Technical field

The present disclosure variously relates to methods, systems and apparatus for use in helping consumers reduce their energy usage, and also to methods, systems and apparatus suitable for consumers who want to embrace a greener lifestyle, for example by using an electric or hybrid car which they charge domestically.

Additionally, the present disclosure relates to methods and systems for actively manage utility consumption. In particular the present disclosure relates to methods and systems for managing energy consumption in a residential home but is equally applicable to commercial buildings and other structures with water and energy supplies.

Background

According to Directive 2012/27/EU buildings represent 40 % of the final energy consumption and 36% of CO ₂ emissions. The EU Commission report of 2016 "Mapping and analyses of the current and future (2020 - 2030) heating/cooling fuel deployment (fossil/renewables)" concluded that in EU households, heating and hot water alone account for 79% of total final energy use (192.5 Mtoe). The EU Commission also report that, "according to 2019 figures from Eurostat, approximately 75% of heating and cooling is still generated from fossil fuels while only 22% is generated from renewable energy". To fulfil the EU's climate and energy goals, the heating and cooling sector must sharply reduce its energy consumption and cut its use of fossil fuels."

Heat pumps (with energy drawn from the air, the ground or water) have been identified as potentially significant contributors in addressing this problem.

In many countries, there are policies and pressures to reduce carbon footprint. For example, in the UK in 2020 the UK Government published a whitepaper on a Future Homes Standard, with proposals to reduce carbon emissions from new homes by 75 to 80% compared to existing levels by 2025. In addition, it was announced in early 2019 that there would be a ban on the fitment of gas boilers to new homes from 2025. It is reported that in the UK at the time of filing 78% of the total energy used for the heating of buildings comes from gas, while 12% comes from electricity.

The UK has a large number of small, 2-3 bedroom or less, properties with gas-fired central heating, and most of these properties use what are known as combination boilers, in which the boiler acts as an instantaneous hot water heater, and as a boiler for central heating. Combination boilers are popular because they combine a small form factor, provide a more or less immediate source of "unlimited" hot water (with 20 to 35kW output), and do not require hot water storage. Such boilers can be purchased from reputable manufactures relatively inexpensively. The small form factor and the ability to do without a hot water storage tank mean that it is generally possible to accommodate such a boiler even in a small flat or house - often wall- mounted in the kitchen, and to install a new boiler with one man day's work. It is therefore possible to get a new combi gas boiler installed inexpensively. With the imminent ban on new gas boilers, alternative heat sources will need to be provided in place of gas combi boilers. In addition, previously fitted combi boilers will eventually need to be replaced with some alternative.

Although heat pumps have been proposed as a potential solution to the need to reduce reliance on fossil fuels and cut CO ₂ emissions, they are currently unsuited to the problem of replacing gas fired boilers in smaller domestic (and small commercial) premises or a number of technical, commercial and practical reasons. They are typically very large and need a substantial unit on the outside of the property. Thus, they cannot easily be retrofitted into a property with a typical combi boiler. A unit capable of providing equivalent output to a typical gas boiler would currently be expensive and may require significant electrical demand. Not only do the units themselves cost multiples of the equivalent gas fired equivalent, but also their size and complexity mean that installation is technically complex and therefore expensive. A further technical problem is that heat pumps tend to require a significant time to start producing heat in response to demand, perhaps 30 seconds for selfchecking then some time to heat up - so a delay of 1 minute or more between asking for hot water and its delivery. For this reason, attempted renewable solutions using heat pumps and/or solar are typically applicable to large properties with room for a hot water storage tank (with space demands, heat loss and legionella risk).

There therefore exists a need to provide a solution to the problem of finding a suitable technology to replace gas combi boilers, particularly for smaller domestic dwellings.

Other concerns also arise from the need to reduce the amount of carbon dioxide released into the atmosphere and more generally to reduce the amount of energy wasted by households. Significant among these is the need to reduce the amount of hot water used by households, which is also a significant consideration given the worldwide need to reduce the demand for water.

Aspects of the present disclosure concern methods and installations that can help to reduce usage of hot water, and in this way contribute to a reduction in the usage of both energy and water.

In an effort to reduce both reliance on hydrocarbons and the amount of carbon dioxide released into the atmosphere, many households are now choosing to buy electric vehicles to replace vehicles powered by petrol or diesel internal combustion engines (albeit that some of these "electric" vehicles are in fact hybrids which use both an internal combustion engine and battery powered electric motors). This move has made it necessary for many households to add a charging station to enable batteries of the electric vehicles to be recharged domestically. Given that in many countries domestic premises receive their power from an electricity grid through a single-phase supply that is subject to a current limit of 100 Amps, situations can arise during the charging of one or two vehicles, in conjunction with other electricity usage, that the 100 Amp ceiling can become an issue. At least one aspect of the disclosure concerns improvements to be made to a domestic electrical supply.

Summary

In a first aspect there is provided a domestic electrical distribution board including a plurality of current conductors, the domestic electrical distribution board being provided with one or more arrangements to cool the current conductors using non-convective flow of a cooling fluid. The temperature of domestic electrical distribution boards may become significantly elevated as the result of Joule or resistive heating caused by current flow through electrical conductors on the board. Although there may be natural convection of air over the board, temperature increases may cause thermally activated circuit breakers to trip at lower currents than their rated currents. By using non-convective flow - for example resulting from the flow of water from a pressurised water supply, or from forced flow of air, (in each case a forced flow of fluid, rather than simple convective flow) temperature rises can be controlled.

At least one of the arrangements may provide active temperature control. In this way, the temperature of the domestic electrical distribution board may be controlled to be less than a target temperature.

An enclosure about the board may have at least one temperature-controlled fan to expel warm air from within the enclosure. Typically, domestic electrical distribution boards are protected by some form of noncombustible enclosure, as is the case with domestic consumer units, but the presence of an enclosure is likely to restrict significantly convective heat loss. By providing a temperature-controlled fan to expel air from within the enclosure, to be replaced with cooler air from outside the enclosure, it may be possible to regulate the temperature inside the enclosure.

A sensor may be provided to sense a temperature in the enclosure, and a control arrangement operatively coupled to the fan and the temperature sensor; the control arrangement being configured to respond to a property of or a signal from the temperature sensor to: activate the fan when a first threshold temperature is reached; and to deactivate the fan when the property of or the signal from the temperature sensor indicate that the temperature of the consumer unit has fallen below a second threshold temperature lower than the first. By using upper and lower temperature thresholds, rather than a single threshold, cooling is improved, and inefficient cycling of the fan reduced.

Optionally, the cooling fluid is a liquid. By using a liquid rather than air, cooling efficiency may be improved, and the energy in the heated liquid may be used to improve energy efficiency.

The plurality of current conductors, which preferably include one or more busbars, may be thermally coupled to but electrically insulated from a heatsink through which the liquid is arranged to flow.

Such an installation is preferably installed in a building, the heatsink including a water inlet coupled to receive water from a cold-water supply, and a water outlet arranged to feed water into a water heating arrangement for a hot-water supply system. In this way, waste heat may be captured and used to reduce the energy demands of a hot water supply system.

Optionally the domestic electrical distribution board is configured to receive power from an electricity grid through a single-phase supply that is subject to a current limit of 100 Amps.

Preferably one of the at least one circuit breakers is the main circuit breaker for an installation protected by the electrical distribution board. Optionally, the main circuit breaker has a current limit of 100 Amps.

Optionally, an enclosure about the board has at least one temperature-controlled fan to expel warm air from within the enclosure. By this means, temperatures may be controlled even when there is no flow of water. A processor is preferably arranged to activate the fan in the event that a measured temperature exceeds a first threshold temperature. A transducer may be arranged to provide the processor with information on a water flow status, and the processor may be arranged only to activate the fan when water does not flow through the heatsink. The water heating arrangement preferably includes a heat exchanger through which water from the water outlet of the heatsink flows to acquire heat, thereby enabling the water to be indirectly heated from some other heat source, such as a solar water heating arrangement or a heat pump.

