Photosynthetic Photon Flux Density Distribution Research Articles

Techno-Economic Assessment of an Office-Based Indoor Farming Unit

Decentralized, smart indoor cultivation systems can produce herbs and vegetables for fresh and healthy daily nutrition of the urban population. This study assesses technical and resource requirements, productivity, and economic viability of the “Smart Office Farm” (SOF), based on a 5-week production cycle of curled lettuce, lolo rosso, pak choi and basil at three photosynthetic photon flux density (PPFD) levels using a randomized block design. The total fresh matter yield of consumable biomass of all crops was 2.5 kg m−2 with operating expenses (without labor costs) of EUR 53.14 kg−1; more than twice as expensive compared to large-scale vertical farm and open-field cultivation. However, there is no need to add trade margins and transportation costs. The electricity supply to SOF is 73%, by far the largest contributor to operational costs of office-based crop production. Energetic optimizations such as a more homogeneous PPFD distribution at the plant level, as well as adaptation of light quality and quantity to crop needs can increase the economic viability of such small indoor farms. With reduced production costs, urban indoor growing systems such as SOF can become a viable option for supporting fresh and healthy daily nutrition in urban environments.

Mobile Device And Method For Photosynthetic Photon Flux Density Measurement In Greenhouse

The paper is devoted to the development of a mo-bile device and method for mobile measurements of photosynthetic photon flux density (PPFD) over the technological area of greenhouses. Within the frame-work of the method, a software product is imple-mented, which calculates PPFD and creates a map of PPFD distribution over the technological area of the greenhouse. The control tests of the device un-der greenhouse microclimate conditions were per-formed, confirming the operability of the installation.

Evaluation of the Light Environment of a Plant Factory with Artificial Light by Using an Optical Simulation

Good lighting designs can establish suitable light environments in plant factories with artificial light (PFALs). This study used optical simulations to investigate the effects of lighting designs in PFALs on the coefficient of variation of light absorption (Φp; CV) of individual plants and the coefficient of utilization for the lighting system (U). Three-dimensional models of canola plants were constructed using a scanner, and a 3D model of the cultivation shelf was also created. The photosynthetic photon flux density (PPFD) distribution in the cultivation spaces, with or without the canola plants, was estimated first. The PPFD on the canola leaves was then estimated when the lighting design parameters, such as number, distance, height, radiant flux, and light distribution of the light-emitting diode lamps, were modified. The optical simulation showed good accuracy when estimating the PPFD distributions on the cultivation shelf and the leaves of the canola plants. The results showed that while the PPFD distribution across the growing area was uniform, it was not on a plant canopy. By appropriately controlling the layout of the lamps and their directionality, lighting designs that reduce Φp; CV and improve U in PFAL could be possible, and optical simulations could help to develop them.

Photosynthetic Photon Flux Density Distribution Inside Photovoltaic Greenhouses, Numerical Simulation, and Experimental Results

<abstract> <b><i>Abstract. </i></b> A methodology for estimating the photosynthetic photon flux density (PPFD) distribution inside a photovoltaic greenhouse using a combination of a commercial lighting simulation software and available meteorological data was investigated in this study. Numerical results were compared with those measured inside an experimental greenhouse partially covered with photovoltaic panels. The PPFD distribution inside the greenhouse was calculated on the basis of outside measurements of PPFD at the site of the experimental greenhouse and data acquired at a nearby meteorological station. Daily average percent differences were in all cases lower than 19.0%. Assuming that such differences are acceptable for agronomic purposes, on a monthly basis the numerical model demonstrated a good capability to predict the shading effect inside the photovoltaic greenhouse. Hourly analysis showed higher fluctuation of measured versus calculated data, meaning that the model was able to predict the qualitative behavior of the distribution and its average value but underestimated the fluctuation of values.

Enhancement of crop photosynthesis by diffuse light: quantifying the contributing factors.

