Eli5: What happens to the source if we don’t consume the generated electricity from the source?



I came across several discussions that made in past but I didn’t get the real question in my mind. When we run a voltage generator (dynamo, fuel generator, etc.) it produces voltages. If there is a load connected to the generator’s output, it will start to pull currents. If there is no load connected to the output, it will still produce voltage but there is no current that will flow through the output … So; zero times current and 220 times volt is equal to zero power… I am okay with that until here…

Here is my question is:

Is this situation harmful to the generator? what happens if we continue to run the generator with no load? Does it burn himself due to increasing inside temperature due to inside consumption such as friction, ventilation, etc. ? Is it dangerous to run a generator with no load? I also wondering this question with other generators such as solar cells…

So my point of the question is: what happens to the source if we don’t consume the generated electricity from the source?

In: Physics

Voltage is potential. It’s like lifting a bucket of water. Nothing needs to flow or transfer to have that potential increase, but if that raised potential is connected to a lower potential (an empty bucket lower down) then stuff will flow.

As far as damage to the dynamo, it depends. Super high voltages can cause electrical bleeding (basically making its own path) and material damage over time. I wouldn’t think you have to worry about that much, though.

Basically, nothing. It is under very low load and just happily spins until someone wants load again.

For generators that can’t control their power source (wind turbines, etc.) you need a way to close off their energy input so they don’t overspend under no load. Wind turbines feather (tilt) their blades.

Generators with a controllable power source, like a hydro dam or a gas plant, will reduce input (close a valve) to prevent the generator from overspending under low load.

A generator produces electrical currents from a rotating source. When you use the electricity it will slow down the input and if you do not use the electricity it will not do anything. There is usually a flywheel attached to the input in some way and if for example an engine is used to power a generator and you suddenly shut off the electricity the engine will spin faster and faster until it will turn down the throttle.

A big part of the issues with wind turbines and solar power is that these do not have a flywheel attached to the electricity grid like traditional power plants. So they are not able to easily store energy which is produced but not consumed in the same way.

For conventional thermal plants that burn something and then use that heat to run a generator, the imbalances between demand and supply are taken up by the mechanical inertia of the generator first, and then by slower mechanisms if the imbalance persists.

How is it that a steam turbine generates electrical energy? Well, as you know, steam is produced by heating water, the steam is allowed to expand while passing through a turbine which extracts the heat energy from the steam and turns it into rotational energy of the turbine components (really, torque on the turbine components because in normal operating conditions the energy of the turbine components doesn’t change much). The turbine blades are mounted to a shaft, and the shaft is used to turn magnets near other magnets which generates an electrical current through coils of wire that are ultimately attached to the electrical grid. So what happens when your electric tea kettle shuts off? Well, there is suddenly slightly more power, a few kilowatts at most, being produced than consumed. As you point out, that energy has to go somewhere. The place it goes is that the torque opposing the rotation of the turbine is slightly reduced, so instead of being at steady state, the turbine starts spinning slightly more rapidly. That’s what happens for transient loads. If more power is demanded then the generators are supplying, the turbines slow down slightly, and if less power is demanded, they speed up slightly. The same thing happens to a bunch of electrical loads linked to the grid that have inertia. For example, anyone running an electrical motor plugged into the wall.

Over a period of a few seconds, changes in demand versus supply are dealt with by changing the fuel supply to the generators first, to either reduce or increase the amount of power they are supplying. If that’s not enough, and still more power is demanded, what are called peaking plants will turn on. These are generators connected to big diesel engines or gas turbines that can start up and begin producing power in only a few seconds. If even more power is demanded, and all the peaking plants and all the main plants are running, that’s when you start getting into things like brownouts and blackouts. On the other hand, if more power is being produced then demanded, and they can’t turn anything else off, they will start doing things like reducing the price of electricity that they charge to their large industrial customers to encourage them to turn on equipment to consume power. And of course grids are generally interconnected, so they can contact their grid interconnection partners and the partners can start addressing imbalances on their end and draw power from the oversupplied grid. Too much power actually isn’t that unusual of a problem, especially in areas where there are a lot of renewable power plants like solar and wind plants. If the wind is blowing strongly, many of your wind turbines are going to start producing a lot of energy, maybe more than you need. The same thing if your solar plants are overproducing on a very sunny day. In the absolute worst case, you can try to do things like turn on giant banks of resistance heaters to consume power. This is obviously wasteful but sometimes it’s the best option.

Any generator that involves a mechanical component will eventually be damaged if it’s producing far more power than is being extracted from it. Your turbines can’t spin infinitely fast. Sometimes this happens to wind turbines if their brakes fail, and you will see the generators catch on fire. For solar panels that generate electricity through the photoelectric effect, nothing bad happens if they’re not connected to a load. The photons hitting the solar cell produce an electric current because they have the right amount of energy to knock an electron out of its position, generating a pair of a hole and an electron. This pair provides the current. However, if there is no load connected, there are eventually enough electrons and holes floating around that they just start recombining without sending current anywhere.