SupraSPL
Well-Known Member
Even then, the uniformity of the light spread will make a big difference. So if your average is 12 PAR W/ft² but there is a big hotspot in the center and dim edges (HPS) then it will decrease the efficacy of the light. The same applies to high powered COBs vs low powered COBs to some extent. And on top of that there are spectral issues that affect the efficacy of the light.
BUT, to the op's question and taking churchs estimation further, approx PAR W of a mars 900 is:
411W - fan power = 400W
400 * .87 driver losses = 348W
348 dissipation W * .25 efficiency = 87 PAR W
87 PAR W = ~426 umol/S (PPF) or 1.22umol/s/ dissipation W
87 * .9 lens losses = 78.3 PAR W
in a 2'X2':
19.6 PAR W/ft²
1026 PPFD average
Ops 30"X30" or 2.5'X2.5'
12.5 PAR W/ft²
655 PPFD average
in a 3'X3'
8.7 PAR W/ft²
456 PPFD average
We may be too generous calling it 25% efficient, especially considering that properly cooled Cree XTEs are around 30%. If there are red leds running hot their output drops off badly. So 25% is probably giving the benefit of the doubt.
BUT, to the op's question and taking churchs estimation further, approx PAR W of a mars 900 is:
411W - fan power = 400W
400 * .87 driver losses = 348W
348 dissipation W * .25 efficiency = 87 PAR W
87 PAR W = ~426 umol/S (PPF) or 1.22umol/s/ dissipation W
87 * .9 lens losses = 78.3 PAR W
in a 2'X2':
19.6 PAR W/ft²
1026 PPFD average
Ops 30"X30" or 2.5'X2.5'
12.5 PAR W/ft²
655 PPFD average
in a 3'X3'
8.7 PAR W/ft²
456 PPFD average
We may be too generous calling it 25% efficient, especially considering that properly cooled Cree XTEs are around 30%. If there are red leds running hot their output drops off badly. So 25% is probably giving the benefit of the doubt.
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................@ the price point and selling it for a profit, wouldn't expect anything better than over-driven generic encapsulated leds. Under a year longevity in a warm ambient environment imo=== a semi-disposable item.
