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What is solar panel and how does it work?

What is solar panel and how does it work?

Solar panels are photovoltaic devices. Photovoltaics means converting light to electricity using semiconducting materials. The discovery of this phenomenon has over 100 years history. Not until 2000, solar panels were mass-produced and achieved economies of scale.

                                                  a solar farm

Light consists of particles called photons while electricity is made up by electrons (to be exact, the movement of electrons). The semiconductor, called solar cell, is able to absorb photons (e.g., from sunlight) and produce electrons that was subsequently stored in batteries for later uses. A solar panel is made up of many solar cells. The number and the quality of the individual solar cells decide the specifications of the solar panels. Their applications range from solar farms which generate power for public, to residential solar system which people use to produce power for their own household uses. Due to their “off grid” advantage, solar panels are customized and fit in various appliances or small devices. Our street lights are a good example. When being presented with products, the shoppers often want to make sure they get good products for their bucks.

                 

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Monocrystalline solar panel                           Polycrystalline solar panel

The most important characteristic of a solar panel is the type of its solar cells - monocrystalline or polycrystalline. Monocrystalline is more efficient and hence more expensive. Also, it has not many choices in the market. Polycrystalline is less expensive and has wide range of selections in the market. You can for sure find out its type from its product sheet or you can tell the differences by their looks. The squares in the monocrystalline type have curved angles while the polycrystalline type has sharp angles in its squares. Another difference is their colors. The monocrystalline is darker and more homogenous in color while the polycrystalline is more like blue and the color is not the same across the panel.

The  is the product label we often find at the back of a solar panel. It shows the output specifications under the bottom testing conditions “All technical data at standard test condition. AM = 1.5; E = 1000 W/m2 ; Tc = 25 oC”. AM = 1.5 means air mass of 1.5. E = 1000 W/m2 means the panel was tested under straight, incident light with intensity of 1000 watts per square meter. Tc = 25 oC  means the solar panel temperature was 25 oC  during the test.

At its best performance, its maximum power (Pmax) is 390 W.

Tolerance 0 ~ +10 W. Its power could go 10 W beyond its Pmax.

At its best performing state, the voltage (Vmp) is 40.21 V and the current (Imp) is 9.70 A.

Without any load, the current, so called Short-Circuit Current (Isc), is 10.22 A. This value can be tested with an ammeter. Using a voltmeter, you can get the Open-Circuit Voltage (Voc) 49.35 V.

Maximum System Voltage 1500 V. This value is important when connecting panels in series.

It means at most you can safely connect 30 panels in series.

Maximum Series Fuse Rating 20 A. It means the wires, diodes, connectors, and other internal components of the solar panel can handle 20 A safely.

Operating Temperature -40­­oC ~ +85oC specifies the application temperature range.

Application Class A. This classification is generated from the test standard IEC 61730 which is a security standard for solar photovoltaic panels’ applications. Class A for buildings, class B for energy suppliers, and class C for low-voltage applications.

The solar panels in our lighting products are less powerful than the examples we discussed above. Nonetheless, they are very capable of doing what they are supposed to do. Most of the solar panels in our lights produce 6 V. Their power (watts) varies from product to product. Some products use monocrystalline panels while others use polycrystalline. Please refer to our product brochure.

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