Electric Fluid Heater

Abstract

Disclosed is a partially or fully electric fluid heater (1) configured to heat a fluid in a first circuit, the fluid including a heating fluid or tap water. The heater comprises a first electric heating element (8) configured to heat the fluid in the first circuit. The first electric heating element is configured to be powered from both an AC power source (22) and a DC power source (20). The heater also comprises a controller (24) configured to control the distribution of power from the DC power source and the AC power source to the first heating element.

Description

[Technical field]

[0001] The present invention relates to electric heaters for fluid heating systems, in particular but not exclusively to electric boilers for wet heating systems or electric furnaces for air heating systems, both of which can supply heated fluid (e.g. via a radiator) or heated tap water, or both, for a heated space. [Background technology]

[0002] Gas boilers can provide hot water and wet heating solutions for space heating needs. For example, domestic gas boilers often supply hot water to heating radiators in a heating system, and also supply hot water on demand to a tap (e.g., for drinking, cleaning, washing). The two supplies (heating and tap) are kept separate because tap water must be clean, while heating water can become dirty as it passes through the radiator circuit. Combination ("combi") boilers are popular because they provide all of this functionality within a sealed, high-pressure environment in a single boiler housing with a relatively small physical footprint. Other types of boilers with separate tanks or cylinders are also used.

[0003] Gas boilers burn fossil fuels, as a result electric boilers are now emerging as a greener alternative. Electric boilers run water through an electric heating element.

[0004] Electric combi boilers use similar technology to electric kettles. They are plugged into a utility power supply and supplied with cold water from the mains. When hot water is demanded (e.g. the hot water tap is opened or the heating switched on), a heating element in the electric boiler generates heat and transfers this heat to the cold water. The heated water is then pumped to the tap or radiator where it is needed.

[0005] Storage electric boilers include a hot water tank (either internal within the unit or external), which allows water to be heated and stored when energy costs are lower (e.g., overnight) for subsequent use when energy costs are higher (e.g., the next day). Such systems take up a lot of space.

[0006] Along the same theme, but offering some of the advantages of a combi boiler, a Combined Primary Storage Unit (CPSU) has a central heating boiler and hot water cylinder combined in one large housing, which provides large amounts of hot water whenever required, but requires a lot of space to house the system.

[0007] All of these electric boiler systems use a heating element that is powered by AC (alternating current) utility power. Summary of the Invention [Problem to be solved by the invention]

[0008] The inventors realised that a better electric boiler could be made and have developed the solution set out in the claims. [Means for solving the problem]

[0009] According to a first aspect of the present invention there is provided a fluid heater as claimed in claim 1.

[0010] Advantageously, a fully electric or hybrid electric fluid heater is provided that can use a combination of DC and AC power sources (i.e., does not have to rely on AC input). This type of heater allows for intelligent use of available power options, thereby allowing it to operate more efficiently in an environmentally friendly manner while still providing high performance. The intelligent mix of AC and DC power sources reduces the risk of overwhelming the domestic power source or local grid (e.g., during peak demand). Additionally, fluid heaters can be provided that typically have higher peak power. Additionally, the intelligent use of DC power is useful in the event of a power cut in the utility AC power source.

[0011] Optional features of the present invention are as claimed in the dependent claims and provide various advantages as described in the detailed description. These optional features add efficiency and intelligence to the heater setup of the present invention. Any of these optional features can be combined with any other optional features as will be understood by those skilled in the art.

[0012] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 shows a schematic diagram of a boiler according to a first embodiment of the present invention. [Diagram 2] 1 shows a schematic diagram of a boiler according to another embodiment of the present invention. [Diagram 3] 1 shows a schematic diagram of a boiler according to yet another aspect of the present invention. [Figure 4] 1 shows a schematic diagram of a boiler according to yet another aspect of the present invention. [Diagram 5] 1 shows a schematic diagram of a boiler according to yet another aspect of the present invention. [Figure 6]Figure 6a shows a rear view of a furnace according to yet another embodiment of the invention, Figure 6b shows a side view of a furnace according to yet another embodiment of the invention, Figure 6c shows a cross-sectional view (on DD shown in the side view) of a furnace according to yet another embodiment of the invention, and Figure 6d shows a cut-away perspective view of a furnace according to yet another embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The exemplary embodiments described in the detailed description and claims are not meant to be limiting. Other embodiments can be used and other changes can be made without departing from the scope of the invention. Various embodiments have been described. The specific embodiments are not intended as exhaustive descriptions or as limitations on the aspects more broadly discussed and claimed. Features described in conjunction with a particular embodiment are not necessarily limited to that embodiment and can be incorporated in any other embodiment or embodiments. The protection afforded by the applicable doctrine of equivalents shall be retained to its fullest extent.

[0015] Terms such as upper, lower, top, bottom, left, right, inside, outside, vertical, upright, etc. are used to simply and clearly describe the present invention. These terms should not be construed as limiting. Those skilled in the art will envision other suitable embodiments within the scope of the present invention.

[0016] With reference to Figure 1, there is shown a schematic representation of a fluid heater in the form of a hot water heater 1 (also referred to herein as a boiler) used to heat water for use in a standard fluid circuit, such as a radiator heated water circuit. Various aspects of boilers and boiler systems are described in detail with reference to non-limiting examples. Further details will be apparent to those skilled in the art. In particular, aspects of known boiler systems (including aspects not described) can be incorporated and used in the present invention by those skilled in the art.

[0017] In general, the boiler may be a tank-type boiler (also known as a system boiler), or a combi boiler, or any other known boiler type, or a furnace-type heater, such as a furnace-type air heater. Those skilled in the art can adapt the described embodiments to boiler types other than the described types. As is known, these boiler types can be used to provide heated water (e.g., to a radiator circuit), or drinking water (e.g., to a tap of the circuit), or both. In other examples, instead of heating radiator water, there may be another type of heating fluid flowing through the heating system, for example another liquid, another gas (e.g., air), or oil, or any combination thereof. In the embodiment

[0018] Such fluid circuits are well known in the art. Any or each fluid circuit may be a substantially sealed fluid circuit in use, or may optionally be pressurized. In a potable water circuit, pressure from a mains or gravity-fed source drives the water so that water flows from the tap in normal use when the tap / faucet is opened. Typically, a radiator circuit is substantially sealed in normal use. Bleed or pressure relief points may be provided at convenient locations to allow inspection or pressure relief or fluid relief for maintenance and repair. It is known to use expansion tanks or expansion vessels, which are small tanks used to protect sealed (i.e. not open to atmospheric pressure) fluid heating systems and domestic hot water systems from excessive pressure. Typically, the expansion tank is partially filled with air, the compressibility of which dampens the shock caused by water hammer and absorbs excess water pressure caused by thermal expansion. In an air heater, the fluid circuit usually comprises at least one vent for the exit of heated air to the space to be heated. In such circuits, the air within the circuit is not sealed from the environment, typically atmospheric or ambient pressure. In some such systems, during normal operation, air is drawn into the furnace, heated, and then blown around the heating network.

[0019] In this embodiment, the hot water heater 1 is a system boiler and includes a boiler housing 2 for housing the boiler components. In many cases, the boiler of the present invention will be required to fit within a small space. In many embodiments, even though the boiler of the present invention includes new components (as described in more detail below), the present invention includes features that make the boiler compact and allow the boiler to fit within the same housing or space footprint as a typical known boiler.

[0020] The boiler 1 is configured to heat water in a first circuit, the first circuit being a heated water circuit, which comprises several components including a standard domestic radiator (not shown) in addition to the boiler 1. In this embodiment, water is used as the heating fluid in the first circuit, in other embodiments other known heating fluids can be used.

