Plant lighting with white LEDs - test work
This article is written under the impression of another article on GT, which is indicated by a similar title. The fact is that I have been interested in this topic for about twelve years and therefore the article iva2000 caused a rather lively response in my mind. The results and conclusions almost convinced me, but there were some moments with which I disagree. I decided to recount everything, and since the result was rather voluminous, I decided to write it as a separate article, not a comment.
After reading the title and introduction, I was critical. Still would! I made the calculations myself, a lot of people produce and use special fitolamps (not only LED lights - look at fluorescent lights in any flower shop!), But here someone says, they say, all this is bullshit, white LEDs are not worse. But having familiarized myself to the end, I changed my opinion and understood that there is a substantial part of truth in this opinion, but we must understand ... Anyone who has not read this article is kindly requested to read for a better understanding, since to reduce the volume and eliminate duplication of information, I will only refer to the data of this article, but not repeat them. The rest - let's continue!
So, at first, what seemed to me controversial .
1. In this article, the McCree light photosynthetic activity curve is given, which means an increase in biomass by a plant when it is illuminated with a narrow band light, but for some reason its value is dismissed altogether under the pretext that “in a wide band the difference will be insignificant). In the section “Results of the analysis of the spectra of white light-emitting diodes” under paragraph 3, the formula for calculating the energy value of light using TWO interesting parameters is given at all: ɳ - light output in lm / W and Ra - color rendering index.
')
Both of these quantities are rigidly tied to another curve, which is called “photopic”. This is the curve of the sensitivity of the human eye to light. Not to be unfounded, look at the picture:
They hardly resemble each other, right? Let me explain that lumens are measured by a sensor that has a sensitivity that strictly corresponds to the reduced photopic curve. And photosynthesis is carried out in accordance with the McCree curve (it is the goafic mapping of the intensity of photosynthesis depending on the wavelength). And, as you have already noticed, there are two curves in the figure. One of them is normalized to the number of photons, and the second to the power of the radiator, which is not even mentioned in the article under discussion. Dear author cites the curve normalized by the number of photons, but does not indicate this and does not use it in the future, but uses the sensitivity curve of the human eye. But, excuse me, where is photosynthesis here? Either do not use any curve and assume all photons are equivalent or use the one that corresponds to the process under study! The color rendition index is generally a kind of virtual indicator that says how precisely colors (photos, fabrics, etc.) will be transmitted when they are illuminated with a given light source. Those. also has nothing to do with photosynthesis. Those. The above formula is too rough an approximation to assess the real quality of sources with a complex emission spectrum!
Further more! I checked the calculated PAR values ​​in μmol / j, which the author cites in the table using the same formula given by him and it turned out in general that:
The numbers are not the same and differ many times from those given. Really the author did not check the data for the article? It did not suit me at all, and I did the calculation as expected - without strange formulas with it is not clear where the coefficients and parameters taken from, which belong to a different field of application.
To begin with, we digitize pictures of various graphs and drive them into a spreadsheet processor. Oops!
Then do so. First, we calculate the coefficient of photosynthetic activity for each source. To do this, for the selected source, we multiply the radiation power at each wavelength by the number from the McCree graph, for the same wavelength. Then we calculate the integral (sum) of the power for the original graph and the result of multiplication. We divide the second by the first - we get a coefficient meaning the effective fraction of radiation for a given source (the one that will take part in photosynthesis):
Here, it is already possible to draw preliminary conclusions!
1. The HPS is great for lighting plants! The efficiency of its spectrum reaches 79% and this is for the lamp, which was originally designed, in general, not for this, but for lighting highways and industrial facilities.
2. Phytolamps, in spite of the “special” spectrum, do not exceed the usual white LEDs with a color temperature of 4000K and not much better than the “cold-white” 6000K.
3. LEDs for red (normal) and far red in general out of competition.
4. It turns out that if you want to squeeze everything out of each watt of illumination, you need to take the usual red LEDs (far red emitters — almost 2 times more expensive), and if you want to save money on equipment, you need to take white LEDs.
