Patent Application
20110087379
The present invention relates generally to an irrigation controller. More particularly, the present invention relates to an efficient solar powered irrigation controller and a method for efficiently operating said controller.
Irrigation controllers are well known as an integral part of an irrigation system for dispersing water across a landscape. Generally, an irrigation system comprises a controller for scheduling irrigation times for a plurality of irrigation zones, each zone further comprising an electrically operated valve, electrically coupled to the irrigation controller, and that is further hydraulically coupled between a water supply line and a plurality of water dispersing elements, such as sprinkles, rotors, emitters, etc.
In designing an irrigation system, the initial cost of materials is considered as well as the cost of operating the system. Large and/or remote commercial irrigation systems are often problematic due to their proximity to water and electrical sources. It is essential to keep the cost of materials to a minimum as it is to keep the cost of operation to a minimum. To that end, it is sometimes desirable to locate the irrigation controller in the approximate midpoint between the irrigation valves. In that way, long runs of conduit and electrical conductors to the valves can be eliminated and the system generally balanced. Long runs of pipe and conductors are more expensive, not only because of the length, but also due to the need for larger gauge pipe and conductors to thwart water pressure and electrical current losses. These problems are exacerbated in large commercial campuses and long, but narrow strips of land, such as easements and medians.
Conventionally, the locations for the irrigation valves were selected based on the terrain and the water supply line run to each valve and, similarly, the location for the irrigation controller was selected based on the locations of the valves and a 110 VAC power line run to the controller. In cases where the power supply is picked off a main line, a power meter was installed for the sole purpose of metering the amount of electrical power to the irrigation system. Alternatively, it was sometimes less troublesome to furnish power to the irrigation controller via a photovoltaic system. Typically, a photovoltaic system consists of a bank of photovoltaic units (solar cells) with their electrical outputs combined through a combiner, in order to reach a predetermined DC voltage level, and charging unit that is electrically coupled between the combiner and a battery. 110 VAC power is supplied to the irrigation controller through an inverter which inverts the DC voltage of the battery(-ies) to the 110 VAC necessary to power the irrigation controller.
While solar powered irrigation controllers do not require the expense associated with a separate power line and therefore, do not incur a charge for the electricity, these photovoltaic irrigation systems are significantly more expensive than conventionally powered controllers due to the addition of photovoltaic systems. While solar cells and batteries have become more efficient and the cost of solar cells continues to decline with their acceptance, these systems remain far more expensive than a conventionally powered irrigation system even considering the long term savings of metered electrical power.
An efficient solar powered irrigation controller system is disclosed with methods for implementing and operating the system. In a solar powered irrigation system, an irrigation controller is configured to deliver a predetermined alternating current voltage to a plurality of solenoid valves for activating the valves. A photovoltaic system is electrically coupled to the irrigation controller and supplies the predetermined alternating current voltage, rather than 110 VAC line voltage, thereby eliminating the necessity for a step-down transformer in the controller. The scheduling of the watering duration in the irrigation cycles is predicating on the amount of solar radiation received at the site, in conjunction with the solar cells in the photovoltaic system, thereby lowering the power consumption of the controller and the plurality of solenoid valves corresponding with solar radiation received at the solar cells. A photovoltaic system is selected for the irrigation system, by matching the power generation capacity of the solar cells to the lowered power demand of the irrigation controller by biasing irrigation zone activation durations with solar radiation.
The novel features believed characteristic of the present invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will be best understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings wherein:
Other features of the present invention will be apparent from the accompanying drawings and from the following detailed description.
In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized. It is also to be understood that structural, procedural and system changes may be made without departing from the spirit and scope of the present invention. The following description is, therefore, not to be taken in a limiting sense. For clarity of exposition, like features shown in the accompanying drawings are indicated with like reference numerals and similar features as shown in alternate embodiments in the drawings are indicated with similar reference numerals.
