1, the preface: with the rapid development of national economy, energy demand is rising, energy prices also heightening. Electricity is an important part of our country's energy, including lighting electricity accounts for a big proportion. Relevant statistics show that as early as 2013, China's total generating capacity of more than 5.2 trillion KWH, and lighting electricity occupies the proportion of total output reached more than 13%, among them, the city road lighting and electricity occupies 30% of the proportion of the light of above. Under the background of accelerating the process of urbanization in our country, the number of city road lighting lamp is increasing at an annual rate of 150-2 million. With the speeding up of urbanization in our country, the proportion of road lighting electricity will gradually increase. Allotted to this, relevant departments in "on further promoting the opinions of the" China green lighting project ", "in the notice, puts forward the concept of green lighting, hope to be able to with energy-saving lamps to replace traditional lamps and lanterns of energy-intensive. This paper elaborates the problems existing in current urban road lighting; From energy conservation and environmental protection requirements, the comparative analysis of high pressure sodium lamp and LED lamp characteristics and energy saving potential in road lighting, which proves that LED wash wall lamp to replace high pressure sodium lamp as the feasibility and necessity of road lighting.
2, high pressure sodium lamp and LED lights used in the comparison of city road lighting
City road lighting light source at present basically has the traditional high pressure sodium lamp, fluorescent lamp, etc., among them, high pressure sodium lamp, with its characteristics of high photosynthetic efficiency, the penetration ability of the fog, used in road lighting is the largest. Combining with the characteristics of China's current road lighting design and adopt the way of high pressure sodium lamp lighting under the following deficiencies:
(1) direct illuminate of lamps and lanterns on the ground, and high intensity of illumination, trunk road in some times also can reach more than 401 x, but obviously, this belongs to excessive lighting illumination, and are responsible for a large number of energy waste. At the same time, in two adjacent the cross position of lamps and lanterns, intensity of illumination reached only about 40% of the direct illuminate the direction, can't effectively meet the demand of lighting.
(2) the efficiency of high pressure sodium lamp reflector are only about 50-60%, which suggests that, in the lighting by nearly 30-40% of the light irradiation inside the lamps and lanterns, the overall efficiency of 60%, only there are serious waste phenomenon.
(3) theory, the life span of the high pressure sodium lamp is 15000 hours, but the influence of the power grid voltage fluctuation and running environment, its service life far cannot reach theory of life, the damage rate of lamps and lanterns is more than 60% a year.
Compared with the traditional high pressure sodium lamp, LED street lamp has the following advantages:
(1) as a kind of semiconductor devices, in theory, the useful lifespan of LED lights up to 50000 hours, 15000 hours of high-pressure sodium lamp is much higher.
(2) compared with high pressure sodium lamp, LED lamp can reach more than 80 color rendering index, very close to natural light, in this light, the eye of recognition can be effectively, thus ensuring road safety.
(3) in the street lamp open, high pressure sodium lamp needs a preheating process, the light from dark to bright need a certain amount of time, not only caused the waste of electricity, and affect the effective development of intelligent control. , by contrast, LED wash wall light at the instant of the opening will be able to achieve the best lighting, there is no such thing as an start time, therefore can achieve good intelligent energy-saving control.
(4) from the luminescence mechanism, high pressure sodium lamp is the mercury vapor light, disposed in the light source, if not effective treatment, will inevitably cause the corresponding environmental pollution. LED is a solid-state lighting, such as there is no harmful substances to human body, is a kind of green light source.
(5) the analysis from the aspects of the optical system, high pressure sodium lamp belongs to the omni-directional lighting, more than 50% of the light after reflector reflects is needed to illuminate to the ground, in the process of reflection, is bound to be part of the light loss, affect its utilization. LED lamp is one-way light, the light can directly a directional light, so the utilization rate is relatively high.
(6) in high pressure sodium lamp, need to be decided by the reflector light distribution curve, so there are a lot of limitations; In LED lights, USES a distributed source, through the effective design of the electric light source, can make the light source of lamps and lanterns presents the ideal state, realize the reasonable light distribution curve adjustment, control the distribution of light, in the available irradiation range of lamps and lanterns, intensity of illumination is relatively uniform.
(7) at the same time, the LED lights have more perfect automatic control system, can according to different time and light conditions, to adjust the brightness of lamps and lanterns, can play a good energy saving effect.
With LED as a street lamp to replace the high-pressure sodium lamp, also there are some different views, for example, compared with high pressure sodium lamp, LED lamp luminous efficiency is low, intensity of illumination is poorer; The illuminate of leds is too concentrated, the homogeneous degree of the exposure is relatively poor; The LED light attenuation is larger, the service life of the far cannot reach theoretical service life, etc. Actually, these views can be through the following analysis.
First of all, is the so-called "" luminous efficiency, under the condition of current technology, the LED luminous efficiency is not high pressure sodium lamp, it is an indisputable fact that, but high pressure sodium lamp spectrum is concentrated in the yellow area, its colour temperature is low, only 2000-2500 k, and relatively high colour temperature such as LED, LED street light neutral white temperature of 4000-5000 k, temperature of cold white LED 5000-8000 k. At the same time compared with high pressure sodium lamp, LED lamps and lanterns with high color rendering index, close to natural light in the actual lighting, can bring a person the sense of comfort.
Followed by "irradiation uniformity", although the LED lighting is relatively concentrated, but can be by the light path of the second design, can make the light source of lamps and lanterns presents the ideal state, realize the reasonable light distribution curve adjustment, control the distribution of light, so as to realize the uniformity of illumination.
Then the problem of "droop", in the process of practical application, due to long-term high temperature working environment, the service life of LED wash wall light will be affected by the corresponding, in the life of the different junction temperature is shown in figure 1. It can be seen that if the junction temperature from 115 ℃ to 135 ℃, the service life of LED lights will from 50000 hours to 20000 hours.
Under the condition of current technology, to improve in a short time of leds luminous efficiency is basically impossible, so only by strengthening the cooling way to prolong the service life of LED lights. In Taiwan, is currently a torch light Technology co., LTD. (LightTorch Technology), the loop heat pipe (LHP) cooling Technology, realize the heat dissipation of LED lights work, has obtained the good effect, can cut the junction temperature of LED lights up to 65 ℃, at that temperature, if the lamps and lanterns to work 12 hours a day, the light failure is less than 3%.
3, LED street light illumination and energy analysis
In a certain city in each of the main road 14 streetlight installed one brand sodium lamp power 400 w and 160 w some brand of LED street lamp, road lighting test, the results are shown in table 1. Results show that with 160 w LED street light instead of 400 w high pressure sodium lamp, lighting effect can completely meet the requirements of city road lighting design standards, and the LED can be a lot higher than the high-pressure sodium lamp. Given in table 2, LED street lamp and high pressure sodium lamp comprehensively compares the energy saving effect.
4, the conclusion: in conclusion, compared with using high pressure sodium lamp road lighting, using LED street light to energy conservation and environmental protection. There is no doubt that with the progress of science and technology, energy-efficient light source will be constantly emerging, as a road lighting designers should be innovative design, at any time to master the use of new technology and new equipment, lighting has always put the energy conservation and environmental protection to work first.