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Learn About Solar Modules

 

What is a solar cell ?


A solar cell or photovoltaic cell is made of special materials called semiconductors, the most common semiconductor material which is used in the manufacture of a solar cell is known as silicon. When a light source strikes a solar cell, a portion of it is absorbed by the semiconductor material. The absorbed light energy knocks electrons loose, allowing them to flow freely. See illustration

 

 

Ordinarily pure silicon is a poor conductor of electricity so impurities such as phosphorus and boron are added to create what is known as a semi-conductor. The addition of these impurities not only allows the silicon to conduct electricity, but also acts to force electrons freed by light absorption to flow in a certain direction. This directional flow of electrons is also referred to as a current. By placing metal contacts on the top and bottom of the solar cell, it then becomes possible to draw that current off to use externally to perform work.


What is a solar electric module ?


A solar electric module consists of an aluminum framed sheet of highly durable low reflective, tempered glass that has had individual solar cells adhered to the inner glass surface. These individual solar cells are wired together in a series parallel configuration so as to obtain the necessary voltage and current. 

 

Individual cells are wired in series strings to increase the module's voltage and the series strings are wired in parallel to increase the module's current. The back of the module is protected by another sheet of tempered glass or a long lasting material such as Tedlar. 

 

            

 

The series parallel connections are passed through the protective backing and then wired to a weather proof junction box which is permanently mounted to the back of the module. The junction box is where the module's output connections are made. 

 

 

Several solar modules wired together are known as a solar panel.

 

 

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What is the difference between monocrystalline and polycrystalline cells ?


There are two cell technologies that are prevalent in today's market, they are referred to as polycrystalline and monocrystalline silicon. Some manufacturers will use one or the other technologies in the manufacture of their product some will use use both. 

 

Solar cells that are created from monocrystalline or (single crystal) technology are cut from a silicon boule that is grown from a single crystal, in other words a crystal that has grown in only one plane or (one direction). Single crystalline are more expensive to manufacture and typically have a slightly higher efficiency than do conventional polycrystalline cells resulting in smaller individual cells and thus typically a slightly smaller module. 

 

Solar cells that are created from polycrystalline or (multicrystalline) technology are cut from a silicon boule that is grown from multifaceted crystalline material, or a crystal that grows in multiple directions. Conventional multicrystalline solar cells typically have a slightly lower efficiency resulting in larger individual cells and thus typically a slightly larger module. All of this has changed with the advent of the new silicon nitride multicrystalline cells which are rated as high or even higher efficiency than similarly sized monocrystalline cells. 

 

It's important to keep in mind that a 100 watt module is a 100 watt module whether it was made from polycrystalline cells or monocrystalline cells. 

 

What about Amorphous technology

 

Amorphous or thin film technology has for years been touted as the technology of the future that would offer a reduction in the cost of manufacturing solar modules. Many companies have entered and promptly exited the market with little success. Thin film or Amorphous technology has a lower efficiency rating so thus panels that are manufactured from this process tend to be substantially larger in size requiring a greater roof area for a typical installation. Questions concerning life expectancy remain unanswered.

 


How many solar modules do I need to power my loads ?


The best method that we've found is to convert both your power consumption and your power production into WATT HOURS that way we can compare apples to apples. step one is to determine the individual wattage rating for each load that you intend to run off solar. Look on the back of each appliance and try to locate a label which indicates the wattage used by the appliance, if it doesn't give you the wattage then it may tell you the amount of volts and amps that the appliance uses. 

 

Remember volts times amps equal watts. Once you have written down the wattage rating for each appliance, you then need to determine the amount of time each appliance will run during the day. For example let's say that you have a television that runs for three and a half hours a day, then write down 3.5 hours, or let's say you have a computer that runs for two hours and 15 minutes, then write down 2.25 hours, or a microwave that runs for 45 minutes, then write down .75 hours.


Next take the wattage rating of each appliance and multiply that by the amount of time it will run, that will give us the WATT HOUR rating. For example a television that draws 200 watts and runs for three hours (200 x 3 = 600) will use 600 watt hours, or a toaster that draws 1100 watts and runs for 15 minutes (1100 x .25 = 275) will use a 275 watt hours. Add the up all of the watt-hour ratings for each appliance and that will equal your total power consumption for each day.


Let's say that your total power consumption equaled 1200 watt hours per day, then that's the amount of solar power you need to produce plus about 10 percent for battery losses. Don't forget that the power you produce with solar panels is also a factor of time as well. So for example let's say you had a 200 watt solar panel and that panel sat in full sun for seven hours, than you would have produced 1400 watt hours (200 watts x 7 hours = 1400 watt hours)

 

Let's say for example that you only had five hours of full sunlight then five hours times two hundred watts would only be 1000 watt hours so you would be at a deficit, so you would need to either add another 40 watts of solar panels or reduce your power consumption by 200 watt hours. 

 

There's no secret formula, what you take out of the batteries you must put back in plus about ten percent or you'll be in the red which can damage your batteries over time.


Who makes the best quality solar modules

Basically quality is pretty much equal across the board when your dealing with major brands such as Suntech, Trina, Kyocera, Sharp and Mitsubishi. The safest thing to do is stick with the major brands.

 

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