WO2017199048A1

WO2017199048A1 - A solar water heating apparatus

Info

Publication number: WO2017199048A1
Application number: PCT/GB2017/051411
Authority: WO
Inventors: Varnavas Varnava
Original assignee: Varnavas Varnava
Priority date: 2016-05-20
Filing date: 2017-05-19
Publication date: 2017-11-23
Also published as: GB2550429A; GB201608955D0; EP3458780A1

Abstract

A solar water heating apparatus (1) comprises at least one enclosed container (2) configured to hold a volume of water; an open-topped housing (3) configured to receive the or each container (2) therein, and a top cover (4) configured to close the open top of the housing (3) and to allow the transmission of solar radiation therethrough; the container (2) comprising an outer surface having a portion configured to face upwards towards the top cover (4) when the water container (2) is located in the housing (3), the container (2) and housing (3) mutually configured so that the width of at least the upwardly-facing portion of the container (2) is greater than the height of the container (2) when the container (2) is located in the housing (3).

Description

A SOLAR WATER HEATING APPARATUS

Field of the Invention The invention relates to a solar water heating apparatus. Background to the invention

Water heaters for direct heating of water using solar power are well known. One well- known type of solar powered water heating system is the 'bread box' solar heater. In this type of solar water heater, a container of water is heated by direct exposure to sunlight. The container is, in use, placed in a box, often formed of wood, which surrounds the container and provides insulation so that the heated water remains warm until use. This feature is particularly important during the night time, when temperatures can fall quite low. The box has a clear lid that allows sunlight to pass through so as to fall directly onto the container of water to heat the contents.

One problem with this type of solar heater is that it can be difficult to effectively heat a large enough volume of water for the required purpose or purposes. One limiting factor is that of the time of exposure to direct sunlight, as light can only impinge directly on a limited section of the outer surface of the water container (i.e. that part of the surface on the top of the container facing outwards/upwards). The contents of a larger container filled to capacity will take longer to heat than a smaller container filled to capacity, and if the container is over a certain size then the contents may not reach the required temperature during the period of exposure to the sun. This problem can be exacerbated by a lack of effective insulation in the box, as the container may not effectively retain any heat that it gains through exposure to the sun. It is an object of the present invention to provide a solar water heating apparatus that goes some way towards solving the problems outlined above, or which at least provides the public with a useful choice.

Summary of the Invention

According to a first aspect of the invention there is provided a solar water heating apparatus comprising two or more enclosed containers each configured to hold a volume of water, wherein an open-topped housing is configured to receive the containers therein, and a top cover configured to close the open top of the housing and to allow the transmission of solar radiation therethrough, the containers comprising an outer surface having a portion configured to face upwards towards the top cover when the water containers are located in the housing, the containers and housing being mutually configured so that the width of at least the upwardly-facing portion of a container is greater than the height of the container when the container is located in the housing said apparatus having a plurality of sequentially arrayed containers, each fluidly connected to the or both adjacent containers, each successive container being at a higher level than the preceding container, and with fluid flowing from the lowermost container and to the uppermost container The above configuration allows a more efficient collection of heat from sunlight impinging on the apparatus. The arrangement of the containers, each at an elevated level, ensures that the heated water rises to the top of the apparatus, to be used. Heated water within the containers, rising to the highest container, ensures that heat within the container is maintained over the course of exposure to the solar source, and after nightfall.

Preferably at least the walls of the open-topped housing comprise spaced apart inner and outer skins. Optionally the space between the skins is filled with insulating material. Further optionally the insulating material comprises polyurethane.

Advantageously, the addition of insulating material between the skins provides a more efficient housing for the containers, which aids in heat retention. The material provides a user with a more efficient system, by maintaining the water at a warmer temperature within the containers, for a longer duration. The further advantage of the insulating material, reduces the effect of a drop of atmospheric temperature on the water within the container.

Preferably the housing is substantially formed from polyethylene. The apparatus can be produced relatively cheaply, and using efficient methods of manufacture.

The use of polyethylene advantageously aids in keeping production costs lower which can be passed on as savings to potential customers to benefit from the apparatus. The polyethylene also provides a durable housing for the apparatus, ensuring the lifespan of the apparatus is sufficient.

