GB2468706A

GB2468706A - Water heating apparatus comprising a first tank coupled to a second tank

Info

Publication number: GB2468706A
Application number: GB0904738A
Authority: GB
Inventors: Richard Arthur Brown
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-03-19
Filing date: 2009-03-19
Publication date: 2010-09-22
Also published as: GB0904738D0

Abstract

An apparatus 100 for heating water comprises a first tank 10 coupled to a second tank 30, a first heating device 16 for heating water in the first tank using a first source of energy and a second heating device 36 for heating water in the second tank using the first source of energy. A first temperature sensor device 20 generates a first indication of a temperature T1 of water in the first tank, and a second temperature sensor device 40 generates a second indication of a temperature T2 of water in the second tank. An indicator device 216 generates a third indication of a temperature TS which can be provided by the first heating device and by the second heating device using the first source of energy. A system controller 90 enables heating by a selected one of the first and second heating devices and inhibits heating by the other of the first and second heating devices, where the selection is dependent on the first, second and third indications of temperature. Preferably, the first source of energy is a renewable energy source such as solar energy, wind power or wave power.

Description

I

DESCRIPTION

APPARATUS FOR HEATING WATER

Field of the Invention

The invention relates to an apparatus for heating water, for use, for example in a domestic or industrial water system, and to a method of controlling such an apparatus.

Background to the invention

A solar water heating system 300 is illustrated in Figure 1. It comprises a water tank 310 which has a water inlet 312 and a water outlet 334. Water in the tank may be heated by means of a heat exchanger 316 which is fed with water heated by a solar panel 320. Water in the tank may be also, or alternatively, heated by means of another heat exchanger 318 which is fed with water heated by a boiler 340.

Another solar water heating system 400 is illustrated in Figure 2. It comprises a first water tank 410 and a second water tank 430. The first tank 410 has a water inlet 412 and a water outlet 414. Water from the water outlet is coupled to a water inlet 432 of the second tank. The second tank 430 has a water outlet 434. Water in the first tank 410 may be heated by means of a heat exchanger 416 which is fed with water heated by a solar panel 420. Water in the second tank 430 may be heated by means of another heat exchanger 438 which is fed with water heated by a boiler 440.

By means of either of these solar water heating systems, water may be heated using solar energy without depleting natural resources, and therefore also without the need to purchase fuel. Whenever sufficient solar energy is not available, a boiler may be used as a back-up source of heat.

An object of the present invention is to provide an improved apparatus for heating water.

Summary of the Invention

According to a first aspect of the invention there is provided an apparatus for heating water, comprising: a first tank coupled to a second tank; a first heating device for heating water in the first tank using a first source of energy; a second heating device for heating water in the second tank using the first source of energy; a first temperature sensor device for generating a first indication of a temperature Ti of water in the first tank; a second temperature sensor device for generating a second indication of a temperature T2 of water in the second tank; an indicator device for generating a third indication of a temperature TS which can be provided by the first heating device and the second heating device using the first source of energy; a system controller for enabling heating by a selected one of the first and second heating devices and inhibiting heating by the other of the first and second heating devices, wherein the selection is dependent on the first, second and third indications.

According to a second aspect of the inventiQn there is provided a method of controlling an apparatus for heating water, the apparatus having a first tank heatable by a first heating device and a second tank coupled to the first tank and heatable by a second heating device, the method comprising: enabling heating of water by a selected one of the first and second heating devices and inhibiting heating of water by the other of the first and second heating devices, wherein the selection is dependent on a temperature TI of water in the first tank, a temperature T2 of water in the second tank, and an indication of a temperature IS which can be provided by the first and second heating devices using a first source of energy.

Thus the invention involves selecting to heat one tank and not to heat the other tank, with the selection being dependent on the temperatures TI, T2 and TS. The choice of which tank to heat may therefore be changed as these temperatures TI, T2 and TS change, for example due to the drawing off of hot water from the system, or the variable power of the first source of energy. In this way, the temperature of hot water delivered by the system can be increased, the volume of hot water delivered by the system can be increased, and the first source of energy can be used more efficiently.

Optionally, the system controller may be adapted to: if 12<11 <TS, enable heating by the first heating device and inhibit heating by the second heating device; if TI <12<TS, enable heating by the second heating device and inhibit heating by the first heating device; if T2<TS<TI, enable heating by the second heating device and inhibit heating by the first heating device; and if TI <TS<T2, enable heating by the first heating device and inhibit heating by the second heating device.

