‘Solar thermal fuel’ polymer film can harvest sunlight by day, release heat on-demand
A new polymer developed by MIT researchers can store solar energy, and release it later as heat. This type of film could be used in BioPharma Cold Chain applications to provide additional low temperature protection to valuable BioPharma products – as an example, an RKN with this film on the top and sides of the container, could absorb solar energy in the tarmac, and later release it when temperatures drop at night. It is also possible that the solar energy that is absorbed by the film while on the tarmac, could provide high temperature protection during the summer.
The finding, by MIT professor Jeffrey Grossman, postdoc David Zhitomirsky, and graduate student Eugene Cho, is described in a paper in the journal Advanced Energy Materials. The key to enabling long-term, stable storage of solar heat, the team says, is to store it in the form of a chemical change rather than storing the heat itself. Whereas heat inevitably dissipates over time no matter how good the insulation around it, a chemical storage system can retain the energy indefinitely in a stable molecular configuration, until its release is triggered by a small jolt of heat (or light or electricity).
To make the film capable of storing a useful amount of heat, and to ensure that it could be manufactured easily and reliably, the team started with materials called azobenzenes that change their molecular configuration in response to light. The azobenzenes can then can be stimulated by a tiny pulse of heat, to revert to their original configuration and release much more heat in the process. The researchers modified the material’s chemistry to improve its energy density — the amount of energy that can be stored for a given weight — its ability to form smooth, uniform layers, and its responsiveness to the activating heat pulse.