Articles and whitepapers

Going Green: Strategies and Technologies for Energy-Efficient Lighting (3/2/2008)

By John Lilley, USD

Until a few years ago, typical lighting in domestic settings comprised a central pendant. For rooms where entertaining was done, such as the lounge or dining room, there might be a couple of wall lights, and the switch plate might be replaced with a dimmer. The total lighting load might typically be 200W, so to make the lighting more energy-efficient, the bulbs were replaced with lower wattage ones, thus reducing the power consumption but also the light level!

These days, many rooms of a similar size have upwards of a dozen 50W downlights installed, resulting in a total of 600W or more lighting load. Our lighting demands are clearly increasing, but at the same time, we are also being encouraged, if not compelled, to be more energy efficient.

Downlights have replaced the central pendant.

The parts of the current and impending building regulations and guidelines that most concern people, are those that cover energy efficiency. These include efficient heating and cooling systems, building insulation against heat loss or heat gain, and having a percentage of the lights as energy efficient. Since most of these energy-efficient lamps are not dimmable however, and are unsuitable for sometimes complex lighting schemes, they tend to be used in places such as utility rooms, loft conversions, spare/guest bedrooms, toilets and cloakrooms.

A large proportion of building owners, both home and business, would be prepared to embrace new technology if they could see a return on their investment sooner. Their main concern is the cost of systems such as LED or compact fluorescent lighting, but rather than focussing on what they perceive as the drawbacks, they should be looking to new technology as being able to provide effective solutions to a range of problems.

Improving efficiency

In short, energy-efficient lighting means getting as much light output from as little energy as possible. One of the best ways of making lighting more efficient is to have the lights on only when they are needed, especially in areas such as bathrooms, hallways, utility rooms and kitchens. Do you remember your parents telling you that a light switch has two functions? Well, if you cannot rely on your home's occupants to switch the lights off when not needed, how about installing presence/movement detectors to control the lights? You need never have lights left on again, unnecessarily for hours.

When a room has multiple uses, for example a lounge that is used as a TV room, reception room or playroom, there will be different lighting requirements, depending on its current use. It may seem obvious, but energy can be saved by only switching on the lights that are required, and possibly at reduced levels if appropriate.

Task lighting in the kitchen.

When using a lighting system to highlight something decorative such as a painting, sculpture, vase or flower arrangement, traditionally a huge, usually brass, fitting would be installed to contain the bulb and reflect the light in the desired direction. The heat and ultra-violet produced by the light would not only be wasteful, but could be extremely detrimental to the item being highlighted. Today however, there are many alternatives, ranging from halogen lights where the heat exits through the reflector and away from the item, to 'cool lights' such as LEDs and some gas discharge lamps. Many of these newer lighting solutions have a very small visual footprint, so you see the item being highlighted and not the lighting system. These newer lighting systems also have the advantages of not damaging the artwork with heat and UV; having more natural colouring with light that has the same frequency as daylight; and the colour being able to be tailored to enhance the item being lit.

Spotlight with small footprint.

Architectural lighting

Using architectural lighting, rooms have the colour, feel and even the perceived texture of the walls changed to suit the use, time of day, or season. This can now be achieved using LED technology, especially the multicolour and colour-changing systems.

Unlike older systems inherited from the stage industry, that use a mechanical system to move different coloured filters in front of the lamp and therefore offer a limited set of colours, contemporary multicolour and colour-changing LED system lamps usually contain elements that individually produce the three primary colours, and an element that produces white light. Via the control system, the full spectrum of colours can be produced by combining various combinations of the primary colours at different intensities.

With the newer LED projection technologies, buildings can be lit from a smaller footprint, hence discreet lamp housings can be used that can be disguised or hidden from view, and out of reach of potential tampering. Such systems are on a par with, and often more energy-efficient than, the older sodium/mercury floodlights. Their lamp life tends to be longer, and they are far more controllable rather than simply flooding everything with sodium yellow!

Another technology that could have an impact on residential interior designs is the electro-luminescent panel. This has been used for a number of years to provide small, thin lighting panels for applications such as signage in passenger aircraft, and is also now being used in the theatrical and stage worlds, where panels of uniform colour are required. For domestic purposes, the entire ceiling of a room could consist of a number of such panels, not only to light the ceiling surface in an interesting way, but to light the whole room. In other words, the entire ceiling, or a wall, becomes the light for the room.

An electro-luminescent panel.

Dimming

Remember those old dimmer plates with a large knob that, along with the plate, got warm, if not hot, and hummed when on? Well those are traditional dimming systems for incandescent lamps that are based on the principle of inserting a variable resistor in series with the lamp.

Unfortunately dimming with fluorescent lamps is not so straightforward. In order to operate, fluorescent lamps basically rely on a current that passes through a gas in the tube. The gas is excited by the current, and light is emitted. If the voltage is reduced below a certain level, the current flow will stop and the light extinguishes. Ballasts (control gear) for dimmable fluorescent lamps require a low-voltage connection in addition to the 230V mains supply. This low voltage is used to control the light output level of the fluorescent lamps, so without such an additional low voltage source, the compact fluorescent lamps that are designed to be a direct physical replacement of incandescent lamps, are not dimmable.

Dimming some of the newer LED technologies can also be complicated as the majority have proprietary controllers and different interfaces. Most LED dimming is achieved using pulse width modulation (PWM). Basically, this involves flashing the LEDs very quickly and varying the duty cycle to achieve the desired light level. LED lighting systems usually have a driver unit that is powered from 230V. This provides the low voltage for the LED elements and may have one of a number of control options which are usually manufacturer-specific, such as contact closure to cycle through the colours or brightness or step to next colour.

Systems designed for architectural lighting have embraced the DMX control system that allows control to be performed within the lamp's assembly using long runs of light-gauge cable that carry control signals and not power. DMX is an RS485-based serial communication protocol that is most commonly used to control stage lighting. The DMX control lamps are supplied with 230V, and via the communications protocol, you can 'tell' the lamp how bright, what colour, etc, you want it to be.

Automation

At the push of a button, automation allows the homeowner to choose the ideal lighting scene for each room or zone in terms of light source, intensity and duration. Automated lighting can be used so that areas nearer windows that enjoy sunlight, will have the lights automatically dimmed to a low level, whereas areas furthest from the windows will have the lights at a higher level, thus achieving the same overall light level, regardless of the position within the space. Automation can also be used to simulate occupancy in a more realistic and therefore energy-saving way, than simply leaving a number of lights on all the time.

Summary

Whether we like it or not, energy efficiency is on the agenda. In the short term, we can choose to conform to the minimum regulatory requirements, or we can go further, and embrace technologies that greatly reduce our consumption over the longer term. The benefits of intelligent lighting control of both new and traditional technologies can result in immediate energy savings as well as other advantages such as prolonged lamp life and increased comfort.

We can manually save energy by only lighting when and where we need to, and we can use automated lighting, for further efficiencies. Indeed lighting control is only one part of the home automation concept. Automation can be used to control all of the home's electrical devices, and can result in significant energy savings. Household appliances, such as washing machines and tumble dryers for example, need only be switched on when the electricity tariff is at its lowest. Depending on weather conditions, shutters or fans can be controlled and the temperature in each room can be adjusted individually, automatically.

And the good news is that automation is no longer just in the realm of high-end homes. There are many affordable systems now available, with some even extending into the DIY market.

John Lilley provides technical support for USD Ltd, UK distributor of Niko, Artsound and Nexus products.

www.usd.uk.com