What is Flood Lighting?
Flood lighting refers to flooding of large surfaces through powerful projectors where the light sources are concentrated into narrow beams using specific reflectors.
We implement flood lighting for outdoor purpose therefore its housing and build should be robust and its design should be whether proof for remote installation purposes.
The reflecting surfaces are made up of silvered glass or chromium plate or stainless steel and the casing and its mounting are arranged so that the inclination of the beam can be varied in both horizontal and vertical direction. In addition to this, ventilation is present for sufficient cooling. In order to facilitate the cooling there is implementation of sufficient radiating surface.
Classification of Flood Lighting Projectors
According to the beam spread angle, the flood lighting projectors can be classified into the flowing three classifications.
|Classification||Beam Spread||Distance of Projection|
|1. Narrow Beam Projectors||12o to 25o||Beyond 70 meters (m)|
|2. Medium Angle Projectors||25o to 40o||Between 30 m to 70 m|
|3. Wide Angle Projectors||40o to 90o||Below 30 meters|
The medium and wide angle projectors make use of standard glass filled tungsten filament lamps of 250 Watts, 500 Watts or 1000 Watts.
The narrow beam projectors make use of special lamps having bunch of filaments. These lamps are known as projector lamps.
In case of flood lighting, wide angle projectors with high wattage lamps will be more economical than the narrow beam projectors with low wattage.
Location and Mounting of Projectors
There are two possible locations of projectors in practice.
- Projectors kept 20 to 35 meters away from the surface to be flood lighted in order to have symmetric illumination.
- When we cannot locate the away from the building then we can make use of unsymmetrical reflector. We can mount these unsymmetrical projectors in a basement area or we can attach them on a bracket with the building so that it will direct more intense light towards the top of the building.
Implementation of Flood Lighting
Flood Lighting are implemented for following purposes:
- Aesthetic Flood Lighting:
For enhancing the beauty of buildings at night. Such as in public places, ancient buildings and monuments, religious buildings and important festivals and occasions.
- Industrial and Commercial Flood Lighting:
For illuminating the places such as railway yards, sports stadium, car parking, construction sites and commercial complex.
For illuminating advertisement boards and showcase.
Flood Lighting Calculation
For the problem of the flood lighting calculation, we can perform the following three steps:
Illumination Level Required
Depending upon the types of building the purpose of flood lighting and the amount of conflicting light in the vicinity should be considered.
Types of Projector
For the types of projector, the following consideration should be taken.
- Beam Size:
The flood lighting will cover some area with its illumination. Meanwhile we can determine this area from beam angle. It also gives the estimation of distance of projector from the surface.
- Light Output:
The illumination required for the projection should be considered as per the surface.
Number of Projectors
To calculate the number of lights or projectors we will be requiring for the flood lighting is
N = Number of projectors (which we will be requiring)
μw = Waste light factor
A = Area of the surface (the surface which we will be illuminating)
μm = Maintenance factor
E = Illumination level (the necessary value of illumination)
μu = Utilization factor or Beam factor
Waste Light Factor (μw)
While illuminating a surface using the flood lights there is always a certain amount of waste of light due to overlapping of light sources and falling of light sources beyond the edge of the surface.
Hence, we have to consider waste light factor by multiplying theoretical value of lumens required by 1.2 for regular or rectangular surface area and 1.5 for irregular surface areas, objects, monuments, statues etc.
Reflection Factor (μr)
When light is projected on a certain surface, a certain portion of the light is absorbed by the surface and the hence the reflected light will not be of same intensity.
Hence, ratio of reflected light to the incident light (initial incident illumination and reflected illumination) is called the reflection factor. This factor is always less than unity.
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