CROSS-REFERENCE TO RELATED APPLICATIONS
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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
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REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is in the technical field of solar water heaters. More particularly, the preferred embodiments of the present invention relate generally to solar water heaters which preheat supply water for standard water heaters in order to improve overall efficiency. More particularly, the preferred embodiments of the present invention relate generally to passive solar water heaters. More particularly, the preferred embodiments of the present invention relate generally to solar water heaters which absorb and retain heat from solar energy in a working fluid. Additionally, the present invention relates generally to a method of constructing an inexpensive heat-storage tank for a solar water heater.
2. Description of the Related Art
With the increasing pressure to utilize renewable or sustainable energy sources and improve the efficiency of existing systems, various systems have been devised to capture and utilize the heat of the sun. Solar water heaters use solar energy to heat water. Conventional solar water heaters typically include a collector and storage tank, and come in a variety of forms including both active and passive systems.
In active systems, a pump is used to circulate water from a storage tank through a solar collector, such as a series of tubes within a box with a transparent cover. Typically, the pump is controlled by a control system which activates the pump when the temperature in the solar collector is higher than the temperature in the storage tank. The water is then heated when pumped through the solar collector. Some active systems use a working fluid to absorb heat in a solar collector and transfer that heat to water in a storage tank. Although active systems provide better control than other systems, control systems and pumps are expensive and require energy to operate.
In passive systems, heated water is moved by natural convection or city water pressure instead of using pumps. Compared to active systems, passive systems are simpler and more economical and do not require control systems, pumps, or other complicated mechanisms, and are therefore less expensive to install and operate. Passive systems include thermosiphon systems and batch systems.
In thermosiphon systems, a storage tank is mounted above a solar collector and water may flow between the storage tank and the collector. Natural convection is used to circulate water between the solar collector and the storage tank. Water which is heated in the solar collector becomes less dense and rises to the higher level of the storage tank. Heavier cold water in the storage tank sinks into the solar collector where it may be heated. Thermosiphon systems installed on roof tops require the accompanying storage tanks to be mounted even higher on the same roof, necessitating structural reinforcement.
In batch systems, the storage tank is integrated into the solar collector and serves as both storage tank and solar collector. Batch systems are typically comprised of a storage tank disposed within an insulated enclosure with a transparent cover. Batch systems use water pressure from a city source to move water through the solar collector/storage tank system. Water heated within the batch system is then delivered to the point of use or used as a source of preheated water for a standard water heater. Batch systems do not need a separate storage tank, but, since batch systems are fed with cool supply water, they usually store large volumes of water in order to maintain a sufficient supply of heated water. Because the storage tank and the solar collector are merged, this large volume of water is stored in the same place where it is exposed to the sun, which is generally on a roof top. In order to support the weight of the storage tank, the roof top must be reinforced, increasing the overall cost of such systems. Furthermore, the solar collector/storage tank must be built to withstand the pressure of water from a city source. Material with the requisite strength to hold pressurized water has substantial weight and is expensive and increases the cost of batch systems as well as the cost of their installation.
Many of the above-mentioned solar water heater systems require a storage tank installed in close proximity to a solar collector. Some of these storage tanks must store large volumes of water. Large volumes of water are heavy and can generate high pressure at certain depths. Others storage tanks must withstand the pressure from a city water source. In order to withstand such pressures, storage tanks must be built from a strong, heavy gauge material. Since solar collectors are often mounted on rooftops, the weight of a standard storage tank requires the underlying roof to be extraordinarily strong or structurally reinforced. The incline of a roof can also increase the pressure of fluid at the bottom of a storage tank. Moreover, systems using heavy storage tanks usually require industrial equipment, such as cranes, to lift the system onto the roof and multiple people to install, further increasing their expense.
