6 Things You Should Know Before Buying Solar Street Lights

In the current trend of advocating green energy saving, solar street lights have become a popular choice for road lighting due to their environmental friendly and energy saving features. However, there are many solar street light products on the market, if you lack the key knowledge, it is easy to fall into the predicament of choosing the wrong product, poor lighting and cost waste. Below is a detailed explanation of the 6 things you must know before buying solar street lights to help you make a scientific decision.
 

Determine the best type of solar panel for you

As the core component of a solar street light, the type of solar panel directly determines the performance and efficiency of the street light. There are three main types of solar panels on the market today, each with its own advantages and disadvantages.
 

Monocrystalline solar panels

Monocrystalline silicon solar panels are made of high-purity monocrystalline silicon ingots sliced to form cells, a manufacturing process that makes them the highest purity type of solar panels and also gives them excellent photoelectric conversion efficiency. Even in cloudy weather, monocrystalline solar panels can effectively capture solar energy. In addition, its compact size and aesthetic appearance often make it useful in government programs and other scenarios that require high performance. However, its high production cost makes it relatively expensive to sell on the market.
 

Amorphous (thin film) solar panels

Amorphous silicon solar panels are made of amorphous silicon material, which is less expensive due to its simple manufacturing process. It consists of three parts: photovoltaic material, conductive sheet and protective layer, which are responsible for light energy conversion, enhancing conductivity and protecting the panel respectively. However, the lower photovoltaic conversion efficiency makes it perform poorly in solar street light applications, so it is not recommended for solar street light projects.
 

Polycrystalline solar panels

Polycrystalline silicon solar panels are made from a combination of multiple silicon crystals with good heat resistance, low manufacturing difficulty and relatively affordable prices. Although their efficiency is not as good as monocrystalline silicon solar panels, they can meet the needs of most scenarios in actual use, and are a good choice when the budget is limited.

Lighting technology

Lighting technology directly affects the brightness, energy consumption and service life of street lights. At present, the lighting technology commonly used in solar street lights mainly includes HID and LED.
 

HID lights

HID lights, all known as high-intensity discharge lights, as the traditional lighting field of the “veterans”, its working principle is based on the complex process of gas ionization. It is mainly composed of three major parts: the inner arc tube, the shell and the filling gas. Among them, the inner arc tube is the core component, usually made of high-temperature-resistant quartz or ceramic materials, and filled with special gases such as argon, mercury vapor or metal halide. When the power supply is turned on, the high-voltage arc generated between the electrodes will instantly activate the gas in the inner arc tube, making it ionized. In this process, the electrons of the gas atoms are excited to a high energy level, followed by a rapid leap back to a low energy level, the excess energy will be released in the form of light and heat, thus producing an extremely bright light. Taking the common high-pressure sodium lamp as an example, its luminous flux can reach a high level, in the past a long time, widely used in roads, squares and other large areas of the lighting scene.

However, in the specific application field of solar street lights, HID lights have exposed many insurmountable drawbacks. First of all, its energy consumption is huge, a large amount of power in the conversion process is wasted in the form of heat, energy efficiency can only reach about 20% - 30%, which is contrary to the original intention of the pursuit of energy saving solar street lights. Secondly, the service life of HID lights is relatively short, in general, they need to be replaced every 3-5 years, and frequent replacement not only increases the maintenance cost, but also brings a lot of inconvenience. Furthermore, HID lights start slowly, from the opening to reach a stable lighting brightness, it often takes 5 - 10 minutes, can not be realized instantly lit, which is extremely unfavorable in the street lighting scene with high reaction speed requirements. In addition, HID lights contain heavy metals such as mercury, which will cause serious pollution to the environment if they are not disposed of properly. With the popularization of green concepts and technological development, HID lights are losing their competitiveness in the field of solar street lights and are gradually leaving the stage of history.
 

LED lights

LED lights, i.e. Light Emitting Diodes, are a revolutionary technological achievement in the field of lighting. Its light-emitting principle is based on the unique characteristics of semiconductors, through the tiny microchip control, when the current through the diode, electrons and holes compound, so that the electrical energy directly into light energy. This unique light-emitting method gives the LED light many incomparable advantages. First, the energy efficiency is very high, the efficiency of its electrical energy into light energy can be as high as 80% or more, compared with the traditional lighting methods, can be less energy consumption to achieve higher brightness output. For example, a 30W LED street light, the lighting effect can be completely comparable to 60W or even 80W of traditional street lights, but the power consumption is greatly reduced.

Secondly, LED lights have a long service life, under normal use, their life expectancy can reach 50,000 - 100,000 hours. Assuming 10 hours of use per day, an LED street light can work continuously and stably for 13 - 27 years, almost no need for replacement, greatly reducing the maintenance cost. Although with the use of time increases, LED lights will also appear brightness decline phenomenon, but this process is very slow, in the use of 5 years, its luminous flux can still be maintained at the initial value of more than 80%, basically will not have a significant impact on the actual lighting effect. In addition, LED lights also have a fast response time (can be lit instantly), compact size, environmental protection and non-polluting (does not contain heavy metals), can achieve accurate dimming and color mixing and many other characteristics, to meet the diverse lighting needs of different scenes. With these excellent performance, LED lights deservedly become the best choice of solar street lighting technology, occupying a mainstream position in the market.

