GB2287057A

GB2287057A - Water storage tank

Info

Publication number: GB2287057A
Application number: GB9403579A
Authority: GB
Inventors: Ian Bruce Pauley
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-02-24
Filing date: 1994-02-24
Publication date: 1995-09-06
Also published as: GB9403579D0; CA2116494A1

Abstract

A water storage tank is composed of a plurality of interlocking or interconnectable segments (112) which when assembled together form at least a base and side walls of the tank, and a thin plastics liner to line the interior of the tank. The interlocking or interconnectable segments may be formed by moulding from a rigid thermally insulative foam material such as polystyrene. The segments may be held in position by bands or straps (113) around the tank. The tank may be a hot water tank with an electric heating element suspended into the tank from the lid of the tank and a water inlet and water outlet also entering through the lid. The tank may be arranged so that it is refilled with cold water and reheated only at night on low tariff electricity. <IMAGE>

Description

A WATER STORAGE TANK Thib invention comprises a water storage tank which may be a hot water tank or a cold or chilled water tank.

A conventional hot water cylinder or tank consists of a copper vessel, thermal insulation around the copper vessel such as fibreglass batts or similar, and an outer shell typically formed of galvanised or painted metal.

The invention provided an improved or at leaet alternative form of water storage tank, which may be a hot water tank but can alteratively be arranged as a cold water tank without any heating element or thermostat control system or a chilled water tank with an associated refrigeration system. The tank of the invention provide. various benefits and advantages a. will be described.

In broad terms the invention comprises a water etorage tank campoeed of a plurality of interlocking or interconnectable segments which when assembled together form at least a base and side walls of the tank, and a thin plastics liner to line the interior of the tank.

Preferably the segments are formed by moulding from a relatively rigid, thermally insulative foam material such ae polystyrene or polyurethane foam for example or a similar material. The foam material is thermally insulative and prevents heat loss from the tank where the tank is a hot water tank, or undesired heat gain where the tank is a cold or chilled water tank, and the foam walls of the tank also provide the structural strength of the tank (with encircling bands or other means assisting in holding the segments together).

The interlocking segments may be held together by bands or straps encircling the tank or a protective cover secured around the tank for example, or by any other suitable means which assists in holding the segments together.

Preferably the liner is formed from a thin, flexible plastics sheet material suitable for prolonged exposure to water, at an elevated temperature in the case of & hot water tank. Such a plastics material might be, for example, polypropylene, polyethylene, polybutylen or polyvinylchlorid material.

Particularly where the tank of the invention is a hot water tank, it is preferred that the tank is a short tub shape having a low surface area for volume to reduce heat loss from the tank. Conventional hot water cylinders or tanks tend to be relatively tall to minimize floor space usage and enable the tank to be placed in a cupboard for example, but the resulting higher surface area increases the potential for heat loss from the tank.

Alternative to a short tub shape with a lid the tank of the invention may be shaped as a sphere formed from interlocking segments, of moulded polystyrene, for example.

The tank of the invention is formed of a number of segments suitably moulded from polystyrene or a similar foam material which give the tank structural strength and also form the thermal insulation of the tank but the tank has a very simple and economic construction. At the same time because the tank io formed from separate segments, this enables the tank to be installed in locations having minimal accessibility such as into the roof cavity of an existing house or similar x or or through an existing ceiling hatch, or into the floor cavity beneath the ground floor of an existing house through an existing trapdoor.

Also where the liner is formed of a thin flexible sheet material it may be folded or crushed down. Thus the water storage tank of the invention may be retrofitted into a roof cavity in place of an older tank which is being removed from a cupboard for example. The tank of the invention can also of course be installed from new into a house or building. Another benefit of the tank of the invention for both existing and new houses is that because it can be installed into a ceiling or floor cavity, floor space of the house is not taken up.

A preferred embodiment tank of the invention which is configured as a hot water tank will now be described, by way of example only, with reference to the accompanying drawings, in which: Pig. 1 is a cross-sectional side view of the preferred embodiment water storage tank; Fig. 2 is a side view of the preferred embodiment tank; Fig. 3 is a partially sectioned plan view of the preferred embodiment apparatus; and Fig. 4 is a schematic aircuit diagram.

