Eli5: how will a power grid that is mostly powered by many non synchronous renewable generators (solar and wind etc) remain stable, when the stability of the grid is currently reliant on the collective inertia of the large scale base load generators of fossil fuel and nuclear power plants?
In: 84
In a word, batteries.
We already know how to store energy for later use. Batteries do exactly that.
This is why renewable energy is not just about the actual devices collecting energy, like solar panels or wind turbines. You need a whole set of things, including batteries.
Most part batteries and nuclear/geothermal
Secondary different pricing according tk amount of energy available on the net.
In addition to chemical and kinetic battery’s, there’s a device called a synchronous condenser.
In ELI5, it’s essentially two motors connected together, one spins up a mass to be faster or slower then the grid by a tiny ammount, depending on what’s needed. The second motor is then a pushing or pulling on the grid.
It also helps keep the electricity in the right position.
Is it allowed to ELI5 when you will need to ELI5 the title to most of us normal folk?
Look at what tesla megapacks do for the southern Australian grid as an example.
Power electronics technology available today already is sufficiently capable of running utility scale grids without any mechanical inertia. Modern inverters can produce power that is indistinguishable from synchronous generators for almost all our needs.
There’s a component called a Grid-Forming Inverter, which can be used instead of conventional inverters to connect solar and wind to the grid. A GFI allows non-rotational generating sources to form a stable grid, such as in the event of a blackout due to plant disruption.
Normal inverters are usually grid-following, which means they need a stable sine wave grid voltage to synchronize to. The use of GFI’s means we can start and maintain a stable grid without conventional rotational generators.
These kind of setups work best on small-scale grids at the moment, such as in Hawaii or in Texas, but their development is still ongoing.
How can the grid remain stable today, when demand fluctuates daily and seasonally? There’s a lot of expensive infrastructure built to support it. Renewables will also need expensive infrastructure, it’ll just look and work a bit different.
Like, Solar meshes pretty well with daily needs. More demand during the daytime when the sun is out, so you get a fairly decent supply / demand match right there. If you over build solar you can then do things like charge cars during the day vs preferring nighttime charging.
A nuclear power plant works best at a steady rate, not turning it up and down. So in New Hampshire, that provides a high level of constant power into the electrical grid. Then there is a smaller fossil fuel power plant that provides the back up, to take care of the ups and downs.
TLDR: some plants focus on the ups and downs.
https://esb.ie/media-centre-news/blog/article/esb/2021/05/11/synchronous-compensator-a-key-part-of-ireland-s-renewable-energy-future-
Things like this are part of it at least.
You can program an inverter (of a battery storage or wind turbine) so that you would not be able to distinguish it from a synchronous generator. That is probably overkill though, a much simpler control algorithm is likely sufficient.
By the way, PV inverters already reduce their output power when the frequency is going over a threshold (50.2 Hz here in Europe).
Also, inverters can react much faster than big power plants. So you don’t need as much inertia to keep the grid frequency stable. And the inertia that exist currently on the grid is already much more than really required. And there are still conventional generators like hydropower or pumped hydro storage, and in the future hydrogen gas turbines. That, together with frequency control in the inverters of battery storage, should be more than enough in most cases. And if that’s not the case, you still can keep “free running” synchronous generators on the grid to provide inertia. Those generators are already existing and are used as “phase shifters” to provide reactive current for example.
Latest Answers