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solar panel and light
- Aug 01, 2017 -

Solar panel refers to a panel designed to absorb the sun's rays as a source of energy for generating electricity or heating.

A photovoltaic (PV) module is a packaged, connect assembly of typically 6×10 photovoltaic solar cells. Photovoltaic modules constitute the photovoltaic array of a photovoltaic system that generates and supplies solar electricity in commercial and residential applications. Each module is rated by its DC output power under standard test conditions (STC), and typically ranges from 100 to 365 watts. The efficiency of a module determines the area of a module given the same rated output – an 8% efficient 230 watt module will have twice the area of a 16% efficient 230 watt module. There are a few commercially available solar modules that exceed 22% efficiency and reportedly also exceeding 24%.A single solar module can produce only a limited amount of power; most installations contain multiple modules. A photovoltaic system typically includes an array of photovoltaic modules, an inverter, a battery pack for storage, interconnection wiring, and optionally a solar tracking mechanism.

Photovoltaic modules use light energy (photons) from the Sun to generate electricity through the photovoltaic effect. The majority of modules use wafer-basedcrystalline silicon cells or thin-film cells. 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 modules are rigid, but semi-flexible ones are available, based on thin-film cells. The cells must be connected electrically in series, one to another. Externally, most of photovoltaic modules use MC4 connectors type to facilitate easy weatherproof connections to the rest of the system.

Modules 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 modules may contain silver, copper or other non-magnetic conductive  Bypass diodes may be incorporated or used externally, in case of partial module shading, to maximize the output of module sections still illuminated.

Some special solar PV modules include concentrators in which light is focused by lenses or mirrors onto smaller cells. This enables the use of cells with a high cost per unit area (such as gallium arsenide) in a cost-effective way.

You"ll see a lot of numbers and details on solar panel specification sheets. Here’s what they mean, and how to calculate and compare the numbers that might not be so obvious.

  • Power (Pmax) – This is the maximum wattage the panel is capable of producing, under absolutely ideal conditions. More wattage is always a good thing, all things being equal.

  • Cell Type & Efficiency – Solar panels are made up of solar cells wired together. The cells are where the magic happens – converting sunlight into electricity. A key point of comparison is just how efficient this conversion process is. The very best commercially available solar cells are still less than 25% efficient at this process, with 15% to 18% efficiency being much more common. In general monocrystalline cells are more efficient than polycrystalline cells, and they are both much more efficient than amorphous silicon thin film cells. (For more on efficiency, see the section below.)

  • Dimensions: Length / Width / Depth / Weight / Flexibility – For installation onto an RV roof, the physical dimensions of a panel become critically important. Narrow panels in particular allow for more flexible roof layouts, working around roof vents and air conditioners. Thin and flexible panels are much lighter weight and have an advantage that they can be mounted directly to a roof, but the downside is that without an airspace underneath they can get a lot hotter. Hot panels are less efficient, and also heat up an RV interior more too.

  • Watts / Square Meter –For solar panel uses on LED solar street light , solar powered lights for yard or walkway , Multiply the width and length to get the square metesr  and divide the panel voltage by this value . the resut comes better when they are bigger . 

  • Voltage at Maximum Power Point (Vmpp) & Current at Maximum Power Point (Impp)– These are the key numbers for any solar panel, and describe the electrical point at which the panel is operating at peak efficiency – the maximum power point. Voltage times current gives you wattage, so (Vmpp x Impp) should always give you Pmax. When you wire different panels in parallel, you should try to match the Vmpp so that they work well together. And when you wire panels in series, try to match the Impp.

  • Open Circuit Voltage (Voc) – If you test a solar panel that is not hooked up to anything other than the sun with a voltmeter, this is what you should read. It will always be higher than Vmpp – this is the maximum voltage the panel can ever produce. You need to make sure that the Voc of you solar panels is within the compatible input range of your solar charge controller – as long as it is, higher voltages can give more headroom above your battery voltage to help with charging.

  • Short Circuit Current (Isc) – This how much current will flow if you touch the two wires coming out of the solar panel together, causing a short circuit. This is primarily important to ensure that you are using large enough wires and fuses for a safe installation.

  • Warranty – A key number that should give you an idea how long the manufacturer expects the panels to perform up to specifications. Some rigid solar panels have warranties to produce 80% of rated power (under standard test conditions) for up to 30 years, but most flexible panels have much shorter warranties. Once a flexible panel has been glued to a roof, you will have a potentially hard time removing it intact for a warranty claim regardless. And of course a warranty is only useful if the company manages to stay in business long enough to honor it.

The key specifications to worry about for RV usage is the overall panel power, the price per watt, the watts per square meter, and the overall dimensions to make sure that the panels will fit where you have room for them.