A follow up point to my post a few weeks back about Simon Michaux's reply to Just Have a Think.
Simon Michaux calculated that the human race would need to use an extra 50% of our fresh water use for 28 days of pumped hydro dams. That's 2000 cubic km of extra water - on top of the 4000 cubic km of water we use each year! That's 50% extra water in a water starved world. That's a lot. It sounds impossible to build 28 days of pumped hydro storage, right?
First, it's good that most renewables engineers plan to Overbuild renewables so that storage is reduced down to 2 days at the most - even during winter. That's 1/14th or 7.2% the water required.
Second, he's forgotten that fresh water is renewable! He behaves like that extra 50% demand is a permanent thing where once we've taken it, we can't use it for anything else. "If you're storing it in storage you can't drink it - you can't use it." Sure! That fresh water. It's a good thing that the oceans and evaporation and rain are a thing though! 
We are putting this water into a closed-loop pumped hydro cycle. It's a one-time deal. Rather than the mistaken belief that we're using an extra 50% fresh water every year, we are only doing this once. So if it takes 10 years to build all the dams, we're talking 5% extra fresh water used each year. Yet we are talking about an enormous, worldwide construction project. It's more likely to take 20-25 years so it's probably more like 2% extra water used each year during this building and filling phase. Basically, as long as an Environmental Impact Study determines how fast we can fill each dam, I'm happy. Once full, the river flows can return almost to normal.
What about evaporation? Now that's the real question. Even though they are closed loop - they'll still lose water. Slowly. The good news? We'll cover these reservoirs in solar panels and other materials that reduce evaporation. The better news? It's been measured, and the water lost lost to evaporation is only 10% of the water lost to a similar amount of energy being generated by a coal fired power plant.
That is, as we build out renewables and PHES - in the long term we'll use 90% LESS water than coal energy systems. Michaux sure is bombastic - but like most doomers - there are gaps in his arguments big enough to drive a Janus Electric Road Train through!
No comments:
Post a Comment