A novel application of carbon nanotubes, developed by MIT researchers, shows promise as an innovative approach to storing solar energy for use whenever it's needed, reports Solardaily.
Storing the sun's heat in chemical form - rather than converting it to electricity or storing the heat itself in a heavily insulated container - has significant advantages, since in principle the chemical material can be stored for long periods of time without losing any of its stored energy.
While the new work shows the energy-storage capability of a specific type of molecule - azobenzene-functionalized carbon nanotubes - Grossman says the way the material was designed involves "a general concept that can be applied to many new materials."
Many of these have already been synthesized by other researchers for different applications, and would simply need to have their properties fine-tuned for solar thermal storage.
The key to controlling solar thermal storage is an energy barrier separating the two stable states the molecule can adopt; the detailed understanding of that barrier was central to Grossman's earlier research on fulvalene dirunthenium, accounting for its long-term stability.
Too low a barrier, and the molecule would return too easily to its "uncharged" state, failing to store energy for long periods; if the barrier were too high, it would not be able to easily release its energy when needed. "The barrier has to be optimized," Grossman says.
Already, the team is "very actively looking at a range of new materials," he says. While they have already identified the one very promising material described in this paper, he says, "I see this as the tip of the iceberg. We're pretty jazzed up about it."
Yosuke Kanai, assistant professor of chemistry at the University of North Carolina at Chapel Hill, says "the idea of reversibly storing solar energy in chemical bonds is gaining a lot of attention these days.
The novelty of this work is how these authors have shown that the energy density can be significantly increased by using carbon nanotubes as nanoscale templates. This innovative idea also opens up an interesting avenue for tailoring already-known photoactive molecules for solar thermal fuels and storage in general."
