Solar has been Widely Applied to Provide Power for Lighting

As a kind of renewable energy, solar power is primarily utilized into lighting product in the civilian field. Presently, in the Western of China’s Brightness Program, the solar application has been increasing scale in the fields of Non-main road solar street light, solar powered LED garden lights, solar lawn light and other solar decorative lights. In the design of solar lighting, it is relevant with lighting source, solar cells system, controller and other factors, any segment problem would cause product defectiveness. As the specialized advantages of solar lighting, it has got rapid development in recent years. The power of solar lawn light is small, its main function is to decorate, it has high movability, easy to install, high waterproof level.

The market demand for solar lawn lamps are huge in the world. In 2002, the consumption of solar cells had reached 2MW to manufacture solar lawn lights only in GuangZhou and ShenZhen, equal to one third of China’s solar cells production capacity, it still keep strong development in this year, which is out of expectation. Decorative solar garden lights have got widely application in public garden, communities and non-main traffic road.

1. Solar Panel is Key important for solar lighting, some points should be noticed when we use solar lights.

1). The Peak Power of solar panel is under standard solar irradiation condition, that is the 101 standard decided by European Commission, solar irradiation is 1000W/M^2, Air Mass is AM1.5, temperature is 25℃. Sunlight is from weak to strong to weak from morning to afternoon a day, so, the output of solar panel is not stabilizing, it is different during a day. The power output of the same solar panel is different in different site or time.

2). The choice of battery capacity. As the power output of solar panel is extremely instability, the battery should be allocated for solar lighting system. The battery capacity can directly influence the system reliability and prices. The allocation of battery should coordinate with below rule: it should meet night illumination condition at first, the battery should store the power generated by solar panel in daytime, at the same time, battery should backup for rainy days to illuminate.

3). The encapsulate of solar panel. Presently, there are two types of encapsulate, tempered glass lamination and epoxy plate, lamination craft can guarantee solar panel to work above 25 years. Although epoxy is beautiful, its lifespan is just about 2-3 years. Therefore, the solar panel whose power is below 1.0W can be encapsulated by epoxy. Regards to the solar panel which has strong request for long time, it is suggested to exploit lamination encapsulate. Another encapsulate type is to adopt silica gel as epoxy, its estimate working time is about 10 years.

4). The installation of solar panel. It is to make a beautiful design by deciding the angle of solar panel and decorative lampshade. When to install solar panel flat on the solar lamp, its efficiency would be decrease, the installation should consider beautiful appearance and efficiency.

5). Heat Island Effect. Solar panel comprises of many solar cells to reach the expectation voltage request. During utilization of solar panel, if one solar cell has been shadowed, the solar cell would produce heat to damage under strong sunlight radiation, hereby to damage whole of solar panel, this is so-said Heat Island Effect. In order to avoid this effect, the solar panel should be installed on the site where is no shadow covering it.

2. The Control of Battery Charging and Discharging. As a solar lighting system, a controller is essential. In order to prolong battery lifespan, its charging and discharging should be controlled to avoid it over-charge or over-discharge. In addition, as the power input is extremely instability in solar lighting system, the battery control is more complicated in solar system. As solar lighting designer, its success depends on the success of control circuit. A better performance solar light should have a great control circuit.

1) Anti-Reverse Charging Function. Usually, a diode should be series connected in the circuit of solar cells, diode can anti-reverse charging. This diode should be Schottky Diode, its voltage drop is lower than traditional diode. In addition, field-effect transistor also can be utilized to control anti-charging function, its voltage drop is lower than Schottky diode, but its circuit control is more complicated.

2) Over-Charging Protection Function. A drain transistor can be series or parallel connected among input circuit, voltage identification circuit can control the power switch of transistor, to drain the surplus power through transistor, guaranteeing moderate voltage to charge battery. The key is the choice of anti-charge voltage, single Lead-acid battery is 2.2V.

3) Over-Discharging Protection Function. The control point of battery is variable with temperature, therefore, solar lighting system should have a reference voltage which is controlled by temperature. For single lead-acid battery, usually it is -3~ -7mV/℃, we always choose -4mV/℃.

4) The choice of solar lighting source. Presently, most of solar lawn light choose LED as lighting source, LED has a long lifespan, it can reach above 100,000 hours, low working voltage, it is very suitable to be applied for solar lawn lamp. Especially the LED technology has got critical breakthrough. Moreover, its characteristic has got great improvement in the past five years. At the same time, the cost-performance also got great improvement. In addition, LED is powered by low voltage, its cost of lighting control is low, it is possible to control its brightness and frequent to switch power. It is also possible to control color, change lighting variation and produce dynamic phantom. So, it is very suitable to exploit for solar lawn lamp.

With technological development, solar power has got widely applied, there are more and more traditional lighting being replaced by solar lighting. With the cost reduction of solar panel, solar lighting products have got popularly welcome in market. We can expect the brilliant future for solar lighting would come before long.

Bingsolar Power, 12th, June, 2018