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An overview of solar lighting solar energy is "inexhaustible", non-polluting, renewable energy, the earth's surface every day to radiation equivalent to about 2.5 hundreds of millions of barrels of oil. In a long time, solar energy away from people all around us, "slip". With the rapid development of science and technology, development and utilization of solar energy gradually and has become one of the most promising environmentally friendly energy sources.

       At present, the use of solar energy, there are two main ways.

       (1) through the solar cells to solar energy into electrical energy for electricity generation, that is, photovoltaic power generation, such as solar lighting, solar power, and so on.

       (2) through the collector to convert solar energy use, such as solar water heaters, solar cookers and so on. The solar lighting using solar energy is the most important way to one of our main object of concern and research. In the outdoor lighting, solar lighting of the strong momentum of development. Solar Street Lights (non-trunk roads), solar courtyard, Solar Garden Light, solar traffic lights, solar lights, and other advertising is not uncommon for both the green light to become the bright spots. We are talking about solar lights, it means the lamps, light sources, including solar cells, batteries, controller, inverter, such as the poles supporting device.

       The principle of solar lighting solar panels to solar energy into electric energy, after a high-power diode and control system for charging batteries. Charge to a certain extent, the controller of self-protection system moves to cut off the power supply charge. At night, solar photovoltaic panels to act as a controller, start the controller, to the battery-powered lights, light the lights; the early hours of solar panels and photovoltaic act as a controller, the controller starts, the lights cut off power supply to re - To begin solar energy into electricity. Kindle in the solar lights also can set up for dimming.

       Solar lighting components of solar lighting from solar panels, batteries, solar lights dedicated controller, and the poles, such as light-emitting body composition. Below, focusing on solar cells, batteries, inverters (AC lighting bulbs use), solar lights dedicated controller, such as light-emitting body.

       Solar cells
       The principle of solar cells

       The use of photovoltaic solar cells so that the principle of converting the sun's radiation through optical semiconductor material electrical energy into the device, the photoelectric conversion process is usually called the "photovoltaic effect" solar cells, also known as "PV cells." When the sun light reach by P, N-conductive two different types of semiconductor material consisting of the same P-N junction when, under certain conditions, solar radiation absorbed by the semiconductor material to form a built-in electric field. If the built-in electric field from both sides of the electrode leads connect to the appropriate load, it will form a voltage and current, which is the basic principle of solar cells, shown in Figure 2. A single solar cell is a semiconductor thin P-N junction. Standard light conditions, the rated output voltage of 0.48V. In order to obtain a higher output voltage and large capacity, often more than the film solar cells connected together. The solar cell output power is random. Different time, different locations and different installation methods, with a power output of solar cells are different.

       At present, solar photovoltaic conversion rate of more than 10 per cent more than in the individual countries of the photovoltaic solar cell conversion rate can reach 30%.

       Classification of solar cells
 

       (1) silicon solar cells;

       (2) to inorganic salts, such as: III-V compounds gallium arsenide, cadmium sulfide, copper, indium and selenium compounds, such as multi-material for the battery;

       (3) functional polymer materials produced by solar cells;

       (4) nano-crystalline solar cells, and so on. Silicon solar cell technology is relatively mature, the band gap semiconductor material is not too wide, photoelectric conversion rates higher material itself does not cause pollution, it is the ideal silicon solar cell material. Other material-based solar cells are in the process of research and development.

       Silicon solar cells
       (1) single crystal silicon cell: At present, the single crystal silicon photovoltaic solar cells convert the highest rate (20%), the most mature technology, but because of monocrystalline silicon material prices were too high and cumbersome process, resulting in cost single crystal silicon High, the development of single crystal silicon solar cells to become a major obstacle now is gradually being polysilicon thin film solar cells and thin film amorphous silicon solar cells to replace and so on.

       At present, the single crystal silicon solar cells on the road lighting, traffic signals, such as outdoor lighting in the more general use, photoelectric conversion rate of 11% to 24% longer service life.

       (2) polycrystalline silicon cells: polysilicon thin film batteries due to the use of silicon less than silicon, there is no recession in the efficiency and other issues, and possible low-cost substrate materials were prepared. Polysilicon thin film solar cells far less than the cost of monocrystalline silicon cell, photoelectric conversion rate of nearly 20% higher than that of amorphous silicon thin film batteries. As a result, polysilicon thin film batteries will be expected to become the leading solar cell products.

       Polycrystalline silicon solar cells in the outdoor lighting application will be more extensive.

       (3) amorphous silicon cells: amorphous silicon thin film solar cells to produce simple, low cost, ease of large-scale production, generally people's attention and to the rapid development of the photoelectric conversion rate of 14.5 percent over, but the stability of the Less. Improve the conversion rate and the stability of amorphous silicon thin film solar cell development. At present, the amorphous silicon in low-power battery power systems in more applications.

       The development of other solar cells
 

       (1) nano-crystalline solar cell chemistry: chemical nano-crystalline solar cells is a new type of solar cells, which are still in the process of development, nano-crystalline TiO2 solar cells has drawn greater attention. Nano-crystalline TiO2 efficiency of the photovoltaic solar cells in more than 10% of the production cost of silicon solar cells 1 / 5 to 1 / 10, life expectancy could reach more than 20 years.

