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Solar street lighting system introduced

Author: Time:2013-11-02
In the world energy shortages, environmental pollution is worsening today, fully develop and utilize solar energy is the world's governments sustainable energy strategy decisions. Solar street without someone to manage and control its installation time investment needed for future electricity costs , no set up transmission lines or trenching laying of cables can be easily installed in the squares, schools , parks , streets , and many other advantages become increasingly attention.

Solar street lighting system usually consists of solar modules , batteries , light source, controller ( inverter AC source needed ) composed of several parts .

This article from :

① source selection ;
② control circuit ;
③ best angle to determine the solar panel ;
④ solar modules and battery capacity determination
And several other aspects of the operation in Zhuhai solar street lighting system design optimization .

Solar street lights different from ordinary , it uses solar power as the only available because the current cost of solar modules is still relatively high , so in order to reduce system cost , you must use efficient light sources. LED is a way to convert electrical energy into visible light semiconductor light emitting device , in recent years, LED technology has been the key breakthrough, the cost performance has greatly improved, compared with conventional street light LED light source has a light , high efficiency, nearly twice as incandescent , long life, can reach more than 105h ; conventional power sources is relatively large , and mostly work under high pressure , using a boost inverter link also reduces the energy efficiency , while the LED uses low-voltage DC power supply, safe and low cost and light control , so adjust the brightness , frequent switching is possible.

Solar street lighting system are generally small-scale photovoltaic system, the World Bank standards is a small photovoltaic system controller from current consumption to less than 1% of rated current , so the controller circuit design and low power consumption device selection is very important. Solar lights are used in integrated operational amplifier constituted by the voltage comparator as a control circuit that is entirely composed by hardware control system is simple and reliable , easy maintenance , low cost, low power consumption circuit itself is a good colors matching circuit . This circuit is the key for the battery charge and discharge characteristics of the design with a relatively good voltage difference, while the device to select reliable light-emitting diode coupled with the charging and discharging status indication circuits , has become a useful function control with circuit , with anti- battery over -discharge , over- charging function . System uses direct coupling mode charge and discharge controller circuit , according to the LED with batteries matching characteristics , able to do adaptive power , lack of solar radiation in a few months , because the battery charge status is usually low, so that the battery discharge when the terminal voltage is low, so that the load current is small , low power, the system can work longer . Conversely, when a more adequate solar radiation , the load current is large, big power, will be brighter.

Determine the best solar panel angle

In stand-alone PV system design, solar modules are usually towards the equator plane , there is a certain angle relative to the ground plane . Since the amount of solar radiation with the seasons , climate change, not the same inclination , each month while making solar irradiance received very different , and because the battery is charging under its rated capacity constraints, discharge limits defined by the depth of discharge , and therefore solar lights optimal design , according to the load conditions , local climate conditions, geographical conditions, to determine the best angle for phalanx amount of solar radiation on the plane try to meet the continuity , uniformity, of the requirements greatly reduce system costs.

Load

Solar street light products mainly include timing and light control work in two ways , in fact, balanced way and seasonal load type load mode T for . Timing Control: free from outside influence , lamp timer switch , light does not exist or the day dark light brighter solar street light control problems in outdoor light dark to a certain extent (200 lx) to automatically turn on the lights , dawn automatically turn off the lights , the advantage is automatically controlled according to light work light conditions , there is no days without the black light on the work and do not work off the black case , can work all year round . Light control mode working time with the local latitude and the day too

Yang Declination related . By the time of sunrise and sunset angle formulas :

COs = COS L a - tan ~ tan8o] (1),

j6 a latitude ; one declination , the day when the declination angle of the sun at noon , the light and the angle between the equatorial plane .

Under normal circumstances , 0.5 h before sunrise and the mouth behind 0.5 h, although there is no sunshine , but the sky still peripheral vision , which is available without lights lighting, solar street light control working time J. To reduce 1 h, you can use the following formula to calculate the lights working hours:

T = 23-2/15cos a [ a tan ~ tan8] (2)

By the formula ( 2 ) calculation , uh, get installed in Zhuhai, solar street light control annual work time Figure 1 , it can be seen from the figure, solar street light control longest working hours in the winter solstice for 12.35 h, at the summer solstice j two for the shortest time of 9.65 h; due Zhuhai relatively low latitude , solar street light control annual work time is not great, so although there are seasonal solar street light control unbalanced load , but load changes not great, not affect the solar cell module load optimum tilt angle of the main factors . Taking into account the reliability of the control switch lights and the controller costs in Zhuhai designed solar lights use light control mode.

Climatic conditions

Zhuhai is located in the south of the Tropic of Cancer , a subtropical marine monsoon climate , abundant sunshine . Annual total solar radiation was 4 651.6MJ / n ~, Guangdong Province is rich in solar energy resources in the world. As can be seen from Figure 2 , Zhuhai year period the total amount of radiation at least in spring , rainy weather are more atmospheric transparency is poor, towels, low clouds covered the sky often , that period of time the total amount of radiation scattered radiation accounted for a high proportion of the amount , it can be seen from Table 2 February scattering radiation exposure ratio is the highest annual value reached 65.6% ; summer mainly fine and hot weather , sunny, level surface solar irradiance is annual maximum , and the amount of solar radiation in a high proportion of direct radiation ; autumn Zhuhai autumn, blue skies, though the sun elevation angle relative decreases, but the amount of solar radiation is still relatively high ; winter , sunny day Tu much, especially the front foot in winter and low rainfall .

