Design and Testing of a Structural Monitoring System in an Almería-Type Tensioned Structure Greenhouse

Greenhouse cultivation has gained a special importance in recent years and become the basis of the economy in south-eastern Spain. The structures used are light and, due to weather events, often collapse completely or partially, which has generated interest in the study of these unique buildings. This study presents a load and displacement monitoring system that was designed, and full scale tested, in an Almería-type greenhouse with a tensioned wire structure. The loads and displacements measured under real load conditions were recorded for multiple time periods. The traction force on the roof cables decreased up to 22% for a temperature increase of 30 °C, and the compression force decreased up to 16.1% on the columns or pillars for a temperature and wind speed increase of 25.8 °C and 1.9 m/s respectively. The results show that the structure is susceptible to daily temperature changes and, to a lesser extent, wind throughout the test. The monitoring system, which uses load cells to measure loads and machine vision techniques to measure displacements, is appropriate for use in different types of greenhouses

Energy Efficiency in Greenhouse Evaporative Cooling Techniques: Cooling Boxes versus Cellulose Pads

Evaporative cooling systems using a combination of evaporative pads and extractor fans require greenhouses to be hermetic. The greatest concentration of greenhouses in the world is located in southeast Spain, but these tend not to be hermetic structures and consequently can only rely on fogging systems as evaporative cooling techniques. Evaporative cooling boxes provide an alternative to such systems. Using a low-speed wind tunnel, the present work has compared the performance of this system with four pads of differing geometry and thickness manufactured by two different companies. The results obtained show that the plastic packing in the cooling unit produces a pressure drop of 11.05 Pa at 2 m·s−1, which is between 51.27% and 94.87% lower than that produced by the cellulose pads. This pressure drop was not influenced by increases in the water flow. The evaporative cooling boxes presented greater saturation efficiency at the same flow, namely 82.63%, as opposed to an average figure of 65% for the cellulose pads; and also had a lower specific consumption of water, at around 3.05 L·h−1·m−2·°C−1. Consequently, we conclude that evaporative cooling boxes are a good option for cooling non-hermetic greenhouses such as those most frequently used in the Mediterranean basin

Research Trends on Greenhouse Engineering Using a Science Mapping Approach

Horticultural protected cultivation has spread throughout the world as it has proven to be extremely effective. In recent years, the greenhouse engineering research field has become one of the main research topics within greenhouse farming. The main objectives of the current study were to identify the major research topics and their trends during the last four decades by analyzing the co-occurrence network of keywords associated with greenhouse engineering publications. A total of 3804 pertinent documents published, in 1981-2021, were analyzed and discussed. China, the United States, Spain, Italy and the Netherlands have been the most active countries with more than 36% of the relevant literature. The keyword cluster analysis suggested the presence of five principal research topics: energy management and storage; monitoring and control of greenhouse climate parameters; automation of greenhouse operations through the internet of things (IoT) and wireless sensor network (WSN) applications; greenhouse covering materials and microclimate optimization in relation to plant growth; structural and functional design for improving greenhouse stability, ventilation and microclimate. Recent research trends are focused on real-time monitoring and automatic control systems based on the IoT and WSN technologies, multi-objective optimization approaches for greenhouse climate control, efficient artificial lighting and sustainable greenhouse crop cultivation using renewable energy

PREDICTING SOIL TEMPERATURES IN HIGH TUNNELS USING A DYNAMIC MODEL BASED ON NEWTONIAN LAW OF COOLING

High tunnels are low cost temporary greenhouses that are often used to extend the growing season for high value crops such as tulips, muscari, sweet pea cultivars, and hyacinth beans. Profitability depends on selection and timing of crops to optimize use of these structures. Predicting soil temperatures in high tunnels as a function of outside temperature is a critical factor in crop selection and timing. However, predicting soil temperatures is difficult because air temperatures constantly change from hour to hour and day to day. We develop a model to account for temperature dynamics in high tunnels by modifying the fundamental differential equation in Newtonian law of cooling. We fit the model to data from high tunnels located in two states - Nebraska, Kansas and predict soil temperature as a function of external air temperatures. The model fits reasonably well at all high tunnel stations with most predictions being within 2° C of the observed value. We also found that the model could be used to adequately predict soil temperatures at one site based on parameter estimates of another nearby site. Thus we conclude that the model is an adequate tool in making high tunnel placement decisions and is useful for selection and timing of crops within established high tunnels

Concrete utopianism in integrated assessment models: Discovering the philosophy of the shared socioeconomic pathways

The Shared Socioeconomic Pathways (SSPs) are at the forefront of climate change science today. As an influential methodology and method, the SSPs guide the framing of numerous climate change research questions and how these are investigated. Although the SSPs were developed by an interdisciplinary group of scientists in a well-documented process, there is no apparent consensus in the literature that answers the question, "What is the philosophy of science behind the SSPs?" To investigate, the paper applies a systematic thematic qualitative content analysis to the dataset of published papers that establish the rules and expectations for using the SSPs. The research determines that there is no obvious and concise statement on the epistemological and ontological foundation of the SSPs. However, based on the evidence identified in the dataset, SSPs are implicitly, though not explicitly, consistent with a critical realist and concrete utopian philosophy as coined by Roy Bhaskar. This is the first paper to discuss the philosophical underpinning of the SSPs