[0021] Relatively cool water from the first circuit enters the boiler 1 through a cold water input pipe 4, is heated, and then relatively warm water leaves the boiler 1 through a hot water output pipe 6 to the first circuit.

[0022] The boiler 1 comprises an electric boiler vessel 10 located within a housing 2 and between an input pipe 4 and an output pipe 6. The electric boiler vessel 10 is a sealed vessel containing a first electric heating element 8 arranged to heat water passing through the vessel 10.

[0023] According to the present invention, the first electric heating element 8 is in communication with both a DC power source and an AC power source such that it can be powered by either or both of these sources.

[0024] In this embodiment, the DC power source is in the form of a battery pack 20 that is part of the heater 1 and is also located within the housing 2. In other embodiments, the DC power source may be located external to the heater.

[0025] In this example, the AC power source comprises a commercial power source 22 (also known as “utility power,” “domestic power,” “household electricity,” “residential current,” “power line,” “home power,” “wall power,” “line power,” “AC power,” “city power,” “street power,” or “hydro”).

[0026] The boiler also includes a controller 24 configured to control the distribution of power from the DC power source 20 and the AC power source 22 to the first heating element 8. As will be apparent to one skilled in the art, the controller may be implemented in hardware or software, or a combination thereof.

[0027] In some embodiments, the controller is computer controlled and configured to control the amount of heating supplied to the fluid based on or in response to any one or more control factors, including the amount of heating required, the fluid input temperature at an input point in one or more fluid circuits, the fluid output temperature at an output point in one or more fluid circuits, the fluid temperature at any given point in one or more fluid circuits, the capacity available from the first heating element, the amount of heating capacity available from the combustible fuel burner, the instantaneous demand for heating fluid or potable water, the forecasted demand for heating fluid or potable water, and the flow rate of the fluid to be heated.

[0028] Additionally, in some embodiments, the fluid heater includes one or more sensors (not shown) configured to sense information related to one or more control factors and provide said control factor information to the controller. Some of the sensors are located inside the boiler housing (e.g., to measure water temperature or flow rate within the boiler). Some of the sensors are located outside the boiler housing (e.g., to measure water temperature or flow rate at a desired location outside the boiler and in the first circuit, such as in a room of the building). The controller is operative to direct heating of the fluid by the fuel burner and the electric heating element in response to information from such sensors.

[0029] In some examples, the controller may have a memory (not shown) associated with it (either integrally or separately), the memory configured to store information about any one or more aspects of the system, such as historical or sensory information related to any of the control factors, control factor information, sensory information from any of the sensors, desired output information (e.g., desired room temperature), etc. The controller can access the information from the memory in known manner. The controller and memory may be implemented in standard computer-controllable networks and systems.

[0030] In this embodiment, the controller 24 includes a hardware thermostat controller and, optionally, a further GUI thermostat controller (not shown) to allow a user to easily input desired fluid heating requirements and receive feedback on fluid heating operating parameters in a known manner.

[0031] In this example, the controller 24 also includes an AC power adapter (not shown) configured to interface with an external AC power source 22 for delivering AC power to the heating elements 8 in a desired power configuration. Although not present in this embodiment, in some embodiments a DC power adapter disposed between the DC power source and the heating elements is similarly configured to interface with the DC power source 22 to deliver DC power to the heating elements in a desired power configuration.

[0032] The controller is configured to take into account a number of factors when controlling the distribution of power to the heating elements: in some cases (at any one time), it is desirable to use only DC power, in other cases (at any one time), it is desirable to use only AC power, and in other cases (at any one time), it is desirable to use a combination of DC and AC power.

[0033] The controller may be configured to control the relative distribution of power from the DC and AC sources taking into account any one or more of the capacity of the or each heating element (e.g., capacity of the maximum safe load (e.g., peak power, or duration of continuous power supply) of a particular heating element), the capacity of the or each power source, the instantaneous demand for heated water or tap water (e.g., tap has just been turned on / radiator has just been started from a cold state), the forecasted demand for heated water or tap water, and the instantaneous or forecasted supply type available. The controller may also be configured to effect a seamless switch from primarily using the DC source to primarily using the AC source, e.g., as the DC battery depletes, the AC source gradually takes over while the power output remains substantially constant or at a desired level. The controller may also control smart charging of the DC source such that heat and charge level (e.g., whether to charge aggressively / fast or slowly) (of the DC battery) are taken into account when controlling charging.

[0034] In some embodiments, the first heating element may have a preferred power demand range, and the controller is configured to supply power within the preferred power demand range while varying the ratio of AC to DC power to the first heating element from 0:100 to 100:0 AC:DC. If the demand is met entirely or mostly by the DC power source, a relatively large DC power source may be required. In some embodiments, the DC power source is sized such that 100% of the heating demand cannot be met by the DC power source alone. In other embodiments, a large DC power source is provided and such demand can be met by the DC power source alone (see examples later in this specification).

[0035] In this embodiment, the boiler is a fully electric boiler, i.e., all heat sources are electrical. In other embodiments, the boiler may be partially electric, e.g., partially electric and partially gas, or partially electric and other combustible fuels, where suitable combustible fuels may be natural gas, hydrogen gas, or a combustible fluid such as propane or methane gas, or ethane or butane gas, or a suitable combustible oil or solid, or mulch such as wood chips or wood pellets, or any combination thereof. Thus, the heating power may be provided by some electric (DC and AC) components, and some more traditional combustion fuels. This may be useful for keeping redundancies within the system, or may be used to operate efficiently in environments where one or the other power sources are in short supply. In the present invention, the combination of DC and AC power sources is large enough to provide nearly all of the power output of a typical boiler as needed.

[0036] Referring to Figure 2, there is shown a schematic diagram of a hot water heater 31 used to heat water for use in a standard radiator heated water circuit. Various aspects of boilers and boiler systems are described in detail with reference to non-limiting examples. Further details will be apparent to those skilled in the art. In particular, aspects of known boiler systems (including aspects not described) can be incorporated and used in the present invention by those skilled in the art.

[0037] In general, the boiler may be a tank-type boiler (also known as a system boiler), or a combi boiler, or any other known boiler type, or a furnace-type heater, such as a furnace-type air heater. Those skilled in the art can adapt the described embodiments to boiler types other than the described types. As is known, these boiler types can be used to provide heated water (e.g., to a radiator circuit), or drinking water (e.g., to a tap of the circuit), or both. In other examples, instead of heating radiator water, there may be another type of heating fluid flowing through the heating system, for example another liquid, another gas (e.g., air), or oil, or any combination thereof.

[0038] In this embodiment, the hot water heater 31 is a system boiler and includes a boiler housing 32 for housing the boiler components. In many cases, the boiler of the present invention will be required to fit within a small space. In many embodiments, even though the boiler of the present invention includes new components (as described in more detail below), the present invention includes features that make the boiler compact and allow the boiler to fit within the same housing or space footprint as a typical known boiler.

[0039] The boiler 31 is configured to heat water in a first circuit, the first circuit being a heated water circuit. In addition to the boiler 31, the heated water circuit comprises several components including a standard domestic radiator (not shown). In this embodiment, water is used as the heating fluid in the first circuit, although in other embodiments other known heating fluids may be used.

[0040] Relatively cool water from the first circuit enters the boiler 31 through a cold water input pipe 34, is heated, and then relatively hot water leaves the boiler 31 through a hot water output pipe 36 to the first circuit. A water pump (not shown) is also provided in this circuit.

[0041] The boiler 31 comprises an electric boiler vessel 40 which is disposed within the housing 32 and between an input pipe 34 and an output pipe 36. The electric boiler vessel 40 is an enclosed vessel which houses a first electric heating element 38 which is arranged to heat water passing through the vessel 40.

