SOLAR THERMAL PANELS

Abstract

Systems and methods for employing solar thermal energy for heating are disclosed. In some embodiments, a system is disclosed, in which a thermal-fluid-filled solar-thermal panel that has been sealed to prevent leakage of the thermal fluid. In other embodiments, a method of sealing a solar thermal panel is disclosed. In one preferred embodiment, the solar thermal panel is sealed by applying heat to one edge of the solar thermal panel, thereby melting the edge and forming a seal.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional patent application Ser. No. 61/381,545, having the title “Solar Thermal System,” filed 2010 Sep. 10, which is incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to solar thermal panels and, more particularly, to systems and methods for manufacturing and sealing solar thermal panels.

BACKGROUND

Collecting the sun's energy with solar panels for use in home heating and water heating is a concept that has previously been explored and implemented. However, most currently-existing designs focus on efficiency, rather than cost. As a result, solar thermal panels have not gained widespread use. Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a diagram that shows one embodiment of a solar thermal system.

FIG. 2 is a front profile view of a solar thermal panel.

FIG. 3 is a side profile view of a solar thermal panel.

FIG. 4 is a side profile view of a solar thermal panel being sealed.

FIG. 5 is a perspective view of a solar thermal panel.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference is now made in detail to the description of the embodiments as illustrated in the drawings. While several embodiments are described in connection with these drawings, there is no intent to limit the disclosure to the embodiment or embodiments disclosed herein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents.

Brief Overview

The present disclosure teaches various systems and methods relating to solar thermal panels and solar thermal systems. Unlike conventional solar thermal panels, various embodiments of the inventive solar thermal panels are cost-effective to manufacture, thereby allowing for mass production of the solar thermal panels. In some embodiments, a method of sealing a solar thermal panel is disclosed. In one preferred embodiment, the solar thermal panel is sealed by applying heat and pressure to one edge of the solar thermal panel, thereby melting the edge and forming a seal. In other embodiments, a system is disclosed, in which a thermal-fluid-filled solar-thermal panel that has been sealed by applying heat to its edge to prevent leakage of the thermal fluid.

Previous Failed Attempts and Eventual Success

Before describing the various embodiments of the invention, it is worthwhile to understand how the inventive solar thermal panels and systems were developed, along with the corresponding processes for manufacturing these panels and systems. Although the inventive solar thermal panel and its method of manufacture may appear simple, numerous failed attempts prior to the eventual success in building the disclosed working models demonstrate the non-trivial nature of the inventive solar thermal panels, systems, and methods. Consequently, one having ordinary skill in the art will appreciate the difficulties associated with manufacturing the disclosed solar thermal panels and systems.

A particularly challenging problem related to properly sealing the panel to prevent leakage of the thermal fluid from the solar thermal panel. As one can imagine, in order to maximize the heat capacity within the solar thermal system, much (if not all) of the thermal fluid should be maintained within the solar thermal panel. Unfortunately, if there are leaks in the solar thermal panel, then the thermal fluid can escape, taking with it any heat that is stored in the thermal fluid.

Sealing the solar thermal panel posed a particularly difficult problem that was not easily overcome. For example, U.S. Pat. Nos. 4,114,597 and 4,178,914 describe headers for unitary solar collectors. These headers are separate components that are attached to the outside of the unitary solar collector. Attempting to attach separate headers to the outside of the solar thermal panel posed problems because the interface between the headers and the unitary solar collector, if not perfectly sealed, created points-of-failure where the thermal fluid escaped from the system. All attempts to externally seal the solar thermal panel with this separate and distinct component (such as a header or a pipe) resulted in incomplete seals, which consequently resulted in leakage of thermal fluid from the system. This occurred despite numerous attempts with many different types of sealants and adhesives. Thus, while it may appear trivial to externally seal the solar thermal panel, the reality of employing a separate component to achieve a leak-resistant seal proved to be unworkable.

Moving away from a separate header that attached to the outside of the solar thermal panel, attempts were also made to seal the solar thermal panel by removing a portion of the inner channel to create a cavity, and then friction-fitting a pipe in the resulting cavity and sealing the interface between the pipe and the wall of the solar thermal panel. Although intuition suggests that both friction and a commercial sealant, when used in conjunction, would provide a leak-resistant seal, all of the attempts to achieve a leak-resistant seal in this manner also failed. The point of failure was, again, the interface between the solar thermal panel and the inner pipe. Again, all attempts using a separate and distinct component resulted in incomplete seals, which again resulted in leakage of thermal fluid from the system. Despite numerous attempts with varying combinations of pipe sizes and sealants, a leak-resistant seal was never achieved. In other words, employing this separate internal component did not achieve a leak-resistant seal. Mainly, the seals were the points-of-failure because the entire length of the solar thermal panel needed to maintain the seal. Thus, over multiple heating-cooling cycles, the solar thermal panel would expand and contract, thereby causing the adhesive (which expanded and shrank at a different rate) to fail and no longer maintain a leak-resistant seal.