System study of the carbon dioxide observational platform system (CO-OPS): Project overview

The resulting options from a system study for a near-space, geo-stationary, observational monitoring platform system for use in the Department of Energy's (DOE) National Carbon Dioxide Observational Platform System (CO-OPS) on the greenhouse effect are discussed. CO-OPS is being designed to operate continuously for periods of up to 3 months in quasi-fixed position over most global regional targets of interest and could make horizon observations over a land-sea area of circular diameter up to about 600 to 800 statute miles. This affords the scientific and engineering community a low-cost means of operating their payloads for monitoring the regional parameters they deem relevant to their investigations of the carbon dioxide greenhouse effect at one-tenth the cost of most currently utilized comparable remote sensing techniques

Annual Report: 2009

I submit herewith the annual report from the Agricultural and Forestry Experiment Station, School of Natural Resources and Agricultural Sciences, University of Alaska Fairbanks, for the period ending December 31, 2009. This is done in accordance with an act of Congress, approved March 2, 1887, entitled, “An act to establish agricultural experiment stations, in connection with the agricultural college established in the several states under the provisions of an act approved July 2, 1862, and under the acts supplementary thereto,” and also of the act of the Alaska Territorial Legislature, approved March 12, 1935, accepting the provisions of the act of Congress. The research reports are organized according to our strategic plan, which focuses on high-latitude soils, high-latitude agriculture, natural resources use and allocation, ecosystems management, and geographic information. These areas cross department and unit lines, linking them and unifying the research. We have also included in our financial statement information on the special grants we receive. These special grants allow us to provide research and outreach that is targeted toward economic development in Alaska. Research conducted by our graduate and undergraduate students plays an important role in these grants and the impact they make on Alaska.Financial statement -- Grants -- Students -- Research Reports: Partners, Facilities, and Programs; Geography; High-Latitude Agriculture; High-Latitude Soils; Management of Ecosystems; Natural Resources Use and Allocation; Index to Reports -- Publications -- Facult

Computational Fluid Dynamic Modeling Application as a Design Tool in Air Assisted Pesticide Sprayer Development

The complex dynamic behaviors of air assisted pesticides spraying, especially inter-droplets interactions as well as effects of prevailing surrounding fluid environment before and after the spray breakup makes development of an ideal sprayer unattainable. Moreover, plants’ canopy architectures are sophisticated mainly due to variations in features’ orientation amongst species. A prior insight of the sprayer’s performance behavior at design phase can significantly help in avoiding unanticipated future failures. This situation has recently, inevitably paved way for the application of numerical analysis such as Computational Fluid Dynamic (CFD) modeling as a robust design tool. Furthermore, movement of spray droplets from the generator to the targets involve fluid flows, heat transfer and mass flow which are the principle fields in CFD simulation of transport phenomena. As the droplets travel, the surrounding environment is likely to interfere with their physical and chemical properties. The concern to fully utilize the technology has nowadays not only drawn the attention of manufacturing industry but has also captured the interests of researchers. Previous applications of CFD modeling have demonstrated its potential to ease the challenges of cost and time consumption that would have been encountered in physical experimental trials tests. Nevertheless, developing a standard ideal model still remains unattainable. Most researchers have developed simple model mainly of Lagrangian approach whose applications have primarily been on open-fields spraying despite the situation still remaining far underway. This paper gives a state-of-art review of the application of CFD modeling in air atomized pesticide spraying with an aim of highlighting future research needs. Keywords: Computational Fluid Dynamic, Air assisted sprayers, Lagrangian approach, Spray droplet

Simulation of site-specific irrigation control strategies with sparse input data

Crop and irrigation water use efficiencies may be improved by managing irrigation application timing and volumes using physical and agronomic principles. However, the crop water requirement may be spatially variable due to different soil properties and genetic variations in the crop across the field. Adaptive control strategies can be used to locally control water applications in response to in-field temporal and spatial variability with the aim of maximising both crop development and water use efficiency. A simulation framework ‘VARIwise’ has been created to aid the development, evaluation and management of spatially and temporally varied adaptive irrigation control strategies (McCarthy et al., 2010). VARIwise enables alternative control strategies to be simulated with different crop and environmental conditions and at a range of spatial resolutions. An iterative learning controller and model predictive controller have been implemented in VARIwise to improve the irrigation of cotton. The iterative learning control strategy involves using the soil moisture response to the previous irrigation volume to adjust the applied irrigation volume applied at the next irrigation event. For field implementation this controller has low data requirements as only soil moisture data is required after each irrigation event. In contrast, a model predictive controller has high data requirements as measured soil and plant data are required at a high spatial resolution in a field implementation. Model predictive control involves using a calibrated model to determine the irrigation application and/or timing which results in the highest predicted yield or water use efficiency. The implementation of these strategies is described and a case study is presented to demonstrate the operation of the strategies with various levels of data availability. It is concluded that in situations of sparse data, the iterative learning controller performs significantly better than a model predictive controller