A leisurely approach to lighting
With soaring energy prices very much in the headlines, leisure operators are taking a much closer look at how they can reduce energy consumption without compromising on lighting quality or health and safety. Lighting specifiers, therefore, have an important role to play in helping them achieve their objectives.
In some areas, such as offices, gymnasia, refreshment areas and staff areas, achieving energy efficient lighting is relatively straightforward and has been for some years. Many leisure buildings will already have efficient fluorescent lighting in these areas, sometimes linked to a control system for even greater savings.
In areas such as sports halls and swimming pools, where low or high bay lighting with high intensity discharge (HID) lamps are normally used, energy efficient lighting has been more of a challenge in the past. This is mainly because of the limited opportunities for control. As a result, many existing installations waste a great deal of energy simply by leaving the lighting on when the space is not in use. This is particularly true of areas that may only have a relatively short unoccupied period between bookings.
Advances in lamp and control technology, though, have now made advanced control of HID fittings considerably more viable. Consequently, areas such as sports halls, squash courts and swimming pools can benefit from the same energy savings techniques as other areas.
At the same time, it is important to ensure a high quality of lighting with good light distribution and minimum shadows for health and safety purposes. At the Wellington Swimming Pool in Telford, for example, lighting levels for pool side illumination were found to be too low when the pool was refurbished.
The pool operators, Telford & Wrekin Council, were keen to improve the quality of the lighting but did not want to increase the facility’s carbon footprint. The answer proved to be the use of Holophane’s Prismalume luminaires, which have a light output ratio of 95%, so that more of the light per kilowatt is directed to where it is needed. As a result, light levels were increased, with a pleasanter, natural white light, with no increase to the installed electrical load.
Just as importantly, the light is distributed from the luminaires more efficiently, projecting light directly onto the pool and pool side as well as illuminating the walls and ceilings without shadows. This meant that fewer lighting points could be used to achieve the specified uniformity criteria. This helped to reduce capital and maintenance costs as well as energy consumption.
In addition to good light distribution, areas such as sports halls, which tend to have multiple courts using different coloured layouts, require good colour rendering for users. For this reason, many leisure building operators are opting for metal halide light sources in luminaires with high optical efficiency to achieve the maximum benefits.
The same principles apply to the lighting of outside sports areas, where good light distribution is essential to avoid light trespass onto neighbouring properties and light pollution into the sky. Well designed luminaires ensure the light is directed precisely to where it is required, again ensuring minimal shadows to maximise visibility.
Staying in control
As mentioned above, a major challenge faced by many such installations is gaining control of the HID lighting, particularly in relation to occupancy and natural daylight levels.
In the past the technology wasn’t available to dim these HID lamps so, traditionally, the control aspects of the lighting weren’t given much consideration. Now, however, there is a system available to do this, so dimming has become an option – and a very important one at that. Apart from saving energy, the ability to dim the lamps can extend their life and reduce maintenance costs as well.
To explain the benefits of dimming further, it’s necessary to understand one of the key characteristics of HID lamps, namely that they take some time to warm up and reach full light output. And, if you switch them off they need to cool down for a while before they can re-strike.
These characteristics have severely limited the control options available to buildings using HID lamps in the past. For instance, it wasn’t practical to use occupancy sensors in squash courts and other areas of variable occupation for switching lighting on and off, because of the time taken to come back on when someone enters the area.
Now that dimming is available, it’s possible to dim the lighting in an area when there’s nobody using it and, because the lamp remains on, the light output can be ramped up again immediately when it is needed. Thus, the problems of re-strike times are eliminated while also saving considerable amounts of energy.
In addition, this approach makes it possible to make better use of natural daylight. For instance, many pool halls have a glass wall that allows in a considerable amount of daylight. So there may be plenty of light on one side of the pool but less on the side of the hall furthest from the windows.
In the past, all of the lighting would have been left on at full output because of the re-strike times mentioned above and the chance of a passing cloud reducing natural daylight. Essentially, from a health and safety point of view, it wasn’t worth risking a lower illuminance in certain areas while the lamps warmed up again.
Using dimming technologies linked to photocells in the pool hall, the lighting can now be controlled in zones to maintain a uniform illuminance while minimising the energy consumption of the lighting. Should a cloud pass and cause a sudden fall in natural daylight, the luminaires will ramp up the light output immediately.
The control can also be very precise, as each photocell sends a 0-10V control signal in direct proportion to the lux levels, via a PLC building controller to the dimmable ballasts. So, for example, a row of luminaires near a window could be dimmed to 10% light output, those in the middle of the hall to 50% and those furthest from the window to 80%.
All of which saves energy, of course, plus it has the added benefit of extending the life of the lamps because they are being used less. This means that lamps do not need to be replaced as often, so all of the disruption and hassle associated with accessing high light fittings is reduced. This includes downtime to erect scaffolding or bring in a cherry picker, as well as the paperwork associated with the latest Working at Height regulations.
A further benefit of longer lamp life is that fewer lamps have to be disposed of each year under the WEEE Directive, so there are additional costs savings from this.
As with any lighting project, the key to achieving the best solution is to gain a good understanding of the client’s requirements. In the case of leisure facilities, where those requirements can be more complex than other buildings, it also makes sense to call on the assistance of specialist lighting companies that have experience of this type of application.