In the modern lighting system, solar LED street lights have become the mainstream lighting choice for urban roads, rural road networks, parks and green areas and other scenarios by virtue of the significant advantages of energy-saving, environmental protection, and no need to rely on grid power. However, with the increase of the use of time, solar LED street lights will generally appear light failure phenomenon. This phenomenon seems to be just a decrease in brightness, but it will directly affect the lighting effect and equipment life, and bring a series of challenges to nighttime travel safety and operation and maintenance costs. Therefore, it is of great significance to explore the causes, impacts and responses to the light decay of solar LED street lights to enhance their use value.
solar street lights
LED street light decay, academically known as “lumen attenuation”, specifically refers to the physical phenomenon of LED street light in the process of long-term use, its luminous brightness gradually weakened over time. Unlike traditional incandescent street that “suddenly go out”, LED street light decay is a slow and continuous process.
Even if the street light can still be lit, its actual luminous intensity will be much lower than the initial state, may be from the initial high luminous efficacy gradually reduced to a level that can not meet the basic lighting needs. This decay is not instantaneous, but the chip, the circuit, the environment and other factors for a long time, so it is often easy to be ignored, until the lighting effect of a significant decline in attention.
LED chip as the “heart” of solar LED street light, its quality directly determines the luminous efficiency and attenuation speed of street light. High-quality chip using high-purity semiconductor materials, the crystal structure is uniform, able to maintain a stable electronic jump efficiency in the long-term energized state, thereby reducing the loss of brightness.
On the contrary, low-quality chips may exist in the material impurities, process roughness and other issues, the use of the process is prone to lattice defects expanding, electrode aging and so on, resulting in a rapid decline in luminous efficiency, within a short period of time there is a significant brightness attenuation, and even local non-luminous phenomenon.
When LED street light works, electric energy is not 100% converted into light energy, about 70%-80% of energy will be released in the form of heat energy. If the design of cooling system is not reasonable, such as insufficient cooling area, poor thermal conductivity of cooling materials, or the existence of dead corners in the cooling structure, the heat generated will not be able to emit in a timely manner.
When the LED chip temperature exceeds its rated operating temperature (usually 60-85 ℃), will accelerate the internal phosphor aging and chip material degradation, resulting in a significant reduction in luminous efficiency. Long-term high-temperature environment, and may even lead to chip solder joints off, short circuit and other problems, further aggravate the light failure.
The drive power supply is a key component to provide stable current and voltage for LED chips, and its performance stability directly affects the light decay rate of street lights. High-quality drive power supply with accurate current control capabilities, able to maintain a stable output current in the input voltage fluctuations, to avoid damage to the chip due to overcurrent or undercurrent.
The poor quality drive power often have capacitor aging fast, circuit design is unreasonable and other problems, easy to appear output current suddenly large and small. When the current is too large, the chip will produce too much heat due to overload; when the current is too small, it will lead to unstable light emission, both of which will accelerate the light failure and shorten the service life of the street light.
solar street lights
Solar LED street lights are mostly installed outdoors, exposed to the complex natural environment for a long time, and the impact of environmental factors on light decay can not be ignored. In high-temperature areas, the road surface temperature may exceed 50℃ at noon in summer, which will further increase the internal temperature of the street light, superimposed on its own heat dissipation problems, accelerating the light failure.
High humidity environment is easy to lead to street light internal components moisture, triggering circuit oxidation, poor contact and other problems; and in industrial or coastal areas, corrosive gases and salts in the air will also erode the chips and circuits, destroying the light-emitting structure, resulting in a continuous decline in brightness.
The core function of street lights is to provide adequate lighting for safe travel at night. When light decay causes the brightness to fall below the national standard (e.g. 20 cd/m² for urban arterial roads), road visibility will be significantly reduced. The recognition distance between pedestrians and vehicles is shortened, making it difficult for drivers to detect changes in road conditions or pedestrians, and for pedestrians to judge the risks of their surroundings, which can significantly increase the incidence of traffic accidents and pose a serious threat to public safety.
Light failure is not only a sign of reduced brightness, but also a signal of aging of the internal components of the solar street light. As light degradation intensifies, the performance of core components such as chips and drive power supplies will continue to deteriorate, ultimately leading to early retirement of street lights. This means the need for early replacement, increasing the equipment procurement costs; at the same time, frequent replacement and maintenance will also generate labor costs, lifting costs, etc., to the municipal departments or operation and maintenance units to bring a heavy economic burden, contrary to the original intention of the solar street lights energy-saving and money-saving.
solar street lights
When purchasing solar energy LED street lights, you should give priority to the products with famous brand chips. When purchasing solar LED street lights, you should give priority to the products with famous brand chips. These chips have gone through strict reliability tests, and the light decay speed is slower under the same working conditions, and the light decay is usually guaranteed to be no more than 30% in 50,000 hours. At the same time, to check the parameters of the chip certification, to ensure that it meets the international or domestic energy efficiency standards, to avoid choosing poor-quality chips because of low prices, to reduce the light failure from the source of the hidden trouble.
The heat dissipation design needs to be optimized with the installation scenario and power size of street. For high-power street lights (e.g. over 100W), integrated aluminum heat dissipation structure can be used to expand the heat dissipation area by increasing the number and length of heat dissipation fins, and at the same time, high thermal conductivity silicone grease can be applied between the chip and the heat sink to reduce the thermal resistance.
In high-temperature areas, a sunshade can also be installed on the top of the street lights to reduce the extra heat caused by direct sunlight and ensure that the chip’s operating temperature is always controlled within a safe range.
Regular cleaning is a simple and effective measure to slow down light decay. For street lights on city roads, it is recommended to clean them every 3 months; in rural or dusty areas, it can be shortened to 1-2 months. When cleaning, use a soft cloth to wipe the dust on the surface of the streethade, and then use a neutral detergent to remove stubborn stains, avoiding the use of hard objects to scratch the streethade to affect the light transmittance.
At the same time, the cleaning process can check whether the heat sink is blocked, clean up debris in a timely manner to ensure that the heat dissipation channel is smooth, indirectly reducing the temperature rise due to the accumulation of dust.
The circuit design should take into account the stability and energy saving. Drive power supply should be selected with over-current protection, over-voltage protection, lightning protection function of the product, to ensure that in the power grid fluctuations or bad weather can still stabilize the output current. In addition, constant-current drive mode can be used to control the current at 80% -90% of the rated current of the chip, not only to ensure sufficient brightness, but also to avoid excessive heat brought about by full-load operation, to extend the service life of the chip and slow down the speed of light degradation.
In the production process, each batch of street lights should be subjected to strict quality testing, including high-temperature aging test (1000 hours of continuous operation at 60℃), cold and hot shock test, etc., so as to screen out the products with abnormal light degradation.
After installation and use, establish a regular inspection system to test the brightness, current, temperature and other parameters of the street light every half a year, and find that the brightness of the street light attenuation of more than 20% in time to investigate the causes and replace the aging parts to avoid further deterioration of the light decay.
Solar LED street light degradation is the result of chip quality, heat dissipation performance, driving power supply, environmental factors and other aspects, which not only brings about a decline in lighting effect, but also affects road safety and increases operation and maintenance costs. Through the selection of high-quality chips, optimize thermal design, regular cleaning and maintenance, rational design of the circuit and strengthen the quality control measures, can effectively slow down the speed of light failure, extend the service life of solar street lights.
Only by paying attention to the light decay problem and adopting scientific coping strategies can we give full play to the energy-saving advantages of solar energy LED street lights and provide long-term stable protection for night lighting.
