WO2021074849A1

WO2021074849A1 - Aeroponic system and misting device

Info

Publication number: WO2021074849A1
Application number: PCT/IB2020/059711
Authority: WO
Inventors: Richard Barr
Original assignee: Richard Barr
Priority date: 2019-10-15
Filing date: 2020-10-15
Publication date: 2021-04-22
Also published as: GB201914915D0

Abstract

The present invention relates to an aeroponic system and in particular to a misting device for use in such a system, the misting device comprising a rotatable atomiser (154, 180, 182, 205, 300, 350, 35) configured to receive and aerosolize a nutrient solution (120) in such a way that maximises the growth rates of plants (110).

Description

AEROPONIC SYSTEM AND MISTING DEVICE

FIELD OF THE INVENTION

The present invention relates to an aeroponic system and in particular to a misting device for use in such a system.

BACKGROUND

Developments in agriculture have led to techniques for growing plants which do not require a soil-based medium. One common method is to immerse the roots of plants in a nutrient solution, which is known as hydroponics. Aeroponics is derived from this method, and involves suspending the plants from a supporting structure and periodically spraying the roots with a nutrient solution.

An aeroponic system allows very high growth rates. An important aspect of an aeroponic system is the delivery of an appropriate amount of nutrient solution. An excess of nutrient solution will over-saturate the roots of the plants and restrict the ability of the roots to extract oxygen from the air. However, a lack of nutrient solution will dry out and damage the roots. Either of these situations will diminish the growth rate of plants.

There are a number of difficulties which are associated with known aeroponic systems. For example, many aeroponic systems use sprinklers relying on a high flow rate of nutrient solution to provide sufficient pressure to spray the nutrient solution onto the roots of plants. Such an approach is inefficient, as large amounts of energy are used to pump the nutrient solution in order to achieve the required pressures. In addition, the high flow rate delivers an excess of nutrient solution to the roots of growing plants. The excess nutrient solution drips from the roots of the plants and is collected for recirculation. Such a recirculation system increases both the cost and complexity of the aeroponic system.

Other known aeroponic systems deliver the nutrient solution to the roots of plants using a number of small nozzles which aerosolize the nutrient solution. However, the nozzles are prone to blockages and so the nozzles must be periodically cleaned to maintain effectiveness. Nozzles also suffer the same problem of delivering excess nutrient solution to the roots, requiring a complex and expensive recirculation system.

In order to obtain optimum growth rate of plants, it is necessary to ensure that droplets of nutrient solution which are delivered to the roots are of a uniform size. Droplet size can be affected by environmental conditions where the aeroponic system is installed, such as temperature, and will also be changed by differences in the composition of the nutrient solution. However, with known aeroponic systems as discussed above, the physical parameters which affect droplet size, such as the size of the aperture through which the nutrient solution is passed, are set during the manufacturing process. This means that current aeroponic systems are unable to react to environmental changes or changes in the nutrient solution, resulting in inconsistent droplet size, thereby impacting on the growth rates of plants.

The present invention aims to address the problems with known aeroponic systems.

SUMMARY OF THE INVENTION

At its most general, the present invention provides an improved misting device for use in aeroponic systems, which is able to more efficiently disperse and distribute nutrient solution to the roots of growing plants.

According to a first aspect of the invention, there is provided a misting device for an aeroponic system, the misting device comprising a rotatable atomiser configured to receive and aerosolize a nutrient solution. The misting device of the first aspect generates aerosolized nutrient solution by rotation of the rotatable atomiser, which causes the nutrient solution to be separated into droplets by centrifugal force. The rotatable atomiser may be configured to received nutrient solution in that it may comprises one or more channels through which the nutrient solution is able to flow, or it may receive nutrient solution from an external source. For example, nutrient solution may be delivered to the rotatable atomiser by a gravity feed arrangement.

The rotatable atomiser may comprise a structure for receiving and holding (i.e. retaining) the nutrient solution. The structure may comprise a recess for receiving the nutrient solution. The recess may have or be defined by an upstanding wall around a periphery thereof. Rotation of the rotatable atomiser may force the nutrient solution in the recess against the upstanding wall, which in turn cause aerosolization and dispersal. The upstanding wall may be shaped to deflect the aerosolized nutrient solution in a desirable direction. The recess may comprise a planar base onto which nutrient solution is deposited, or through which nutrient solution is passed.

In some embodiments, the upstanding wall may comprise a plurality of lateral apertures through which the nutrient solution is passed at high pressure in order to cause rotation of the rotatable atomiser.

The speed of rotation of the rotatable atomiser may affect the size of the droplets which are produced when the nutrient solution is aerosolized. For example, a higher rotation speed may lead to smaller droplets and a lower rotation speed may lead to larger droplets. In addition, the rotation speed of the rotatable atomiser may affect how far the nutrient solution is dispersed by the misting device. In particular, a higher rotation speed may result in nutrient solution being dispersed over a larger area, and a lower rotation speed may result in nutrient solution being dispersed over a smaller area. In particular, the rotation of the rotatable atomiser may be sufficient to both aerosolize the nutrient solution and also produce sufficient air flow to disperse the nutrient solution throughout an aeroponic system to deliver nutrient solution to the roots of growing plants.

Furthermore, the misting device according to the first aspect of the present invention may generate very little noise, which may be particularly preferable for aeroponic systems which comprise a large number of such misting devices. The misting device according to the first aspect of the invention is low maintenance as the rotatable atomiser will not become clogged with salts and compounds present in the nutrient solution.

The rotatable atomiser may comprise a base section (for retaining the nutrient solution) and an upstanding sidewall. The base section may be provided as a disc, and the sidewall may stand circumferentially on the base section such that the rotatable atomiser is generally in the form of an upturned cup, bowl or bell shape. In some examples, the rotatable atomiser may have a maximum outer diameter of less than 70 mm, such as 50 mm or less. Preferably, the rotatable atomiser may have an outer diameter of at least 10 mm. The shape and form of the upstanding sidewall may be chosen to effect dispersion of the aerosolized nutrient solution, for example the sidewall may be angled to alter the trajectory of the aerosolized nutrient solution as it is ejected from the rotatable atomiser. In some embodiments, the upstanding sidewall may not be a continuous structure. For example, the upstanding sidewall may be provided in the form of a plurality of fan blades configured to provide an air flow as the rotatable atomiser is rotated.

