Plant lighting with white LEDs - test work
This article was inspired by another GT article, as the similar name suggests. The fact is that I have been interested in this topic for about twelve years, and therefore the iva2000 article caused a rather lively response in my mind. The results and conclusions almost convinced me, but there were moments with which I do not agree. I decided to recount everything and since the result was quite voluminous, I decided to write it as a separate article, not a comment.
After reading the headline and the introduction, I was critical. Still would! I made the calculations myself, a lot of people produce and use special phytolamps (not only LED ones - look at the fluorescent lamps in any flower shop!), But here someone says that they are all bullshit, white LEDs are no worse. But having read it to the end, I changed my mind and realized that there is a significant share of truth in this opinion, but I need to understand ... Everyone who has not read this article is kindly requested to get acquainted for a better understanding, because To reduce the volume and avoid duplication of information, I will only refer to the data of the specified article, but not repeat them. The rest - let's continue!
So, first, what seemed controversial to me .
1. In this article, a McCree photosynthetic light activity curve is given, which means biomass is increased by a plant when it is illuminated with narrow band light, but for some reason its value is completely eliminated under the pretext that “the difference in a wide band will be insignificant). In the section “Results of the analysis of spectra of serial white LEDs” under point 3, the formula for calculating the energy value of light using TWO interesting parameters is given: ɳ is the light output in lm / W and Ra is the color rendering index.
Both of these quantities are rigidly linked to another curve, which is called “photopic”. This is the curve of the sensitivity of the human eye to light. In order not to be unfounded, look at the picture:
They hardly look alike, right? Let me explain that lumens are measured by a sensor having a sensitivity that strictly corresponds to the photopic curve. And photosynthesis is carried out in accordance with the McCree curve (it is the goafic representation of photosynthesis intensity depending on the wavelength). And, as you already noticed, there are two curves in the figure. One of them is normalized to the number of photons, and the second to the emitter power, which is not even mentioned in the article under discussion. Dear author, the curve is 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 then? Either do not use any curve and consider all photons to be equivalent or use the one that corresponds to the process under study! The color rendering index, on the other hand, is generally a virtual indicator that says how accurately the colors will be transmitted (photographs, fabrics, etc.) when illuminated by this 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 spectrum of radiation!
Further more! I checked the calculated values of PAR in micromol / j, which the author gives in the table using the formula given by him, and it turned out in general that:
The numbers are not at all the same and differ many times from the above. Has the author really not checked his own data for the article? This did not suit me in any way and I did the calculation as expected - without strange formulas with factors and parameters related to another field of application that are not taken from anywhere.
First, we digitize pictures of various graphs and drive them into a table processor. Oops!
Then we 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 power for the original graph and the result of multiplication. We divide the second into the first - we get a coefficient that means the effective fraction of radiation for a given source (the one that will take part in photosynthesis):
Now, we can already draw preliminary conclusions!
1. DNAT - this is super 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.Despite the “special” spectrum, phytolamps do not surpass ordinary white LEDs with a color temperature of 4000K and not much better than “cold white” 6000K.
3. The LEDs of red (normal) and far red are generally out of competition.
4. It turns out that if you want to squeeze everything out of every watt of lighting, you need to take ordinary red LEDs (far red emitters are almost 2 times more expensive), and if you want to save in the price of equipment, you need to take white LEDs.
But, as I have already said, these conclusions are preliminary and are based only on assessing 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 sources? The efficiency data was partially taken from the iva2000 article, but I didn’t find exact data on the red LEDs, but in my old records according to the literature there were fewer numbers than for the blue LEDs, because Recently, the entire development of the technology was aimed specifically at blue LEDs, while others remained in 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 that's 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 even better than DNA! Moreover, if the advantage is not significant for a 1000 Watt lamp, then for low-power sodium lamps (100 W), the advantage already reaches 2.4 times! And the phytolamp is a waste of money - it is 25% behind ordinary white LEDs! So much for the phytolamp!
And in order to do everything very accurately, we count on photons by the formula:
Where h is the Planck constant, c is the speed of light.
But we do not need the number of photons, so to translate everything into moths, divide everything by the Avogadro number and multiply by a million to represent it in micromoles.
