Burner vessel and fluid heater

Abstract

A burner vessel (5400) for a hybrid electric-combustible fuel fluid heater configured to heat fluid in one or more fluid circuits is disclosed. The vessel comprises a vessel housing (5401) that houses a combustible fuel burner (5405) configured to combustible fuel, and one or more electric heating elements (5410) configured to generate heat and transfer the heat to fluid in one or more fluid circuits. The vessel further comprises a first cold fluid inlet (5404) configured to input a relatively cold fluid into the vessel, a first hot fluid outlet configured to output a relatively hot fluid from the vessel, a first fluid duct (5403) extending between the first cold fluid inlet and the first hot fluid outlet and configured to convey fluid through the vessel, and a flue (5407) configured to convey flue gas from the vessel. Both the combustible fuel burner and the one or more electric heating elements are configured to heat the fluid in the first fluid duct.

Description

[Technical field]

[0001] The present invention relates to heaters for fluid heating systems, particularly but not exclusively to boilers for wet heating systems or 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 the tap water must be clean, while the 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 utility power 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 volumes of hot water whenever needed. However, a lot of space is required to house this system.

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

[0008] The inventors realized that better fluid heaters and heater vessels could be made and developed the solution set forth in the claims. [Means for solving the problem]

[0009] According to a first aspect of the present invention there is provided a burner vessel as claimed in claim 1. According to another aspect of the present invention there is provided a fluid heater as claimed in claim 21.

[0010] Advantageously, a hybrid electric-combustible fuel burner vessel / fluid heater is provided that is configured to heat fluids in one or more fluid circuits that can efficiently heat the fluids based on either or both of a number of energy sources. This type of heater is environmentally friendly compared to pure gas-fired (or other combustible fossil fuel-fired) boilers. Fluid heating resources (from electrical power sources or combustible fuel sources) can be intelligently sourced based on a number of desired supply and demand factors.

[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 is a schematic diagram of a burner vessel according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic diagram of a burner vessel according to a first embodiment of the present invention. [Diagram 3] FIG. 1 is a schematic diagram of a burner vessel according to a first embodiment of the present invention. [Figure 4] FIG. 1 is a schematic diagram of a burner vessel according to a first embodiment of the present invention. [Diagram 5] FIG. 5 is a cross-sectional view taken along line AA in FIG. [Figure 6] FIG. 6 is an enlarged view of section D in FIG. 5. [Figure 7] FIG. 2 is an exploded view showing components of the container of the first embodiment. [Figure 8] FIG. 1 is a schematic cut-away view of a burner vessel according to a first embodiment of the present invention. [Figure 9] FIG. 1 is a schematic cut-away view of a burner vessel according to a first embodiment of the present invention. [Figure 10] FIG. 4 is a schematic diagram of a burner vessel according to a second embodiment of the present invention. [Figure 11] FIG. 11 is a cross-sectional view taken along line BB in FIG. [Figure 12] FIG. 12 is an enlarged view of cross section E in FIG. [Figure 13] FIG. 4 is a schematic diagram of a burner vessel according to a third embodiment of the present invention. [Figure 14] FIG. 14 is a cross-sectional view taken along line CC in FIG. [Figure 15] FIG. 15 is an enlarged view of section F in FIG. [Figure 16] FIG. 13 is an exploded view showing components of a burner vessel of the fourth embodiment of the present invention. [Figure 17] FIG. 17 is a schematic diagram with a cutaway section of the burner vessel of FIG. 16. [Figure 18] This is an enlarged version of Figure 6. [Figure 19] This is an enlarged version of Figure 12. [Figure 20] This is an enlarged version of Figure 15. [Figure 21] FIG. 17 is an enlarged view of a portion of the cross-section through the burner vessel of FIG. [Figure 22] FIG. 10 is an enlarged view of a portion of a cross-section through a burner vessel according to a fifth embodiment of the present invention. [Figure 23] FIG. 29 is a schematic diagram of a heating element or part thereof forming part of the vessel of FIGS. 24-28; [Figure 24] FIG. 28 is a schematic cutaway view of a burner vessel according to a sixth embodiment of the present invention, and is an enlarged view of FIG. 27. [Diagram 25] FIG. 13 is a schematic cut-away view of a burner vessel according to a sixth embodiment of the present invention. [Figure 26] FIG. 13 is a schematic cut-away view of a burner vessel according to a sixth embodiment of the present invention. [Figure 27] FIG. 29 is an enlarged view of cross section A in FIG. 28. [Figure 28] FIG. 13 is a schematic cut-away view of a burner vessel according to a sixth embodiment of the present invention. [Figure 29]FIG. 29 is a schematic diagram of a heating element or part thereof forming part of the vessel of FIGS. 24-28; [Diagram 30] FIG. 29 is a schematic diagram of a heating element or part thereof forming part of the vessel of FIGS. 24-28; [Diagram 31] FIG. 35 is a schematic diagram of a heating element forming part of the vessel of FIGS. 32-34. [Diagram 32] FIG. 35 is a schematic diagram of a burner vessel of a seventh embodiment of the present invention, showing an enlarged portion of the cross-sectional view through the burner vessel of FIGS. 33 and 34. [Diagram 33] FIG. 13 is a schematic cut-away view of a burner vessel according to a seventh embodiment of the present invention. [Diagram 34] FIG. 13 is a schematic cut-away view of a burner vessel according to a seventh embodiment of the present invention. [Diagram 35] FIG. 39 is a schematic diagram of a heating element forming part of the vessel of FIGS. 36-38. [Diagram 36] FIG. 39 is a schematic diagram of a burner vessel of an eighth embodiment of the present invention, showing an enlarged portion of the cross-sectional view through the burner vessel of FIGS. 37 and 38. [Figure 37] FIG. 13 is a schematic cut-away view of a burner vessel according to an eighth embodiment of the present invention. [Figure 38] FIG. 13 is a schematic cut-away view of a burner vessel according to an eighth embodiment of the present invention. [Figure 39] FIG. 13 is a schematic cut-away view of a burner vessel of a ninth embodiment of the present invention, taken along a cross section through the burner vessel. [Diagram 40] FIG. 13 is a schematic cut-away view of a burner vessel according to a ninth embodiment of the present invention. [Diagram 41] FIG. 13 is a schematic diagram of some components separated from a burner vessel of a ninth embodiment of the present invention. [Diagram 42] FIG. 13 is a schematic cut-away view of a burner vessel according to a ninth embodiment of the present invention. [Diagram 43] FIG. 10 shows a schematic diagram of a fluid heater according to another embodiment of the present invention, comprising the burner vessel of FIGS. [Diagram 44] FIG. 4 is a schematic diagram of a burner vessel according to a further embodiment of the present invention. [Diagram 45] 13 is a schematic cut-away view of some components of a burner vessel according to a further embodiment of the present invention; FIG. [Diagram 46] FIG. 4 is a schematic diagram of a burner vessel according to a further embodiment of the present invention. [Figure 47] FIG. 47 is a cross-sectional view taken along line AA in FIG. 46. [Figure 48] FIG. 48 is an enlarged view of cross section A1 in FIG. 47. [Figure 49] FIG. 48 is an enlarged view of FIG. [Figure 50] FIG. 49 is an enlarged cross-sectional view of another embodiment of the present invention (equivalent to FIG. 49). [Figure 51] FIG. 49 is an enlarged cross-sectional view of another embodiment of the present invention (equivalent to FIG. 49). [Figure 52] FIG. 49 is an enlarged cross-sectional view of another embodiment of the present invention (equivalent to FIG. 49). [Diagram 53] FIG. 49 is an enlarged cross-sectional view of another embodiment of the present invention (equivalent to FIG. 49). [Figure 54] 2 is a schematic diagram of another embodiment of the present invention with some parts cut away or components removed; [Figure 55] 2 is a schematic diagram of another embodiment of the present invention with some parts cut away or components removed; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] For clarity, some components may be omitted from some figures to make other components or features more easily visible.

[0015] 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.

[0016] 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.

[0017] Referring to FIG. 1, there is shown a burner vessel 100 of the present invention according to a first embodiment of the present invention, the burner vessel 100 being part of a fluid heater used to heat water for use in a standard fluid circuit, such as a radiator heated water circuit. Various aspects of the burner vessel and the fluid heater are described in detail with reference to non-limiting examples. Other details will be apparent to those skilled in the art. In particular, known boilers have a burner vessel configured to combust a fuel and efficiently transfer heat to a fluid, such as water (via a heat exchanger). Those skilled in the art will be able to incorporate and use aspects of known burner vessels and fluid heater systems (including aspects not described) in the present invention.

[0018] In general, the fluid heater 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.

[0019] Such fluid circuits are well known in the art. The or each fluid circuit may be a substantially sealed fluid circuit in use, or may be optionally 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.

[0020] In this embodiment (see Figures 1-9 and 18), the burner vessel 100 is part of a hot water heater that is a system boiler. The burner vessel 100 includes a vessel housing 102 for housing its components. A feature of this burner vessel 100 is that it is compact and can fit into a small space. In many embodiments, even when the burner vessel of the present invention includes new components (as described in more detail below), the present invention includes features that make the burner vessel 100 compact and allow the burner vessel to fit within the same housing or space footprint as a typical known burner vessel.

