What are Photovoltaic Solar Panels and How Do They Work?
Photovoltaic Solar Panels generate electricity by using a phenomenon first discovered in 1839 by a young scientist called Edmund Becquerel. This phenomenon, called the photovoltaic effect occurs when certain materials produce electric currents as they are exposed to light.
A photovoltaic solar panel is essentially a huge series of semiconductor PN junctions. One half of each junction is electron deficient, the other half electron rich. The photovoltaic cell is designed to create an electric field across the junction between two halves of the crystal, and electrons flow from the rich half to the poor half. A potential barrier exists between the p and n-type sides of the crystal and this prevents further electrons from traveling across the junction until sunlight hits the solar cell and releases electrons with enough energy to overcome the barrier.
High School physics taught us that the light from the sun is made up of packets of energy called Photons. Each photon carries an amount of energy corresponding to the wavelength of its light. When a photon strikes a photovoltaic solar panel it can do one of three things. It can pass straight through, be reflected, or be absorbed. If the photon is absorbed, its energy is absorbed by an electron in an atom of the solar cell enabling it to escape from its normal position, cross the junction and fill a hole. The electrons then flow through a load (e.g. charging a battery, lighting a light, or powering a motor), and complete the circuit by recombining with the holes they left behind. In so doing energy from the sunlight has been extracted and used at an efficiency of around 5-15%. This process can be repeated over and over again over the decades of lifetime of solar cells.
Frequently Asked Questions
-
QUESTION:
Are Photovoltaic Solar Panels that are currently on the market, environmental friendly upon disposal?
Photovoltaic Solar Panels/ Cells are getting more efficient & affordable. But are they safe for the environment when it is time to dispose them?-
ANSWER:
The components of a solar panel are designed to be inert: they sit exposed to the environment for 20 or more years with little degradation.
The creation of photocells is not so benign: it takes a fair amount of strong chemicals and energy to produce a photovoltaic panel. The payback, economically and in terms of environmental damage (tradeoff on energy/chemicals used to create it vs. CO2, Hg etc. reduced during cell's lifetime), may take twenty or thirty years.
-