CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from South African provisional patent application number 2019/02357 filed on 15 April 2019, which is incorporated by reference herein.

FIELD OF THE INVENTION

This invention relates to water heaters.

More particularly, but not exclusively, the invention relates to methods and systems for controlling temperature of water in an electric water heater.

BACKGROUND TO THE INVENTION

Growing population and temperature changes are leading to a substantial increase in energy demand worldwide, particularly in developing countries. However, due to economic and environmental constraints, such as harsh operating conditions due to low maintenance and depletion of resources, the supply is struggling to meet the demand. In order to curb the increasing energy demand energy tariffs are regularly increased. These tariffs are usually substantially increased during peak hours when the demand is high and makes a large difference on utility bills.

These rising energy costs have placed a financial burden on poorer communities, with many municipalities accumulating debts to the energy supplier, which in turn leads to accelerated tariff increases, affecting more municipalities and placing further constraints on already restricted local economies. As a result of the high cost, numerous unsafe and illegal power connections are made, and local governments are forced to divert public funds to pay off debts.

Some relief to the above-mentioned problems could be achieved by employing alternative energy generation methods such as solar power or through the introduction of smart technologies such as smart grids. Driven by technological advances, economies of scale and deployment subsidies, the installation costs of such alternative energy generation methods have declined. However, many organisations still lack the necessary resources required to determine the benefits of renewable energy solutions, particularly due to the complexity involved in determining an accurate cost versus benefit forecast, as it will vary on a case by case basis. Another challenge faced when designing such energy systems, is that a system may provide excess energy during certain times of the day or during certain seasons.

Methods of managing the energy demands of buildings to reduce their energy costs have therefore been widely discussed and explored. It is well known that electrical water heaters (EWH) use large amounts of energy in order to ensure that water stays heated at a specific regulated temperature. Consequently, various methods of reducing the energy usage of such EWHs have been explored. The Applicant is aware that in some countries, for example South Africa, EWHs in multiple cities are retrofitted with control systems allowing the energy provider to switch off the EWHs during peak hours to reduce the stress on the supply by means of direct control. Different forms of centralised EWH control have been proposed, with three key control objectives, namely, cumulative energy usage reduction, efficiently managing the load, and consumer comfort. Direct control provides the benefit of being able to reduce the strain on the grid during high demand periods, but does not take the comfort of the consumer into account, for example, if a consumer wants to use warm water during peak hours the water may be cold.

It may furthermore be impractical to implement direct control methods for extended periods since the consumer may not desire such functionality and may merely desire the EWH to be switched on or off at times which best suits the individual consumer.

Conventionally, temperature measurements in EWH’s are taken at or near a heating element of the EWH. This is usually done by way of a mechanical thermostat which includes a temperature sensor in the form of a bimetallic strip. However, providing the bimetallic strip near the heating element may cause element to switch off prematurely. This may, in turn, cause bacterial growth in areas of the EWH that are further away from the heating element.

Two heating elements are sometimes used in a single EWH, particularly in vertically oriented EWHs. However, implementing two heating elements may be impractical or undesirable in some applications and it may make the EWH unnecessarily complex. The addition of a second heating element may also make the EWH more expensive.

Further methods used by consumers to reduce energy demand and save costs is to install solar EWHs. These solar EWHs are solar powered and therefore do not require any power from the conventional grid. The problem with such EWHs is that in times where access to solar power is scarce, the water may not be sufficiently heated. The Applicant considers there to be room for improvement.

The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was part of the common general knowledge in the art as at the priority date of the application.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present disclosure there is provided a method for controlling temperature in an electric water heater, the method comprising:

providing a single heating element in the water heater to heat water therein;

sensing temperature of water in the water heater with a temperature sensor;

determining whether an amount of available electrical power from a first power source is sufficient to drive the heating element, and if it is, driving the heating element by applying power from the first power source to heat the water up to a first temperature threshold based on feedback from the temperature sensor; and

if the amount of available electrical power from the first power source is not sufficient to drive the heating element, driving the heating element with power from a second power source, to heat the water up to a second temperature threshold that is lower than the first temperature threshold.

The single heating element may be a resistive element with a rated power consumption, and the amount of electrical power sufficient to drive the heating element may be equal to the rated power consumption.

The method may include providing at least a first thermostat; and the first thermostat may be set to the first temperature threshold.

The first temperature threshold may be adjustable.

The temperature sensor may be a mechanical temperature sensor such as a bimetallic strip.

The temperature sensor may be an electric temperature sensor such as a thermistor, a thermocouple, a resistance thermometer, a silicon bandgap temperature sensor or the like.

The feedback from the temperature sensor may be any one of mechanical feedback or electrical feedback.

The method may include implementing a first switch, relay or contactor; and the first switch may be operable to supply power to the heating element from the first power source.

The method may include providing a controller operable to switch the heating element on or off by activating or deactivating the first switch.

The method may include receiving, by the controller, feedback from the temperature sensor and switching the first switch based on the feedback to heat the water up to the first temperature threshold.

The method may include implementing a second switch, relay or contactor operable to supply power to the heating element from the second power source.

The method may include, by the controller, receiving data from a power supply device associated with the first power source, the data being indicative of whether the amount of available electrical power at the first power source is sufficient to drive the heating element or not. Alternatively, the data may be indicative of whether any amount power is available at the first power source or not.

The method may include, by the controller, accessing the data from the power supply device, and switching the second switch to provide power to the heating element from the second power source if the amount of available electrical power from the first power source is not sufficient to drive the heating element.

The method may include, by the controller, accessing the data from the power supply device, and switching the second switch to provide power to the heating element from the second power source responsive to the amount of power from the first power source not being available.

The method may include, by the controller, receiving feedback from the temperature sensor and switching the second switch on or off based on the feedback to heat the water up to the second temperature threshold that is lower than the first temperature threshold.

The method may include providing the electric temperature sensor at a remote location from the heating element, for example at or near an outlet of the water heater; and the method may include retrofitting the electric temperature sensor to the water heater. The method may include, by the controller, sampling the electric temperature sensor to receive electrical feedback therefrom, the electrical feedback being indicative of water temperature near the outlet, and switching either or both of the first or second switches based on the received electrical feedback to heat water up to the first temperature threshold, or the second and lower threshold, as the case may be.

The method may include, adjusting the first thermostat to the first temperature threshold.

The method may include, by the controller, if the amount of available electrical power from the first power source is sufficient to drive the heating element, switching the first switch to drive the heating element with power from the first power source, to heat the water up to the first temperature threshold.

The method may include, by the controller, if the amount of available power from the first power source is not sufficient to drive the heating element, switching the second switch to drive the heating element with power supplied by the second power source, to heat the water up to the second lower temperature threshold.

The method may include, by the controller, if power from the first power source is not available, switching the second switch to drive the heating element with power supplied by the second power source, to heat the water up to the second lower temperature threshold based on feedback received from the electric temperature sensor; and the method may also include, by the controller, switching the heating element off agnostic to, or irrespective of the first temperature threshold of the first thermostat, in the event that power from the first power source is not available.

The method may include, bypassing or short circuiting a mechanical temperature sensor associated with the first thermostat, such as a bimetallic strip thereof, and controlling water temperature based on feedback from the electric temperature sensor.

The method may include providing a second thermostat; alternatively, the method may include retrofitting a second thermostat to the water heater; and the second thermostat may be set to the second temperature threshold that is lower than the first temperature threshold.

Either or both of the first and second temperature thresholds of the first and second thermostats may be adjustable.

The method may include implementing the first and second thermostats so as to form a parallel connection to the heating element.

The method may include providing a power switching device, relay or contactor.

The power switching device may be operable to supply power to the heating element from the second power source.

The power switching device may be switched if the amount of available electrical power from the first power source is sufficient to drive the heating element.

The power switching device may be responsive to any amount of power from the first power source being available, for example, the power switching device may be a relay which is opened or closed when it is energized by power from the first power source.

The power switching device may be operable to disable the second thermostat in the event that the amount of available power from the first power source is sufficient to drive the heating element, thereby causing the heating element to heat the water to the first temperature threshold with power from the first power source.

The power switching device may be operable to disable the second thermostat in the event that any amount of power is available from the first power source, thereby causing the heating element to heat the water to the first temperature threshold with power from the first power source.

The first power source may be a renewable energy source such as a solar power source, a wind power source, a geothermal power source, a hydroelectric or tidal power source, or any other type of renewable energy source.

The second power source may be mains electricity or grid electricity.

The power supply device may be an inverter associated with the solar power source, or another type of power supply device associated with the renewable energy source.

The inverter may have a communications interface for providing data communications with the controller.

The first temperature threshold may be between 60°C and 100°C, preferably about 90°C, however other temperatures may be used, such as about 85°C or about 80°C, or about 75°C, or about 70°C, or about 65°C or about 60 °C, or about 95°C.

The second temperature threshold may be between 40°C and 60°C, preferably about 50°C, or about 55°C or about 60°C.

The method may include determining whether the amount of available electrical power from the first power source is greater than zero, and the amount of available electrical power from the first power source may be sufficient to at least partially drive the heating element with power from the first power source if the amount of available power from the first power source is greater than zero. The method may include driving the heating element with power from both of the first and second power sources simultaneously.

Whether the amount of available electrical power from the first power source is sufficient to drive the heating element may be predetermined, or based on a power threshold value, for example based on the rated power consumption or power draw of the heating element.

The rated power consumption may be about 2 kW, or 3kW or 4 kW or any other power rating associated with the heating element.

The method may include only applying power from the first power source to the heating element if the amount of available electrical power from the first power source is equal to or exceeds the power rating or power threshold value.

The method may include only applying power from the first power source to the heating element if the feedback is indicative that the water temperature is below the first temperature threshold.

The method may include only applying power from the first power source to the heating element if the feedback is indicative that the water temperature in the water heater is below the first temperature threshold and above the second temperature threshold.

The method may include applying power from the first power source to drive the heating element, if it is sufficient to drive the heating element (or if it is available at all), and also providing power from the second power source, when the feedback is indicative that the water temperature is below the second temperature threshold.

In accordance with another aspect of the present disclosure there is provided a water temperature control system comprising: an electric water heater that includes a single heating element to heat water therein, driven by power from a first power source or from a second power source;

a temperature sensor for sensing temperature of water in the water heater; and a temperature controlling component arranged to determine whether an amount of available electrical power from the first power source is sufficient to drive the heating element, and if it is, to drive the heating element by applying power from the first power source to heat the water up to a first temperature threshold based on feedback from the temperature sensor, wherein the temperature controlling component is further arranged, if the amount of available electrical power from the first power source is not sufficient to drive the heating element, to drive the heating element with power from the second power source, to heat the water up to a second temperature threshold that is lower than the first temperature threshold.

The system may include at least a first thermostat; and the first thermostat may be set to the first temperature threshold.

The first temperature threshold may be adjustable.

The temperature sensor may be a mechanical temperature sensor such as a bimetallic strip.

The temperature sensor may be an electric temperature sensor such as a thermistor, a thermocouple, a resistance thermometer, a silicon bandgap temperature sensor or the like.

The feedback from the temperature sensor may be any one of mechanical feedback or electrical feedback.

