WATER HEATING APPARATUS

Abstract

Disclosed is a solar water heating apparatus comprising a central tank and one or more outer layers wherein at least part of the exterior of the outermost layer is adapted to be exposed to the sun. The outer layers also form water pathways such that, when the tank is substantially filled with water, said water is able to circulate around a path formed by said central tank and the outer layers. A pulsing pump may help circulate the water. An auxiliary heating element may be also provided, such as a small gas burner.

Description

This invention relates to water heating apparatus and in particular solar water heating apparatus and/or combined solar and gas water heating apparatus.

Simple water solar absorbers are not as effective in the Northern part of the temperate zone as they are in the Southern part of the same band. The length of sunshine or its strength limits severely the value for money of these devices, in many cases realistically prohibiting their use or at the very least limiting their use to a small part of the year. Other problems like altitude, climatic considerations also add to the problem. Too often, the water heated is too cool by the time it is needed for use. In this case the cool water has to be reheated before use, even more heat energy is to be used.

The invention in its various aspects aims to enable the provision of hot water while avoiding or reducing one or more of the problems identified above.

In a first aspect of the invention there is provided a solar water heating apparatus comprising a central tank and one or more outer layers, said outer layers also forming water pathways, wherein, when substantially filled with water, said water is able to circulate around a path formed by said central tank and at least one of said one or more outer layers, and wherein at least part of the exterior of the outermost layer is adapted to be exposed to the sun, in use.

In a main embodiment said apparatus should be arranged such that water is able to circulate between the outermost layer and the central tank via any intermediary layers.

Pumping means may be provided to circulate the water. Said pumping means may comprise a pulsing pump. Said pump may be arranged to operate continuously or intermittently. Said apparatus may further comprise controller means to control said pumping means depending on sensed water temperature at predetermined points in the apparatus.

Said tank and or the outer layers may be comprised of a plastic material. Said plastic may be polypropylene or similar material.

Said tank and or the outer layers may be comprised of a metallic material. Said metal may be copper or similar material.

Said at least one layers may comprise one or more outer tanks around said central tank. Said outer tanks may comprise water outlets/inlets at opposing points to adjacent tanks, to provide a tortuous path for said water to circulate.

Alternatively said at least one layers may comprise a hollow jacket wrapped at least once around said inner tank. The cross section of said jacket may be in the shape of a symmetrically flattened round tube. Ideally said jacket is wrapped around the inner tank a plurality of times.

Said apparatus may comprise a cold water input and warm water output. Said warm water output is preferably drawn from said central tank. In one embodiment this output is drawn from a point at or above halfway from the bottom of the central tank. Said cold water input may also feed into the central tank, preferably at the bottom, or alternatively into the outermost layer.

Said apparatus may comprise insulation around its outside, of which at least a portion of which is arranged to move so as to expose an uninsulated portion of the outside of said apparatus to allow for direct solar heating. Said insulation may be arranged to move based on the time of day, readings from a temperature sensor, readings from a light sensor, or a combination thereof. Alternatively said insulation may simply be arranged to be moved manually.

Said apparatus may further comprise gas burner apparatus, said gas burner apparatus being substantially immersed in said tank. Said gas burner apparatus may be arranged, in normal use, to burn an amount of gas comparable to that of a domestic pilot light flame. It may have a further setting to burn gas at a greater rate for fast heating. The flame of said gas burner apparatus may be located at a point approximately half way from the bottom of the central tank.

In a further aspect of that invention there is provided a combined gas and solar water heating apparatus comprising a central tank and a gas burner apparatus, said gas burner apparatus being substantially immersed in said central tank, and wherein at least part of the exterior of said apparatus is adapted to be exposed to the sun so as to heat the contents by solar energy, in use. As an alternative, said gas heating apparatus may be replaced with an electric heating apparatus.

Said apparatus is preferably made of a plastic. Said plastic may be polypropylene or similar material.

Said apparatus may further comprise one or more outer layers, said outer layers also forming water pathways, wherein, when substantially filled with water, said water is able to circulate around a path formed by said central tank and at least one of said one or more outer layers. In a main embodiment said apparatus should be arranged such that water is able to circulate between the outermost layer and the central tank via any intermediary layers. Pumping means may be provided to circulate the water. Said pumping means may comprise a pulsing pump. Said pump may be arranged to operate continuously or intermittently. Said apparatus may further comprise controller means to control said pumping means depending on sensed water temperature at predetermined points in the apparatus. Said at least one layers may comprise one or more outer tanks around said central tank. Said outer tanks may comprise water outlets/inlets at opposing points to adjacent tanks, to provide a tortuous path for said water to circulate. Alternatively said at least one layers may comprise a hollow jacket wrapped at least once around said inner tank. The cross section of said jacket may be in the shape of a symmetrically flattened round tube. Ideally said jacket is wrapped around the inner tank a plurality of times.

