With the continuous development of technology in our country, the application scope of solar photovoltaic power generation technology in the lighting field is becoming increasingly broad. At present, many countries around the world are still exploring the application of solar photovoltaic power generation technology. In order to maximize the role of solar energy technology, China needs to learn from the relevant experience of developed countries in utilizing solar energy, in order to promote the development of China’s solar photovoltaic power generation technology.
1. Overview of solar photovoltaic power generation
The so-called solar photovoltaic power generation is based on the photovoltaic effect, using solar panels to convert solar energy into electricity. The core component in solar photovoltaic power generation is solar cells, and commonly used types of cells include amorphous silicon, monocrystalline silicon, polycrystalline silicon, and thin film cells. In practical applications, polycrystalline silicon and monocrystalline silicon batteries are the most widely used, while amorphous silicon batteries are mainly used in calculator auxiliary power supplies and small system power supplies. The total efficiency of crystalline silicon batteries produced in our country is 25%, which is on the same level as the usage efficiency of similar foreign products. A solar panel composed of several or individual solar cells belongs to a photovoltaic module. In municipal road photovoltaic power generation systems, it is usually composed of controllers, batteries, solar panels, and inverters. The above components are all composed of electronic components and have no relation to the mechanical parts. Therefore, solar photovoltaic power generation equipment is relatively simple, with low requirements for installation and maintenance, and has characteristics such as long service life, high stability, and sustainability. Through the control of the controller, when the sun appears during the day, the solar panel receives solar energy and stores the generated electricity in the battery. When night falls and solar panels are unable to produce electricity, the battery will use an inverter device to continuously supply power to the lighting system. This cycle can not only solve municipal lighting work, but also effectively reduce lighting costs.
2. Application of solar photovoltaic power generation in municipal lighting
2.1 Components of solar photovoltaic power generation in municipal lighting
2.1.1 Battery
In solar photovoltaic power generation, batteries with the function of storing electrical energy are one of the main components and play an important role in solar photovoltaic power generation. Batteries can store a large amount of electrical energy and can operate continuously for a long time. Their characteristics are low pollution and high work efficiency. When selecting batteries for municipal lighting, it is necessary to consider the local climate conditions and scientifically choose the capacity of the batteries. If the sunshine time is short and rainy days are prone to occur, large capacity batteries must be used. On the contrary, ordinary batteries are sufficient to prevent resource waste.
2.1.2 Inverter
The main function of a rectifier circuit is to connect AC batteries into DC power, while an inverter, on the other hand, can convert DC power into AC power. This method of reversing the conversion process of electrical energy belongs to inversion. The solar cells used in solar photovoltaic power generation systems can generate direct current by receiving sunlight. However, the use of direct current power supply in power supply systems is rare and has certain limitations. In addition, when the power supply system increases or decreases the voltage, only the transformer needs to be added to the AC system. From the perspective of a DC system, the technology used to increase or decrease voltage is complex and requires high demands from personnel. From the perspective of photovoltaic power generation systems, there are extremely high requirements for inverters, which require inverters to have high stability and inverter quality, ensuring that the voltage generated when inputting DC power has a wide range of applications. Therefore, when using solar photovoltaic power generation in municipal lighting, the inverter should be selected reasonably to ensure that it can meet the application requirements.
2.1.3 Solar cells
In solar photovoltaic power generation systems, solar cells belong to the core part, and the basic unit of conversion between electrical energy and light energy belongs to each individual cell in the solar cell. Currently, the commonly used size specifications are 166 (i.e. 166 mm) × 166 mm and 182 mm (i.e. 182 mm) × 182 mm, the working voltage is usually 0.5-0.6 V, and the working current is basically 10-13 A. Normally, the individual cells in a solar cell cannot be used independently. Solar modules refer to the parallel or series connection of individual solar cells, which are then packaged together. The power range of the modules is between a few watts and a few hundred watts, and they can be used separately. However, when installing components in parallel or series, a square array can be formed, and the output power generated at this time can meet the power requirements of the load. Therefore, when selecting solar cells, it is necessary to make a reasonable selection based on the specific electrical requirements of the design drawings, in order to ensure that the output power can meet the requirements of the load.
