NL1031357C2 - Fog greenhouse. - Google Patents

Description

Title: Spray greenhouse 5 The invention relates to a new type of greenhouse for growing crops in agriculture and / or horticulture, more particularly a greenhouse in which the control of the climate conditions is regulated on the basis of measurements in the greenhouse.

Nowadays, growers in agriculture and horticulture are paying more and more attention to regulating the climate conditions in greenhouses, not least because of the environmental and energy-saving effects of such measures. In addition, many systems have already been developed in which excess heat that is present in the greenhouse in the summer is stored (usually in the soil) and returned in a colder period via a heat pump, thus leading to a lower total energy consumption. These systems are often self-controlling, that is, switching on and off heat storage or heat return is controlled via a system that measures the temperature at different places in the greenhouse and links it to a control system.

20 There are already various innovations in the field of climate control in greenhouses. Innogrow BV, for example, has developed the Closed Greenhouse concept, which uses a mixture of mechanical cooling by means of heat exchangers and fans that bring cooled air into the greenhouse via perforated air hoses, and ventilation through air vents to dehumidify at night. . There are also (test) greenhouses that work with side wall ventilation, separate cooling units above the crop (eg with the cultivation of Phalaenopsis) and the like.

These greenhouses are therefore always equipped with large installations such as cooling and heating systems, watering systems and associated water collection systems, and the like. The presence of all these technical provisions often complicates cultivation due to the large amount of pipes that run through the cultivation area and the large installations that are required to achieve the desired result.

In addition, there are still problems in the existing greenhouse systems, eg

· To limit the greenhouse temperature due to mechanical cooling in the summer when sunlight is high, a large installed cooling capacity is required.

• to achieve a good temperature distribution in the greenhouse, high air flow rates must be used.

· Mechanical cooling generates much more heat from the greenhouse air in the summer than is required for the same area in the winter. This heat is no longer economically usable.

One of the measures that can be taken to better regulate the temperature management in greenhouses is cooling by means of a misting installation. Such a spraying installation can be incorporated in a control system as described, for example, in Japanese patent specification JP 2003/289728 wherein, driven by a temperature measurement, cooling by spraying is switched on or off as required. The fogging is also switched off when a humidity limit is reached.

In Japanese Patent Specification JP 2005/176721, fogging is used to maintain a certain relative humidity (less than 90% RH). U.S. Pat. No. 4,856,227 describes a (temperature and humidity) controlled irrigation or spraying for maintaining a vapor above a bed of flower bulbs.

Although, therefore, there are already greenhouses in which the climate is controlled by means of nebulization, the control of the degree of nebulization is controlled on the basis of temperature and / or humidity 3 measurements. As a result, optimum climate conditions are not yet achieved for the plants, because in addition to these parameters, the CO2 content of the air and the amount of light that reaches the plants also influence the effect of the atomization on the growth of the plants.

The invention now solves this problem by making the control of the atomization, optionally in combination with other climate-influencing installations, such as cooling or heating installations, etc., dependent on the status of the stomata of the plant. To this end the invention comprises in its broadest form a greenhouse system for use in agriculture and / or horticulture, comprising: a. A detector for the direct or indirect detection of the status of the stomata of one or more plants in the greenhouse system; b. an adjustable water spraying installation; C. a control unit that controls the water spraying installation based on the data obtained by the detector from a.

The greenhouse system of the invention preferably further comprises one or more of the group of detectors consisting of one or more infrared meters for measuring the leaf temperature, one or more light meters for measuring the light level above the plant, one or more thermometers for measuring of the temperature of the greenhouse and one or more hygrometers for measuring the humidity.

The greenhouse system according to the invention can furthermore comprise one or more of the group of installations consisting of one or more controllable ventilation systems, one or more controllable cooling installations; one or more controllable heating installations, one or more controllable CO2-producing installations, one or more heat storage installations and one or more light control installations.

4

With such a system, the control of said installation (s) can take place on the basis of the data obtained by said detectors.

In another embodiment, the invention further comprises a method for controlling the climate conditions in a greenhouse, comprising: a. Directly or indirectly detecting the status of the stomata of one or more plants in the greenhouse; and B. on the basis of the detection under a. controlling a spraying installation and possibly other climate control means in the greenhouse to influence the status of the stomata.

