> What we need is a storage technology with a duration of months
Actually, having expandable, highly re-usable tech like this is much better when the capacities are in terms of hours.
This storage, combined with say 2.5x solar panel installation, could essentially provide power at 1x day and night.
Yes, and we have that. It's called Li-ion batteries.
They are good for about 1000 cycles.
This system can run for decades.
Utility-scale Li-ion batteries are good for an order of magnitude more than that.
"LFP chemistry offers a considerably longer cycle life than other lithium-ion chemistries. Under most conditions, it supports more than 3,000 cycles; under optimal conditions, more than 10,000 cycles."
https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery...
https://iopscience.iop.org/article/10.1149/1945-7111/abae37/...
This is the paper that claims 10,000 cycles under optimal conditions.
But if you read it, they measure Equivalent Full Cycles, and it seems that implies 10000 cycles at partial discharge, not full discharge.
The paper calculates everything at nominal discharge upto 80%. Meaning, the installed capacity has to be 25% more than paper value, leading to increased costs.
Add to that, batteries are complex to manufacture, degrade, lose capacity, etc. You need high level of quality control to actually ensure you are getting good batteries. This means, the cost of QA and expertise increases. They are costly to replace, even at an avg of 3000 cycles (roughly 10 years). Bad cells in one batch accelerate degradation and are difficult to trace out. Batteries operate best at low temperatures, so the numbers may vary based on installed location and climatic conditions.
A turbine and co2 compressor system is dead simple to manufacture, control and maintain. A simple PLC system and some automation can make them run quite well. Manufacturing complexity is low, as there are tried and tested tech. Basically piping, valves, turbines and generators. These things can be reliably run for 30 to 40 years. Meaning, the economics and cost efficiency is wildly different.
With such simplicity, they can be deployed across the world, especially in places like Africa, middle east, etc.
On the whole, batteries are not explicitly superior as such. There are pros and cons on both sides.
3000 is still 3x your number.
In evaluating the importance of this, you need to consider not only the time value of money, but also what one might call the "time value of technology". Does it make sense to make the technology long lived when it's improving so quickly? Or do you just replace it in a decade when things are much cheaper? Was "this PC will last 20 years!" ever a selling point?
When evaluating these technologies, you have to look at not just what they cost now, but how rapidly the cost is improving. Batteries are likely improving more quickly than turbines and heat exchangers.