Bright idea?

Ian Orchard investigates the pros and cons of energy-saving light bulbs.

With New Zealand's lighting requiring nearly 5GWh a year, releasing over 2.6 million tonnes of CO2, the Government is discouraging inefficient incandescent lamps. Questions have been raised about compact fluorescent lamps (CFLs), so we have left no tome unturned to bring you answers.

What's wrong with the old bulbs?

The traditional lamp heats a tungsten filament to 2000-3400K, but less than 5 percent of the energy is emitted as light, with the rest lost as heat. Quartz-halogens are better. New technologies are becoming available, but we need to move towards them promptly.

How do CFLs work?

The mains electricity AC is "amplified" from 50Hz up to 40,000Hz by the electronics in the base of the lamp. This high frequency excites a neon-mercury gas within the tube to emit ultra- violet light which is converted to visible light by the phosphor coating lining the tube.

Isn't the mercury dangerous if the lamp is broken?

CFLs contain 3mg to 5mg of mercury, about equal to a ballpoint pen's ball. If a lamp is broken, leave the room well ventilated for an hour to allow any mercury vapour to disperse, brush the broken glass or powder into a plastic bag and wipe the area with damp paper towels to pick up powder and glass shards. Dispose of the bag and towels immediately and rinse the brush. For more details, see the Ministry for the Environment website.

What about these reports of CFLs overheating or even catching fire?

Of the millions sold, a few have caused problems, but to date too few to identify the particular batches, models or brands implicated. To be absolutely safe, install in fittings that are well ventilated.

Is the ultra-violet light a problem?

Very little UV gets past the phosphors and the UV-opaque glass. People with exceptional sensitivity to UV, who have problems with fluorescent tubes, should be careful with the CFLs.

Someone said they cause epileptic fits or migraines. Should that be a concern?

The brain can be affected by flickering lights, but if CFLs flickered at all, it would be at 80kHz, far beyond the range of human vision.

They're such ugly bulbs.

The light-fitting industry (or the NZ importers) are only just starting designing luminaires for CFLs. Ask for spiral lamps or tiny-spiral, that will fit in typical lights. CFLs similar to in appearance to conventional bulbs are appearing in the shops.

Why don't CFLs come on at full brightness like incandescents?

They are fluorescents after all. We are used to tubes flickering until they get started. More recent CF models are better at lighting immediately and reaching nearly full brightness within 10 seconds or so.

How do I safely dispose of dead CFLs?

Currently, Christchurch has no procedure in place, so they are dumped. This may be very shortsighted, although not for the obvious reason. An important element used to manufacture the green phosphor is terbium, the world supplies of which should be depleted by 2020. A stockpile of old CFLs may be very, very valuable.

On balance, are compact fluorescent bulbs a good thing?

Definitely. True, they contain mercury, but burning coal to make electricity releases more into the environment. They do have their quaint ways but nothing we can't adapt to in return for the much better energy efficiency they offer.

- © Fairfax NZ News