Here's another article making grandiose claims about low-cost energy storage: Silicon will blow lithium batteries out of water says Adelaide firm
Signs of the Times wrote:1414 Degrees had its origins in patented CSIRO research and has built a prototype molten silicon storage device which it is testing at its Tonsley Innovation Precinct site south of Adelaide.
Chairman Kevin Moriarty says 1414 Degrees' process can store 500 kilowatt hours of energy in a 70-centimetre cube of molten silicon - about 36 times as much energy as Tesla's 14KWh Powerwall 2 lithium ion home storage battery in about the same space.
As always, the key to reading this type of claim is to look for the specification which is NOT mentioned and find out how bad things are in that area. In this case, the missing specification is efficiency.
Basically, the technology being put forth is to melt silicon and store heat in the latent heat of fusion of the silicon. In other words, the electrical energy is converted into heat for storage and then converted back into electricity for usage. Conversion of electricity into heat is 100% efficient and you can even achieve a COP above that if you can come up with a high-temperature heat pump (and have something you want to remove heat from at the same time). OTOH, the conversion of heat into electricity is subject to Carnot's limit on efficiency. At such high temperatures, the theoretical limit is not terrible, but in reality, the numbers are lower.
Looking at the company's website, we find out where this efficiency stands today
: 31%. That number is lower than what is achieved today using hydrolysis and a fuel cell for H2 storage. Of course the difference is that this technology is MUCH cheaper than H2 fuel cells. OTOH, fuel cells have the dual benefits of offering long-term storage and the ability to store the H2 in existing natural gas pipelines.
To say that this technology "will blow lithium batteries out of water" is a real stretch. Sure, cheap storage is attractive, but ultra-high-efficiency storage is also extremely attractive since electricity is a much more valuable commodity than heat, especially in the summertime. Where do lithium batteries stand today in terms of efficiency?
- Battery round-trip energy efficiency: 98%
- Inverter one-way energy efficiency (3-phase): >98%
Overall Li-ion electrical-energy storage efficiency: >94%
This efficiency number continually approaches unity and the costs of both the battery and the power converter continue to drop. Cost notwithstanding, Li-ion battery storage has come about as close to ideal as can be achieved. As costs come down, the barrier to entry for other technologies will only get higher.