Solar Heat Exchange Panel

FIELD OF THE INVENTION

The invention described herein generally relates to a solar heat transfer panel and more particularly to a lightweight and easily manufactured polymer or polymer composite panel which can be flexibly combined in various configurations to heat both liquid fluids and air simultaneously.

BACKGROUND OF THE INVENTION

Solar heat exchange panels typically include a plurality of channels through which a fluid, such as a heat exchange fluid (e.g., water) is passed. Typically, a heat exchange panel is oriented so as to expose the exterior surfaces of the channels to a source of thermal energy, such as radiant heat (e.g., the sun). The channels are heated by exposure to the heat source, and thermal energy is transferred to the fluid passing through the interior of the channels. The heated fluid may be used directly or indirectly, e.g., to heat another fluid, such as air or water, in which case the heated fluid is typically described as a heat exchange fluid.

The cost and difficulty of manufacture has been a limiting factor to acceptance of many of these systems. Especially those made of metals. A number of plastic based systems have been proposed in an attempt to lower both the cost and the weight of the systems, particularly because of a desire to place many of these systems on rooftops. The use of plastic materials have then introduced issues of strength and rigidity.

In addition many of these systems have been limited to either liquid (e.g. water) or gas (e.g. air) systems.

Attempts have been made to improve the efficiency of solar heat exchange panels by increasing the surface area of the exterior channel surfaces that are exposed to radiant energy. For example, solar heat exchange panels having V-shaped or triangular shaped exterior channel surfaces have been disclosed. See for example, U.S. Pat. Nos. 4,290,413; 4,243,020; and 4,171,694.

U.S. application Ser. No. 13/144,254 describes a heat exchange panel comprising an upper and lower plate with a series of extensions between them defining a hollow interior space used to pass a fluid through. It provides a panel that can be used for solar heating but is relatively difficult to manufacture and does not provide a top surface that effectively captures enough solar energy.

It would be desirable to develop a new solar heat exchange panels having improved efficiencies. In particular, it would be desirable that such newly developed heat exchange panels provide a favorable balance and coupling of factors including light weight, optimum thermal transfer, optimum heat exchange fluid through-put, minimum panel dimensions, the ability to heat both fluids and gases, and the ability to easily connect multiple arrays of the panels for various applications. In addition, it would be further desirable that such newly developed heat exchange panels lend themselves to relative ease of manufacture, assembly and use.

SUMMARY OF THE INVENTION

These needs are met by providing a solar heat exchange panel (10) that includes a lower plate (320) and an upper plate (310) that together define an interior volume containing a flowing heat transfer fluid. The upper plate (310) includes a plurality of upward extensions (50), herein referred to as dimples, and downward extensions (60), herein referred to as pockets, that cover the top surface of the solar heat transfer panel and are configured to capture solar radiant energy. The lower plate (320) plate includes a plurality of upwardly extending hollow lower plate extensions (330). The lower plate extensions (330) are aligned with the center bottom portions of each upward extension (50) of the upper plate and almost touching. Each of the downward extensions (60) from the upper plate (310) extend down and are joined to the base of the lower plate (320). In operation, a heat transfer fluid introduced into an inlet (30) on one end of the solar heat transfer panel passes through the defined interior volume and is intimately contacted with the solar heated surfaces extending down into the solar heat transfer panel from the upper plate. A substantially infrared transparent plate across the top surface of the solar heat transfer panel creates a top interior space that encloses a path of flowing air which is simultaneously heated along with the enclosed heat transfer fluid in the lower interior space.

In another aspect the solar heat transfer panel is molded in such a way that in such a way that the upwardly extending hollow lower plate extensions (330) are molded to join or knit to the center bottom portions of each upward extension (50) of the upper plate.

The features that characterize the solar heat transfer panel are described in this disclosure. The operating advantages and the capabilities obtained by its use will be more fully understood from the following detailed description and accompanying drawings in which preferred (though non-limiting) embodiments are illustrated and described.

