RE: [AGA Member] how many wpg is the sunlight?

["roger" <roger@spinn.net>]

Years ago I figured out that I would need to rack 20 40-watt flourescent
lights over my 55 gallon tank to get sunlight-like intensities.  I may have
been optimistic.

Phil gave us an average of about 80 watts/square foot for Amazon sunlight.  My
CRC Handbook says that for light distributed over the visible range (almost
like sunlight) there would be 200 lumen/watt.  Phil's 80 watts/square foot
would then be 16000 lumens/square foot.

Light fixtures aren't often very efficient.  Say we have a reflector that can
put 2/3 of the lumen produced onto the water surface.  That means to get 16000
lumens/square foot on the water surface I would need to start with 24000
lumens of lighting per foot.  40 watt daylight bulbs (also according to CRC)
have an efficacy of about 65 lumens/nominal watt under average conditions.  To
get 24000 lumens/square foot I would need (rounding down) 360 watts of
daylight flourescents per square foot; for a 55 gallon tank with about 4
square feet of surface area that means 1440 watts or 36 lamps -- 26
watts/nominal gallon.

It's no wonder that when sunlight falls on my 55 gallon tank I can't even tell
that the tank lights are on.


Roger Miller


On Wed, 7 Apr 2004 07:19:19 -0700 (PDT), S. Hieber wrote
> --- Phil Edwards <biotypical@hotmail.com> wrote:
> > On a totally clear day, but accounting for humidity, the
> > middle of the open 
> > Amazon is going to get 1000 watts per square meter.
> 
> Is that the actual energy, as light, it will receive,
> expressed in watts or is that the amount of watts necessary
> for a fluorescent lamp to give an equivalent amount of
> light?
> 
> sh
> > That's approximately 
> > 1000w/10 sq. ft or 100w/sq. ft.
> > 
> > Taking into consideration the averages for atmospheric
> > conditions and shade 
> > from various things like trees the actual average amount
> > is closer to 
> > 800watts/sq. meter, or 80 watts/sq. ft.
> > 
> > 
> > 
> > Hope this helps some,
> > Phil Edwards
> > Charlotte, NC
> > 
> >
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> =====
> S. Hieber
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