WO2007105168A2

WO2007105168A2 - Mist greenhouse

Info

Publication number: WO2007105168A2
Application number: PCT/IB2007/050844
Authority: WO
Inventors: Pieter Arie Van Weel; Jan Otto Voogt
Original assignee: Praktijkonderzoek Plant & Omgeving B.V.
Priority date: 2006-03-13
Filing date: 2007-03-13
Publication date: 2007-09-20
Also published as: NL1031357C2; WO2007105168A3

Abstract

The present invention relates to a greenhouse system with a climate regulation which is controlled through measuring the stomatal aperture of the plants present in the greenhouse. The regulation mainly consists of controlling a misting installation and optionally of adjusting other, conventional climate regulating installations in the greenhouse (such as ventilation windows, heating/cooling, screening, etc.). Due to the combination of optimizing the stomatal aperture and the regulation through a misting installation, optimal conditions for the biomass production can be obtained and maintained.

Description

Title: Mist greenhouse

The invention relates to a new type of greenhouse for cultivation of crops in agriculture and/or horticulture, more in particular 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 pay more and more attention to regulation of the climate conditions in greenhouses, not least because of the environment-saving and energy-saving effect of such measures. By now,, many systems have already been developed in which excess heat which is present in the greenhouse in summer is stored (usually in the soil) and is fed back through a heat pump in colder periods, resulting in a lower total energy consumption. These systems are often self- controlling, i.e. switching-on and switching-off of heat storage or heat feedback is controlled through a system which measures the temperature in various places in the greenhouse and couples this with a regulating system. There are already various innovations in the field of climate control in greenhouses. Thus, by the firm of Innogrow BV, the "GeslotenKas" ("closed greenhouse") concept has been developed, in which a combination of mechanical cooling by means of heat exchangers and fans which bring cooled air to the bottom of the greenhouse through perforated air hoses, and ventilation by air windows to dehumidify at night. Further, there are also (experimental) greenhouses in which side wall ventilation, loose cooling units above the crop (e.g. with the cultivation of Phalaenopsis) and the like.

So, these greenhouses are always equipped with large installations such as cooling and heating systems, watering systems and water-collecting systems connected therewith, and the like. The presence of all these technical facilities often hinders the cultivation due to the large amount of lines running through the cultivation area and the large installations needed to realize the desired result.

In addition, in the existing greenhouse systems, there are still problems, e.g.: - to limit the greenhouse temperature with high solar irradiation in summer by means of mechanical cooling, a large installed cooling output is needed;

- to obtain a good temperature distribution in the greenhouse, high airflow rates need to be used; - by mechanical cooling, in summer, much more heat is recovered from the greenhouse air than is needed in winter for the same surface area.

This heat is no longer economically usable.

One of the measures which can be taken to be able to better regulate the temperature balance in greenhouses is cooling by means of a misting installation. Such a misting installation can be included in a regulating system as, for instance, described in Japanese patent publication

JP 2003/289728 where, driven by a temperature measurement, cooling by misting is switched on or off as desired. Further, the misting is switched off when an air humidity limit is reached. In Japanese patent publication JP 2005/176721, misting is used for maintaining a particular relative air humidity (less than 90% RH). In

American patent 4,856,227, a (temperature and air humidity) regulated irrigation or misting is described for maintaining a vapor above a bed of flower bulbs. So, although there are already greenhouses in which the climate is regulated by means of misting, the regulation of the extent of misting is controlled on the basis of temperature and/or air humidity measurements. Thus, for the plants, still no optimal climate conditions are realized, because, in addition to these parameters, the CO2 content of the air and the quantity of light reaching the plants also influence the effect of the misting on the growth of the plants. The invention now solves this problem by making the regulation of the misting, optionally in combination with other climate-influencing installations, such as cooling or heating installations, and the like, depending on the status of the stomata of the plant. To this end, the invention in the broadest sense comprises 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. a regulable installation for misting water; c. a regulating unit which controls the installation for misting water on the basis of the data obtained by the detector of a.