[0042] In accordance with the present invention, the first electric heating element 38 is in communication with and can be powered by either or both of a DC and an AC power source.

[0043] In this embodiment, the DC power source is in the form of a battery pack 50 that is part of the heater 31 and is also located within the housing 32. In other embodiments, the DC power source may be located external to the heater.

[0044] In this embodiment, the AC power source comprises a utility power source 52 .

[0045] The boiler also includes a controller 54 configured to control the distribution of power from the DC power source 50 and the AC power source 52 to the first heating element 38. As will be apparent to one skilled in the art, the controller may be implemented in hardware or software, or a combination thereof.

[0046] In this embodiment, the controller 54 includes a hardware thermostat controller and, optionally, a further GUI thermostat controller (not shown) to allow a user to easily input desired fluid heating requirements and receive feedback on fluid heating operating parameters.

[0047] In this embodiment, the controller 54 also includes an AC power adapter (not shown) configured to interface with an external AC power source 22 for delivering AC power to the heating elements 8 in a desired power configuration.

[0048] The controller 54 includes a DC-AC converter (not shown separately from the controller in the drawings) disposed between the DC power source and the heating elements and configured to interface with the DC power source 22 to convert the DC to AC in a known manner before delivering power to the heating elements in the desired power configuration.

[0049] In this embodiment, the controller is configured to control the combination of outputs from the AC and DC power sources to send only AC power to the heating element. An advantage of this feature is that it simplifies the input circuitry to the heating element (resulting in fewer wet circuit components (i.e., components that contain fluid / water), resulting in improved reliability, maintenance, and space savings) than if both AC and DC were supplied directly to the heating element.

[0050] In other embodiments, the controller may be configured to control a mixture of outputs from the AC and DC power sources to achieve different goals.

[0051] In other examples, the heater may include (instead of a DC-AC converter) an AC-DC converter disposed between the AC power source and the heating element and configured to interface with the AC power source to deliver AC to DC in a known manner and then send only DC power to the heating element in a desired power configuration. Again, an advantage of this feature is that it simplifies the input circuitry to the heating element rather than providing both AC and DC directly to the heating element. In this situation, in some embodiments, the AC-DC converter may be disposed inside the boiler housing, and in other embodiments, it may be disposed outside the boiler housing.

[0052] The controller is configured to consider a number of factors when controlling the distribution of power to the heating elements. In some cases (at any one time), it is desirable to use only DC power, in other cases (at any one time), it is desirable to use only AC power, and in other cases (at any one time), it is desirable to use a combination of DC and AC power. In one embodiment, DC power is used most of the time, and AC power is used during cold spells. In some embodiments, when heating hot water for drinking or the like, DC power is ideally used (to provide a fast heating response time, at least for the initial heating).

[0053] The controller is configured to control the relative distribution of power from the DC and AC sources taking into account any one or more of the capacity of the or each heating element (e.g., the capacity of the maximum safe load (e.g., peak power, or duration of continuous power supply) of a particular heating element), the capacity of the or each power source, the instantaneous demand for heated water or tap water (e.g., when the tap has just been turned on / the radiator has just been started from a cold state), the forecasted demand for heated water or tap water, and the instantaneous or forecasted supply type available. The controller can learn user behavior over time (e.g., when a shower event occurs, when one or more users normally wake up, etc.). One or more sensors can feed back sensed information to the controller to improve this learning.

[0054] In some embodiments, the first heating element may have a preferred power demand range, and the controller is configured to supply power within the preferred power demand range while varying the ratio of AC to DC power to the first heating element from 0:100 to 100:0 AC:DC. If the demand is met entirely or mostly by the DC power source, a relatively large DC power source may be required. In some embodiments, the DC power source is sized such that 100% of the heating demand cannot be met by the DC power source alone. In other embodiments, a large DC power source is provided and such demand can be met by the DC power source alone (see embodiments later in this specification).

[0055] In this embodiment, the boiler is a fully electric boiler, i.e., all heat sources are electrical. In other embodiments, the boiler may be partially electric, e.g., partially electric and partially gas, or partially electric and other combustible fuels, where suitable combustible fuels may be natural gas, hydrogen gas, or a combustible fluid such as propane or methane gas, or ethane or butane gas, or a suitable combustible oil or solid, or a mulch such as wood chips or wood pellets, or any combination thereof. Thus, the heating power may be provided by some electric (DC and AC) components, or by more traditional combustion fuels. This may be useful for keeping redundancies within the system, or may be used to operate efficiently in environments where one or other power sources are scarce. In the present invention, the combination of DC and AC power sources is large enough to provide nearly all of the power output of a typical boiler as needed.

[0056] The features of the controller and the method of intelligently distributing power from AC and DC power sources when powering heating elements described with reference to Figures 1 and 2 may be used in combination with the embodiments described below, and protection for such combinations is particularly desired.

[0057] With reference to Figure 3, a hot water heater 100 similar to that described with reference to Figure 1 is shown. Unless otherwise specified, the technical features are similar to those described with reference to the previous embodiments (e.g. with reference to Figure 1 or Figure 2). The heater 100 is used to heat water for use in a standard radiator heated water circuit. Various aspects of the boiler and boiler system are described in detail with reference to non-limiting examples. Further details will be clear to the skilled person. In particular, aspects of known boiler systems (including aspects not described) can be incorporated and used in the present invention by the skilled person.

[0058] In this embodiment, the hot water heater 100 is a system boiler and includes a boiler housing 102 for housing the boiler components.

[0059] The boiler 100 is configured to heat water in a first circuit, the first circuit being a heated water circuit that includes several components including a standard domestic radiator (not shown) in addition to the boiler 100. In this embodiment, water is used as the heating fluid in the first circuit, although in other embodiments other known heating fluids may be used.

[0060] Relatively cool water from the first circuit enters the boiler 100 through a cold water input pipe 104, is heated, and then relatively warm water leaves the boiler 100 through a hot water output pipe 106 to the first circuit.

[0061] The boiler 100 comprises an electric boiler vessel 110 located within the housing 102 and between an input pipe 104 and an output pipe 106. The electric boiler vessel 110 is an enclosed vessel that houses a first electric heating element 108 configured to heat water passing through the vessel 110.

[0062] In accordance with the present invention, the first electric heating element 108 is powered by a combined DC and AC power supply of the type described with reference to Figure 1, and in alternative embodiments the combined DC and AC power supply may be of the type described with reference to Figure 2 or related embodiments. For clarity, most of the common components shown in Figure 1 (e.g. the controller and its associated circuitry) are not reproduced in Figure 3.

[0063] In this embodiment, the DC power source is in the form of a battery pack 120, which is also located within the housing 102. In this embodiment, the boiler is a fully electric boiler, i.e., all of the heat sources are electrical. In other embodiments, the boiler may be partially electric, e.g., partially electric and partially gas, or partially electric and other combustible fuels, where the suitable combustible fuels may be natural gas, hydrogen gas, or propane or methane gas, or ethane gas, or butane gas, or suitable combustible oil or combustible solid, or mulch, or any combination thereof. Thus, some of the heating power is provided by DC electrical components, while others are provided by more traditional combustion fuels. This can be useful to add redundancy within the system, or can be used to operate efficiently in environments where one or other power sources are scarce. In the present invention, the DC power source is large enough to provide nearly all of the power output of a typical boiler as needed.

[0064] In this embodiment, the DC power source has a capacity of 1 kWh.

[0065] In another example for a small gas-electric hybrid boiler system setup, the battery capacity may be about 1 kWh (which may be useful in a small residential facility, such as a small apartment block, or may be more useful in a larger residential facility as a boost to a regular hot water source).

