WO2012080722A2

WO2012080722A2 - Apparatus for hot water storage

Info

Publication number: WO2012080722A2
Application number: PCT/GB2011/052467
Authority: WO
Inventors: Peter Holdsworth
Original assignee: Peter Holdsworth
Priority date: 2010-12-13
Filing date: 2011-12-13
Publication date: 2012-06-21
Also published as: WO2012080722A3; GB201021035D0

Abstract

A hot water cylinder (1) includes two zones (2), (3), for hot water storage. The upper zone (2) is physically separated from the lower zone (3) by a dome shaped barrier plate (4). Fluid communication between the two zones (2), (3) is allowed via a flow port (5) at the top of the dome-shaped barrier (4) The upper zone (2) includes two direct heating devices (6), (7) to heat the water and the lower zone (3) includes a heating coil (8) that is arranged to be connected to a heat exchanger forming part of a system for waste water recycling and heat recovery. The dome shaped barrier (4) is arranged to present a physical barrier between two zones (2), (3) containing fluid at different temperatures. The use of a physical barrier (4) having a flow port (5) putting the two zones (2), (3) in fluid communication helps to avoid the forming of layers that may act as barriers to water mixing.which could lead to an inefficient heating and storage system. The heating coil (8) in the lower zone (3) acts as a pre-heater for the water in the zone (3) which means that the temperature gradient to be delivered by the heating devices (6), (7) in the upper zone (2) is considerably reduced.

Description

APPARATUS FOR HOT WATER STORAGE

The present invention relates to an apparatus for hot water storage. More particularly, the present invention relates to an apparatus for hot water storage using recycled heat. BACKGROUND

Historically domestic hot water systems have been total loss systems. That is to say grey water such as the waste hot water used for baths or showers simply enters the house drainage system after use such that the water and any remaining heat it contains is discarded after a single use. Increasing population densities put greater demands on water supplies. This coupled with greater rainfall variations may lead to potential supply shortages. Accordingly, there is a growing awareness of a need to reduce water supply usage and waste where possible. At the same time increasing demands on finite energy supplies and environmental concerns have led to a growing need to use energy more efficiently. Previous proposals have been made for recycling grey water for toilet usage and also for extracting heat from it. However such systems suffer from inefficiencies and a lack of flexibility with the availability of grey water and extracted heat not necessarily best matching the demands for recycled water and recovered heat.

It is desirable to provide an improved hot water storage device adapted to use recovered heat.

It is also desirable to provide a hot water storage device that is adapted to recycle heat extracted from available grey water. BRIEF SUMMARY OF THE DISCLOSURE

In accordance with the present invention there is provided a hot water storage vessel comprising: at least a first storage zone and a second storage zone, wherein the second storage zone is arranged below a barrier configured to at least partially separate the first storage zone from the second storage zone; wherein the first storage zone comprises at least one heat source adapted to heat water contained in the storage vessel; and wherein the second storage zone comprises a heat exchanger adapted to extract heat from an external heat source and to transfer the extracted heat to water contained in the storage vessel.

The present invention therefore relates to a hot water storage vessel that improves the efficiency of heating water in the storage vessel because the heat extracted from an external source may provide a degree of preheating such that the demands on the heating sources in the first storage zone is reduced. The temperature gradient required by the heating sources in the first zone may be greatly reduced if the contained water is pre heated.

The heat extracted by the heat exchanger in the second zone may be heat extracted from a grey water system, for example a system containing waste water from a bath or shower for example.

The barrier between the two zones may be a plate comprising at least one flow port to allow fluid communication between the two separate storage zones. The plate forms a physical barrier between the zones and thus acts to reduce stratification or natural layering of the two zones where a temperature differential is present between two zones.

The plate may be dome shaped. A dome shaped barrier may ensure efficient transfer of the extracted heat to the water contained in the vessel. The size of the flow port may be such that efficient transfer of the extracted heat to the water contained in the vessel is promoted. The size of the flow port may ideally be between 25mm and 50mm in diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

Figure 1 is a schematic representation of a hot water storage vessel in accordance with an embodiment of the present invention; and

Figure 2a is a schematic representation of a waste water recycling and heat recovery system for use with a hot water storage vessel in accordance with an embodiment of the present invention; and

Figure 2b is a schematic representation of the waste water recycling and heat recovery system of Figure 2a connected to a hot water storage vessel in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION Referring to Figure 1 , an unvented hot water cylinder 1 is shown. The hot water cylinder 1 includes two zones 2, 3, for hot water storage. The upper zone 2, as viewed in Figure 1 , is physically separated from the lower zone 3 by a dome shaped barrier plate 4. Fluid communication between the two zones 2, 3 is allowed via a flow port 5 at the top of the dome-shaped barrier 4. The flow port 5 is an opening in the barrier 4 of approximately 25mm to 50mm diameter.