2.1.4 Controller
To effectively solve the impact of charging and discharging during the operation of batteries, ensure that the batteries used can play their own role and have a long service life, and prevent the problem of excessive discharge and charging of batteries, a controller with control functions for charging and discharging should be added. The basic working principle of the controller is to detect the actual charge or voltage state of the battery, analyze whether it has reached the critical point of charging and discharging, and then issue commands to the battery in the solar photovoltaic power generation system based on the detection results, in order to ensure the service life of the battery and delay its damage speed.
2.2 Cable laying for solar photovoltaic power generation in municipal lighting
There are two commonly used methods for cable laying of solar photovoltaic power generation in municipal lighting: the first is to lay the cable in the planned dedicated channel. The second method is to lay cables and other public pipelines together in the same trench. Regardless of the laying method used, it has the following characteristics:
(1) Can use a corridor together with other equipment to reduce the difficulty of excavation work.
(2) Can be applied in projects where pipeline laying engineering cannot be used.
(3) Can lay several different cables together.
(4) The cable situation is quite complex.
(5) Helps reduce the difficulty of replacing cables in the future.
When excavating the channels required for laying solar cables, in addition to being able to excavate on the ground, excavation can also be carried out underground. If there are many building obstacles when excavating the trench on the ground, underground excavation should be given priority in constructing the trench.
2.3 Advantages and disadvantages of applying solar photovoltaic power generation in municipal lighting
2.3.1 Advantages of applying solar photovoltaic power generation in municipal lighting
The application of solar photovoltaic power generation technology in municipal lighting can not only save energy and improve the safety of electricity resource utilization, but also shorten the distance of cable laying. At present, solar energy is basically converted into usable energy in two ways: the first is to convert the energy produced by solar energy
The generated radiation is converted into thermal energy; The second method is to convert sunlight into electricity, but it requires the use of optoelectronic devices, namely photovoltaic power generation. From the current municipal lighting situation, the solar power generation used is photovoltaic technology. This technology uses equipment that converts light energy into electricity, installs semiconductors in the system, and directly converts solar energy into electricity based on the relevant principles of the photovoltaic effect. In municipal lighting, the advantages of using solar photovoltaic power generation include the following two points.
(1) The characteristics of solar energy are infinite and distributed, and it belongs to renewable resources. When applying this resource in practice, there is no need to worry about energy depletion. On Earth, apart from the visible sunlight at night, the biggest difference is that the intensity of sunlight produced by different regions and climates varies to a certain extent, but it does not disappear due to factors such as climate and region.
(2) The power generation principle applied in solar photovoltaic power generation is relatively direct. The power generation principle of this technology is to directly convert electrons and photons without any intermediate processes or related device movements. The intermediate process here is to convert thermal energy into mechanical energy, and then convert mechanical energy into electromagnetic energy. Therefore, the form of solar photovoltaic power generation is relatively fast, and compared with traditional power generation technologies, it has higher quality and is more environmentally friendly.
2.3.2 Shortcomings in the application of solar photovoltaic power generation in municipal lighting
Firstly, among all electric energy sources, the single construction cost of using solar energy for power generation is relatively high, which can easily increase the cost of lighting engineering. Secondly, in municipal lighting systems, such as solar street lights, batteries are used as safety hazards such as battery explosion, and the cost of energy storage media is relatively high. Finally, municipal lighting is a functional lighting that requires high reliability and requires stable and safe lighting equipment for vehicles and pedestrians. However, the energy in solar cells comes from solar energy, which cannot generate enough electricity on cloudy and rainy days. The lighting system can only use the remaining energy in the battery to generate electricity. In specific applications, it is necessary to continuously increase the battery capacity and expand solar modules, Ensure that the system can collect and store electricity that can be used for two or even more days within 1 day. However, the changes in weather are unpredictable, and municipal lighting should fully consider the battery capacity matching and photovoltaic module power matching required to meet the lighting electricity demand in the event of prolonged cloudy and rainy weather.
