S. Hemming

Wageningen University, Wageningen, Gelderland, Netherlands

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Publications (109)11.64 Total impact

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    ABSTRACT: Worldwide competitive challenges urge growers to further improve operational performance. In this paper, the objective ‘model-based analysis and improvement of the operation of horticultural production systems’ was narrowed to ranking simulated labour management scenarios in a multi-operations and multi-worker static cut-rose cultivation system. Eight scenarios with worker skill as a central theme were simulated including a practical labour management scenario applied by a Dutch cut-rose grower. The GWorkS-model was prepared for simulation of disbudding and bending in addition to harvest, three crop operations representing over 90% of crop-bound labour time, as well as for full scale simulation of the greenhouse using all workers and equipment. The sub-models on disbudding and bending were verified using data acquired in practice. Both processes were reproduced accurately. The model study on work scenarios showed that labour organisation choices might yield up to 5 s per harvested rose difference in total labour time for harvest, bending and disbudding between the best and worst scenario, which is equivalent to 7.1 € m−2 labour costs difference per year. Scenarios pointed out that working with low skilled, low paid workers is not effective. Specialised workers were most time effective, −17.5% compared to the reference, but overall a permanent team of skilled generalists ranked best in a multi-factorial assessment. Reduced crop operation diversity per day improved labour organisational outputs but ranked almost the same as the reference. The reference scenario was outranked by 5 scenarios. Overall, the GWorkS-model provided clear answers to research questions using the full complexity of crop operations.
    No preview · Article · Jul 2015 · Biosystems Engineering
  • S. Hemming · Os, E.A., van
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    ABSTRACT: Taiwan is een van de meest innovatieve landen in de wereld als het gaat om technologische ontwikkelingen. Dat geldt echter in mindere mate als het gaat om de lokale productie van verse groenten in kassen. De Taiwanese overheid heeft daarom een strategie uitgezet om de lokale tuinbouwsector te moderniseren, de bijdrage aan de nationale economie te verhogen en de positie op binnen- en buitenlandse markten te versterken. Wageningen UR Glastuinbouw speelt daarin een belangrijke rol.
    No preview · Article · Jan 2015

