Since, and unless electricity has properties I’m not aware of, it’s not possible for electric power plants to produce only and EXACTLY the amount of electricity being drawn at an given time, and not having enough electricity for everyone is a VERY bad thing, I’m assuming the power plants produce enough electricity to meet a predicted average need plus a little extra margin. So, if this understanding is correct, where does that little extra margin go? And what kind of margin are we talking about?
In: Engineering
In some cases, the electricity is stored for later use. While large-scale betteries are talked about as a new thing, there are older methods that work by changing the spare electricity into other forms of energy.
Here in Michigan, our two biggest power companies share ownership of the [Ludington Pumped Storage Facility](https://en.m.wikipedia.org/wiki/Ludington_Pumped_Storage_Power_Plant), which is a big reservoir uphill from Lake Michigan. It has been in use for 50 years to store energy from when the utilities’ nuclear plants are making “too much”, and then put that energy back onto the grid when it’s needed. Now that Michigan is investing heavily in wind and solar, it works well for those too.
When there’s “extra” electricity, the pumped storage facility uses that extra to pump water uphill, from the lake to the reservoir, converting electrical energy into potential energy. When the power is needed back on the grid, the storage facility lets the water run back downhill from the reservoir to the lake – spinning turbines on the way to make electricity just like a regular hydropower dam.
In Michigan’s Upper Peninsula, there’s also work being done on gravity storage using the old copper mines: using a winch to pull a heavy load up to the top of the mine shaft when there’s too much electricity on the grid, then letting the load lower back down to spin a turbine when the energy is needed again. (I understand there are places in Europe that do something similar with heavy trains on mountain slopes?)
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