Thus, if both tanks are cooler than IS, only the hotter tank may be heated.

This can maximise the temperature at which water can be delivered.

If one tank is cooler and one tank is hotter than IS, only the cooler tank may be heated. Heating can proceed even though the hotter tank can already provide water hotter than TS. In this way, the volume of available hot water may be increased by increasing the temperature of water in the cooler tank. The cooler tank can provide a reserve of hot water should the hotter tank be unable to satisfy demand.

Optionally, the first tank may have a first inlet for coupling to a supply of water and a first outlet for delivering water heated in the first tank; the second tank may have a second inlet for coupling to the supply of water and a second outlet for delivering water heated in the second tank; and the apparatus may comprise: an output for delivering heated water from the apparatus; and an output controller having a selectable first state for delivering water from the first outlet to the output and for inhibiting delivery of water from the second outlet to the output, and a selectable second state for delivering water from the second outlet to the output and for inhibiting delivery of water from the first outlet to the output; wherein the system controller is adapted to select the first state if Ti exceeds T2 and select the second state if T2 exceeds TI.

The feature enables the hottest available water to be delivered at the system output.

Optionally, the apparatus may comprise: first coupling means for coupling water from the first outlet to the second inlet; and second coupling means for coupling water from the second outlet to the first inlet; and the system controller may be adapted to: if the output controller is in the first state, inhibit the flow of water from the first outlet to the second inlet via the first coupling means and enable the flow of water from the second outlet to the first inlet via the second coupling means; and if the output controller is in the second state, enable the flow of water from the first outlet to the second inlet via the first coupling means and inhibit the flow of water from the second outlet to the first inlet via the second coupling means.

By means of this feature, the cooler tank may supply water to the hotter tank, whilst the hotter tank may not supply water to the cooler tank. This feature can reduce the energy required to heat the water in the hotter tank by taking advantage of any heating that has taken place in the cooler tank, whilst ensuring that all the water in the hotter tank is availabJe for delivery at the output. In effect, the cooler tank provides pre-heated water to the hotter tank.

Optionally, the first and second heating devices may be heat exchangers for employing a first liquid for heating water, and the first and second heating devices may be adapted for coupling to a first energy conversion device for heating the first liquid using the first source of energy. This feature provides versatility, enabling a wide variety of heaters to be used for heating the first liquid, according to the availability of heaters and types of energy source.

Optionally, the apparatus may comprise the first energy conversion device, and the first source of energy may be a renewable energy source. This feature enables the environmental impact of heating water to be reduced. For example, the renewable energy source may be solar radiation.

Optionally, the first energy conversion device may comprise a first solar panel. Solar panels are readily available, are reliable, have a low maintenance requirement, and enable generation of heat independently of a supply network.

Optionally, TS is dependent on the temperature of the first liquid in the first solar panel. This temperature is variable, depending on the prevailing solar radiation, which enables the system to adapt to changing levels of solar radiation.

Optionally, the first energy conversion device may comprise a second solar panel for heating the first liquid, and the system controller may be adapted to determine which one of the first and second solar panels is able to heat the first liquid to a hotter temperature and to enable flow of the first liquid to one of the first and second heating devices from the determined one of the first and second solar panels and to inhibit flow of the first liquid to said one of the first and second heating devices from the other of the first and second solar panels.

This feature enables two solar panels to be deployed, for example with different orientations, and the first liquid to be heated by whichever of the solar panels can provide the greatest heating, thereby increasing the heating effect.

Optionally, TS may be dependent on the higher of the temperature of the first liquid in the first solar panel and the temperature of the first liquid in the second solar panel. This temperature is variable, depending on the prevailing solar radiation, which enables the system to adapt to changing levels of solar radiation.

Optionally, the first and second heating devices may be adapted for coupling to a second energy conversion device for heating the first liquid using a second source of energy, and the system controller may be responsive to an indication of a desired water temperature TD to: if TS<TD and T2<T1 <TD, enable heating of the first liquid by the second energy conversion device, enable heating of the first heating device by the first liquid, and inhibit heating of the second heating device by the first liquid; and if TS<TD and Ti <T2<TD, enable heating of the first liquid by the second energy conversion device, enable heating of the second heating device by the first liquid, and inhibit heating of the first heating device by the first liquid.

