EP2951522A1

EP2951522A1 - Heating system and thermal energy store

Info

Publication number: EP2951522A1
Application number: EP14701799.0A
Authority: EP
Inventors: Stuart J. CURTIS; Andrew Fogg; Simon HOLROYD; James SIMONDS; George R. SAVELL; Lucy A. SHELDON; Martin Betz
Original assignee: Basic Holdings
Current assignee: Basic Holdings
Priority date: 2013-01-31
Filing date: 2014-01-31
Publication date: 2015-12-09
Also published as: GB2510375A; GB201301773D0; WO2014118338A1; GB2510375B

Abstract

There is provided a heating system including one or more heat sources, a tank, and one or more heat sinks. The tank containing a heat transfer medium and an energy storage medium defining a thermal energy store, The energy storage medium comprising a phase change material and the phase change material is packed in pouches, and the pouches are arranged in the tank such that the heat transfer medium can at least partially flow around the pouches to charge and discharge them. According to another aspect a heat store is provided.

Description

Title

Heating system and thermal energy store

Field

The present application relates to a heating system and a thermal energy store. The heating system including means for preparation of domestic hot water.

Background

In the prior art a domestic hot water cylinder may be used as means for heat storage and as a source of domestic hot water. The dimensions of the water cylinder are typically selected to provide an adequate volume of hot water to a user (or household) within a prescribed time period- typically a 24 hour window. The energy used to heat the water within these known cylinders comes from a variety of sources including electrical, gas or oil powered boilers. It is also known to provide such cylinders with a primary source of energy and then use a secondary source for specific actions such as a top-up or where the primary source fails or is deactivated. Some issues around the supply of hot water from the cylinder include maintaining supply to meet demand, providing sufficient heat to provide water that is safe for domestic use, and providing a system having improved energy efficiency. For example, it is often necessary to heat the whole tank to achieve a desired water temperature even though a user may only require a limited amount of hot water at a particular time. There is also a need for an improved energy store and improved system for heating hot water.

There has been an increase in the availability of types of heat sources that may be connected to a domestic heating system. For example a local heat source might be connected into a household system to provide heating of hot water in a hot water cylinder and/or space heating means. However, in domestic and other settings, there remains a challenge of how to store energy. There is a need for improved energy storage and energy efficiency within a domestic or other heating systems.

Summary

The invention is aimed at addressing the above noted problems and others. Accordingly, there is provided a heating system defined in independent claim 1.

Advantageous features are provided in the dependent claims.

According to another aspect there is provided a heat store as defined in claim 57.

Advantageous features are provided in the dependent claims.

According to a first aspect there is provided a heating system comprising one or more heat sources, a tank, and one or more heat sinks, the tank containing a heat transfer medium and an energy storage medium defining a thermal energy store, the energy storage medium comprising a phase change material, wherein the phase change material is packed in pouches, and the pouches are arranged in the tank such that the heat transfer medium can at least partially flow around the pouches to charge and discharge them. The pouches are preferably configured to provide optimal heat transfer and extraction such that the molecules of the phase change material are provided close to the heat transfer surface for contact with the heat transfer medium. The phase change material may be provided packaged in pouches on a sheet support or provided packaged in pouches connected by string. The vertical extent of the pouches may be limited to prevent convection or to prevent separation of the PCM. The vertical extent of the pouches may be limited to substantially 50mm or less. The pouches may have a depth of less than 20mm and having a low temperature differential in the phase change material across the depth of the pouch. The pouches may have a depth in the range of 5 to 20mm, preferably 8-12 mm, most preferably 10mm. In one arrangement the pouches are formed of a plastics material. The pouches may comprise a coat for example, an aluminium coating to prevent ingress of the heat transfer medium into the pouches.

The thermal energy store may have one or more temperature zones with a temperature differential between different temperature zones. The tank may have an upper portion and a lower portion, the upper portion providing a hot temperature zone and the lower portion providing a medium temperature zone. The upper portion may have a temperature in the range of 50 -60 degrees Celsius, preferably in the range of 55- 60 degrees Celsius. The lower portion may have a temperature in the range of 35-45 deg C, preferably of the order of 45 degrees C. The tank may include one or more different phase change materials of different operating temperature in the different zones or areas thereof.

The one or more heat sinks may include a fresh water station to provide sanitary hot water on demand, wherein the fresh water station comprises a heat exchanger fuelled directly by thermal energy from the tank for heating water. Preferably, hot water from the hot zone or upper portion of the energy store is provided to one side of the fresh water station heat exchanger and fresh water from the mains supply is pumped through the other side of the fresh water station heat exchanger. In one arrangement, after hot water from the hot zone of the tank has passed through the heat exchanger it is returned to the lower portion of the tank. According to one arrangement, the heating system comprises a controller having control means for controlling operation of the thermal energy store and connected heat sources and heat sinks. Preferably, the controller comprises a single integrated controller for controlling the heat store, heat sources, and heat sinks. Preferably, the controller comprises communication means for communicating internally with the heat sources and heat sinks, and for communicating externally with utilities. Optionally, the controller comprises a user interface to allow the user monitor the operation of the system. Optionally, the controller is configured to adaptively learn the energy usage patterns of the user. Optionally, the controller is configured to determine the amount of heat that needs to be stored to meet the energy or heating requirements of a heat sink to which it is coupled. Optionally, the controller controls demand side management such that the tank energy store is charged during off peak periods or heat sources are turned on/off as required to build back up the store of energy. Optionally, controller controls the freshwater station, wherein flow rate and temperature data are provided as an input to the controller which processes this data to control the speed of the pump of maintain a constant hot water temperature. Optionally, the controller includes a self-learning algorithm to enable automatic setting of the pump speed for future operation. According to another arrangement the one or more of heat sinks include a space heater wherein the space heater is connected to the medium temperature zone of the tank. Optionally, the heat sources include one or more of a solar PV, a solar thermal, and heat pump. Optionally, the system uses the excess electricity of the PV for charging the heat store. Optionally, a heat source is connected to the tank to heat a particular zone of the tank. Optionally, a heat source is used to heat the tank from the upper part downwards. Alternatively, a heat source is used to heat the tank from the bottom part upwards.

In one arrangement the energy storage medium comprises a phase change material having a high energy storage density. The phase change material may a high mass energy storage density in the range of 150-300kJ/kg, preferably in the range of 200- 250kJ/kg. The phase change material may have a high mass energy storage density of the order of 210kJ/kg. The phase change material may have an operating temperature in the range of 35 to 60 degrees Celsius, preferably in the range of 45-60 degrees C. The phase change material may comprise a phase change material having an operating temperature of substantially 46 degrees Celsius, or a phase change material having an operating temperature of substantially 55 degrees Celsius or phase change material having an operating temperature of substantially 58 degrees Celsius. According to one arrangement the thermal energy store has a thermal energy capacity of latent heat in the order of 20 -30KWH. The thermal energy store may have a power output of 5-60KW, depending on load. The thermal energy store has an output temperature of the order of 35 to 60 degC, most preferably 40 to 55 degC. Tank having dimensions of the order of a typical domestic hot water cylinder, for example a 3001 cylinder. In one arrangement, the heat transfer medium is water and the tank is configured such that the water circulates throughout the volume of the tank and at least partially in contact with the pouches containing the phase change material. Optionally, the pouches of phase change material are optimised for heat extraction such that the molecules of the phase change material are provided close to the heat transfer surface. The geometry of the pouches may be optimised for heat transfer out of the pouches at a desired rate. In one arrangement, the pouches are provided in modular form. According to another aspect, the tank is comprised of a plurality of inter-connectable tank modules, which are connected to provide the thermal heat store. Optionally, the tank modules comprise connection means for connecting tank modules mechanically and to provide a hydraulic connection. In one arrangement the tank modules contain a energy storage medium, comprising a phase change material provided packed in pouches, and the pouches are arranged in the tank modules such that a heat transfer medium can at least partially flow around the pouches to charge or discharge energy to or from the energy storage medium. In one arrangement the tank is decoupled from the connected heat sinks and heat sources via heat exchangers. In one arrangement the tank is sized and shaped to fit in the space usually provided for a domestic hot water cylinder. In another arrangement, the tank is configured for retrofitting into a heating system to replace an existing hot water cylinder.

