As increasing amounts of intermittent renewable energy such as wind and solar come online, there is a growing demand for reliable and efficient storage methods. Described in the journal Energy, the new system converts solar or excess renewable energy into heat, which is stored in the molten silicon at up to 1400°C. This energy can then provide electricity on demand via a thermophotovoltaic converter.
According to the researchers, the isolated molten silicon can store more than 1MWh of energy per cubic metre, over ten times the capacity of current systems which use molten salts.
“At such high temperatures, silicon intensely shines in the same way that the sun does, thus photovoltaic cells, thermophotovoltaic cells in this case, can be used to convert this incandescent radiation into electricity,” said research lead Alejandro Datas, from UPM’s Solar Energy Institute.
“The use of thermophotovoltaic cells is key in this system, since any other type of generator would hardly work at extreme temperatures.”
The UPM team claims that these cells produce 100 times more electric power than conventional solar cells per unit of area, and can achieve conversion efficiencies above 50 per cent.
As well as having an impressive capacity to store thermal energy, silicon is also the second most common element on earth after oxygen. This makes it a better prospect for wide scale use than salts, which are significantly less abundant. On top of this, the system designed by the UPM researchers is compact, has no moving parts, and operates silently.
The researchers are currently developing the first lab-scale prototype and are seeking to commercialise the technology through a business venture called SILSTORE.