  • No preview · Article · Jan 2015
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    ABSTRACT: Dit project richt zich op mogelijk om vooral in de wintermaanden meer licht in de kas te kunnen krijgen. Middels metingen en modelberekeningen wordt onderzocht in hoeverre er mogelijkheden v.w.b. kasdek, coatings en condensatiegedrag.
    No preview · Article · Jan 2015
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    ABSTRACT: Combination of production of algae and tomato increases efficient use of available resources of greenhouse enterprises, such as controlled environment, water and nutrients, carbon dioxide, greenhouse space and infrastructure and knowledge. No information is available, however, about the potential productivity and related costs of a combined tomato and algae production in Dutch greenhouses. The objective was to determine the algae productivity in tubular photobioreactors (PBRs) and the economic feasibility of combined production of tomato and algae in Dutch greenhouses. A model was developed to predict greenhouse climate from outside climate, to predict tomato and algae biomass production and to analyse scenarios of different locations and dimensions of tubular PBR in the greenhouse with regard to algae productivity and cost price of algae production. The results show that algal productivity is low if PBRs are installed under a tomato crop due to limited light levels. Areal algal productivity was calculated to be 5–6.5 kg DM m−2 if PBRs are installed in a separate greenhouse compartment next to tomato. In this case the minimum cost prices of algae production was calculated to be €11 kg−1 DM algae, which give perspectives for the future. The proposed model is important because it gives insight into the feasibility of algae and tomato production in Dutch greenhouses. This novel model approach and the scenario results provide better knowledge about the potential productivity and related costs and returns of algae production in greenhouses.
    No preview · Article · Jun 2014 · Biosystems Engineering
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    ABSTRACT: Crop production per unit greenhouse area has doubled during the last 25 years in The Netherlands, while the energy use has been drastically reduced. The growth conditions for plants have been improved significantly through understanding crop physiology in combination with new technologies. In this paper some of the recent innovations in greenhouse horticulture are discussed. Semi-closed greenhouses combine energy saving by storing heat in aquifers with yield improvement. These effects on yield are mainly due to a higher CO 2 concentration. The next generation cultivation focuses on energy saving with lower costs. The main components of this concept are an intensive use of energy screens to conserve heat, controlled inlet and distribution of outside air to regulate air humidity, and flexible temperature set-points based on energy losses and plant demand. Greenhouse covers that scatter direct solar radiation without influencing the transmissivity improved crop production in several crops up to 10%. In tomato this increase was due to the improved vertical and horizontal light distribution, a larger photosynthetic capacity of the lower leaves and a larger leaf area index. In heavily shaded potted plants like anthurium and bromeliads, substantially less shading is necessary under diffuse light and well controlled growth conditions, which enhances crop photosynthesis. In this way yield improvements of up to 50% were observed. Some growers have already installed LED lamps as source for assimilation light. Modern LEDs may convert electricity into light 25% more efficiently than high pressure sodium lamps. Even more important are the possibilities to influence physiological and morphological processes by manipulating the positioning, timing and spectrum of the lamps. A large number of these innovations began with crop and greenhouse models, which are powerful tools in research. New developments in simulating plant processes can be found in functional-structural models (FSPM) and systems biology models. They can be used to design new production systems or to predict the ideal phenotype of plants. Plant monitoring based on combinations of plant sensors (e.g., chlorophyll fluorescence) and models will be used more and more to adjust the greenhouse environment to the needs of the plants. Application of models through web-based services are likely to be at the point of large scale introduction to support growers in their decisions.
    No preview · Article · May 2014 · Acta horticulturae
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    ABSTRACT: Two new greenhouse concepts have been developed and evaluated which combine electricity production with plant production, while different principles are used to separate sunlight into a part for plant production and a part for energy production. An important principle in Dutch greenhouse production is: Make maximum use of natural sunlight. It gives free energy and light to crop production. Only in case solar energy provides more light than favourable for crop production, solar energy can be harvested and transformed into heat and/or electricity, crop production remains to be the primary function. In the first greenhouse concept, energy is produced from sunlight surpluses that are normally reflected by shading screens and therefore not usable for crop production. This is realised by focussing the direct part of the sunlight by linear Fresnel lenses in the greenhouse roof to a focal line. There the concentrated sunlight is converted into electricity and heat by a Concentrated Photo Voltaic (CPV) collector. The collector moves automatically depending on the position of the sun. The diffuse part of the sunlight is used for the crop. Light levels in the greenhouse can