Hot stuff for renewable energy storage

One energy storage idea is just to heat stuff up when you have enough spare power, and use the hot stuff to make steam for a turbine when the renewables are off line.

While we would have all heard of that as being an advantage of solar thermal plants which use molten salts, there are simpler materials that can be used for heat storage.  Surprisingly, Siemens has just opened one in Germany that uses volcanic rock:

Spanish renewable energy giant and offshore wind energy leader Siemens Gamesa Renewable Energy last week inaugurated operations of its electrothermal energy storage system which can store up to 130 megawatt-hours of electricity for a week in volcanic rock....

The newly-opened electric thermal energy storage system is billed by Siemens Gamesa as “The Future Energy Solution” and as costing “significantly” less than classic energy storage solutions. Specifically, according to the company, even at the gigawatt-hour (GWh) pilot scale, ETES “would be highly competitive compared to other available storage technologies.”

The heat storage facility consists of around 1,000 tonnes of volcanic rock which is used as the storage medium. The rock is fed with electrical energy which is then converted into hot air by means of a resistance heater and a blower that, in turn, heats the rock to 750°C/1382 °F. When demand requires the stored energy, ETES uses a steam turbine to re-electrify the stored energy and feeds it back into the grid.

In the comments to that article, someone points out that an Australian company has just started using hot molten silicon!:

1414 Degrees is pleased to report progress with the GAS-TESS implementation at the Glenelg Wastewater Treatment Plant.

The full suite of ten biogas burners are commissioned and performing above expectations. The silicon storage reached operating temperature and the turbine started generating electricity on Saturday 25th May. It is supplying hot water from the turbine exhaust to the treatment plant, augmenting the continuous hot water supply from the biogas burners exhaust. Electricity is being delivered to our load bank pending SA Water completing the approval processes to connect to the National Electricity Market.

An innovative energy storage system from South Australia?   I hope it works...