Some people say that if LED street lights are not powered by solar energy, they will have no further value for use; Some people also say that solar power supply will only make the production cost of LED street lights more expensive, making it difficult for LED street lights to be promoted and used in real society; Some people also say that LED street lights should be powered by a combination of solar energy and AC power There are different opinions. Now let's take a look at why solar LED street lights can replace AC LED street lights?
At present, most LED street lights still use AC power supply. On the one hand, the technology of AC circuit lights is already very mature, while solar street lights have many uncertain factors. On the other hand, the main consideration is still that the initial investment in solar energy is too large, thus ignoring many fundamental advantages of solar power supply.
The most important advantage of solar energy, as we all know, is that it is an inexhaustible and cleanest renewable energy source! It can truly solve the problem of global warming! It will ultimately replace all energy sources!
However, truly replacing all energy sources with solar energy is still a long-term and difficult task. Although solar energy is ubiquitous, its collection requires a certain amount of irradiation area. Obviously, the desert is the most ideal location, but long-distance power transmission and distribution will consume a large amount of expensive copper materials, and only large cities adjacent to the desert have trial value. It is difficult to find such a spacious and open place in large cities with high population density. Rural areas are limited by economic conditions and it is unlikely to be widely promoted now. It is best to start with small activities for any new things, and adopt a "self-produced and self sold" method. Street lights are one of the best pilot projects that first use solar energy. Moreover, energy conservation, like emission reduction, must first be advocated by the government, and even promoted through government subsidies like in Germany. Fortunately, the street lighting project was originally a government project and was tendered by the government. So government decision-makers must be aware that LED street lights will definitely replace high-pressure sodium lights, and solar LED street lights will also replace AC LED street lights.
Changing all street lights to solar street lights can save the power generation of a Three Gorges hydropower station
LED street lights are more energy-efficient than high-pressure sodium lights and have long been recognized by people. However, there may still be a lack of quantitative concepts. It is now recognized that 100 watt LED street lights can replace 250 watt high-pressure sodium lights, so it can be simply assumed that each LED street light can save 150 watts of electricity.
However, if solar power is used instead, even this 100W of electricity can be saved, which means that each street lamp can save 250 watts of electricity. According to relevant estimates, the total number of street lights in China is about 100 million or more, and it is growing at a rate of 20% per year. In 2008, 20 million new street lights were added. If these 100 million street lights can be converted into 60 million 250 watt street lights, and if all these 60 million street lights are converted into solar LED street lights, a total of 15 million kilowatts of power can be saved. Assuming that each street lamp works 12 hours a day, it will save 65.7 billion kilowatt hours of electricity within one year. The total power generation of the Three Gorges Hydropower Station in 2007 was 61.603 billion kilowatt hours. Therefore, the electricity saved by converting all streetlights nationwide to solar streetlights will exceed the annual power generation of a Three Gorges hydropower station. This is an extremely astonishing number.
Moreover, solar energy is a clean and renewable energy source that not only saves electricity but also reduces carbon dioxide emissions. Each 250 watt high-pressure sodium lamp will produce 1290 kilograms of carbon dioxide within a year, so converting all 60 million street lamps to solar powered ones will reduce 77.4 million tons of carbon dioxide. So after switching to solar energy, not only did it save electricity costs, but it also saved the cost of reducing carbon dioxide. The reduction cost per ton of carbon dioxide is $345-404. Reducing 77.4 million tons of carbon dioxide is equivalent to saving $31 billion in carbon dioxide reduction costs!
The preceding numbers are just a comparison between LED street lights and high-pressure sodium lights. For both 100W LED street lights, the energy-saving comparison between using AC power and using solar energy can be obtained by dividing the above data by 2.5. That is to say, if all 60 million 100 watt LED street lights are powered by solar energy, they can save 26.28 billion kilowatt hours of electricity compared to when all AC power is used, and the cost of reducing carbon dioxide emissions is 12.4 billion US dollars.
The efficiency of AC power supply will be 15% lower than that of solar power supply
Because when using AC power supply, a switch mode power supply must be used to convert it into DC. The efficiency of a typical switching power supply is about 80%. So for a 100W LED street light, its AC input power is approximately 120W (120W is used in the comparison table below). When using solar power supply, as long as a DC/DC constant current source is used, its efficiency can reach up to 95%. Therefore, the total efficiency of using AC power is about 15% lower when combined. So the above numbers should be increased by 15%.
AC power supply and power factor issues
In relatively low-end switch mode power supplies, the lack of power factor compensation will lead to a decrease in the overall efficiency of the power grid if widely adopted.
