WO2017210674A1

WO2017210674A1 - Tankless solar water heater using bottomless vacuum tubes

Info

Publication number: WO2017210674A1
Application number: PCT/US2017/035921
Authority: WO
Inventors: Julian Chengjun CHEN
Original assignee: Columbia University in the City of New York
Current assignee: Columbia University in the City of New York
Priority date: 2016-06-03
Filing date: 2017-06-05
Publication date: 2017-12-07
Anticipated expiration: 2018-12-03

Abstract

Methods and systems for heating a liquid using solar energy are disclosed. One or more bottomless vacuum tubes include an outer tube, an inner tube, and a vacuum disposed therebetween, as well as open top and bottom ends to allow liquid flow therethrough. The top open ends of the bottomless vacuum tubes are connected to a hot liquid chamber. A source of cold liquid is used to fill the liquid heater system and the bottomless vacuum tubes are positioned to allow daylight to be transmitted therethrough. The daylight heats the liquid in the bottomless vacuum tubes, and separates itself into the hot liquid chamber by being lighter than the remaining "cold" liquid in the tankless liquid heater system. Steam outlets are positioned on the system to enable any evolved air pockets or evaporated liquid to escape.

Description

TANKLESS SOLAR WATER HEATER USING BOTTOMLESS VACUUM TUBES

CROSS REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of U.S. Provisional Application Nos. 62/345,336, filed June 3, 2016, and 62/378,857, filed August 24, 2016, which are incorporated by reference as if disclosed herein in their entirety.

BACKGROUND

[0002] Solar water heater technology is being developed as a more environmentally friendly alternative to providing temperature controlled water to users. Due to the inherent cyclical nature of the sun as the renewable energy source, one of the main challenges in implementing a solar energy water heater on a practical scale is the storage of hot water for use at times when hot water production is limited.

[0003] Tankless solar water heater designs can employ a plurality of glass tubes having a vacuum lumen, wherein the glass tubes include plastic capsules filled with an energy storage medium. The vacuum tubes are arranged in a parallel structure, with cold-water pipes connected in parallel and residing inside parallel vacuum tubes. However, while these systems are an improvement over traditional hot water tank systems, the water levels in all glass vacuum tubes are not always equalized because the pipes are connected via inversed siphon tubes, and it is not always possible to eliminate air pockets at the top of siphon tubes. SUMMARY

[0004] Some embodiments of the disclosed subject matter are directed to a tankless liquid heater system using substantially transparent bottomless vacuum tubes. In some embodiments, the bottomless vacuum tubes are substantially transparent and include an outer tube, an inner tube, and a vacuum disposed between the inner and outer tubes, as well as open top and bottom ends to allow liquid flow through the bottomless vacuum tubes. The top open ends of the bottomless vacuum tubes are connected to a hot liquid chamber. In some embodiments, the bottom open ends are connected to a cold liquid chamber. A source of cold liquid is used to fill the tankless liquid heater system, and the bottomless vacuum tubes are positioned to allow daylight to be transmitted to the liquid within. The daylight heats the liquid in the bottomless vacuum tubes. The lighter hot liquid "rises" to the hot liquid chamber, while the remaining "cold" water in the system "sinks" to the cold liquid chamber. Liquid at a desired temperature is then provided on demand via a mixing valve, which mixes liquid from the hot water chamber and liquid from the source of cold liquid to achieve the desired temperature liquid. Steam outlets are positioned on the system to enable any evolved air pockets or evaporated liquid to escape.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The drawings show embodiments of the disclosed subject matter for the purpose of illustrating the invention. However, it should be understood that the present application is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein: [0006] FIG. 1 is a schematic drawing of a liquid heating system according to some embodiments of the present disclosure;

[0007] FIG. 2 is a schematic drawing of a liquid heating system according to some embodiments of the present disclosure;

[0008] FIG. 3 is a schematic drawing of a liquid heating system according to some embodiments of the present disclosure; and

[0009] FIG. 4 is a chart of a method of heating a liquid according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

[0010] Referring now to FIG. 1, aspects of the disclosed subject matter include a liquid heating system 100 including a liquid source inlet 102, vacuum tubes 104, and a hot liquid chamber 106, all of which cooperate to heat a liquid 108.

