Method for irrigating plants with an irrigation system

Abstract

The invention relates to an irrigation system, in particular for use in urban environments such as balconies. The irrigation system comprises a battery, a pump and a communication unit. In particular, the system is energy-efficient and able to operate autonomously over a long time, e.g. several weeks. This is achieved by a method for irrigating plants according to the invention. The method comprises the following steps: (a) receiving a charge level of the battery and a detected connectivity status of the communication unit, (b) according to an irrigation time interval, controlling the pump to pump water towards the plants, (c) depending on the charge level and the detected connectivity status, determining a sleep cycle duration, (d) controlling the communication unit to transmit status data of the system according to a communication time interval adapted to the sleep cycle duration, and (e) deactivating the communication unit at other times. Advantageously, the irrigation system has IoT capability.

Description

[0001] Method for irrigating plants with an irrigation system

[0002] Technical Field

[0003] The invention relates to a method for irrigating plants with an irrigation system, to the irrigation system, to a corresponding computer program and to a distributed gardening system.

[0004] Background Art

[0005] The irrigation of plants, i.e. watering the plants, poses challenges in particular in urban areas, e.g. on balconies, and other places with a lack of a continuous power and / or water supply. For instance, during an absence of the plant owner, e.g. during the holiday season, the plants are often left without adequate irrigation and, consequently, dry up and die.

[0006] A known solution is an irrigation system, typically comprising a pump that pumps water from a water tank or from the tap via hoses to the plant pots. Conventional irrigation systems mostly implement drip irrigation, i.e. they supply water from above, e.g. through drip irrigation valves. Further, conventional irrigation systems may include a clock timer for the pump, and they may be powered by the electric supply network, by a battery or by a solar panel.

[0007] Conventional irrigation systems, e.g. for private use on a balcony, suffer from several disadvantages. Often, they are not autonomous, in particular not in the sense that they may run without human interaction for a sufficient time, e.g. for more than 14 days, which is a typical duration of a holiday. For instance in case of a power failure, e.g. due to an empty battery or insufficient sunlight, the plants are left without irrigation for the remaining time; the same is true in case of a failure in the water supply, e.g. an empty water tank. Such problems are typically encountered on balconies with rough and changing weather conditions, in particular with high temperatures and solar irradiation causing increased water consumption. In the opposite case, conventional irrigation systems may overwater the plants with similar undesired consequences for the plants.

[0008] Further, conventional irrigation systems are often complicated to set up and maintain, and they are often prone to mechanical failures. Disclosure of the Invention

[0009] The problem to be solved by the present invention is therefore to provide a plant irrigation that overcomes these disadvantages. In particular, it is an objective of the present invention to provide a method of irrigating plants and an irrigation system that works autonomously for a sufficient time, e.g. for more than 14 days. Further, it is a particular objective that the method and irrigation system are water-saving, energy-efficient, robust and / or simple to implement and maintain.

[0010] This problem is solved by the method for irrigating plants with an irrigation system according to a first aspect of the invention. The system comprises a battery, a pump and a communication unit. In particular, the pump is configured to pump water from a water tank towards the plants; pumping or supplying water “towards” the plants shall in particular include supplying the water to a soil in which the plants grow, either directly or e.g. via wick irrigation from a water reservoir separate from the water tank. The communication unit may e.g. comprise a WLAN, Bluetooth or LoRaWAN transmitter or transceiver. The battery advantageously is a rechargeable battery and configured to power the pump and the communication unit. Further advantageous features of the irrigation system are described below in the relevant section.

[0011] The method, which is advantageously computer-implemented, e.g. on a microcontroller, comprises the following steps:

[0012] - receiving a charge level of the battery and a detected connectivity status of the communication unit: In particular, the charge level, e.g. given in percent, may be the ratio of a present energy stored in the battery to the battery capacity. The connectivity status may e.g. be online or offline, or in other words, connected to a remote device, e.g. a server, or not.

[0013] - according to an irrigation time interval, controlling the pump to pump water towards the plants: In particular, the irrigation time interval may be understood as the time interval between consecutive activations of the pump. In an embodiment, the irrigation time interval is 1 day, meaning that the pump is activated every day at the same time.

[0014] - depending on the charge level and the detected connectivity status, determining a sleep cycle duration: Advantageously, the sleep cycle duration is increased for lower charge levels in order to save energy.

