My neighbour installed a solar array recently. It's about 30X50 feet. It's currently pumping about 8kW directly into the grid all day long, for which he gets credit from the local utility. He draws down that credit in winter when he heats his house with an electrically powered heat pump. He has effectively zero Canadian Winter heating costs for the foreseeable future. Ten year payback on his capital investment. After that, it's all gravy.
"Stagnent (sic) ? Really? All water is ancient. It doesn't rot. It just is. "Not being used" is just silly. And what's a "normal damn" (sic)
British Columbia, where I live, has lots of falling water. It rains here. The mountain reservoirs store vast amounts of energy during the spring runoff and release that energy via hydro power all summer. About 50,000 gWh annually. That is a LOT of energy. The interior of BC is effectively a colossal battery. We profitably sell this energy to Arizona where they use it to cool their shopping malls because it's 35C down there.
I pay about 10c a kWh for electricity. (converted to USD) That's the going rate here. Anybody wanna buy our "stagnent" water?
Before Alan chimes in with a few "whattabouts", yes, the reservoirs do flood some pristine valleys. Fortunately, we have lots of them. The reservoirs can also impede fish reproduction. We're working on it. We have hatcheries. In some cases, they flooded farm land, but many of them are in wilderness. Sports fishermen and boaters love 'em.
In short, solar and hydro can be very efficient and clean sources of endlessly renewable power.
Do you realize the vast amount of fresh water that would need to be stored in order to get a decent amount of eletricty for usage during the off season. It would be huge.
Given the fact that fresh water is a valuable commodity, it would be absolutely foolish to let it sit not used for a long period of time. Sure, water does not rot or go bad, but farm plants and animals do. Fresh water is needed to keep us alive, to keep farm animals alive, to irrigate crops, etc. Our whole civilization is based upon the quest to find potable water. To choose not to use it just because we need it during the off season to generate power when there are plenty of other power sources that we could use is stupid to say the least.
Plus, the idea that we could store water all over the world and not feel the negative effects of locking up a valuable resource is asinine, especially in places short of fresh water, which there are plenty of.
Even in your British Columbia, the price of water is not comparable to the actual value. Most of the developed world has set up systems that drastically undercharge for fresh water, which lead many to not even realize how limited a commodity it is.
My point, it is a much more limited commodity then people realize and if we started to locking it up to use months down the road, the consequences would quickly present themselves in the form of drought and famine. As soon as farms start dying from not having enough water, your hydro-storage idea will quickly evaporate. And before you start talking about how we have current fresh water reservoirs, these are currently used throughout the year to mitigate drier periods. What you are suggesting would not allow access to the water stored except during period of low electricity production, which would limit access in a fashion not in use with our reservoirs now.
Additionally, your example of citing where you live really serves no purpose what so ever. It rains a lot in British Columbia, good for you, that's great, but it really does not matter for the majority of the rest of world. You citing your massive amount of rain as a reason to use this type of power storage would be like Iceland telling the rest of the world to just use geothermal because it works so well for them. The only problem is that there are very limited locations in the world where this type of power is feasible.
Insofar as you selling your power to AZ, that is just a fairy tale. The fact is that you loose energy when you transport it, and transporting it from BC to AZ would really decrease the amount of energy. This is not even something worth thinking about.
Last, your statement that wind and solar are efficient sources of power is currently being completely negated by the real life fact that Germany has seen it energy prices rise 2.5 times since it started down the wind/solar rabbit whole, and I should add that their CO2 emissions have not decreased at all.
So, once again, wind and solar are nothing but fairy tales, and the sooner we start putting all our efforts into nuclear, the better!