Conveniently the containers and the floor of the housing are mutually contoured, the floor of the housing receiving and holding the underside of the at least one enclosed container.

Contoured flooring of the housing advantageously aids in the maintaining of a container positioning within the housing. The contouring aids in maintaining space between the containers, so as to reduce the effect of a cooler container on that of a warmer container. Contouring can reduce the need for extra cost incurring through the installation of fixing parts to the container from the housing.

Preferably the at least one container comprises multiple elongate sections, joined to form a single container, the axes of the sections substantially parallel.

Preferably the cross-section of at least one container or section thereof is elliptical in shape. Advantageously, utilising an elliptical shape for the container increases the surface area that is exposed to the sun. An increased surface area of exposure provides a container which can heat a larger volume of water within its structure at any one time. The cylindrical shape also provides a greater surface are, with reduced likelihood of the effects of shadowing, as the sun's position alters throughout the course of the day.

Optionally a container is formed from stainless steel. Alternatively, a container is formed from polyethylene. Advantageously, the containers can be formed from a variety of materials. The choice of production material can be the result of the climate in which the apparatus installed, dependant on the temperature fluctuations that will be experienced. A further benefit of a range of production materials includes cost reduction, to be passed on to potential purchasers of the apparatus.

Optionally at least one container includes a heating element. Further optionally the uppermost container includes a heating element.

The containers can be fitted with individual heating elements to advantageously provide heated water immediately from the apparatus. The inclusion of a heating element is particularly beneficial for heating the water within the container following a cold night, or can be utilised in the winter when nights are longer and temperatures lower.

Optionally the housing contains at least one partitioning wall, preferably extending between adjacent containers to restrict air flow within the housing and between containers.

A partitioning wall advantageously provides a further insulating means for the apparatus. The partitioning wall, or walls, provide a separation of the air between the tanks. The air between the tanks can cool the containers and subsequently the water therein, and therefore the partitioning wall prevents the cooler air from cooling the space around a warmer container. A housing for use as part of a solar water heating apparatus substantially as herein described with reference to the accompanying figures.

Brief Description of the Figures

The invention is now described with reference to the accompanying drawings, which show, by way of example only, one embodiment of an apparatus for solar heating. In the drawings: Figure 1 shows a perspective view from the front and to one side of two separate solar water heating apparatuses each according to an embodiment of the present invention, the apparatuses installed on a sloping tile roof, each of the apparatuses comprising an open- topped housing into which three enclosed elongate containers that hold a volume of water are received, each container having an outer surface with a portion that faces upwards towards the top cover when the water container is located in the housing, a transparent top cover closing the open top of the housing and allowing the transmission of sunlight or solar radiation therethrough;

Figure 2 shows an exploded perspective view from one end and slightly above of one of the solar water heating apparatuses of figure 1, showing detail of the elongate containers and the floor of the housing, each of the containers and the floor of the housing contoured so that the floor receives and securely holds or cradles the containers;

Figure 3 shows an exploded perspective view from one side of the apparatus of figure 2;

Figure 4 shows a cross-sectional end view of the apparatus of figures 1 to 3, showing detail of the walls and floor of the housing, spaced-apart inner and outer skins forming the walls and floor, the figure also showing detail of the cross-section of the three containers, each formed with an elliptical cross-section so that the upwardly-facing upper surface has a width greater than the height of the container, when the container is located in the housing, so that a large surface area of the container is presented towards direct sunlight;

Figure 5 shows a variation of the apparatus of figure 4, showing a second embodiment or variation of the container, the single container of this embodiment similar in appearance to the three containers of the preceding figures when located in the housing, the single container formed from three elongate sections, each substantially the same shape and size as a single container of the first embodiment, the elongate sections joined along their common edges to form a single container.

Figure 6 illustrates in more detail the base of a housing; and

Figure 7 illustrates fitment of a cover to a housing. Detailed Description of the Figures

An embodiment of the solar water heating apparatus, generally referenced 1, is shown in the figures. The solar water heating apparatus 1 has three main parts: an open-topped housing 3, a container or containers 2, and a lid or top cover 4. It will be recognised that the number of containers utilised depends upon the use, space available, cost etc.

