Reducing the energy consumption of lighting

Passive infrared sensors can turn lighting on and off depending on whether a room is occupied or not.
PAUL DAVIDSON explores a range of approaches to reducing longer-term lighting costs.The 24/7 culture that currently prevails in the UK, results in about 20% of the electrical energy generated being used to provide the immense amount of interior and exterior illumination required to create both the aesthetic and the pleasing environment for work, relaxation and leisure activities. The focus on lighting has changed dramatically in recent years with the requirement for a more sophisticated lighting installation to address the consumer’s artistic or practical application. As a result, the lighting industry has seen the advent of new lamp technologies which offer a wider and more comprehensive range of linear/compact fluorescent and metal-halide light sources. Responsibility Also, the introduction of new lighting luminaires not only offers optimum optical control but also provides the opportunity to produce maintained illumination levels by way of lighting-control systems. With all this technology comes the responsibility to reduce energy wastage to meet European directives. In the past, advice and influence came from the lighting specifier, who laid down the specification requirements for a client’s lighting installation to be made energy efficient. Today, with the increase of the design-and-build sector, this role is tending to be passed down from the main building contractors to the electrical installer who, more often than not, decides on the suitability of the luminaires for the required task, whilst ensuring that the selected fittings also provide the all-important aesthetically pleasing environment and give compliance with energy-based legislation. When considering a lighting application, there are a number of ways in which the lighting specifier can optimise the use of electrical energy. However, it should be remembered that the energy usage and, ultimately, the efficiency of the project is determined purely by the electricity consumption over a given period. The importance of using energy-efficient lamps to reduce energy consumption cannot be overstated, but there is also the need to provide excellent lamp efficacy with high lumen-per-watt values. This can be achieved by using high-efficiency control gear with power consumptions that are within the prescribed limits. At the same time luminaires with a high light-output ratio can make best use of the lumens produced by the lamps(s) within the luminaire. To further reduce energy consumption, the lighting scheme can be designed so that rather than illuminating the whole room to a level required to complete a task which may only be undertaken in a small area within the room, the lighting can instead be directed to where it is required to accommodate this localised working.
Where daylight is available, lamps should be equipped with dimming control to minimise electrical consumption.
The surrounding area could then be lit with a lower level of illumination. For certain suitable applications, the use of fluorescent dimming systems can be installed to control the levels of illumination provided for certain areas. Zoning Zoning is another way of reducing energy consumption. By controlling the lighting via strategically placed wall switches to meet current legislation, luminaires in unoccupied areas can be switched off when not required, whilst leaving luminaires illuminated in the occupied zones. Luminaires next to windows can also be switched off to save energy when there is adequate daylight. Timers provide a popular and easy method of reducing energy usage by automatically turning off the lighting at predetermined times when the area is not in use. However, timers have the disadvantage of providing little flexibility. Passive infrared occupancy sensors offer another method of addressing the requirement for energy efficiency. Such systems are designed to energise the lighting upon detection of a person entering an area. Once the detector fails to sense a presence within the defined field of coverage and following a preset time, the sensor automatically switches off the lighting to conserve energy. Daylight sensors can control the amount of artificial light according to the availability of external daylight. These types of products can typically save up to 40% of energy usage each year, enabling capital and installation costs to be recovered after only a few years. However, the payback period depends on the suitability of the installation and its geographical position as this can only be achieved with dimming luminaires to provide the required amount of artificial illumination to supplement natural illumination and provide a maintained illuminance in the area. Maintenance Correct and regular maintenance can also play an important role in reducing energy wastage, as it can be used to determine the on-going efficiency of a lighting installation. This is because that, over time, there is a marked deterioration in the lumen output from lamps due to factors such as lamp lumen depreciation, lamp mortality survival, the aging of the luminaire and the deteriorating state of the environment. The use of an effective lighting design in conjunction with suitable interior surfaces is an extremely effective way of saving energy. By utilising high reflectance values on the ceiling, walls and floor, along with light colours in the interior décor, the lighting installation could require fewer luminaires. Reflected light from a room’s surfaces can contribute towards the illumination of the working plane. Making the most of the available daylight by, for example, positioning desks near existing windows can also save energy. However, it is appreciated that this solution may not be possible in restricted locations, and creating additional windows may also not be an option. All the above suggestions could provide a basis for selecting energy-efficient lighting, but it is also very important to select lighting equipment that is suitable and applicable to the task which it is being asked to perform. The type of fitting used will depend on the application and whether it is being expected to illuminate an office, a restaurant or leisure facility. The Building Regulations — Approved Documents L1A, L1B, L2A and L2B provide information relating to the requirements of the types and wattages of lamps together with the restrictions on control-gear losses for all lighting applications. Benefits The use of such light sources as T5 linear fluorescent lamps and compact fluorescent lamps can provide numerous benefits such as lower running costs, higher efficacy with good colour-rendering properties and longer life of up to 16 000 h when operated utilising high-frequency control gear. High-intensity discharge lamps have similar benefits — with low running costs and high efficacies, combined with long life, but these solutions may cost more and may not be suitable for some applications where a long run-up time period of up to six minutes for some lamps is not acceptable. The EU Directive: 2000/55/EC — Energy Efficiency aims to reduce the energy consumption of lamp ballasts for fluorescent luminaires. Phase 1 of the directive in 2002 banned the use of Class D (high loss) ballasts. More recently in 2005, Phase 2 banned the use of Class C (moderate loss) ballasts. Consequently, the use of Class B (low loss) ballasts is still allowed, and to date there is no planned phase-out date. It is therefore suggested that for energy-efficient installations, only high-frequency ballasts are used with fluorescent lamps, as this provides much lower losses and power savings on lamp operation. Whilst lighting is critical to a person’s sense of well being, it is important to remain aware of the need to reduce energy wastage to minimise the impact that its generation will have on the world’s resources. By following a few of these simple steps, it is possible to substantially reduce a building’s ongoing energy costs whilst achieving this important aim. Paul Davidson is lighting design manager with Ansell Lighting, Units 2-3 Chetham Court, Calver Road, Warrington WA2 8RF
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