How to design and calculate Solar Street Light system?
Jul 07, 2021
As a new energy street lamp, solar street lamps have been widely used all over the world. However, there are various street lamps on the market with different wattages. When consumers buy solar street lights, they often have such questions: How many wattage solar panels should I equip to ensure the working time and brightness of the street lights? This article will tell you the answer.
Question: How to design and calculate a Solar Street Light system?
This problem is essentially a balance between the power consumption of LED lights and the power generation of solar panels. Therefore, we must first learn to calculate the power consumption of LED lights.
Taking a 30W lamp working for 6 hours as an example, we assume that its brightness is 100% for the first three hours and 50% for the next three hours. Then, its power consumption is 30*(3*100%+3*50%)=135WH
If your lamp is 100W, and its brightness is 100% for 12 hours, then its power consumption is 100*12*100%=1.2KWH
And so on. (It should be noted that if a solar panel provides power to two LED lights at the same time, the sum of the power consumption of the two LED lights needs to be calculated.)
Through the calculation of power consumption, it is not difficult to find that: when you choose a solar street light, you must first understand your lighting needs. In other words, what wattage LED lights do you want to buy? How long do you need it to light each day? Does the LED light need to maintain 100% brightness continuously during the lighting period, or is the brightness different at different times?
After figuring out the basic question, let's look at the original question: How much power should I equip my street lights with solar panels? (Take the above 30W LED lamp as an example again. We have just calculated that its power consumption is 135WH.)
Now we start calculating:
1 Step 1: Calculate the current.
Our battery is usually 12V, when the power of the LED is 30W (that is, the power consumption is 135WH), the corresponding current is: 135WH/12V=11.25Ah
2 Step 2: Calculate the battery capacity requirement.
Continuing to take the 30W LED lamp working for 6 hours as an example, when the customer’s demand is to ensure that it can be illuminated for 3 consecutive rainy days, then plus the lighting demand of the previous night, the battery capacity must reach 4 days.
The battery capacity at this time is: 11.25Ah*4 days=45Ah
In order to prevent the battery from over-charging and over-discharging, the general battery capacity needs to be 20% higher than the actual demand. In other words, when our actual demand for capacity is 45Ah, we should at least equip a battery with a capacity of 45*(1+20%)=54Ah.
3 Step 3: Calculate the required power of the solar panel.
Before calculating power, we need to understand 3 concepts.
The power generation of solar panels. It needs to increase by about 30% on the basis of electricity consumption.
Average effective lighting time. Generally speaking, the effective light time is 4-5 hours, and the specific conditions are different in different parts of the world.
Power generation efficiency. The power generation efficiency of solar panels is generally 70%-80%. This efficiency is related to the material and quality of the solar panel. We calculate according to 75%.
The basic formula is: Power generation of solar panels = power *average effective light time * power generation efficiency.
In other words, power = required power consumption / (lighting time * power generation efficiency)
Substituting the numbers: power=(135WH*130%)/(4.5H*75%)=52W
To sum up, you need a solar panel with a power greater than 52W, and the corresponding battery capacity must be greater than 54Ah.