[0021] The burner vessel 100 is configured to heat water in a first circuit, which is a heated water circuit. The heated water circuit comprises several components including a standard domestic radiator (not shown) in addition to the burner vessel 100. In this embodiment, water is used as the heating fluid in the first circuit, although in other embodiments other known heating fluids can be used.

[0022] The burner vessel 100 comprises a hybrid electric-combustible fuel vessel, i.e., it provides heating using conventional combustion technology, and the vessel also provides heating via an electrical power source. Within the same enclosed boiler vessel chamber, multiple heating mechanisms are provided; one is an electric heating mechanism, and the other, in this embodiment, is a gas burner mechanism. The gas burner mechanism is of generally known type. Other embodiments may use other fuels, for example, suitable combustible fuels may be natural gas, hydrogen gas, or a combustible fluid such as propane gas or methane gas, or ethane gas, 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 electrical components and some more traditional combustion fuels.

[0023] The electric heating mechanism may take any suitable form. In this embodiment, it is in the form of an electric heating element powered by a DC power source that is large enough (although in other embodiments it may not be as large) to provide the electric heating element with enough power to supply all or most of the required heating fluid / water. This can be useful for adding redundancy within the system, or can be used to operate efficiently in environments where one or the other power source is insufficient.

[0024] Relatively cool water from the first circuit enters the burner vessel 100 through a cold water input pipe 104 and is heated, and then the relatively hot water exits the burner vessel 100 through a hot water output pipe 106 to the first circuit. A first water duct 105 extends between the cold water input pipe 104 and the hot water output pipe 106. The burner vessel 100 is an enclosed vessel having a combustion zone 112 therein in which fuel is combusted to provide heat to the water flowing in the first water duct 105. The housing also houses a combustion fuel heat exchanger 120 configured to assist in the transfer of heat from the fuel combusted in the combustion zone to the water in the water circuit.

[0025] The vessel 100 contains within its housing 102 a combustible fuel burner 110 of a known type. The vessel 100 further includes a fuel inlet pipe 108 in communication with the fuel burner 110 and configured to safely and efficiently convey an air-fuel mixture to the burner in a known manner. The vessel 100 also includes a flue 114 configured to convey flue gases away from the combustion zone and the vessel. In this embodiment, the vessel 100 includes a base frame 116 with which the flue and hot water output pipe 106 are integrally formed.

[0026] In this embodiment, the burner 110 comprises a perforated burner bar 1101 with jet holes that can evenly burn around the combustion zone. A seal ring 1102 is positioned to seal the bottom of the burner bar 1101 to minimize uncontrolled combustion of the fuel, for example by preventing the escape of hot air and unburned gases from the combustion assembly other than the flue. A pair of igniters 1103 are configured to ignite the air-fuel mixture on demand. For convenient access, the igniters 1103 are positioned to protrude from the top end of the housing in use. In some embodiments, multiple burners may be provided.

[0027] The burner 110 is configured to provide efficient heating in the combustion zone, thereby transferring heat to the fluid in the first water duct 105 via a combustion fuel heat exchanger 120. The combustion fuel heat exchanger increases the efficiency of heat transfer from the combustion fuel in a known manner. In particular, in this embodiment, the heat exchanger is configured to concentrate heat from the combustion gases (or other fuel in other embodiments) into the fluid duct.

[0028] In other embodiments, instead of water ducts, ducts for different fluids may be provided, for example in some embodiments the fluid to be heated may not be a liquid, for example it may be air in an air heater and a typical air heating pipe may be provided, in other examples the water may be potable water for use in a potable water circuit, in other examples the fluid may be oil in an oil heater circuit.

[0029] In this embodiment (see FIG. 7), the combustion-fuel heat exchanger comprises a generally cylindrical metal cast heat exchanger body 121 of known type. The heat exchanger body substantially surrounds the combustion zone and efficiently captures heat from the combustion zone. The cylindrical wall of the heat exchanger body is about 6 mm thick in this embodiment. In other similar embodiments, it may be about 3 mm to about 15 mm thick, depending on the materials used in construction. The upper limit is selected to avoid thermal mass issues, and potentially casting issues; it is possible to construct the heat exchanger beyond these limits, but may not be ideal. In this embodiment, the heat exchanger body is about the same thickness as the duct, i.e., the thickness of the wall of the heat exchanger body is about the same as the depth of the duct. Different configurations will be apparent to those skilled in the art. In general, efficient heat transfer at a velocity from the body to the fluid in the duct is provided. The base frame 116 is configured to seat the cylindrical heat exchanger body so that exhaust gases discharged from within the body outlet through the flue 114 and heated water exiting the first water duct 105 exit through the hot water outlet pipe 106.

[0030] In this embodiment (see FIG. 7), the housing comprises a multi-layer cover 130 configured to substantially enclose the combustion fuel heat exchanger. The multi-layer cover comprises an insulating layer 131 (made from a suitable material such as ceramic wool or brick) sandwiched between an inner skin layer 132 and an outer skin layer 133. The multi-layer cover is generally cylindrical and effectively covers the generally cylindrical combustion fuel heat exchanger body 121. In another embodiment, the housing comprises a single layer cover with the insulating layer being a synthetic skin.

[0031] As can be seen in FIG. 7, the components of the vessel are designed to be easily assembled by placing them (in this example, by sliding them) onto one another around the heat exchanger body 121 in the desired order.

[0032] In this embodiment, the first water duct 105 comprises a channel 1050 defined between an outer wall of the heat exchanger body 121 and an inner surface of the inner skin layer 132. The inner skin layer 132 has a section of cold water input pipe 104 formed therewith and configured to supply relatively low temperature water to the first water duct 105.

[0033] In other examples, other configurations of the ducts and cold water inlets are described below, and further examples will be apparent to one of ordinary skill in the art. For example, in some other embodiments, the ducts may comprise a sealed pipe disposed through a space or channel between the wall and cover of the heat exchanger, or a channel defined entirely within the heat exchanger, such as within the body of the heat exchanger, or a sealed pipe disposed through a space or channel within the heat exchanger, or a sealed pipe passing through the housing and optionally through the combustion zone, and optionally spaced from the heat exchanger.

[0034] In this embodiment, the outer wall of the heat exchanger body 121 is provided with a continuous open C-shaped recess in its outer surface, and a channel 1050 is defined between the surface of the recess and the cover (see Figures 3, 6, 8, and 9). The channel extends in a spiral configuration around the outer wall of the heat exchanger from a first cold fluid inlet to a first hot fluid outlet, downwardly in an in-use configuration. The flow of water through the channel may be facilitated by a pump (not shown) or an otherwise pressurized fluid source (e.g., commercial water), or a gravity-fed source. In use, the water flows from top to bottom and is heated as it flows along the spiral.

[0035] The inner skin surface abuts and seals the channel openings (see Figures 6, 8, and 9) so that water flows only along the desired circuitous path, promoting efficient heat transfer as water flow time and distance to absorb heat is increased / maximized.

[0036] In this embodiment, the heat exchanger further comprises a plurality of heat exchanger protrusions in the form of heat exchanger fins 122 configured to efficiently transfer heat from the burning fuel by increasing the area and time available for interaction between the burning fuel and the heat exchanger material. The fins 122 extend from the heat exchanger body towards the combustion zone and exchange heat with the heat exchanger body 121. The fins may be formed integrally with the body 121 or may be formed separately. In this embodiment, vertical fins 1221 are equally spaced concentrically disposed around the combustion zone (extending from the heat exchanger body 121 near the periphery of the housing 102) and horizontal fins 1222 are disposed at the base of the combustion zone (towards the bottom of the heat exchanger body 121). In this embodiment, the fins are approximately 16 mm deep (i.e., from tip to base). In other embodiments, the fins may be any suitable depth, for example, 1 cm to 4 cm in other embodiments, and the depth of the fins may vary depending on factors such as vessel size, material, power, etc. This, in combination with the walls of the heat exchanger body, provides efficient heat transfer to the fluid within the tubes.

[0037] This provides a compact and efficient burner assembly for transferring heat from a burning fuel to a fluid (in this case, heated water).Those skilled in the art will appreciate that other burner assemblies may be configured differently and that the present invention may be adapted to operate with such other assemblies.

[0038] The invention further provides one or more electric heating elements 140 configured to heat the water in the first water duct 105. In this embodiment, the one or more electric heating elements 140 are accommodated within the housing 102.

[0039] In this embodiment, the electric heating element 140 comprises a continuous helical element 1401 configured to fit within the spiral water channel 1050. The electric heating element 1401 is located within the channel 1050 near the base of the open recess of the channel 1050 and is spaced from the heat exchanger body 121 so as not to contact the walls of the heat exchanger (in this embodiment). Advantages of this include transferring all heat directly to the heated fluid without going through a heat exchanger, ease of assembly / repair / service etc., and allowing space for movement if expansion / contraction occurs due to heating. In this embodiment, the heating element 140 is a metal clad ceramic powder insulated cable with high power nichrome elements. In other embodiments, ceramic preform beads may be used instead of powder. Such preform beads are often crushed into powder during a rolling / die drawing operation on the cable. An electrical connector 1402 extends from the element 1401 and protrudes from the top end of the housing in use for convenient access. Electrical connector 1402 is suitable for connecting element 1401 to a suitable power source.

[0040] In this embodiment, the power source is a DC power source, in this embodiment in the form of a battery pack (not shown) formed outside the burner vessel 100 .

