Solar parabolic collector - Patent Review 4561423

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BACKGROUND OF THE INVENTION

This invention relates to a solar parabolic collector, more particularly for water heating, and has as an object the provision of a low cost, efficient collector of this nature, which may be adapted for tracking the sun on a time basis.

STATEMENT OF PRIOR ART

The following U.S. patents pertain to solar collecting and concentrating devices. However, none of these discloses the features of the present invention.

______________________________________ 811,274 Jan. 30, 1906 2,182,222 Dec. 5, 1939 3,990,430 Nov. 9, 1976 4,011,855 Mar. 15, 1977 4,103,672 Aug. 1, 1078 4,167,936 Sept. 18, 1979 4,203,426 May 20, 1980 4,205,659 June 3, 1080 4,241,726 Dec. 30, 1980 ______________________________________

SUMMARY OF THE INVENTION

The invention provides a solar water-heating device comprising an elongate parabolic solar reflector mounted on an incline on a rotary frame with a water circulation tube disposed along the focal line of the reflector, whereby location of the device in suitable disposition facing the sun provides concentration of solar energy on the tube to heat water circulating therethrough. Preferably, the tube is divided longitudinally by a vane into forward and reverse flow channels connected respectively to water inlet and outlet hoses at the base of the tube, the tube having a space at its upper end for reversal of the water flow. The tube may have radially projecting external fins, preferably forming extensions of the vane, to enhance the heat transfer coefficient of the tube. The frame may be automatically rotated under the control of an automatic timer, by an electric motor, to track the sun on a day-to-day basis.

By dividing the tube with the vane, causing water to flow both in forward and reverse direction through the tube, the time available for heating water at the focal line of the collector is increased, allowing a higher temperature to be achieved. Conveniently in manufacture, the tube may, for example, be slotted longitudinally to receive the vane, which may be of sufficient width also to provide fins projecting diametrically from opposite sides of the tube.

For optimum heat transfer, compatible with most ambient conditions, it is desirable for the collector and tube to be inclined at about 47.degree. to the horizontal. Stepped rotation of the collector to track the sun may be provided, for example, by a timer-controlled motor driving a turntable on which the collector is mounted. In one preferred form of the invention, two like collectors are arranged side by side on a common rotary frame.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a solar water heater in accordance with the invention.

FIG. 2 is a rear perspective view of the heater.

FIG. 3 is an enlarged sectional view on line 3--3 of FIG. 1.

FIG. 4 is an enlarged sectional view on line 4--4 of FIG. 1.

FIG. 5 is a sectional view on line 5--5 of FIG. 3.

FIG. 6 is a sectional view on line 6--6 of FIG. 5.

FIG. 7 is an enlarged sectional view of an upper section of one of the heating tubes of the apparatus.

FIG. 8 is a view similar to FIG. 7 of the lower part of the tube.

FIG. 9 is a sectional view on line 9--9 of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIGS. 1 and 2 in particular, a solar water heater, generally indicated 10, comprises a supporting framework 12 for a pair of inclined dished elongate parabolic solar concentrating-type heaters 14, 16 arranged side by side in inclined position on the framework so as to face the sun, the framework having circumferentially disposed wheels or casters 18 for rotatably supporting the framework on a suitable base plate 20. An electric motor 22 in combination with a turntable assembly 24 is provided for rotating the framework, as will be described, so as to enable the heaters 14, 16 to track the sun.

Each of the heaters 14, 16 is of box-like form, comprising an elongate parabolic reflector having respective mirrored Mylar sheets 26, 28 (see FIGS. 3 and 4) supported in parabolic shape on metal backing sheets 30, 32 to which the Mylar sheets are adhered, sheets 30, 32 themselves being backed by fiberglass insulation 34, 36 and support plates 38, 40. At the front, the heaters are covered by respective glass plates 42, 44 in suitable support frames 46, 48, and the heaters have respective metal or the like end plates 50, 51, 52, 53. The glass plates and frames may, for example, comprise standard glass plates and frames may, for example, comprise standard 1/4-inch plate, 4-foot patio doorframes and glass. The heaters are provided with heating tubes 54, 56 disposed along the focal lines of the respective parabolic reflectors, the construction of the tubes being described in more detail below.

Heating tubes 54, 56 comprise lengths of 2-inch copper pipe 58, 60 slotted lengthwise to receive vanes 62, 64 dividing the tubes into longitudinal forward flow passages and reverse flow passages. Forward flow passage 66 and reverse flow passage 68 of pipe 58 are shown in FIGS. 7 to 9, and it will be understood that like passages are formed by vane 64 in pipe 60. The vanes terminate short of the tops of the respective pipes to provide spaces, such as space 70, FIGS. 3 and 7, for reversal of the water flow. Further, the tops of the pipes are bent and provided with vent caps 74, 76 for release of water vapor and the like. At the bottom of each pipe is a base plate (as 78 in FIGS. 8 and 9) with threaded nipples, such as 78, 80 forming water inlets and outlets for connecting the pipes to flexible hoses 82, 84, 86, 88 for the supply of cold water to the respective pipes and delivery of heated water therefrom. It will be noted that vanes 62, 64 are of a width to provide diametrically opposed fins such as 90, 92, (FIG. 9) protruding from the respective pipes with the vanes and pipes being sealed by welding or the like. The fins enhance the heat transfer characteristics of the respective pipes, so as to maintain effective water heating even if the collectors are not optimally aligned in relation to the position of the sun. The tubes 54, 56 are supported in the respective heaters between end plates 50, 52 and internal supporting plates 94, 96. It will be understood that the tube design provides flow of water from the respective inlet up the forward flow passage of the respective tube and then down the reverse flow passage to the heated water outlet. Accordingly, water flowing through the tube has two passes substantially along the focal line of the respective parabolic reflector.

Hoses 82 and 84 extend through a sheath 98 and hoses 86 and 88 extend through a corresponding sheath 100, the sheaths being connected by a T-fitting 102 to common sheathing 104 for the hoses extending down through the center of turntable assembly 24, the sheathing incorporating a rotary joint 106 with a stationary hose sheath 108. The flexibility of hoses 82-88 allows the heaters to be rotated reversely through 180.degree. for sun tracking.

Framework 12 may conveniently be formed of welded metal struts or the like with suitable cross-braces, and the base struts 110 may carry a central plate 112 for supporting a dependent flanged ring member 114 (FIG. 5) forming part of the turntable assembly. Heaters 14 and 16 may be supported on framework 12 by any suitable means, e.g. by welding or by means of support brackets (not shown). The heaters are inclined to the horizontal perferably at an angle of about 47.degree. which is found to provide optimum solar heating in winter conditions compatible with good efficiency in summer. Wheels 18 may be suitably journalled in support brackets 19.

Turntable assembly 24 includes the afore-noted flanged ring member 114 supported for rotation on a similar ring member 116 attached to base plate 20 with an interposed ball bearing 118, the races of which are secured to the respective ring members. Ring member 114 has an external ring gear 120 driven by motor 22 for intermittently rotating the framework 12 for sun tracking.

Motor 22 may, for example, include a suitable reduction gear box (not shown) and may be controlled by a programmed timer to rotate the heater apparatus for say 20 seconds every 15 minutes through the day, for sun tracking, the total swing of the apparatus being through about 180.degree.. The motor may be reversible and the programmed timer may include means for returning the apparatus to the starting position at the end of each day. Limit switches may terminate rotation of the framework at each end of its 180.degree. travel. The timer may be fixed and set to suit the shortest day of the year.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

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