But, as I have already said, these conclusions are preliminary and are based only on an assessment of the effectiveness of the spectrum of sources, without taking into account their efficiency and some other points. Therefore, we understand further.
What will happen if we take into account the efficiency of the sources? The efficiency data is taken partly from the iva2000 article, but I did not find exact data on the red LEDs, but in my old records according to the literature there were numbers less than for the blue LEDs, since Recently, the entire development of the technology was directed specifically to the blue LEDs, while others remained at the tail of progress.
By and large, their numbers are taken at random, but in this case they do not play a major role, so enough about that. And if someone reports more reliable data, I will only be grateful.
This is where the alignment of forces is already changing!
It turns out that LEDs with CCT 4000K are better than even DNAT! Moreover, if the advantage for a 1000-watt lamp is not significant, then for low-power sodium lamps (100W) the advantage already reaches 2.4 times! And the phytolamp is a waste of money - it is 25% less than ordinary white LEDs! So much for the phytolamp!
And in order to do everything very precisely, we count on photons by the formula:
Where h is Planck's constant, c is the speed of light.
But we don’t need the number of photons, so in order to translate everything into moths, we divide everything by the Avogadro number and multiply by a million for representation in micromoles.
Now you can make final conclusions:
1. DNaT has comparable efficiency only when using high power lamps (600-1000W). If you are the owner of a large greenhouse, then in terms of the performance characteristics of a lamp per kilowatt - your choice! The cost of installing lighting and replacing lamps will be significantly lower, and the cost of electricity is about the same as the LEDs. A small amount of blue rays in the spectrum of lamps is compensated by their high number in natural light, especially in winter (the color temperature of the sky reaches 15000K!) - this is exactly the situation with greenhouses, when the light turns on in the morning and evening, and during the day natural lighting is used.
2. The most effective LEDs with a color temperature of 4000K. A 100 watt LED lamp gives 43% more phytoactive radiation than a DNaT lamp of the same power! The price, oddly enough, is also on the side of the LEDs - at the time of this writing, the price of the DNAZ lamp is slightly more than 1000r., While the LEDs with the same power at aliexpress go for 360r. (performed by COB - many chips on one substrate)! This is not counting the ballast in both cases. If you grow greens on the windowsill or in the growing box, the white LEDs are out of competition. It is enough to buy good LEDs and their strapping once and you are provided with excellent economical lighting for years.
3. Phytolamps. I initially had a different opinion, but based on the data on the practical use of white LEDs from the iva2000 article, now confirmed by my own research, we have to state that they do not have any advantage in energy efficiency or in the quality of grown plants, but everything is exactly the opposite! The violinist is not needed!
* A small explanation of the combinations of white LEDs with red ones that appeared in the tables. I have considered for interest the variant of illumination, when in addition to white LEDs the usual red or special ones are installed with the far red glow spectrum (in the 3: 1 ratio by power). It is necessary to stimulate flowering. If you plant flowers or strawberries or other plants whose flowering or fruit formation is the main goal, this may be justified. If you grow lettuce and parsley, then it is hardly worth bothering - red LEDs are more expensive than white ones by 2.5 times, and special “phyto” with far red - 4 times! If the goal - to increase the green mass for the minimum money, it is better to take another one or even two white LEDs - it will be better and cheaper! Just do not drive the poor diodes into the coffin - knowing the Chinese comrades love to overestimate the parameters, you need to make sure that when working the base of the LEDs warm up as little as possible - take care of an efficient heat sink and limit the operating current. It is better to buy 20% more diodes and put 20% less current on them and thus significantly increase their lifetime, than pile on to full capacity and get 50% of the initial luminous flux and half of the non-working buildings in a year!
In general, it should be noted that the revolution in small plant farming has come about and this is good news! Several powerful LEDs are coming to me now, and if everything goes with free time, then in the continuation there will be a practical result in addition to this purely theoretical part.