In the illustrated embodiment, the upper zone 2 includes two direct heating devices 6, 7 to heat the water contained in the cylinder. Examples of direct heating devices are heating coils 6 from a solar thermal unit or heating coils 6 from a standard home heating system and/or an electric immersion heater 7. The lower zone 3 includes a heating coil 8 that is arranged to be connected to a heat exchanger forming part of a system for waste water recycling and heat recovery as discussed below with reference to Figure 2. The dome shaped barrier 4 is arranged to present a physical barrier between two zones 2, 3 containing fluid at different temperatures. If the physical barrier 4 was not in place then a barrier due to stratification of the preheated water may be formed where the two zones may contain water at different temperatures which may lead to the forming of layers that may act as barriers to water mixing. Such an arrangement could lead to an inefficient heating and storage system. Therefore, the use of a physical barrier 4 having a flow port 5 putting the two zones 2, 3 in fluid communication may alleviate the problem.

The heating coil 8 in the lower zone 3 acts as a pre-heater for the water in the zone 3 which means that the temperature gradient to be delivered by the heating devices 6, 7 in the upper zone 2 is considerably reduced. Referring to figure 2, a waste water recycling and heat recovery system 10 is illustrated connected to the hot water cylinder 1 as illustrated in Figure 1 . The water recycling and heat recovery system 10 is the subject of a co-pending UK patent application GB 1010059. The water recycling and heat recovery system 10 comprises a pair of copper tanks 1 1 , 12 joined together by a pair of pipes 13, 14. The lower of the two pipes, 13, allows water to move between the tanks 1 1 , 12 while the upper pipe, 14, allows air to move between the tanks. The system is air tight but has an air admittance valve at the top which allows air in while a non return valve 15 on an overflow pipe 16 allows excess air to exit the system. The first tank 1 1 , to the right in Figure 2, is supplied with used bath or shower water through an inlet 17 while the tank 12, situated between the tank 1 1 and the hot water cylinder 1 in Figure 2, is supplied from a cold water supply, for example mains water supply, via an inlet 18. A deflector plate in tank 1 1 shrouds the lower pipe 13 to allow sedimentation in the tank 1 1 and to prevent larger solids being drawn into the smaller tank 12. A heat exchanger 19 is housed in the first tank 1 1 and connects to the hot water cylinder 1 as indicated by HWC in Figures 2(a) and 2(b).

A ball valve arrangement 21 controls the flow of fresh water into the second tank 12. The overflow pipe 16 connects to a purge pipe 22 controlled by a valve 23 and exits to waste at 24. Water is supplied from the system to toilets via a pumped outlet 25 with overall control being provided by a control system 26.

In operation waste water from a bath or shower enters and fills up the system through the inlet 17 and has any remaining heat extracted from it by the heat exchanger 19. The heat from the heat exchanger 19 is extracted by the heating coil 8 in the lower zone of the hot water cylinder 1 and is used to pre heat water contained in the hot water cylinder 1 (see Figure 1 ).

The waste water system 10 simultaneously provides a supply of water for flushing toilets via the pumped outlet 25 and the heat from the water to the lower zone 3 of the hot water cylinder 1 thus ensuring that the water from baths and/or showers is fully recycled.

In the event that the amount of waste water available exceeds the capacity of the system, the excess water exits as waste water via the overflow pipe 16. Conversely, if an inadequate supply of used bath or shower water is available the ball valve arrangement 21 allows clean water to enter the system up to a minimum level 26 to ensure there is always water available for toilet flushing via the pumped outlet 24.

A further benefit of the clean water supply is that a layer of cold water is formed at the bottom of the tanks 1 1 , 12 which creates a cold water buffer at the bottom of the tanks 1 1 , 12 and stops the flow of heat from the first tank 1 1 to the second tank 12 of the waste water system 10 when waste water from a bath or shower enters the tank 1 1 . This arrangement allows for a large temperature differential to exist between the first tank 1 1 with the heat exchanger 19 and the second tank 12 which supplies the toilets for a period of time to allow effective extraction of heat HWC from the water in the first tank 1 1 to the hot water cylinder 1 .

