[nicodds]

That is not completely true. Thermodynamics tells that, overall, to produce energy, you must spend a lot more energy. You may think to the nuclear plant: it doesn't build by itself, you produce lots of environmental pollution to get it

[tsimionescu]

Unfortunately the same is true of the dams required for hydro - after all, concrete is a major green house polluter itself. Not sure which requires more concrete though, per MW.

Still, nuclear requires fuel, and mining is an extraordinarily dirty industry, so I would guess hydro generally wins out overall.

However, if we are to avoid global climate catastrophe, we need to consume less energy, there is no future in consuming ever more but slightly cleaner. Especially given that in Europe and the US and so on we already have enough energy for all basic human needs, while the developing world still needs far more energy to achieve this. So to make room for them in the planet's remaining budget, we would have to not just stop building more, but actually reduce some of our power most likely.

The chances of this happening are... Slim.

[jhgb]

Concrete is not really the issue for hydro, it's the decomposing plant matter.

[nicodds]

You're right, that is big issue. Anyway, it's a matter of a lot of things that adds up together.

[nicodds]

An Hydro plant doesn't have the same security requirements as a nuclear one. You may think for example to shielding for ionizing radiation. It all adds up to the count.