Patent Description:
Deep water culture (DWC) hydroponic systems are widely used. Such systems generally include individual growing buckets interconnected by a common pipeline for (a) circulating nutrient solution to the buckets and (b) maintaining a common liquid level in the buckets. Various designs are used, depending on the number of buckets in the system. Reference may be made to <CIT> which relates to an aeroponic growing system, double T-shaped sprayer design and method for cultivating larger plant crops and increasing harvest frequency. The system comprises a series of aeroponic growing units, each of which supports a plant's roots within an enclosure. The enclosure houses a sprayer, an interior volume of plant nutrient solution and a plumbing system for accepting and distributing the aqueous water-nutrient solution. Reference may be made to <CIT> which relates to systems and methods for aeroponic plant growth involving closed loops of growing units linked by plumbing sections. The system comprises N growing units, where N is an integer greater than <NUM>; and N-<NUM> supply plumbing sections that each connects one of the growing units to another, such that a linear array of N growing units linked by supply plumbing sections is formed.

The most commonly used designs are bottom systems, such as those manufactured by Current Culture H2O, especially under the UNDER CURRENT® trademark. These systems feature an "epicenter" or reservoir tank, which serves as the nutrient mixing tank and usually includes a float valve to maintain a pre-set liquid level. The epicenter tank feeds nutrient solution to one or more rows of growing buckets connected to the epicenter tank by the common pipeline, which is near the bottom of the tanks. At the end of each row, a pump is provided to draw nutrient solution from the pipeline and return it to the epicenter tank. This design creates a circulation in which nutrient flows from the epicenter tank, progresses from one tank to the next in a sequential or serial order, and then returns to the epicenter tank. This design often includes a system air pump and bubblers in each grow tank to oxygenate the nutrient solution.

Unfortunately, existing bottom systems have a number of shortcomings in their design and performance.

First, existing bottom systems generally require a large diameter (<NUM>" or more) pipeline to enable nutrient solution circulation and to maintain a common nutrient solution level in the tanks by gravity. Accordingly, labor and material costs are relatively high. Installation and assembly require skill and precision to assure proper leak-free operation. Tanks become rigidly constrained to each other.

Second, existing bottom systems use progressive or sequential circulation, which leads to variation in nutrient solution quality delivered to each bucket. Circulation rate is limited in order to assure gravity equalized tank levels. As a result, plants are not consistently maintained in equal nutrient environments. This manifests itself in roots seeking nutrient and growing into the circulation piping between tanks, potentially partially blocking circulation of nutrient.

Third, in existing bottom systems, nutrient concentrations and pH level must be adjusted as plants grow. These adjustments are slow to make in bottom systems. Chemicals must be added slowly to the epicenter tank to avoid shocking the plants, particularly the plants in the first buckets downstream of the epicenter. This process reduces the time that system operators have for other tasks.

The aforementioned problems are overcome by the present invention.

The present invention is defined by the appended independent claim to which reference should now be made. Specific embodiments are defined in the dependent claims. In a first arrangement of the invention, the DWC nutrient circulation system supplies the grow tanks in parallel and empties the grow tanks at essentially the same rate as the tanks are filled. Therefore, each grow tank receives the same volume and the same quality of nutrient solution, and the level of the solution across grow tanks is equal.

The hydroponic system of the first arrangement includes a plurality of grow tanks arranged in pairs, a circulation pump having an inlet and an outlet, a nutrient supply line fluidly connecting the outlet of the circulation pump to the grow tanks, and a tank drain line fluidly connected to the grow tanks. Each of the grow tanks is fluidly connected in parallel between the nutrient supply line and the tank drain line. The system further includes (a) a pump suction line fluidly connected to the inlet of the circulation pump and (b) a plurality of bridge connectors each fluidly connecting the tank drain line to the pump suction line.

This first arrangement of the DWC plumbing system provides a number of advantages over known systems. The DWC system maintains equalized tank solution levels across the grow tanks, and the system delivers fresh nutrient to the grow tanks essentially simultaneously in essentially equal volumes. The DWC system enables the use of relatively small diameter pipe, fewer and simpler tank connections, and a consistent method for scaling system size from two to virtually any number of tanks operating together. The DWC system eliminates the need for the series connection of grow tanks. The DWC system enables flexible grow tank configurations and connections, which simplify setup, operation, and maintenance, all using relatively low-skilled labor. The DWC system enables grow tanks to be individually moved or removed for cleaning.

