Science Forums 2

[engineerdude]

Hey Roadam,

I am an engineer, and my degree was in power systems design, so I have a little knowledge about this issue.

In water-turbine electrical generation, a variable pitch rotor is generally used to provide for different torques. So, when the load is very light, the turbine does not allow much water through, when the load is heavy a bunch of water is used. Electrical generators are synchronous machines, and are tied into the electrical grid, and so always have to spin at a constant speed. Once you hook your generator to the grid, the generator will always spin synchronized at exactly the same speed as every other generator that is tied to the system. If you do not apply force to spin the generator, it will turn into a motor and pull power off the grid instead of putting it in. If you are going to use this generator to power your house, and if your house is connected to the electric grid, you have to take this into consideration.

As far as capacitors go, they are not for energy storage. You cannot store any practical amount of energy in a capacitor. There have been theoretical designs to store energy in an inductive loop with superconductors, but that is still a long way off, if ever. Batteries are the only viable way directly store electrical power currently, and they can't store much.

One of the replies mentioned pumping water up hill during off hours. This is called pumped hydro storage, and is commonly used by utilities with hydroelectric plants to use up excess power in the middle of the night. Nuclear Power Plants in particular can't easily lower their power outputs, so when the power consumption on the grid is very low and there no buyers off grid for the power they have to do something. It is very inefficient to do pumped hydro storage - you end up getting maybe 10-20% of your electricity back once all the losses are figured in.