be controlled by moving the collector in or out of focus. An advanced prototype of that principle has been investigated the last three years on a 500 m2 scale in Bleiswijk, The Netherlands. In the second greenhouse concept, sunlight is split into PAR and NIR by a NIR reflecting film placed on transparent lamellae inside the greenhouse. The lamellae are curved to create a focussing mirror. They are turned depending on the position of the sun to focus the direct NIR radiation on a CPV collector placed in the ridge facing downwards. PAR passes the lamellae and provides light for the crop. A prototype of that principle has been realised and tested last year on a 100 m2 scale in Wageningen, The Netherlands. In both greenhouse concepts the practical working of the systems was evaluated and measurements of thermal and electrical output of the CPV collectors, heat and electricity production and daily light integral in the greenhouse have been carried out.
    No preview · Article · May 2014 · Acta horticulturae
  • S. Hemming · V. Mohammadkhani · J. van Ruijven
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    ABSTRACT: During the last years it has been shown that diffuse light is advantageous for many greenhouse crops. Modern greenhouse covering materials are able to transform direct sunlight into diffuse light. After entering the greenhouse sunlight is scattered and penetrates into the crop, where it is absorbed and used for photosynthesis. Experimental research with different crops (e.g., tomato, cucumber, roses) over the last years showed an improved production under diffuse light conditions, expressed in growth rate or yield of up to 10% in The Netherlands. In the last five years different glass producers have put a lot of effort in development of diffusing greenhouse covering materials. Different structures have been developed and applied on glass for greenhouse application. Glass surface treatments result in regular or irregular patterns on glass such as matt/matt, prismatic, satin, texture and v-grooves. Next to that micro structures are combined with nanostructures, such as anti-reflection treatments (AR), in order to improve light transmission into the greenhouse. It can be shown that material development was able to improve hemispherical light transmission of diffuse glasses by at least 5% in 2013 compared to before 2007, glasses with larger hemispherical transmission and highly diffusing properties are available. Earlier an evaluation method for diffuse materials had been proposed. That method is mainly based on a measurement of the so-called hemispherical light transmission and haze. New possibilities in material technology and increasing knowledge of the relation of diffuse light and crop reactions caused a need to extend evaluation methods. Measuring spatial distribution of transmitted light is suggested next to measuring angular and spectral light transmission. Different new diffuse materials of different producers are measured and evaluated. The results show that diffuse glasses differ in haze and hemispherical light transmission. As well, the choice of basic glass material as the type of anti-reflection treatment are main causes of light spectrum changes. Diffuse structures alone do not cause differences in spectral light transmission. Different structures and AR treatments result in different angular light transmission, which explains differences in hemispherical light transmission. Measurements of spatial light transmission show that many diffusing glasses only cause a narrow light scattering pattern so far.
    No preview · Article · May 2014 · Acta horticulturae
  • F.L.K. Kempkes · J. Janse · S. Hemming
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    ABSTRACT: The goal of the Dutch horticultural sector is to build new greenhouses in 2020 without the use of fossil energy and reduce CO2-emissions with 45% compared to 1990. Closing several screens, mainly during night, is in practice the most common way to reduce heat loss through the cover. In winter during day time transparent screens are closed resulting in significant reduction of light at plant level. Insulating double covering materials can reach higher insulation rates compared to the use of single glass with screens. In an earlier study we showed that new developed coverings using anti-reflection coatings to increase light transmission and low-emission coatings to reduce energy losses only show minor light losses and are suitable as double glazing. This high insulating glass has been integrated in a total greenhouse concept of 500 m2, realized in summer 2010 at the research station of Wageningen UR Greenhouse Horticulture in Bleiswijk. The glass used has a light transmission of 88% perpendicular (πp) and 79% hemispherical (πh) and an u-value of 1.2 Wm-2 K-1 (compared to πp= 90%, πp=82%, u=6.7 Wm-2 K-1 of single glass). In cooperation with growers an optimum growing strategy scenario is developed. Special attention is taken for an energy saving technique for dehumidification while it's known that condensation at double glass will decrease compared to single glass. Two years of tomato growing have showed that energy savings up to 60% of energy use at commercial nursery farms is possible without affecting the production level. In the second year the dehumidification system has been improved and the final result is an energy use of only 456 MJ for heat and 6 kWh electricity to run fans with a tomato production of 72 kg m-2, cultivar 'Komeett'. In that way the energy consumption per kg tomato would be reduced from 18.5 MJ kg-1 to 6.6 MJ kg-1.
    No preview · Article · May 2014 · Acta horticulturae