The system may include a first switch, relay or contactor; and the first switch may be operable to supply power to the heating element from the first power source.

The system may include a controller operable to switch the heating element on or off by activating or deactivating the first switch.

The controller may be arranged to receive feedback from the temperature sensor and to switch the first switch based on the feedback to heat the water up to the first temperature threshold.

The system may include a second switch, relay or contactor operable to supply power to the heating element from the second power source. The controller may be arranged to receive data from a power supply device associated with the first power source, the data being indicative of whether the amount of electrical power the first power source is sufficient to drive the heating element or not.

The controller may be arranged to access the data from the power supply device, and to switch the second switch to provide power to the heating element from the second power source if the amount of available electrical power from the first power source is not sufficient to drive the heating element, or if no power is available at the first power source.

The controller may be arranged to receive feedback from the temperature sensor and to switch the second switch on or off based on the feedback so as to heat the water up to the second temperature threshold that is lower than the first temperature threshold.

The system may include the electric temperature sensor provided at a remote location from the heating element, for example at or near an outlet of the water heater.

The controller may be arranged to sample the electric temperature sensor to receive electrical feedback therefrom, the electrical feedback being indicative of water temperature near the outlet, and the controller may be arranged to switch either or both of the first or second switches based on the received electrical feedback to heat water up to the first temperature threshold, or the second threshold that is lower than the first threshold, as the case may be.

The system may include the first thermostat set to the first temperature threshold.

The controller may be arranged such that, if the amount of available power from the first power source is sufficient to drive the heating element, or if it is available at all, the controller switches the first switch so as to drive the heating element with power from the first power source, to heat the water up to the first temperature threshold of the first thermostat.

The controller may be arranged such that, if the amount of available power from the first power source is not sufficient to drive the heating element, or if it is not available at all, the controller switches the second switch to drive the heating element with power supplied by the second power source, to heat the water up to the second temperature threshold based on feedback received from the electric temperature sensor.

The controller may be arranged to switch the heating element off agnostic to, or irrespective of the first temperature threshold of the first thermostat, in the event that the amount of power from the first power source is not sufficient to drive the heating element, or if it is not available at all.

The system may include a bypassing device, a short circuiting device or a switch arranged to bypass or short circuit a mechanical temperature sensor associated with the first thermostat, such as a bimetallic strip thereof; and the controller may be arranged to control water temperature based on feedback from the electric temperature sensor.

The system may include a second thermostat; and the second thermostat may be set to the second and low temperature threshold.

Either or both of the first and second temperature thresholds of the first and second thermostats may be adjustable.

The system may include the first and second thermostats arranged in parallel with the heating element.

The system may include a power switching device, relay or contactor.

The power switching device may be operable to supply power to the heating element from the second power source.

The power switching device may be switched if the amount of available electrical power from the first power source is sufficient to drive the heating element.

The power switching device may be responsive to any amount of power from the first power source being available, for example, the power switching device may be a relay which is opened or closed when it is energized by power from the first power source.

The power switching device may be operable to disable the second thermostat in the event that the amount available electrical power from the first power source is sufficient to drive the heating element, thereby causing the heating element to heat the water to the first temperature threshold of the first thermostat.

The system may include a controller that includes the temperature controlling component.

The system may include the first switch operable to supply power to the heating element from the first power source and a second switch operable to supply power to the heating element from the second power source, and the controller may be operable to heat water up to the first temperature threshold or the second temperature threshold by switching either or both of the first and second switches on or off based on feedback from the temperature sensor.

In accordance with another aspect of the present disclosure there is provided a method for controlling temperature in an electric water heater, the method comprising:

determining whether excess power supplied by a first power source is available, and responsive thereto, setting a temperature threshold of a thermostat to a first temperature and utilising the excess power of the first power source to heat water in the water heater with a heating element; and

alternatively, if no excess power from the first power source is available, setting the temperature threshold of the thermostat to a second temperature that is lower than the first temperature and utilising power from a second power source to heat water in the water heater.

The first power source may be a renewable energy source such as solar power or wind power. The second power source may be mains electricity, and optionally, one or more further power sources may be provided.

The method may include: setting the temperature threshold of the thermostat to one or more further threshold temperatures, each threshold temperature being associated with one of the power sources.

The first temperature may be between 60°C and 100°C, preferably about 90°C; and the second temperature may be between 40°C and 60°C, preferably about 50°C.

The method may extend to measuring a power draw of an infrastructure where the water heater is located; determining whether power available from the first power source is greater than the required power draw by an excess amount; and in the event that excess power is available, utilising the excess power to heat water in the water heater.

The method may include determining whether or not to enable or disable the heating element of the water heater, based on the current power draw of the infrastructure, or alternatively to determine whether to use the first energy source or the second energy source to drive the heating element of the water heater.

The method may include: setting a temperature threshold of a thermostat of the water heater to a single temperature. The single temperature of the temperature threshold may be between 40°C and 90°C, preferably about 70°C.

In accordance with yet another aspect of the present disclosure there is provided a system for controlling temperature in an electric water heater which includes a heating element for heating water, the system comprising:

a first power source and a second power source for providing power to an infrastructure where the water heater is provided;

a thermostat for regulating heating of water in the water heater; and

a temperature controlling component which is configured to determine whether excess power supplied by the first power source is available, and responsive thereto, to set a temperature threshold of the thermostat of the water heater to a first temperature and to cause the heating element to heat water in the water heater utilising the excess power of the first power source when available, alternatively, if no excess power from the first power source is available, to set the temperature threshold of the thermostat to a second temperature that is lower than the first temperature to cause the heating element to heat water in the water heater utilising power from the second power source.

The system may include a power draw determining component. The power draw determining component may be operable to determine a power draw of an infrastructure where the water heater is located, and in the event that excess power is available from the first power source, the temperature controlling component may be operable to set the temperature threshold of the thermostat to the first temperature and to cause the excess power to heat water in the water heater.

The power draw determining component may be operable to determine whether or not to enable or disable the heating element, based on a current power draw of the infrastructure.

The system may include a plurality of water heaters, each water heater having a power rating.

The system to include a database in which data relating to the power rating of each water heater may be stored.

The temperature controlling component may be configured to enable or disable the heating element of each of the water heaters based on the power rating data, thereby prioritising which water heater to heat.

Identification data of each water heater may be stored in the database. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Figure 1 is a block diagram of an exemplary water temperature control system showing a water heater and various components that may form part of the system;

Figure 2 is a block diagram similar to Figure 1 , showing an alternative exemplary embodiment of the system;

Figure 3 is a block diagram of a prior art system for controlling temperature in a water heater;

Figure 4 is a block diagram of another example embodiment of a water temperature control system;

Figure 5 is a flow diagram of an exemplary method for controlling temperature in a water heater;

Figure 6 is a high-level block diagram of an exemplary system for controlling temperature in one or more electric water heaters;

Figure 7 is a high-level block diagram of an experimental simulation setup for an exemplary embodiment of the system of Figure 6;

Figures 8-9 are graphs showing exemplary results from a simulation for an embodiment of the present disclosure, indicating average daily kWh grid-usage and peak monthly kVA for a year;

Figures 10-1 1 are graphs illustrating exemplary results from a simulation for another embodiment of the present disclosure, indicating average daily kWh grid- usage and peak monthly kVA for a year; Figures 12-13 are graphs illustrating exemplary results from a simulation for various embodiments of the present disclosure, indicating kWh used for each month and peak monthly kVA for each month in a year;

Figure 14 is a satellite image of an exemplary infrastructure such as a school where embodiments of the present disclosure may be implemented, showing suitable roof areas for photovoltaic solar panel installations;

Figure 15 is a flow diagram illustrating another exemplary method of controlling temperature in an electric water heater; and

Figure 16 illustrates an example of a computing device in which various aspects of the disclosure may be implemented.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

Embodiments described herein provide methods and systems for controlling temperature in one or more water heaters such as electric water heaters (EWFIs). Embodiments are described that use feedback from one or more temperature sensing devices to regulate temperature in the water heater(s) depending on whether power is available from a first or renewable power source. A controller may be configured to determine whether a quantity or amount of available power is sufficient to drive a heating element of the water heater. Excess power may be supplied by the first energy source, for example if the power supplied by the first energy source exceeds a load demand, or if the power supplied by the first energy source exceeds a power threshold or is greater than zero. Embodiments of the present disclosure that do not implement a microcontroller may also be possible, and mechanical feedback (such as mechanical displacement of a bimetallic strip or other temperature sensor) may instead be used to control the water temperature. In embodiments that do implement a controller or microcontroller, if the quantity of power or excess power is supplied by the first energy source, this power may be used to heat water in the water heater by driving a heating element thereof to heat the water to a first temperature threshold which may be a hot or a high temperature. If, on the other hand, the quantity of power from the first power source is not available or insufficient, the systems and methods of the present disclosure may use power from a second power source, or grid power, to heat the water to a medium or low temperature. The medium or low temperature may be lower than the hot or high temperature, but it may still be higher than ambient temperature, to prevent the growth of bacteria, legionella or the like in the water heater. One or more devices that automatically regulate temperature may be used, such as thermostats. Switches, relays, flip-flops or latches may be used to switch power to the heating element, from the first power source, or from the second power source, as the case may be. Embodiments of the present disclosure may implement a single heating element in a water heater, but it may also be possible to provide more than one heating element in the water heater.

Embodiments may also be possible that implement thermostats that have temperature thresholds which are manually adjustable (for example with a tab, dial, slider, button or knob). Other embodiments may implement thermostats that have temperature thresholds that are digitally adjustable by receiving a signal from the controller. A temperature threshold value of a thermostat may be set to a first temperature and the power supplied by the first power source may be utilised to heat water in a water heater when it is available. Alternatively, if no excess power is supplied by the first power source, the controller may set the threshold temperature of the thermostat to a second temperature, which may be lower than the first temperature, and use a second power source to heat the water in the water heater. In an embodiment of the present disclosure, the first power source may be a renewable power source such as solar or wind power, and the second power source may be mains electricity. Embodiments are also possible that implement an electrical temperature sensor, which measures the water temperature and transmits temperature data to the controller, which may then access this data and determine whether or not to switch a heating element of the water heater on or off.

Referring now to Figure 1 , there is provided a water temperature control system (100) according to an exemplary embodiment of the present disclosure. The system (100) may include a water heater (1 10), preferably an electric water heater, that includes a tank, vessel, container or reservoir (1 12) for holding water (1 14) to be heated. The tank or reservoir (1 12) may include an inlet (not shown) and an outlet (1 16). The water heater (1 10) may include at least one heating element (1 18) to heat the water (1 14) therein, driven by power supplied by a first power source (123) or a second power source (125). In the present embodiment, the water heater (1 10) includes a single heating element (1 18), but embodiments are also possible that implement a plurality of heating elements. The first power source (123) may be a renewable energy source, in this instance provided by one or more photovoltaic solar panels connected to an inverter (126). The second power source (125) may be provided by mains electricity, or grid power. In the present embodiment, the heating element (1 18) is an electric heating element such as a heating coil or resistance heating element, however it will be appreciated by those skilled in the art that other water heating devices may also be used in the various embodiments of the present disclosure.