As used herein and in the claims, terms of orientation and position, such as, “upper”, “lower”, “top”, “bottom”, “exterior”, “interior” and similar terms, are used to describe the invention as oriented and depicted in the drawings. Unless otherwise indicated, the use of such terms is not intended to represent a limitation upon the scope of the invention, in that the invention may adopt alternative positions and orientations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative perspective top view of a solar heat exchange panel.

FIG. 2 is a representative perspective view of a series of the solar heat exchange panel of FIG. 1 configured for both liquid and gas communication between panels.

FIG. 3 is a representative perspective view of a cross section of the heat exchange panel of FIG. 1.

FIG. 4 is another perspective view of a cross section of the heat exchange panel of FIG. 1.

FIG. 5 is another perspective view of a cross section of the heat exchange panel of FIG. 1.

FIG. 6 is another perspective view of a cross section of the heat exchange panel of FIG. 1.

FIG. 7 is a perspective view of a cross section of an embodiment the heat exchange panel of FIG. 1.

FIG. 8 is a representative perspective bottom view of a solar heat exchange panel.

FIG. 9 illustrates a stimulation of the flow patterns achieved in the design illustrated in FIGS. 1-8.

In FIGS. 1 through 9, like reference numerals designate the same components and structural features, unless otherwise indicated.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 are perspective views that exhibit a single solar heat exchange panel 10 and a system of connected solar heat exchange panels 100 connected into a network. Beginning with FIG. 1 a perspective view of a solar heat exchange panel is shown as the numeral 10. The view is looking down on the top surface of the solar panel, which would receive the solar radiation. On each end of the solar heat exchange panel is an inlet 30 and an exit 35 for the transfer of a heat exchange fluid into and out of the interior volume of the panel. The interior arrangement and volume of the solar heat exchange panel will be shown in subsequent drawings. The heat exchange fluid would commonly be water but could be other suitable fluids. The interior top surface of the solar heat transfer panel consists of a repeated series of deep pockets 60 and raised dimples 50 that make up an upper plate of the solar heat transfer panel. That upper plate and a lower plate to be described in subsequent drawings enclose the interior volume of the panel. Solar heat exchange panel 10 is surrounded by a sidewall structure 25 and the top of that structure has a shelf structure 40 substantially encircling the top of the solar panel. Shelf 40 can accept a flat infrared transparent plate (not shown) that would cover the top portion of the solar heat transfer panel, creating an enclosed volume between the interior top surface of the solar heat transfer panel and the infrared transparent plate. This enclosed volume can be used for heating air which can then flow from panel to panel through interconnecting pipes 130.

At selected locations around the sidewall structure 25 there are small valleys 20 that allow the insertion of the interconnecting pipes 130. As shown in FIG. 2 the air flow pipes 130 are used to connect panels 110 and 120 as well as panels 120 and 125. For configurations in which no interconnecting air pipe is needed a suitable plug 150 is inserted in valleys 20. In a similar manner inlet 30 and exit 35 are used to flow the heat transfer liquid fluids from panel 110 to panel 120. As can be seen an important aspect of the solar heat transfer panels is the ability to simultaneously heat both air and a liquid fluid simultaneously in the same system. These air and liquid flows can flow concurrently or counter currently from panel to panel.

In FIG. 3, shown as the numeral 300 is a perspective view of the panel of FIG. 1, this time shown in a cross section to show the interior structure of the solar heat transfer panel. The cross section is cut through the center of a row of the dimple structures 50. The solar heat transfer panel is shown to have an upper plate 310 and a lower plate 320. The lower surface surface of upper plate 310 and the upper surface of lower plate 320 bound an interior volume of the solar heat transfer panel through which the liquid heat transfer fluid flows as it enters one end of the panel at inlet 30 and exits at the other end at outlet 35. Lower plate 320 has a continuing series of extensions appearing as “hills” 330 extending up from the lowest plane of lower plate 320, each one extending up to and very near the bottom of the dimples 50 immediately above them.

This is further exhibited in FIG. 4, in a side view represented by the numeral 400 showing how each of the lower plate extensions 330 extend up almost to the bottom trough of each of the upper plate dimples 50. This design choice ensures turbulent flow and mixing of the heat transfer fluid as it passes through the solar heat transfer panel.