Said apparatus may comprise a cold water input and warm water output. Said warm water output is preferably drawn from said central tank. In one embodiment this output is drawn from a point at or above halfway from the bottom of the central tank. Said cold water input may also feed into the central tank, preferably at the bottom, or alternatively into the outermost layer.

Said apparatus may comprise insulation around its outside, of which at least a portion of which is arranged to move so as to expose an insulated portion of the outside of said apparatus to allow for direct solar heating. Said insulation may be arranged to move based on the time of day, readings from a temperature sensor, readings from a light sensor, or a combination thereof. Alternatively said insulation may simply be arranged to be moved manually.

Said gas burner apparatus may be arranged, in normal use, to burn an amount of gas comparable to that of a domestic pilot light flame. It may have a further setting to burn gas at a greater rate for fast heating. The flame of said gas burner apparatus may be located at a point approximately half way from the bottom of the central tank. If instead an electric heating apparatus is used, said apparatus may use less power than 100 w, and possibly in the region of 50 w-80 w.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, by reference to the accompanying drawings, in which:

FIG. 1 shows a cross section of a domestic water heater according to an embodiment of the invention, comprising one micro furnace having a single burner inside;

FIG. 2 shows a top view of the water heater shown in FIG. 1 showing the non-dynamic insulation surrounding the apparatus;

FIG. 3 shows a cross section of a domestic water heater according to a second embodiment whereby the cold mains supply is connected directly to the central tank;

FIG. 4 is a top view of the apparatus of FIG. 3;

FIG. 5 shows a perspective view of the second embodiment of the invention with the jacket rolled out; and

FIG. 6 shows a cross-section view A-A of the jacket for the second embodiment.

FIG. 7 shows a different embodiment of the micro-furnace and burner.

FIG. 8 shows a different embodiment of the apparatus enabling water to flow tortuously into the central container using a different pathway.

FIG. 9 shows an embodiment of the jacket comprising spacers that keep the layers at a distance apart.

FIG. 10a shows the apparatus according to the embodiment described in FIG. 3 in more detail, including a dome at the top of the central tank.

FIG. 10b shows the above view from cross-section S-S of FIG. 10a.

FIG. 11 shows a pattern for manufacturing the first spiral layer of the jacket of FIG. 10.

FIG. 12 shows a side view of the formers placed on the same plane.

FIG. 13 shows the covered pattern to build the layers.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a cross sectional view of a water heating apparatus. 10. It shows an outer container or tank 11 having (in this example) three further smaller containers 12, 13 and 14 fitted one inside the other in a “Russian-doll” style to form a multi-layered tank. Water space layers 16, 17 and 18 are therefore formed between the outside and inside shell of adjacent containers. The outer shell of the inner containers is surrounded by a heat insulation material 15 (which is only shown on one half of the apparatus in FIG. 1). There are openings 35, 36 and 37 in each of the inner containers 12, 13 and 14, the last of these, opens into the innermost container via a chimney 29. The outermost container 11 has a main inlet 41 connected to cold water supply 19 via solenoid switch 30, and the innermost container has a main hot water outlet 32, which in turn connects to the sink 31a, basin 31b, bath 31c or washing machine 31d taps and a release valve 38. There is also a connection 21 between the outermost 11 and innermost 14 containers in which there is a pulsing pump 20.

A metal tube 40 is fitted through the axial vertical centre of the containers and accommodates a metal tube 22 to form a micro-furnace 60. The micro-furnace consists of a u-shaped secondary metal tube 22 into which there feeds a gas inlet 23 and air inlet 24. An air blower 25 may be used to supply air to the micro-furnace. A constricted opening 27 allows the expulsion of combusted gases. A removable cap 41 is placed on one end of the metal tube 40.

FIG. 2 shows insulation door 52 surrounding the tank to provide full insulation when in a closed position. The insulation door is not shown in FIG. 1 for the purpose of clarity. When in an open position, the door enables at least 50% of the tank to be exposed to the outside environment.

The tank apparatus, including the inner containers 12, 13, 14, is preferably made of a polypropylene drum, but can be constructed using copper where it is more efficient, both in terms of cost and functionality, to do so. The tanks can be constructed using any heat conducting material, according to the size of the apparatus being constructed, which is the most economical and will perform or benefit the purpose of the invention. The outside shell of the outermost drum 11 forming the tank is preferably black to maximise the amount of heat gathered, by its exposed surface, from the sun. The shell can also be coated in a suitable material that aid to capture solar heat energy. The two extremities of the tube 40 are sealed at the outermost drum using suitable grommets or slip rings (70) to make a waterproof connection.

