Date: Mon, 29 Sep 1997 12:22:40 +0300 From: Emre_Gurcan@philips.com.tr To: cp@opus.hpl.hp.com Message-Id: <aabcdefg3757$foo@default> Subject: Artificial lighting
Being in the lighting business, my two cents on lamp efficiency:
>From a light intensity point of view, High Intensity Discharge (HID) lamps
are the best source of lighting. They also produce the highest lumen
efficacy (lm/watt,) meaning their energy consumption is usually the lowest
per lumen of light output. Also, the color rendering for metal halide lamps
is exceptionally good. The best choice for flora lighting would be a
compact metal halide lamp (ranges from 35 watts to 150 watts) which
produces 6000 lumens with a 70 watt lamp (86 lumens/watt) and the color
rendering is over 90 (measured in Ra - sunlight is 100 Ra). HID lamps also
usually have the longest lamp life at over 10,000 hours. Although
flourescent lamps have long lives as well, but their luminous flux
decreases 70- 90% after 8000 hours. HID lamps have almost constant luminous
flux.
Just to show a comparison on light eficacy, while compact HID lamps measure
at over 85 lm/watt, incandescent lamps have a luminous eficacy of 53
lm/watt and cool daylight flourescents lamps at around 65-70.
My personal opinion is that HID lamps are the best source of flora
lighting, followed by tubular flourescent lamps. However, the initial
investment for an HID lamp setup will be high. With 15 hour a day usage, it
may take a few years to amortize this cost.
I have a 70 watt compact HID at home and the quality of the light is
impressive. It is very strong (6000 lumens- about twice as much as
flourescent or incandescent lamps). The only handicap is that the bulb
emits more heat than flourescent lamps. For that reason, the lamp should be
at least two feet away from the plants (although may be a good heating
alternative). I must point out that I don't use this lamp (or any
artificial ligthing) for my CP's, but use it in our living room.
To sum it up, I suggest a compact HID lamp (comes in different brands) for
those who can afford it. But for more economic budgets, flourescent lamps
(especially daylight or cool daylight) are the best option. I have
questionmarks on special flora lamps, and I personally don't believe in
their added value. Any lamp which has a color rendering of over 90 and a
color temperature of 5000 or higher (daylight kinds) is the closest thing
to natural sunlight.
As I mentioned, I've never used HID lamps for CP lighting and I speak
purely about concept but if anyone has experienced HID lighting for CP's I
would be interested to learn about their experience.
Happy growing!
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