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Scientists developing battery that releases energy in response to light


Published On Nov. 27, 2017 By Jeena

Scientists from MIT(Massachusetts Institute of Technology) are developing solar thermal material compose of chemical composite that can absorb heat through source(sun), accumulate it, and released it in controlled manner when expose to light. The material is mixture of organic compound and fatty acid and called as Phase Changed Material(PCM). Also developing a solar power cooking stove that could absorb heat from sun and release it on command during night.

PCMs can absorb or release big amount of heat during changing states, i.e. solid to liquid or liquid to solid, this potential application interest scientists and engineers. They have already been explored as a way of regulating heat in buildings, creating "heat batteries," and even keeping coffee hot on the drive to work.

PCMs as a heat source is based on simple principle. for example, when you melt ordinary ice, it takes significant heat to change it into liquid water. This is one reason why snow doesn't suddenly all melt at once on an unseasonably warm day and why ice cubes cool drinks better than dropping in stainless steel cubes kept in the freezer.

Getting PCM to stay longer in liquid state, change its phase at reasonable temperature, and make it release the heat on command is a difficult work. For many substances, the second requires heavy insulation, while the third depends on creating a PCM that releases its energy when slightly heated or exposed to a catalyst. Unfortunately, once the average PCM starts to release its heat, it does so all at one go as the PCM shifts from liquid to solid.

The MIT approach is to essentially introduce little molecules that act as photo triggers into conventional PCMs, and project is led by postdocs Grace Han and Huashan Li and Professor Jeffrey Grossman. In this case, it's the fatty acid tridecanoic acid mixed with an organic compound of an azobenzene dopant and a tridecanoic ester group.

This hybrid material liquefies when heated, but when it's exposed to ultraviolet light, it remains liquid even when it cools down. This means that most of the heat is locked up in the compound at 200 joules per gram, which is good for an organic PCM. Another pulse of light triggers the fatty acid and the PCM solidifies, releasing the heat.

What this means is that the material can be used as a chemical heat "battery" that allows heat to be released on demand and in the quantity desired. In addition, the PCM can store the heat for over 10 hours and the researchers say that this time could be improved upon.