Are you visiting from outside your region? Visit your regional site for more relevant services and pricing.

Letters October 2007October 2007

Reader replies from BSRIA's 'Views on replacing traditional lightbulbs with CFLs' feature.

We need to know more

Congratulations on your article on low energy light bulbs. This is the first honest appraisal I have seen of them.

I removed them from my own home because of the very poor quality of the light, but there are other issues that give me cause for concern, such as the mercury content.

You are quite right that more research and investigation needs to be carried out before they are made compulsory.

Michelle Barkley
Technical Director
Chapman Taylor LLP

Factoring in the power

In the article about GLS versus CFL lamps in the June edition of Delta T, the table on page 8 states: "Many CFLs have a low power factor of approximately 0.5 so a reduction in CO2 emissions will be only half the reduction in wattage". This is not true.

The reduction in current will be only half of that which would occur if the power factor were unity, so the transmission loss reduction would be only 0.25 (most of the losses would be I2R losses) but you still have the reduction in load power. There are lots of variables (such as portions of distribution at the various voltages).

Having made up a spreadsheet to allow various assumptions to be tested, I came to the conclusion that even if you assume the total transmission losses from power stations to load with unity power factor were 40 percent, a 1000 W reduction in load power (for example) combined with a power factor change to 0.5 would result in a generation power requirement reduction of at least 800 W.

I do, however, share concerns about CFLs: how do the energy requirements for manufacture, transport and disposal compare with GLS lamps?

Brian Hyams
Foggo Associates

Richard Forster replies
My brevity appears to have sacrificed clarity.
Compact fluorescent lamps of low power factor are electrically inefficient inasmuch as the apparent power (Volts times Amps) is approximately double the real power (Watts). This is in contrast to mains voltage filament lamps which have unity power factor and where real power equals apparent power.

Domestic metering measures real power, so for economic comparisons the real power of CFLs is appropriate. However, when considering the environmental impact of electricity generation from power stations burning fossil fuels, then lamp wattage is inappropriate and VA should be used.

Typically, a low power factor 20 W CFL uses 42 VA, and it was this difference I was attempting to highlight.

Historically, for fluorescent fittings of less than 30 W, power factor correction was considered unnecessary as their limited use was insignificant in relation to the total electrical load.

However, the current Building Regulations call for 25 percent of fixed domestic lighting points to be low energy, while the Code for Sustainable Homes suggests a preferable target of 75 percent. Add to this the Government's plans to ban the sale of GLS lamps by 2011, and power factor correction becomes a serious domestic issue.

As demand and generation capacity becomes more critical, perhaps a move for domestic metering to be based on VA rather than Watts would focus attention on producing high power factor electrical and electronic equipment. This issue is not only related to discharge lamps.

I agree about transmission losses but feel these relate to distribution efficiency rather than equipment efficiency.

Regarding embodied and through-life energy, I wish there was more information available from manufacturers. Like-for-like comparison of CFLs and GLS lamps raises difficulties because light output, lumen maintenance and lamp life are expressed differently.

Disposal of CFLs now involves recycling and special handling. As this process is only just becoming mandatory, I doubt if real data has yet been gathered.

Richard Forster, BSRIA

Carbon truths

I read with great interest your feature article 'How many politicians does it take to change a light bulb?' in the June issue of Delta T.

I am writing a paper on the banning of incandescent light bulbs and wish to provide a reasonably accurate assessment of the reduction in CO2 emissions that will result from the replacement of 40 W, 60 W and 100 W GLS lamps with equivalent CFLs.

If you have data or knowledge of reliable sources of data for domestic and/or non-domestic applications I would be very much appreciate it.

Brian Spires
HLM Architects

Life-cycle analysis

There is a part of the equation that your lighting article seems to miss completely: the environmental impact of the manufacturing process and subsequent disposal of lamps.

Although I am an electrical engineer, I have no knowledge of the relative energy usage in making the different types of lamp nor of the environmental impact of obtaining the raw materials for their manufacturer.

All CFL lamps seem to use mercury in the arc tube, a substance that the EU is banning the use of in other fields, for example in barometer production, so there is an environmental impact from the use of this material alone. This will be aggravated by poor disposal methods and the lack of local authority recycling facilities.

It seems to me that a complete life-cycle cost analysis of both types of lamp needs to be undertaken before anyone is in a position to determine which lamp type is better for the environment.

David Simcox
Associate Director
Environmental Engineering Partnership

There seems to be a lot of hype regarding the savings to be made by changing from GLS to CFL lighting. I have not seen any figures to show the savings (if any) in embedded energy used to manufacture said lamps.

Could we end up using more energy overall? What of disposal of expired CFLs and the materials contained within them which presumably come within the remit of the WEEE Directive?

My personal experiences of CFLs both at home and at work are that, for long-term use (where the lamp is left on for long periods of time), there can be significant savings. However, for short periods (where lights are turned on to descend stairs or to cross a room) the time taken for the lamp to reach full brightness is a problem.

Another factor not considered is the radio frequency interference caused by CFLs to AM radios. This can be considerable, especially with some of the cheaper CFLs.

Andy Carter
Maintenance Engineer
Somerset County Council

What about the extra manufacturing electrical requirement and materials which have a cost? The cost for safe disposal should include the transportation and recycling requirements. I believe that these elements have been conveniently ignored.

With the continual switching that occurs in the domestic situation, I think the estimated life of CFLs is overstated. I would appreciate your views.

Ray Newman
Hurley Palmer Flatt

Many GLS lamps are used only for short times during the day. I have 16 lightpoints that I use for less than five minutes per day.

So the energy for producing a CFL will never be gained back in my life.

A. van Melle
(by email)

Richard Forster replies
I found little information about embodied energy although some figures are quoted by Rod Elliott from Australia in his article 'Ban incandescent lamps' which he has updated recently. Try [link= caption=]

There are complications in arriving at an average figure. Many CFLs come from China so what is reasonable distribution cost? Claimed life varies from 6,000 to 15,000 hours, although this may not be replicated in the field with frequent switching.

Then there is the cost of disposal under the WEEE Regulations, just introduced. Their relatively long life means that CFLs could last decades in domestic use, whereas there are reports that GLS lamps will be banned in the UK by 2011. Are comparisons going to be like-for-like?

Long-life lamps can hold back the benefits of technological advances, a criticism that can also be applied to light emitting diodes.

Hence the simple approach of assuming energy consumed in use as the main factor; this should be adjusted for power factor so as to reflect the generation from burning hydrocarbon fuels.

Richard Forster, BSRIA

Editor's note
Letters correspondent Michelle Barkley suggested that Delta T readers could visit the following web sites that cover other issues associated with low energy lamps:  

NVM digital
Epilepsy; The Information

For more details contact Information at BSRIA:

Tel: +44 (0) 1344 465600
or email