[0015] - controlling the communication unit to transmit status data of the system according to a communication time interval adapted to the sleep cycle dura- tion: In particular, the communication time interval may be understood as the time interval between consecutive activations of the communication unit and, thus, consecutive transmissions of status data. For a high charge level, e.g. of greater than 90 %, the communication unit may also be continuously activated, in a sense corresponding to a communication time interval of zero.

[0016] - deactivating the communication unit at other times: In particular, the communication unit is set into a sleep mode with minimal energy consumption, e.g. less than 1 mA, in particular less than 0.5 mA. The energy consumption in the sleep mode may e.g. be less than 1 % of the energy consumption of an online mode characterized by the communication unit being activated. Hence, deactivating the communication unit and entering sleep mode saves energy and, thus, increases the time span for which the system is able to run without recharging the battery.

[0017] Such method of irrigating plants and irrigation system save energy, in particular the electrical energy in the battery, by adapting dynamically communication time interval and, thus, the energy consumption due to the communication unit depending on the charge level and on the connectivity status. In this way, the method and system facilitate irrigating plants for a longer time than conventional irrigation systems. In particular, the method and system facilitate autonomous irrigation for more than one, more than two or even more than three weeks, as is shown in the examples further below.

[0018] Further, such method and system save water by adapting, in particular increasing, the irrigation time interval. This, again, contributes to a longer period of autonomous irrigation. Further, such method and system prevent overwatering of the plants, which improves plant health.

[0019] Even further, the method and irrigation system work reliably and are easy to maintain due to the status data that are transmitted. The status data may be sent to a plant owner or a user who may then act accordingly, e.g. by refilling the water tank in case of a low water fill level. Further, the status data may be processed to generate a warning or forecast to the plant user or user, e.g. regarding the charge level of the battery or the fill level of the water tank.

[0020] These features and advantages make the method and irrigation system particularly useful for applications with difficult or no access to water and electrical energy. Accordingly, the method and irrigation system are optimally suited for urban outdoor environments, such as e.g. balconies. Adapting the communication time interval

[0021] As explained above, adapting the communication time interval is useful for saving energy. In an embodiment, for a second charge level being smaller than a first charge level, a second sleep cycle duration corresponding to the second charge level is longer than a first sleep cycle duration corresponding to the first charge level.

[0022] Further, in a particular embodiment, for a third charge level being smaller than the second charge level, a third sleep cycle duration corresponding to the third charge level is longer than the second sleep cycle duration corresponding to the second charge level.

[0023] Accordingly, the sleep cycle duration may increase continuously or stepwise, e.g. from zero or a few minutes to a few hours, e.g. eight hours, or a day, with decreasing charge level of the battery, e.g. from 90 % or more to 10 % or less. A further example is given in the description of the figures further below.

[0024] A further measure to save energy on the communication unit is the following: In an embodiment, a duration of transmitting status data via the communication unit is limited to a defined duration per communication time interval, in particular to 1 min. This is sufficient for transmitting all required data and in particular even for transmitting a short time series of the status data, which may be useful for deriving robust data, e.g. by averaging.

[0025] Advantageously, receiving a charge level of the battery comprises receiving a measured battery voltage and deriving the charge level. Such derivation may in particular be done via a defined relationship between battery voltage and charge level. As such relationship may be specific for a type or model of battery, it is advantageously characterized during development or manufacture and stored in a memory of the system, e.g. as a mapping or look-up table.

[0026] Using an accurate relationship between battery voltage and charge level facilitates a reliable estimate of the charge level and, thus, of the energy- saving functionality described above.

[0027] In different embodiments of the method and system, the status data of the system that are transmitted by the communication unit include one or more of the following parameters: - the battery voltage: As explained above, the battery voltage may be used to derive the charge level.

[0028] - a charging voltage, in particular for charging the battery;

[0029] - a system current: This may e.g. be taken as a measure for an overall energy consumption of the system.

[0030] - an output current of a renewable energy supply unit configured to charge the battery: Such renewable energy supply unit may e.g. be a solar panel or a wind turbine. Depending on a location of the system, e.g. on a balcony, either of these energy supply units may be suitable to supply a sufficient amount of electrical energy for an autonomous operation of the system.