The described arrangement provides a tortuous path for the water from cold water supply 19, which enters the tank through inlet 41 at its top, then proceeds to flow through openings 35, 36 and 37, formed in the inner containers successively in their top ends and bottom ends, up chimney 29, and into the central inner container 14. A hot water outlet 32 enables hot water to be drawn from the central container 14 to supply water to various outlets, such as the sink 31a, basin 31b, dishwasher (not shown in FIG. 1), washing machine 31d or bath 31c in a house. A pipe 21 with pulsing pump 20 is connected from the central container 14 to one of the water space layers 16, 17, 18 of the tank to draw/circulate water from the central container 14 to said layer 16, 17 18. This example shows the pulsing pump 20 connected between the central container 14 and the outermost water space layer 16 of the tank. The pulsed water, drawn from the central container 14, thereby pushes water in the water space layers 16, 17 and 18 so that the water circulates through the same tortuous path, described above.

In operation, water in the outermost layer 16 is heated using solar heat by exposing at least a portion of the exterior of the outermost tank 11 to the sun's rays. There will also naturally be some heating, via conduction, of the next layer 17, in contact (albeit via insulation) to the solar heated layer 16. Pump 21 is operable to pump the cooler water from inside the central reservoir 14 to the outer layer 16 where it will be heated, the action of the pump forcing the already heated water further along the tortuous path, to the other outer layers 17 and/or 18, and ultimately towards the centre. Ideally, the water temperature should be measured at or near the bottom of the central reservoir 14, with the pump 20 controlled depending on this measured temperature, thereby keeping this measured temperature acceptably high.

Every time hot water is drawn off from the hot supply 32, the solenoid switch 30 is triggered to replace substantially the same amount of cold water from supply 19 in the tank. This also causes the heated water in the outer layers 16, 17 and 18 to be pushed (by the mains supply 19) towards the central container 14, while the newly introduced water should be in the outer layers, where it will be heated up by the sun.

In operation, the water in the central container 14 will have a temperature profile from top to bottom, the water being warmer at the top of the central container compared to the bottom. Hot water, being less dense than cold water, will always find its way on top of the cooler water, and move faster, in any situation. Hot water entering the central container 14 from opening 37 is directed to the warmer part of the central container by chimney 29. The chimney 29 creates a plume that delivers the hot water directly to the warmer top layers of the central container.

One advantage of having this tortuous flow of water into the central container is that the water does not lose a lot of its heat to its adjacent layers by remaining stationary. Every time hot water is used, the solar heated water from the outermost layer 16 flows towards or into the central container 14. Moreover, any heat that escapes from the central container is captured in the layers of water surrounding it, and will timely find its way back into the centre. As explained above, this system is further aided by the use of the pulsing pump 20 which circulates water around the tank 10 at an appropriate rate, the cooler water from the bottom of the central container being pumped out to the outermost layer 16 to be heated by the solar energy. The connecting pipe 21, of pulsing pump 20, connected to the central container can be further extended in the central container 14 to extract water found at about the same level as where the warmer water is situated. By the time the hot water reaches the pump 20, it will lose its heat to the surrounding cooler water found at the base of the containers. It is also preferable to connect the other end of the connecting pipe 21, connected to the outermost layer, to the side of the apparatus which will be exposed to the sun. The frequency and the quantity of water to be circulated can be selected by the user or alternatively, it can be done automatically using a microprocessor and a system of temperature sensors placed strategically around the tank 10. The pulsing rate of the pump will depend on which of the various embodiments of the invention is used, as described hereafter together with their pathway for the flow of water, and also on the climate in which the apparatus is being used, for example, the climate in the northern part and southern part of a temperate zone will require different pulse rates.

The apparatus can be further made more efficient by connecting the cold water inlet 19/305 directly to the base of the central container. If the cold water inlet 19 is connected to the top of the outermost layer as shown in FIG. 1, in operation, the apparatus may pulse heated water from the central container 14 out to the outermost layer 16. This heated water, now in the outermost layer, may lose a portion of its heat if there is no sun shining on the apparatus, which would be undesirable.

In order to avoid this situation, and to make the apparatus more efficient, the cold mains supply 19 may connect directly to the base of the central container 14. As shown in FIG. 3, when the user draws water from outlet 332 of the central container 301, the solenoid switch 330 and the pump 320 are switched on simultaneously. The pump will pulse out substantially all water as it enters the central container 301, from the cold main supply 305, to the outermost space layer 303 and as a result, will push/suck heated water from the other space layers into the central container 301. This ensures that only water from the cold mains supply 19/305, and no heated water, is pulsed out of the central container 14/301 to the outermost layer via connecting pipe 321/21. A solenoid switch 30/330 may be used to operate the cold mains supply 19/305 and a secondary switch may be used to operate the pump 21/320.

