Tagged: Motion (physics)

What if the world used hydraulic power?

Electricity is awesome.  It used to be, back in olden days, that if you wanted to get mechanical power, you would build a giant windmill and then use that mechanical motion to do something like mill wheat.  That’s where the “mill” part of windmill comes from. You either had to have your own windmill or share one with other farmers.  The awesome thing about electricity is that you can transfer that energy over vast distances and then use it for whatever you want. In short, electricity is universal.  What if we, as the human race, had never discovered electricity?  Would we the industrial revolution never have happened? What else could act as a universal portable source of energy? The problem boils down to this:

1. How do you convert mechanical energy in one form, like wind or water turbines, into another useful form, like plowing a field or mixing cookie dough?

2. How do you move mechanical energy over vast distances?

My first thought would be to take a rotating disk and move it from one location to another. But even the fastest rotating things I’ve seen only rotate for at most 10 minutes, which doesn’t leave much time to move it a long distance. But then the answer, an answer, hit me.


Think about it, water in pipes could have replaced electricity.  You could harness the energy in flowing water and pipe it from one location to another, satisfying both conditions above.  Yes hydraulic power is analogous to electrical power.


It would probably be best to keep the system closed so that you don’t lose any water. The whole system needs less maintenance that way.  But then you’re left with the problem of extracting energy from a closed system.  You could do the same thing that we do for electricity today, use oscillating pressure/voltage. Imagine that instead of a power outlet you had a vibrating membrane that you could connect a hose to. That hose would power your device by converting that mechanical energy to whatever mechanical motion you needed.

It’s no surprise that this hydraulic power acts synonymous to electricity. Electricity is essentially electrons flowing through pipes, i.e. wires. Electrical inductors are like coils of pipe that store a large mass of moving water, that is inertia, and capacitors are like elastic membranes placed between two sections of pipe. The equations of motion are identical.  A one way valve could act as a diode and pressure dependent valves could even act as logic gates, closing off a tube if the pressure is high, 0, and opening the tube when the pressure is low, 1.  So we could even build a computer using hydraulics! That’s pretty freakin’ amazing.

There are some draw backs. If you wanted to power your house by storing a tank of water on top of your house, say 3 meters off of the ground, you would need a pipe of a diameter of 7 or 8 cm(about 3 inches) to produce 1000 Watts.  That’s much bigger than an electrical wire but not unreasonable.

I wonder how thick the pipe would have to be to send hundreds of megawatts thousands of miles away without more than a few percent energy loss? I don’t know the answer but I have some thoughts about how to minimize energy loss. You would want to minimize motion as to reduce energy loss from friction and so you would naturally use very large pressures in transmitting energy long distances hydraulically. This is exactly what we already do with electricity. We step up the voltage to ridiculously high values, about 100,000 volts compared to the 120 volts that I use in my home power outlet (I live in the U.S.). Energy is force times distance and so if the pressure is high, the force is very high and the distance moved doesn’t have to be large to transmit a lot of power.  Frictional force times distance the water moves is the frictional energy loss and frictional force doesn’t depend on pressure. So by maximizing pressure, we minimize the percentage of energy lost due to friction.

Imagine a world powered by hydraulic power? People into steam punk would love this world! I want to experiment with this. Maybe I should experiment with hydraulic systems? What do you think? I don’t know about you, but I’m getting excited about making some stuff using hydraulics.

-Sebastian Spiegel