The hottest led plant lighting system should consi

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A good led plant lighting system should consider these factors

enterprises will face many considerations when evaluating the light source of gardening lighting, including light intensity, spectrum, light distribution uniformity, energy efficiency and lamp life. Horticultural lighting system can convert electric energy into light for plant growth and development and promote photosynthesis, while LED based light source can provide tuned spectrum for applications

however, determining the efficiency or effectiveness of such solid-state lighting (SSL) systems is a challenge. There are several factors that affect the overall efficiency of the lighting system. This paper discusses how the design of lighting equipment will affect energy efficiency, and how energy efficiency in turn affects the overall profitability of the controlled plant growth environment

in fact, the effectiveness of gardening lamps in converting electrical energy into usable light for plant growth is critical to the success of controlled environmental agriculture (CEA). Figure 1 shows an example of a vertical farm in controlled environmental agriculture (CEA)

installing lighting solutions within a few inches of crop canopy is a breakthrough in vertical agricultural applications. Compared with poorly designed led solutions and other lighting technologies such as HPS and fluorescent lamps, correctly designed led solutions can achieve higher output per square foot

gardening related indicators

plants mainly use visible light with a wavelength of nm for photosynthesis (Fig. 2). Therefore, this section is usually also called photosynthetically active radiation (PAR). Photosynthetic photon flux (PPF) measures the total amount of par produced by the lighting system per second. When measuring, an integrating sphere is used to capture and measure almost all photons emitted by the lighting system. The unit of PPF is the number of moles of photons per square meter per second( μ mol/s)。

Figure 2 average response of plants to photosynthetic effective radiation (PAR)

photosynthetic photon flux density (PPFD) measures the amount of par reaching the plant canopy. PPFD refers to the number of light quanta in the visible wavelength range per unit time area, and the unit is μ mol/m2/s。 PPFD also indicates the correlation between the number of light quanta and photosynthesis

finally, we discuss the efficacy of photons. Photon efficiency refers to the efficiency of horticultural lighting system to convert electrical energy into par photons. If the PPF and input power of light are known, the photon efficiency of gardening lighting system can be easily calculated. The unit of the given PPF is μ Mol/s, the unit for measuring watt is joules per second (j/s), and the number of seconds in the numerator and denominator is eliminated to obtain the unit of μ Mol/J, this unit is used to express efficacy. The higher the number, the more effective the lighting system will be in converting electrical energy into par photons

common methods of gardening lighting

next, we need to understand the subtle differences in lamp design and the reasons for energy saving of gardening lighting system. The most commonly used gardening lighting system in the world is based on high intensity discharge (HID) lighting and high pressure sodium lamp (HPS). The high-pressure sodium lamp was not specially designed for planting plants, but for light rail and parking garage. However, the ready availability and high output level have led to their wide application in gardening, because they provide very high light intensity. Most of the emitted light is in the nm range, which can accelerate photosynthesis

one disadvantage of using high-pressure sodium lamp for gardening lighting is that it produces a lot of radiant heat. The surface temperature of high-pressure sodium lamp can reach a temperature higher than 800 ° f (about 430 ℃), so there must be enough distance between plant canopy and high-pressure sodium lamp to avoid damaging plant tissue. When the installation height of lamps is increased, the inverse square law begins to work, which can reduce the lighting rate. With the passage of time, the energy efficiency of high-pressure sodium lamps increases, and the emergence of double ended HPS lamps can achieve 1.7 μ Mol/j photon efficiency

turn to LED

let's review the process of using led in gardening lighting. In 2014, the most efficient LED gardening lighting system was as efficient as the double ended high-pressure sodium lamp. Compared with high-pressure sodium lamp, LED has a long service life (L70 ≥ 50000 hours), which makes many growers turn to LED. However, compared with high-pressure sodium lamp, the cost of LED gardening lighting system is relatively high, which limits the transition to LED lamp

led chip manufacturers have improved the efficiency of existing components in the past few years, enabling them to significantly improve the photon efficiency, and will continue to improve every year. In fact, led based gardening lighting systems can now achieve photon efficiency 45% greater than double ended high-pressure sodium lamps. Although the efficiency of a single component improves the efficiency of LED gardening lighting, it is only a variable that led surpasses high-pressure sodium lamp technology

led system heat

when talking about the heat generated by LED lighting, there is a common misunderstanding mentioned by Ian Fuller, vice president of business development and engineering of the company, to reinforced plastics. Many growers believe that LEDs produce less heat than high-pressure sodium lamps, which is true when LED lamps are driven at a lower wattage. If there is a 600W LED lamp and a 600W double ended high-pressure sodium lamp, from a macro point of view, the heat they produce is within the same approximate range