3. Application cases of solar photovoltaic power generation in municipal lighting
This article takes a municipal lighting project as an example to explore the effectiveness of applying solar photovoltaic power generation.
The municipal lighting project uses ordinary municipal lighting fixtures in the pedestrian walkway. Practice has shown that the walkway has good lighting effects at night, but there are still some problems in designing the power distribution of the circuit. In this design case, the street light cables were not laid separately, but were connected to the surrounding street lights, resulting in the street lights in the pedestrian walkway only being able to provide illumination at night and unable to provide illumination during the day. When encountering cloudy, rainy or snowy days, the lighting effect of street lights in the passage is relatively poor, especially in the middle part of the passage, where visibility is very low at night, which cannot ensure the safety of pedestrians on this section of the road. Therefore, the local government has designed several remedial plans for this, but most of them have the problem of high installation costs, and some plans may even affect local transportation. Through multiple comparisons, solar power generation was ultimately used to solve the lighting problem in the pedestrian walkway.
Firstly, the government installs 7 sets of 15 watt solar lamps in the pedestrian walkway to enhance visibility in the middle section of the walkway, effectively meeting people’s needs during use. The pedestrian passage in this case has a length of 100 meters, a width of 5 meters, and an overall height of 2.7 meters. The middle section of the passage is not equipped with a light harvesting port. When installing the required solar street lights, install a set of energy-saving lights every 10 meters in this channel. The power source of the energy-saving lamp is the solar panel outside the channel. The original designer planned to use a 15 V DC power supply, but due to channel length issues, it was easy to generate large voltages in the cable lines. Eventually, an inverter was used to convert the 15 V DC power supply to a 250 V AC power supply for the street lights. The solar street lights installed in the channel are only used for daytime lighting, and at night lighting is connected to the surrounding street lights. The average lighting time of the solar street lights installed is 12 hours, which can effectively solve the problem of insufficient power supply due to the small capacity of solar cells. In the morning, turn on the solar street lights in the channel. After the solar battery receives the power signal transmitted from the controller, it will provide electricity to the street lights. The overall response time of the solar battery is fast, and once started, it can directly supply power until night. At 7 pm, the charging and discharging controller sends a signal to stop the power supply to the solar battery, and then it will respond accordingly by stopping the power supply to the street lights. The solar street lights in the channel can use the municipal street light power supply to illuminate pedestrians. This power supply method that combines solar photovoltaic power generation systems with municipal power supply systems can achieve the effect of interactive power supply between municipal cables and solar batteries, ensuring 24-hour lighting for pedestrian walkways. In addition, in order to prevent sudden power outages of municipal cables, the solar battery used in the specific design can continuously supply power to the street lights in this channel for 3 days after the cable power outage, ensuring that the lighting of the street lights in the channel can meet people’s needs. Moreover, this scheme can use municipal cables to continuously supply power to the street lights in this channel when the solar photovoltaic power generation system is unable to supply power to municipal roads during continuous cloudy and rainy days, ensuring that people can also obtain a good lighting environment while driving in this channel. The solar street lights used in pedestrian walkways cannot maximize their effectiveness when there is sufficient sunlight, but they can effectively improve their visibility in the evening and early morning, creating good travel conditions for citizens.
4. Conclusion
In summary, the use of solar photovoltaic power generation in municipal lighting can effectively reduce lighting costs, and at the same time, it can solve the problem of inability to supply power when municipal cables are cut off, ensuring that municipal lighting has extremely high stability and safety, and bringing a good living experience to citizens. Based on the development of science and technology in our country and the demand for green energy, the scope of solar photovoltaic power generation will become increasingly widespread for a long time in the future. Practice has continuously proven that the application of solar photovoltaic power generation technology can effectively save energy resources and achieve low-carbon and energy-saving effects.