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prankster1590
- 14
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In most of the agricultural and HVAC world they use the unit W/m^2 for the lightpower in most of the design calculation. But these numbers are never given for LED growlights. There are some empirical equations to convert from Umols/s/m^2 to Wm but those can be quite off since the lightpower is dependant on the spectrum of the light. And spectrums of different growlight are almost never identical. And you cant base your calculation on the power rating of the growlight since it doesn't only reflect the power of the light being transmitted but also the power used to operate the machinery of the light growlight.
So I tried to calculate the power of the light being transmitted by the Mars Hydro FC 3000
First I needed a spectrum so I took a picture from google and counted pixels to copy that spectrum in excel.
This was the result:
A relative intensity of 1 equals 1057.71 mW/nm.
So if all wavelengths have a relative intensity of 1 than the power transmitted would be (780 nm - 380 nm)*1057.71 mW/nm = 423084 mW = 423 Watts. But since most wavelength have a different relative intensity, this is not the case. I have to integrate the spectrum. I did this with simpson's rules.
The result is the following. The total relative intensity is 151.5. This number multiplied with 1057.71 is 160 Watts. So the power of the light transmitted is 160 Watts.
The following is the problem: The number 1057.71 mW/nm is usually given with an area. Like mW/nm*m^2. This is not the case here. They did say that the light was tested on a 3ft x 3ft area. So that would make this number 1057.71 mW/nm*9 ft^2 = 117.53 mW/nm*ft^2. This would give 17,8 Watts/sq ft.
Do you think this number is correct because in a lot of growroom design calculation they use the number 50 Watts/sq ft. Which is a lot more than 17.8 Watts/sq ft?
So I tried to calculate the power of the light being transmitted by the Mars Hydro FC 3000
First I needed a spectrum so I took a picture from google and counted pixels to copy that spectrum in excel.
This was the result:
A relative intensity of 1 equals 1057.71 mW/nm.
So if all wavelengths have a relative intensity of 1 than the power transmitted would be (780 nm - 380 nm)*1057.71 mW/nm = 423084 mW = 423 Watts. But since most wavelength have a different relative intensity, this is not the case. I have to integrate the spectrum. I did this with simpson's rules.
The result is the following. The total relative intensity is 151.5. This number multiplied with 1057.71 is 160 Watts. So the power of the light transmitted is 160 Watts.
The following is the problem: The number 1057.71 mW/nm is usually given with an area. Like mW/nm*m^2. This is not the case here. They did say that the light was tested on a 3ft x 3ft area. So that would make this number 1057.71 mW/nm*9 ft^2 = 117.53 mW/nm*ft^2. This would give 17,8 Watts/sq ft.
Do you think this number is correct because in a lot of growroom design calculation they use the number 50 Watts/sq ft. Which is a lot more than 17.8 Watts/sq ft?
