Solar energy storage is an important issue because solar is available only during day time. In order to provide the continuous availability of energy throughout the year, you must store the energy. Solar energy is a periodical energy source which means that the output must be taken when it is available. The stored energy is either used when it is needed or even transported to the places where it is required. Solar energy is more in summer than in winter. Solar power is seasonal, particularly in northern/southern climates, away from the equator, suggesting a need for long term solar energy storage method.
Energy storage method using salts
Molten salts are used to store the solar energy at high temperature.
Since salts are low-cost, have a high specific heat capacity and can deliver heat at temperatures compatible with conventional power systems they are used
as an effective storage medium. This method of energy storage is allowing to store 1.44TJ in its 68m3 storage tank, enough to provide full output for close to 39 hours with an annual storage efficiency of about 99%.
Using pumped-storage hydroelectricity
Pumped-storage hydroelectricity is a type of solar energy storage. In this method, the energy is stored in the form of water, it is pumped when excess electricity is available, from a lower elevation reservoir to a higher elevation one. The energy is recovered when demand is high by releasing the water: the pump becomes a turbine, and hydroelectric power is generated by the motor.
Artificial photosynthesis refers to the use of nanotechnology to store the solar energy in chemical bonds, by splitting water to produce hydrogen fuel or combining with carbon dioxide to make bio polymers such as methanol. Many research projects on artificial photosynthesis are trying to operate under a variety of atmospheric conditions.