WO2008060167A1

WO2008060167A1 - System and method for heating water

Info

Publication number: WO2008060167A1
Application number: PCT/NZ2007/000336
Authority: WO
Inventors: Colin David Hook
Original assignee: Lanwood Industries Limited
Priority date: 2006-11-14
Filing date: 2007-11-14
Publication date: 2008-05-22
Also published as: US20100199973A1; AU2007320186A1; NZ551361A

Abstract

A system for heating a liquid, such as water, the system including a collector and a storage tank, wherein the collector and the storage tank are fluidly coupled together via a manifold. The collector includes a plurality of heat pipes which extend into the manifold. Solar energy is absorbed by the heat pipes and passed to liquid in the manifold, which in turn, is passed to the storage tank.

Description

V SYSTEM AND METHOD FOR HEATING WATER

Field of the Invention

The present invention relates to systems and methods for heating a liquid, such as water, in particular, the invention relates to systems and methods involving use of thermosiphoning and / or heat pipes.

Background

Thermosiphoning solar systems have conventionally consisted of a collector and a water tank for storing hot water. The hot water tank is located above the collector. As water in the collector is heated, it expands, lowering its density and causing it to rise up through an outlet at the top of the collector and into the hot water tank through an iniet generally provided near the top thereof. At the same time, colder, more dense water is drawn into an inlet at the bottom of the collector either from an outlet generally positioned at the bottom of the hot water tank or from an alternative source, such as the mains water supply, another tank, etc.

US 2006/0219237 A1 describes a thermosiphoning system with side mounted storage tanks. The system includes ^"a substantially^{^} planaF collector that ^' has ¥ plurality of heat exchange channels (e.g. small diameter plastic tubes) that are positioned next to one another in a parallel relationship. Headers (e.g. large diameter plastic pipes) are provided at the top and bottom of the collector and storage tanks (e.g. large diameter plastic pipes) are provided on either side of the collector.

US 2006/0219237 A1 differs from earlier systems in that tanks are provided either side of the collector as opposed to being above the collector. As liquid is heated in the collector by solar power, it moves upwards towards the header at the top of the collector and then into an inlet provided at the top of each of the storage tanks. Water from the bottom of the storage tank may enter through one or more inlets in the header at the bottom of the collector such that water circulates through the system. Hot water may be utilized by pumping it through an outlet provided in the header at the top of the collector, or through outlets provided at the tops of the storage tanks. This water may be replenished using an inlet provided in the header at the bottom of the collector that is coupled to a water source such as a mains pipe. Whilst US 2006/0219237 A1 takes some advantage of thermosiphoning principles, pumps are stil! required to move hot water to where it is required, which expend electrical energy and complicate the system.

Summary of the Invention

It is an object of the invention to provide an improved system and / or method for heating a liquid, such as water, or at least to provide a useful choice.

According to a first aspect of the invention, there is provided a system for heating a iiquid, such as water, the system comprising a collector and a storage tank, wherein the collector and the storage tank are each sealably coupled to a manifold.

Preferably, the collector comprises a heat pipe. More preferably, the collector comprises a plurality of heat pipes.

Preferably, the heat pipes are arranged to be substantially parallel.

Preferably, each heat pipe comprises an at least partially evacuated tube that houses a first portion of a sealed, ^"preferably copper,^' rise? thereinT

Preferably, each said at least partially evacuated tube is an at least partially evacuated glass tube.

Preferably, each said at least partially evacuated tube has first and second ends.

Preferably, each said at least partially evacuated tube is coupled to the manifold proximate the first end thereof, and the second end is distal therefrom.

Preferably, a second portion of each said riser extends out of the at least partially evacuated tube at the first end thereof and into the manifold. Preferably, each said second portion of the riser is in the form of a bulb.

Preferably, the second portion of each said riser is oriented above the respective first portion thereof. Preferably, sealing means, such as a plug, is provided proximate the first end of each said at least partially evacuated tube so that at least a partial vacuum is maintained therein.

Preferably, each said sealing means sealably engages an inside wall of a corresponding said at least partially evacuated tube and has an aperture for sealably receiving and holding a corresponding said riser.