Referring to the drawings, the preferred embodiment tank has sides 101 and a base 103. The exterior of the sides of the tank and the tides of the interior of the tank are shown tapered inwardly, but alternatively both the external and internal side. of the tank could be vertical or near vertical or the external sides of the tank could be vertical and the aide.

of the internal tank cavity tapered for example. The tank has a lid 104, The sides 101 and base 103 of the tank are made up of a number of aegmontss 112. The segments 112 may be interlocked or interconnected together using dove tail joints or similar between adjacent segments, dowels and holes, or simply overlapped Steps for example.The aegments 112 are preferably moulded from a rigid foam material such as expanded polystyrene or polyurethane or similar material having high thermal insulative properties to thermally insulate and minimise heat lose in the case of a hot water tank for exaz:le. Typically the wall thickness of the moulded segments may be in the range 25-250mm to provide sufficient rigidity and strength. The preferred embodiment tank shown in the drawings is formed of three segments which are all similar in ize and shape. A portion of each segment forms a part of the baste of the tank and another integral portion of each segment form part of the side walls of the tank.

While the preferred embodiment tank is made up of three such segments it could alt.rnatively be formed of two or four or more segments. In an alternative construction of a tank of the invention, the base and side walls could each be formed of separate oogment, instead of each segment providing a part of the base and a part of the side walls of the tank as shown in the drawings. For example, the side walls of the tank could be formed from four quadrant shaped segments, or alternatively less than four or more than four similarly shaped segments, and a circular baee could be formed from two sezni-circular segments or four quarter circle shaped segments for example. In such a construction the lid could also be formed of a number of segments. Preferably the segments interlock or interconnect together by dovetail joints, overlap steps etc as referred to above. The exterior surfaces of the segments may be painted or coated with a plastics film such as a PVC film or any other protective finish such as a fibreglass layer for example, or alternatively the exterior of the segments may be loft without any such additional finish or coating. Further alternatively, thin tough sheet material such ae galvanised or painted metal sheet or a strong synthetic sheet material may be wrapped around the exterior of the tank after assembly of the segments together, and held in place by any suitable arrangement of for example clipa, screws or similar.

In the preferred embodiment tank shown in the drawings the interlocking segment. 112 are held together by several bands 113 which extend around the tank and which are tightened like large hose clips. In another arrangement galvanised metal sheeting or similar or a strong synthetic material wrapped around the exterior of the tank as referred to above may also act to hold the segments forming the tank together, instead of the bands 113. For example a single metal sheet may wrap around the exterior of the tank and be provided with clips along its edge.

to hold the eheet securely in place enclosing the polystyrene or similar segments. In a further alternative arrangement the bands 113 may extend around the exterior of such a metal or synthetic sheet. Various arrangements are possible.

The tank has a thin plastics liner 108 formed from polypropylene, polyethylene, polybutylene, PVC or the like. The liner has a wall thickness that gives a firm but crushable shape.

The liner preferably comprises a thin flexible plastics sheet that lines the interior of the tank. If the interior of the tank is tapered inwardly the liner will tend to conform to the internal shape of the tank even when the tank is virtually empty, which may be preferable in the case of a hot water tank as using an adhesive which could be affected by heat to hold the liner in place. In the preferred embodiment the liner 108 is also held in position by being clamped between the top edge of the tank walls and the lid 104.

Optionally, to further reduce radiant heat losa the interior surfaces of the interlocking segments and/or the liner 108 may have a highly reflective surface, such as for example aluminium foil laminated on to the liner or similar.

The base 103 of the tank 101 may have a moulded rim 114 whereby the tank can be fastened to part of the building structure 115 (see rig, 2) on which it ie a placed. Hold down plates 116 acting on the rim 114 can be bolted or otherwise attached to the structure 115.

The tank of the invention may be used as either a hot water or a cold or chilled water tank. In the case of a hot water tank the tank haa a heating element 105 and a water inlet 106 and water outlet 107. Preferably the lid 104 mounts the heating element and other ancillary equipment through various apertures through the lid as shown to maintain the integrity of the liner. The inlet pipe 117 io press fitted into aperture 116 in the lid, with the water inlet 106 itself being suspended near the bottom of the tank.The water outlet 107 is suspended in the interior of the tank at a height defining the minimum water level that will always be retained in the tank in use, and forms the inlet end of a supply pipe 119 feeding a pump 120 mounted on the lid 104. From the pump 120 hot water ie fed into the main hot water supply line 121. Ideally the pump 120 incorporates a flow switch to automatically activate the pump 120 when a demand ie made for hot water from the supply line 121. Preferably the pump is self priming but if a non-self priming pump is used a float valve at the water outlet 107 or non-return valve will be required to prevent the pump supply pipe 119 from sucking in air if the water level becomes too low.

