Murat Kacira

A CFD EVALUATION OF NATURALLY VENTILATED, MULTI-SPAN, SAWTOOTH GREENHOUSES

A computational fluid dynamics (CFD) program, Fluent V4, was used to predict natural ventilation rates and airflow patterns of a multi-span, sawtooth greenhouse for various roof and side vent openings and outside wind speeds. Predicted rates were found to be both well above and well below a standard volumetric air exchange rate of 1.0 A.C. min–1. The maximum and most acceptable ventilation rates were obtained with the combined use of a windward side vent and leeward roof vents on all multi-span sections. Ventilation rates ranged from 1.4 to 4.01 A.C. min–1 for the best two-span case and 0.14 to 2.0 A.C. min–1 for the similar four-span case for outside wind speeds of 0.5 and 2.0 m s–1, respectively. Predicted ventilation rates ranged from 0.17 to 0.7 A.C. min–1 when no side vent was used and the roof vents were fully open.

A Comparison of Nannochloropsis salina Growth Performance in Two Outdoor Pond Designs: Conventional Raceways versus the ARID Pond with Superior Temperature Management

The present study examines how climatic conditions and pond design affect the growth performance of microalgae. From January to April of 2011, outdoor batch cultures of Nannochloropsis salina were grown in three replicate 780 L conventional raceways, as well as in an experimental 7500 L algae raceway integrated design (ARID) pond. The ARID culture system utilizes a series of 8–20 cm deep basins and a 1.5 m deep canal to enhance light exposure and mitigate temperature variations and extremes. The ARID culture reached the stationary phase 27 days earlier than the conventional raceways, which can be attributed to its superior temperature management and shallower basins. On a night when the air temperature dropped to −9°C, the water temperature was 18°C higher in the ARID pond than in the conventional raceways. Lipid and fatty acid content ranged from 16 to 25% and from 5 to15%, respectively, as a percentage of AFDW. Palmitic, palmitoleic, and eicosapentaenoic acids comprised the majority of fatty acids. While the ARID culture system achieved nearly double the volumetric productivity relative to the conventional raceways (0.023 versus 0.013 g L−1day−1), areal biomass productivities were of similar magnitude in both pond systems (3.47 versus 3.34 g m−2day−1), suggesting that the ARID pond design has to be further optimized, most likely by increasing the culture depth or operating at higher cell densities while maintaining adequate mixing.

MACHINE VISION EXTRACTED PLANT MOVEMENT FOR EARLY DETECTION OF PLANT WATER STRESS

A methodology was established for early, non-contact, and quantitative detection of plant water stress with machine vision extracted plant features. Top-projected canopy area (TPCA) of the plants was extracted from plant images using image-processing techniques. Water stress induced plant movement was decoupled from plant diurnal movement and plant growth using coefficient of relative variation of TPCA (CRV[TPCA)] and was found to be an effective marker for water stress detection. Threshold value of CRV(TPCA) as an indicator of water stress was determined by a parametric approach. The effectiveness of the sensing technique was evaluated against the timing of stress detection by an operator. Results of this study suggested that plant water stress detection using projected canopy area based features of the plants was feasible.

ESTABLISHING CROP WATER STRESS INDEX (CWSI) THRESHOLD VALUES FOR EARLY, NON-CONTACT DETECTION OF PLANT WATER STRESS

Early, non–contact, non–destructive, and quantitative detection of plant water stress with the application of infrared thermometry using a crop water stress index (CWSI) was established. A CWSI model for plants grown under controlled environments was developed using thermodynamic principles and energy balance of the plant. CWSI threshold values were established with a parametric approach. The effectiveness of the sensing technique was evaluated using timing of the stress detection by a grower. The CWSI–based technique was able to detect the stress one to two days prior to the time of stress detection by visual observation. Overall results of this study suggested that pre–visual and non–contact detection of plant water stress with infrared thermometry application using CWSI is feasible.

Optimization of vent configuration by evaluating greenhouse and plant canopy ventilation rates under wind-induced ventilation

The effects of greenhouse vent configurations, plant existence, and external wind speeds on ventilation rates and airflow patterns in a greenhouse and plant canopy zone under wind-induced ventilation were investigated. The optimization of traditional vent configuration for a two-span glasshouse for better air renewal, especially in the plant canopy zone, was attempted by three-dimensional numerical simulations using a computational fluid dynamics (CFD) approach. The realizable k-. model was used for a turbulent model, and the existence of the plants in the greenhouse was modeled by a porous medium method. Prior to the optimization, the CFD model was verified with the results of an experimental study of natural ventilation. The CFD model adequately matched those results. The ventilation rates, both in the greenhouse and in the plant canopy zone, were proportional to external wind speed. Maximum greenhouse ventilation rates were achieved when rollup type side vents were used in the side walls and both side and roof vents were fully open (case 3). For example, the ventilation rate for this vent configuration was 6.03 m3 m-2 min-1 at an external wind speed of 1.5 m s-1. The greenhouse ventilation rate for this vent configuration was almost the same as when the butterfly-type side and roof vents were fully open (case 1). However, the use of a rollup side vent considerably improved the ventilation rate in the plant canopy zone. This showed that ventilation in the plant canopy zone was significantly affected by internal airflow patterns caused by different vent configurations.

