Abstract:
A lightweight and low cost solar water heating apparatus which is comprised of an insulated container with a transparent cover enclosing a folded tank is provided. The 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 pre-heated supply water for a standard hot water heater.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX 
       [0003]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    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. 
         [0006]    2. Description of the Related Art 
         [0007]    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. 
         [0008]    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. 
         [0009]    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. 
         [0010]    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. 
         [0011]    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. 
         [0012]    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 
       [0013]    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. 
         [0014]    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. 
         [0015]    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. 
         [0016]    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. 
         [0017]    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. 
         [0018]    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 
         [0019]    Illustrative and preferred embodiments of the present invention are shown in the accompanying drawings in which: 
           [0020]      FIG. 1  is a cross-sectional perspective view of a solar water heater of the present invention; 
           [0021]      FIG. 2  is a cross-sectional side view of a solar water heater of  FIG. 1 ; 
           [0022]      FIG. 3  is an exploded view of a solar water heater of  FIG. 1 ; 
           [0023]      FIG. 4  is a cross-sectional perspective view of a solar water heater of the present invention; and 
           [0024]      FIG. 5  is a cross-sectional perspective view of a solar water heater of the present invention. 
           [0025]      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; 
           [0026]      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; 
           [0027]      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 
       [0028]    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. 
         [0029]    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 . 
         [0030]    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 . 
         [0031]    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. 
         [0032]    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 . 
         [0033]    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 . 
         [0034]    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. 
         [0035]    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 . 
         [0036]    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. 
         [0037]    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. 
         [0038]    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 . 
         [0039]    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 . 
         [0040]    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. 
         [0041]    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. 
         [0042]    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. 
         [0043]    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.