The problem with solar energy is that energy is only generated during the day. By using excess solar energy during the day to pump water to a reservoir, it is possible to release that water at night to generate energy when solar energy is not being generated. This day/night cycle can be repeated through the use of an upper and a lower reservoir. It would be interesting to see the cost/benefit ratio for such a system that would cover the needs for a community such as Pioneer Point. In fact, it would be an interesting experiment if funding were available.
When there is excess electricity, water is pumped through a pipe or tunnel, to the upper reservoir. The energy is later recovered by letting the water flow back down again, through a turbine that converts it back into electricity. Efficiencies of 90% in each direction are possible.
In an “off-river” system, the same water circulates in a closed loop between the upper and lower reservoirs, eliminating the need for the facility to be built on a river. The amount of energy stored is proportional both to the elevation difference between the upper and lower reservoirs (typically between 100 and 1000 m), and to the volume of water stored in the upper reservoir.
Of the available electricity storage options, such as batteries and flywheels, pumped hydro is by far the cheapest. It has no standby losses while the water waits in the reservoir, and can reach full power in 30 seconds.
LINK: http://theconversation.com/how-pushing-water-uphill-can-solve-our-renewable-energy-issues-28196