[0041] In this example, the capacity of the DC power source is 0.5 kWh. In another example for a small gas-electric hybrid boiler system setup, the battery capacity may be about 1 kWh (this 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). In another example for a larger gas-electric hybrid boiler system setup, the battery capacity may be about 3-5 kWh (this may be useful in a larger residential facility). In another example for a large or industrial hybrid system setup, the battery capacity may be about 5 kWh or more. In some examples, the battery capacity may be about 90 kWh, for example, to provide heating fluid and heated potable water to a large building. One skilled in the art will appreciate that different battery capacities may be appropriate for different applications (there is no upper limit to the battery capacity that may be needed / useful).

[0042] In this embodiment, the peak power output of the DC power source is between 10 kW and 20 kW in some embodiments, and up to 200 kW in some embodiments. 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.

[0043] In another embodiment, the power source is an AC power source (e.g., commercial AC). In yet another embodiment, the power source may be a combination of AC and DC power sources.

[0044] A computer implemented controller (not shown) is configured to control the amount of heating provided to the fluid by the combustible fuel burner and the first heating element. The control may be based on one or more control factors. The control factors include the amount of heating required, a fluid input temperature at an input point in one or more fluid circuits, a fluid output temperature at an output point in one or more fluid circuits, a fluid temperature at any given point in one or more fluid circuits, an amount of heat capacity available from the first heating element, an amount of heat capacity available from the combustible fuel burner, an instantaneous demand for heating fluid or potable water, a forecasted demand for heating fluid or potable water, and a flow rate of the heated fluid.

[0045] One or more sensors (not shown) may be provided to sense information regarding one or more control factors and provide the control factor information to the controller. In one embodiment, for efficiency, the controller may be configured to primarily use the electric heating element(s) to heat the fluid, e.g., via a primarily DC power source, when a demand for hot fluid is first detected.

[0046] In general, the electric heating element of the present invention can be wrapped around a pipe or component of the first fluid circuit in the vessel. Its advantages include ease of manufacture (since the heating element is located outside the pipe / component (and does not need to touch the wet side)) and ease of reconfiguration / replacement / upgrade / repair when necessary. The heating element is easily visible and therefore convenient to inspect (e.g. during routine inspection) if it is deteriorating. Also, such heating elements are easy to clean. Such heating elements are not susceptible to sludge and / or calcification in the water circuit (a problem common in radiator water circuits). In air furnace circuits, similar problems arise due to the accumulation of dirt, dust and other debris.

[0047] In other embodiments, the electric heating element can be located inside the first circuit conduit / pipe, the advantages of which include compactness, low heat loss to the environment (heat is almost entirely retained within the desired water circuit during normal heating operation).

[0048] In other embodiments, electric heating elements can be integrated into the walls of the water circuit conduits of the first circuit, the advantages of which include that these elements are more robust, less susceptible to damage from dirty water, and suffer less heat loss (than an equivalent wrapped heating element).

[0049] 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).

[0050] In yet another embodiment, the types and arrangements of electric heating elements used may be combined depending on the particular application.

[0051] The, or any, electric heating element may be located anywhere within or around the burner vessel so as to enable water to be heated by either or both of the gas and electric heating mechanisms.

[0052] The heating element may be an electrical wire that can be heated by passing an electric current through it, and may be suitably positioned to deliver heat to where it is needed (e.g., wrapped around a water pipe, or a baffle (or any other component within the burner vessel)).

[0053] In this embodiment (see Figs. 6 and 18), the continuous helical element 1401 is configured to fit within the helical water channel 1050 without touching the walls of the heat exchanger. The element 1401 is continuously formed as a double helical profile that doubles back on itself from top to bottom in use corresponding to the profile of the helical water channel 1050 such that each pocket of the channel 1050 accommodates two strands of the element in use when the element is placed within the channel. As can be seen, the element is located near the inside of the channel 1050 in this embodiment. Not touching the walls of the heat exchanger results in an easy to assemble configuration and also ensures that the cable element 1401 easily transfers heat to the water on all its surfaces. In other embodiments, the cable element may be located elsewhere in the channel, for example in the center of the channel. The cable element may be configured with a spacer (such as a metal spacer) to hold it in the desired position. In this embodiment, the rigidity of the element 1401 maintains its desired position. Additionally, in some embodiments there may be features to increase the surface area for heat transfer, for example the heating element may have a non-circular cross-section, such as a fin-like cross-section.

[0054] In this embodiment (and many other described embodiments), the electric heat source and the combustible fuel heat source are configured to heat the fluid in the fluid duct at the same location (or overlapping locations in some embodiments) in the duct. In other words, the fluid in a single location can be heated by either the electric heating element or the combustible fuel heat source, or both, simultaneously. In this embodiment, the electric heating element and the gas burner are configured to heat along substantially all / most of the length of the fluid duct passing through the vessel. The effect of this feature is to allow (in some embodiments) the entire heating demand of a typical domestic hot water heater to be supplied by the electrical source if desired (and still have the option of using a gas source to heat the same fluid in the same location). Another effect is to efficiently provide a stronger instantaneous response (e.g., when drinking water is initially required from a cold state and a quick / instantaneous response is desired). Moreover, as a result of being configured to heat the fluid simultaneously at the same location via combustible fuel or electricity, or both, another advantage of some embodiments is that the electric heating element can initially preheat the water in the duct using itself, without water flow. Heating with combustible fuel can then be operated in the normal manner with fluid flow. As a result, the initial cold water period when the tap is first turned on can be reduced / avoided entirely (in an efficient manner that avoids wasting water and / or combustion fuel). As mentioned above, in this example, the heating of the combustible fuel is done via a heat exchanger, and the electric element directly heats the water in the duct. In other similar embodiments, the electric element may alternatively / additionally heat via a heat exchanger (e.g., if the element is not completely located in the fluid (e.g., if the element is located near, e.g., on the surface of, the duct)) or via the tube wall (e.g., if the element is located to heat the heat exchanger).

[0055] A burner vessel 200 according to another embodiment of the present invention (see Figs. 10-12 and 19) houses elements similar to those of the first embodiment described. For the sake of brevity, elements identical / similar to their counterparts in the first embodiment will not be described in detail again and will be labeled with reference numbers in the format "2xx" / "2xxx" instead of "1xx" / "1xxx".

[0056] The burner vessel 200 includes a cold water input 204, a hot water output 206, and a first water duct 205 therebetween. The vessel has a housing 202 that contains a fuel burner 210, a combustion fuel heat exchanger 220, and a multi-layer cover 230.

[0057] The heat exchanger body 221 differs from the body 121 of the first embodiment in that the outer wall of the heat exchanger body 221 includes a continuous open C-shaped recess on its outer surface, and a channel 2050 is defined between the surface of the recess and the cover, but the channel 2050 does not have a smooth base. Instead (see FIGS. 11, 12, and 19), the base of the channel 2050 has a pair of grooves 2051 formed therein. The pair of grooves are formed in a helical configuration that corresponds to the shape and orientation of the channel. The pair of grooves are configured to receive and hold two strands of the heating element 2401. The grooves are sized and shaped to receive the heating element cable 2401 as an interference fit, so that the element cannot be dislodged by flowing fluid during normal use. However, in this example, the element can be forcefully removed for inspection, repair, or replacement.

[0058] In this embodiment, the elements are supported at the base of the channels within the heat exchanger body 221. In other embodiments, the grooves may be formed elsewhere, for example in the sides of the channels.

[0059] The heating element is partially embedded in the heat exchanger, resulting in better heat transfer from the electric heating element to the heat exchanger body (which can be transferred more slowly to the fluid) compared to the first embodiment, while the heating element is still partially directly exposed to the fluid.

[0060] A burner vessel 300 according to another embodiment of the present invention (see FIGS. 13-15 and 20) houses elements similar to those of the first embodiment described. For the sake of brevity, elements identical / similar to their counterparts in the first embodiment will not be described in detail again and will be labeled with reference numbers in the format "3xx" / "3xxx" instead of "1xx" / "1xxx".

[0061] Burner vessel 300 includes a cold water input 304, a hot water output 306, and a first water duct 305 therebetween. The vessel has a housing 302 that contains a fuel burner 310, a combustion fuel heat exchanger 320, and a multi-layer cover 330.

[0062] In this embodiment, the positioning of the helical cable element 3401 within the channel 3050 is different than the positioning of the helical cable element 1401 within the channel 1050 of the first embodiment. The cable element 3401 is wound to fit against the insulating cover 330 (see Figures 15 and 20). As a result, the heating effect is spread across the width of the channel and is greater than in the first embodiment.

[0063] In this embodiment, the cover 330 is a multi-layer cover, so that the element abuts the inner skin layer 333. The cable element 3401 is disposed completely within the fluid channel, i.e., in this embodiment, the cable element 3401 is not embedded at all within the heat exchanger or cover. In other embodiments, the cable element may be partially or completely embedded within the cover.

[0064] A burner vessel 400 according to another embodiment of the present invention (see Figs. 16, 17 and 21) contains elements similar to those of the first embodiment described. For the sake of brevity, elements identical / similar to their counterparts in the first embodiment will not be described in detail again and will be labeled with reference numbers in the format "4xx" / "4xxx" instead of "1xx" / "1xxx".

[0065] Burner vessel 400 includes a cold water input 404, a hot water output 406, and a first water duct 405 therebetween. The vessel has a housing 402 that contains a fuel burner 410, a combustion fuel heat exchanger 420, and a multi-layer cover 430.

