Future of Solar Energy

Steckborn, Switzerland. A tower clock using solar cells

The success of solar power will depend on the answer to the following question: 'What do you do when the sun goes down?'
The simple answer is to build an auxiliary system that will store energy when the sun is out.. However, the problem is that such storage systems are unavailable today. Simple systems, like water pipes surrounded by vacuum, do exist. It is based on the concept that provided the pipes are insulated, the water will store thermal energy.
The ocean is a natural reservoir of solar power and could be used as a source for thermal energy. If we can draw warm water from the surface and cold water from the depths, an ocean thermal plant could operate 24 hours a day. George Claude tested this hypothesis as early as 1930 in Cuba. Cold water from the pipe and warm water from the surface were pumped into a plant on shore. It produced 22KW when the water temperatures were optimum and 12KW when seasonal current fluctuation reduced the efficiency.
There are also the hybrid systems. Wyoming has a system that holds back water on a neighboring hydroelectric plant when the wind is blowing, which for the time being, runs the turbines. As discussed earlier, wind is an indirect form of solar energy. Thus the hybrid system is used in the fuel saver mode.
Research on photovoltaic cells will continue. Compared to the other options, majority of the resources will probably flow into research for developing better and more efficient solar cells. Parallel to that, more research will be undertaken to develop rechargeable batteries that will last longer hours.

Source: http://www.history.rochester.edu/class/solar/future.htm