The heat exchanger preferably includes a phase change material to store energy as latent heat, in this way energy from a "green" energy source - such as solar water heating, a heat pump, etc., may be stored and used to heat water even when the "green" heat source is offline or otherwise unable to provide energy. The heat exchanger is also preferably configured to receive energy from a heat pump. By providing an energy store in the form of a PCM it becomes possible to overcome some of the drawbacks of using a heat pump for domestic hot water in smaller properties.

The hot water supply system may include an instantaneous water heater downstream of, or in parallel with, the heat exchanger, preferably controlled by a processor that also controls the heat pump. An instantaneous water heater may be used to "top up" the temperature of the water when the energy store and/or green energy source is either unavailable or when it may be more efficient or cheaper to do so.

According to a second aspect there is provided a domestic electrical distribution board including a plurality of current conductors, an enclosure being provided about the board, the plurality of current conductors including at least one thermally activated contact breaker, wherein the plurality of current conductors are thermally coupled to but electrically insulated from a heatsink through which a bore is provided for the passage of a liquid cooling fluid; and at least one temperature-controlled fan to expel warm air from within the enclosure. In this way the performance of the at least one thermally activated contact breaker may be maintained and "waste" energy harvested, for example to be supplied to a domestic hot water system. The temperature- controlled fan in effect provides active temperature control - which is particularly useful in the event that there is no or only a little flow of cooling liquid through the heat sink.

The domestic electrical distribution board according to the second aspect may further comprise a sensor to sense a temperature in the enclosure, and a control arrangement operatively coupled to the fan and the temperature sensor; the control arrangement being configured to respond to a property of or a signal from the temperature sensor to: activate the fan when a first threshold temperature is reached; and to deactivate the fan when the property of or the signal from the temperature sensor indicate that the temperature of the consumer unit has fallen below a second threshold temperature lower than the first.

The domestic electrical distribution board according to the second aspect may be configured to receive power from an electricity grid through a single-phase supply that is subject to a current limit of 100 Amps. In this way it may be possible for the distribution board to continue to supply close to the maximum current with less drop off caused by heat released by conductors within the enclosure. This is particularly helpful in installations where close to the maximum allowable current is drawn - such as those including one or more chargers for electric or hybrid vehicles (EV chargers).

In the domestic electrical distribution board according to the second aspect one of the at least one circuit breakers may be the main circuit breaker for an installation protected by the electrical distribution board. Optionally, the main circuit breaker has a current limit of 100 Amps. In the domestic electrical distribution board according to the second aspect the heat sink is preferably formed of two halves, wherein the bore is defined by a surface of each of the two halves.

In a third aspect there is provided a domestic electrical distribution board including at least one thermally activated contact breaker and a plurality of current conductors including one or more busbars, an enclosure being provided about the board, one or more arrangements being provided to cool the current conductors using forced flow of a cooling fluid. Preferably at least one of the arrangements provides active temperature control.

In the domestic electrical distribution board according to the third aspect preferably at least one temperature-controlled fan is provided to cause a cooling flow of air to impinge on the plurality of current conductors. This may be achieved by suitably locating one or more fans to direct the air, and/or air-guiding formations such as ribs, channels, or nozzles may be provided between one or more air inlets to the enclosure and the conductors to be cooled.

In a fourth aspect there is provided a building including a domestic electrical distribution board according to the second aspect, wherein the heatsink includes a water inlet for the bore, the water inlet coupled to receive water from a cold-water supply, and a water outlet of the bore arranged to feed water into a water heating arrangement for a hot-water supply system.

According to a fifth aspect, there is provided an electrical installation including a plurality of current conductors, an electrically conductive heatsink, the current conductors being thermally coupled to but electrically insulated from the heatsink, a water inlet and a water outlet being coupled together by a water flow path, the water flow path and the heatsink being so configured that, when water with a temperature below a temperature of the heatsink flows from the water inlet to the water outlet along the flow path, heat flows from the heatsink into water in the flow path. In this way, waste heat may effectively be extracted.

According to a sixth aspect, there is provided a domestic electrical distribution board including a plurality of current conductors, an electrically conductive heatsink, the current conductors being thermally coupled to but electrically insulated from the heatsink, the heatsink having a water inlet and a water outlet coupled together by a water flow path, the water flow path and the heatsink being so configured that, when water with a temperature below a temperature of the heatsink flows from the water inlet to the water outlet along the flow path, heat flows from the heatsink into water in the flow path. In this way, waste heat may effectively be extracted.

According to a seventh aspect there is provided a method of operating a hot water supply system of a domestic premises, the method including using waste heat from a domestic electrical installation to heat water for use in the hot water supply system. In this way, waste heat may be utilised to reduce the amount of energy needed to run the hot water supply system.

The method may comprise passing water through a heatsink of an electrical distribution board of the premises to cool the electrical distribution board. In this way, thermally activated circuit breakers may be enabled to operate at closer to their design parameters. The method may further comprise passing water from the heatsink through a heat exchanger to acquire heat, and optionally comprises acquiring heat from a phase transition of a phase change material in the heat exchanger. The method may further comprise supplying heat from a heat pump to the phase change material.

According to a eighth aspect there is provided a premises hot water supply installation including a heating appliance arranged to receive, from a cold-water supply, water to be heated, the installation including a heat exchanger through which water to be heated passes on its way from the cold-water supply to the heating appliance, the heat exchanger being arranged to harvest heat from an electrical installation of the premises, the harvested heat being transferred to water in the heat exchanger. The heat exchanger may include a heatsink for one or more thermally activated circuit breakers. The heating appliance preferably includes a thermal energy store including a phase change material that stores energy using the latent heat of the phase change material, and optionally the thermal energy store is arranged to receive heat from a heat pump. An instantaneous water heater may be provided downstream of the thermal energy store.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of various aspects of the disclosure will now be described by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic diagram showing a potential arrangement of components of an electrical distribution board with provision for forced cooling;

Figure 2 is a schematic diagram showing in greater detail some of the elements of the electrical distribution board shown in Figure 1;

Figure 3 is a schematic diagram showing an energy bank including a phase change material and a heat exchanger coupled to a heat pump energy source, the energy bank including one or more sensors to provide measurement data indicative of the amount of energy stored as latent heat in the phase change material; and

Figure 4 is a schematic diagram showing a potential arrangement of components of an interface unit, incorporating energy bank according to an aspect of the disclosure.

DETAILED DESCRIPTION

Figure 1 shows schematically, in simplified form, a domestic electrical distribution board 10 including a heatsink 12. The domestic electrical distribution board supplies current to various electrical circuits of a building such as a domestic house. The heatsink 12 is provided with a water inlet 14 and a water outlet 16, a water flow path connecting the water inlet to the water outlet. When water with a temperature lower than the temperature of the heatsink flows from the water inlet 14 to the water outlet 16 along the flow path, heat flows from the heatsink into water in the flow path. The water outlet 16 feeds a water heating appliance 18, which will be described later, which in turn supplies hot water to a hot water supply system 19 having one or more hot water supply outlets 20.

Mounted to the heatsink are a plurality of current conductors. In the illustrated embodiment, the plurality of current conductors includes a bank of miniature circuit breakers (MCBs) 22, comprising a collection of individual MCBs 24. A live busbar 26 connects the supply-side of the MCBs 24 and receives current from a metering unit 28, via a main switch/circuit breaker 29, that is in turn connected to an electrical power supply 30, in this case an electricity grid 32. A neutral feed from the metering unit 28 also feeds the main switch/circuit breaker 29, which in turn supplies a neutral busbar or common neutral 34. Individual electrical circuits of the house are each protected by one of the MCBs, although for ease of illustration Figure 1 illustrates only one of these circuits, and that is a circuit feeding an electric car charger 36 which is, like all the other protected circuits, coupled between the common neutral busbar 34 and one of the MCBs 24.