According to another aspect there is provided a heat store for storing thermal energy comprising a tank containing a phase change material and a heat transfer medium, wherein the phase change material is packed in pouches, and the pouches are arranged in the tank such that a heat transfer medium can at least partially flow around the pouches to charge or discharge the phase change material therein. In one arrangement, the heat store is configured to store energy for preparing sanitary hot water and for space heating. In one arrangement, the tank is sized to fit in the space usually provided for a domestic hot water cylinder. Preferably, the tank is configured for installation into a heating system to replace a hot water cylinder and to perform the functions of a hot water cylinder. Preferably, the pouches are configured to provide optimal heat transfer and extraction such that the molecules of the phase change material are provided close to the heat transfer surface for contact with the heat transfer medium. In one arrangement, the phase change material is provided packaged in pouches on a sheet support or connected by string. In one arrangement, the vertical extent of the pouches is limited to prevent convection. The vertical extent of the pouches may be limited to substantially 50mm or less. Preferably, the pouches have a depth of less than 20mm and having a low temperature differential in the phase change material across the depth of the pouch. In a preferred arrangement, the pouches have a depth in the range of 5 to 20mm, preferably 8-12 mm, most preferably 10mm. The pouches may be formed of a plastics material. The pouches may comprise a coating. The pouches may comprise an aluminium coating to prevent ingress of the heat transfer medium into the pouches. In one arrangement, the heat store may have one or more temperature zones with a temperature differential between different temperature zones. Optionally, the tank may have an upper portion and a lower portion, the upper portion providing a hot temperature zone and the lower portion providing a medium temperature zone. The upper portion may have a temperature in the range of 50 -60 degrees Celsius, preferably in the range of 55- 60 degrees Celsius and the lower portion may have a temperature of the order of 35-45, preferably 45 degrees C. The tank may include one or more different phase change materials of different operating temperature in the different zones or areas thereof. In one arrangement, the tank is comprised of a plurality of inter- connectable tank modules, which are connected to provide the thermal heat store.

Preferably, the tank modules comprise connection means for connecting tank modules mechanically and to provide a hydraulic connection. In one arrangement, the tank modules contain an energy storage medium, comprising a phase change material provided packed in pouches, and the pouches are arranged in the tank modules such that a heat transfer medium can at least partially flow around the pouches to charge or discharge energy to or from the energy storage medium. In one arrangement, the thermal energy store has a thermal energy capacity of latent heat in the order of 20 - 30KWH. In one arrangement, the thermal energy store has a power output of 5-60KW, depending on load. In one arrangement, the thermal energy store has an output temperature of the order of 35 to 60 degC, most preferably 40 to 55 degC.

According to a further aspect, there is provided a heating system comprising one or more heat sources, a tank for storing thermal energy and one or more heat sinks, wherein the tank contains a phase change material and wherein the tank is decoupled from the connected heat sinks and heat sources via heat exchangers.

According to a further aspect, there is provided a heating system comprising one or more heat sources, one or more heat sinks and a thermal heat store, the one or more heat sources including a solar PV, and the system comprising a single integrated controlled for controlling operation of the system including to effect charging and discharging of the heat store. In one arrangement, the system uses the excess electricity of the PV for charging the heat store.

According to a further aspect there is provided, a tank for a heating system, the tank comprised a plurality of inter-connectable tank modules, which are connected to provide the thermal heat store. Preferably, the tank modules comprise connection means for connecting tank modules mechanically and to provide a hydraulic connection.

These and other features will be better understood with reference to the following drawings. Brief Description Of The Drawings

The present application will now be described with reference to the accompanying drawings in which:

Figure 1 is a schematic showing an exemplary domestic heating system according to the present invention including a tank according to the present specification;

Figure 2 is an isometric view of an energy storage medium/heatable material comprising a packaged phase change material for use in the tank according to Fig. 1 according to an exemplary embodiment;

Fig. 3 is a cross-sectional view of the energy storage medium/heatable material of Fig. 2.

Fig. 4 is a graph illustrating water energy loss on melting a phase change material sheet according to an exemplary arrangement of the present specification;

Fig. 5 shows energy release from an exemplary phase change material sheet;

Fig. 6 shows the effect of thickness of pouch used as packaging in a preferred exemplary arrangement on time to melt in water at 50 degrees C.

Fig. 7 is an illustration of a thermal transfer fluid passing through cell comprising a number of interconnected PCM packages. Fig. 8 is a schematic diagram showing an exemplary domestic heating system 100 in accordance with the present specification.

Fig. 9 is a schematic diagram showing an exemplary domestic heating system 100 in accordance with the present specification.

Figs. 10 and 11 are schematic diagrams showing exemplary system 100 including a fresh water station.

Figs. 12 and 13 are graph showing firstly flow rates and percentage of total volume drawn off for water a different temperatures, and secondly flow and return between the thermal store and heat exchanger.

Figs 14A, B, C and D are illustrations of a tank 1210 in accordance with an exemplary arrangement of the specification.

Figs 15 A, B, C and D are illustrations of a tank 1110 in accordance with an exemplary arrangement of the specification.

Fig 16 is a graph showing data from operation of an exemplary arrangement of the specification.

Detailed Description Of The Drawings

Referring to Fig. 1 an exemplary system 100 is illustrated. The system 100 is a heating system and includes tank 110. The system 100 also includes heat sources 130 and heat sinks 150. The heating system 100 may for example, be a domestic heating system or other building system. Heat sources 130 may include a solar PV heat source 131, a solar thermal heat source 132, or heat pump 133. The system 100 may include one or more heat sources 130. Heat sinks 150 may include space heating means 151 and fresh water station 152 connected to domestic hot water supply means 153. The system 100 may include one or more heat sinks 150.

The tank 110 is configured to contain an energy storage medium and a heat transfer fluid. The energy storage medium may comprise a heatable material. The heat transfer fluid may be water. The heat transfer fluid flows throughout the volume of the tank in at least partial contact the energy storage medium. The tank 110 containing the energy storage medium and the heat transfer fluid defines within the system 100 an energy store 111 and an energy source. In the present specification, the terms tank and heat store, energy store, thermal energy store and energy source are used essentially interchangeably. The tank 110 is arranged primarily to store energy in the form of heat. The tank 110 acts as an energy store 111 for thermal energy drawn from heat sources. The tank 110 acts as an energy source for the heat sinks for example, for space heating and the fresh water station. The tank 110 is configured to limit or prevent loss of energy by means of insulation.

