Solar Street Light Configuration and General Calculations

Solar street lights are composed of solar panels (including brackets), light heads, control boxes (with controllers, batteries, etc.) and light poles, foundations, etc. Solar street lights are generally separated into power supply systems and are not connected to conventional streetlight power networks. Solar street light system is mainly 12V and 24V.

solar street light calculation

A. Solar Panel Selection

1. PV-cells type

Solar cells convert solar energy into electricity. More practical have monocrystalline silicon, polysilicon, amorphous silicon solar cells and so on.

• The performance of monocrystalline silicon solar cells are stable. Suitable for use in the rainy days more, relatively not very abundant sunshine in the southern region;
• Polycrystalline solar cell production process is relatively simple, the price is lower than monocrystalline solar cell. It is suitable for use in the regions with sufficient sunlight and good sunshine;
• Amorphous silicon solar cells have relatively low requirements for solar lighting conditions and are suitable for use in areas where outdoor sunlight is insufficient.

2. Solar panel operating voltage

The operating voltage of the solar cell is about l.5 times the battery voltage to ensure proper charging of the battery. For example, 8 to 9V is required to charge the 6v battery

Solar cells require 15 to 18V solar cells to charge a 12V battery. A 33 to 36V solar cell is required to charge the 24V battery.

3. Output power (Wp).

The output power per unit area of the solar cell is approximately 127Wp/m2.

Solar cells are generally composed of multiple solar cell batteries in series, the capacity of which depends on the total consumption of light sources and line transmission components

Power and local solar radiation energy. The output power of the solar cell group should be more than 3 to 5 times the power of the light source: rich in light and when the lights are turned on

The short area is more than (3 to 4) times, and the opposite is more than (4 to 5) times more.

4. Average peak hours of daylight(h).

Solar cell output power Wp is the standard solar light conditions, the EuropeanCommission defined 10 1 standard, radiation intensity 1000W/m² , atmospheric mass AM1.5, battery temperature 25.2C conditions, solar cell output power. The output power of the same solar cell is different at different times, at different locations. The so-called standard conditions, close to the usual sunny around noon solar light conditions.

Table – 1 -Sunny conditions in different parts of China

Table 2 – The total amount of radiation over 2 years corresponds to the average daily peak number of hours of daylight

5.Solar battery group selection and installation

Street light poles are generally above 5m and have a higher center of gravity. Most solar panels are suspended to enhance the wind resistance of the entire equipment, generally select multiple solar panels to form the required component power.

Table 3 Average annual sun time and optimal installation inclination in major cities in China

B. Battery selection

The battery stores the electricity emitted by the solar panels in light and releases it when lighting is needed at night.

Some manufacturers have developed solar streetlight systems that do not use batteries; solar cells are connected to the grid. Switched by the control circuit. Investment

Less, less running and maintenance costs, less energy consumption, stable system operation. Suitable for streetlights in near-market networks. Courtyard lights. Advertising light boxes, etc.

Focus on solar streetlight systems with batteries.

1. Type selection

• Lead Acid battery: suitable for low temperature high multiplication discharge, lower than energy, most solar street lights are currently used. Seals are maintenance-free, the price is low. Attention should be taken to prevent lead-acid contamination and should be phased out.
• Nickel cadmium (Ni-Cd) battery: high discharge multiple, good low temperature performance, long cycle life, small system. Take care to prevent cadmium contamination.
• Ni-H battery: high multiply discharge, good low temperature performance, cheap, non-polluting, green battery. Small system mining use. We should vigorously advocate.

At present, widely used lead-acid maintenance-free batteries, ordinary lead-acid batteries and alkaline nickel cadmium batteries three.

2. Capacity selection

The battery capacity is too small to meet the needs of night lighting, the capacity is too large, the battery is always in a loss of power state, affecting battery life,

It also causes waste. The ratio of battery capacity (Ah) to load capacity (Ah) should be more than 3 to 6 times: the number of consecutive rainy days is about 3 to 4 times higher

The area with more continuous rainy days is about 5 to 6 times more.

3. Battery serial-parallel

When connected in a union. The effect of imbalance between individual batteries should be considered. The number of groups in union should not exceed 4 groups. Pay attention to battery theft prevention.

C. The controller

The operation of solar streetlights is controlled by the controller. Most of the controllers achieve intelligent control. The controller should have the following features:

1. Street light control

Light control, time control, temperature control and other functions to choose from. Has the function of d?ed (or midnight light).

2. Battery management

Limit the charging and discharge conditions of the battery and extend its service life:

• Anti-recharge control:
• Anti-charging control:
• Anti-discharge control;
• Temperature compensation.

