• What is PV or Solar Cell?
• How long does photovoltaic last?
• How efficient are Solar cells?
• How does Solar Cell store energy?
• Will PV's efficiency reduce in warm temperature?
• What does "A PV is environmental-friendly." mean?
• Can the solar panels be installed anywhere?
• What happens if solar panels are covered with the dirt?
• Where is suitable place for installation the solar panels?
• Can 220 V AC appliances be used?
• How to connect batteries to increase voltage?
• How does overcharging damage the battery?
• How LES can help you save the money?
• How LES can help prolong lamp's lifespan?
• What kind of lamp LES is applicable to? How much it can save?

A PV is an abbreviation for photovoltaic, also called Solar Cell. A PV is a device that directly converts sunlight or light into DC electricity. A PV is made up of semiconductor materials such as silicon, gallium arsenide, indium phosphide, cadmium telluride and copper indium diselenid, etc. which absorb sunlight and convert them into electrical carrier, then separate to electrons and holes to produce energy at positive/negative junctions. If the positive and negative junctions of PV are connected to DC electrical load, it is workable.

In photovoltaic electrification, the interaction of sunlight with certain semiconductor materials makes the electrons free and becomes electricity. There is no moving parts, therefore, no vibration in photovoltaic. The lifetime of photovoltaic will typically last for 20-25 years.

Sunlight falls on the Earth's surface, it provides energy approximately 1000 watt per square meter per hour. The daily average of hours of full sunlight is 4-5 hours. And the energy conversion efficiency of solar cell is 10-16%, it depends on the cell types. This means 1 square meter of solar cell will produce energy about 100-160 watt per hour or about 500-800 watt per day.

Solar Cell itself cannot store energy. It just converts sunlight into direct current from the absorbed sunlight to use with DC appliances. To store energy, the batteries are needed. So that the stored energy during sunshine can be used later or when the sunlight is not visible. Some also install charge controller to regulate charging current and protect the batteries from overcharge.

Yes, a PV works better and more efficient at cooler temperature. This is because PV is electronic device that its efficiency varies by temperature. In temperate climates, PV generates less energy in winter than in summer because to the shorter daytime, lower sun angles and greater cloud cover.

Present day, natural energy sources are widely used. PV is one of the most attractive methods of renewable energy, which are worth used and environmental-friendly.

• Use no fuel other than the sunlight and therefore clean
• No burning and therefore no air and water pollution
• No moving parts so there is no mechanical noise being operation
• Reduce collection of gases such as carbon dioxide, carbon monoxide, sulfur dioxide, hydrocarbon, nitrogen, etc. which generated from fuel, coal and fossil fuel burning power plants. All decrease the impacts of energy on the environment like greenhouse effect, global warming, acid rain, air pollution, etc.
• Give off no waste and therefore harmless environment

The solar panels can be installed everywhere by the following conditions

• Clear, unobstructed and no shading site
• Without dirt, it is recommended to install at the rooftop or mounting structures.
• To be tilted up from horizontal about 10°-15° and set the solar panel facing to south at a tilt angle equal to your latitude, the tilted solar panels will help to release the rainwater and prevent the solar panels from the hold water.

Dirt including dust, soil, fallen leaves, smog, bird droppings, etc., covering will prevent the panels from sunlight's radiation so it reduces producing energy. Although, the solar system requires very little maintenance, if the users find the dirt covered your solar panels, wash them by water. Do not use the washing liquid or scrub by sandpaper. The users should periodic wash the solar panels or as soon as they notice the covered dirt.

A suitable place for installation the solar panels is the place where the panels get direct sunlight for the most of the day such as the rooftop of houses, office buildings and mounting structures. Free from shading like trees, building or other constructions, etc. The solar panels should be pointed towards the sun during the day to produce the most electricity too. For the stand-alone solar system, the solar panels should be installed closer the batteries to be the low power loss in the wire.

Sure. By installing an inverter in your solar system, the DC current produced by the solar panels can be converted into 220 V AC. Solar systems are versatile and therefore you can use 220 V AC and DC as required.

The connecting batteries can increase both voltage and current. It depends on the application requirements. When connecting batteries they have to be the same batteries. If users want to increase the battery voltage, we recommend you to connect in series (see item 1). The ways to connect batteries are

1. Series connecting, the positive terminal of the first battery is connected to the negative terminal of the second battery, the positive terminal of the second is connected to the negative of the third, etc.
   The voltage of the assembled battery is the sum of the battery voltages of the individual batteries.
   The battery current remains the same as one battery, it is unchanged.
   
   
2. Parallel connecting, the positive terminal of the first battery is connected to the positive terminal of the second battery, the positive terminal of the second is connected to the positive terminal of the third, etc. And the negative terminal of the first battery is connected to the negative terminal of the second battery, the negative terminal of the second is connected to the negative terminal of the third, etc.
   The battery voltage remains the same as one battery, it is unchanged.
   The current of the assembled battery is the sum of the battery currents of the individual batteries.
   
   
3. Series-Parallel connecting, combination of series and parallel connecting can be extended voltages and amperage to get the application requirements.

Overcharging the battery occurs when the total capacity removed has been replaced by recharging and the battery remains on charge. The overcharging creates too much heat that can cause the battery plates inside the cells to buckle and shed their active material, also produce an excessive amount of hydrogen and oxygen. These gases are the result of the breakdown of the water molecules within the electrolyte. In the maintenance-free sealed battery, permanent capacity loss will result.
The excessive discharging the battery can also damage battery. It depends upon the chemistry of the battery, but in general, a lead acid battery will discharge less than a Ni-cad battery or Ni-MH battery. Sealed lead acid battery will discharge about 85% of nominal voltage (10.2 on 12 volt battery).

LES helps prolong lifespan of lamps. Therefore, LES helps you save not only your utility expense of lighting system and air conditioner, if air conditioner is used, but also other expenses of the lighting system, including maintenance expense.

The energy from the utility power supply that is higher than usual causes the lamp to get too much energy. Therefore, the lamp's efficiency deteriorates quickly. The lifespan of the lamp is shorten, wastage. Consequently, stabilizing the energy supplied to the lamp (or lighting system) at the normal level help extend the lamp's lifespan.

LES is applicable to fluorescent lamps and gas-discharged lamps, such as high-pressure sodium lamps, low-pressure sodium lamps, metal halide lamps, etc... The below table shows the average energy saving rate for each type of lamp when connected to LES.