High-tech Greenhouse Research Articles

Technological and ecological approaches to design and manage sustainable greenhouse production systems

Protected cultivation or Controlled Environment Agriculture (CEA) system has increased tenfold in the last 25 years thanks to tremendous scientific and technical breakthroughs, mainly directed to increasing crop yields and adapting to tough ambient conditions. Currently, greenhouse areas are still spreading and the CEA system is one of the keystones for the agriculture forecasting scenario. However, the environmental acceptability of this very intensive agro-ecosystem is now being questioned. Energy inputs are source of the main economic and environmental weakness, especially for high-tech greenhouses, where IPM is well-established. Pesticides, common in low-cost greenhouses systems, are a major barrier-to IPM. To design and manage more robust CEA systems, both technological and ecological approaches have been chosen. This allowed for increased consideration of IPM issues among global greenhouse engineering innovation and better use of greenhouse system capacities to enhance dedicated IPM high-tech tools and management practices. On the other hand, ecological concepts were used to determine and characterize complex biotic interactions that lead to question the tenant of biological control as soon as IPM is implemented in greenhouses with sub-optimum physical pest control means. More specifically, microclimate at the boundary layer level has been investigated both from a physical and biological point of view in order to determine the best climate preferences of the main pests and beneficials. By the same token, the efficiency of diverse biocontrol plants to provide accurate shelter to natural enemies has been assessed

Modeling of Energy Demand of a High-Tech Greenhouse in Warm Climate Based on Bayesian Networks

This work analyzes energy demand in a High-Tech greenhouse and its characterization, with the objective of building and evaluating classification models based on Bayesian networks. The utility of these models resides in their capacity of perceiving relations among variables in the greenhouse by identifying probabilistic dependences between them and their ability to make predictions without the need of observing all the variables present in the model. In this way they provide a useful tool for an energetic control system design. In this paper the acquisition data system used in order to collect the dataset studied is described. The energy demand distribution is analyzed and different discretization techniques are applied to reduce its dimensionality, paying particular attention to their impact on the classification model’s performance. A comparison between the different classification models applied is performed.

Economic analysis of High-tech Glass Greenhouse through the Convergence of New Renewable Energy -Focusing on the Convergence of Geothermal and Solar Power-

Economic analysis of High-tech Glass Greenhouse through the Convergence of New Renewable Energy -Focusing on the Convergence of Geothermal and Solar Power-

SYSTEM INTEGRATION AND OPTIMIZATION MODEL (SIOM)

Modern high tech greenhouses are a combination of various technical systems. There are more and more interactions between those systems. Therefore it is hard to adapt greenhouse design to another climate/situation. There is a need for a decision support system, combining practical know how, local parameters, available design models and validation data. This decision support system should also support growers in optimizing their business case. A publish/subscribe framework originally designed for urban planning is adjusted for the greenhouse design application. Design models such as climate, light, economy, crop growth are connected to this framework. In a case study the functioning of the framework is illustrated. The publish/subscribe framework is an easy way of connecting a wide range of existing design models. It requires low maintenance, several models with different abstraction level can be connected and models can be exchanged easily. The publish/ subscribe approach allow parallel processing, speeding up calculation time. SIOM is an effective approach to combine knowledge stored in various design models and gives an end user insight in the consequences of their design choices. Validation of the results, additional design models and a design process scheme is needed to make SIOM applicable by greenhouse builders.

Persistence of fenhexamid in the nutrient solution of a closed cropping system

There are concerns about emissions of plant protection products (PPP) from protected cultivations, including high-tech production systems. Modern high-tech greenhouse horticulture is performed in cropping systems with closed water and nutrient loops, so PPP residues are not leaked to the external environment, but are captured and may accumulate within the recycled greenhouse solution. In this pilot study, the botryticide fenhexamid (FEX; Teldor WG50®) was used as a model PPP and incubated (0.01 times the recommended concentration spray solution) in the colonized nutrient solution from a closed tomato production system in darkness at 20°C. Samples were taken after 0h, 24h, 48h, 96h, 192h and 504h (0, 1, 2, 4, 8 and 21 days) of incubation to monitor FEX concentration, dissolved organic carbon content (DOC), electrical conductivity, pH and microbial dynamics. Culture-dependent (viable counts for general bacterial, fungal flora and fluorescent pseudomonads on stationary agar, with/without supplement of FEX) and independent (denatured gradient gel electrophoresis, PCR-DGGE) methods were used for microbial analyses.DOC and FEX concentration did not change during incubation, whereas pH and electrical conductivity increased significantly. Density of culturable fungi decreased from the start of incubation, while density of culturable bacteria declined in late incubation. Fluorescent pseudomonads declined in early incubation but increased significantly at later stages. Under nutrient-deprived conditions, density of culturable bacteria decreased during the course of incubation. Microbial community analysis by DGGE supported these findings. Differences between the density of culturable bacteria assessed on semi-selective media with and without FEX supplementation were low. However, addition of FEX to diluted malt extract agar negatively affected the density of culturable fungi.