the main difference between LED and high-pressure sodium lamp lies in the amount of par energy generated by these two 600W and how the heat is emitted from the lamp. Most of the heat from the high-pressure nano gas lamp radiates downward to the crop canopy, while most of the heat of the LED is generated at the connection between the component and the printed circuit board (PCB), and the heat is usually transmitted to the PCB. It is also possible that 3. To explore the establishment of a cooperative mechanism is the heat sink, which is removed by upward convection

therefore, one of the main advantages of LED as a gardening lighting system is that it can be placed near plants and protect plants from thermal radiation. However, if the heat is not effectively removed from the PCB through an appropriate thermal management system, the life of the LED components will be significantly reduced

there are two ways to cool the lighting system in a commercial horticultural environment. Passive cooling accounts for 95% of the total global production and sales. Lamps that use the bridge principle to test the cable fault distance use heat sinks to dissipate heat from the circuit board, while lamps that use active cooling rely on fans or water to dissipate heat. The fan used to cool the lamp will consume energy and reduce the overall photon efficiency of the lamp. In addition, if the fan fails during the operation of the lamp, the LED on the PCB may overheat and burn out. Even if there is no catastrophic failure, the reduced power output will greatly reduce the service life of LED lamps. This is a very important factor that growers need to consider when comparing gardening lighting systems

spectrum and efficacy

another important factor affecting the photon efficacy of horticultural lighting systems is the spectrum of luminescence. The most effective wavelengths for gardening lighting systems are red (660nm) and blue (450nm). Traditional LED gardening lighting technology mainly uses blue LEDs with a small proportion of red bands to achieve the highest photon efficiency

although the red LED has the highest photon efficiency, the plant itself does not grow at narrow-band wavelengths. Therefore, in terms of optimizing plant growth and development, a single red LED will not produce the most effective spectrum. This is particularly the case with single source lighting in vertical farms compared to supplementary greenhouse lighting (Figure 3)

harsh and dirty environments (such as greenhouses) may quickly lead to the failure of the active cooling system, resulting in the failure of the entire lighting system. In addition to improving energy efficiency, the passive cooling system does not need moving parts that are easy to break and block

many horticultural lighting manufacturers claim that their products have "special spectra" according to the absorption peaks of chlorophyll a and B. However, they did not mention that these chlorophyll pigments were extracted from plant leaves and measured in vitro. The action spectrum of light quality on photosynthesis (Fig. 2) was proposed by Mccree and Inada in the 1970s. Studies have shown that there is a correlation between the rate of photosynthesis and the action spectrum of chlorophyll a and B, but they are not the only wavelength of photosynthesis. Before this study, there was a common misconception that chlorophyll mainly absorbs the red and blue parts of the visible spectrum, so plant photosynthesis does not use green light

the research conducted by Mccree and Inada is the basis for understanding the influence of spectral light quality on Photosynthesis; However, they studied the action spectrum based on the measurement of photosynthesis in a single leaf under low light intensity. In the past 30 years, there have been many studies on plant photosynthesis under high light intensity, indicating that the influence of spectral quality on growth speed is much smaller than that of light intensity

spectral light quality has a great impact on plant development, such as seed germination, stem elongation and flowering, as well as secondary metabolites and flavonoids, which affect the taste, appearance and odor of plants. Therefore, LED manufacturers need to find a balance between using the most electrically efficient LED and the LED that growers want to promote the best growth and development habits of plants

shape factors and beam control

the last topic we discuss is related to the shape, beam optics and light intensity of lamps. PPFD and Cu need to be considered when considering the overall efficiency of gardening lighting system. However, although the photon effect of the lamp itself is very important for gardening lighting, if the light generated in practical applications does not shine evenly and effectively on crops, the real energy efficiency of this scheme will be greatly reduced

because each high-pressure sodium lamp has only one light source (360 ° bulb), it is necessary to rely on reflectors to distribute light evenly on the canopy of crops. Another advantage of led over high-pressure nano gas lamp is that led has hundreds of light sources, which can form a very uniform light band through customized beam optics, without the use of reflectors. Figure 4 depicts a typical LED light engine

the spectrum (i.e. color) of light emitted from gardening lighting system has a significant impact on energy efficiency and the growth and development of the whole plant. Although the efficiency of red and blue light is higher, the broad spectrum achieved by the light engine in the picture can improve the culture for more photoreceptors

when properly designed, the flexibility of this form makes the lighting scheme with very high Cu very advantageous, and most of the light generated falls on the plant canopy instead of being wasted on the channel or wall. This is very important for growers to choose gardening lighting system

not all LED lighting systems are the same, so it is very important for growers to obtain lighting designs from manufacturers, which will show the average PPFD at the specified installation height and the light distribution pattern in the plant growth chamber. The shape factor and light distribution of gardening lighting system will affect the number of lamps required, which is another factor affecting the overall energy efficiency of plant growth room

the energy efficiency of garden lighting systems depends on several factors, not just one. Using the correct measurement method, understanding several factors that affect the energy efficiency of gardening lighting system will affect the overall profitability of plant growth room

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