The control system 25 operates the pumped outlet 24 to ensure that pressure is maintained in the toilet supply. A low and high pressure switch arrangement operates to turn on the pumped outlet 24 when pressure in the distribution pipe to the toilets falls below 0.5 bar and pressurises the system while filling the toilets in the normal way through the toilets internal ball valve. The control system 25 turns off the pumped outlet 24 when the toilet is full and the pipe pressure reaches 3 bar. A small pressure reservoir stops shunting of the pump as the pressure drops back and compensates for the effect of slightly leaky ball valves. The control system 25 is also thermostatically controlled to monitor the system temperature and to operate the heat exchanger circuit as appropriate to maximise the heat transfer to the hot water cylinder 1 .

The system also works in conjunction with a solar panel system, the control system 26 monitors which part of the composite system has the highest temperature and operates so that heat is transferred first to the hot water cylinder 1 before transferring to the other source as the relative temperatures change.

The benefit of this combination in domestic installations is that baths and showers are typically taken in the morning when the solar panel is at its lowest temperature. The latent heat in the recycled water is moved first to the hot water cylinder 1 and then as the temperature builds up in the solar panels during the day the system switches over to take advantage of this heat. Still later as the solar panel becomes less efficient in the evening then heat is likely to be available from evening baths and showers and so the system switches over once again. The hot water system efficiency is thus enhanced with a reduced reliance on external heating input.

The tanks and pipe work are of copper construction which helps to minimise bio film build up but the build up of bacteria is also discouraged by introducing appropriate quantities of disinfectant and soap neutralising material. The control system 25 can also be set to empty both tanks before refilling with clean water to the minimum level 26 on a regular basis, for example every 24 or 72 hours.

The control system 25 also provides further control options. For example manual control of system purging can be provided allowing the system to be purged outside the automatic cleaning cycle if required. The system can also have a sleep function which puts the system to sleep or on standby when the premises are unoccupied for any length of time such as for holiday periods. Water and energy savings provided by the system vary with system size, usage patterns and availability of solar energy. However typically savings of 25% -30% of water use per household are envisaged which equates to an annual saving of 54750 litres for a typical family of four. Heat available is typically 5 kWh per 100 litres of water. Thus again for a typical family of four usage of around 140 litres per day can be expected thus providing an energy store of around 7 kwh of which, after losses, around 4 kwh per day can be saved providing 1460 kwh annually. A typical solar panel hot water installation can save around 900 kWh per year making a total potential saving of 2360 kWh per average household. Referring to Figure 2(b), the hot water cylinder 1 is connected to the waste water system 10 as shown in Figure 2(a). Waste heat HWC from the grey water system 10 is transferred to the heating coil 8 contained in the lower zone 3 of the hot water cylinder 1 . As with conventional unvented hot water cylinders the cylinder 1 is connected to a suitable expansion tank 30 as is generally used in closed water heating systems and domestic hot water systems to absorb excess water pressure that is caused by thermal expansion as water in the cylinder 1 is heated.

The use of words such as "comprise" and "contain" and variations of them in the description and claims of this specification, should be taken to mean the words "including but not limited to". The use of the words "comprise" and "contain" and variations of them are not intended to exclude other components, integers or steps.

Features, integers and characteristics described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1 . A hot water storage vessel comprising at least a first storage zone and a second storage zone, wherein the second storage zone is arranged below a barrier configured to at least partially separate the first storage zone from the second storage zone.

2. A hot water storage vessel as claimed in Claim 1 , wherein the first storage zone comprises at least one heat source adapted to heat water contained in the storage vessel and wherein the second storage zone comprises a heat exchanger adapted to extract heat from an external heat source and to transfer the extracted heat to water contained in the storage vessel.

3. A hot water storage vessel as claimed in Claim 2, wherein the heat extracted from an external source may provide a degree of preheating such that the demands on the heating source in the first storage zone is reduced.

4. A hot water storage vessel as claimed in Claim 2 or 3 wherein the heat extracted by the heat exchanger in the second zone is heat extracted from a grey water system.

5. A hot water storage vessel as claimed in Claim 4 wherein the grey water system is a system containing waste water from a bath or shower.

6. A hot water storage vessel as claimed in any one of the preceding Claims wherein the barrier between the two zones is a plate comprising at least one flow port to allow fluid communication between the two separate storage zones.

7. A hot water storage vessel as claimed in Claim 6 wherein the plate forms a physical barrier between the zones and thus acts to reduce stratification or natural layering of the two zones where a temperature differential is present between two zones.

8. A hot water storage vessel as claimed in Claim 6 or 7 wherein the plate is dome shaped.

9. A hot water storage vessel as claimed in any one of Claims 6 to 8 wherein the size of the flow port is such that efficient transfer of the extracted heat to the water contained in the vessel is promoted.

10. A hot water storage vessel as claimed in Claim 9 wherein the flow port is between 25mm and 50mm in diameter.