Hot new discovery: Rare metal that stores heat from sun makes the ‘rechargeable solar battery’ possible
By Niall Firth
Last updated at 2:02 PM on 30th November 2010
Scientists have discovered how a rare metal is able to absorb sunlight and store it as pure heat until it is needed.
The breakthrough paves the way for the next generation of solar power devices that are able to harness energy and heat collected from the sun and store it indefinitely.
Researchers at the Massachusetts Institute of Technology say it could be used to create a ‘rechargeable heat battery’ that could be used to heat a home.
A crystal of ruthenium, which is used to create the fulvalene diruthenium molecules
The remarkable material is known as fulvalene diruthenium. When a molecule of the substance absorbs sunlight it changes shape into a semi-stable, but perfectly safe, state.
It can stay like this indefinitely until combined with a catalyst when it will snap back to its original form releasing a huge amount of heat. This heat could then be used to heat a home.
Most solar power device used today convert energy from the sun into electricity or heat but do not store the energy that is not used.
When the heat is released, fuel made from fulvalene diruthenium is capable of becoming as hot as 200C.
This is known as the thermo-chemical approach, and would be far more effective than conventional solar-thermal systems which need insulation and which gradually let the heat leak away.
Ruthenium is a metal, related to platinum, which is rare and so extremely expensive
Jeffrey Grossman, lead author on the study, said: ‘It takes many of the advantages of solar-thermal energy, but stores the heat in the form of a fuel. It’s reversible, and it’s stable over a long term.
‘You can use it where you want, on demand. You could put the fuel in the sun, charge it up, then use the heat, and place the same fuel back in the sun to recharge.’
The main obstacle to the new technology is the relative rarity of fulvalene diruthenium, making it extremely expensive to use.
Fulvalene diruthenium comes from ruthenium, which is a rare, expensive hard white metal element of the platinum group.
Only about twelve tons of ruthenium are mined each year. It is also a byproduct of nuclear fission but the process to create it is extremely expensive.
However scientists believe that now they understand how it works, other cheaper materials with similar properties will be found.