ELECTRICITY GENERATION METHOD ADAPTED TO CROPS

Abstract

The invention relates to an electricity generation method using orientable photovoltaic sensors (10) disposed above crops (C), the shadow projected onto the crops being altered by changes in the orientation of the sensors. The method is characterised in that the orientation of the sensors is controlled in a computerized and automatic manner in order to affect the microclimatic conditions of the crops by changing the orientation of the sensors, in particular in order to place crops in microclimatic conditions more suited to obtaining a desired agricultural result, while seeking to achieve an optimum, reducing electricity generation as little as possible in relation to a reference that is not combined with crops.

Claims

1. A method for generating electrical power using orientable photovoltaic collectors placed above crops, the shadow projected onto the crops being modified by the change of orientation of the collectors, this method being characterized in that the orientation of the collectors is automatically controlled by computer on the basis at least of data representative of the local environmental conditions of the crops, so as to act on the microclimatic conditions of the crops by way of a change of orientation of the collectors, while seeking to achieve an optimum decreasing as little as possible the generation of electrical power with respect to a reference without combination with crops.

2. The method as claimed in claim 1, the orientation of the collectors being automatically controlled by computer on the basis at least of data representative of the local environmental conditions of the crops chosen from the temperature of the crops, the moisture content of the soil and/or rainfall.

3. The method as claimed in claim 1, the orientation of the collectors being modified depending at least on a crop insolation and/or rainfall history.

4. The method as claimed in claim 1, the collectors being oriented in the evening so as to maximally or minimally reflect toward the ground the thermal radiation of the soil during the night.

5. The method as claimed in claim 1, including measuring the temperature of the crops, the orientation of the collectors being controlled at least depending on the measured temperature.

6. The method as claimed in claim 1, the collectors being placed in parallel spaced-apart rows.

7. The method as claimed in claim 1, the collectors being orientable about a single axis of rotation.

8. The method as claimed in claim 1, the crops being vines.

9. The method as claimed in claim 1, the crops being market-farming crops

10. The method as claimed in claim 1, the orientation of the collectors depending on the state of development of the crops.

11. The method as claimed in claim 1, the orientation of the collectors being controlled so as to keep the crops in a preset maximum and/or minimum temperature range.

12. The method as claimed in claim 1, the orientation of the collectors being controlled depending on a target amount of light energy to be achieved.

13. The method as claimed in claim 1, the orientation of the collectors being controlled so as to keep the crops in a state of minimum stress by recourse to a crop stress model.

14. The method as claimed in claim 1, the structure supporting the panels being used in order to deploy a netting above the crops with the aim of protecting the latter from hail, this being done in response to a weather forecast and/or of protecting the crops from animal attacks and/or of increasing the shade on the crops, and/or of participating in the control of the night-time microclimate above the crop by acting on the heat and moisture transfer with the exterior environment, the netting being deployed depending on an identified thermal and/or hydric need of the crop, a hydric and/or thermal and/or light history of the crop, on a measurement of the hydric and/or thermal state of the crop, and/or on a weather forecast, the electrical power required by this operation possibly being generated by the specific generation capacity of the collectors or coming from the mains if the installation is connected thereto.

15. A system for generating electrical power, including: a bearing structure, orientable solar collectors maintained a distance away from the ground by the bearing structure, one or more actuators for modifying the orientation of the solar collectors and the shadow cast on the ground, and a computer for automatically determining the orientation to give to the collectors depending on the need of the crops affected by the shadow cast by the collectors as regards insolation.

16. The system as claimed in claim 15, including a temperature sensor informing the computer of the local temperature level with the crops.

17. The system as claimed in claim 15, the computer being arranged to determine the orientation of the collectors depending on an insolation and/or rainfall history and/or the state of development of the crops.

18. The system as claimed in claim 15, the computer being local.

19. The system as claimed in claim 18, the orientation of the collectors being determined autonomously by the computer.

20. The system as claimed in claim 15, the computer being at least partially remote.

21. A method for growing plants, wherein the plants are cultivated so as to be affected by the shadow cast on the ground by the collectors of a system as defined in claim 15.

22. A method for growing plants, using the system of claim 15, wherein orientable occulting elements are placed above the crops, the shadow projected onto the crops being modified by the change of orientation of the occulting elements, this method being characterized in that the orientation of the occulting elements is automatically controlled by the computer on the basis at least of data representative of the local environmental conditions of the crops, in order to act on the microclimatic conditions of the crops by way of a change of orientation of the occulting elements.

