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Dams have huge environmental impacts: flooding large areas of valuable land, blocking sediment flows and fish migrations, water losses by evaporation and possible catastrophic failure. So we are removing dams, rather than building more of them.

https://www.americanrivers.org/2023/02/dam-removals-continue-across-the-u-s-in-2022/

https://youtu.be/laTIbNVDQN8?si=fdNjasywGTmA0Ap6

https://en.wikipedia.org/wiki/1975_Banqiao_Dam_failure

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We don’t need a lot of storage if we generate electricity when and where it’s needed, rather than when and where weather and geography favor. So no big dams or ugly, lossy transmission lines and permits or batteries needed.

https://youtu.be/mbfN_aR-Gno?si=-k8fLAGxr9V363G6

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Interesting article. I like how you differentiate between duration of storage for each technology. I have not seen that before, but it makes a lot of sense.

One additional point. It is not just storing the electricity in hydro-electric dams, it also transporting the electricity to the dams and then back to the consumer at a later date. Given that the vast majority of hydro storage is in Norway and Sweden on the northwest edge of Europe, the geography and distance add another layer of complexity.

For example, can Ireland even transport its excess electricity from wind to Norway or Sweden?

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Jan 31Liked by Julien Jomaux

What level of depletion of the water reservoirs do the energy storage numbers assume? And what would be the rate of refill? Isn’t the average seasonal refill rate a more realistic measure of the true available energy storage capacity?

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For the total stored energy, I consider the lowest and the highest water level, and took the difference.

I did not consider rate of refill. I am assuming that it is very much dependant on weather conditions mostly. Check the example of Sweden, in 2023, lowest and almost highest levels were reached in the same year.

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Jan 31Liked by Julien Jomaux

Thanks for the confirmation, makes sense. Don't take me wrong, just trying to understand the usefulness of the model.

Water reservoirs are also used, often used, to provision water to cities or other populated areas, as well as irrigation. I know for a fact that in Spain, that is the case. Isn't emptying a reservoir based on energy needs with a timing which does not necessarily correspond to other critical uses' needs, a potential issue and limiting factor?

Furthermore, just to take the Spain case in point, the past and current government are blowing up dams because they impact the environment (which is true) and therefore bad (which is not necessarily true compared for instance with replacing said dam with solar panels).

What would be the minimum acceptable level and how would that affect the usable storage capacity. Luckily Norway has few people and lots of water elsewhere and comparatively little agricultural needs, but what about Spain and other populous countries?

My point here, and I do appreciate your posts, is that "back of the envelope" numbers can paint a too rosy picture of the situation.

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I agree that "back of the enveloppe" has very strong limits. Indeed, there are many limitations in how to use the water from the dams. I put a few lines on that but I could have said more I guess.

As you rightly point, hydro has also environmental impact, but there is no silver bullet, every source has its disadvantages.

Even though, my point was that hydro with large reservoirs would be increasingly more useful as we are moving away from fossil fuels. Of course, every country is specific and a large chunk if not all the potential of hydro has been used.

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