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
A lot of great responses here about how power demands increase or reduce the speed of the turbine generators. I work in nuclear power and I thought I’d offer some facts about how nuclear works that I find interesting.
There is a saying in nuclear that “reactor power follows load”. What this means is that if you have a reactor system operating at steady state, an increase or decrease in load demand will have an automatic increase or decrease in reactor power (within limits, or course).
I’m simplifying here, but the way it works is say you have a spike in demand. The increased load from the generator will translate to more energy being extracted from the steam moving through the turbines. This means that the water on the low pressure side of the turbine will be cooler. In PWR nuclear plants, this cooler water moves back into the steam generator. Since it’s cooler, it extracts more heat energy from the water loop that runs through the reactor (the reactor loop and turbine loop are separate in a PWR, with heat transfer happening at the steam generator). More energy being extracted from the reactor at the steam generator means that the water returning from the steam generator is cooler, where it heads back into the reactor to be heated by the fuel. PWRs are designed with a negative “moderator temperature coefficient”, which means that lower temperature moderator (water in this case) does a better job of moderating the neutrons, which is better for the chain reaction. So the cooler water returning to the reactor naturally adds reactivity to the core, increasing the power output.
All of the systems that are operating to deliver electricity are balanced, and if you tip one of the systems off balance a bit by changing the load demand, the systems are engineered to rebalance themselves by feedback mechanisms.
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