Addition of a pump 120 allows the tank to be located anywhere and still deliver a high pressure water supply from a low pressure storage vessel. However, the tank will work on a syphon basis if it 1 is located above the desired water del-4very point, the attic being an example of a suitable location. A syphon delivery system requires a float valve on the water outlet to avoid sucking in air if the water level becomes too low. A pump may be ueed with a hot, cold or chilled water tank.

The heating element 105 which may be of any known type and a thermostat 122 are mounted in apertures 123 and 124 respectively in the lid 104, with their operating portion.

suspended down into the tank to below the level of the water outlet 107, thereby ensuring in the case of the heating element 105, that it doesn't burn out.

A vent pipe 125 and maximum water level switch 126 are also mounted in the lid 104.

An orifice plate, jet or flow control valve or other flow control device is preferably used in series with the cold water supply through the inlet pipe 117 to limit the flow of incoming cold water to match the capability of the electrical heating element, so that cold water is not delivered into the hot water tank faster than the element 105 can heat it. The stored water is thus maintained hot at all times and the life of the tank may be prolonged by avoiding thermal cycling.

Alternatively, the thermostat 122 may be coupled in eeries with a solenoid operated inlet valve such that the solenoid valve is shut off to etop cold water entry when the water temperature drops below a certain point, and is opened to allow more cold water to enter the tank only when the water in the tank has been heated to the desired t;emperature by the electric heating element.

Where the tank is a hot water tank it may be arranged such that the water level in the tank reduces as hot water is drawn off, rather than the hot water drawn off being iznzriediately replaced by cold water entering at the water inlet. The tank ie refilled with cold water which is then heated only at night at a low tariff electricity cost.In a conventional hot water tank mixing of incoming cold water with the remaining hot water during the day reduces the overall stored water temperature and neoeesitates heat input during the day at high tariff electricity rats. To achieve this result thu tank may further comprise a water inlet valve in the form of a solenoid valve 127 in the inlet pipe 117. In operation, the solenoid valve 127 is opened to allow cold water to refill the tank only when low tariff electricity is available to the heating element 105 e.g. at night.Referring to Fig. 4, in this diagram line b is the high tariff electricity supply line which is live with power during the day, line N is the power supply line which is live only at night providing power at a lower tariff, and line C is a common or neutral line. When switch 15 (the function of which will be described later) is in the position shown in hard outline i.e.

the water heater ie in economy mode, the heating element 105 and thermostat 122 are connected to the night rate power line N.

Water level indicator 130 is also connected to the night rate power line N in series with the solenoid operated flow valve 127 on the water inlet line 117. When the night rate power line gores live as controlled by the local electrical power authority e.g.

after llpm, provided the water level in the tank is below full as indicated by the level switch 130, power will be supplied through the level switch 130 to the solenoid valve 127 opening the valve and allowing cold water to enter the tank to refill the tank (preferably at a controlled rate as referred to previously).

At the same time, power is supplied in parallel to the heating element 105 which will heat the contents of the tank as the tank is repleniehed, under control of the thermostat 122. The next morning when the power to the night rate line N is dieconriected e.g. after 7am, the heating element 105 and water inlet valve 127 will be disconnected until the following evening, so that during the day (when the tank is in economy mode) it will not be refilled with cold water and the heating element 105 will not operate. During the day the hot water stored in the tank can be drawn off ao required and the tank ie refilled and reheated the following evening.Desirably the capacity of the tank is matched to a households daily hot water requirements so that the tank will not normally require refilling until the low tariff electricity is again available the next night.

In case on a high usage day the tank should be emptied of hot water, a switch is may be provided to temporarily connect the water tank to the high tariff power line D ae shown, in boost mode. When this switch 15 is operated the tank is connected to the power line b supplying full tariff electricity and this will immediately initiate the refilling and reheating of the tank during the day, which in economy mode will normally occur only at night. Bowever, it is anticipated that by correctly sizing the capacity of the vessel to the requirements of a household this boost feature would only be used on occasions when hot water Consumption was unusually high.

It is possible (although unlikely) that even when there is hot water still remaining in the tank during the day, that the temperature of that hot water nay have dropped unacceptably. One way of countering this is to provide a second heating element 131 which would typically be lower power than the main element 105, and associated thermostat 132 which are permanently connected to the day power line D as shown. The main element 105 which normally operates at night in economy mode may be set to heat the water to 65 C. The low power day maintenance element 131 may be arranged to come on and provide "maintenance heating" if the water temperature drops below 55.C during the day.Other arrangements for maintaining the water temperature above a preaet minimum during the day are possible, but it is envisaged with the tank of the invention that in fact such a system is likely to be unnecessary.