The electrical distribution board 10 is enclosed in a housing 38 made of a non-combustible material, typically a metal, commonly steel with a protective coating such as paint, or powder coating. The housing 38 includes at a lower portion having an air inlet 40 that includes a filter arrangement, not shown, to keep insects and rodents from entering the housing 38. At an upper portion, the housing 38 includes at least one air outlet coupled to an electrically powered fan 42. The fan 42 is coupled to a processor 44 which in turn is coupled to a temperature sensor or transducer 46. The processor 44 is also connected to a low voltage power supply which includes battery backup 45 so that the processor can maintain its state even in the event of a power cut or other interruption of supply.

The miniature circuit breakers 24 are designed, like the main switch/circuit breaker 29, to protect their associated electrical circuits from overcurrent conditions, so that short-circuits, or equipment malfunctions do not cause the electrical wiring in the house to overheat or worse, give rise to a fire. The circuit breakers 24 and 29 provide this protection by means of a thermally activated contact breaker, typically including something like a bimetallic strip which deforms, to break a circuit, when its temperature rises above a predetermined value. The temperature rise to which the bimetallic strip is designed to respond is meant to come from current carried by a conductor of or associated with the bimetallic strip. Each circuit breaker has a current rating, and that current rating is related to the current at which the circuit breaker should open and break the circuit. In order to trip at the intended overcurrent, the ambient temperature for the circuit breaker has to be within a target range. Because the circuit breaking is based on operation of a thermally activated element, the current at which the circuit breaker will trip depends upon the ambient temperature. Here, the "ambient temperature" is actually the temperature inside the housing of the electrical distribution board. This can be a problem, because the electrical conductors within the housing 38 heat up when they carry current - because they have non-zero electrical resistance. Because the amount of heat generated is proportional to the square of the current times the resistance, circuits, such as that of the main switch 29 and that feeding electric car charger 36, that carry high currents can lead to very significant temperature rises within the housing 38.

Consequently, particularly for circuit breakers protecting higher current circuits, there is a risk that the circuit breakers will trip when the relevant circuit is carrying a current less than the designed tripping current. This means that it may not be possible to run some circuits at their intended current rating, so that, for example, the charging rate of an electric vehicle has to be reduced compared to the design or optimum charging rate. Typically, the main switch/circuit breaker 29 in a domestic installation will be rated at 100 Amps, but when the temperature inside the housing 38 rises significantly the circuit breaker 29 may trip at currents well below 100 Amps. Thus, the domestic electrical installation may have in effect a much lower current ceiling than intended, and this may cause problems when the electric vehicle is being charged, especially if other circuits in the house are carrying close to their design currents. Embodiments of the present disclosure seek to reduce the likelihood of thermally activated circuit breakers tripping at lower currents than intended. To this end, the electrical distribution board is provided with active temperature control. Active temperature control is provided by the processor-controlled fan 42, the processor 44 being responsive to temperature signals from the temperature sensor/transducer 46 which is preferably configured to sense the temperature of the air inside the enclosure of the consumer unit. Typically, the processor will be set to turn the fan on when a temperature of somewhere in the range of 22 to 1 Celsius (for example 25 Celsius) is detected by the sensor 46, depending both upon the intended operating parameters of the circuit breakers and the external air temperature (whether actual, or predicted). When the fan 42 is turned on it expels warm air from within the enclosure, sucking external air into the enclosure through the air inlet 40. Preferably, rather than just providing the fan 46 as an extractor which sucks air from within the enclosure, a fan (or one or more other fans) may be so placed that it preferentially blows air onto at least the neutral busbar 34 and the exposed conductors of the protected circuits that connect to the circuit breaker(s), as well as preferably onto the circuit breakers themselves. In this way, the conductors within the enclosure - which are the things dissipating most heat, may be cooled thereby reducing the temperature within the enclosure and thereby enabling the circuit breakers to operate as close as possible to the design parameters. A similar effect may also be achievable even with the use of an extractor fan if suitable structures are provided within the housing to direct incoming air preferentially onto the conductors to be cooled, and ribs and other structures may also be provided to guide air driven by a fan upstream of the ribs or structures.

Clearly, this forced ventilation can only reduce the internal temperature of the housing 38 when the external air temperature is lower than the internal air temperature. It is therefore desirable to provide at least one further temperature sensor to detect either the external air temperature directly or to detect the temperature of air as it enters the housing through the air inlet 40. For example, as shown, a second temperature sensor 48 may be provided in the lower portion of the enclosure defined by the housing 38, where air that enters through the inlet, as the result of expulsion of air through the fan 42, will impinge on the second temperature sensor 48. In this way the sensor 48 can provide a useful measure of the temperature of the incoming air, and hence how much, if any, cooling can be provided. Preferably the processor 44 is configured to turn the fan(s) off again at a lower temperature (typically by 4 or 5 degrees or more) than the temperature at which the fan(s) is/are initially activated, thereby reducing the risk that the fan(s) will continually cycle from off to on and back again.

In addition to the forced expulsion of air, embodiments of the present disclosure potentially provide a second mechanism for cooling thermally activated circuit breakers such as the main switch and MCBs shown, and this involves the use of water (or potentially some other liquid , potentially a non-flammable and electrically non-conductive liquid within a closed-circuit cooling arrangement, optionally with a further heat exchanger by means of which energy may be transferred to water for the hot water supply system) to transfer heat away from the heatsink 12 to which the circuit breakers are mounted, as already described with reference to Figure 1. Heat extracted from the heatsink by the liquid (water) flowing out of liquid (water) outlet 16 can conveniently be used to reduce the heating burden of the water heating appliance 18, thereby potentially reducing the energy demands of the house/household. The use of the extracted heat in this way is particularly beneficial when the heating appliance involves the use of a green energy device such as a heat pump, as will be explained later with reference to Figure 3.

As will be appreciated, Figure 1 is a highly simplified and schematic drawing, which necessarily omits many details. One detail which should be mentioned, even though it is not illustrated, is the desirability of providing some form of flow sensor or transducer to provide a signal when liquid (water) flows through the heatsink. In the absence of flow, liquid (water) within the heatsink will absorb energy from heatsink, but significant extraction of heat requires liquid (water) to flow through the heatsink. In the absence of liquid (water) flow, therefore, the processor is preferably configured to activate the fan 42 to expel hot air from within the housing, drawing cooler air in through the air inlet 40, thereby cooling the circuit breakers. But using the fan in this way, although it can help reduce the temperature inside the housing and thereby facilitate normal operation of the circuit breakers, doesn't really contribute to energy saving. Whereas heat extracted into liquid (water) that subsequently transfers heat to the hot water supply system (for example water that passes through the heat exchanger may pass into the hot water supply system) is useful. Consequently, the processor 44 is preferably arranged to rely preferentially on cooling by liquid (water) flow, rather than by the use of the fan, and this means using some mechanism to detect water flow - albeit the detection of flow may be remote from the electrical distribution board. For example, a flow sensor may be provided at the liquid (water) inlet 14, or at the liquid (water) outlet 16, but may additionally or alternatively be provided in association with the water heating appliance 18, or the hot water supply system 19, the processor 44 being supplied with flow data either via a wired connection or a wireless one.

The heatsink 12 will generally be made of metal, typically brass, bronze, or copper or another copper alloy - because this is both desirable from an electrochemical perspective, given the preponderance of copper and copper alloys in many domestic water systems , and from a thermal efficiency perspective as, these metals all have high thermal conductivities, and acceptable corrosion resistance. Preferably the heatsink 12 is earthed, preferably bonded to the main earthing point of the domestic electricity system. Clearly, the live and neutral conductors, including the busbars, need to be electrically insulated from the heatsink 12. At the same time, it is desirable to minimise the thermal resistance between the electrical conductors , particularly these main conductors, and the heatsink.

