Solar street lighting system design

1.0 Overview

Nowadays, solar energy has become a well-recognized green energy source that is gradually applied to people's livelihood for the benefit of mankind. Among them, the solar garden light is one kind of solar energy application method, and it depends on the solar radiation of solar photovoltaic modules during the daytime to generate electrical energy, and the generated electrical energy is transferred to the storage battery for storage. In the evening, when the illumination falls to a certain degree or reaches a certain point, the controller controls the battery to discharge the light to the electric appliance. When the illuminance rises to a certain degree or at a certain moment, the electricity is automatically turned off.

2.0 system overall design

Solar street lights are mainly composed of solar battery components, component brackets, electric control boxes (built-in controllers, batteries), lamp posts (including lamps and lanterns) and other parts. The system diagram is as follows:

Figure 1 Solar street light system

2.1 System Settings

The area used by this system is **, and its average standard light hours is 4.46 hours. Let the system work normally for 8 hours a day, 5 days per month for continuous rainy days, and 20 days for every two consecutive rainy days.

2.2 Design Process

The system design process mainly includes: the selection of lamp poles, the selection of lamps, the configuration of solar modules, the configuration of storage batteries and controllers, and the setting of system protection measures.

3.0 lamp pole selection

The light pole is the supporting part of the entire street light, and has high requirements for its hardness, height, wind resistance, anti-corrosion, etc. Now the commonly used material is Q235, which is processed through a series of processes and the surface is sprayed with an 80 μm coating.

The road conditions of this system are main trunk roads with a width of 30 meters and symmetrical arrangement on both sides. According to the street lamp construction design specification (see Table 1), the system uses a light-cut type lighting fixture, and the installation height is 10 meters (according to the standard, the installation height should be 15M, but the higher the height, the greater the power of the lamps and the pole design The more complex, the comprehensive selection of lamp poles is 12 meters, the lamp installation height is 10 meters, and the spacing is 30 meters. The upper and lower diameters of the pole are Ф70/Ф250, the material thickness is 3.75mm, the taper is 11‰, the foundation size is 500*500, the flange size and hole spacing are 400*400*18-300, and the base frame size is 300*300 - Ф 18.

Table 1 The relationship between the type and arrangement of the light distribution and the installation height and spacing of the lamps

Note: Weff is effective road width (m).

4.0 Lamp Power Selection

According to the requirements of the road lighting design standards for motor vehicles in the street lamp construction design specification (see Table 2), this system belongs to level I, and the average illuminance of the road surface takes 20 lux (lx). It can be concluded that the total luminous flux of the luminaire is: total luminous flux = (average illuminance * maintenance factor * irradiation area) / (lamp quantity * luminaire utilization factor) = (20 * 0.9 * 15 * 30) / 0.95 = 8526 lm .

Table 2 Standard value of road lighting for motor vehicle traffic

(Including Yingbin Road, main road leading to government agencies and large public buildings, roads located in downtown or commercial centers)

At present, there are many types of lamps that are used as road lighting, including high-pressure/low-pressure sodium lamps, energy-saving lamps, and LED lamps. Among them, LED has obvious advantages and is the trend of road lighting in the future. Its advantages are as follows:

1, LED lighting, high efficiency, long life, can use more than 50,000 hours; easy installation: no need to bury the cable without rectifiers, etc.; has a unique secondary optical design, the LED street light to the desired lighting area, Further increase the efficiency of light to achieve the purpose of energy conservation;

2. LED's light source efficiency has reached 90-110lm/W at present, and the light decay is small. The light decay of one year is less than 3%, and the use of road illumination is still required in 10 years.

3. Low maintenance cost: Compared with traditional street lamps, LED street lamps have extremely low maintenance costs. After comparison, the total input costs can be recovered in less than 6 years.

Based on the above principles, the energy-saving effect of high-power LED street lamps is significant. In place of high-pressure sodium lamps, it can save electricity by 60%. According to the power and luminous flux data of LED lamps on the market, 120W (DC 24V) is more appropriate.

The LED lamp has two kinds of AC and DC. In order to reduce the cost and power loss, this system selects the DC LED lamp, type D24/120.

Note: The luminaire utilization factor refers to the ratio of luminous flux projected onto a straight road of infinite width and the output luminous flux of the LED luminaire.

