Abundant silicon at heart of new system to make ‘sun power’ batteries
A TEAM of researchers from Madrid is developing a thermal energy storage system that uses molten silicon to store up to 10 times more energy than existing thermal storage options.
Their system could replace wallmounted batteries several car makers, from Tesla Motors to Mercedes-Benz and Nissan, are rolling out to power homes and recharge eletric cars. Storage is the current major challenge faced by renewable energy sources like wind and solar, with batteries not able to copy yet.
Researchers have been exploring a range of new ideas to improve energy storage, including a commercialized solar thermal energy system that stores concentrated heat from the sun in the form of molten salts and converts the heat back to electricity via a thermal generator. The salt-based systems work quite well, but they require complex pumps, pipelines and heat transfer fluids to generate electricity, making them expensive and vulnerable to safety issues.
They’re also not based on particularly abundant materials — if we scale up the use of these plants, we could find ourselves running low on the elements needed to make these salts within a few decades. That’s why researchers worldwide are looking for safer alternatives that use cheaper and more abundant materials.
The silicon-based solution proposed by the team from the Universidad Polytechnic de Madrid (UPM) could be a winner because silicon is one of the world’s cheapest and most abundant elements — second only to oxygen.
The proposed new thermal energy storage system involves heating the silicon in a container using either concentrated sunlight on surplus electricity generated by renewable power. The molten silicon — which can reach temperatures of around 1 400° C — can be isolated from its environment until energy is needed, at which point the heat is converted to electricity. Silicon’s unique properties allow it to store more than 1 MWh of energy in a cubic meter — ten times more energy than salts.
The key to making the new system work, according to research leader Alejandro Datas, is the use of thermophotovoltaic cells, a fairly new technology that sees solar panels generating electricity from heat as well as light.
“At such high temperatures, silicon intensely shines in the same way that the Sun does,” says Datas. “Thus thermophotovoltaics can be used to convert this incandescent radiation into electricity.”
The researchers believe their invention could dramatically reduce the cost of storing and producing energy in the thermal energy sector.
The UPM team is now looking to commercialize the system. Towards that end, they have founded a business project called Silstore and have started building a laboratory-scale prototype.
Scientists can now use silicon to store and re-use the sun’s energy