A CONCEPT FOR REDUCED ENERGY DEMAND OF GREENHOUSES: THE NEXT GENERATION GREENHOUSE CULTIVATION IN THE NETHERLANDS

In high tech greenhouse cultivation like in The Netherlands, large amounts of fossil energy are used to optimize climate conditions like temperature and humidity. To achieve a more sustainable greenhouse horticulture, a considerable reduction in energy use is needed, but tradeoffs with production and quality are not acceptable. Therefore, we developed a novel cultivation system for tomato to meet the goal: reduction of the energy input by 40% from 1.3 to 0.75 GJ.m-2.y-1, maintaining a production level of 60 kg.m-2.y-1. This concept, the Next Generation Greenhouse Cultivation, is based on the intensified use of thermal screens combined with control of humidity, maximizing the use of the integration capacity of the crop, growing at high humidity, improved efficiency of CO2 supply by reduction of ventilation and the use of cooling combined with a heat pump and an aquifer. In this approach, the main element is the prolonged use of screens with a high insulating value (>70%) to reduce the energy demand, combined with a forced ventilation system that injects relatively dry outside air into the greenhouse. The maximal use of the integration capacity of the crop implies a strong relation between daily radiation sum and diurnal mean temperatures, and a large difference between night and day temperatures on sunny days. This reduces the energy input and ventilation rate. Growing at increased humidity, achieved by misting, reduces ventilation rates because of the increased enthalpy of the greenhouse air. When supplying CO2, reduced ventilation results in higher CO2 concentrations and hence a higher energy efficiency. Cooling can be used in combination with a heat pump and an aquifer to reduce the need for fossil fuel. This approach, in which proven technologies are combined, enables growers to implement the elements step by step, leading to an easy acceptance.

A methodology for model-based greenhouse design: Part 4, economic evaluation of different greenhouse designs: A Spanish case

An economic model was developed as a key component of a model-based method to design greenhouses for a broad range of climatic and economic conditions. This economic model was linked to an existing greenhouse climate-crop yield model to calculate the annual Net Financial Result (NFR) of a greenhouse. The aim of this study was to identify – among ten predefined design alternatives – the greenhouse with the highest annual NFR for tomato production under southern Spanish conditions. The basic designs were either the parral greenhouse, or a multi-tunnel, possibly fitted with any combination of heating, fogging and CO2 enrichment. Results demonstrated that the multi-tunnel, fitted with only a fogging system was most profitable, followed by the multi-tunnel with heating, CO2 enrichment and fogging. However, the difference in NFR between such a design and a simple parral was small with respect to the difference in investment. A sensitivity analysis of the NFR of the two technology extremes shows that tomato price, the fraction of marketable yield and the Photosynthetically Active Radiation (PAR) transmission of the cover had the largest bearing on NFR. With increasing technology level, the NFR depended less on outdoor climate and more on tomato price. This indicates that a low-tech greenhouse diminishes the risk of variations among price paths in different years, whereas a high-tech greenhouse covers better the “weather risk”. The best design was also affected by climate management and the joint impact of climate modification techniques. These results demonstrated that a model-based design approach can cope with multi-factorial design aspects.

A methodology for model-based greenhouse design: Part 3, sensitivity analysis of a combined greenhouse climate-crop yield model

Greenhouse design is an optimisation problem that might be solved by a model-based greenhouse design method. A sensitivity analysis of a combined greenhouse climate-crop yield model of tomato was done to identify the parameters, i.e. greenhouse design parameters, outdoor climate and climate set-points, that most strongly influence greenhouse performance. The analysis was performed for a low-tech greenhouse in Almeria, Spain, and a high-tech greenhouse in Texas, USA. A single-variate sensitivity analysis showed that outdoor climate has the strongest impact on the performance of the greenhouse system, followed by greenhouse design parameters and greenhouse climate set-points. The high impact of the outdoor conditions stresses the need to select a proper location for the greenhouse. Concerning the design parameters, the analysis revealed different results for the two locations and greenhouses studied. This emphasises that a ‘custom made’ approach to greenhouse design should be followed exploiting local conditions. In both cases, structures with a higher PAR transmission and a NIR-selective whitewash should be used. Seasonal patterns in the model sensitivity of for instance PAR, NIR and FIR emission coefficients of the cover indicate that a greenhouse with adjustable cover parameters will be advantageous over a design with fixed greenhouse cover parameters, as is usually implemented. A multi-variate sensitivity analysis revealed strong joint effects of parameters on crop yield. A joint increase of the PAR transmission and temperature set-point for ventilation favoured the crop yield for both greenhouses, stressing a simultaneous approach to both design and control of greenhouse systems.

Effect of near-infrared-radiation reflective screen materials on ventilation requirement, crop transpiration and water use efficiency of a greenhouse rose crop

The effect of Near Infrared (NIR)-reflective screen material on ventilation requirement, crop transpiration and water use efficiency of a greenhouse rose crop was investigated in an experiment whereby identical climate was ensured in greenhouse compartments installed with either NIR-reflective or conventional material as internal movable screens. The NIR-filter reduced the energy load of the greenhouse by 8%. The high reflectivity of the canopy in the NIR range caused the energy input of the greenhouse to be reduced by less than the properties of the material would suggest (25%). Both the ventilation requirement of the greenhouse and crop transpiration were reduced by the NIR-selective screen, consistently with the reduction in energy load of the greenhouse and the crop. The potential for commercial application of such material - either as movable screen or semi-permanent screen in addition to cooling - seems limited to high-tech greenhouse production in arid regions, where the reduction in cooling requirement could significantly lower water use for evaporative cooling. The potential for application of a photo-selective paint as alternative to the seasonal whitewash in low-tech greenhouses is obviously much larger. For it to make a difference, however, the NIR-reflectance must be much higher than the value of the present commercially available paints.