Patent Application
20240349660
The disclosures herein relate to an energy-efficient and space-saving arrangement, apparatus, and method for managing vapor pressure difference (VPD) in a multilayered controlled environment agriculture (CEA) cultivation facility, providing uniform airflow with multiple small air-moving devices or air delivery terminus having perpendicular airflow relative to the plant's canopy. Regarding light waves and airflow, the term perpendicular and parallel may be considered “substantially” perpendicular or parallel.
Plant cultivation through the use of a Controlled Environment Agriculture (CEA) is a rapidly growing industry worldwide.
Plant life depends on 1) A suitable climate and water with nutrients, 2) Carbon dioxide (CO2), and 3) Photosynthesis for growth.
The most critical component of a suitable cultivating climate, and a primary driver of crop quality, is the vapor pressure difference (VPD). VPD is the force that moves water, with nutrients, through a plant. It is calculated by subtracting the room vapor pressure (VP) (VP of the air surrounding the plants) from the plant VP.
The room VP is a function of the temperature and humidity established by the cultivator. The Heating, Ventilating, Air Conditioning, and Dehumidification (HVACD) system precisely controls the temperature, humidity, and room VP.
In general, when made with reference to a forest of trees, the term “canopy” refers to the branches and leaves that spread out at the top of the tree. As utilized herein, the term “canopy” refers to the region above the roots and surrounding the leaves of the plants in the CEA and even the leaves themselves. The plant VP is a function of lighting intensity and airflow velocity and temperature over the plant leaves. Since light intensity is typically a fixed value, the only remaining variables are airflow velocity and temperature, which are directly associated with VPD. The plant leaves and canopy need uniform airflow and uniform temperature to prevent hot spots and support the uniform VPD designed for the crop. For plants to thrive in their natural environment, sun, rain and soil nutrients are needed. But wind plays a critical role in sustaining plants. Wind removes a plant's waste products—oxygen and water vapor—cools the leaves' surface from the radiant heat delivered with sunlight, and supplies CO2 and some O2.
In nature, plants grow on a single layer and the wind blows substantially parallel to the earth's surface, and from a powerful and unpredictable source. A light breeze has an airspeed of 300-600 f/m. Reproducing this air velocity in even a single layer is impractical, as it would require an abnormally large and impractical amount of air moving apparatus.
Researchers conducted a CFD analysis of airflow uniformity in a Shipping-Container vertical farm, using average velocities ranging from 43 to 199 f/m (0.22 to 1.01 m/s). Resource Innovation Institute suggests “many experts recommend an air velocity of 60 to 100 f/m (0.3-0.5 m/s) to remove the saturated vapor of the leaf boundary layer”. Otherwise, the CEA community offers little definitive advice regarding the air velocity needed in the canopy. It may depend on the type of plants and the environmental conditions. Therefore, we will assume it is desirable to maintain an average air velocity of 80 f/m (0.41 m/s) and can adjust this value as more information becomes available. This velocity translates to 80 ft3/m/ft2 of canopy. In comparison, and to demonstrate an order of magnitude, the temperature and humidity control (HVACD) system in a typical CEA facility typically requires airflow of less than 4 ft3/m/ft2 of canopy area.
An efficient way to achieve sufficient air volume to the canopy is by using air amplifiers that use a primary airflow that locally induces another airflow. Assuming an amplified air induction ration of 10:1, only 8 ft3/m/ft2 of primary air is needed to generate 80 ft3/m/ft2 of total. With high induction ratios, mixing air from the HVACD system with canopy air is possible because the air temperature delivered at the plants is much higher than the lowest air temperature delivered from the HVACD system. Further, this arrangement can cause significant savings in the cost of installation and operation.
Restricted room for ductwork makes smaller high-velocity and high-pressure ducting system connected to air amplifiers, a viable alternative to large low velocity and low-pressure ducting. High pressure air connected to air amplifiers may carry as little as 4% of the total required air volume. The air amplifier can make up the difference with local canopy air.
There is clear evidence showing that vibration applied to heat exchangers will enhance heat transfer by disrupting the boundary layer. A boundary layer also exists on plant leaves, and it is reasonable to assume that vibration will also help disrupt this boundary layer and improve heat transfer.
Plants expel oxygen and take in CO2. Therefore, CO2 gas is essential for plant growth and requires monitoring and replenishment as needed. However, CO2 makes up only 0.04% of our atmosphere, or about 420 ppm, and cultivators require up to 1,500 ppm at times to help produce superior crops.
