Photo Voltaic Electricity from the Sun
In this article we shall dwell upon the mechanism of Producing Photo Voltaic Electricity from the light of the Sun.
Photovoltaic principles are used to produce electricity. A solar panel (PV panel) is made of silicon, which becomes charged when subjected to sunlight. The electrical charge is consolidated in the PV panel and directed to the output terminals as Direct Current.
Photo-Voltaics essentially means Volts produced by photons. The panels are made out of silicon wafers, which let out (release) electrons when impinged upon by photons ( light). This is a rare property of some semi-conductors.
The intensity of Solar radiation changes during the course of the day, year and weather conditions. To facilitate calculations in planning a system, the total amount of solar radiation energy is expressed as Peak Sun Hours. United States Department of Energy indicates the amount of solar energy that hits the surface of the earth every +/- hour is greater than the total amount of energy that the entire human population requires in a year.
We had discussed the components of a solar generator in one of our earlier posts.
Solar Panels: The output of a solar panel is usually stated in watts (V x A = W)
Since the intensity of sunlight contacting the solar panel varies throughout the day, we use the term “peak sun hours” as a method to average out variations into a daily average.
Battery: Deep Cycle batteries are preferably used in Solar Generators for back-up. Lead-acid batteries are the most common in PV systems because their initial cost is low. Lead-acid batteries are available in both wet-cell (requires maintenance) and sealed no-maintenance versions.
Using an Inverter: An inverter is a device which changes DC power stored in a battery to standard
120/240 VAC electricity (also referred to as 110/220). In an inverter, direct current (DC) is switched back and forth to produce alternating current (AC). Then it is transformed, filtered, stepped, etc. to get it to an acceptable output waveform. The more processing, the cleaner and quieter the output, but the lower the efficiency of the conversion. The goal becomes to produce a waveform that is acceptable to all loads without sacrificing too much power into the conversion process.
Inverters come in two basic output designs – sine wave and modified sine wave.
In all systems there are losses due to such things as voltage losses as the electricity is carried across the wires, batteries and inverters not being 100 percent efficient, and other factors. These efficiency losses vary from component to component, and from system to system and can be as high as 25 percent.