The more the generation of electrical energy by sustainable means (solar and wind) spreads, the more it is seen the need to find ways to obtain electrical energy at times when there is no sun or wind blowing.
There are different ways to get that energy, and one of them known for more than 100 years is the hydroelectric system, which is usually called pumped hydroelectric energy storage.
In these cases, it is very interesting and necessary to know the locations where this type of installation could be carried out. They have to be places where two lakes can be placed (both natural or artificial), from which water can be transferred from one to the other.
In the upper part, turbines are placed that produce electricity when the water circulates through them, and in the lower part, pumps are placed to send the water back to the lake at the top.
The water is stored in the upper lake, and when it is needed to produce electrical energy, the water goes through the turbines, produces energy, and said water is stored in the lower lake.
And when there is surplus energy, by means of pumps the water from the lower lake is sent to the upper one, so that it can be used when electricity is needed.
You can see a simple explanatory video at: https://youtu.be/ehskGrg8hEA
This is a technology that is perfectly mastered and that can be applied beginning now. The drawback is that building these infrastructures takes a long time, with the subsequent advantage that they last for many decades in operation.
And what not many people know, at least I did not know until recently, is that someone has dedicated himself to "studying" global geography to detect the possible locations of this type of facility around the world.
And that has been done by the ANU (Australian National University) that has published the photo that can be seen below.
And to our surprise (at least mine) they have shown hundreds of thousands of possible locations all over the world. And the message is: that if a small part of these possible structures were made (about 1% of them) it would be possible to have electrical networks with 100% renewable energy.
You can see the most complete information on the possible locations at the following link: http://re100.eng.anu.edu.au/global/
It is a matter to think about. And thinking, thinking, I ask myself: if this is known, why is it not done?
It may have to do with the fact that these types of works take around 10 years to complete, and politicians are only interested in short-term "things" that they can use for their political revenues and stay in power.
Or it is possible that I am getting older and I am becoming mischievous.
I do not know,
EN 
ES_ES 