To assist the user in making best uee of the available hot water a visual display such as a meter or digital display can be provided to show the amount of hot water remaining at any time. The display could be located, for example, in the bathroom or kitchen of a dwelling. A level indicator such as a float switch in the tank may provide level information to the display or alternatively a pressure measurement or ultra-sonic system could be used to indicate the remaining water level. Such a level indicator system would act as a guide to whether the booster heating system would be required.

Also, the water outlet from the tank may have a main opening of large diameter. By positioning this opening at a particular height within the tank it may be used to drain, for example, 80% of the volume of the water in the tank at a high flow rate. However, below the 8Os level a reduced flow rate may be obtained by way of a secondary outlet opening of smaller size.

Thus, the reduced flow of hot water would indicate to someone using the system, for example while showering, that only a limited capacity remained. Care in locating the secondary opening would be required to ensure that sufficient water remained in the tank to cover the heating element.

Finally, it will be understood that this invention is not limited to the particular embodiment described or indicated but is intended to cover all alteration., additions or modifications which are within the scope of the appended claims.

Claims

1. A water storage tank composed of a plurality of interlocking or interconnectable segments which when assembled together form at least a base and side walls of the tank, and a thin plastic. liner to line the interior of the tank.

2. A tank according to claim 1, wherein the interlocking or interconnectable segments are formed by moulding from a rigid thermally insulative foam material.

3. A tank according to claim 2, wherein the interlocking or interconnectable segments are moulded from polystyrene.

4. A tank according to any one of claims 1 to 3, wherein the segments are held in position by means encircling the exterior of the tank.

5. A tank according to any one of the preceding claims wherein the segments are held in position by bands or straps around the tank.

6. A tank according to any one of claims 1 to 5, wherein the tank is composed of between two and eight of said interlocking or interconnectable segments.

7. A tank according to any one of claims 1 to 6, also including a lid to close the top of the tank.

6. A tank according to any one of the preceding claims, wherein the liner is formed of a thin plastics flexible sheet material.

9. A tank according to any one of the preceding claims, wherein the tank is a hot water tank and additionally comprises a thermoetatically controlled electric heating element to heat water in the tank.

10. A tank according to claim 9, wherein the electric heating element is suspended into the tank from the lid of the tank and a water inlet and water outlet to the tank also enter the tank through the lid of the tank.

11. A tank according to either one of claims 9 and 10 wherein the tank is a short tub shape having a low surface area for volume to reduce heat lose from the tank.

12. A tank according to claim 11, wherein the interior surfaces of the tank or the liner comprise a reflective layer to reflect radiant heat back into hot water in the tank.

13. A hot water tank and water supply and heating system comprising a tank to contain hot water with a water supply inlet to the tank and a water outlet; a thermostatically controlled electric heating element to be powered by regulated low tariff electricity supply; a water level indicator to indicate the water level in the tank; and a water inlet valve to control the flow of water into the tank; wherein the electric heating element, level indicator and water inlet valve are connected such that the water inlet valve remains closed until regulated low tariff power is supplied to the heating element and the water level in the tank is below maximum.

14. A tank according to any one of claims 9 to 13, wherein the electric heating element of the tank is powered by a regulated low tariff electricity supply, and the tank also compriB a water level indicator to indicate the water level in the tank; and a water inlet valve to control the flow of water into the tank; wherein the electric heating clement, level indicator, and water inlet valve are connected such that the water inlet valve remain closed until regulated low tariff power is supplied to the heating element and the water level in the tank is below maximum.

15. A tank according to either one of claims 13 and 14, including means to temporarily connect the heating element and water inlet valve to full rate power to allow immediate refilling of the tank and heating thereof on higher tariff power.

16. A tank according to any one of the preceding claims wherein a pump is provided on the water outlet to boost the pressure of the water as it is supplied from the tank.

17. A tank according to any one of claims 9 to 16 further comprising a level indicator system to show the level of hot water remaining in the tank on a display locatable at a readily accessible location.

18. A tank according to any one of the preceding claims wherein the water outlet comprise. a main outlet and a secondary outlet of reduced flow capacity, the main outlet accessing a major proportion of the tank capacity and the secondary outlet accessing a minor proportion of the tank capacity not available to the main outlet.