The difference between LED lamp and high pressure sodium lamp in greenhouse farming

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Update time : 2018-05-09 13:06:27
In the future, the greenhouse producction will play an important role in meeting the demand for food growth.
In recent years, the shortage of greenhouse lighting is more and more get the attention of people, on the one hand is due to greenhouse azimuth, structure, cover material characteristics caused by the greenhouse light transmittance drop, on the other hand is caused by a lack of sunlight greenhouse crops, as a result of climate change, such as a continuous wet weather of winter and early spring season, frequent fog weather, etc.
The lack of light has a direct impact on greenhouse crops, causing serious damage to production.
These problems can be alleviated or resolved effectively by the plant replenishment lamp.
Incandescent lamps, fluorescent lamps, gold halide lamps, high pressure sodium lamps, and new LED lights have all been used or are being used in greenhouse lighting.
In these type of light source, high pressure sodium lamp with high luminous efficiency, long service life, high efficiency, occupy a certain market position, but high pressure sodium lamp lighting sustainability, security (mercury) problems such as low, do not close exposure is also very prominent.
Some scholars have a positive attitude towards the future or overcoming the low performance of high-pressure sodium lamps.
However, the LED price is expensive, the complementary light technology is difficult to support, the complementary light theory is not perfect, and the product specification of LED plant's lighting lamp is confused, which makes the user question the application of the LED in the plant.
Therefore, this paper summarizes previous research results and its application status, and provides reference for light source selection and application in greenhouse.

1. The difference between high pressure sodium lamp and LED lighting.
1.1 luminescence principle and the difference of external structure.
High - pressure sodium lamp is composed of mercury, sodium, xenon arc lamp core, glass shell, air - reducing agent lamp, etc.
Due to the difference of the ballast of the core parts, it is divided into inductive high voltage sodium lamp and electronic high pressure sodium lamp. The high voltage sodium lamp of different power needs to use the corresponding specification ballast.
Leds are also called light-emitting diodes, and the core is a chip composed of p-type semiconductor and n-type semiconductor. There is a transition layer between P and n-type semiconductors, called p-n junction.
When the current flows from the LED anode to the cathode, the semiconductor crystal emits light from the purple to the red, and the intensity of the light is associated with the current.
The luminescence intensity and working current can be divided into ordinary brightness (luminescence intensity < 10mcd), high brightness (10-100mcd) and ultra-high brightness (> 100mcd).
Its structure is divided into four parts: the structure of the distribution system, the structure of the cooling system, the driving circuit and the mechanical/protective structure.
1.2 differences in exposure range and spectral range.
High pressure sodium lamp bulb light Angle is 360 °, most have to pass a reflector to exposure to the designated area after reflection, spectral energy distribution is roughly as red, orange, yellow green, light LanZiGuang (account for only a small part).
According to the different distribution of the LED light is designed, the effective light Angle can be roughly divided into 180 ° or less, 180 ° ~ 300 ° and 300 ° or three categories.
LED light source has the wavelength tunability, can emit the light wave narrower monochromatic light, such as infrared, red, orange, yellow, green, blue, can according to different needs any combination.
1.3 the difference of applicable conditions and life span.
The high pressure sodium lamp is the third-generation lighting source, and the conventional alternating current has a wide range of use, high luminous efficiency and strong penetration ability, with a maximum life span of 24000h, and the lowest can be maintained at 12000h.
When the sodium lamp is illuminated, it will be accompanied by the production of heat, so the sodium lamp is a kind of thermal light source.
In the process of use, there are self-extinguishing problems.
LED as the fourth generation of new type of semiconductor light source, with dc drive, the life can reach up to 50000h, and the attenuation is small. As a cold light source, it can be close to the plant irradiation.
Liao ruihui compared LED and high pressure sodium lamp, pointing out that LED security is high, does not contain harmful elements, more environmental protection.
2. The difference of high pressure sodium lamp and LED patch on crop impact.
Agricultural production in a large number of production practice and scientific research proves that the artificial plant light supplement can increase not only crop yields, shortening the period of cultivation, also can effectively improve the quality of crops, is important guarantee of modern agricultural efficient production methods.