[0066] In another embodiment for larger gas electric hybrid boiler system setups, the battery capacity may be about 3-5 kWh (this capacity may be useful in large residential facilities).

[0067] In another embodiment for a fully electric boiler system setup, the battery capacity may be about 5 kWh or more. In most cases, a capacity of 15 kWh to 20 kWh is sufficient to cover most of the hot water needs with only a boiler using DC power. For example, for a fully electric boiler in a small apartment block, the battery capacity may be about 10 kWh, for a medium house, about 15 to 20 kWh, and for a large house, about 25 to 30 kWh.

[0068] In some implementations, the battery capacity may be approximately 90 kWh, for example, to supply heating fluid and heated drinking water to a large building.

[0069] In this embodiment, in some embodiments, the peak power output of the DC power source is between 10 kW and 20 kW, and in some embodiments up to 200 kW. In low peak demand circuits, the peak power output may be 1 kW or 2 kW. Providing an appropriate peak power output can be made according to the particular circuit requirements and will be apparent to one of ordinary skill in the art. For example, in one exemplary situation, a 90 kWh battery can provide 350 kW for 10 minutes.

[0070] In this embodiment, the battery pack 120 comprises a stack of batteries in a compact cell ordered array.

[0071] In this example, the 1 kWh DC battery pack 120 includes 100 replaceable or rechargeable cylindrical cells, such as standard size 18650 type cells (18 mm diameter, 65 mm length), each cell having approximately 10 Wh capacity. In this example, the rechargeable cells are arranged in a 10×10 stack for compactness, and the entire stack can be removed from the battery pack 120 and recharged outside the housing 102. In another example, the stack may be a 5×20 stack. Other suitable stack configurations will become apparent depending on the available space in the battery pack. The stack is configured such that each cell in the stack can be used approximately consistently over time in a known manner, so that the stack effectively operates as a single unit. In some examples, the DC power source can also be charged from a renewable heat source, such as solar or wind power, or a heat pump, or any other suitable power source.

[0072] In other embodiments, the DC battery pack can be charged in situ, ie, without removing the battery from the housing 102, through a charging connection (not shown).

[0073] Charging of the battery pack is performed in this embodiment by an AC-DC converter (not shown), and in embodiments where charging is performed in situ, the boiler further comprises an AC-DC converter disposed within the housing.

[0074] A typical 18650 type cell has a voltage of 3.6V. In this embodiment, the cells in the pack 120 are arranged in series, i.e., the effective voltage is about 3600V. The pack is well insulated. In other embodiments, the cells may be arranged in a different configuration, for example, all in series (so that the maximum voltage in any single path is 3.6V) or in parallel paths with several cells in series, for example 10 parallel paths with each path having 10 cells (36V) in series.

[0075] In some embodiments, the cells may be configured to provide approximately the same voltage as the AC input supply voltage, allowing for easier combination of AC and DC and easier charging. For example, in the UK, 240V battery packs may be provided.

[0076] In some embodiments, instead of a single battery pack, multiple battery packs or stacks within a battery pack are provided.

[0077] The boiler 100 housing also utilizes the housing's AC connection 130 to power small electronic components such as switching circuits, boiler display screen, boiler user interface, sensors, Wi-Fi, Bluetooth, sub-1 GHz communications, etc., LED lighting, and other standard boiler components (these have relatively low power demands compared to the power required to heat water during normal boiler operation). Other such components include an igniter or spark generator, ignition / ionization electrodes, pressure sensor / transmitter (water), water pressure switch, flow sensor / switch (ensuring the gas / air mixture is flowing properly before ignition can occur), combustion sensor (thermal switch, sometimes listed separately from temperature sensor by manufacturer), thermostat, thermocouple / PRT, control PCB, multimedia interface, power electronics for the power pack, pumps for water and gas (simple electric pumps, sometimes more complex pumps with drive electronics). In some embodiments, this power may also be provided by a renewable heat source such as solar or wind, or a heat pump, or any other suitable power source. In some other embodiments, these small electronic components may be powered directly from a DC power source.

[0078] In this embodiment, the boiler 100 also includes a controller (not shown) configured to control any one or more of the heating, battery charging, battery discharging, system requirements, and switching of the DC power supply as described with reference to the embodiment of FIG. 1.

[0079] The relatively large battery of the present invention generates heat. Other electrical components of the boiler also generate heat. The inventors have realized that there is a need for a compact and efficient non-standard cooling system.

[0080] The boiler 100 of this embodiment also includes a cooling system (not shown). Due to the extra switching associated with the intelligent use of the large DC battery and the operation of the controller and its associated circuitry due to the desire to intelligently use the DC-v-AC, the electronics may get hotter than in a normal boiler due to the large DC battery power.

[0081] In some embodiments, the heater includes a high power switching module configured to efficiently switch high currents so that the heater can vary power in the same resistive electric heating element and smoothly vary the fluid temperature. This is particularly important in potable water circuits. This feature allows for pulse width modulation within the control circuitry. The high power switching module may be configured to switch 30 amps or more.

[0082] In embodiments housing a battery charging mechanism, the inventors have further found that heat generation in the battery charging system, specifically in an AC-DC converter battery charging system capable of charging a DC battery pack / cell with a voltage, can be problematic. This type of battery charging system generates heat, which is not yet present in the boiler system or boiler housing. Therefore, a further advantage of some embodiments of the present invention is to use the cooling system as a heat sink (or provide an additional separate cooling system) to also cool the battery charging mechanism. This system can be particularly useful since charging can (and should) occur even when the cooling system of the battery charging mechanism is not on (i.e., when the cooling system is not heating the building or providing hot drinking water, e.g., during the night). The cooling system of the present invention allows the heating system to run during periods of charging only, which takes away the heat. The controller may be configured to flow fluid through the fluid heater system to cool the battery charging mechanism even when heated fluid is not needed, for example, the controller may operate in response to predicting, being notified, or sensing (e.g., via feedback from a temperature sensor located near the battery charger or after the battery has been continuously charged for a threshold minimum time period) that the battery charging system should be cooled. This battery charging mechanism cooling function may be implemented using any of the described embodiments, including the battery charger to create new embodiments of the present invention.

[0083] In some embodiments (e.g., where the flow of heated fluid / potable water is responsible for cooling), cooling is provided via the flow of heated fluid / potable water through the controller / battery / battery charger when the heating system is operational (e.g., when potable water or heated radiator fluid is required). However, when the heating system is not operational, the present invention allows the charger cooling system to operate (whether via the flow of heated fluid / potable water or via the cooling system's own dedicated refrigerant in its own dedicated refrigerant circuit) specifically for the purpose of cooling the battery charger.

[0084] In some embodiments, the cooling system uses a portion of the water output from the radiator, which reaches the cooling input pipe 104 (typically at about 35-40°C) for cooling the electronic components, which are much hotter (ideally intended to keep the electronic components well below 100°C). In some embodiments, the cooling system elements include locating the first circuit piping from the inlet 104 in the boiler 100 adjacent or near the components requiring cooling. As a result, the overall efficiency of the fluid heater is increased, as the need for full electronic efficiency with switching power is reduced, and the electronics of the fluid heater can be made more compact / simpler.

[0085] The cooling system of this example includes a refrigerant circuit having a sealed refrigerant piping system (not shown) through which refrigerant is routed. The sealed refrigerant piping system is configured to facilitate heat transfer between the refrigerant and the boiler's chilled water input to transfer heat to the refrigerant, and between the refrigerant and the battery cells or other components to transfer heat away from those components. This is accomplished by disposing the piping system near any one or more of the boiler components, the battery cells, and the chilled water input at suitable locations.

