Patent Application
20150024674
The production of citrus is a worldwide industry worth many billions of dollars. Much of the world supply of citrus fruit is cultivated in the sub-tropical regions of the Earth's temperate zones and many of the prime citrus growing areas, though not subject to severe winters, are subject to occasional freezing.
Citrus varieties harvested in winter, such as California's famous oranges and lemons, are prone to frost damage and must be protected from the occasional light frost endemic to some citrus growing regions. Frost protection is a major cost of citrus production.
Protection from frost is critical. Most citrus will freeze when fruit temperature drops to 27-28° F. The main methods of frost protection in California and similar growing regions, such as Arizona, are by wind and water.
Water application allows for heat built up in the soil during the day to be lost more slowly, and air temperatures around the fruit stay warm a little longer. The temperature ranges of effective water usage are limited and, since the frost protection is most critical as the fruit nears harvestability, a wet orchard can inhibit harvesting access.
Wind machines, large fans on structures extending above the grove's tree tops and above the temperature inversion that forms on frosty nights, are used to force warmer inversion air above the orchard down to tree level, warming the fruit. The machines, whose large propellers are typically powered by stationary diesel engines, are turned on when the temperatures near freezing. The fans mix the slightly warmer air above the grove with the colder air near the ground, warming the area around the trees.
A few growers use oil-burning orchard heaters, but this once common method is seldom used now because of the enormous cost in fuel and labor, because of the limited effectiveness of the practice, and because of its attendant pollution.
Wind machines tend to be very popular in growing areas characterized by valley floors where temperature inversions are common during freezes. In these areas, it is not uncommon to see many machines in larger groves, population densities of machines approximating one for every five to ten acres.
However effective they may be, wind machines are very expensive to purchase, operate and maintain. They require year-long maintenance and, during periods of nightly frosts, they require frequent refueling. The location of the machines, isolated from each other and from constant supervision, makes the fuel in their tanks an attractive target for fuel thieves. Additionally, in order to reduce the necessary maintenance of a wind machine that is performed well above ground level, some wind machines have their engines located at ground level, with the propeller being powered through a system of drive shafts and gearing. This additional complexity results in more rapid wear and more frequent breakage which incurs additional expense. Furthermore, wind machines in groves adjacent to residential areas cause significant noise nuisance and, in some instances, birds have been killed by the rotating propellers.
Propeller-driven wind machines also are very inefficient. Such machines, lose much of their energy to moving their propeller blades through essentially all of the air moved by the machine. Because of the efficiency losses of propellers, the equivalent energy input, through fuel or electricity, can be as much as five times the energy output in the form of moving air. The air so moved is also very turbulent due to the rotating action of the propeller blades, resulting in energy being expended to rotate the air mass, in addition to moving it toward the crops needing frost protection.
The present invention provides a method and apparatus for protecting agricultural crops from frost damage by the use of induction flow fans.
A system for protecting an agricultural field from frost damage, comprising: one or more induced flow devices, each comprising an induced flow fan that has a primary air flow inlet, a primary air flow outlet, a secondary flow inlet and a secondary flow outlet wherein said primary air flow induces a larger volume of secondary air flow; a primary air flow impellor, powered by a motor, and a duct arrayed to conduct the primary flow from the primary flow impellor to the induced flow fan. The induced flow devices, commonly of a type known as bladeless fans, are disposed to induce the flow of warmer, upper-level, air into a lower level, displacing cooler air in an agricultural field.
These and other objects and advantages of the present invention will become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures.
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with these embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it should be understood by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present invention. At times, concepts disclosed in this discussion of embodiments of the present invention will be made more readily apparent by reference to the Figures.