Preferably, each said riser contains a liquid, such as water. More preferably, each said riser contains distilled water or alcohol.

Preferably, the manifold comprises a conduit having a preferably substantially square cross- section.

Preferably, the manifold comprises a plurality of apertures.

Preferably, each of the apertures is adapted to allow the bulb of a corresponding said riser to pass^' therethrough such that the bulbs are situated inside the conduit.

Preferably, the manifold comprises an inlet and an outlet.

Preferably, the storage tank comprises a hot water cylinder that is oriented such that its axis is substantially horizontal.

Preferably, the manifold outlet is fluidly coupled to a first storage tank inlet.

Preferably, the first storage tank inlet is oriented above the manifold outlet.

Preferably, the manifold inlet is fluidly coupled to a first storage tank outlet.

Preferably, the first storage tank outlet is oriented above the manifold inlet.

Preferably, the storage tank comprises a second storage tank inlet adapted to receive liquid from an external source, such as the water mains. Preferably, the storage tank comprises a second storage tank outlet. Preferably, the second storage tank outlet is adapted to enable users to draw hot liquid from the storage tank, as required.

Note that the first and second storage tank inlets and the first and second storage tank outlets are used to denote inlets and outlets of the same storage tank (i.e., the first and second storage tank inlets are first and second inlets of the same storage tank).

Preferably, the storage tank comprises auxiliary heating means, such as an electrical heating element. The auxiliary heating means may be used to provide additional heat to liquid in the storage tank such as at times when there is a high demand on the system or when there is little or no soiar power available (e.g. at night or during cloudy conditions).

Where an electrical heating element^' is used, preferably, the storage tank comprises an anode for preventing corrosion to the lining of the storage tank due to galvanic action or electrolysis.

Preferably, the system comprises remote heating means, such as a wetback, which may be used to generate additional hot liquid.

Preferably, the ^'remote heating^" means^' comprises an ^"inlet arid an outlet:

Preferably, the storage tank comprises a generally serpentine conduit or coil that has an inlet and an outlet. Preferably, the inlet and the outlet are provided proximate a wall of the storage tank and the coil is substantially housed within the storage tank.

Preferably, the remote heating means outlet is fluidly coupled to the coil inlet, such that liquid heated by the remote heating means may flow through the coil and thereby provide heat to the liquid that is held in the storage tank outside of the coil.

Preferably, the remote heating means inlet is fluidly coupled to the coil outlet so that liquid may return to the remote heating means as it cools down and be reheated. Alternatively, the remote heating means inlet may be adapted to receive^" liquid from an external source so that liquid leaving the remote heating means is replenished as opposed to simply circulating between the coil and the remote heating means. Preferably, the coil outlet is oriented below the coil inlet.

Preferably, the coil inlet comprises a valve, such as a ball valve, which enables excess pressure to be relieved.

According to second through fourth aspects there are respectively provided a collector, a manifold or a storage tank adapted for use in the system of the first aspect.

A fifth aspect of the invention is to use of the system of the first aspect and / or use of one or more apparatus of the second through fourth aspects for heating a liquid.

According to a sixth aspect, there is provided a method of heating a liquid, such as water, the method comprising providing a solar power collector in thermal communication with a manifold and the manifold in fluid communication with a storage tank such that, in use, solar power received by the collector causes heat to be transferred to the manifold and to any liquid therein, and the heated liquid then passes to the storage tank by thermosiphoning.

Preferably, the method comprises providing an electoral heating element in the storage tank, such that, in use, liquid may be heated therein. "^{' " '} - - ^{. . . ..} . ^.

Preferably, the method comprises thermally coupling the storage tank to an external heating means, such as a wetback.

Further aspects of the invention, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading the following description which provides at least one example of a practical application of the invention.