[0031] - an ambient temperature, in particular measured by a temperature sensor: The ambient temperature may e.g. be used for monitoring purposes and / or for assessing environmental conditions for the plants.

[0032] - a connection strength, in particular a WLAN strength, e.g. measured in dBm. This parameter allows to perform predictive maintenance. In particular, the system may output feedback to the user where to place the system, in particular the communication unit, in order to get a sufficient connection strength.

[0033] - a flow rate generated by the pump: This, again, may e.g. be used for monitoring purposes.

[0034] - a fill level of a water tank connected to the pump: The fill level may in particular be measured by a level sensor, e.g. an ultrasound sensor, a TOF (time of flight) sensor, an IR (infrared) sensor, a capacitive sensor or a pressure sensor. Advantageously, the fill level is used for monitoring purposes or for generating warnings or forecasts regarding the amount of water in the water tank.

[0035] As is understood from the above, transmitting the status data, e.g. to a server, and advantageously processing and / or outputting the status data makes the irrigation system an Internet-of- Things (loT) device with the known related advantages. In particular, a user may monitor the status data from remote and, if necessary, take action accordingly, e.g. refill the water tank, check the battery, the pump or the solar panel, etc.

[0036] In an advantageous embodiment, transmitting the status data of the system is effected by a message queuing service, in particular via MQTT, e.g. via a WLAN. Alternatively, the transmission may e.g. be effected by Bluetooth or Lo- RaWAN.

[0037] Advantageously, the method further comprises the following steps: - controlling the communication unit to request update data for the system according to the communication time interval: Update data may in particular comprise a firmware update. In particular, the update data may comprise updated values of at least one of the first charge level, the second charge level, the third charge level, the first sleep cycle duration, the second sleep cycle duration, the third sleep cycle duration, the irrigation time interval and / or the communication time interval. In general, the update data may be configured to optimize the operation of the irrigation system, in particular its energy efficiency.

[0038] - if available, updating the system with the update data.

[0039] In other words, the communication unit may not only be used for a one-way communication for transmitting status data but also for receiving data, e.g. from a server. For energy-saving purposes, the communication is advantageously kept to a minimum in normal operation mode.

[0040] In a further embodiment, the method additionally comprises the following steps:

[0041] - if the detected connectivity status is off, in particular meaning that there is currently no connection e.g. via WLAN, Bluetooth or LoRaWAN, initiating a defined number of reconnection attempts: In particular, the defined number may be 0, 1, 2, 5 or 10.

[0042] - if the reconnection attempts fail, adapting the sleep cycle duration: In particular, the sleep cycle duration may be set to a defined value, e.g. 2 h, or increased by a certain amount or factor.

[0043] These additional method steps contribute to the energy saving of the method and system as searching for a network and connecting to the network consume a significant amount of energy, in particular more energy than just transmitting the status data.

[0044] The pump and the irrigation time interval

[0045] Further advantageous features relate to the pump and to the irrigation time interval. Advantageously, the method further comprises the following steps:

[0046] - receiving a flow rate generated by the pump: The flow rate may e.g. be measured by a flow sensor. For controlling the pump, the following conditions apply: - if the flow rate is above a flow rate threshold, continuing to pump: Advantageously, the flow rate threshold is adapted such that this condition applies as long as the plants or e.g. a water reservoir for wick irrigation still require more water.

[0047] - if the flow rate is below the flow rate threshold, deactivating the pump: In particular, the flow rate may fall below the flow rate threshold because a valve is closed, e.g. a float valve in case of a water reservoir for wick irrigation.

[0048] These features contribute to both, water and energy saving. Further, an undesired overwatering of the plants is prevented.

[0049] Further and as explained above, it is advantageous to deactivate the pump at times other than the ones indicated by the irrigation time interval. This, again, saves energy and water. In particular, the irrigation time interval may be preset to a default value, e.g. to 1 day. Additionally or alternatively, the irrigation time interval may be adjustable by the user, which may be useful to adapt the method and system to differing climatic conditions.

[0050] In advantageous embodiments, the method may further comprise at least one of the following steps:

[0051] - adapting the irrigation time interval depending on the charge level of the battery: As the pump is typically the largest energy user of the system, in particular during pumping roughly a factor of 100 more than the remaining components, increasing the irrigation time interval is useful for saving energy. At the same time, this will decrease the water supply to the plants - conditions which the plants tolerate only to a certain extent and for a certain time.