The system (100) may further include a temperature sensor (124) for sensing temperature of water (1 14) in the water heater (1 10). The temperature sensor (124) may be an electrical temperature sensor which is inserted into a cavity (128) defined by the heating element (1 18). The water heater (1 10) may further include a first thermostat (130) which may implement a thermal cut-out at a temperature that may be adjusted. The thermal cut-out may be referred to as a first temperature threshold, and it may be implemented by way of a bimetallic strip (which may be provided separately from the electric temperature sensor (124), for example also in the cavity (128) of the heating element (1 18)). Alternatively, the first temperature threshold may be implemented by way of the electric temperature sensor (124) and a switch of the thermostat (130). The thermal cut-out temperature or first temperature threshold may for example be about 90°C. However, the first temperature threshold may also be between 60°C and 100°C, or about 95°C, or about 90°C, or about 85°C or about 80°C or about 75°C, or about 70°C, or about 65°C, or about 60°C. Embodiments are possible where the first threshold is adjustable by way of a physical dial (132), or it may be digitally adjusted, or it may be adjustable in another way. The first thermostat (130) may be operable to interrupt the flow of electricity through the element once the first temperature threshold is reached. The system (100) may include the first thermostat (130) set to the first temperature threshold. The first thermostat (130) may form part of a thermostat unit (133) or module which may be retrofitted to an existing water heater (1 10).

The system (100) may include one or more temperature sensors. In Figure 1 , the temperature sensor (124) is an electric temperature sensor such as a thermistor, a thermocouple, a resistance thermometer, a silicon bandgap temperature sensor or the like. However, it will be appreciated by those skilled in the art that one or more mechanical temperature sensors such as bimetallic strips may also be implemented as part of the system (see for example Figure 2 and its related description below). Feedback may be received from the temperature sensors of the present disclosure, and this feedback may be any one of mechanical feedback (e.g. mechanical displacement from the bimetallic strip) or electrical feedback (e.g. a signal from the electric temperature sensor (124)). In the present embodiment shown in Figure 1 , electrical feedback may be received by the controller (136) from the electrical temperature sensor (124), and electrical feedback may be received by the first thermostat (130) from the electrical temperature sensor (124). It may, however, also be possible to implement features of any of the other embodiments described herein, in the embodiment of Figure 1 . For example, the first thermostat (130) may receive mechanical feedback from a mechanical temperature sensor.

The system (100) may include a first switch (142), relay or contactor connected to the controller (136). The connections referred to in the present disclosure may be provided by either wired or wireless connections as will be understood by those skilled in the art. The controller may be operable to switch the first switch (142) by activating it or deactivating it (in other words, switching the switch (142) on or off) to switch the heating element (1 18) on or off. It will also be appreciated that Normally Open (NO) or Normally Closed (NC) configurations may be implemented in the various switches described in the present disclosure. The first switch (142) may be operable to supply power to the heating element (1 18) from the first power source (123).

The system (100) may further include a second switch (144), relay or contactor operable to supply power to the heating element from the second power source (125). The second switch (144) may be similar to the first switch (142) and the controller may also be operable to switch the second switch on or off to supply power to the heating element (1 18) from the second power source (125) in the event that power from the first power source (123) is not available, or if there is not enough power available from the first power source (123), as will be described in more detail below. Exemplary live (L) and neutral (N) connections are also shown in Figures 1 to 4, but it will be understood that the present disclosure is not limited to the specific arrangement shown in the Figures.

In the example embodiment shown in Figure 1 , a temperature controlling component (134) may, at least partially, be provided by a controller (136) such as a microcontroller. The controller (136) may include a processor (138) and a memory (140). It will be appreciated that embodiments are possible that do not require a controller or microcontroller, for example as described below with reference to Figure 4. Still referring to Figure 1 , the controller (136) may be connected to the electric temperature sensor (124) to receive temperature data therefrom which indicates water temperature in the reservoir (1 12). The controller (136) may also be connected to a power supply device such as the inverter (126) which may, in turn, be connected to the first energy source (123). In the present embodiment, the inverter (126) may be operable to convert direct current from the solar panels to alternating current. The inverter (126) may include a communications interface such as a Controller Area Network (CAN) bus, serial port or other data interface, and the controller (136) may receive data from the inverter, and this data may be indicative of whether the first energy source (123) has an amount of power available thereat, or not. The data may also be indicative of whether the amount of power available at the first power source (123) is sufficient to drive the heating element (1 18). The controller (136) may further include a transmitting component (146), a receiving component (148) and a timing component (150) or clock. The controller may be arranged to access the data from the power supply device (126), and to switch the second switch (144) to provide power to the heating element from the second power source (125) if the amount of available electrical power from the first power source (123) is not sufficient to drive the heating element (1 18), or if no power is available at the first power source (123).

The controller may be arranged to access the received data from the power supply device or inverter (126), and the controller (136) may, in response thereto, switch the second switch (144) to provide power to the heating element (1 18) from the second power source (125) responsive to the amount of available power from the first power source (123) not being sufficient to drive the heating element (1 18), or if no power is available at the first power source. If, on the other hand, the controller (136) determines that the amount of power is indeed available from the first power source (123) or sufficient to drive the heating element (1 18), the controller may switch the first switch (142) to provide power to the heating element (1 18) from the first energy source (123) to heat the water up to the first temperature threshold. In such a scenario, the controller may switch off the second switch (144) for example in order to conserve grid or mains power while the first switch is switched on. Embodiments may also be possible where the controller switches both the first and second switches (142, 144) on or off at the same time, to provide parallel heating power, or augmented heating power to the heating element from the first and second power sources (123, 125). Although not shown in Figure 1 , the power supply device or inverter (126) associated with the first power source (123) may also have a neutral (N) connection. Power draw from the heating element may be fixed, for example at 2 kW, 3 kW, or 4 kW (but other power ratings are also possible). In the present embodiment, and in any of the embodiments of the present disclosure, the controller may determine if the amount of electrical power available from the first power source is sufficient to drive the heating element or not.

The controller (136) may be operable to heat water (1 14) up to the first temperature threshold by driving the heating element (1 18) when the amount of available electrical power at the first power source is sufficient to drive the heating element (1 18), or if the amount of power is available at all. In the example embodiment shown in Figure 1 , the first temperature threshold may be that of the first thermostat (130). The controller (136) may be arranged, responsive to the amount of power from the first power source (123) being available (e.g. determined as described above) or responsive to the available power being sufficient, to drive the heating element (1 18) by applying power from the first power source (123) to heat the water (1 14) up to a first temperature threshold, for example by switching the first switch (142). In the present embodiment the controller (136) may determine if power is available from the first power source (123) (or determine if the power is sufficient) and then cause the heating element (1 18) to heat the water based on electrical feedback from the temperature sensor (124). The controller (136) may thus be arranged to receive feedback from the temperature sensor (124) and to switch the first switch (142) based on the feedback to heat the water up to the first temperature threshold.

It may also be possible that the controller (136) may provide power to the heating element (1 18) from the first energy source (123) and the first temperature threshold may be implemented by way of the first thermostat (130) based on electrical feedback from the electrical temperature sensor (124). In the embodiment shown in Figure 1 , electrical feedback from a single temperature sensor (124) may be used.

In the present embodiment, the controller (136) and/or the temperature controlling component (134) may thus be arranged to determine whether an amount of power supplied by the first power source (123) is available or not (for example by receiving data from the CAN bus of the inverter (126)), or whether the amount of power at the first power source is sufficient to drive the heating element. The temperature controlling component (134) and/or the controller (136) may further be arranged, if the amount of power from the first power source (123) is not available, or insufficient, to drive the heating element (1 18) with power supplied by the second power source (125), to heat the water up to a second temperature threshold that is lower than the first temperature threshold. This may be implemented, for example by the controller (136) switching on the second switch (144) as described above, so that power flows from the second power source (125) to the heating element (1 18). The controller (136) may be arranged to receive electrical feedback from the temperature sensor (124) and to switch the second switch (144) on or off based on the feedback so as to heat the water up to the second lower temperature threshold. The second temperature threshold may be between 40°C and 60°C, or about 50°C, or about 55°C or about 60°C. The second temperature threshold may be selected so as to conserve power used from the second power source (125), however it may preferably be higher than about 55°C to inhibit the growth of bacteria, legionella or the like in the water. The present disclosure may thus implement“solar dumping” whereby excess solar power, or any available amount of solar power may be applied to heat the water up to the higher temperature threshold, thereby storing the solar energy as thermal energy in the water to conserve or limit grid usage. Optionally, the controller (136) may also determine if the amount of power is available from the first power source, or if it is sufficient, by measuring a voltage supply from the power supply device or inverter (126), instead of receiving data from the CAN bus as described above.

The first temperature threshold and the second lower temperature threshold may also be referred to as a first high setpoint and a second low setpoint, which may be implemented by the temperature controlling component (134) of the controller (136). These setpoints may however also be implemented without use of a microcontroller as will be described below with reference to Figure 4. The embodiments shown in Figures 1 and 2 may implement external switching, whereas the embodiment shown in Figure 4 may, at least partially, implement internal switching.

In the embodiment shown in Figure 1 , or in any of the other embodiments of the present disclosure, the heating element may be a resistive element with a rated power consumption. Whether the amount of available electrical power from the first power source (123 in the case of Figure 1 ) is sufficient to drive the heating element (1 18) may be predetermined, or based on a power threshold value, for example based on the rated power consumption or power draw of the heating element (1 18). The rated power consumption may be about 2 kW, or 3kW or 4 kW or any other power rating associated with the heating element. The controller (136) may be arranged to only apply power from the first power source (123) to the heating element (1 18) if the amount of available electrical power from the first power source (123) is equal to or exceeds the power rating or power threshold value associated with the heating element. The controller (136) may be arranged to only apply power from the first power source to the heating element if the feedback is indicative that the water temperature is below the first temperature threshold. The controller may alternatively or in addition be arranged to only apply power from the first power source (123) to the heating element (1 18) if the feedback is indicative that the water temperature in the water heater is below the first temperature threshold and above the second temperature threshold. The controller may be arranged to apply power from the first power source (123) to drive the heating element (1 18), if the power available at the first power source (123) is sufficient to drive the heating element (or if it is available at all), and the controller (136) may also provide power from the second power source (125), when the feedback is indicative that the water temperature is below the second temperature threshold. It will be appreciated that these features may be implemented in any of the other embodiments of the present disclosure.