3. Automatic protection

Solar cell reverse protection, battery reverse protection, battery open-circuit protection, night anti-recharge protection, output short-circuit protection, etc.

4. Digital display

Show solar street lights mainly teach: battery voltage, solar cell photovoltaic voltage, etc.

5. Controller voltage

The controller voltage is the battery voltage.

D. Solar cell inclination design

Solar cell inclination refers to the angle between the solar panel plane and the horizontal ground.

The inclination of solar cell modules (refers to the angle between solar panel plane and ground plane) has been discussed in the technical circle. The tilt angle is positioned by location set (latitude, etc.) to determine, the front of the solar panel is facing the sun (or slightly westerly south), the inclination is consistent with the local latitude can be. If conditions permit.

The inclination of the solar panels can be adjusted accordingly with the seasonal changes.

Solar cell installation inclination in major cities in China refers to Table 3.

E. Solar street light wind-resistant design

1. Wind-resistant design of solar modules

Solar street light wind resistance design according to the size of the maximum wind:

Table – 4 The correspondence between wind and wind speed

Note: Excerpted from “GB/T 19201-2006”.

If have more typhoons on the south coast, solar street light poles should be able to resist at least 12 typhoons, most areas in the north should be able to resist 10 strong winds.

2. Wind-resistant design of street light poles

• Solar modules: Manufacturers should ensure that they can withstand local wind speeds without damage, with a focus on the connection of the battery module support to the light pole.
• Light poles and foundations, street light poles and foundations wind-resistant design and battery board height, area, inclination and light rod structure, maximum local wind speed, etc

Relatedly, the light manufacturers or structural expertise should be calculated and designed to ensure the stability of solar street light poles at maximum wind speed.

F. Solar lighting is the main light source and application

There are two forms of light source and solar system:

• Solar-powered HID light electronic townifier (or trigger, the same between. ): Powered directly by the battery. It’s actually a DC/AC high converter. So. Solar street lighting systems generally do not require additional DC/AC inverters, reducing circuit losses. This form is suitable for new solar street light projects.
• With traditional HID light electronic water mains: connected to AC220 mains power supply. Its electronic marketifier is essentially an AC/DC/AC high-frequency converter. If connected to a solar system, a DC/AC small power inverter needs to be added between the battery and the HID light electronic barge. This form is suitable for street light retrofitting.
• Application: Solar LED light, HID light, induction light power is more than 70W. Some above l00W. It is generally used for branch road and sidewalk lighting. Small-power solar LED lights, energy-saving lights used in garden, landscape lighting.

G. Lightning and grounding

1. Safety voltage

Solar street lights generally use DCl2V or DC24V. Is a safety voltage, do not do electrical protection grounding.

2. Lightning-proof grounding
   • Street lights and solar panels are not available as flashers;
   • Use a metal light post as a flasher and lead down:
   • Street light base steel cage at -0.50m below its steel surface area is too much than 0.37m2, can be used as a lightning-proof grounding body. Otherwise, the artificial ground pole should be increased and the ground resistance ≤ 10 euros. Connect the ground body if necessary. Grounding practices are the same as general streetlights
   • Set up TVS (transient voltage suppression) lightning protection in the street light controller.

Examples of solar street light design

Example: A road sidewalk is to be installed LED solar street lights.

Pole height 5m

Street light input voltage 24V

Street light power 70W

Daily work 8.5h.

Lighting is guaranteed for 7 consecutive rainy days.

Try to carry out LED solar street light design:

1. Solar cell selection

• Average annual sun time: Check Table – 3″: 4.04h.
• Street light day power consumption: (70/24)8 5-24.79 (Ah)
• Total charging current of the battery pack: (24．79*1 05)／(4．04*0 85)=7.58(A）

* l.05 is the comprehensive loss factor of solar module system, O. 85 Charging efficiency for the battery.

• Total power of the solar cell set: 7.58*34.8=263.78(W)

Select 2 pms and 135W solar panels in a side -by-side. The optimum operating voltage is 34.8v. Best working current 3.88A. Component size 800 x 1580 x 50(mm)。

2. Battery selection

Battery capacity: 7.58 x (7 plus 1) x 60.64 (Ah)

Choose a 24V170Ah maintenance-free lead-acid battery.

3. Controller

Select the smart controller. According to the requirements of the street light system to adjust the controller parameters, wells for street light batteries and other protection

4. The inclination of the solar cell

Refer “table – 3”, solar cell inclination: 34．72⁰+7⁰=41.72⁰

The solar cell group is slightly west-south, with an inclination of 41.72⁰ from the horizon.