A Nature News Alert, 20 May09,
Lighting technology: Time to change the bulb, I felt, was a particularly well written “up-date”, for the wider public seeking an overview on light bulbs to choose, from an increasing variety, hence this post, at this particular time. Nature's article relates the evolution in domestic and commercial light sources (bulbs) from the standard incandescent (being phased out) to the innovative, not yet fully commercial, electromagnetic induction types, through the low energy compact fluorescent (CFL) and the now most awaited source, white-light emitting diodes, white LEDS.
A funny thing though, I got a quick read at the article online, referenced it to read again, but the online reader will either have to take my word for it or better ferret out the paper edition or subscribe to the journal, since it is no longer freely available online. Nevertheless the above link will give the reader many thoughtful comments with links for the scientists among us to delve into.
Like many in this part of the world, I have a sample of all sorts of light sources including my recent change of 4 halogen spots 50W each for 4 LED spots (18 diodes each, power consumption per “spot”= 1W ) almost for the fun I tell my sceptical or vested interest friends.
Compound this with my recent encounter with D. MacKay’s powerfully simple well documented approach to energy (production - consumption balance) which includes a chapter on light sources. In fact I had intended to use without restraint MacKay’s work, as invited, in order to clarify any further study of lighting issues. Even after reading the comments some from true experts in lighting sources and design, I still feel that all could benefit from the Mackay’s book, his approach and clear thinking thinking.
Cable-up and bare with “us”.MacKay's power standard unit is the kilowatt-hour per day (kWh/d).
ref. D MacKay Ch.2, The balance sheet, § Energy and power P.24 in the free online edition of his book "without" full title “Sustainable Energy — without the hot air” cf. Link2 below.
One of the most common, if not the most commonly encountered domestic unit of energy is the Watt due to the many domestic electrically powered appliances from cooking, cleaning, communication-phone, PC and leisure TV and audio (especially electric but not only, since any energy form can be converted to equivalent electric energy units)
Power is the rate at which we use or produce energy,
From energy to power:The watt (40W = about 1 kWh/d) and the kilowatt (1 kW = 1000W = 24 kWh/d)
"What Watt"?
Use what is commonly known as dimensional analysis to work that thru'
(40W x 24h)/d = 960 Wh/d nearly 1000 Wh/d or 1 KWh/d.
[Error of 4% cf. Bank account return Rates?
MacKay, who may have played rugby, kicks such considerations into touch and as in the same keeps the playing field clear and allows the suffocating players breathing space.]
To quote MacKay again "The kilowatt-hour per day is a nice human-sized unit: most personal energy-guzzling activities guzzle at a rate of a small number of kilowatt-hours per day. For example, one 40W light bulb, kept switched on all the time, uses one kilowatt-hour per day.
(In his book ref.2 below, he uses the common analogy with fluids (water)
-volume or quantity is in litres,
-flow is litres/minutes.
Spending some time to allow the widest public reading of his book and approach)
Light cf. MacKay, Ch 9, Lighting home and work
“The brightest domestic light bulbs use 250W, and bedside lamps use 40W.
In an old-fashioned incandescent bulb, most of this power gets turned into heat, rather than light.
A fluorescent tube can produce an equal amount of light using one quarter of the power of an incandescent bulb. "
How much power does a moderately affluent person use for lighting?
My [MacKay’s] rough estimate, based on table 9.2, above, is that a typical two-person home with a mix of low-energy and high-energy bulbs uses about 5.5 kWh per day, or 2.7 kWh per day per person. I assume that each person also has a workplace where they share similar illumination with their colleagues; guessing that the workplace uses 1.3 kWh/d per person, we get a round
figure of
4 kWh/d per person.”
Street-lights in fact use about 0.1 kWh per day per person, and traffic lights only 0.005kWh/d per person – both negligible, compared with our home and workplace lighting.
What about other forms of public lighting – illuminated signs and bollards, for example?