Alternatively, using this same configuration of the cold mains supply 19/305, when the user draws water from outlet 32/332, the solenoid 30/330 can be switched on, for a period, to allow an amount of cold water to enter and settle at the base of the central container 14/301. The pulsing pump 20/320 is then switched on to pump the cold water settled at the base of the central container 14/301 out to the outermost layer 16/303 of the apparatus, and by action will also tend to push/suck hot water, found in the layers surrounding the central container, through inlet 37/437 into the central container 14/301. The pump 20/320 and the solenoid 30/330 may also use other sequences as separate devices to regulate the temperature of the water in the apparatus or the central container accordingly.

FIG. 8 shows an alternative construction of the apparatus enabling water to flow tortuously into the inner container 14 using a different pathway. Inlet openings 837 and 835 are constructed on opposite sides of containers 14 and 12 respectively, at a level about mid-way length from the base of the central container. The chimney 29, openings 37, 35 of the embodiment are no longer present. When the pump 20 is put into action, the water sucked into inlet 835 and 837 will be the less dense and faster moving warmer water formed mostly in the top half part of the apparatus of space layers 16, 17 and 18 (the top half part being above the openings 837 and 835). This ensures that less cool water, if there is any present, does not migrate into the adjacent space layers (and ultimately into the inner container) to cool the water found therein. Previously, this unwanted cooling effect may occur because of inlets 37, 35 being situated at the base of the apparatus.

This dynamic insulation system described enables the temperature of the water in the central container to be kept at a usable temperature not only during the day but also during the evening and night by appropriately pulsing the pump 20 to move the heat that has escaped into the outer layers back into the central container 14.

The apparatus can also accommodate a micro-furnace 60 to heat water in the central container 14 if necessary, such as during the night, when there is not enough sunlight during the day or when the user needs water at a higher temperature than the normal operating temperature of the apparatus. The micro-furnace 60 works together with the dynamic insulation system to help provide hot water to the user when solar energy alone will not suffice. A suitable type of micro-furnace has been proposed in document WO 85/02899 entitled “Gas Immersion Heater”. This shown a water heating apparatus which uses a gas burner to heat water in the tank. It also discloses a system of using water layers as insulation. However, this system is prone to ultimately lose any captured heat as, while a portion of the heat lost by the central tank is captured in the surrounding jacket of water, the warmer water from the jacket cannot flow into the central tank until water is drawn off from the central tank. Again, the water might be too cool by the time it is needed. Alternatively, the micro-furnace may be operated by means of an electric heater.

As mentioned previously, the water in the central container 14 has a temperature profile from warmer water at its top to cooler water at its bottom. Water heated by the micro-furnace 60 in the central container will lose a portion of its heat to its surrounding space layers 18, 17 and 16. This portion of “lost” heat can be returned to the central container by pulsing pump 20 appropriately (as before). Thus, the preheated water which migrates into the central container 14 will need very little gas heating to establish the acceptable hot water temperature if not already at that temperature.

The micro-furnace 60 consists of the primary metal tube 40 having a u-shaped secondary metal tube 22. The metal tube 22 further consists of a third tube 23 also in a u-shape to act as a gas supply. The metal tube 22 is sealed to be airtight on one end, whereas the other end found in the central container 14 is left open to accommodate for a burner flame 26 arising from tube 23. Tube 23 can be affixed to the secondary tube 22 by bolts placed at a small distance apart. Metal tube 22 is also supplied with air through air supply 24 which can be aided in operation using an air blower 25.

The burner flame 26 may comprise a pilot light and/or a main light, which is very common in the industry. The pilot light in itself may form part of the heating mechanism and may mostly be used to increase the amount of hot water in the apparatus when the temperature in the top of the central container 14 is sufficiently high. The pilot light may also serve to increase the amount of usable hot water when very little is drawn off, e.g. at night. The main light, which may be controlled automatically or manually by a thermo-couple switch and/or temperature sensors in the apparatus, will switch on when the device has an overall loss of hot water due to baths or other uses. Alternatively the burner flame 26 can be lit using an electrical method such as a peizo-electric igniter. The pilot light burner flame can be lighted by removing cap 41 to access the burner and can use a separate or the same gas tube supply as the main light burner flame. The cap 41 is preferably made transparent to be able to view the burner/pilot light before removing cap 41.

The burner flame 26 creates hot gases which then release their heat in the primary metal tube 40 to heat the water in the central container 14. These combusted gases and any other residues will find their exit way towards the open end 27 of metal tube 40 (due to cap 41 being present on the other end). The open end of tube 40 preferably uses a constricted design to avoid draught air which could lead to a flameout condition. A removable or fixed collection tray may also be provided for collecting any deposition of condensate and acids from the burning gas. It is very likely that the collection tray will not need emptying often, as evaporation will take place. Furthermore, in this embodiment of the micro-furnace 60, it is also preferable to have an outlet such a hole or a plurality of small holes in tube 22, directly below the burner flame 26, to let any condensate out.