In a second arrangement of the invention, the DWC system includes a nutrient supply tank fluidly connected to the circulating pump intake through a valve arrangement. This enables fresh nutrients and/or pH change chemicals to be added to the system through the nutrient supply tank. The contents of the nutrient supply tank are drawn into the pump suction line and are mixed with the recirculating solution from the grow tanks. The mixture or blend is pumped through the piping, and is injected into the grow tanks in a relatively short time, essentially simultaneously and in essentially equal amounts to each grow tank.

This second arrangement of the DWC plumbing system provides a number of advantages over known systems. For example, the DWC system enables the relatively simple, safe, and rapid adjustment of nutrient and pH levels of the nutrient solution, thereby reducing the risk of shocking the plants.

These and other advantages and features of the invention will be more fully understood and appreciated by reference to the description of the current arrangement and the drawings.

Before the embodiments of the invention are described, it is to be understood that the invention is not limited to (a) the details of operation or construction or (b) the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is limited by the appended claims.

In addition, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of "including" and "comprising" and variations thereof encompasses the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. Further, enumeration may be used in the description of various embodiments.

Directional terms, such as "vertical," "horizontal," "top," "bottom," "upper," "lower," "inner," "inwardly," "outer," and "outwardly," are used to assist in describing the invention based on the orientation of the embodiments shown in the illustrations. The use of directional terms should not be interpreted to limit the invention to any specific orientation.

A deep water culture (DWC) hydroponic system constructed in accordance with a first embodiment of the invention is illustrated in the drawings and generally designated <NUM>. The system <NUM> includes a plurality of buckets or grow tanks <NUM> and a nutrient supply system <NUM>.

The disclosed embodiment includes twenty-four buckets or grow tanks <NUM>. However, virtually any number of buckets could be included. The buckets <NUM> are arranged in pairs such as the bucket pair <NUM>, which includes bucket 12a and bucket 12b. As seen in <FIG>, the buckets <NUM> are arranged into two banks 18a and 18b of twelve buckets (and therefore six pairs) each.

The nutrient supply system <NUM> includes a pump suction line <NUM>, a tank drain line <NUM>, a nutrient feed line <NUM>, a plurality of bridge connectors <NUM>, a nutrient tank <NUM>, a level control tank <NUM>, a plurality of circulators <NUM>, a plurality of tank drain hoses or tank drain connection lines <NUM>, a plurality of circulator supply hoses <NUM>, a chiller <NUM>, a fresh water feed line <NUM>, a circulation pump <NUM>, and various valves.

The pump suction line <NUM>, the tank drain line <NUM>, and the nutrient feed line <NUM> preferably are parallel to one another within each bank <NUM> of grow tanks <NUM>. The pump suction line <NUM> is fluidly connected to the inlet or suction <NUM> of the circulation pump <NUM>. The tank drain line <NUM> is fluidly connected to the level control tank <NUM>. The nutrient feed line <NUM> is fluidly connected to the output of the chiller <NUM>.

The output <NUM> of the circulation pump <NUM> is fluidly connected to the chiller <NUM> by line <NUM>. The output of the chiller <NUM> is fluidly connected to the nutrient supply line <NUM> by the hose <NUM>. The inclusion of the chiller <NUM> is optional. If the chiller <NUM> is not included, the nutrient supply line <NUM> is connected directly to the output <NUM> of the circulation pump <NUM>. Typically, the lines of one or two banks <NUM> would be served by one circulation pump <NUM>.

Each of the grow tanks <NUM> is fluidly connected by a drain hose <NUM> to the drain line <NUM>. Each grow tank <NUM> includes a circulator <NUM> mounted on and/or in the tank. Each circulator <NUM> is fluidly connected by a circulator supply hose <NUM> connected to the nutrient feed line <NUM>. Fresh nutrient is introduced into each tank <NUM> through the circulator <NUM>, while stale nutrient leaves each tank through the drain hose <NUM>. The circulators <NUM> may be of any suitable type known to those skilled in the art. Example circulators are disclosed in (a) <CIT> entitled "Hydroponic Nutrient Aeration and Flow Control Device and System" and (b) <CIT> entitled "Hydroponic Nutrient Solution Aeration Device.

