Do you know solar street lights, and what are the traps of solar street lights?

The main components of the LED solar light: solar panel, street lamps, and the battery charge and discharge controllers. Its working principle is that during the daytime, the photovoltaic panel absorbs the radiant energy of solar energy through radiation, generates electromotive force, generates current, and charges the battery through the charge and discharge controller. When its current is less than 6 amperes, the system assumes that the sun has already reached this time. When going down the mountain, the controller will stop charging and start to enter the discharge mode to release the power from the battery to the lamp. At this time, the street lamp head can be lit.

There are several key points in the system design of solar street light. The first is the lumen luminous flux of the lamp and the power of the lamp. The second is the length of time the lights are on every night. Because each place is different, or the owner is different, or the application environment is different, the requirements for the length of lighting and the dimming curve every night are also different. The third is the requirement for the number of consecutive rainy days. The so-called consecutive rainy days means that the rainy days do not charge. To put it simply, it means that you unplug the photovoltaic panel, then the number of days the battery can work at full load when the battery is fully charged. Fourth, it is where to apply, the situation of solar radiation resources in this place, and the best angle of illumination.

Through my analysis, my purpose is to let everyone through this sharing today, let everyone roughly learn how to do the configuration calculation of the solar street light system.

First, the lamp has a power. Suppose it is 30w, the lighting time every day, 100% for 5 hours, 50% for 5 hours. This means that the full power is on for 7.5 hours per day. To support three consecutive rainy days. Here the popular 12.8 volt lithium iron phosphate battery is selected here. First of all, we must calculate the amount of electricity consumed per day. Full power of 30W per day, 7 hours of full power per day, using 30 times 7 hours, means 210 watt-hours per day, in a 12.8 volt system, the capacity of this battery is 16.4 ampere hours. But it must be noted that 12.8 volts, because many now use 3.2V voltage.

We know that 210 watt hours or 12.8 volts and 16.4 amperes of electricity is the daily energy consumption. If you want to continue for two or three days, it means 630 watt hours. Consider the depth of discharge of the lithium battery. Assuming 100 watt-hours are discharged, it is impossible to discharge all 100 watt-hours. It can be discharged at most 90%. Therefore, 90% of the discharge depth should be considered. Since the battery is low-voltage, the power is transmitted to the lamp through the cable, there will be certain loss, line loss, assuming 10% line loss, so, 630w Divide 0.9 by watt hour and divide by 0.9 again. 778 watt-hours were obtained. This capacity is the capacity of the battery that we need when doing this system configuration.

Let's look at the quick calculation of the photovoltaic panel capacity. We have just calculated that if 210 watt hours are consumed per day, there is a condition when calculating the photovoltaic panel capacity, that is, to replenish the power consumption that day, that is to say, the daily power consumption is 16.4 ampere hours. According to the difference in available sunshine time in different regions, assuming available sunshine time, the effective time is four hours. 16.4 ampere hours divided by 4 hours is equal to 4.1 amperes, because photovoltaic panels usually use 17.5 volts in 12 volt systems and 35 volt photovoltaic panels in 24 volt systems. So the 30 watt lamp normally uses a 17.5 volt photovoltaic panel. This is the nominal voltage of the photovoltaic panel. I multiply 4.1 amps by 17.5 volts to get 71.75 watts. At the same time, we must consider sand, dust, shielding, rain and snow. The loss of other factors, the line loss of the photovoltaic panel in the middle of the charging process. To deduct 15% loss, 71.75 watts divided by 0.85 is 84 watts. To meet such a situation, the photovoltaic panel needs to reach 84 watts.

In this calculation, you can see that many parameters are actually variables. Therefore, different calculations should be made according to the actual application situation and needs in various places. Next, let me talk about the lumen output and power of this lamp. The purpose of luminaire application is to illuminate the irradiated subject, and one of the criteria for evaluating luminaires is the luminous flux of the luminaire. That is how much light can be output, the unit of luminous flux is lumens. There are two misunderstandings here. The first misunderstanding is that the larger the luminous flux, the better? No, this is a pseudo-proposition. Because the lamp has a light distribution curve according to different applications, that is, the radiation curve of the lamp light irradiation, or the irradiation angle of the irradiation curve is different. Take the simplest example: tie a flashlight to the pole of a street lamp. Can it be used as a street lamp? Obviously, it ca n’t be done because the width and breadth of the irradiation are not enough. If the flashlight is tied to the roof of your living room Or can the ceiling light be used on the roof of the bedroom? It doesn't work because the breadth and width of his illumination are not enough.