The micro-furnace 60 can further accommodate in space 33 safety and flame guard features that are known in the industry, such as over heating detection, flame cut out or power cut out devices. For example, if the temperature in any part of the apparatus reaches a threshold level (for example 75° C.), the flameout switch will operate, which in turn cuts out the gas supply. In case of using a pilot light and/or main light, the gas supply tube(s) may have a cut-off valve that cuts the gas supply to the tube(s), in the event that the flame ever blows out, or the apparatus is overheated.

FIG. 7 shows a different embodiment of the micro-furnace 60. Metal tube 740 now contains the secondary tube 722 with its open end 760 formed at an angle in relation to the metal tube 740. The burner flame 26 is now closer to the metal shell of 740 and delivers heat directly to the shell of metal tube 740 and not to the atmosphere inside the tube. This heats up water in the inner container 714 quicker and more efficiently.

It is also preferred that in the construction of FIG. 8, the opening 837 and 835 are formed just below the level at which the burner flame 26 is situated.

The apparatus in an alternative embodiment can have more than one micro-furnace 60 and can accommodate one or more burner flame 26 in each micro-furnace 60.

The apparatus described herein is designed to maintain hot water created from solar energy should that be available or gas energy at any other time and to avoid the heat, which has been heated by any other source, to escape.

It is preferable to make the water move faster when in the layers closest to the outermost drum 11 than when in the layers closest to the central container 14. This ensures the system heats water quickly and efficiently by the solar rays. FIG. 1 shows an example of this configuration where the space layers 16 are thinner than space layer 17 which in turn are thinner than space layer 18. In one embodiment, each adjacent outer space layer is half as thick as the previous layer. Furthermore, it is also preferable to make the water move faster near the top of the apparatus, because more heat is dissipated by the hot water at the top of the apparatus, and therefore spaces 16, 17 and 18 may be made thinner at the top than at the bottom.

The apparatus can be further made more efficient by adding thermal insulating material 15 to surround the outer shells of all the inner containers 13, 13 and 14, including the whole of the chimney 29 going inside the central container 14. This insulation inhibits the transfer of heat to neighbouring layers of water. It is preferable to also have the top and bottom insulation thicker than on the sides. FIG. 2 shows a non-dynamic thermal insulation 53 present around the outer shell of outermost container 11 of approximately seven inches thick. This non-dynamic insulation 53 consists of a sliding door 52 which can be opened to expose at least 50% of the tank to the outside environment. The opening and closing of the door 52 can be controlled using a light sensor monitoring the amount of sunshine available together with temperature sensors present in the tank to optimise the efficiency of the device. When in a closed position, such as at nights, this non-dynamic insulation 53 will prevent heat escaping from the tank 10. It is also preferable to embed the pipes surrounding the apparatus, such as the cold water inlet supply and/or the hot water outlet pipes, within the non-dynamic thermal insulation.

In the case where the sliding door 52 of the non dynamic insulation is open and heat is being transferred to the apparatus from the sun, any warm water pumped out of the central container 14 to the outermost layer will tend to absorb heat from the sun in the outermost layer 16. Should the doors 52 be closed, however (at night for example) the pulsating of water in the central container 14 will also tend to lower the “level” of the hotter water towards the base, by bringing more hot water, previously heated in the surrounding layers, inside the central container 14. This may cause colder water to gather in the outer layers, but in time an equilibrium will be set up inside the apparatus, particularly as little hot water is likely to be drawn at night.

Bleed valves 28 are present on each container to remove any air bubbles formed in the process.

In operation, the hot supply 32 connects to various outlets in the house for distribution of hot water, such as the sink 31a, basin 31b or bath 31c. A release valve 38 is also connected to hot supply 32 and is kept open when all the other outlets are closed. This ensures that pressure is not built up in the apparatus due to expansion of the heated water. By triggering a switch in the bathroom for hot water, the user opens both the solenoid switch 30 and a relay switch 31c in the bathroom. This will allow cold water from supply 19 to enter the tank and heated water in the tank will move in a torturous manner to push hot water out of the central container to the hot water supply 32 to the bathroom.

FIG. 3 shows a second embodiment of the invention, where the apparatus consist of a central container 301 which has a hollow jacket 540 wrapped in layers 302 around it. The hollow jacket 540 may surround the central container 301 completely or partially. A main cold water supply 305 controlled by a solenoid switch 530 connects to the base of the central container 301. A water pump 320 also connects the base of the central container 301 to the outermost layer 303 formed by the jacket. The central container 301 also has an inlet 437 to allow water from the jacket 540 to enter the central container 301. An outlet 332 is used to draw water from the central container by the user to distribute water around as described in the previous embodiment.

At the start of operation, the central container 301 and the jacket 540 (FIG. 5) is filled with water from the cold mains supply 305, helped by the pump 320. The jacket 540 will comprise an absorber portion 501 on its outermost layer 303 which will be exposed to sun rays. Water in the absorber portion 501 of one end 503 of the jacket 504 will be heated by sun rays and can flow into the central container 301 by using opening inlet 437 at the inner end 502 of the jacket.

