can be used.\u201d<\/p>\n
The performance of a thermocell is assessed by how much voltage 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.<\/p>\n
The Seebeck coefficient of thermocells using organic compounds is usually less than 1 microvolt (one-millionth of a volt) per kelvin unit of temperature, but in this test they exceeded 2 microvolts per kelvin.<\/p>\n
\u201cThis is a remarkable achievement,\u201d said Yamada. \u201cAlthough we have previously created thermocells which produce 2 microvolts per kelvin by using a change in pH, this is the first time that the energy from a phase transition was directly used.\u201d<\/p>\n
<\/noscript> <\/p>\nDiagram of phase transitions in the thermocell. This diagram illustrates the polymer phase transitions of the modified PNIPAM hydrogel, showing how the polymer elongates into a coil and dissolves at low temperatures, and curls up into a globule and becomes solid at high temperatures. When used as a thermocell battery, temperatures above 25 degrees Celsius generated a voltage. Image credit: Zhou et al., University of Tokyo<\/p>\n<\/div>\n
The researchers hope that this work will help to improve refrigeration technology, temperature management devices and other tech like temperature sensors.<\/p>\n
\u201cWe have already reached the stage where we can consider practical applications of thermocells. For example, we expect it would be possible to generate electricity while cooling a server room or the engine of a car,\u201d said Yamada.<\/p>\n
\u201cThe real challenge now is that this technology is not well known, so we need industry, government and academia to work together to achieve rapid social implementation.\u201d<\/p>\n
Source: University of Tokyo<\/a><\/span><\/span><\/p>\n<\/div>\n