SUMMARY OF THE INVENTION
The embodiments of the present invention are lightweight and low cost solar water heaters which are comprised of a covered container enclosing an inner tank which is substantially filled with a working fluid. The container is comprised of a bottom panel and a plurality of side panels. The cover of the container allows solar energy to enter the container. The inner tank is comprised of a lightweight, thin, high gauge material which is painted black. A tube which distends from the container and connected into the inner tank allows the inner tank to be substantially filled with a working fluid and further allows the inner tank to be vented to the atmosphere. A supply-water pipe with an inlet and an outlet enters through the container into the inner tank, in which a substantial portion of the supply-water pipe is submerged in the working fluid, and then exits the inner tank and the container. The inlet for the supply water pipe can be connected to a source of pressurized supply water, such as a city water source. The outlet can be connected to a standard water heater. Solar energy enters the container through the cover and heats the inner tank and subsequently the working fluid. Cool supply water travels through the supply-water pipe, and is heated while traveling through the portion of supply-water pipe submerged in the working fluid. Because only the supply water is pressurized, only the supply-water pipe must be made of a material which may withstand pressure; the inner tank does need to withstand the pressure from a city water source. Heated supply water exits the system and is supplied to a standard water heater, thereby increasing the overall efficiency of the water heating system.
In other more preferred embodiments, the container around the inner tank is insulated. The bottom and side panels of the container are comprised in whole or in part of an insulating material. Additionally, the cover is comprised in whole or in part of an insulating material which allows solar energy to enter the container. Although the added material increases the overall cost of the system, the insulation substantially increases the efficiency of the system.
In other more preferred embodiments, the inlet of the supply-water pipe enters and outlet of the supply-water pipe exits the inner tank above the surface of the working fluid contained within the inner tank. This configuration decreases the likelihood of the inner tank leaking by limiting the openings in the inner tank to areas above the surface of the enclosed working fluid.
In other preferred embodiments, the inlet of the supply-water pipe enters and outlet of the supply-water pipe exits the inner tank below the surface of the working fluid contained within the inner tank. This configuration allows the system to be cleaned out easily because it can be drained using gravity.
In the most preferred embodiments, the inner tank is comprised of a lightweight material which is folded into a shape that allows any seams in the material to be held above the surface of fluid within the tank. The folded tank further contains a working fluid which absorbs solar energy when the tank is exposed to sun light through the transparent cover. A length of lightweight pipes is coiled in a serpentine fashion within the folded tank and is surrounded by the working fluid. Pressurized supply water flows through the serpentine length of pipe and absorbs heat from the working fluid as it travels through the folded tank. The heated supply water is then used as a pre-heated supply for a standard hot water heater. The folded tank of this embodiment is mounted substantially horizontal within the container. This horizontal orientation minimizes the pressure at the bottom of the tank when it is installed on an incline. Because all seams are above the surface of the contained fluid, the folded tank is able to deform while resisting breakage or leakage, and may be comprised of an inexpensive, lightweight, thin, high gauge material. The relatively low volume of working fluid and lightweight material used to construct the folded tank decrease the overall weight of the system, reducing the need to reinforce underlying structures and lowering the overall cost of the system. Additionally, the lower weight allows for installation without the use of heavy equipment, such as cranes, and requires fewer people. Another advantage of this system is that the lightweight high gauge material used to construct the inner tank is thin and allows for a quick transfer of heat to the contained working fluid.
Another preferred embodiment of the present invention is a method of constructing a folded tank. The tank is formed by first taking a rectangle of lightweight foldable material and folding it in half lengthwise while maintaining curvature around the lengthwise fold and drawing the lengthwise edges towards each other. Next, fold the widthwise ends of the rectangle by drawing the center points of the widthwise edges of rectangle between the lengthwise edges so that the center points of both widthwise edges are aligned with the lengthwise edges when the lengthwise edges are drawn together. Complete the folded tank by sealing the lengthwise and the widthwise edges together.
BRIEF DESCRIPTION OF THE DRAWING
Illustrative and preferred embodiments of the present invention are shown in the accompanying drawings in which:
FIG. 1 is a cross-sectional perspective view of a solar water heater of the present invention;
FIG. 2 is a cross-sectional side view of a solar water heater of FIG. 1;
FIG. 3 is an exploded view of a solar water heater of FIG. 1;
FIG. 4 is a cross-sectional perspective view of a solar water heater of the present invention; and
FIG. 5 is a cross-sectional perspective view of a solar water heater of the present invention.