DESIGN AND DEVELOPMENT OF AN AUTOMATED AND NON-CONTACT SENSING SYSTEM FOR CONTINUOUS MONITORING OF PLANT HEALTH AND GROWTH

An automated system was designed and built to continuously monitor plant health and growth in a controlled environment using a distributed system approach for operational control and data collection. The computer-controlled system consisted of a motorized turntable to present the plants to the stationary sensors and reduce microclimate variability among the plants. Major sensing capabilities of the system included machine vision, infrared thermometry, time domain reflectometry, and micro-lysimeters. The system also maintained precise growth-medium moisture levels through a computer-controlled drip irrigation system. The system was capable of collecting required data continuously to monitor and to evaluate the plant health and growth.

The effects of different drip irrigation regimes on watermelon [Citrullus lanatus (Thunb.)] yield and yield components under semi-arid climatic conditions

This study was conducted to investigate the effects of drip irrigation on yield and yield components of watermelon [Citrullus lanatus (Thunb.) Crimson Tide F1] under semiarid conditions in the Southeastern Anatolian Project Region, Harran Plain, Şanliurfa, Turkey, during 2002 and 2003. Using a 4-day irrigation period, 4 different irrigation regimes were applied as ratios of irrigation water/cumulative pan evaporation (IW/CPE): 1.25 (I125), 1.00 (I100), 0.75 (I75), and 0.50 (I50). Seasonal crop evapotranspiration (ETc) rates were 720, 677, 554, and 449 mm in the first year and 677, 617, 519, and 417 mm in the second year for irrigation treatments I125, I100, I75, and I50, respectively. Amounts of irrigation water applied to the 4 respective treatments were 764, 642, 520, and 398 mm in 2002 and 709, 591, 473, and 355 mm in 2003. Maximum yield was obtained from I125, with 84.1 t/ha in 2002 and 88.6 t/ha in 2003. Yield was reduced significantly as the irrigation water was reduced. The values of water use efficiency ranged from 9.6 to 11.7 kg/m3 in 2002 and 10.8 to 13.1 kg/m3 in 2003. The unstressed I125 treatment produced 10.1 kg marketable watermelons/m3 irrigation in 2002, and 11.3 kg/m3 in 2003. By comparison, the least irrigated (I50) treatment produced 12.4 kg/m3 in 2002, and 14.9 kg/m3 in 2003. A yield response factor (ky) value of 1.15 was determined based on averages of 2 years, and watermelon was found to be sensitive to water stress. This result showed that yield loss (1 – Ya/Ym) is more important than evapotranspiration deficit (1 – ETa/ETm). The study demonstrates that 1.25 IW/CPE water applications by a drip system in a 4-day irrigation frequency might be optimal for watermelon grown in semi-arid regions similar to those in which the work was conducted.

Strategy development and determination of barriers for thermal energy and electricity generation from agricultural biomass in Turkey

The present work deals with determining barriers for thermal energy and electricity generation from agricultural biomass in Turkey. Strategy development and determination of barriers were investigated in accordance with the work program requirements for the project entitled “Exploitation of Agricultural Waste in Turkey” under the European Life Third Countries Program. The study has been organized and presented according to the following three phases: (i) market barriers for electricity and thermal energy generation (ii) identification of barriers to the promotion of agricultural waste exploitation in Turkey, and (iii) conclusions for strategy development.

Design and implementation of a computer vision-guided greenhouse crop diagnostics system

An autonomous computer vision-guided plant sensing and monitoring system was designed and constructed to continuously monitor temporal, morphological, and spectral features of lettuce crop growing in a nutrient film technique (NFT) hydroponics system. The system consisted of five main components including (1) a stepper motor-driven camera positioning system, (2) an image acquisition system, (3) a data logger monitoring root and aerial zone of the growing environment, (4) a dynamic SQL database module for data storage, and (5) a host computer running the collection, processing, storage, and analysis functions. Panoramic canopy images were dynamically created from the images collected by color, near-infrared (NIR) and thermal cameras. From these three images, the crop features were registered such that a single extracted crop (or a crop canopy) contained information from each layer. The extracted features were color (red–green–blue, hue-saturation-luminance, and color brightness), texture (entropy, energy, contrast, and homogeneity), Normalized Difference Vegetative Index (NDVI) (as well as other similar indices from the color and NIR channels), thermal (plant and canopy temperature), plant morphology (top projected plant and canopy area), and temporal changes of all these variables. The computer vision-guided system was able to extract these plant features and stored them into a database autonomously. This paper introduces the engineering design and system components in detail. The system’s capability is illustrated with a one-day sample of the lettuce plants growing in the NFT system, presenting the temporal changes of three key crop features extracted, and identification of a stress level and locality detection as example applications.

Wind Tunnel Measurement of Aerodynamic Properties of a Tomato Canopy

This study was conducted to determine the drag coefficient and the relationship between permeability (K) and momentum loss coefficients (Cf) of a tomato canopy for various leaf area densities. The experiments were conducted in a large-scale wind tunnel system with a tomato canopy. The static pressures and air velocity measurements were performed at several heights in the y-direction and various positions in the z-direction in the wind tunnel test section. The relationship between pressure drop and air velocity across the tomato canopy was determined using a porous medium approach. A drag coefficient of 0.31 was obtained for the tomato canopy used in the experiment. The permeability of the tomato canopy ranged from 0.006 to 0.65 for a leaf area density (L) of 4 (m2 m-3), from 0.004 to 0.41 for L = 5, and from 0.003 to 0.3 for L = 6 as Cf changed from 0.1 to 1. Thus, a mature tomato canopy having L = 6 could be used with a canopy permeability of K = 0.017 and a momentum loss coefficient of Cf = 0.245.