Brief Description of the Drawings

One or more embodiments of the invention will be described below by way of example only and without intending to be limiting with reference to the following drawings, in which:

Figure 1 is a schematic perspective view of an embodiment of a system according to the invention; Figure 2 is a perspective view of an embodiment of the system of the invention, similar to that of Figure 1 , with a portion removed to aid understanding;

Figure 3 is a cross-sectional side view of a portion of the system of Figure 1 or 2;

Figure 4 is a cross-sectional view of a storage tank, such as for use with the system of Figure 1 and / or 2;

Figure 5 is an alternative cross-sectional view of the storage tank of Figure 4;

Figure 6 is a- schematic diagram of an alternative embodiment of the system of the invention;

Figures 7A-7Cshow embodiments of fixings that may be used with embodiments of the invention; and

Figure 8 is a flow diagram of an embodiment of the method of the invention.

Detailed Description of Preferred Embodiments

Figures 1 and 2 show system 1 according to slightly varying embodiments of the invention, which do not materially differ. System 1 includes a collector 10, a manifold 12 and storage tank 14. Storage tank 14 may be referred to as a hot water cylinder and is abbreviated hereinafter to hwc.

^" Collector 10^" comprises a^" plurality^" of ^"Meat pipes 16 which^" are preferably arranged substantially parallel to each other to form a preferably substantially planar collector of solar power. Figure 3 is a cross-sectional side view of a heat pipe 16 of collector 10 and manifold 12 that shows the internal configuration thereof and the presently preferred manner in which they are coupled together. Heat pipe 16 comprises tube 30 which houses a first portion 31 of sealed or closed, preferably copper, riser 32 therein. Tube 30 is preferably an at least partially evacuated glass tube so that the sun's rays may pass therethrough and impinge on riser 32, thereby causing riser 32 to heat up, but heat loss by conduction from riser 32 is reduced.

Riser 32 is at least partially filled with a liquid, preferably alcohol, so that as riser 32 heats up, this heat is transferred to the liquid therein. Moreover, liquid in first portion 31 of riser 32 heats up and may vaporise. As it does so, it moves towards second portion 33 of riser 32, second portion 33 preferably being in the form of a bulb and above first portion 31.

Manifold 16 comprises a conduit having a preferably substantially square cross-section, although other cross-sections, including generally circular, are also within the scope of the invention. Manifold 16 comprises a plurality of apertures 34, each of which is adapted to receive and sealably engage a corresponding tube 30. Preferably, manifold 12 sealably engages tube 30 at, or at least proximate to, a first end 35 thereof so that tube 30 does not significantly extend into the space inside manifoid 12 and inhibit flow of liquid therethrough, as will be descried in more detail below.

Preferably, second portion 33 of each riser 32 extends out of tube 30 at first end 35 thereof and into manifold 12. Sealing means, such as plug 36, is provided proximate first end 35 of each said at least partially evacuated tube so that at least a partial vacuum is maintained inside tube 30. Each plug 36 sealably engages an inside wall of a corresponding tube 30 and has an aperture for sealably receiving and holding a corresponding riser 32. Preferably, each plug 36 is configured as the sole support for the corresponding riser 32.

The extension of risers 32 into manifold 12 enables the transfer of heat from first portion 31 of riser 32 to second portion 33 and then to the inside of manifold 12. The configuration of second portion 33 of riser 32 as a bulb improves the rate of heat exchange with a liquid that may be present in manifold 12. insulation 37 may be provided to reduce heat loss from manifold 12 to the surroundings.

^{"" ' "}Referring back^~tό ^"Figures f arϊd 2; manifold ^"12 comprises^" inlet 38 and outlet 39^~which enable^" liquid to enter through inlet 38, flow through manifold 12 and exit through outlet 39. During passage of the liquid through manifold 12, the temperature of the liquid rises as -the liquid is heated by the bulbs of risers 32.

Hwc 14 is preferably substantially cylindrical and oriented such that its axis is substantially horizontal. Hwc 14 is fluidly coupled to manifold 12 such as by conduits or pipes so that liquid, generally water, may flow therebetween. In particular, manifold outlet 39 is fluidly coupled to first storage tank inlet 40 and manifold inlet 38 is fluidly coupled to first storage tank outlet 41.

Preferably, first storage tank inlet .40 is oriented above manifold outlet 39. While not such in such a configuration in the Figures, preferably, the first storage tank inlet 40 is located towards the top of hwc 14. Preferably, first storage tank outlet 41 is oriented above manifold inlet 38.

