SOLAR PANELS A solar panel (also solar module , photovoltaic module or photovoltaic panel ) is a packaged, connected assembly of photovoltaic cells . The solar panel can be used as a component of a larger photovoltaic system to generate and supply electricity in commercial and residential applications. Each panel is rated by its DC output power under standard test conditions, and typically ranges from 100 to 320 watts. The efficiency of a panel determines the area of a panel given the same rated output - an 8% efficient 230 watt panel will have twice the area of a 16% efficient 230 watt panel. Because a single solar panel can produce only a limited amount of power, most installations contain multiple panels. A photovoltaic system typically includes an array of THEORY AND CONSTRUCTION Solar panels use light energy (photons ) from the sun to generate electricity through thephotovoltaic effect . The majority of modules use wafer - based crystalline silicon cells or thin-film cells based on cadmium telluride or silicon . The structural (load carrying ) member of a module can either be the top layer or the back layer. Cells must also be protected from mechanical damage and moisture. Most solar panels are rigid, but semi-flexible ones are available, based on thin-film cells. These early solar panels were first used in space in 1958. Electrical connections are made in series to achieve a desired output voltage and/or in parallel to provide a desired current capability. The conducting wires that take the current off the panels may contain silver, copper or other non-magnetic conductive transition metals . The cells must be connected electrically to one another and to the rest of the system. Externally, popular terrestrial usage photovoltaic panels use MC3 (older) or MC4 connectors to facilitate easy weatherproof connections to the rest of the system. Bypass diodes may be incorporated or used externally, in case of partial panel shading, to maximize the output of panel sections still illuminated. The p-n junctions of mono-crystalline silicon cells may have adequate reverse voltage characteristics to prevent damaging panel section reverse current. Reverse currents could lead to overheating of shaded cells. Solar cells become less efficient at higher temperatures and installers try to provide good ventilation behind solar panels.
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SOLAR PANELS
A solar panel (also solar module, photovoltaic module or photovoltaic panel) is a packaged, connected assembly of photovoltaic cells. The solar panel can be used as a component of a larger photovoltaic system to generate and supply electricity in commercial and residential applications. Each panel is rated by its DC output power under standard test conditions, and typically ranges from 100 to 320 watts. The efficiency of a panel determines the area of a panel given the same rated output - an 8% efficient 230 watt panel will have twice the area of a 16% efficient 230 watt panel. Because a single solar panel can produce only a limited amount of power, most installations contain multiple panels. A photovoltaic system typically includes an array of
THEORY AND CONSTRUCTION
Solar panels use light energy (photons) from the sun to generate electricity through thephotovoltaic effect.
The majority of modules use wafer-based crystalline silicon cells or thin-film cells based on cadmium
telluride or silicon. The structural (load carrying) member of a module can either be the top layer or the
back layer. Cells must also be protected from mechanical damage and moisture. Most solar panels are
rigid, but semi-flexible ones are available, based on thin-film cells. These early solar panels were first
used in space in 1958.
Electrical connections are made in series to achieve a desired output voltage and/or in parallelto provide
a desired current capability. The conducting wires that take the current off the panels may contain silver,
copper or other non-magnetic conductive transition metals. The cells must be connected electrically to
one another and to the rest of the system. Externally, popular terrestrial usage photovoltaic panels
use MC3 (older) or MC4 connectors to facilitate easy weatherproof connections to the rest of the system.
Bypass diodes may be incorporated or used externally, in case of partial panel shading, to maximize the
output of panel sections still illuminated. The p-n junctions of mono-crystalline silicon cells may have
adequate reverse voltage characteristics to prevent damaging panel section reverse current. Reverse
currents could lead to overheating of shaded cells. Solar cells become less efficient at higher
temperatures and installers try to provide good ventilation behind solar panels.
