Researchers devise way to generate solar power in the dark

April 17, 2014 by  
Filed under Solar Energy Tips

A new report from MIT and Harvard University describes the development of a switchable material that could harness the power of the sun, even when the sun is not shining.

Still in its infancy, this solution is no solar-energy cure-all.  Although the switchable material could generate electricity, it would be inefficient at doing so.  However, for applications where heat is the desired output – such as for heating buildings, cooking, or powering heat-based industrial processes — this could provide an opportunity for the expansion of solar power into new applications.

“It could change the game, since it makes the sun’s energy, in the form of heat, storable and distributable,” said Jeffrey Grossman, an associate professor of materials science and engineering, and a coauthor of a paper describing the new process in the journal Nature Chemistry. Timothy Kucharski, a postdoc at MIT and Harvard, is the paper’s lead author.

Some molecules, known as photoswitches, can assume either of two different shapes.  Exposing them to sunlight causes the shapes to absorb energy and hop from one configuration to the other, which then becomes stable for long periods of time.  However, these photoswitches can be triggered to go back to the other arrangement by applying a small shock of heat, light, or electricity.  Then, when the photoswitches relax, they emit heat.  In effect, the photoswitches behave as rechargeable thermal batteries, taking in energy from the sun, storing it indefinitely, and then releasing it on demand.

The new research is a follow-up to research by Grossman and his team three years ago, based on computer analysis.  However, translating that theoretical work into a useful material proved overwhelming.  To attain the desired energy density, it is essential to pack the molecules tightly together, which proved to be more difficult than anticipated.

Grossman said there are numerous applications where heat might be the desired outcome of solar power.  For example, in large parts of the world the primary cooking fuel is wood or dung, solar cooking could alleviate harmful indoor pollution and soften the bite of deforestation.

Photo credit: MIT

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