The second question is, is the higher the power the better? This is also a pseudo-proposition. The efficiency of the lamps and lanterns is different. The high-efficiency lamps can achieve 186 lumens, and the low-efficiency lamps can also have 90 lumens. Some owners do n’t understand it and say that I want 30 watts and ask him how many lumens he wants, but he ca n’t tell. Speaking of a case, the courtyard street lights of the community, I have done a project before. In Inner Mongolia, the owner of the property must have 30 watts. I said mine, 30 watts is 6,000 lumens. She said that I would have 30 watts, because we used 30 watts for the last project. Later, after using 30 watts for him, the owner started to complain. The complaint kept on, the lamp was too bright, and shot through their windows and curtains, so that the residents on the first and second floors had poor rest at night. The power is reduced by half. Therefore, whether the larger the luminous flux is, the better the higher power is, it should be calculated according to the actual application and the actual light distribution of the lamp and the actual efficiency of the lamp. There are several points, according to the actual demand for brightness and illuminance uniformity, to meet the needs of luminous flux or lumen, when the luminous flux is satisfied, the smallest power is selected. After meeting the lighting needs, choosing the minimum power of the lamp must be the most energy-saving. If the lighting needs are met and the power or luminous flux is simply talked about, it is almost a hooligan.

Then talk about the lighting time and dimming curve of street lamps. Because the length of night in each place is different throughout the year, and in different places, even in the same season, the length of night is different. The longer the light is turned on, the more energy is consumed. Does it mean that the entire Need to turn on all lights at night? No, assuming that a 30-watt lamp may not need to work 30 watts before entering dusk, it may be enough to work at 20 watts or 15 watts, because the sun is going down at this time In the process, it still has some afterglow. After the sun goes down, the period of time when the traffic flow is relatively large must be fully loaded. In the second half of the night, in some places after **, when the traffic flow is scarce, you can appropriately lower or even turn off the lights.

Earlier talked about the daily power consumption, which affects the capacity of the battery. Another parameter is the number of consecutive rainy days. Solar street lights basically produce very little electricity in continuous rainy days, but its power consumption will not be reduced because of the daily lighting requirements, even worse, rainy days will be more slippery, but instead require lighting effects The requirements will be higher, which means that your power consumption is more.

What determines the number of consecutive rainy days is the size of the battery capacity. The larger the battery capacity, the longer you can support it. How to detect it is very simple. After the battery is fully charged, unplug the photovoltaic panel and keep the lamp on for a long time. Now someone claims to be able to turn on the lights for 365 days. After the battery is fully charged, can the photovoltaic panel be bright for 365 days after being pulled out, but in theory, 365 days can be achieved. There is actually a black technology in it. What is it called automatic power reduction? The charge and discharge controller is responsible for charging and discharging the battery, and can also detect the capacity of the battery. With the advancement of technology, a function is added to the charge and discharge controller to check the capacity of the battery every day, that is, to check the capacity of the battery before discharge, and after the test, to discharge at a rate of 70% or 80%, that is to say, If the capacity of the battery is full, 100 watt-hours, then discharge 100 watt-hours and release according to the watts. With this automatic power reduction function, the new controller will first detect the battery capacity. Assuming that the detection is not enough for 100 watt-hours, only 80 watt-hours, how to discharge, only 8 watt-hours, equal proportion, Make sure that the electricity in the battery is never exhausted. The advantage is that the light is always on, and the disadvantage is that it may not be lit by fireflies.

We often see some demands in the bidding, asking this solar street light to turn on 365 days. This black technology is necessary, this thing is a double-edged sword, because once this function is activated, this lamp can never return to the original factory state, assuming this lamp is a lamp with 1000 watts per hour, in the solar street light system Once the automatic power reduction function is triggered, the lamp can no longer return to the state of 1000 lumens per hour.