Photosynthesis is the process used by plants and other organisms to convert light energy into chemical energy through cellular respiration, which energy is later released to fuel the organism's activities. Chemical energy, stored in carbohydrate molecules such as sugars and starches, uses water and carbon dioxide to synthesize. In a CEA facility, lights directed at the plants activate photosynthesis.
The open space between the lighting and plants cannot contain objects that could cast shadows or interfere with light that triggers photosynthesis. Light waves heat objects in their path. In CEA facilities, light waves that land primarily on plant leaves, may potentially create hot spots that the canopy ventilation system is designed to prevent.
In a multilayer and multirow cultivation facility, the space immediately above the lighting begins a new layer of plants, followed by another layer of lights, which arrangement is repeated up to the final layer. Efficient use of space in a CEA facility requires the maximum number of plants per cubic foot. Therefore, space for aisles and utilities such as electric cables, water pipes, and air ducts needs to be minimized. Air ducts are of particular concern due to their size. Typically, airflow is through low-pressure air ducts that are too large to fit through the structural members supporting the layers and rows of plants. The ducts weave through the restricted area with sharp turns and pinching, resulting in restricted airflow and excessive pressure drop. Airflow reaching the canopy is parallel to the plants and canopy (see e.g., prior art
Low-pressure ducts must serve multiple plant assemblies and require significant space to route. It is easy to see the difficulty in routing large ducts through the maze of plant assemblies especially considering that the zone between lights and plants is off-limits.
Managing cultivation room climate, nutrients, CO2, and photosynthesis has tended
to receive considerable attention. However, controlling the plant's vapor pressure difference (VPD) tends to succumb to amateur judgment and trial and error. HVAC equipment currently designed for CEA facilities has high dewpoint supply temperatures, resulting in excessive air volumes that do not serve the VPD issue. There are attempts to weave ductwork through tight support structures in a multi-layer/multi-row facility. Fans are haphazardly located, attempting to create sufficient air flow, much of which has no effect. Controlling VPD in these systems is problematic because it involves a mixture of art and science.
Parallel airflow, relative to the canopy, has typically been utilized for moving air in a cultivation room (see e.g., prior art
Airflow leaving a terminus will entrain a secondary airflow. In traditional HVAC applications, the velocity of air leaving a terminus will entrain a secondary airflow is about equal to the terminus airflow, providing an entrainment ratio of 1:1. However, as the terminus airflow velocity increases, so does the entrainment ratio.
Airflow amplifiers or multipliers rely on a high velocity air jet to induce another airstream much the same as air entrainment, but with higher velocity resulting in a significantly higher induction ratios compared with air entrainment ratios. With high primary air velocities, the combined induction and entrainment ratios can reach 25:1. This means that a low volume of high velocity primary air can entrain a significantly higher volume of secondary air. This can result in small air ducts with low primary air volume, capable of generating significant secondary air volume in the canopy.
Primary air entering the canopy creates a pressure that forces an equal volume of air from the canopy and into the surrounding environment for processing by the humidity and temperature control equipment.
Secondary air (entrained or inducted) is recirculated within the canopy and does not help the purging process. Therefore, it is necessary to introduce sufficient primary air in an effective manner to purge the canopy of high temperature and high humidity air, and plant gas, which is accomplished by the herein disclosed CEA facility.
The herein disclosed apparatus, arrangement, and method of use provides improvements upon prior art systems.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
The present invention addresses the issue of precise control of VPD, which has received little attention in the CEA industry, but is, nevertheless, critical in the cultivation environment. Current systems designed to promote airflow and VPD have been haphazard due to the difficulty of getting uniform airflow to the plants.
The herein disclosed configuration for a CEA facility emphasizes space efficiency and enables filling the allotted space with the maximum number of plants, which typically will be organized to have multiple layers and multiple rows of plants. The distance between layers is minimized to optimize the room height. The distance between rows is also minimized for optimal use of the room width and length. Irrigation pipes and electric power lines for lighting are small and easily routed through the structure. In the prior art CEA facilities, achieving adequate airflow was attempted through the introduction of air flowing over the canopy, and is usually an afterthought. In the herein disclosed CEA facility, the airflow originates from centralized fans and is delivered through ducts that weave through the structure, to achieve airflow throughout and within the canopy, which is minimally assisted by airflow through the HVACD system, whose primary purpose is to control humidity and temperature. The herein disclosed design utilizes a novel configuration for air flow ducts, permitting greater airflow that is strategically directed towards the plants being cultivated by the CEA facility, enabling improved results.
