green energy, how?

We need power, power is not just energy, but it is like a concentrated form of energy. We consume energy in bursts and lot of it in such a small time. That is why we live in the petroleum era and which shall eventually decay and leave space to a new era.
A study says that if 1% of the Sahara were transformed into a solar farm, then we should solve our present need for energy.
But we need to harness energy so as to consume it in bursts far away from where it is generated. Transporting energy in its electrical form proved to be efficient and so far the only method which we know. Storing energy in its electrical form may not really prove efficient or possible on a large scale. Though once, I suggested to store energy in batteries scattered in distribution points round the island. These batteries are charged when we produce extra energy and then discharge during peak energy consumption.
Now I had this idea. We have sea, lots of it an very little land. Sun farming is possible but truly limited because of space, so why not use the sea surface? So I thought... what if we have a closed eco-water cycle? Water from the sea evaporates by using the sun's energy and then it condenses at an altitude. Water is stored (accumulator) at a higher altitude in a reservoir - something similar to a dam. Water from the reservoir will then drive a turbine and transform the potential energy in kinetic and eventually electric.

here's a diagram

               /----------------------|
              /                       |
  sun >      /             vapour     |
            /    \      condenses     | 
  sun >    /      \ ==================| 
          /        \ =================|
  sun >  /          \ === reservoir ==|
        /            \ ===============|
       /   green      \ ==============|
      /    house       \---------- --/|
     /     effect                | |  |
    /    evaporation             |X|  | turbine
   /                             | |  |
  /================ water=============|
 /====================================|

The scale involved is not on the small side but works very well in nature and should be tuned to work efficiently in a closed system. The trick is how to effectively condensate the vapour. The top of the structure may be covered in PV panels while the south facing side should all be in glass and well insulated. The area below the sun exposed area must cover an area much larger than that of the reservoir.