Although the arrangement shown in Figure 1 includes multiple circuit breakers, here exemplified as miniature circuit breakers, some electrical installations are protected by just a single main circuit breaker, typically with a rating of something like 100 Amps (e.g., 100 Amps, 110 Amps, or 120 Amps). In effect such installations are protected using just a main switch like switch/circuit breaker 29 previously described. Installations of this type can also benefit from the approach outlined above, with forced air cooling, using a processor-controlled fan to expel warm air from within an enclosure about the circuit breaker, as well as using liquid (water) cooling of the heatsink to which the main circuit breaker is thermally coupled.

Figure 2 shows details of the heatsink 12 and MCBs 24. For purposes of illustration these are shown without the main switch /circuit breaker 29, although in practice one would be provided. In one configuration, the heatsink 12 may comprise two main parts, a front body 12a to which the electrical conductors in the form of the neutral and live busbars 34 and 26 and the bank of MCBs 22 are connected, and a rear body 12b. As shown, the water inlet 14 and the water outlet 16 couple to the front body 12a, a serpentine water flow path is provided in the back face of the front body 12a for example by machining or by casting. The water inlet 14 and the water outlet 16 are both preferably in the form of spigots or couplings screwed into internally threaded bores in the front body 12a. The rear body 12b may also include a corresponding portion of the serpentine water flow path or may function simply as a closure. The mating surfaces of the two bodies include one or more seals and, preferably also matching dowels and sockets to ensure to ensure correct registration of the two parts. The two parts are bolted together using a plurality of screws or bolts distributed across the surface of the bodies. The one or more seals may be provided in one or both of the bodies.

Each of the busbars 26 and 34 is coupled to but electrically insulated from the front face of the front body 12a, and secured thereto using, for example bolts or screws. The individual miniature circuit breakers couple in the conventional way to the live busbar and a possibly conventional locating arrangement (e.g. using a DIN rail, shown schematically as 50) attached to, but electrically insulated from, the front face of the front body 12a. Because of the desire to sink heat from the various electrical conductors 22,26, and 34, to the heatsink 12, the electrical insulation provided between these conductors and the front body 12a should be chosen to minimise thermal resistance while providing the necessary level of electrical insulation.

Alternatively, rather than forming the heatsink from two parts, with the flow path machined or cast into one or both parts, the heatsink may be a one-piece item, with the flow path formed using lost-wax casting or some other suitable casting technique.

The assembly shown in Figure 2 can be mounted inside the housing 38 of Figure 1, so that the heatsink and the electrical conductors are all fully enclosed, consistent for example with UK regulations on domestic consumer units. The heatsink assembly can be secured within the housing by screws passing through holes in the rear of the housing into corresponding screw holes in the heatsink (typically formed just in the rear body 12b), and the housing then secured to a wall of the building using wall plugs and screws, in the conventional manner, for example. After the housing 38 is secured, meter tails that supply current from the metering unit 28 to the electrical distribution board are connected in the conventional manner, for example to a main two-pole switch/circuit breaker 29 of the installation. Current feeds from the main switch 29 then couple to the busbars or other current distribution arrangements in a conventional manner.

Although Figures 1 and 2 illustrate a consumer unit (more generally electrical distribution board) which is provided both with liquid cooling and forced air cooling, it will be understood that each of these two cooling aspects may be provided on its own, without the other. That is, the provision of forced air cooling can still be expected to improve the performance of circuit breakers that are temperature sensitive - particularly in temperate climates or where ambient air temperature is controlled (e.g., by means of air conditioning). Conversely, a consumer unit or electrical distribution board provided with water cooling may both improve the performance of circuit breakers that are temperature sensitive and provide a means to harvest and utilise energy that would otherwise be wasted - for example by using the harvested energy for domestic hot water (and/or optionally for space heating).

Figure 3 shows schematically an example of a water heating appliance 18 suitable for use with an installation, including a water-cooled electrical distribution board, as shown in Figurel. In the illustrated example, the water heating appliance 18 includes an energy bank 60 including a heat exchanger, the energy bank comprising an enclosure 62. Within the enclosure 62 are an input-side circuit 44 of the heat exchanger for connection to an energy source - shown here as a heat pump 66, an output-side circuit 68 of the heat exchanger for connection to an energy sink - shown here as a hot water supply system connected to a cold-water feed 70 and including one or more outlets 20. Within the enclosure 62 is a phase-change material for the storage of energy. The energy bank 60 also includes one or more status sensors 74, to provide a measurement of indicative of a status of the PCM. For example, one or more of the status sensors 74 may be a pressure sensor to measure pressure within the enclosure. Preferably the enclosure also includes one or more temperature sensors 76 to measure temperatures within the phase change material (PCM). If, as is preferred, multiple temperature sensors are provided within the PCM, these are preferably spaced apart from the structure of the input and output circuits of the heat exchanger, and suitably spaced apart within the PCM to obtain a good "picture" of the state of the PCM.

The energy bank 60 has an associated system controller 78 which includes a processor 80. The controller may be integrated into the energy bank 10 but is more typically mounted separately. The controller 78 may also be provided with a user interface module 81, as an integrated or separate unit, or as a unit that may be detachably mounted to a body containing the controller 78. The user interface module 81 typically includes a display panel and keypad, for example in the form of a touch-sensitive display. The user interface module 81, if separate or separable from the controller 78 preferably includes a wireless communication capability to enable the processor 80 of controller 78 and the user interface module to communicate with each other. The user interface module 81 is used to display system status information, messages, advice and warnings to the user, and to receive user input and user commands - such as start and stop instructions, temperature settings, system overrides, etc.

The status sensor(s) is/are coupled to the processor 80, as is/are the temperature sensor(s) 76 if present. The processor 80 is also coupled to a processor/controller 82 in the heat pump 66, either through a wired connection, or wirelessly using associated transceivers 84 and 86, or through both a wired and a wireless connection. In this way, the system controller 78 is able to send instructions, such as a start instruction and a stop instruction, to the controller 82 of the heat pump 66. In the same way, the processor 80 is also able to receive information from the controller 82 of the heat pump 66, such as status updates, temperature information, etc.

The hot water supply installation also includes one or more flow sensors 88 which measure flow in the hot water supply system. As shown, such a flow sensor may be provided on the cold-water feed 70 to the system, and or between the output of the output-side circuit 68 of the heat exchanger. Optionally, one or more pressure sensors may also be included in the hot water supply system, and again the pressure sensor(s) may be provided upstream of the heat exchanger/energy bank, and/or downstream of the heat exchanger/energy bank - for example alongside one or more of the one or more flow sensors 88. The or each flow sensor, the or each temperature sensor, and the or each pressure sensor is coupled to the processor 80 of the system controller 78 with either or both of a wired or wireless connection, for example using one or more wireless transmitters or transceivers 90. Depending upon the nature(s) of the various sensors 74, 76, and 88, they may also be interrogatable by the processor 80 of the system controller 28.

An electrically controlled thermostatic mixing valve 160 is preferably coupled between the outlet of the energy bank and the one or more outlets of the hot water supply system and includes a temperature sensor 162 at its outlet. An additional instantaneous water heater, 170, for example an electrical heater (inductive or resistive) controlled by the controller 28, is preferably positioned in the water flow path between the outlet of the energy bank and the mixing valve 160. A further temperature sensor may be provided to measure the temperature of water output by the instantaneous water heater 170, and the measurements provided to the controller 28. The thermostatic mixing valve 160 is also coupled to a cold-water supply 180 and is controllable by the controller 28 to mix hot and cold-water to achieve a desired supply temperature.