One concept of this invention is to promote uniform air movement over the plants and canopy by placing the airflow source close to the point of use. As a result, energy is saved by eliminating the ductwork pressure drop. Further, airflow perpendicular to the plants and the canopy is significantly more effective than random airflow parallel to the plants and canopy. In addition, each plant's exposure to air, water, nutrients, light, and CO2 is provided in uniform proportions in the herein disclosed CEA facility to ensure the crop development is uniform. But it is noted that uniformity can differ between the growth stages. For example, early-stage plants entering the process should receive uniform and equal exposure to all elements, while grown plants, leaving the process at harvest-stage should also receive uniform exposure, but exposure can differ between growth stages.
The basic concept of this invention is to optimize VPD, and conserve space, in an energy-efficient manner by bringing the source of airflow close to the canopy and delivering it perpendicular to the canopy.
Air movement directed towards the plants is essential. Delivering air in a structurally dense environment where nothing can interfere with the light waves serving the plants is difficult. Generating air movement as close to the plants as possible and delivering this air perpendicular to the plant canopy ensures it is most effective.
The disclosed apparatus and arrangement and method of use provide local air-moving devices that create perpendicular airflow relative to the plant canopy to better meet the canopy airflow needs.
The herein disclosed apparatus and arrangement and method of use operate to maintain VPD, in a tight space, with low energy consumption.
The herein disclosed apparatus and method for managing vapor pressure difference (VPD) in an improved multilayered controlled environment agricultural facility, including plants and irrigation tray assemblies. The section above the roots and surrounding the plant leaves is the “canopy.” The light waves from multiple light sources are directed perpendicular to said plant and irrigation tray assemblies; and multiple air terminus are mingled with the light sources for directing airflow perpendicular toward the plant and tray assemblies.
The apparatus may include electrically powered multiple muffin fans strategically positioned between the light sources. The light sources may comprise light bars or individual light bulbs, but light-emitting diodes (LEDs) and/or other fiber optic light sources are more preferably used.
Air amplifiers are driven by a primary air source delivered through conduits that induce a secondary airflow directed perpendicular to said plant and irrigation tray assemblies. These air amplifiers are preferably located between adjacent light bars.
A separate conduit may also be utilized to feed a measured supply of CO2 from its contained source to the primary air supplying the terminus, where an air/CO2 mixture is directed substantially downward to the canopy. By “directed downward,” it means that the airflow is perpendicular to the plant trays holding the plants, as further discussed hereinafter. As a result, the air amplifiers generate up to twenty-five times the airflow volume of the high-pressure air or compressed air input to the plants.
In a preferred embodiment, a controlled environment agricultural (CEA) facility includes:
As used throughout this specification, the word “may” is used in a permissive sense (i.e., meaning having the potential to, or being optional), rather than a mandatory sense (i.e., meaning must), as more than one embodiment of the invention may be disclosed herein. Similarly, the words “include”, “including”, and “includes” mean including but not limited to.
The phrases “at least one”, “one or more”, and “and/or” may be open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C”, “one or more of A, B, and C”, and “A, B, and/or C” herein means all of the following possible combinations: A alone; or B alone; or C alone; or A and B together; or A and C together; or B and C together; or A, B and C together.
Also, the disclosures of all patents, published patent applications, and non-patent literature cited within this document are incorporated herein in their entirety by reference. However, it is noted that the citing of any reference within this disclosure, i.e., any patents, published patent applications, and non-patent literature, is not an admission regarding a determination as to its availability as prior art with respect to the herein disclosed and claimed apparatus/method.
Furthermore, any reference made throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection therewith is included in at least that one particular embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Therefore, the described features, advantages, and characteristics of any particular aspect of an embodiment disclosed herein may be combined in any suitable manner with any of the other embodiments disclosed herein.
Additionally, any approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative or qualitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value or recitation modified by a term such as “about” is not to be limited to the precise theoretical characteristic or value specified, and may include values that differ from the specified value in accordance with design variations that may be described in the specification, as well as applicable case law. Also, in at least some instances, a numerical difference provided by the approximating language may correspond to the precision of an instrument that may be used for measuring the value or characteristic. A numerical difference provided by the approximating language may also correspond to a manufacturing tolerance associated with production of the aspect/feature being quantified/described (see e.g., Ex Parte Ollmar, Appeal No. 2014-006128 (PTAB 2016)). Furthermore, a numerical difference provided by the approximating language may also correspond to an overall tolerance for the aspect/feature that may be derived from variations resulting from a stack up (i.e., the sum) of a multiplicity of such individual tolerances.
