Preliminary Study on the Design Scheme of Solar LED Garden Light

Preliminary Study on the Design Scheme of Solar LED Garden Light

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u003cbru003e Solar LED garden lights are composed of the following parts: solar panels, solar controllers, battery packs, LED light sources, light poles and lamp housings. Because the load uses direct current, no inverter is required. Assuming that the 15W solar LED garden light illuminates for 10 hours every night, it can ensure continuous rainy and cloudy lighting for 3 days. The power system and capacity design steps are as follows:

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u003cbru003e  1. The power and working time of the load are the prerequisites for the selection of solar cell components and battery capacity 

u003cbru003e  15W solar LED garden light for 10 hours per night, the average daily load power consumption is 15W×10hu003d150Wh. 

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u003cbru003e  2. Calculation of solar cell module power 

u003cbru003e  Solar panels are the core part of solar street lights, and they are also the most valuable part of solar street lights. Its function is to convert the sun's radiant power into electric energy, or send it to a battery for storage. 

u003cbru003e  Solar battery power can be calculated by the following simple formula:  

u003cbru003e  Solar cell module power u003d electrical appliance power×electricity time local peak sunshine time×loss factor 

u003cbru003e  The loss factor can be 1.6-2.0, here is 1.6; the local peak sunshine time is 4 hours according to the geographic location of Shandong. 

u003cbru003e  Then: 15W solar LED garden light solar cell module poweru003d15W×10h4h×1.6u003d60Wp 

u003cbru003e  So, choose the battery pack with peak power of 60Wp. 

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u003cbru003e  3. Determine the number of solar cell modules in series and the voltage of the battery according to the operating voltage level of the system 

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u003cbru003e   General selection principles of system working voltage: household system is 12VDC or 24VDC; communication system is 48VDC; power system is 110VDC; large power station is 220VDC or higher. 

u003cbru003e  Here the 15W LED solar light is a low-power electrical appliance. The operating voltage of the system can be 12VDC, and the number of solar cell modules in series is 1, so that the peak voltage of the solar panel is 17V, which is just for charging the 12V battery. 

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u003cbru003e  4. Calculate the required battery capacity 

u003cbru003e  Because the input energy of the solar photovoltaic power generation system is extremely unstable, it is generally necessary to configure a battery system to work. Generally, there are lead-acid batteries, Ni-Cd batteries, and Ni-H batteries. The selection of battery capacity generally follows the following principles: First, on the premise that it can meet the lighting at night, store the energy of the solar cell components during the day as much as possible, and at the same time, it must be able to store the electrical energy that can meet the lighting needs of continuous rainy days at night. The battery capacity is too small to meet the needs of night lighting. The battery is too large. On the one hand, the battery is always in a state of power loss, which affects the battery life and causes waste. The battery should match the solar battery and the electric load (street lamp). 

u003cbru003e  Battery capacity u003d electrical appliance power × power time system voltage × number of rainy days × system safety factor 

u003cbru003e  The system safety factor is generally selected as 1.4-1.8, here is 1.4, then  

u003cbru003e  15W solar LED garden light battery capacityu003d15W×10h12V×3×1.4u003d52.5AhAh 

u003cbru003e  So choose a 12V, 50Ah lead-acid battery.

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u003cbru003e  5. Selection of solar controller 

u003cbru003e  Regardless of the size of solar lamps, a good performance charge and discharge controller is essential. The following functions are required:

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u003cbru003e  (1) High voltage (HVD) disconnection and recovery function: The controller shall have the function of inputting high voltage disconnection and recovery connection. 

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u003cbru003e   (2) Undervoltage (LVG) alarm and recovery function: When the battery voltage drops to the undervoltage alarm point, the controller should automatically send out an audible and visual alarm signal.

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u003cbru003e  (3) Low voltage (LVD) disconnection and recovery function: This function can prevent the battery from over-discharging. The load is connected through a relay or electronic switch, which can automatically cut off the load at a given low voltage point. When the voltage rises to the safe operating range, the load will automatically reconnect or require manual reconnection.

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u003cbru003e  (4) Protection function: ①Circuit protection to prevent any load short circuit; ②Circuit protection to prevent internal short circuit of the charge controller; ③Prevent reverse discharge protection of the battery at night through solar cell components; ④Prevent load, solar cell components or Circuit protection for battery polarity reversed connection; ⑤ Protection against breakdown caused by lightning strikes in mine areas.

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u003cbru003e  (5) Temperature compensation function: When the battery temperature is lower than 25℃, the battery should require a higher charging voltage to complete the charging process. On the contrary, the battery requires a lower charging voltage above this temperature. Usually the temperature compensation coefficient of lead-acid batteries is -5mv/oC/CELL.

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u003cbru003e  LED light source, long life, up to 1000000 hours, low working voltage, no inverter, high light efficiency, domestically made 50Lm/w, imported 80Lm/w. As technology advances, the performance of LEDs will further improve, and LEDs will be a trend as the light source of solar street lights.