The heat dissipation performance

Heat dissipation performance is a measure of the core indicators of the quality of LED lights, directly determines the service life of the semiconductor devices in the street light and work stability.LED chip in the work, although the conversion of electrical energy into light energy is more efficient, but there will still be a considerable part of the electrical energy in the form of heat energy released. When the heat dissipation is not timely or poor heat dissipation, the temperature of the semiconductor device will continue to rise. Excessive temperature will accelerate the physical and chemical changes of the materials inside the chip, resulting in a decline in semiconductor device performance, accelerating the aging process. Research data show that when the LED chip operating temperature exceeds 80 ℃, every 10 ℃, its service life will be shortened by about 50%, while the luminous efficiency will be significantly reduced, the light failure phenomenon intensified.

Therefore, in the purchase of solar street light LED lights, we must pay attention to its heat dissipation design and protection characteristics. Priority should be given to LED lights with UV resistance and fire protection characteristics, UV-resistant materials can effectively resist the erosion of ultraviolet rays in the sunlight to prevent premature aging of the lightshade and other parts of the brittle; fire protection characteristics can be avoided due to the high temperature of the fire hazards. At the same time, good heat dissipation design through the reasonable heat dissipation structure and high quality heat dissipation materials, can quickly emit heat to ensure that the LED chip in the appropriate temperature range, so as to ensure that the street lights in the long-term use of light-emitting properties to maintain a stable and long service life.

Luminous efficiency

Luminous efficacy is an important indicator to measure the ability of light source to convert electrical energy into light energy, the unit is lumen/watt (lm/W), calculated by dividing the total luminous flux by the input power. The higher the luminous efficacy, the more light is emitted by the light source under the same amount of power, and the higher the efficiency of energy utilization.

However, luminous efficacy is not the only measure of lighting performance. In practice, we should pay attention to the light distribution curve and light intensity distribution of the luminaire. Light distribution curve describes the distribution of light intensity in different directions of the lights and lanterns, and a reasonable design can make the light evenly distributed in the target area to avoid uneven light and darkness. For example, road lighting commonly used bat wing type light distribution curve, can let the light in the road to form a wide light band, improve road illumination uniformity, reduce glare. In addition, the quality of the design of the lamps and lanterns optical lenses, reflectors and other components, also affects the light utilization and projection effect.

When choosing solar street lights, you can not only look at the LED light source luminous efficacy values, but also to understand the overall optical design of the lamps and lanterns. Manufacturers can be asked to provide light distribution curve reports and light intensity distribution diagrams to compare the optical parameters of different products. You can also refer to the third-party test reports to ensure that the light efficiency and optical performance of the product meets the standard specifications.
 

False solar lamp power (wattage)

The phenomenon of false power labeling of solar street lights on the market is not uncommon, and the difference between the labeled power and the actual power and brightness is often huge. The reasons for this phenomenon are mainly three: the lack of uniform standards in the industry, the lack of convenient power measurement tools, consumers blindly pursue high power. In fact, the power of solar street lights is limited by the battery capacity and photovoltaic panels, for example, to achieve 100 watts of actual brightness and work 8 hours a day, at least 3.7V 220AH Li-ion ternary batteries and 6V 260-watt photovoltaic panels, which is not only costly, but also difficult to realize the technology. Therefore, it is necessary to combine the battery and PV panel parameters and make rational judgment when purchasing to avoid being misled by the false power labeling.
 

Battery system and safety

Solar street light batteries have gone through an update from lead-acid, colloidal batteries to lithium batteries. Nowadays, the lithium battery market has various types, each with its own characteristics.
 

3.2V system: the choice of low-power civilian use

3.2V solar street light adopts multiple 3.2V lithium iron phosphate batteries connected in parallel, which is suitable for civilian wholesale scenarios with power less than 30W. The performance of this system is stable, and after technological breakthroughs, the power can reach 40W, and the cost has been reduced. However, it should be noted that there are many second-hand batteries in the market, so you should be careful when purchasing.
 

11.1V System: high energy but risky

11.1V ordinary lithium ternary batteries have high energy density, small size and outstanding cost performance, but the performance of high-temperature resistance is poor, and there is a risk of fire, but the performance is good in the low-temperature environment.
 

12.6V system: marketing misinformation to be recognized

12.6V solar street light is essentially 11.1V battery, 11.1V lithium battery charging termination voltage of 12.6V, some manufacturers use this to mislead consumers that the battery capacity is higher.
 

12.8V System: a stable and reliable choice

12.8V solar street lights through the series-parallel connection of lithium iron phosphate batteries to achieve the required capacity, the quality of the battery requires high, to ensure good performance and stability.
 

25.6V System: specialized for high power

25.6V solar street light is specially designed for high power LED street light, which reduces the charging and discharging current by high voltage and improves the safety of the system.

Comprehensive comparison, 12.8V Li-FePO4 battery is the ideal choice for solar street light projects, taking into account both performance and safety.

Before buying solar street lights, a full understanding of the solar panel type, lighting technology, heat dissipation performance, light source efficiency, power labeling and battery system of these 6 key aspects, can help you avoid shopping traps, to pick a good performance, cost-effective products.