Turning now to Figure 2, there is shown another exemplary embodiment of a water temperature control system (200). The system may be similar to the system (100) of Figure 1 , however, some of the features of the system (200) are different as will be described below. As with the system (100) of Figure 1 , the system (200) of Figure 2 may include a water heater (210) including a reservoir or container (212) for holding water (214) and heating the water with a heating element (218). The reservoir (212) may also include an outlet (216) and an inlet (not shown). In the embodiment of Figure 2, a first thermostat (230) may form part of a unit or module (233) which is connected to the heating element (218). A knob or dial may be used to manually adjust the first temperature threshold of the first thermostat (230). Flowever, in this instance, a mechanical temperature sensor (224) may be associated with or connected to the first thermostat (230). The mechanical temperature sensor may form part of the thermostat unit (233), and it may for example extend into a cavity (228) of the heating element (218). The first temperature threshold may be implemented by adjusting or setting the first thermostat to a maximum temperature, for example by adjusting the dial (232). This may cause the first thermostat (230) to automatically cut out or switch off, only if the first temperature is reached. As before, the first temperature threshold may be about 90°C, or above 80°C or one of the other values mentioned above for the first temperature threshold, or any suitable high value as required. In the embodiment of Figure 2, the system (200) may also include a controller (236) which includes processor (238), memory (240), temperature controlling component (234), timing component (250), transmitting component (246) and receiving component (248). These components may be similar to their equivalents in Figure 1 described above. A first switch (242) and a second switch (244) may also be provided similarly to those in Figure 1 . A first power source (223), inverter (226) or power supply device, a second power source (225) may also be provided, similarly to the embodiment described with reference to Figure 1 . Flowever, in the embodiment of Figure 2, a separate temperature sensor may be provided independently from the mechanical temperature sensor. The system (200) may include the separate temperature sensor (270) at a remote location from the heating element (218), for example at or near the outlet (216) of the water heater (210). The separate temperature sensor may be an electrical temperature sensor (270) or probe that may be inserted or retrofitted through a so-called“pocket” (272) near the outlet (216). The electrical temperature sensor (270) may be in data communications with, or it may provide data or temperature feedback to the controller (236). The electrical temperature sensor may also be provided elsewhere in the tank or reservoir (212), preferably remotely from the heating element. This may provide the advantage that premature switching of the thermostat (230) may be alleviated or prevented, since the temperature at the outlet or other remote location from the heating element may be significantly lower than close to the heating element. This may inhibit the formation of bacteria or legionella, as temperature may be more accurately controller as described herein.

As with the embodiment of Figure 1 , the controller in Figure 2 (and/or the temperature controlling component (234)) may be arranged to determine whether an amount of power supplied by the first power source (223) is available, or if it is sufficient to drive the heating element (218), and responsive thereto, to drive the heating element (218) by applying power from the first power source (223) to heat the water up to a first temperature threshold based on feedback from the temperature sensor, in this case based on feedback received from the separate electrical temperature sensor (270). As before, the controller may determine if the amount of power is available from the first power source or not, or if the amount of power available at the first power source is sufficient to drive the heating element (218). The controller (236) may switch first switch (242) on if the amount of power from the first power source (223) is available (or if it is sufficient), to drive the heating element (218) until the first temperature threshold is reached. The first temperature threshold may be that of the thermostat (230) and the thermostat may automatically switch off when it receives mechanical feedback from the mechanical temperature sensor (224) that the first temperature threshold is reached.

If the controller determines that the amount of power from the first power source (223) is not available, or if the controller determines that the available power at the first power source (223) is insufficient, the second switch (244) may be switched on by the controller (236), to provide power to the heating element from the second power source (225) (i.e. to drive the heating element). In this case, the controller (236) may continue to keep the second switch (244) switched on to drive the heating element (218) until the second and lower temperature threshold of the water is reached at or near the outlet (or wherever the electrical temperature sensor (270) is located). This may alleviate the growth of bacteria or the like. The controller may thus continue to cause water to be heated, and when the second and lower temperature threshold is reached, the controller may switch off the second switch (244) i.e. switch off the heating element (218) irrespective of the first temperature threshold or setting of the first thermostat (230). This embodiment may also provide the advantage that an existing thermostat (which may include a mechanical temperature sensor) may be used by retrofitting the water heater which may be desirable from a practical perspective, and to provide a cost-effective system which provides more effective heating control than a regular thermostat would be able to. The controller may be arranged to switch the heating element (218) off agnostic to, or irrespective of the first temperature threshold of the first thermostat (230), in the event that the amount of power from the first power source (223) is not available or insufficient.

Embodiments are possible wherein the first temperature threshold is not provided by the thermostat (230), but instead by the controller (236), by receiving feedback from the temperature sensor (270). The first temperature threshold, and the second and lower temperature threshold may both be implemented by the controller (236) by receiving feedback from the temperature sensor (270), and the first temperature threshold as well as the second and lower temperature threshold may both be below a temperature threshold of the thermostat (230) which is for example manually adjusted. It will also be appreciated that the temperature sensor (270) may be provided anywhere inside the water heater.

Still referring to Figure 2, the controller (236) may be arranged to sample the electric temperature sensor (270) to receive electrical feedback therefrom, the electrical feedback being indicative of water temperature near the outlet (216). The controller (236) may be arranged to switch either of the first or second switches (242, 244) based on the received electrical feedback to heat water up to the first temperature threshold, or the second and lower threshold, as the case may be. The live (L) and neutral (N) connections are for exemplary purposes and other arrangements may be possible.

It will be appreciated that the controller (236) need not provide direct input to the thermostat (230) and the thermostat may work independently from the controller (236) in this embodiment. However, other embodiments may also be possible and the system may include a bypassing device, a short-circuiting device or a switch arranged to bypass or short circuit the mechanical temperature sensor associated with the first thermostat, such as a bimetallic strip thereof. The controller may in such a scenario be arranged to control water temperature based purely on feedback from the electric temperature sensor to drive the heating element to heat water up to the first temperature threshold (if power from the first power source is available) or to the second and lower temperature threshold (if only grid power is available), as the case may be.

It may be possible that the controller (236) may heat the water (214) up to the first temperature threshold based on mechanical feedback, for example, the controller may drive the heating element with power from the first power source to reach the first temperature threshold based on mechanical feedback from the mechanical temperature sensor associated with the first thermostat (230). Once the first temperature threshold is reached, the first thermostat (230) may automatically switch off based on the mechanical temperature feedback.

It may, further be possible to implement features of any of the other embodiments of the present disclosure in the embodiment of Figure 2 or to implement features of this embodiment to any one of the other embodiments.

In Figure 3 is shown a conventional or prior art water heater (300). The conventional water heater (300) may include an electric heating coil (310). A regular thermostat (312) which is manually adjustable by a dial (314) is operable to switch off the heating element (310) when a setpoint temperature of the water is reached. The heating element (310) is powered by conventional grid or mains power (316).

In Figure 4 is shown another example embodiment of a water temperature control system (400). A first power source (423), inverter (426) or power supply device, a second power source (425) may also be provided, similarly to the embodiments described above with reference to Figures 1 and 2. The inverter may have a live terminal (L) and a neutral terminal (N) which may be connected as shown in Figure 4. The embodiment shown in Figure 4 may be referred to as a mechanical embodiment, or a partially mechanical embodiment, or an embodiment that does not require a microcontroller or controller. Instead, temperature control may be implemented mechanically and/or in an analogue way.

In the embodiment shown in Figure 4, a mechanical temperature sensor (424) such as a bimetallic strip (or a number of mechanical temperature sensors) may be provided in a cavity (428) of a heating element (418) of a water heater (410). Alternatively, one or more mechanical temperature sensors may be provided elsewhere in the water heater, for example at or near an outlet (416) of a reservoir or tank (412) of the water heater (410).

In this embodiment, the system (400) may include a first thermostat (430) and a second thermostat (433). The first thermostat (430) may be adjustable by way of a first adjustment device, dial (431 ), slider, button(s) or the like, and the second thermostat (433) may be adjustable by way of a second adjustment device or dial (437). The first thermostat (430) may be set to the first temperature threshold, and the second thermostat (433) may be set to the second and low temperature threshold. As before, the first temperature threshold may be between 60°C and 100°C, or about 95°C, or about 90°C, or about 85°C, or above 80°C, or about 80°C, or one of the other values mentioned above for the first temperature threshold, or any suitable high value as required. The second temperature threshold may be between 40°C and 60°C, or about 50°C, or about 55°C or about 60°C, or any other suitable value as required. The system (400) may include the first and second thermostats (430, 433) arranged in a parallel connection (477) with the heating element (418). This may also be referred to as a bi-thermostat or dual-thermostat arrangement. A temperature control component may thus be provided by an arrangement of the first and second thermostats (430, 433). This temperature control component may be provided instead of a microcontroller, and may provide temperature control to heat water to the first temperature threshold, or to the second and low temperature threshold, as the case may be.

Optionally, a power switching device or power switch such as a relay (442), switch or contactor may be provided and electrically connected to the power supply device or inverter of the first power source (423). In this instance the relay (442) or power switching device may for example be Normally Open (NO), and it may not let current from the second power source (425) through to the heating element if it is energized by power from the first power source, as is diagrammatically shown by the dashed arrow (443) in Figure 4. A Normally Closed (NC) relay may also be used as will be understood by those skilled in the art. The power switching device (442) may be operable to supply power to the heating element (418) from the second power source (425) in the event that an amount of power is not available from the first power source (423), or if the amount of available electrical power at the first power source is insufficient to drive the heating element (418). If the available power of the first power source is non-existent or insufficient, the power switch or relay (442) may not be energized by power from the first power source (or not energized enough, or below a power threshold that may be predetermined), thereby closing the connection between the second power source (425) and the heating element (418). The power switching device (442) may be operable to supply power to the heating element from the second power source (425) in the event that the amount of power from the first power source (423) is not available or insufficient. The power switching device (442) may be responsive to the amount of power from the first power source being available, and it may for example be opened or closed when it is energized by power from the first power source (423). The relay or power switching device (442) may be operable to disable the second thermostat (433) in the event that the amount of power is available from the first power source (423), thereby causing the heating element (418) to heat the water to the first temperature threshold of the first thermostat (430). If on the other hand, the amount of power is not available from the first power source (423), the power switch (442) may cause the heating element (418) to heat the water to the second (lower) temperature threshold of the second thermostat (433).

The power switching device (442) may be switched if the amount of available electrical power from the first power source (423) is sufficient to drive the heating element. The power switching device (442) may be responsive to any amount of power from the first power source (423) being available, for example, the power switching device or relay (442) may be opened or closed when it is energized by power from the first power source (423) or from the inverter (426). The power switching device (442) may be operable to disable the second thermostat (433) in the event that the amount available electrical power from the first power source (423) is sufficient to drive the heating element, thereby causing the heating element (418) to heat the water to the first temperature threshold of the first thermostat.

Alternatively, the relay or power switch (442) may be omitted, and in such a scenario the first power source (423) may assist or supplement the second power source (425) if the amount of power from the first power source is available. In other words, parallel heating may be provided between the first and second power sources (423, 425) up to the second and low temperature threshold of the second thermostat (433) and once it switches off, the first power source may continue to drive the heating element (provided that it has power available) up to the first threshold of the first thermostat (430), while the second thermostat has already cut out or reached its own setpoint.

Each of the first and second thermostats (430, 433) may receive mechanical feedback from the mechanical temperature sensor (424) (as shown by the further dashed arrows in Figure 4 extending to the thermostats) and each of the thermostats (430, 433) may have its own adjustable setpoint or temperature threshold. It may, further be possible to implement features of any of the other embodiments of the present disclosure in the embodiment of Figure 4 or to implement features of this embodiment to any one of the other embodiments.

