Protected cultivation in greenhouses makes it possible by capturing the suns energy to raise inside temperature. Several properties of the cover materials contribute to crop productivity, quality and even the content of healthy compounds.
The amount of sun radiation entering the greenhouse determines its temperature; light in the PAR wavelength range drives photosynthesis, the fundamental motor of crop production; the wavelength composition of light has a signalling effect on crop development and on the content of nutraceuticals of food products and the geometrical distribution of light affects crop productivity. In addition, the properties of the cover (and additional screen) material(s) determine the energy that is lost at night, requiring replacement by heating.
There is a great need and a huge potential for the development and application of smart or adaptable cover materials that would make it possible to control the quantity, spectral composition and geometrical distribution of solar radiation entering the greenhouse. Next to light and temperature, a smart control of the growth factors CO and humidity is very important to optimize crop production and nutritional food products. New selective membranes and other smart or adaptable materials are needed so that a microclimate and light environment is generated that maximizes food production and desired quality aspects and containing healthy components, while minimizing/nullifying the need for fossil energy. This program will benefit from a two pronged approach: the adaptation of existing knowledge and materials to solve horticultural challenges, but also new higher-risk/higher-reward research to solve these challenges.
Goals of this study
The long-term goal is that new greenhouse production systems will utilize sunlight in a very efficient way since they will be covered with smart or adaptable materials. Solar light at any climate zone in the world will be converted into a form (quantity, quality, geometrical distribution) exactly needed by the crop to produce fresh products with high yield, good taste and high in healthy components. All growth factors (light, temperature, CO, humidity) will be controlled by smart or adaptable materials in order to reach a minimum input of resources during food production (energy, CO, water).
The program is a cross over of TKI TU and HTSM (High-tech 2 Feed the World) and offers a unique collaboration of horticultural supply industry with high-tech industry, as well as a unique collaboration between academic researchers in the areas of horticulture and chemistry to design new greenhouse production concepts with smart materials for the horticultural industry that could be applied on a huge scale.
The Dutch horticultural sector will profit from knowledge brought in from the international high-tech industry and will benefit from the knowledge and new products developed in this program. At the same time the visibility of the Dutch greenhouse horticulture as a high-tech production sector is directly enlarged.
The following smart materials were developed either as prototype, demonstrator and have been tested in a laboratory environment at WUR LightLab and/or with computer simulations with WUR dynamic greenhouse climate and crop models:
- Functional film with selective permeability to water vapour for control of humidity and energy saving.
- Glass cover combining a low emissivity coating (and high diffusivity) for energy saving and increase of crop performance.
- Alternative screen or insect netting, made from different materials than the conventional ones, these materials combine high air permeability and insect barrier.
- High transmission polycarbonate sheet. Different technologies to improve light transmission have been developed in the project and assessed in the laboratory e.g. anti-reflection (AR), microstructures or additional anti-dripping.
- Antimicrobial glass.
- Self-cleaning coating.
- First versions of thermotropic and phototropic pigments and highly diffusing pigments.
The following smart materials were developed either as prototype, demonstrator and have been tested in a small-scale greenhouse environment at WUR in Bleiswijk:
- Very high light scattering material. A first test was performed in a climate chamber (constant light conditions), comparing the performance of the very high light scattering materials with a medium scattering material with small tomato seedlings at a very high density to mimic a high LAI. Results indicated an increased light interception and dry matter production under the lamellae in relation to the medium diffusivity treatment. A new small test was afterwards performed in a greenhouse compartment in Bleiswijk, tomato seedlings were grown in elevated tables, this time in a greenhouse compartment under natural (varying) light conditions. Result: Very high light scattering, which was not available so far, would lead to even better crop performance compared to commercially available scattering materials.
- Electrochromic glasses. Different greenhouse trials have been conducted with two types of electrochromic glasses, one with light intensity switching glass prototypes and a second with light diffusion switching glass products. The focus of the experiments was to learn more about the crop physiology behind.
