Starting with the basics a photovoltaic cell, average solar cell, consists of negative silicon, silicon containing phosphorous impurities, layered over positive silicon, boron impurities. Connect them with a wire and there you go. Your typical rooftop solar panel is comprised of these cells, which is not very cost effective, these panels could absorb more rays than they receive. Also, storing this electricity on a residential level, usually in the form of batteries, lithium-ion batteries have been found to be the most efficient, can be costly.
Another method to harvesting solar energy is by using solar thermal, or Concentrated Solar Thermal (CST). This is done by concentrating the suns rays onto one spot, and then converting this energy into electricity. Mirrors can be used to redirect the rays onto a tower, using this heat, water can be boiled and the steam can be used to generate the electricity. This is somewhat similar to how some power plants work, using hot oil to boil the water. CST avoids the costs of the solar panels and reserving the electricity, but requires more area, and converting the energy to electricity.
Two of the world’s largest plants started generating power this year, yet still not supplying electricity, Ivanpah and Topaz, use the two different methods. Topaz, recently purchased by Warren Buffet, uses 9 Million modules to generate 550 megawatts of constant power, enough to power approximately 160,000 homes. Ivanpah, on the other hand, uses 300,000 mirrors and three plants, or towers, generating 392 megawatts to power approximately 140,000 homes.
Concentrated Photovoltaic, which combines the two techniques, concentrates the sunlight directly onto the cells using mirrors or lenses. This will most likely be the most efficient method, and due to their size, they do not require massive amount of land, and can be used residentially and on rooftops. Concentrated Photovoltaic is still in the works, as it is more pricy due to extra costs such as the lenses/mirrors, and cooling systems.