Similarly, the term “substantially” means that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
The herein disclosed multilayered controlled environment agricultural facility 100 may be seen in
Plant leaves have a specific vapor pressure that is determined using the leaves surface temperature and relative humidity within a thin “boundary layer” on the leaves surface. Plants are transpiring continuously, and therefore the relative humidity in the boundary layer may always be 100%.
However, the leaf surface temperatures may also vary with light intensity and air turbulence. Uniform air turbulence on the canopy leaf surfaces may be a function of the canopy ventilation system 200.
The multilayered controlled environment agricultural facility 100 may have a specific vapor pressure that is determined from the temperature and relative humidity of the room, which are selected by the cultivator and becomes a key ingredient in their “recipe” for the plants being cultivated.
The difference between the plant and room vapor pressures is the vapor pressure difference (better known as the vapor pressure deficit or VPD) which is also selected by the cultivator and becomes a key ingredient in their “recipe.” With uniform canopy ventilation, the leaf vapor pressures, and vapor pressure deficit (VPD) are also uniform.
Therefore, the airflow generated by the canopy ventilation system 200 has two functions. First, to break up the boundary layer and provide uniform air turbulence on the plant leaves. Second to purge the heat and humidity produced as radiant heat and transpiration originating from the plants using.
For simplicity.
Also, for simplicity,
The agricultural facility 100 may have an enclosure 101 that may form a sealed and controlled environment for the layers and rows. The environment of the agricultural facility 100 within the enclosure 101 may be controlled by one Heating, Ventilating, Air Conditioning, and Dehumidification canopy ventilation system 200 that is configured to precisely control the temperature, humidity, and room vapor pressure (VP).
As may be seen in
An HVACD system may maintain the temperature surrounding the canopy. Each HVACD system 110 may have a main inlet 110I, into which may be drawn the return air RAIR, as described hereinafter. Each HVACD system 110 may additionally have an air outlet 110T (which is in fluid communication with at least one overhead duct 112, as noted above). An overhead supply air duct 112 may be positioned over the agricultural facility 100. Each duct 112 may be formed to include a plurality of spaced apart openings 113 to facilitate outflow of the supply air CAIR into the room 100 throughout the length of each layer. Each HVACD system 110 may deliver conditioned/controlled air CAIR, to maintain room temperature, humidity, and room vapor pressure (VP). The conditioned/controlled air CAIR may be delivered from the HVACD system 110 to a primary air supply duct 112.
Each layer, as seen in
The delivery of the conditioned/controlled air CAIR to each of the trays underlying the respective primary air supply duct may be seen in the enlarged views of
As seen in
In one embodiment, the phrase “substantially perpendicular,” in relation to the angle θ may be deemed to mean an angle θ that is ninety-degrees angle plus or minus about 15 degrees in each direction, and in another embodiment, the phrase “substantially perpendicular” may be deemed to mean a ninety degree angle plus or minus about 15 degrees in each direction, and in yet a further embodiment, the phrase “substantially perpendicular” may be deemed to mean a ninety degree angle plus or minus 5 degrees in each direction, and in yet a different embodiment, the phrase “substantially perpendicular” may be deemed to mean a ninety degree angle plus or minus 2 degrees in each direction. The number of branches utilized may be increased as necessary (i.e., is not limited to two), to facilitate any one of the above-noted embodiments and provide the requisite “substantially perpendicular” airflow (see e.g.,
As seen in
Since a boundary layer is essentially a microclimate that surrounds each leaf of each plant, and because it affects the speed at which heat, CO2, and water vapor are exchanged between the leaves and the surrounding air, and since a thicker boundary layer reduces this rate of transfer, vibrations are used in the agricultural facility 100. As shown in
While illustrative implementations of one or more embodiments of the disclosed system are provided hereinabove, those skilled in the art and having the benefit of the present disclosure will appreciate that further embodiments may be implemented with various changes within the scope of the disclosed system. Other modifications, substitutions, omissions and changes may be made in the design, size, materials used or proportions, operating conditions, assembly sequence, or arrangement or positioning of elements and members of the exemplary embodiments without departing from the spirit of this invention.
Accordingly, the breadth and scope of the present disclosure should not be limited by any of the above-described example embodiments, but should be defined only in accordance with the following claims and their equivalents.
This application claims benefit in part under 35 U.S.C. § 119 (e) from provisional application No. 63/460,217, filed Apr. 18, 2023, the disclosures of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63460217 | Apr 2023 | US |