[0052] - receiving a fill level of a water tank connected to the pump, and adapting the irrigation time interval depending on the fill level: Here, the main focus is on saving water, e.g. to increase an overall time in which the system operates autonomously, i.e. in particular without user interaction, while keeping the plants alive. In particular, adapting and in particular increasing the irrigation time interval may lead to an adaptation mechanism in the plants, which may cope with water stress e.g. by tolerance mechanisms. This may cause the plants to try and keep the plant function on the same level as unstressed plants and, thus, improve the plant’s tolerance against water stress, i.e. in particular against declining water availability.

[0053] In particular, for the above two steps, the irrigation time interval may be increased in case of the charge level and / or the fill level being below a limit level, in particular below 20 % or below 10 %. Irrigation system

[0054] A second aspect of the invention relates to an irrigation system, in particular with the features described above. The irrigation system comprises

[0055] - a water tank: In particular for use on a balcony, the water tank may e.g. have a volume between 10 1 and 200 1, in particular between 20 1 and 50 1.

[0056] - a pump configured to supply water from the water tank towards the plants: The pump may e.g. be a diaphragm pump. Advantageously, the pump has a low power consumption, e.g. of 500 mA or less.

[0057] - a communication unit configured to transmit status data about the system: As mentioned above, the communication unit may e.g. comprise a WLAN, Bluetooth or LoRaWAN transmitter or transceiver.

[0058] - a battery configured to power the pump and the communication unit: Advantageously, the battery is rechargeable. In an embodiment, the battery is a Lithium-ion battery. Alternatively, the battery may comprise a LiFePo or a NiMH battery. Advantageously, the battery has a capacity of at least 1000 mAh, more advantageously at least 2000 mAh. In particular for use in outdoor environments, e.g. on a balcony, the battery advantageously has an operation that covers at least -10 to 50 degrees Celsius.

[0059] - a control unit configured to execute the steps of the method described above: The control unit may e.g. comprise a microcontroller.

[0060] In a space-saving embodiment, the communication unit, the control unit and the battery are arranged in a lid of the water tank. Further, also the pump is advantageously arranged in the lid of the water tank.

[0061] In an advantageous embodiment, the system is autonomous, in particular for a longer autonomous operation time. In such embodiment, the irrigation system may further comprise a renewable energy supply unit configured to charge the battery. The renewable energy supply unit may e.g. comprise a solar panel or a wind turbine. Depending on the setup and location of the system, e.g. on a balcony, one or the other renewable energy supply unit may be more suitable.

[0062] In case of a solar panel, even a small-size solar panel is sufficient to charge the battery due to the energy-saving design of the system. In particular, the size of the solar panel may e.g. not exceed 20 cm x 20 cm, in particular not exceed 15 cm x 15 cm. Evidently, such irrigation system is compact and, thus, well suited for urban and / or domestic environments, be it indoors or outdoors. In a typical environment, the irrigation system additionally comprises a plant pot that is irrigable. In particular, the plant pot may be irrigable, e.g. sub-irrigable, via a wick from a water reservoir. In case of sub-irrigation, the plant pot may be placed on the water reservoir in the intended use, which forms a compact arrangement. Typically, the water reservoir is fluidically connected to the water tank, e.g. via a hose, and fillable from the water tank via the pump.

[0063] Advantageously, the irrigation system comprises several plant pots and corresponding water reservoirs which are supplied with water from the water tank. In particular, the system may be configured to autonomously operate with at least six or even twelve plant pots and water reservoirs or more, e.g. for at least 14 days.

[0064] Further, the irrigation system may advantageously comprise one or more of the following features:

[0065] - a valve in the water reservoir configured to close a water supply to the water reservoir above a defined water level: The valve may e.g. be a float valve, an electrical valve with associated sensor, or the like. The valve prevents an overfilling of the water reservoir and, thus, saves water. It is particularly useful for wick irrigation systems.

[0066] - a flow sensor configured to measure a flow rate generated by the pump: In particular, the flow sensor may be configured to measure the flow rate, and by integration over time the volume, of water from the water tank towards the plants, in particular into the one or more water reservoirs. Further and as described above, the flow sensor is particularly advantageous in combination with the flow valve in the water reservoir. When the float valve closes, the flow rate measured by the flow sensor drops. If the flow rate drops below the flow rate threshold, the pump is deactivated.