The bridge connectors <NUM> fluidly connect the drain line <NUM> to the pump suction line <NUM> at selected locations. The circulator pump <NUM> draws the stale nutrient into the suction line <NUM> from the drain line <NUM> through the bridge connectors <NUM>. The number and the location of the bridge connectors <NUM> preferably follows a pattern that depends on the number of tank pairs <NUM> located along the banks <NUM>.

<FIG> shows the bank 18a of tanks <NUM>. As previously noted, the tanks <NUM> are arranged in pairs <NUM>, such as the pair including tanks 12a and 12b. In the current embodiment, each bank <NUM> includes six pairs <NUM> of tanks <NUM> for a total of twelve tanks in the bank. A first half <NUM> of the pairs (i.e. three pairs) in the bank 18a is relatively close to the circulation pump <NUM>, and a second half <NUM> of the pairs (i.e. three pairs) is relatively remote from the circulation pump. When a bank <NUM> includes an even number of pairs <NUM> (as illustrated), each half <NUM>, <NUM> includes an equal number of tanks <NUM>. When a bank includes an odd number of pairs <NUM>, one of the halves <NUM>, <NUM> includes one more pair than the other half.

The number and the pattern of the bridge connectors <NUM> is a function of the number of tank pairs <NUM> within the bank <NUM>. This number of tank pairs is designated N. In the disclosed system, N is <NUM> for each of the banks 18a, 18b.

For the first half <NUM> of the tank pairs, the number of bridge connectors within the half is:.

Because N is <NUM> in the disclosed embodiment, and because <NUM> is greater than or equal to <NUM>, one bridge connector is included in the area of the first half <NUM>. This one bridge connector is designated 26a in <FIG>. The bridge connector 26a may be located anywhere within the first half <NUM>, but preferably is somewhat centrally located.

For the second half <NUM> of the tank pairs, the number of bridge connectors within the half is:.

The above formulas result in an even number N and the next higher odd number N+<NUM> having the same number of bridge connectors.

Because N is <NUM> in the disclosed embodiment, four (i.e. <NUM>/<NUM> + <NUM>) bridge connectors are included in the second half <NUM>. These bridge connectors are designated 26b, 26c, 26d, and 26e. Preferably the bridge connectors are located at somewhat regular intervals within the second half <NUM>.

With the number and the location of the bridge connectors <NUM> according to the pattern, the bridge connectors assist in providing an essentially uniform suction line vacuum pressure in the drain line <NUM>. Consequently, each grow tank <NUM> empties at essentially the same rate as the tank is filled by the circulator <NUM>. This issue is discussed below in more detail in the section entitled "Computational Fluid Dynamic Verification of DWC System" and illustrated in <FIG>.

Currently, the drain hoses <NUM> and the circulator supply lines <NUM> are flexible hoses to allow some tank movability. Further, the hoses may be fitted with quick disconnects so the individual grow tanks <NUM> can be removed, for example, for cleaning.

Currently, the lines <NUM>, <NUM>, and <NUM> may be <NUM> inch (<NUM>) ID polyethylene pipe with push-together fittings for ease of assembly and handling, eliminating the need to use large tank bulkhead fittings and PVC pipe. Other materials may be used for the lines <NUM>, <NUM>, and <NUM>, including flexible hose. For longer lines, larger diameter may be used to reduce pump pressure drop.

As described, the system <NUM>, including the nutrient circulation system <NUM>, maintains an essentially equal liquid level in each grow tank as fresh oxygenated nutrient is introduced equally and simultaneously into each tank.

The nutrient supply tank <NUM> and its connection within the system <NUM> reduce the time required for nutrient and pH adjustment from as much as one hour down to several minutes. The nutrient supply tank <NUM> and its connection within the system <NUM> also virtually eliminate the possibility of shocking the plants with high concentrations of chemicals.

The following steps are followed when the nutrient level and/or the pH are to be adjusted.

The DWC system <NUM> is filled with fresh water and/or is otherwise prepared for nutrient and/or pH adjustment.

The circulation pump <NUM> is turned off, and the shut-off valve <NUM> is opened, enabling the water level in the nutrient tank <NUM> to rise to the same level as the water level in the grow tanks <NUM>.

The nutrient chemicals in the amount required for all the grow tanks together are introduced into the nutrient tank <NUM> and preferably are stirred until mixed.