Many other attempts were made to create a leak-resistant seal, those also failed.

Insofar as sealing the solar thermal panel with a separate component resulted in failures, despite the numerous permutations of pipe sizes and sealing compounds, efforts were directed to finding ways to seal the solar thermal panel without the use of separate components. Eventually, attempts were made to achieve a leak-resistant seal by melting the open ends of the solar thermal panel, rather than employing separate and distinct sealing components. Early attempts included melting the edge of the solar thermal panel by applying heat to the edge. While applying heat to the edge of the solar thermal panel may seem trivial, even this method posed challenges. For example, finding the right conditions under which a proper seal would form was not a trivial task.

In terms of heat exposure, prolonged exposure caused not only the edge of the solar thermal panel to melt, but also caused the internal ribs and layers to melt, thereby resulting in an internal leakage of thermal fluid from one layer to another. In terms of finding the correct temperature, if the applied heat was insufficient, then the edges would not melt together. Conversely, if the applied heat was too high, then undesirable effects were seen, such as the melting of the internal ribs and layers as well as material breakdown. Additionally, when there was uneven heat distribution, this resulted in non-uniform melting of the edges, thereby creating an unsightly solar thermal panel.

Persistence in view of all of those failures eventually led to a redirection of research efforts to the panels, methods, and systems that are described with reference to FIGS. 1 through 5. In other words, the embodiments of the invention, as herein described, are the result of numerous failures and difficulties, all of which may appear trivial in hindsight, but which were in reality extraordinarily difficult to overcome.

Various Embodiments

With these difficulties in mind, attention is turned to FIGS. 1 through 5, which show preferred embodiments of a solar thermal panel, a solar thermal system employing the solar thermal panel, and methods for manufacturing the solar thermal panel.

FIG. 1 is a diagram that shows one embodiment of a solar thermal system. While the system of FIG. 1 shows a closed loop that circulates thermal fluid 2, it should be appreciated by those having skill in the art that the system may also be configured as an open-loop system.

The system, as shown in FIG. 1, comprises a closed loop that circulates thermal fluid 2. This closed loop includes a solar thermal panel 1a, a control unit 5, a storage tank 3, and a first pump 4. The solar thermal panel 1a comprises a panel temperature gauge 7, which measures the temperature of the fluid 2 within the solar thermal panel 1a. The storage tank 3 comprises a fluid temperature gauge 6, a heat exchanger 12, a cold water inlet 11, and a hot water pipe (not labeled). The control unit 5 is operatively coupled to the first pump 4, the panel temperature gauge 7, and the fluid temperature gauge 6.

In operation, the thermal fluid 2 circulates through the solar thermal panel 1a, where the fluid 2 absorbs solar energy and heats up as a result. The thermal fluid 2 can reach temperatures up to 150 degrees Fahrenheit, which is typical for hot water heaters. Based on the readings of the panel temperature gauge 7 and the fluid temperature gauge 6, the control unit 5 will either activate or deactivate the first pump 4. For example, when the reading of the panel temperature gauge 7 is higher than the reading of the fluid temperature gauge 6, the control unit 5 will activate the first pump 4, which pumps the thermal fluid 2 from the tank 3 to the solar thermal panel 1a.

The storage tank 3 receives cold water through a cold water inlet 11, and the cold water is pumped through the heat exchanger 12. As the cold water travels through the heat exchanger 12, the temperature difference between the cold water and the thermal fluid 2 causes the cold water to heat, while simultaneously causing the heated thermal fluid 2 to cool. The heated water exits through the hot water pipe (not labeled). The first pump 4 circulates the cooled thermal fluid 2 back to the solar thermal panel 1a, where the fluid 2 absorbs solar energy and heats up, thereby repeating the cycle.

For some embodiments, such as the one shown in FIG. 1, the hot water pipe (not labeled) of the storage tank 3 is operatively coupled to a booster heater 13, which includes a hot water outlet 14. For those embodiments, the hot water pipe (not labeled) provides the heated water to the booster heater, which further heats the water. That water can then be used by drawing it from the hot water outlet 14.

In addition to using the thermal fluid 2 to heat water for use, the system of FIG. 1 also shows a closed loop in which the thermal fluid 2 is used for space heating. An exemplary system for space heating comprises a booster heater 13, a second pump 9, an ambient temperature gauge 10, and a hydronic heating system 8. The second pump 9 and the ambient temperature gauge 10 are operatively coupled to the control unit 5, which activates or deactivates the second pump 9 based on the reading of the ambient temperature gauge 10.