Advantageously, an interior surface of the upstanding sidewall may be textured to augment aerosolization of the nutrient solution. For example, the interior surface may comprise a plurality of grooves and or ridges which help to break apart a film of nutrient solution as the nutrient solution passes over the interior surface due to centrifugal force generated by rotation of the rotatable atomiser. In particular, the textured surface may ensure that the misting device produces small droplets of nutrient solution. Additionally or alternatively, an upper edge of the sidewall may be serrated to augment aerosolization of the nutrient solution in a like manner.

The rotatable atomiser may have rotational symmetry about its rotation axis. This may ensure even dispersal of the nutrient solution in a region around the misting device.

The rotatable atomiser may have an upper face and further comprise a cover which is spaced apart from the upper face.

For example, the cover may have a diameter which is equal to or less than that of the rotatable atomiser. In this way, the cover may ensure that the generation of nutrient solution droplets is not adversely impacted by air flow effects caused by a difference in air pressure at the sides of the rotatable atomiser and the centre of the rotatable atomiser when the misting device is in use. In some embodiments, the upper face of the rotatable atomiser may have a domed shape. This may be particularly advantageous in reducing noise and turbulence during use of the atomiser, and the domed shape may help guide air flowing over the upper surface towards a region where nutrient solution is atomised, to aid atomisation and/or dispersal of the nutrient solution. In some examples, the upper face comprises one or more openings through which nutrient solution passes. For example, the domed shape may be a generally hemispherical or conical shape.

The misting device may further comprise a fan arranged to generate an air flow for conveying the aerosolized nutrient solution away from the rotatable atomiser. Advantageously, the fan may be located proximate to or adjacent to the rotatable atomiser to ensure that an air flow for dispersing atomised nutrient solution is generally confined to, or is strongest in, the region where the droplets of nutrient solution are produced (e.g. the outer edges of the rotatable atomiser). As the air flow is strong in this region, air movement (particular turbulent air movement) is confined to a region proximal the outer edges of the rotatable atomiser, avoiding unnecessary disturbance of roots of growing plants whilst optimising generation and dispersal of nutrient solution droplets. For example, the fan may comprise a plurality of fan blades on the rotatable atomiser. In some examples the fan may be a separate component on the rotatable atomiser, a separate component from the atomiser (for example on a spindle connected to a motor driving the atomiser), or may be unitary with the atomiser. In a particularly preferred embodiment, the rotatable atomiser may comprise a base section and an upstanding sidewall, wherein a plurality of fan blades are mounted to an exterior surface of the upstanding sidewall. The air flow generated by the fan may aid dispersal of the aerosolized nutrient solution over a larger area, without unduly increasing airflow within the aeroponic system. To minimise the risk of fan blades becoming entangled with the roots of growing plants in the aeroponic system, the fan blades may have a length of 35 mm or less, for example.

Preferably, the misting device may further comprise a collar arranged to surround the rotatable atomiser. Such a collar may provide protection for the rotatable atomiser by defining a space within which the rotatable atomiser is rotated, and may protect the rotatable atomiser from roots or the like. The collar may also act as a guide for air flow generated by rotation of the rotatable atomiser, where the air flow is confined to a region proximal the outer edges of the rotatable atomiser. In some arrangements, the rotatable atomiser may also provide a mounting location for an electric field generating element. Advantageously, the collar may be part of the rotatable atomiser itself. For example, the collar may be attached to the atomiser by spacing elements or the like, or, in some arrangements, the collar may be mounted at the radially outer edge of fan blades which generated additional air flow.

Optionally, the misting device may comprise a pump for delivering nutrient solution to the rotatable atomiser. Preferably, the pump is a peristaltic pump, which may help to minimise the maintenance of the misting device which is required. The pump may be configured to deliver nutrient solution at a rate of 600 ml per minute. However, it is particularly preferred that the rate at which nutrient solution to delivered to the rotatable atomiser may be adjusted by a user. For example, the pump may comprise a control unit allowing adjustment by a user either directly or remotely, for example using Wi-Fi or Bluetooth connections. By increasing the rate at which nutrient solution is delivered, a user may increase the size of droplets which are produced by the misting device. Reducing the rate at which nutrient solution is delivered, the size of droplets produced by the misting device may be reduced. In some embodiments, the flow path for nutrient solution may pass from the pump through the rotatable atomiser. For example, the fluid flow path may pass through a base section of the rotatable atomiser in some embodiments.

Preferably, the flow path comprises a passageway in communication with the pump for receiving the nutrient solution. For example, the passageway may terminate at an opening formed in the rotatable atomiser, and so may be configured to deliver nutrient solution directly to a location where it may be dispersed by the atomiser. For example, the opening may be located in an upper face of the rotatable atomiser. Advantageously, there may be a plurality of such openings, for example three or more openings. The openings may take any suitable shape, but it may be preferably for the openings to be elongate so as to aid dispersion of the nutrient solution over a large area. In some embodiments, the upper face of the rotatable atomiser may have a domed shape, and the one or more openings may be located on the surface of the domed shape. The one or more openings may be numbered, positioned, and/or shaped to disperse nutrient solution in a volume of air above the upper surface, such that dispersal of the nutrient solution is not limited to a generally two- dimensional plane or sheet (e.g. a sheet such as a conical surface) extending outwardly from the atomiser.

Preferably, the misting device may comprise a motor arranged to drive rotation of the rotatable atomiser. For example, the motor may be configured to rotate the rotatable atomiser at a speed of at least 1000 revolutions per minute (rpm), preferably at least 15000 rpm, such as 20000 rpm. It is preferred that the speed of the motor may be adjusted by a user, as the speed of rotation of the rotatable atomiser may affect the size of droplets which are produced by the misting device. For example, a higher rotation speed may result in smaller droplets and a lower rotation speed may result in larger droplets. In some examples, the motor may comprise a controller allowing a user to set the rotation speed of the rotatable atomiser either directly or remotely, such as over Wi-Fi or Bluetooth connections for example.