This feature can provide a back-up means of heating using a back-up source of energy for use when neither tank can deliver water at the desired temperature and when the first energy conversion device using the first source of energy cannot provide the desired level of heating.. By sharing the first and second heating devices between the first energy conversion device and the second energy conversion device, system complexity is reduced.

Optionally, the first and second heating devices may employ electricity to generate heat. Such heating devices are efficient, generating heat within the tanks and avoiding any loss due to transferring heat from an external heater, and providing a wide choice of energy source.

In this case, the apparatus may comprise a first energy conversion device for generating electricity using a renewable energy source. This feature enables the environmental impact of heating water to be reduced. For example, the renewable energy source may be solar radiation, wind power or wave power.

Optionally, such a first energy conversion device may comprise a solar panel. Solar panels are readily available, are reliable, have a low maintenance requirement, and enable generation of electricity independently of a supply network.

Optionally, the first and second heating devices may be both adapted for selectably using the first source of energy or a second source of energy, and the system controller may be responsive to an indication of a desired water temperature ID to: if TS<TD and T2T1<TD, enable heating by the first heating device using the second source of energy and inhibit heating by the second heating device using the second source of energy; and if TS<TD and TI <T2<TD, enable heating of the second heating device using the second source of energy and inhibit heating by the first heating device.

By means of this feature, the first and second heating devices may employ either of two energy sources, with the second source of energy being used if the desired water temperature TD exceeds the temperature of both tanks and exceeds the temperature that can be provided by using the first source of energy.

Heating is applied to only the hotter of the tanks. This feature can enable the second source of energy to be used as a back-up source when the first source of energy cannot satisfy the desired water temperature TD, and can enable minimum energy to be used from the second source of energy by heating only the hotter of the tanks. This can be beneficial if, for example, the second source of energy is non-renewable, has a less reliable supply, requires bulky or expensive storage, or is of high cost.

Optionally, the first tank may have a third heating device for heating water in the first tank using a second source of energy and the second tank may have a fourth heating device for heating water in the second tank using the second source of energy, and the system controller may be responsive to an indication of a desired water temperature TD to: if 12<11 <ID, enable heating by the third heating device and inhibit heating by the fourth heating device, and if T1<12<TD, enable heating of the fourth heating device and inhibit heating by the third heating device.

By means of this feature, each tank may have two heating devices using different sources of energy, with the second source of energy being used if the desired water temperature ID exceeds the temperature of both tanks and exceeds the temperature that can be provided by using the first source of energy.

Heating is applied to only the hotter of the tanks. This feature can enable the second source of energy to be used as a back-up source when the first source of energy cannot satisfy the desired water temperature TD, and can enable minimum energy to be used from the second source of energy by heating only the hotter of the tanks. This can be beneficial if, for example, the second source 8 F of energy is non-renewable, has a less reliable supply, requires bulky or expensive storage, or is of high cost. This feature can also enable a different type of heating device to be used for the third and fourth heating devices, compared with the first and second heating devices, providing flexibility in how the energy from the second source of energy is employed to generate heat. For example, the first and second heating devices may be heat exchangers for employing a first liquid for heating water, whilst the third and fourth heating devices may be a different type of heating device. This can provide increased reliability in case of equipment malfunction, by providing independence between the heating devices.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter, by way of

example only.

Brief Description of the Drawig

Figure 1 is a block schematic diagram of a known apparatus for heating water; Figure 2 is a block schematic diagram of another known apparatus for heating water; Figure 3 is a block schematic diagram of an apparatus for heating water in accordance with an embodiment of the invention; and Figure 4 is a block schematic diagram of an apparatus for heating water in accordance with another embodiment of the invention.

Detailed Description of the Invention

Referring to Figure 3, there is an apparatus 100 for heating water. The apparatus 100 is coupled to a supply of water 200, and delivers water at an output 102.

