Solar energy, as we all know, is a great source of renewable energy. Though it has a bunch of advantages; it has some disadvantages also. One of them being how can we use this energy at night. A simple suggestion would be to use batteries to store the energy. But the problem is it is really costly.
There are two great solutions to this problem: sand batteries and water batteries. For a sand battery, we gather piles of sand at a place and cover it with a thermally isolated system (you can imagine it as a huge thermo flux). At day time, excessive solar energy is used to heat the sand. Sand is cheap, easily available, and stores heat very efficiently. This stored thermal energy is then converted to electricity at night.
At hilly areas, water batteries (pumped hydroelectric storage) can be used. Two connected water reservoirs are created at different altitudes. Daytime solar energy pumps water up, and at night, gravity-driven hydro turbines generate electricity. They are cost effective, scalable, and provide dependable power.