Referring to Fig. 1 an exemplary arrangement of the tank or thermal store 110 in system 100 in accordance with the present specification is described. Tank 110 has a housing 111 for containing energy storage medium 160 is provided. The energy storage medium 160 comprises a thermal storage material. The energy storage medium 160 is heatable and charged by heat sources 130 connected to the tank 110 to effect storage of thermal energy therein. The tank has an upper part 114 and a lower part 115. The tank 110 may include one or more temperature zones. A temperature differential is provided between different temperature zones or areas thereof. For example, in one exemplary arrangement the tank may include two temperature zones, namely a hot zone 120 and a relatively cooler or medium temperature zone 125. The tank 110 as shown in the exemplary arrangement comprises a substantially vertical arrangement the hot zone 120 being located near the upper side and the cooler medium temperature zone 125 being located to the lower side thereof.

The tank 110 may be a stratified heat store. For example the tank 110 having two temperature zones may include different energy storage mediums 160, for example a primary thermal storage material and a secondary thermal storage material. In one exemplary arrangement, the hot and medium temperature zones 120, 125 are provided through stratification as the heat store or tank 110 builds up heat, for example, by use of a mesh 181 or other boundary layers 182. The tank 110 may include a combination of stratification and energy storage medium 160.

In the exemplary arrangement of present specification and the drawings including Figs 1 to 3, 7 to 9, 10 and 15, the energy storage medium 160 is a phase change material (PCM) 170. Different phase change materials may be provided in the different heat/temperature zones of the tank.

In the exemplary arrangement according to the present specification, the phase change material 170 is packed in pouches 175. An exemplary arrangement of pouches 175 containing PCM 170 is illustrated in Figs. 2 and 3. The PCM 170 in pouches 175 is provided for arranging in the tank and is configured as the thermal storage medium in the heat store or tank 110. Thermal transfer fluid 165 is provided for both charging and discharging of the thermal energy store 110. The terms thermal transfer medium, thermal transfer fluid, thermal energy fluid and thermal energy transfer fluid have been used essentially interchangeably in the specification. In a preferred exemplary arrangement, the thermal transfer fluid is water. Pouches 175 are arranged in the tank such that the thermal transfer fluid circulates in at least partial contact with the pouches. The thermal energy transfer fluid 165 flows around and between the pouches 175 within the internal volume of the tank. The pouches are configured to optimise contact between the PCM and the contact surface for heat transfer. The pouches 175 have a depth (front to back) of less than 20mm. The pouches may have a depth in the range 5- 20mm. The pouches may have a depth in the range of 8- 12mm. In a preferred exemplary arrangement the pouches may have a depth of 10mm. In the arrangement of Fig. 2 and 3, the pouches are provided on sheets 176. The heat transfer fluid will flow around and between sheets contacting the front and rear surface of the sheets and the pouches. It will be appreciated that various geometries and forms of pouch 175 may be provided as appropriate for particular applications. The pouches 175 have a depth of less than 20mm. In the arrangement of Fig. 2 and 3, the pouches are provided on sheets 176 and the heat transfer fluid will flow to the front and rear of the sheet contacting the front and rear surface of the sheets and the pouches. The pouches 175 are configured to optimise contact between the PCM and the contact surface/heat transfer surface for heat transfer. The geometry of pouches and their arrangement in the tank 110 is optimised for heat transfer out of the pouches 175 at a desired rate.

The pouches 175 may be of a plastics material. A plastics material having suitable resistance to the PCM 170 is used. This avoids any corrosion problems. The material of the pouches is also selected to assist with heat transfer. The pouches may further comprise a coating. The coating may comprise an Aluminium coating. The Aluminium coating is provided to limit or prevent ingress of water into the pouches. The pouches 175 may be provided arranged in modular form or modular packs. The pouches in modular form provide for ease handling and ease of installation of the tank 110 to provide a thermal heat store. The tank may be installed as an empty tank

(advantageously at light weight) which is then be populated with the PCM 170 after installation. The modular arrangement also permits for selection or tailoring of the type PCM 170 to particular applications and requirements. Further provision of the PCM 170 in modular form provides for the use of more than one PCM 170 in the same tank 110. The use of the PCM 170 in modular form also provides for the efficient production of a range of thermal energy stores of different capacities. In practice when energy is put into a PCM 170 in pouch 175, the PCM melts next to the heat exchange surface of the pouch first. The liquid PCM transfers heat much better than the PCM in solid form. When extracting energy from the store, the PCM freezes on the heat exchange/transfer surface first and may accordingly create an insulating blanket on the heat exchange/transfer surface. To improve heat extraction, packaging 175 (176) is configured so that each molecule of the solid PCM 170 is provided as close as possible to the heat transfer surface. The PCM 170 as shown in exemplary Figs 2 and 3 packaged in thin pouches 175 in sheets 176 of plastic film immersed in water is effective. Further, the packaging 175, 176 obviates the need for complex surface forms. The arrangement has also been found to be advantageously more effective and efficient than providing a PCM 170 in bulk volume in a heat exchanger tank and passing water through the heat exchanger tubes.

The exemplary arrangement of Figs. 2 and 3 the present specification allows energy from the PCM 170 in sheet 176 to be discharged in a few minutes. The sheet 176 may be scaled as required to make them larger and/or vary the number in a tank 110 such that the thermal store can be discharged at the required rate. Further the exemplary sheet 176 packaging method as described provides a good volume fraction of PCM 170 in the store 110, advantageously permitting the store 110 to be compact for its thermal energy storage capacity. It will be appreciated that while exemplary arrangements of packaging 175, support structures 176, water flow rates and flow paths of the present specification has been described, different alternative arrangements may also be used to achieve the required performance.

The tank 110 containing the PCM and heat transfer fluid defines the thermal energy store 111. The PCM pouches 175 are advantageous from the point of view of achieving a volume fill fraction. A volume fill fraction of PCM 170 can be provided in tank 110 to provide thermal storage densities around double that of liquid water in a hot water tank of similar size.

The tank 110 and thermal energy store 111 is configured taking account of the energy storage requirements and load requirements of a heating system. The provision of a PCM 170 in tank 110 provides a high thermal storage density for a thermal store 110 having size generally equivalent to a DHW tank. The dimensions of the tank 110 are selected for conformity with typical hot water cylinders/tanks. The tank 110 may be configured for retrofitting to a heating system to replace a hot water cylinder/tank. The size is similar to current domestic hot water (DHW) tanks. The tank 110 is configured to take over the functions of the DHW tank. In one exemplary arrangement, tank or thermal store 110 may be provided configured to replace a DWH. Tank 110 properties include a 20kWh latent heat store target and parameters include a 3001 water store capacity; Diameter 580mm, Height 2000mm, approx. 400kg of PCM, for example divided into 25kg packets or <30kg packets would be required.

In an exemplary arrangement, the system 100 and heat store 110 may be an unvented, having normal operating pressures of up to 3 Bar, accordingly the thermal store is configured to withstand 6 Bar maximum pressure.

Advantageously, as noted above, the tankl 10 or thermal store 111 is specially configured for retrofitting to existing buildings. More particularly, the tank or thermal store is configured for retrofitting to an existing heating system such as a domestic heating system. The tank or thermal store comprises connection means for connecting to existing pipe work, heat sinks and heat sources. Size of the thermal store (relative to the equivalent water tank) is a key parameter, together with the ability to place the tank/ store in position empty and put the relatively heavy PCM in place afterwards.

Advantageously, the tank 110 and separately packaged PCM 170 as described in the present specification do address such requirements.