In Figure 5 is shown an exemplary method (500) for controlling temperature in a water heater such as an electric water heater. A heating element may be provided (510) in the water heater to heat water therein. Temperature of water in the water heater may be sensed (512) with a temperature sensor. The method (500) may include determining (514) whether an amount of available electric power from a first power source is sufficient to drive a heating element, or if it is available at all. If the amount of power from the first power source is available, or if it is sufficient to drive the heating element, the heating element may be driven (516) by applying power from the first power source to heat the water up to a first temperature threshold based on feedback from the temperature sensor. The heating element may, in this case, be switched off (517) if the first temperature threshold is reached. If (514) the amount of power from the first power source is not available, or if it is insufficient to drive the heating element, the heating element may be driven (518) with power supplied by a second power source, to heat the water up to a second temperature threshold that is lower than the first temperature threshold. The heating element may, in this case, be switched off (519) if the first temperature threshold is reached.

Referring to Figures 1 , 2, 4, and 5, the method may include retrofitting an existing water heater (e.g. as shown in Figure 3) with the electric temperature sensor (as shown in Figure 2) or with the controller, or with the first and second switch (See Figures 1 and 2), or with the second thermostat (as shown in Figure 4), as the case may be. Combinations of any one or more of these or other features may also be possible.

The method may also include, by the controller (136, 236), receiving data from the power supply device (126, 226) associated with the first power source (123, 223), the data being indicative of whether the amount of power from the first power source is available or not. The method may include, by the controller, accessing the data from the power supply device, and switching the second switch to provide power to the heating element from the second power source responsive to the amount of power from the first power source not being available or if it is insufficient to drive the heating element. The method may also include, by the controller (136, 236), receiving feedback from the temperature sensor (124, 270) and switching the second switch (144, 244) on or off based on the feedback to heat the water up to the second temperature threshold that is lower than the first temperature threshold.

The method may further include, bypassing or short circuiting a mechanical temperature sensor associated with the first thermostat (130, 230), such as a bimetallic strip thereof, and controlling water temperature based on feedback from the electric temperature sensor (124, 270). For example, in the embodiment of Figure 2, it may be possible to bypass the first thermostat (230) and the controller (236) may receive feedback from the temperature sensor (270) and control temperature in the water heater based thereon, instead of a mechanical temperature sensor. It will further be appreciated that in Figure 4, the relay or power switching device (442) may be arranged to bypass or to short circuiting the first thermostat so as to enable heating to the first temperature threshold. The method may also include implementing the first and second thermostats (430, 433) so as to form a parallel connection to the heating element as described above with reference to Figure 4.

It will further be appreciated that any of the features of Figures 1 , 2, 4 and 5 may be used separately or in conjunction with one another, and features of Figures 6-15 may also be used independently, or in conjunction with one another, or in conjunction with any of the features of the embodiments described above with reference to Figures 1 , 2, 4 and 5.

Referring to Figure 6, there is shown another exemplary system (10) for controlling temperature in an electric water heater (12.1 ) which includes a heating element (14.1 ) for heating water. The system (10) may be used to control temperature in a plurality of water heaters (12.1 to 12.n) each including a respective heating element (14.1 to 14.n) and a thermostat (16.1 to 16.n). The plurality of water heaters may be provided at an infrastructure (18). In exemplary embodiments of the present disclosure described with reference to Figures 6 to 15, the infrastructure (18) may be a school infrastructure, which will be described in more detail below. Flowever, the system may also be used in other infrastructures with one or more water heaters.

The system (10) may include a first power source (20) and a second power source (22) which may be arranged to provide power to the infrastructure (18) where the water heater (12.1 ) is provided. The thermostat (14.1 ) may be operable to regulate heating of water in the water heater (12.1 ). A controller (24) may be provided, and may include a processor (26) for carrying out instructions and to provide intelligent control. The controller of the present embodiment may be similar to the controller described with reference to Figures 1 and 2, and vice versa. The controller (24) may be in communication with one or more of the water heaters and may enable or disable heating of the heating elements (14.1 to 14.n) and may be operable to adjust temperature settings or thresholds of the one or more thermostats (16.1 to 16.n). In the present embodiment, each water heater (12.1 to 12.n) may have a single thermostat (16.1 to 16.n), but embodiments may be possible where more than one thermostat is provided per water heater. The controller (24) may include a temperature controlling component (28). The temperature controlling component (28) may be configured to determine whether excess power supplied by the first power source (20) is available. Responsive thereto, the temperature controlling component (28) may set a temperature threshold of the thermostat (16.1 ) of the water heater (12.1 ) to a first temperature and cause the heating element (14.1 ) to heat water in the water heater (12.1 ) utilising the excess power of the first power source (20) when it is available. Alternatively, if no excess power from the first power source (20) is available, the temperature controlling component (28) may set the temperature threshold of the thermostat (16.1 ) to a second and low temperature and cause the heating element (14.1 ) to heat water in the water heater utilising power supplied by the second power source (22).

Each of the water heaters (12.1 to 12.n) may be similar to the water heaters described above with reference to Figures 1 , 2, 4 and 5. It may, further be possible to implement features of any of the other embodiments of the present disclosure in the embodiment of Figure 6, or to implement features of this embodiment to any one of the other embodiments described herein.

The first power source (20) may be a renewable energy source such as photovoltaic (PV) solar power or wind power, whereas the second power source (22) may be mains electricity. Optionally, one or more further power sources (not shown) may be provided, such as one or more generators, batteries, etc.

The controller (24) may further include a timing component (30) for providing timing data, and a scheduling component (32) (preferably a smart scheduling component) which may be configured to provide smart scheduling data utilising the timing data. The temperature controlling component (28) may be configured, based on the smart scheduling data, to utilise power supplied by either or both of the first and second power sources (20, 22) to heat water in the water heater (12.1 ), or to heat water in any of the further water heaters (12.2 to 12.n). The temperature controlling component (28) may set the temperature threshold of the thermostat (16.1 ) to one or more further threshold temperatures, where each threshold temperature may be associated with one of the power sources (20, 22).

A comparing component (38) may be provided and configured to compare a current time value provided by the timing component (30) to a time value of a predicted water usage event and to calculate a time difference between the current time value and the time value of the predicted usage event. The temperature controlling component (28) may in turn be operable to enable or disable the heating element (14.1 to 14.n) of each of the water heaters (12.1 to 12.n) based on the calculated time difference. Each water heater (12.1 to 12.n) may also include a temperature sensor (17.1 to 17.n) for measuring real time temperature of water in the relevant water heater. The temperature sensors (17.1 to 17.n) may alternatively form part of the thermostats (16.1 to 16.n). Real time temperature data may be relayed to the controller (24).

The controller (24) may further include a power draw determining component (34) that may be operable to determine a power draw of the infrastructure (18) where the water heater (12.1 ) is located. It will be appreciated that the infrastructure (18) may include further equipment (not shown) that require or draw power. In the event that excess power is available from the first power source (20), the temperature controlling component (28) may be operable to set the temperature threshold of the thermostat (16.1 ) to the first temperature and to cause the excess power from the first power source (20) to heat water in the water heater (12.1 ). This may be referred to as “solar dumping”. The power draw determining component (34) may be operable to also determine whether or not to enable or disable the heating element (14.1 ) (or to cause it to be enabled or disabled), based on a current power draw of the infrastructure (18). Hence, the excess power of the first power source (20) may be used to heat the water to a higher temperature, thereby storing the excess energy and limiting the amount of power needed from the second power source (22) (also referred to as“grid power”). It will be understood that if no power is available from the second power source (22) (i.e. mains or grid power is interrupted or not available), then any power supplied by the first power source (20) may be regarded as excess power.

Each one of the plurality of water heaters (12.1 to 12.n) may have a power rating. The system may include a database (36) in which data relating to the power rating of each water heater (12.1 to 12.n) may be stored. The temperature controlling component (28) may be configured to enable or disable the heating element (14.1 to 14.n) of each of the water heaters (12.1 to 12.n) based on any one or more of: the smart scheduling data, the timing data and the power rating data, thereby prioritising which of the water heaters’ heating elements (14.1 to 14.n) to enable or disable to heat water at any given point in time. Identification data of each water heater may also be stored in the database (36).

The controller (24) may access smart scheduling data which may be either pre-stored in the database (36), or generated in real time. The smart scheduling component (32) may cause the smart scheduling data to be updated in real time. The smart scheduling data may include data relating to peak demand times, and the controller (24) may utilise the smart scheduling data to limit power usage of one or more of the water heaters (12.1 to 12.n) during the peak demand times. This may enable a utility bill of an operator of the infrastructure (18) to be lowered.

The smart scheduling data may include: historical data relating to past water usage events or data relating to predicted usage events. The controller (24) may utilise the smart scheduling data to determine whether a respective heating element (14.1 to 14.n) of a relevant water heater (12.1 to 12.n) should be enabled or disabled.

The timing component (30) may be operable to determine a current time value and the controller (24) may further include a comparing component (38) which may be arranged for comparing the current time value to a time value of a predicted usage event. A time difference between the current time value and the time value of the predicted usage event may be calculated and the controller (24) may, in turn, enable or disable the relevant heating element (14.1 to 14.n) of the respective water heater (12.1 to 12.n) based on the calculated difference.

The applicant has found that it may be advantageous for the first temperature to be between 60°C and 100°C, preferably about 90°C. The second temperature may be between 40°C and 60°C, and preferably about 50°C.

In the alternative to having two set temperature thresholds for the thermostat (16.1 ) depending on whether or not solar power (20) is available, embodiments are possible wherein a single set temperature threshold is used for the thermostat. The applicant has found that about 70°C may be preferable, but temperature values of between 40°C to 90°C or even values of more than 90°C or less than 40°C may be used if appropriate. The controller (24) may be arranged to determine whether excess power supplied by the first power source (20) is available, and if such excess power is not available, the smart scheduling data may be used to determine whether to use power from the second power source (22) to heat water in the water heater (12.1 ). If excess power from the first power source (20) is indeed available, the excess power may be utilised to heat water in the water heater (12.1 ).

A temperature sensor may be provided near an outlet of the water heater, for example in an outlet flow pipe. Only one temperature sensor is needed, and two setpoints or thresholds may be implemented. The first temperature threshold may be implemented if solar power is available, and the second and lower temperature threshold may be implemented if solar power is not available.

Example embodiments of the system (10), and experimental results of a simulation of the system (10) will now be described with reference to the drawings.

The applicant has found that known systems and methods do not present a demand-limiter through intelligent electric water heater (EWH) control that may reduce demand charges at institutions billed on a demand-based tariff structure, combined with a preferably optimally sized solar system for maximal utility bill reduction. In developing countries like South Africa, effectively managing the available energy supply is important. Additionally, none of the systems and methods that the applicant is aware of implement user-specific EWH control schemes using real time usage data to maximise utility bill and carbon emission savings while maintaining user comfort. In this specification, the use of a grid-tied photovoltaic (PV) system (10) in combination with load shifting through smart scheduling of energy-storing electric water heaters (14.1 to 14.n) is assessed, to reduce both energy usage from the grid (22) (and resultant C02 emissions), peak load, and the electricity bill of an exemplary school facility (40) (shown in Figure 14) in South Africa, while ensuring that hot water demand is met. Exemplary locations of PV solar panels (42) are illustrated in Figure 14. Three example embodiments of Figures 6 to 15 the present disclosure are compared with a conventional“always on" thermostat control method. All three embodiments may use excess solar dumping to augment supply and a centralised demand-drive priority water heating.