[0011] Liquid 108, which is typically, but not always, stored at a liquid source 110, enters heating system 100 via liquid source inlet 102. In some embodiments, liquid source inlet 102 includes a conduit, plenum, manifold, chamber, valve, or a combination thereof for accepting liquid 108 from liquid source 110 into liquid heating system 100 and subsequent distribution to other components of the system. In some embodiments, liquid 108 is water, such as cold or ambient temperature water and liquid source 110 is a well or public water supply. In some embodiments, liquid heating system 100 includes a steam outlet 111 in fluid communication with hot liquid chamber 106 in the event of a phase change of liquid 108 as a result of system operation.

[0012] In some embodiments, liquid heating system 100 includes a cold liquid

chamber 112, which is positioned generally below or at a lower elevation than hot liquid chamber 104. As used herein, the terms "hot" and "cold" are used generally as relative terms to describe liquid 108 that has yet to be heated by liquid heating system 100 ("cold") and liquid 108 that has been heated by liquid heating system 100 ("hot"). As such, there is no specific temperature at which liquid 108 is no longer "cold" but is instead "hot." However, as evidenced by the presence of steam outlet 111, liquid heating system 100 is capable of heating liquid 108 to temperatures up to and in excess of 100°C.

[0013] In some embodiments, vacuum tubes 104 extend from hot liquid chamber 106 to cold liquid chamber 112. Vacuum tubes 104 include a first end 114 at cold liquid chamber 112 and a second end 116 at hot liquid chamber 106 and a body 118 therebetween. Vacuum tubes 104 are composed of an inner tube 120 and an outer tube 122, with a lumen 124 disposed therebetween. In some embodiments, lumen 124 is a vacuum. Vacuum tubes 104 are considered "bottomless" because each of first end 114 and second end 116 are open, allowing liquid 108 flow through the first end, along a length of an interior 126 of the tube, and out the second end. Vacuum tubes 104 are substantially transparent so that when exposed to a daylight source, e.g., direct contact with the sun, daylight is transmitted through inner tube 120 and outer tube 122 to interior 126 where it heats liquid 108 contained therein. In some embodiments, vacuum tubes 104 are composed of polycarbonate, acrylic, or glass, e.g., Pyrex, borosilicate glass, and the like, and combinations thereof. Vacuum tubes 104 are positioned to maximize contact between daylight and liquid 108 in interior 126, as well as provide a flow path for the liquid from first end 114 to hot liquid chamber 106. In some embodiments, liquid heating system 100 includes a plurality of vacuum tubes 104. In some embodiments (not pictured), liquid heating system 100 includes a single vacuum tube 104.

[0014] Lumen 124 helps prevent heat loss from liquid 108 through vacuum tubes 104. In some embodiments, body 118 has a larger diameter than first end 114 and/or second end 116. In some embodiments, a selective absorption film 128 is positioned on vacuum tubes 104 composed of material effective to increase transfer of solar energy from the daylight to liquid 108 in interior 126. In some embodiments, selective absorption film 128 is disposed on a surface of inner tube 120. In some embodiments, selective absorption film 128 is disposed on a surface of inner tube 120 and between the inner tube and outer tube 122. In some embodiments, selective absorption film 128 is composed of silver, aluminum, copper, steel, e.g., stainless steel, and combinations thereof. In some embodiments, selective absorption film 128 includes a first layer and a second layer. In some embodiments, the first layer is a metal, e.g., those described above. In some embodiments, the second layer is a semiconductor that absorbs visible and near- infrared light. In some embodiments, the second layer is composed of aluminum nitride, copper oxide, chromium oxide, silver sulfide, and the like, and combinations thereof. In some embodiments, the first layer is positioned between the surface of inner tube 120 and the second layer. [0015] In some embodiments, hot liquid chamber 106 includes hot liquid inlets 130. In some embodiments, cold liquid chamber 112 includes cold liquid outlets 132. Hot liquid outlets 130 and cold liquid outlets 132 extend from hot liquid chamber 106 and cold liquid chamber 112, respectively. In some embodiments, hot liquid outlets 130 and cold liquid outlets 132 extend into vacuum tubes 104. Hot liquid outlets 130 and cold liquid outlets 132 provide fluid communication between hot liquid chamber 106 and cold liquid chamber 112 and vacuum tubes 104.