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    ABSTRACT: Labour is the most dominant cost factor in Dutch cut-rose production. To improve crop production systems and labour management, a generic process modelling approach was developed enabling the impact of different scenarios on labour productivity to be assessed. The crop production system with crop handling processes is defined as a stochastic discrete event system. This paper demonstrates the model flexibility and transferability by adapting an existing model developed for a mobile rose production system to a model for a static growing system for cut roses. The paper describes the adaptation process. The adapted model was validated for the harvest process at a 3.6 ha production site in the Netherlands. Work scenarios were simulated to examine effects of skill, equipment, and harvest management. The model reproduces the harvest process accurately. A seven workday validation for an average skilled harvester showed a relative root mean squared error (RRMSE) under 5% for both labour time and harvest rate. A validation over 96 days for various harvesters showed a higher RRMSE, 15.2% and 13.6% for labour time and harvest rate respectively, mainly caused by the absence of model parameters for individual harvesters. The model was successfully used in scenario studies and indicated that worker skill was an important cost factor, differences associated with harvest trolley type are small, and that an extra harvest cycle per day is only feasible when compensated by product price. Overall, the generic model concept performs well for a static growing system when extended with system specific properties and process elements.
    No preview · Article · Apr 2014 · Biosystems Engineering
  • T. Kierkels · S. Hemming · T.A. Dueck
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    ABSTRACT: Diffuus glas is over vijftien jaar de standaard. Wie nu nieuw bouwt, heeft veel goede redenen om voor diffuus te kiezen en vrijwel geen om het te laten, zeggen Silke Hemming en Tom Dueck van Wageningen UR Glastuinbouw. De inzichten in het nut van diffuus licht én de technische ontwikkelingen schrijden nog elk jaar voort. Een update.
    No preview · Article · Jan 2014
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    ABSTRACT: Een consortium van tuinbouw toeleveranciers bestaande uit Boal systems, VDH Foliekassen, AGC Chemicals Europe (AGCCE) en Van der Valk Systemen heeft een kasconcept ontwikkeld dat een hoge isolatiegraad van het kasdek met beperkte investeringen bereikbaar moet maken. In deze haalbaarheidsstudie zijn de energetische, gewas technische en economische haalbaarheid van dit Glas-Film-Kasconcept, beter bekend als het 2saveEnergy concept bestudeerd.
    No preview · Article · Jan 2014
  • S. Hemming · W. Voogt · A. Sapounas
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    ABSTRACT: De productie van hoogwaardige stoffen zoals kleurstoffen of voedingssupplementen uit algen biedt perspectief voor Nederlandse tuinbouwondernemers. Tuinbouwondernemers hebben veel ervaring om de teeltcondities van hun huidige gewassen door klimaatregeling, CO2 dosering, water- en nutriënten voorziening optimaal te sturen voor een hoogwaardig eindproduct. Ze hebben ervaring met de productie van voedingsmiddelen en om aan de daaraan gestelde kwaliteitseisen te voldoen en logistiek en afzet te organiseren. Het ligt voor de hand om deze ervaring te benutten voor de teelt van algen en hiermee nieuwe duurzame producten te leveren en bij te dragen aan de biobased economy. In dit project is experimenteel onderzoek uitgevoerd naar de invloed van verschillende teeltfactoren op de algenproductie in een nieuwe proeffaciliteit met buisvormige algenreactoren in kassen in Bleiswijk. Daarnaast zijn in dit project economische getallen van investerings- en exploitatiekosten verzameld en is er een economisch rekenmodel ontwikkeld om een realistisch perspectief van algenteelt in kassen in schetsen. Hiermee wordt nieuw strategisch inzicht verkregen wat een geschikt teeltsysteem voor de teelt van hoogwaardige algen in combinatie met tuinbouwproductie op grote schaal in de toekomst is.
    No preview · Article · Jan 2014
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    ABSTRACT: Greenhouse crop system design for maximum efficiency and quality of labour is an optimisation problem that benefits from model-based design evaluation. This study focussed on the harvest process of roses in a static system as a step in this direction. The objective was to identify parameters with strong influence on labour performance as well as the effect of uncertainty in input parameters on key performance indicators. Differential sensitivity was analysed and results were tested for model linearity and superposability and verified using the robust Monte Carlo analysis method since in the literature, performance and applicability of differential sensitivity analysis has been questioned for models with internal stochastic behaviour. Greenhouse section length and width, single rose cut time, and yield influence labour performance most, but greenhouse section dimensions and yield also affect the number of harvested stems directly. Throughput, i.e. harvested stems per second, being the preferred metric for labour performance, is most affected by single rose cut time, yield, number of harvest cycles per day, greenhouse length and operator transport velocity. The model is insensitive for σ of lognormal distributed stochastic variables describing the duration of low frequent operations in the harvest process, like loading and unloading rose nets. In uncertainty analysis, the coefficient of variation for the most important outputs, labour time and throughput, is around 5%. Total sensitivity as determined using differential sensitivity analysis and Monte Carlo analysis essentially agreed. The combination of both methods gives full insight into both individual and total sensitivity of key performance indicators.
    No preview · Article · Dec 2013 · Biosystems Engineering
  • L.F.M. Marcelis · S. Hemming

