0 Foreword
With the development and progress of solar photovoltaic technology, solar energy has become more and more widely used. In recent years, due to the dual advantages of environmental protection and energy saving, the application of solar garden lights, solar lawn lamps and solar energy decorative lamps has gradually taken shape. In many dazzling commercial advertisements, how to choose a solar lighting product that is more suitable for local climate conditions and economical and practical? This has always been a topic of concern for users.
In the design of solar lighting fixtures, many factors such as light sources, solar battery systems, battery charge and discharge control, etc., any of which may cause product defects. Solar lighting consists of five parts: solar panels, charge and discharge controllers, batteries, loads, and fixture housings.
1 solar battery
The main function of solar cells is to convert light energy into electrical energy. This phenomenon is called photovoltaic effect. Among the many types of solar cells, three types of solar cells, namely, monocrystalline silicon, polycrystalline silicon, and amorphous silicon, are relatively popular and practical. In areas with abundant sunlight and good sunlight, polysilicon solar cells are preferred. Due to the relatively simple production process of polycrystalline silicon solar cells, the price is lower than that of single crystals, and the conversion efficiency is continuously improving. In the rainy days, where the sunlight is relatively insufficient and the sunlight is relatively insufficient, monocrystalline silicon solar cells are preferred because the electrical properties of monocrystalline silicon solar cells are relatively stable. Amorphous silicon solar cells are better when the sunlight in the room is weak, because amorphous silicon solar cells have lower requirements for sunlight conditions.
First of all, for any solar lighting product, we must first understand the solar battery. The solar battery has five major electrical performance parameters: short circuit current, peak current, open circuit voltage, peak voltage, and peak power.
For general users, how can we know its five parameter values? To teach you a simple method, let us know this parameter relatively. We can use a multimeter to test these five parameters at 12 o'clock noon. (Of course, there will be a slight error in the measured value.)
For a monolithic solar cell, it is a PN junction. It has all the characteristics of a PN junction except that it can generate electrical energy when sunlight shines on it. Its rated output voltage is 0.48V under standard light conditions. Solar modules used in solar lighting fixtures are made up of multiple solar cells.
Users can look at solar cells first to understand the price, performance and stability of solar lighting fixtures. Below I will introduce charging and discharging controllers, loads, and batteries.
2 charge and discharge controller
Regardless of the size of the solar lamp, a good charge and discharge control circuit is essential. In order to prolong the service life of the battery, it is necessary to limit its charge and discharge conditions to prevent overcharge and deep discharge of the battery. In addition, since the input energy of the solar photovoltaic power generation system is extremely unstable, the control of the battery charging in the photovoltaic power generation system is more complicated than the control of the ordinary battery charging. For the design of solar luminaires, success and failure often depend on the success and failure of charge and discharge control circuits.
Without a good charge-discharge control circuit, it is not possible to have a good solar lamp. The charge-discharge controller must have the following characteristics: anti-reverse charge control, anti-overcharge control, anti-overdischarge control, and temperature compensation.
3 Battery
Since the input energy of the solar photovoltaic power generation system is extremely unstable, it is generally necessary to configure a battery system in order to work. Solar energy lamps are no exception and batteries must be configured to work. Lead-acid batteries, Ni-Cd batteries, and Ni-H batteries are generally used, and their capacity selection directly affects the reliability of the system and the system price. The choice of battery capacity generally follows the following principles: First, the energy of daylight solar modules should be stored as much as possible while meeting the requirements of night lighting, and at the same time it must be able to store the electrical energy needed to meet the lighting needs of continuous rainy days. The battery capacity is too small to meet the needs of night lighting. When the storage capacity is too large, the battery is always in a lossy state, which affects the battery life and causes waste.
load
Solar energy lamp products have the advantage of energy saving and environmental protection. Of course, the load must be energy-saving and have a long life. We generally use LED DC energy-saving lamps and low pressure sodium lamps.
At present, most lawn lamps use LEDs as the light source. The LED has a long service life and can reach more than 100 000 hours. The working voltage is low and it is very suitable for application to solar lawn lamps.
Garden lights generally use LED and DC energy-saving lamps. DC energy-saving lamp voltage is DC, no need for inverter, convenient and safe.
Street lights generally use low-pressure sodium lamps. The low-pressure sodium lighting effect is high (up to 200 lm/W) but low-pressure sodium lamps are expensive.
Lamp shell
We have collected a lot of data on solar lights abroad. Most of them choose energy efficiency between aesthetics and energy saving. The appearance of lamps and lanterns is not required to be high, and it is relatively practical. At present, there are many lamps in China that have a beautiful appearance and are made of stainless steel. But what about performance? This again allows us to think deeply!
The key to a good solar lighting product is the system design. What is a reasonable system design? Let us first understand several important factors that affect the system. This is the latitude, the total amount of annual solar radiation, the maximum number of days without sunshine, the daily power consumption, and the average number of hours of sunshine.
Let's think about it: If the solar battery is not fully charged, what will be the daily discharge? Can you still light the rainy days? These issues must be taken seriously by our designers.
Finally, I will introduce a simple way to determine the performance of solar lighting system: First, the solar battery power must be more than 4 times higher than the load power, the system can work properly. Second, the battery capacity must be more than 4 times higher than the daily power consumption of the load (western region), and the southern region should be more than 6 times higher.
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