A rechargeable device that stores thermal energy from the sun in a liquid or solid form and converts it to electricity when needed could one day be used to power your smartphone and eliminate the need for batteries.
at Chalmers University of Technology in Gothenburg, Sweden, and his colleagues have designed a substance consisting of molecules made up of carbon, hydrogen and nitrogen that is capable of storing solar energy for months or even years.
The molecules change shape when hit by light from the sun鈥檚 ultraviolet and visible range, trapping energy in the form of heat. Extracting this heat returns the molecules to their original configuration, which can be recharged with solar energy, creating a renewable, closed system. The charge is also long-lasting, with a half-life of up to 18 years.
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The researchers initially designed their molecules for use in a scalable, emission-free system for , but have found a way to potentially power portable devices too by combining these with a new thermoelectric generator developed by a team at Shanghai Jiao Tong University in China. Such generators already exist at large scale, but the Shanghai researchers have made one that is the size of a microchip.
鈥淭hey were making this heat-to-power generator chip and we were making the molecular solar thermal material, and we basically combined the two,鈥� says Moth-Poulsen.
He and his colleagues charged molecules in 20 millilitres of liquid in Sweden, then shipped them to China. The team there converted the heat stored in the liquid into small amounts of electricity, with minimal heat loss, in a proof-of-concept demonstration.
Moth-Poulsen says a film version of the molecules and the generator chip could be integrated with a phone or tablet that had a transparent screen to allow light penetration. This might be possible in the next 10 to 15 years, he says.
at Carnegie Mellon University in Pittsburgh, Pennsylvania, says that the miniaturisation of the thermoelectric generator is impressive, but the molecular material鈥檚 power and energy storage density will need to be 鈥渙rders of magnitude鈥� higher before any real-world applications are viable.
鈥淥ne of the tough things about this chemistry right now is that it really doesn鈥檛 make use of the sun鈥檚 light where [the spectrum] carries the most energy,鈥� says Wang, meaning the infrared range.
The molecules currently capture only about 3 per cent of the energy from sunlight, says Moth-Poulsen. Along with improving this, 鈥渙ne of our key objectives is to expand the range of wavelengths that the system can work with鈥�, he says.
Cell Reports Physical Science
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