[0066] In this embodiment, the electric heating element 440 is configured differently than the electric heating element 140. Instead of a cable heating element 1401, the electric heating element 440 comprises a helical wire element 4401 (as can be clearly seen in FIGS. 16, 17, and 21). The helical element 4401 comprises an enamel coating for electrical insulation. The helical element 4401 fits loosely within the channel 4050. As a result, this configuration is easy to assemble, repair, and replace. In some implementations, one or more spacers may be provided to position the element 4401 at a desired location within the channel.

[0067] A burner vessel 500 according to another embodiment of the present invention (see FIG. 22) includes elements similar to those of the previous embodiment. For the sake of brevity, elements identical / similar to their counterparts in the first embodiment will not be described in detail again and will be labeled with reference numbers in the format "5xx" / "5xxx" instead of "4xx" / "4xxx".

[0068] Burner vessel 500 includes a cold water input 504, a hot water output 506, and a first water duct 505 therebetween. The vessel has a housing 502 that contains a fuel burner 510, a combustion fuel heat exchanger 520, and a multi-layer cover 530.

[0069] In this embodiment, the electric heating element 540 comprises a helical wire element 5401 partially embedded in a pair of grooves 5051. A pair of grooves 5051 are formed in the base of the channel 5050. The pair of grooves are formed in a helical configuration that corresponds to the shape and orientation of the channel. The pair of grooves are configured to receive and hold two strands of the helical wire heating element 5401. The grooves are sized and shaped to hold the heating element cable 5401 such that the element cannot be dislodged by flowing fluid during normal use. However, in this example, the element can be forcefully removed for inspection, repair, or replacement.

[0070] In this embodiment, the elements are supported at the base of the channels within the heat exchanger body 521. In other embodiments, the grooves may be formed elsewhere, for example in the sides of the channels.

[0071] As a result of the heating element being partially embedded in the heat exchanger, there may be better heat transfer from the electric heating element to the heat exchanger body (and less heat transfer to the fluid) compared to the first embodiment, while the heating element is still partially directly exposed to the fluid.

[0072] A burner vessel 600 according to another embodiment of the present invention (see FIGS. 23-30) houses elements similar to those of the first embodiment described. For the sake of brevity, elements identical / similar to their counterparts in the first embodiment will not be described in detail again and will be labeled with reference numbers in the format "6xx" / "6xxx" instead of "1xx" / "1xxx".

[0073] Burner vessel 600 includes a cold water input 604, a hot water output 606, and a first water duct 605 therebetween. The vessel has a housing 602 that contains a fuel burner 610, a combustion fuel heat exchanger 620, and a multi-layer cover 630. The combustion fuel heat exchanger 620 has vertical fins 621.

[0074] In this embodiment, the electric heating element 640 is pre-formed and configured to wrap around the heat exchanger fin 6221 (as can be clearly seen in FIGS. 24-26). The pre-formed element 6401 has an enamel coating for electrical insulation. The pre-formed element 6401 comprises a continuous thin wire element configured in a pre-configured flat pattern (pre-wound / formed into a flat or pyramidal spiral) and configured to be easily pressed (telescopically) into position on the fin and secured in place during assembly to achieve the desired coverage of the fin by the heating element.

[0075] In other embodiments, different types of heating elements may be wrapped around or partially or completely embedded in the heat exchanger fins 6221. A similar heating element configuration may be provided on the lateral fins 6222 (not shown).

[0076] A burner vessel 700 according to another embodiment of the present invention (see FIGS. 31-34) houses elements similar to those of the first described embodiment. For brevity, elements identical / similar to their counterparts in the first embodiment will not be described in detail again and will be labeled with reference numbers in the format "7xx" / "7xxx" instead of "1xx" / "1xxx".

[0077] Burner vessel 700 includes a cold water input 704, a hot water output 706, and a first water duct 705 therebetween. The vessel has an enclosure 702 that houses a fuel burner 710, a combustion fuel heat exchanger 720, and a multi-layer cover 730.

[0078] In this embodiment, the electric heating element 740 comprises a thick film heating element 7401. As seen in FIG. 32, the heating element 7401 includes a flat conductor 7403 encapsulated by an encapsulation film 7404. The encapsulation film 7404 is a high temperature film (i.e., arranged to withstand high temperatures). The thick film heating element 7401 is not embedded in the heat exchanger or cover at all in this example (but may be in other examples). The reduced direct contact between the heated fluid and the heat exchanger increases the average life of the heating element. Additionally, the heat provided by heating the conductor 7403 is efficiently and consistently distributed over a relatively large area (the surface area of ​​the encapsulation film 7404).

[0079] A burner vessel 800 according to another embodiment of the present invention (see FIGS. 35-38) houses elements similar to those of the first described embodiment. For the sake of brevity, elements identical / similar to their counterparts in the first embodiment will not be described in detail again and will be labeled with reference numbers in the format "8xx" / "8xxx" instead of "1xx" / "1xxx".

[0080] Burner vessel 800 includes a cold water input 804, a hot water output 806, and a first water duct 805 therebetween. The vessel has a housing 802 that contains a fuel burner 810, a combustion fuel heat exchanger 820, and a multi-layer cover 830.

[0081] In this embodiment, the electric heating element 840 comprises a cylindrical sleeve-like thick film heating element 8401. The sleeve-like heating element 8401 can be made by spiral winding (e.g. like a cardboard tube) or rolling together and bonding flat sheets. The heating element 8401 comprises a flat conductor 8403 encapsulated by an encapsulating film 8404 in the form of a sleeve. The encapsulating film 7404 is a high temperature film (i.e. arranged to withstand high temperatures). The cylindrical sleeve-like thick film heating element 8401 is arranged around a substantially cylindrical heat exchanger body 821. In this example, the sleeve-like element 8401 is sandwiched between the cover 830 and the heat exchanger body 821.

[0082] A burner vessel 900 according to another embodiment of the present invention (see FIGS. 39-42) houses elements similar to those of the first described embodiment. For the sake of brevity, elements identical / similar to their counterparts in the first embodiment will not be described in detail again and will be labeled with reference numbers in the format "9xx" / "9xxx" instead of "1xx" / "1xxx".

[0083] Burner vessel 900 includes a cold water input 904, a hot water output 906, and a first water duct 905 therebetween. The vessel has a housing 902 that contains a fuel burner 910, a combustion fuel heat exchanger 920, and a multi-layer cover 930.

[0084] In this embodiment, the heat exchanger body 921 and the heating element 940 are integrally formed as a single inseparable unit. The heating element 940 comprises a metal-clad ceramic powder insulated cable with a high power Nichrome element (e.g., Kanthal (RTM)). The cable is cast into the metal of the heat exchanger during manufacture. The sheath material can withstand the molten metal of the casting during manufacture. The cable is not prone to calcification because it is away from the heated fluid. In another similar embodiment, the electric heating assembly can be overmolded, for example, using die-cast aluminum. In this embodiment, the cylindrical wall of the heat exchanger body is thicker (potentially about 140%-200% thicker) than a similar embodiment without the heating element cast therein, in this embodiment the cylindrical wall of the heat exchanger body is about 10 mm thick.

[0085] Any feature of the described embodiments may be used with any other feature of the described embodiments, and the disclosure consists of and protection is sought for any such combination. In particular, different types of elements (e.g., cables or helical wires, or flat encapsulated or sleeved elements) may be used together. In particular, the electric heating element may be embedded partially or completely, or not at all, in the heat exchanger or the cover, or both, or in any combination in the same embodiment. In particular, the heating element(s) may interact as described above in any combination with the heat exchanger fin(s) or heat exchanger body, or in the fluid channels, or in any combination thereof.

[0086] According to another embodiment of the invention, and referring to Fig. 43, a fluid heater 4300 configured to heat a fluid in a fluid circuit is shown. The fluid circuit comprises a radiator circuit including at least one radiator 4310. In this example, the fluid heater comprises a system boiler 4300 having a boiler housing 4301. Within the boiler housing 4301, the boiler comprises a burner vessel 100 of the first embodiment and a controller 4302 in communication with the vessel 100 and configured to control the amount of heating provided to the water in the fluid circuit by the combustible fuel burner 110 and the heating element 140. The controller controls the operation of the burner via a suitable control circuit in a known manner, and also controls the operation of the heating element 140 by controlling the current through the heating element 140 using a suitable control circuit.

[0087] The fluid heater comprises a DC power source (of the type described above) in the form of a battery pack 4303 configured to provide power to the heating element 140 .

[0088] The fluid heater also utilizes an AC connection 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 driving 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 embodiments, these small electronic components are powered directly from a DC power source, in which case there is no AC connection to the boiler.

[0089] In other embodiments, the fluid heater (and its electric heating element) is alternatively or additionally configured to be powered by an AC power source, such as a commercial AC power source.

[0090] In this embodiment, the boiler also includes an electrical control unit (not shown) configured to control any one or more of heating, battery charging, battery discharging, system requirements, and switching of the DC or AC power source. In this embodiment, the boiler also includes an insulating layer or heat shield (not shown) disposed between the DC power source and the vessel. The insulating layer or heat shield may include any one or any combination of air gaps, gaps filled (partially or completely) with insulating material, gaps filled (partially or completely) with infrared reflective material, gaps filled (partially or completely) with insulating material or low thermal conductivity material.

[0091] 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) located within the boiler housing and generally enclosing 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.