PS: Friends! Thank you very much for the positive assessment of my small, but I really hope useful for all the work! It is interesting for me to talk on this topic and answer all the questions on it, within the scope of my knowledge. So do not hesitate - go into the discussion. Especially welcome additions and links to other information that could fill in possible gaps in this material!
After reading the title and introduction, I was critical. Still would! I made the calculations myself, a lot of people produce and use special fitolamps (not only LED lights - look at fluorescent lights in any flower shop!), But here someone says, they say, all this is bullshit, white LEDs are not worse. But having familiarized myself to the end, I changed my opinion and understood that there is a substantial part of truth in this opinion, but we must understand ... Anyone who has not read this article is kindly requested to read for a better understanding, since to reduce the volume and eliminate duplication of information, I will only refer to the data of this article, but not repeat them. The rest - let's continue!
So, at first, what seemed to me controversial .
1. In this article, the McCree light photosynthetic activity curve is given, which means an increase in biomass by a plant when it is illuminated with a narrow band light, but for some reason its value is dismissed altogether under the pretext that “in a wide band the difference will be insignificant). In the section “Results of the analysis of the spectra of white light-emitting diodes” under paragraph 3, the formula for calculating the energy value of light using TWO interesting parameters is given at all: ɳ - light output in lm / W and Ra - color rendering index.
')
Both of these quantities are rigidly tied to another curve, which is called “photopic”. This is the curve of the sensitivity of the human eye to light. Not to be unfounded, look at the picture:
They hardly resemble each other, right? Let me explain that lumens are measured by a sensor that has a sensitivity that strictly corresponds to the reduced photopic curve. And photosynthesis is carried out in accordance with the McCree curve (it is the goafic mapping of the intensity of photosynthesis depending on the wavelength). And, as you have already noticed, there are two curves in the figure. One of them is normalized to the number of photons, and the second to the power of the radiator, which is not even mentioned in the article under discussion. Dear author cites the curve normalized by the number of photons, but does not indicate this and does not use it in the future, but uses the sensitivity curve of the human eye. But, excuse me, where is photosynthesis here? Either do not use any curve and assume all photons are equivalent or use the one that corresponds to the process under study! The color rendition index is generally a kind of virtual indicator that says how precisely colors (photos, fabrics, etc.) will be transmitted when they are illuminated with a given light source. Those. also has nothing to do with photosynthesis. Those. The above formula is too rough an approximation to assess the real quality of sources with a complex emission spectrum!
Further more! I checked the calculated PAR values ​​in μmol / j, which the author cites in the table using the same formula given by him and it turned out in general that:
The numbers are not the same and differ many times from those given. Really the author did not check the data for the article? It did not suit me at all, and I did the calculation as expected - without strange formulas with it is not clear where the coefficients and parameters taken from, which belong to a different field of application.
To begin with, we digitize pictures of various graphs and drive them into a spreadsheet processor. Oops!
Then do so. First, we calculate the coefficient of photosynthetic activity for each source. To do this, for the selected source, we multiply the radiation power at each wavelength by the number from the McCree graph, for the same wavelength. Then we calculate the integral (sum) of the power for the original graph and the result of multiplication. We divide the second by the first - we get a coefficient meaning the effective fraction of radiation for a given source (the one that will take part in photosynthesis):
Here, it is already possible to draw preliminary conclusions!
1. The HPS is great for lighting plants! The efficiency of its spectrum reaches 79% and this is for the lamp, which was originally designed, in general, not for this, but for lighting highways and industrial facilities.
2. Phytolamps, in spite of the “special” spectrum, do not exceed the usual white LEDs with a color temperature of 4000K and not much better than the “cold-white” 6000K.
3. LEDs for red (normal) and far red in general out of competition.
4. It turns out that if you want to squeeze everything out of each watt of illumination, you need to take the usual red LEDs (far red emitters — almost 2 times more expensive), and if you want to save money on equipment, you need to take white LEDs.
But, as I have already said, these conclusions are preliminary and are based only on an assessment of the effectiveness of the spectrum of sources, without taking into account their efficiency and some other points. Therefore, we understand further.