Presented herein is a system for protecting an agricultural field from frost damage. The system comprises one or more bladeless fans for moving air in the manner needed to protect agricultural crops from freezing air, in accordance with common practice for displacing colder air in an inversion with warmer air from higher levels. Embodiments of the present invention use induced flow technology in a novel fashion to provide that frost protection of vulnerable crops. One embodiment of the present invention, utilizing bladeless induction fans to displace relatively cool air in the vicinity of a vulnerable crop with relatively warmer air from above, is illustrated in
A duct in the induced flow duct 10 allows the primary air to exit the duct through a slot (81 in
In another embodiment, the duct 12 functions as support structure or stanchion for the induced flow fan housing 11. It is noted here that, in an embodiment of the present invention, the warm total air flow 17 is directed by the pointing of the induced flow housing 11. In addition to downward deflection, five to eight degrees in one embodiment, consistent with prior art propeller-driven machines, the housing is enabled to rotate about a vertical axis on a slewing bearing 15 which, in this embodiment, is powered by motor 16. The action of motor 16 and slewing bearing 15 serves to direct total air flow 17 over 360 degrees, enabling the coverage of a relatively large area. In prior art implementations of propeller-based warming fans, the coverage area can be on the order of 5-10 acres. In one embodiment of the present invention, the ground level cool air is displaced by warmer air up to a distance of nearly 400 feet, encompassing an area of more than 10 acres.
It is noted here that, in another embodiment, not shown, a primary air inlet duct provides primary air flow 19 to be drawn from the warmer region supplying secondary air 18. This duct lies, in this embodiment, essentially parallel to duct/station 12 but is not directly connected to it.
Because of the nature of induced flow fans as shown in these illustrations of the present invention, the cost of operation of crop protection fans can be much lower that of the prior art propeller-based fans. Most especially, the energy cost of running a crop protection fan, which can be thousands of dollars in a single season, is much reduced. This is due to the inherent efficiency of induced flow.
In both the embodiments illustrated here, the only moving part above the slewing bearing is the duct/stanchion 12 and the induced flow fan housing 11. This provides the significant advantages over prior art of reduced mechanical complexity which results in a reduced cost of maintenance as well as a potentially reduced acquisition cost. Furthermore, by providing non-moving means of inducing airflow, potential bird-strikes/injuries are significantly reduced and, significantly, environmental noise of operation is very much reduced. This allows growers to more aggressively protect their crops while remaining good neighbors and good stewards of the land.
It is also noted here that induced flow housing 10, shown in both
In the embodiment illustrated in
It is also noted here that, because flow 17 is less turbulent that prior art propeller-driven machines, damage to crops from excessive flow can be avoided at higher primary velocities when using embodiments of the present invention. This can enable higher primary velocities, resulting in a warming coverage greater than that afforded by the equivalent prior art machine.
In this illustration, slewing bearing 15 and slewing motor 16 are shown, for the purpose of illustration, as being close to the underside of induced flow duct 10. In another embodiment, slewing bearing 15 and slewing motor 16 are near ground level. In such an embodiment, there can be a higher moment load on slewing bearing 15 due to wind gusts on induced flow duct 10 and the length of duct/stanchion 12. Slewing bearing 15 enables these moment loads by being of a very robust type associated with the slewing bearings of cranes and excavators. Slewing motor 16 is geared to slewing bearing 15, in this embodiment, much in the way such motors are enabled in cranes and excavators.
Also illustrated in
It is noted here that, in both duct embodiments shown here, secondary air flow enters induced flow duct 10 past rounded leading edges 71 of the upper and lower flow nozzles 9 and 11 and structural members 28 and 29. The rounded leading edges allow the maintenance of laminar flow for a longer time on entry into duct 10, reducing the downstream turbulence of total flow 17 which can be associated with some crop damage.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.
This application claims priority from, Provisional U.S. Patent application: Ser. No. 61/741,464, entitled “AGRICULTURAL FROST PROTECTION USING INDUCTION FANS,” filed Jul. 18, 2012. The referenced Provisional U.S. patent application is hereby incorporated herein by reference in its entirety.