       (2) multi-layer polymer-modified electrode solar cells: raw materials for organic materials, flexible, easy to produce, the source of a wide range of materials with low costs. Performance and battery life than silicon, but the possibility of providing low-cost power. The study has just begun.

       (3) multi-film compound solar cells: some metal compounds such as cadmium sulfide, cadmium telluride polycrystalline thin film battery efficiency than the amorphous silicon thin film solar cell efficiency, lower costs than single crystal silicon cells, as well as easy-to large-scale production, However, due to cadmium are highly toxic, can cause serious pollution, development can not be applied.

       The choice of the capacity of solar cells
       Solar power load than 4 times more power than the system can work properly.

       Battery

       Lighting must be equipped with solar batteries

       Lighting must be equipped with solar batteries in order to work, because:

       (1) solar cells can only be carried out during the day and photoelectric conversion work in the electrical energy used for lighting at night in order thus to be in the reserve battery inside. The reserves should be sufficient local capacity for a few cloudy lighting needs.

       (2) solar energy output of a very unstable and is equipped with batteries, solar lights to work load.

        Battery types and applications

       (1) lead-acid batteries: the traditional batteries, low energy density, the more serious environmental pollution will gradually be eliminated.

       (2) Ni-Cd (nickel - cadmium) batteries: superior performance than lead-acid batteries, but less than energy density, the cadmium pollution is serious, most of these countries to strictly control the production and use of batteries.

       (3) Ni-H (nickel - hydrogen) batteries: with a high energy density, light weight, long life, free of environmental pollution, etc., are being actively developed. Developed in the 1990s, has entered the industrialization stage.

       (4) lithium batteries: a new type of chemical high-energy power, high-capacity, high-power, small-and pollution-free characteristics. Lithium batteries for notebook computers and mobile phones.

       At present, a large number of outdoor lighting the use of closed, the maintenance-free lead-acid batteries. Small lighting projects, such as laptops and cell phones use lithium batteries, nickel-metal hydride batteries. Li-ion battery applications are expanding. The development, promotion of pollution-free batteries is the development of solar lighting is an urgent need to address a major issue.

       Battery capacity to choose

       China's vast, very different climate, the energy storage battery during the day should be able to meet the demand for lighting at night and at the same time meet the local rain in a row when the night lighting needs. However, the selected battery capacity do not have too much, otherwise, often at a loss battery power, will have an impact on battery life, and an unnecessary waste. On the battery capacity to choose the size of China's western region than the proposed lights on more than four times the power consumption; in the north than the proposed lighting on power for more than 5 times; in the south than the proposed lighting on power for more than 6 times .

       Controller
       The role of controller is a solar energy lamp control system, such as lighting control or light switch settings, dimming, lightning protection, short circuit protection, carried out on the battery charge protection, anti-charge protection, over-discharge protection, temperature compensation And so on. The controller is a solar energy lamp, "the brain." With the passing of the controller, solar lights can work smoothly and at the same time, and other devices to extend battery life.

       Inverter
       Inverter battery is direct current into alternating current output of the device, the lighting load for DC do not have time to set, lighting load when the load for the exchange must be used. According to our current situation, the general battery for 24V (or 12V, 36V), Lighting outdoor light (lamp) to 220V, 50Hz AC, to INVERTER more DC24V (or 12V, 36V) / AC220V the form of voltage. Inverter should also have short-circuit protection, under-voltage protection, over-current protection, reverse protection and lightning protection.

       Lighting load
       Due to the existence of solar lighting optoelectronic conversion rate low, the cost of higher prices and other factors make the current scope of its application is limited to traffic lights, landscape lighting, decorative lighting and so on in order to Garden lamp, garden lights, low-power path (non-trunk roads) The main lights. Solar Lighting LED light source to light-emitting diode, three high-color-based energy-saving lamps, may also use the low-pressure sodium lamp, the non-polar lights, case-by-case use of low-power HID lamps.

       LED lights with energy-saving, the former long life, low luminous efficiency; the latter a shorter life expectancy, higher optical performance. In different circumstances, to go through economic and technical comparison, select the appropriate source.

       Solar LED traffic lights using light-emitting diode light source, long life, LED lights with the performance. There are light-conditioning, frequent switching function below the low-power 1W Solar Garden Light, LED general should be used as a light source. For larger power Solar Garden Light, currently used by the three primary colors more reasonable and efficient energy-saving lamps. Courtyard and decorative street lamps in the main, the choice of the proposed LED light-emitting diodes; to the main lighting, the proposed three primary colors to choose high or low pressure sodium lamp energy-saving lamps.

       With the LED light emitting diodes to improve efficiency, solar lighting of the light source to support the increasing use of LED light-emitting diodes.

       Solar lighting trends

       (1) to enhance cell plate of the photoelectric conversion rate;

       (2) to increase system capacity to meet the power requirements of outdoor lighting;

       (3) to reduce costs. At present, a set of solar lights (full set) is a general lighting (set of) several times, the impact on promoting the use of solar lighting;

       (4), and other devices to extend battery life and prolong the life span of solar lighting system;

       (5) to reduce battery panels, batteries, such as the size of the bar-type landscape;

       (6) to phase out the serious pollution of lead-acid batteries, Ni-Cd batteries, and so on, to speed up development of pollution-free batteries, real environmental protection;

       (7) in the solar lighting through technological advances and lower prices, in the new century will be one of the leading sources.