Preferably, the greenhouse system of the invention further comprises one or more of the group of detectors consisting of one or more infrared meters for measurement of the leaf temperature, one or more photometers 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 air humidity.

In addition, the greenhouse system according to the invention may further comprise one or more of the group of installations consisting of one or more regulable ventilation systems, one or more regulable cooling installations, one or more regulable heating installations, one or more regulable CO2-P reducing installations, one or more heat storage installations and one or more light-regulating installations. With such a system, the control of the above-mentioned installation(s) can take place on the basis of the data obtained by the above-mentioned detectors.

In another embodiment, the invention further comprises a method for regulating the climate conditions in a greenhouse comprising: a. direct or indirect detection of the status of the stomata of one or more plants in the greenhouse; and b. control, on the basis of the detection of a., of a misting installation and any other climate regulating means in the greenhouse to influence the status of the stomata.

DESCRIPTION OF THE FIGURES

Fig. 1 shows the relation between the quantity of light, percentage of CO2 present, and the amount of photosynthesis (source: http://www.egbeck.de/skripten/12/bsl2.htm).

Fig. 2 shows the relation between the leaf temperature and photosynthesis with different CO2 concentrations (source: Intelligrow: a component-based climate control system for decreasing greenhouse energy consumption. Aaslyng,-J-M; Ehler,-N; Karlsen,-P; Rosenqvist,-E, Acta-Horticulturae. 1999; (507): 35-41).

Fig. 3A shows the status of the stomata in a leaf of a plant (Crassula oυatd). In the left panel, the stoma is open, in the right panel it is closed. 1 = open stoma, 2 = closed stoma, 3 = guard cells, 4 = subsidiary cells, 5 = wax platelets.

The stoma is opened or closed by the movement of the two guard cells. Under the stoma, there is a so-called air space. Fig. 3B shows a schematic cross section of such a stoma. The gas exchange between the air space and the air under light conditions is indicated.

Fig. 4 shows the relation between the stomatal aperture (expressed as a percentage of the maximum aperture = 100%), temperature and moisture deficit (vapor pressure difference between air and leaf) with a particular 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 regulating diagram for controlling the climate regulation in the greenhouse according to the invention. See text for a description.

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

Fig. 7 is a Psychometric Chart, one of the many possible forms of a diagram in which inter alia the relation between air temperature, moisture content of the air expressed in absolute moisture content (g/kg of air) and relative moisture content (% of the maximum moisture content), the specific weight of air and the enthalpy, consisting of sensible and latent heat, is indicated.

From such a diagram, it can inter alia be read how much energy is needed to heat a particular quantity of air with a particular humidity a particular number of degrees, what the dew point of this air is, how much energy is needed to cool this air, what the effect on the air temperature and humidity is, if a particular quantity of water is misted in the air per time unit, etc.

Because the properties of moist air also depend on the air pressure, in practice, different diagrams are used 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 it is used in agriculture and/or horticulture, utilizing a minimal adjustment, viz. by using misting as (a supplement to the) regulation of the greenhouse climate. For installing a misting installation — compared to the cooling and heating installations used in the prior art — only a minimal technical and economic effort is needed. For use of misting according to the invention in conditions as in the Netherlands, where the solar radiation can reach values up to approx. 800 W/m²(in the greenhouse), a misting capacity of approx. 0.5-1 liter of water/m²/hour needs to be installed.

In addition to the advantage of obtaining a higher biomass per m² of greenhouse surface area (due to an optimal photosynthesis of the crop), also, less energy is needed for operating the installation, compared to existing greenhouse systems. In addition, the CO2 emission is reduced, so that the greenhouse system of the invention is optimally suitable to meet the increasingly more stringent norms set by the authorities. This may even result in positive effects on emission rights. Finally, the quantity of residual heat which needs to be stored in summer is minimized, so that it can be reused in its entirety. Thus, the size of the storage and recovering installation remains limited and no losses occur.

