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If you are planning the purchase of a complete solar panel system or if you are shopping for parts to assemble your own solar panels you want to make sure to purchase the best solar panels for your individual purpose. This article puts up some basic information on solar panels to help you make the right decision. One thing right at the beginning, there is nothing like "the world's best solar panels for everyone." It makes a big difference whether you want to generate electricity for your home and even feed surplus capacity in the power grid or if you want to charge a car battery now and then. And producing hot water from a solar installation needs actually a complete different technology. In narrower sense those so called "thermal solar collectors" or "solar collectors" are not even proper solar panels. So what's the difference? Solar panels (photovoltaic panels, photovoltaic modules) convert shortwave radiation, e.g. parts of the sunlight, into electrical power. They consist of interconnected solar cells which are protected by a range of different materials. The surface is transparent and the solar panel is framed, mostly in an aluminum frame. Solar collectors on the other hand, are a system of liquid filled tubes. Sunlight heats up the tubes and the liquid. A heat exchanger now transfers the heat to the facility water circuit for warm water and heating. Since this article discusses "best solar panels" let's get back to generating electricity out of sunlight and save solar collectors for another article. Before you purchase solar panels make sure you take a close look at the Solar Panel Specification Sheet. It gives you vital details of the particular solar module and helps you choose the best solar panels for your purpose. You may want to look especially at the following data: Solar cell itself - what kind of semiconductor material is being used? -- Monocrystalline silicon cells (c-Si) have an efficiency degree of more than 20% -- Polycrystalline silicon cells (mc-Si) have an efficiency of 16% -- Flat film amorphous silicon cells (a-Si) have an efficiency of 5%--7% (best solar panels in sales at thetime) -- Microcrystalline silicon cells (µc-Si) in combination with a-Si cells have up to 10% -- Gallium-Arsenik cells (GaAs), Cadmium-Tellur cells (CdTe) and Chalkopyrite cells (CIS, CIGS) have degrees of efficiency from 10 to over 40% (GaAs). They are not (yet) suitable for most private customers, because either they are very expensive or they are not fully developed, yet. -- Panels containing organic solar cells may become the best solar panels in the future, as they can be produced at relatively low costs. At this time their efficiency is still low (pigmented Grätzel-cells have max. 10 %, others are lower) and their life expectancy is short (5000 hours). But keep them in mind for portable electric devices. Solar module efficiency Always look at the efficiency of the total solar module, not only of the individual solar cell and be aware that high efficiency degrees are nothing without a high minimum warranted power rating. (see next paragraph) Solar module power rating It tells you about the wattage of the particular solar electric module. Make sure to check the (warranted) minimum power since the maximum power, stated in Peak Watt (Wp), is always measured under standard test conditions (STC). As you know, nature is not a laboratory. It provides real live conditions and they can differ surprisingly in many ways. Operation voltage Open circuit voltage, stated in Volts (V), is the maximum voltage a solar cell produces when illuminated and not connected to a load. The hotter the Solar Panels get, the lower the open circuit voltage gets. Temperature operating range (TOR) As mentioned above, operation voltage decreases with increasing temperatures. Make sure the TOR suits your local climate conditions. Construction Consider that you are purchasing a fragile high tech product that may be installed on your rooftop and should be be able to withstand roasting sun as well as wind, hail and heavy snow loads. Choose the right mounting system. Medium duty is good, heavy duty is better. The best solar panels are useless when blown down the roof and crashed on the ground. Dimensions Compare the panel dimensions to the active area to avoid a waste of space. Inverter An inverter converts the solar produced electricity (direct current, DC) to alternate current (AC). Look for inverters with heavy duty copper wound output transformers. You set it and forget it. Otherwise you will have your inverter getting repaired or replaced - sooner or later. In worst case that can become necessary on a regular basis. This is no fun and a waste of time and money. Warranty 20 - 25 years warranty on mono- and polycrystalline silicon solar panels are common. This should be the minimum when purchasing solar panels, since today best solar panels have life expectancies of 30 years and even longer. Take a look at the factory warranty and do not accept only a dealer's warranty. Now it's up to you to choose the best solar panels for your needs. Take your time to compare different panels, inverters and mounting systems. If you want to purchase a complete solar system and get it installed, contact more than one dealer. Now you can ask them the right questions.
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