The thermal energy store as provided by tank 1 10 with energy storage medium for example, PCM 170, address the requirements of network utilities by virtue of the high thermal storage densities provided. For example, taking account of increasing requirements for peak load limitation as the electricity utilities place increasing emphasis on peak load limitation (taking account for example, of how use of heat pumps for domestic space heating becomes more prevalent), and as domestic solar energy installations become more common. The tank 110 and thermal store 111 also address increasing requirements from the utility side arising from frequency monitoring from which requirements to affect local storage may arise.

The operating temperature of the thermal energy store 111 is determined by the selection of phase change material 170. The exemplary arrangement described providing pack/pouches 175 of the PCM 170 which allows the use of for example, any salt hydrate, and many organic PCMs. Such arrangement thereby advantageously allows considerable freedom in the choice of operating temperature, or of different operating temperatures for different zones of the tank. Further as described, the arrangement of the present specification allows for the use of more than one PCM 170 in the same heat store or tank 110 which is advantageous in some applications.

For example, in one arrangement according to the present specification a PCM comprising a salt hydrate PCM 170a having a high mass energy storage density and also a volumetric storage density (210 kJ/kg, 333 kJ/litre) having a phase change

temperature of 46°C is used. This temperature is also the operating temperature for the preferred PCM 170a (S46). In an alternative arrangement, phase change material 170b comprising for example sodium acetate trihydrate having a phase change temperature of 58°C is used. (Both PCM 170a and 170b could be provided arranged in different zones of tank 110.) Taking account that different heat sinks may have different temperature requirements, one heat sink may be optimally connected to a relatively hot zone and another heat sink may be optimally connected to a relatively cooler zone.

The example, phase change temperatures and operating temperatures noted above are convenient temperatures for initial use with heat sources, for example, heat pump 133. In some applications (eg underfloor heating driven by a heat pump) a lower temperature e.g. 46°C may be used, to the advantage of the heat pump's co-efficient of performance (COP). For domestic hot water, for example, a fresh water station 152 heat sink might require a higher temperature, for example using a phase change material 170b comprising sodium acetate trihydrate at 58°C. Therefore, as noted the thermal energy store may comprise two or more different temperature zones, e.g. having different phase change materials for connecting to heat sinks having different temperature

requirements. In a preferred exemplary arrangement according to the present specification a heat store or tank 110 having a thermal capacity of the order of 20k Wh latent heat is provided. Such arrangement has target extraction rates in the range of 5kW to lOkW. For example using an exemplary PCM 170, for a 20k Wh store 293kg of salt hydrate would be used having the ability to provide around lOkW for two hours or, with a different flow rate, 5kW for four hours. Reference is made to Figs. 4 and 5. Different packaging geometries and flow rates may be used as required. Similarly different phase change materials 170 may be used as required.

Considering one exemplary arrangement of PCM packaging geometry of the present specification as described, heat store 110 is provided with a volumetric fill fraction of around 70%. To store 20kWh (72MJ) in S46 requires 343kg (216 litres) of the salt. A fill fraction of 70% indicates a total tank internal volume of 309 litres, giving 93 litres and hence 93 kg of water. A 20kWh latent heats store will have contents with a mass of 436kg and a volume of 309 litres, to which the mass of the actual tank and PCM support fittings and the volume of external insulation are added. The end result will be a thermal store 110 which advantageously weighs less than a 500 litre domestic hot water cylinder and has about 60% of the volume. For 20kWh (72MJ) store this corresponds to a mass energy density of around 153kJ/kg (roughly equivalent to water over a 40°C operating range) and a volumetric energy density of around 206kJ/litre (water over a 50°C range).

The PCM energy storage medium 170 is advantageously durable and maintains thermal performance. Many of the tank/heat store components use existing, proven materials and construction. The system is advantageously sustainable. The tank may be of steel with insulation, which can be recycled by the usual route. The PCM support structure may be engineered in a recyclable material. The PCM packaging is a suitable plastic film; a recyclable polymer may be chosen. The PCM comprises a salt hydrate. The PCM as such can be reprocessed and reused; most salt hydrates are benign substances, so small losses to the environment will be harmless. (Sodium acetate trihydrate, for instance, is edible.)

When using salt hydrates segregation of the salt after multiple cycles of freezing and thawing can be an issue. In the packaging of the present description, the vertical dimension of the salt pockets has been restricted. Limiting the vertical height of the body of PCM provides that convection cannot become established. For example, for some particular phase change material the height dimension of the packaging may be limited to substantially 50mm or < 50mm. Further, with this configuration and if the upper operating temperature of the salt is not exceeded then the issue of segregation should not occur. Further the service life of the salt should be essentially infinite.

The arrangement of heat store/ tank 110 provides for extraction of energy from the store 110 and in particular the PCM 170 at an adequate rate and using a tank 110 of reasonable capacity and size. The arrangement according to the present specification obviates the need for the store to have a much higher capacity (and hence size, mass and cost) for the same energy. As noted above the tank 110 and energy storage medium 160 may be provided for retrofitting. The tank 110 is provided for fitting empty and as described above the PCM is provided for adding with the tank in place. The tank is provided with an opening and removable cover. In one arrangement the removable cover may be a removable lid. The tank includes sealing means for sealing the lid for use.

Effectively, as discussed above, the PCM 170 is configured taking account of factors including: storage capacity, and manufacturing costs. For example, when providing a store with a thermal capacity of 20k Wh and having target extraction rates between 5kW to lOkW. Parameters to be considered include: Charge time for the heat store; amount of energy that can be charged; energy loss during stagnant periods (heat loss); rate at which energy can extracted and distributed to the house; potential energy savings can be achieved through an integrated approach.

In addition to the above noted PCMs, different exemplary PCMs may be provided, as follows:

PCM 170c having melting temperature of 46°C,

PCM 170d having melting temperature above 50°Ce.g. C58 which has a melting temperature of 58°C

In one exemplary arrangement, a PCM having relatively large energy density, comprising small crystals and configured such that there is no or limited segregation, having a 55 degree latent heat was provided.

In alternative exemplary arrangements, an energy store according to the present specification may be configured to contain phase change material in different temperature ranges packed in pouches 175, for example, comprising change material in the range of 5degC to 18 degC configured to store energy and in which exemplary case, the stored energy may be reused or provided as output for cooling. The advantages of the packs/pouches 175 of phase change material as described in the present

specification would also apply in such application with the advantageous transfer of energy at the energy transfer surface of the pouches. In an alternative exemplary arrangement the phase change material may comprise water, which can be used to store energy and for cooling.

Example 1

Exemplary thermal store 110 in accordance with the present specification: A thermal store 110 is configured for installation in a system 100, typically a domestic heating system. The thermal store has a storage capacity of the order of 30 KWH of which 22KWH latent. The thermal store has a power output: of the order of 20KW sustained and of the order of 60 KWmax. The thermal store has an output temperature of the order of 55 degrees Celsius. The thermal store 110 as energy store for system 100 is configured to deliver domestic hot water DHW and space heating function. The thermal store has typically a 20 year life. Charging of the thermal store 110 is by heat sources 130 for example, heat pump, solar, immersion or combination. The thermal store 110 is configured and insulated such that heat loss is less than 10% stored heat in 24 hrs. The thermal store is dimensioned and shaped to fit into standard 'airing cupboard' space (0.6m^A2 x 2.1m). The thermal store is configured for retro-fiting, having components of <30kg, the components being configured for assembly on site.