The apparatus 100 has a first tank 10 which has an inlet 12 coupled to the supply of water 200 and an outlet 14 coupled to the output 102 by means of an output controller 60. The first tank 10 has a first heating device 16, which in this embodiment is a heat exchanger, for heating water in the first tank 10. The first heating device 16 is coupled to a first energy conversion device 210, which in this embodiment comprises a first solar panel 212 and a second solar panel 214, by pipes, and a first liquid is heated by the first energy conversion device 210, and circulates through the first heating device 16 to heat water in the first tank 10. In this way the first heating device 16 heats water in the first tank 10 by using solar radiation as an energy source. The first energy conversion device 210 may comprise a pump to facilitate the circulation of the first liquid, or such a pump may be located elsewhere in the apparatus. In other embodiments the first energy conversion device 210 may comprise a single solar panel.

The apparatus 100 also has a second tank 30 which has an inlet 32 coupled to the supply of water 200 and an outlet 34 coupled to the output 102 by means of the output controller 60. The second tank 30 has a second heating device 36, which in this embodiment is a heat exchanger, for heating water in the second tank 30. The second heating device 36 is coupled to the first energy conversion device 210 by pipes, and the first liquid heated by the first energy conversion device 210 circulates through the second heating device 36 to heat water in the second tank 30. In this way the second heating device 36 heats water in the second tank 30 by using solar radiation as an energy source.

The first liquid may be water or water-based, although other liquids, for example oil, may be used. In this specification, and the accompanying claims, the term liquid is used to differentiate from the water delivered from the water supply, even though the first liquid may in fact be water.

The first tank 10 has a first temperature sensor device 20 for measuring the temperature TI of water inside the first tank 10. The second tank 30 has a second temperature sensor device 40 for measuring the temperature T2 of water inside the second tank 30. The first and second temperature sensor devices 20, are illustrated in Figure 3 mounted inside the respective first and second tanks 30, 40 although, less-preferably, they may be mounted on the external surface of the tanks.

The output controller 60 has valves arranged to control the flow of water from the outlets 14, 34 to the output 102. More specifically, the output controller can adopt a first state in which water at the outlet 14 is delivered to the output 102 and the flow of water from the outlet 34 to the output 102 is inhibited, and a second state in which water at the outlet 34 is delivered to the output 102 and the flow of water from the outlet l4tc the output 102 is inhibited.

There is a system controller 90 coupled to the first temperature sensor device 20 for receiving an indication of the temperature TI and coupled to the second temperature sensor device 40 for receiving an indication of the temperatureT2.

The system controller 90 is further coupled to control the output controller dependent on the measured temperatures Ti and T2 such that water from only the hotter tank is delivered to the output 102. In particular, if Ti exceeds T2, the output controller 60, under the control of the system controller 90, adopts the first state, and if T2 exceeds Ti, the output controller 60, under the control of the system controller 90, adopts the second state. This arrangement ensures that the output 102 receives the hottest available water. For clarity, the coupling between the system controller 90 and the output controller 60 has been omitted from Figure 3.

The first energy conversion device 210 has an indicator device 216 for generating a indication of a temperature TS which can be provided by the first heating device 16 and by the second heating device 36 using the first liquid heated by the first energy conversion device 210 using a first source of energy, in this case solar radiation. In this embodiment, the first and second solar panels 212, 214 may have the same orientation and may be coupled in series, such that the first liquid flows first through first solar panel 212, then through the second solar panel 214. In this case the indication of temperature TS may be derived by measuring the temperature of the first liquid flowing through the second solar panel 214, which is dependent on, not only heating provided by the second solar panel 214, but also any preceding heating provided by the first solar panel 212.

The system controller 90 is coupled to the first energy conversion device 210 for receiving the indication of the temperature IS.

In a further variation of this embodiment, the first energy conversion device 210 may be adapted to permit flow of the first liquid through only one of the first and second solar panels 212, 214. The selection of one of the solar panels for the liquid flow is made by measuring the temperature of the first liquid separately in both solar panels, and selecting the solar panel able to heat the first liquid to a higher temperature. In this case the indication of temperature TS is derived from this hotter temperature. This variation is advantageous if the first and second solar panels 212, 214, have different orientations optimised for different elevations of the sun at different times of the day. For example, on a ridged roof having slopes facing east and west, the first solar panel 212 may be located on an east facing slope and the second solar panel 214 may be located on a west facing slope. In this variation, additional restrictions may be placed on the selection of the solar panels 212, 214, in order to prevent continual switching between the solar panels, because the temperature in the hotter of the solar panels may fall when that solar panel is selected and the first liquid begins to flow through it. Such an additional restriction may, for example, permit only a single switch between the solar panels 212, 214 in a twenty four hour period.

