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
The excess energy is accelerating the turbines in the power plants, so the energy is stored in the inertia of the generators. The same happens when there is not enough production for the current demand, the energy comes from the inertia of the generators which causes them to speed down.
This acceleration can be measured in the grid frequency. If the frequency goes up, the operators know that they have to reduce power of power plants, and vice versa if the frequency down. Even huge demand spikes can be balanced within seconds, so the frequency doesn’t even change that much (normally less than 0.1 Hz). For this purpose, plants with very fast reaction speed (like hydropower) are used, also battery storage is a very good solution, because they could react within less than a millisecond (that’s not really necessary though).
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