S. Hemming

Plastic Nets in Agriculture: A General Review of Types and Applications

At the moment, there are a large number of agricultural net types on the market characterized by different structural features such as type of material, type and dimensions of threads, texture, mesh size, porosity / solidity and weight; by radiometric properties like color, transmissivity/reflectivity/shading factor; by physical properties like air permeability and several mechanical characteristics such as tensile stress, strength, elongation at break, and durability. Protection from hail, wind, snow, or strong rainfall in fruit-farming and ornamentals, shading nets for greenhouses and nets moderately modifying the microenvironment for a crop are the most common applications. A systematic review of the current state-of-the-art of structural parameters, standard and regulations, most common agricultural net applications, and their supporting structures has been developed by means of a literature study, technical investigations, concerning characteristics and use of nets. As a result, the survey highlighted that in many cases different, not even similar, net types were adopted for the same application and the same cultivations by various growers. Results show that neither growers nor net producers have clear ideas about the relationship between the net typology optimization for a specific application and the construction parameters of the net. The choice often depends on empirical or economic criteria and not on scientific considerations. Moreover, it appears that scientifically justified technical requirements for nets used in specific agricultural applications have not been established yet.

The Systematic Design of Greenhouse Crop Production Systems

Protected cultivation systems are used throughout the world as a powerful instrument to produce crops. They protect the crops from unfavorable outdoor climate conditions and pests and offer the opportunity to modify the indoor climate to create an environment that is optimal for crop growth and production, both in terms of quality and quantity. Designing protected cultivation systems is a multi-factorial optimization problem. During this process, choices have to be made with respect to construction, cladding material, climate conditioning equipment, energy sources and management, growing substrates, water and nutrient supply, internal logistics and labour, to mention a few. All of these choices mutually influence each other and are influenced by local boundary conditions like climate, economics, market, legislation and availability of resources. This paper presents the outlines of a systematic design methodology to design protected cultivation systems including several design examples of modern greenhouses production systems.

Feasibility study thin glasses for greenhouse roof designs

In this study, the feasibility of the application of flexible thin glass in greenhouses was investigated. With the development of thin but very strong glass plates like for mobile phones, new possibilities are being created for new greenhouse roof designs, the usage in multi-layered glass roof give possibilities for high-insulation greenhouse coverings. Flexible thin glass is a tempered glass. While standard tempered glass goes through a thermal process, this is a chemical process, which makes the glass five times stronger, creating the possibility of thickness reduction and bending. By adding nanocoatings the reflection can be reduced and the light transmission can be increased. Multi-layered greenhouse roofs can be created, resulting in a higher light transmission than currently available multilayer polycarbonate (PC) sheets, but also a higher transmission than today’s insulating double glass. The study shows that such glass combinations lead to an additional 20% energy savings based on heat demand for Phalaenopsis. Thin glasses are particularly strong and can also be used in curved form. This makes new greenhouse roof designs with these glasses possible. Especially the low weight offers advantages here. Important mechanical aspects and bottlenecks for the use in greenhouses have been mapped out. Due to limitations in today’s available dimensions and high prices, the use of thin glass in greenhouses will be further away in the future