Besoeker

http://www.irf.com/technical-info/designtp/irplcfl1.pdf
High frequency operation (34kHz)

The Bear

If you look a little further into this what you’ll find is that the 50 Hz mains supply frequency is superimposed onto the HF feed to the lamp.

This is because it is in effect an amplitude modulation of the power rail to the oscillator (there is no reservoir capacitor to take it out) and so the 50 Hz is still present as an amplitude modulated HF feed.

The phosphor within the lamp envelope being of sufficiently long persistence takes most of this effect out, and is why when you turn such a light off there is a short afterglow as the phosphor darkens.

Besoeker

Capacitor C1 is directly across the single phase input rectifier in the diagram shown.

youcanhandlethetruth

This is a specification for a light bulb.

I don't see anything regarding coal fired power plants.

__________________
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The Bear

That's not a single phase rectifier, and C1 isn't a part of a “smoothing” circuit to take out line ripple. It’s a part of the voltage doubler, and works in conjunction with C2 in order to cater for the US market where the line voltage is 110 volts.

The Bear

You need to look several kilometers to the left!

Besoeker

I stand corrected - I should have said C1 and C2 in series. I was considering the 220V input. In that case BR1 acts as a single phase rectifier and C1 + C2 provide smoothing. Note that they are shown as electrolytics which is typical for smoothing capacitors.
Smoothing is a compromise so won't be perfect and, from a 220Vac 50Hz supply, there will be a 100Hz component in the DC.

This is what I was looking for and shows it more clearly.
http://www.nxp.com/acrobat_download/applicationnotes/AN98091_1.pdf
I have a hard copy of it but was too idle to scan it in.

The Bear

Right, now you’re “cooking with gas”! That circuit is different as in that circuit C1 is of course the smoothing capacitor to take out much of the (now) 100 Hz. Component.

You know, it really makes me step back in amazement sometimes when I look at what progress has been made in the last forty-ish years.

I am reminded of a piece of graffiti that was (and maybe still is?) on the wall of the downstairs toilets in the Computer Science buildings at Essex University that read “There is a disturbing increase in the world in the number of things that I know nothing about”. The number of times that I now feel that way is, well, disturbing!

(That blo*dy IC must be a jungle inside as well!)

Besoeker

Mostly I see it that way too. But I sometimes have to deal with the negative aspects.
The input for the CFLs is just one example of equipment that takes non-sinusoidal current from the supply. Computers, televisions, anything using SMPS does similar things.
The result is that they pollute the electrical supply.
You then need to add equipment to mitigate the effects.
Progress is rarely without some pain.

Besoeker

OK.
I questioned whether new power stations would be required for the production of CFLs and you asked for supporting information on why I should have raised that question/doubt. Fair enough.
My first thought, an obvious one I suppose, was that, if the CFL consumes less energy in use than the bulb it replaces, that reduction should be set against the energy used to produce it. That’s why I asked the question.

Anyway, a little bit of arithmetic, some inferred data, and a little bit of qualified assumption.
I can buy a CFL for £2.00 from a retailer.
That price pays for production and the margin made by every link in the chain that gets it from the manufacturer to the retailer. The original manufacturer might get £1.00. That includes any profit he might make, cost of materials, cost of labour, cost of manufacturing plant – and energy. All out of £1. A reasonable assumption would be that the energy cost for production is less than £0.50 and possibly very much less than that. At most efficient UK production* 50p is the production cost for about 20 kWh.

Looking at the other side of the picture…
Compared to a conventional 60W tungsten filament lamp an equivalent CFL will save about 47W. Over a projected life expectancy of around 10,000 hours that amounts to 470 kWh. Compared to the cost of 20 kW h production.

Even if the cost of electrical production in China was just one tenth of that in UK CFL production would consume much less energy than they save in operation.

In short, CFL production wouldn’t need more power stations.


*Based on BWEA figures.