Now we can draw the final conclusions:
1.DNaT has comparable efficiency only when using high power lamps (600-1000W). If you are the owner of a large greenhouse economy, then in terms of the aggregate operational characteristics of the lamp per kilowatt - your choice! The cost of installing lighting and replacing the lamps will be significantly lower, and the cost of electricity is approximately the same as LEDs. The small amount of blue rays in the spectrum of lamps is compensated, on the contrary, by their high number in natural light, especially in winter (the color temperature of the sky reaches 15000K!) - this is just the situation with greenhouses when the backlight turns on in the morning and evening, and in the afternoon natural light is used.
2.The most effective LEDs with a color temperature of 4000K. A 100 Watt LED lamp provides 43% more phytoactive radiation than a DNaT lamp of the same power! The price, oddly enough, is also on the side of the LEDs - the price of a DNaZ lamp at the time of writing is a little more than 1000 rubles, while LEDs with the same power on aliexpress go for 360 rubles. (in the performance of COB - many chips on one substrate)! This is not counting the ballast in both cases. If you grow greens on a windowsill or in a grow box, then white LEDs are beyond any competition. It is enough to buy good LEDs and their wiring 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, I have to admit that they do not give any advantages 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 and red LEDs appearing in the tables. For interest, I considered the option of lighting, in addition to the white LEDs, additional usual red or special ones with a far red glow spectrum (in the ratio 3: 1 in power) are additionally installed. This is necessary to stimulate flowering. If you plant flowers or strawberries or other plants for which flowering or fruit formation is the main goal, this may be justified. If you grow lettuce and parsley, then it’s hardly worth bothering - red LEDs are 2.5 times more expensive than white, and special “phyto” with far red - 4 times! If the goal is to build up green mass for minimal money, it is better to take one or even two white LEDs - it will be better and cheaper! Just do not drive poor diodes into the coffin - knowing the love of Chinese comrades for overstating, you need to make sure that the base of the LEDs is heated as little as possible during operation, take care of efficient heat dissipation and limit the operating current. It is better to buy 20% more diodes and put a 20% lower current on them and thus increase their life time by several times than toss them to the fullest and get 50% of the initial light flux and half of the non-working cases in a year!
On the whole, it should be noted that the revolution in small crop production has taken place and this cannot but rejoice! Several powerful LEDs are coming to me now, and if everything turns out with free time, then there will be a practical result in addition to this purely theoretical part.
PS: Friends! Thank you very much for the positive evaluation of my small one, but I really hope the work is useful for everyone! I am interested in talking about this topic and answering all the questions on it within the scope of my knowledge. So do not be shy - go to the discussion. Especially welcome additions and links to other information that could fill in the possible gaps in this material!
After reading the headline and the introduction, I was critical. Still would! I made the calculations myself, a lot of people produce and use special phytolamps (not only LED ones - look at the fluorescent lamps in any flower shop!), But here someone says that they are all bullshit, white LEDs are no worse. But having read it to the end, I changed my mind and realized that there is a significant share of truth in this opinion, but I need to understand ... Everyone who has not read this article is kindly requested to get acquainted for a better understanding, because To reduce the volume and avoid duplication of information, I will only refer to the data of the specified article, but not repeat them. The rest - let's continue!
So, first, what seemed controversial to me .
1. In this article, a McCree photosynthetic light activity curve is given, which means biomass is increased by a plant when it is illuminated with narrow band light, but for some reason its value is completely eliminated under the pretext that “the difference in a wide band will be insignificant). In the section “Results of the analysis of spectra of serial white LEDs” under point 3, the formula for calculating the energy value of light using TWO interesting parameters is given: ɳ is the light output in lm / W and Ra is the color rendering index.
Both of these quantities are rigidly linked to another curve, which is called “photopic”. This is the curve of the sensitivity of the human eye to light. In order not to be unfounded, look at the picture:
They hardly look alike, right? Let me explain that lumens are measured by a sensor having a sensitivity that strictly corresponds to the photopic curve. And photosynthesis is carried out in accordance with the McCree curve (it is the goafic representation of photosynthesis intensity depending on the wavelength). And, as you already noticed, there are two curves in the figure. One of them is normalized to the number of photons, and the second to the emitter power, which is not even mentioned in the article under discussion. Dear author, the curve is 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 then? Either do not use any curve and consider all photons to be equivalent or use the one that corresponds to the process under study! The color rendering index, on the other hand, is generally a virtual indicator that says how accurately the colors will be transmitted (photographs, fabrics, etc.) when illuminated by this 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 spectrum of radiation!
Further more! I checked the calculated values of PAR in micromol / j, which the author gives in the table using the formula given by him, and it turned out in general that:
The numbers are not at all the same and differ many times from the above. Has the author really not checked his own data for the article? This did not suit me in any way and I did the calculation as expected - without strange formulas with factors and parameters related to another field of application that are not taken from anywhere.
