There needs to be a way to send electricity price down the lines in real time or close to it (15 minute intervals?).
Are you just not aware that this already exists?
A giant grid level battery removes the incentive to conserve and has a greater possibility of polluting the local area with toxic magic smoke as has happened too frequently in other places. I can see it boosting executive bonuses and as a way to get free government grant money. If that same grant money was divided up amongst private individuals, I think it would do more good.
Ah grand, so you don't know how any of this works. Brilliant.
There is no government grant money here, just good old fashioned commercial price arbitrage. Prices are expensive between 4-8pm, and cheaper at other times, especially over night. This company has built something so they can buy cheap electricity, store it, and sell it later when its more valuable. They aren't getting public funding to do this.
It has been built in Scotland, because they have a surplus of green energy, often very cheap green energy - its often windy overnight, when prices are low. If there is no demand in Scotland for energy, but there is in the rest of the UK, the grid pays the windfarm operators to not generate electricity. This project captures that energy, increasing the MWh of green energy produced, and reducing the MWh of gas burned to generate electricity.
The amount a supplier pays for a unit of electricity depends on 2 things - the unit rate, and the standing charge. The unit rate comes from the cost of providing all the energy needed in every 30 minute block of the day, and is set by auction, with every winning generator being paid the price of the highest winning bid for that 30 minute block - almost always a gas generator. If the amount of gas required at peak times is reduced, the winning price in this auction will be lower, and all electricity at the peak times will be cheaper.
The amount they pay for the standing charge/network costs depends on the amount of curtailment in the system - how much the grid pays wind farm operators to not generate electricity. As curtailment goes up, so does the standing charge. This plant will reduce curtailment by providing additional demand for energy in Scotland.
The demand curve for electricity in the UK is extremely variable. The evening peak of 4-8pm can cost 5-20x the unit rate of off peak electricity. Most customers use a fixed rate tariff rather than agile ones, but the cost of providing that peak is the same for all customers - its just priced in to the fixed rate tariffs, and the customers on fixed rates can't avoid it. Reducing the height of that peak is the number one way of reducing electricity costs.