Researchers have created a new material capable of storing solar energy and releasing it on demand as heat energy – a property that can be used for a number of applications including electric cars.
A team of Massachusetts Institute of Technology (MIT) researchers created the new material, which can be produced as a transparent polymer film. Researchers say that the key to storing solar energy for longer time is to store it in some form of energy other than heat as heat will eventually dissipate.
The team says that storing the energy from the Sun in a chemical storage is ideal for it can be stored for long periods of time and can be released through a trigger in the form of small jolt of heat (or light or electricity). The key is to have a material or a system that can retain the solar energy in a stable molecular configuration and then release it as well.
Through their study published in the journal Advanced Energy Materials, MIT researcher reveal that the requirement for such a chemical storage system is to have a molecule that can remain stable in either of two different configurations – the first wherein it should enter a charged state once the light from the Sun hits it, and the second state wherein it should snap back into its original state while giving off a burst of heat in the process.
These materials that exhibit such properties are called solar thermal fuels (STF) and were developed earlier by MIT professor Jeffrey Grossman, but they were designed to be used in liquid solutions and not capable of making durable solid-state films. However, scientists have now developed a new method that is not only simple but also scalable and involve the use of material called azobenzenes.
Azobenzenes change their molecular configuration in response to light and when they are stimulated by a tiny pulse of heat, they revert to their original configuration and release much more heat in the process. The researchers modified the material’s chemistry to improve its energy density—the amount of energy that can be stored for a given weight—its ability to form smooth, uniform layers, and its responsiveness to the activating heat pulse.
The material they ended up with is highly transparent, which could make it useful for de-icing car windshields, says Grossman.
The team is continuing to work on improving the film’s properties, Grossman says. The material currently has a slight yellowish tinge, so the researchers are working on improving its transparency. And it can release a burst of about 10 degrees Celsius above the surrounding temperature—sufficient for the ice-melting application—but they are trying to boost that to 20 degrees.
Already, the system as it exists now might be a significant boon for electric cars, which devote so much energy to heating and de-icing that their driving ranges can drop by 30 percent in cold conditions. The new polymer could significantly reduce that drain, Grossman says.