Solar channel light system design method - Power Circuit - Circuit Diagram

Abstract: Solar energy has the advantages of energy saving, environmental protection and convenience. Through the design of a reasonable solar channel light system, it not only solves the problem that the channel does not have the power to light during the day, but also saves energy.

Keywords: solar energy, photoelectric conversion, channel light, solar panel, controller, battery, inverter

Foreword

The sun is a huge, long-lasting, endless source of energy. Solar energy is both primary energy and renewable energy. It is rich in resources, can be used free of charge, without transportation, has no pollution to the environment, and has the advantages of energy saving, environmental protection and convenience.

According to the amount of solar radiation received, China can be roughly divided into five categories. Shenzhen is located in the subtropical zone. The climate is warm in winter and hot in summer. It belongs to three types of areas. The annual sunshine hours are 2200-3000 hours, which has favorable natural conditions for using solar energy.

Direct solar energy applications include photothermal conversion, photoelectric conversion, and photochemical conversion, and the types of indirect and comprehensive utilization are more numerous. Photoelectric conversion mainly includes solar panels and solar power supply systems; photothermal conversion mainly includes water heaters, water heaters, solar cookers, dryers, etc.; photochemical conversion is mainly applied to photosynthesis and photoelectrochemistry, and is still in the experimental research stage.

First, the introduction of solar channel light system

1, solar channel light system installation background

Shenzhen has many overpasses with a length of more than 40 meters. Due to insufficient lighting, these passages appear dark during the day, especially when the street lights are turned on and after more than one hour and rainy days after the lights are turned off, the passages are darker. For the safety of the citizens, the passage must be illuminated 24 hours. However, the original channel light connection lamp power can only be lit at night. If the mains supply is used to light the daylight, it is necessary to re-lay the line, the investment is large, and the construction is difficult; the solar photovoltaic system is used for small power supply and the construction is convenient.

On the other hand, in recent years, Shenzhen's power supply has been tight, and the government has advocated saving electricity. Therefore, it is necessary to install a solar channel light system.

2, channel situation

The following is an example of the channel on the south side of the Honghu Interchange to discuss the composition of the system.
The south channel of the Honghu Interchange is 40 meters long and 6 meters wide. The distance from the passage to the installation of solar installations is about 15 meters. The original three sets of 250W high-pressure sodium lamps have power supply at night.

3, system principle

Photoelectric conversion of solar energy refers to the process by which the radiant energy of the sun is converted into electrical energy through a semiconductor material, commonly referred to as the "photovoltaic effect."
The principle of the solar channel light system is shown in Figure 1. The main components include solar cell arrays, controllers, batteries, inverters, and lamps.

Figure 1 Schematic diagram of solar channel light system

The original channel lamp has a total power of 750W. The solar cell power and battery capacity required for power supply by solar energy are large, the system cost is high, and a set of lamps is always on for 24 hours*365 days, and the lamp life will be reduced. Therefore, in order to ensure a stable lighting effect, a solar channel light system is additionally installed. When the mains supply is powered at night, the original channel lights are on; when the mains fails or during the daytime, the solar-powered channel lights are illuminated to ensure that the channels are always on.

Second, DC / AC load comparison and selection

If the DC load is selected, the intermediate part of the inverter can be omitted to improve energy efficiency. However, since the channel length is 40 meters, the battery to the end lamp is about 40+15+5=60 meters, and the 24V DC voltage line loss is as high as 10%. In addition, the DC low voltage and large current control loss is large, and the lifting voltage technology is more complicated. Low light efficiency (45Lm/W), short life (5000 hours), difficulty in purchasing, etc.

In contrast, although the AC load utilization rate is slightly lower, the inverter conversion efficiency is >90%, the loss is not large, and the AC load is more practical and convenient, so the AC load is selected.

Third, the choice of light source and lighting arrangement

Through the comprehensive comparison of light source efficacy, life, price and versatility, 5*25W high-efficiency energy-saving lamps are selected. The lighting fixtures are arranged as follows:

Figure 2 Lighting arrangement

Fourth, solar panels

Solar panels are the main components of solar photovoltaic conversion. The peak power Pk of the solar cell module is determined by the local average solar radiation intensity and the end of the electrical load (required power).

1. Peak power selection (estimation formula):

Pk=lamp power×number of lamps×daily use time÷day effective sunshine time÷solar battery array actual use power coefficient÷battery conversion efficiency÷inverter efficiency Pk=25(W)×5(set)×12(H )÷5(H)÷0.7÷0.85÷0.9=560.22W

among them:

1) Since the lighting time of the mains channel lights is adjusted by the theodolites with the seasons, the solar channel lights are turned on for 11 to 14 hours per day for 12 hours.
2) The actual power factor of the solar cell array takes into account the charging efficiency of the solar panel and the loss during charging, taking 0.7.
Therefore, the solar panel power is chosen to be 600W (75W × 8pcs)

3, the installation tilt angle is 33 ~ 35 degrees, the direction is south, not only easy to fully absorb solar energy, but also use the rain to self-clean the solar panels.

Five, the controller

The controller uses a PWM pulse width modulation controller. Has the following features:
1. Overcharge protection: When the battery voltage exceeds 28V, stop charging;
2. Over-discharge protection: When the battery voltage is lower than 22V, the load is cut off;
3. Battery charging temperature compensation;
4. Positive pole reverse connection protection;
5, short circuit protection;
6, overload protection;
7, overheat protection (with heat sink);
8, lightning protection;
9, small power AC supplementary charging system: When the rainy days, solar energy is insufficient, the battery voltage is lower than DC 22V, in the evening through the high-frequency rectifier switch AC 220V mains into DC 24V, the battery is recharged;
10. Detecting mains and switching: When there is mains power at night, the mains channel lights up and the controller turns off the solar channel lights; when the mains fails or during the day, the controller detects that there is no mains signal and turns on the solar channel. light. This ensures that the channel is illuminated for 24 hours than when the control switch is installed.