The great advantage of a greenhouse system according to the invention is that, by measuring and adjusting on the basis of the status of the stomata of the plant(s), an optimal climate condition is created for the photosynthesis and the physiological processes (growth, bloom) of the plant depending thereon. Photosynthesis is the motor of the growth process of the plant. (Sun)light yields the energy with which, in the green parts, assimilates (carbohydrates) are formed from CO2 and water. These assimilates are later converted into energy and building materials by the plant. Through the stomata, CO2 is taken up from the environment. With larger quantities of light, the plant can process more CO2 than is naturally present in the environmental air. However, solar irradiation also results in evaporation from the leaf. That evaporation process is regulated by opening the stomata to a greater or lesser extent. With danger of withering, the stomata close so that the uptake of CO2 is also hindered. Thus, the growth potential is only partly utilized. By cooling with misting, the humidity in the greenhouse remains structurally high and the danger of withering does not occur, so that the stomata remain opened to a maximum and the supply of CO2 can proceed without hindrance.

Due to the high air humidity reached due to misting, 'tropical' climate conditions are created in the greenhouse. It is known, however, that plants thrive extremely well in a tropical environment. The plants can endure the combination of increased air humidity and high temperature well when the climate regulation is geared to the behavior of the stomata with which the plant itself regulates the uptake of CO2 from the air and the leaf evaporation.

Due to the rise of the temperature and the air humidity, the enthalpy of the air in the greenhouse increases strongly compared with the enthalpy of the outside air. This enables large quantities of energy to discharge from the greenhouse with relatively slight air exchange (ventilation). The ventilation fold will be limited to a value of approx. 10, for which only a small opening of the air windows of the greenhouse is needed. Due to the slight ventilation, the CO2 emission will be reduced proportionally strongly, viz. with a factor 3 to 5, i.e. a reduction of 60-80%. This effect is reinforced further because, due to the stomata remaining opened, compared to the conventional systems, lower CO2 concentrations can be used, while still a complete utilization of the potential photosynthesis can be achieved. If too little CO2 is available in the greenhouse air, this can be supplemented with technical measures (installation for enrichment of greenhouse air with CO2, for instance with a gas cylinder or through a carbon dioxide generator, which combusts propane or another natural gas). What is central in the concept is the measurement of the status of the stomata of the plant. This may take place through a direct visual measurement at a micro level of the stomata themselves, but this may also take place in an indirect manner by measurements in the direct environment of the stomata.

Direct, visual measurement is preferably done by means of a camera connected 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, very close to the stomata, the levels of inter alia CO2, O2 and light as well as the temperature of the leaf and the environment, and then using this these signals as input of a calculation model which, on the basis of comparison with stored values, produces as output for instance the stomatal aperture. This method is indicated as "software sensor" or "softsensor" for short.

The optimal position of the stoma is completely open, because this allows a maximum access of CO2 and consequently a maximum use of the potential photosynthesis. There are different mechanisms which ensure that the stoma will 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 stoma partly closes if the leaf evaporation becomes too high (danger of withering). Apparently, then the supply of energy to the leaf due to solar radiation and/or convection is too high. By the closing of the stoma, the supply of CO2 stagnates, which is at the expense of the dry matter production. At such a moment, the misting needs to be switched on to realize not only a decrease of the temperature, but also an increase of the air humidity. As a result, the leaf will evaporate less, the danger of withering is over and the stoma will open again.

In addition, it is preferred to measure the leaf temperature of the crop, e.g. by means of an infrared meter, and to measure the quantity of available light for photosynthesis (PAR light, Photosynthetically Active Radiation) above the crop, e.g. by means of a photometer suitable for this purpose. This is because the photosynthesis process depends on these factors (see Fig. 1). From the CO2, leaf temperature and light measurements, together with the information about the condition of the stomata, a regulating method can be arranged to optimally adjust the climate in the greenhouse to the need and optimal growth of the crop. A general overview of a regulating diagram is shown in Fig. 5.

