Solar panel is one of the important elements in solar photovoltaic system. Choosing the correct solar panel is crucial factor. You need to determine the right wattage of a solar panel. The size of the solar panel in watts directly affect the cost which is basically priced in dollars per watt. Watts are related to the output of each module. For example, a 50 watt panel installed under ideal condition will generate 50 watt-hours of electricity each hour and a 100 watt panel will generate 100 watt-hours each hour in each day. So, you can expect to pay double the price for 100 watt panel compare to 50 watt panel.

There are three main stages in solar photovoltaic system. They are:

·         Generating power by the solar panel.

·         Storing power by the battery.

·         Using the power.

In order to determine the wattage correctly, you need to size the panel according to your required power usage. Battery stores power to be used later on. To maintain the constant level power storage in the battery, the solar panel needs to supply the battery same amount of outgoing power.

The cost of solar panel depends on the size (in watts), the physical size, quality of materials, warranty period, brand and certification of the solar panel. The price also depends on how many solar panels you are purchasing as part of full system package. In general, purchasing large amount of solar panels will cost less per unit. But, choosing solar panels based on only the price is not a wise decision. Because, it may not fit the area where you want to install, not having required certifications to qualify for government subsidies and lack of solid warranty period.

Besides cost, it is important to consider the manufacturing process and materials used in the solar panel. Since all panel manufactures are not the same, therefore you should consider other factors before the decision of purchasing panels. They are:

·         You need to consider the tolerance rate of solar panel. For example, you have purchased a panel mentioned 100 watts in the "nameplate". But, in reality it will be 95 watts only because of quality control issues. Therefore, a positive tolerance rate is crucial. That is, under standard condition, a panel of 100 watts will not only generates 100 watts, but also performs more effectively.

·         There is a significant impact on temperature co efficient of solar panel. It is better having less percentage per degree Celsius. The price of solar panel with less percentage of temperature co efficiency is comparatively higher.

·         Conversion efficiency of solar panel is also vital. It determines how much power is generated by solar panel during the conversion of light into electrical energy. For example, you have purchased two panels with same price. But, one has higher conversion efficiency than other, then it provides better value for money with correct efficiency.

·         In certain climate condition, Potential Induced Degradation (PID) can be caused by stray currents triggered which is the reason for substantial power loss in the panel. Solar panel with little or no PID is considered as good.

·         Embodied energy of the solar panel is another crucial factor. Here, panel’s initial energy intensive production is compared with the time of pay back producing more energy.

·         After installing solar panels, Light Induced Degradation (LID) may occur within few months which decreases the amount of power produced in the module. If there is little or no LID in the panel, then the panel is considered as good.

·         Based on your installation application, the best type of solar cell will vary for you. There are three major types of solar cell remain. They are mono-crystalline, poly-crystalline (or multi-crystalline) and amorphous (or thin-film) silicon. High efficiency and good heat tolerance characteristics remain in mono-crystalline silicon. Due to recent development in poly-crystalline panel technology, it has been observed that panels with poly-crystalline silicon are equal to or better than many mono-crystalline in terms of heat tolerance, size and efficiency. Least amount of silicons are used in amorphous (or thin-film) silicon. Typically, thin-film contains least efficient solar cells. At present, some panel manufacturers are producing thin-film module with highest conversion efficiency.

Next Chapter: CHAPTER-3: SOLAR CHARGE CONTROLLER