Is weight a better way to derive energy than flow?

[cjl]

Ah. So there’s the tie-in to momentum. So if it traveled the 30m in 1 minute then it would be 294.3 mw divided by 60?

Yep. It's worth noting that this is per bucket as well, so if you had 10 full buckets descending at once, it would be 294.3/60 per bucket * 10 buckets for a total of around 50 MW.

 

[CherryB]

As demanded by conservation of energy, yes.

Yes, mgh... but I don't see why pulley radius matters. bucket speed insofar as it tells you mass flow rate, yes.

It depends where the water level is at the bottom. If the buckets are submerged they act like paddles. If not, they drop the water and you aren't using all the available "h".

I guess I'm confusing moment with force, and translating that conflation into energy, because I can definitely hold a 10 lb barbel in my hand indefinitely if it's close to my body, but I can't do the same if my arm is outstretched. Seems to make some sense for me viscerally

 

[CherryB]

Yep. It's worth noting that this is per bucket as well, so if you had 10 full buckets descending at once, it would be 294.3/60 per bucket * 10 buckets for a total of around 50 MW.

Right. So that's quite a bit of power, but it just seems like an awfully fast rotation to keep up with mechanically. I'm guessing that I would have to utilize a gearbox like the ones they use for wind turbines. I saw something about a 600 shaft rpm turbine gearbox yielding 8mw, but I'm not sure how to calculate the shaft input power needed to turn the gearbox

 

[CherryB]

 

[cjl]

A full minute of descent time to cover 30m seems fast to you? Sure, you can gear them however you want, but if anything, I'd actually expect you'd want to gear it up, since generators are smaller, cheaper, and more efficient if spun faster.

EDIT: Also, the power you get out of a gearbox is the same as the power you put in (minus losses). If the gearbox is outputting 8MW at 600 RPM, the input will also be 8MW (at some other RPM - probably around 9RPM for a turbine that size).

 

[CherryB]

What I meant to say is that maybe a gearbox like that could be used, just to slow things down, then connect it to the near 50mw input from buckets. The speed of 30 meters per minute seems large to me, only due to the buckets having to turn around the sprocket, and how much destructive force will be acting on the chain and buckets. But I may be overly conservative about that