In such a regulating diagram, preferably three starting situations are distinguished on the basis of the available quantity of light, i.e. whether the light source is sunlight or lamplight and/or no light source is present (dark). For each of these three situations, an ideal starting condition (G, H and L, respectively, see Fig. 5) need to be defined on the basis of the presence of the climate facilities in the greenhouse (presence/absence of one or more regulable ventilation systems, one or more regulable cooling installations, one or more regulable heating installations, one or more regulable Cθ2-producing installations, one or more heat storage installations and one or more light-regulating installations) and depending on the requirements of the crop to be cultivated. Some plants will, for instance, thrive better at a higher temperature, higher light intensity and/or higher relative air humidity than other plants. Also, with artificial lighting, the day/night rhythm needs to be set, so that it is optimal for the crop to be cultivated. If necessary, these settings can be adjusted to the growth stage of the crop. So, the starting conditions G, H, L consist of a collection of target values for the different greenhouse conditions which are considered ideal for the crop.

These target values corresponding to these starting conditions can, inter alia, be read from diagrams known for most crops such as, for instance, shown in Figs. 1, 2 and 4. If the ventilation windows in a greenhouse are closed by day, then the result thereof is that the temperature, the CO2 content and the air humidity increase. If sufficient CO2 is available in the greenhouse, the quantity taken up by the plant is primarily determined by the quantity of light, as can be seen in Fig. 1. In case of sufficient available light, the (leaf) temperature is also found to have an effect. With an increased concentration of CO2, as can occur in a closed greenhouse or can be created by extra CO2 supply, the maximum uptake is at a higher temperature than with a limiting CO2 content (Fig. 2).

This starting condition corresponds to a (usually maximum) position of the stomata. With an unchanged position of the stoma, the climate system in the greenhouse is controlled such that this starting condition is maintained. Although the stomatal aperture is primarily determined by the quantity of light, a stoma also provides evaporation and therefore influences the leaf temperature. Thus, the evaporation may 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 of the leaf) plays an important role, as appears from Fig. 4. This also shows that, for a maximum photosynthesis, the range is limited: between 60-100% RV and a temperature between 20-30°C. If the stomata indeed close due to evaporation, according to the diagram of Fig. 5, the climate regulation in the greenhouse will be controlled such that a new optimum condition is reached (corrected G, H or L). Preferably, this is solved by controlling the misting installation, so that the air humidity and the CO2 concentration increase and the temperature does not rise too much (this in contrast to the conventional manner of cooling as described hereinabove due to which the air humidity and CO2 concentration decrease). After this, it needs to be controlled whether the plant temperature is still above the dew point of the greenhouse air. If this drops below the dew point, the moisture from the air will condense on the plants, which not only results in a decrease of the photosynthesis, but can also promote the development of decay and infectious diseases. Preferably, the difference between the plant temperature and the dew point temperature of the greenhouse air is increased again by switching on the misting (and/or additional cooling). By means of this adjustment, the value of G, H or L is again corrected.

By continuously measuring the position of the stomata and continuously adjusting the settings of the misting and any other climate installations in the greenhouse thereto upon change of one of the climate-influencing factors (e.g. light, temperature, relative humidity and the like), the system is capable of very quickly regulating the climate in the greenhouse to a stable condition again, while the position of the stomata is kept optimal under the prevailing conditions. Preferably, each minute, the position of the stomata is measured and the cycle is gone through, so that a virtually continuous regulation is created.

With a non-ventilated greenhouse (i.e. a greenhouse with closed air windows), when the leaf temperature exceeds a critical upper limit

(depending on the crop to be cultivated), the air windows 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, while these installations, and the dosed quantity of CO2, can be geared to the position of the position of the stomata. This is because it is known that the plant can also close the stomata with too high a concentration of CO2.

The greenhouse temperature and the air humidity need to remain within a certain optimal "working range". If either the greenhouse temperature or the air humidity comes outside this working range, this indicates insufficient discharge of energy. This is then increased by gradually increasing the (mechanical) ventilation.

As said, too high a CO2 concentration makes the stomata close. If the other conditions are optimal, upon detecting closing stomata, the addition of CO2 is gradually decreased. In the night, when there is no solar radiation or growth light, the greenhouse climate will be regulated in a conventional manner by means of ventilation and optionally additional dehumidification. Because no or little photosynthesis (in the case of artificial growth light) takes place and, in addition, there is hardly any crop evaporation, switching on the misting installation will usually not be necessary. Of course, it has advantages, also during the dark situation, to regulate the greenhouse climate in such a manner that the stomatal aperture (where now CO2 is released to the air) is kept optimal.