The three embodiments of Figures 6 to 15 of the present disclosure may be incremental approaches: a first embodiment may include a single target-temperature thermostat with modulated schedule employed; a second embodiment may include a bi-thermostat (i.e. utilising a first temperature threshold and a second and low temperature threshold) and modulated schedule employed; and a third embodiment may include demand-limiting control with the bi thermostat. These three embodiments (which may also referred to as“interventions”) of Figures 6 to 15 are described in more detail below. The first and second embodiments aim to manage a total amount of energy through schedule control, while the third manages a peak power demand. Importantly, the evaluated school (40) may be billed for basic energy used and monthly peak power demand, as opposed to a flat energy rate or time of use rate. It should be appreciated that the term“bi-thermostat” or“bi-thermal control” may refer to a single thermostat (16.1) per water heater (12.1 to 12.n), with one, two, or more threshold temperatures as determined by the controller (24). More than one thermostat per EWFI may also be used if needed.

1 . Proposed EWFI heating prioritisation algorithm

This section describes three embodiments of Figures 6 to 15 the present disclosure. There is provided intelligent water heater control schemes that the applicant has evaluated in combination with an appropriately sized solar PV installation (42) (which may be as near to optimal as possible), to minimise the utility bills of the evaluated school (40) where the infrastructure (18) is provided. The system (10) may of course be applied to other facilities or infrastructures as well. A feature table highlighting the capabilities of each evaluated configuration (i.e. each embodiment of Figures 6 to 15 of the present disclosure, compared to prior art conventional thermostat control) is presented in Table 1 below. To determine the consumption profiles for each EWH (12.1 to 12.n) and to establish when hot water may be needed, the measured hot water usage may be analysed for each month, and a probability of hot water use may be calculated for each half hour of each day of the week. An iterative process may then be followed to remove outlier consumption events by applying a threshold to the probabilities. Table 1 : Feature table of evaluated interventions

In Table 1 , Thermostat-control may refer to conventional or prior art thermostat-control for comparison to the three embodiments of Figures 6 to 15 of the present disclosure. The first embodiment is termed“Smart-schedule control and solar PV”; the second embodiment is termed “Bi-thermal control and solar PV”; and the third embodiment is termed“Demand-limiting control and solar PV”. The first and second embodiments may include smart scheduling.

1 .1 Prioritised heating

A principal priority control (appropriately termed“Prioritised heating” in Table 1) may be included in all three embodiments of Figures 6 to 15 of the present disclosure (which may be referred to as“Energy saving interventions”), and may calculate the urgency with which each EWH (12.1 to 12.n) needs to be heated using a cost function. The cost function may be based on two key factors: (a) the time until the next expected water usage event, and (b) time required to heat the water from its real-time measured temperature (17.1 to 17.n) to a target or set internal temperature, T _set . Assuming both factors carry the same weight, the cost function can be defined as:

The cost function (1 ) may be calculated by the controller (24). In a test simulation for example, each simulated minute for every EWH (12.1 to 12.n), where t _eVent represents the time before the next expected water usage and where t _heat may be the required heating time from the present EWH (e.g. 12.1 ) outlet temperature to the target temperature T _set . The time before the next expected usage may be determined based on historical usage patterns with margins for error, and the time to heat the EWH (12.1 ) may be determined by its measured internal temperature (17.1 ), a volume of the EWH (12.1 ) and a rating of its heating element (14.1 ). In an example embodiment, only the EWHs (12.1 to 12.n) with highest priority, k _n , may be heated such that a minimal amount of energy may be used while maintaining user comfort and limiting the power draw of the EWFI elements (14.1 to 14.n), depending on a selected peak power demand manager control configuration.

1 .2 Excess solar dumping

All three embodiments of Figures 6 to 15 of the present disclosure may use excess energy from the solar supply (20) to augment water heating in the water heaters (12.1 to 12.n). A priority list may be used to assign water heaters to excess solar supply (20), but only as much as is available and based on the prioritised water heaters’ (12.1 to 12. n) element rating. For example, if 5 kW excess solar power were available, and the top three water heaters (e.g. the first second and third water heaters (12.1 , 12.2 and 12.3)) in decreasing priority had respective element ratings of 3 kW, 3 kW and 2 kW, in a present embodiment, an algorithm performed by the processor (26) may cause solar power (20) to be utilised heat the first water heater (12.1 ) with 3 kW rating, and the third water heater (12.3) with 2kW rating (the third water heater is not shown in Figure 6 for the sake of brevity). Grid power (22) may be used for the second water heater (12.2), but only if the chosen smart scheduling component (32) of the controller (24) allows for 3 kW grid draw at the particular time.

1 .3 Smart Schedule control and solar PV

The first embodiment of Figures 6 to 15 of the present disclosure may provide an energy-saving intervention and may use a smart schedule provided by the smart scheduling component (32) of the controller (24), that may override the prioritisation control to only heat for a set time before hot water use (or before an expected hot water usage event) to reduce standing losses. Standing losses may be referred to in the art as heat losses from water heaters (12.1 to 12.n) to their surrounding environment. The first embodiment may use only a single target temperature on the relevant thermostat (e.g. 16.1 ), namely 70 °C. The smart schedule may be arranged to balance the need to limit the standing losses of the water heaters (16.1 to 16.n) and the need to deliver hot water when needed, while dumping the excess energy from the solar supply (20) into the EWFIs (12.1 to 12.n). Unless solar power is available, the smart scheduling component (32) may only allow turning the relevant element (14.1 to 14.n) on if the time until the next event, t _e ent, is for example less than three hours. The applicant has performed iterative simulations and has found that the three hour heating period may provide good results with the least number of cold water usage events per kWh used. Flowever, it should be appreciated that other time periods may be used as and when appropriate.

1 .4 Bi-thermal control and solar PV (with Smart schedule) The second embodiment of Figures 6 to 15 of the present disclosure may provide an energy- saving intervention. The second embodiment of Figures 6 to 15 may include features of the first embodiment of Figures 6 to 15 and/or may be based thereon. The second embodiment of Figures 6 to 15 may include a bi-thermal heating mechanism (may be referred to as“BiTherm + PV” or “Bi-Thermal+PV”). In the second embodiment the EWFIs (12.1 to 12.n) may be heated to different target temperatures, T _set , for grid (22) heating and solar heating (20). In other words, a target temperature for grid heating may be different from a target temperature for solar heating. In the present embodiment, the target temperature for solar heating is higher than the target temperature for grid heating. This may allow solar energy (20) to be diverted or relayed to the EWFIs (12.1 to 12.n) if excess solar is available, even if the water temperature is higher than the grid target temperature. In the third exemplary embodiment of Figures 6 to 15, the bi-thermostat (16.1 ) may heat to a target temperature of about 50 °C for grid heating and about 90 °C for excess solar heating (but other target temperatures may be used).

By utilising a higher target temperature for solar heating, the EWFIs (12.1 to 12.n) may remain suitably hot for usage for longer periods before needing to use energy from the grid (22). In addition to increasing the target temperature for solar heating, the temperature difference between the grid target temperature and the solar target temperature can be increased by lowering the target temperature T _set for grid heating. A suitable temperature delta may be determined by maximising cost savings while maintaining user comfort. It should be noted that the bi-thermal control scheme of the second embodiment of Figures 6 to 15 may include the features of a prioritisation scheduler which may be provided by the smart scheduling component (32), in addition to having heating thresholds as shown in the feature table, Table 1 . The specific thresholds are defined in a parameter table, Table 2 below.

Table 2: Parameters used during experimental setup

1 .5. Demand-limiting control and solar PV (with bi-thermostat) The third embodiment of Figures 6 to 15 of the present disclosure may provide a control scheme which may include a demand-limited heating method in conjunction with the bi-thermal heating mechanism (may be referred to as“BiTherm + DemLim + PV” or“Bi-Thermal + Demand-Limiter + PV”), and may control the EWHs (12.1 to 12.n) such that the buildings' (40) peak monthly, power demand is not affected by the water heaters (12.1 to 12.n), or so that such effect may be reduced or inhibited. This may have the result that EWH heating does not contribute to any of the school's (40) peak demand charges. In some municipalities or areas, electricity is charged more heavily during peak demand times and the present disclosure may aim to reduce or prevent these excess charges. The algorithm performed by the processor (26) may retrieve historical, and current building energy usage data from the database (36). The comparing component (38) may compare current power usage to a recorded maximum retrieved from the historical data. The EWHs (12.1 to 12.n) may then be heated according to priority without exceeding a calculated power limit, preferably in order to not increase the recorded peak monthly demand.

In the third embodiment of Figures 6 to 15, the intention may be to perform demand limiting, and hence the three hour limitation (the time until the next event, t _{e ent} being less than three hours as referred to above under 1 .3) may be removed, allowing the EWHs (12.1 to 12.n) to be heated to their target temperatures and to remain hot enough during peak-demand times to minimise the number of cold events at the cost of increased standing losses.

2. Experimental setup

This section expands on an experimental setup performed by the applicant, including validated EWH and solar PV generation models. There is also explained how performance of the simulation results are evaluated for the various interventions and control schemes proposed. A high-level diagram (1 1 ) of the simulation setup is presented in Figure 7.

2.1 . Simulation Setup

The simulation (1 1 ) utilised measured energy data, and hot water usage data from the school (40) over a 12-month period, and implements a validated thermal EWH model and solar PV generation model for water heater and solar PV generation modelling respectively. The evaluated building (40) was selected by the applicant due to having measured energy data and EWH usage data, allowing for more accurate modelling for all seasons.

2.1 .1 Solar PV Simulation

Solar PV generation modelling may be performed using SAM (System Advisor Model) open- source libraries that may employ a photo-voltaic (PV) performance model developed by the National Renewable Energy Laboratory (NREL “Solar advisor model technical reference."

, 2018. Accessed on 2018-08-22), and calculates

the AC electrical output for each hour over a one-year period. The model may gather solar resource and temperature data from a weather file obtained, for example, by using the European Commission's photo-voltaic geographical information system for a specified location (E.C. PVGIS, “Photovoltaic geographical information system."

2018. Accessed on 2018-07-12).

The specific module sub-model implementation may provide an improvement over other known parameter models such as the five-parameter model defined by De Soto (W. De Soto, S. Klein, and W. Beckman,“Improvement and validation of a model for photovoltaic array performance", Solar Energy, vol. 80, pp. 78-88, 2004.), and may use a six-parameter single-diode model, for example one proposed by the California energy commission (CEC). The SAM's inverter model may be an implementation of an empirical model described by King (D. King, S. Gonzalez, G. Galbraith, and W. Boyson, “Performance model for grid-connected photovoltaic inverters.", Sandia National Laboratories 2007, vol. 50, p. 44, 2007) that may use manufacturer specifications with empirically derived coefficients to simulate the AC output power for a specific DC input.