The following smart materials were developed as product and been tested in a relevant environment:
- Air bubbles film. One of the main limitations of single plastic film greenhouse covering is that it does not provide a high insulation during cold periods. This is the reason why double inflated plastic film systems have been developed in the past. However, such systems cost a decrease in PAR transmission and rely on an inflating system that must function continuously. An alternative material, consisting on a single layer film containing medium size air bubbles has been developed. Such material combines, light diffusion, a larger PAR transmission and a lower global heat transmission coefficient than double inflated polyethylene. In addition to the lab evaluation, the material has been tested in two experiments at the Innovation and Demonstration Centre of Energy (IDC Energy) at WUR in Bleiswijk, in the BEST (Bubble Energy Saving Technology) project. In this project, the materials have been proposed to grow berry fruits indoor. The results for raspberry obtained so far indicate a saving in energy of 37% and 25% more production.
- Film with high NIR reflection. This is a commercial product whose target market are traditionally buildings (not greenhouses) for warm regions. We concluded that one of the possible target markets could also be greenhouses in the Middle East, where such a material can be used as a greenhouse cover and would result in energy and water savings in both closed and pad and fan greenhouse types. Simulations indicated interesting savings in water and electricity. It could potentially also be used as mobile shading screen in different climates.
The half-yearly project meeting in October was held at the Technical University of Eindhoven (TU/e). The goal was to share the current status of all workpackages and to focus on integration of results for future practical application. Fundamental research on material development of switchable light scattering, switchable NIR control and switchable spectrum control has been carried out by a phd student of TU/e. All the work will finally be published in scientific papers. The group got inspired by visiting different laboratories of TU/e in which student collaboration takes place, new start-ups are formed and new material development is carried out.
All partners shared their newest improved materials on the field of higher light transmission, almost perfect diffusion, higher NIR reflection, anti-soiling, self-cleaning, anti-drip, anti-septic, humidity transport, high insulation, higher TIR reflection and low-e coatings. New plastic sheets, films, screens and polymers have been developed as well as new coatings or surface treatments. Materials can be used as greenhouse covering, screen of insect netting in the future. Target markets are different climate zones worldwide and high value food and ornamental crops for healthy food supply and a healthy green environment for consumers.
WUR has finished two small scale crop trials on the field of switchable light intensity and highly diffusive materials. Switchable electrochromic glasses were tested in an anthurium potplant trial in a greenhouse in Bleiswijk. Highly diffusive materials were tested in a climate chamber with young tomato plants in Wageningen. More switchable materials (light intensity, light diffusion, light spectrum) will be tested in small scale greenhouse experiments in 2020.
April 2019: Official project meeting Smart Materials at RKW Hyplast, Belgium, and Mardenkro, The Netherlands
A very inspiring project meeting has taken place at RKW Hyplast in Hoogstraten and at Mardenkro Baarle-Nassu. The group visited the plastic film factory of Hyplast including their new 7-layer film extrusion plant, a modern strawberry grower and the laboratory and production site of Mardenkro.
Newest developments of smart materials were shared by all partners. What might be expected in the future? Almost perfectly diffusive materials with high light transmissivity, insulating materials with high light transmissivity, light intensity switching materials, thermo-, electro- and phototropic materials switching light intensity at higher temperatures, an electric impulse, higher light intensities or a combination of them. Other highlights are antiseptic, easy-to-clean and self-healing coatings. Several coinnovations between different project partners are ongoing. Technical evaluations of materials and also crop physiological experiments are promising.
All project participants gathered for a one day workshop on effects of light spectrum on crops. Anja Dieleman (WUR) gave an overview of the effect of different light colours on various crops, mainly results gained by LED research. Cecilia Stanghellini (WUR) gave an overview of earlier research on the effect of UV, NIR and fluorescent pigments in coverings. In the afternoon the group visited the Daylight Greenhouse of Ter Laak orchids and learned about the importance of diffuse light for shade tolerant crops and the possibilities of energy saving by Fresnellenses and thermal solar collectors in the greenhouse roof during Phalaenopsis production. During a visit to Anthura the group learned on the importance of constant light conditions at various stages of Anthurium production. The group got inspired for the development of new smart materials. The workshop was co-organised by LTO Glaskracht.
