> I'm very interested in the dimming process you describes with the
> magnetic ballasts. What is the extra investments needed for this method?
> On witch level you can do it (electricity cabine?)

Yes, it's done within the control box from which the lighting system
(several dozens of lamps, or even several hundred of them, when on all 3
phases) is supplied and switched on an off. There are over 76 such boxes
containing dimming technology now in Brno, out of more than 400. Next year
the total number of boxes should be around 430 and one fourth of them
should be equipped with dimming (all the control boxes are connected via
GSM modems to the city control centre, so the supervisors there know which
lighting circuit is switched on, which box is open, at which power runs
any circuit with dimming, etc.). In several other local capitals in Czech
Republic, dimming is applied too (Olomouc, Zlin, Uherske Hradiste, Most,
and even in Prague it began). Sine wave with reduced amplitude is used a
bit more often than waveform-modifying technology. It pays of quickly for
installations with lamps of 100 W and more. The Brno-based enterprise has
some realizations even in Bulgary

Various suppliers of dimming (and voltage stabilising in the same time;
stabilising itself saves not only lamp life, but prevents overlighting
and excessive power consumption due to overvoltage as well, what works
even for 50W HPS, which is otherwise not much dimmable):

 http://www.datmolux.cz/en
 http://www.mpes.it/english/prodotti
 http://www.irem.it/en/Lfr/Lfrset.htm

It's obvious that the claim contained in the new Chapter 7 of the draft
(available since Nov 16 on the www.eup4light.net, after you login as a
shareholder), that there is no technology to dim MV lamps, is wrong.

But even I was wrong saying that LPS cannot be dimmed. Obviously, at least
some of them can (I assume the strongest models, over 100 W), even if less
then other types. Still, even there the electricity savings are
interesting. And of course, any dimming technology will prevent
overvoltage and extend the lamp life a lot. An indicative table is at
  http://www.irem.it/en/Lfr/LFRsa.htm

(I should remark that the adapted Intelux waveform-cut technology, by
which the original capacitors may remain in the luminaires, is rather new,
being marketed since perhaps one year. This is the proper way of how to do
it.  Some people prefer the Reverberi way, however, namely just regulating
the amplitude of the sine wave. This works even for many hundreds of lamps
on a single 3-phase controller.)

> I was very suppriced that you declared that LED is the most efficient
> lighting system for outdoor lighting. As far as I know LED's have an
> efficiency about 25 lm/watt, some of them 34 lm/watt but these are
> rarely and have some difficulties with cooling and so the lifetime is
> reduces a lot. For that reason the 25lm/Watt are still most used. MH
> with ceramic have an efficiency of 90 lm/Watt, HPS 110 lm/watt and LPS
> about 180 lm/Watt. So the efficiency of LED's are a lot lower. The optics
> can be better. They succeed in a lot of cases to have twice so much in
> the light beam than with fixtures for other lamp types. But the
> efficiency of the other lamp types are a lot more then 3 times of the
> LED's so even with more lighting in the beam it is still less efficient
> for outdoor lighting. I can understand when you are talking for low
> lighting levels as for pedestrian environments because the other lamp
> types have only higher wattages and luminances. Is it in that option
> that you mean your comment?

Yes, LEDs are competitive now mainly for situations when one or two lux
are enough, especially where the ubiquitous luminous flux of discharge
lamps would be mostly wasted by going outside the target areas (such as
narrow paths). With LEDs, over 80 per cent of their luminous flux can hit
the proper target area, and the illuminance or luminance can be perfectly
uniform. With discharge lamps, the proportion of their flux hitting the
proper target can be easily below 30 per cent, sometime it's even much
less. And, typically, even on the target area, some spots get orders of
magnitude more light than needed. Then LEDs (each equipped with Luxeon
Collimator or analogous optics) can produce the needed minimum values of
illuminance or luminance with twice less electricity than discharge lamps.
And reduce the amount of light pollution ten times or more.

For low light fluxes, the task of cooling the LEDs is far easier than for
high fluxes: in case of a steel mast, it should do to connect the LEDs
thermally with as well as possible. This would make the LED lighting
systems still cheaper than when the luminaires are to be air-cooled as
standalone units.

The main obstacle for LED technology is that false, completely wrong
metrics of standards, which is harmful for vision and promotes light
pollution: demanding minimum average values. Any bright light spot near to
a discharge-based luminaire is (by the wrong standard) treated as
beneficial (if it does not violate the loose uniformity limits), as it
raises the averages. Standards promote bad lighting.

But standards are no laws, they need not be obeyed. Any good designer
might choose to pick up just the minimum values from them, and even ignore
any deprecation factors. If the amount of light will become too low in
future (after more than ten years for LEDs), it's easy to change the
light-producing parts together with proper the power-supplying parts
(ballasts, for discharge lamps), using the new technology which will
surely be available -- it's much cheaper than replacing whole luminaires.
Such an approach may well pays off due to the lower initial electricity
consumption.

cheers,
 jenik

reminder:
 learn about the main environmental impacts of outdoor lighting
 and their remedies from
                          www.savethenight.eu