There are fewer of them than street-lights; and street-lights already came in well under our radar, so we don’t need to modify our
overall estimate of 4 kWh/d per person."
Car lightsIn some countries, drivers must switch their lights on whenever their car is moving. How does the extra power required by that policy compare with the power already being used to trundle the car around? Let’s say the car has four incandescent lights totalling 100W. The electricity for
those bulbs is supplied by a 25%-efficient engine powering a 55%-efficient generator, so the power required is 730W. For comparison, a typical car going at an average speed of 50 km/h and consuming one litre per 12 km has an average power consumption of 42 000W. So having the lights on while driving requires 2% extra power.
What about the future’s electric cars? The power consumption of a
typical electric car is about 5000W. So popping on an extra 100W would
increase its consumption by 2%. Power consumption would be smaller
if we switched all car lights to light-emitting diodes, but if we pay any
more attention to this topic, we will be coming down with a severe case of
every-little-helps-ism.”
The economics of low-energy bulbs (MacKay word for word)
“Generally I (MacKay) avoid discussing economics, but I’d like to make an exception
for light-bulbs. Osram’s 20W low-energy bulb claims the same light output as a 100W incandescent bulb. Moreover, its lifetime is said to be 15 000 hours (or “12 years,” at 3 hours per day). In contrast a typical incandescent bulb might last 1000 hours. So during a 12-year period, you have this choice (figure 9.3): buy 15 incandescent bulbs and 1500 kWh of electricity (which costs roughly £150); or buy one low-energy bulb and 300 kWh of electricity (which costs roughly £30).
Should I wait until the old bulb dies before replacing it?
It feels like a waste, doesn't it? Someone put resources into making the
old incandescent light bulb; shouldn't we cash in that original investment
by using the bulb until it’s worn out? But the economic answer is clear:
continuing to use an old light-bulb is throwing good money after bad.
If you can find a satisfactory (affordable) low-energy replacement, replace the old bulb now."NB. From MacKay ref. Mythconceptions Ch. 9, p59:
Here MacKay answers one argument made by a comment contributor to Nature’s article which opened my post (above) hence my early recommendation to consider comment not only in themselves but to weigh them against “the MacKay” criteria:
To the often made argument in favour of light bulbs as a source of domestic heating;
“There is no point in my switching off lights, TVs, and phone chargers during the winter. The ‘wasted’ energy they put out heats my home, so it’s not wasted.”
MacKay replies; "This myth is True for a few people, but only during the winter; but False for most.
If your house is being heated by electricity through ordinary bar fires or blower heaters then, yes, it’s much the same as heating the house with any electricity-wasting appliances. But if you are in this situation, you should change the way you heat your house. Electricity is high-grade
energy, and heat is low-grade energy. It’s a waste to turn electricity into heat. To be precise, if you make only one unit of heat from a unit of electricity, that’s a waste. Heaters called air-source heat pumps or ground-source heat pumps can do much better, delivering 3 or 4 units of heat for every unit of electricity consumed. They work like back-to-front refrigerators, pumping heat into your house from the outside air (see Chapter 21, MacKay's book Link 2 below).
For the rest, whose homes are heated by fossil fuels or bio-fuels, it’s a good idea to avoid using electrical gadgets as a heat source for your home – at least for as long as our increases in electricity-demand are served from fossil fuels. It’s better to burn the fossil fuel at home. The point is, if you use electricity from an ordinary fossil power station, more than half of the energy from the fossil fuel goes sadly up the cooling tower. Of the energy that gets turned into electricity, about 8% is lost in the transmission system. If you burn the fossil fuel in your home, more of the energy goes directly into making hot air for you.
Mercury in CFL's.
What about the mercury in compact fluorescent lights? Are LED bulbs better than fluorescents?
Researchers say that LED (light-emitting diode) bulbs will soon be even more energy-efficient than compact fluorescent lights.