DESCRIPTION OF THE FIGURES 15

Figure 1 shows the ratio between the amount of light, the percentage of CO2 present and the amount of photosynthesis (Source: http://www.egbeck.de/skripten/12/bsl2.htm). Figure 2 shows the relationship between leaf temperature and photosynthesis at different CO2. concentration (source: Intelligrow: a component-based climate control system for decreasing greenhouse energy consumption. Aaslyng, -JM; Ehler, -N; Karlsen (-P; Rosenqvist, -E., Acta-Horticulturae. 1999; (507): 35-41) 25

Figure 3 Shows the status of stomata in a leaf of a plant (Crassula ovata). The stomata is open in the left panel and closed in the right panel. 1 = open stomata, 2 = closed stomata, 3 = closing cells, 4 = neighboring cells, 5 = wash plates.

5

The stomata is opened or closed by the movement of the two closing cells. The so-called breathing cavity is located under the stomata. Figure 3B shows a schematic cross section of such a stomata. The gas exchange is indicated under light conditions between the respiratory cavity and the air.

Figure 4 shows the relationship between the opening of the stomata (expressed as a percentage of the maximum opening = 100% [stomatal aperture]), temperature and moisture deficit (vapor pressure difference between air and leaf) at a certain light intensity. Source: Wilson, C-C., The effect of some environmental factors on the movements of guard cells. Plant Physiol. 1948; 23: 5-37.

FIG. 5 shows a schematic control diagram for controlling the climate control in the greenhouse according to the invention. See text for description.

FIG. 6 is a schematic drawing of a greenhouse system according to the invention. See text for description.

FIG. 7 is a Psychrometric Chart, one of the many possible forms of a diagram in which, among other things, the relationship between air temperature, moisture content of the air expressed in absolute moisture content (g / kg air) and relative moisture content (% of the maximum moisture content), the specific gravity of air and the enthalpy, consisting of palpable and latent heat, is indicated.

From such a diagram can be read, among other things, how much energy is needed to heat a certain amount of air with a certain humidity, a certain number of degrees, what the dew point of this air is, how much energy is needed to cool this air, what the effect on is the air temperature and humidity if a certain amount of water is sprayed into the air per unit of time, and so on.

Because the properties of moist air also depend on the air pressure, different diagrams are used in practice for different heights. The example given is suitable for use at sea level.

DETAILED DESCRIPTION

The invention shows that it is surprisingly possible to generate more biomass in a standard greenhouse, such as that used in agriculture and / or horticulture, using a minimal adaptation, namely by making use of atomization as a supplement on the) regulation of the greenhouse climate. Installing a misting installation requires - compared to the cooling and heating installations used in the prior art - only a minimal technical and economic effort. For an application of fogging according to the invention under conditions such as in the Netherlands, where the solar radiation can reach values up to approximately 800 W / m2 (in the greenhouse), a spraying capacity of approximately 0.5-1 liter of water / m2 / hours to be installed.

In addition to the advantage of obtaining a higher biomass per m2 of greenhouse area (due to an optimum photosynthesis of the crop), less energy is also required for operating the installation, compared to existing greenhouse systems. In addition, CO2 emissions are reduced, making the greenhouse system of the invention optimally suitable for meeting the increasingly strict standards set by the government. This can even result in positive effects on emission allowances. Finally, the amount of residual heat to be stored in the summer is minimized, so that it can be reused in its entirety.

7

As a result, the size of the storage and recovery installation remains limited and no losses occur.

The major advantage of a greenhouse system according to the invention is that by measuring and adjusting the status of the stomata of the plant (s) an optimum climate condition is created for the photosynthesis and the physiological processes (growth, flowering) of it that depend on it the plant. Photosynthesis is the engine of the plant's growth process. (Sun) light provides the energy with which in the green parts assimilates (carbohydrates) are formed from CO2 and water. These assimilates are later converted by the plant into energy and building materials. CO2 from the environment is absorbed through the stomata. With larger amounts of light, the plant can process more CO2 than is naturally present in the ambient air. However, solar radiation also leads to evaporation from the leaf. That evaporation process is controlled by opening the stomata more or less far away. In the event of a risk of wilting, the stomata close, which also makes it more difficult to absorb CO2. As a result, the growth potential is only partially utilized. By cooling with atomization, the humidity of the greenhouse remains structurally high and the risk of wilting does not occur, as a result of which the stomata remain maximally opened and the supply of CO2 can continue unimpeded.

