How Solar Panels Create Electricity from the Sun's Rays

At present there are two commonly used ways of collecting the Sun's energy and both use solar panels. I want to deal specifically with the solar panel that comprises many photovoltaic (PV) cells to turn sunlight into electricity.

The term photovoltaic is derives from the Greek  phos which means Light and voltaic from an early pioneer of electricity, Alessandro Volta. PV cells play an important part in our life today from powering pocket calculators to highway emergency telephones and much more. A number of PV cells joined together form a module, and several modules together form an array. The first PV effect was noticed by a young French physicist way back in 1839, but it was not until the 1950s that research and breakthroughs occurred. The advent of the space age saw a rapid acceleration in the use of solar panels as a power source for satellites.

Typical of the materials used in PV cells are crystalline silicon and gallium arsenide. The former is readily available and relatively cheap whereas the latter has to be specially grown in crystal form for the industry, it is therefore more expensive but is more efficient. Ingots of the relevant material are sliced into wafer thin strips, which are polished, coated with a metallic finish. The wafers are then bonded onto a glass cover and joined with metal ribbon either in series or in parallel before being backed with a substrate. The substrate must be a good heat conductor as the cells heat up during the energy conversion and lose their efficiency. This assembly is called a solar panel. Although each individual cell only produces a very small current, many cells together in a panel or array provide a current powerful enough to be useful.

The power output of a solar panel depends on the amount of sunlight landing upon it, otherwise known as the insolation. For an Earthbound system, this will vary depending on its location on the Earth's surface. Because of the curvature of the Earth, more sun falls on the surface at the Equator than in high latitudes, and at these latitudes the solar panel should be tilted at an angle equal to that of the latitude in order to gain most sunlight. The cost of solar panels has come down dramatically over the last ten years, and as people become more and more aware of the need to reduce greenhouse gas emission so are we seeing more and more panels used in everyday applications.