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Comment by slaymaker1907 | Hacker News Reader

slaymaker1907

Yeah, let's get rid of one of the most effective sources of green energy that works around the clock! The environmental concerns around dams are legitimate, but they need to be balanced against the consequences of how those energy sources will be replaced. There are also mitigation strategies that can be done instead, like the fish ladders that were mentioned in passing, to help mitigate the environmental impact.

Edit: I see climate change isn't even mentioned which is an enormous red flag when talking about hydro power.

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According to the article, not that effective:

> Evaluations concluded that their electricity production had become unprofitable for the power plant owners – especially when the costs of maintenance and mandatory environmental protections, such as fish-ladder introductions, were taken into account, Ollikainen says. So the dams were sold and dismantled. [..] Across Europe, many dams are either approaching the end of their operational life, or the costs of their maintenance are outweighing the benefits they provide.

Aside from various other problems mentioned in the article, which really don't seem that easy to work around, and doing so would make them even less cost-efficient. Never mind all of this takes energy so would reduce the efficiency (although I don't know by what amount, but it does need to be factored in).

> So the dams were sold and dismantled.

Sold to who? Who would buy it just to dismantle it?

My guess would be "governments"

The buyers of a certain bridge in Brooklyn, clearly.

Local governments or consortiums. You usually need to own something before you can destroy it. Besides, the government has a vested interest in acting before the dams fail and kill people.

I'd guess it's often the owner of the dam's surrounding property, or the property surrounding the reservoir. That'd make it easier to make sensible use of the "new" land, after the dam is removed.

Were the dams ineffective or is the regulation ineffective?

Neither. Almost all of the dams involved were built before 1920 and before we had powergrids. They were usually originally intended for some local industrial use and put out a (now) negligible amount of power.

They're also at the end of their service life. You can't leave them, they will eventually burst and kill people. Replacing them is useless, they don't do anything useful. The best solution is to remove them, which has the huge added bonus of unclogging the rivers and restoring the ecosystem and fish habitat.

Also, the dams silt up over time anyways, so unless you dredge them they are not very good at generating power if the river generates enough silt.

Pumped hydro is more promising in this regard; they don't have to be in the river course itself, so do not run into silting issues, or block fish migration, or any of many other negatives. And because they are basically only required to be battery storage in hours, days or weeks rather than a main source of power generation, they can also be much smaller.

> Research now shows that at least 1.2 million instream obstacles block river flows in 36 European countries, with about 68% less than 2m (6.6ft) in height

I think we are talking about those dam, not the big ones.

> "Absolutely nobody is proposing to blow up or remove barriers which are in use," clarifies Garcia de Leaniz, "We are targeting barriers which are obsolete, which are no longer providing any services to society, that have silted up, and pose a flow hazard."

I don't think any dams that produce meaningful amount of energy are going to be removed any time soon. These are the ones that used to power mills and like. So we are talking about way under 1MW in power each.

They are removing all the old dams on the Klamath River. Company that ended up owning them considers them a white elephant because the revenue from power isn't enough to pay for needed refurbishment, operating costs, and insurance.

This is the real reason most of these are removed. No one wants a 100+ year old dam that need several million dollars worth of work and the ROI is negative. So they remove them and everyone is happy. Most of the ones that are removed are well past their use by sticker date.

Even according to the owners, the Klamath River dams represent less than 2% of the power generated by that electric company. https://www.opb.org/article/2022/11/18/klamath-river-dam-rem...

I've been meaning to compare the energy produced by those dams to a similar area of solar panels. Square miles of reservoir to similar square miles of solar farm.

The Three Gorges Dam covers 419 sq miles. Produces 100 X 10^12 watt hours a year.

Internet: 1,000 megawatt-hours per year requires, on average, 2.8 acres for the solar panels.

Calc: 2.3 X 10^11 watt-hours per square mile.

100 X 10^12 wh / 2.3 X 10^11 wh/mile2 => 437 square miles.

The Chinese done goofed.

Forgetting the slight thing that you might want to have electricity at night too...

Grid-level batteries and pumped hydro (which only requires a height differential, not a riverbed) have been a thing for quite a while now.

So where exactly do you find the hundreds of square miles of space to fit pumped hydro to match this scale? Or even tens square miles with thousand meter drop height? And if that was so easy and cheap, why isn't it already build?

Or grid level batteries storing 140 GWh for even intra-day storage...

Admittedly pumped hydro can't be scaled up that much. However, the few places that are suitable are very well appreciated and likely won't ever be dismantled like these dams.

For grid-level batteries, absolute space efficiency is not critical, so they allow a wider range of battery types to be used. Prices are rushing down. They are being deployed on such a massive scale that many new gas powerplant projects get cancelled.

Bedtime is 7:30 pm Comrade Ekaros.

I mean, Three Gorges opened in 2012, when solar panels were more expensive and leas efficient; and the Chinese are the primary reason why they are so cheap and efficient today.

Three Gorges comes with its own battery setup. They can basically generate electricity on demand from that battery, assuming no drought. You don’t get that with wind or solar without separate battery setup. That battery could even be the three gorges reservoir itself if you can pump water back up (not sure if they have a bottom reservoir for that).

Drought has hit China very hard recently.

The problem is that some amount of water does have to flow through the Three Gorges since it is a major transportation artery and source of drinking water.

Drinking water isn’t a major use case, but water for farming is, south China gets enough rain at least that drought isn’t so common (for now), but definitely not unheard of since it happened in 2022, see: https://www.theguardian.com/world/2022/aug/22/china-drought-...

From that article:

> The Yangtze is the world’s third largest river, providing drinking water to more than 400 million Chinese people, and is the most vital waterway to China’s economy.

Dams are terrible for the environment(generally poison everything with methyl mercury), and in many cases aren't even that green, since they produce a lot of methane (dam water goes down in summer, that area growns plants, fills up in winter, plants then decompose in an anaerobic environment, producing methane). Depending on the size of the lakes this can be a very large area, ie: big hydro dams in Quebec/BC. There's been research to show one hydro dam produces more greenhouse gases than an equivalently sized coal plant in Brazil.

>Dams are terrible for the environment(generally poison everything with methyl mercury)

What? Where does that mercury come from?

mercury in the soil ends up being converted to methyl mercury. Generally anything forested with large amounts of carbon in the soil tend to be the worse.

It sounds like you're trying to speak for everyone. Clearly there is a balance (money needs to be spent building new generation of some type). But we can work on climate -and- avoiding the extinction of vital fish species by restoring the flows of rivers. I don't think the systems at large will afford humanity a second chance or "over time" if we fail to act.

Most of these dams are explicitly uneconomical to run with modern safety standards and 50 years of being under-maintained. There's a lot of dams that were built, the original owners eventually figured out they weren't as profitable as planned, and just wanted to abandon it. An abandoned dam is a future "natural" disaster waiting to happen. And most of these dams were built with pretty mediocre standards, and we don't even build these kinds of dams anymore because they have all sorts of ways of failing unexpectedly.

They have to come down because they were privatized gains, socialized losses as usual. Private companies built them, decided they didn't want them anymore, and basically handed communities unmaintained dams and said "deal with this or drown when it fails". Communities generally don't like being saddled with the waste and consequences of a failed or finished private venture.

We in the US had a huge dam boom at one point, turns out most of them were over-optimistic.

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