Each of the containers 2 is formed as an elongate member, with, in a preferred embodiment, an elliptical cross-section when viewed from one end, and rounded end caps. Apertures (not shown) are formed, typically in the end caps but also in other regions of the containers 2 to allow the containers to be filled or for water to be drawn off from the containers 2. The containers 2 can be formed from any suitable material, such as stainless steel or polyethylene. In this embodiment, each of the containers has a width of substantially 300mm and a height of approximately 200mm, and typically can contain between 50 and 70 litres of water. The total volume in the 3 containers shown is therefore around 200 litres. A higher volume of water resists freezing of the water in the container in comparison to many prior art devices which utilise low water volumes to extract heat. This provides a more robust apparatus.

The housing 3 has continuous side walls and base (that is, there are no apertures passing through the walls or base save to allow water pipes to enter and exit the containers), and an open top. In plan view, the housing is rectangular, and in this embodiment the housing 3 is shaped and sized to receive three of the containers 2, aligned in a row next to one another along the floor of the housing 3, with the long axis of the containers 2 aligned in parallel with the longer side of the housing 3. The floor of the housing 3 is contoured to receive and hold or cradle three of the containers 2 next to one another in such a way that the longer axis of the ellipse is parallel to the floor or base of the housing 3, and the shorter axis is aligned directly upwards towards the open top. In a further embodiment, not illustrated, the longer axis is non-parallel to the floor of the housing 3 which allows the installer to orientate the containers to receive the maximum amount of sunlight, for example in the event the surface (usually a roof) is not at a convenient angle to achieve this orientation.

The housing 3 is formed with double-skin walls and floor. That is, (see Figure 4) the shell or skin of the housing 3 is formed from spaced apart inner and outer skins 3a, 3b. The skins are formed from a suitable material such as polyethylene. The space between the inner and outer skins 3a, 3b can be filled with an insulating material such as polyurethane. Alternatively, the space can be filled with air, either at atmospheric pressure or at reduced pressure.

Where polyurethane is utilised, the polyurethane precursor material can be passed into the space between the skins 3a, 3b the formation of the foam material of the polyurethane then causing the volume to be filled. Vents provided to allow precursor material to be passed into the housing and for gas generated from polymer formation can be sealed once the reaction is complete.

The containers are able to be manufactured by the preferred process known as rotomoulding which allows a container to be relatively cheaply produced. However other methods of manufacture such as injection moulding or 3D printing can be used.

The top cover 4 is formed from a layer or multiple layers of transparent Perspex (RTM), glass which can be tempered or otherwise strengthened or similar material. In this embodiment, two layers are sandwiched together to form the top cover. The top cover allows sunlight (solar radiation), including infra-red wavelengths, to pass through, while closing the top of the housing 3 and providing insulation to help prevent heat escaping from the interior of the housing 3.

When the containers 2 are located in the housing 3, the upper part of their outer surfaces faces upwards towards the open top of the housing 3 and the top cover 4. As the longer elliptical axis is parallel to the housing floor, the width of the upwardly-facing portion of the container 2 is greater than the height of the container 3. This assists with heating the contents of the container 2, as the largest possible outer surface area of the container 2 is exposed to direct sunlight. If required, for example by space considerations, or desired, other shapes of container can be used such as a right cylinder or polygonal cylinder.

In use, the containers are arrayed within the housing with their long axis horizontal. This minimises the mixing of hotter water which rises upwardly within a container from being cooled by the cooler water within the container. The containers 2 are fluidly linked together to enable the water contained therein to flow between the containers 2. Moreover, successive containers are deployed at different heights to allow hotter water produced to rise to the next, higher, container. The fluid linkage or linkages therefore proceed from the hotter region of a lower container to the lower region of the upper container. This provides a flow of heat in the upward direction and again minimises the chance of the hotter water being cooled by cooler water within the same container.

In use, as sunlight falls on the surface of the containers, the energy, in particular heat energy, is absorbed by the water within the container 2, the temperature of which water is thereby raised. As there is no means of physically mixing the water within the container, mixing of the heated water (usually formed in the region onto which the sunlight is falling) does not readily occur. However, due to the heated water's lower density, the heated water rises upwards and is replaced by colder water from below. Heated water therefore moves towards the top of the container, from where it can flow by means of pipes or conduits to the fluidly adjoined container located higher up, which adjoined container 2 is also receiving sunlight, water therefore flows up towards the highest container 2, becoming progressively hotter as it does so.

