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Re: [APD] hydroponics lights ?

Metal Halides and compact fluorescent lights have about he same energy efficiency, about 30-35%. It varies from one ballast and bulb combination to another, but they are basically, not only in the same ballpark but, on the same infield. And it follows, then, that the amount of energy shed as heat is the same. Because the light and heat source is in a more concentrated space with a MH, the local temperature will be much higher, but the heat produced is the same as fluorescent. Consider, a lit match head has a very high temperature very near the match head yet it produces very little heat compared to say a 40 watt incandescent light bulb. I have not done the math on this example, but you get the idea.
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----- Original Message ----
From: boolybooly <boolybooly at ntlworld_com>
To: aquatic plants digest <aquatic-plants at actwin_com>
Sent: Saturday, July 8, 2006 3:34:52 AM
Subject: Re: [APD] hydroponics lights ?

>> Anyone tried it ? Any other recommendations  ? (I am in the UK).
> I have used metal halide bulbs with great results.  I also lost several
> gallons a day to evaporation and my electric bill went through the roof.
> I was running 2 X 250W MH bulbs on a 55 gallon.
> The mercury and sodium lights don't have as nice a spectrum as MH, but
> as Tom Barr will tell you, plants are not that picky about spectrum.  I
> just don't think they look as good.
> -Nick

I suppose in this day and age I should be thinking about a more energy 
efficient light system, it has crossed my mind that an array of 3x3 (9) 30W 
energy saving bulbs should be able to provide the light at about half the 
power consumption. Then I could change the number of daylight bulbs in the 
array to vary the hue towards the blue spectrum v yellow. It would be 
cheaper to make and to run saving a couple of kW/h a day and I haven't heard 
of anyone else trying this yet and it might be fun to pioneer !

Metal halide looks good though because of the refraction effect in the 
water, wavelets and ripples making patterns and so on. An array of energy 
savers would not give you that. I know what you mean about evaporation as 
mercury vapour also produces a lot of heat and I have a RO system set up so 
I can top up as much as needed.

I also invested in a TDS meter (Total Dissolved Solids for any who havent 
heard of these) so I can tell exactly how concentrated the water is getting. 
When I first got the meter after 5 years running the tank the reading was 
quite high, over 500, tap water is about 450 but I setup the tank 50/50 with 
RO which has a TDS of 10 so it was probably at 250 ish to start with, but a 
few 100% RO water changes soon fixed that. The rummy nose tetras seemed to 
appreciate it!


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