Solar Street Lamp System Design Scheme

- Jul 12, 2019-

  1.   Today, solar energy has become a recognized clean green energy, and gradually used in people's livelihood, benefit mankind. Among them, the solar courtyard lamp is one of the application ways of solar energy. It relies on the solar photovoltaic modules illuminated by the sun during the day to generate electric energy, which is transferred to the storage battery for storage. At night, when the illuminance falls to a certain degree or reaches a certain moment, the battery is controlled by the controller, so that the electric discharge of the light source. When the light level rises to a certain degree or at a certain moment, the electricity is automatically turned off.

  2. Overall system design

  3.   Solar street lamp is mainly composed of solar cell module, module bracket, electric cabinet (built-in controller, battery), lamp pole (including lamps) and other parts.

  4. 1 system Settings

  5. The average standard illumination hours of this system are 4.46 hours. The system is set to work normally for 8 hours every day, with 5 consecutive rainy days every month and 20 consecutive rainy days every two days.

  6. 2 design process

  7.   The system design process mainly includes: lamp pole selection, lamp selection, solar module configuration, battery, controller configuration, system protection measures setting.

  8. 3. Selection of lamp posts

  9.   The lamp pole is the supporting part of the whole street lamp, which has high requirements on its hardness, height, wind resistance and corrosion resistance. The commonly used material is Q235, which is processed by a series of processes and coated with an 80 micron coating.

  10. The installation of this system is the main road with a width of 30 meters and a symmetrical arrangement on both sides. According to construction design specification (see table 1), this system USES the sectional type lamps and lanterns, light installation height of 10 meters (this should be installed in accordance with the standard height of 15 m, but considering the higher the altitude, the greater the need the power of lamps and lanterns, the more complex the lighting design, choose light pole after comprehensive consideration of 12 meters, lamps and lanterns installation height of 10 meters), span of 30 meters. Light pole fluctuation mouth diameter for 70 / Ф 250 Ф, material thickness is 3.75 mm, conicity of 11 ‰, the foundation and the size 500 * 500 flange size and hole spacing of 18-300, 400 * 400 * foundation frame size is 300 * 300 - Ф 18.

  11. 4. Selection of street lamp power

  12.   According to the requirements of road lighting standards for motor vehicles in the street lamp construction design specifications, this system belongs to level I, and the average illumination of road surface is 20 lux (lx). Therefore, it can be concluded that the total light flux of lamps is: total light flux = (average light intensity * maintenance coefficient * exposure area)/(number of lamps * lamp utilization coefficient) = (20*0.9*15*30) /0.95=8526lm.

  13.   At present, there are many kinds of lamps for road lighting, including high/low pressure sodium lamp, energy-saving lamp, LED lamp and so on. Among them, LED has obvious advantages and is the trend of road lighting in the future. Its advantages are shown as follows:

  14. LED light has high efficiency and long service life, which can last for more than 50,000 hours; Easy installation: no need to add cable without rectifier, etc. With a unique secondary optical design, LED street lamp light to the required lighting area, further improve the lighting efficiency, to achieve the purpose of energy saving;

  15. 2. High efficiency of LED light source has reached 90-110lm/W at present, and light decay is small, less than 3% in one year, which still meets the requirements of road illumination after 10 years of use.

  16. 3. Low maintenance cost: compared with traditional street lamps, LED street lamps have very low maintenance cost. After comparison, all the investment cost can be recovered in less than 6 years.

  17. Based on the above principles, the energy-saving effect of high-power LED street lamp is significant, which can save 60% of electricity instead of high-pressure sodium lamp. According to the power and luminous flux data of LED lamps in the market, 120W (dc 24V) is more appropriate.

  18. There are two kinds of LED lamps: ac and dc. In order to reduce the cost and power loss, the system chooses dc LED lamp, the model is d24/120.

  19. Note: lamp utilization coefficient refers to the ratio of the luminous flux projected onto a straight road of infinite length and certain width to the output luminous flux of LED lamp.

  20. 5. Battery and panel selection

  21. Selection process:

  22. (1) load daily consumption Q=W*H/U=120*8/24=40Ah. Where U is the nominal voltage of the system battery

  23. (2) charging current I1=Q*1.05/h/0.85/0.9=40*1.05/4.46/0.85/0.9A=12.3 in formula A, 1.05 refers to comprehensive loss coefficient of solar charge, 0.85 refers to battery charging efficiency, 0.9 refers to controller efficiency, and h refers to standard peak hours and 4.46 hours.