In operation, the water in the inner layers closer to the central container 301, formed by the wrapped jacket 540 will usually contain more heat than the water contained in the layers closer to the outermost layer 303. When water is drawn from the tank by the user, the solenoid 330 controlling the cold main supply 305 and the pump 320 are simultaneously switched on. The pump 320 will pump water that had earlier entered the central container 301, from the cold main supply, to the outermost space layer 303 and as a result will push heated water, mostly found in the top section of the apparatus, from the jacket 540 into the central container 301, through inlet 437. The hot water from the central container can thus be accessed by the user through 332. The water remaining in the outermost layer 303 will be heated by the sun.

The pulsing pump 320 may also be used to flow/circulate water around the apparatus to move the heated water from the central container 301 to the outermost layer 303 as described in the first embodiment. This can apply in any situation when it is beneficial to do so, such as at the start of operation of the apparatus when there is a lot of cold water in the apparatus. It is also preferred to have a system of temperature sensors placed around the apparatus to optimise the rate of pulsing of the pump 320. For example, a temperature sensor can be placed at the base of the central container 301, where the pump 320 normally is, to monitor the temperature and operate the pump accordingly.

The cross section of the jacket is preferably in the shape of a symmetrically flattened round tube, wrapped around the outer shell of the central container 301. FIG. 6 shows a preferred cross section shape of the material with the water space 601. Furthermore, it may be preferable to provide the apparatus with metal straps, such as copper, around it or by placing the apparatus inside an outer container to prevent the apparatus from collapsing due to pressure, such as in cases when water inside the apparatus expands. This is particularly important when the jacket 540 is long, thus forming a large number of layers 302. The outer container preferably having recesses/holes formed in its walls to allow sun rays to reach and heat the outermost layer 303 of the apparatus. It is also desirable to use some type of attachment means, such as studs, to secure together adjacent layers formed by the jacket, again to make the apparatus more rigid.

The jacket is preferably wrapped around the central container 301 such that it forms one or more layers 302 (as shown in FIG. 3), with each layer formed adding to the thickness of the material wrapped around the container 301. In a preferred embodiment, the jacket 540 is about 2.54 cm×75 cm×457 cm and is shaped in one piece with the hollow water space 601 inside. It is also preferable to use a corrugated plastic material, such as polypropylene, which is able to withstand the forces in this situation. As shown in FIG. 9, in one embodiment, the jacket may be provided with spacers 901 moulded or bonded thereto and may be constructed in one piece or several pieces joined together.

FIGS. 10a and 10b are schematic drawings showing in more detail the jacket 540 wrapped around the central tank 1014 together with insulation 1016 to form a spiral water pathway, as seen more clearly form FIG. 10b. The apparatus is further contained in an outer container 1018 and the side facing north of the outer container is provided with further insulation 1020.

A preferred method to manufacture and assemble the jacket with the insulation will now be described. In this preferred embodiment, the jacket covers the top 1022 of the central tank 1014 to form a semi-spherical dome around the top and is assembled in a plurality of layers/joins. Preferably, a portion of the circumference of the smallest spiral path formed is flush with the external circumference of the central tank.

FIG. 11 shows the method used to manufacture the first (smallest) spiral layer formed by the jacket 540. FIG. 11 shows a base 1101 with a central tube 1103 arranged near the middle of the base. Preferably, the tube has a circular cross-section to accommodate the circular tube of the micro-furnace explained before. A plurality of formers 1105, are spaced apart, preferably equally, around the central tube 1103. The formers are preferably all flush with the base 1101, as shown. Preferably, the formers are built using card or plywood.

Each former has the same shape but are sized differently. Former 1 is slightly smaller than former 2, which is slightly smaller than former 3 so that former 9 is the largest former used to manufacture the first spiral layer. Each former is larger in dimensions than the previous former in both the x-axis and the y-axis directions, as shown in FIG. 12. Preferably, the difference in sizes between formers follow a linear interpolation (for example B-A divided by 7) between the largest and the smallest former to form intermediate formers so that a smooth regular mould or pattern may be achieved for manufacturing the spiral layers. The number of intermediate formers used is not important so as long as enough is used to be able to form a pattern that will be used to shape the layers.

Each spiral layer comprises insulation 1016 which, in turn, comprises two layers of plastic walls 1024 and 1026, preferably fibre glass. When two or more spiral layers are joined together, a spiral pathway 1028 for water between the two fibre glass walls is formed. Preferably, in each layer, the layer of insulation is 16 mm, each layer of fibre glass is ⅔ mm and the layer for water to travel is about 10 mm, such that the difference between the former 1 and 9 in the direction of the y-axis, shown by C, is about 30 mm. Each revolution therefore increases in height by approximately 30 mm.

