SYSTEMS AND METHODS FOR HYBRID HEATING SYSTEM CONTROL

Abstract

In accordance with various embodiments of the present disclosure, a control system for a hybrid air heating system is provided. In some embodiments, the hybrid air heating system has at least one electric heating element capable of generating an electric thermal output and at least one burner capable of generating a combustion thermal output. In some embodiments, the control system comprises a controller configured to, based on a desired total thermal output of the hybrid air heating system, determine an amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element and an amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner.

Claims

1. A control system for a hybrid air heating system having at least one electric heating element capable of generating an electric thermal output and at least one burner capable of generating a combustion thermal output, the control system comprising: a controller configured to, based on a desired total thermal output of the hybrid air heating system, determine an amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element and an amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner.

2. The control system of claim 1, wherein the controller is adapted to send a modulated signal to the at least one electric heating element corresponding to the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element and/or a modulated signal to the at least one burner corresponding to the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner.

3. The control system of claim 1, wherein, when the desired total thermal output of the hybrid air heating system is less than a first threshold value, the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element is 100 percent.

4. The control system of claim 3, wherein the first threshold value is between a minimum combustion thermal output and a maximum electric thermal output.

5. The control system of claim 4, wherein, when the desired total thermal output of the hybrid air heating system is greater than the first threshold value, the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner is 100 percent.

6. The control system of claim 4, wherein, when the desired total thermal output of the hybrid air heating system is greater than the first threshold value but less than a second threshold value, the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element is the desired total thermal output of the hybrid air heating system minus the minimum combustion thermal output and the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner is the minimum combustion thermal output; wherein, when the desired total thermal output of the hybrid air heating system is greater than the second threshold value, the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element is the maximum electric thermal output and the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner is the desired total thermal output of the hybrid air heating system minus the maximum electric thermal output; and wherein the second threshold value is the first threshold value plus the maximum electric thermal output.

7. The control system of claim 1, wherein the electric thermal output generated by the at least one electric heating element is increased during an air purge prior to startup of the at least one burner.

8. A hybrid air heating system comprising: at least one electric heating element capable of generating an electric thermal output; at least one burner capable of generating a combustion thermal output; and a control system comprising a controller configured to, based on a desired total thermal output of the hybrid air heating system, determine an amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element and an amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner.

9. The hybrid air heating system of claim 8, wherein the controller provides a modulated signal to the at least one electric heating element corresponding to the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element and/or a modulated signal to the at least one burner corresponding to the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner.

10. The hybrid air heating system of claim 8, wherein, when the desired total thermal output of the hybrid air heating system is less than a first threshold value, the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element is 100 percent.

11. The hybrid air heating system of claim 10, wherein the first threshold value is between a minimum combustion thermal output and a maximum electric thermal output.

12. The hybrid air heating system of claim 11, wherein, when the desired total thermal output of the hybrid air heating system is greater than the first threshold value, the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner is 100 percent.

13. The hybrid air heating system of claim 11, wherein, when the desired total thermal output of the hybrid air heating system is greater than the first threshold value but less than a second threshold value, the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element is the desired total thermal output of the hybrid air heating system minus the minimum combustion thermal output and the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner is the minimum combustion thermal output; wherein, when the desired total thermal output of the hybrid air heating system is greater than the second threshold value, the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element is the maximum electric thermal output and the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner is the desired total thermal output of the hybrid air heating system minus the maximum electric thermal output; and wherein the second threshold value is the first threshold value plus the maximum electric thermal output.

14. The hybrid air heating system of claim 8, wherein the electric thermal output generated by the at least one electric heating element is increased during an air purge prior to startup of the at least one burner.

15. A method for controlling a hybrid air heating system having at least one electric heating element capable of generating an electric thermal output and at least one burner capable of generating a combustion thermal output, the method comprising: determining, based on a desired total thermal output of the hybrid air heating system, an amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element and an amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner.

16. The method of claim 15, wherein, when the desired total thermal output of the hybrid air heating system is less than a first threshold value, the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element is 100 percent.

