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Comment by ciconia | Hacker News Reader

Strictly speaking there's never been an energy transition in the sense of replacing one source of energy with another. Instead, the different sources of energy have been piling on top of each other. [1]

So while PV is growing at an unprecedented pace, it still represents only 2-3% of total energy production. About 75% still comes from fossil fuel. Today we burn more fossil fuels (and incidentally more wood) than ever before in human history. So the term "energy transition" is inaccurate at best.

[1] https://ourworldindata.org/grapher/global-energy-substitutio...

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> there's never been an energy transition in the sense of replacing one source of energy with another

We have. This is thinking too narrowly about energy as "driving a turbine" rather than doing work in general. Horses, oxen, and other beasts of burden have been almost completely marginalized in our modern economy. The same could certainly happen to steam-powered turbines (coal, gas, nuclear, etc) if the economics end up working out that way.

Also, human slaves have been almost completely marginalized even thought they were the main source of mechanical energy in ancient Rome.

Yeah, even old water mills - while the weirs and water supply channels might still stand, the water wheels are long gone, with a few exception not worth replacing by a modern small water turbine generating electricity.

It is simply not economical to exploit this (originally critical) source of power as its is so small in absolute numbers compared to all the necessary maintenance.

A few years back I visited an old water mill called Itaipú. It has forty water wheels still in operation, providing a total of 14 gigawatts peak. At the time I visited, one of the water wheels was providing 95% of Paraguay's electricity, and the other 39 were providing 25% of Brazil's electricity. It turns 50 years old next year. In 02020 its average production was 8.7 gigawatts. They did have to replace one of the water wheels a few years after I visited: https://www.youtube.com/watch?v=thcIrM31tZ4

Brazil uses more electricity now, some 80 gigawatts, so this one water mill only produces about 10% of it now.

It is true that many older water mills are no longer in use, though. Maybe 50 years to you is not old!

That's a hydroelectric dam, not a water wheel. A water wheel captures mechanical energy directly for eg grain milling, not conversion to electricity via turbine.

Yeah, I'm talking of mediaval or early modern water wheel powered mills for milling flour, not hydropower dams. :)

https://en.wikipedia.org/wiki/Watermill

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