The Phase Change Material (PCM) 170 of the thermal store 110 is judiciously configured to meet energy store and supply requirements. The PCM 170 has excellent energy storage density e.g. comparable to batteries. It is noted that PCMs typically range from 30< to <100 Wh/Kg Being a salt hydrate, PCMs typically aggressively attacks some metals including standard pipe copper. The PCM is contained and packaged for the present application. Further the PCM 170, PCM packaging 175 and thermal store 110 are all configured to provide for the required heat in and out.

Special arrangements of the PCM and packaging are provided to take account of, for example, low thermal conductivity. The packaging 176 is arranged such that every portion or molecule of PCM 170 is as close as possible to a molecule of heat transfer fluid (for example, water), see for example, Fig. 7. The packaging comprises sheets surface area for heat transfer of increased speed and efficiency. The packaging provides thin PCM sections for low temperature variation across the depth of the pouch.

The packet material provides for use of the packets and PCM for a lifetime of the order of 20 years in hot water, taking account of the salt material which constitutes a very aggressive environment. Taking account of the user environment of the packaged PCM structural supports may be provided such that the packets are supported as required and kept separate for flow. Packets need to be tightly packed to get maximum PCM volume and to provide a high packing density. Various forms of packet separators have been provided. Packet separators may comprise gridded plastic packet separators configured to provide resistance to crushing, manufacturability and minimal impedance to flow. In one optional arrangement end supports for the packets and separators may be provided.

Referring to Figs. 1, 7, 8 and 10 the heating system 100 and the related operation for heat storage and management of heating a domestic environment are described.

This heat storage process is a key component of the overall heat/thermal store or tank 110. By the arrangement of the heat store and connection of heat source or heat sources 130 to the heat store a heat source 130 may be used to heat from the upper part 114 of the heat store 110 down. (Heating may also be from the lower part to the upper part 114, depending on the configuration of connections to heat sources.)

As noted previously, in the prior art a DHW tank is typically heated from the bottom up. In a DHW tank, it is necessary to heat the whole tank to achieve a desired water temperature. The arrangement of the present specification thus provides an alternative heating process.

Heat source 130 is provided to charge the heat store 100. One or more renewable heat sources 130 may be combined to charge the heat store, including as follows:

· Heat Pump (air or ground source) 133

• Solar Thermal 132

• Solar PV 131 in conjunction with Solar PV Optimiser 134 Heat sources 131, 132, 133 are connected to the heat store 110 via different respective elements. The Solar PV 131 is connected to the heat store 110 via a Solar PV optimiser 134. The Solar PV optimiser 134 is configured to optimise delivery of energy to the heat store or tank 110 from the Solar PV source 131. PV optimiser 134 is a current transducer which communicates with a heating element with variable output.

The heat store 110 is configured to store energy in the region of 20kwh latent heat. The heat store 110 may be arranged to provide energy storage in 2 zones. Heat store 110 includes an upper part 114 and lower part 115. The upper part 114 provides the hot zone 120 (high temperatures 50-65 degC, most preferably 55-60degC). The lower part 115 provides the cooler zone 125 (medium temperature 30 -50 degreesC, preferably 40- 48degC, most preferably 45degC). The heat store 110 of a preferred embodiment includes a smart controller 118.

Controller 118 controls operation of the heat store 110, heat sinks and heat sources.

Controller and controls communication and interaction with connected components.

Controller 118 is a single integrated controller for providing integrated control of all connected components taking account of load requirements, heat source outputs and data from the utility side.

Communication includes the following:

External communications (sending/receiving) to utilities companies. These could be used to ensure that heat sources (such as Heat Pumps) cannot be turned on at peak time.

Internal communications to the heat sources and heat sinks.

In an exemplary arrangement according to the present specification, the internal heat sources 130 are arranged to communicate directly with the heat store 110, for control and energy transfer. The controller advantageously manages the energy flow to and from the energy store and heat sources to ensure the most efficient use of the energy of the heat store and heat sources, depending on availability and demand. Controller 118 is also arranged for access by the home user for monitoring purposes. The controller 118 may adaptively learn the usage patterns of the user and ensure that it has enough heat for all requirements. The controller may determine the amount of heat that needs to be stored in order to meet the usage requirements of the devices to which it is coupled. This may be achieved through historical monitoring of the energy required to meet the desired operating temperature of the room. The heat store may be used to store energy and to absorb additional energy capacity available within a system or network during periods of excess availability. The energy stored thereby serves to providing the desired heat- be that space heating or heating of domestic hot water. The controller 118 may also be configured to monitor the actual usage of the heat sinks within the heating system and the capacity of the system to provide sufficient energy to adequately heat space or water as required. Controller 118 is configured to run a control algorithm to eliminate the requirement for an additional controller and to make performance optimization of the entire system easier. The heat store and controller is provided as part of an overall fully integrated system.

Similarly, heat sinks 150 may be controlled by the controller 118. The heat sinks 150 may include fresh water station 152 and space heating 151. Fresh water station is 152 comprises a pump and heat exchanger. Fresh water station is arranged such that fresh water from mains supply is pumped through one side of a heat exchanger 154. Hot water from the hot zone 120 or upper part 114 of the heat store 110 is provided to the other side of the heat exchanger 154. After the hot water has passed through the heat exchanger 154 it is returned to the lower part 115 (cooler) medium temperature zone 125 in the heat store/tank 110. The fresh water station 152 is provided by a heat exchanger fuelled directly by the tank. It is coupled directly to the tank and derives energy from the arrangement of the energy store of the tank.

The heating system 100 of the present specification having an energy store of high capacity provides for different work streams for the management of charging, heat or thermal energy storage, and energy extraction. The heat store or thermal store 110 defines a key component of the overall system. The heat store 110 provides an enhanced energy storage capacity. The Heat store 110 may be integrated into an existing heating system, to replace a conventional hot water cylinder. The system comprises a controller 118, for controlling charging from heat sources. The system controller 118 also controls discharging to heat sinks.

Referring to Figs. 9 and 14 an alternative tank or thermal energy store 1 110

arrangement according to the present specification, is described. Tank/thermal energy store 1110 is comprised of a plurality of tank modules 1150 (comprising tank cells 1151). The tank modules 1150 or tank cells 1151 are inter-connectable. The tank modules 1151 are connected to provide the thermal energy store 11 10. Thermal energy store 1110 has external walls 1155 and base 1157. Thermal energy store 1110 may include central support 1156. Tank modules 1150 comprise connection means 1160 for connecting tank modules 1150 mechanically and to provide a hydraulic connection. The tank or thermal store 1110 is configured for ease of installation for retrofitting on site. Tank or thermal store 1110 comprises an unpressurised thermal store. The tank modules 1150 contain a energy storage medium, comprising a phase change material 170 provided packed in pouches 175, and the pouches are arranged in the tank modules 1150 such that a heat transfer medium 165 can at least partially flow around the pouches to charge or discharge energy to or from the energy storage medium. The tank 1110 also comprises connection means 1170 for connection in the heating system 100.