Optionally, the misting device may further comprise an electric field generating element arranged to generate an electric field in a region where aerosolized nutrient solution is generated by the rotatable atomiser. The electric field may induce a charge in the droplets of aerosolized nutrient solution to aid dispersal. The electric field generating element may comprise a first conductive element disposed in the region where aerosolized nutrient solution is generated by the aerosolizer. The first conductive element may be an annular electrode that encircles the rotatable atomiser, for example.

In some embodiments, the misting device may comprise any or all of the features discussed below with respect to the second aspect of the invention.

In a second aspect of the invention, there is provided a misting device for an aeroponic system, the misting device comprising: an aerosolizer (which may also be referred to herein as an atomiser) configured to aerosolize a nutrient solution delivered thereto, and an electric field generating element configured to generate an electric field in a region where aerosolized nutrient solution is generated by the aerosolizer. Preferably, the atomiser comprises a rotatable atomiser configured to receive and aerosolize the nutrient solution. The electric field may induce a charge in the droplets of aerosolized nutrient solution to aid dispersal.

In this way, the electric field generating element may ensure that droplets of the nutrient solution produced by the misting device spread apart from one another as they mutually repel, aiding dispersal of nutrient solution to the roots of growing plants. In addition, when the nutrient solution reaches the roots of plants, the electrostatic charge of the nutrient solution may ensure that the solution is dispersed evenly across the surface of the roots. For example, the electric field generating element may be used as an alternative to a fan or fan blades, as the charge of the droplets may be sufficient to disperse the droplets over a large area. Of course, in some embodiments the electric field generating element may be used in conjunction with a fan or fan blades for an enhanced effect.

Preferably, the misting device comprises a support element for holding the electric field generating element in a fixed position relative to the aerosolizer. For example, the support element may be formed by a portion of a main body of the misting device, or the support element may be a component additional to the main body. The position of the electric field generating element relative to the aerosolizer may be important to ensure that an appropriate level of charge is induced in each droplet which is produced. In some embodiments, the support element may be integrated into a main body of the misting device.

In other embodiments, the electric field generating may be positioned in an upstream location, for example positioned within the flow path of nutrient solution as it is dispersed from the atomiser. In this way the electric field generating element may directly charge droplets of the nutrient solution (e.g. by contact with the nutrient solution). For example, an electric field generating element utilised in this manner may take the form of a needle electrode or the like, or a wire mesh, which may protrude into the flow path of the nutrient solution from a body of the misting device. Of course, any suitable electrode arrangement may be considered. Optionally, the support element may have a textured surface, for example comprising ridges and/or grooves, for conveying nutrient solution away from the electrode. In this way, the textured surface of the support element may help ensure that the electric field generating element does not become coated in any salts or other dissolved elements of the nutrient solution which could otherwise impair operation of the electric field generating element. In some examples, the support element may comprise a hydrophobic material, such as a hydrophobic coating, to similarly convey nutrient solution away from the electric field generating element. Advantageously, the electric field generating element itself may have a hydrophobic coating.

The electric field generating element comprises a first conductive element disposed in the region where aerosolized nutrient solution is generated by the aerosolizer. The first conductive element may be connected to a voltage source to introduce a potential difference (voltage) between it and the nutrient solution before the nutrient solution is aerosolized. For example, the voltage source may be a low voltage source which is external to the misting device, and the misting device may comprise a step up transformer to increase the voltage for the first conductive element. The first conductive element may be an annular electrode disposed in position that encircles the aerosolizer. This may ensure that substantially all of the aerosolized nutrient solution can be charged by the electrode.

The misting device may further comprise a second conductive element in contact with the nutrient solution before it is delivered to the aerosolizer, wherein a voltage is applied between the first conductive element and the second conductive element. The second conductive element may be grounded, for example. This may increase the efficacy of the first electrode in inducing a charge in the aerosolized nutrient solution.

Preferably, the aerosolizer comprises a rotatable atomiser configured to receive and aerosolize the nutrient solution. In particular, the misting device according to the second aspect of the invention may comprise any and/or all of the features described above with respect to the first aspect of the invention. In some such embodiments, the support element for holding the field generating element may comprise at least one blade element which is configured to direct an air flow generated by the rotatable atomiser. For example, the at least one blade element may space the support element away from the main body and/or from the rotatable atomiser.

In a third aspect of the present invention, there is provided an aeroponic plant growing system comprising a misting device according to the first aspect and/or the second aspect of the present invention. Of course, it will be recognised that the aeroponic may comprise any suitable number of misting devices, depending on the size of the system and/or the number of plants which are to be grown. Preferably, the aeroponic system may comprise a control unit for a user to control operation of the misting device. For example, the user may be able to control a flow rate of nutrient solution delivered to the aerosolizer or rotatable atomiser. The user may also use the control unit to control the rotation speed of the rotatable atomiser. In some embodiments, the control unit may comprise a timer to control operation of the misting device at times determined by a user. For example, a user may set the misting device to activate periodically, having 'on' periods when the misting device is active and 'off' periods where the misting device is inactive. In one example, a user may choose that the misting device cycles between active and inactive states, wherein the active state lasts for a predetermined amount of time and the inactive state lasts for a predetermined amount of time. For example, the active state may last for between 0.5 and 30 seconds and the inactive state may last for between 30 seconds and 7 minutes. In some embodiments, the control unit may be integrated into the misting device. Additional or alternatively, the control unit may be wirelessly accessible by a user, for example over the internet, such as using a Wi-Fi connection, or by Bluetooth.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the invention may be understood, and so that further aspects and features thereof may be appreciated, embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a schematic view of an aeroponic system according to an embodiment of the present invention;

Fig. 2 is a perspective view of an aeroponic misting device according to an embodiment of the present invention;

Fig. 3 is a perspective view of an alternative aeroponic misting device which is an embodiment of the present invention;

Fig. 4 is a perspective view of a rotatable atomiser which may be used with an aeroponic misting device;

Fig. 5 is a perspective view of an alternative rotatable atomiser;

Fig. 6 is a perspective view of another alternative rotatable atomiser;

Fig. 7 is a perspective view of an aeroponic misting device according to another embodiment of the present invention;

Fig. 8 is a cut-away side view of the rotatable atomiser in the aeroponic misting device of Fig. 7;

Fig. 9 is a bottom perspective view of the rotatable atomiser from the aeroponic misting device of Fig. 7;

Fig. 10 is a cross-sectional side view of the rotatable atomiser from the aeroponic misting device of Fig. 7

Fig. 11 is a perspective view of a further alternative rotatable atomiser; and

Fig. 12 is a perspective view of another alternative rotatable atomiser.

