Can you use hydraulics in energy generation?

[TheManicMonocle]

So I was wondering, it seems to me that using hydraulics, you can get more force for less, like how it lets you use your arm strength to lift a car. So why can't we use that on something like a windmill?

[NichG]

Gears give you the equivalent kind of thing for rotational motion, and we do use them. The basic principle behind both gears and hydraulics is that the work done (F*dx) is the conserved thing (e.g. the energy transferred from the input to the system), so if you change dx (applying the force over a greater distance) you can change F (requiring a smaller magnitude of force on the worker side). This is also, very roughly speaking, why we can build voltage converters as well - keep the energy the same, but either have a high voltage/low current or high current/low voltage.

The input still uses the same amount of energy in either case, of course.

[Fri]

Basically my understanding is, to use gear equivalent, think of it as making you work longer for same amount of energy to lift heavier thing.

You spin the smaller gear once, the bigger gear move a quarter turn. So you spin the small gear four time, the bigger gear move a full turn. You exchange the amount of time you spin the smaller gear with bigger gear distance turn.

[factotum]

Yeah, I agree with Fri. Hydraulics don't give you something for nothing--the additional power of the hydraulic ram comes from sacrificing the amount of movement you have (compare it to an old-fashioned block and tackle, which works the same way). So, there's nothing stopping you attaching a hydraulic pump to your windmill and using the generated fluid pressure to do work somewhere else, but it's not going to produce any more power than just attaching the windmill directly to the thing you want to turn does.

[ace rooster]

We can, and in fact we do (http://www.windpowerengineering.com/design/goodbye-gearbox-hello-hydraulics/).

It doesn't do anything not already done by gears though, so not a game changer.

[Rockphed]

And gears that get a little out of alignment don't turn into deadly mist showers.

[dehro]

Yes.. If you put Mario bros on a treadmill.

This is more fun if you realise that in Italian we us the same word for hydraulic and plumber