Comment by pbmonster | Hacker News Reader

Comment by pbmonster | Hacker News Reader

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> I'd imagine ideally you would have to build a generating station and a new catch reservoir at the perfect elevation because if you are pumping a lot higher than needed the efficiency is going to drop significantly.

I don't think that's a concern. There's hydro plants with more than 6000' of head, leading to almost 3000 psi of pressure at the turbine and an exit velocity of the water jet of over 600 ft/s. From an engineering standpoint its totally manageable, and results in a highly efficient turbine.

> I think some of the challenges are that while most resorts have a fairly massive pumping system, it's usually geared towards slowly filling the reservoir, with the rest direct feeding the snow guns. Not many places have the need to fill a 20 million gallon reservoir in a couple of days.

Good news is that adding another pipe with its own pump/generator is relatively cheap. Bad news is that 20 million gallons is a relatively small reservoir for pumped hydro, and increasing that is expensive.

Still, seems like an easy and fast way to get some additional capacity online, especially in cases where a couple of megawatt of new solar get build in the vicinity of that damn...

The only problem of 3000 PSI is 99% of the snowmaking pipelines out there would instantly blow up at that pressure :)

You would also need to have PRVs anyways, because anything above about 700psi (900 if you are pushing it) is unusable/unsafe to use by the actual snowmakers and equipment. You also run soft 2" "fire" hose from a hydrant to a gun, and those are not rated for those pressures and the nozzles of the snow guns would wear out super quick as well (and the internal plumbing of the gun would probably blow up too).

You'd generally have a max of about 900 PSI and ideally much lower as most of these pipes are relatively old, have no maintenance (until they blow up and a quick patch is made) and were welded up by "Bob the maintenance guy"!

I suppose you could design a brand new system to be capable of such pressures when run in "generation" mode and still have some PRVs to keep it at a usable pressure during snowmaking operations.

If you pump up the hill, say to 3000PSI, then waste pressure on the way down: you lose said wasted energy.

Pumped Hydrogen Storage requires maintaining full pressure across the entire pipe. Which should be reasonable: the "fill up" pipe already needs to go from the bottom to top at full pressure. Reversing the flow should be enough.

The issue would be if the fill method was staged pumps.

> an exit velocity of the water jet of over 600 ft/s.

I’m completely unfamiliar with any of this stuff so please keep this in mind…

If that’s the exit velocity, shouldn’t the turbine it’s spinning be geared to give a bit more resistance?

Or is that the velocity of the water if its path is unimpeded?

Exit velocity is the nozzle exit speed. The water exists the nozzle and hits the turbine.

With that said, turbine efficiency is not strictly based on resistance. Rather it is about extraction of energy. In a few designs it looks like resistance, others it is about redirection: https://www.energy.gov/eere/water/types-hydropower-turbines

> exit velocity of the water jet of over 600 ft/s

What are the reasons not to set up secondary turbines / other mechanisms to capture that energy in turn?

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