DETAILED DESCRIPTION; FURTHER OPTIONS AND PREFERENCES

Fig. 1 shows a schematic view of an aeroponic system 100 according to an embodiment of the present invention. The aeroponic system 100 comprises a growing chamber 102, which may also be referred to as a reservoir as it is configured to hold a supply of nutrient solution 120, having sidewalls and a base. The top of the growing chamber 102 is covered with a support structure 104 which is able to support a number of plants 110 which are grown in the aeroponic system 100. The roots 115 of the plants 110 are exposed to air and also to a nutrient solution in the interior space 130 of the growing chamber. The nutrient solution 120 is dispersed throughout the interior space as an aerosol, in a manner which will be explained below.

The system 100 comprises a misting device 10, which uses a pump 50 to draw up nutrient solution 120 from within the growing chamber 102 and disperse the nutrient solution 120 throughout the interior space 130 of the growing chamber 102 as an aerosol. In particular, the misting device 10 is provided to deliver the nutrient solution 120 to the roots 115 of the plants 110 in a manner which will be described in more detail below. Although only one misting device 10 is shown in Fig. 1, any suitable number of misting devices 10 may be selected for the aeroponic system 100, depending on the size of the growing chamber 102, the number of plants 110 which are present, and the amount of nutrient solution 120 which is required to be delivered to the roots 115 of each plant 110.

The aeroponic system 100 may include a control system so that a user is able to adjust the amount of nutrient solution which is delivered, and the rate at which the nutrient solution is delivered. The control system may communicate with the misting device 10 to allow setting of the motor and/or pump, as discussed in more detail below. The control system may comprise a timer to allow a user to set operation times of the misting device 10. For example, a user may wish to run the misting device 10 continuously, or may wish to set on/off cycles. A range of 0.5 to 30 seconds for the 'on' period of the misting device 10 may be chosen, and between 30 seconds to 7 minutes for the 'off' period of the misting device 10, for example.

Fig. 2 shows an example misting device 150 which is an embodiment of the present invention, and is suitable for use in an aeroponic system 100 such as that shown in Fig. 1.

The misting device 150 comprises a body portion 152 which houses a pump and a motor (not shown). The pump takes up nutrient solution from the growing chamber 102 to be delivered to the roots of plants 110 growing in the aeroponic system 100. The body 152 may be substantially water tight such that the misting device 150 can operate when submerged or partially submerged in the growing chamber 102 of an aeroponic system. Preferably, the body 152 is made of a plastics material, such as polyethylene, polyvinyl chloride (PVC) or polypropylene, for example. The pump may be any suitable pump, but a peristaltic pump may be particularly preferred as a low maintenance solution. A peristaltic pump is also beneficial as it may be easily calibrated and controlled to provide a desired amount and/or flow rate of nutrient solution. The pump may draw in nutrient solution directly through an aperture in the body portion or the pump may draw nutrient solution through a tube lying on the base of the growing chamber 102 or from a separate reservoir. Such arrangements may avoid the need for a separate system for recirculating nutrient solution. However, in some embodiments, nutrient solution may be directly supplied to the pump, for example from a separate recirculation system, which may help to ensure that the nutrient solution drawn into the pump has the appropriate composition of nutrients.

A motor within the body 152 is configured to drive a rotatable atomiser 154 which is positioned on top of the body portion 152. The rotatable atomiser 154 is driven by the motor via a spindle 156 which passes through the top end of the body portion 152. The motor may be configured to drive the rotatable atomiser 154 at around 15000 revolutions per minute (rpm). By driving the rotatable atomiser 154 at a high speed, nutrient solution which is deposited therein may be aerosolized and dispersed throughout the aeroponic system. The speed of rotation of the rotatable atomiser 154 may be changed to provide a suitable droplet size of nutrient solution to be delivered to the roots 115, as desired by a user. For example, a higher rotational speed of the rotatable atomiser 154 may provide smaller droplets of nutrient solution, and a lower rotational speed may provide larger droplets of nutrient solution.

As shown in Fig. 2, in this example the rotatable atomiser 154 is a cup or bowl-shaped receptacle. The rotatable atomiser 154 may have rotational symmetry about its rotation axis. It may comprise a recess for receiving nutrient solution (e.g. from the pump). The recess may have a upwardly sloping wall around its periphery to direct the mist upwards from the atomiser. In one example, the rotatable atomiser 154 is generally formed as a hollow truncated cone, having a maximum diameter of around 70 mm. However, the invention need not be limited by the form of the rotatable atomiser 154. Any spinning structure capable for receiving and atomiser nutrient solution may be used.

The body portion 152 may also contain one or more electronic control units so that a user is able to adjust control of the motor and/or the pump, for example to change the rotation speed of the rotatable atomiser 154 and the flow rate of the nutrient solution. The electronic control unit or electronic control units may be in communication with a control system as discussed above with respect to Fig. 1, for example, which may allow the user to set the operating parameters for multiple misting devices simultaneously. Additionally or alternatively, a control panel may be present on the outer surface of the body portion 152, or the electronic control unit may be accessible remotely, for example over a wireless connection such as Wi-Fi or Bluetooth, to adjust control of the motor and/or the pump.

In the depicted embodiment, the nutrient solution is deposited into the rotatable atomiser 154 by a fluid outlet 158 which is located above the rotatable atomiser 154. The fluid outlet 158 is connected to the body portion 152 by a support bracket 160. The fluid outlet 158 may have an outlet diameter of 3 mm or more, which may help to ensure that the outlet 158 does not become clogged over time due to exposure to the nutrient solution. In this example, the pump operates to deliver nutrient solution through a feed conduit that passes through the bracket 160 to the fluid outlet 158, from where it drops into the rotatable atomiser 154.

