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The lighting project at Portsmouth City Council has made massive savings
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Lighting is a key element in modern office buildings and facilities managers are becoming increasingly aware that correct specification and use of office lighting ensures compliance with environmental and other legislation. Not only that, office workers are at their most productive when levels of light are at the optimum.
On the downside, lighting comes at a cost, both financial and environmental. Lighting can account for up to half of a typical office building’s total electricity use. So cutting the amount of lighting used can produce some significant energy cost savings. The Carbon Trust estimates that non-residential buildings alone are responsible for around 20% of the UK’s total carbon emissions. As artificial lighting accounts for a signification proportion of that, it is clear that controlling office lighting should be top of the agenda for buildings and facilities managers to allay environmental concerns as well as to cut energy costs.
Behavioural change
The best way to eliminate the unnecessary use of office lighting is to ensure all occupants only switch on the lights when needed, and switch them off again when they leave. Unfortunately, human nature dictates that this just will not happen. We are all familiar with the sight of huge office blocks where lights remain blazing long after the workers have gone home for the night. So there is a need to eliminate unnecessary use of lighting automatically.
There are various ways to automatically control lighting in office buildings in order to cut energy consumption. The crudest method is by timer control. But it is not difficult to see the disadvantages of this. In an age of flexitime and hot-desking, there are few offices today where such a rigid approach to controlling the lighting would be appropriate.
Building management systems (BMS) are ideal for controlling a small number of large and static loads such as heating and ventilation plant. But lighting management is all about controlling a large number of small loads (the light fittings themselves) distributed throughout the whole building, and so this is also not an ideal solution for lighting control.
Intelligent solutions
It is clear that technology should be employed to control individual light sources and lighting patterns in direct response to the needs of the individual building occupants. Enter lighting management and control systems using presence detection. The principle is simple. The technology ensures that lighting is switched on only when needed, when monitored areas are occupied and daylight levels are insufficient.
Intelligent lighting control enables a building to think for itself. It knows the movements of occupants and maintains the correct level of lighting wherever they happen to be. It turns the lights off when an area is no longer occupied. It automatically adjusts the lighting for optimum working levels. And of course, it can keep certain key areas permanently lit such as corridors, exit routes and toilet facilities if required.
The end result is a simple, reliable and effective method of lighting control which affords substantial energy savings, as well as guaranteeing adherence to health and safety legislation and producing the ideal lit atmosphere for productive working.
Delivering results
So what are the control technologies that really work and successfully deliver these results? Lighting management systems incorporate detectors which are either ceiling-mounted units or tiny units built into the luminaires themselves and linked to the luminaire ballasts. Controls utilise various presence-detecting technologies: passive infrared, ultrasonic or microwave. The choice of technology will be determined by the specifics of the building and the requirements of the application.
Natural light plays an important part in automatic lighting control. It would be wasteful to have a system that responds only to the presence of occupants and switches lights on during periods of bright natural lighting. So photocells are built into the systems along with the presence detectors. Photocells measure the levels of natural light and switch or regulate the lights accordingly.
Case study
A recent Ex-Or project was the installation of lighting controls throughout Portsmouth City Council's civic headquarters, designed to automatically eliminate the unnecessary use of its office lighting. This led to the council cutting its annual energy consumption for lighting in the offices and corridors from 1,259,398 to 655,211 KWh. This represents annual cost savings of approx £39,151 and annual CO2 savings of 326 tonnes.
So making carbon savings, and dramatically cutting energy costs, are the main benefits of installing office lighting control. We have already seen that optimum lighting levels create a more comfortable and productive working environment for staff within the building. Incorporation of lighting management controls automatically ensures compliance with various pieces of workplace and environmental legislation. In particular, it ensures compliance with Part L of the Building Regulations and it enables the building to demonstrate higher ratings in the Energy Performance and Display Energy Performance certificates (EPC and DEC).
John Forsyth is general manager of Ex-Or , a division of Honeywell
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