 Lightglobes?
Don’t be Dim.
Let LED Lightglobes
Light
up your Life!
by David Vernon
 In
mid-February 2007 the Australian Government announced that from
2009 it would ban the use of incandescent light bulbs. The reason
according to the Government is to reduce Australia’s annual
greenhouse gas emissions by some 800,000 tonnes. The Environment
Minister, Malcolm Turnbull, said Australians would replace the millions
of incandescent bulbs with compact fluorescent lamps (CFLs).
The
Government should be applauded for this idea, for although we have
known for years that switching to CFLs will save us money in the
long term, we are notoriously short sighted and most of us will
happily choose a 60 cent incandescent light (IL) bulb over an equivalent
$3.00 CFL, even though the CFL will last five times longer and consume
four times less electricity than an IL bulb. The average cost of
electricity to run a 60 watt IL bulb for three hours per night,
for one year is about $8.50. The total cost, including purchase
of the bulb is about $9.10. The equivalent total cost for a CFL
is $2.70 (assuming a five year bulb life span). Despite such massive
savings in total cost, we seem to be mesmerized by the 60c cost
of the IL bulb and buy it instead of the cheaper CFL. No wonder
the Government believes it needs to ban the IL bulb — we consumers
are economically irrational.
But
has the Government thought through all the implications of this
ban? The CFL, whilst a remarkable technology, is not without its
problems and cannot be used to replace all IL bulbs. Most cheap
CFLs will not operate properly where temperatures fall below 0°C
and so they aren’t much use in low temperatures, such as outside
lights in Canberra’s winters. They also fail reasonably quickly
where they are turned off and on frequently, such as in motion sensors,
or in rooms where you dash in and out in a short time, such as pantries
or toilets. CFLs require extra electronics to be able to be dimmed,
which makes them difficult to use in circumstances where light control
is required, such as restaurants, theatres and cinemas. Even when
the CFLs have the additional dimming controls, they do not dim ‘orange’
as ILs do, but retain their white light output and thus as they
dim they go grey, which doesn’t usually provide the romantic
and intimate atmosphere that dimming tries to achieve.
 Unfortunately,
the environmental benefits of the CFL are not completely straightforward
either. CFLs are far more complex than ILs and contain intricate
electronics within their base. These electronic components require
sophisticated recycling equipment to handle and the CFLs also contain
low levels of the toxic heavy metal mercury in the form of mercury
vapour and thus CFLs should not be disposed in domestic waste collections.
Europe
has built a recycling system for electronic waste and all CFLs include
in their retail cost a recycling levy to pay for the safe disposal
of old CFLs. Australia has no such system in place and there is
a danger that if there is a massive increase in the use of CFL bulbs,
an electronic waste problem will arise. The Government has not yet
announced any corresponding electronic waste collection scheme with
its proposed banning of ILs.
CFLs
also suffer from a light quality problem compared to IL bulbs. Light
from lighting sources is measured using a scale called the ‘colour-rendering
index’ (CRI). This index indicates how well the light source
provides an accurate rendering of the real colour of the object
being lit. The sun has a CRI of 100 and everything is measured relative
to sunlight. An IL bulb, because it emits a full spectrum of colours
in its light, has a CRI of nearly 100. This makes IL bulbs useful
for task lighting where eyestrain needs to be avoided. CFL manufacturers
can make ‘sunlight’ CFLs but at the expense of efficiency.
CFLs work by passing electricity through mercury vapour inside the
bulb. The vapour gives off ultraviolet light. This light strikes
the sides of the glass bulb that is covered in a material called
a phosphor that gives off visible light when struck by ultraviolet
light. Cheap CFLs use only one phosphor on the glass of the bulb
and this phosphor gives off only harsh light, often perceived as
a blue/white light. Manufacturers describe this light as ‘cool
white’ and it has a CRI of only 63. However, the quality of
the light can be improved by using different kinds of phosphors
as coatings. The more expensive, ‘triphosphor’ or ‘sunlight’
CFLs use mixtures of phosphors that give off light in the blue,
red and green light frequencies. These triphosphor CFLs can have
a CRI as high as 90. Unfortunately, the more phosphors used, the
greater the manufacturing cost of the CFL and the less electrically
efficient the CFL becomes, and thus the lower the environmental
benefits from changing from IL to CFL.
A further
disadvantage of CFLs is that their light output is proportional
to the area of glass covered in phosphors — so to get greater
light output, a greater surface area is required. This contrasts
to ILs where to get greater light output a different filament, either
in size, shape, length or composition, can be used and a greater
voltage forced through the filament. In practice, this means that
some light fittings will not take a CFL unless smaller and therefore
lower light emitting CFLs are used.