FIG. 5, shown generally as the numeral 500 is the same cross sectional view as FIGS. 3 and 4 but from a different angle and shows the interior volume bounded by the upper surface of lower plate 320 and the lower surface of plate 310. Also shown here is how the lower portion 355 of the deep pockets 60 extend all the way down to the upper surface of lower plate 320 and are molded to that upper surface of plate 320 to increase the strength and stiffness of the solar heat transfer panel. In addition those deep pockets represent a way of capturing many of the incident solar rays deep into the space of the solar heat transfer panel as rays that enter are reflected deeper into the pockets rather than reflecting back into space. These deep pockets then extend well down into the interior volume occupied by the flowing heat transfer fluid. Similarly the dimple structures 50 have a curvature that captures much more of the radiant energy, and effectively transfers it into the interior fluids. Thus the alternating deep pocket/dimple configuration provides improved energy capture from the radiant solar energy, effectively transfers it deep into the panel, and provides increased turbulent flow of the heat transfer fluids which provides improved heat transfer from the upper plate into the contained fluids.

In FIG. 6 the same solar heat transfer panel as shown in FIGS. 3,4, and 5 is shown but with the cross section being taken through a row of the deep pockets to show the interior volume in a different way. The deep pockets 60 are now seen more directly and in particular their contact 420 with the bottom plate 320 at 420. The deep pockets are thus molded to the bottom plate 320 at multiple position across the solar heat transfer panel during the molding process to improve the strength and stiffness of the resultant solar heat transfer panel.

FIG. 7 is the same view as FIG. 5 but showing another embodiment in which the panel is molded in such as way that the deepest center portion of each dimple 50 on the upper plate is molded to the top of each extension 330 from lower plate 320. This embodiment provides stiffness and strength to the solar heat transfer panel. The joined portions 55 are shown. The stiffer design allows thinner upper and lower plates and therefore improved heat transfer internally to the heat transfer fluids.

FIG. 8, shown generally as numeral 800 is a perspective view of the bottom side of the solar heat transfer panel—that is the side on the opposite side that receives the solar rays. The deep areas 430 are the undersides of the extensions or ‘hills” 330 shown in for example FIGS. 4 and FIG. 7. Indentations 450 in the sidewalls 25 are molded into the design to break the flow patterns in the lower interior volume and insure that the flow of the heat transfer fluid through the panel does not short circuit around the outside but instead maintains a well mixed flow through the portion of the panel interior that maximizes heat transfer to the fluid from the deep pocket surfaces 355 of FIG. 5.

The plastic materials of these solar heat transfer panels are molded thin to minimize weight and improve conductive heat transfer. For very high operating temperatures the bottom side of the solar heat transfer panel, as shown in FIG. 8, may lose too much heat to the environment. For that possibility an additional insulated box or panel (not shown) could be placed around the bottom base of the solar heat transfer panel. This insulated “box” could be manufactured of any suitable insulating material. An example could be a box of suitably thick Styrofoam, but other insulating materials are possible.

In use it is desirable to achieve a good turbulent flow of the heat transfer fluid through the interior of the solar heat transfer panel to maximize efficiency. In the design process a finite element flow simulation was used to evaluate different configurations. The flow analysis for the solar heat transfer panel shown in FIGS. 1-8 is shown in FIG. 9. The flow pattern is very efficient and shows the importance of the indentations 450, without which the flow exhibits a highly by-passed behavior with most of the fluid flowing around the outside walls of the panel. The indentations 450 create a structures within the lower interior volume that force the heat transfer fluid to follow a tortuous path through the lower interior volume in each panel.

In operation of the solar heat exchange panel, a heat exchange fluid enters into inlet 30, and follows a tortuous path through the lower interior space and experiences turbulent flow around the downward solar heated extensions 355 (FIG. 5) from the upper plate and the upward extensions 330 (FIG. 3) of the lower plate, transferring the collected radiant heat from the solar side of the solar heat transfer panel into the fluid, which eventually exits at 35.