FIG. 13 shows the formers of FIG. 11 suitably covered to form a pattern for manufacture of the first spiral layer. It is preferably covered with plaster or clay but any other method can be used so that a smooth regular pattern (following the dimensions of the formers) can be obtained. The first spiral layer comprises only one layer of fibre glass and is preferably moulded over the pattern in the following sequence: the insulation followed by the layer of fibre glass.

The second and subsequent spiral layers are manufactured in the same way using larger patterns accordingly and include two layers of fibre glass each. Each subsequent layer is preferably moulded over the pattern following the sequence; a first layer of fibre glass, the layer of insulation, the second layer of fibre glass.

The last former of each spiral layer is the first former to be used to for the pattern of the next layer. For example, former 9 is the last largest former for the first spiral layer built, and a similar sized former is used as the first smallest former of the second layer to be built.

The plurality of insulated spiral layers built are joined together at their corresponding ends to form an insulated jacket comprising a spiral water path connecting the outermost spiral layer to the innermost spiral layer and a central opening to accommodate the micro-furnace.

It is understood that each former follows substantially the profile of the shape of the final jacket desired, for example in this case a semi-archway shape is used for the formers. It is also understood that the smallest former of the first layer is sized such that after the first layer is formed it may accommodate the central tank 1014 within it or the assembled jacket.

Preferably, a valve is used at the inlet 437 to ensure that water flows in only one direction, into the central container.

Preferably, the apparatus in this embodiment is held in a structure, such as a barrel to avoid any deformation in shape of the apparatus.

This apparatus in this embodiment can also accommodate one or more micro-furnace 60 with one or more burners incorporated, similar to the one described for the first embodiment.

The apparatus in all embodiments may also incorporate baffles 580 inside the tank to stop swirl mixing of water inside the central container, when water is introduced into the central container. In case where the cold water supply 305/19 is situated at the base of the central container, the baffles ensure that newly introduced water tends to stay in the lower section of the central container.

The apparatus in all embodiments can be placed inside a protective dome with at least part of the dome allowing sun rays to reach the sun exposed part of apparatus. The dome may be made of a transparent material, such as glass or Perspex. Preferably an air gap is left between the dome and the apparatus to act as further insulation. The dome will stop any blowing air or breeze to influence the apparatus, making it more efficient, and the dome may also be used to add to the aesthetics of the apparatus. The air inlet to the air blower 25 and the constricted opening 27 to allow gases to exit the micro-furnace 60 are preferably situated outside the dome.

The above embodiments are for illustration only and other embodiments and variations are possible and envisaged without departing from the spirit and scope of the invention. It should also be clear to the skilled person that any features described in the content of one embodiment may equally be applicable to any of the other embodiments, if appropriate.

Claims

1. A solar water heating apparatus comprising

a central tank and one or more outer layers,

said outer layers also forming water pathways, wherein, when substantially filled with water, said water is able to circulate around a path formed by said central tank and at least one of said one or more outer layers, and

wherein at least part of the exterior of the outermost layer is adapted to be exposed to the sun, in use.

2. The apparatus as claimed in claim 1 wherein said apparatus is arranged such that water is able to circulate between the outermost layer and the central tank via any intermediary layers.

3. The apparatus as claimed in claim 1 wherein pumping means may be provided to circulate the water.

4. The apparatus as claimed in claim 3, wherein said pumping means is a pulsing pump.

5. The apparatus as claimed in claim 3 wherein said pumping means is arranged to operate continuously or intermittently.

6. The apparatus as claimed in claim 3, wherein said apparatus comprises a controller means to control said pumping means depending on sensed water temperature at predetermined points in the apparatus.

7. The apparatus as claimed in claim 1, wherein said tank and/or the outer layers comprise a plastic material.

8. The apparatus as claimed in claim 7, wherein said plastic material is polypropylene or a similar material.

9. The apparatus as claimed in claim 1, wherein said tank and/or the outer layers comprise a metallic material.

10. The apparatus as claimed in claim 9, wherein said metal is copper or a similar material.

11. The apparatus as claimed in claim 1, wherein said at least one layers comprises one or more outer tanks around said central tank.

12. The apparatus as claimed in claim 11, wherein said outer tanks comprise water outlet(s)/inlet(s) at opposing points to adjacent tanks, to provide a tortuous path for said water to circulate.

13. The apparatus as claimed in claim 1, wherein said at least one layers comprises a hollow jacket wrapped at least once around said inner tank.

14. The apparatus as claimed in claim 13, wherein the cross section of said jacket may be in the shape of a symmetrically flattened round tube.

15. The apparatus as claimed in claim 1, wherein said apparatus comprises a cold water input and warm water output.

16. The apparatus as claimed in claim 15, wherein said warm water output is drawn from said central tank.

17. The apparatus as claimed in claim 16, wherein said output is drawn from a point at or above halfway from the bottom of the central tank.