Inclined surface solar irradiance calculation

Solar irradiance on inclined surfaces is generally calculated based on the last 10 to 20 years of meteorological information and data as the basis for the provision of horizontal solar irradiance data base , you can use Hay_I proposed model anisotropic sky diffuse radiation is calculated towards the equator different square surface inclination to the connected Su amount of solar radiation .

Its expression is :

HT: H R8 + Ho I_R H} H +0. s, ~ HB | Ho)

(1 + cosf1) J +0.5 pH (1 a cosp) (3)

R: cos0 / cos0

Angle : = COS [cos0 cosfl + sin0 sinflcos

(y a y J J

Zenith : = c0s [sinasin ~ + c0s c0s c0s ∞] [3

Solar azimuth : ys = d * d y. +

f_l 1 ** 180. _3

Hot n [= {. } '

f l ≯ (≯ a 01 f l ∞ 01

I-l Others " 'I-l Others" '

= ar ~ cos (tan3/tan ~) Lu as slope angle , f0 is the feature surface reflectivity , as the angle of incidence , mortar , for the solar zenith angle ; a ;) for the solar elevation angle , the surface azimuth , y is solar azimuth . Hay model through the above calculations, the different inclination plane of Figure 3 the average monthly amount of solar radiation changes . As can be seen from Figure 3, the dip in February to April is the lowest plane of the solar irradiance time , and that time several inclination plane solar irradiance received little difference , analytical reason is mainly because 2-4 March is the rainy season in Zhuhai , overcast , rain weather more, the amount of scattered radiation in the total amount of radiation a high proportion , as can be seen from Table 2, three months the amount of scattered radiation in the proportion of more than 55% , due to changes in inclination for solar modules receive more direct radiation effect is relatively large, but little effect on the scattering of radiation , so these three months in 2-4 different plane acceptance angle of the amount of solar radiation difference is not significant ; in 5-8 children summer months to 0 . Plane largest amount of solar radiation received , 15. And 22. Plane acceptance angle of inclination of the solar irradiance is very close , but 40. Flat amount of solar radiation received compared to other three kinds of dip is much lower radiation decay ; Zhuhai area in autumn autumn weather , blue skies , though the sun elevation angle decreases, the amount of solar radiation is still relatively high , 15 ° , 22 °, 40 ° tilt angle plane to get some amount of solar radiation is very close, but after September 0 . Flat amount of solar radiation received rapid decrease , a decline greatly ; winter , mostly sunny , especially before winter rainfall, the winter one and l2 months, the annual minimum elevation angle is the period, from Figure 3 shows the different angle inclined surface , the amount of solar radiation vary greatly , when the 40o maximum amount of solar radiation , the amount of horizontal surface solar irradiance is severely reduced, while the winter solstice light control solar lighting system is the annual working time the longest , so proper care should tilt angle winter sun irradiation .

Through different angle plane in Figure 3 the average monthly change in the amount of solar radiation , combined with our use of load conditions , the solar street lighting system design , we must first consider the system in February-April low amount of solar radiation the normal work situation demands in Zhuhai area using solar street light control seasonal winter large power load , but the load trend change is not large , the load situation is not the best movie Tu solar panel inclination of the main factors , consolidated several factors Zhuhai solar lights solar module arrangement inclination is to take the local latitude 22. This will not only be able to properly care for winter electricity load increased, and 2-3 months in the spring with the best output , but also more than 40 after the summer . f are angles produce more power, rapid recovery of charging the battery to extend battery life .

Solar panels and battery capacity determination

Solar cells and battery capacity combinations , both to ensure the reliability required load lights under the premise of hope , determined using a minimum of solar modules and battery capacity , in order to achieve optimum reliability and economy of design the best combination . Reliability and abroad mostly used for load power shortage rate (LOLP) to be measured. Which is defined as a system of electricity needed to power outages and the actual ratio when asked . LOLP value between 0 to 1 , the smaller the value , the higher reliability . For uh reliability requirements should have certain limits , in the past in the domestic photovoltaic system is not time, how their use is often not perish , always designed to achieve uninterrupted power , which requires IJ ( ] IJP = 0, in fact, for large AC grid urban power supply can only reach IJ ( ] LP = 10I3 magnitude [ big one this requires relatively expensive PV systems up to 100 % reliability , is clearly unreasonable . therefore in the design of solar lights , to meet the reasonable load reliability, have the best economy , the recommendation from Table 3 , the Zhuhai design reliability L0LP solar street value of 0.1 , to ensure the supply 4-5 rainy days according to the reliability of the design, system configuration shown in Table 4 , the use of 8 1W high power white LED as light load , 2 20Wp solar modules ( South 220 tilt angle arrangement ), 12V, 40AH maintenance-free lead-acid batteries .

Summary

In photovoltaic applications in the process, many products because there is no work in accordance with photovoltaic characteristics and operation rules for design , tend to make long-term system can not run normally , according to the Zhuhai local climatic conditions , combined with the solar photovoltaic power generation characteristics of where running lights too I5} j can optimize the design work is very meaningful , it not only reduces the cost of solar street lighting system , and improve system reliability. After a semiconductor solar street lighting system is actually nearly a year test observation, the results are consistent with the design requirements, solar street light controller can accurately control the entire system can correct the battery to overcharge, over -discharge protection, battery after 4 days Lianyin days, lights still work .