Plants use diffuse light more efficiently than direct light. However, experimental comparisons between diffuse and direct light have been obscured by co-occurring differences in environmental conditions (e.g. light intensity). This study aims to analyse the factors that contribute to an increase in crop photosynthesis in diffuse light and to quantify their relative contribution under different levels of diffuseness at similar light intensities. The hypothesis is that the enhancement of crop photosynthesis in diffuse light results not only from the direct effects of more uniform vertical and horizontal light distribution in the crop canopy, but also from crop physiological and morphological acclimation. Tomato (Solanum lycopersicum) crops were grown in three greenhouse compartments that were covered by glass with different degrees of light diffuseness (0, 45 and 71 % of the direct light being converted into diffuse light) while maintaining similar light transmission. Measurements of horizontal and vertical photosynthetic photon flux density (PPFD) distribution in the crop, leaf photosynthesis light response curves and leaf area index (LAI) were used to quantify each factor's contribution to an increase in crop photosynthesis in diffuse light. In addition, leaf temperature, photoinhibition, and leaf biochemical and anatomical properties were studied. The highest degree of light diffuseness (71 %) increased the calculated crop photosynthesis by 7·2 %. This effect was mainly attributed to a more uniform horizontal (33 % of the total effect) and vertical PPFD distribution (21 %) in the crop. In addition, plants acclimated to the high level of diffuseness by gaining a higher photosynthetic capacity of leaves in the middle of the crop and a higher LAI, which contributed 23 and 13 %, respectively, to the total increase in crop photosynthesis in diffuse light. Moreover, diffuse light resulted in lower leaf temperatures and less photoinhibition at the top of the canopy when global irradiance was high. Diffuse light enhanced crop photosynthesis. A more uniform horizontal PPFD distribution played the most important role in this enhancement, and a more uniform vertical PPFD distribution and higher leaf photosynthetic capacity contributed more to the enhancement of crop photosynthesis than did higher values of LAI.

Estimation of supplemental lighting efficiency based on PPFD distribution on the canopy surface

Criteria for evaluation of the efficiency of supplemental lighting based on photosynthetic photon flux density (PPFD) distribution on a canopy surface under artificial light were proposed, and the possibility of a reflection-image-based estimation of PPFD distribution on the canopy surface was discussed. Reflection images of plant canopy surfaces under various artificial lighting conditions were acquired from three directions with a digital camera equipped with a blue-green band-pass filter. PPFD was measured at one point on the canopy by a quantum sensor simultaneously with imaging, and the result was used to determine a regression model to estimate PPFD on leaves from pixel values of the image. The histogram of pixel values after gamma correction was converted into a PPFD histo- gram. The histogram pattern depended on the light source and canopy structure. Histograms estimated from images could depict the differences, showing mean values and coefficients of variation (CV) close to the measured values. Integrated PPFD over all illuminated leaves per unit power consumption (IPPC) was calculated from the histogram as a criterion for evaluating the efficiency of supplemental lighting. The efficiency also depended on the light source, canopy structure, and distance from the canopy surface. The estimated efficiency approximately agreed with the measured value in each case. These results suggest that reflection-image-based estimation of light intensity distribution can be used for simple evaluation of the efficiency of supplemental lighting.

Design and Operation of a Test Facility for Determining Photosynthetic Photon Flux Density Distribution of Luminaires for Greenhouses

ABSTRACT AfaciUty was designed and constructed for testing luminaires which are used for supplemental greenhouse lighting, to determine their photosynthetic photon flux density (PPFD) distribution patterns. In the facility, a microcomputer controls the movement of a luminaire and a quantum sensor, and collects and records data from the sensor. To demonstrate the use of this facility, a single luminaire was tested at heights of 1.5 and 2.0 m. Test data were analyzed and contour plots of PPFD were produced. PPFD distributions were then calculated for 2.0 m and 3.0 m luminaire spacing grids with a luminaire height of 1.5 m. The uniformity coefficient was determined and a contour plot of PPFD was made of a typical grid sector for each spacing. The 2.0 m spacing had an average PPFD of 90.5 jLimol s^ m^ and a uniformity coefficient of 0.84; whereas for the 3.0 m spacing, these values were 40.2 and 0.75 respectively.