[0092] The boiler of this embodiment also includes a cooling system (not shown).Due to the extra switching and the operation of the controller and its associated circuitry due to the desire to intelligently use DC-v-AC, the electronics may get hotter than a typical boiler.

[0093] 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.

[0094] 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 is not yet present in 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 (or providing an additional separate cooling system) as a heat sink to also cool the battery charging mechanism. This battery charging mechanism cooling system can be particularly useful since charging can (and should) occur when the system is not heating the building or providing hot drinking water (e.g., overnight). The cooling system of the present invention allows the operation of 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. This battery charging mechanism cooling function may be implemented using any of the described embodiments, including the battery charger to create a novel embodiment of the present invention.

[0095] 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.

[0096] In some embodiments, the cooling system uses a portion of the water output from the radiator, which arrives at a cooling inlet pipe (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 in the boiler 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 in switching power is reduced, and the electronics of the fluid heater can be made more compact / simpler.

[0097] The cooling system of this example also includes a refrigerant circuit having a sealed refrigerant piping system (not shown) through which the 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 to facilitate heat transfer between the refrigerant and the DC battery cells or other components (if any in any particular embodiment) 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.

[0098] 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 other combustible fuel), the cooling system may include using the air intake to cool the battery pack and / or electronic components because the air taken in will be relatively cool while at the same time heating up, making the combustion process more efficient. This may be accomplished by locating the air intake path near the battery pack or components requiring cooling.

[0099] In this example, the boiler 4300 is configured to be compact. The boiler housing 4301 has dimensions 400cm wide by 300cm deep by 700cm high and houses the vessel 100 and any necessary control circuitry. In other embodiments, the housing may have different dimensions, for example 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.

[0100] More compactly, the DC power supply is located in the front of the boiler housing when in use, filling substantially 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.

[0101] In some embodiments, the fluid heater housing 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 source 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).

[0102] One or more heating elements can be wrapped around the pipes or components of the first circuit, outside the vessel 100 and inside the boiler housing 4301. Advantages of this include ease of manufacture, ease of reconfiguration / replacement / upgrade / repair if necessary (as the heating elements are located outside the pipes / components and do not need to touch the wet side). The heating elements are easily visible and therefore convenient to check (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 that is common in radiator water circuits.

[0103] In some embodiments, the vessel houses at least one baffle configured to bypass air heated by the fuel burner and to increase heat exchange between the heated air and the heat exchanger. The, or any, electrical element may be partially or completely embedded within or wrapped around the at least one baffle.

[0104] In other embodiments, the electric heating element can be located inside the first circuit conduit / pipe (outside the vessel 100 and inside the boiler housing 4301), the advantages of which include compactness and less heat loss to the environment (heat is almost entirely retained within the desired water circuit during normal heating operation).

[0105] In another embodiment, the electric heating elements can be integrated into the walls of the water circuit conduits of the first circuit (external to the vessel 100 and internal to the boiler housing 4301). Advantages of this 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).

[0106] The controller 4302 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.

[0107] The fluid heater further comprises one or more sensors configured to sense information relating to one or more control factors and provide said control factor information to the controller 4302. Some of the sensors 4305 are located inside the boiler housing 4301 (e.g., to measure water temperature or flow rate within the boiler). Some of the sensors 4306 are located outside the boiler housing 4301 (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 operates to direct heating of the fluid by the fuel burner and electric heating elements in response to information from such sensors.

[0108] The controller may have a memory (not shown) associated with it (either integrally or separately) that is 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 information from the memory in known manner. The controller and memory may be implemented in standard computer-controllable networks and systems.

[0109] 44-49 show a burner vessel 4400 according to another embodiment. In this example, the burner vessel 4400 is part of a water heater that is a combi boiler that supplies heated fluid to two fluid circuits, a first circuit containing a heat rejection fluid and a second circuit containing potable water. The burner vessel 4400 includes a vessel housing 4402 for housing its components. A feature of this burner vessel 4400 is that it is compact and can fit into a small space. In many examples, the present invention includes features that allow the burner vessel 4400 to be compact and fit into the same housing or space footprint as a typical known burner vessel, even when the burner vessel of the present invention includes new components.

[0110] The first circuit is a heating fluid circuit and includes several components in addition to the burner vessel 4400, 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 can be used. The second circuit (potable water circuit) includes several components in addition to the burner vessel 4400, including a standard hot water tap (not shown).

[0111] The burner vessel comprises a hybrid electric-combustible fuel vessel, i.e. a vessel that uses conventional combustion technology to provide heating, and also provides heating via an electrical power source. Within the same closed boiler vessel chamber, multiple heating mechanisms are provided, one an electric heating mechanism, the other a gas burner mechanism in this example. The gas burner mechanisms are generally of known type. Other examples may use other fuels, for example as specified above in relation to other embodiments. Thus, in some cases the heating power is provided by electrical components, in others by more traditional combustion fuels.

[0112] The electric heating mechanism may take any suitable form. In this embodiment, it is in the form of an electric heating element powered by a DC power source large enough (in other embodiments, it may not be as large) to provide enough power to the electric heating element to supply all or most of the required heated fluid / water. This can be useful to add redundancy within the system, or can be used to operate efficiently in environments where one or the other power source (gas / electricity) is in short supply.

[0113] Relatively cool water from the first circuit enters the burner vessel 4400 through a first cold radiator water input pipe 4404a, is heated, and then the relatively hot water leaves the burner vessel 4400a through a first heating radiator water output pipe 4406a to the first circuit. A first water duct 4405a extends between the cold water input pipe 4404a and the hot water output pipe 4406a.

[0114] Relatively cool water from the second circuit enters the burner vessel through a second low temperature radiator water input pipe 4404b (through a commercial water heater in this embodiment) and is heated, and then the relatively hot water leaves the burner vessel 4400 through a second potable water output pipe 4406b to the second circuit. A second water duct 4405b extends between the second cold water input pipe 4404b and the second hot water output pipe 4406b.

[0115] Burner vessel 4400 is a closed vessel having therein a combustion zone 4412 in which fuel is combusted to provide heat to water flowing in water ducts 4405a, 4405b.

[0116] Within the housing 4402 of the vessel 4400, the vessel 4400 houses a combustible fuel burner of a known type. The vessel further comprises a fuel inlet pipe in communication with the fuel burner and configured to safely and efficiently convey an air-fuel mixture to the burner in a known manner. The vessel also comprises a flue 4414 configured to convey flue gases away from the combustion zone and the vessel. In this embodiment, the fuel burner is positioned horizontally when in use.

[0117] In this embodiment, the burner comprises a perforated burner bar 4408 (similar to that described in connection with the previous embodiment) with jet holes that can evenly burn around the combustion zone. A seal ring is positioned to seal the bottom of the burner bar 4408 to minimize uncontrolled fuel combustion, for example by preventing the escape of hot air and unburned gases from the combustion assembly other than the flue. A pair of igniters are configured to ignite the air-fuel mixture on demand.

[0118] The burners are configured to provide efficient heating in the combustion zone, thereby transferring heat to the fluid in the first water duct 4405a and the second water duct 4405b. In this embodiment, heat is transferred from the hot gases in the combustion zone to the fluid in the tubes via the tube walls, which are configured to efficiently transfer heat in a known manner.

[0119] In this embodiment, but not in all embodiments, the vessel housing further contains a baffle 4407 disposed within the combustion zone and configured to divert gases heated within the combustion zone along a desired path to increase heat exchange between the heated air and duct walls. In particular, the baffle promotes movement of hot gases toward a radially outer region of the generally cylindrical combustion zone where the ducts are disposed.

[0120] In other embodiments, instead of a water duct, a duct for a different fluid may be provided, for example in some embodiments the heated fluid may not be a liquid, for example it may be air in an air heater and a typical air heating pipe may be provided, in other examples the water may be potable water for use in a potable water circuit, in other examples the fluid may be oil in an oil heater circuit.

[0121] In this embodiment, the combustion zone, housing and duct have a generally cylindrical shape of known type. The ducts 4405a, 4405b generally surround the combustion zone in a spiral configuration to efficiently capture heat from the combustion zone. The duct pipe is spiraled about the periphery of the housing to efficiently capture the heat generated. There is a gap between adjacent portions of the duct to allow hot gases to flow through and thereby transfer heat to the fluid within the duct and then to the flue for efficient transfer.

[0122] Exhaust gases from within the combustion zone exit through flue 4414 and heated water from ducts 4405a, 4405b exits through hot water outlet pipes 4406a, 4406b. Baffles direct the movement of the hot gases along desired paths.

[0123] In this embodiment, the first water duct pipe 4405a is helically positioned near the mouth of the combustion chamber and adjacent to the burner bar. The second water duct pipe 4405b is helically positioned at the distal end of the combustion chamber away from the burner bar. Hot air still reaches the second water duct pipe 4405b, facilitated by the baffle 4407, and effectively flows over and around it. Other specific configurations will be apparent to those skilled in the art.

[0124] In this embodiment, each duct 4405a, 4405b has an elongated elliptical cross-sectional profile that extends radially away from the center of the combustion zone, which can be seen diagrammatically in Figures 48 and 49-53. This feature allows for longer contact time between the hot gases and the ducts.

