There are three types of collectors are used to collect the sun’s radiation: 1) flat-plate collectors, 2) focusing collectors and 3) passive collectors. Any thing from water to batteries and even stones can be used to store the potential energy.

http://www.pier55.com/technology/energy/how-to-store-solar-energy/

I think the best way for sub-sahara region is not to store but to convey the energy via superconductive wires

I would imagine storing energy always as ice cube kept inside a box at room temperature. It is quite impossible to store solar energy without losses with current technology. However, there can be solar panels or solar cells, solar arrays, Solar hot water system to collect solar energy. I do not think storing would be mandatory for sub shara region. But exporting would be beneficiary (not sure economically sustainable with current technology). Again it requires research in developing a regenerating technology in terms of economical trade offs.

Solar energy in principle is low intensity...and thus concentration the for export will not be economical easily. Having said that, it will be interesting if electricity produced using photovoltaics is converted to hydrogen...to be exported.

While storing generally makes sense for compensating fluctuations in energy demand and supply, it does not make sense to store large amounts of energy. Using technology that already is available, HVDC would likely the most economic way to export energy. In a second step, HVDC could be combined with high temperature supra conductors. Cabling and cooling pipes for liquid Hydrogen could be used for transporting both, electricity and Hydrogen.

You can store energy from sun in solar pond which provide hot water, although there are also losses but u dont need separate storage