The invention need not be limited to a particular type of fluid delivery. For example, it is also envisaged that the nutrient solution may be delivered to the interior of the rotatable atomiser 154 through a conduit formed through the spindle 156, where the conduit has an outlet at the base of the rotatable atomiser 154.

The pump within the body portion 152 delivers nutrient solution to the fluid outlet 158 at a rate which may be selected by a user, for example 600 ml per minute. As the rotatable atomiser 154 rotates, the nutrient solution deposited therein is drawn to the outer rim of the rotatable atomiser 154 by centrifugal force due to rotation of the rotatable atomiser 154. The nutrient solution is then discharged from the rotatable atomiser 154 in the form of a spray of droplets, which disperse throughout the interior space 130 of the aeroponic system 100 to supply nutrients to the roots 115. If the flow rate is increased then, all other factors being equal, the droplet size also increases. Correspondingly, a reduction in the flow rate of nutrient solution leads to a decrease in droplet size. In this way, by controlling the flow rate of nutrient solution fed into the rotatable atomiser 154, a user may control the size of droplets which are delivered to the roots of plants growing in the aeroponic system.

Conventional rotary atomisers uses large fan blades to generate an air flow which can carry an atomised liquid to a target, which may require carrying the droplets over large distances. Alternatively, some known devices use an external air source to provide the necessary air flow, such as an air pump or a source of compressed gas. However, it may be desirable to minimise air movement in an aeroponic system, in particular in the growing chamber 102, in order to avoid damaging the delicate roots of growing plants. In order to keep air flow to a minimum necessary to both atomise and disperse the nutrient solution, the misting device 150 may generates air flow only through rotation of the rotatable atomiser 154. The air movement which is generated due to rotation of the rotatable atomiser 154 is confined to a region proximal the outer edges of the rotatable atomiser 154, where the air flow helps to aerosolize the nutrient solution and also to disperse the aerosolized nutrient solution to the roots of the growing plants without unnecessary disturbance of the roots.

The misting device 150 comprising a rotatable atomiser 154 having a maximum outer diameter of 70 mm used in conjunction with a flow rate of nutrient solution of around 600 ml per minute may be suitable for dispersing atomised nutrient solution over an area of 1.2 m². The coverage area may be increased by increasing the rate of rotation of the rotatable atomiser 154, though in order to maintain droplet size the flow rate of nutrient solution should also be increased appropriately.

An alternative misting device 170 is shown in Fig. 3. Features in common with the misting device 150 of Fig. 2 are given the same reference number. The misting device 170 comprises a body portion 152, which is configured to house a pump and a motor as discussed above. The motor within the body 152 is connected to a rotatable atomiser 154 by a spindle 156, such that the motor is able to rotate the rotatable atomiser 154 in order to aerosolize nutrient solution which is deposited therein by a fluid outlet 158. The fluid outlet 158 is positioned above the rotatable atomiser 154 by a support bracket 160, which is also connected to the body portion 152.

In the embodiment shown in Fig. 3, the misting device 170 comprises an electric field generating element 172 arranged to generate an electric field (e.g. a high voltage DC electric field) in a region where aerosolized nutrient solution is generated by the rotatable atomiser 154. The electric field imparts a charge to the droplets of nutrient solution to facilitate dispersal.

In the example shown in Fig. 3, the electric field generating element 172 comprises an annular conductive element (referred to herein as an annular electrode) mounted to surround a periphery of the rotatable atomiser 154. The annular electrode is preferably mounted to lie in a plane that is perpendicular to the rotation axis of the rotatable atomiser 154. Such an orientation may ensure that the electric field is applied evenly around the periphery of the rotatable atomiser 154. However, other orientations may be used, e.g. to obtain a desired dispersal profile.

As depicted, the electric field generating element 172 is mounted on the support bracket 160 which also houses the fluid outlet 158. However, it will be appreciated that the electric field generating element 172 may be mounted in other ways, e.g. by a separate supporting element or mounted directly on the main body.

The electric field generating element 172 produces a high voltage electric field to impart a charge to the droplets of nutrient solution after the solution has been aerosolized by the rotatable atomiser 154. The electric field generating element 172 is connected to a high voltage power source, for example providing 500 V DC or up to 7000 V DC. The power source may be contained within the body portion 152, or the power may be provided by a component external to the aeroponic system and/or misting device. For example, in some embodiments a low voltage may be delivered to the main body, and the main body may comprise a high voltage step up transformer to deliver a high voltage to the electric field generating element 172. By charging the droplets of nutrient solution using the electric field generating element 172, the nutrient solution is more effectively dispersed throughout the interior space of the aeroponic system, as the charged droplets tend to repel each other and so spread apart. The nutrient solution is thereby distributed more evenly among the growing plants, and more evenly cover the roots with nutrient solution. The electric field generating element 172 may have a hydrophobic coating to prevent build-up of nutrient on the electric field generating element 172 which would otherwise hinder the ability of the electric field generating element 172 to impart charge to the aerosolized nutrient solution. To make the electric field generating element 172 more effective at imparting charge to the nutrient solution, the nutrient solution may be in contact with a ground electrode as it is passed from the pump to the fluid outlet 158.

To generate a desired shape for the electric field, the misting device 170 may include a second electrode having an opposite polarity to the annular electrode. The second electrode may be part of the rotatable atomiser 154 or spindle 156, or may be mounted in the housing 152. The nutrient solution may be in contact with the second electrode before it is aerosolized.

Fig. 4 is a perspective view of a rotatable atomiser 154 which may be used with an aeroponic misting device, such as the misting devices 150, 170 discussed above in relation to Figs. 2 and 3. The rotatable atomiser 154 is generally formed as a hollow truncated cone having a substantially planar base 141 and a circumferential upstanding sidewall 142 extending therefrom. The sidewall 142 may have a substantially smooth surface or, in some embodiments, the inside surface of the sidewall 142 can comprise ridges or grooves to help shear the film of nutrient solution to form droplets as the nutrient solution passes over the sidewall 142. Additionally or alternatively, the top edge of the sidewall 142 may be serrated, which may also help to form droplets of the nutrient solution.

