Solar is the Latin word for sun. Solar energy is the radiation from the sun that is used to generate electricity, heat, or other forms of power. Solar power is a renewable resource, meaning it can be replenished naturally and does not produce greenhouse gases when generating electricity. There are two main types of solar power: photovoltaic (PV) cells and concentrated solar power (CSP). PV cells convert sunlight into direct current (DC) electricity, while CSP uses mirrors to reflect and concentrate sunlight onto a small area to generate DC electricity or heat a fluid to create steam that drives an electric turbine.
Solar PV cells are made of semiconductor materials like silicon that absorb photons from sunlight and release electrons. The electrons flow through circuitry in the cell to create an electric current. A typical home PV system has around 10-20 panels installed on the roof, each panel containing about 30-60 PV cells connected in series. The number of panels and their size depend on the amount of electricity you want to generate – typically, a 5 kilowatt (kW) system will have 20-40 panels. The efficiency of PV cells has increased significantly over time and currently ranges from 15-22%.
Concentrated solar power systems use mirrors or lenses to concentrate a large area of sunlight onto a small area. This focal point then heats up a fluid passing through it, which can be used to drive an electric turbine or simply stored as heat energy for later use. CSP systems are usually much larger than PV systems, with some plants covering several square kilometers. However, they have the potential for very high efficiency – up to 40% – making them attractive for large-scale applications such as utility companies providing electricity to cities