Preferably, hwc 14 comprises second storage tank inlet 42 (see Figure 2) which is adapted to receive liquid from an external source, such as the water mains. Hwc 14 also comprises second storage tank outlet 43. Second storage tank outlet 43 is adapted to enable users to draw hot liquid from hwc 14, as required. For example, second storage tank outlet 43 may be fluidly coupled to one or more hot water taps (not shown) using appropriate piping. As hot liquid is drawn off. through second storage tank outlet 43, liquid stored in hwc 14 is replenished through second storage tank inlet 42.

Operation of the invention will now be described. Rays from the sun pass through tubes 30 and heat risers 32 and the liquid therein. As the liquid in risers 32 heats, it expands and may vaporise. The heated liquid and / or vapours become more buoyant and rise into second portion 33 of riser 32 inside manifold 12 i.e., the bulb. A liquid, generally water, is present in manifold 12 and is heated as it comes into contact with the bulbs. As the liquid in the manifold 12 heats up, it expands and passes out of manifold outlet 39 and into hwc 14 through first storage tank inlet 40. If there is no external draw operating on system 1 through second storage tank outlet 43 (e.g. no one is running a hot water tap), cooler liquid from the bottom of hwc 14 is drawn into manifold 12 through manifold inlet 38, where it is in turn heated, thereby circulating the liquid between manifold 12 and hwc 14. If there is an external draw on system 1 , cooler liquid from an external source, such as the water mains, enters hwc 14 via second storage tank inlet 42 so that as hot liquid is drawn from system 1 , it is replenished. The liquid in hwc 14 may then pass to manifold 12 to be heated. Alternatively, the external source of liquid may be ^"fluidly^" coupled to^" manifold^" 12 as ^"opposed to^" hwc 14. Thus,^" liquid may be replenished in manifold 12 as opposed to hwc 14.

Due to the particular vertical arrangements of each of the components of system 1 , system 1 may operate on the basis of thermosiphoning and does not require the use of pumps. However, the present invention does not preclude the use of pumps in combination with any of the embodiments thereof.

Preferably, hwc 14 comprises auxiliary heating means, such as electrical heating element 45. Electrical heating element 45 may be used to directly provide additional heat to liquid in hwc 14 such as at times when there is a high demand on system 1 or when there is little or no solar power available (e.g. at night or during cloudy conditions). Electrical heating element 45 may comprise, or be coupled to, a thermostat so that heating by electrical heating element 45 is controlled to prevent overheating. In embodiments including electrical heating element 45, preferably, hwc 14 comprises anode 46 for preventing corrosion to the lining of the storage tank due to galvanic action or electrolysis. Anode 46 may be comprised of magnesium or aluminium and preferably has a higher potential than the material it is protecting, namely a lining of hwc 14, which acts as a cathode. Anode 46 is sacrificed or dissolved in order to prevent corrosion of hwc 14.

Electrical heating elements and anodes are well known in the art and the skilled man would be able to modify and / or select an appropriate element and / or anode depending on the desired application. The invention is therefore not limited to the particular type or configuration of element and / or anode shown but it is intended to include any such modifications.

As shown in Figures 1 and 2, hwc 14 comprises coil 50. Coil 50 is shown in more detail in Figures 4 and 5, Coil 50 comprises a generally serpentine conduit having inlet 51 and outlet 52. Preferably, inlet 51 and outlet 52 are provided proximate a wall of age to receive 14 and coil 50 is contained within hwc 14. Coil inlet 51 is preferably arranged to be above coil outlet 52. Each serpentine coil of coil 50 comprises a substantially linear section followed by an arcuate section and then another substantially linear section. Each linear section, as one moves from coil inlet 51 to coil outlet 52, has a downward gradient. In a preferred embodiment, each linear section has a length of between 2 and 2.5 m and preferably falls by between 6 and 12 millimetres over that length, so as to facilitate thermosiphoning. Coil 50 may be secured using plates 47 and fixings 48 (e.g. nuts and bolts). " . . . - ^• - . - . .

