I think that the energy produced via hydroelectric plants is more and more clean and sustainable and is like the solar energy, but in the case oh hydroelectric energy, it is produced even at night when the sun is go down.... unlike for the solar.
So mining coin will be more green and sustainable.... now bitcoin and other POW crytocoin mining is very intensive and require more pollution... so! think about it
I'm agree with you... hydro-mining is a very good and innovative idea.
But also the solar mining can be doable, for example by complementing solar power with another clean energy source, or maybe utilizing a lithium battery that accumulate energy for the night.
All the other clean energy sources, like wind or solar energy, are discontinuous sources and the only way to utilize these sources are by accumulate the produced energy into large batteries pack.... with more and much expense of money.
You so must buy the equipment to mine the coin, the solar panels or the wind rotors and the battery packs.
With hydromining you will only buy the mine equipment... and you can go to mine clean and green!!!