A spindle 143 extends downwardly from a lower face of the planar base 141, allowing the rotatable atomiser 154 to be connected to a shaft of a motor in the misting device 150,

170, such that the motor is able to rotate the rotatable atomiser 154 about its axis when the misting device is in use. In some embodiments, the spindle 143 may have a conduit formed therethrough to allow nutrient solution to be supplied directly to the interior space of the rotatable atomiser 154, which may aid in making the misting device more compact, and also help to ensure even dispersal of nutrient solution which may be otherwise impacted by the presence of a bracket for the fluid outlet. The bottom end of the spindle 143 has a recess 144 to allow the rotatable atomiser 154 to be mounted to a shaft of a motor. The recess 144 may be keyed to help engage the shaft and ensure that the spindle 143 does not slip on the shaft of the motor. The spindle 143 also comprises a lateral through-hole 145 for receiving a grub screw to affix the rotatable atomiser 154 to the shaft of the motor.

Fig. 5 is a perspective view of another example of a rotatable atomiser 180 which may be used with a misting device, such as misting devices 150, 170 discussed above with respect to Figs. 2 and 3. As shown, the rotatable atomiser 180 comprises a substantially planar base 141 and a plurality of fan blades 146 upstanding from the top surface of the base 141, in a similar manner to the sidewall shown in Fig. 4. The depicted embodiment shows six fan blades 146, though of course any suitable number of fan blades may be selected. In use, nutrient solution is delivered to a top surface of the planar base. The fan blades 146 are configured to produce a horizontal air flow when the rotatable atomiser 180 is rotation about its longitudinal axis. In this way, the rotatable atomiser 180 is able to disperse atomised nutrient solution over a large area. A spindle 143 projects from the bottom surface of the planar base 141 for affixing the rotatable atomiser 180 to the shaft of a motor in a misting device, as described above with respect to Fig. 4. In some embodiments, the spindle 143 may comprise a conduit therethrough for delivering nutrient solution to the top surface of the planar base 141.

Fig. 6 is a perspective view of another example of a rotatable atomiser 182 which may be used with a misting device according to an embodiment of the present invention, such as misting device 150, 170 discussed above with respect to Figs. 2 and 3, respectively. The rotatable atomiser 182 comprises a planar base 141 and an upstanding circumferential side wall 142. As discussed above with respect to Fig. 4, the sidewall 142 may comprise ridges or grooves on its interior surface, and/or may be provided with a serrated upper edge to help create droplets of the nutrient solution.

In the depicted embodiment, a plurality of fan blades 147 project laterally from the outer edge of the sidewall 142. Six fan blades 147 are shown, though any suitable number of fan blades may be chosen. The fan blades 147 are configured to produce a substantially vertical air flow as the rotatable atomiser 182 spins. In this way, nutrient solution droplets produced by the misting device may be projected upwards by the air flow, and outwards due to the centrifugal force generated by the rotatable atomiser 182. These effects efficiently distribute atomised nutrient solution throughout an internal space of an aeroponic system, such as aeroponic system 100, and onto the roots of growing plants. Preferably, the fan blades 147 extend no more than 35 mm radially from the outer edge of the sidewall 142. Other sizes may be considered by the skilled person, but if the fan blades 147 are too small then they may not generate the desired air flow to aerosolize droplets. If the fan blades 147 are too large then there is a risk of entanglement with the roots of growing plants, which can cause damage to both the plant and the misting device.

Fig. 7 is a perspective view of an aeroponic misting device 200 according to another embodiment of the present invention. Features in common with the misting device 150 of Fig. 2 are given the same reference number. The misting device 200 comprises a body portion 152, which is configured to house a pump and a motor as discussed above. The motor within the body 152 is connected to a rotatable atomiser 205 by a spindle, such that the motor is able to rotate the rotatable atomiser 205 in order to aerosolize nutrient solution which is deposited therein by a fluid outlet 158.

In this example, the rotatable atomiser 205 comprises a disc-shaped recess for receiving nutrient solution through an outlet located on its rotation axis (which lies vertically through the device in this example). The recess has a upstanding lip around its periphery for deflecting and aerosolizing the nutrient solution when the rotatable atomiser 205 is driven by (i.e. spins under the control of) the motor.

In this example, the body 152 includes a reservoir for holding the nutrient solution before delivery to the rotatable atomiser 205. The body 152 includes a input port 202 for delivering nutrient solution to the reservoir, and a window 204, which may permit inspection of the fluid level in the reservoir. A pump in the housing is arranged to deliver the nutrient solution from the reservoir to the disc-shaped recess through a passage in the spindle, as discussed in more detail below, and may be inspected through the window 204 (for example to check that the pump is operating correctly).

The body 152 further comprises a collar 206 mounted to surround the rotatable atomiser 205. In this example the collar 206 is in the form of a truncated cone that flares outward from the top of the device. The collar 206 has three functions.

Firstly, it provides protection for the rotatable atomiser 205 by defining a space within which the rotatable atomiser 205 is mounted. The disc-shaped recess of the rotatable atomiser 205 is substantially flush with the top edge of the collar 206.

Secondly, the collar 206 acts as a guide for air flow generated by rotation of the rotatable atomiser 205. In particular, the collar 206 defines an annular spacing between its inner surface and an outer surface of the rotatable atomiser 205 that provides a preferential flow path for air movement caused by rotation of the rotatable atomiser 205.

This is explained in more detail with reference to Fig. 8 below.

Thirdly, the collar 206 provides a mounting location for an electric field generating element (not shown) arranged to apply an electric field in a region when the aerosolized nutrient solution is formed. In this example, the collar 206 includes an annular channel 207 formed around an upper surface thereof. The annular channel 207 may be arranged to receive an annular electrode of the type discussed above.

