micromoles versus lumens / lux

[whazzup]

As promised a bit more information about light, and specifically how to measure it. As you might know The Netherlands is really big in greenhouse industry. After Mexico we are the largest producers of tomatoes in the world, and we all do it in greenhouses. Our flower auction (Flora holland) is the largest in the world with over 60% of all flowers world-wide auctioned there. It is the third largest building in the world by floorspace, 7 times bigger than the pentagon. The Westland is the largest greenhouse area in the world, with over 6,500 acres of greenhouses.

 

This is what a big customer looks like, 12,000 1 kW electronic luminaries over tomatoes on this site:

 

So measuring light is turned into an art actually, as every photon counts. The renown Wageningen University is very active in the field of light research.

 

The standard measurements of light output have traditionally been done through the foot-candle, lumens and lux. They quantify how humans experience the intensity of light, based on the limited sensitivity of the human eye in the yellow/green area of the spectrum (around 550 nm). Plants however use a much wider spectrum for photosynthesis, called the PAR spectrum (Photo-synthetically Active Radiation), ranging from 400-700 nm

 

Human eye sensitivity versus plant sensitivity

 

Photosynthesis is not driven by brightness of the light according to the human eye or the energy of a photon (which varies for different colors) but purely by the number of photons in the PAR spectrum. You need about eight photons to bind one CO2 molecule. So to quantify potential photosynthesis it is all about the number of photons within the PAR spectrum hitting the plant. This is expressed as Photosynthetic Photon Flux (PPF – total photons emitted from a light source per second) and Photosynthetic Photon Flux Density (PPFD – the number of photons hitting one square meter of surface per second) and it is measured in moles or micromoles (µmol) of photons.

 

You can measure the number of photons hitting your plant (PPFD) using a quantum meter, predicting the potential photosynthetic capacity of your light.

 

You can measure the total number of photons emitted by a lamp (PPF)by putting it in an Ulbricht integrating sphere

 

So where we used to have luminous flux in lumens, we now have PPF in µmol/s, and where we used to have illuminance (light incident on a surface) in lux, we now have PPFD in µmol/m²/s

 

Lamps with high lumens output are not necessary high par output lamps: some lamps with lower lumens output have higher micromole output.

 

Another important issue is of course the spectrum of a lamp. Micromoles alone is not enough - or blue and red LEDs would have worked

 

Here is an example of a lamp measurement. We measured 2 1000 watt lamps in one of our new dimmable ballasts (that's why you see the different ballast settings). Now you see the top lamp has great lumens output, a lot more than the bottom one but... in PPF it lacks...

 

These are calibrated Ulbricht sphere measurements.

 

So, will it turn your world upside down? Maybe, maybe not. It might influence which lamp you will buy next time. But then you also need to consider spectrum, light maintenance and if the lamp is suitable for an electronic ballast. Ask your supplier for PPF and the light maintenance curve. Any serious horticultural lighting manufacturer has them on their website. Those who only talk about lumens have probably missed the horticultural lighting developments over the last 10 years.

 

So now you have seen the light! (it comes from holland )

[Samurai]

hey whazzup

cheers man good read and great info there..

whoooaa thats a greenhouse ..massive ...

must be alot of work for the locals ..no wonder you are all green thumbs..

thanks for sharing ...hope you enjoy your new year..HM

[Chato]

Thanks for taking the time to post Whazzup it's much appreciated. And clever thread title

 

I'll have to read it again to digest it properly but i get the gist of it and your explanation was easy to read

 

On a slightly diff topic but still concerning light and output...

 

What are your thoughts on vertical lighting? What are the experts opinions'?

 

I can probably slightly anticipate your reply, not very efficient, but i'd still like to hear what you have to say.

 

Cheers mate.

 

peace

c

[whazzup]

For high crops such as tomatoes, which are grown in long high rows, there is always a problem with deep light penetration. But here we deal with crops that are a few meters high. For those crops Interlighting is developed, basically light that hangs between the rows and provide horizontal lighting. Philips experiments with LED technology (LINK), others use for example HPS vertical lights. Example:

 

The problem with free hanging lamps is temperature. Without a reflector the lamps will not come to their optimal operating temperature. In a verical situation the top of the lamp will also be warmer than the bottom part. The optimal position for a HID lamp to burn and the best way to reflect the light is by using it horizontal. This way you have direct light as well as reflected light which can overlap to create a uniform light from all directions.

 

Now cannabis can be very high too, but the easiest solution for that is to have less plants per meter. Here is an example of the medicinal cannabis producer in The Netherlands, Bedrocan. They grow Jack Herer in 3,5 liter pots, 2,5 meters high, yielding 150 grams per plant, but the only have about 2-3 plants per square meter and have the lights high at the ceiling to make sure that the penetration from all angles is optimal. The topic is in Dutch but google toolbar translator is your friend and the pictures speak for themselves, here is my report: http://www.wietforum.nl/index.php?showtopic=45960

 

Enjoy the read, hope this answers your question.