There is a first heating controller 70 having valves arranged to, under the control of the system contrOller 90, enable or inhibit the flow of the first liquid from the first energy conversion device 210 to the first heating device 16 and the second heating device 36. The system controller 90 is coupled to control the first heating controller 70 to enable heating by a selected one of the first and second heating devices 16, 36 and to inhibit heating by the other of the first and second heating devices 16, 36, the selection being dependent on the indications of the temperatures Ti, T2 and TS. The coupling between the system controller 90 and the first heating controller 70, and between the system controller 90 and other elements described below, has been omitted from Figures 3 and 4 for clarity.

A set of criteria which the system controller 90 may employ for the selection is as follows: if T2<T1 <IS, enable heating by the first heating device 16 and inhibit heating by the second heating device 36; if TI <T2<TS, enable heating by the second heating device 36 and inhibit heating by the first heating device 16; if T2<TS.<T1, enable heating by the second heating device 36 and inhibit heating by the first heating device 16; and if Ti <TS<T2, enable heating by the first heating device 16 and inhibit heating by the second heating device 36.

Thus, if both the first tank 10 and the second tank 30 are cooler than IS, only the hotter tank is heated, If one tank is cooler and one tank is hotter than TS, only the cooler tank is heated.

There is a pipe 50 coupling the outlet 14 of the first tank 10 to the inlet 32 of the second tank 30, and a pipe 52 coupling the outlet 34 of the second tank 30 to the inlet 12 of the first tank 10. By this means, water pre-heated in either the first tank 10 or the second tank 30 may be fed from the respective outlet 14, 34 to the inlet 12, 32 of the other tank.

There is a coupling controller 80 located in the path of the pipes 50 and 52 for enabling and inhibiting the flow of water in the pipes 50 and 52, for example by means of non-return valves or check valves. The coupling controller 80 is coupled to the system controller 90. If TI exceeds T2, such that the output controller 60 is in its first state and delivers water from the first tank 10 to the output 102, the system controller 90 controls the coupling controller 80 to inhibit the flow of water in the pipe 50 from the outlet 14 to the inlet 32, and enable the flow of water in the pipe 52 from the outlet 34 to the inlet 12. If 12 exceeds TI, such that the output controller 60 is in its second state and delivers water from the second tank 30 to the output 102, the system controller 90 controls the coupling controller 80 to enable the flow of water in the pipe 50 from the outlet 14 to the inlet 32, and inhibit the flow of water in the pipe 52 from the outlet 34 to the inlet 12.

The coupling controller 80 performs a non-return function, inhibiting under all circumstances the flow of water in pipe 52 from the inlet 12 to the outlet 34 and in the pipe 50 from the inlet 32 to the outlet 14. This is to prevent water from the input 200 reaching the output 102 by bypassing both the first and second tanks 10, 30. Also illustrated in Figure 3 is an input controller 230 comprising valves for, under the control of the system controller 90, selectively routing water from the input 200 to whichever of the first and second tanks 16, 36 is delivering water to the output 102.

The first tank 10 has a third heating device 18 for heating water in the first tank 10 and the second tank 30 has a fourth heating device 38 for heating water in the second tank 30. In this embodiment the third and fourth heating devices 18, 38 are heat exchangers. The third and fourth heating devices 18, 38 are coupled to a second energy conversion device 220 by pipes, and a second liquid is heated by the second energy conversion device 220 and circulates through the third heat exchanger 18 to heat water in the first tank 10 and through the fourth heat exchanger 18 to heat water in the second tank 30. The second energy conversion device 220 may be any type of heater employing any source of energy. The second liquid may be water or water based, although other liquids, for example oil, may be used.

There is a second heating controller 72 having valves arranged to, under the control of the system controller 90, enable or inhibit the flow of the second liquid from the second energy conversion device 220 to the third heating device 18 and the fourth heating device 38. The system controller 90 is coupled to control the second heating controller 72 to enable heating by a selected one of the third and fourth heating devices 18, 38 and to inhibit heating by the other of the third and fourth heating devices 18, 38, dependent on the indications of the temperatures Ti and T2 and on an indication of a desired water temperature ID.

