lighting
For the first time in over 100 years the look and feel of general lighting solutions are changing dramatically. The Lighting Industry provides a guide to LEDs.
IN RECENT years we’ve seen the rapid adoption of LED light sources in many markets. Their low energy consumption, long life and ruggedness have made LEDs an obvious choice for coloured lighting applications. For general lighting, however, white light is required and in the past 18 months, white LEDs offering energy efficiency to rival fluorescent tubes have become available. These latest power LEDs offer efficiency, lifetime and design benefits that are driving new designs and applications. But those who specify lighting in buildings should make appropriate comparisons between conventional light sources, such as fluorescent tubes and power LEDs.
One crucial parameter to compare is efficiency. Improving lighting efficiency reduces the electrical consumption of the lighting system and cuts the amount of heat it generates. The higher efficacy lightens the load on HVAC systems, further increasing energy savings. Incandescent and halogen light sources are fairly inefficient, delivering only 12-20 lumens per Watt; fluorescent lamps can deliver 45- 100 lumens per Watt. Today, the most advanced power LEDs deliver 40–80 lumens per Watt. On a lumens per Watt basis, the technology decision might seem obvious, but it’s not that simple. The effectiveness of the fixture is more
important than the raw lumens per Watt figure. What actually matters is how much energy it takes to get the right amount of light where it’s needed. This means evaluating the complete system, not just the light source. The performance of the system must take into account the driver electronics, reflector or lens optics, and the light source. Only then can a direct comparison be made. An LED is a directional light source; all the emitted light falls within a hemisphere.
spotlight In the
Hatfield Swim Centre installed 12 Pulsar ChromaFlood 200 fixtures containing a combination of red, green and blue LEDs as part of moves to reduce its carbon footprint. With a maximum power consumption of 200 watts, the high-powered LED fixtures are housed in a compact IP65 flood enclosure, ideal for architectural applications in high-humidity environments
By contrast, a fluorescent tube distributes its light 360 degrees around the long centre axis of the tube. In the case of an under- cabinet light, all the light output from LEDs will go in the desired direction, while half the light of the fluorescent tube goes in the wrong direction. In fact, an important function of the housing of a fluorescent tube is to capture and redirect light that’s going the wrong way. Clearly, the efficiency of the complete system will be less than that of the raw light source. The electronic circuitry of the system also has an impact on the system’s efficiency. A fluorescent system uses a ballast, an LED system uses an electronic driver. Neither of these components is 100
per cent efficient. Optics can significantly affect system efficiency. Any lens, filter or diffuser will cause light losses and lower overall system efficiency. In an under- cabinet light, it’s possible that the overall efficiency of an LED system is equivalent to a fluorescent system even when the LEDs themselves are less efficient than the fluorescent tube. Over the coming years we will see a range
of new LED lighting applications such as downlights, spotlights, area lighting and task lighting on the market offering new tools to reduce both energy consumption and the life-cycle costs of lighting.
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