Solar power irrigation controllers are known in the prior art but are also known to be extremely expensive in comparison to a conventional controller. A solar powered irrigation controller system is depicted in
Generally, irrigation controller 120 is powered by line AC of 110 VAC which is received at transformer 122 which converts the line AC voltage to one or more working voltages, for instance n VAC. It should be mentioned, for the purposes of describing the present invention the terms “house current”, “line voltage”, “wall voltage” or the “mains” are synonymous and reference the 110/120 Volts, 60 Hz standard in the United States. Those of ordinary experience in the relevant technological art will readily understand that the line voltage of the present invention correlates to line voltages standards in other countries and would be able to modify the present invention accordingly without any undue experimentation.
Transformer 122 may be a multi-tap transformer for providing various AC voltages to the different components of controller 120 and water distribution system 150. The n VAC may be further conditioned at optional power converter/inverter 124 into other AC and DC voltage levels, again as required by components of controller 120 and water distribution system 150. Operationally, irrigation controller 120 comprises processor unit 126 that works in conjunction with user interface 130 via I/O 128 for receiving user input parameters for scheduling watering times and durations during predetermined irrigation cycles for the various irrigation zones in water distribution system 150 based on an internal irrigation scheduling program. In practice, processor unit 126 is representative of a CPU, RAM and ROM memory, busses, clocks, timers and/or other electrical and electronic elements necessary for storing and executing instructions in a irrigation scheduling program, as well as receiving and displaying inputs, data and other information for modifying the schedule and as disclosed in U.S. Pat. No. 6,314,340. Operational events and user input are optically displayed on display 132. I/O 128 is electrically coupled to p electronic switches 138 through p signal control leads 134. Each of the p electronic switches 138a-138p is further coupled to processor unit 126 for receiving a solenoid activation signal over a dedicated lead. Each of p electronic switches 138a-138p is also electrically coupled between an m V source and irrigation valve connector 140a-140p. The m V may come from either of optional power converter/inverter 124 or transformer 122 via power leads 136. Each electronic switch 138 is a normally open electronic switch, such as a triac, that is switched closed in the presence of the control signal on lead 134 that is initiated by processor unit 126. When closed, the m V present at a particular electronic switch 138a-138p is received at a corresponding irrigation valve connector 140a-140p and on to a connected solenoid valve 152a-152p for controlling water from water supply 154 to a particular irrigation zone. Essentially, the m V becomes the actuation signal for a solenoid valve.
Most conventional solenoid irrigation valves are currently rated at 24 VAC (actually 24 VAC/VDC), so the irrigation controller generates a control signal of approximately 24 volts (m≈24 V). That is, the electrical solenoid on an irrigation valve is designed to actuate the valve when a 24 V current is applied across the wire coil of solenoid, and release the valve when the voltage is discharged. Nevertheless, most valves actually function in a wide voltage range and may operate reliably in a range between 18 V and 27 V and even lower provided that an electrical current sufficient to create a magnetic field is present with the voltage. This is necessary to accommodate long conductor runs to valves with high resistive losses. Furthermore, because the electrical component in a solenoid is merely a coil of wire, the frequency of the control signal is inconsequently to its operation, in fact, a DC voltage will actuate the valve. Finally, although they are rarely used in the United States, irrigation valves are known with ratings of 12 VAC/VDC and 9 VAC/VDC. Therefore, irrigation controllers produce a control signal voltage that is compatible with the irrigation solenoid valve, typically with an additional 1.0 V to 4.0 V to accommodate long wire runs to irrigation valves, hence, for the purposes of describing the present invention, m<100 V and 9 VAC/VDC≦m≦29 VAC/VDC.
As may be appreciated from the foregoing, the solar powered irrigation systems known in the prior art cobbled together off-the-shelf components to complete the system. However, because the power requirements for an irrigation system can be substantial, the capacity of photovoltaic system 110 had to be determined on a worst case scenario. For example, if each irrigation cycle required X kWh for completion, then the minimum capacity of battery 114 must be no less than X kWh. More importantly, the minimum capacity of solar cell 111 must also be X kWh. However, since the capacity of solar cell 111 to generate electricity is based on the size of the cell per time of exposure to sunlight, the cell must be large enough to generate the minimum power requirement during periods of low sunlight. Hence, for even a small irrigation system, the effective surface area of solar cell 111 must be quite large. Since the solar panel is often the most expensive single component in the system, costs tend to escalate rapidly for large commercial systems and for locations that receive little sunlight (i.e., locations at higher latitudes and experience more cloudy days).