In the process of seedling and greenhouse crop management, the use of high pressure sodium lamp and LED to supplement light can promote the growth and development of crops and change the yield, morphology and physiological indexes of crops.
2.1 yield and quality difference.
The high yield and high quality of crops are the ultimate aim of cultivation.
LED filling can improve the quality of chilli, tomato and eggplant seedlings, and increase the yield of single fruit and single plant in 10h.
The effect of LED completion is also shown on cucumber planting.
Leds can improve the quality of the grapes, the blue light processing fruit grows rapidly, the fruit quality of single grain is higher, the highest sugar content, ultraviolet light when handling the fruit maturity the largest single grain quality.
Similarly, the 70W high pressure sodium lamp significantly increased the yield of the single plant of strawberries, with a yield increase of 17.9%.
High - pressure sodium lamp and LED fill light have a significant effect on plant morphology.
The quality of cucumber visual fruit was also improved by using the LED side.
On the basis of sodium lamp add LED, compare only sodium lamp treatment, the color of cucumber is more bright.
2.2 morphological index differences.
Plant morphological index is an important index in plant growth, especially in seedling production, which determines whether the plant can grow healthily after transplanting.
Under normal circumstances, the seedlings of conifers under LED growth have a better growth potential compared with high pressure sodium lamps.
Cycle 12 h, light density 50 mu mol/s. (m2), the LED red light (630 ~ 660 nm), orange (590 ~ 610 nm), blue (450 ~ 460 nm), green (520 ~ 540 nm), respectively, than the natural light [120 mu mol/(m2 · s)] were significantly improved the field of the strong seedling index of tomato seedlings.
Gong Ting after using self-made leds light up, also found that pepper, tomato and eggplant seedlings of plant height, stem diameter, leaf area increase obviously, and between strains of LED lighting to make tomatoes mass per unit area of the upper, middle and lower leaves were significantly increased.
Greenhouse tomato varieties' Maxifort early use 61 + 2 mu mol/(m2 · s) high pressure sodium lamp, natural light, 3 kinds of different proportion of red and blue light up, found that 95% red + 5% blue leds tomato leaf area and leaf number higher than under high pressure sodium lamp.
The effect of LED lamp patch on the growth of seedling height, stalk and leaf area of watermelon is better than that of high pressure sodium lamp.
These results show that the growth of the plant leaves is higher than that of the high pressure sodium lamp.
However, LED by rose stem elongation and low leaf area, dry weight between several processing plants and fresh weight had no significant difference, in line with the research treatment and high pressure sodium lamp or LED pepper, tomato, geranium, petunias and goldfish grass seedlings have similar quality of dry matter.
The height, number of leaves, fresh weight and dry weight of the tomato seedlings under the high pressure sodium lamp of 200 mmol /(m2·s) were greater than that of the red and blue LED lamps under the same light density.
And high pressure sodium lamp and LED alternately under the irradiation of tomato plant fresh weight was lower than that of single use high pressure sodium lamp, leaf blade under high pressure sodium lamp transmittance and high reflectivity, this also make the light better into the canopy.
After a series of comparisons, it was found that different test results appeared, which were different from the design of the experimental method, and there was a significant relationship between different LED lighting proportions, temperature and light density.
2.3 physiological differences
The content of chlorophyll directly affects the accumulation of photosynthetic products.
Studies have shown that the gas exchange law and chlorophyll content in conifer seedlings under LED growth are higher than that of high pressure sodium lamps.
The content of chlorophyll content of the root stock was significantly higher than that of natural light in the treatment of high pressure sodium lamp.
LED light supplementation is beneficial to the accumulation of photosynthetic pigments.
Of the eight growth trials conducted by Ptushenko, five of the plants that grew under LED supplemental light had a higher average photosynthetic pigment content (per unit of leaf area) than high pressure sodium lamps.
The chlorophyll a and chlorophyll b content in the red and blue LED lamp combination of 200 mmol /(m2·s) were higher than the high pressure sodium lamps under the same light density.
