Amos,

In general I agree with you ( on this) It is always possible to store energy by using excess to pump water to an elevated location ( water towr or resevoir in the mountains) and use turbines to recover ( most ) of the energy when it is needed.

HOWEVER, you state "Once the capital investment is made the cost of production is maintenance only."

You ALSO have to factor in

1. the environmental impact of the manufacturing process ( very high for solar power)
2. The environmental impact of operations (CO2, acid rain, hazards to birds, etc)
3. The cost and environmental impact of disposal at end of life.

ALL of these add to the true cost- and should be considered for any energy source ( INCLUDING oil, gas, coal, nuclear, hydroelectric, geothermal, tidal, solar, and wind.)