[0086] In the embodiment of Figure 3, the boiler is configured to be compact. The housing has dimensions of 400cm wide x 300cm deep x 700cm high and houses the first heater vessel 110 housing the first heating element 108, the DC power supply 102, and (in this embodiment) the cooling system. In other embodiments, the housing may have dimensions of 390mm wide, 270mm deep, 600mm high, or 400mm wide, 300mm deep, 724mm high, or 400mm wide, 310mm deep, 724mm high, or 440mm wide, 365mm deep, 780mm high, or 440mm wide, 364mm deep, 825mm high, or 440mm wide, 365mm deep, 780mm high, or any other suitable dimensions apparent to one skilled in the art.

[0087] In a more compact case, the DC power supply is located in the front side of the housing when in use, substantially filling the space between the front and rear ends of the housing, and substantially filling the space between the left and right sides of the housing. The boiler has walls on the left and right sides that are relatively inaccessible when in use. The front side is relatively accessible and is typically used to access the internal components during maintenance.

[0088] In some embodiments, the housing 100 includes an access door positioned to provide access to the internal components of the heater (e.g., for maintenance or repair), and the DC power supply is positioned within or integral with the access door, which also increases overall compactness and ensures that the DC battery does not need to be further removed or manipulated to access the internal boiler components (e.g., for repair / service).

[0089] In this embodiment, the boiler 100 includes an insulating layer or heat shield (not shown) disposed between the DC power supply and the first heater vessel, and also includes an insulating layer or heat shield (not shown) disposed between the controller and the first heater vessel. The insulating layer or heat shield may include any one or any combination of voids, gaps filled (partially or completely) with insulating material, gaps filled (partially or completely) with infrared reflective material, gaps filled (partially or completely) with insulator or low thermal conductivity material.

[0090] In some embodiments, the heat shield may include an associated heat shield cooling mechanism positioned to transfer heat from a region of the heat shield towards another region where it is safer to dissipate the heat, the cooling mechanism comprising: A fluid material that carries heat away from an area (e.g., a heat shield area) to a heat dissipation area (i.e., another area where it is safer to dissipate heat than the heat shield area); Active cooling mechanisms such as Peltier elements (which actively move heat from one side to another, e.g., to another area where it is safer to dissipate heat than the heat shield area); A cooling cabinet (similar to a typical refrigerator) disposed within the boiler housing and positioned to substantially enclose the DC power supply; An airflow mechanism, such as a blower, arranged to draw air from outside the housing or from inside the housing to provide the required cooling effect; Any one or more of the following may be included.

[0091] The electric heating element can be wrapped around the pipe or component of the first circuit. Advantages of this include ease of manufacture, ease of reconfiguration / replacement / upgrade / repair if necessary (as the heating element is located outside the pipe / component and does not need to touch the wet side). The heating element is easily visible and therefore convenient to inspect (e.g. during routine maintenance) for deterioration. Such heating elements are also easier to clean. Such heating elements are not affected by sludge in the water circuit (a problem common in radiator water circuits).

[0092] In other embodiments, the electric heating element can be located inside the first circuit conduit / pipe, the advantages of which include compactness and low heat loss to the environment (heat is almost entirely retained within the desired water circuit during normal heating operation).

[0093] In other embodiments, the electric heating element may be incorporated into the walls of the water circuit conduits of the first circuit, the advantages of which include that these walls are more robust, less susceptible to damage from dirty water, and suffer less heat loss (than an equivalent wrapped heating element).

[0094] In other embodiments, heating may occur in a chamber (rather than in a pipe). In such an embodiment, the pipes of the first circuit may run in and out of the chamber, and one or more electric heating elements may be provided anywhere in the chamber, embedded in the walls of the chamber, wrapped around the walls of the chamber, or any combination thereof. The advantage of using such a chamber, rather than simply heating the water / heating fluid as it passes through the fluid pipes of the circuit, is that a longer or more circuitous path can be provided, and this circuitous path allows the heating fluid to remain close to the heating element(s) for a longer period of time where more heat can be transferred (compared to a direct path through a straight section of pipe).

[0095] In yet another embodiment, the types and arrangements of electric heating elements used may be combined depending on the particular application.

[0096] In a further embodiment (not shown), the boiler comprises a hybrid electric-gas boiler vessel instead of a vessel with only an electric heating element. In such an embodiment, multiple heating mechanisms are provided in the same sealed boiler vessel chamber. One is an electric heating mechanism and the other is a gas burner mechanism. The gas burner mechanism is of known type. The other mechanism may be a burner burning a different fuel (e.g., hydrogen gas, propane gas, oil) instead of natural gas. The electric heating mechanism may be in any suitable form. In this example, it is in the form of an electric heating element. In such an example, the DC power supply is still large enough to provide the electric heating element with enough power to obtain all or most of the required heated fluid / water. The boiler may be configured in one example to heat water in the first circuit (such as to heat water for supplying to a radiator circuit). The electric heating element or multiple such elements may be located anywhere in or around the burner vessel so that the water can be heated by either or both the gas and the electric heating mechanism. The heating element can be an electrical wire that can be heated by passing an electric current through it and appropriately positioned (e.g., wrapped around a water pipe, or a baffle (or any other component in the burner vessel)) to deliver heat to where it is needed.

[0097] There may be a heat exchanger in the gas burner vessel. The heat exchanger is positioned to focus heat from the combustion gases, the heated electric element(s), or both, to the or each water pipe. The heat exchanger may be metallic or ceramic. In one embodiment, the heat exchanger may be in the form of one or more plates (e.g., metal plates) positioned partially or completely around the water pipe. The electric heating element may be positioned between the plates. In another embodiment, there may be a block of suitable material (e.g., a ceramic block) positioned around the water pipe.

[0098] 4, in another embodiment, a hot water heater 200 comprises a combi boiler arranged to heat water in a second circuit (for heating and supplying drinking water) and a first circuit (for heating a heating fluid and supplying the radiator network). The second circuit has a different conduit arrangement, i.e. piping, than the first circuit, so that the fluids in the two circuits do not merge (so that the drinking water is not contaminated by the radiator water).

[0099] Some components of boiler 200 are similar to components of boiler 100 and have similar reference numbers in the format 2xx instead of 1xx.

[0100] The boiler 200 includes a housing 202 that contains a first heater vessel 210 that houses a first heating element 208, a DC power supply 202, and a cooling system (not shown).

[0101] Relatively cool water from the first radiator circuit enters the boiler 200 through a cooling radiator fluid input pipe 204, is heated, and then relatively warm water leaves the boiler 200 through a hot water output pipe 206 to the first radiator network circuit.

[0102] Boiler 200 includes an electric boiler vessel 210 located within housing 202 and between input 204 and output 206 pipes. Electric boiler vessel 210 is an enclosed vessel that houses a first electric heating element 208 configured to heat water passing through vessel 210.

[0103] According to the present invention, the first electric heating element 208 is powered by a combination of DC and AC power sources, which in this example (similar to that of any of the previous embodiments) is not shown except for the DC power source, which is in the form of a battery pack 220, which is also located within the housing 202. In this example, the boiler is a fully electric boiler, i.e., the heat source is all electric. In other examples, the boiler may be partially electric, for example partially electric and partially gas, or partially electric and partially other combustible fuels, and the suitable combustible fluid may be hydrogen gas or propane gas, or a suitable combustible oil, or a combustible solid, or mulch, or any combination thereof. In this way, the heating power is provided by some of the power sources (which are an AC-DC combination) and some of the more traditional combustion fuels. This can be useful to add redundancy within the system, or can be used to operate efficiently in environments where one or other power sources are scarce. In the present invention, the power supply (which is a combination AC-DC) is large enough to provide all or nearly all of the power output of a typical boiler, if desired.

