Page 36 - Energize December 2022

TECHNICAL

With LED technology, very specific beam angles such as 20°,
30°or 40° are possible. Stadium light towers vary in height
according to application, and they are offered with different
beam angles to achieve the required coverage. Choosing the
proper light and beam angle will depend on the size of area
being covered by light, the illumination level required on the
ground and the height of the luminaires.

LED stadium lighting fixtures

High powered LED stadium lights are based on combinations of
Omnidirectional source (HID) Unidirectional source (LED)
the high-powered chip on board (COB) LED assemblies (Figure
Figure 1: Directionality of light source
2). COB units are combined in different ways to give both the
required lumen output and beam angle or coverage pattern.
Flood lighting light levels With COBs, modules can be assembled in any shape from
Light levels depend on three factors, the luminous flux (lx), the round to rectangular, allowing the light beam to be pre-shaped
luminous efficacy (how well a light source produces visible light) and give the type of lighting required.
and the luminous intensity or directionality. Luminous flux is the
total amount of light emitted measured in lumens. Luminous
efficacy is the amount of light emitted per unit of input electrical
power, measured in lumen/watt. LEDs have a higher efficacy
than other forms of stadium lighting, typically 150 lumen/watt.
Luminous intensity will depend on the directionality of the light
source (see Figure 1). Floodlights are intended to direct light to
a particular area and the directionality of the light source will Figure 2: LED COB clusters (Brightstar)
determine how effective the floodlight is in achieving this goal.
HID lighting and other discharge lighting is omnidirectional
by nature and a high portion of the output needs to be reflected
to achieve the desired flood or spot lighting effect. LED lighting is
unidirectional by nature and the total light output is beamed in
a 180° cone. For the same lumen output, the luminous intensity
of the LED will be much higher in one direction than that of the Figure 3: Typical LED floodlights (Telco)
discharge lamp, and the LED floodlight will require less reflected
light to achieve the desired floodlighting or spotlighting effect. Wattage
The luminous intensity in the target area (illuminance) will LED stadium luminaires are rated in wattage.
be higher for LED lighting than for other types of lighting of the
same lumen capacity, due to lower reflection losses. This leads to Type Wattage Lumen output
higher system efficiency. Circular spot 500 70 000
Square flood 190 22 492
Beam angles 230 30 000
The beam angle of a light source is the angle at which the Rectangular flood 600 90 000
light is emitted, and luminaires with different beam angles are 900 135 000
required to provide the required light pattern in a stadium. As 1200 155 000
LED stadium lighting has beam angles ranging from 12 to 120°,
they provide better uniformity and brightness than earlier light Table 2: LED stadium light wattage
sources. LED fixtures can provide a range of beam angles on
the same fitting by the use of optics. LED floodlights allow a Lighting controls
wide variety of beam shapes, ranging from circular, through Electronic control of LED stadium luminaires makes dimming
rectangular to square. Lighting types are also classified by the possible. Since different events require different lighting, the
angles of the light spread. Below are the most commonly used ability to adjust the brightness on the fly is useful. Not only does
abbreviations for the angle spreads. this help provide different end results with the same luminaires
but also helps reduce energy costs.
• SP or Spotlight: 4 to 19°
• FL or Flood Light: 20 to 35° References available on request
• WFL or Wide Flood Light: 36 to 49°
• VWFL or Very Wide Flood Light: 50 to 120° or more Send your comments to rogerl@nowmedia.co.za

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