So, the added value of the invention is that, on the basis of the status of the stomata, that position of equilibrium where the photosynthesis process proceeds optimally can accurately be reached.

An additional advantage of the above-described greenhouse system is that the quantity of acceptable light (and heat) can be larger than in conventional greenhouse systems. There, screening of sunlight regularly needs to be deployed to limit the cooling load, which proportionally decreases the potential photosynthesis and consequently the crop growth. In the greenhouse system of the invention, the misting can provide a more efficient (and less expensive) cooling, so that an excess of sunlight never, or only sporadically, needs to be screened. This effect can be enhanced further by extra misting of water just above the greenhouse cover, i.e. on the outside of the greenhouse, in case of very much solar radiation. In this context, the air layer just below the greenhouse cover and the air layer just above the greenhouse cover can be seen as one whole. The enthalpy of the outside air does not change when the misted water is taken up therein in an adiabatic manner. Thus, in principle, it makes no difference whether the water is misted above the greenhouse cover in the outside air or below the greenhouse cover in the greenhouse air. This is because the cooling effect in the greenhouse is the same, since the air humidified outside the greenhouse can take up more energy now in the greenhouse. However, a precondition for this is that the wind speed above the greenhouse is not too high because otherwise the humidified air above the greenhouse blows away before it can enter the greenhouse. So, the greenhouse cover misting can contribute to the increase of the air humidity in the greenhouse, so that, inside the greenhouse, less water needs to be misted and the chance of drop formation and the crop becoming wet is reduced.

In some conventional systems, roof irrigation is used to cause a cooling effect in the greenhouse. Due to the higher greenhouse temperature and the high relative air humidity, this cooling effect will be much greater with the greenhouse system according to the invention than in conventional systems. Further, more condensation will occur, which promotes the heat transfer. At night, roof irrigation can have a useful effect as well: by cooling the greenhouse cover, the condensation against the greenhouse cover inside the greenhouse is promoted, so that the air humidity is controlled without air exchange.

Due to a strongly increased enthalpy of the greenhouse air, more efficient methods can be deployed for the harvesting of (solar) heat and reusing it for greenhouse heating. In the conventional systems, heat is recovered from the greenhouse air for storage in the soil and later use. With this later use, a heat pump is deployed. In these conventional systems, a relative air humidity of 70-80% is used. So, in the present greenhouse system, where the air has a typical relative air humidity of 90-95%, the air has a higher enthalpy and will condense at higher temperatures than dry, colder air. Thus, in a heat exchanger, solar heat can be harvested with a smaller volume of greenhouse air to be displaced and with water temperatures on the cooling side which are closer to the greenhouse temperature. Further, alternative forms of heat recovery come within reach. Harvesting (solar) heat may, for instance, take place with a cooling surface which is located under the plants and can therefore form a large surface which takes no light away for plant growth and cannot cause any dripping damage to the plants due to falling condensation drops. The water temperature in this cooling surface will be relatively high (> 2O⁰C) in normal conditions. Because the cold air sinks, no fans are needed to be able to harvest the heat. These higher temperatures also increase the heat content of a stored water volume, so that a water recovery pump needs to displace less water. In addition, better use can be made of the existing heating systems, such as a pipe-rail network.

By using a climate system as described hereinabove, the regulation is no longer based on greenhouse air temperature and RV, but on energy balance and moisture balance, while temperature and relative air humidity are prior conditions (see also the diagram of Fig. 7).