Optionally, as shown, the energy bank 60 may include, within the enclosure 62, an electrical heating element 92 which is controlled by the processor 80 of the system controller 78, and which may on occasion be used as an alternative to the heat pump 66 to recharge the energy bank.

Figure 3 is merely a schematic, and only shows connection of the heat pump to a hot water supply installation. It will be appreciated that in many parts of the world there is a need for space heating as well as hot water. Typically therefore the heat pump 66 will also be used to provide space heating. An exemplary arrangement in which a heat pump both provides space heating and works with an energy bank for hot water heating will be described later in the application. For ease of description, the following description of a method of operation of an energy bank according to an aspect of the invention applies equally to the energy bank installation whether or not the associated heat pump provides space heating.

Having described an energy bank and the installation and operation of an energy bank in a hot water supply installation, we will now consider how the energy bank and heat pump may be integrated into both a hot water supply system and a space heating arrangement.

Figure 4 shows schematically a potential arrangement of components of an interface unit 60 according to an aspect of the disclosure. The interface unit interfaces between a heat pump (not shown in this Figure) and an in-building hot water system, and corresponds to the energy bank 60 described with reference to Figure 3. The interface unit includes a heat exchanger 12 comprising an enclosure (not separately numbered) within which is an input-side circuit, shown in very simplified form as 14, for connection to the heat pump, and an output-side circuit, again shown in very simplified form as 16, for connection to the in-building hot water system (as described above with reference to Figure 3). The heat exchanger 12 also contains a thermal storage medium for the storage of energy, but this is not shown in the figure. In the example that will now be described with reference to Figure 4 the thermal storage medium is a phase-change material. It will be recognised that the interface unit corresponds to he previously described energy bank. Throughout this specification, including the claims, references to energy bank, thermal storage medium, energy storage medium and phase change material should be considered to be interchangeable unless the context clearly requires otherwise.

Typically, the phase-change material in the heat exchanger has an energy storage capacity (in terms of the amount of energy stored by virtue of the latent heat of fusion) of between 2 and 5 MJoules, although more energy storage is possible and can be useful. And of course, less energy storage is also possible, but in general one wants to maximise (subject to practical constraints based on physical dimensions, weight, cost and safety) the potential for energy storage in the phase-change material of the interface unit 10. More will be said about suitable phase-change materials and their properties, and also about dimensions etc. later in this specification.

The input side circuit 14 is connected to a pipe or conduit 18 which is in turn fed from node 20, from pipe 22 which has a coupling 24 for connection to a feed from a heat pump. Node 20 also feeds fluid from the heat pump to pipe 26 which terminates in a coupling 28 which is intended for connection to a heating network of a house or flat - for example for plumbing into underfloor heating or a network of radiators or both. Thus, once the interface unit 10 is fully installed and operational, fluid heated by a heat pump (which is located outside the house or flat) passes through coupling 24 and along pipe 22 to node 20, from where, depending upon the setting of a 3-port valve 32, the fluid flow passes along pipe 18 to the input-side circuit 14 of the heat exchanger, or along pipe 26 and out through coupling 28 to the heating infrastructure of the premises.

Heated fluid from the heat pump flows through the input-side circuit 14 of the heat exchanger and out of the heat exchanger 12 along pipe 30. In use, under some circumstance, heat carried by the heated fluid from the heat pump gives up some of its energy to the phase change material inside the heat exchanger and some to water in the output-side circuit 16. Under other circumstances, as will be explained later, fluid flowing through the input-side circuit 14 of the heat exchanger actually acquires heat from the phase change material. Pipe 30 feeds fluid that leaves the input-side circuit 14 to a motorized 3-port valve 32 and then, depending upon the status of the valve out along pipe 34 to pump 36. Pump 36 serves to push the flow on to the external heat pump via coupling 38.

The motorized 3-port valve 32 also receives fluid from pipe 40 which receives, via coupling 42, fluid returning from the heating infrastructure (e.g., radiators) of the house or flat.

Between the motorized 3-port valve 32 and the pump 36 a trio of transducers are provided: a temperature transducer 44, a flow transducer 46, and a pressure transducer 48. In addition, a temperature transducer 49 is provided in the pipe 22 which brings in fluid from the output of the heat pump. These transducers, like all the others in the interface unit 10, are operatively connected to or addressable by a processor, not shown, which is typically provided as part of the interface unit - but which can be provided in a separate module.

Although not illustrated in Figure 4, an additional electrical heating element may also be provided in the flow path between the coupler 24, which receives fluid from the output of the heat pump. This additional electrical heating element may again be an inductive or resistive heating element and is provided as a means to compensate for potential failure of the heat pump, but also for possible use in adding energy to the thermal storage unit (for example based on the current energy cost and predicted for heating and/or hot water. The additional electrical heating element is also of course controllable by the processor of the system.

Also coupled to pipe 34 is an expansion vessel 50, to which is connected a valve 52 by means of which a filling loop may be connected to top up fluid in the heating circuit. Also shown as part of the heating circuit of the interface unit are a pressure relief valve 54, intermediate the node 20 and the input-side circuit 14, and a strainer 56 (to capture particulate contaminants) intermediate coupling 42 and the 3-port valve 32. The heat exchanger 12 is also provided with several transducers, including at least one temperature transducer 58, although more (e.g., up to 4 or more) are preferable provided, as shown, and a pressure transducer 60. In the example shown, the heat exchanger includes 4 temperature transducers uniformly distributed within the phase change material so that temperature variations can be determined (and hence knowledge obtained about the state of the phase change material throughout its bulk). Such an arrangement may be of particular benefit during the design/implementation phase as a means to optimise design of the heat exchanger - including in optimising addition heat transfer arrangements. But such an arrangement may also continue to be of benefit in deployed systems as having multiple sensors can provide useful information to the processor and machine learning algorithms employed by the processor (either of just the interface unit, and/or of a processor of a system including the interface unit.

The arrangement of the cold-water feed and the hot water circuit of the interface unit 10 will now be described. A coupling 62 is provided for connection to a cold feed from a water main. Typically, before water from the water main reaches the interface unit 10, the water will have passed through an anti-syphon nonreturn valve and may have had its pressure reduced. From coupling 62 cold-water passes along pipe to the output-side circuit 16 of the heat exchanger 12. Given that we provide a processor that is monitoring numerous sensors in the interface unit, the same processor can optionally be given one more task to do. That is to monitor the pressure at which cold-water is delivered from the mains water supply. To this end, a further pressure sensor can be introduced in to the cold-water supply line upstream of coupling 62, and in particular upstream of any pressure reducing arrangement within the premises. The processor can then continually or periodically monitor the supplied water pressure, and even prompt the owner/user to seek compensation from the water supply company if the water main supplies water at a pressure below the statutory minimum.

From the output-side circuit 16 water, which may have been heated by its passage through the heat exchanger, passes along a pipe 66 to an electrical heating unit 68. The electrical heating unit 68, which is under the control of the processor mentioned previously, may comprise a resistive or inductive heating arrangement whose heat output can be modulated in accordance with instructions from the processor.

The processor is configured to control the electrical heater, based on information about the status of the phase-change material and of the heat pump.

Typically, the electrical heating unit 68 has a power rating of no more than lOkW, although under some circumstances a more powerful heater, e.g., 12kW, may be provided.

From the electric heater 68, what will by now hot water passes along a pipe 70 to a coupling 74 to which the hot water circuit, including controllable outlets such as taps and showers, of the house or flat will be connected.

A temperature transducer 76 is provided after the electric heater 68, for example at the outlet of the electric heater 68 to provide information on the water temperature at the outlet of the hot water system. A pressure relief valve 77 is also provided in the hot water supply, and while this is shown as being located between the electric heater 68 and the outlet temperature transducer 76, its precise location is unimportant - as indeed is the case for many of the components illustrated in Figure 4. Also somewhere in the hot water supply line is a pressure transducer 79 and or a flow transducer 81 either of which can be used by the processor to detect a call for hot water - i.e., detect the opening of a controllable outlet such as a tap or shower. The flow transducer is preferably one which is free from moving parts, for example based on sonic flow detection or magnetic flow detection. The processor can then use information from one or both of these transducers, along with its stored logic, to decide whether to signal to the heat pump to start.

