Control of water supply and specific nutrient application in closed growing systems

T.H. Gieling

    Research output: Thesisinternal PhD, WU

    Abstract

    <strong><font size="4"><p>Keywords:</strong></font>Tichelmann layout, constant drain flow, constant drain concentration, mass-flow, diffusion flow, sensor, Isfet, Chemfet, closed growing system, robust control, loopshaping, Simulink<FONT FACE="Symbol">Ò</font>, MIMO controller, SISO controller, simplex routine, simplex matrix.</p><p>Plants in modern greenhouses receive water and nutrients from a diluter of chemical solutes. Supply lines of a trickle irrigation system dispense the nutrient solution by means of thin capillary hoses, to each individual plant. Dependent on the type of growing system - either a NFT or a substrate system - the drain will run-off immediately or it will linger for some time in the substrate mat. In a closed system for water and nutrient supply, the drain water returns to the nutrient dispenser, where it is prepared for reuse by mixing it with clean water. The thesis starts with an overview of the state of the art of water supply and nutrient application systems.</p><p>The purpose of the design study in this thesis is to enable completely closed growing systems for water and nutrients, to be applied in horticulture practise, and to improve the technological level of their control to such an extend that it is comparable to the level of computerised climate controllers in greenhouses. It is argued that as a basic requirement the system should have the ability to control the drain flow and the concentration of individual ions in the drain to any predefined set value. An analysis is given of the dynamics of movement of water and nutrients in substrates in relation to nutrient uptake, supply-flow and mass-flow. From a mass balance of nutrients, a control strategy for nutrient application in closed growing systems is suggested that is useful in the design of control algorithms. This strategy keeps the concentration of the individual ions in the drain constant by feedback of ion concentration and drain flow. In doing so, it compensates intrinsically for the plant's uptake of ions.</p><p>The creation of a system with feedback control requires appropriate sensors and the ability to blend nutrient solution for values demanded by the controller. The ion specific feedback control of fertiliser application implies that ions need to be measured individually. The thesis describes a novel type of ion specific analyser, based on a set of Chemfet sensors. This instrument, as a result of this research, is the prototype of the first series of commercially available equipment for horticulture. Continuous measurement implies sensors with an electrical output, connected to an automatic data acquisition system with in-line calibration. In horticulture applications the lifetime expectancy of a sensor should at least be 6 to 9 months.</p><p>In contrast to open loop control based on a prediction of uptake, feedback control automatically compensates for fluctuations in evapo-transpiration and nutrient uptake. Uptake by the plant is treated as a disturbance. Comparison of simulation results, with data from an implemented controller in a greenhouse, shows the success of the design.</p><p>The so-called "Tichelmann" layout of supply lines is proposed to improve the dynamic properties of the supply system. The design study demonstrates and recommends robust controller design as a tool to achieve robust performance and robust stability as qualities of the controlled process to compensate for seasonal changes in the root mat or imperfect models. The modifications to the ideal design arising from the desire in practice for pulse wise water and nutrient injection, as well as aspects related to the blending are considered as well.</p>
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    • Wageningen University
    Supervisors/Advisors
    • van Straten, Gerrit, Promotor
    • Bontsema, J., Promotor, External person
    Award date5 Nov 2001
    Place of PublicationS.l.
    Publisher
    Print ISBNs9789058085252
    Publication statusPublished - 2001

    Fingerprint

    water supply
    controllers
    sensors (equipment)
    nutrients
    ions
    horticulture
    mass flow
    water
    greenhouses
    nutrient uptake
    nutrient solutions
    experimental design
    hoses
    uptake mechanisms
    dispensers
    nutrient balance
    closed loop systems
    drainage water
    ion transport
    microirrigation

    Keywords

    • closed systems
    • nutrient balance
    • nutrients
    • application
    • water supply
    • automatic control
    • greenhouse horticulture

