Research On Complementary Control Of Solar Energy And City Electricity Driven By LED Street Lights

- Dec 28, 2019-

Photoelectric complementary LED street lamp lighting system is a street lamp lighting system mainly based on solar cell power generation and supplemented by ordinary 220V AC power. Using this system, the capacity of photovoltaic battery packs and batteries can be designed to be smaller, basically there is sunshine during the day. On the same day, the battery was charged with solar power at the same time. When it was dark, the battery was discharged to light up the load LED. In most parts of our country, there are basically more than two-thirds of sunny weather throughout the year. In this way, the system will have more than two-thirds of the year illuminate the street lights with solar energy, and the remaining time will be replenished with city electricity. It reduces the one-time investment of solar photovoltaic lighting system and has significant energy saving and emission reduction effects. It is an effective method for the promotion and popularization of solar LED street lighting at this stage.


1 photoelectric complementary LED lighting system design


1.1 LED lighting load


It is assumed that the height of the pole of the photoelectric complementary LED street lamp is 10m, and the light flux is about 25lm. The 1W, 3.3V, 350mA LED lights are selected to form two street lights, each of which is 14 strings 2 and 28W in total, and the two are 56W. It is assumed that the street lights are illuminated for an average of 10 hours a day, and the LED street lights are fully lit in the first 5 hours, and the brightness is halved in the next 5 hours, that is, the battery consumption is reduced by half.


The actual drive current required is:


350mA × 2 × 2 = 1.4A


Calculated in 10 hours per day, the number of ampere hours required for the load is:


1.4A × 5h + 1.4A × 0.5 × 5h = 10.5Ah


The voltage is:


3.3V × 14 = 46.2V


1.2 Battery pack capacity design


1.2.1 Selection of battery


As the battery for solar street lamps is frequently in the charging and discharging cycle, and overcharge or deep discharge often occurs, the working performance and cycle life of the battery have become the most concerned issues. Valve-regulated sealed lead-acid batteries have the advantages of no maintenance, no discharge of hydrogen and acid mist into the air, good safety, and low price, so they are widely used. Battery overcharging, overdischarging, and battery ambient temperature are all important factors affecting battery life, so protective measures must be taken in the controller.


1.2.2 Calculation of battery pack capacity


In the photoelectric complementary street lamp system, solar street and city power are complementary to power LED street lamps. Because the sunlight varies greatly with the weather, when the sunlight is strong during the day, the solar panel charges the battery; at night the battery supplies power to the load. On a cloudy day, the load uses electricity from the battery. When the battery discharge voltage drops to the minimum allowable limit, it automatically switches to the mains supply. The capacity of the battery is important to ensure reliable power supply. Too large a battery capacity leads to an increase in cost and price, and a too small capacity cannot fully utilize solar energy to achieve the purpose of energy saving.


Calculation formula of battery capacity Bc:


Bc = A × QL × NL × T0 / CCAh (1)


In formula (1), A is the safety factor, which is between 1.1 and 1.4, and this formula is A = 1.2; QL is the average daily power consumption of the load, which is the working current multiplied by the daily working hours, and QL = 10.5Ah; NL is the maximum The number of long continuous rainy days can be taken as NL = 1 day due to the use of photoelectric complementary; T0 is the temperature correction coefficient, which is generally 1.1 above 0 ° C, 1.2 below -10 ° C, and T0 = 1.1 in this formula; Depth, generally 0.75 for lead-acid batteries, 0.8 for alkaline nickel-cadmium batteries, CC = 0.75 in this formula.


Therefore, Bc = A × QL × NL × T0 / CC = 1.2 × 10.5 × 1 × 1.1 / 0.75 = 18.5Ah. In actual design, we choose 48V, 40Ah maintenance-free valve-controlled sealed lead-acid batteries.