Re: HID vs fluorescent + a cacti Q.

Hi there!

    Some one asked what HID lights are.  HID stands for High Intensity 
Discharge.  When speaking of lighting related to plants, HID usually 
refers to either MH (Metal Halide) or HPS (High Pressure Sodium).  I 
have however seen people effectively use MV (Mercury Vapor) and LPS (Low 
Pressure Sodium).  Halogens, while technically a HID are nearly useless 
as plant lights, as they generate far too much heat per lumen.  (Lumens 
of output is the most accurate way to measure indoor lighting.)  


<<2) HID systems are in fact far more energy-efficient.  My 18 40 watt 
tubes consume 720 watts, and I doubt very much that they illuminate a 
larger area than a 250 watt HID unit.  Also, everything I've read & 
heard from other horticulturists agrees that HID produces a better 
spectrum, particularly if the new Philips HPS bulbs are used.>>

   The new Philips bulb?  Is that the Son Agro bulb?  If so it is a 420 
watt bulb with the primary filament being a HPS, and a 20 watt filament 
of the MH variety.  MH gives a better spectrum, but HPS provides the 
best lumen output per watt with the least waste heat generated.  It 
supposedly fits any 400 W HPS base.

    I wouldn't necessarily say that a HID covers more area than equal 
wattage florescents, I would definitely say the area covered is much 
better illuminated though.  Anyone who is serious about growing more 
(frost sensitive/tropical/etc) plants than can fit under, say 4, 
flourescents should consider HID lighting.  For starting seeds I would 
stick with the florescents though, no matter how many you are starting.  

<<The reason I do not have HID yet is the same one for not replacing by 
tubes with Verilux.  I simply haven't budgeted to save the money to 
afford the larger initial expense.  I also haven't quite figured out how 
I'll deal with the waste heat problem; obviously it's not _that_ much of 
a problem, otherwise more folks would have burned down their houses.>>

    Of course the initial outlay of cash is the most prohibitive fault 
of the HID.  Frankly, I wouldn't get any less than a 400 W.  The price 
difference in purchasing the ballast, and replacement bulbs is very 
small, between 250, 400, and 1000 watt HID.  And the 400's are so much 
more useful.  1000 watts is even better, but then you are starting to 
get into a significant operating expense.  12 hours a day, at 1000 
watts, equals 12 KWH per day.  10 cents per KWH is what I'd consider a 
decent guess at electricity pricing (plus convenient for in your head 
math).  This means $1.20 per day, or $36 per month in electric bills.  I 
imagine for most people raising a family and with just a little 
gardening on the side, 400 W is as much as they will be willing to pay 
to operate.  (Using the above figures a 400 W light would cost less than 
$15 monthly in operating costs.)

    Oh, and as for heat?  The fan mentioned earlier goes a long way to 
helping with this, as well as supplying fresh CO2 to the plants, which 
can become a concern if you use a HID in a small space.  The more light, 
the more the plants need fresh CO2.  Normally (going from the top of my 
head, correct me if I'm out of line) there is about 350 ppm CO2, and 
photosynthesis is stopped if it drops below 200 ppm.  On the assumpmtion 
that this is more than anyone really cared to know, I'll stop now.
    
<<I'm looking forward to the day when I can contribute my own experience 
with HID to the discussion.>>

    Hey Philip, I'm looking forward to the day I can volunteer my own 
experiences with growing succulents.  Frankly, I kill most of them.  
Just today I started a dozen seeds of Trichocerus terscheckii, using 
GA-3 I got from J L Hudson's.  Any advice on this one?

Glider, zone 5

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