Innovative dimming system cuts lighting costs

Use of Holophane’s innovative Prismatron dimming system is enabling Broadwater School in Godalming,
Surrey to make significant energy savings in lighting its sports hall.

As part of refurbishment of the sports hall at Broadwater School, standard high bay lights were replaced with Holophane’s Vantage lighting fixtures, using the Prismatron dimming system. The combination of Vantage and Prismatron was chosen to address the common problem experienced in many sports halls and other spaces with high ceilings of only having limited control of the lighting. In taking more effective control of the lighting, the school is also able to control its energy consumption to reduce costs and carbon footprint.

Major challenge

Traditionally a major challenge in lighting sports halls has been the need to mount light fittings high in the ceiling to avoid damage by balls and other projectiles. This means the light from the fittings has to travel a long distance to the area being lit at floor level. Achieving this necessitates the use of powerful, high wattage lighting using high intensity light sources.

Equally important is the quality of the lighting, as it does not just have to be of sufficient intensity, it also needs to have good colour rendering - the ability to show colours well. This ensures that fast moving objects can be seen clearly and it is easy to distinguish courts for different sports, indicated by lines of different colours.

A further challenge comes from the fact that this type of space is frequently used for a wide range of sporting activities and for examinations. Each of these activities has different optimum lighting levels.

Clearly, the ideal situation is to dim the lighting in relation to the levels of light required. However, until the Prismatron system was introduced the technology was not available to dim the special high intensity light sources used in these spaces.

As a result, the options for energy conservation were limited. Essentially, before Prismatron, this type of lighting could be switched on and off. However, it also takes a long time to warm up when first switched on, so switching it off for short periods of time was not a viable option.

Thanks to the Prismatron system, these limitations have been overcome, as it enables high intensity light sources to be dimmed and very quickly ramped back up again. This has enabled Broadwater School to be very flexible in the way it uses the lighting, striking the right balance between energy consumption and delivering the right level of light for the activity in progress.

“The key to the way the lighting has been set up is the versatility it offers the school to adapt to changing requirements,” commented David Goodchild of Holophane Lighting. “Not only will different light levels be required for varying activities, but the usage of the space will also vary through the day.

“Because of the warm-up times required by this type of lighting, it may not be worth switching the lighting off if the hall is only going to be out of use for half an hour, but it will certainly be worth dimming the lighting to a low level. When the hall is re-occupied the lighting can be turned back up again without delay because the lamps are still warm. Before Prismatron was introduced, this would not have been possible and the chances are the lighting would have been left on at full output at times when the hall was not in use,” he added.

Lighting levels

For activities such as examinations, for instance, the lighting can be ramped up to its highest output. Where appropriate, the same levels may be chosen for competition sports, whereas lower lighting levels may be suitable for practice and training. As the hall receives quite a lot of natural daylight there is also a possibility to link the lighting to a photocell. This would allow the lighting to dim automatically on a sunny day, so that lighting levels remain constant while use of the electric lighting is minimised.

The Vantage light fittings supplied by Holophane also help to improve the quality of the lighting, as they incorporate a unique optical assembly that provides a wide light distribution with some upward light. This ensures that light is evenly distributed through the space, using the minimum number of fittings. The upward element of light helps to illuminate the ceiling and upper walls to provide a bright and spacious feel.

Reduced cost of ownership

As well as reducing energy consumption, Broadwater School is also able to reduce the maintenance costs associated with changing the light sources. This is because, in dimming the lamps, the system also increases their life so longer intervals can be allowed between relamping visits.

These savings can prove to be significant over the life of the lighting system. As the light fittings are mounted high in the ceiling they can only be accessed via a scaffold tower, so that the sports hall needs to be closed during this time. Also, the Working At Height regulations require that a risk assessment be carried out and documented for any such work, so associated administration is reduced.