First, we digitize pictures of various graphs and drive them into a table processor. Oops!
Then we 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 power for the original graph and the result of multiplication. We divide the second into the first - we get a coefficient that means the effective fraction of radiation for a given source (the one that will take part in photosynthesis):
Now, we can already draw preliminary conclusions!
1. DNAT - this is super 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.Despite the “special” spectrum, phytolamps do not surpass ordinary white LEDs with a color temperature of 4000K and not much better than “cold white” 6000K.
3. The LEDs of red (normal) and far red are generally out of competition.
4. It turns out that if you want to squeeze everything out of every watt of lighting, you need to take ordinary red LEDs (far red emitters are almost 2 times more expensive), and if you want to save in the price of equipment, you need to take white LEDs.
But, as I have already said, these conclusions are preliminary and are based only on assessing 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 sources? The efficiency data was partially taken from the iva2000 article, but I didn’t find exact data on the red LEDs, but in my old records according to the literature there were fewer numbers than for the blue LEDs, because Recently, the entire development of the technology was aimed specifically at blue LEDs, while others remained in 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 that's 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 even better than DNA! Moreover, if the advantage is not significant for a 1000 Watt lamp, then for low-power sodium lamps (100 W), the advantage already reaches 2.4 times! And the phytolamp is a waste of money - it is 25% behind ordinary white LEDs! So much for the phytolamp!
And in order to do everything very accurately, we count on photons by the formula:
Where h is the Planck constant, c is the speed of light.
But we do not need the number of photons, so to translate everything into moths, divide everything by the Avogadro number and multiply by a million to represent it in micromoles.
Now we can draw the final conclusions:
1.DNaT has comparable efficiency only when using high power lamps (600-1000W). If you are the owner of a large greenhouse economy, then in terms of the aggregate operational characteristics of the lamp per kilowatt - your choice! The cost of installing lighting and replacing the lamps will be significantly lower, and the cost of electricity is approximately the same as LEDs. The small amount of blue rays in the spectrum of lamps is compensated, on the contrary, by their high number in natural light, especially in winter (the color temperature of the sky reaches 15000K!) - this is just the situation with greenhouses when the backlight turns on in the morning and evening, and in the afternoon natural light is used.
2.The most effective LEDs with a color temperature of 4000K. A 100 Watt LED lamp provides 43% more phytoactive radiation than a DNaT lamp of the same power! The price, oddly enough, is also on the side of the LEDs - the price of a DNaZ lamp at the time of writing is a little more than 1000 rubles, while LEDs with the same power on aliexpress go for 360 rubles. (in the performance of COB - many chips on one substrate)! This is not counting the ballast in both cases. If you grow greens on a windowsill or in a grow box, then white LEDs are beyond any competition. It is enough to buy good LEDs and their wiring 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, I have to admit that they do not give any advantages 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 and red LEDs appearing in the tables. For interest, I considered the option of lighting, in addition to the white LEDs, additional usual red or special ones with a far red glow spectrum (in the ratio 3: 1 in power) are additionally installed. This is necessary to stimulate flowering. If you plant flowers or strawberries or other plants for which flowering or fruit formation is the main goal, this may be justified. If you grow lettuce and parsley, then it’s hardly worth bothering - red LEDs are 2.5 times more expensive than white, and special “phyto” with far red - 4 times! If the goal is to build up green mass for minimal money, it is better to take one or even two white LEDs - it will be better and cheaper! Just do not drive poor diodes into the coffin - knowing the love of Chinese comrades for overstating, you need to make sure that the base of the LEDs is heated as little as possible during operation, take care of efficient heat dissipation and limit the operating current. It is better to buy 20% more diodes and put a 20% lower current on them and thus increase their life time by several times than toss them to the fullest and get 50% of the initial light flux and half of the non-working cases in a year!
On the whole, it should be noted that the revolution in small crop production has taken place and this cannot but rejoice! Several powerful LEDs are coming to me now, and if everything turns out with free time, then there will be a practical result in addition to this purely theoretical part.
PS: Friends! Thank you very much for the positive evaluation of my small one, but I really hope the work is useful for everyone! I am interested in talking about this topic and answering all the questions on it within the scope of my knowledge. So do not be shy - go to the discussion. Especially welcome additions and links to other information that could fill in the possible gaps in this material!