[0016] In some embodiments, an interface 134 between cold liquid chamber 112 and vacuum tubes 104 is a first plug 136. Similarly, in some embodiments, the interface 134 between hot liquid chamber 106 and vacuum tubes 104 is a second plug 138. First plug 136 and second plug 138 substantially prevent liquid 108 from leaking out of liquid heating system 100.

[0017] Referring now to FIG. 2, in some embodiments, first plug 136 and second plug 138 include at least one gasket 200 to provide a seal between vacuum tubes 104 and the plugs. In some embodiments, gasket 200 is composed of silicone. In some embodiments, gasket 200 is an o-ring. In some embodiments, a plurality of gaskets 200 are included on first plug 136 (not shown) and second plug 138. In some embodiments, first plug 136 and second plug 138 are substantially cylindrical. In some embodiments, first plug 136 and second plug 138 are tapered. In some embodiments, first plug 136 and second plug 138 include grooves 202 for retaining gaskets 200. In some embodiments, first plug 136 and second plug 138 are composed of an elastic material. In some embodiments, first plug 136 and second plug 138 are composed of polycarbonate. [0018] Referring again to FIG. 1, in some embodiments, liquid heating system 100 includes a filling chamber 140. In some embodiments, filling chamber 140 is in fluid communication with liquid source 110, liquid source inlet 102, cold liquid chamber 112, and/or first end 114. In some embodiments, fluid communication between filling chamber 140 and liquid source 110, liquid source inlet 102, cold liquid chamber 112, and/or first end 114 is through a cold liquid pipe 142. In some embodiments, cold liquid pipe 142 extends through a vacuum tube 104, such as through interior 126. In some embodiments, filling chamber 140 also includes an outlet for steam, i.e., steam outlet 111. In some embodiments, filling chamber 140 is positioned generally above or at a higher elevation than cold liquid chamber 112 and/or hot liquid chamber 106. Although it is unlikely that "hot" liquid will be held in filling chamber 140, air pockets may evolve in the filling chamber or elsewhere in liquid heating system 100, such as cold liquid pipe 142. Having steam outlet 111 in filling chamber 140 helps evacuate these air pockets to prevent gas build within liquid heating system 100.

[0019] In some embodiments, filling chamber 140 includes a filling valve 144. Filling valve 144 controls flow of liquid 108 into filling chamber 140 and thus to liquid source inlet 102, cold liquid chamber 112, and/or first end 114 and into hot liquid chamber 106. Thus, filling valve 144 controls the fluid level in liquid heating system 100, as will be discussed in greater detail below. Hot liquid chamber 106, cold liquid chamber 112, vacuum tubes 104, and filling chamber 140 hold hot liquid for use in a building, such as a home. In some embodiments, liquid heating system 100 is sized to supply substantially all hot liquid necessary for use in the home. In some embodiments, a plurality of liquid heating systems 100 are provided and sized to supply hot liquid to a building, for example an apartment complex with multiple units drawing hot water. In some embodiments, the overall dimensions of liquid heating system 100 and/or its components are varied by one having ordinary skill in the art to have associated characteristics and functionality for use in a specific application.