17. The method of claim 16, wherein the first threshold value is between a minimum combustion thermal output and a maximum electric thermal output.

18. The method of claim 17, wherein, when the desired total thermal output of the hybrid air heating system is greater than the first threshold value, the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner is 100 percent.

19. The method of claim 17, wherein, when the desired total thermal output of the hybrid air heating system is greater than the first threshold value but less than a second threshold value, the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element is the desired total thermal output of the hybrid air heating system minus the minimum combustion thermal output and the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner is the minimum combustion thermal output; wherein, when the desired total thermal output of the hybrid air heating system is greater than the second threshold value, the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one electric heating element is the maximum electric thermal output and the amount of the desired total thermal output of the hybrid air heating system to be generated by the at least one burner is the desired total thermal output of the hybrid air heating system minus the maximum electric thermal output; and wherein the second threshold value is the first threshold value plus the maximum electric thermal output.

20. The method of claim 15, wherein the electric thermal output generated by the at least one electric heating element is increased during an air purge prior to startup of the at least one burner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The description of the illustrative embodiments may be read in conjunction with the accompanying figures. It will be appreciated that, for simplicity and clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale, unless described otherwise. For example, the dimensions of some of the elements may be exaggerated relative to other elements, unless described otherwise. Embodiments incorporating teachings of the present disclosure are shown and described with respect to the figures presented herein, in which:

[0017] FIG. 1 is a perspective view of an example system for controlling a hybrid air heating system in accordance with example embodiments of the present disclosure;

[0018] FIG. 2 is a flowchart illustrating an example method of controlling a hybrid air heating system in accordance with example embodiments of the present disclosure;

[0019] FIG. 3 is a graph illustrating the output of an example system for controlling a hybrid air heating system in accordance with example embodiments of the present disclosure;

[0020] FIG. 4 is a flowchart illustrating an example method of controlling a hybrid air heating system in accordance with alternative example embodiments of the present disclosure;

[0021] FIG. 5 is a graph illustrating the output of an example system for controlling a hybrid air heating system in accordance with alternative example embodiments of the present disclosure; and

[0022] FIG. 6 is a graph illustrating the output of an example system for controlling a hybrid air heating system in accordance with alternative example embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

[0023] Some embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the disclosure are shown. Indeed, these disclosures may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0024] As used herein, terms such as front, rear, top, bottom, left, right, etc. are used for explanatory purposes in the examples provided below to describe the relative position of certain components or portions of components. Furthermore, as would be evident to one of ordinary skill in the art the terms substantially and approximately indicate that the referenced element or associated description is accurate to within applicable engineering tolerances.

[0025] As used herein, the term comprising means including but not limited to and should be interpreted in the manner it is typically used in the patent context. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of.

[0026] The phrases in one embodiment, according to one embodiment, in some embodiments, and the like generally mean that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present disclosure and may be included in more than one embodiment of the present disclosure (importantly, such phrases do not necessarily refer to the same embodiment).

[0027] The phrases in one example, according to one example, in some examples, and the like generally mean that the particular feature, structure, or characteristic following the phrase may be included in at least one example of the present disclosure and may be included in more than one example of the present disclosure (importantly, such phrases do not necessarily refer to the same example).

[0028] If the specification states a component or feature may, can, could, should, would, preferably, possibly, typically, optionally, for example, as an example, in some examples, often, or might (or other such language) be included or have a characteristic, that specific component or feature is not required to be included or to have the characteristic. Such component or feature may be optionally included in some examples, or it may be excluded.

[0029] The word example or exemplary is used herein to mean serving as an example, instance, or illustration. Any implementation described herein as example or exemplary is not necessarily to be construed as preferred or advantageous over other implementations.

[0030] The term electronically coupled, electronically coupling, electronically couple, in communication with, in electronic communication with, or connected in the present disclosure refers to two or more elements or components being connected through wired and/or wireless means, such that signals, electrical voltage/current, data and/or information may be transmitted to and/or received from these elements or components.

