MIT researchers have developed a new transparent polymer film that can store solar energy during the day and release it later as heat whenever needed. The material could be applied to many different surfaces, such as window glass or clothing.
An obvious problem that faces solar is the unavailability of the sun at night or on dark days. Some solutions have focused on storing and recovering solar energy as electricity or other forms, but this new study could show a highly efficient method for storing the Sun’s energy through a chemical storage system that can hold on to the energy indefinitely in a stable molecular configuration and release it later as heat. The study is published on the journal Advanced Energy Materials.
An azobenzene molecule is the primary component of the new material. It can remain stable in a charged or uncharged configuration. When exposed to sunlight (or UV), the energy of the light stimulates the molecules into their charged configuration, and they can stay that way for long periods. When triggered by a very specific temperature or other stimulus, the molecules return to their original uncharged configuration, giving off a burst of heat in the process.
Source: Zhitomirsky, D., et al. A spin-coating process enables the solar thermal fuel polymer material to deposit from solution. The film can then be readily charged with UV light. This process can be extended to a variable-thickness layer-by-layer process.
The material is also transparent, making it feasible for other applications, including as a defrosting device for vehicles windows . Many cars already have fine heating wires embedded in rear windows for that purpose, but they are inapplicable for the front windows as anything that blocks the view through the front window is forbidden by law. BMW, a sponsor of this research, is very interested in this potential application.