[0020] In some embodiments, liquid heating system 100 includes a mixing valve 146. In some embodiments, mixing valve 146 is in fluid communication with liquid source 110, liquid source inlet 102, filling chamber 134, and/or hot liquid chamber 106. Mixing valve 140 provides a liquid at a desired temperature to a liquid outlet 148 by mixing hot liquid from hot liquid chamber 106 and cold liquid from liquid source 110, liquid source inlet 102, and/or filling chamber 140. Mixing valve 146 is configured to provide liquid outlet 148 with mixtures ranging from pure cold liquid to pure hot liquid depending the user's desired temperature. In some embodiments, a liquid pressure booster 150 is included to increase the flow rate of liquid from liquid outlet 148. In some embodiments, cages 152 are included to insulate hot liquid chamber 106 and/or cold liquid chamber 112. In some embodiments, cages 152 have a similar or identical diameter as vacuum tubes 104. [0021] Referring now to FIG. 3, in some embodiments, liquid heating system 100 includes a radiation shield 300. In some embodiments, radiation shield 300 is composed of polycarbonate, glass, acrylic, and combinations thereof. Radiation shield 300 is disposed over at least one of vacuum tubes 104. In some embodiments, radiation shield 300 is disposed over all of vacuum tubes 104. In some embodiments, radiation shield 300 is disposed over only a portion of at least one vacuum tube 104. Radiation shield 300 is positioned to protect vacuum tubes 104 from projectiles and environmental forces, e.g. hail, snow, vandalism, etc. Further, radiation shield 300 is positioned to limit radiation heat loss of off vacuum tubes 104, resulting in a higher efficiency system with minimal increases in manufacturing complexity or cost.

[0022] Referring now to FIG. 4, some embodiments of the disclosed subject matter include a method 400 of heating a liquid. At 402, a hot liquid chamber is provided in fluid

communication with a liquid source inlet. At 404, a vacuum tube is positioned in fluid communication with the hot liquid chamber and the liquid source inlet. As discussed above, the vacuum tube is bottomless, with a first or "cold" open end and a second or "hot" open end. At 406, a cold liquid from the liquid source inlet is allowed to flow to the cold open end, along the vacuum tube, and through the hot open end into the hot liquid chamber. The flow from 406 fills the system with liquid to be heated by, at 408, exposing the now liquid-filled vacuum tube to daylight. As the liquid within the vacuum tube is heated, it rises within the tube and is eventually collected in the hot liquid chamber. Meanwhile, colder liquid stays within the vacuum tube (where it will be heated) or falls back towards and through the cold open end.

[0023] At 410, a substantially constant liquid level is maintained in the hot liquid chamber via a filling valve in fluid communication with the liquid source inlet and the cold open end. In some embodiments, the hot liquid chamber is maintained about half full. At 412, a mixed liquid stream of hot liquid from the hot liquid chamber and cold liquid from the liquid source inlet is output at a desired temperature via a mixing valve. A substantially constant liquid level is maintained at 410 so as to have a reliable amount of hot liquid available on demand for a user of the system. After the initial filling at 406, the liquid level of the system will decrease in response to liquid drawn from the system by the user, as well as liquid lost from the system due to evaporation. As discussed above, in some embodiments, a filling chamber and/or a cold liquid chamber are provided as sources of cold liquid, along with the cold liquid source itself. When the liquid level is brought below a predetermined fill level, additional cold liquid is brought in, such as through the fill valve described above. [0024] The systems and methods of the present disclosure provide effective and

environmentally conscious on-demand access to hot water. The vacuum tubes harness the heating power of daylight to produce a reserve of hot water from an available source of cold water. The bottomless construction of the vacuum tubes, as well as the configuration of the bottomless vacuum tubes with the hot and cold water chambers, allows for the hot water to continuously self-organize in a location accessible by a user. This has the benefit of simplifying construction and operation of the system, and eliminating build-up of air pockets in the water chambers which are detrimental to system operation. In some embodiments, external power is only necessary to mix cold water with an amount of the hot water to extract water having a desired temperature from the system. The system is can also include a radiation shield, which provides further advantages in the forms of increased system efficiency and protection against external effects that could shorten the system's operational lifecycle or increase maintenance frequency, yet is simple to install. Thus, the system is highly energy efficient and can be operated at a low burden on an available power supply. Further, the modular nature of the water chambers and vacuum tubes means the system is simple to operate and maintain. Finally, the configuration of the hot water chamber, cold water chamber, vacuum tubes, and filling chamber prevent gas buildup which is known to hamper performance of traditional tankless solar water heater designs.

[0025] Although the disclosed subject matter has been described and illustrated with respect to embodiments thereof, it should be understood by those skilled in the art that features of the disclosed embodiments can be combined, rearranged, etc., to produce additional embodiments within the scope of the invention, and that various other changes, omissions, and additions may be made therein and thereto, without parting from the spirit and scope of the present invention.

