You don't need battery storage if you've got hydro.

You need solar. Make hydro the backup, fill reservoirs as your reserve and sell extra energy when they're nearly full.

tialaramex 2 days ago | parent | next [-]

I can see this makes sense especially for medium term storage. A lot full of batteries is great for the next ten seconds, next ten minutes, even to some extent the next ten hours, but it surely doesn't make much sense to store ten days of electricity that way compared to just keeping the water behind a dam. We know that many of the world's large dams are capturing snow melt or other seasonal flows, running them only when solar or wind can't provide the power you need lets you make more effective use of the same resource.

	▲	hvb2 2 days ago \| parent \| next [-]
		Except that in many cases there's people living downstream doing agriculture using that water for irrigation. There's just this tiny dispute about that in the nile delta between Egypt and Ethiopia https://en.wikipedia.org/wiki/Grand_Ethiopian_Renaissance_Da...
	▲	colechristensen 2 days ago \| parent \| prev [-]
		Except for very short term peaks (less than 15 minutes-ish) it doesn't make any sense at all to use hydro to charge batteries. You've got a dam, you might as well let water through later than incur the losses of a round trip to batteries and back to the grid.

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znkynz 2 days ago | parent | prev | next [-]

There are two types of hydro - run of river, and ones with large lake storage. You need the ones with large lake storage, rather that the ones with a lake to build a head.

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XorNot 2 days ago | parent | prev [-]

Pumped hydro storage only holds about 8-12 hours of power. To be economically viable to build you need to cycle it daily.

It uses enormous amounts of land and capital to build, and is ongoingly dangerous in a unique way. If LiFePO4 can do 4 hours at full output already, and be placed anywhere using volume manufacturing to expand, then batteries are straight up better.

Pumped hydro is an expensive dead end.

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peterashford 2 days ago | parent | next [-]

In NZ we're discussing pumped hydro in Lake Onslow which will provides months of backup for the country

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hunterpayne a day ago | parent [-]

Each way you move the energy costs you 50% in efficiency. Which is why pumped hydro has to have a 4x different in the price of energy in vs energy out to make it economically viable. That's why PG&E almost never uses their pumped storage. Only on days where the mid day price of power is very low does it make sense. And keep in mind that California is the ideal place for pumped storage. I seriously doubt that NZ has a 3x duck curve in its energy demand.

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tialaramex a day ago | parent [-]

It's nowhere close to 50%. Round-trip (so that's after both ways) efficiency is about 70-80% for a pumped storage scheme. Buy 10MW to pump the water, and get back 7-8MW when you release it. Contrast that with a reality here in the UK where the gas dominated spot price this morning when I woke up was about £180 per MWh, yet yesterday afternoon solar and wind had it down to £25 per MWh, so you could buy 100MWh of energy for £2500 but sell it less than a day later and make 400% on your investment in under 24 hours despite the efficiency loss. Very silly to insist this can't be profitable.

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XorNot a day ago | parent [-]

For the cost and expense of building a pumped hydro plant though, you could just deploy batteries which will do the same thing for a much lower capital and management investment and vastly simplified engineering. And a higher round-trip efficiency.

LiFePO4 works to demand shift on a daily cycle just fine and scales better to solar input (where you need much higher power handling so you can charge it on limited sunlight - a pumped hydro system is limited to charging at about half its discharge rate).

	▲	peterashford 4 hours ago \| parent [-]
		I think that's the point about the lake Onslow project - its MASSIVE. So yes, expensive, but months of backup for the whole country would not be cheap even with batteries

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colechristensen 2 days ago | parent | prev [-]

I'm not talking about pumped hydro.

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XorNot a day ago | parent [-]

The you're talking about a geographical limited, extremely finite resource with a substantial ecological footprint.

	▲	colechristensen 21 hours ago \| parent [-]
		Yes... countries with extensive existing hydro using less of it by displacing it with solar, ultimately enabling the dismantling of some of the dams.