18. The apparatus as claimed in claim 15, wherein said cold water input feeds into the outermost layer of the apparatus.

19. The apparatus as claimed in claim 15, wherein said cold water input feeds into the bottom of the central tank.

20. The apparatus as claimed in claim 1, wherein said apparatus comprises insulation around its outside, of which at least a portion of which is arranged to move so as to expose an uninsulated portion of the outside of said apparatus to allow for direct solar heating.

21. The apparatus as claimed in claim 20, wherein said insulation is arranged to move based on the time of day, readings from a temperature sensor, readings from a light sensor, or a combination thereof.

22. The apparatus as claimed in claim 20, wherein said insulation may simply be arranged to be moved manually.

23. The apparatus as claimed in claim 1, wherein said apparatus further comprises a gas burner apparatus.

24. The apparatus as claimed in claim 23, wherein said gas burner apparatus is substantially immersed in said tank.

25. The apparatus as claimed in claim 23, wherein said gas burner apparatus is arranged, in normal use, to burn an amount of gas comparable to that of a domestic pilot light flame.

26. The apparatus as claimed in claim 23, wherein said gas burner has a further setting to burn gas at a greater rate for fast heating.

27. The apparatus as claimed in claim 23, wherein the flame of said gas burner apparatus is located at a point approximately half way from the bottom of the central tank.

28. A water heating apparatus comprising a central tank and an auxiliary heating element, said auxiliary heating element being substantially immersed in said central tank, and wherein at least part of the exterior of said apparatus is adapted to be exposed to the sun so as to heat the contents by solar energy, in use.

29. The apparatus as claimed in claim 28, wherein said apparatus is made of a plastic material.

30. The apparatus as claimed in claim 29, wherein said plastic is polypropylene or a similar material.

31. The apparatus as claimed in claim 28, wherein said apparatus further comprises one or more outer layers, said outer layers also forming water pathways, wherein, when substantially filled with water, said water is able to circulate around a path formed by said central tank and at least one of said one or more outer layers.

32. The apparatus as claimed in claim 31, wherein said apparatus is arranged such that water is able to circulate between the outermost layer and the central tank via any intermediary layers.

33. The apparatus as claimed in claim 31, wherein said at least one layers comprises one or more outer tanks around said central tank.

34. The apparatus as claimed in claim 33, wherein said outer tanks may comprise water outlet(s)/inlet(s) at opposing points to adjacent tanks, to provide a tortuous path for said water to circulate.

35. The apparatus as claimed in claim 31, wherein said at least one layers comprises of a hollow jacket wrapped at least once around said inner tank.

36. The apparatus as claimed in claim 35, wherein the cross section of said jacket is in the shape of a symmetrically flattened round tube.

37. The apparatus as claimed in claim 31, wherein pumping means may be provided to circulate the water.

38. The apparatus as claimed in claim 37 wherein said pumping means comprises of a pulsing pump.

39. The apparatus as claimed in claim 37, wherein said pumping means is arranged to operate continuously or intermittently.

40. The apparatus as claimed in claim 37, wherein said apparatus further comprises controller means to control said pumping means depending on sensed water temperature at predetermined points in the apparatus.

41. The apparatus as claimed in claim 28, wherein said apparatus comprises a cold water input and warm water output.

42. The apparatus as claimed in claim 41, wherein said warm water output is drawn from said central tank.

43. The apparatus as claimed in claim 42, wherein said warm water output is drawn from a point at or above halfway from the bottom of the central tank.

44. The apparatus as claimed in claim 41, wherein said cold water input feeds into the bottom of the central tank or alternatively into the outermost layer.

45. The apparatus as claimed in claim 28, wherein said apparatus comprises insulation around its outside, of which at least a portion of which is arranged to move so as to expose an uninsulated portion of the outside of said apparatus to allow for direct solar heating.

46. The apparatus as claimed in claim 45, wherein said insulation is arranged to move based on the time of day, readings from a temperature sensor, readings from a light sensor, or a combination thereof.

47. The apparatus as claimed in claim 45, wherein said insulation is simply be arranged to be moved manually.

48. The apparatus as claimed in claim 28, wherein said auxiliary heating element is a gas burner apparatus, and is arranged, in normal use, to burn an amount of gas comparable to that of a domestic pilot light flame.

49. The apparatus as claimed in claim 48, wherein said gas burner has a further setting to burn gas at a greater rate for fast heating.

50. The apparatus as claimed in claim 48, wherein the flame of said gas burner apparatus may be located at a point approximately half way from the bottom of the central tank.

51. The apparatus as claimed in claim 28, wherein said an auxiliary heating element is an electric immersion heater, having a power output comparable to a domestic incandescent light bulb.

52. (canceled)

53. (canceled)