[0067] - a level sensor: The level sensor may in particular comprise an ultrasound sensor, a TOF (time of flight) sensor, an IR (infrared) sensor, a capacitive sensor and / or a pressure sensor. The level sensor is configured to measure the fill level of the water tank. For a compact arrangement, the level sensor may be arranged in the lid of the water tank. The fill level data may be used in loT applications as described above, such as monitoring the fill level, outputting a warning in case of a low fill level, or forecasting a remaining time until a refill is required. Such monitoring, warning or forecasting may be output remotely, e.g. on a smartphone of the user. As explained before, an important advantage of the irrigation system is its energy efficiency, which allows it to operate autonomously, in particular for a sufficient time. Advantageously, a power consumption of the system with the pump deactivated is below 100 mA, in particular below 30 mA. Further, the power consumption of the system with the pump and the communication unit deactivated may e.g. be below 1 mA, in particular below 0.5 mA.

[0068] In an advantageous embodiment, the system is configured to run autonomously, in particular for more than 14 days or even more than 21 days at a pump rate of 2 1 / day which, under typical environmental conditions, is sufficient for irrigating around four plant pots. This allows the irrigation system to be used in urban environments, such as on balconies, or in remote areas, where the plant owner may be absent for some time, e.g. during holidays.

[0069] In an advantageous embodiment, the system is configured to irrigate the plants autonomously even when the connectivity status is permanently off, e.g. when the WLAN connection is permanently lost.

[0070] In a further advantageous embodiment, the system is configured to irrigate the plants, in particular to supply water from the water tank to the plant pot(s) or to the water reservoir(s) even when the pump is permanently switched off, e.g. because the battery is empty. This may be achieved by placing the water tank at least at the same height as the water reservoir and filling the hose with water. The water will then continue to flow from the water tank to the water reservoir even when without an action of the pump.

[0071] As an alternative to an outdoors environment, the irrigation system may also be operated indoors. Due to its energy efficiency, the system may e.g. be powered by a regular USB charger.

[0072] Computer program and distributed system

[0073] A further aspect of the invention relates to a computer program comprising instructions to cause the described irrigation system to execute the steps of the above method for irrigating plants.

[0074] An even further aspect of the invention relates to a distributed gardening system. The distributed system comprises the described irrigation system and a computing device configured to receive the status data transmitted by the communication unit and potentially to output the status data to a user. In particular, the computing device may be configured to derive and output a warning and / or a forecast from the status data. Further, the computing device may be configured to provide update data to the irrigation system via the communication unit.

[0075] As described before, such distributed gardening system allows to make use of the loT capability of the irrigation system. For instance, the communication unit may be configured to communicate with a dedicated server or a specific cloud service, e.g. via MQTT. The server or cloud server may then route the status data or any derived data, such as a warning or forecast, to the user’s remote device, e.g. smartphone, in particular upon request or as a push message.

[0076] Evidently, the features and advantages described in the context of one embodiment or one aspect of the invention may be realized and are meant to be disclosed also in the context of the other embodiments and aspects of the invention. Further advantageous embodiments are listed in the dependent claims as well as in the description below.

[0077] Brief Description of the Drawings

[0078] The invention will be better understood and objects other than those set forth above will become apparent from the following detailed description thereof. Such description makes reference to the annexed drawings, wherein:

[0079] Fig. 1 schematically shows an irrigation system and distributed gardening system according to an embodiment of the invention.

[0080] Fig. 2 shows a flow chart of a method for irrigating plants, in particular of controlling the communication unit, according to an embodiment of the invention.

[0081] Fig. 3 shows an exemplary battery discharge model as used in the method according to an embodiment of the invention.

[0082] Fig. 4 shows empirical examples of the resulting battery lifetime for different water consumption scenarios in an irrigation system according to an embodiment of the invention.

[0083] Modes for Carrying Out the Invention

[0084] The irrigation system of Fig. 1 comprises a water tank 1 with a container 11 that is fillable with water, a lid 12 with an openable portion 13 and electronic components (not shown) advantageously arranged in the lid 12. Having the container 11 closed with the lid 12, 13 in the intended use reduces evaporation of water and the deposition of undesired dirt or organic material in the water tank 1.