Referring to Figure 6, coil 50 is fluidly coupled to a remote heating means, such as wetback 60. Wetback 60 preferably comprises a furnace which may be used to remotely heat a liquid, such as by burning solid fuel. Wetback 60 comprises outlet 61 and inlet 62. Wetback outlet 61 is fluidly coupled to coil inlet 51 , such that liquid heated by wetback 60 may flow through coil 50 and thereby provide heat to the liquid that is held in hwc 14. Coil outlet 52 is preferably fluidly coupled to wetback inlet 62 so that after the liquid has passed through coil 50 and cooled down due to its use in heating the relatively cooler liquid inside hwc 14, it is recircuiated to wetback 60 for reheating. Additionally or alternatively, wetback 60 may be adapted to receive liquid from an auxiliary source, such as the water mains, so that liquid leaving wetback 60 is otherwise replenished.

Preferably, coil inlet 51 is situated at a height greater than that of wetback outlet 61. Preferably, coil outlet 52 is at a height greater than that of wetback inlet 62. Preferably, wetback outlet 61 is above wetback inlet 62. A pressure relief valve or vent, such as ball valve 63, may be used to relieve excess pressure proximate coil inlet 51.

Also shown in Figure 6 is the connection of system 1 to external liquid supply 65, such as the water mains. Other supplies of liquid may be used as would be apparent to one of skill in the art, such as reservoirs, separate containers or tanks, wells etc. External liquid supply 65 is fluidly coupled to second storage tank inlet 42, such as by suitable piping. External liquid supply 65 may further be coupled to wetback 60. Preferably, this coupling comprises isolation valves 66 with pressure reducing valve 67 fiuidly coupled therebetween. This arrangement of valves enables flow of liquid in the correct direction and also allows for the relief of any excess pressure.

Figures 7A through 7C show various fittings that may be used with system 1. Referring to Figure 7A, there is shown tray 70. - Tray .70 is adapted such that hwc 14 may be seated thereon. Tray 70 may include tray outlet 71 which is adapted to allow liquid leaking from hwc 14 and the various inlets and outlets thereof to be captured in tray 70 and passed through tray outlet 71 to an appropriate drain.

Figure 7B shows means 72 for retaining hwc 14 in position. Means 72 preferably comprises an angled bracketr Means^""72 preferably worksin combination^" with retaining τneans^"73^~σf Figure

7C, such that rotational or sliding movement of hwc 14 is prevented. Thus, hwc 14 is held between means 72 and first face^' 74 of retaining means 73. Second face 75 of retaining means 73 is preferably adapted to fixedly hold manifold 12 in position.

Various elements of system 1 may be provided with insulation. For example, hwc 14 may be provided with heat insulation as would be apparent to one of skill in the art.

According to preferred embodiments of the invention, collector 10, manifold 12 and hwc 14 are adapted for installation outside, such as on the roof of a building. However, according to an alternative embodiment, hwc 14 may be installed inside a building, such as in the roof cavity thereof, with the conduits from manifold 12 appropriately extended. Thus, at least hwc 14 may be remotely located from collector 10 and/or manifold 12. Preferably, the generally upward gradient is maintained from the free ends of heat pipes 16 to manifold 12 and then to first storage tank inlet 40. " . ^• A preferred method of the invention is set out in Figure 8. The method depends on whether or not there is solar power available, or moreover, whether there is sufficient solar power available. If there is, the liquid in heat tubes 16 is heated and the risers then heat the liquid in manifold 12. As the liquid is heated in manifold 12, it expands and becomes more buoyant, causing it to pass to hwc 14. Then, depending on whether there is an external drain on hwc 14, such as through use of a hot water tap coupled to second storage tank outlet 43, liquid from an external source, such as the water mains, may pass into hwc 14. In either case, colder liquid from hwc 14 passes to manifold 12 through a manifold inlet 38 as warmer liquid exits through manifold outlet 39.

If there is not sufficient solar power available, one or both of two additional methods may be used. Firstly, electrical heating element 45 may be switched on to heat liquid in hwc 14 as required. Alternatively or additionally, wetback 60 may be activated to heat liquid therein, such as by using a furnace. The heated liquid expands and becomes more buoyant, causing it to rise to coil inlet 51. The liquid flows through coil 50 until it reaches coil outlet 52 where it is passed back to wetback 60 for reheating. As the liquid flows through coil 50, it heats liquid held in hwc 14.