It will be appreciated that the processor can call on the heat pump to start either based on demand for space heating (e.g., based on a stored program either in the processor or in an external controller, and/or based on signals from one or more thermostats - e.g., room stats, external stats, underfloor heating stats) or demand for hot water. Control of the heat pump may be in the form of simple on/off commands, but may also or alternatively be in the form of modulation (using, for example, a ModBus).

As is the case with the heating circuit of the interface unit, a trio of transducers are provided along the cold-water feed pipe 64: a temperature transducer 78, a flow transducer 80, and a pressure transducer 82. Another temperature transducer 84 is also provided in pipe 66 intermediate the outlet of the output-side circuit 16 of the heat exchanger 12 and the electric heater 68. These transducers are again all operatively connected to or addressable by the processor mentioned previously.

Also shown on the cold-water supply line 64 are a magnetic or electrical water conditioner 86, a motorised and modulatable valve 88 (which like all the motorised valves may be controlled by the processor mentioned previously), a non-return valve 86, and an expansion vessel 92. The modulatable valve 88 can be controlled to regulate the flow of cold-water to maintain a desired temperature of hot water (measured for example by temperature transducer 76).

Valves 94 and 96 are also provided for connection to external storage tanks for the storage of cold and heated water respectively. Finally, a double check valve 98 connects cold feed pipe 64 to another valve 100 which can be used with a filling loop to connect to previously mentioned valve 52 for charging the heating circuit with more water or a mix of water and corrosion inhibitor.

It should be noted that Figure 4 shows various of the pipes crossing, but unless these crossing are shown as nodes, like node 20, the two pipes that are shown as cross do not communicate with each other, as should by now be clear from the foregoing description of the Figure.

Although not shown in Figure 4, the heat exchanger 12 may include one or more additional electrical heating elements configured to put heat into the thermal storage medium. While this may seem counter intuitive, it permits the use of electrical energy to pre-charge the thermal storage medium at times when it makes economic sense to do so, as will now be explained.

It has long been the practice of energy supply companies to have tariffs where the cost of a unit of electricity varies according to the time of day, to take account of times of increased or reduced demand and to help shape customer behaviour to better balance demand to supply capacity. Historically, tariff plans were rather coarse reflecting the technology both of power generation and of consumption. But increasing incorporation of renewable energy sources of electrical power - such as solar power (e.g., from photovoltaic cells, panels, and farms) and wind power, into the power generation fabric of countries has spurred the development of a more dynamic pricing of energy. This approach reflects the variability inherent in such weather-dependent power generation. Initially such dynamic pricing was largely restricted to large scale users, increasingly dynamic pricing is being offered to domestic consumers.

The degree of dynamism of the pricing varies from country to country, and also between different producers within a given country. At one extreme, "dynamic" pricing is little more than the offering of different tariffs in different time windows over the day, and such tariffs may apply for weeks, months, or seasons without variation. But some dynamic pricing regimes enable the supplier to change prices with a day's notice or less - so for example, customers may be offered today prices for half-hour slots tomorrow. Time slots of as short as 6 minutes are offered in some countries, and conceivably the lead time for notifying consumers of forthcoming tariffs can be reduced further by including "intelligence" in energy-consuming equipment.

Because it is possible to use short- and medium-term weather predictions to predict both the amount of energy likely to be produced by solar and wind installations, and the likely scale of power demand for heating and cooling, it becomes possible to predict periods of extremes of demand. Some power generation companies with significant renewable generation capacity have even been known to offer negative charging for electricity - literally paying customers to use the excess power. More often, power may be offered at a small fraction of the usual rate.

By incorporating an electric heater into an energy storage unit, such as a heat exchanger of systems according to the disclosure, it becomes possible for consumers to take advantage of periods of low-cost supply and to reduce their reliance on electrical power at times of high energy prices. This not only benefits the individual consumer, but it is also beneficial more generally as it can reduce demand at times when excess demand must be met by burning fossil fuels.

The processor of the interface unit has a wired or wireless connection (or both) to a data network, such as the Internet, to enable the processor to receive dynamic pricing information from energy suppliers. The processor also preferably has a data link connection (e.g., a ModBus) to the heat pump, both to send instructions to the heat pump and to receive information (e.g., status information and temperature information) from the heat pump. The processor has logic which enables it* to learn the behaviour of the household, and with this and the dynamic pricing information, the processor is able to determine whether and when to use cheaper electricity to pre-charge the heating system. This may be by heating the energy storage medium using an electrical element inside the heat exchanger, but alternatively this can be by driving the heat pump to a higher-than-normal temperature - for example 60 Celsius rather than between 40 and 48 Celsius. The efficiency of the heat pump reduces when it operates at higher temperature, but this can be taken into account by the processor in deciding when and how best to use cheaper electricity.

*Because the system processor is connectable to a data network, such as the Internet and/or a provider's intranet, the local system processor can benefit from external computing power. So, for example the manufacturer of the interface unit is likely to have a cloud presence (or intranet) where computing power is provided for calculations of, for example, predicted: occupancy; activity; tariff (short/long); processed for easy use by the local processor, and they may also be tailored very specifically to the situation, location, exposure of the property within which the interface unit is installed); identification of false positives and/or false negatives. To protect users from the risk of scalding by overheated water from the hot water supply system it is sensible to provide a scalding protection feature. This may take the form of providing an electrically controllable (modulatable) valve to mix cold-water from the cold-water supply into hot water as it leaves the output circuit of the heat exchanger.

Figure 4 shows schematically what might be considered the "guts" of the interface unit, but does not show any container for these "guts". An important application of interface units according to the disclosure is as a means to enable a heat pump to be used as a practical contributor to the space heating and hot water requirements of a dwelling that was previously provide with a gas-fired combination boiler (or which might otherwise have such a boiler installed), it will be appreciated that it will often be convenient both to provide a container both for aesthetics and safety, just as is the case conventionally with combi boilers. Moreover, preferably any such container will be dimensioned to fit within a form factor enabling direct replacement of a combi boiler - which are typically wall mounted, often in a kitchen where they co-exist with kitchen cabinets. Based on the form of a generally rectangular cuboid (although of course, for aesthetics, ergonomics, or safety, curved surfaces may be used for any or all of the surfaces of the container) with a height, width and depth, suitable sizes may be found in the approximate ranges: height 650mm to 800mm; width 350mm to 550mm; depth 260mm to 420mm; for example 800 mm high, by 500mm wide, and 400mm deep, although larger, and in particular taller, units may be provided for installation where these can accommodated.

One notable distinction of interface units according to the disclosure with respect to gas combi boilers is that while the containers of the latter generally have to be made of non-combustible materials - such as steel, due to the presence of a hot combustion chamber, the internal temperatures of an interface unit will generally be considerably less than 100 Celsius, typically less than 70 Celsius, and often less than 60 Celsius. So, it becomes practical to use flammable materials such a wood, bamboo, or even paper, in fabricating a container for the interface unit.

The lack of combustion also opens up the possibility to install interface units in locations that would generally never be considered as suitable for the installation of gas combi boilers - and of course, unlike a gas combi boiler, interface units according to the disclosure, do not require a flue for exhaust gases. So, for example, it becomes possible to configure an interface unit for installation beneath a kitchen worktop, and even to make use of the notorious dead spot represented by an under counter corner. For installation in such a location the interface unit could actually be integrated into an under-counter cupboard - preferably through a collaboration with a manufacturer of kitchen cabinets. But greatest flexibility for deployment would be retained by having an interface unit that effectively sits behind some form of cabinet, the cabinet being configured to allow access to the interface unit. The interface unit would then preferably be configured to permit the circulation pump 36 to be slid out and away from the heat exchanger 12 before the circulation pump 36 is decoupled from the flow path of the input-side circuit.