    Cite this

    @phdthesis{1b6da1d2729947bfa570d7a53029b5f8,
    title = "Control of water supply and specific nutrient application in closed growing systems",
    abstract = "Keywords:Tichelmann layout, constant drain flow, constant drain concentration, mass-flow, diffusion flow, sensor, Isfet, Chemfet, closed growing system, robust control, loopshaping, Simulink<FONT FACE={"}Symbol{"}>{\`O}, MIMO controller, SISO controller, simplex routine, simplex matrix.Plants in modern greenhouses receive water and nutrients from a diluter of chemical solutes. Supply lines of a trickle irrigation system dispense the nutrient solution by means of thin capillary hoses, to each individual plant. Dependent on the type of growing system - either a NFT or a substrate system - the drain will run-off immediately or it will linger for some time in the substrate mat. In a closed system for water and nutrient supply, the drain water returns to the nutrient dispenser, where it is prepared for reuse by mixing it with clean water. The thesis starts with an overview of the state of the art of water supply and nutrient application systems.The purpose of the design study in this thesis is to enable completely closed growing systems for water and nutrients, to be applied in horticulture practise, and to improve the technological level of their control to such an extend that it is comparable to the level of computerised climate controllers in greenhouses. It is argued that as a basic requirement the system should have the ability to control the drain flow and the concentration of individual ions in the drain to any predefined set value. An analysis is given of the dynamics of movement of water and nutrients in substrates in relation to nutrient uptake, supply-flow and mass-flow. From a mass balance of nutrients, a control strategy for nutrient application in closed growing systems is suggested that is useful in the design of control algorithms. This strategy keeps the concentration of the individual ions in the drain constant by feedback of ion concentration and drain flow. In doing so, it compensates intrinsically for the plant's uptake of ions.The creation of a system with feedback control requires appropriate sensors and the ability to blend nutrient solution for values demanded by the controller. The ion specific feedback control of fertiliser application implies that ions need to be measured individually. The thesis describes a novel type of ion specific analyser, based on a set of Chemfet sensors. This instrument, as a result of this research, is the prototype of the first series of commercially available equipment for horticulture. Continuous measurement implies sensors with an electrical output, connected to an automatic data acquisition system with in-line calibration. In horticulture applications the lifetime expectancy of a sensor should at least be 6 to 9 months.In contrast to open loop control based on a prediction of uptake, feedback control automatically compensates for fluctuations in evapo-transpiration and nutrient uptake. Uptake by the plant is treated as a disturbance. Comparison of simulation results, with data from an implemented controller in a greenhouse, shows the success of the design.The so-called {"}Tichelmann{"} layout of supply lines is proposed to improve the dynamic properties of the supply system. The design study demonstrates and recommends robust controller design as a tool to achieve robust performance and robust stability as qualities of the controlled process to compensate for seasonal changes in the root mat or imperfect models. The modifications to the ideal design arising from the desire in practice for pulse wise water and nutrient injection, as well as aspects related to the blending are considered as well.",
    keywords = "gesloten systemen, voedingsstoffenbalans, voedingsstoffen, toepassing, watervoorziening, automatische regeling, glastuinbouw, closed systems, nutrient balance, nutrients, application, water supply, automatic control, greenhouse horticulture",
    author = "T.H. Gieling",
    note = "WU thesis 3071 Met lit. opg. - Met samenvatting in het Engels en Nederlands Proefschrift Wageningen",
    year = "2001",
    language = "English",
    isbn = "9789058085252",
    publisher = "S.n.",
    school = "Wageningen University",

    }

    Gieling, TH 2001, 'Control of water supply and specific nutrient application in closed growing systems', Doctor of Philosophy, Wageningen University, S.l..

    Control of water supply and specific nutrient application in closed growing systems. / Gieling, T.H.

    S.l. : S.n., 2001. 133 p.

    Research output: Thesisinternal PhD, WU

    TY - THES

    T1 - Control of water supply and specific nutrient application in closed growing systems

    AU - Gieling, T.H.

    N1 - WU thesis 3071 Met lit. opg. - Met samenvatting in het Engels en Nederlands Proefschrift Wageningen