The input parameters required for the simulation may be: the maximum power voltage, maximum power current, open circuit voltage and short circuit voltage per solar panel. For an inverter, the maximum AC output power, maximum DC input power and nominal operating ranges may be required. The parameters and their respective values are listed in Table 2 above. The number of modules chosen during simulation may be selected based on the schools’ (40) energy usage and peak-demand profile obtained from the school's (40) energy usage data (which may be retrieved by the controller (24) from the database (36)). For the exemplary simulation this included hourly smart meter telemetry from 1 June 2017 until 31 May 2018.

2.1 .2 EWH Simulation

In the simulation, the building's (40) EWH (12.1 to 12.n) water consumption and energy usage data was captured with one or more smart water heater controllers that were retrofitted to seven EWHs (12.1 to 12.7) installed within the school (40), and simulated for the three embodiments of Figures 6 to 15 of the present disclosure that may provide intelligent water heater control as discussed above. In the example simulation, all the EWHs (12.1 to 12.7) are mounted horizontally, the norm in South Africa, and the EWHs (12.1 to 12.7) are modelled using a computationally efficient two-node model (such as the model proposed by P.J.C. Nel, M.J. Booysen, and B. van der Merwe, “Using thermal transients at the outlet of electrical water heaters to recognise consumption patterns for heating schedule optimisation," in 2015 7 ^th International Conference on New Technologies, Mobility and Security (NTMS), pp. 1 -5, July 2015).

The two-node model may account for stratification, whereby less dense, warm water rises above the cold water and separates the two masses by a thermocline. The temperature of the separate masses may be governed by two differential equations effectively acting as two separate single nodes. The recorded internal temperature of the relevant EWH (12.1 to 12.n) may be selected from an upper, outlet node. The parameters required to model an EWH may include: the orientation, tank volume, element power rating, and thermal resistance. To execute the model, the following measurements may be required for each sample period (chosen as 1 minute): volume water used, inlet water temperature, and ambient temperature. Using these parameters, the model may estimate electrical energy used, energy lost to the environment (standing losses) and thermal energy used (the hot water leaving the EWH). The EWH model may be used with two heating control schemes for comparison, thermostat control and priority-driven smart-schedule control. Under prior art thermostat control, the thermostat measures the internal water temperature and regulates the heating element to maintain a target temperature T _set . Thermostat control does not take demand into account, and while user-comfort may be maintained through best-effort heating, as much as 20% of the used energy is lost through the heater surface as standing losses.

In the present disclosure, a suitable level of user-comfort may be selected as: fewer than one of every one hundred usage events being a cold-water event. In the example simulation, the three control schemes are simulated for a 365-day period, using simulation time steps of 1 minute. The evaluated output may include the energy used, peak power consumption, cold event count and mean event temperature for each EWH (12.1 to 12.n).

2.1 .3 Cost Estimation

In the example simulation, the assessed building (40) was subject to a demand-based tariff structure by which the school is charged for basic energy used, as well as the peak monthly power demand, which is sampled and returned every 30 minutes. As such, the simulation setup's primary goal may be to not only reduce the building's (40) total grid energy consumption and C02 emissions, but its peak power demand as well. A solar array may be optimally sized and a suitable intelligent water heater control scheme may be selected, preferably to provide maximal cost savings for an amount of money invested for installation etc. The cost estimation may be performed by calculating the utility bill reduction for each energy-saving configuration (i.e. for each of the three embodiments of Figures 6 to 15 of the present disclosure) compared to a baseline (i.e. regular prior art thermostat control), and hence a basic payback period may be determined to investigate the validity of the exemplary simulation. Table 2 above lists the parameters used during the simulation.

2.2 Evaluation and metrics

The system (10) may be evaluated by comparing the utility bill reduction, basic energy- and peak- demand savings, user-comfort, and carbon emission savings for the different energy-saving interventions compared to the school's baseline usage throughout the evaluated period. The baseline usage of the school may be defined as the total energy usage without a solar system installed, with all installed EWHs employing thermostat heating control with a target temperature of 70°C. The performance of the three intelligent water heater control schemes may be measured in terms of total basic energy usage, reduction in peak monthly power demand and user comfort. The solar PV generation optimisation methods performance is evaluated by the peak power demand reduction, total grid energy saved and reduction in carbon emissions. A potential return on investment (ROI) period may be calculated for the school with solar and smart scheduling using available balance of system (BOS) and labour cost estimates (International, Renewable Energy Agency, \Solar PV in Africa: Costs and markets."

2016. Accessed on 2018-07-26.)

2.3 Results and discussion

This section details the results obtained using the simulation setup and parameters discussed. The baseline energy cost for the school without any intervention was R292 176 ($20 971 ) for 157 MWh used during the evaluation period, generating an estimated 1 17 tons of C02 emissions. For the solar PV simulations an array size of 1 10 modules with an installed capacity of 35.2 kWp (Kilowatt peak, or peak power) was chosen, providing the greatest cost to benefit ratio while fully utilising the inverter capacity. The installed cost of the solar system is estimated to be R453 500 ($30 750), and reduced the school's yearly energy cost by 24% to an estimated R220 950 ($15 859) without any intelligent water heater scheduling. Additional improvements in utility bill reduction from EWH scheduling were as follows. With the solar system and EWH prioritisation scheduler (first embodiment of Figures 6 to 15) the yearly energy cost was lowered to R216 757 ($15 558). By implementing the second EWH control scheme using a bi-thermal heating threshold of 55°C from grid heating and 90°C from solar heating (second embodiment of Figures 6 to 15) the utility cost was R210 288 ($15 093). A temperature delta of 40°C was selected after multiple simulations and determined to be the most cost effective, without negatively impacting user comfort. Finally, when using the demand-limiter control scheme by limiting the maximum power usage of the EWHs (third embodiment of Figures 6 to 15) the demand-charge savings reduced the utility cost to R204 400 ($14 671 ) for the year, a reduction of more than 30% compared to the school's baseline, reducing the estimated yearly carbon emissions to 78 tons of C02 per year while maintaining user comfort. This allowed for additional yearly savings of R16 550 ($1 188) through the use of intelligent water heater scheduling while minimising "lost" solar energy and reducing the demand of the school and local municipality while maximising warm usage events. A warm usage event may be defined as an event with a water temperature above 40°C, therefore, all usage events that are not cold events are defined as warm usage events. Additional results comparing the simulated energy saving interventions with the school's baseline can be found in Table 3 below. Figures 8 and 9 show the average daily kWh grid-usage and total peak kVA for the year for the second simulated intervention (second embodiment of Figures 6 to 15), the bi-thermal heating mechanism with a prioritisation scheduler and solar power system (BiTherm + PV). The plotted results show the usages for various scheduling periods t _eve m. A longer scheduling period results in larger standing losses as the EWHs are heated earlier, and reduces the number of cold events by allowing the heater elements to be switched on for a longer period. From Figure 9 it is seen that the maximum monthly kVA usages for the year, defined as the sum of the building's peak monthly demand throughout the evaluation period, remain the same for all scheduling periods. This is due to the water heaters being scheduled to heat for first usages very early in the morning. By the time the peak-demand period arrives late morning during winter months or early afternoon during summer months the water has already been heated to a suitable temperature regardless of the scheduling period. From the results the cold event percentages reached a steady state for scheduling periods of greater than 3 hours, and was selected as the optimal scheduling period providing maximal user comfort for the energy used. The dashed line represents the warm event percentage of the thermostat or baseline EWH control scheme. The increased user comfort compared to thermostat control for scheduling periods greater than 3 hours can be attributed to the higher EWH target temperature of 90°C for solar heating. This allows the water to remain at a suitable temperature for late evening and early morning usages while allowing the heating elements enough time to heat the water from the grid to be at the required target temperature for peak usage times.

Figures 10 and 1 1 present the average daily kWh grid-usage and maximum (peak) monthly kVA for the year for solar intervention with a bi-thermal threshold as well as limiting the demand of the EWHs (BiTherm + DemLim + PV) (third embodiment of Figures 6 to 15). The plotted results show the usages as the demand limit is raised. A higher demand limit increases the peak monthly kVA for the year while reducing cold events by allowing more EWHs to be heated simultaneously. The large increase in kWh usage compared to the (BiTherm + PV) intervention is due to the 3 hour scheduling period, t _eve m, being removed. As a result, the EWHs (12.1 to 12.n) enter a thermostat control state, ensuring that the water heaters are always above the minimum threshold temperature of 40 °C without taking the estimated time before the next water usage event into account. This was done to allow the water sufficient time to heat, as no EWH elements are allowed to be active during the demand-limited period with a 0% increase in peak monthly demand.

From the maximum monthly kVA graph (Figure 10) the cold events for the 4% and 6% as well as the 8% and 10% increases are exactly the same. It should be noted that this is due to the percentage increase in allowable demand not being greater than the EWH element rating of (2kW and 3kW). From the results a demand-limiter with 0% demand increase was selected as a result of providing the greatest demand-charge savings while maintaining a suitable level of user comfort.

Figures 12 and 13 present the kWh used and the peak monthly power demand for each intervention (for each of the three embodiments of Figures 6 to 15 of the present disclosure), for each month of the year. From the graphs it is apparent that all three interventions provide a noticeable improvement compared to the measured baseline. From the kWh per month graph the slight increase in energy usage by the (BiTherm + DemLim + PV) control scheme compared to the (BiTherm + PV) configuration is visible, but it is clear that the introduction of bi-thermal temperature thresholds allowed for a sizeable reduction in energy usage compared to the Smart Schedule and PV control scheme. The peak demand savings graph shows large improvements for the simulated interventions when compared to the building's baseline. The relatively small improvements during the winter months can be attributed to the fact that the school's monthly peak demand occurs earlier in the morning when solar PV generation is minimal. During the summer months the school's energy usage profile is better suited for solar intervention, with the peak monthly demand occurring early afternoon when solar PV generation is at its highest. Moreover, from the graph the improvements seen from the demand limited control scheme (BiTherm + DemLim + PV) is clearly visible compared to the other two simulated configurations. This resulted in the largest cost savings, reducing the school's monthly energy bill by an average of 30% per month, with an estimated basic payback period of six and a half years.

An improvement to the demand-limiting approach presented may be to employ optimal battery sizing methods to achieve further demand reduction, reducing the peak power usage during the early mornings, particularly during winter months while further reducing potential lost solar energy. This should be done while remaining cost effective through large demand-charge savings.

