Talking about the advantages of solar LED street lights compared to AC LED street lights?
1. Changing all street lights to solar street lights can save the power generation of a Three Gorges Hydropower Station
LED street lamps are more energy-efficient than high-pressure sodium lamps, and people have long known it. However, some quantitative concepts may still be lacking. It is now recognized that a 100-watt LED street lamp can replace a 250-watt high-pressure sodium lamp, so it can be simply considered that each LED street lamp can save 150 watts of electricity.
However, if it is changed to solar power, then even the 100W of electricity can be saved, that is to say, each street lamp can save 250W of electricity. According to estimates by relevant parties, the total number of existing street lights in China is about 100 million, and it is growing at an annual rate of 20%. In 2008, 20 million street lights were added. If these 100 million street lamps can be converted into 60 million 250-watt street lamps, and if all these 60 million street lamps are changed to solar LED street lamps, a total of 15 million kilowatts of power can be saved. Assuming that each street lamp works 12 hours a day, 65.7 billion kilowatt-hours of electricity will be saved in one year. The total power generation of the Three Gorges Hydropower Station in 2007 was 61.603 billion kWh. Therefore, the electricity saved by changing all the street lights across the country to solar street lights will exceed the annual power generation capacity of a Three Gorges hydropower station. This is an extremely alarming number.
Not only that, solar energy is a clean and renewable energy source, which not only saves electricity, but also reduces carbon dioxide emissions. Each 250-watt high-pressure sodium lamp will produce 1,290 kilograms of carbon dioxide within a year, so after all 60 million street lamps are converted to solar street lamps, 77.4 million tons of carbon dioxide will be reduced. So after changing to solar energy, not only the electricity bill is saved, but also the cost of carbon dioxide reduction. The reduction cost per ton of carbon dioxide is US$345-404. Reducing 77.4 million tons of carbon dioxide is equivalent to saving US$31 billion in carbon dioxide reduction costs!
The previous figures are just a comparison between LED street lights and high-pressure sodium lights. For the same 100W LED street lamp, the energy saving comparison between using AC power and using solar energy can be obtained by dividing the above data by 2.5. In other words, 60 million 100-watt LED street lights, if all powered by solar energy, can save 26.28 billion kWh of electricity compared to when all AC power is used, and the cost of carbon dioxide emission reduction is 12.4 billion US dollars.
2. The efficiency of AC power supply will be 15% lower than that of solar power supply.
Because when using AC power supply, a switching power supply must be used to convert it to DC. Generally, the efficiency of a switching power supply is about 80%. Therefore, for a 100W LED street light, the AC input power needs about 120W (120W is used in the comparison table below). When using solar power as long as DC/DC constant current source is used, the efficiency is as high as 95%. Therefore, the total efficiency of using alternating current after adding up is about 15% lower. So the above figures should also increase by 15%.
3. AC power supply also has power factor problems.
Power factor compensation is not used in relatively low-end switching power supplies. After a large number of them are used, the overall efficiency of the power grid will be reduced.
4. The main problem of using AC power supply is to reduce the life of the entire lamp
Because alternating current must be rectified and filtered to become direct current, electrolytic capacitors must be used for filtering in all switching power supplies. It is well known that the life of electrolytic capacitors is very low. The life of general electrolytic capacitors is only 1000 hours, and the life of long-life electrolytic capacitors is only 10,000 hours. Moreover, every time the ambient temperature rises by 10 degrees, the life span is reduced by half. In the high-power LED street lamp, the temperature rise is very high, so the life of the electrolytic capacitor is shorter. Generally, the life expectancy of LED street lights is more than 50,000 hours. The life of the entire lamp will inevitably be dragged down by the short life of the electrolytic capacitor. It can be considered that in the past, many low-quality LED street lights quickly failed. In addition to the failure to deal with the heat dissipation problem of the LED itself, the light decay was accelerated, and the failure of the electrolytic capacitor in the AC power supply was also an important factor. There is no electrolytic capacitor in the solar-powered system. Therefore, the life of the constant current source can be guaranteed to match the life of the LED.
5. The overall cost of solar-powered LED street lights is much lower than that of AC-powered LED street lights.
Although the initial installation cost of solar street lights is high, the cost of laying cables and long-term electricity bills for AC power supply are much higher than those of solar systems.