March 2018: Official project meeting Smart Materials on 14-16th March at DOMO lab Saint-Gobain, Paris, France
The first scientific publications are available. You can access them via the following links:
- Multistate Luminescent Solar Concentrator “Smart” Windows (by Jeroen A. H. P. Sol, Gilles H. Timmermans, Abraham J. van Breugel, Albertus P. H. J. Schenning, Michael G. Debije in Advanced Energy Materials)
- Temperature-Responsive Luminescent Solar Concentrators: Tuning Energy Transfer in a Liquid Crystalline Matrix (by Jeroen A. H. P. Sol, Dr. Volker Dehm, Reinhard Hecht, Prof. Dr. Frank Würthner, Prof. Dr. Albertus P. H. J. Schenning, Dr. Michael G. Debije in Angewandte Chemie International Edition)
November 2017: Official project meeting Smart Materials on November 29th, at Sabic, Bergen op Zoom, The Netherlands
The project partners of PPS Smart Materials for greenhouses had another fruitful meeting combined with an interesting lab tour at Sabic. In the meantime many existing materials have been screened by WUR in the laboratory and several new materials are currently under development by the company partners for horticultural application.
Topics for material development are e.g. light transmittance, light diffusion, high insulation with new technologies, new polymers, new insect and shading netting technologies, heat reflection, humidity control by foils, membranes and coatings, materials with switchable properties triggered by temperature or electrical. Application fields are greenhouse systems world-wide depending on the innovation. Targeting crops are high-value food crops and ornamental. Networking of different partners plays an important role in the project. First ideas for co-creation have already been developed between partners. Growers might expect new ways of controlling the crop environment in the future.
September 2017: 2nd Workshop Technical requirements for Smart Materials on September, 20th, at Fujifilm Innovation Hub, Tilburg, The Netherlands
The second workshop on smart materials has been held with the projectteam consisting of commercial and R&D members of participating companies and knowledge institutes. A study was presented by WUR exploring the opportunities of smart greenhouse covering materials with switchable filters allowing for the instantaneous modification of relevant optical properties of the cover. Greenhouse simulation models have been modified andnused in the study to explore the potential effect on microclimate, use of resources and crop growth and development. Until recently, the only possibility to modify the amount and quality of the light reaching the crop in a greenhouse was the use of temporary coatings (i.e. whitewash) or screens/netting (fixed or mobile, internal or external).
Nowadays and in the near future, new filters are being developed that allow for almost instantaneous change of relevant optical properties directly in the cover where the filter is added. This allows an optimization of the amount and quality of the light entering the greenhouse instantaneous induced by different triggers and can be applied for different crops and regions in the world. Different switchable filters were compared in the study, different climate regions and greenhouse types were analysed to analyse the potentials of smart materials compared with existing solutions.
Next to that, first switchable materials have been produced by TU/e and were presented on the workshop. Materials were either switchable on an electric voltage or on temperature change. Again, a very creative brainstorm session has been held with the group resulting in new ideas and solutions for smart materials for greenhouses.
May 2017: Workshop Requirements and Markets for Smart Materials on May, 10th, at Bleiswijk, The Netherlands
An informative and creative workshop on has been held with 30 members of the projectteam. Commercial and R&D members of participating companies came from all over the world to join the meeting. They discussed and brainstormed together with researchers on new smart materials of greenhouses. High-tech industry learnt about requirements of crops and greenhouses, horticultural industry learnt about possibilities of new materials for greenhouses. We shared information on market trends and drivers and discussed on the development of greenhouse horticulture worldwide. We shared information on the function of a greenhouse, important growth factors for crop production and challenges for production in different climate zones worldwide.
Specific attention has been paid to the brainstorm on new smart materials for greenhouses in cold climates (e.g. The Netherlands), mild winter climates (e.g. Mediterranean), tropical climates (e.g. South America) and desert climates (e.g. Middle-East). We discussed on new solutions for light, temperature and humidity management for future greenhouses.
The group visited several research greenhouses at WUR in Bleiswijk, a Chinese Solar greenhouse, lettuce on hyproponics in a plastic multi-tunnel and the Winterlight greenhouse with the latest developments on the field of smart glass, coatings, greenhouse construction and crop management. During the visit the group exchanged creatie ideas on new materials for different technology levels and crops. During the workshop the group could network and make new contacts.
First presentation during Agrifood Tech Platform conference in Den Bosch, The Netherlands, on December, 14th, in presence of State Secretary Martijn van Dam of the Ministry of Economic Affairs.