Hydro isn’t clean (extreme ecosystem damage, both up and down stream); and if we dammed every river it’s a drop in the bucket of what we need.

I don’t know how far solar/wind can get us. But hydro sucks more than most people realize.

My assumption is that rising CO2 levels in the atmosphere pose a much greater existential threat to humanity than localized ecosystem damage resulting from river blockages. But maybe I'm wrong.

Speaking of hydro, I do think pumped hydro-storage ought to be looked at a lot more for energy storage (esp. versus giant lithium-ion battery banks), especially as we transition to inconsistent renewable sources like solar and wind. I'd assume that creating new, isolated bodies of water wouldn't incur as much ecological damage as blocking off existing rivers or greatly increasing our mining of rare earth minerals)

But it isn't "localized ecosystem damage". Building dams absolutely fucking destroys the ecosystems upstream and downstream. It's the civil engineering of burning the crops when you retreat. The "new" ecosystem has nothing in common with the prior ecosystems.

I'd rather some species of fish die out than the ocean boils, personally

Yeah. And dams can be removed (and as far as I can tell, nature is relatively adaptable and can recover).

True but PV+wind make our existing dams go much further - recall most of them operate as giant annual batteries, they refill in the rainy season once per year, then dispense that energy over the dry season.

Adding PV means hydro can save much more of its water, just dispensing to “fill in the gaps”. This is already how the hydro in Norway and Sweden operates, you can see it daily if you look at the hourly power breakdowns by generation type.

But I agree, I hope we will get to a point where we can decommission the big dams..

> recall most of them operate as giant annual batteries, they refill in the rainy season once per year, then dispense that energy over the dry season

That’s not quite how it works.

Consider the biggest hydro project in US, the Columbia river, with its 14 dams.

The system does fill up in the rainy season, but the crucial thing is that it’s not the dams that do fill up, but rather the whole watershed, meaning things like snowfall and ground water. This means that we have very limited amount of control over when we let the water through. We can’t just dam the river for an extended period: if we don’t use it for generating power, we must spill (waste) it. This means in practice that the dams are not batteries: to a large degree, it‘s use-it-or-lose-it.

To make these into batteries, we’d need to somehow refurbish the dams to tremendously increase the power generating capacity on each dam, so that instead of assumption of continuous flow (either through turbines or spillways), we make the flow more intermittent, so that we can make up for closed times by pushing more water through during open times.

This is tremendously difficult in practice: dams are simply not designed to allow for refurbishing with many more turbines or much more flow through them than they were originally designed for, the upstream reservoirs are not designed for quickly varying water levels, etc.

Point is, we can’t just “save the water”.

> That’s not quite how it works.

Yeah in reality there are two forms of hydropower: the classic reservoir dam, and 'run of the river' powerplants. You're absolutely right, even reservoir dams don't really fulfill the 'annual battery' idea, since they must maintain some minimum outflow for downstream consumers and can't shut it off entirely if it better suits the power generation goal.

> Point is, we can’t just “save the water”.

The storage level at Lake Mead has an annual spread of ~100ft; the dam is currently at historic low capacity and could hold about twice its current level: https://www.usbr.gov/lc/region/g4000/lakemead_line.pdf

Reservervoir dams certainly can store water and dispense it when appropriate.

Like I said, this is happening every day already, you can see it in the hourly data on wind/hydro generation share, and you can see it in the annual storage capacity data for Norwegian hydro.

Yes, we can do this for some dams, but not enough to move the needle. Hoover Dam’s generating power is quite tiny relative to the total storage needs, and if you add up all the other viable dams, you’ll find that it doesn’t add up to a lot.

To put it in context: Columbia River basin produces 40% of US hydroelectricity. Out of 14 dams on Columbia River, 12 of them produce (each individually) more electricity than Hoover Dam, most by a factor of 3x or more. Very little of it can be turned into storage as of today, what does not get used must be spilled.

This is not to say that using dams for energy storage is a bad idea, it’s not. It just will not work well in practice with most of currently existing dams, at least without huge retrofits and/or screwing over downstream water consumers and upstream reservoir users.

Canada's energy mix is roughly 60% hydro, and some provinces are well past 90%. You ought to check your numbers.

No offense, but Canada isn’t relevant on the global scale.

Hydro use is growing, especially in developing countries. However it’s a shrinking percentage of total energy generation. There is an absolute cap on theoretical hydro energy production, and it isn’t enough.

Hydro is low carbon and renewable. But it isn’t green, and it’s not enough.

Canada is second-largest country by area, occupying around 6.5% of Earth's land surface. It's only 37th by population, with 0.5% of world's population. It's very non-representative example.