The biggest problem with using AC power supply is reducing the lifespan of the entire lighting fixture
Because alternating current must be rectified and filtered to become direct current, electrolytic capacitors must be used for filtering in all switching power supplies. As is well known, the lifespan of electrolytic capacitors is very low, with a typical lifespan of only 1000 hours and a long-lived lifespan of only 10000 hours. Moreover, for every 10 degrees increase in ambient temperature, the lifespan decreases by half. In high-power LED street lamps, the temperature rise is very high, so the lifespan of electrolytic capacitors is also shorter. The usual requirement for the lifespan of LED street lights is over 50000 hours. The lifespan of the entire lighting fixture will inevitably be affected by the short lifespan of the electrolytic capacitor. It can be considered that many low-quality LED street lights in the past quickly failed, not only because the heat dissipation problem of the LED itself was not properly handled, which accelerated its light decay, but also because the failure of the electrolytic capacitor in the AC power supply was an important factor. In solar powered systems, there are no electrolytic capacitors. So the lifespan of its constant current source can be guaranteed to match the lifespan of the LED.
The overall cost of solar powered LED street lights is much lower than that of AC powered LED street light systems
Although the initial installation cost of solar street lights is higher, the cost of laying AC power cables and long-term electricity bills is much higher than that of solar systems. Let's do a detailed analysis below.
(1) The cost of LED lamp holders and poles for the two systems is generally the same, with the main difference being the solar panels. The power of solar panels is usually about three times that of LED lighting fixtures. If the LED is 100 watts, then a 300 watt solar panel is required. At present, the price of solar panels has been reduced to 23 yuan/watt, and 300 watts is 6900 yuan. In addition, solar systems also require batteries, but their cost is equivalent to the cost of switching power supplies in AC power supply. So the two can offset each other. So the main difference in the cost of the lighting fixtures themselves is the solar panels.
(2) The maximum expenditure for the initial installation of AC powered LED street lights is the laying of cables. Most people think that the main cost is the cable itself, but in addition to the cable itself, its laying, auxiliary facilities (inspection wells, distribution equipment), etc., are much more expensive than the cable itself. Assuming a 10 kilometer long road as an example, with one LED street light placed every 30 meters on the opposite side, a total of 666 LED street lights are needed. If solar street lights are used, the cost can be recovered within five years and an additional 430000 yuan can be saved. After five years, the annual electricity bill can be saved by 1.22 million yuan.
AC circuit lights and cables are the best targets for theft
This is no longer sensational news. Reports of street light cables being stolen can be seen everywhere online. Only Changfeng Avenue in Wuhan has been in operation since 2005, and more than 36000 meters of cables have been stolen. A total of 1900 kilometers of street light cables have been stolen in Hangzhou, of which 140 kilometers have been stolen. Even the street light cables on the Shanghai Inner Ring Road and the Shanghai Nanjing Expressway have been stolen. Even the street light cables on the Fifth Ring Road in Beijing are often stolen. It can be seen that this kind of thing does not only happen in remote and impoverished areas, but is a common occurrence everywhere. Perhaps it is because the voltage of the street light cable is relatively low, the current is relatively high, the cable is relatively thick, and the copper content is relatively high. This is an important issue that must be considered when choosing AC power supply.
The safety of AC power supply is a hidden danger
In addition to posing a personal safety hazard to thieves who steal cables and appliances, it can also pose a certain safety hazard to nearby farmers digging soil.
AC power supply may also pose safety issues for equipment
AC power operates online, and due to lightning strikes and other reasons, high-voltage surges often occur online, posing a certain threat to the safety of equipment.
Solar LED street lights, on the other hand, do not have the aforementioned drawbacks at all. Their composition is very simple and consists of only five parts:
How can solar LED street lights replace AC LED street lights?
And its installation is very simple, just make a cement base, stand up the lamp pole, and install the foundation screws. Especially, there is no need to trouble the power system personnel to design, install and construct, dig trenches, lay cables, dig inspection wells, install transformers, etc. This is a very important advantage.
Shortcomings of solar street lights
Some people are concerned about the environmental pollution caused by lead-acid batteries. In fact, the largest user of lead-acid batteries is automobiles. Currently, China produces and sells 7 million cars annually, and each car uses at least one lead-acid battery. And lead-acid batteries in cars have long had a very complete recycling system, in which the lead plates will be recycled and regenerated. So the lead-acid battery in the solar street light system can be fully utilized by the car's recycling system without causing environmental pollution. Moreover, the cost of lithium batteries has now been reduced to the point where they can be practically adopted*** A company that produces solar LED street lights (KESC) has developed street lights using lithium iron batteries. There are also factories in Dongguan, China that produce lithium-iron automotive batteries. It can be guaranteed for five years.
The only issue with solar street lights currently is the cost of solar panels, but their prices are currently decreasing at an astonishing rate. In 2008, it had already reduced its price by one-third. The price of its main raw material, polycrystalline silicon, has decreased from $300 per kilogram in 2007 to $200 in 2008. It is expected that the price of polycrystalline silicon will decrease to $100 per kilogram by 2009. Especially in China, the production of polysilicon is growing rapidly. After all 33 ongoing projects are put into operation, the production will reach over 146000 tons, while the current domestic demand is only 8000 tons. Therefore, how to expand domestic demand is the top priority. Vigorously developing solar LED street lights is undoubtedly the best way.
In summary, the use of solar energy in street lights has many advantages but no disadvantages. Why not do it? Do you still doubt whether solar LED street lights have the power to replace AC LED street lights now?