23. A method according to claim 1, wherein the orientation of the collectors is aimed at placing the crops under microclimatic conditions that are more favorable to the obtainment of a sought after agricultural result.

24. A method according to claim 4, wherein the collectors are positioned horizontally.

25. A method according to claim 7, wherein the collectors are substantially parallel to the north south direction.

26. A method according to claim 14, wherein the choice of the occulting power of the netting is made depending on an identified need of the crop for light, an isolation history and/or an isolation forecast.

27. A system according to claim 16, wherein the temperature sensor is an infrared video camera.

Description

[0062] The invention will possibly be better understood on reading the following detailed description of nonlimiting examples of implementation thereof, and on examining the appended drawings, in which:

[0063] FIG. 1 schematically shows a system for generating electrical power according to the invention,

[0064] FIG. 2 schematically shows a system for controlling the orientation of a solar collector according to the invention,

[0065] FIG. 3 schematically shows the variation over time of the light energy received by the crops and collectors,

[0066] FIGS. 4 to 7 illustrate examples of control of the collectors as a function of time,

[0067] FIG. 8 is a simplified representation of a crop stress model based on foliar temperature, and

[0068] FIG. 9 is an view analogous to FIG. 1 of a variant embodiment.

[0069] FIG. 1 shows a system for generating electricity according to the invention, including a plurality of solar collectors 10 that are movable about respective axes of rotation R. These collectors 10 are held by a bearing structure 20, allowing a sufficient height to be provided under the collectors 10 for the passage of agricultural machines, in particular a height comprised between 3 and 5 m.

[0070] The bearing structure 20 includes poles 21 that support a framework 22 to which the collectors 10 are hinged.

[0071] Each collector 10 is pivoted about the corresponding axis R using at least one actuator 30.

[0072] The actuators 30 are for example provided individually for each collector 10, as illustrated. As a variant, one and the same actuator 30 may rotate a plurality of solar collectors 10.

[0073] The actuators 30 for example each include one or a plurality of electrical motors, and for example consist of servomotors.

[0074] The crops C are placed in the shadow projected on the ground by the collectors 10. The crops C may be of any type and may for example be market-farming crops or vines.

[0075] If the reader refers to FIG. 2, it may be seen that the position to give to the collectors 10 may be determined by a local computer 40 that is connected via any suitable power interface to the actuators 30.

[0076] The computer 40 preferably receives information from one or more local probes, for example a temperature probe 41 placed level with the crops C and a moisture probe 42 placed in the soil level with the crops C. Other sensors may be added, such as a rain gauge, an anemometer and/or a video camera for viewing the state of development of the crops, and one or more biosensors where appropriate.

[0077] It is particularly advantageous, generally, to use a contactless infrared sensor to measure the temperature of the crops. Thus an infrared video camera that is pointed at the crops in various locations and that allows a spatially averaged temperature to be calculated may be used.

[0078] The computer 40 may also exchange data, for example via a wireless telephone network, with a remote server 50, which may for example inform the computer 40 of the weather to come.

[0079] The computer 40 may be produced on the basis of any microprocessor or piece of computational equipment allowing the orientation of the collectors 10 to be controlled according to one or more control laws giving the orientation to be imposed on the collectors depending on the place, on the date, on the time and on a number of other parameters related to the crops C.

[0080] The computer 40 may thus include a processing unit and a local memory in which the measured local data, for example temperature, moisture-content and rainfall data, may be recorded in order to keep the history of the environmental conditions of the crops.

[0081] The memory of the computer may also include automatic control parameters that govern the orientation of the collectors depending on the needs of the crops. These parameters may vary over time and, depending for example on the season, may privilege the insolation of the crops.

[0082] The one or more control laws may be programmed into the computer 40 from the start, or as a variant be downloaded by the computer 40 from the remote server 50, or else be updated periodically by the remote server 50.

[0083] In one exemplary embodiment, the computer 40 operates autonomously. Depending on the season, on the sowing date and optionally on other parameters input by the farmer, it controls automatically and daily the orientation of the collectors 10 so as to meet the need of the crops with regard to insolation, temperature, moisture content and rainfall over a given period of time. In this case, the collectors are for example oriented during a fraction of the day to let as much light as possible pass, to the detriment of the generation of electricity. Next, once the need for insolation has been met, the collectors are brought by activating the actuators to an orientation aiming to maximize the generation of electricity.

[0084] However, if the local temperature measured level with the crops is excessive, or higher than the set objective, the orientation of the collectors may be modified to shelter the crops from the sun and prevent excessive heating.

