Quote:
Originally Posted by StirCrazy
wohwoh man, I never said they wern't related only not the only factor. the simmple fact is if the big blue spike shifts to the left, PAR will drip off as it shifts compound this with a decrease in intensity and it will be compounded.
you can not gage PAR out put with LUX, two totaly diferant and unrelated measurments. you are in one case measuring the amount of the emitted light with in a specific wave length, in the other you are measuring the amount of visiable light that falls on a given area. kind of a mass vs PSI but of different componants. Like I said in the previous post, no two MH or T5, ect age identicaly. this is due to various factors, including gas concentrations/types inside and so on. LED eliminates this by using a solid state chip encapsulated with no air/gas/ect surounding the chip, but they do have a problem as mentioned... heat. if they are allowed to warm up they will go through a reduction in PPF, which rises again once cooled. this can be as much as a 30% reduction in as little as 1/2 an hour with out any cooling and no drop in intensity. so using a heat sink and fans properly is a twofold benifit.. maintains the PPF output and the life on the LED. I think you would need the fans personaly, other wise the fixtures would be huge inorder to give each LED enough heatsink to make passive cooling possible. by having fans and preperly using them you will be able to produce lighter, more sleak fixtures. for what it is worth I had 4 computer fans running over my sump for 8 years starting and stopping 4 times a day. although they were coated with salt spray they still worked..
Steve
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Agreed that you can't measure PAR from lux directly, obviously the PAR of a bulb depends on the spectrum distribution. However that was never my point. I'm purely talking about bulb wear and the simple fact is a decrease in PAR over time is the result in an overall decrease in intensity which could be measured by LUX. For example mass and psi are separate measurements but if you have a mass over a given area and the area and gravitation force remains constant then a decrease in PSI means a decrease in mass.
Your "big blue spike" does not shift, or move to the left or right, it simply decreases in intensity and the overall CCT shifts to a lower K rating. Depending on the bulb you can also see an increase in other areas of the spectrum like red and green which is why some bulbs will actually increase in PAR overtime or stay relatively constant. In order for PAR to decrease the overall intensity of the bulb must decrease.
As for fans, they are not needed, there are already plenty of LED lights for other applications which use high powered LEDs with properly designed heat sinks and no fans. It's a simple mater of cutting costs and the temperature gradient and heat transfer rate of LEDs is high and low enough respectively to eliminate the need for convective cooling. Computer components like CPUs run much hotter, their heat flux is way higher than an LED and require convective cooling. Computers are also built as cheap as possible, it's a huge commodity market.