[0104] In some such embodiments, for example, embodiments in which the air intake is used to assist in the combustion process (e.g., when burning gas or combustible fuel), the cooling system may include using the air intake to cool the battery pack and / or electronic components because the air being drawn in will be relatively cool while at the same time the air is being heated, making the combustion process more efficient. This may be accomplished by locating the air intake path near the battery pack or components requiring cooling.

[0105] In this example, the DC power source has a capacity of 5 kWh.

[0106] Other variations (e.g., hybrid electric-gas power configuration, AC-DC controller configuration, cooling configuration, etc.) are similar to those described with reference to previous embodiments (e.g., with reference to FIG. 3).

[0107] In the embodiment of Figure 4, the hot water in the first boiler vessel 210 is also configured to heat water in the second circuit (without directly heating the water in the second circuit). The second circuit comprises a potable water circuit (e.g., providing tap water for washing, bathing, drinking, etc.). Relatively cooler water from the second circuit enters the boiler 200 through a main cold water input pipe 205 (supplied through a water main pipe) and is heated, and then the relatively warmer potable water leaves the boiler 200 through a hot water output pipe 207 to a second tap circuit.

[0108] The second circuit comprises a pipe section between the inlet 205 and the outlet 207, arranged for heat to be transferred from the first container 210 to the second circuit. In this embodiment, this is achieved by locating this pipe section in close proximity to the container 210 so as to effectively transfer heat to the section of pipe in use. The pipe section comprises a helical pipe wrapped around the container 210 to further aid in the transfer of heat between the pipe section and the container 210. In another embodiment, instead of or in addition to a helical pipe wrapped around the container, the water is heated via a wet heat transfer box. In this way, it is not necessary to heat the radiator water every time drinking water is heated. In such an embodiment, the water of either circuit can be heated separately, i.e. pipes from both circuits can enter the heat exchanger container to provide heating for either or both circuits.

[0109] The battery pack 220 is positioned at the top of the housing 202, spaced from the heating vessel 210, and is shielded from the heating vessel 210 by a heat shield (not shown), as described with respect to the other embodiments.

[0110] Referring to Fig. 5, in another embodiment, a hot water heater 300 comprises a combi boiler configured to heat water in a second circuit (for heating and supplying drinking water) and a first circuit (for heating and supplying a heating fluid to a radiator network). The system of Fig. 5 is similar to the system of Fig. 4, except that the drinking water in the second circuit is primarily heated through a different mechanism (similar reference numbers are in the format 3xx instead of 2xx). The combi boiler 300 includes an electric boiler vessel 310, which is located within the housing 302 and between the input 304 pipe and the output 306 pipe. The electric boiler vessel 310 is a sealed vessel housing a first electric heating element 308 configured to heat water passing through the vessel 310.

[0111] In accordance with the present invention, the first electric heating element 308 is powered by a combination DC-AC power source, the components of which are not shown (but are similar to those of any of the previous embodiments), except for a DC power source in the form of a battery pack 320 also located within the housing 302. In this example, the boiler is a fully electric boiler, i.e., the heat sources are all electric. In other examples, the boiler may be partially electric, for example partially electric and partially gas, or partially electric and partially other combustible fuels, where suitable combustible fuels may be hydrogen gas or propane gas, or suitable combustible oil or combustible solids or mulch, or any combination thereof. In this way, the heating power is provided by some of the power sources (which are AC-DC combinations) and some by more traditional combustion fuels. This can be useful to add redundancy within the system, or can be used to operate efficiently in environments where one or other power sources are scarce. In the present invention, the power supply (which is an AC-DC combination) (and in fact the DC supply alone) is large enough to provide all or nearly all of the electrical power output of a typical boiler, if desired.

[0112] In this embodiment, the DC power source has a capacity of 20 kWh.

[0113] In contrast to the embodiment of Figure 4, the electric heating arrangement of the embodiment of Figure 5 comprises a second electric heating element configured to efficiently deliver heat to the water in the second circuit. In this embodiment, the boiler 300 comprises a second electric boiler vessel 311 housing the second electric heating element 309 in the path of the second circuit and between the input pipe 305 and the output pipe 307. In this embodiment, the DC battery pack also powers the second electric heating element 309.

[0114] Various modifications can be made to the present invention without departing from the scope of the invention.

[0115] Optionally, in embodiments where the heater comprises two (or more) heating elements (whether the heating elements heat the fluid in a single circuit or in different circuits, or whether the heating elements are housed in the same heater vessel or in different heater vessels), the controller is configured to power the first heating element only via a DC power source and the second heating element only via an AC power source, or vice versa. This feature reduces the need for complex circuitry and therefore reduces the risk of circuit failure. Furthermore, if one power source fails, the other power source still operates.

[0116] Optionally, in embodiments where the heater serves two (or more) circuits (whether there are multiple heating elements or only a single heating element) in which fluid is to be heated, the controller is configured to power the or each associated heating element using only a DC power source when heating liquid in a first circuit and only an AC power source when heating water in a second circuit, or vice versa. This feature takes into account that a particular power source (AC or DC) may be more efficient overall for a particular fluid circuit or type of fluid circuit (e.g., a radiator circuit or a drinking water circuit), reducing the need for more complex circuitry and therefore reducing the risk of circuit failure.

[0117] Although embodiments of the present invention are described with respect to a water boiler, the same inventive concepts may be applied to other (partially or wholly) electric fluid heaters, for example air heaters (also known as furnaces) which are common in North America. Typically such systems include a fan to blow out the heated air, but for clarity, a fan is not shown in any of the drawings. Systems for heating other fluids will be apparent to those skilled in the art.

[0118] 6a-6d show one such example, according to which a furnace heater 400 is arranged to supply heated (or cooled) air. The furnace 400 includes a housing 402, an air inlet 404, and a fan 406 arranged near the air inlet to draw air from the environment into the furnace housing 402. The housing also has an air outlet 408 through which the heated air leaves the furnace housing. Between the air inlet 404 and the outlet 408, there is an air duct 410. Variations of such a furnace air heater will occur to those skilled in the art.

[0119] The furnace includes a heat exchanger 412 configured to provide heat to air passing through a duct 410. In this example, the heat exchanger is disposed within the duct (but in other examples, it may be disposed outside the duct). In this example, a plurality of electric heating elements 414 are disposed within the body of the heat exchanger 412. The electric heating elements 414 are arranged to provide heat when powered by an electric current. The furnace includes a large DC power source, in this example in the form of six DC battery packs (other configurations will be apparent). The DC power sources in this example include power sources of the type described above with respect to the boiler. Additionally, an AC power source (not shown) is also configured to power the heating elements. A controller (not shown) is configured to control the distribution of power from the DC power source and the AC power source to the heating elements in a similar manner as described above with respect to the boiler embodiment. In this example, the battery capacity is approximately 5 kWh. This value may be different in other examples, as described with respect to the previous examples. In this example, the power pack provides surge and steady state power for the heating elements in the heated air delivery system.

[0120] In some embodiments, a second fluid circuit for hot water is also provided, and in such embodiments, on-demand hot water may be managed within the furnace by the power electronics (used to power the furnace's electronic components). The number / combined power of DC power packs may be tailored to the requirements of a particular installation. In some embodiments, the power electronics may be cooled by circulating air or other fluid and may also be used to preheat the air flowing through the ducts. The modular DC power packs are designed for easy replacement and are conveniently located on an accessible side of the housing.

[0121] There is very little wasted space within the furnace housing 402. The battery packs are both useful and fill space that would normally be empty.