The highest of the containers has a fluid outflow linked directly to the hot water supply system of the building to which the water is being supplied. There the water can be used either directly at the temperature produced or fed into a heater to bring to the final use temperature. Additionally or alternatively one or more containers includes a heating element and preferably the uppermost container includes a heating element to bring water up to the required temperature. In a further embodiment the containers 2 within the housing 3 comprise heating elements. The heating element can consist of a heat pump, or electrical heating means. Desirably, the lowest, and the highest of the three containers 2 contain the heating elements. By arranging the heating elements in this manner, a user can turn on the heating element to heat the immediate water supply should they require warmer water. By incorporating a heating element in the lower most container 2, the heated, by convection, circulates through the containers which increases the supply of heated water, whilst maintaining a lower energy consumption compared to if all containers 2 featured heating elements. Thus no energy is expended by the householder in heating the water towards or to the desired temperature. Water exiting the uppermost container is replenished by cold water, for example from the mains supply entering at the base of the lowermost container.

In order to prevent a build-up of pressure in the event of blockage of a fluid connection, a container can include a pressure relief valve. Normally, the pressure in a container is maintained below 2 bar, when a polyethylene container is utilised to reduce the risk of container rupture. Where the container is formed of a steel, pressures of up to 8 bar can be retained. Referring now to Figure 6, the base 60 of a housing includes a plurality of ribs 61. The ribs 61 act to strengthen the base 60 and thereby the housing 3, and in particular to resist flexing of the housing, for example during transportation and installation or under temperature changes. Figure 7 illustrates a weatherproof fitment of a transparent cover 4 across the open top of the housing 3. To achieve fitment, a fixing frame 70, formed for example of aluminium to reduce weight, is secured to the housing 3 by means of a screw fitment 71. It will be recognised that other types of fitment means can be used. One end 72 of the frame 70 engages an upwardly facing outer surface 73 of the housing 3, bridging over a lip 74 of the housing 3 and engaging an inner upwardly facing surface 75. The elements 76/77 engage the lip 74 and act to prevent sideways motion of the frame 70 once positioned, and also prevents ingress. The frame 70 includes a recess 78 to receive the cover 4. The cover 4 comprises two transparent elements 4a, 4b held in spaced relationship by a spacer 79 to provide an insulating air layer therebetween. If desired the gap between the elements 4a, 4b can be of reduced pressure to reduce heat transmission therethrough, in which case, the spacer 79 also acts to seal the gap between the elements 4a, 4b. A securing member 80 holds the cover 4 in position.

In the embodiment described above, three containers 2 are located in parallel in the housing 3. In a variation of this embodiment, a single container 20 can be used instead with the same housing 3. The single container 20 has a very similar form to the three containers in parallel of the embodiment above, with three elongate sections joined to form a single container. Each of the elongate sections is substantially the same shape and size as a single one of the containers 2 of the embodiment above. The axes of the sections are substantially parallel, and the sections are joined along their common edges by a narrow bridging section 21 that passes between adjacent sections.

In the illustrated embodiment, the apparatus is shown secured to the sloping roof of a building. It will be recognised that where suitable or convenient the apparatus can be freestanding and/or located on a flat roof. In this case, means known in the art may be provided to hold the apparatus in the required orientation and also enabling movement of the apparatus to follow the sun's movement.

In a further embodiment, the housing 3 comprises a series of inner walls, or partitions. The partitions are constructed so as to lie between neighbouring containers 2 within the housing 3. The partitions preferably extend from the top cover or lid 4 to the interconnecting portions of the containers 2. The partitions act to reduce the flow of colder air, usually from the lowermost regions to the uppermost regions throughout the housing 3. By preventing the movement of colder air throughout the housing 3, the cold air effect on the container 2 temperature and subsequent water temperature is reduced. The partitions within the housing 3 can be insulated or formed from an insulating material. The atmospheric temperature drop throughout evening hours increases the likelihood of frost occurring, therefore it is advantageous that the housing 3 components be constructed so as to withstand the effects of freezing on their structural components. In a further embodiment, each container 2 is individually boxed within the housing 3. This embodiment is a variant on the partitioned housing 3, and provides the user with the option of selecting the number of containers 2 to be linked together to form the system. Advantageously, this embodiment further prevents the effect of cold air on the water within a container 2. With the inclusion of water heaters within the containers 2, each container can individually be heated by activation of the heating means, however, the reduced air space surrounding an individually boxed container 2 aids in the reduction of energy demand to heat the water.