What will happen if we take into account the efficiency of the sources? The efficiency data is taken partly from the iva2000 article, but I did not find exact data on the red LEDs, but in my old records according to the literature there were numbers less than for the blue LEDs, since Recently, the entire development of the technology was directed specifically to the blue LEDs, while others remained at the tail of progress.
By and large, their numbers are taken at random, but in this case they do not play a major role, so enough about that. And if someone reports more reliable data, I will only be grateful.
This is where the alignment of forces is already changing!
It turns out that LEDs with CCT 4000K are better than even DNAT! Moreover, if the advantage for a 1000-watt lamp is not significant, then for low-power sodium lamps (100W) the advantage already reaches 2.4 times! And the phytolamp is a waste of money - it is 25% less than ordinary white LEDs! So much for the phytolamp!
And in order to do everything very precisely, we count on photons by the formula:
Where h is Planck's constant, c is the speed of light.
But we don’t need the number of photons, so in order to translate everything into moths, we divide everything by the Avogadro number and multiply by a million for representation in micromoles.
Now you can make final conclusions:
1. DNaT has comparable efficiency only when using high power lamps (600-1000W). If you are the owner of a large greenhouse, then in terms of the performance characteristics of a lamp per kilowatt - your choice! The cost of installing lighting and replacing lamps will be significantly lower, and the cost of electricity is about the same as the LEDs. A small amount of blue rays in the spectrum of lamps is compensated by their high number in natural light, especially in winter (the color temperature of the sky reaches 15000K!) - this is exactly the situation with greenhouses, when the light turns on in the morning and evening, and during the day natural lighting is used.
2. The most effective LEDs with a color temperature of 4000K. A 100 watt LED lamp gives 43% more phytoactive radiation than a DNaT lamp of the same power! The price, oddly enough, is also on the side of the LEDs - at the time of this writing, the price of the DNAZ lamp is slightly more than 1000r., While the LEDs with the same power at aliexpress go for 360r. (performed by COB - many chips on one substrate)! This is not counting the ballast in both cases. If you grow greens on the windowsill or in the growing box, the white LEDs are out of competition. It is enough to buy good LEDs and their strapping once and you are provided with excellent economical lighting for years.
3. Phytolamps. I initially had a different opinion, but based on the data on the practical use of white LEDs from the iva2000 article, now confirmed by my own research, we have to state that they do not have any advantage in energy efficiency or in the quality of grown plants, but everything is exactly the opposite! The violinist is not needed!
* A small explanation of the combinations of white LEDs with red ones that appeared in the tables. I have considered for interest the variant of illumination, when in addition to white LEDs the usual red or special ones are installed with the far red glow spectrum (in the 3: 1 ratio by power). It is necessary to stimulate flowering. If you plant flowers or strawberries or other plants whose flowering or fruit formation is the main goal, this may be justified. If you grow lettuce and parsley, then it is hardly worth bothering - red LEDs are more expensive than white ones by 2.5 times, and special “phyto” with far red - 4 times! If the goal - to increase the green mass for the minimum money, it is better to take another one or even two white LEDs - it will be better and cheaper! Just do not drive the poor diodes into the coffin - knowing the Chinese comrades love to overestimate the parameters, you need to make sure that when working the base of the LEDs warm up as little as possible - take care of an efficient heat sink and limit the operating current. It is better to buy 20% more diodes and put 20% less current on them and thus significantly increase their lifetime, than pile on to full capacity and get 50% of the initial luminous flux and half of the non-working buildings in a year!
In general, it should be noted that the revolution in small plant farming has come about and this is good news! Several powerful LEDs are coming to me now, and if everything goes with free time, then in the continuation there will be a practical result in addition to this purely theoretical part.
PS: Friends! Thank you very much for the positive assessment of my small, but I really hope useful for all the work! It is interesting for me to talk on this topic and answer all the questions on it, within the scope of my knowledge. So do not hesitate - go into the discussion. Especially welcome additions and links to other information that could fill in possible gaps in this material!
Source: https://habr.com/ru/post/374173/
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