Solar energy – detail the structure and advantages of LED street lights and incandescent light sources

  1. Solar LED Street Light

Street lamps generally use high pressure discharge lamps such as high pressure sodium lamps or mercury lamps. Advances in LED technology have made it possible to replace 250W mercury lamps with 120w LED lighting systems. For many municipal administrations, public lighting accounts for a large proportion of the budget, and this budget must be reduced. Investing in LED street lighting is an opportunity to meet budget reduction goals.
Advantages of LED street lights:
1) Lower energy consumption;
2) Lower maintenance costs;
3) Longer life;
4) Excellent automatic control;
5) Quick response;
6) Does not pollute the environment;
7) The illumination is more uniform;
8) Higher color rendering produces better night lighting effects;
9) No mercury pollution and other hazards.

Solar street lights (Figure 1) can reduce the energy consumption and maintenance costs of street lights, only need to regularly
Replacing the battery (if it is lead acid) (every 3-5 years) will solve the power outage.
To design a solar LED street light:
Target: Lamp with a height of 8-10m and a ground illumination of 25~50lx.
LED 120W
Working time per day: 10h
Electricity required per day: 120W x10h = 1200wh
The power of the solar panel for 4h light during the day: 300w
Lead-acid battery 12V: 100Ah/0.5=200Ah
Charge controller: 12V-30A
Inverter: 200w
In this example, the system operates normally under basic sunlight conditions without any additional self-powered energy. In commercial street lights, consumers should choose the number of days to use self-powered energy according to the severity of the weather.

Figure 1 - Example of solar LED street light
Figure 1 – Example of solar LED street light

The opening angle of the LED street light beam determines the installation distance between the two light poles, so that the light emitted by the light can cover the ground 100%.
If the same system, using a 250W mercury lamp, the total energy required per day would be:
250W x 10h = 2500Wh
The power of the solar panel for 4h light during the day: 625W
Battery: 210A//0.5 =420Ah Charge Controller 12V-50A
In addition to the cost increase in the case of using mercury lamps, the need for more space for installing solar panels and placing batteries is also a practical problem. This also provides another advantage to the application of LEDs in street lamps.

Solar street lights composed of LEDs can use an intelligent controller to further reduce energy consumption. The most basic smart controller can turn lights on at dusk and turn them off at dawn; this can be done by testing the current and voltage on a solar panel. In addition, some other controllers can be equipped with a timer, which will cause the LED light to turn off after a fixed period of time. The smartest controllers can dim the LEDs gradually or periodically, depending on the environment and surrounding brightness, and turn the lights off completely at dawn. For example, the LED light can work at full power for the first 4 hours after entering dusk, reduce the brightness by 30% for the next 2 hours, reduce the brightness by 30% for the next 2 hours, and finally turn off the light at dawn. LED street lights can use DC systems. In solar street lights, they are generally 12V and 24V DC systems. In this case, there is no need to use an inverter.

To replace the existing street lights, LED street lights must be designed according to the actual situation of heat sinks and lamp bases such as E40 (see Figure 2); LEDs and heat sinks can also be integrated (see Figure 3). In either case, LED lamps do not use reflectors like HPS lamps, thus reducing energy losses.

Figure 2-E40 screw LED light, Figure 3-Integrated LED street light fixture
Figure 2-E40 screw LED light, Figure 3-Integrated LED street light fixture
  1. Incandescent light source

Incandescent bulbs consist of a thin glass envelope and a tungsten filament that conducts electricity (see Figure 4).

Usually it is a device with two terminals without positive and negative polarity. The glass cover is filled with an inert gas such as argon to reduce the evaporation of the filament and prevent the oxidation of the filament. When an electric current is passed through the tungsten wire, the temperature of the tungsten wire usually rises to 20003300K (lower than the melting point of the tungsten wire, which is 3695K). For a given amount of current, the elevated temperature of the tungsten wire is primarily determined by its thickness. It radiates outward in a continuous spectrum, but only a small fraction of the radiation falls in the visible range. Most of the energy is radiated out as heat.

Figure 4 - Incandescent light bulb
Figure 4 – Incandescent light bulb

Higher energy incandescent bulbs are tee bulbs. They consist of two filaments and three feedback adapters installed in the lamp head. The two filaments share a ground terminal and can be lit individually or simultaneously. Incandescent light bulbs or incandescent lamps emit light by heating a tungsten filament to such a high temperature that it achieves a glowing state. The hot filament is protected by a glass cover. In order to isolate the filament from the air, the glass cover is either filled with an inert gas or a vacuum.

Incandescent lamps vary in size, light output, and voltage rating, from 1.5V to 300V. They do not require external conditioning equipment, require low manufacturing and operating costs, and operate on both AC and DC. Therefore, incandescent lamps are widely used in home or commercial lighting, or portable lighting, such as desk lamps, car lights and flashlights, or for decorative and advertising lighting.

Incandescent lamps are gradually being replaced by fluorescent or LED lamps in many applications. Compared to incandescent technology, the application of new technologies such as fluorescent lamps and LED lamps has increased the ratio between visible light and thermal energy consumption. About 90% of the energy of incandescent lamps cannot be converted into visible light energy, but is converted into thermal energy and radiated out. Tungsten filaments of incandescent lamps in the solid state dissipate most of the input electrical power in the infrared radiation region, even as the filament temperature increases, the radiated visible light increases, but at high temperatures (below the filament melting point), most of the radiation Still in the infrared and ultraviolet regions. The theoretical value of the highest luminous efficacy of tungsten wire is about 52lm/w at its melting point.

Compared to LED and fluorescent lamps, incandescent lamps generate more heat, so more power needs to be dissipated to output a given amount of light (measured in Im). LED lights or fluorescent lights emit light by photoluminescence, not by heating tungsten filaments like incandescent lights.

Tungsten halogen lamps are also an incandescent light source. However, it is an improvement over standard incandescent lamps. It is more efficient, up to 20%, and has a longer lifespan. Traditional incandescent lamps fail because the tungsten filament evaporates over time, becomes thinner and eventually breaks. In halogen lamps, the halogen gas causes the vaporized material to re-precipitate on the filament, extending its life. These lamps are more expensive than standard incandescent lamps and are often used for commercial lighting or outdoor lighting.

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