[0125] The ducts, in use, extend in a spiral configuration from right to left around the outer wall of the housing from their respective cold fluid inlets to their hot fluid outlets, as seen in Figure 47. The flow of water through each duct may be facilitated by a pump (not shown) or an otherwise pressurized fluid source (e.g., a commercial water supply), or a gravity-fed source.

[0126] This provides a compact and efficient burner assembly for transferring heat from a burning fuel to fluids (in this case radiator fluid and drinking water in different circuits). Those skilled in the art will appreciate that other burner assemblies may be configured differently and that the present invention may be adapted to operate with such other assemblies. For example, the present invention may be readily adapted to operate with only a single fluid circuit, for example in a system boiler configuration.

[0127] The invention further provides one or more electric heating elements 4440 configured to heat the water in the first duct 4405a and the second duct 4405b. In this embodiment, the one or more electric heating elements 4440 are contained within the housing 4402.

[0128] In this embodiment, the electric heating element 4440 comprises a continuous helical element configured to fit around and closely follow the helical path of the ducts 4405a, 4405b. The element 4440 is held in place relative to the ducts, in this embodiment by spot welds.

[0129] The electric heating element 4440 is located outside the duct and is radially spaced from the center of the combustion zone relative to the duct.

[0130] In this embodiment, the heating element 4440 is a metal coated ceramic powder insulated cable with multiple high power nichrome elements therein (two elements are shown in the figure, in the embodiment shown there can be up to seven elements). For convenient access, an electrical connector 4502 extends from the element and also protrudes from the top end of the housing in use. The electrical connector 4502 is suitable for connecting the element to a suitable power source.

[0131] In this embodiment, the power source is a DC power source, in this embodiment in the form of a battery pack (not shown) located outside the burner vessel.

[0132] In this embodiment, the capacity of the DC power source is 0.5 kWh. In another embodiment, the capacity may be similar to the capacities described above for other embodiments.

[0133] In this embodiment, the peak power output of the DC power source is between 10 kW. In other embodiments, the peak power output may be similar to that described above for other embodiments. For example, in one exemplary situation, a 90 kWh battery can provide 350 kW for 10 minutes.

[0134] In another embodiment, the power source is an AC power source (e.g., a commercial AC power source). In yet another embodiment, the power source may be a combination of AC and DC power sources.

[0135] A computer implemented controller (not shown) is configured to control the amount of heating provided to the fluid by the combustible fuel burner and the first heating element. The control may be based on one or more control factors, including the amount of heating needed, a fluid input temperature at an input point in one or more fluid circuits, a fluid output temperature at an output point in one or more fluid circuits, a fluid temperature at any given point in one or more fluid circuits, an amount of heat capacity available from the first heating element, an amount of heat capacity available from the combustible fuel burner, an instantaneous demand for heating fluid or potable water, a forecasted demand for heating fluid or potable water, and a flow rate of the heated fluid.

[0136] In some multiple fluid circuit (e.g. combi boiler) embodiments, the controller is configured to direct the use of only combustible fuel for heating purposes (e.g. heating the radiator fluid) and exclusively electricity for heating potable water.

[0137] One or more sensors (not shown) may be provided to sense information regarding one or more control factors and provide the control factor information to the controller. In one embodiment, for efficiency, the controller may be configured to primarily use the electric heating element(s) to heat the fluid, e.g., via a primarily DC power source, when a demand for hot fluid is first detected.

[0138] In general, the electric heating element of the present invention can be wrapped around a pipe or component of the first and / or fluid circuit in the container. Its advantages include ease of manufacture (since the heating element is located outside the pipe / component (and does not need to touch the wet side)), ease of reconfiguration / replacement / upgrade / repair when necessary. The heating element is easily visible and therefore convenient to inspect (e.g. during routine inspection) whether the heating element is deteriorating. Also, such heating elements are easy to clean. Such heating elements are not affected by sludge in the water circuit (a problem common in radiator water circuits).

[0139] Figures 49-53 show close-up views of pairs of heating elements and duct configurations from different embodiments. Features of these embodiments are similar to features of the previous embodiments unless otherwise stated.

[0140] In the embodiment of Figure 50, the heating element is in the form of a metal clad ceramic powder insulated cable with multiple high power nichrome elements therein. The cable is welded to the duct in a manner similar to that of the embodiment of Figures 44-49, but is radially closer to the center of the combustion zone than the duct, i.e., on the inside or flame side of the duct. In other embodiments, instead of welding, the cable can be (vacuum) brazed to the duct.

[0141] In the embodiment of Fig. 51, the electric heating element is placed inside the duct pipe, the advantages of which are compactness, low heat loss to the environment (heat is almost entirely retained within the desired water circuit during normal heating operation).

[0142] In the embodiment of FIG. 52, the electric heating elements are in the form of a conductive coating 5201 around the exterior surface of each duct. The conductive coating is configured to generate heat when an electric current is passed through it, thereby efficiently transferring heat to the fluid within the duct. The conductive coating may be applied by spraying. Insulating layers are provided on the inside and outside of the conductive coating, sandwiching the conductive coating between these insulating layers. In this embodiment, the insulating layers are plasma sprayed or applied by dipping. Other techniques for applying these layers will be apparent to those skilled in the art. In some embodiments where the 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 during the coating / spraying process (e.g., with a spray mask).

[0143] In the embodiment of Figure 53, the electric heating element is in the form of a conductive coating 5301 on the inside of each duct. The conductive coating is configured to generate heat when an electric current is passed through it, thereby efficiently transferring heat to the fluid within the duct. The conductive coating may be applied by spraying. Insulating layers are provided on the inside and outside of the conductive coating, sandwiching it between the insulating layers. In this embodiment, the insulating layers are plasma sprayed or applied by dipping. Other techniques for applying these layers will be apparent to those skilled in the art.

[0144] In other embodiments, electric heating elements can be integrated into the walls of the first and second circuit ducts, the advantages of which include that these elements are more robust, less susceptible to damage from wastewater, and lose less heat (than comparable wrapped heating elements).

[0145] In yet another embodiment, there may be a combination of types and arrangements of electric heating elements used depending on the particular application.

[0146] The, or any, electric heating element may be located anywhere within or around the burner vessel so as to enable water to be heated by either or both of the gas and electric heating mechanisms.

[0147] The heating element may be an electrical wire that can be heated by passing an electric current through it, and may be suitably positioned to deliver heat to where it is needed (e.g., wrapped around a water pipe, or a baffle (or any other component within the burner vessel)).

[0148] In another embodiment (see FIG. 54), a burner vessel 5400 comprises a generally rectangular box-like housing 5401 and a rectangular block-like heat exchanger 5402 towards the top end (in use) of the housing. Many features of this example are functionally similar to those of the first described example and will not be described again for brevity. In this example, a water duct 5403 is fully embedded in the heat exchanger (shown cut away in FIG. 54). The water duct is fed through a cold water inlet 5404 and doubles back on itself within the exchanger (to enhance heat transfer). Heated water exits through a hot water outlet (not visible in FIG. 54 as it is on the opposite side of the housing). A burner 5405 heats gases in a combustion zone 5406 within the housing, which heats the heat exchanger and thus the embedded ducts and the fluid carried within them. At the top of the housing, a flue 5407 is provided for the exhaust gases.

[0149] In yet another embodiment (see FIG. 55), the burner vessel 5500 comprises a generally rectangular box-like housing 5501 and a rectangular block-like heat exchanger 5502 towards the top end (in use) of the housing. Many features of this example are functionally similar to those of the previous example and will not be described again for brevity. In this example, the water duct 5503 is fully embedded in the heat exchanger (shown cut away in FIG. 55). The water duct is fed from a cold water inlet (not shown) and doubles back on itself within the exchanger (to enhance heat transfer). Heated water leaves the vessel housing 5501 through a hot water outlet 5504. The burner 5505 burns gases in a combustion zone 5506 within the housing to heat the heat exchanger, which in turn heats the embedded duct 5503 and the fluid carried within the duct. At the top of the housing, a flue 5507 is provided for the exhaust gases.

[0150] The burner vessel housing 5501 is housed within a larger boiler housing (not shown) which houses the vessel 5501 along with other boiler components (electric boiler components, a computer control system with switches and valves for controlling the operation of gas and electric heating power in the standard manner).

[0151] The outlet 5504 leads to a nearby further duct section 5508. The further duct section 5508 is disposed within the boiler housing. An electric heating element 5410 is configured to heat a fluid conveyed within the further duct section 5508. In this embodiment, the electric heating element 5510 is disposed within the further duct section 5408. In this embodiment, the further duct section 5508 comprises a double duct section that is folded back on itself to provide a compact configuration for increasing the efficiency of heat transfer to the fluid in a small space. In this embodiment, a heating element 5510 is located in each of three branches of the further duct section 5508; in other embodiments, a heating element is located in only some of the branches.

[0152] 54 and 55, heat may be provided to the fluid conveyed through the burner vessel by electrical heating or by burning gas, or both. Computer control by hardware or software (or a combination thereof) can be used to intelligently determine when to use either or both fuel sources.

[0153] In yet another embodiment (not shown), the heating element may be associated with both a duct portion within the burner vessel and a further duct portion external to the vessel.

[0154] These examples serve to illustrate that one skilled in the art can find numerous exemplary configurations that are within the scope of the present invention.

[0155] Various modifications can be made to the present invention without departing from the scope of the invention.

[0156] The heat exchanger may be configured to concentrate heat from the, or any, electric heating element, as well as heat from the combusted fuel, into a fluid duct containing a heated fluid.