The tank 1110 of the exemplary arrangement of Fig. 9 is decoupled from the connected heat sinks 150 and heat sources 130 via heat exchangers/pumps 1115. Accordingly, the tank/thermal store 11 10 is isolated from and has a barrier to salt entering the heating circuit or heat source circuits. Therefore, any leak of a PCM material would be contained and prevented from entering and contaminating the heating circuit or heat source circuits. The tank modules 1150 have different forms may be provided and may be arranged in different configurations to allow for example, a tank 1110 of a substantially square form or square cross section. The modular thermal store 1110 advantageously provides a cheaper arrangement from the point of view of manufacture and installation, increased flexibility and more space efficient. The end load is lower and the modular thermal store has lower strength requirements for example in comparison with a hot water cylinder.

Thermal store 1110 is unpressurised. Thermal store 1110 therefore is advantageously not directly linked to the heating system. The store 1110 comprises a vented store. The modular arrangement of store 1110 provides for expansion. Referring to modular heat store 1110, of Fig 12, one module 1215 out of 18, comprises 4 layers of 11 packets/pouches 175 and 12.3kg of PCM 170. Therefore typical parameters of heat store 1110 include a 40Kw (2.2) max steady power output,

103000KJ (5700) energy storage at At of 40 degrees and Latent energy of 240 Kj/Kg). Referring to Figs. 8 and 15, a modular thermal store 1210 of an alternative arrangement according to the present application is described. Tank/thermal energy store 1210 is comprised of a plurality of tank modules 1215 (tank cells 1215). The tank modules or tank cells are inter-connectable. The tank modules are connected to provide the thermal energy store 1210. Tank modules comprise connection means 1226, 1227 for connecting tank modules mechanically and connection means comprising and inlet and outlet 1228, 1229 to provide a hydraulic connection. The tank or thermal store 1210 is configured for ease of installation for retrofitting on site. Tank or thermal store 1210 comprises an unpressurised thermal store. The tank modules 1215 contain an energy storage medium, comprising a phase change material 170 provided packed in pouches 175, and the pouches are arranged in the tank modules such that a heat transfer medium 165 can at least partially flow around the pouches to charge or discharge energy to or from the energy storage medium. Similarly to tank 110 (having zones 120 and 125), tank 1210 may comprise one temperature zone or two or more different temperature zones 1220 and 1225. There is provided a temperature differential between zones.

Referring to Figs. 14 the tank 1110 comprises 18 modules tank modules 1115 effectively behaves in manner similar to the overall tank, and contains pcm material and heat transfer fluid circulating throughout the volume of the module. Tank 1210 of for example Figs 9 and 15 comprises a similar modular arrangement.

Thermal stores 1110 and 1210 provides an increased space efficiency, being configured for stacking and further has reduced support structure. The pouches 175 of PCM 170 are not packed into a large volume per tank 110, in the exemplary arrangements of 1110 and 1210, the pouches are packed in modules 1150/1151 and 1215

Referring to Figs 15 thermal store 1210 comprises a stacked configuration of modules 1121 and 1122. As illustrated the modules are packed with PCM material 170 in cells 1215. Different PCM materials may be provided in different modules 1221 and 1222 to provide a temperature differential. For example, the lower modules 1222 may be packed with a PCM of lower melting temperature than modules 1221. The thermal stores 1110 or 2110 are connected to the domestic hot water or heating system for example as shown in Figs. 8 or 9. The flow of water through the tank effects charging and discharging of the PCM. For tank modules 1150/1151 and 1215 of tanks 1110 and 1210, the module housing 1270 may be a plastics material for example, PP, ABS and CPVC. The thermal stores 1110 or 1210 are unpressurised.

Three plastics were identified as potentially suitable for modules: PP, ABS and CPVC. No adverse chemical interactions between the material and the salt or water below 70 degrees were noted. In one exemplary arrangement a 5mm ABS was used as the material for the tank walls. Medium-high impact acrylic was also used as an alternative to the aforementioned materials. It will be appreciated that other suitable plastics materials may also be used

An energy store 110, 1110 or 1210 configured for 4 hours heating demand requires approx. 300kg of PCM. As described, in one arrangement the energy store comprises a thermal store. Some of the important features of the configuration and parameters of the thermal store include the Transfer Rate. Preferably the extraction rate is in the range 5kW to lOkW. The packaged PCM 176 of Fig. 1, 2, 7 provides a high surface area for fast heat transfer. The PCM further provides a thin PCM section for low At

(temperature differential).

The exemplary modular arrangement 1110, 1210 is configured for assembly on site. Packet weight is limited and selected to enable ease of handing for assembly on-site for example, in one arrangement packets have a weight of 25kg each. It is will be appreciated that packets of other weight in a range suitable for manual handling may also be provided.

The thermal store or energy store 110, 1110, 1210 may be provided as the energy store of an overall domestic heating system 110 or other building heating system. Typically, an insulated home requires an average heat input of 5kW to maintain comfortable temperature. Accordingly a 20kWh store supports and entire heating system for 4 hours. In the event that the heating system has double the load, the store will support entire heating system for 2 hours. The system 100 incorporates the energy store 110, 1110, 1210 to provide energy and cover for the early evening peak demand load.

The thermal store or may be integrated as heat store into a heating system for a new build or in a retrofit situation. The thermal store 110, 1110, 1210 is configured to store up to 20kW Latent heat in a 3001 domestic hot water tank. For integration, the heat store 110, 1110, 1210 should provide enough energy to heat a home up to 4 hours, thus, reducing the peak in electricity demand.

Factors to be considered when configuring the system of the present specification include identifying the space to be heated; and requirements for a particular space e.g. residential homes have particular profiles of demand. The system is adapted to be retrofitted.

The fresh water station 152 advantageously provides for heating of water on demand using the energy store. Water may typically be heated in heat exchanger 154 to a temperature of the order of 35°C or other selected temperature. As water is drawn from the mains and heated on the demand the water is fresh and not at risk of contamination as is the case for water that is stored. The fresh water station is further an energy efficient method of providing hot water. Advantageously, it is not necessary as per a domestic hot water cylinder to heat a large volume of water (typically the contents of the cylinder) to provide water. Features of the freshwater station 152 are described for example with reference to Figs. 10 -11.

Controller 118 receives flow rate and temperature readings. The controller 118 processes this information to control the speed of the pump to maintain a constant hot water temperature. The system and controller includes a self-learning algorithm so that it can automatically set the pump speed in the future.

The system 100 and the energy store 110 are configured such that the hot water preparation meets requirements i.e. the energy transfer from the tank 110 is sufficient to allow enough flow of hot water for i.e. showers

The fresh water station 152 advantageously provides instantaneous hygienic hot water. The fresh water station 152 may advantageously be charged by a renewable heat source or multiple heat source possibilities. The system 100 comprises a controller 118 which provides control and demand side management such that the energy store 110 is charged during off peak periods. A plate heat exchanger is provided to transfer energy to the water to provide hot water. The risk of water borne bacteria (legionella) is avoided.

To determine requirements for producing hot water using the freshwater station 152. The operating limits of the freshwater station were considered including: Temperature, Flow Rate, and Utilisation Ratio. Varied flow rates and temperature settings are accommodated. At higher flow rates the percentage volume drawn off decreases.

Storage temperature of 53°C limits achieves higher temperatures. Heat Exchanger of the Fresh water system is sized to provide the necessary efficiency to support higher flow rates. The system 100 may further include space heating means 151 connected to the heat source being heat emitters having increased heating capacity at lower water

temperatures. The space heating means 151 may be connected to the medium temperature zone 125 of the heat store 1 10. This provides for increased efficiency.