FIG. 6 is a top view of a rectangular sheet of material used to construct a tank of a solar water heater of the present invention with lines showing places along which the rectangle is folded;
FIG. 7 is a top perspective view of a sheet of material used to construct the tank of a solar water heater of the present invention in the process of being folded into a tank;
FIG. 8 is a top perspective view of a tank of a solar water heater of the present invention after being folded into shape;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
For the purpose of illustration, the present invention is shown in the preferred embodiments of a solar water heater with input and output pipes which enter a folded tank above the surface of a working fluid, a solar water heater with input and output pipes which enter a folded tank below the surface of a working fluid, and a solar water heater with a heating element attached to a folded tank to prevent a working fluid from freezing in cold weather. Additionally, a method of constructing a folded tank suitable for a solar water heater is demonstrated. These embodiments are not intended to limit the scope of the present invention.
Referring now to the most preferred embodiment of the invention in more detail, in FIG. 1, FIG. 2, and FIG. 3 a solar water heater 101 is illustrated. FIG. 1 shows a cross-sectional perspective view of the solar water heater 101 installed on a roof 170. FIG. 2 illustrates a cross-sectional side view of a solar water heater 101 mounted on a roof 170. FIG. 3 depicts an exploded view of a solar water heater 101. The solar water heater 101 is comprised of an insulated container 110 with a transparent cover 120 enclosing a folded tank 100 which further contains serpentine supply water pipes 145 surrounded by a working fluid 135.
In further detail, still referring to the invention of FIG. 1, FIG. 2, and FIG. 3, the insulated container 110 is a box, with a bottom 111, four sides 112 and a cover 120, lined with an insulating material 160. The cover 120 for the insulated container 110 is comprised of a material which allows solar energy to enter the insulated container 110 and heat the folded tank 100. The folded tank 100 is installed horizontally within the insulated container 110 with the tapered end 102 of the folded tank 100 at the highest level and the rounded end 103 at the lowest level. The folded tank is constructed such that all seams are along the tapered end 102 and at the highest level of the folded tank 100 and along the tapered end 102. The folded tank 100 is attached to the insulated container along the tapered end 102 at a plurality of points 150. A fill tube 155 allows the folded tank to be substantially filled with working fluid 135. A length of pipe 145 with an inlet 130 and an outlet 140 enters the insulated contained and enters the folded tank 100 where the length of pipe is substantially surrounded by a working fluid 135. In the embodiment of FIGS. 1, 2 and 3 the inlet 130 enters and outlet 140 exits the folded tank 100 above the fluid surface 136 of the working fluid 135, preventing the folded tank 100 from leaking or being susceptible to leakage. The length of pipe 145 is coiled within the folded tank 100 in a serpentine fashion. Supply water 147 enters the length of serpentine pipe 145 through the inlet 130, travels through the length of pipe 145 absorbing heat from the working fluid 135, and exits the length of pipe 145 through the outlet 140. The heated supply water 147 is transferred to a separate storage tank or to a standard water heater. The solar water heater 101 is attached to the roof 170 by bolting the attachment plate 125 to support beams 172 of the roof 170.
The construction details of the invention as shown in FIG. 1, FIG. 2, and FIG. 3 are that the solar water heater 101 is comprised of an insulated container 110 with a transparent cover 120 enclosing a folded tank 100 which further contains serpentine supply water pipes 145 surrounded by a working fluid 135. The insulating material 160 which lines the insulated container 110 is comprised of foam insulation, natural fiber, fiberglass, or the like. The transparent cover 120 of the insulated container 110 is comprised of a transparent material such as glass, double-paned glass, plastic, or the like, or a transparent material within a frame. The folded tank 100 is comprised of a rectangle of foldable material, such as sheet metal, sheet steel, galvanized steel, stainless steel, rubberized silicone, sheet aluminum, plastic, composite material, or the like. To form the folded tank, the rectangle of foldable material is folded in half lengthwise while maintaining a rounded form along the lengthwise fold and drawing the lengthwise edges together; then the widthwise ends of the rectangle are folded by drawing the center point of widthwise edge of the rectangle between the lengthwise edges so that the center point of the widthwise edge is aligned with the lengthwise edge and between the lengthwise edges when the lengthwise edges are drawn together; and the lengthwise and widthwise edges are sealed or bound together. The inner tank may be painted black. The length of pipe 145 is comprised of a material suitable to contain pressurized supply water, such as copper, PVC, or the like. The working fluid 135 is comprised of a fluid suitable for absorbing heat, such as water, antifreeze, mineral oil, or the like.