Fig. 8 is a cut-away side view of a top portion of the misting device 200. The collar 206 defines an annular passageway 208 around the rotatable atomiser 205 through which air is drawn in an upward direction as shown by arrow 212 when the rotatable atomiser 205 spins. The air is drawn in through an inlet 210 around a base of the collar 206 and exits at an outlet 214 at a top of the collar 206. The rotatable atomiser 205 in this example includes a plurality of fan blades 216 that project laterally from a sidewall 218 thereof. The fan blades 216 are configured to produce a substantially vertical air flow as the rotatable atomiser 205 spins. In this way, nutrient solution droplets produced by the misting device may be projected upwards and outwards by the air flow, and outwards due to the centrifugal force generated by the rotatable atomiser 205. In particular, the air flow may help project droplets outwards as the centrifugal force alone may not be sufficient for all uses.

Figs. 9 and 10 are respectively a bottom perspective view and a cross-sectional side view of the rotatable atomiser 205 from the aeroponic misting device 200 of Fig. 7. Features in common with Figs. 7 and 8 are given the same reference number. In this example, the rotatable atomiser 205 includes a spindle 222 that extends downwardly from the disc-shaped recess. The spindle is hollow to define a passageway 230 through which the nutrient solution is supplied. An upper end of the passageway terminates at an outlet 232 formed in the disc-shaped recess. Although not shown in Fig. 10, a second electrode (e.g. ground electrode) may be located within the passageway 230 to ensure that the electric field produced by the annular electrode mounted in the collar 206 is effective in charging the droplets of aerosolized nutrient solution.

The rotatable atomiser 205 is mounted on a base 220 that is fixed to the housing 152. The base 220 resembles an upturned funnel having a central passage that receives the spindle 222. In some examples the base 220 may house the motor for driving the rotatable atomiser 205. The base 220 is connected to the rotatable atomiser 205 via an upper bearing 228 and a lower bearing 226 that are mounted between an outer surface of the spindle 222 and an inner surface of the rotatable atomiser 205. A circlip 224 is mounted around the spindle 222 to hold the assembly together.

The lower face of the base 220 comprise a number of mounting holes 225 to corresponding with features on the body portion 152 to hold the base 220 and the rotatable atomiser 205 in place. The base 220 also comprises a through hole 227, which is provided to allow electricity to be passed to a motor within the base 220 for driving the rotatable atomiser 205.

Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

Fig. 11 shows a perspective view of a further example of a rotatable atomiser 300 which may be used with a misting device according to an embodiment of the present invention, such as misting devices 150, 170, 200 described above with respect to Figs. 2, 3, and 7, respectively. The rotatable atomiser comprises a planar base 302 having a domed upper face 304 (a top surface of the atomiser) and an upstanding sidewall from which fan blades 308 extend. The rotatable atomiser 300 is configured to receive nutrient solution through a passageway in a spindle (not shown) at the base of the atomiser 300, in a similar manner as described above with respect to Figs. 9 and 10 for example. An upper end of the passageway terminates at three outlets 306a, 306b, 306c formed in the upper face 304. When the rotatable atomiser 300 is in use, nutrient solution is passed through the passageway and dispersed by the atomiser through the outlets 306a, 306b,

306c. The outlets 306a, 306b, 306c are shown as generally elongate openings in the upper face 304, but it is to be understood that the outlets may take substantially any suitable shape. Indeed, although three outlets 306a, 306b,

306c are shown, any suitable number of outlets may be chosen. Preferably, however, the outlets are positioned, shaped, and numbered so as to maintain rotational symmetry of the atomiser 300 about its rotational axis in order to ensure even dispersal of nutrient solution when in use. In the particular example shown in Fig. 11, each outlet 306 is shaped as an elongate slit which curves or slants inwards towards the rotational axis of the atomiser 300. By being shaped in this way, nutrient solution is dispersed along the length of each outlet 306a, 306b, 206c and so is dispersed in a large, 3- dimensional, volume of air about the upper face 304, and the dispersal is not limited to a generally two-dimensional plane or sheet (e.g. a sheet such as a conical surface) extending outwardly from the atomiser 300. In some arrangements, the inner surface of each outlet 306 may be textured (e.g. having grooves or ridges) so as to help break apart a film or sheet of water which passes over the surface, and so creating atomised droplets of water.

The rotatable atomiser 300 further comprises a plurality of fan blades 308 disposed radially about the periphery of the planar base 302, extending outwards from a sidewall of the base 302. As discussed above with respect to other embodiments, any suitable number of fan blades may be selected. The fan blades 308 are configured to provide a generally vertical air flow which passes over the upper face 304 so as to help project droplets of nutrient solution from the outlets 306a, 306b, 306c. As the air flow is directed over the upper face, air movement (particular turbulent air movement) is confined to a region proximal the outer edges of the rotatable atomiser, avoiding unnecessary disturbance of roots of growing plants. In this way, the rotatable atomiser 300 is able to disperse atomised nutrient solution over a large area. By being provided as a generally domed arrangement, the upper face 304 guides air flowing over the upper surface 304 from the fan blades 308 and towards atomised nutrient solution dispersed from the outlets 306a, 306b, 306b. In addition, the shaping of the upper face 304 reduces turbulence, thereby reducing noise generated by the rotatable atomiser 300 and increasing the efficiency and effectiveness of the airflow when in use. Of course, any suitable domed shape may be chosen for the upper face 304. For example, the upper face 304 may be hemispherical or generally hemispherical, for example a generally conical shape, but may also take any other suitable shape. In some embodiments of the present invention, the fan blades 308 may be enclosed within a collar of a misting device, similar to the arrangement described above with respect to Figs. 7 and 8.

Fig. 12 shows a perspective view of a further example of a rotatable atomiser 350 which may be used with a misting device according to an embodiment of the present invention, such as misting devices 150, 170, 200 described above with respect to Figs. 2, 3, and 7, respectively.

The rotatable atomiser 35 comprises a planar base section 352 and an upstanding circumferential sidewall 354. As shown in Fig. 12, the sidewall 354 comprises a number of grooves at its upper edge which help to create droplets of nutrient solution when the nutrient solution passes over the sidewall in use. Of course, other features such as ridges or corrugations as described above may be used as an alternative or in addition to the grooves.