The circulation pump <NUM> is then turned back on. The nutrient tank contents are drawn into the pump suction line <NUM> and are mixed with the return solution from the grow tanks <NUM>, diluting the nutrient tank contents to a safe level. Generally speaking, it takes approximately two minutes to empty the nutrient tank <NUM>. A foot valve <NUM> in the bottom of the nutrient tank <NUM> closes as the tank empties, preventing air from entering the pump suction line <NUM>.

The circulation pump <NUM> delivers the solution to the nutrient feed line <NUM>, from which the solution is fed into each grow tank <NUM> essentially equally and essentially simultaneously.

Computer-aided design (CAD) models of various configurations of the DWC system <NUM> incorporating the bridge system design methodology of the present invention have been modeled using SOLIDWORKS® Flow Simulation program. The models indicate, among other factors, the uniformity of the solution levels within the individual tanks <NUM> of the system. The results of the computational fluid dynamics (CFD) models of configurations of systems having <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> tanks are illustrated in <FIG> respectively.

The CFD models were compared with actual laboratory results. In all cases, the CFD models matched the laboratory results, and the models met the design goal of less than <NUM> inch (<NUM>) variation among the solution levels within the individual tanks. The CFD models accurately predict system performance. And the CFD models may be used to determine the appropriate inside diameters of the bridge connectors <NUM> for optimum solution level equalization.

A variation of using the nutrient tank <NUM> to add liquid nutrients to the system is illustrated in <FIG>. This variation includes a syringe <NUM> that may be releasably fluidly connected to the pump suction line <NUM>, which in turn is connected to the intake <NUM> of the pump <NUM>. The syringe <NUM> in essence replaces the nutrient supply tank <NUM>. The syringe <NUM> is fitted with a quick coupling <NUM> that may be snapped into a mating coupler <NUM> mounted to the pump suction line <NUM> proximate the pump inlet <NUM>.

To add liquid nutrient, the syringe <NUM> is removed (if not already removed) by disconnecting the quick coupling <NUM> from the coupler <NUM>. The syringe <NUM> is then filled by positioning the quick coupling in a supply of liquid nutrient (not shown) and drawing the nutrient into the syringe. The quick coupling <NUM> is then reconnected to the coupling <NUM>, and the liquid nutrient within the syringe <NUM> may be pushed into the pump suction line <NUM> to mix with the returning nutrient. This variation is both fast and convenient.

A second embodiment <NUM> is illustrated in <FIG>. Elements of the second embodiment that correspond to elements in the first embodiment have designating numbers that are the same plus <NUM>. For example, the tanks <NUM> in the second embodiment correspond to the tanks <NUM> in the first embodiment. In <FIG>, the circulation pump, and inlet of the circulation pump, are denoted by reference signs <NUM> and <NUM>, respectively.

The tanks <NUM> as illustrated are arranged in single row. Multiple rows may be included in the system <NUM>. The tanks <NUM> are supported by legs <NUM>, which enable the plumbing lines to be routed under the tanks, thereby freeing up floor space between the tanks. Each tank <NUM> includes a cylindrical boss <NUM> (see <FIG>), which enables the tank to be plugged into the tank drain line <NUM>. This connection arrangement enables each tank <NUM> to be installed and removed relatively easily, for example for service.

Preferably, the plumbing includes a modular design that enables snap-together installation. Each modular section includes a bridge connection <NUM>. However, only those connection bridges <NUM> required for solution level equalization include flow passages.

The above descriptions are those of the current embodiments of the invention. Various alterations and changes can be made without departing from the broader aspects of the invention as defined in the appended claims.

Claim 1:
A hydroponic system (<NUM>) comprising:
a plurality of grow tanks (<NUM>);
a circulation pump (<NUM>) having an inlet and an outlet;
a nutrient supply line (<NUM>) fluidly connected to the outlet of the circulation pump (<NUM>);
a plurality of tank supply lines (<NUM>) each fluidly connecting the nutrient supply line (<NUM>) to one of the grow tanks (<NUM>);
a tank drain line (<NUM>);
a plurality of tank drain connection lines (<NUM>) each fluidly connecting one of the grow tanks (<NUM>) to the tank drain line (<NUM>), whereby each of the grow tanks (<NUM>) is fluidly connected in parallel between the nutrient supply line (<NUM>) and the tank drain line (<NUM>);
a pump suction line (<NUM>) fluidly connected to the inlet of the circulation pump (<NUM>); and
a plurality of bridge connectors (<NUM>) each fluidly connecting the tank drain line (<NUM>) to the pump suction line (<NUM>).