Solar PV (PhotoVoltaics) is the generation of electricity by capturing the power of the sun (daylight).
PV technology dates back to 1839 when a French Scientist Antoine Becquerel first noticed the effect of Photovoltaics, but he was unable to produce a solar cell. It wasn't until PV was used for powering satellites in the 1950's that cost effective practical uses of Solar PV began to be developed.
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PV (photovoltaic) solar panels produce electricity through the PhotoVoltaic Effect. The photovoltaic effect is a phenomenon where certain materials generate an electric current when they are exposed to light. Each PV cell is made up of one or two layers of semiconducting material (usually silicone).
When light shines onto the cell it creates an electric field across the layers. The stronger the sunshine, the more electricity is generated. PV cells in solar panels are usually either 5" or 6" square. Monocrystaline cells are usually black/dark and have the corners of the square cells trimmed. This is because they are made from slices of pure silicone ingots. Polycrystaline (multicrystaline) cells are made up of various silicone ingots fused together giving a sandwiched effect. The colour of multicrystaline cells is normally slightly lighter and do not have the corners trimmed. Monocrystaline cells usually have a slightly higher efficiency than polycrystaline cells.
PV panels (modules) are made up of rows & columns of PV cells. The more solar cells that are in a solar panel and the higher the quality of the solar cells, the more total electrical output the solar panel can produce. The output of a PV module is measured in kilowatt peak (kWp) at a pre determined sunlight intensity (1000W/m2) called Standard Test Condition (STC).
PV panels are available in various sizes & output capacities. The most common outputs range from 180W to 250W. The different sizes allow configurations that best suit the size of the roof area available. As monocrystaline cells are generally slightly more efficient the PV panel sizes tend to be slightly smaller than a polycrystaline panel of the same output.
PV Panels are connected in series, this is called a string. Parallel strings can also be connected together. The combination of the strings is called a solar array. The bigger the array (the more panels), the greater output your system will produce. A typical domestic installation can be from 1.5KW up to 4KW. Typically a 4KW installation would consist of 16 to 20 panels dependant upon the panels' output rating. The panels can be installed in various configurations that suite the available roof space and the client's preferences.
PV panels in a domestic installation create DC electricity from approximately 30V per panel up to 700V for the array depending on how the panels are connected together. However, a house runs off 230V AC. By using an inverter the generated electricity is transformed to 230V which is then fed in to the house's consumer unit (fuse board) and can be used to power your home or building whilst also generating an income from the feed in tariff. The inverter is often fitted in the loft or another suitable position such as the garage or utility room.
Inverters come in different shapes, sizes, capacities & colours. The correct capacity of inverter is selected according to the output capacity & arrangement of the solar PV array. Most inverters come with a standard 5 year warranty. However, an extended warranty can be purchased. An inverter is estimated to last approximately 10 years but like most electrical items the working life can be substantially longer or shorter.