Referring now to another embodiment of the invention, in FIG. 4 a solar water heater 201 is illustrated. FIG. 4 shows a cross-sectional perspective view of the solar water heater 201 installed on a roof 270. The solar water heater 201 is comprised of an insulated container 210 with a transparent cover 220 enclosing a folded tank 200 which further contains serpentine supply water pipes 245 surrounded by a working fluid 235.
In further detail, still referring to the invention of FIG. 4, the insulated container 210 is a box, with a bottom 211, four sides 212 and a cover 220, lined with an insulating material 260. A cover 220 for the insulated container 210 is comprised of a transparent material which allows solar energy to enter the insulated container 210 and heat the folded tank 200. The folded tank 200 is installed horizontally within the insulated container 210 with the tapered end 202 of the folded tank 200 at the highest level and the rounded end 203 at the lowest level. The folded tank is constructed such that all seams are along the tapered end 202 and at the highest level of the folded tank 200 and along the tapered end 202. The folded tank 200 is attached to the insulated container along the tapered end 202 at a plurality of points 250. A fill tube 255 allows the folded tank to be substantially filled with working fluid 235. A length of pipe 245 with an inlet 230 and an outlet 240 enters the insulated contained and enters the folded tank 200 where the length of pipe is substantially surrounded by a working fluid 235. In the embodiment of FIG. 4 the inlet 230 enters and outlet 240 exits the folded tank 200 below the fluid surface 236 of the working fluid 235, allowing the system to be cleaned out easily. The length of pipe 245 is coiled within the folded tank 200 in a serpentine fashion. Supply water 247 enters the length of serpentine pipe 245 through the inlet 230, travels through the length of pipe 245 absorbing heat from the working fluid 235, and exits the length of pipe 245 through the outlet 240. The heated supply water 247 is then transferred to a standard water heater. The solar water heater 201 is attached to the roof 270 by bolting the attachment plate 225 to support beams of the roof 270.
The construction details of the invention as shown in FIG. 4 are that the solar water heater 201 is comprised of an insulated container 210 with a transparent cover 220 enclosing a folded tank 200 which further contains serpentine supply water pipes 245 surrounded by a working fluid 235. The insulating material 260 which lines the insulated container 210 is comprised of foam insulation, natural fibers, fiberglass, or the like. The transparent cover 220 of the insulated container 210 is comprised of a transparent material such as glass, double-paned glass, plastic, or the like, or a transparent material within a frame. The folded tank 200 is comprised of a rectangle of foldable material, such as sheet metal, sheet steel, galvanized steel, stainless steel, rubberized silicone, sheet aluminum, plastic, composite material, or the like. To form the folded tank, the rectangle of foldable material is folded in half lengthwise while maintaining a rounded form along the lengthwise fold and drawing the lengthwise edges together; then the widthwise ends of the rectangle are folded by drawing the center point of widthwise edge of the rectangle between the lengthwise edges so that the center point of the widthwise edge is aligned with the lengthwise edge and between the lengthwise edges when the lengthwise edges are drawn together; and the lengthwise and widthwise edges are sealed or bound together. The inner tank may be painted black. The length of pipe 245 is comprised of a material suitable to contain pressurized supply water, such as copper, PVC, or the like. The working fluid 235 is comprised of a fluid suitable for absorbing heat, such as water, antifreeze, mineral oil, or the like.