Then talk about an optimal radiation angle of solar radiation. Usually the sun must be in the south, rising in the east and setting in the west, so it must be in the south when it is the most dazzling. The angle of solar radiation is determined according to the latitude and longitude. For example, in an equatorial country, the installation angle is actually 90 degrees. The photovoltaic panel is parallel to the ground and 90 degrees perpendicular to the lamp post. The photovoltaic panel faces south in the northern hemisphere and faces north in the southern hemisphere. I once made a joke when I went to Johannesburg that year to watch them install on site. After the installation, I subconsciously said that the direction of your photovoltaic panel is reversed. Colleagues over there smiled to me and said, You are in the southern hemisphere now, I am the northern hemisphere. Therefore, the solar radiation angle is related to the geographic application location.

Basically speaking, we have already mentioned some key parameters or key factors of the solar street light system configuration. Then, let's briefly talk about some common pitfalls.

The first is to only talk about power and not luminous flux. The same is 30 watts, which may be 3000 lumens or 6000 lumens.

The second is to only talk about the luminous flux and not the light distribution curve. Everyone now knows that people in the countryside or those in factories and mines who look at the woods and those who look at the woods use glare flashlights, and those with high glare flashlights can achieve 54,000 lumens. But can this be used as a floodlight? Can it be used to illuminate a stadium? No, because the dimming curve is wrong. Therefore, whether the luminous flux is sufficient is the first factor. The second factor is the light shape. Is the light shape irradiated can be inserted into the surface area that needs to be irradiated?

Third, talk about the length of lighting, only talk about the length of time without dimming curve. Sometimes some manufacturers will give the owner fooling me that this light is on every night and can be on for 12 hours. But he will not tell you how to dim these 12 hours. Every day, this road lighting effect is actually different.

Fourth, it is about the number of consecutive rainy days. He said that the lights can be turned on for 365 days, but he does not tell you this kind of power, which is also a deep hole.

The fifth is the pit of lithium batteries. Since last year, lithium batteries in solar street lighting applications are very popular. But for lithium batteries, the pit is also the deepest. Assume that the nominal is a 12 volt 120 amp battery. If you use lithium iron phosphate, because the single cell of lithium iron phosphate is 3.2 volts, it can be three strings or four strings. If the three strings are only 9.6 volts, 9.6 volts 120 ampere hours is actually only 960 watt hours. It's four strings, 12.8 volts times 100 amps has 1280 watt-hours. This is a quarter of the difference, which means that the cost is a quarter. Because the price of lithium batteries is not calculated in ampere hours, but in watt-hours, but many owners do not know. If you are using a ternary lithium battery, the single cell of the ternary lithium battery is 3.7 volts, usually three strings, 11.1 volts by 100, and only 1110 watt-hours.

In the selection of batteries, the other is the battery recovered by the power car, which reuses the old battery core. This is also a matter that the country is advocating recently, advocating the battery recycling of the power car. But whether this battery can be used or not can only be luck, which means that it has a practical application rate, which depends on the number of battery cycles. If it is used a lot, it may have used 80% of its life, and there is no recycling value. If only 60% is used. Or no more than 60%, then for solar street light applications, there is practical use value. Because the life of all lithium batteries is the number of charge and discharge cycles, here, to share with you a little knowledge, that our mobile phone batteries and laptop batteries are actually lithium batteries. In order to protect the life of this battery, do not charge it to 100% every day, basically unplug it when it is charged to 80%. Then wait for the discharge, and start charging again when it is placed at 30%. This is called shallow charging. Shallow charge and shallow discharge, the life of the battery can be used for many cycles, if deep charge and deep discharge, it will die quickly, taking lithium iron phosphate as an example.

In lithium iron phosphate batteries, the life of deep charge and deep discharge is actually only 800 to 1200 times. If it is shallow charge and shallow discharge, it can be done at least 2000 times.

 According to different manufacturers or different battery cells, the number of cycles will vary.

Sixth, the worst thing I have done now is the solar photovoltaic panels. How did the photovoltaic panels come from? The photovoltaic panels are mainly made of photovoltaic power plants used as power plant chips. But these chips will have a defect rate, what is the defect rate? 10%, where did these 10% defective products go, and they all flow out to make small components, that is, the photovoltaic panels we usually see on these solar street lights And sometimes I see some backpacks with a photovoltaic panel lens or the small yellow car that is more popular now. Worship, there will be a photovoltaic panel on these shared bicycles. These photovoltaic panels are actually outflows from large factories. The product. You said there are good photovoltaic panels in solar street lights, yes. But the price is completely different, you must choose the original factory, as long as not all original products are defective products.

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