Claims

CLAIMS What is claimed is:

1. A method of heating a liquid comprising: providing a hot liquid chamber that is in fluid communication with a liquid source inlet; positioning a vacuum tube in fluid communication with said liquid source inlet and said hot liquid chamber, said vacuum tube having a hot open end and a cold open end; allowing a cold liquid from said liquid source inlet to flow to said cold open end for a predetermined amount of time, along said vacuum tube, through said hot open end, and into said hot liquid chamber; and exposing said vacuum tube to daylight.

2. The method according to claim 1, wherein said allowing step further comprises maintaining a substantially constant liquid level in said hot liquid chamber via a filling valve in fluid communication with said liquid source inlet and said cold open end.

3. The method according to claim 1, further comprising outputting a mixed liquid stream of hot liquid from said hot liquid chamber and said cold liquid from said liquid source inlet at a desired temperature via a mixing valve.

4. A liquid heating system comprising: a liquid source inlet conduit; a cold liquid chamber including a cold liquid outlet extending from said cold liquid chamber; a hot liquid chamber including a hot liquid inlet extending from said hot liquid chamber; a bottomless vacuum tube extending between said cold liquid chamber and said hot liquid chamber; a first plug providing an interface between said cold liquid outlet and said bottomless vacuum tube; and a second plug providing an interface between said hot liquid outlet and said bottomless vacuum tube.

5. The system according to claim 4, further comprising a filling chamber including a filling valve in fluid communication with said liquid source inlet conduit and said cold liquid chamber.

6. The system according to claim 4, further comprising a mixing valve in fluid communication with said liquid source inlet conduit and said hot liquid chamber.

7. The system according to claim 4, further comprising a cold liquid pipe in fluid

communication with said liquid source inlet conduit and said cold liquid chamber, said cold liquid pipe extending through said bottomless vacuum tube.

8. The system according to claim 4, further comprising an insulating cage substantially

covering at least one of said hot liquid chamber and said cold liquid chamber.

9. The system according to claim 4, said first plug further comprising at least one first gasket providing a seal between said bottomless vacuum tube and said first plug, and said second plug further comprising at least one second gasket providing a seal between said bottomless vacuum tube and said second plug.

10. The system according to claim 9, wherein said first plug and said second plug include an o- ring.

11. The system according to claim 4, further comprising a radiation shield.

12. The system according to claim 11, wherein said radiation shield is disposed over said

bottomless vacuum tube.

13. The system according to claim 12, wherein said radiation shield is composed of

polycarbonate, glass, acrylic, or a combination thereof.

14. The system according to claim 4, further comprising a selective absorption film on said bottomless vacuum tube.

15. The system according to claim 14, wherein said selective absorption film is composed of silver, aluminum, copper, steel, or a combination thereof.

16. The system according to claim 15, said bottomless vacuum tube further comprising an inner tube and an outer tube, wherein said selective absorption film is disposed on said inner tube between said inner tube and said outer tube.

17. The system according to claim 4, said bottomless vacuum tube further comprising a first end, a second end, and a body disposed between said first end and said second end, wherein said body has a larger diameter than said first end and said second end.

18. The system according to claim 4, further comprising a plurality of bottomless vacuum tubes.

19. A tankless water heater system comprising: a plurality of substantially transparent vacuum tubes, said substantially transparent vacuum tubes including a first open end, a second open end, and an inner tube, an outer tube, and a vacuum disposed between said inner tube and said outer tube; a cold water source inlet conduit; a cold water chamber including a cold water outlet extending from said cold liquid chamber and a hot water chamber including a hot water inlet extending from said hot liquid chamber, said cold water outlet extending into said first open end and said hot water inlet extending into said second open end; a filling chamber including a filling valve in fluid communication with said cold water source inlet conduit and said cold water chamber; a first plug providing an interface between said cold water outlet and said substantially transparent vacuum tube; a second plug providing an interface between said hot water outlet and said substantially transparent vacuum tube; a mixing valve in fluid communication with said filling chamber, said hot water chamber and a water outlet; and a steam outlet in fluid communication with said hot water chamber.

0. The system according to claim 19, further comprising a radiation shield disposed over said plurality of substantially transparent vacuum tubes.