[0085] The electronic components comprise a battery, a pump, a control unit and a communication unit as described above. Further, the electronic components advantageously comprise a level sensor for measuring the water fill level in the container 11 and a flow sensor for measuring the water flow out of the water tank 1.

[0086] The irrigation system further comprises at least one planter 2. Each planter 2 is connected to the water tank 1 via a hose 3. In this way, water from the water tank 1 may be supplied to the planters 2 via the hose 3 by means of the pump.

[0087] Advantageously, each planter 2 is a sub-irrigated planter and comprises a plant pot 21 for the soil and the plants and a water reservoir 22, e.g. arranged below the plant pot 21, and fluidically connected to the plant pot 21 via at least one wick. Sub-irrigation reduces the evaporation of water, avoids water logging and prevents overwatering of the plants.

[0088] In an advantageous embodiment, the irrigation system comprises a solar panel 14 for recharging the battery. This increases the time for which the system may operate autonomously. Advantageously, the solar panel 14 is mounted to the water tank 1, thus yielding a compact arrangement of the different components, and in particular oriented to face a main direction of solar irradiation. Such irrigation system is well suited for operation in urban environments, e.g. on balconies.

[0089] Further, the irrigation system of Fig. 1 advantageously is connectable to a remote computing device 4, e.g. a server or a cloud service, via a wireless connection as schematically illustrated by the arrow. The wireless connection between the communication unit of the irrigation system and the remote computing device 4 may e.g. be effected via WLAN, via Bluetooth or via LoRaWAN. Together, the irrigation system and the remote computing device 4 of Fig. 1 form a distributed gardening system with loT capability as described before.

[0090] The flow chart of Fig. 2 shows a control scheme for activating and deactivating the communication unit of the irrigation system. In general, wireless connection at common places of installation of the irrigation system (e.g. balconies, terraces) is often weak and since solar irradiation is strongly variable and dependent both on how the users place the system, the environment (e.g. shadowing through nearby trees and buildings), and current cloud cover. Since the communication unit consumes a significant part of the system’ s energy, an adaptive power saving and communication error handling solution is required in order to maximizes longevity of the system’s battery lifetime. The adaptive power saving solution illustrated in Fig. 2 is implemented around a deep sleep mode of the control unit, e.g. a microcontroller. In this mode, the power consumption of the irrigation system (including peripherals) is reduced to around 0.5 mA, compared to around 10 to 30 mA in normal operation mode (called "online mode" in the following).

[0091] According to the shown exemplary power saving solution, five operation modes are distinguished:

[0092] - Online Mode (around 30 mA)

[0093] - Offline Mode (around 30 mA)

[0094] - Pumping Mode (around 500 mA)

[0095] - Provisioning Mode (around 100 mA)

[0096] - Deep Sleep Mode (around 0.5 mA)

[0097] “Around” may in particular mean + / -10 % of the given value.

[0098] Based on these operation modes, the following power saving logic is advantageously devised (see also Fig. 2):

[0099] 1. When the irrigation system is activated and a WiFi (i.e. WLAN) SSID and password are already provisioned, the system attempts to connect to this WiFi network.

[0100] 2. If connection cannot be established, the system enters so-called "offline mode" where it continuously seeks to establish WiFi connection. In Offline mode, the duration of the next sleep cycle is set to e.g. 2 h.

[0101] 3. If connection can be established, the system enters the so- called "online mode" where it continuously streams data to a cloud backend service via MQTT (in particular via remote electronic device 4 of Fig. 1). In online mode, the duration of the sleep cycle is set to a value between 10 min and 8 h, depending on the current battery charge level. In that way, the system adapts for limited recharge through the solar panel, caused, for example, by unfavorable weather conditions (i.e. strong cloud cover) or increased use of power. This occurs, e.g., when the control unit is connected to a lot of plant pots or when the water consumption of plants is intermittently increased due to very dry weather - both require the pump to supply more water, i.e. operate longer, thus consuming more power.