[0157] The heat exchanger can be made of any suitable material, for example, metal or ceramic. In some embodiments, the heat exchanger may be in the form of one or more plates (e.g., metal plates) that are placed partially or completely around the water pipe. An electric heating element may be placed between the plates. In another embodiment, there may be a block of suitable material (e.g., a ceramic block) that is placed around the water pipe.

[0158] For example, although embodiments of the present invention have been described with respect to a water boiler, the same inventive concepts may be applied to other (partially or wholly) electric fluid heaters, e.g., air heaters (also known as furnaces) are common in North America. Typically, such systems include a fan for blowing out the heated air, but for clarity, a fan has not been shown in any of the drawings. Systems for heating other fluids will be apparent to those skilled in the art.

[0159] In some embodiments, the heating element may be powered by both a DC power source and an AC power source. In such embodiments, the DC power source is configured to at least partially power the heating element. In some such embodiments, the DC power source may power the heating element fully at some times and partially at other times (depending on factors such as the time of day or the availability of power from renewable energy sources).

[0160] In some embodiments, fluids in multiple independent fluid circuits are heated, for example a first circuit for radiator water and a second circuit for potable water, such as in a combi boiler. In such embodiments, the second circuit has a different conduit configuration, i.e., different ducts / pipes to the first circuit, such that the fluids in the two circuits do not merge (e.g., potable water is not contaminated by the radiator water). A person skilled in the art would have knowledge of how to construct a suitable container to house the separate fluid circuits. For example, a suitable container may include a second fluid inlet and a second fluid outlet with a second fluid pipe therebetween, and combustion of a fuel in a combustion zone or heating of an electric element, or both, are configured to heat the fluid in the second fluid pipe.

[0161] One or more or all of the heating elements may be located outside the burner vessel (but inside the housing of a larger boiler (or other fluid heater, e.g., air furnace)). Such an embodiment is particularly suited for retrofitting an existing gas boiler with electric heating capacity. For example, the electric heating elements may be coated on, coated within, sprayed, housed, wrapped around, partially or fully embedded in, or otherwise associated with ducting at or near the burner vessel, i.e., at the outlet from the burner vessel, the inlet to the burner vessel, or both. The heating elements 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, along with a control mechanism (e.g., control electronics and / or software) may be attached to the burner vessel to control the amount of heating provided by the electric heating element(s) to the combustible fuel source. The control mechanism may also control the amount of heating provided by DC, AC, or a combination thereof.

[0162] In most of the above examples, the heating element extends along substantially the entirety of the fluid duct. In other examples, one or more heating elements are provided only in some parts of the fluid duct, while other parts do not experience significant heating caused by the heating element(s). As a result, a system that is easier to assemble and more resource efficient can be provided.

[0163] In the described embodiment, the heating element(s) are powered by passing an electric current through them, in other embodiments the heating element may have a different configuration, for example it may be powered by induction (without direct contact).

[0164] In some embodiments, multiple separate sections of the heating element may be provided within the fluid duct, with each section controlled together or separately, for example to provide different levels of heating at different sections. This may be effective when combustion heating levels are different at different locations in the burner vessel, and the electric heating element(s) may provide less heating in sections where the burner can provide more heat, and more heating in sections where the burner can provide less heat. 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, since the starting input fluid is particularly cold.

[0165] In some of these embodiments, the elements may be fully embedded within the fluid duct, such that no part of the element protrudes or sticks out from the duct (eg, there are no external electrical connection points).

[0166] In embodiments having multiple fluid circuits, e.g., a combi boiler embodiment, a first heating element (powered by a DC or AC power source or a combination thereof) may be configured to heat only the fluid in one of the first and second circuits, and a combustion heater may be configured to heat only the fluid in the other of the first and second circuits. For example, tap water is heated only by the power source, and heated water is heated by a combustible fuel source. In some embodiments, the controller is configured to control the heaters such that gas (or other combustible fuel) and electric hybrid heating is used only to heat fluid (e.g., radiator water) in the first fluid circuit, and only electric heating is used to heat potable water in the second fluid circuit.

[0167] There may be more than one heating element per vessel.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] In some embodiments, the DC power supply is located in the top of the boiler housing. In such embodiments, wetted components (such as pipes or chambers that contain fluids) are located only below the DC power supply. The DC power supply may occupy about 80% of the top of the space in the housing in some embodiments.

[0173] In some embodiments, a heating element is configured exclusively for heating in a first fluid circuit and a second heating element is configured exclusively for heating in a second fluid circuit, or vice versa. For example, one heating element may be dedicated to heating a radiator circuit and another heating element may be dedicated to heating a drinking water circuit. This allows suitable custom-made dedicated elements to be used for different circuits with different needs.

[0174] In any of the embodiments described, the, or any, heating element may be any element that emits heat when an electric current passes through it, such as a resistive wire, or any wiring that emits heat when an electric current passes 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.

[0175] In any embodiment where a single heating element is described, that heating element may be replaced by one or more different heating elements, as will be apparent to one of ordinary skill in the art.

[0176] The embodiments of the invention are described with respect to a vessel having a spiral fluid channel defined between the heat exchanger body and the cover. Other configurations, e.g., configurations without such a channel, are within the scope of the invention. For example, in other embodiments, instead of (or in addition to) such a fluid channel, a sealed fluid pipe (e.g., carrying drinking water in a drinking water circuit) may pass through the vessel and be heated by fuel combustion in a combustion zone.

[0177] In some embodiments, the fluid heater may have a DC connection or an AC connection, or both (a combination of AC and DC), through which power is transferred to the electric heating element(s). In any embodiment having a battery pack, the battery pack may be internal to the fluid heater or external to the fluid heater.

[0178] In some embodiments, the heat exchanger and the duct are not separate components. The heat exchanger and the duct are formed by a common element. For example, the duct may comprise a pipe of suitable construction such that the wall(s) of the pipe transfer heat from the surroundings of the pipe (e.g. from the combustion zone) to the fluid in the pipe to be heated. The pipe may have a heating element wrapped around the wall of the pipe or embedded (partially or completely) or located within the pipe (e.g. in direct contact with the flowing fluid).

[0179] In other embodiments, the heat exchanger and the duct are separate components.

[0180] In many embodiments, the one or more electric heating elements can alone provide enough heat (without burning fuel) to meet all of the heating requirements, including potable water. In this regard, for purposes herein, the heating element may be a high-power heating element, for example, powered by a large battery (e.g., a DC power source having a capacity of at least 0.5 kWh, or at least 1 kWh, or at least 5 kWh, or at least 20 kWh) or a similarly powerful AC power source, for example, via a national power grid. In such embodiments, the peak power output of the DC power source is between 10 kW and 20 kW in some embodiments, and up to 200 kW in some embodiments.

[0181] Combustible fuels alone can provide enough heat to supply all of the heating requirements.

[0182] The combustible fuel and the electric heating element heat the fluid at the same location within a single chamber in at least some regions (i.e., the combustible fuel and the electric heating element fully or partially overlap with respect to heat delivery along the extent of the fluid duct). The combustible fuel and the electric heating element can also be used in combination to provide heating requirements, if desired.

[0183] As mentioned above, in some examples, heating of the combustible fuel occurs via a heat exchanger and one or more electric elements heat the water directly within the duct. In other embodiments, one or more electric elements can alternatively / additionally provide heating through the tube wall (e.g., if the element is not located completely within the fluid (e.g., if the element is located near the duct, e.g., on a surface of the duct), or through a heat exchanger (e.g., if the element is configured to heat the heat exchanger), or in any other suitable configuration as will be apparent from the teachings herein.

[0184] In some embodiments (including most of the embodiments described above), the electric heat source and the combustible fuel heat source are arranged to heat the fluid in the fluid duct at the same location (or in some embodiments, overlapping locations). In other words, the fluid in a single location can be heated simultaneously by either the electric heating element or the combustible fuel heat source, or both. In some such embodiments, the electric heating element and the gas burner are configured to heat along substantially all / most of the length of the fluid duct that runs through the vessel. The advantage of this feature is that (in some embodiments) the entire heating demand of a typical domestic hot water heater can be powered by the electrical source as needed (and still have the option of using a gas source to heat the same fluid in the same location). Another advantage is that it efficiently serves a stronger instantaneous demand (e.g., when drinking water is initially required from a cold state and a quick / instantaneous response is desired). Furthermore, as a result of being configured to heat fluids simultaneously in the same location via combustible fuel or electricity, or both, another advantage of some embodiments is that the electric heating element can first use itself to preheat the water in the duct without water flow, to preheat the water in the duct. The combustible fuel heating can then be operated in the normal manner with fluid flow. As a result, the initial cold water period when the faucet is first turned on can be reduced / avoided entirely (in an efficient manner that avoids wasting water and / or burning fuel).

[0185] In many of the described embodiments, the combustible fuel and the electric heating element are configured to heat the fluid in the fluid duct using a single sealed fluid heating vessel chamber. An advantageous effect is that there is no need for a main burner chamber and an auxiliary heating chamber (such as an electrically heatable buffer tank). This is especially true for air furnaces.