[0085] In one variant embodiment, the computer 40 receives collector control instructions from the remote server 50, to which it may for example transmit local temperature and insolation data, and data relating to the crops and their stage of development. The server 50 in return transmits to the computer information relating to the orientation to give to the collectors, in real time or over a certain period to come.

[0086] When the collectors 10 are oriented to maximize the generation of electricity, they may follow in real-time the course of the sun from east to west.

[0087] FIG. 3 shows the variation in the light energy received over time, for the collectors and crops. When the collectors follow the course of the sun, they receive about one third of the light energy. The crops receive two thirds thereof. It is possible to increase the amount of energy received by the crops by modifying the orientation of the collectors so as to decrease the occultation of the crops.

[0088] A target amount of energy may be set in advance for a day j depending on the light energy needed by the crops, on the energy deficit or surplus received the previous day or the preceding days, and on weather forecasts allowing the amount of energy expected for this day j to be estimated.

[0089] Where appropriate, the model that sets the target amount of energy is more elaborate and takes into account the cost of electricity or its potential market value.

[0090] The dashed line in FIG. 3 shows the variation over time in the energy received until it reaches the target quantity. To achieve this, the energy received by the crops is increased while decreasing that Q.sub.collectors received by the collectors to the benefit of a lesser occultation of the crops.

[0091] FIG. 4 shows the variation in the angle of the collectors over time. The dashed curve corresponds to a conventional tracking of the course of the sun.

[0092] To increase the light energy received by the crops, it is possible to leave the collectors horizontal between sunrise and t1, then after t2 until sunset. Between t1 and t2, the collectors are oriented so as to track the course of the sun.

[0093] Leaving the panels horizontal does not minimize the occultation but makes it possible not to consume electricity orienting them.

[0094] In the variant illustrated in FIG. 5, between sunrise and t1 the orientation of the collectors is modified to let a maximum of light pass to the crops, and likewise after t2 up to sunset.

[0095] In FIG. 6 it may be seen that the collectors are controlled as in the example in FIG. 4. However, between t2 and t3 the sun is once again tracked in order to allow the crops to benefit from a maximum occultation in order to protect the latter from an excessive temperature. In this example, the temperature of the crops is monitored, for example by virtue of an infrared video camera. It is assumed in this example that the temperature exceeded a limiting value at the time t3. The system controlling the panel thus triggered the passage to a sun tracker mode from t3 to sunset.

[0096] FIG. 7 shows an example of the variation in the angular travel of the collectors at the end of the winter period.

[0097] It may be seen in this figure that the collectors are oriented during the day j1 to minimize occultation, by orienting them substantially parallel to the sun's rays over time.

[0098] If the weather forecast has predicted that on day j it will be cold and overcast, the collectors may be kept horizontal during the day and night so as to maximally reflect infrared from the ground toward the crops. On day j+1, the collectors are controlled in a way similar to that of the day j1.

[0099] The target amount of energy for the day j+1 may be calculated from the amount of light energy actually received by the crops on day j and, optionally, the prior days. To determine the amount of light energy actually received, it is possible to use a pyrheliometer or pyranometer. Better still, this energy is calculated from that received by the collectors, knowing their orientation and that of the sun and using a mathematical model that gives the average energy at the ground taking into account the occultation provided by the collectors.

[0100] FIG. 8 is a simplified representation of crop stress level based on foliar temperature. This curve shows that in order to meet a maximum crop stress criterion the control system may seek to keep the foliar temperature in an interval comprised between Tmin and Tmax by acting on the orientation of the collectors.

[0101] Of course the invention is not limited to the examples just described.

[0102] For example, the collectors use may be placed so as to be orientable about two axes of rotation.

[0103] FIG. 9 illustrates that it is possible to use the bearing structure 20 to support a system providing protection 60 against bad weather, especially hail, and for example taking the form of a netting that is deployed between the poles 21 of the structure 20. This deployment may be automated where appropriate, by virtue of permanently present cables that are stretched between the poles 21. It is possible in this case not to use the collectors to protect the crops during periods of bad weather, and to orient them for example so as to minimize the risk of them being damaged.

[0104] In one variant implementation of the invention, more particularly relating to the optimization of the yield of the agricultural production independently of the generation of electricity, the collectors are replaced by occulting elements such as sheet-metal or composite panels that may optionally be apertured.

[0105] The expression including a must be understood as being synonymous with comprising at least one unless specified otherwise.