  24. (3) the determination of battery capacity meets the battery capacity CC=Q* (d+1) /0.8*1.1=40*6/0.8*1.1=330Ah, in which 0.8 is the battery discharge depth and 1.1 is the battery safety factor. Two 12V180Ah batteries are selected to form battery packs.

  25. (4) charging current I2I2=C*0.8/h/D=330*0.8/4.46/20=2.96 after continuous overcast and rainy days; in formula A, 0.8 is the discharge depth of the battery; D is the number of days between two consecutive overcast and rainy days.

  26. (5) the power of solar cell modules is (I1+I2) *30= (12.3+2.96) *30=457Wp. In the formula, 30 is the working voltage of solar cell modules. Two solar cell modules with peak power of 230W are selected.

  27. Controller selection

  28. The controller is the key part that ACTS as the manager in the whole street lamp system. Its biggest function is to carry out comprehensive management of the battery. A good controller should set each key parameter point according to the characteristics of the battery, such as the overcharge point, overdischarge point and recovery connection point

  29. The configuration and selection of photovoltaic controller shall be determined according to the technical indicators of the whole system and reference to the product sample manual provided by the manufacturer. Generally, the following technical indicators should be considered:

  30. (1) system operating voltage

    Refers to the working voltage of the battery group in the solar power generation system, which should be determined according to the working voltage of the dc load or the configuration of the ac inverter, generally 12V, 24V, 48V, 110V and 220V.

    (2) rated input current and number of input channels of photovoltaic controller

    The rated input current of photovoltaic controller depends on the input current of solar cell module or square array. The rated input current of photovoltaic controller should be equal to or greater than the input current of solar cell. The number of input ways of photovoltaic controller is more than or equal to the number of input ways of solar cell array design. In general, low-power controller only has one solar cell array input, while high-power photovoltaic controller usually adopts multiple input channels, and the maximum current of each input channel = rated input current/number of input channels. Therefore, the output current of each cell array should be less than or equal to the maximum current value allowed for each input channel of photovoltaic controller.

    (3) rated load current of photovoltaic controller

    That is, the output current of the photovoltaic controller to the dc load or inverter, which should meet the input requirements of the load or inverter.

    In addition to the above main technical data to meet the design requirements, the use of environmental temperature, altitude, protection level and dimensions and other parameters, as well as manufacturers and brands are also factors to be considered when configuring the controller.

    The system adopts the controller with rated voltage of 24V and rated current of 20A.

    7. Installation requirements

    (1). Lamp post: the installation site of lamp post should not have tall trees, because the installation point of lamp post should be a certain distance from the roadside.

    2). Cantilever: the cantilever length of lamps shall not exceed 1/4 of the installation height.

    (3) lamps and lanterns: the elevation Angle of lamps and lanterns should not exceed 15°, and the projection direction of maximum light intensity and the intersection Angle of perpendicular line should not exceed 65°.

    (4) foundation: the foundation setting site must be well drained; If there are low-lying water points such as rivers and puddles within 10 meters from the installation site, the lowest point of foundation must be higher than the highest water level within 50 years. Public facilities such as cables and optical cables cannot be laid underground at the installation site, which will affect the construction and installation.

    8.The advantages of solar street lamps are undeniable, but their economy has always been questioned. The reason is that its initial investment was too large. The most expensive are solar panels. In order to ensure normal operation during 3-5 consecutive rainy days, solar cells usually consume 2-3 times more power than leds. Another relatively expensive is the LED lamp holder. Lead batteries also account for a fraction of the cost. Although the initial installation cost of solar street lamps is higher than that of municipal street lamps, the additional cost of solar street lamps after installation is very low. In addition to the daily fixed consumption of electric power from the grid, the frequency and cost of line maintenance and lamp replacement are much higher than that of solar street lamps, and the long-term cost is much higher.

      Other advantages of solar lighting: green environmental protection, for the development and promotion of noble ecological community to add new selling points; Sustainable reduction of property management costs, reduce the owners of the public share of the cost.

    To sum up, the inherent characteristics of solar lighting, such as no hidden danger, no consumption of energy conservation, green environmental protection, easy installation, automatic control and maintenance free, will directly bring obvious advantages for the sale of real estate and the construction of municipal projects.