The
final major disadvantage of CFLs are that because they produce diffuse
light as opposed to a brightly glowing filament in a IL, CFLs cannot
be used where bright beams are required. CFLs cannot replace car
headlights, torches, spotlights and other such intense lighting
requirements.
 Has
the Government jumped in too quickly with its statement that it
will ban incandescent lights in 2009? Certainly CFLs are a marvellous
advance for general lighting and a great environmental improvement
in terms of reduced greenhouse gas production, but they still have
a range of drawbacks that appear not to have been considered by
the Government. The ban is only two years away, and that may not
be nearly enough time to develop a nationwide CFL recycling program.
Fortunately,
there is another technology waiting in the wings, which has only
recently appeared commercially, and that is the white light emitting
diode. It is this technology that the Government could be promoting
as our greenhouse saviour, rather than the CFL.
Light
emitting diodes (LEDs) have been around for a long time. The first
LEDs came onto the market in 1962 and they are now common in every
house. Nearly every indicator light on electronic equipment is an
LED. The great advantage of LEDs as a light source is that they
use tiny amounts of energy to illuminate and they are practically
indestructible in normal use — they can be shaken, jolted
and dropped with little likelihood of damage.
While
IL bulbs work by heating up a bit of wire until it glows and gives
off light, and CFLs give off light when phosphors are encouraged
to glow by ultraviolet radiation, LED lights work on a completely
different basis. LEDs are a kind of semi-conductor. A semi-conductor
is a material that only partially conducts electricity. Its conducting
ability has been limited by the introduction of impurities into
it. These impurities are simply other chemical compounds. It is
the different types of impurities that give LEDs different colours.
In LEDs two zones are created by the zones having different amounts
of impurities. One zone has extra electrons (called the N-type zone)
and the other zone has holes that electrons can jump into (called
the P-type zone). When an electrical charge is put across the zones,
electrons jump from the N-zone into the holes in the P-zone. As
an electron drops into the hole a tiny packet of energy, called
a photon, is emitted. Photons are what our eyes see as light. This
process uses very small amounts of electricity to work, and thus
LEDs are incredibly energy efficient.
Until
recently, LEDs for lighting have suffered from a range of technical
difficulties — the main ones being brightness and colour.
Getting a true white light with a CRI close to 100 has been difficult.
Techniques to obtain a white light are varied. The cheapest way
is to use blue LEDs to excite phosphors to give off yellow light.
The blue and yellow light blended doesn’t give green light
as might be expected but a white light. Unfortunately this technique
only gives a CRI of 70. A better way is to blend the light from
multiple coloured LEDs. By blending four coloured LEDs of different
intensities a much better white light can be achieved, in the order
of 85 CRI.
These
four coloured LED lights are now commercially available. One brand,
made by the US company Enlux, states that their lights last 50,000
hours (which equals 34 years if the lights are on four hours per
day), produce CRI of 85 and produces 26 lumens (a measure of light)
per watt. Its 15 watt globe produces 400 lumens of light, which
is the equivalent of a 40 watt IL or an 8 watt CFL, without the
mercury residue of the CFL. Whilst the light output per watt of
the Enlux LED is not competitive with a CFL, LED research is leaping
ahead at such a pace that shortly CFLs will be left behind.
 Seoul
Semiconductor, based in Korea has created a LED that produces
135 lumens per watt (equivalent to a 200 watt IL!) or in other words
can produce the light of a 60 watt IL with 4.5 watts of power. To
run this light for 3 hours per night for a year would cost less
than 65c per year. This LED will be commercially available later
this year.
LEDs
can operate at temperatures down to -40°C, do not lose light
quality when dimmed, can last up to 50,000 hours (although Philips
has just released their Luxeon range which claims 100,000 hours
of life), use no mercury, can be dropped and mishandled, can be
used in spotlights and headlights, have a rapidly improving CRI
and use 10% of the power of equivalent ILs. Let’s hope that
the Government doesn’t push consumers down the CFL path, when
affordable LED light technology is just around the corner.
David Vernon
is a freelance writer. Based in Canberra he writes about science,
parenting, health and history. In mid-2006 he completed his third
book, an anthology of birth stories told by men, called Men at Birth.
Website: http://web.mac.com/david.vernon
Email: dvbooks@mac.com
© David Vernon , 2007
This article was first published on 9 April 2007 in the Science
and Technology Insert of The Canberra Times, p6
Call
Enviro-Friendly today on (02) 6282 6266, and find out how we can
help you
"Save water, save energy, save
money, and save the environment."
For
enviro-friendly tips and news, be sure to
and please, tell your friends about us!
|