[0102] 4. When the system is in online mode while it loses connection, it will set to sleep mode with a duration of 10 min after 10 reconnection attempts. This allows for a resilient WiFi reconnection without excessive power consumption in cases of intermittent connection loss. An advantageous ingredient of the solution described above is a careful estimation of battery discharge behaviour to derive a mapping from battery voltage to the charge level of the battery. Fig. 3 shows such mapping between the battery voltage in V on the abscissa and the charge level (called “battery capacity in Fig. 3) in percent on the ordinate. As shown, the measured discharge data of the exemplary Lithium-ion battery (drawn as solid line) can be approximated by a piecewise linear regression (drawn as dashed line) to build a simple battery capacity model. This model is then advantageously used to derive the charge level of the battery, in particular for the purpose of controlling the activity of the communication unit and adapting the energy consumption to the charge level.

[0103] In a further advantageous mapping between battery voltage and charge level, at least one of the following parameters is taken into account: temperature and number of recharge cycles already performed on the battery. This may e.g. implemented by a dedicated fuel gauge IC electrically connected to the battery.

[0104] In summary, the energy-saving control logic described above results in an optimal utilization of the available battery charge level under a broad range of conditions (e.g. weather, water usage). Empirical examples of the resulting battery lifetime (without recharging) for different water consumption scenarios are shown in Fig. 4.

[0105] The tested water consumption scenarios of Fig. 4 range from 0 1 / day, meaning no pumping action but the communication unit and sensors operated according to the control logic of Fig. 2, to 14 1 / day, meaning additionally a pumping action of 14 1 / day for supplying water to the plants. Of the different stages of the charge level for controlling the operation mode in Fig. 2, a change in energy consumption, meaning a change of slope in Fig. 4, is in particular visible at a charge level (i.e. “Remaining Battery Capacity” in Fig. 4) of 50 % and of 10 %. When the charge level drops below these limits, the sleep cycle duration is significantly increased, i.e. the communication unit is active less often, thus saving energy and increasing the autonomous operation time of the irrigation system.

[0106] From the empirical examples of Fig. 4, it can be seen that the irrigation system is able to irrigate plants with 14 1 / day without any recharging for more than 6 days. As a typical average water consumption of one plant pot on a sunny day is around 0.5 1 / day, this corresponds to sub-irrigating around 28 plant pots on a sunny day. Assuming a more realistic average water supply of 4 1 / day (corresponding to around 8 plant pots), the irrigation system is able to operate autonomously (without recharging) for more than 15 days, i.e. more than two weeks, which may be the typical length of a holiday. When the battery is recharged in the meantime, e.g. by a solar panel or a wind turbine, the autonomous operation time of the system is even longer and rather limited by the volume of the water tank than by the energy supply. Evidently, the proposed irrigation system and method for irrigation is able to work autonomously for a sufficient time, e.g. for more than 14 days. Further, the system and method are water-saving, energy-efficient, robust and simple to implement and maintain. Additionally, the loT capability facilitates a reliable operation and maintenance when required.

Claims

Claims1. A method for irrigating plants with an irrigation system comprising a battery, a pump and a communication unit, comprising the steps of- receiving a charge level of the battery and a detected connectivity status of the communication unit,- according to an irrigation time interval, controlling the pump to pump water towards the plants,- depending on the charge level and the detected connectivity status, determining a sleep cycle duration,- controlling the communication unit to transmit status data of the system according to a communication time interval adapted to the sleep cycle duration,- deactivating the communication unit at other times.

2. The method according to claim 1, wherein, for a second charge level being smaller than a first charge level, a second sleep cycle duration corresponding to the second charge level is longer than a first sleep cycle duration corresponding to the first charge level, in particular wherein, for a third charge level being smaller than the second charge level, a third sleep cycle duration corresponding to the third charge level is longer than the second sleep cycle duration corresponding to the second charge level.

3. The method according to any one of the preceding claims, wherein receiving a charge level of the battery comprises receiving a measured battery voltage and deriving the charge level, in particular via a defined relationship between battery voltage and charge level.

4. The method according to any one of the preceding claims, wherein the status data of the system include at least one of the following:- the battery voltage,- a charging voltage,- a system current,RECTIFIED SHEET (RULE 91 ) ISA / EP- an output current of a renewable energy supply unit, in particular a solar panel (14) or a wind turbine, configured to charge the battery,- an ambient temperature, in particular measured by a temperature sensor,- a flow rate generated by the pump,- a fill level of a water tank (1) connected to the pump,- a connection strength, in particular a WLAN strength.

