Formula for lighting

[fanleaf]

Tomatoes, tomottos... Most meters for solar installations read watts/sq. meter. That is what I use to test my lights. Simple cheap meters. Newer CFL and LED lights are sold in units of lumens and watt "equivalents". Older bulbs and halide lights are sold in units of watts. You can convert them mathematically. So for your physics lesson of the Day:

The luminous flux ΦV in lumens (lm) is equal to the power P in watts (W) times the luminous efficacy η in lumens per watt (lm/W), giving us the formula: ΦV(lm) = P(W) × η(lm/W), or lm = W × (lm/W)

Luminous efficiency varies with the type of bulbs used. Here are typical values for bulb types used for growing weed:

Tungsten incandescent 12.5-17.5 lm/W
Fluoro tube/CFL lamp 50-75 lm/W
LED lamp 30-90 lm/W
MH lamp 75-100 lm/W
HPS lamp 85-150 lm/W

If you want to talk about indoor lights for growing MJ, you also need to talk about the color temperature (in degrees Kelvin). You also have to consider the intensity of the light at the distance that the plant is from the bulb. Light energy from a bulb falls off at the square of the distance.

Just wondered where you got your Luminous efficiency chart?

• HID lamp: Source efficiency is typically 120 lumens/watt or higher. However, losses from trapped light, protective covers and lenses, inefficient ballasts and unfavorable operating temperature typically result in a measured system efficiency of 30 lumens/watt or less.
• LEDs: Source efficiency can be 100 lumens/watt or higher, depending on the type and manufacturer of the LED used. There are no losses from trapped light due to the focused output of the LED, and secondary optics and protective covers generally reduce output by only 25% or less. LED power drivers are also more generally efficient than HID ballasts, and reduce system efficiency by 10-15%. However, even when efficiency reductions due to high operating temperatures are included, LED system efficiency often remains above 50 lumens/watt or higher.

[h=3]Lumen Depreciation & Useful Life[/h]A second important factor involved in comparing the efficiency of LEDs to traditional lamp sources is accounting for the lumen depreciation of both sources. HID sources, especially metal halide, suffer from substantiallumen depreciationover relatively short periods:

	High Pressure Sodium	Metal Halide
Lumen Depreciation	20%	50%
Maximum Useful Life (Hours)	24,00	60,00 – 10,00

[h=6]Note: The data above reflect typical performance and are intended for illustrative purposes.[/h]The useful life of LEDs is typically defined as the operating time prior to 30% lumen depreciation, or 70% lumen maintenance (L70) . This level of LED lumen depreciation has been widely adopted as the standard for useful life since a 30% decline in lumen levels is not easily detectable by most people. Although the time required to reach L70 lumen levels is directly related to the typical TJ, LED life expectancy can be 50,000—10 0,000 hours or more if TJ remains low. This means that you can enjoy higher LED system efficiency for many more years than traditional sources, and postpone costly maintenance required to change dim or failed traditional lamps.
[h=3]The Results: LED vs. HID Lighting Efficiency[/h]Higher system efficiency and slower lumen depreciation combine to provide substantially higher overall efficiency with LEDs compared to HID sources. For example, the chart below shows the expected performance of a 100 watt MH street light versus a comparable the DuraStreet Series LED Light Engine:
As shown in the chart above, the lumens per watt provided by a DuraStreet Series LED Light Engine decline gradually over a long period. However, the lumen output of the equivalent HID lamp declines much more rapidly, and the HID lamp must be repeatedly replaced during the same operating period.

 

[Big Sur]

Just wondered where you got your Luminous efficiency chart?

I pulled it off the web and removed several bulb types not used to grow with. It is lost in last weeks "history" list now that it is Monday morning here. PITA to find it now. It was used just as an example, not the end all. Bulbs vary highly within type, which is why I use a watt meter to test my lighting.

 

[fanleaf]

I pulled it off the web and removed several bulb types not used to grow with. It is lost in last weeks "history" list now that it is Monday morning here. PITA to find it now. It was used just as an example, not the end all. Bulbs vary highly within type, which is why I use a watt meter to test my lighting.

Yea man I hear ya!

Who ever thought there would be conflicting info on the internet right...

 

[Fuzzy Duck]

Correct me if I'm wrong, but if we are talking about light we should be talking lumens not watts.

You might find that lumens is only a measurement of light visible to the human eye aka brightness !

To which you may find plants respond to light wave length which some is measured in kelvins or Nm to the key areas of photosynthetic reaction & stage of growth.


I would be more concerned about correct spectrum of light to use in veg / flowering tho for the best results which may lead to ideal PAR or Umol needed for growing which is largely a debated area & or with in the lighting industry to provide such info as they is no real guide lines ! Could be a big difference between brand names & cheap buget stuff tho...

One may like to read this link - The Basics Of Plant Lighting & perhaps little bit more research as a suggestion.

 

[fanleaf]

You might find that lumens is only a measurement of light visible to the human eye aka brightness !

To which you may find plants respond to light wave length which some is measured in kelvins or Nm to the key areas of photosynthetic reaction & stage of growth.


I would be more concerned about correct spectrum of light to use in veg / flowering tho for the best results which may lead to ideal PAR or Umol needed for growing which is largely a debated area & or with in the lighting industry to provide such info as they is no real guide lines ! Could be a big difference between brand names & cheap buget stuff tho...

One may like to read this link - The Basics Of Plant Lighting & perhaps little bit more research as a suggestion.

Very well put!

 

[Big Sur]

Yea man I hear ya!

Who ever thought there would be conflicting info on the internet right...

Well, lighting efficiency is a moving target. The numbers have changed greatly over time (see the graph below). The issue of lighting is also muddied when it comes to watts, lumens, bulb type and fall-off, scotopic/photopic ratios of bulb types, bulb decline/depreciation/life, fixtures, wiring, ballast, initial cost, cost to run, heat management, reflectivity, intensity drop with distance, efficacy, spectrum/light temperature, wiring, timers, etc. etc.

 

[Big Sur]

IMO a big issue that is lost in the discussion is that light intensity falls off with distance from the light source. The sun is so far away that the intensity is virtually the same anywhere that sunlight hits a plant. Growing outdoors it is a non-issue. But move a watt meter around a plant under any kind of fixed bulb or LED, and the farthest leaves are getting far less energy than the leaves nearest the source. So it seems that the better way to light is to use correct color temperature floro tubes or LEDs standing on edge running the length of the plants. Point source lights like CFLs and MH/HPS, or even incandescent light bulbs all have the problem of light intensity fall-off. Unless you use a gang of low intensity CFLs all around the plant, as was mentioned as an option above (and then dealing with the wiring nightmare).

 

[fanleaf]

Well, lighting efficiency is a moving target. The numbers have changed greatly over time (see the graph below). The issue of lighting is also muddied when it comes to watts, lumens, bulb type and fall-off, scotopic/photopic ratios of bulb types, bulb decline/depreciation/life, fixtures, wiring, ballast, initial cost, cost to run, heat management, reflectivity, intensity drop with distance, efficacy, spectrum/light temperature, wiring, timers, etc. etc.

Actually, that's exactly what the article I was reading was speaking about.