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Re: Potassium and CF Lighting

Steve Dixon  wrote

>There are a number of reports, starting
with the manufacturers
>(CustomSeaLife, for example), that CF
light produce more light per watt than
>regular (NO) fluorescent bulbs,
including more light than the new
>T-8 bulbs.  Now I realize the term
"lumen" includes an element of human
>perception.  That a light might seem
"bright" to the eye and yet a bulb that
>seems less bright might actually have
more output as measured in lumens,
>that perception of light may not
correlate with the actual output of the
>bulb-referred to as PAR, if I recall.

>Does anyone have a definitive answer to
this question?  Do CF bulbs put out
>more light per watt (lumen or PAR) than
regular fluorescent bulbs; than T-8
>bulbs?  Do we have data on this point?

I think it is definate that  T5 lamps
and T8 lamps are generally more
efficient than NO T12s but not so much
as retailers would lead you to believe.
It is a very simple matter to determine
indirectly which is the more efficient
style of lamp. All you have to do is
compare the lumen output of different
diameters of lamps that have the same
length and use the same phosphor. A 54
watt 4' T5 lamp with an 841 phosphor is
about 95 lumens/watt, a 35 watt 4' 841
T5  lamp is 104 about lumens per watt. A
32 watt 4' 841 T8 is about 92 lumens per
watt and a 40 watt 4' 841 T12 lamp is
about 84 lumens per watt.  That is not a
whole lot of difference but every little
bit helps. The PAR efficiency values,
whatever they are, will be proportional
to these values if as I stated
comparisons are made using only the same
phosphors. So as long as they are not
overdriven too much,  the lamp diameter
does make a difference in the efficiency
of the lamp.

I would like note that  folding the lamp
to make a compact fluorescent has only a
slight negative impact on the efficiency
of T5 lamps but it does allow a longer
lamp to be used in a smaller space and
longer lamps are more efficient.

The main advantage of these lamps
though, is not so much in there
increased efficiency but in their
compact size and in their smaller more
intense light source. A lot of light can
be concentrated in a small area which
allows for better fixture designs and
better reflector designs. The reflector
design can have a dramatic impact on the
amount of light that penetrates the
surface of the water and since fewer
lamps are required there is more space
for a more sophisticated reflector
design that directs light downward at a
better angle. The smaller lamp diameter
is closer to a point source of light
when compared to T12s which means that
an optimized reflector design is more
effective with the smaller light source.
So not only do you get higher
efficiencies with CFs which produces
more light per watt, more of the light
that is produced makes it to the plants.
When that is combined with the
electronic ballast that comes with these
types of lamps the overall system
efficiency can be much higher than a
typical NO T12 system.

One drawback of these lamps is that
there is not the same selection of lamps
as can be had with T12s which means that
maybe the best spectrum lamps are not
available. On the other hand the proof
that the lack of a perfect spectrum
(even if it could be defined and that is
the case) can be offset by extra light
intensity is in the fact that many
people report great success with these
lamps. Another problem is the cost of
the lamps. T5s cost a lot more than T12s
but this expense is mainly offset by the
long life of T5s and by the fact that
fewer lamps and fewer reflectors are
required. T8s actually cost less than
their high CRI T12 counterparts with 800
series phosphors and have even longer
lives than either one. If it is feasable
to use them then they are probably the
lowest cost lighting system. I think it
is only a matter of time though before
T5 lamps are much more commonplace and
the price drops a lot.

I am trying to aquire some T5 4' HO
linear fluorescents at a reasonable
price so that I can marry them to a
specular parabolic reflector. I think
that this combination might perform very
well and I would like to give it a try.
Has anyone tried these lamps in an
aquarium setup and if so what do you