5.0 Battery and Battery Board Selection

Selection process:

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

(2) The charging current of the solar battery module satisfying the daily load of the load I1=Q*1.05/h/0.85/0.9=40*1.05/4.46/0.85/0.9A=12.3A where 1.05 is the comprehensive loss coefficient of the solar charging, 0.85 is the battery charge efficiency, 0.9 is the controller efficiency, and h is the standard peak hour, which is 4.46 hours.

(3) Determination of battery capacity to meet the battery capacity for five consecutive cloudy and rainy days. CC=Q*(d+1)/0.8*1.1=40*6/0.8*1.1=330Ah where 0.8 is the battery discharge depth, 1.1 For the battery safety factor, select two 12V180Ah battery strings into battery packs.

(4) The solar battery module charging current I2 I2=C*0.8/h/D=330*0.8/4.46/20=2.96A is required to recover the battery capacity after continuous rainy days, where 0.8 is the battery discharge depth, and D is twice The number of days between consecutive rainy days.

(5) The power of the solar cell module is (I1+I2)*30=(12.3+2.96)*30=457Wp where 30 is the operating voltage of the solar cell module and two solar cell modules with a peak power of 230 W are selected.

6.0 controller selection

The controller is the key component of the entire street lighting system as a manager. Its maximum function is to conduct comprehensive management of the battery. A good controller should set various key parameters, such as the overcharge point of the battery, according to the characteristics of the battery. Overplay points, restore connection points, etc.

The configuration of the photovoltaic controller shall be determined according to the technical specifications of the entire system and with reference to the product catalog manual provided by the manufacturer. Generally consider the following technical indicators:

1, the system operating voltage

Refers to the operating voltage of the battery pack in the solar power system. This voltage is determined based on the operating voltage of the DC load or the configuration of the AC inverter, typically 12V, 24V, 48V, 110V and 220V.

2. Rated input current and input path of photovoltaic controller

The rated input current of the photovoltaic controller depends on the input current of the solar cell module or the square array, and the rated input current of the photovoltaic controller when selecting the type should be equal to or greater than the input current of the solar cell. The number of input channels of the photovoltaic controller is more than or equal to the number of design input channels of the solar cell array. Low-power controllers generally have only one solar cell array input, and high-power photovoltaic controllers usually use multiple input channels. The maximum input current per channel is the rated input current/input channel number. Therefore, the output current of each cell array should be Less than or equal to the maximum current allowed by each input of the PV controller.

3, the rated load current of the photovoltaic controller

That is, the PV controller outputs the DC output current to the DC load or inverter, which must meet the input requirements of the load or inverter.

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

The system uses a controller with a rated voltage of 24V and a rated current of 20A.

7.0 Installation Requirements

1. Lamp post: The lamp post should not be installed with tall trees. The lamp post should have a certain distance from the road because of the installation point.

2. Cantilever: The cantilever length of the luminaire should not exceed 1/4 of the installation height.

3. Luminaires: The elevation angle of the luminaire should not exceed 15°, and the maximum light projection direction and perpendicular angle should not exceed 65°.

9.0 summary

The superiority of solar street lights is indisputable, but its economy has been questioned. The reason is that its initial investment is too large. One of the most expensive is solar panels. In order to ensure normal operation for 3-5 consecutive rainy days, the power of solar cells is usually 2-3 times greater than the LED power consumption. Another expensive is the LED lamp. Lead-acid batteries also take up no cost. Although the initial installation cost of solar street lamps is greater than that of the city circuit lamps, the additional cost of solar street lamps after installation is very low. In addition to the fixed consumption of grid electrical energy per day, the city circuit lamps are far more frequent and costly in terms of line maintenance and lamp replacement. Far longer than solar street lights, the long-term costs are much greater.

Other advantages of solar lighting: Green and environmental protection, which can add new selling points for the development and promotion of noble ecological communities; it can continuously reduce the cost of property management and reduce the cost of owners' public apportionment.

In summary, the intrinsic characteristics of solar lighting, such as safety, no hidden dangers, energy-saving and non-consumption, environmental protection, easy installation, and automatic maintenance-free maintenance, will directly bring obvious advantages to the sale of real estate and the construction of municipal projects.

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