US MIT team uncovers workings of ‘chemical heat battery’

26 October 2010 23:01  [Source: ICIS news]

WASHINGTON (ICIS)--Scientists at the Massachusetts Institute of Technology (MIT) have discovered how a rare molecule can store solar energy indefinitely and then release it on demand as a chemicals-based heat battery, researchers said on Tuesday.

An MIT spokesperson said that institute researchers along with colleagues at Lawrence Livermore Laboratory and the University of California at Berkeley have uncovered the process by which a molecule called fulvalene diruthenium can absorb and store solar heat - perhaps for years without “leakage” - and then release that energy on command.

The molecule, which was discovered in 1996, “undergoes a structural transformation when it absorbs sunlight, putting it into a higher-energy state where it can remain stable indefinitely”, the institute said.

Then, triggered by a small addition of heat or a catalyst, the molecule reverts to its original state, releasing stored heat in the process.

This property of fulvalene diruthenium has been known for years, but the process by which the molecule achieves long-term and stable heat storage and release was not previously understood.

Professor Jeffrey Grossman, lead investigator who works in power engineering at MIT’s materials science and engineering department, said the research team discovered that the molecule goes through an intermediate step between its normal state and its heat-charged storage form.

Now that the fundamental mechanism of how the fulvalene diruthenium molecule works in absorbing, storing and releasing heat on demand is understood, “it should be easier to find other materials that exhibit the same behaviour”, said Grossman.

Fulvalene diruthenium is too costly for practical use as a “heat battery” in large scale or commercial applications, MIT said.

But knowing how the process works opens the potential for a major breakthrough in solar energy.

When stored solar energy is released from fulvalene diruthenium, “it can get as hot as 200 degrees Celsius, plenty hot enough to heat your home, or even to run an engine to produce electricity”, Grossman said.

“It takes many of the advantages of solar-thermal energy,” said Grossman, “but stores the heat in the form of a fuel.” 

“It’s reversible, and it is stable over a long term, so you can use it where you want, on demand,” he said.  “You could put the fuel in the sun, charge it up, then use the heat, and place the fuel back in the sun to recharge.”

Grossman said the next step will be a collaboration with Daniel Nocera, an MIT professor of chemistry, to use a combination of simulation, chemical intuition and databases of tens of millions of known molecules to look for other chemicals that have structural similarities and might exhibit the same behaviour at lower cost.

MIT officials were not available on Tuesday to say whether Grossman and his colleagues have a commercial partner in the work.

Grossman’s research was first published in the journal Angewandte Chemie.

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By: Joe Kamalick
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