Consideration can also be given to taking advantage of other space frequently wasted in fitted kitchens, namely the space beneath under-counter cupboards. There is often more a space with a height of more than 150mm, and a depth of around 600mm, with widths of 300, 400, 500, 600mm or more (although allowance needs to be made for any legs supporting the cabinets). For new installations in particular, or where a combi boiler is being replaced along with a kitchen refit, it makes sense to use these spaces at least to accommodate the heat exchanger of the interface unit - or to use more than one heat exchanger unit for a given interface unit.

Particularly for interface units designed for wall mounting, although potentially beneficial whatever the application of the interface unit, it will often be desirable to design the interface unit as a plurality of modules. With such designs it can be convenient to have the heat exchanger as one of the of modules, because the presence of the phase-change material can result in the heat exchanger alone weighing more than 25kg. For reasons of health and safety, and in order to facilitate one-person installation, it would be desirable to ensure that an interface unit can be delivered as a set of modules none of which weighs more than about 25kg.

Such a weight constraint can be supported by making one of the modules a chassis for mounting the interface unit to a structure. For example, where an interface unit is to be wall mounted in place of an existing gas combi boiler, it can be convenient if a chassis, by which the other modules are supported, can first be fixed to the wall. Preferably the chassis is designed to work with the positions of existing fixing points used to support the combi boiler that is being replaced. This could potentially be done by providing a "universal" chassis that has fixing holes preformed according to the spacings and positions of popular gas combi boilers. Alternatively, it could be cost effective to produce a range of chassis each having hole positions/sizes/spacings to match those of particular manufacturer's boilers. Then one just needs to specify the right chassis to replace the relevant manufacturer's boiler. There are multiple benefits to this approach: it avoids the need to drill more holes for plugs to take fixing bolts - and not only does this eliminate the time needed to mark out, drill the holes and clean up, but it avoids the need to further weaken the structure of the dwelling where installation is taking place - which can be an important consideration given the low cost construction techniques and materials frequently used in "starter homes" and other low cost housing.

Preferably the heat exchanger module and the chassis module are configured to couple together. In this way it may be possible to avoid the need for separable fastenings, again saving installation time.

Preferably an additional module includes first interconnects, e.g., 62 and 74, to couple the output side circuit 16 of the heat exchanger 12 to the in-building hot water system. Preferably the additional module also includes second interconnects, e.g., 38 and 24, to couple the input side circuit 14 of the heat exchanger 12 to the heat pump. Preferably the additional module also includes third interconnects, e.g., 42 and 28, to couple the interface unit to the heat circuit of the premises where the interface unit is to be used. It will be appreciated that by mounting heat exchanger to the chassis, which is itself directly connected to the wall, rather than first mounting the connections to the chassis, the weight of the heat exchanger is kept closer to the wall, reducing the cantilever loading effect on the wall fixings that secure the interface unit to the wall.

Phase change materials

One suitable class of phase change materials are paraffin waxes which have a solid-liquid phase change at temperatures of interest for domestic hot water supplies and for use in combination with heat pumps. Of particular interest are paraffin waxes that melt at temperatures in the range 40 to 60 Celsius, and within this range waxes can be found that melt at different temperatures to suit specific applications. Typical latent heat capacity is between about 180kJ/kg and 230kJ/kg and a specific heat capacity of perhaps 2.27Jg ^_1 K ¹ in the liquid phase, and 2.1Jg ^_1 K ¹ in the solid phase. It can be seen that very considerable amounts of energy can be stored taking using the latent heat of fusion. More energy can also be stored by heating the phase change liquid above its melting point. For example, when electricity costs are relatively low and it can be predicted that there will shortly be a need for hot water (at a time when electricity is likely to, or known to be going to, cost more perhaps), then it can make sense to run the heat pump at a higher-than-normal temperature to "overheat" the thermal energy store.

A suitable choice of wax may be one with a melting point at around 48 Celsius, such as n-tricosane C ₂₃ , or paraffin C ₂₀ -C ₃ 3. Applying the standard 3K temperature difference across the heat exchanger (between the liquid supplied by the heat pump and the phase change material in the heat exchanger) gives a heat pump liquid temperature of around 51 Celsius. And similarly on the output side, allowing a 3K temperature drop, we arrive at a water temperature of 45 Celsius which is satisfactory for general domestic hot water - hot enough for kitchen taps, but potentially a little high for shower/bathroom taps - but obviously cold-water can always be added to a flow to reduce water temperature. Of course, if the household are trained to accept lower hot water temperatures, or if they are acceptable for some other reason, then potentially a phase change material with a lower melting point may be considered, but generally a phase transition temperature in the range 45 to 50 is likely to be a good choice. Obviously, we will want to take into account the risk of Legionella from storing water at such a temperature.

Heat pumps (for example ground source or air source heat pumps) have operating temperatures of up to 60 Celsius (although by using propane as a refrigerant, operating temperatures of up to 72 Celsius are possible), but their efficiencies tend to be much higher when run at temperatures in the range of 45 to 50 Celsius. So, our 51 Celsius, from a phase transition temperature of 48 Celsius is likely to be satisfactory.

Consideration also needs to be given to the temperature performance of the heat pump. Generally, the maximum AT (the difference between the input and output temperature of the fluid heated by the heat pump) is preferably kept in the range of 5 to 7 Celsius, although it can be as high as 10 Celsius.

Although paraffin waxes are a preferred material for use as the energy storage medium, they are not the only suitable materials. Salt hydrates are also suitable for latent heat energy storage systems such as the present ones. Salt hydrates in this context are mixtures of inorganic salts and water, with the phase change involving the loss of all or much of their water. At the phase transition, the hydrate crystals are divided into anhydrous (or less aqueous) salt and water. Advantages of salt hydrates are that they have much higher thermal conductivities than paraffin waxes (between 2 to 5 times higher) , and a much smaller volume change with phase transition. A suitable salt hydrate for the current application is Na ₂ S ₂ O ₃ .5H ₂ O, which has a melting point around 48 to 49 Celsius, and latent heat of 200/220 kJ/kg.

In terms simply of energy storage, consideration can also be given to using PCMs with phase transition temperatures that are significantly above the 40-50 Celsius range. For example, a paraffin wax, waxes being available with a wide range of melting points: n-henicosane C ₂₄ which has a melting point around 40 Celsius; n-docosane C _2i which has a melting point around 44.5 Celsius; n-tetracosane C ₂₃ which has a melting point around 52 Celsius; n-pentacosane C ₂₅ which has a melting point around 54 Celsius; n-hexacosane C ₂₆ which has a melting point around 56.5 Celsius; n-heptacosane C ₂₇ which has a melting point around 59 Celsius; n-octacosane C ₂₈ which has a melting point around 64.5 Celsius; n-nonacosane C ₂₉ which has a melting point around 65 Celsius; n-triacosane C ₃ o which has a melting point around 66 Celsius; n-hentriacosane C _3i which has a melting point around 67 Celsius; n-dotriacosane C ₃₂ which has a melting point around 69 Celsius; n-triatriacosane C ₃₃ which has a melting point around 71 Celsius; paraffin C ₂₂ -C ₄ s which has a melting point around 58 to 60 Celsius; paraffin C ₂ i-C ₅ o which has a melting point around 66 to 68 Celsius;

RT 70 HC which has a melting point around 69 to 71 Celsius.

Alternatively, a salt hydrate such as CH ₃ COONa.3H ₂ O - which has a melting point around 58 Celsius, and latent heat of 226/265 kJ/kg may be used, for example.