One of the key problems in deploying heat stores in residential homes has been to find the space to accommodate it. If heat pumps are to be installed in retrofit situations a heat store therefore also needs to be integrated into existing buildings. The system of the present specification provides an integrated heat store configured such that it is installable to replace the current cylinder which is used for sanitary hot water. Sanitary hot demand is met via a fresh water station 151 (pump/heat exchanger 154) operable to heat the fresh water supply with the energy from the heat store. This accordingly frees up the space which is currently occupied by a DHW cylinder for the heat store 110. Further the system of the invention advantageously minimizes costs associated with installation by providing any necessary controls (i.e temperature and water flow controls) integrated into the heat pump controller 118.

Advantages include cost savings to a user based on the cost difference of electricity in Off and On peak times and taking account of the additional benefit of a large enough store 110 for space heating 151 and provision of more efficient use of technologies like solar thermal and solar PV. This in comparison for example, with prior art domestic systems in which solar thermal is typically limited to provide a fraction of the DHW. If the energy from the solar thermal panels could also be used for space heating than a higher portion of the freely available energy could be used and additional energy and cost savings realized.

The same is true for Solar PV. Using the heat store 110 and system the energy which is exported from domestic dwellings can be stored within the house providing further cost savings. While with existing systems energy may be stored in the DHW tank, an advantage of the heat store 110 is in providing that this energy can also be used for space heating. As described above heat pump, solar thermal and solar PV can be combined with the thermal store 110 in a fully integrated system advantageously bringing energy efficiencies. Further the system and arrangement of the present heat store 110, controller, fresh water station as described, provide a solution to problems with system integration and poor control of the overall system that may often be a problem in the prior art.

The words comprises/comprising when used in this specification are to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers , steps, components or groups thereof.

Claims

1. A heating system (100) comprising one or more heat sources (130), a tank (110, 1110, 1210), and one or more heat sinks (150),

the tank (110, 1110, 1210) containing a heat transfer medium (165) and an energy storage medium defining a thermal energy store, the energy storage medium comprising a phase change material (170), wherein the phase change material is packed in pouches (175), and the pouches are arranged in the tank such that the heat transfer medium can at least partially flow around the pouches to charge and discharge them.

2. The heating system (100) as claimed in claim 1, wherein the pouches (175) are configured to provide optimal heat transfer and extraction such that the molecules of the phase change material (170) are provided close to the heat transfer surface for contact with the heat transfer medium (165).

3. The heating system (100) as claimed in any preceding claim, wherein the phase change material (170) is provided packaged in pouches (175) on a sheet support (176).

4. The heating system (100) as claimed in any preceding claim wherein the phase change material (170) is provided packaged in pouches (175) in modules.

5. The heating system (100) as claimed in any preceding claim, wherein the vertical extent of the pouches (175) is limited to prevent convection.

6. The heating system (100) as claimed in any preceding claim, wherein the vertical extent of the pouches (170) is limited to substantially 50mm or less.

7. The heating system (100) as claimed in any preceding claim wherein the pouches (175) have a depth of less than 20mm and having a low temperature differential in the phase change material across the depth of the pouch.

8. The domestic heating system (100) as claimed in any preceding claim wherein the pouches have a depth in the range of 5 to 20mm, preferably 8-12 mm, most preferably 10mm.

9. The heating system (100) as claimed in any preceding claim wherein the pouches are formed of a plastics material.

10. The heating system (100) as claimed in any preceding claim wherein the pouches comprise a coating.

11. The heating system (100) as claimed in any preceding claim wherein the pouches comprise an aluminium coating to prevent ingress of the heat transfer medium into the pouches.

12. The heating system (100) as claimed any preceding claim, the thermal energy store having one or more temperature zones with a temperature differential between different temperature zones.

13. The heating system (100) as claimed in claim 12, the tank having an upper portion and a lower portion, the upper portion providing a hot temperature zone and the lower portion providing a medium temperature zone.

14. The heating system (100) as claimed in claim 13, wherein the upper portion has a temperature in the range of 50 -60 degrees Celsius, preferably in the range of 55- 60 degrees Celsius.

15. The heating system (100) as claimed in claim 13, wherein the lower portion has a temperature in the range of 35-45 deg C, preferably of the order of 45 degrees C.

16. The heating system (100) as claimed in any preceding claim wherein the tank includes one or more different phase change materials of different operating temperature in the different zones or areas thereof.

17. The heating system (100) as claimed in any preceding claim, wherein the one or more heat sinks include a fresh water station (152) to provide sanitary hot water on demand, wherein the fresh water station comprises a heat exchanger fuelled directly by thermal energy from the tank (110) for heating water.

18. The heating system (100) as claimed in claim 17, wherein hot water from the hot zone or upper portion of the energy store is provided to one side of the fresh water station heat exchanger and fresh water from the mains supply is pumped through the other side of the fresh water station heat exchanger.

19. The heating system (100) as claimed in claim 18, wherein after the hot water from the hot zone of the tank has passed through the heat exchanger it is returned to the lower portion of the tank.

20. The heating system (100) as claimed in any preceding claim, comprising a controller (118) having control means for controlling operation of the thermal energy store and connected heat sources and heat sinks.

21. The heating system (100) as claimed in claim 20, wherein the controller (118) comprises a single integrated controller for controlling the heat store, heat sources, and heat sinks.

22. The heating system (100) as claimed in claims 20-21 wherein the controller (118) comprises communication means for communicating internally with the heat sources and heat sinks, and for communicating externally with utilities.

23. The heating system (100) as claimed in claims 20-22 wherein the controller (118) comprises a user interface to allow the user monitor the operation of the system (100).

24. The heating system (100) as claimed in claims 20-23 wherein the controller 118 is configured to adaptively learn the energy usage patterns of the user.

25. The heating system (100) as claimed in claim 20-24 wherein the controller 118 is configured to determine the amount of heat that needs to be stored to meet the energy or heating requirements of a heat sink to which it is coupled.

26. The heating system (100) as claimed in claims 20-25, wherein the controller 118 controls demand side management such that the tank energy store is charged during off peak periods or heat sources are turned on/off as required to build back up the store of energy.

27. The heating system (100) as claimed in claims 20-26, wherein the controller (118) is configured to monitor network frequency or to receive a signal from the network pertaining to network frequency and is configured to effect storage in the frequency in response to frequency requirements.

28. The heating system (100) as claimed in claims 20 -27 wherein controller 118 controls the freshwater station, wherein flow rate and temperature data are provided as an input to the controller 118 which processes this data to control the speed of the pump of maintain a constant hot water temperature.

29. The heating system (100) as claimed in claim 28 wherein the controller includes a self-learning algorithm to enable automatic setting of the pump speed for future operation.

30. The heating system (100) as claimed in any preceding claim wherein the one or more of heat sinks include a space heater (151) wherein the space heater (151) is connected to the medium temperature zone of the tank.

31. The heating system (100) as claimed in any preceding claim wherein the heat sources include a solar PV, a solar thermal, and heat pump

32. The heating system (100) as claimed in claim 31 wherein the system uses the excess electricity of the PV for charging the heat store.

33. The heating system (100) as claimed in any preceding claim wherein a heat source is connected to the tank to heat a particular zone of the tank.

34. The heating system (100) as claimed in any preceding claim wherein a heat source is used to heat the tank from the upper part downwards.

35. The heating system (100) as claimed in any preceding claim wherein a heat source is used to heat the tank from the bottom part upwards.

36. The heating system (100) as claimed in any preceding claim wherein the energy storage medium comprises a phase change material having a high energy storage density.