Carotenoids are chloroplasts auxiliary photosynthetic pigment, its function is to consume system Ⅱ (PS Ⅱ) in excess energy, protect the chlorophyll from light damage.
The Dlugosz study showed that the use of high pressure sodium lamps to fill the light would increase the concentration of carotenoids and nitrates in lettuce.
The soluble sugar, carotenoid and nitrogen content in the leaves of chilli, tomato and eggplant were increased by different degrees, and the transpiration rate was accelerated.
Jason in plant growth and at the same time with high-pressure sodium lamp and LED lighting (RB, RW) observed when testing, fill with high-pressure sodium lamp light tomato and the characteristics of water use efficiency is higher than the LED processing, transpiration rate lower than that of LED, in the net CO2 exchange rate and there is no difference between the final biomass, however, the maximum photosynthetic rate under different processing are the same.
In addition, LED(R:FR=3.09)500 mu /(m2·s) can significantly affect the flowering time and flowering rate of lentils.
LED and the high-voltage sodium lamp light supplement can improve the content of photosynthetic pigment, and the LED on the accumulation of photosynthetic pigment than high pressure sodium lamp, transpiration rate is higher than sodium lamp, LED special spectral ratio also can affect the bloom effect of certain plants.
In addition, it must be noted that, chlorophyll content index, alone can't positive indicator light effect on plant photosynthetic capacity, because when confronted with low light density environments, plants will automatically adapt to weak light stress, more chlorophyll concentration in leaves in order to get more light.
3. Difference of high pressure sodium lamp and LED production cost.
Compared with traditional light source, the advantages of high pressure sodium lamp and LED are obvious.
With high pressure sodium lamps and red and blue LED lights, the crown layer of the plant can be filled with the top filling. The two can achieve the same output, and the LED consumes only 75% of the energy.
Reports have pointed out that to achieve the same conditions of energy efficiency, LED the initial investment cost is high pressure sodium lamp device 5 ~ 10 times that of the early high cost makes using five years LED per mole light quantum costs are high pressure sodium lamp 2 ~ 3 times.
For flowerbed plants, 150W high pressure sodium lamp and 14WLED can achieve the same effect, compared with 14WLED more economical.
In 550 m2 area, single use of high pressure sodium lamp cost is $1.3 per kg cucumber, sodium lamp, plus the cost of single row LED lamp is $1.45, sodium lamp, plus the cost of 2 rows of leds is $1.72, cost profit ratio is 2.31, 2.07, 1.74, respectively.
The use of LED in the shed requires a large amount of erection, and the cost of one-time investment is large. For individual vegetable farmers, the investment is more difficult.
Whether the reduction effect generated by LED power saving can fully compensate for its initial investment and subsequent financial cost in its effective life period requires careful calculation and measurement.
4. Conclusions and prospects.
Green plants absorb most of the red orange light and wavelength of 400~500nm with wavelength of 600~700nm. The green light with wavelength of 500~600nm is only absorbed by micro.
High pressure sodium lamp and the LED can meet the needs of the plant lighting, NASA (NationalAeronauticsandSpaceAdministration) using LED the original research purpose is in order to improve the energy efficiency, reduce the cost of operation and management, improve the quality of the crops.
In addition, LED can be widely used in the production of high-quality medicinal crops, and some scholars have pointed out that LED technology has great potential in improving plant growth.
High pressure sodium lamp price is moderate, can be accepted by the majority of farmers, short-term effect ability is better than LED, its complementary light technology has been relatively mature, still in large-scale use at present.
However, the high-pressure sodium lamp needs to install ballast and related appliances, increasing its use cost.
Compared with high-pressure sodium lamps, leds have narrow spectral tunability, safety and reliability.
Leds are flexible in plant physiological test applications.
However, in the actual production, the cost is higher, the light decline is larger, and the service life is far from the theoretical value. In the crop yield, the LED compares the high pressure sodium lamp with no obvious advantage.
In the specific use, it should be rationally selected according to the actual situation of cultivation demand, greenhouse type, application target, investment ability and cost control.