A set of criteria which the system controller 90 may employ for the selection is as follows: if T2<Ii <ID, enable heating by the third heating device 18 and inhibit heating by the fourth heating device 38, and if Ti <T2<TD, enable heating by the fourth heating device 38 and inhibit heating by the third heating device 18.

Therefore, if T2<T1 <TD, the system controller 90 enables heating of the second liquid by the second energy conversion device 220, enables heating of the third heating device 18 by the second liquid, and inhibits heating of the fourth heating device 38 by the second liquid. Conversely, if T1.<T2cTD, the system controller 90 enables heating of the second liquid by the second energy conversion device 220, enables heating of the fourth heating device 38 by the second liquid, and inhibits heating of the third heating device 18 by the second liquid. In this way, only the hotter of the first and second tanks 10, 30 is heated using the second energy conversion device 220.

In this way, heat from the second energy conversion device 220 is employed to heat water only if the water in both tanks 10, 30 is below the desired temperature TD. Furthermore, heat from the second energy conversion device 220 is employed to heat only the hotter of the two tanks 10, 30. Therefore, the first energy conversion device 210 is the primary source of heating, and the second energy conversion device 220 is a secondary source of heating used only when the primary source of heating is insufficient.

While the second energy conversion device 220 is employed in heating water in conjunction with the third and fourth heating devices 18, 38, the first energy conversion device 210 may continue to be employed in heating water in conjunction with the first and second heating devices 16, 36.

The second energy conversion device 220 preferably uses a different source of energy than the first energy conversion device 210, for example a fossil fuel. Examples of suitable fuels for the second energy conversion device 220 are gas, coal, wood and oil-based products. In this way the second energy conversion device 220, which acts as a secondary source of heating, can provide a back-up source of heating in case the primary source of heating, the first energy conversion device 210, fails or is impaired, such as if solar radiation is temporarily unavailable, If desired, a renewable source of energy may be used for both the first and the second energy conversion devices 210, 220.

When heating by the second energy conversion device 220 is not required, the system controller 90 may inhibit the generation of heat by the second energy conversion device 220, for example switch off the gas supply if the second energy conversion device 220 is fuelled by gas, or switch off the electricity supply if the second energy conversion device 220 is fuelled by electricity. Furthermore, the system controller 90 may employ a timer to inhibit the use of the second energy Conversion device 220 outside of desired time periods.

Referring to Figure 4, there is illustrated another embodiment of an apparatus 500 for heating water. Elements that are identical to elements in Figure 3 have the same reference number and are not described again; only the differences of the apparatus of FiOure 4 will be described.

Instead of having two heating devices in each of the first and second tanks 10, 30 to provide a primary means and a back-up means of heating each tank, the embodiment of Figure 4 has a single heating device in each of the first and second tanks 10, 30. The first and second heating devices 16, 36 are heat exchangers which are heated by the first liquid, and these are coupled to both the first energy conversion device 210 and the second energy conversion device 220 for heating the first liquid. Check valves 72 are coupled between the first and second energy conversion devices 210, 220 and the first heating controller 70 to prevent reverse flow of the first liquid to the first and second energy conversion devices 210, 220. The system controller 92 controls whether the first liquid is heated by the first energy conversion device 210 or the second energy conversion device 220.

A set of criteria which the system controller 92 may employ for controlling the first heating controller 70 and the second energy conversion device 220, is as follows: if TS<TD and T2czTl <ID, enable heating of the first liquid by the second energy conversion device 220, enable the flow of the first liquid from the second energy conversion device 220 to the first heating device 16, and inhibit the flow of the first liquid from the second energy conversion device 220 to the second heating device 36; and if TS<TD and Ti <T2<TD, enable heating of the first liquid by the second energy conversion device 220, enable the flow of the first liquid from the second energy conversion device 220 to the second heating device 36, and inhibit the flow of the first liquid from the second energy conversion device 220 to the first heating device 16.

As in the embodiment of Figure 3, the second energy conversion device 220 is used for heating only if TS<TD, such that the first energy conversion device 210 employing the first source of energy cannot satisfy the desired water temperature, and in this circumstance, only the hotter of the two tanks is heated.

Also, the system controller 92 may employ a timer to inhibit the use of the second energy conversion device 220 outside of desired time periOds.

In all other respects, the operation of the system controller 92 in controlling the elements of the apparatus illustrated in Figure 4 is identical to the operation of the system controller 90 as described above with reference to Figure 3.