Efforts for lowering the power consumption of the irrigation system have largely been limited to more electrically efficient irrigation valves because it has been understood that the conventional irrigation valve, as well as the long runs of conductors, consume large amounts of electricity. Therefore, it follows that the greatest power reduction could also be derived by improving operational efficiency of irrigation valves. One such improvement is the invention of a latching irrigation valve that receives separate open and close signals without a sustained power signal for maintaining the valve in an open position. While these valves are more efficient, they are much more expensive than conventional solenoid valves and, of course, that expense is multiplied by the number of irrigation zones in the water distribution system.
In view of the shortcomings of the prior art solar powered irrigation controller system, a transformer-less irrigation controller with a modified photovoltaic system is presented that significantly reduces the power consumption of the system. As was previously mentioned, traditionally it was assumed that the solenoid valves consume the most power, as can be generally understood from the power consumption diagram in
Conventionally, the photovoltaic system used for powering an irrigation controller is an off-the-shelf device to provide 110 VAC to the controller because conventional irrigation controllers are designed to operate on a 110/120 VAC line power. However, in the case of a solar powered irrigations system, the requirement of line power is superfluous as it adds an extra and unnecessary voltage converse. In analyzing a solar powered irrigation system, irrespective of inefficiencies in the transformer and photovoltaic system, the larger power consuming component is the irrigation valves, which operate on an AV current, but at a fraction of line voltage. Therefore, in actuality the base voltage level that should predicate an irrigation system is not 110 AC line voltage, but instead m V necessary to actuate the valves. Moreover, since one primary function of the transformer in many irrigation controllers is to step down the line voltage to a level near or equivalent to that required by the solenoid valves, providing that voltage directly to the irrigation controller can eliminate the power consumption of the transformer. The key here is to do so in such a manner as to not increase the power consumption of another component.
A solar powered irrigation controller system is depicted in
Photovoltaic system 210 is identical to system 110 depicted in
Therefore, as can be seen from the diagram of irrigation controller 220 the n VDC originating at photovoltaic system 210 is routed directly to each of p electronic switches 138a-138p. and to optional power converter/rectifier m V to m DC and to q VAC/VDC 224. Power converter/rectifier 224 in some form may be necessary to rectify the AC voltage from photovoltaic system 210 to a DC form that can be used by processor unit 126, perhaps at a different level. It should be mentioned that most irrigation controllers rely on the 60 cycle AC sine wave for timing and clocking latches, so it should be present in the input unless the controller is heavily modified.
Interestingly, preliminary tests with lower voltage inverters suggest that additional power consumption efficiency is gained due to the lower voltage requirement of the controller. In any case, the present invention allows for a substantial reduction of the overall power consumption that is directly attributable to the transformer, represented as the shaded area between the curve representing the total power consumption of the present transformer-less system and the total power consumption curve taken from the diagram in
As discussed briefly above, accurately matching the power requirement of the irrigation system, usually in kilowatt-hours (kWh) (or joules (j)), to the capacity of the photovoltaic system is key to lowering the initial cost of the system and efficiently maintaining thereafter, hence lowering the overall cost of ownership. Irrigation professionals readily understand the power demands of the irrigation equipment they support through vendor publications or experience and understand the watering needs of the foliage on a site. From that information, the professional can readily calculate the peak demand for the irrigation system at a particular location. Photovoltaic systems are typically rated in watts (W) or peak watts. Converting the watt rating to kWh requires knowing the amount of peak sunlight. For instance, due to the position of the sun in the sky, length of the day and average weather conditions, a solar cell in Phoenix, Ariz. will generate approximately sixty percent more power in May and June than in January. Therefore, a good solar radiation source is essential, such as the Solar Radiation Data Manual for Flat-Plate and Concentrating Collectors available from the Renewable Resource Data Resource Center of the U.S. Department of Energy. With that data, the professional matches the peak power demand of the irrigation system (over an irrigation cycle) to a photovoltaic system capable of sustaining that demand at any time.
