like Paul I also work at a power station, ours is coal fired.
the only way we will get proper sized grid "storage" will be with large scale pumped hydro. let the water out during the day when the demand is there and pump it back up at night using cheap electricity.
the problem with ALOT of projects is that the government will not subsidise the grid connection, its why there are so many approved solar farms, hydro dams etc but bugger all actually being built. its because the cost of the getting connected to the grid is insanely high. 900k's of new grid interconnection between S.A and N.S.W is going to cost us (the tax payers and elect users) 2.6 billion. Further blowout for vital NSW-SA grid interconnector
that's 2.8million per kilometre of wires and its not even finished. once you start asking private companies to pay huge connection fee's like that it just becomes unrealistic unless you are very close to the grid. which most of the times all these area's aren't. The government has actually just made some chunk of NSW a green energy zone where I believe they are actually going to contribute funding to help connect some of these renewable projects with in that zone.
Also don't always worry about spot prices TOO much, larger stations will also contract out part of there generating capacity. I'm at a 2 unit coal fired power station and I believe we've basically contracted out 1 units worth of capacity. So we're constantly being paid for that generation. but if the spot market prices go high and we have 1 unit out of service we obviously can't make the bulk of our actual profits, which means maintenance gets cut as we don't have the money to spend.
really the 3 big killers for coal fired power stations will be:
Ash Dam storage - The old addage of "you can't you die" rings true. if you have nowhere to store your ash you can't burn coal
Profitability - Market conditions means you won't make any money so just turn the thing off and walk away, this is both profit from generating or coal becoming to expensive to buy etc.
Plant Failure - Aging plant breaks and becomes to costly to fix
My view of the situation (in NSW) will be:
one or two of the older coal fired stations will close around the 2023 - 2025 mark (about when snowy 2.0 will come in). this will provide a small price increase which will be enough for the remaining stations to stay open until 2029 - 2032 which by then either a new base load gas or stored hydro will be in a much better place to take over.