Energy-efficient lighting

FLUORESCENT
Compact Fluorescent Lamps (CFLs) are about the only option in most homes for meeting energy-efficiency requirements in Building Regulations and EcoHomes. Compared to the traditional, incandescent (or “GLS”) light bulbs they are reckoned to be about 4 times more efficient and to last about 6 times longer. As legislation gradually forces them upon us, it’s not surprising that there is dissatisfaction. Two causes can be identified: their performance and environmental concerns.

On the environment there are worries about disposal (especially the toxic mercury they contain), materials consumption and embodied energy. Comprehensive analysis however has shown that the increased life and reduced energy consumption more than compensate for any increase in embodied energy and materials. As for mercury, traces of the substance are emitted by coal-fired power stations – it turns out that less mercury escapes when a CFL is broken up than is emitted as a result of burning the extra coal needed to power the equivalent GLS bulbs during its lifetime.

On the performance side, CFLs are perceived as bulky, unattractive, flickering and slow to warm up. When they were introduced in the 1980s they suffered from all these faults and more, but development since then has improved them considerably. However, many consumers still dislike them, and not without cause. The main reasons are as follows:

• Most of them you can’t use with a conventional dimmer.
• They’re not as bright as would be expected.
• They can take a long time to reach full brightness.
• Colours look wrong. (Colours are rendered better under a GLS lamp.)

Claims made about CFLs have been tested by various bodies. It has been noted that CFLs lose brightness by up to 20% over their lifetime. The Energy-Saving Trust recognises that CFLs take time to reach full brightness, and to achieve its “Energy Savings Recommended” (“ESR”) status they must reach 20% of full brightness within 2 seconds and 70% within a minute.

A point that consumers may not be aware of is that, although CFLs last much longer than GLS bulbs, manufacturers’ claims may not always be realised, particularly as their life is shortened according to the number of times they are switched on. A lamp should be expected to survive being switched on 3000 times during a 6000-hour lifespan, i.e. once per 2 hours on average, but more switching than that could shorten its life.

Of course there are other forms of fluorescent lamp, for example 2D fittings and similar. The configuration of the tube in a 2D fitting results in the light being emitted away from the base of the fitting, i.e. downwards if mounted on a ceiling. On the other hand that of the CFL could result in most light being emitted sideways if the lamp is installed in a pendant fitting. This may be one reason why CFLs appear to give less light than they should.

What of future development for the CFL? It’s probably nearing the end of the line, as attention is turned to newer technologies.


LEDS
LED (light-emitting diode) technology is thought of as the successor to the CFL, although application of this technology to domestic lighting is in its infancy. While LED lamps are already available, manufacturers seem to be making exaggerated claims on their performance. The US Department of Energy’s testing programme has revealed that the lamps produce only between 10% and 60% of their claimed light output, and often the directional nature of the light makes them unsuitable for general use. Furthermore, the colours often do not match that of the GLS and might take some getting used to. Life expectancy is quoted at 20,000 hours (20 times that of GLS), which is over 2 years’ continuous running.


GLS BULBS HEAT YOUR HOME
One fact that is largely ignored is that for about 7 months of the year the extra energy consumed by GLS bulbs is not wasted. A 60-watt GLS produces 57 watts of heat and 3 watts of light. The 57 watts contribute to the warmth of the home, and during the winter months a thermostatically-controlled heating system uses less fuel as a result. For a number of reasons the full 57 watts is not saved, but nevertheless the true energy advantage of installing CFLs is not as great as it might seem.


RECOMMENDATIONS
Whilst CFLs are not all that they are made out to be, they are still far more energy-efficient than the GLS. However, when specifying CFLs it is advisable to be realistic about the amount of light they will provide, taking into account warm-up and late-life reduction. Instead of the usual 5:1 wattage ratio, the Lighting Research Centre in New York recommends a 3:1 ratio “… to avoid possible disappointment” (i.e. install a 20W CFL to replace a 60W GLS).

 

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