Looking this up.

https://www.usbr.gov/lc/hooverdam/faqs/powerfaq.html

> Hoover Dam generates, on average, about 4 billion kilowatt-hours. And the lake covers an area of 1,495,806 acres

Rough estimate, 2GW worth of solar produces that much in a year. And requires I think 12000 acres of land. (Open to have phat fingered the calcs)

My take away is it's not even economic anymore and requires flooding 100 times more land then a solar plant.

Dams still get built for non-power reasons, to manage water supplies, so adding turbines (and floating solar PV) to them might make sense, but yes I think we're now at the point where new hydro purely for energy production is going to struggle to make a case for itself against just deploying renewables and batteries and interconnects.

edit: to add some context re the Hoover dam:

> Upon becoming Secretary of Commerce in 1921, Hoover proposed the construction of a dam on the Colorado River. In addition to flood control and irrigation, it would provide a dependable supply of water for Los Angeles and Southern California.

It's not exactly relevant how much solar produces per year - it's very important _when_ the energy can be produced and how much you can control that.

Absolute nonsense. Your attitude is actively harmful to decarbonization.

Ecosystem change =/= ecosystem destruction. The lake produced by a dam is a far more beneficial ecosystem to a much broader range of life than the river that preceded it

Source?

I like hydro but this is not at all what people I know working in this field believe to be true.

> But hydro sucks more than most people realize.

There's a reason Russia blew up the Kakhovka hydro dam. The down-stream impacts of the flooding were more devastating than what they could reasonably accomplish with conventional weapons.

No.

It killed <75 people.

They blew up the dam because it was also a bridge and removing it allowed them to redeploy troops to the east.

I'm as far from russia apologist as can be - but they blew the bridge part few months earlier, in November. https://www.youtube.com/watch?v=xxHLImMbnAw

They dented and rendered the road inoperable months earlier.

But the thing about dams is that they're over-engineered and massive. Even with high explosives it's difficult to demolish one. Hence why dam busting bombs were large (>4000 kg) and still required underwater detonation to boost their power [0].

It wasn't unreasonable for the Russians to expect Ukraine might be able to seize a bridgehead on the far side, rebuild an operable road over the dam, and then rush armor (and logistics) across it.

Much harder and more time consuming when there are no longer any load bearing remnants available.

[0] https://en.m.wikipedia.org/wiki/Operation_Chastise#The_attac...

>It wasn't unreasonable for the Russians to expect Ukraine might be able to seize a bridgehead on the far side, rebuild an operable road over the dam, and then rush armor (and logistics) across it.

It was, as much as it was unreasonable for russians - that's why they ran over to that side of river.

Hydro is only source of renewable power that generates >50% of any country's electricity grid: https://en.wikipedia.org/wiki/List_of_countries_by_renewable...

Wind caps out at 42% with Denmark, solar at 15% in Australia. Many countries have nearly 100% of their electricity coming from hydroelectricity. Besides nuclear power, hydroelectricity is one of the few non-intermittent sources of renewable energy - sure, rainfall does technically make hydro intermittent in a sense, but it's not going to change output on a dime when the sun goes down or the wind stops blowing.

Well, you also have geothermal power, but that's even more geographically constrained than hydro.

That’s a non sequitur.

I never said hydro wasn’t renewable. I said it wasn’t clean. Most people think of hydro as renewable and low carbon and clean. Two are true, one is false. Hydro is dirty and, imho, we should phase it out the same way we should phase coal out.

Nuclear isn’t renewable by most definitions. But it is low carbon and clean.

Nuclear was good 40 years ago. Solar is getting good. Wind I don’t know much about. Hydro is an ok bootstrap but is much dirtier and more problematic than most people realize.

Hydro is indeed clean in that it does not emit greenhouse gases. Sure, it disrupts life around the dammed waterway. But that's way less of an impact than climate change.

Hydro emits huge amounts of GHG when flooded organic matter decomposes btw.

This is a one-time overhead emission, and I doubt it's "huge" compared to even a small amount of fossil fuel use.

In comparison to FF it’s small of course. But it’s billions of tons, globally more than Germany’s footprint. Which is larger than most peoples assumptions, hence the “huge”.

Nuclear is renewable and generates more than 50% of many countries electricity.

Every serious analysis in green energy has never been able to make it work without nuclear.

This is a baldfaced lie (unless you are engaging a No True Scotsman dismissal of the large number of studies that say otherwise.)

Not wasting 100 minutes of my life on that. I'd read a paper defending such a claim. In the meantime, here are a large number of abstracts of peer reviewed papers showing 100% RE is feasible:

https://web.stanford.edu/group/efmh/jacobson/Articles/I/Comb...

Here's a review article on 100% RE studies:

https://ieeexplore.ieee.org/document/9837910

"The main conclusion of most of these studies is that 100% renewables is feasible worldwide at low cost."