What is Lux in Lighting? Solar Street Lighting Lux Level standard

What is Lux in Lighting

Lux measures the amount of light falling on a surface and is the standard unit of photometry used to specify brightness levels across various lighting types, including household, office, automotive, and street lighting.

The Importance of Lux Levels

While lumens measure the total light output from a source, Lux measures the intensity of that light at the surface, indicating how effective the lighting setup is. For example, a bulb producing 1000 lumens can have different Lux levels depending on its distance from the surface being lit. Thus, understanding and applying Lux metrics can significantly enhance the effectiveness of lighting deployments.

Solar Street Lighting Lux Level standard

Highway Lighting Lux Levels

• First-Class and Second-Class Highways: Minimum average illuminance maintenance value 20 Lux (low standard) / 30 Lux (high standard), uniformity minimum value of 0.4;
• Third-Class Highways: Minimum average illuminance maintenance value 15 Lux (low standard) / 20 Lux (high standard), uniformity of 0.4;
• Fourth-Class Roads: Average illuminance 10 Lux (low standard) / 15 Lux (high standard), uniformity of 0.3;

Note: The above requirements apply only to asphalt roads; concrete roads may reduce these requirements by up to 30%.

Urban Road Lighting Lux Levels

• Express and Main Roads: Minimum average illuminance maintenance value 20 Lux (low standard) / 30 Lux (high standard), uniformity minimum value of 0.4;
• Secondary Roads: Minimum average illuminance maintenance value 15 Lux (low standard) / 20 Lux (high standard), uniformity of 0.4;
• Side Roads: Average illuminance 10 Lux (low standard) / 15 Lux (high standard), uniformity of 0.3;

These requirements are based on asphalt roads, with potential adjustments for concrete surfaces as noted above.

Rural Road Lighting Lux Levels

• Primary Roads: Minimum average illuminance maintenance value 10 Lux (low standard) / 15 Lux (high standard), uniformity minimum value of 0.3;
• Side Streets and Lanes: Minimum average illuminance maintenance value 5 Lux (low standard) / 8 Lux (high standard);
• Public Activity Squares: Minimum average illuminance maintenance value 10 Lux (low standard) / 15 Lux (high standard);

How bright the solar lights should be?

The lumen requirement forsolar lights varies based on factors like pole height, road width, and ambient light. Generally:

• Solar landscape light: 3000-5000 lumens, illumination requirements 10-100 lux
• Solar path light: 30-60 lumens, illumination requirements 5-10 lux
• Solar floodlight: 1000-3000 lumens, illumination requirement 10-100 lux
• Solar garden light: 50-100 lumens, illumination requirement 5-15 lux
• Solar trail light: 30-50 lumens, illumination requirements 5-10 lux
• Solar decorative lights: 10-30 lumens, illumination requirements 1-5 lux

Calculating Illuminance (Lux) for Solar Street Lights

The illuminance (Lux) calculation for solar street lights involves multiple factors, including total luminous flux from the light source, utilization coefficient, light loss factor, lamp spacing, and road width. Below are specific calculation methods and relevant details:

Lighting Lux Calculation Formula

Average Illuminance (Lux):

Average Illuminance (Lux) = (Total Luminous Flux (Lumen) * Utilization Coefficient (UC) * Light Loss Factor (LLF)) / (Road Width (m) * Lamp Spacing (m))

E=(Φ×UC×LLF )/(W×S)

• Where:
  • E = Average Illuminance (in Lux)
  • UC= Utilization Coefficient
  • W = Road Width (in meters)