37. The heating system (100) as claimed in any preceding claim wherein the phase change material has a high mass energy storage density in the range of 150-300kJ/kg, preferably in the range of 200-250kJ/kg.

38. The heating system (100) as claimed in any preceding claim wherein the phase change material has a high mass energy storage density of the order of 210kJ/kg

39. The heating system (100) as claimed in any preceding claim wherein the phase change material has an operating temperature in the range of 35 to 60 degrees Celsius, preferably in the range of 45-60 degrees C.

40. The heating system (100) as claimed in any preceding claim wherein the phase change material comprises a phase change material having an operating temperature of substantially 46 degrees Celsius.

41 The heating system (100) as claimed in any preceding claim wherein the phase change material comprises a phase change material having an operating temperature of substantially 55 degrees Celsius.

42. The heating system (100) as claimed in any preceding claim wherein the phase change material comprises a phase change material having an operating temperature of substantially 58 degrees Celsius.

43. The heating system (100) as claimed in any preceding claim wherein the thermal energy store has a thermal energy capacity of latent heat in the order of 20 -30KWH.

44. The heating system (100) as claimed in any preceding claim wherein the thermal energy store has a power output of 5-60KW, depending on load.

45. The heating system (100) as claimed in any preceding claim wherein the thermal energy store has an output temperature of the order of 35 to 60 degC, most preferably 40 to 55 degC.

46. The heating system (100) as claimed in any preceding claim the tank having dimensions of the order of a typical domestic hot water cylinder, for example a 3001 cylinder.

47. The heating system (100) as claimed in any preceding claim wherein the heat transfer medium is water and the tank is configured such that the water circulates throughout the volume of the tank and at least partially in contact with the pouches containing the phase change material.

48. The heating system (100) as claimed in any preceding claim wherein the pouches of phase change material are optimised for heat extraction such that the molecules of the phase change material are provided close to the heat transfer surface.

49. The heating system (100) as claimed in any preceding claim wherein the geometry of the pouches is optimised for heat transfer out of the pouches at a desired rate.

50. The heating system (100) as claimed in any preceding claim wherein the pouches are provided in modular form.

51. The heating system (100) as claimed in any preceding claim wherein the tank is comprised of a plurality of inter-connectable tank modules, which are connected to provide the thermal heat store.

52. The heating system (100) as claimed in claim 51 wherein the tank modules comprise connection means for connecting tank modules mechanically and to provide a hydraulic connection.

53. The heating system (100) as claimed in claims 51 or 52 wherein the tank modules contain a energy storage medium, comprising a phase change material provided packed in pouches, and the pouches are arranged in the tank modules such that a heat transfer medium can at least partially flow around the pouches to charge or discharge energy to or from the energy storage medium.

54. The heating system (100) as claimed in any preceding claim wherein the tank is decoupled from the connected heat sinks and heat sources via heat exchangers.

55. The heating system (100) as claimed in any preceding claim, wherein the tank is sized and shaped to fit in the space usually provided for a domestic hot water cylinder.

56. The heating system (100) as claimed in any preceding claim wherein the tank is configured for retrofitting into a heating system to replace an existing hot water cylinder.

57. An store for storing thermal energy comprising a tank containing a phase change material and an energy transfer medium, wherein the phase change material is packed in pouches, and the pouches are arranged in the tank such that an energy transfer medium can at least partially flow around the pouches to charge or discharge the phase change material therein.

58. The store of claim 57 configured to store energy for preparing sanitary hot water and for space heating.

59. The store of claims 57 to 58 wherein the tank is sized to fit in the space usually provided for a domestic hot water cylinder.

60. The store of claims 57 to 59 wherein the tank is configured for installation into a heating system to replace a hot water cylinder and to perform the functions of a hot water cylinder.

61. The store of claims 57 to 60, wherein the pouches (175) are configured to provide optimal energy transfer and extraction such that the molecules of the phase change material (170) are provided close to the energy transfer surface for contact with the transfer medium (165).

62. The store of claims 57 to 61, wherein the phase change material (170) is provided packaged in pouches (175) on a sheet support (176) or connected by string (177).

63. The store of claims 57 to 62, wherein the vertical extent of the pouches (175) is limited to prevent convection.

64. The store of claims 57 to 63, wherein the vertical extent of the pouches (170) is limited to substantially 50mm or less.

65. The store of claims 57 to 64 wherein the pouches (175) have a depth of less than 20mm and having a low temperature differential in the phase change material across the depth section of the pouch.

66. The store of claims 57 to 65 wherein the pouches have a depth in the range of 5 to 20mm, preferably 8-12 mm, most preferably 10mm.

67. The store of claims 57 to 66 wherein the pouches are formed of a plastics material.

68. The store of claims 57 to 67 wherein the pouches comprise a coating.

69. The store of claims 57 to 68 wherein the pouches comprise an aluminium coating to prevent ingress of the energy transfer medium into the pouches.

70. The store of claims 57 to 69 having one or more temperature zones with a temperature differential between different temperature zones.

71. The store of claims 57 to 70, the tank having an upper portion and a lower portion, the upper portion providing a hot temperature zone and the lower portion providing a medium temperature zone.

72. The store of claims 57 to 71, wherein the upper portion has a temperature in the range of 50 -60 degrees Celsius, preferably in the range of 55- 60 degrees Celsius and wherein the lower portion has a temperature of the order of 35-45, preferably 45 degrees C.

73. The store of claims 57 to 72 wherein the tank includes one or more different phase change materials of different operating temperature in the different zones or areas thereof.

74. The store of claims 57 to 73 wherein the tank is comprised of a plurality of inter- connectable tank modules, which are connected to provide the thermal energy store.

75. The store of claim 74 wherein the tank modules comprise connection means for connecting tank modules mechanically and to provide a hydraulic connection.

76. The store of claims 74 to 75 wherein the tank modules contain a phase change material provided packed in pouches, and the pouches are arranged in the tank modules such that an energy transfer medium can at least partially flow around the pouches to charge or discharge energy to or from the phase change material.

77. The store of claims 57 to 76 wherein the thermal energy store has a thermal energy capacity of latent heat in the order of 20 -30KWH.

78. The store of claims 57 to 77 wherein the thermal energy store has a power output of 5-60KW, depending on load.

79. The store of claims 57 to 78 wherein the thermal energy store has an output temperature of the order of 35 to 60 degC, most preferably 40 to 55 degC.

80. The store of claims 57 to 79, comprising a heat store configured to store heat and to provide heat as an output to connected heat sinks.

81. The store of claims 57 to 76, comprising an energy store comprising a phase change material in the range of 5degC to 18 degC configured to store energy and to resuse the stored energy for cooling.

82. The store of claims 57 to 76 comprising an energy store wherein the phase change material is water configured to store energy and to reuse the stored energy for cooling.

83. A heating system comprising one or more heat sources, a tank for storing thermal energy and one or more heat sinks, wherein the tank contains a phase change material and wherein the tank is decoupled from the connected heat sinks and heat sources via heat exchangers.

84. A heating system comprising one or more heat sources, one or more heat sinks and a thermal heat store, the one or more heat sources, and the system comprising a single integrated controlled for controlling operation of the system including to effect charging and discharging of the heat store.

The heating system of claim 84, the heat sources including a solar PV

78. A heating system as claimed in claim 77, wherein the system uses the excess electricity of the PV for charging the heat store.