It should be noted that any combination of the three methods of heating may be used. For example; in times of high demand, all three-methods may be- used simultaneously. -

Dimensions included in any of the Figures are preferred dimensions and are not intended to be limiting.

It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is therefore, intended that such changes and modifications be included within the present invention.

Claims

1. A system for heating a liquid, such as water, the system including a collector and a storage tank, wherein the collector and the storage tank are fluidly coupled together via a ( manifoid.

2. The system of claim 1 , wherein the collector includes a plurality of heat pipes.

3. The system of claim 2, wherein the heat pipes are arranged to be substantially parallel to one another.

4. The system of claim 2 or claim 3, wherein each heat pipe includes an at least partially evacuated tube that houses at least a first portion of a sealed riser therein.

5. The system of any one of claims 2 to 4, wherein at least a portion of each heat pipe extends into the manifold.

6. The system of claim 5 when dependent on claim 4, wherein the at least a portion of each heat pipe that extends into the manifold comprises a second portion of the respective ^" riser: . - .

7. The system of claim 6, wherein the second portion of each riser is in the form of a bulb.

8. The system of claim 6 or claim 7, wherein the second portion of each said riser is configured to be oriented above the respective first portion thereof when in use.

9. The system of any one of claims 2 to 8, wherein the manifold comprises a conduit having a substantially constant cross-section and a plurality of apertures in at least one wall thereof, each of the apertures being configured to receive a respective one of the plurality of heat pipes, such that a portion thereof is located inside the manifold.

10. The system of any one of the preceding claims, wherein the storage tank comprises a hot water cylinder that is oriented such that its major axis is substantially horizontal.

11. The system of any one of the preceding claims, wherein the manifold comprises an inlet and an outlet, wherein the manifold outlet is fluidiy coupled to a first storage tank inlet and the manifold inlet is fluidiy coupled to a first storage tank outlet.

12. The system of claim 11 , wherein the first storage tank inlet is oriented above the manifold outlet and the first storage tank outlet is oriented above the manifold inlet.

13. The system of 11 or claim 12, wherein the storage tank comprises a second storage tank inlet adapted to receive liquid from an external source.

14. The system of any one of claims 11 to T3, wherein the storage tank comprises a second storage tank outlet for enabling hot liquid to be drawn off from the storage tank.

15. The system of any one of the preceding claims, wherein the storage tank comprises auxiliary, heating means.

16. The system of any one of the preceding claims, wherein the system comprises remote heating means for generating hot liquid, the remote heating means having an inlet and an outlet. - - - - - - . .. . .

17. The system of claim 16, wherein the remote heating means comprises a wetback.

18. The system of claim 16 or claim 17, wherein the storage tank comprises a generally serpentine conduit or coil housed within the storage tank and having an inlet and an outlet.

19. The system of claim 18, wherein the remote heating means outlet is fluidiy coupled to the coil inlet, such that, in use, liquid heated by the remote heating means flows through the coil and provides heat to liquid held in the storage tank outside of the coil.

20. The system of claim 19, wherein the remote heating means inlet is fluidiy coupled to the coil outlet.

21. Preferably, the coil outlet is oriented below the coil inlet.

22. A collector configured for incorporation in the system of any one of the preceding claims.

23. A manifold configured for incorporation in the system of any one of claims 1 to 21.

24. A storage tank configured for incorporation in the system of any one of claims 1 to 21.

25. A method of heating a liquid, such as water, the method comprising providing a solar power collector in thermal communication with a manifold and the manifoid in fluid communication with a storage tank such that, in use, solar power received by the collector causes heat to be transferred to the manifold and to any liquid therein, and the heated liquid^' then passes to the storage tank by thermosiphoning.

26. The method of claim 25, comprising providing an electrical heating element in the storage tank, such that, in use, liquid may be heated thereby.

, .

27. The method of claim 25 or claim 26, comprising thermally coupling the storage tank to an external heating means.