Lux Detailed Calculation Steps

1. Determine the Total Luminous Flux:The total luminous flux refers to the total amount of light emitted by a fixture. For example, a 70W ceramic metal halide lamp with an efficacy of 100 lumens per watt would result in:Total Luminous Flux (Φ) = 70W * 100 lumens/W = 7000 lumens
2. Determine the Utilization Coefficient (UC):The utilization coefficient indicates what portion of the light emitted effectively illuminates the target surface. It depends on fixture design, installation height, and road shape. For instance, assume the utilization coefficient is 0.6.
3. Determine the Light Loss Factor (LLF):The light loss factor accounts for the decay of the light source over time and the reduction in transmissivity due to aging and dirt accumulation on the lampshade. Typically, LLF ranges from 0.7 to 1, and specific values can be adjusted based on actual conditions. For example, assume an LLF of 0.8.
4. Determine the Road Width (W):For example, let’s say the road width is 10 meters.
5. Determine the Lamp Spacing (S):For example, assume the lamp spacing is 30 meters.

Light Lux Calculation Example

Suppose we have a 70W ceramic metal halide lamp installed on a road that is 10 meters wide with a lamp spacing of 30 meters, a utilization coefficient of 0.6, and a light loss factor of 0.8.

• Total Luminous Flux (Φ): 7000 lumens
• Utilization Coefficient (UC): 0.6
• Light Loss Factor (LLF): 0.8
• Road Width (W): 10 meters
• Lamp Spacing (S): 30 meters

Substituting into the formula:

Average Illuminance (E) = (7000 * 0.6 * 0.8) / (10 * 30) = 11200 / 300 = 37.33 Lux

Other Influencing Factors

Maintenance Factor (K)

The maintenance factor considers the effects of light source decay, fixture protection levels, and long-term dust obstruction on average road illuminance. Maintenance factors typically range from 0.65 to 0.7. For example, assume a maintenance factor of 0.7:

Average Illuminance (E) = (7000 * 0.6 * 0.8 * 0.7) / (10 * 30) = 7840 / 300 = 26.13 Lux

Fixture Installation Height (H)

The height at which fixtures are installed affects the distribution of light. According to the inverse square law, the required power for fixtures at different heights can be approximated based on illuminance. For instance, a 9W DC energy-saving lamp at a height of 2.41 meters would provide ground illuminance of 8–11 Lux.

Optimizing Configuration

Solar Panel Capacity Design

The solar panel capacity is closely related to daily load consumption, geographical conditions, solar resources, and climate conditions. For example, with a 24V 40W non-directional lamp used for 8 hours over 4 consecutive cloudy days, the required battery capacity is:

Battery Capacity = (1.1 * 40 * 8 * 4) / (0.85 * 0.75 * 24) ≈ 92.1 Ah

This could typically lead to selecting two 12V/100Ah batteries in series.

Component Configuration Optimization

To ensure quick recovery back to operational status after deep discharge over four consecutive days, the capacity of the components must be increased to reduce charging time.

For instance, a 160Wp component can be estimated for charging time:

Average Battery Charging Time = (2 * 100 * 12 * 0.75) / (0.9 * 0.78 * 160 * 4.45) ≈ 3.6 days

If charging time is too long, consider increasing the component capacity.

Engineering Application Example

Yangtiangang Avenue

This road is approximately 4.5 kilometers long and 60 meters wide, classified as a primary thoroughfare with asphalt concrete pavement.

The road lighting uses solar street lights, operating at full power for the first 6 hours and half power for the remaining time.

Fixture Configuration:

• Solar Panel: 6 * 90W/24V monocrystalline silicon with conversion efficiency over 16%
• Installation Height: 12 meters
• Lamp Spacing: Approximately 30 meters

System Requirements:

• Average Road Illuminance: 20 Lux
• Illuminance Uniformity: Not less than 0.4

Conclusion

In conclusion, understanding how to properly calculate and optimize the Lux levels for solar street lights is essential for effective design and implementation. By considering factors such as the total luminous flux, utilization, adjustment factors, and road specifications, we can ensure that solar lighting systems meet required standards and provide adequate illumination for safety and visibility.

For more information on lumens and their significance in lighting design, check out this article: Understanding Watts and Lumens.