Since there may be schools that pay a at fee for energy, simulations for the scenarios for a fixed cost per kWh used of 1 .6727 R/kWh and a basic charge of R273.96 per month for an 80A one- or three-phase line have also been performed. For the same period analysed above (1 June 2017 to 31 May 2018), the flat-fee cost was R266 443 for thermostat control, R185 947 for Solar& prioritisation scheduling (a saving of 30.21 % ), and R175 91 1 for the Solar & bi-thermostat (providing a saving of 34%). Table S: Simulation results for evaluated school for the period 1 June 2017 to 31 May 2018

To date, the applicant is not aware of any other system or method which has provided effectively managing electric water heaters combined with a solar power system to reduce the utility bills and carbon emissions within a school environment. The present disclosure may also be applied in other schools or other infrastructures with larger, or smaller energy- and water usage footprints or requirements. From the results obtained through simulation, it is evident that the reduction of the cost of energy used is viable for the evaluated school. By designing an optimal solar power system it has been found that the school's grid usage and peak monthly power demand was reduced significantly, with a 24% reduction in monthly energy costs and minimal excess solar energy lost. Three embodiments of Figures 6 to 15 for control schemes of intelligent water heater scheduling are proposed herein. Firstly, a priority-based scheduler configured to heat water using the school's water usage history, while diverting any excess solar energy to the water heaters to exploit their energy storage capabilities, further increasing the school's energy bill savings to 26% per month. Secondly, a bi-thermal control method was added to the priority-based scheduler, employing a temperature delta to increase the amount of solar energy to be stored within the water heater tank while minimising their grid reliance and improving the monthly savings to 28% per month. Thirdly, a demand-limiter control scheme was implemented in conjunction with bi- thermal control resulting in large demand-charge savings and an average energy bill reduction of 30% per month, producing the maximum savings while maintaining suitable levels of user comfort. Therefore, with the above interventions, the 30% utility savings can be used to improve the quality of education delivered by the school without placing further pressure on the budget.

The system (10) described above may implement controlling temperature in an electric water heater. An exemplary method (1000) for controlling temperature in an electric water heater is illustrated in the flow diagram shown in Figure 15. The method may be conducted at a controller controlling the temperature in the electric water heater. It will be appreciated that any one of the other systems described herein with reference to Figures 1 , 2, and 4 may also implement a similar method.

The controller may access (1 100) smart scheduling data captured or generated by a smart scheduler and stored in a database associated with the controller. The smart scheduler may track or monitor user activities and update the smart scheduling data in real-time based on the user activities.

The smart scheduling data may include any one or both of historical data relating to past water usage events and data relating to predicted usage events.

The controller may determine (1 1 10) the current time value, for example 12:15 pm, and compare (1 120) the current time value to a time value of one of the predicted usage events stored in the smart scheduling data. The controller may calculate a time difference between the time values and based on the time difference determine whether (1 130) an element of the electric water heater should be enabled or disabled. For example, if the current time value is two hours less than the time value of the predicted usage event, the controller may be enable the element of the electric water heater. In a further example, if the current time value is an hour greater than the predicted usage event, the controller may disable the element of the electric water heater. It should be appreciated that the time threshold values to either enable or disable the element of the water heater may differ from system to system.

If (1 130) the element needs to be enabled, the controller may determine (1 140) the amount or quantity of power supplied by a first power source. Optionally the controller may determine if the amount or quantity of available electrical power at the first power source is sufficient to drive the heating element or not. As discussed above, the power source may be any renewable power source, such as a solar power generator, a wind power generator or a hydro power generator. The controller may optionally determine if (1 150) excess power is supplied by the first power source (in other words, if the available power exceeds a power threshold, if it exceeds a required power draw, or if it is equal to or greater than a power rating of the heating element). In one embodiment of Figures 6 to 15 the power source may be associated with only a single electric water heater. In such a configuration any power generated by the first power source may be referred to as excess power. In an alternative embodiment of Figures 6 to 15 the power source may be required to supply power to a load including various appliances, for example, a stove, lights, an electric water heater, a fridge, or the like. In such an embodiment the controller may determine the required load demand and compare the power supplied by the first power source to the load demand. If the power supplied by the first power source exceeds the load demand, the first power source may supply excess power.

If (1 150) excess power is supplied by the first power source, the controller may set (1 160) a temperature threshold of a thermostat of the water heater to a first temperature. The first temperature may be a high temperature, in water heating terms, such as 90°C. This temperature may be higher than in normal circumstances in which no excess power is available.

The controller may enable (1 170) the heating element which may be supplied with power from the first power supply and thereby utilise (1 180) the excess power supplied by the first power source in the water heating process.

If (1 150) no excess power is supplied by the first power source, for example in the first exemplary embodiment when the first power source is inactive due to environmental constraints, or for example in the alternative embodiment where the supply is less than the load demand, the controller may set (1 190) the temperature threshold of the thermostat to a second temperature. The second temperature may be a low temperature (for example lower than the first temperature threshold), such as about 50°C.

The controller may enable (1 170) the heating element and utilise (1200) power provided by a second power source to the water in the water heater.

It should be appreciated that when excess power is supplied by the first power source, controller may utilise the power provided by the first power source in order to heat the water in the water heater, and if the first power source does not supply excess power, the controller may utilise the power provided by the second power source, such as grid mains, to heat the water in the water heater. It should be appreciated that the temperature threshold to which the thermostat is set may be any suitable threshold.

In a further exemplary embodiment, there may be provided a plurality of water heaters with each water heater having a power rating associated with the specific water heater. The power rating of each water heater may be stored in the database accessed by the controller. The controller may be configured to use the smart scheduling data, the timing data and the power rating data to prioritise which of the water heaters in the system needs to be heated first.

Figure 16 illustrates an example of a computing device (1600) in which various aspects of the disclosure may be implemented. The computing device (1600) may be embodied as any form of data processing device including a personal computing device (e.g. laptop or desktop computer), a server computer (which may be self-contained, physically distributed over a number of locations), a client computer, or a communication device, such as a mobile phone (e.g. cellular telephone), satellite phone, tablet computer, personal digital assistant or the like. Different embodiments of the computing device may dictate the inclusion or exclusion of various components or subsystems described below.

The computing device (1600) may be suitable for storing and executing computer program code. The various participants and elements in the previously described system diagrams may use any suitable number of subsystems or components of the computing device (1600) to facilitate the functions described herein. The computing device (1600) may include subsystems or components interconnected via a communication infrastructure (1605) (for example, a communications bus, a network, etc.). The computing device (1600) may include one or more processors (1610) and at least one memory component in the form of computer-readable media. The one or more processors (1610) may include one or more of: CPUs, graphical processing units (GPUs), microprocessors, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs) and the like. In some configurations, a number of processors may be provided and may be arranged to carry out calculations simultaneously. In some implementations various subsystems or components of the computing device (1600) may be distributed over a number of physical locations (e.g. in a distributed, cluster or cloud-based computing configuration) and appropriate software units may be arranged to manage and/or process data on behalf of remote devices.

The memory components may include system memory (1615), which may include read only memory (ROM) and random access memory (RAM). A basic input/output system (BIOS) may be stored in ROM. System software may be stored in the system memory (1615) including operating system software. The memory components may also include secondary memory (1620). The secondary memory (1620) may include a fixed disk (1621 ), such as a hard disk drive, and, optionally, one or more storage interfaces (1622) for interfacing with storage components (1623), such as removable storage components (e.g. magnetic tape, optical disk, flash memory drive, external hard drive, removable memory chip, etc.), network attached storage components (e.g. NAS drives), remote storage components (e.g. cloud-based storage) or the like.

The computing device (1600) may include an external communications interface (1630) for operation of the computing device (1600) in a networked environment enabling transfer of data between multiple computing devices (1600) and/or the Internet. Data transferred via the external communications interface (1630) may be in the form of signals, which may be electronic, electromagnetic, optical, radio, or other types of signal. The external communications interface (1630) may enable communication of data between the computing device (1600) and other computing devices including servers and external storage facilities. Web services may be accessible by and/or from the computing device (1600) via the communications interface (1630).

The external communications interface (1630) may be configured for connection to wireless communication channels (e.g., a cellular telephone network, wireless local area network (e.g. using Wi-Fi™), satellite-phone network, Satellite Internet Network, etc.) and may include an associated wireless transfer element, such as an antenna and associated circuitry.

The computer-readable media in the form of the various memory components may provide storage of computer-executable instructions, data structures, program modules, software units and other data. A computer program product may be provided by a computer-readable medium having stored computer-readable program code executable by the central processor (1610). A computer program product may be provided by a non-transient computer-readable medium, or may be provided via a signal or other transient means via the communications interface (1630).

Interconnection via the communication infrastructure (1605) allows the one or more processors (1610) to communicate with each subsystem or component and to control the execution of instructions from the memory components, as well as the exchange of information between subsystems or components. Peripherals (such as printers, scanners, cameras, or the like) and input/output (I/O) devices (such as a mouse, touchpad, keyboard, microphone, touch-sensitive display, input buttons, speakers and the like) may couple to or be integrally formed with the computing device (1600) either directly or via an I/O controller (1635). One or more displays (1645) (which may be touch-sensitive displays) may be coupled to or integrally formed with the computing device (1600) via a display (1645) or video adapter (1640).

Any of the steps, operations, components or processes described herein may be performed or implemented with one or more hardware or software units, alone or in combination with other devices. In one embodiment, a software unit is implemented with a computer program product comprising a non-transient computer-readable medium containing computer program code, which can be executed by a processor for performing any or all of the steps, operations, or processes described. Software units or functions described in this application may be implemented as computer program code using any suitable computer language such as, for example, Java™, C++, or Perl™ using, for example, conventional or object-oriented techniques. The computer program code may be stored as a series of instructions, or commands on a non-transitory computer-readable medium, such as a random access memory (RAM), a read-only memory (ROM), a magnetic medium such as a hard-drive, or an optical medium such as a CD-ROM. Any such computer-readable medium may also reside on or within a single computational apparatus, and may be present on or within different computational apparatuses within a system or network.

Flowchart illustrations and block diagrams of methods, systems, and computer program products according to embodiments are used herein. Each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, may provide functions which may be implemented by computer readable program instructions. In some alternative implementations, the functions identified by the blocks may take place in a different order to that shown in the flowchart illustrations.

It will be appreciated by those skilled in the art that there are many variations to the invention as herein defined and/or described with reference to the accompanying drawings, without departing from the spirit and scope of this disclosure.

For example, the present disclosure may be used for other types of water heaters (not necessarily electric water heaters), such as gas water heaters, for example to minimise gas usage. The heating element may thus be replaced by a gas heating apparatus or element for heating by way of combustion of gas or burning another type of fuel. In such an embodiment, the gas heating may be provided if renewable or solar energy from the first power source is not available, and if the renewable energy from the first power source is available, it may be used to heat the water with a separate heating element such as a resistance heating element that may work independently from the gas heating. Moreover, in the case of an electric heating element being implemented in the various embodiments described above, it may also be in the form of other types of heating elements, for example using inductive heating or other means of heating water. It may also be possible to implement one or more thermostats that have temperature thresholds or setpoints that are adjustable by receiving an electrical signal from a controller.

The present disclosure may thus facilitate providing efficient water heating notwithstanding varying energy supply availability during different times of the day, or during different seasons. The present disclosure may also facilitate energy management during varying load conditions, and it may manage excess supply of energy in an effort to provide efficient water heating. The unwanted growth of bacteria or legionella may also be prevented or alleviated and the present disclosure may enable an existing water heater to be retrofitted to include any one or more of the features described. The present disclosure may further provide efficient water heating with a single heating element and may provide advantages over known water heaters. Implementing a single heating element may provide the advantage of reducing the overall complexity of the system and it may enable installations where two or more heating elements per EWFI are not desirable. Retrofitting of existing water heaters may be performed. The present disclosure may also provide cost effective systems and methods.

The foregoing description has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure.

The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.

Finally, throughout the specification and accompanying claims, unless the context requires otherwise, the word‘comprise’ or variations such as‘comprises’ or‘comprising’ will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.