Due to the high humidity that is achieved through misting, 'tropical' climate conditions arise in the greenhouse. However, it is known that plants thrive extremely well in a tropical environment. The plants can withstand the combination of increased air humidity and high temperature when the climate control is adjusted to the behavior of the stomata with which the plant itself regulates the absorption of CO2 from the air and the leaf evaporation.

Due to the rise in temperature and air humidity, the enthalpy of the air in the greenhouse increases sharply in comparison with the enthalpy of the outside air. This makes it possible to have large amounts of energy removed from the greenhouse with relatively little air exchange (ventilation). The ventilation rate will be limited to a value of approximately 10., for which only a small opening of the air vents of the greenhouse is required. Due to the low air exchange, the CO2 emission will be reduced considerably, namely by a factor of 3 to 5, i.e. a reduction of 60-80%. This effect is further enhanced by the fact that the stomata remains open compared to the current systems with lower CO2 concentrations, while still making full use of potential photosynthesis. If too little CO2 is available in the greenhouse air, this can be supplemented with technical measures (installation for enriching greenhouse air with CO2, for example with a gas cylinder or via a carbon dioxide generator, which burns propane or another natural gas).

Central to the concept is the measurement of the status of the stomata of the plant. This can be done via a direct visual measurement at the micro level of the stomata itself, but this can also be done indirectly through measurements in the immediate vicinity of the stomata.

Direct, visual measurement is preferably performed by a camera attached to a microscope (e.g. as described in Zhu et al., Plant Cell Environment, 21, 813, 1998).

Indirect determination of the position of the stomata is carried out by measuring the levels of, among other things, CO2, O2 and light very close to the stomata as well as the temperature of the leaf and the environment and then using these signals as input for a calculation model that based on comparison with stored values as output, for example, provides the opening of the stomata. This method is referred to as "software sensor" or simply "soft sensor".

9

The optimum position of the stomata is completely open, because this allows a maximum entry of CO2 and thus a maximum utilization of the potential photosynthesis. There are various mechanisms that cause the stoma to close if the environmental conditions are not optimal, or if the internal processes in the leaf give cause for this.

One of those mechanisms is that the stomata partially closes if the leaf evaporation becomes too high (risk of wilting). Apparently the supply of energy to the leaf by solar radiation and / or convection is then too high. By closing the stomata, the supply of CO2 stagnates, which is at the expense of dry matter production. At such a moment the misting must be switched on in order to effect not only a reduction in the temperature, but also an increase in the air humidity. This will cause the leaf to evaporate less, the danger of wilting has disappeared and the stomata will open again.

In addition, it is preferable to measure the leaf temperature of the crop, eg by means of an infrared meter, and to measure the amount of available light for photosynthesis (PAR light, Photosynthetically Active Radiation) above the crop, e.g. suitable light meter. The photosynthesis process is in fact dependent on these factors (see Figure 1). From the CO2, leaf temperature and light measurements, together with the information about the condition of the stomata, a control method can be drawn up to optimally adapt the climate in the greenhouse to the needs and optimum growth of the crop. A general overview of a control scheme is given in Figure 5.

In such a control scheme, three starting situations are preferably distinguished on the basis of the available amount of light, i.e. whether the light source is sunlight or lamp light and / or no light source is present (dark). For each of these three situations, an ideal initial state (G, H and L, see Figure 5, respectively) must be defined on the basis of the presence of the climate provisions in greenhouse 5 (presence / absence of one or more adjustable ventilation systems, a or more controllable cooling installations, one or more controllable heating installations, one or more controllable CO2-producing installations, one or more heat-storage installations and one or more lighting control installations) and depending on the requirements of the crop to be grown. For example, some plants will thrive better at a higher temperature, higher light intensity and or higher relative humidity than other plants. With artificial lighting, the day / night rhythm must also be set so that it is optimal for the crop to be grown. If necessary, these settings can be adjusted to the growth stage of the crop. The initial states G, H, L therefore consist of a set of target values for the different greenhouse conditions that are considered ideal for the crop.