[The Hash Nibbler]

Awesome read Whazzup , Wow , things change over the years. I still test the heat of the globe with the back of my hand........... ........... Caveman! he-he. Very interesting information . If I could ask a quick question...........Are there any signifigant advances in LED technology to allow them to flower plants on Par with the yields from HID lights without breaking the bank or are we still a long way off?

I find a lot of Newcomers being dazzled by the lure of cheap running costs and low heat but they just don't seem to cut it, Flowering wise, yet, unless you flower a lot longer and use plenty of them and even then...............

What is the problems being encountered with spectrum? Thanks, I have a morbid curiousity with them. . Gh72

[whazzup]

Well I can truly say that there is a lot of research going on with LED and alternative light sources and there is progress, but the manufacturers pretend to have more and are far more positive about it than what we see in results from the field trials. The only crop that currently is being grown commercially under LED is lettuce in small crops. And that's a very simple plant to grow, it's just leafs and water, vegetative. For propagation and vegetative growth the results are getting better, but the flowering process is much more complicated. General opinion is that sunlight is the best light for plants.

 

Personally I am convinced that some day we will probably use alternative light sources such as LED or plasma, but even with plasma there are problemt so overcome, for example the absence of heat radiation. lamps under the same PPFD plasma light use about 30% less water than their equivalents under HPS or MH, so you need to adjust your ec as well and, in the Dutch situation, add or recycle heat!

 

In tests by Wageningen University young cucumber plants grown under plasma light had 64% more dry weight than HPS lit plants with the same intensity (100 micromoles), and more than 120% more dry weight than fluorescent light grown plants. This is not due to the photosynthesis (that was the same in all three tests, proving btw that the micromole theory stands) but the effects of light quality on morphology. The plasma "sunlight" lit plant stretched more, had longer stems and bigger stretched leaf, basically enlarging the surface so photosynthesis is optimal. It just set itself much better to the light, which creates a ++ situation: better reception of light is faster growth is more reception of light and more photosynthesis, so a plus on a plus.. This can only be a result of the better light quality. You can see that in every plasma grown crop, the very even distribution of leafs (and flowers!!). Here is an example with a cannabis plant in scrog under a combination of plasma and HPS light:

 

 

Here is an example of a same plant under grown under HPS and under plasma (also a clone from same mother, both Anesthesia herijuana pheno breeders cuttings, one week less vegetative growth as the previous example). What you see here is one plant (yes, these are all single plants) under just plasma (very green, thinner stems, buds-on-sticks, a very even canopy, less leafs and also very deep penetration into the crop, leafs better directed to intercept the light) and HPS (much more uneven, thicker stems, ripens earlier, shorter internode distance, much more leafs, more popcorn in the lower layer of the scrog). We harvested both plants at the same time and though the plasma grow had been much cooler, was not completely ripe yet and produced smaller buds the dry weight was substantially higher, so both tents performed about the same. The potency of the plasma grown was better, which we can explain by the UVB light emitting from the plasma lamp: Trichomes are the only plant parts that actively absorb UVB, supposedly to protect the plant from it. We are currently investigating whether that has influence on the levels of cannabinoids (UVB is supposed to increase THCV levels for example). This would coincide with high THVC levels in crops grown oh high altitudes such as nepal and african hash plant. If you can influence the cannabinoids in the plant that can have major implications for making medicine.

 

A problem is: the plasma lamp does not emit a lot of heat and our cannabis plant loves red light. The plasma lamp is lacking red light and lacking heat. In our tests the combination plasma / HPS performed very well. We are currently continuing those tests with different combinations, having HPS, MH and a combination of MH/HPS as reference grows.

 

Learning every day

Edited December 28, 2010 by whazzup

[The Hash Nibbler]

Thanks a heap Whazzup . Mate, your a wealth of knowledge, and thanks so much for the fast reply and great comparison shots.

. Maybe one day someone could try a Plasma/ Cree led(or another high output LED) grow using the red from the high powered led's. This would be perfect for Australian conditions...........................as long as the Led's had enough punch to get through the canopy in combination with the Plasma. . Alles Komt Goede . Dankuvel Whazzup, always a pleasure. You make me wish I was back over there.

. . Gh72

[whazzup]

don't count on it that I will be that responsive in the future

 

As said, I learn every day. I can tell you it is a good idea to turn your hobby into your profession

[Samurai]

hey whazzup cheers mate that was a great read ..

learnt lots from that ..really envy the way of life over there..

very interesting .....all the best ...HM

[whazzup]

btw you already had a good post on the forum about it: https://cannabis.community.forums.ozstoners.com/index.php/topic/489-fluro-light-fo-veg/page__view__findpost__p__2386

 

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