The first word in the title of this thread is Cheap. Where is the proof of this? I don’t see it.
The following article says this Energy Dome technology has a round-trip efficiency of 75%.
This is a little worse than other storage technologies. The Energy Information Administration says battery storage is about 82% efficient, and pumped (hydro) storage is 79%.
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The Dome has not been verified as being cheap and 75% efficiency because it has never been built. The first Dome is now being built and that will document cost and efficiency.
The Dome should be cheap compare to other energy storage systems because it does not need exotic metals, materials or equipment. The Dome can provide long duration electricity 4-24 hours. Batteries currently are not capable of long duration discharge. Pumped hydro is more expensive to build because of the need for a large head (height between upper and lower reservoirs). Other long term energy storage systems have efficiencies of 40-50%.
My engineering opinion is that Dome will turn out to be cheaper and more efficient than batteries, pumped hydro storage and other currently known energy storage systems.
Jaak