[This article](https://www.theguardian.com/business/2020/jul/06/giant-flywheel-project-in-scotland-could-prevent-uk-blackouts-energy) describes a “world’s first” flywheel being built in Scotland to “mimic the spinning turbines of a traditional power station” to maintain grid stability. So how do traditional turbines (hydro and steam, I presume) maintain stability that a flywheel is useful to mimic them, and why are renewable turbines (wind) not useful. Is this the same problem that Tesla’s Australian battery is tasked to solve?
In: Engineering
Here’s an important line from the article you linked:
> The task of keeping the electrical frequency of the grid steady is becoming more challenging because Britain’s growing stable of renewable energy projects do not use the same giant spinning turbines that typically help to keep frequency stable.
The spinning turbines in fossil fuel plants usually rotate at 50 Hz in the UK (60 in the US). Because generators produce one full cycle of AC in a single rotation (the voltage goes up to +320V, then down to -320V, then back to zero), this 50 Hz rotation was responsible for making sure that the AC in the entire electrical grid was at 50 Hz. A lot of equipment relies on this frequency being fairly precise, or else it can’t function correctly.
When power is drawn from a turbine (for a small scale example, imagine turning on the lights), the coils of wire inside it will actually generate a magnetic field opposing its movement. Which means that when a whole lot of power is drawn all of a sudden, or if some turbines go offline (which is what happened during the blackout), the turbines can actually slow down because they have to push against this magnetic field. When the turbines slow down, the AC frequency drops, and if it drops enough then they have to disconnect people’s power to reduce the load, which is the cause of the blackout.
The UK has been switching over to wind energy more and more lately. The turbines in a windmill do not oscillate at a steady 50 Hz, which makes it harder to keep the grid at a constant frequency.
Basically, the flywheel is connected to a generator, and they will use a motor (powered by the grid) to spin the flywheel at 50 Hz. It won’t actually generate any new electricity (since it’s powered off the grid), but it will help to keep the grid frequency at 50 Hz by acting like a generator turbine.
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