

by W.A. Steer PhD



Back to contents About...

Yes, I'm concerned about the environment, global warming, and about the profligate and spiralling energy consumption of the developed- and developing world. I'm also irritated by many of the headline-grabbing campaigns which, though well-meaning, appear to be more about gaining environmental 'brownie points' than actually making any real difference. Space-heating and transport use far more energy than lighting, so why the demonisation of the humble incandescent lightbulb?

Introduction

Fluorescent lamps distort colours making a room appear grey, flat, lifeless, and even "clinical". Wood and skin colours often take on an unhealty greenish tinge, and make food look most unappetising.

As a colour-scientist and amateur photographer, my eyes are offended by the colour-characteristics of fluorescent light.

As a physicist my intellect is offended by disproportionality of the notion of calling for a ban on a form of lighting which accounts for less than 1% of the total national CO 2 generation while largely ignoring car-use and the over-heating of homes and business premises where vastly greater savings could be made.

generation while largely ignoring car-use and the over-heating of homes and business premises where vastly greater savings could be made. I'm quite happy to aim for a low-energy lifestyle, but please, stop the nannying and leave the details of how I achieve that up to me!

Savings from the use of CFLs are small or comparable to other household activities...

In a typical British household, replacing standard bulbs with CFLs would save not much more than 2% of the total household direct CO 2 emissions (from electricity+gas+car use)

emissions (from electricity+gas+car use) Daily, this amount of CO 2 is roughly equivalent to that emitted by: driving a car 1 or 2 miles half a drying programme in a tumble dryer refining primary aluminium to manufacture two aluminium drinks cans a typical TV/satellite box/DVD player installation being left in standby rather than switched off at wall when not in use

is roughly equivalent to that emitted by: At typical UK mileage you'd save ten times more CO 2 by swapping a gas-guzzling 4x4 for a smaller family car.

more CO by swapping a gas-guzzling 4x4 for a smaller family car. Many households could probably also save ten times as much CO 2 , relatively painlessly, by being more frugal with their heating, reducing the thermostat temperature, and using the timeswitch to turn off (or manually turn right down) the heating during the hours when the house is unoccupied, or overnight.

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British cars are usually reckoned to have a typical annual mileage of 10000 miles.

3300 kWh electricity 1800 kg CO 2 assorted uses 20500 kWh gas 3900 kg CO 2 primarily used for heating, some cooking 10000 car miles 2900 kg CO 2 Total: 8600 kg CO 2

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0.54kgCO 2 per kWh electricity, 0.19kgCO 2 per kWh natural gas, 2.3kgCO 2 per litre of petrol (gasoline) http://www.defra.gov.uk/environment/business/envrp/gas/envrpgas-annexes.pdf

Replacing three 60W conventional bulbs with 15W compact fluorescent equivalents burning for 5 hours per day saves 246kWh of electricity per year, around 140kg of CO 2 (a mere 1.6% of 8600kg total).

CFLs are not perfect replacements for traditional incandescent bulbs...

Aesthetics:

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The poor colour-rendering is very bad for everyone that notices it, but will be disasterous for photographers and artists.

Most CFLs cannot be dimmed

There's no CFL equivalent to the miniature halogen spotlights producing a narrow beam of light, popular in kitchens or above tables.

Because the source is "extended", CFLs cannot reproduce the "sparkle" of the light from a clear-glass (as opposed to "pearl" or frosted) conventional bulb.

Practicalities

Owing to their extra complexity they are more likely to have reliability issues when subject to repeated temperature changes in such locations too.

For little-used lights in cupboards, the energy saving is utterly negligible.

Fluorescent lamps always emit a certain amount of radiofrequency interference (RFI) which may cause hums, buzzes, or whines in radio receivers and audio equipment. If this is a problem then conventional bulbs need to be used in the vicinity of the affected equipment.

A "ban" on conventional lightbulbs is disproportionate, and any law to enforce it would be disproportionate too.

There are all sorts of miniature and specialist conventional bulbs, for ornamental lights, for ovens and sewing machines. Torch bulbs. Old, even antique, slide and cine-projectors. Where are you going to draw the line?

How do you propose to enforce the law? What will be the penalty for violating it? And will it be proportionate, considering that, for example, cars are responsible for vastly more CO 2 than domestic lightbulbs?

Given that the "wasted" energy from lightbulbs is merely heat, yet dedicated electric heating appliances are widely used, and many new homes are being built with solely electric heating throughout, a law banning lightbulbs would be daft.

How dare the government propose meddling with the lights in peoples own homes, while in the meantime building new roads and airport runways!

In Britain we already pay tax (VAT) on fuels; since electricity is around 3~4× the price of gas, comparing gas with electricity the tax is already roughly in proportion to the CO 2 emissions.

Lighting basics

Incandescent bulbs

The only 'problem' with incandescent lamps is their poor efficiency; a very high proportion (perhaps 95%*) of the power put into them is turned into heat, rather than useful light. Standard (40W/60W/100W) mains lightbulbs have efficiencies around 15lm/W, while quartz-halogen bulbs may be around 24lm/W.

Fluorescent lamps

The best modern narrow-diameter (T5) fluorescent tubes claim an electricity-to-light conversion efficiency of around 100lm/W, while compact fluorescents are typically only half as efficient (40-60lm/W). A CFL lamp of the same nominal light output as an incandescent typically consumes one quarter the electrical power and therefore runs much cooler.

Lamp efficiency

The real energy issue: heating and transport

Contrary to popular perception, it actually takes less, and often much less, energy to heat up a house which has been left to go cold [e.g. during the day, or overnight] than it would have done to keep it warm all along.

The rate of heat loss (energy loss) from a premises due to conduction through the walls and windows etc is proportional to the difference between the inside and outside temperature. Far better to be tucked up under a thick duvet at 5am than have the central heating working hard to keep the whole house at 21 Celcius while the outdoor temperature is at its coldest!

Further reading