Although not shown in Fig. 12, the base section 352 has an outlet therein through which nutrient solution is introduced to the atomiser. The outlet is a termination point of a passageway formed through a spindle (not shown) at the base of the atomiser 350, in a similar manner as described above with respect to Figs. 9 and 10 for example.

The rotatable atomiser 350 further comprises a plurality of fan blades 356 extending radially about the base section 352. As discussed above with respect to other embodiments, the fan blades 356 provide a generally vertical air flow when in use to help disperse nutrient solution from the atomiser 350. Any suitable number of fan blades 356 may be selected in accordance with the present invention.

The rotatable atomiser 350 also comprises a collar 358, which is mounted at the radially outer tips of the fan blades 356 so as to surround the rotatable atomiser 350. In this embodiment, the collar 358 forms part of the rotatable atomiser 350, and so rotates in use. The collar 358 provides protection for the rotatable atomiser 350, for example by helping to avoid entanglement with plant roots. The collar 358 also acts as a guide for air flow generated by rotation of the rotatable atomiser 350. In particular, the collar 358 defines an annular spacing between its inner surface and the outer surface of the base section 352 that provides a preferential flow path for air movement caused by rotation of the rotatable atomiser 350. In particular, the preferential flow path is directed towards the aerosolised droplets of nutrient solution. As the air flow is directed towards the aerosolised droplets, air movement (particular turbulent air movement) is confined to a region proximal the outer edges of the rotatable atomiser, avoiding unnecessary disturbance of roots of growing plants. In some arrangements, it is also envisaged that the collar may provide a mounting location for an electric field generating element (not shown) arranged to apply an electric field in a region where the aerosolized nutrient solution is formed. In addition, the collar 358 may help reduce turbulence, thereby reducing noise generated by the rotatable atomiser 350 and increasing the efficiency and effectiveness of the airflow when in use.

All of the features disclosed in this specification

985 (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including

990 any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purposes, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclose is one example only of a generic series of equivalent or similar

995 features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims,

1000 abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1005 1. A misting device for an aeroponic system, the misting device comprising a rotatable atomiser configured to receive and aerosolize a nutrient solution.

2. A misting device according to claim 1, further

1010 comprising an electric field generating element arranged to generate an electric field in a region where aerosolized nutrient solution is generated by the rotatable atomiser.

3. A misting device according to claim 1 or claim 2,

1015 wherein the rotatable atomiser comprises a recess for receiving the nutrient solution.

4. A misting device according to claim 3, further comprising an upstanding wall around a periphery of the

1020 recess, wherein rotation of the rotatable atomiser is arranged to force the nutrient solution in the recess against the upstanding wall.

5. A misting device according to claim 4, wherein a

1025 surface of the upstanding wall facing towards the recess is textured to augment aerosolization of the nutrient solution.

6. A misting device according to claim 4 or claim 5, wherein an upper edge of the upstanding wall is serrated to

1030 augment aerosolization of the nutrient solution.

7. A misting device according to any preceding claim, wherein the rotatable atomiser has rotational symmetry about its rotation axis.

1035

8. A misting device according to any preceding claim further comprising a fan arranged to generate an air flow for conveying the aerosolized nutrient solution away from the rotatable atomiser.

1040

9. A misting device according to claim 8, wherein the fan comprises a plurality of fan blades on the rotatable atomiser.

1045 10. A misting device according to any preceding claim, further comprising a pump arranged to deliver nutrient solution to the rotatable atomiser.

11. A misting device according to claim 10, wherein the

1050 pump is a peristaltic pump.

12. A misting device according to claim 10 or claim 11, wherein the rotatable atomiser comprises a passageway in fluid communication with the pump for receiving the nutrient

1055 solution.

13. A misting device according to claim 12, wherein the passageway terminates at an opening formed in the rotatable atomiser.

14. A misting device according to claim 13, wherein the opening is located in an upper face of the rotatable atomiser.

15. A misting device according to any preceding claim,

1065 wherein the rotatable atomiser has an upper face, and wherein the rotatable atomiser further comprises a cover spaced apart from the upper face.

16. A misting device according to claim 14 or claim 15,

1070 wherein the upper face of the rotatable atomiser has a domed shape.

17. A misting device according to any preceding claim, wherein the misting device further comprises a collar arranged

1075 to surround the rotatable atomiser.

18. A misting device according to claim 17, wherein the collar is part of the rotatable atomiser.

1080 19. A misting device according to claim 17 or 18, wherein the collar provides a mounting location for an electric field generating element arranged to generate an electric field in a region where aerosolized nutrient solution is generated by the rotatable atomiser. 1085

20. A misting device according to any preceding claim, further comprising a motor arranged to drive rotation of the rotatable atomiser.

1090 21. A misting device for an aeroponic system, the misting device comprising: an atomiser configured to aerosolize a nutrient solution delivered thereto, wherein the atomiser comprises a rotatable atomiser configured to receive and aerosolize the nutrient

1095 solution; and an electric field generating element configured to generate an electric field in a region where aerosolized nutrient solution is generated by the atomiser.

1100 22. A misting device according to claim 21, wherein the misting device comprises a support element for holding the electric field generating element in position relative to the atomiser.

1105 23. A misting device according to claim 22, wherein the support element has a textured surface for conveying nutrient solution away from the electric field generating element.

24. A misting device according to claim 22 or claim 23,

1110 wherein the support element comprises a hydrophobic material.

25. A misting device according to any one of claims 21 to 24, wherein the electric field generating element comprises a first conductive element disposed in the region where

1115 aerosolized nutrient solution is generated by the atomiser.

26. A misting device according to claim 25, wherein the first conductive element is an annular electrode, and wherein the annular electrode is disposed in position that encircles

1120 the atomiser.

27. A misting device according to claim 25 or claim 26, further comprising a second conductive element in contact with the nutrient solution before it is delivered to the atomiser, 1125 wherein a voltage is applied between the first conductive element and the second conductive element.

28. An aeroponic plant growing system comprising a misting device according to any one of the preceding claims.

1130

29. An aeroponic plant growing system according to claim 28 further comprising a control unit in communication with the misting device, wherein the control unit is operable to control operation of the misting device.