Some recent solar panel designs include concentrators in which light is focused by lenses or mirrors onto
an array of smaller cells. This enables the use of cells with a high cost per unit area (such as gallium
arsenide) in a cost-effective way
Efficiencies
Depending on construction, photovoltaic panels can produce electricity from a range offrequencies of
light, but usually cannot cover the entire solar range (specifically, ultraviolet,infrared and low or diffused
light). Hence much of the incident sunlight energy is wasted by solar panels, and they can give far higher
efficiencies if illuminated with monochromatic light. Therefore, another design concept is to split the light
into different wavelength ranges and direct the beams onto different cells tuned to those ranges. This has
been projected to be capable of raising efficiency by 50%.
Currently the best achieved sunlight conversion rate (solar panel efficiency) is around 17.4% in new
commercial products typically lower than the efficiencies of their cells in isolation. The energy density of a
solar panel is the efficiency described in terms of peak power output per unit of surface area, commonly
expressed in units of watts per square foot (W/ft2). The most efficient mass-produced solar
panels[disputed – discuss] have energy density values of up to 16.22 W/ft2 (175 W/m2).
TYPES OF SOLAR PANELS
Most solar modules are currently produced from silicon photovoltaic cells. These are typically categorized as monocrystalline orpolycrystalline modules.
The difference between monocrystalline vs polycrystalline solar cells is simply that one is produced from a single crystal of silicon and the other is produced from a piece of silicon consisting of many crystals.
Since polycrystalline cells contain many crystals, they have a less perfect surface than monocrystalline cells.
This means that they absorb slightly less solar energy and produce slightly less electricity per square metre. On the
plus side, the process of creating the silicon for a polycrystalline cell is much simpler, so these cells are generally
cheaper per square metre.
Polycrystalline Monocrystalline
Low cost Slightly higher cost than polycrystaline
Bigger size with the same watt rating Slightly smaller in size with the same rating
Less efficient in catching sunlight rays Slightly more effecient in catching sunlight rays
On balance, the cost of monocrystalline vs polycrystalline based panels per Watt of power output works out about the
same, but the polycrystalline panels will be slightly larger than equivalent monocrystalline panels. This is generally
not a problem unless you have a very limited area available for the installation, in which case you will want to
maximise the power output per square metre.
Monocrystalline and polycrystalline can also look different. Monocrystalline cells will usually have a perfectly uniform
appearance, but polycrystalline cells will appear “grainy” – think of how a granite worktop looks and you’ll get the
idea. From a distance this will not be noticeable, so if they are going on your roof this is unlikely to worry you.
SunTechSTP240-20/Wde240 Watt, 20 VoltPolycrystalline Solar PanelBlack Frame
Suntech's technology yields improvements to BSF structure and anti-reflective coating to increase conversion efficiency. The STP module's new rigid and reliable hollow chamber frame provides additional grounding options for increased design flexibility and easier installation.
Features
High Power Tolerance (0-5%) High conversion efficiency (up to 14.4%) Withstands high wind-pressure, snow load and extreme temperature variations
Excellent performance in low light conditions
Built for long service life
Industry-leading, transferable 25-year power output warranty Rigorous quality control meeting the highest international standards
ISO 9001:2000 (Quality Management System) and ISO 14001:2004(Environmental Management System) certified factories deliverworld class products
Certification and standards: UL1703, IEC 61215, IEC 61730, conformity to CE
Specifications
Model STP240-20/Wde
Maximum Power at STC* 240 W
Number of cells 60 (6 x 10)
Dimensions64.6" x 39.1" x 1.4"
(1640 x 992 x 35mm)
Weight 40.1 lb (18.2 kg)
Open Circuit Voltage (Voc)
37.2 V
Maximum Power Point Voltage (Vmp)
30.2 V
Short Circuit Current (Isc) 8.43 A
Maximum Power Point Current (Imp)
7.95 A
Operating Temperature -40ºC to +85ºC
Maximum System Voltage
1000 VDC (IEC) / 600 VDC (UL)
Output Cables4.0 mm2 (0.006 inches2), symmetrical lengths (-) 1100 mm
(43.3 inches) and (+) 1100 mm (43.3 inches)
Series Fuse Rating 20 A
Connectors MC4 connectors
* STC: Standard Test Conditions - Irradiance 1000 W/m2, Module temperature 25 ºC, AM = 1.5