Also, you're simply unaware of commercially successful energy storage. The most high profile example being perhaps the battery pack Tesla installed in Australia for $90.6M AUD, and generated $13.1M AUD in revenue in just six months[1]. Clearly a very good ROI. Pumped Hydro is used all over the world and is even more cost effective.
[1] https://www.theverge.com/2019/6/25/18715585/tesla-australia-...
Pumped Hydro like Bath County Pumped Storage Station does exist but do not seem to buy cheap renewable when the price is low and resell it when it is high, but rather operate as a balancer for PJM Interconnection which get almost all its power from fossil fuels.
So do you have a link for a profitable battery that buys energy from renewables when there is an overproduction from renewable sources and then later sold when the prices has risen? That would be a solar / wind and storage combination. Using energy from fossil fuels to pump water is just not the same, even if doing so creates a profit for the company.
Every time I have read about a new storage facility they usually start with first describing capacity, then go on to say that this can enable a future use with renewables, but that right now it operate to balance the grid of existing (mostly fossil fuel based) power plants. I would very much like to be proven wrong and that there exist a viable commercial operation where we can see X amount of green energy produced by wind and solar going into the storage, and X (minus a conversion cost) of that energy going out, with one table showing how much the green energy costed when going in and an other table showing how much they got in profit when it went out.
"Tesla applies for UK power generation licence in [virtual power plant] play. ... The move suggests Tesla may be planning to build large-scale battery storage projects in the UK"[0]
[0] https://theenergyst.com/tesla-applies-for-uk-power-generatio...
There dose not exist to my knowledge (would be happy to be proven wrong) any storage solution that currently operated commercial from buying cheap renewable energy at peak production and regain investment and operational costs by selling it expensive during lows. Not a single one in the world.
At best any comparison between storage and nuclear plants is between two currently non-viable commercial alternatives, both requiring massive government funding to be built. The only commercial viable power source right now is renewable that can compete against fossil fuels when the weather make it viable, and fossil fuels as base load and as a dynamic source that can spin up based on weather conditions and demands.