RE: Strange but true - energy storage rocks13 Jun 2019 10:05
Aaaaaaaargh
Electrical energy is converted into hot air by means of a resistance heater and a blower that heats the rock to 750° Celsius.
So you convert electrical energy to heat using a resistance wire. Cheap, yeah. Efficient - a big NO
1) you lose perhaps 50% in comparison with a heat pump on the warming cycle and 2) you also lose on the way back down due to the intrinsic Carnot limits of a heat engine - so overall perhaps you only recover 25% of the electricity you pump into this 'battery'.
I am surprised by Siemens as they have good engineers - this must be a marketing led decision to make out that they are doing something in battery storage having evidently missed the boat. In a few years, or perhaps sooner, they will realise their mistake and end up having to buy BMN for a minimum of $5 Billion