In a further embodiment, any or all of the first, second, third and fourth heating devices 16, 36, 18, 38 may be replaced by heating arrangements other than heat exchangers, in particular electrical heaters. In this case, the associated first and second energy conversion devices 210, 220 may comprise electricity generators, and the first and second heating controllers 70, 72 may comprise electrical switching devices for routing electrical current to the heating devices to be activated.

In particular, the first energy conversion device 210 may comprise an electricity generator fuelled by renewable energy, such as a photovoltaic solar panel for employing solar radiation, a wind turbine for employing wind power, or a wave turbine for employing wave power. In the case that the first and second heating device 16, 36 are electrical heaters, the indication of IS may be derived by measuring the electrical current generated by the first energy conversion device 210.

The apparatus 100, 500 for heating water may be used for domestic or industrial purposes, for example a cleaning plant such as a bottle washing plant.

The apparatus 100, 500 may be used to supply hot water for general use and additionally, or alternatively, for supplying hot water to a space heating system, such as a domestic central heating system. If the heated water serves more than one purpose, then there may be a desired temperature for each purpose, and separate thermostats for detecting whether TI or 12 exceed each desired temperature. In this case, the value of ID will normally be the higher, or highest, of the desired temperatures.

The apparatus 100, 500 may comprise elements and modes of operation other than those described herein. For example, a mode may be provided in which hot water is delivered to the output 102 from both the first tank 10 and the second tank 30. This may be employed, for example, when a higher volume of hot water is required than can be supplied from only a single tank. In such a mode of operation, different criteria may be used for controlling the first, second third and fourth heating devices 16, 18, 36, 38, and for controlling the first and second energy conversion devices 210, 220. Also, in such a mode of operation, the input controller 230 may supply water from the supply of water 200 to both tanks 10, 30.

In addition to the first energy conversion device 210 used in conjunction with the first and second heating devices 16, 36, the apparatus 100, 500 may comprise a further energy conversion device and corresponding further heating devices operated independently according to the same criteria as the first energy conversion device 210 and the first and second heating devices 16, 36. Such an embodiment is advantageous if a further source of energy is available.

From reading the present disclosure, other variations and modifications will be apparent to the skilled person. Such variations and modifications may involve equivalent and other features which are already known in the art of water heating and which may be used instead of, or in addition to, features already described herein.

Although the appended claims are directed to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention.

