1 the functional characteristics of solar street lamps

Urban road lighting is closely related to people's production and life. With the acceleration of urbanization in China, green, efficient, environmentally friendly and long-lived LED street lamps have gradually entered people's production and life; The greatest advantage of solar road lighting is that it can be conveniently installed in urban roads, squares, parks, parking lots and highways without setting up power lines, digging trenches, laying cables, and managing and controlling by special people. Compared with the traditional lighting lamps, the ultra-high brightness LED lighting source is small in size, light in weight, good in directivity, able to withstand all kinds of harsh weather conditions, and has incomparable advantages over other light sources in terms of power consumption, service life and environmental protection. In addition, the energy-saving efficiency and simple installation and maintenance of solar lamps will surely lead us into a new era of green lighting. Solar street lamps are composed of solar panels, storage batteries, high-brightness lamps, controllers and other components. During normal operation, there are few moving parts and basically no noise. The function of the control circuit in the solar street lamp controller is basically the same as that of the common street lamp controller, which is to complete the operation of turning on the lights at dark and turning off the lights at dawn. The difference is that there is an additional charge and discharge management for the storage battery. There are three kinds of street lamp controllers commonly used at home and abroad: individual light controller, clock controller and longitude and latitude controller. Their working principles are different, and each has its own advantages and disadvantages. Now, they are briefly discussed as follows.

1.1 separate light controller

The single light controller adopts a photosensitive probe, and automatically turns on the street lamp when the dark light is weak; When the sky is a fish-belly grey in the early morning, the street lamp will be turned off automatically, which can achieve the function of automatic control. The early light-controlled switch uses discrete semiconductor components, so the circuit is complex and the failure rate is high. With the development of semiconductor technology, time-base integrated circuit appears, which simplifies the optical switch circuit, and the photosensitive probe is the key component of the optical switch.

1.2 clock controller

The controller should set the switching time in advance, so that the street lamps can turn on and off on time, thus achieving the purpose of automatic control and saving electricity consumption. Its advantage is that the preset switch will be disturbed by external light, and it will not cause misoperation except for its own fault. Its disadvantage is that it can't automatically change the switch time according to seasonal changes and special weather conditions, and it is necessary to assign a special person to adjust the switch time, for example, it gets dark earlier and dawn later in winter and spring; In summer, dawn is earlier and darkness is later; There are fewer vehicles and pedestrians on the road after midnight, so the number of lights should be appropriately reduced, and they should be lit before dawn, so as to facilitate traffic safety and power 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, which has accurate travel time, but the plastic gear used in the movement will deform at high temperature, resulting in inaccurate travel time or even shutdown. The timing switch of the latter is usually an electronic clock circuit centered on integrated blocks such as LR6818 and LM8650. In recent years, an integrated block integrating electronic clock circuit board with LED liquid crystal display has appeared, which can be provided with six groups of switching points and has the function of day. Many component manufacturers rush to produce this product, and now it is mostly used in street lamp controllers.

1.3 latitude and longitude controller

The longitude and latitude controller adopts single-chip microcomputer technology to simulate the sunshine law, and can automatically turn on the light in dark and turn off the light in early morning. It adopts the advantages of light-controlled switch timing, overcomes the disadvantages of light-controlled switch being interfered by the outside world, absorbs the advantages of accurate clock controller time, and avoids the disadvantages of timing switch not automatically changing switching time. At present, many street lamps in large and medium-sized cities mostly adopt this control mode, but the disadvantage is that the price is higher.

2 Functional characteristics and applications of solar street lamp components

In the development of new energy, it is unanimously recognized at home and abroad that solar power generation is the one with the highest technical content and the most promising development prospect. Solar power generation mainly includes solar thermal power generation and solar energy power generation. This paper focuses on solar energy power generation. Solar energy power generation is a power generation mode that directly converts solar energy into electric energy. It can be divided into four types: photovoltaic power generation, photo-induced 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 impinging on the solar panel into direct current power output, and its structure is generally composed of solar panel, battery, controller, inverter, bracket and other components. The disadvantages of photovoltaic power generation are: high initial investment cost; Low energy density; Intermittent power generation; It is greatly affected by climatic conditions (it can't generate electricity in rainy days); At present, photovoltaic power generation is mainly used in three aspects, namely: providing power for places without power; Grid-connected power generation; Make solar electronic products, such as various solar chargers, solar lamps (including solar street lamps), solar water heaters, etc.

2.1 Basic characteristics and applications of solar panels

In order for the solar panel module to receive as much solar radiation energy as possible in a year, it is necessary to select an optimal inclination angle for the solar panel module during installation. Through the calculation of the special model, we can get the variation value of the monthly average solar irradiance of planes with different inclination angles, and the solar irradiance varies greatly on the inclined planes with different angles. Therefore, when installing the solar panel module, we should choose the inclination angle suitable for the local area through experiments to obtain the maximum solar irradiance.

2.2 Basic characteristics and application of solar battery pack

Solar battery pack is the energy storage device of solar panels, and its function is to store the electric energy emitted by the panels when there is sunshine, and it can be used by the load at night or in rainy days. The battery pack is made up of several batteries connected in series and parallel, and its capacity requires that it can meet the power supply time and quantity requirements of street lamps in the days without solar radiation. At present, lead-acid batteries are commonly used in China, and cadmium-nickel batteries can also be used in important occasions, but the latter is more expensive. The storage battery stores chemical energy, which converts DC electric energy into chemical energy and stores it. When necessary, it converts chemical energy into electric energy and releases it. It can be seen that the energy conversion process is reversible, the former is called battery charging, while the latter is called battery discharging. Therefore, in the photovoltaic power generation system, the storage battery plays a role in storing and regulating (releasing) the electric energy generated by the system; As the power output of photovoltaic power generation system changes every day, the battery can also provide relatively stable electric energy when the sunshine is insufficient or the photovoltaic power generation system needs to be repaired.

2.3 Basic characteristics and applications of solar lighting lamps and lanterns

Because LED is a DC power supply device, it can be easily made into DC lamps and is widely used in DC systems, such as solar lamps and lanterns. There are three types of flat ultra-high brightness LED, single beam ultra-high brightness LED and combination of flat and beam ultra-high brightness LED. Because the single beam ultra-high brightness LED has too strong light directionality and poor comprehensive visual effect, flat ultra-high brightness LED or combination of flat and beam ultra-high brightness LED should be the first choice, and a plurality of LEDs should be gathered together and arranged to form LED light sources with certain rules, which can be used as lighting fixtures for solar street lamps.

2.4 overcharge and overdischarge protection function of solar street lamps

In the application of solar street lamp, we should pay attention to the control of overcharge and overdischarge of its battery. The so-called overcharge control means that the charging circuit should be disconnected in time when the battery is in overcharge state, while the over-discharge control means that the discharging circuit should be disconnected in time when the battery is in over-discharge state. This is done to protect the battery and prolong its service life. The judgment of overcharge and overdischarge is based on the fluctuation of battery voltage: when the sun shines on a sunny day, the solar photovoltaic panel absorbs 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 battery is in an overcharge state, and the normally closed point of the relay switch is turned off and closed, so that the charging circuit is automatically disconnected, and the charging to the battery is stopped, thus realizing the 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 an overdischarge state, and the relay switch is turned from the normally closed point to the normally open point. The discharge circuit is automatically disconnected, and the power supply to the load (street lamp) is stopped, thus realizing the overdischarge protection function.