These target values associated with these initial conditions can be read, inter alia, from graphs known for most crops as shown, for example, in Figs. 1, 2 and 4. If the ventilation windows in a greenhouse are closed during the day, the temperature, the CO2 content and the humidity increase. If sufficient CO2 is available in the greenhouse, the amount that the plant absorbs is primarily determined by the amount of light, as seen in Figure 1. Based on sufficient available light, the (leaf) temperature also appears to have an influence. With an increased concentration of CO2, such as can occur in a closed greenhouse or can be created via extra CO 2 supply, the maximum uptake is at a higher temperature than with a limiting CO2 content (Figure 2).

11

With this starting condition there is a (usually maximum) position of the stomata. If the stomata is unchanged, the climate system in the greenhouse is controlled in such a way that this initial state is maintained. Although the opening of the stomata is primarily determined by the amount of light, a stomata also causes the evaporation and therefore has an effect on the leaf temperature. Therefore, the evaporation can be a limiting factor for the stomata being open. In particular the VPD (Vapor Pressure deficit) (difference in vapor pressure between air in the environment of the leaf and the air in the cavities 10 of the leaf) plays an important role as shown in figure 4. This also shows that for maximum photosynthesis the playing field is limited: between 60-100% RH and a temperature between 20-30 ° C. If the stomata indeed start to close due to evaporation, the climate control in the greenhouse will be controlled according to the diagram of figure 5 in such a way that a new optimum condition is achieved (corrected G, H or L). This is preferably solved by controlling the atomizing installation, as a result of which the humidity and the CO2 concentration rise and the temperature does not rise too high (this in contrast to the conventional way of cooling as discussed above, whereby the air humidity and CO2 concentration fall).

Then it must be checked whether the plant temperature is still above the dew point of the greenhouse air. If it drops below the dew point, the moisture from the air starts to condense on the plants, which not only results in a reduction of photosynthesis, but can also promote the development of rot and infectious diseases. The difference between the plant temperature and the dew point temperature of the greenhouse air is preferably increased again by switching off the spraying (and / or additional cooling). As a result of this adjustment, the value of G, H or L is corrected again.

12

By continuously measuring the position of the stomata and constantly adapting the settings of the atomization and any other climate installations in the greenhouse, the system is able to change one of the climate influencing factors (eg light, temperature, relative humidity, etc.) to regulate the climate in the greenhouse very quickly again to a stable condition, whereby the position of the stomata is optimally kept under the prevailing conditions. The position of the stomata is preferably measured every minute and the cycle is completed, so that an almost continuous control is created.

10

With a non-ventilated greenhouse (ie a greenhouse with closed air vents), when the leaf temperature exceeds a critical upper limit (depending on the crop to be grown), the air vents can be opened and / or an additional cooling installation (with which water vapor can be condensed and heat can be discharged) can be switched on, whereby these installations, as well as the dosed amount of CO2, can be adjusted to the position of the stomata. It is known that the plant can also close the stomata with a too high concentration of CO2.

20 The greenhouse temperature and the humidity must remain within a certain optimal "working area". If either the greenhouse temperature or the humidity falls outside this working area, this indicates insufficient energy dissipation. This is then increased by gradually increasing the (mechanical) ventilation.

As stated, a too high CO2 concentration causes the stomata to close. If the other conditions are optimal, the addition of CO2 is gradually reduced when detecting closed stomata.

During the night, when there is no sunlight or growth light, the greenhouse climate will be regulated in a conventional manner by means of ventilation and possibly additional dehumidification. Because little or no photosynthesis takes place (in the case of artificial growth light) and, moreover, there is hardly any crop evaporation, switching on the misting installation will generally not be necessary. Of course, it is advantageous to control the greenhouse climate during the dark situation, as indicated in Figure 5, in such a way that the opening of the stomata (whereby CO2 is now released to the air) is optimally maintained.

The added value of the invention is therefore that the equilibrium position can be accurately achieved on the basis of the status of the stomata, whereby the photosynthesis process proceeds optimally.