Thus far, the thermal energy store has largely been described as having a single mass of phase change material within a heat exchanger that has input and output circuits each in the form of one or more coils or loops. But it may also be beneficial in terms of rate of heat transfer for example, to encapsulate the phase change material in a plurality of sealed bodies - for example in metal (e.g. copper or copper alloy) cylinders (or other elongate forms) - which are surrounded by a heat transfer liquid from which the output circuit (which is preferably used to provide hot water for a (domestic) hot water system) extracts heat.

With such a configuration the heat transfer liquid may either be sealed in the heat exchanger or, more preferably, the heat transfer liquid may flow through the energy store and may be the heat transfer liquid that transfers heat from the green energy source (e.g. a heat pump) without the use of an input heat transfer coil in the energy store. In this way, the input circuit may be provided simply by one (or more generally multiple) inlets and one or more outlets, so that heat transfer liquid passes freely through the heat exchanger, without being confined by a coil or other regular conduit, the heat transfer liquid transferring heat to or from the encapsulated PCM and then on to the output circuit (and thus to water in the output circuit). In this way, the input circuit is defined by the one or more inlets and the one or more out for the heat transfer liquid, and the freeform path(s) past the encapsulated PCM and through the energy store.

Preferably the PCM is encapsulated in multiple elongate closed-ended pipes arranged in one or more spaced arrangements (such as staggered rows of pipes, each row comprising a plurality of spaced apart pipes) with the heat transfer fluid preferably arranged to flow laterally (or transverse to the length of the pipe or other encapsulating enclosure) over the pipes - either on route from the inlets to the outlets or, if an input coil is used, as directed by one or more impellers provided within the thermal energy store.

Optionally, the output circuit may be arranged to be at the top of the energy store and positioned over and above the encapsulated PCM - the containers of which may be disposed horizontally and either above an input loop or coil (so that convection supports energy transfer upwards through the energy store) or with inlets direction incoming heat transfer liquid against the encapsulated PCM and optionally towards the output circuit above. If one or more impellers is used, preferably the or each impeller is magnetically coupled to an externally mounted motor - so that the integrity of the enclosure of the energy store is not compromised.

Optionally the PCM may be encapsulated in elongate tubes, typically of circular cross section, with nominal external diameters in the range of 20 to 67 mm, for example 22 mm, 28 mm, 35mm, 42mm, 54mm, or 67mm, and typically these tubes will be formed of a copper suitable for plumbing use. Preferably, the pipes are between 22mm and 54mm, for example between 28mm and 42mm external diameter. The heat transfer liquid is preferably water or a water-based liquid such as water mixed with one or more of a flow additive, a corrosion inhibitor, an anti-freeze, a biocide, - and may for example comprise an inhibitor of the type designed for use in central heating systems - such as Sentinel X100 or Fernox Fl (both RTM) - suitably diluted in water. Thus, throughout the description and claims of the present application the expression input circuit should be construed, unless the context clearly requires otherwise, to include an arrangement as just described and in which the path of liquid flow from the input of the input circuit to its output is not defined by a regular conduit but rather involves the liquid flowing substantially freely within the enclosure of the energy store.

The PCM may be encapsulated in a plurality of elongate cylinders of circular or generally circular cross section, the cylinders preferably being arranged spaced apart in one or more rows. Preferably the cylinders in adjacent rows are offset with respect to each other to facilitate heat transfer from and to the heat transfer liquid. Optionally an input arrangement is provided in which heat transfer liquid is introduced to the space about the encapsulating bodies by one or more input ports which may be in the form of a plurality of input nozzles, that direct the input heat transfer liquid towards and onto the encapsulating bodies fed by an input manifold. The bores of the nozzles at their outputs may be generally circular in section or may be elongate to produce a jet or stream of liquid that more effectively transfers heat to the encapsulated PCM. The manifold may be fed from a single end or from opposed ends with a view to increasing the flow rate and reducing pressure loss.

The heat transfer liquid may be pumped into the energy store 12 as the result of action of a pump of the green energy source (e.g. a heat pump or solar hot water system), or of another system pump, or the thermal energy store may include its own pump. After emerging from the energy store at one or more outlets of the input circuit the heat transfer liquid may pass directly back to the energy source (e.g. the heat pump) or may be switchable, through the use of one or more valves, to pass first to a heating installation (e.g. underfloor heating, radiators, or some other form of space heating) before returning to the green energy source. The encapsulating bodies may be disposed horizontally with the coil of the output circuit positioned above and over the encapsulating bodies. It will be appreciated that this is merely one of many possible arrangements and orientations. The same arrangement could equally well be positioned with the encapsulating bodies arranged vertically. Alternatively, an energy store using PCM encapsulation may again use cylindrical elongate encapsulation bodies such as those previously described, but in this case with an input circuit in the form of conduit for example in the form of a coil. The encapsulation bodies may be arranged with their long axes disposed vertically, and the input 14 and output 18 coils disposed to either side of the energy store 12. But again this arrangement could also be used in an alternative orientation, such as with the input circuit at the bottom and the output circuit at the top, and the encapsulation bodies with their long axes disposed horizontally. Preferably one or more impellers are arranged within the energy store 12 to propel energy transfer liquid from around the input coil 14 towards the encapsulation bodies. The or each impeller is preferably coupled via a magnetic drive system to an externally mounted drive unit (for example an electric motor) so that the enclosure of the energy store 12 does not need to be perforated to accept a drive shaft - thereby reducing the risk of leaks where such shafts enter the enclosure. By virtue of the fact that the PCM is encapsulated it becomes readily possible to construct an energy store that uses more than one phase change material for energy storage, and in particular permits the creation of an energy storage unit in which PCMs with different transition (e.g. melting) temperatures can be combined thereby extending the operating temperature of the energy store. It will be appreciated that in embodiments of the type just described the energy store 12 contains one or more phase change materials to store energy as latent heat in combination with a heat transfer liquid (such as water or a water/inhibitor solution). A plurality of resilient bodies that are configured to reduce in volume in response to an increase in pressure caused by a phase change of the phase change material and to expand again in response to a reduction in pressure caused by a reverse phase change of the phase change material are preferably provided with the phase change material within the encapsulation bodies (they may also be used in energy banks using "bulk" PCMs as described elsewhere in this specification.

The present application contains a number of self-evidently inter-related aspects and embodiments, generally based around a common set of problems, even if many aspects do have broader applicability. In particular the logic and control methods, whilst not necessarily limited to operating with the hardware disclosed and may be more broadly applied, are all particularly suited to working with the hardware of the various hardware aspects and the preferred variants thereof. It will be appreciated by the skilled person that certain aspects relate to specific instances of other features and the preferred features described or claimed in particular aspects may be applied to others. The disclosure would become unmanageably long if explicit mention were made at every point of the inter-operability and the skilled person is expected to appreciate, and is hereby explicitly instructed to appreciate, that preferred features of any aspect may be applied to any other unless otherwise explicitly stated otherwise or manifestly inappropriate from the context. Again, for the sake of avoiding repetition, many aspects and concepts may be described only in method form or in hardware form but the corresponding apparatus or computer program or logic is also to be taken as disclosed in the case of a method or the method of operating the hardware in the case of an apparatus discussion. For an example of what is meant by the above, there are a number of features of both hardware and software relating to the combination of a fluid based (typically air source) heat pump and a phase change material and an electric supplementary heating element and control by a processor (within the unit or remote or both). Although this is the preferred application, most methods and hardware are more generally applicable to other heat pumps (thermoelectric and ground source) and to other renewable energy sources (a pump for a solar array for example) and to alternative supplementary heating (including the less preferred arrangement of a combustion heater such as a gas boiler, or even a less efficient higher temperature lower COP heat pump) and alternative thermal storage, including multi-temperature thermal storage arrays. Moreover, aspects which give particular arrangements for any of the components, or their interaction can be used freely with aspects which focus on alternative elements of the system.