The efficiency of a light is measured in lumen's per watt. I checked the numbers on my latest
purchases: the Philips Genie 11W compact fluorescent bulb (figure 9.4) has a brightness of 600 lumens, which is an efficiency of 55 lumens per watt; regular incandescent bulbs deliver 10 lumens per watt; the Omicron 1.3W lamp, which has 20 white LEDs hiding inside it, has a brightness of 46 lumens, which is an efficiency of 35 lumens per watt. So this LED bulb is almost as efficient as the fluorescent bulb. The LED industry still has a little catching up to do. In its favour, the LED bulb has a life of 50 000 hours, eight times the life of the fluorescent bulb. As I write, I see that
CREE is selling LEDs with a power of 100lumens per watt. It’s projected that in the future, white LEDs will have an efficiency of over 150 lumens per watt [
Model by Azevado in pdf].
I expect that within another couple of years, the best advice, from the point of view of both energy efficiency and avoiding mercury pollution, will be to use LED bulbs.
cf. graph on page 58 of his book ref.2 below.
MY LOW ENERGY CFL and LED INITIATIVES:
What about transition from 4 small halogen 50W spots to LEDS. This was a simple thing to do since the light sockets were of the same type, "nail head form". Efficiency? Three are in the kitchen and if fairly weak (how many lumens? - I was told on buying them that here, 1W was roughly 10 watts standard incandescent say 30W...) They give off a rather attractive bluish-white light in three different directions according to how they are positioned, and are certainly sufficient to make a tea-pot of late night infusion, wash-up dishes etc. The other LED is in the toilet where the socket is suitable and is largely sufficient for late night contemplation of say the paper version of David Mackay's book or an Ian Rankin detective story. Most of my remaining light sources are I back-up kitchen neon (if needed) and 6 CFL's 11 to 20W. I must admit I feel a bit abused since mostly unaware of the mercury issue I went for the energy economy. When the full picture struck home I checked the recycle bin in my favourite "do-it-yourself store". I must admit that I have strong doubts concerning the procedures used in practice to recycle CFL's and neons. The proportion of bulb breakage in any handling and transport will be, in all probability, important!
Relative contributions to mercury pollution may be found in ref.3 below.
Of course my efforts as a low to average car user will largely out-weigh my efforts of "enlightenment." cf Mackay again ref2.
Further reading
1.
“Lighting technology: Time to change the bulb”2.
online book "Without Hot Air"3.
More on Mercury, Hga.
Hg Fluorescent Light Bulbs.
b.
Consumer products containing mercury
processes which release Hg.
c.
Released to the atmosphere in process esp. Coal fired Power Gen.
4.
CREE LED light source.
Other:
5.
http://www.eup4light.net/My first favourite site on LED-lighting.
6
LED light Directionality_Light-up the WorldNotes:
Add my early strong intuition, from my readings, that LED lighting was the future’s pack leader or LEDER putting links on my first personal pages which unfortunately for me gave any publicity revenue to my Internet provider at the time, Orange which was making me see LED- Red with anger and LED-Green with envy - notice in passing that these two colours were the first wavelengths-colour to be obtained from LEDS. My admiration for semi-conductor materials stems from an all too-short spell in that industry almost 20 years earlier. The careful, finely tuned precision and pluri-disciplinarity of the semiconductor materials field of applied solid state physics and chemistry was to my mind, extremely intellectually satisfying. Here small was beautiful. Here was the setting for today’s nano-age. If this is not sufficient some years ago I found some comfort for my own intuition in the choice of research themes made by
Prof. Colin Humphries, Cambridge Univ, a past President of
The Institute of Materials, Minerals and Mining (IOM3) to work on gallium nitride (GaN) based LEDS not only for Lighting but also for the medical applications of the technology.
PS. Due to comments a Definition of Luminaires is given :
Luminaires is a complete lighting unit that consist of a lamp or lamps. Luminaires also refer to the parts that help position, protect and connect the lamps.
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