Claims

1. A solar water heating apparatus (1 ), comprising:

two or more enclosed containers (2), each configured to hold a volume of water;

an open-topped housing (3) configured to receive the containers therein, and;

a top cover (4) configured to close the open top of the housing and to allow the transmission of solar radiation therethrough;

the containers (2) comprising an outer surface having a portion configured to face upwards towards the top cover when the water containers are located in the housing, the containers and housing being mutually configured so that the width of at least the upwardly-facing portion of a container is greater than the height of the container when each container is located in the housing;

said apparatus having a plurality of sequentially arrayed containers, each fluidly connected to the or both adjacent containers, each successive container being at a higher level than the preceding container, and with fluid flowing from the lowermost container and to the uppermost container.

2. A solar water heating apparatus as claimed in claim 1 wherein at least the walls of the open-topped housing comprise spaced apart inner and outer skins.

3. A solar water heating apparatus as claimed in claim 2 wherein the space between the skins is filled with insulating material.

4. A solar water heating apparatus as claimed in claim 3 wherein the insulating material comprises polyurethane.

5. A solar water heating apparatus as claimed in any one of claims 1 to 4 wherein the housing is substantially formed from polyethylene.

6. A solar water heating apparatus as claimed in any one of claims 1 to 5 wherein the containers and the floor of the housing are mutually contoured, the floor of the housing receiving and holding the underside of the at least one enclosed container.

7. A solar water heating apparatus as claimed in any preceding claim, wherein the containers comprise multiple elongate sections, joined to form a single container, the axes of the sections substantially parallel.

8. A solar water heating apparatus as claimed in any preceding claim, wherein the cross- section of a container or section thereof comprises an elliptical shape.

9. A solar water heating apparatus as claimed in any preceding claim, wherein a container is formed from stainless steel.

10. A solar water heating apparatus as claimed in any one of claims 1 to 8 wherein a container is formed from polyethylene.

11. A solar water heating apparatus as claimed in any preceding claim, wherein at least one container includes a heating element.

12. A solar water heating apparatus as claimed in claim 11, wherein the uppermost container includes a heating element.

13. A solar water heating apparatus as claimed in any preceding claims, wherein the housing contains at least one partitioning wall.

14. A solar water heating apparatus as claimed in claim 13, wherein the wall extends between adjacent containers.

15. A solar water heating apparatus substantially as herein described with reference to the accompanying figures.

16. A container for use as part of a solar water heating apparatus substantially as herein described with reference to the accompanying figures.

17. A housing for use as part of a solar water heating apparatus substantially as herein described with reference to the accompanying figures.

18. A method of a solar water heating apparatus, comprising:

at least one enclosed container configured to hold a volume of water;

an open-topped housing configured to receive the or each container therein, and; a top cover configured to close the open top of the housing and to allow the transmission of solar radiation there through;

the or each container comprising an outer surface having a portion configured to face upwards towards the top cover when the water container is located in the housing,

characterised in that

the or each container and housing are mutually configured so that the width of at least the upwardly-facing portion of the or each container is greater than the height of the container when the or each container is located in the housing;

said apparatus having a plurality of sequentially arrayed containers, each fluidly connected to the or both adjacent containers, each successive container being at a higher level than the preceding container, and with fluid flowing from the lowermost container and to the uppermost container, the method comprising the steps of;

i) Solar heating of the containers within the apparatus;

ii) Heating of the containers heats the water therein;

iii) The heated water rises to the top of the respective container, as a result of the hotter water having the lower density;

iv) The heated water passes from a lower to a higher container, due to the lower density, wherein the highest point of the lower container is at the lowest point of the next subsequent container;

v) The water of the highest temperature within the respective container, passes to the next container;

vi) The number of containers is dependent on the user preference;

vii) Due to the lower density of water with a higher temperature, and the closer proximity to the solar heating source, the water in the most elevated container is of the highest temperature.