In operation, when the reading of the ambient temperature gauge 10 is below a set thermostat temperature, the control unit activates the second pump 9, thereby circulating the heated thermal fluid 2 from the storage tank 3 to the booster heater 13. The booster heater 13 further heats the thermal fluid 2, which is then pumped through the hydronic heating system 8 via the second pump 9. As the fluid 2 travels through the hydronic heating system 8, it cools as a result of heat transfer to the heated space. The cooled thermal fluid 2 is then pumped back to the storage tank 3, where the cycle may repeat.

As one can appreciate, the efficiency of the entire system depends in large part on the efficiency of the solar thermal panel 1a, which allows the thermal fluid to collect and store the solar thermal energy. Having described the system, the solar thermal panel 1a of FIG. 1 is described in greater detail with reference to FIGS. 2 through 5.

FIG. 2 is a front profile view of a preferred embodiment of the solar thermal panel 1a of FIG. 1.

As shown in FIG. 2, the solar thermal panel 1a comprises horizontal layers 15a, 15b, 15c (collectively 15), which horizontally separate the internal space within the solar thermal panel 1a into top channels 17 and bottom channels 18. Preferably, these layers comprise clear polymer material that allows a large percentage of solar radiation to pass through the layers 15. The solar thermal panel 1a also comprises vertical ribs 16, which vertically separate the internal space within the solar thermal panel 1a into channels that carry the thermal fluid 2 through the solar thermal panel 1a. Preferably, the solar thermal panel 1a is placed above a solid structure, such as a residential roof (not shown). To increase the heat absorption by the thermal fluid 2, and also to reduce heat loss from a residential structure, the bottom of the solar thermal panel 1a can be coated with an absorbing layer 19, and the solar thermal panel 1a can be placed above an insulating layer 20.

Given this multi-layered structure, the solar thermal panel 1a carries the thermal fluid 2 through its bottom channels 18. The top channels 17 act as both a transmissive layer and an insulating layer. In other words, the air gap within the top channels 17 allow for transmission of solar radiation while simultaneously providing insulation to the bottom channels 18. For some embodiments, the top channels 17 can be evacuated to provide a partial vacuum, thereby improving the solar thermal panel's insulation properties. Once the solar radiation reaches the absorbing layer 19, the solar radiation is converted to thermal energy. The thermal energy is then absorbed by the thermal fluid 2, which is carried in the bottom channels 18 adjacent to the absorbing layer 19. The heated thermal fluid then circulates through a solar thermal system, similar to that shown in FIG. 1.

As one having skill in the art can appreciate, the solar thermal panel 1a is sealed in such a way that the thermal fluid 2 does not undesirably leak out of the system. Attention is now turned to processes for manufacturing sealed solar thermal panels.

FIG. 3 is a side profile view of a solar thermal panel as it is manufactured through an extrusion process. Specifically, the solar thermal panel comprises an extruded polymer sheet 1d. One particular type of multi-layered extruded polymer sheet is LEXAN®, a product from General Electric Company. As shown in FIG. 3, when the extruded polymer sheet 1d is extruded in accordance with known methods, the resulting sheet comprises multiple layers 15a, 15b, 15c, which define top channels 17 and bottom channels 18. Since the process of extruding multi-layered polymer sheets is well known in the art, further discussion of that particular process is omitted here.

FIG. 4 is a side profile view of a solar thermal panel 1c being sealed. As noted above, although the process of fabricating an extruded polymer sheet 1d is widely known in the industry, the process of sealing the extruded polymer sheet 1d is non-trivial. FIG. 4 shows one embodiment of a process for manufacturing a sealed extruded polymer panel 1c.

In a preferred embodiment, the extruded polymer panel 1c is sealed as it emerges from the extrusion process. As the extruded polymer panel 1c passes over a bottom die 22, a heating die 21 is applied in a direction that is vertical to the extruded polymer panel 1c, thereby creating an impact seal 23, which melts the extruded polymer panel 1c at the point of impact to create a sealed edge.

As described above, the temperature of the heating die 21, the heat distribution within the heating die 21, and the speed at which the heating die 21 is applied should be controlled so as to provide a proper seal. Specifically, the heating die 21 should be at a temperature that is slightly higher than the melting temperature of the polymer material, but not so high as to char or burn the polymer material. Also, the heating die 21 should be uniformly heated in order to avoid non-uniform melting of the extruded polymer panel 1c. Finally, the rate at which the heating die 21 is applied should be sufficiently slow enough that the extruded polymer panel 1c melts, rather than being crushed by the weight of the heating die 21. Insofar as all of these factors depend on the characteristics of the polymer material, and insofar as one having skill in the art can calculate these factors, further discussion of applying the heating die 21 is omitted here. It should also be appreciated by those skilled in the art that the heat-sealing of the extruded polymer panel 1c can be done by other forms of conduction, convection heating, radiant heating, or various combinations thereof. Thus, for example, should the extruded polymer panel not be sealed immediately after extrusion, a different manufacturing process using conduction, convection, or radiation may be employed to achieve the seal after the extrusion process.