    No preview · Article · Jan 2013
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    ABSTRACT: The light transmission is an important property for horticultural screens. For energy screens in particular, an accurate measurement of the light transmission is important because these screens are often used during the day, in the winter period when radiation is limited. For shading screens the shading factor is an important factor. To enable a fair comparison between horticultural screens Wageningen UR in collaboration with screen producers Ludvig Svensson, Novavert and Bonar, developed a new protocol for measuring the transmission of horticultural screens. The protocol is based on the earlier developed protocol for measuring the light transmission of greenhouse covering materials, which was developed by TNO and Wageningen UR. The protocol covers the measurement of the transmission of horticultural screens for photosynthetically active radiation (PAR) in terms of hemispherical transmission. The scope of the protocol is limited to transparent screens with hemisferical transmittance greater than 10% and does not include the measurement of blackout screens. The protocol is regarded as the standard by the parties involved. The transmission measured can serve as a basis for comparing horticultural screens and can be used in calculating the performance of greenhouses.
    No preview · Article · Jan 2013

  • No preview · Article · Jan 2013
  • J. Bezemer · T.A. Dueck · S. Hemming
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    ABSTRACT: Het gebruik van diffuus glas heeft een positief effect op de teeltresultaten. Maar de teler die voor de investering wil kiezen, ziet verschillende vragen op zich afkomen. Want het ene diffuse glas is het andere niet. De teler moet de verschillen kennen en de effecten van diffuus glas op zijn gewas begrijpen. Daarna kan hij op zoek naar het glas van zijn keuze.
    No preview · Article · Jan 2013
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    ABSTRACT: 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. A quick scan of protected cultivation systems presently in use reveals that quite a variety of protected cultivation systems can be found throughout the world. They range from fully passive “solar greenhouses” with thick energy storage walls as found in China to the high-tech “closed greenhouses” in Western Europe. This variety is due to local conditions, including the local climate, the availability of resources like water, energy, capital, labor and materials, local legislation and social aspects, to mention a few. This paper presents a methodology of a model based method for designing protected cultivation systems. First results will be reported as well as directions for future research.
    No preview · Article · Nov 2012 · Acta horticulturae
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    ABSTRACT: The Dutch horticultural sector shows interest in production of microalgae. When microalgae and a tomato crop are produced in the same greenhouse, both shared advantage of and competition for resources will occur. In this study a model was developed to predict algae biomass production in tubular photobioreactors (PBR) and to assess the economic feasibility of combined production of tomatoes and algae. The effects of the location of the PBR in the greenhouse, the diameter of the PBR tubes, the algae biomass concentration, the light intensity and the PBR temperature were considered. The economic feasibility of combined production was calculated, taking into account both investment and running costs. Three possible locations for the PBRs were considered. The most sensitive growth factor influencing economics of the systems was light. Economic feasibility of algae production underneath the tomato crop was poor; a minimum unit biomass production cost of 70 € kg-1 dry matter (DM) was calculated. Increasing the light intensity by decrease of the tomato LAI through extra leaf picking increases economic feasibility of algae production underneath the crop. Economic feasibility of algae production in a separated compartment was computed to be good with a minimum unit biomass production cost of 11 € kg-1 DM. The developed model can function as a basis for further research on combined production of a crop and microalgae in Dutch greenhouses.
    No preview · Article · Oct 2012 · Acta horticulturae

Publication Stats

302 Citations
11.64 Total Impact Points

Institutions

  • 2005-2014
    • Wageningen University
      • • Department of Farm Technology
      • • Plant Research International
      • • Department of Food Sciences and Agrotechnology
      Wageningen, Gelderland, Netherlands
  • 2005-2008
    • Wageningen UR
      Wageningen, Gelderland, Netherlands