Claims

CLAIMS1.. An apparatus for heating water, comprising: a first tank coupled to a second tank; a first heating device for heating water in the first tank using a first source of energy; a second heating device for heating water in the second tank using the first source of energy; a first temperature sensor device for generating a first indication of a temperature TI ofwaterinthefirsttank; a second temperature sensor device for generating a second indication of a temperature T2 of water in the second tank; an indicator device for generating a third indication of a temperature TS which can be provided by the first heating device and by the second heating device using the first source of energy; a system controller for enabling heating by a selected one of the first and second heating devices and inhibiting heating by the other of the first and second heating devices, wherein the selection is dependent on the first, second and third indications.
2. An apparatus as claimed in claim 1, wherein the system controller is adapted to: if T2<T1 <TS, enable heating by the first heating device and inhibit heating by the second heating device; if TI <T2<TS, enable heating by the second heating device and inhibit heating by the first heating device; if T2<TS<T1, enable heating by the second heating device and inhibit heating by the first heating device; and if TI <TS<T2, enable heating by the first heating device and inhibit heating by the second heating device.
3. An apparatus for heating water as claimed in claim 1 or claim 2, wherein the first tank has a first inlet for coupling to a supply of water and a first outlet for delivering water heated in the first tank; wherein the second tank has a second inlet for coupling to the supply of water and a second outlet for delivering water heated in the second tank; and the apparatus comprising: an output for delivering heated water from the apparatus; and an output controller having a selectable first state for delivering water from the first outlet to the output and for inhibiting delivery of water from the second outlet to the output, and a selectable second state for delivering water from the second outlet to the output and for inhibiting delivery of water from the first outlet to the output; wherein the system controller is adapted to select the first state if TI exceeds T2 and select the second state if T2 exceeds TI
4. An apparatus as claimed in claim 3, comprising: first coupling means for coupling water from the first outlet to the second inlet; and second coupling means for coupling water from the second outlet to the first inlet; wherein the system controller is adapted to: if the output controller is in the first state, inhibit the flow of water from the first outlet to the second inlet via the first coupling means and enable the flow of water from the second outlet to the first inlet via the second coupling means; and if the output controller is in the second state, enable the flow of water from the first outlet to the second inlet via the first coupling means and inhibit the flow of water from the second outlet to the first inlet via the second coupling means.
5. An apparatus as claimed in any preceding claim, wherein the first and second heating devices are heat exchangers for employing a first liquid for heating water, and wherein the first and second heating devices are adapted for coupling to a first energy conversion device for heating the first liquid using the first source of energy.
6. An apparatus as claimed in claim 5, further comprising the first energy conversion device, and wherein the first source of energy is a renewable energy source.
7. An apparatus as claimed in claim 6, wherein the renewable energy source is solar radiation.
8. An apparatus as claimed in claim 6, wherein the first energy conversion device comprises a first solar panel.
9. An apparatus as claimed in claim 8, wherein IS is dependent on the temperature of the first liquid in the first solar panel.
10. An apparatus as claimed in claim 8, wherein the first energy conversion device comprises a second solar panel for heating the first liquid, and the system controller is adapted to determine which one of the first and second solar panels is able to heat the first liquid to a hotter temperature and to enable flow of the first liquid to one of the first and second heating devices from the determined one of the first and second solar panels and to inhibit flow of the first liquid to said one of the first and second heating devices from the other of the first and second solar panels.
11. An apparatus as claimed in claim 10, wherein TS is dependent on the higher of the temperature of the first liquid in the first solar panel and the temperature of the first liquid in the second solar panel.
12. An apparatus as claimed in any one of claims 5 to 11, wherein the first and second heating devices are adapted for coupling to a second energy conversion device for heating the first liquid using a second source of energy, and wherein the system controller is responsive to an indication of a desired water temperature TD to: if TS<TD and T2<T1 <TD, enable heating of the first liquid by the second energy conversion device, enable heating of the first heating device by the first liquid, and inhibit heating of the second heating device by the first liquid; and if TS<TD and TI <T2<TD, enable heating of the first liquid by the second energy conversion device, enable heating of the second heating device by the first liquid, and inhibit heating of the first heating device by the first liquid.
13. An apparatus as claimed in any one of claims 1 to 4, wherein the first and second heating devices employ electricity to generate heat.
14. An apparatus as claimed in claim 13, comprising a first energy conversion device for generating electricity using a renewable energy source.
15. An apparatus as claimed in claim 14, wherein the renewable energy source is any of: solar radiation, wind power, wave power.
16. An apparatus as claimed in claim 14, wherein the first energy conversion device comprises a solar panel.
17. An apparatus as claimed in any one of claims I to 4 and 13 to 16, wherein the first and second heating devices are both adapted for selectably using the first source of energy or a second source of energy, and wherein the system controller is responsive to an indication of a desired water temperature TD to: if TS<TD and T2<TI <TD, enable heating by the first heating device using the second source of energy and inhibit heating by the second heating device using the second source of energy; and if TS<TD a.nd Ti <T2<TD, enable heating of the second heating device using the second source of energy and inhibit heating by the first heating device
18. An apparatus as claimed in any one of claims ito 11 and 13 to 16, wherein the first tank has a third heating device for heating water in the first tank using a second source of energy and the second tank has a fourth heating device for heating water in the second tank using the second source of energy, and wherein the system controller is responsive to an indication of a desired water temperature ID to: if T2<T1 <TD, enable heating by the third heating device and inhibit heating by the fourth heating device and if Ti <T2<TD, enable heating of the fourth heating device and inhibit heating by the third heating device.
19. A method of controlling an apparatus for heating water, the apparatus having a first tank heatable by a first heating device and a second tank coupled to the first tank and heatable by a second heating device, the method comprising: enabling heating of water by a selected one of the first and second heating devices and inhibiting heating of water by the other of the first and second heating devices, wherein the selection is dependent on a temperature Ti of water in the first tank, a temperature 12 of water in the second tank, and an indication of a temperature TS which can be provided by the first and second heating devices using a first source of energy.
20. An apparatus for heating water substantially as herein described with reference to the accompanying Figures 3 and 4.