[0186] In some examples, the cooling system may be a passive cooling system (instead of or in addition to the cooling systems described above) 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 burner vessel for a hybrid electric-combustible fuel fluid heater configured to heat fluid in one or more fluid circuits, comprising: a combustible fuel burner configured to combustible fuel; one or more electric heating elements configured to generate heat and transfer heat to fluid in the one or more fluid circuits; a first cryogenic fluid inlet configured to input a relatively cryogenic fluid into the vessel; a first hot fluid outlet configured to output a relatively hot fluid from the vessel; a first fluid duct extending between the first cold fluid inlet and the first hot fluid outlet and configured to convey fluid through the vessel; a flue configured to convey flue gas from the vessel; a container housing configured to contain the The burner vessel, wherein the combustible fuel burner and the one or more electric heating elements are both configured to heat a fluid in the first fluid duct.

2. 10. The burner vessel of claim 1, wherein the one or more electric heating elements are high-power heating elements.

3. The burner vessel of claim 1 , wherein the combustible fuel burner and the one or more electric heating elements are both configured to heat fluid at the same location within the first fluid duct.

4. The burner vessel of claim 1 , wherein the housing further houses a combustion fuel heat exchanger configured to transfer heat from a combustion fuel to a fluid in the one or more fluid circuits.

5. 5. The burner vessel of claim 4, wherein the combustible fuel burner and the one or more electric heating elements are both configured to heat the same combustion fuel heat exchanger, optionally in the same location.

6. 5. The burner vessel of claim 4, wherein the first fluid duct comprises at least one duct wall through which heat is transferred from the combustion fuel to fluid in the one or more fluid circuits.

7. 7. The burner vessel of claim 6, wherein the combustible fuel burner and the one or more electric heating elements are both configured to heat the same at least one duct wall, optionally in the same location.

8. 10. The burner vessel of claim 1, further comprising: a second cryogenic fluid inlet configured to input a relatively cryogenic fluid into the vessel; a second hot fluid outlet configured to output a relatively hot fluid from the vessel; a second fluid duct extending between the second cold fluid inlet and the second hot fluid outlet and configured to convey fluid through the vessel; Equipped with The burner vessel, wherein either or both of the combustible fuel burner and the one or more electric heating elements are configured to heat fluid in the second fluid duct, optionally at the same location.

9. 5. The burner vessel of claim 4, wherein one or more of the electric heating elements are partially or completely embedded in the combustion fuel heat exchanger.

10. 7. The burner vessel of claim 6, wherein one or more of the electric heating elements are partially or completely embedded in the at least one duct wall.

11. 5. The burner vessel of claim 4, wherein the heat exchanger has one or more grooves formed therein, the one or more grooves of the heat exchanger configured to position the one or more electric heating elements.

12. 7. The burner vessel of claim 6, wherein the at least one duct wall has one or more grooves formed therein, the one or more grooves in the duct wall configured to position the one or more electric heating elements.

13. 2. A burner vessel according to claim 1, wherein one or more of said electric heating elements are located wholly or partly within the, or any or each, duct.

14. The burner vessel of claim 13, wherein the housing further houses a combustion fuel heat exchanger configured to transfer heat from combustion fuel to fluid in the one or more fluid circuits; The burner vessel, wherein one or more of the electric heating elements are spaced apart from the combustion fuel heat exchanger.

15. 10. The burner vessel of claim 1, comprising a plurality of separate electric heating elements configured to heat fluid in separate sections of the first fluid duct.

16. 7. The burner vessel of claim 6, wherein one or more of the electric heating elements comprises an electrically conductive heating element coating on one or more of an inner surface of at least one duct wall and an outer surface of the at least one duct wall.

17. The burner vessel of claim 4 wherein one or more of the electric heating elements comprises an electrically conductive heating element coating on a surface of the combustion fuel heat exchanger.

18. 10. The burner vessel of claim 1, wherein the one or more electric heating elements are positioned outside the vessel housing near the first hot fluid outlet, instead of being housed within the vessel housing.

19. 5. The burner vessel of claim 4, wherein the combustible fuel burner is configured to combust fuel in a combustion zone, and the combustion fuel heat exchanger comprises a heat exchanger body, such as a cast heat exchanger body, and optionally The heat exchanger body includes: a) substantially surrounding said combustion zone; b) optionally having a block within or adjacent to the combustion zone, near the top of the combustion zone; or c) a combination of both a) and b); Burner vessel.

20. 20. The burner vessel of claim 19, wherein the combustion fuel heat exchanger comprises at least one heat exchanger protrusion, such as a heat exchanger fin, configured to efficiently transfer heat from the combustion fuel, and optionally the at least one protrusion extends from the heat exchanger body toward the combustion zone and exchanges heat with the heat exchanger body.

21. 5. The burner vessel of claim 4, wherein the housing further comprises a cover, optionally a multi-layer cover, positioned to substantially surround the combustion-fuel heat exchanger, and optionally the first fluid duct is defined between the cover and the combustion-fuel heat exchanger.

22. 22. The burner vessel of claim 21, wherein the multi-layer cover includes at least one skin layer and at least one insulation layer.

23. 20. The burner vessel of claim 19, wherein the housing further comprises a cover, optionally a multi-layer cover, disposed to substantially surround the combustion-fuel heat exchanger, and optionally the first fluid duct is defined between the cover and the combustion-fuel heat exchanger; The or any duct, wherein the or each duct is a channel defined between the wall of the heat exchanger and the cover, optionally between the outer wall of the heat exchanger body and the inner surface of the cover; or a sealed pipe configured to pass through the space or channel between the wall of the heat exchanger and the cover; or a channel defined entirely within said heat exchanger; or a sealed pipe configured to pass through the entire space or channel within the heat exchanger; or The housing is optionally enclosed by a pipe passing through the combustion zone and spaced from the heat exchanger. A burner vessel comprising:

24. 24. The burner vessel of claim 23, wherein the heat exchanger outer wall comprises a continuously open recess, optionally a U-shaped or C-shaped recess, in an outer surface of the outer wall, the channel being defined between a surface of the recess and the cover, and optionally the channel extending in a spiral configuration around the heat exchanger outer wall from the first cold fluid inlet to the first hot fluid outlet, optionally downwardly in an in-use configuration.

25. 25. A burner vessel according to claim 24, wherein the or each electric heating element comprises: disposed within or coated on or within the channel, optionally near the base of the open recess, and further optionally spaced from the heat exchanger; or be partially or completely embedded in or coated on or within the heat exchanger near the base of the recess; or disposed within or coated on or within the channel, optionally in contact with or adjacent to the cover and spaced from the base of the open recess; or be partially or completely embedded in, wrapped around, or coated on or within at least one heat exchanger fin; or be integrally cast within the heat exchanger or coated on or within the heat exchanger, for example coated within a channel, such as a spiral channel, defined entirely within the heat exchanger; or be wrapped around or coated on or within said duct, any or each duct; or It is a combination of these forms A burner vessel.

26. 2. The burner vessel of claim 1, wherein either or each of the electric heating element, any electric heating element or each electric heating element comprises: Metal-clad ceramic powder insulated cable with nichrome elements; Spiral wire elements, encapsulated metal-etched elements, such as silicone-encapsulated metal-etched elements; a preformed element having a desired shape profile; Enamel-coated elements, and conductive coating a burner vessel comprising one or more of:

27. 5. The burner vessel of claim 4, wherein the vessel housing further houses at least one baffle configured to bypass air heated by a fuel burner and to increase heat exchange between the heated air and at least one duct wall or the heat exchanger, or both, and optionally the, or any, electric heating element is partially or completely embedded in, or coated on or within, or wrapped around the at least one baffle.

28. 10. The burner vessel of claim 1, configured to heat water in separate first and second water circuits, the first water circuit configured to supply heated water for a radiator circuit and the second water circuit configured to supply potable water, the burner vessel configured to heat water for both circuits.

29. 10. A burner vessel according to claim 1, wherein the or each electric heating element is configured to be powered by either or a combination of a DC power source and an AC power source.

30. 1. A fluid heater configured to heat a fluid in one or more fluid circuits, the heater comprising: A burner vessel according to any one of claims 1 to 29; a controller configured to control an amount of heating provided by the combustible fuel burner and first heating element to fluid in the one or more fluid circuits; A fluid heater comprising:

31. 31. The fluid heater of claim 30, further comprising: a DC power source, such as a battery pack, for powering the or any heating element, optionally the DC power source having a capacity of at least 0.5 kWh, further optionally at least 1 kWh, and still further optionally at least 5 kWh or at least 20 kWh; an AC power source configured to power the heating element, or any or each heating element; A fluid heater comprising:

32. 32. The fluid heater of claim 31, wherein the controller is configured to control the supply of power from the DC power source, the AC power source, or both, to the electric heating element.

33. 31. The fluid heater of claim 30, wherein the controller is configured to control the amount of heating supplied to the fluid based on or in response to any one or more control factors, the control factors including: the amount of heating required, a fluid input temperature at an input point within the one or more fluid circuits; a fluid output temperature at an output point within the one or more fluid circuits; the fluid temperature at any given point within said one or more fluid circuits; the amount of heat capacity available from the first heating element; the amount of heat capacity available from said combustible fuel burner; Instantaneous demand for heating fluid or drinking water, Projected demand for heating fluid or potable water; and Flow rate of the heated fluid Including, Optionally, the fluid heater further comprises one or more sensors configured to sense information regarding the one or more control factors and provide the control factor information to the controller, and further optionally, the controller is configured to heat the fluid primarily using the one or more electric heating elements, e.g., primarily via the DC power source, when a demand for high temperature fluid is first detected.

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