The amount of overcapacity in the photovoltaic system is represented in the diagram by the distance between the consumption and (solar cell) capacity curves. Ideally, the distance between the curves should remain relatively constant. Optimally, the two curves should be separated by only the amount of the safety factor. From the diagram depicted in
This can be accomplished without substantial harm to foliage because the water usage of most plants and turf (the evapotranspiration rate, usually measured in inches of water) is dictated to a large extent by the amount of solar radiation received by the foliage. Therefore, it can be assumed that the duration of the watering cycle, hence the power consumption of the irrigation controller, are proportional to the power production of the solar cells. That is to say, irrigation cycles in which the plants use more water (and more power is consumed by the controller for watering) correspond to irrigation cycles with high power production from solar cells. The common factor between the power consumption of the irrigation system and the water needs of the foliage is solar radiation, both are proportional to the amount of solar radiation received at the site. Thus, rather than operating the irrigation system throughout the year with constant watering durations in each irrigation cycle, as in the prior art, optimally, the duration of the watering period is adjusted in each irrigation cycle based on the solar radiation received by the foliage at the site. Ideally, in irrigations cycles were the foliage water usage increases, there is a corresponding increase in the amount of power reserve in the batteries from solar cells and, conversely, irrigation cycles where the foliage water usage decreases, there is a corresponding decrease in the amount of power reserve in the batteries because less solar radiation received by the solar cells than can be converted to energy. Seasonally, the two concepts track. In fact, some more advanced irrigation controllers now use the evapotranspiration rate of foliage in an irrigation zone for calculating the duration of the watering period of that zone. One line of advanced irrigation controllers is the family of Smartline irrigation controllers, which is a registered trademark of and available from Telsco Industries, Inc. of Garland, Tex. Typically, these controllers use historic solar radiation data, indexed by latitude, latitude-longitude, ZIP code, address or some other common nomenclature for geographic locations, for calculating a base evapotranspiration rate for foliage water usage. That rate can be further adjusted for any irrigation zone by manually entering the type of foliage present in the zone. Additionally, many controllers have a separate water rate adjustment for fine tuning watering rate by manually increasing or decreasing the calculated watering rate for an irrigation zone.
Matching the power generation capacity of a photovoltaic system (solar cells) with the power consumption requirements of an irrigation system that utilizes solar radiation for calculating watering durations in an irrigation cycle is far more complicated than in the prior art. Here, since the power consumption of each irrigation cycle changes with the amount of solar radiation received at the site, the power consumption should be calculated for each cycle to find the minimum power generation capacity of the solar cells of the photovoltaic system. The process for matching the power generation capacity of the photovoltaic system is depicted in
The use of solar radiation for limiting the power consumption of the irrigation system greatly decreases the amount of overcapacity in the photovoltaic system and provides for a better match to the power consumption of the irrigation system. This is so because both power consumption and power generation are proportion, or at least related, to the amount of solar radiations received at the site. A further objective of using solar radiation to reduce the power consumption of the irrigation controller is for the consumption profile to match the capacity profile, in all irrigation cycles during the year. That is, for the consumption curve to track the capacity curve, or perhaps offset it by the approximate value of the safety factor. This is only possible in cases where the power consumption in the winter months can be decreased and that is only possible if the watering duration can be reduced a corresponding amount in the winter months. Both objectives are realized by basing the watering amount with the amount of solar radiation at the site.