5. The method according to any one of the preceding claims, wherein transmitting status data of the system is effected by a message queuing service, in particular via WLAN.

6. The method according to any one of the preceding claims, wherein a duration of transmitting status data via the communication unit is limited to a defined duration per communication time interval, in particular to 1 min.

7. The method according to any one of the preceding claims, further comprising the steps of- controlling the communication unit to request update data for the system according to the communication time interval,- if available, updating the system with the update data, in particular wherein the update data comprise updated values of at least one of the first charge level, the second charge level, the third charge level, the first sleep cycle duration, the second sleep cycle duration, the third sleep cycle duration, the irrigation time interval and / or the communication time interval.

8. The method according to any one of the preceding claims, further comprising the steps of- if the detected connectivity status is off, initiating a defined number of reconnection attempts,- if the reconnection attempts fail, adapting the sleep cycle duration.

9. The method according to any one of the preceding claims, further comprising the steps of- receiving, in particular from a flow sensor, a flow rate generated by the pump,RECTIFIED SHEET (RULE 91 ) ISA / EP- if the flow rate is above a flow rate threshold, continuing to pump,- if the flow rate is below the flow rate threshold, deactivating the pump.

10. The method according to any one of the preceding claims, further comprising the step of- deactivating the pump at times other than the irrigation time interval, in particular wherein the irrigation time interval is preset to a default value, in particular to 1 day, and / or adjustable by a user.

11. The method according to claim 10, further comprising at least one of the following steps:- adapting the irrigation time interval depending on the charge level of the battery,- receiving a fdl level of a water tank (1) connected to the pump, and adapting the irrigation time interval depending on the fdl level, in particular increasing the irrigation time interval in case of the charge level and / or the fill level being below a limit level, in particular below 20 % or below 10 %.

12. An irrigation system comprising- a water tank (1),- a pump configured to supply water from the water tank (1) towards the plants,- a communication unit configured to transmit status data about the system, in particular over WLAN,- a battery configured to power the pump and the communication unit,- a control unit configured to execute the steps of the method of any one of the preceding claims, in particular wherein the communication unit, the control unit and the battery are arranged in a lid (12) of the water tank (1).

13. The irrigation system according to claim 12, further comprising- a renewable energy supply unit configured to charge the battery,RECTIFIED SHEET (RULE 91 ) ISA / EPin particular wherein the renewable energy supply unit comprises a solar panel (14) or a wind turbine, and in particular wherein a size of the solar panel (14) does not exceed 20 cm x 20 cm.

14. The irrigation system according to any one of claims 12 to 13, further comprising- a plant pot (21) that is irrigable, in particular sub-irrigable, via a wick from a water reservoir (22), wherein the water reservoir (22) is fluidically connected to the water tank (1) and tillable from the water tank (1) via the pump.

15. The irrigation system according to claim 14, further comprising- a flow sensor configured to measure a flow rate generated by the pump, and- a valve, in particular a float valve, in the water reservoir (22) configured to close a water supply to the water reservoir (22) above a defined water level.

16. The irrigation system according to any one of claims 12 to 15, further comprising- a level sensor, in particular an ultrasound sensor, configured to measure a fill level of the water tank (1), in particular wherein the level sensor is arranged in a lid (12) of the water tank (1).

17. The irrigation system according to any one of claims 12 to 16, wherein a power consumption of the system with the pump deactivated is below 100 mA, in particular below 30 mA, wherein the power consumption of the system with the pump and the communication unit deactivated is below 1 mA, in particular below 0.5 mA.

18. The irrigation system according to any one of claims 12 to 17, wherein the system is configured to run autonomously, in particular for more than 14 days at a pump rate of 2 1 / day.RECTIFIED SHEET (RULE 91 ) ISA / EP19. A computer program comprising instructions to cause the irrigation system according to any one of claims 12 to 18 to execute the steps of the method according to any one of claims 1 to 11.

20. A distributed gardening system, comprising- the irrigation system according to any one of claims 1 to 18, and- a computing device (4) configured to receive the status data transmitted by the communication unit and to output the status data to a user, in particular wherein the computing device (4) is configured to de- rive and output a warning and / or a forecast from the status data.RECTIFIED SHEET (RULE 91 ) ISA / EP

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