[0122] In other examples, the fluid heater comprises a portable air heater (similar to the furnace described above, but smaller). In such examples, the first circuit (as described in claim 1) is within the stand-alone fluid heater itself. In such examples, the portable air heater comprises a small fan blower in conjunction with one or more electric heating elements (of the type described in connection with the previous examples) and powered by a DC battery pack and by an AC power source (e.g., commercial AC power). The controller is configured to control the distribution of power from the DC power source and the AC power source to the heating elements in a manner similar to that described above in connection with the previous embodiment. In some other examples, the portable heater does not have a blower, and instead the heater comprises a natural convection heater or a radiant heater.

[0123] In some such embodiments, the AC may be cut off (or may be unavailable, for example, during a power outage) and the heater may run solely from a DC power source.

[0124] In such embodiments, the DC battery capacity may be at least 0.2 kWh of power, such as about 0.5 kWh or about 1 kWh. The peak power output may be about 3 kW DC plus 3 kW AC in some embodiments.

[0125] The housing of such a portable air heater is smaller than a typical furnace, for example, about 20 cm in diameter and 35 cm in height.

[0126] In an embodiment of a multiple fluid circuit, e.g., a combi boiler, where other power sources are present in addition to the combined AC-DC power source, a first heating element may be configured to heat a fluid in one of the first and second circuits and a fired heater may be configured to heat a fluid in the other of the first and second circuits, e.g., tap water is heated only by the power source and heated water is heated by a combustible fuel source.

[0127] There may be more than one heating element per heating vessel.

[0128] For any embodiment described as being solely electric, those skilled in the art will appreciate that it may alternatively be provided in a partially electric and partially combustible fuel form.

[0129] Any of the embodiments may include a DC power interface configured to accept a DC power source, the DC power interface configured to accept two or more types of DC power sources, such as any combination of Ni-MH battery cell packs, Ni-Cd battery cell packs, and Lithium battery cell packs, or hybrid packs containing a hybrid of any of these types of cells. A supercapacitor may be used instead of or in addition to a conventional DC battery pack to provide the DC power source.

[0130] Any of the embodiments including a DC power cell may include a safety shut-off mechanism configured to disconnect the cell from powering the electric heating element. The safety shut-off mechanism may comprise a master switch or an automatic master switch, and in some embodiments the safety shut-off mechanism comprises a contactor. Advantageously, this provides a safe and simple DC switching mechanism.

[0131] Existing electric, gas (or other combustible fuel), or gas-electric hybrid (not previously known, but described in applicant's co-pending applications) fluid heaters can be fitted with electric heating element(s), or batteries, or both, of the types described above, along with a control mechanism (e.g., control electronics and / or software) that controls the amount of heating provided by DC, AC, or a combination thereof, to provide a fluid heater within the scope of the present invention.

[0132] The fluid heater of the present invention is more powerful and efficient than the original fluid heater. Such embodiments are particularly suited for introducing electric heating capabilities to existing AC electric or gas boilers. For example, an electric heating element may be coated on, coated within, sprayed into, housed within, wrapped around, partially or fully embedded in, or otherwise associated with, a duct section at or near the outlet from the combustible fuel burner vessel, the inlet to the burner vessel, or both. The heating element(s) may be powered by DC, AC, or a combination thereof. In some embodiments, a battery, such as a large battery of the type described above, may be attached to the burner vessel along with a control mechanism (e.g., control electronics and / or software) to control the amount of heating provided by the electric heating element(s) relative to the combustible fuel source. The control mechanism may also control the amount of heating provided by DC, AC, or a combination thereof. When attached to an AC electric boiler, a DC power pack may be added along with appropriate control electronics to allow for balanced use of DC and AC depending on demand requirements and / or supply.

[0133] In an embodiment in which the circuit comprises a heated water circuit, such as a radiator circuit, the boiler / heater comprises a pump, such as a water pump (not shown in any of the drawings for clarity), as is known in the art.

[0134] In embodiments where the circuit comprises a potable water circuit, typically the inlet is from a water mains inlet, which is pressurized so no pump is required, in some embodiments a pump may be provided where the input is from a non-pressurized clean water source.

[0135] In any, all, or some embodiments, the battery charging mechanism is configured to charge the DC power sources taking into account and in response to any one or more of the current battery charge level of the DC power source, the capacity of the power source or each power source, the instantaneous demand for heating or tap water, the forecasted demand for heating or tap water, the instantaneous or forecasted supply type available, and the household demand, the regional demand, the national demand, the international demand, or any combination thereof. Typically, the battery packs are charged during off-peak hours, e.g., overnight or during the day (usually when the controller is informed that demand is low, or in some cases when the controller learns that demand is low).

[0136] In any of the described embodiments, any or each heating element may be any element that emits heat when an electric current is passed through it, such as, for example, a resistive wire, or any wiring that emits heat when an electric current is passed through it, such as, but not limited to, Thin films (polyimide on conductive metal), Ceramic wire (ceramic sheath with nickel-chromium-aluminum embedded), Bare wire (nickel, nichrome, Kanthal, Stellite, etc., tungsten), Encapsulated wire (e.g., nichrome with silicone sheath), Inorganic insulated wires, such as copper sheath / nichrome, cupronickel / inconel, steel sheath / nickel, inconel sheath / nickel wire, and all kinds of hybrids of these (elements may be drawn to size or manufactured to finished size. Insulation is typically Al2O3 or MgO); Simple wire with elements wound between the wires, spiral wire, busbar wire, may be also possible.

[0137] In any embodiment where a single heating element is described, that heating element may be replaced by one or more different heating elements, as would be apparent to one of ordinary skill in the art. For example, one or more of the electric heating elements may comprise an electrically conductive heating element coating on one or more of an inner surface of at least one duct wall, an outer surface of at least one duct wall, and a surface of the combustion fuel heat exchanger, baffle, or any other component. One or more of the electric heating elements may comprise, for example, an inductive heating element that may be powered by induction (without direct contact).

[0138] In some cases, multiple separate electric heating elements are configured to heat the fluid in separate sections of the duct. In some embodiments, multiple separate sections of the heating element are provided in the fluid duct, and each section may be controlled together or separately, for example to provide different levels of heating at different section locations. This may be effective when combustion heating levels are different at different locations of the burner vessel, and the electric heating element(s) may provide less heating in sections where the burner can provide more heating, and more heating in sections where the burner can provide less heating. In another use case, it may be desirable to provide different heating levels to different sections of the fluid path, such as at the initial start of heating when the fluid is first heated from a low temperature, e.g., when a tap is first turned on, and more heating may be provided at the beginning of the fluid path than at the end of the fluid path because the starting input fluid is particularly cold.

[0139] In some of these embodiments, the elements may be fully embedded within the fluid duct, such that no part of the element emerges or protrudes from the duct (eg, there are no external electrical connection points).

[0140] In some embodiments where heating elements are provided in separate zones (not continuous along the entire length of the duct), gaps between the separate zones may be formed by masking the gap portions of the tube (e.g., with a spray mask) during the coating / spraying process.

[0141] In some embodiments, the present invention provides a single-housing fluid heater having an electric heating element configured to be powered by both a larger DC power source and an AC power source with an on-board controller and controller cooling system. The inventors have recognized that the components of this type of system have significantly different cooling needs.