In other embodiments of the solar heat transfer panel shown, the shape of the upper portion of the lower plate extensions 330 is not limited to the ones shown, but could be selected from more rectangular shapes or from truncated pyramidal shapes having an upper truncated surface. The upper truncated surface would define the upper transverse surface of the upper portion of the lower plate extension. Similarly the shape of the lower portion of the upper plate extensions 355 is not limited to the ones shown, but could be selected from more rectangular shapes or from truncated pyramidal shapes having an upper truncated surface. The upper truncated surface would define the upper transverse surface of the upper portion of the lower plate extension. The inventive concept in the solar heat transfer panel is not limited to the shapes shown in FIGS. 1-8.

As described earlier the solar heat exchange panel may optionally further include a plate (not shown) that covers the open top defined by the sidewall structure. The plate is typically substantially transparent to infrared radiation, and may rest on and optionally be fixedly attached to the upper terminus of the sidewall structure. The term “substantially infrared transparent” and similar terms means the plate allows a major amount (e.g., at least 50 percent) of the incident infrared radiation to pass therethrough and into the interior sidewall structure space. The substantially infrared transparent plate may optionally be fixedly attached across the top of sidewalls 25 by for example: adhesives (not shown); fasteners (not shown) extending through the plate and into the sidewall structure; and/or snap fittings (not shown). The plate substantially encloses the interior sidewall structure space.

In a further embodiment of the present invention, the sidewall structure includes a shelf 40 upon which the infrared transparent plate is placed. With the shelf embodiment, the height of the sidewall structure is greater than the maximum height of the plurality of upper plate dimples 50.

The substantially infrared transparent plate of the solar heat exchange panel, allows infrared radiation to enter the interior sidewall structure space, and be absorbed at least in part by the exterior surfaces of upper plate dimples 50, the deep pockets 60, and other exterior surfaces of upper plate 310, such that a substantial part of the heat energy is transferred to a heat exchange fluid flowing through the interior passages. In addition, the infrared transparent plate prevents foreign materials (e.g., precipitation, leaves and bird droppings) from entering interior sidewall structure space and fouling the exterior surfaces of the upper plate extensions. The infrared transparent plate itself can be easily cleaned. The infrared transparent plate also allows a gas, such as air, to be retained within interior sidewall structure space and heated by the incident infrared radiation, thus resulting in convective transfer of heat energy from the heated entrapped gas to/through the upper plate 310 and into the heat exchange fluid flowing through the interior passages of the solar heat transfer panel.

In addition the capacity to heat the air within the interior sidewall structure can be used to pass air through the solar heat transfer panel simultaneously with an interior heat transfer fluid, making the solar heat transfer panel into a dual purpose heater that can, for example, simultaneously heat water and air.

The infrared transparent plate covering the open top and enclosing the interior sidewall structure space of the sidewall structure may be fabricated from any suitable infrared transparent material, such as glass and/or plastics, such as thermoset plastic materials and/or thermoplastic materials (e.g., thermoplastic polycarbonate). Typically, the infrared transparent plate is rigid and substantially self-supporting.

The heat exchange panel of the present invention, and the various components may each be independently fabricated from any suitable material or combinations of materials. Materials from which the heat exchange panel of the present invention, and the various components thereof, may be fabricated, include but are not limited to, metals (e.g., ferrous metals, titanium, copper and/or aluminum), cellulose based materials, such as wood, ceramics, glass, and/or plastics (e.g., thermoplastic materials and/or thermoset plastic materials).

In a preferred embodiment that leads to lighter weight and ease of manufacture the solar heat exchange panel can be manufactured from polymer or polymer composite materials in a molding operation, using either thermoplastic or thermoset polymers. The molded plastic components of the heat exchange panel of the present invention may be prepared by a number of molding methods, including, but not limited to, blow molding, injection molding, reaction injection molding, compression molding and sheet thermoforming.

In a further embodiment of the solar heat transfer panel the top surface (solar facing) of the panel can be coated by “selective surfaces” or selective absorbers. These surfaces take advantage of the differing wavelengths of incident solar radiation and the emissive radiation from the absorbing surface. Different combinations of materials are often used. Example selective surfaces include copper with a layer of back cupric oxide, steel plated with gold, silicon, and silicon dioxide, and black chromium nickel plated copper.