Additionally, a greenhouse system of the invention enables accurate determination of uptake of CO2. Due to the fact that much less CO2 leaks away, the uptake of CO2 can be derived from the dosing rate and the measured concentration in the greenhouse. This allows measurement of the efficiency of the photosynthesis process. In addition, it is usable to measure and prevent stress. Plant stress is characterized in that the plant is in such a situation that it is necessary to take emergency measures as a result of which the normal growth process is stopped and a switch is made to a survival strategy. The closing of the stomata in case of danger of withering is a good example thereof. Because the evaporation and therefore the cooling is reduced, the leaf temperature strongly increases (with danger of local dehydration). Then the CO2 uptake and the photosynthesis stop, but this is still a better survival strategy for the plant than to dehydrate completely. Because, in the new greenhouse system of the invention, the climate regulation is no longer primarily geared to the greenhouse temperature, but to energy discharge, a more accurate control of the ventilation (through ventilation openings) is required, particularly in the lower range of the temperature/air humidity diagram (see Fig. 7). This means that ventilation windows and/or a mechanical ventilation will need to be able to be regulated accurately.

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

However, in practice, effective regulating strategies with inter alia crop condensation models are already used, with which the risk of condensation on the crop can be reduced strongly.

In addition, these diseases and pests, in the unlikely event that they occur, can be controlled in the conventional manner, e.g. by admixing antibiotics in the water to be misted.

All in all, the many advantages offset the two drawbacks just mentioned. These advantages are also of an economic nature: the greenhouse system of the invention requires only a relatively limited investment, which can be installed in existing greenhouses without any problem. In addition, much less electric energy is necessary to operate the installation. Also, the size of heat storage and recovery installations may be more limited than with conventional systems. Further, the reduced CO2 emission offers possibilities for a permanent future use and optionally transferability of emission rights.

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

The regulating diagram shown in Fig. 5, which has been discussed in the above description, is a good example of a greenhouse system of the present invention. On the basis of this description, a skilled person will be able to use the invention in a greenhouse as desired according to the specific situation. The above description provides a skilled person with guidelines and specific directions which need to be met to make optimal use of the invention.

Fig. 6, finally, shows a schematic example of a greenhouse system according to the invention. A measuring and regulating system is central therein, which, on the basis of measuring the stomatal aperture, and measurement of air humidity, sunlight (energy) and CO2 concentration, controls a misting installation and any other equipment. The misting installation is preferably suspended at the top of the whole greenhouse space. Additionally, the greenhouse also contains an air treatment unit with fan, so that the air cannot only be heated or cooled, but where an air filter is also present to filter out germs (spores of bacteria and fungi) present in the air. In addition, the greenhouse contains ventilation openings (windows) which may 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 dimmed. The above-mentioned air treatment unit is fed via a heating boiler and/or cooling machine. Storage of excess energy preferably takes place in so-called aquifers. An aquifer is a water-bearing soil layer. An aquifer suitable for heat storage usually consists of a sand layer surrounded by 'watertight' (horizontal) layers of clay. The groundwater flows in the sand layer can only have a limited rate to limit heat losses. With an aquifer, the heat is stored directly in the (ground)water and the sand. Aquifers may be used for storage of both high and low temperatures. The aquifer is connected with the cooling/heating system through a conventional heat pump. The greenhouse system shown in Fig. 6 further comprises an installation to supply CO2 and a system to supply water to a greenhouse system as input for the misting installation, for energy transport and/or for watering the plants.

Claims

1. 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. a regulable installation for misting water; c. a regulating unit which controls the installation for misting water on the basis of the data obtained by the detector of a.

2. 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 measurement of the leaf temperature, one or more photometers 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 air humidity.

3. A greenhouse system according to claim 1 or 2, further comprising one or more of the group of installations consisting of one or more regulable ventilation systems, one or more regulable cooling installations, one or more regulable heating installations, one or more regulable Cθ2-producing installations, one or more heat storage installations and one or more light-regulating installations.

4. A 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.

5. A method for regulating the climate conditions in a greenhouse, comprising: a. direct or indirect detection of the status of the stomata of one or more plants in the greenhouse; and b. control of a misting installation on the basis of the detection of a.

6. A method according to claim 5, comprising regulating the climate conditions according to the diagram of Fig. 5.

7. A method according to claim 6, wherein the target values for the greenhouse conditions corresponding to the starting conditions G(I.. n), H(I..n) and L(I..n) are periodically validated during the regulating process on the basis of the 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 starting conditions G(I..n), H(I..n) and L(I.. n) are gradually optimized for the given greenhouse installation and the given properties of the crop.