An additional advantage of the greenhouse system described above is that the amount of acceptable light (and heat) can be greater than in conventional greenhouse systems. There, it is necessary to work regularly with shielding sunlight to limit the cooling load, which reduces the potential photosynthesis and therefore crop growth proportionally. In the greenhouse system of the invention, the atomization can provide for more efficient (and cheaper) cooling, so that an excess of sunlight need never or only occasionally be protected. This effect can be further enhanced by using extra spraying of water just above the greenhouse cover, that is to say on the outside of the greenhouse in the case of very much solar radiation. The air layer just below the greenhouse cover and the air layer just above the greenhouse cover can be seen as a whole in this context. The enthalpy of the outside air does not change if the sprayed water is absorbed in it adiabatically. As a result, it makes no difference in principle whether the water above the greenhouse cover is sprayed in the outside air or below the greenhouse cover in the greenhouse air. After all, the cooling effect in the greenhouse is the same, because the air humidified outside the greenhouse can now absorb more energy in the greenhouse. A condition here, however, is that the wind speed above the greenhouse is not too great, because otherwise the humidified air blows away above the greenhouse before it can enter the greenhouse. The greenhouse covering can therefore contribute to increasing the air humidity in the greenhouse, so that less water needs to be sprayed inside the greenhouse and the chance of the crop dropping and becoming wet is reduced.

In some conventional systems, roof watering is used to cause a cooling effect in the greenhouse. Due to the higher greenhouse temperature and the high relative humidity, this cooling effect will be much greater in the greenhouse system of the invention than in conventional systems. More condensation will also occur, which promotes heat transfer. Roof irrigation can also have a useful effect at night: by cooling the greenhouse cover, condensation against the greenhouse cover within the greenhouse is promoted, so that the air humidity is controlled without air exchange.

15 Thanks to a greatly increased enthalpy of the greenhouse air, more efficient methods can be used for harvesting (solar) heat and reusing it for greenhouse heating. In conventional systems, heat is extracted from the greenhouse air for storage in the soil and for later use. A heat pump is used for this later use. A relative humidity of 70-80% is maintained in these 20 conventional systems. In the current greenhouse system, where the air has a typical relative humidity of 90-95%, the air therefore has a higher enthalpy and will condense at higher temperatures than dry, colder air. As a result, solar heat can be harvested in a heat exchanger with a smaller volume of greenhouse air to be displaced and at water temperatures on the cooling side that are closer to the greenhouse temperature.

Alternative forms of heat recovery are also within reach. Harvesting (solar) heat can, for example, with a cooling surface that is located underneath the plants and can therefore form a large surface that does not remove light for plant growth and cannot cause dripping damage to the plants due to falling condensation drops. The water temperature in this cooling surface will be relatively high under normal conditions (> 20 ° C). Because the cold air drops, no fans are needed to harvest the heat. These higher temperatures also increase the heat content of a stored water volume, so that a heat recovery pump needs to move less water. Moreover, better use can be made of the existing heating systems, such as a tube-rail network.

10

By applying a climate system as described above, the regulation is no longer based on greenhouse air temperature and RH, but on energy balance and moisture balance, where temperature and relative humidity are preconditions (see also the diagram of Figure 7). Additionally, a greenhouse system of the invention makes it possible to accurately determine CO2 uptake. Due to the fact that much less CO2 leaks out, the uptake of CO2 can be derived from the dosing rate and the measured concentration in the greenhouse. This makes it possible to measure the efficiency of the photosynthesis process. Moreover, this is useful for measuring and preventing stress. Plant stress is characterized by the fact that the plant is in such a situation that it is necessary to take emergency measures to stop the normal growth process and to switch to a survival strategy. Closing the stomata in the event of the risk of wilting is a good example of this. Because the evaporation and therefore the cooling is reduced, the leaf temperature increases considerably (with the risk of local dehydration). CO2 absorption and photosynthesis then stop, but this is a better survival strategy for the plant than to dry out completely.

16

Because in the new greenhouse system of the invention the climate control is no longer primarily geared to greenhouse temperature, but to energy discharge, a more accurate control of the ventilation (via ventilation openings) is required, in particular in the lower range of the temperature / humidity graph (see Figure). 7) This means that ventilation windows and / or mechanical ventilation must be able to be precisely controlled;

A possible drawback of the system of the invention is that the high air humidity entails the risk of diseases and pests coupled with condensation on the crop.

However, effective control strategies with crop condensation models, among other things, are already being applied in practice, with which the risk of condensation on the crop can be greatly reduced.