In comparing the consumption-capacity diagram in
The foregoing has been devoted to improvements in a solar powered irrigation system that tend to lower the estimated power consumption of the irrigation system, thereby lessening the front-end cost of ownership. Once the power consumption of the irrigation system has been estimated and photovoltaic system matched to the irrigation system based on capacity, no more capacity can be added without significant added expense. Therefore, the focus of operating the irrigation system should be the efficient use of power that is available from the photovoltaic system while simultaneously meeting the water needs of the foliage, in other words, reducing power consumption wherever possible. Before discussing the operations of the irrigation controller, a brief discussion on selecting battery storage capacity is in order. Ideally, the storage capacity of the battery should be sufficient to hold all power generated by the solar cells (or at least the power that is not immediately consumed). While the objective is simple, the practice is slightly more complicated. Consumption is, as discussed above, uneven between hours, days, or even weeks. At best, the estimated power consumption can only be characterized as matching the power capacity of the solar cells over an entire irrigation cycle. Therefore, the power reserve in a battery should be approximately equivalent to the power consumption over an irrigation cycle (plus the safety factor). Thus, if the irrigation cycle is a week, which is common, the battery's capacity should hold a week's power in reserve. This is necessary for an irrigation system because up to ninety percent of the power consumption is by the water distribution system (consumed by the solenoid valves and losses in the conductors), which might be scheduled for one watering day per week. The size of the safety factory assumes a predetermined inequality in the power consumption and generation, for instance, to allow for some manual watering or for overcast days or foggy days, or maintenance or some combination of each. As a practical matter, the size of the safety factor for the battery might be as little as ten percent or twenty percent of the total power consumption in an irrigation cycle. In situations where operating conditions are known and well understood, to fifty percent or one-hundred percent of a cycle's total power consumption, in situations where operating conditions are not well known or understood.
In either case, however, power consumption should be kept to a minimum to ensure that power reserve in the battery is optimal. The sole mechanism for limiting power consumption during operation is to decrease the duration of activation time and consequently the amount of water delivered to the foliage; ideally, without any detrimental impact on the foliage. This is only possible when the foliage watering needs has decreased. One condition that lessens plants' need for irrigation watering is a precipitation event, rain, snow, ice, perhaps thick fog, heavy dew. Therefore, the use of a moisture sensor (such as the SLW10, SLW15 or SLW20 Smartline Weather Stations, which are available from Telsco Industries, Inc. of Garland, Tex.) for reducing watering and/or canceling watering cycles is advantageous. Thus, power reserve in the battery is not expended unless the foliage actually needs watering.
Another condition that lowers foliage watering needs is less solar radiation being received by the foliage. A historical average of solar radiation used by advanced irrigation controllers for computing the evapotranspiration rates usually accounts for reduction in solar radiations due to annual cloudiness. However, even as few as several additional hours of overcast conditions will lower the evapotranspiration rate for the foliage below that calculated by the controller, and consequently shorten the time needed for watering. Since overcast conditions also have a detrimental affect on power generation by solar cells, the ability to correct watering durations mid-cycle is advantageous for the efficient operation of the irrigation system. Therefore, in accordance with another exemplary embodiment of the present invention, the solar radiation at the site is measured and used to correct the watering cycle. Measuring the amount is solar radiating is usually problematic, however in this case the photovoltaic system reacts to the amount of solar radiation received at the solar cells by converting sunlight to energy. For the purposes of the present invention, that amount can be quantified based on the amount of power available to the battery and, if below a threshold amount, used to bias the watering duration, and thereby decrease the power consumption. Hence, power consumption can be reduced correspondingly with power generation due to overcast conditions.
As will be appreciated by one of skill in the art, aspects of present invention may be embodied as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Furthermore, some aspects of the present invention may take the form of a computer program product on a computer-usable storage medium having computer-usable program code embodied in the medium.
Any suitable computer readable medium may be utilized. The computer-usable or computer-readable medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device. More specific examples (a nonexhaustive list) of the computer-readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a transmission media such as those supporting the Internet or an intranet, or a magnetic storage device. Note that the computer-usable or computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory. In the context of this document, a computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-usable medium may include a propagated data signal with the computer-usable program code embodied therewith, either in baseband or as part of a carrier wave. The computer usable program code may be transmitted using any appropriate medium, including but not limited to the Internet, wireline, optical fiber cable, RF, etc.
The exemplary embodiments described below were selected and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. The particular embodiments described below are in no way intended to limit the scope of the present invention as it may be practiced in a variety of variations and environments without departing from the scope and intent of the invention. Thus, the present invention is not intended to be limited to the embodiment shown, but is to be accorded the widest scope consistent with the principles and features described herein.
The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
