If you had a billion tons [one cubic kilometer] of water at GEO and a pipe which was say 1 meter in diameter which could [somehow] go from GEO to the earth surface.
You would have a dam with a lot of head [36,000,000 meters]. If the flow rate was 30 cubic meters per second [with 31,536,000 seconds in a year] one would use up .94 of a cubic kilometer per year. If one could harness this energy it would represent a lot of energy:
POWER (kW) = 5.9 x FLOW x HEAD

5.9 x 30 x 36,000,000 meters = 6,372,000,000 kw power plant [6,372 gigawatts]. The 30,364 billion kilowatthours needed in global electrical power in year 2030 requires generation capacity of about 3.4 billion kw [3,466 gigawatt power generator]. So assuming one could capture this energy one would enough electrical power for Earth.

The volume of Earth's oceans is about 1.2 billion cubic kilometers- and there is far more water in space than in Earth's oceans. So one could have enough water to do this for a billion years- assuming one wasn't concerned about rising sea levels. If you concerned about this than one do this for a thousand to million years [a thousand years would be hardly measurable, and 10,000 years would be a few feet].

Now, perhaps this idea has little use for humans living at the moment and perhaps will never have any possibility of being done- though if we ever make a space elevator, one might use something like this on a smaller scale- say to provide the energy needed to lift the payload to GEO [using say 3" pipe with microgenerators say every 100 meters or something].

So, if this idea is impractical, why bother mentioning it?
Well, it illustrates what orbital energy is. And in terms of significance something like the above would be utterly insignificant in regard to other uses of orbital energy.
With gravity sling shot one can move any size mass anywhere in this solar system [or at a relatively slow rate beyond this solar system]. Mass sizes that make a large cargo ship on Earth's ocean seem quite tiny

Now we are familiar with using gravity sling shot to give us energy- we done it dozens times.
A space rock 1 mile in diameter flies by earth at 20 km/sec. That rock if it hit earth would wreck our day- it would release more energy than all the nuclear bombs we have ever made. Or it has about 5 times more energy than the electrical power we produce per year. There are about 700 of these rocks crossing our orbit or equal to +3000 years of energy used on Earth. But this is nothing it's utterly insignificant in comparison to other bodies- there is an asteroid belt with 1000s times more of these rocks. And the asteroid belt is nothing compared to all the other rocks beyond Jupiter [more in terms of mass and more in terms of energy and generally requiring less energy to change their vector].

Now, as far as I know no one has figured how to convert the orbital energy of rocks into a perhaps more useful electrical energy. I see no reason why it couldn't be done; though at this point in time I see little use in trying working out the details of how this could be done. It would be sort like the 36,000,000 meter head dam- strange and perhaps as useful as plans to fly using bird feather wings.

But there primitive things one could do. One use a small rock to hit a bigger rock to change it's vector. You could cause an impact [say on the Moon] and in some manner capture and use the heat- some how process the material.