Moreover, these diseases and pests, if they occur unexpectedly, can be controlled in the usual way, for example by admixing antibiotics into the water to be sprayed.

All in all, the many advantages outweigh the last two disadvantages. These advantages also have an economic character: the greenhouse system of the invention requires only a relatively limited investment, which can be built into existing greenhouses without any problem. In addition, much less electrical energy is required to operate the installation. The size of heat storage and recovery installations can also be more limited than with conventional systems. Furthermore, the reduced CO2 emission gives possibilities for a permanent future use and possibly tradability of emission allowances.

In the example below, which is not to be construed as limiting, a description is given of a greenhouse system according to the invention.

30 17

EXAMPLE

The control scheme given in Figure 5, discussed in the above description, is a good example of a cash register system of the present invention. On the basis of this description, the skilled person will be able to apply the invention in a greenhouse of his choice, depending on the specific situation. The above description provides those skilled in the art with guidelines and specific instructions that must be met to make optimum use of the invention.

Figure 6, finally, gives a schematic example of a greenhouse system according to the invention. Central to this is a measuring and control system that, based on the measurement of the opening of the stomata, and measurement of humidity, sunlight (energy) and CO2 concentration, controls a spraying installation and possibly other equipment. The mist installation is preferably suspended at the top of the entire greenhouse space. The greenhouse additionally contains an air treatment unit with a fan, so that the air can not only be heated or cooled, but where an air filter is also present to filter out the germs (traces of bacteria and fungi) that occur in the air. In addition, the greenhouse contains ventilation openings (windows) which can be designed both in the roof and in the side walls, and a screen cloth (also for roof and / or side walls) with which the incident sunlight can be tempered.

The aforementioned air handling unit is fed via a heating boiler and / or cooling machine. The surplus energy is preferably stored in so-called aquifers. An aquifer is a water-bearing soil layer. An aquifer suitable for heat storage usually consists of a layer of sand that is surrounded by 'waterproof' (horizontal) layers of clay. The groundwater flows in the sand layer may only have a limited speed to limit heat losses. With an aquifer, the heat is stored directly in the (ground) water and the sand 18. Aquifers can be used for both high and low temperature storage. The aquifer is connected to the cooling / heating system via a conventional heat pump. The embodiment shown in FIG. The greenhouse system shown in Fig. 6 further comprises an installation for supplying CO2 and a system for supplying water to the greenhouse system as feed for the mist installation, for energy transport and / or for watering the plants.

10 1031357

Claims (7)

A greenhouse system for use in agriculture and / or horticulture, comprising: a. A detector for the direct or indirect detection of the status of the stomata of one or more plants in the greenhouse system; 5 b. an adjustable water spraying installation; c. a control unit that controls the water spraying installation based on the data obtained by the detector from a. Greenhouse system according to claim 1, further comprising one or more of the group of detectors consisting of one or more infrared meters for measuring the leaf temperature, one or more light meters for measuring the light level above the plant, one or more thermometers for measuring the temperature of the greenhouse and one or more hygrometers for measuring the humidity. Greenhouse system according to claim 1 or 2, further comprising one or more of the group of installations consisting of one or more controllable ventilation systems, one or more controllable cooling installations; one or more controllable heating installations, one or more controllable CO2 producing installations, one or more heat storage installations and one or more light control installations. 4. Greenhouse system according to claim 2 or 3, wherein the control of the installation (s) of claim 1 or 3 takes place on the basis of the data obtained by the detectors of claim 1 or 2. 1031357 5. Method for controlling the climate conditions in a greenhouse, comprising: a. Directly or indirectly detecting the status of the stomata of one or more plants in the greenhouse; and 5 b. controlling a misting installation based on the detection under a. The method of claim 5 comprising controlling the climate conditions according to the diagram of Figure 5. 10 Method according to claim 6, wherein the set values for the greenhouse conditions associated with the initial states G (l..n), H (l..n) and L (l..n) are periodically validated on the basis of the 15 measured status of the stomata, and wherein these target values are adjusted according to such an algorithm that a self-learning system is created and the initial states G (l..n), H (l ... n, and L (l..n) gradually are optimized for the given greenhouse installation and the given characteristics of the crop