Referring now to another embodiment of the invention, in FIG. 5 a solar water heater 301 is illustrated. FIG. 5 shows a cross-sectional perspective view of the solar water heater 301 installed on a roof 370. The solar water heater 301 is comprised of an insulated container 310 with a transparent cover 320 enclosing a folded tank 300 which further contains serpentine supply water pipes 345 surrounded by a working fluid 335.
In further detail, still referring to the invention of FIG. 5, the insulated container 310 is a box, with a bottom 311, four sides 312 and a cover 320, lined with an insulating material 360. A cover 320 for the insulated container 310 is comprised of a transparent material which allows solar energy to enter the insulated container 310 and heat the folded tank 300. The folded tank 300 is installed horizontally within the insulated container 310 with the tapered end 302 of the folded tank 300 at the highest level and the rounded end 303 at the lowest level. The folded tank is constructed such that all seams are along the tapered end 302 and at the highest level of the folded tank 300 and along the tapered end 302. The folded tank 300 is attached to the insulated container along the tapered end 302 at a plurality of points 350. A fill tube 355 allows the folded tank to be substantially filled with working fluid 335. A length of pipe 345 with an inlet 330 and an outlet 340 enters the insulated contained and enters the folded tank 300 where the length of pipe is substantially surrounded by a working fluid 335. In the embodiment of FIG. 5 the inlet 330 enters and outlet 340 exits the folded tank 300 above the fluid surface 336 of the working fluid 335, preventing the folded tank 300 from leaking or being susceptible to leakage. The length of pipe 345 is coiled within the folded tank 300 in a serpentine fashion. Supply water 347 enters the length of serpentine pipe 345 through the inlet 330, travels through the length of pipe 345 absorbing heat from the working fluid 335, and exits the length of pipe 345 through the outlet 340. The heated supply water 347 is then transferred to a standard water heater. The solar water heater 301 is attached to the roof 370 by bolting the attachment plate 325 to support beams of the roof 370. A heating element 375 attached to the folded tank 300 and extending into the working fluid 335 is actuated by an internal thermostat and prevents the working fluid from freezing is cold weather.
The construction details of the invention as shown in FIG. 5 are that the solar water heater 301 is comprised of an insulated container 310 with a transparent cover 320 enclosing a folded tank 300 which further contains serpentine supply water pipes 345 surrounded by a working fluid 335. The insulating material 360 which lines the insulated container 310 is comprised of foam insulation, natural fiber, fiberglass, or the like. The transparent cover 320 of the insulated container 310 is comprised of a transparent material such as glass, double-paned glass, plastic, or the like, or a transparent material within a frame. The folded tank 300 is comprised of a rectangle of foldable material, such as sheet metal, sheet steel, galvanized steel, stainless steel, rubberized silicone, sheet aluminum, plastic, composite material, or the like. To form the folded tank, the rectangle of foldable material is folded in half lengthwise while maintaining a rounded form along the lengthwise fold and drawing the lengthwise edges together; then the widthwise ends of the rectangle are folded by drawing the center point of widthwise edge of the rectangle between the lengthwise edges so that the center point of the widthwise edge is aligned with the lengthwise edge and between the lengthwise edges when the lengthwise edges are drawn together; and the lengthwise and widthwise edges are sealed or bound together. The inner tank may be painted black. The length of pipe 345 is comprised of a material suitable to contain pressurized supply water, such as copper, PVC, or the like. The working fluid 335 is comprised of a fluid suitable for absorbing heat, such as water, antifreeze, mineral oil, or the like.
Referring now to FIG. 6, FIG. 7, and FIG. 8 the method of constructing a folded tank 401 of the present invention is illustrated. In FIG. 6 the top view of a rectangle 400 of foldable material is shown with lines 425, 435, 445, 455, 465, and 475 indicating where the rectangle 400 is folded to form a folded tank 401. FIG. 7 depicts a perspective view of the rectangle 400 in the process of being shaped into a folded tank 401. FIG. 8 shows a perspective view of the completed shape of the folded tank 401.