    PY - 2001

    Y1 - 2001

    N2 - Keywords:Tichelmann layout, constant drain flow, constant drain concentration, mass-flow, diffusion flow, sensor, Isfet, Chemfet, closed growing system, robust control, loopshaping, Simulink<FONT FACE="Symbol">Ò, MIMO controller, SISO controller, simplex routine, simplex matrix.Plants in modern greenhouses receive water and nutrients from a diluter of chemical solutes. Supply lines of a trickle irrigation system dispense the nutrient solution by means of thin capillary hoses, to each individual plant. Dependent on the type of growing system - either a NFT or a substrate system - the drain will run-off immediately or it will linger for some time in the substrate mat. In a closed system for water and nutrient supply, the drain water returns to the nutrient dispenser, where it is prepared for reuse by mixing it with clean water. The thesis starts with an overview of the state of the art of water supply and nutrient application systems.The purpose of the design study in this thesis is to enable completely closed growing systems for water and nutrients, to be applied in horticulture practise, and to improve the technological level of their control to such an extend that it is comparable to the level of computerised climate controllers in greenhouses. It is argued that as a basic requirement the system should have the ability to control the drain flow and the concentration of individual ions in the drain to any predefined set value. An analysis is given of the dynamics of movement of water and nutrients in substrates in relation to nutrient uptake, supply-flow and mass-flow. From a mass balance of nutrients, a control strategy for nutrient application in closed growing systems is suggested that is useful in the design of control algorithms. This strategy keeps the concentration of the individual ions in the drain constant by feedback of ion concentration and drain flow. In doing so, it compensates intrinsically for the plant's uptake of ions.The creation of a system with feedback control requires appropriate sensors and the ability to blend nutrient solution for values demanded by the controller. The ion specific feedback control of fertiliser application implies that ions need to be measured individually. The thesis describes a novel type of ion specific analyser, based on a set of Chemfet sensors. This instrument, as a result of this research, is the prototype of the first series of commercially available equipment for horticulture. Continuous measurement implies sensors with an electrical output, connected to an automatic data acquisition system with in-line calibration. In horticulture applications the lifetime expectancy of a sensor should at least be 6 to 9 months.In contrast to open loop control based on a prediction of uptake, feedback control automatically compensates for fluctuations in evapo-transpiration and nutrient uptake. Uptake by the plant is treated as a disturbance. Comparison of simulation results, with data from an implemented controller in a greenhouse, shows the success of the design.The so-called "Tichelmann" layout of supply lines is proposed to improve the dynamic properties of the supply system. The design study demonstrates and recommends robust controller design as a tool to achieve robust performance and robust stability as qualities of the controlled process to compensate for seasonal changes in the root mat or imperfect models. The modifications to the ideal design arising from the desire in practice for pulse wise water and nutrient injection, as well as aspects related to the blending are considered as well.

    AB - Keywords:Tichelmann layout, constant drain flow, constant drain concentration, mass-flow, diffusion flow, sensor, Isfet, Chemfet, closed growing system, robust control, loopshaping, Simulink<FONT FACE="Symbol">Ò, MIMO controller, SISO controller, simplex routine, simplex matrix.Plants in modern greenhouses receive water and nutrients from a diluter of chemical solutes. Supply lines of a trickle irrigation system dispense the nutrient solution by means of thin capillary hoses, to each individual plant. Dependent on the type of growing system - either a NFT or a substrate system - the drain will run-off immediately or it will linger for some time in the substrate mat. In a closed system for water and nutrient supply, the drain water returns to the nutrient dispenser, where it is prepared for reuse by mixing it with clean water. The thesis starts with an overview of the state of the art of water supply and nutrient application systems.The purpose of the design study in this thesis is to enable completely closed growing systems for water and nutrients, to be applied in horticulture practise, and to improve the technological level of their control to such an extend that it is comparable to the level of computerised climate controllers in greenhouses. It is argued that as a basic requirement the system should have the ability to control the drain flow and the concentration of individual ions in the drain to any predefined set value. An analysis is given of the dynamics of movement of water and nutrients in substrates in relation to nutrient uptake, supply-flow and mass-flow. From a mass balance of nutrients, a control strategy for nutrient application in closed growing systems is suggested that is useful in the design of control algorithms. This strategy keeps the concentration of the individual ions in the drain constant by feedback of ion concentration and drain flow. In doing so, it compensates intrinsically for the plant's uptake of ions.The creation of a system with feedback control requires appropriate sensors and the ability to blend nutrient solution for values demanded by the controller. The ion specific feedback control of fertiliser application implies that ions need to be measured individually. The thesis describes a novel type of ion specific analyser, based on a set of Chemfet sensors. This instrument, as a result of this research, is the prototype of the first series of commercially available equipment for horticulture. Continuous measurement implies sensors with an electrical output, connected to an automatic data acquisition system with in-line calibration. In horticulture applications the lifetime expectancy of a sensor should at least be 6 to 9 months.In contrast to open loop control based on a prediction of uptake, feedback control automatically compensates for fluctuations in evapo-transpiration and nutrient uptake. Uptake by the plant is treated as a disturbance. Comparison of simulation results, with data from an implemented controller in a greenhouse, shows the success of the design.The so-called "Tichelmann" layout of supply lines is proposed to improve the dynamic properties of the supply system. The design study demonstrates and recommends robust controller design as a tool to achieve robust performance and robust stability as qualities of the controlled process to compensate for seasonal changes in the root mat or imperfect models. The modifications to the ideal design arising from the desire in practice for pulse wise water and nutrient injection, as well as aspects related to the blending are considered as well.

    KW - gesloten systemen

    KW - voedingsstoffenbalans

    KW - voedingsstoffen

    KW - toepassing

    KW - watervoorziening

    KW - automatische regeling

    KW - glastuinbouw

    KW - closed systems

    KW - nutrient balance

    KW - nutrients

    KW - application

    KW - water supply

    KW - automatic control

    KW - greenhouse horticulture

    M3 - internal PhD, WU

    SN - 9789058085252

    PB - S.n.

    CY - S.l.

    ER -