[0142] In embodiments housing a battery charging mechanism, the inventors have further found that heat generation within the battery charging system, and more particularly within the AC-DC converter charging system capable of charging DC battery packs / cells with a voltage, can be problematic. This type of battery charging system is not yet present within the boiler system or boiler housing and generates heat. Therefore, a further advantage of some embodiments of the present invention is the use of a cooling system as a heat sink (or providing an additional separate cooling system) to also cool the battery charging mechanism. This system can be particularly useful since charging can (and should) occur when the cooling system of the battery charging mechanism is not heating the building or providing hot drinking water (e.g., overnight). The cooling system of the present invention can run a heating system that takes away heat during charging. The controller may be configured to flow fluid through the fluid heater system to cool the battery charging mechanism even when heated fluid is not needed, for example, the controller may operate in response to predicting, being notified, or sensing (e.g., via feedback from a temperature sensor located near the battery charger or after the battery has been continuously charged for a threshold minimum period of time) that the battery charging system should be cooled.

[0143] In some embodiments, the controller may be configured to provide a shower saving algorithm, such as: if DC power is unavailable (e.g., battery level is low or zero), switch to powering the electric heating element only via AC power. In that case, direct (i.e., on-demand when the tap is turned on) hot water is provided only by AC power, which provides less power than a large DC power source can provide. Thus, the controller is programmed to ensure that some minimum threshold of DC capacity remains at all times, to allow, for example, high power showers. This feature can be selectively activated or deactivated by the user via a user interface that sends instructions to the controller. In some embodiments, the minimum threshold of DC capacity may be 5% of the total battery capacity held in the reservoir.

[0144] In some embodiments, the present invention provides a fluid heater that achieves the safe provision of a large modular power pack that is easily replaceable within the confines of the heater housing. The large power pack has sufficient capacity to provide the entire heating load for a typical domestic dwelling via the mains. A power pack of this size is safely located within the confines of the housing using a heat shield as described above. Because the battery charger cooling mechanism may often be operated at different times relative to the controller and the battery cooling mechanism, the battery charger cooling mechanism may comprise or include a separate or distinct cooling mechanism relative to the controller and the battery cooling mechanism.

[0145] In some cases, there may be multiple cooling mechanisms, for example, at least one cooling mechanism associated with the controller, at least one cooling mechanism associated with the battery, and at least one cooling mechanism associated with the battery charger.

[0146] In some examples, the cooling system (alternatively or in addition to the cooling systems described above) may be a passive cooling system configured to transfer heat from a component to be cooled (such as a boiler electronics or a DC power source or a battery charger or any combination thereof). A passive cooling system may not include a flowing fluid. A passive cooling system may include a thermal heat sink (e.g., an aluminum block, such as a 20 mm x 40 mm x 80 mm aluminum block) with natural convection fins for heat dissipation to the environment. A passive cooling system may include a large thermal mass, such as a heater housing.

Claims

1. 1. A partially or fully electric fluid heater configured to heat a fluid in a first circuit, the fluid comprising a heating fluid or tap water, the heater comprising: a first electric heating element configured to heat a fluid in the first circuit, the first electric heating element configured to be powered by both an AC power source and a DC power source; and a controller configured to control the distribution of power from the DC power source and the AC power source to the first heating element; a heater housing configured to house the heater;

2. 10. The heater of claim 1, further comprising a battery pack configured to power the DC power source and optionally the first heating element, optionally the DC power source having a capacity of at least 0.5 kWh, further optionally at least 1 kWh, and further optionally at least 5 kWh.

3. 10. The heater of claim 1, further comprising a DC power charging mechanism.

4. The heater of claim 3 , further comprising a cooling system configured to cool any one or more of the controller, the DC power supply, and the DC power supply charging mechanism.

5. 10. The heater of claim 1, wherein the AC power source comprises an AC power adapter configured to connect to an external AC power source, such as a commercial AC power source.

6. 10. The heater of claim 1, further configured to heat a fluid in a second circuit, wherein the fluid in the first circuit comprises a heating fluid and the fluid in the second circuit comprises tap water, or vice versa, and the first heating element is configured to heat the fluid in the first circuit, the fluid in the second circuit, or both.

7. 10. The heater of claim 1, wherein at any given moment, the first heating element is configured to be powered only by either the DC power source or the AC power source.

8. 2. The heater of claim 1, a DC-AC converter between the DC power source and the first heating element, such that the first heating element is configured to receive only AC power from either the AC power source, the DC power source, or both; or an AC-DC converter between the AC power source and the first heating element, such that the first heating element is configured to receive only DC power from either the AC power source, the DC power source, or both; Including, a heater.

9. 10. The heater of claim 1, wherein the controller is configured to control a mix of outputs from the AC power source and the DC power source.

10. 10. The heater of claim 1, wherein the controller is configured to vary a ratio of AC power to DC power to the first heating element.

11. 7. The heater of claim 6, wherein the controller is configured to power the first heating element using only the DC power source when heating liquid in the first circuit and only the AC power source when heating water in the second circuit, or vice versa.

12. 7. The heater of claim 6, further comprising a second heating element configured to heat fluid in the first circuit, the second circuit, or both.

13. 13. The heater of claim 12, wherein the first heating element is configured to be powered only by the DC power source rather than by both the AC power source and the DC power source, and the second heating element is configured to be powered only by the AC power source, or vice versa, and the controller is configured to control the distribution of power from the DC power source and the AC power source to the heating elements.

14. 2. The heater of claim 1, wherein the controller: - the capacity of the or each heating element; the capacity of the or each power source, - Instantaneous demand for heated water or tap water, - Forecasted demand for heated or tap water, and - Available instantaneous or forecast supply type; a heater configured to control distribution of power taking into account any one or more of:

15. 4. The heater of claim 3, wherein the DC power charging mechanism is a battery charging mechanism, optionally configured to communicate with the controller, and optionally configured to: - current DC power supply battery charge level, the capacity of the or each power source, - Instantaneous demand for heated water or tap water, - predicted demand for heated or tap water; · Available instantaneous or forecast supply type, and ・Household demand a heater configured to charge the DC power source in consideration of any one or more of:

16. 7. The heater of claim 6, further comprising a combustion heater, such as a gas burner or an oil burner, configured to heat fluid in the first circuit, the second circuit, or both.

17. 17. The heater of claim 16, wherein the first heating element is configured to heat fluid in one of the first circuit and the second circuit, and the combustion heater is configured to heat fluid in the other of the first circuit and the second circuit.

18. 5. The heater of claim 4, comprising a fluid heater housing, optionally having dimensions of 390-440 cm wide, 270-365 cm deep, and 600-825 cm high, the housing configured to house a first fluid heater vessel, such as a first boiler vessel, that houses the first heating element and the DC power source, and optionally one or both of the cooling system and the DC power source charging mechanism.

19. 20. The heater of claim 18, further configured to heat a fluid in a second circuit, wherein the fluid in the first circuit comprises a heating fluid and the fluid in the second circuit comprises tap water, or vice versa, and the first heating element is configured to heat the fluid in the first circuit, the fluid in the second circuit, or both; the heater further comprises a second heating element configured to heat fluid in the first circuit, the second circuit, or both; The first fluid heater vessel further houses the second heating element.

20. 20. The heater of claim 18, further configured to heat a fluid in a second circuit, wherein the fluid in the first circuit comprises a heating fluid and the fluid in the second circuit comprises tap water, or vice versa, and the first heating element is configured to heat the fluid in the first circuit, the fluid in the second circuit, or both; a second heating element configured to heat fluid in the first circuit, the second circuit, or both; The heater, wherein the housing is further configured to house a second fluid heater vessel, such as a second boiler vessel, that houses the second heating element.

21. 10. The heater of claim 1, wherein the controller includes a hardware thermostat controller and, optionally, a further graphical user interface thermostat controller.

22. 22. A method of heating a fluid in a partially or wholly electric fluid heater according to any one of claims 1 to 21, the method including controlling the distribution of power from the DC power source and the AC power source to the first heating element, optionally by only either the DC power source or the AC power source at any given moment.

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