The function characteristics and application of solar street lamp

1.Functional characteristics of solar street lamps  

Urban road lighting is closely related to people’s production and life.  With the development of urbanization, green, high efficiency, environmental protection, longevity LED street lamp has gradually entered people’s production and life.  The biggest advantage of solar road lights is that they can be easily installed on urban roads, squares, parks, parking lots and expressways without the need to erect power lines, dig trenches or lay cables.  Compared with the traditional lighting, the ultra-high brightness LED lighting source is small in size, light in weight, good in direction, can withstand all kinds of bad weather conditions, in power consumption, service life and environmental protection and other aspects of the incomparable advantages of other light sources, coupled with the energy saving efficiency of solar lamps and easy installation and maintenance, will lead us into a new era of green lighting.  Solar street lamps are composed of solar panels, batteries, high-brightness lamps, controllers and other components. During normal operation, there are very few moving parts and basically no noise.  The control circuit in the solar street lamp controller, its function is basically the same as that of the ordinary street lamp controller, which is to complete the operation of the dark light and the light out at dawn. The difference is that there is a charge and discharge management of the battery.  There are three kinds of street lamp controllers commonly used at home and abroad: single light controller, clock controller and warp and weft controller. Their working principles are different, and each has advantages and disadvantages.

1.1 Separate light controller  

A separate light controller uses a photosensitive probe, which automatically opens the street lamp when the dark light is weak.  In the east of the morning, the street lamp can be automatically turned off to achieve automatic control.  The early light switches used separate semiconductor components, the circuit is complex, and the failure rate is high;  With the development of semiconductor technology, the emergence of time based integrated circuit, which simplifies the optical switch circuit, photosensitive probe is the key component of the optical switch.  

1.2 Clock controller  

The controller should set the switch time in advance, so that the street light on time, on time off, so as to achieve the purpose of automatic control, save electricity.  Its advantage is the pre-set switch by the outside light interference, in addition to the fault itself, will not produce wrong action, the disadvantage is not according to the seasonal changes and special weather conditions automatically change the switch time, need to set someone to adjust the switch time, such as: winter and spring dark earlier, dawn later;  Summer and autumn dawn earlier, dark later;  After midnight, there are fewer vehicles and pedestrians on the road, so the number of lights should be properly reduced and then lit up before dawn to facilitate traffic safety and electricity saving.  The timing switch in the clock controller can be divided into two types: mechanical clock type and electronic clock type. The former is mainly quartz clock, accurate time, but because the plastic gear used in the movement will be deformed at high temperature, resulting in inaccurate time and even shutdown;  The timing switch of the latter is commonly used in the electronic clock circuit centered on the integrated block such as LR6818 and LM8650. In recent years, there is also an integrated block that integrates the electronic clock circuit board and LED liquid crystal display, which can set six groups of switching points and has the function of week. Many component manufacturers compete to produce this product, which is now mostly used in the street lamp controller.  

1.3 Warp and weft type controller  

The weft and longitude controller adopts single-chip microcomputer technology to simulate the sunshine law, which can automatically turn on the light when it is dark and automatically turn off the light in the morning.  It adopts the advantages of the light switch control time, overcomes the disadvantages of the light switch by external interference, absorbs the advantages of the clock controller time accuracy, avoids the timing switch will not automatically change the switch time shortage.  At present, many large and medium-sized city street lights are mostly used in this way of control, the disadvantage is the high price.  

2.Function characteristics and application of solar street lightcomponents  

In the development of new energy, domestic and foreign unanimously recognized the highest technology content, the most promising development is solar power generation.  Solar power generation mainly includes solar thermal power generation and solar solar solar energy generation two ways.  This paper focuses on solar energy generation.  Solar solar power generation is the direct conversion of solar energy into electricity generation, which can be divided into photovoltaic power generation, photoinduction power generation, photochemical power generation and photobiological power generation.  At present, the most widely used photovoltaic power generation is to directly convert the photovoltaic effect generated by the light irradiated to the solar panels into direct current power output. Its structure is generally composed of solar panels, batteries, controllers, inverters and supports.  The disadvantages of photovoltaic power generation are: high initial investment cost;  Low energy density;  Intermittent power generation;  Affected by climate conditions (can not generate electricity on rainy days);  Photovoltaic power generation is currently mainly used in three aspects, namely: to provide power for places without power;  Grid-connected power generation;  Make solar electronic products, such as all kinds of solar chargers, solar lamps (including solar street lights), solar water heaters, etc.  

2.1 Basic characteristics of solar cell panels and their applications  

In order for the solar panel assembly to receive as much solar radiation as possible during the year, an optimal Angle for the solar panel assembly should be selected for installation.  Through the calculation of the special model, the variation value of the monthly average solar radiation amount of the plane with different inclination angles can be obtained. The solar radiation amount varies greatly on the inclined plane with different angles. Therefore, when installing the solar panel module, the suitable dip Angle should be selected through the test to obtain the maximum solar radiation amount.  

2.2 Basic characteristics and applications of solar cells  

Solar battery group is the energy storage device of solar panels. Its function is to store the electric energy emitted by the panels when there is sunshine for load use at night or in cloudy and rainy days.  The battery group is composed of a number of batteries in series and parallel, and its capacity requires that it can meet the power supply time and electricity demand required by the street lamp in the days without solar radiation.  At present, lead-acid battery is commonly used in China, and nickel-cadmium battery can also be used in important occasions, but the latter price is higher.  Battery storage is chemical energy, it will be DC electric energy into chemical energy storage, when needed to change chemical energy into electrical energy released, visible energy conversion process is reversible, the former is called battery charging, the latter is called battery discharge.  Therefore, in the photovoltaic power generation system, the battery plays a role in the storage and regulation (release) of the electric energy generated by the system;  Because the power output of the photovoltaic power generation system changes every day, the battery can also provide relatively stable electric energy in case of insufficient sunshine or maintenance of the photovoltaic power generation system.  

2.3 Basic characteristics of solar lighting and its application  

As LED is a DC power supply device, it is easy to be made into DC lamps, which are widely used in DC electric systems, such as solar lamp products.  It has flat type ultra-high brightness LED, single beam ultra-high brightness LED, flat type and beam type ultra-high brightness LED combination, because the light produced by a single beam ultra-high brightness LED light tube is too directional, the comprehensive visual effect is poor, so,  Flat type ultra-high brightness LED or flat type ultra-high brightness LED combined with beam type ultra-high brightness LED should be preferred. Multiple leds are concentrated together, arranged and combined into LED light source with certain rules, which can be used as the lighting fixture of solar street lamps.  

2.4 Overcharge and overdischarge protection energy of solar street lamps 

In the application of solar street lamp, attention should be paid to the control of battery overcharge and overdischarge.  The so-called over-charge control is to disconnect the charging circuit in time when the battery is in the over-charge state, and the over-discharge control is to disconnect the discharge circuit in time when the battery is in the over-discharge state. This is to protect the battery and extend its service life.  The basis for judging the overcharge and overdischarge is the voltage variation of the battery:  When the sun shines on a sunny day, the solar photovoltaic panel absorbs the light energy to charge the battery through the normally closed point of the relay switch. When the voltage of the battery is higher than 26V, the storage battery is in an overcharged state. The normally closed point of the repeater switch is disconnected and the normally open point is closed.  Realize overcharge protection function;  At night, the battery supplies power to the street lamp. When the voltage of the battery is lower than 22V, the battery is in the over-discharge state. The relay switch is transferred from the normally closed point to the normally open point, and the discharge circuit is automatically disconnected to stop the power supply to the load (street lamp). 

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