As used in this description, the term “thermoset polymers” and similar terms, such as “thermosetting or thermosetable polymers” means plastic materials having or that form a three dimensional crosslinked network resulting from the formation of covalent bonds between chemically reactive groups, e.g., active hydrogen groups and free isocyanate groups, or between unsaturated groups. Thermoset plastic materials from which the various components of the solar heat exchange panel may be fabricated include for example crosslinked polyurethanes, crosslinked polyepoxides, crosslinked polyesters (such as sheet molding compound compositions) and crosslinked polyunsaturated polymers. The use of thermosetting plastic materials typically involves reaction injection molding. Reaction injection molding typically involves injecting separately, and preferably simultaneously, into a mold, for example: (i) an active hydrogen functional component (e.g., a polyol and/or polyamine); and (ii) an isocyanate functional component (e.g., a diisocyanate such as toluene diisocyanate, and/or dimers and trimers of a diisocyanate such as toluene diisocyanate). The filled mold may optionally be heated to ensure and/or hasten complete reaction of the injected components.

As used in this description, the term “thermoplastic polymer” and similar terms, means a polymer material that has a softening or melting point, and is substantially free of a three dimensional crosslinked network resulting from the formation of covalent bonds between chemically reactive groups (e.g., active hydrogen groups and free isocyanate groups) of separate polymer chains and/or crosslinking agents. Examples of thermoplastic materials from which the various components of the solar heat exchange panel may be fabricated include, but are not limited to, thermoplastic polyurethane, thermoplastic polyurea, thermoplastic polyimide, thermoplastic polyamide, thermoplastic polyamideimide, thermoplastic polyester, thermoplastic polycarbonate, thermoplastic polysulfone, thermoplastic polyketone, thermoplastic polyolefins, thermoplastic (meth)acrylates, thermoplastic acrylonitrile-butadiene-styrene, thermoplastic styrene-acrylonitrile, thermoplastic acrylonitrile-stryrene-acrylate and combinations.

In an embodiment of the present invention, the thermoplastic material from which each of the various components of the heat exchange panel may be fabricated is independently selected from thermoplastic polyolefins. As used herein and in the claims, the term “polyolefin” and similar terms, such as “polyalkylene” and “thermoplastic polyolefin”, means polyolefin homopolymers, polyolefin copolymers, homogeneous polyolefins and/or heterogeneous polyolefins. For purposes of illustration, examples of a polyolefin copolymer include those prepared from ethylene and one or more C₃-C₁₂alpha-olefins, such as 1-butene, 1-hexene and/or 1-octene.

The plastic materials of the various components of the solar heat exchange panel may in each case independently and optionally include a reinforcing material selected, for example, from glass fibers, glass beads, carbon fibers, metal flakes, metal fibers, polyamide fibers (e.g., KEVLAR polyamide fibers), cellulosic fibers, nanoparticulate clays, talc and mixtures thereof. If present, the reinforcing material is typically present in a reinforcing amount, e.g., in an amount of from 5 percent by weight to 60 or 70 percent by weight, based on the total weight of the component (i.e., the sum of the weight of the plastic material and the reinforcing material).

Fibers are typically present in the plastic components of the heat exchange panel in amounts independently from 5 to 70 percent by weight, 10 to 60 percent by weight, or 30 to 50 percent by weight (e.g., 40 percent by weight), based on the total weight of the plastic component (i.e., the weight of the plastic material, the fiber and any additives). Accordingly, the plastic components of the heat exchange panel may each independently include fibers in amounts of from 5 to 70 percent by weight, 10 to 60 percent by weight, or 30 to 50 percent by weight (e.g., 40 percent by weight), based on the total weight of the particular component.

The fibers may have a wide range of diameters. Typically, the fibers have diameters of from 1 to 20 micrometers, or more typically from 1 to 9 micrometers. Generally, each fiber comprises a bundle of individual filaments (or monofilaments). Typically, each fiber is composed of a bundle of 10,000 to 20,000 individual filaments.