In further detail, still referring to the method of FIG. 6, FIG. 7, and FIG. 8, the first step of forming a folded tank is folding the rectangle 400 lengthwise across a rounded form and drawing the lengthwise edges 405 and 415 towards each other. Next, the midpoint 430 of the widthwise edge 485 is drawn between the two lengthwise edges 405 and 415 and towards the center of the rectangle 400, forming folds 425, 435, and 445, and the midpoint 470 of the widthwise edge 495 is drawn between the two lengthwise edges 405 and 415 and towards the center of the rectangle 400, forming folds 455, 465, and 475. The next step is drawing the lengthwise edges 405 and 415 together until they substantially meet with the widthwise edges 485 and 495 of the rectangle 400 folded between them. When the lengthwise edges 405 and 415 are drawn together, the midpoints 430 and 470 of the widthwise edges 485 and 495 sit on the lengthwise edges 405 and 415 a distance substantially equal to half the width of the rectangle 400. The last step is to seal the widthwise and lengthwise edges along the tapered end 411 of the folded tank 401. Once the lengthwise and widthwise edges of the rectangle are all aligned along the tapered end 411 of the folded tank 401, all seams of the folded tank 401 are along the tapered end 411.
The construction details of the invention as shown in FIG. 6, FIG. 7, and FIG. 8 are that the folded tank 401 is comprised of a rectangle of foldable material, such as sheet metal, sheet steel, galvanized steel, stainless steel, rubberized silicone, sheet aluminum, plastic, composite material, or the like. To form the folded tank, the rectangle of foldable material is folded in half lengthwise while maintaining a rounded form along the lengthwise fold and drawing the lengthwise edges together; then the widthwise ends of the rectangle are folded by drawing the center point of widthwise edge of the rectangle between the lengthwise edges so that the center point of the widthwise edge is aligned with the lengthwise edge and between the lengthwise edges when the lengthwise edges are drawn together; and the lengthwise and widthwise edges are sealed or bound together.
The advantages of the present invention include, without limitation that it provides for a solar water heaters which weigh less than other systems because the inner tank is constructed of a lightweight material which does not need to withstand high pressure. Because the invention is lightweight, the underlying structure on which the solar water heater is mounted does not need to be reinforced. Furthermore, heavy equipment, such as cranes, is not required to install the present invention. Additionally, fewer people are needed to install the present invention than are required with heavier solar water heating systems. Also, the folded inner tank has the advantage of having all seams along the tapered edge of the tank and above the surface of the contained working fluid. Having all seams above the surface of the contained fluid allows the inner tank to be constructed of light gauge material and allows for the tank to be deformed while resisting breakage and leakage. Another advantage of this system is that the lightweight high gauge material used to construct the inner tank is thin and allows for a quick transfer of heat to the contained working fluid.
In broad embodiment, the present invention is a solar water heater comprising an insulated container with a cover which allows solar energy to enter the container, enclosing a tank which further contains a length of supply water pipes surrounded by a working fluid. The container is comprised of a bottom panel and a plurality of side panels. The cover of the container allows solar energy to enter the container. The inner tank is comprised of a lightweight, thin, high gauge material which is painted black. A tube which distends from the container and connected into the inner tank allows the inner tank to be substantially filled with a working fluid and further allows the inner tank to be vented to the atmosphere. A supply-water pipe with an inlet and an outlet enters through the container into the inner tank, in which a substantial portion of the supply-water pipe is submerged in the working fluid, and then exits the inner tank and the container. The inlet for the supply water pipe can be connected to a source of pressurized supply water, such as a city water source. The outlet can be connected to a standard water heater. Solar energy enters the container through the cover and heats the inner tank and subsequently the working fluid. Cool supply water travels through the supply-water pipe, and is heated while traveling through the portion of supply-water pipe submerged in the working fluid. Because only the supply water is pressurized, only the supply-water pipe must be made of a material which may withstand pressure; the inner tank does need to withstand the pressure from a city water source. Heated supply water exits the system and is supplied to a standard water heater, thereby increasing the overall efficiency of the water heating system.
While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiments, methods, and examples, but by all embodiments and methods that are within the scope and spirit of the invention as claimed.
Patent Application
20110146665