The polymer panel 1c, once sealed, now provides a base from which a functional solar thermal panel can be fabricated. One such panel is shown with reference to FIG. 5.

FIG. 5 is a perspective view of a functional solar thermal panel 1b, which has been fabricated from the sealed extruded polymer panel 1c of FIG. 4. Specifically, FIG. 5 shows a solar thermal panel 1b, with a first set of holes 24a associate with an inlet 25a, and a second set of holes 24b, associated with an outlet 25b. One can readily appreciate that the inlet 25a and the outlet 25b may be reversed, depending on the direction of the flow of the thermal fluid 2. The first set of holes 24a are drilled through the bottom channels 18 (FIG. 2) near a distal edge of the solar thermal panel 1b, and the inlet 25a is connected to the first set of holes 24a. The second set of holes 24b are drilled through the bottom channels 18 (FIG. 2) near a proximal edge of the solar thermal panel 1b, and an outlet 25b is connected to the second set of holes 24b. In preferred embodiments, the holes 24a, 24b are located approximately one inch from their respective edges.

In operation, the inlet 25a allows for entry of thermal fluid 2 (FIG. 2) into the solar thermal panel 1b. Once the thermal fluid 2 enters the solar thermal panel through the inlet 25a, the fluid travels through the bottom channels 18 (FIG. 2) of the solar thermal panel 1b. Eventually, the fluid 2 fills the bottom channels 18 of the solar thermal panel 1b and is expelled through the outlet 25b.

Placing this in the context of FIG. 1, the fluid that gets pumped into the solar thermal panel 1a by the first pump 4 will enter the solar thermal panel 1a through the inlet 25a. Consequently, once that fluid 2 has traveled through the solar thermal panel 1a and has been heated by the solar radiation, the fluid 2 is expelled through the outlet 25b and pumped to the storage tank 3.

As shown in FIG. 1, the solar thermal panel 1a can be attached to a residential roof, or mounted on walls, or can be used in any position that is consistent with the desired purpose. Typically, polymer materials, such as LEXAN®, have an estimated life of 30 years. These types of solar thermal panels can be configured for use in existing structures, or as roofing materials for new structures.

Variants

Although exemplary embodiments have been shown and described, it will be clear to those of ordinary skill in the art that a number of changes, modifications, or alterations to the disclosure as described may be made. For example, while a residential roofing system has been described with reference to the solar thermal panels, it should be appreciated that the system can be used in residential, commercial, or industrial settings. Additionally, one having skill in the art will understand that the system of FIG. 1 can be configured to be wholly programmable and automated, or can require manual input by a user. Also, one having skill in the art will understand that the thermal fluid can be water, glycol, or other fluid that has desired heat capacity properties. Furthermore, one having skill in the art will appreciate that the absorbing layer 19 can comprise tar paper, paint, or other substance that is conducive to absorbing solar energy. Finally, it should be appreciated that, while FIG. 1 shows an embodiment that employs pumps 4, 9 to transport the fluid 2, a wholly passive system that is based on thermal convection can be used to transport the thermal fluid 2.

All such changes, modifications, and alterations should therefore be seen as within the scope of the disclosure.

Claims

1. A method of manufacturing a solar thermal panel, comprising the steps of:

extruding a polymer panel comprising layers, the polymer panel further comprising an open edge; and

melting the open edge to form a sealed edge.

2. The method of claim 1, wherein the melting step comprises the steps of:

pressing the top of the polymer panel with a heated die, thereby causing the layers to melt together to form a seal.

3. The method of claim 1, wherein the melting step comprises the steps of:

heating the open edge with a radiative heat source.

4. The method of claim 1, wherein the melting step comprises the steps of:

heating the open edge with a convective heat source.

5. The method of claim 1, wherein the melting step comprises the steps of:

heating the open edge with a conductive heat source.

6. A solar thermal panel manufactured using the method of claim 1.

7. A solar thermal panel comprising:

a bottom channel for carrying thermal fluid, the bottom channel having a bottom-channel seal to prevent leakage of the thermal fluid from the bottom channel;

a first hole located near a first edge of the bottom channel, the first hole for receiving the thermal fluid from an external source;

a second hole located near a second edge the bottom channel, the second hole for expelling the thermal fluid from the solar thermal panel; and

a top channel located above the bottom channel, the top channel having a top-channel seal.

8. The panel of claim 7, further comprising:

an inlet attached to the first hole; and

an outlet attached to the second hole.