In addition or alternatively to reinforcing material(s), the plastic components of the solar heat exchange panel may in each case independently and optionally further include one or more additives. Additives that may be present in the plastic components include, but are not limited to, antioxidants, colorants, e.g., pigments and/or dyes, mold release agents, fillers, e.g., calcium carbonate, ultraviolet light absorbers, fire retardants and mixtures thereof. Additives may be present in the plastic material of each plastic component in functionally sufficient amounts, e.g., in amounts independently from 0.1 percent by weight to 10 percent by weight, based on the total weight of the particular plastic component.

Alternatively, the molded plastic components (e.g., the lower and upper plates) of the heat exchange panel of the present invention may be prepared by a sheetless thermoforming process, in which a heated sheet of thermoplastic material is formed (e.g., from an extruder coupled to a sheet die) and then vacuum drawn over the internal surfaces of a mold portion, while the extruded sheet is still thermoformable (and before it cools to a non-thermoformable temperature). After cooling to a non-thermoformable temperature, the molded article (e.g., in the form of the lower plate or upper plate) is removed from the mold portion, and typically subjected to post-molding operations, such as joining the molded lower plate and molded upper plate together. The heat exchange panel and the various components thereof may be prepared by the sheetless thermoforming processes as described, for example, in U.S. Pat. Nos. 7,955,550 and 7,842,225.

In one embodiment, the lower plate is a substantially unitary lower plate molded from a first plastic material, and the upper plate is a substantially unitary upper plate molded from a second plastic material, in which the first and the second plastic materials are each independently selected from thermoplastic materials, thermoset plastic materials and combinations thereof, as discussed previously herein. Further to this embodiment, the upper plate is substantially transparent to infrared radiation, the lower plate is substantially optically opaque, and the interior surface of the lower plate absorbs infrared radiation.

The heat exchange panel of the present invention may have any suitable shape and dimensions. For example, the heat exchange panel may have a generally circular or oval shape, a polygonal shape (e.g., triangular, rectangular, pentagonal, hexagonal, heptagonal, octagonal shapes, etc.), an irregular shape (e.g., so as to fit around another structure, such as a structural beam or chimney), or any combination thereof. More generally, the heat exchange panel may be a substantially flat heat exchange panel (as depicted in the drawings), or a non-flat (e.g., arcuate) heat exchange panel (not depicted). A non-flat heat exchange panel may, for example, be used to fittingly and securely rest over the apex of a gabled roof structure.

The heat exchange panel of the present invention may be used to absorb thermal energy from any suitable source of thermal energy, such as: a source of radiant thermal energy (e.g., infrared radiation from the sun); or a source of convective thermal energy, such as a fluid heat sink or source (e.g., a pool of heated liquid, such as water, or stream of heated gas, such as air). In the case of a source of radiant thermal energy, the heat exchange panel is typically oriented so as to expose the exterior surfaces of the upper plate and the upper plate extensions to the source of radiant thermal energy, such as the sun. The radiant thermal energy is transferred primarily through the upper plate extensions (and to a lesser extent also through the exterior surfaces of the upper plate), and into the fluid (e.g., a heat exchange fluid) passing through the upper plate extension passages and underlying channels. The heated fluid upon exiting the heat exchange panel may be used directly (e.g., in the case of a shower), or indirectly, e.g., to heat another fluid, such as water or air, in which case the fluid may be described as a heat exchange fluid. When used to absorb radiant thermal energy from the sun, the heat exchange panel may be described as a solar heat exchange panel.

Alternatively, the heat exchange panel of the present invention may itself be used as a source of thermal energy. For example, a separately heated fluid may be passed through the interior volume of the heat exchange panel, resulting in thermal energy being transferred out of (rather than into) the upper plate extensions and into a separate medium, such as a gas (e.g., air) or a liquid (e.g., water). The separately heated fluid may be heated in and provided by one or more separate heat exchange panels according to the present invention that are set up so as to absorb thermal energy from another source of thermal energy (e.g., the sun), and which are in fluid communication with the heat exchange panel that is itself acting as a source of thermal energy.

The present invention has been described with reference to specific details of particular embodiments thereof. It is not intended that such details be regarded as limitations upon the scope of the invention except insofar as and to the extent that they are included in the accompanying claims.

Solar Heat Exchange Panel

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