Novel Way To Store Sun's Heat - MIT

MIT researchers developed a newfangled application of carbon nano-tubes , which shows promise as an ground-breaking approach to storing solar energy for use whenever it’s needed. Rather than storing the sun's energy in an heavily insulated container or by converting it into electricity, storing the heat in chemical form has much more significant advantages, since in maxim the chemical material can be stored for long periods of time minus any loss in its stored energy. The trouble with that approach has been that till now the chemicals were supposed to perform this conversion and storage either degraded within a few cycles, or included the element ruthenium, which is rare and expensive.

#-Link-Snipped-#
Azobenzene functioanalized Carbon Nano-tubes!

Last year, #-Link-Snipped-# associate professor Jeffrey Grossman and four co-authors puzzled out exactly how fulvalene Di-ruthenium (known to scientists as the most effective chemical for reversibly storing solar energy, since it did not degrade) was able to execute this feat. Grossman said at the time that better understanding of this process could make it easier to search for other compounds, made of ample and inexpensive materials, which could be used in a similar way. Now, he and postdoc Alexie Kolpak have accomplished just that. Their new findings were published online#-Link-Snipped-#in the journal #-Link-Snipped-#, and will appear in print in a forthcoming issue.

#-Link-Snipped-#
How they function!

Grossman explains that one of the greatest advantages of the new approach to harnessing solar energy, is that it simplifies the procedure by fusing energy harvesting and storage into a single step. “You’ve got a material that both converts and stores energy. It’s robust, it doesn’t degrade, and it’s cheap,”he says. One limitation, however, is that while this process is useful for heating applications, to produce electricity would require another conversion step, using thermoelectric devices or producing steam to power a generator.

The key to operating solar thermal storage is an energy barrier distinguishing the two stable states the molecule can assume; the elaborated understanding of that barrier was fundamental to Grossman’s previous research on fulvalene dirunthenium, accounting for its long-term stability. Too low a barrier, and the molecule would revert easily to its “uncharged” state, failing to store energy for long durations; if the barrier were too high, it would not be able to easily release its energy when needed. “The barrier has to be optimized,” says Grossman. Already, the team is “very actively looking at a range of new materials. While we have already identified the one very promising material described in this paper, I see this as the tip of the iceberg. We’re pretty jazzed up about it,” he says.