[0031] The term component may refer to an article, a device, or an apparatus that may comprise one or more surfaces, portions, layers and/or elements. For example, a component may comprise one or more substrates that may provide underlying layer(s) for the component and may comprise one or more elements that may form part of and/or are disposed on top of the substrate. In the present disclosure, the term element may refer to an article, a device, or an apparatus that may provide one or more functionalities.

[0032] The term burner is used herein to mean a device that converts the chemical energy stored in any suitable liquid or gas fuel (including but not limited to natural gas, propane, hydrogen, methane, or fuel oil) to heat. Burners can typically provide more thermal power for a given size than electrical heating elements. Burners typically have a finite turndown ratio expressed as a fraction of the maximum capacity. For example a 5:1 turndown means the burner can operate between 20% () and 100% of its rated capacity. The burner cannot effectively operate below its turndown.

[0033] The term electric heating element is used herein to mean a heating element that generates heat by passing electricity through a resistive material. An electric heating element has a practically infinite turndown ratio. An electric heating element has a predetermined maximum output capability limited by the available system voltage and the resistance of the elements.

[0034] The term hybrid air heating system is used herein to mean a system which uses one or more burners and one or more electric heating elements to heat air that is to be used, for example, in an industrial process. A hybrid heating system uses less electricity than a fully electric system and can be installed in places that do not have electrical capacity for full electrification. Because hybrid heating systems include both electric heating elements and burners, the turndown of hybrid heating systems is extended because the electric heating element(s) enables operation at thermal powers below the minimum burner capacity.

[0035] Many industrial machines and processes use a centralized system controller to modulate the output of the thermal system. The system controller typically determines how much heated air is needed and at what temperature and sends a signal to an air heating system indicating a desired firing rate (from 0 to 100%) of the air heating system. The firing rate is a specified percentage of the air heating system's total possible energy output. For example, if an air heating system has a possible heat energy output of 2,000,000 BTUs (British thermal units), then at a 50% firing rate the air heating system would output 1,000,000 BTUs of heat energy. The system controller typically sends an analog signal (commonly a 4-20 milliamp (mA) signal, with 4 mA equal to a 0% firing rate and 20 mA equal to a 100% firing rate) to the thermal system.

[0036] Various embodiments of the present disclosure overcome the above technical challenges and difficulties and provide various technical improvements and advantages. For example, various embodiments of the present disclosure provide an example control system for a hybrid air heating system that controls the output of the electric heating elements and the burners. Various embodiments of the present disclosure include novel methods of switching between the electric heating elements and the burners in a hybrid air heating system.

[0037] In various embodiments, the control system for such a hybrid air heating system receives a signal (directly or indirectly) from a system controller that is controlling an industrial system/machine/process that requires heated air. As described above, such a signal indicates a desired firing rate (from 0 to 100%).

[0038] In various embodiments, based on the firing rate as received from the system controller that is controlling the industrial system/machine/process, a control system for a hybrid air heating system determines the amount of energy to be generated by the electric heating element(s) and the amount to be generated by the burner(s).

[0039] Various embodiments of the present disclosure include novel methods of switching between the electric heating elements and the burners in a hybrid air heating system during an air purge that occurs prior to igniting the burners and/or after turning off the burners.

[0040] For example, the control system for a hybrid air heating system may include digital and/or analog outputs that are used to control actuators that modulate the firing rate of the burners. The burner firing rate may be controlled by control valves (such as ones used for parallel positioning) or on/off solenoid valves for pulse firing. The digital and/or analog outputs also control the heating power of the electric heating elements. This may be done, for example, by providing a heat demand to a separate electric heating controller or by using high power control elements such as thyristors or silicon-controlled rectifiers.

[0041] Various embodiments of the present disclosure include novel methods of switching between the electric heating elements and the burners in a hybrid air heating system using at least two different modes of operation. In one mode of operation (termed an economy mode herein) of various embodiments, the electric heating elements are used exclusively to increase turndown. That is, in the economy mode, the electric heating elements are used exclusively at the lower range of the firing rate (i.e., from 0% up to a predetermined switchover point) and the burners are used exclusively from the switchover point up to 100% firing rate (with a small overlap as the switchover occurs). As described herein, this switchover point may be termed a first threshold.

[0042] In another mode of operation (termed a sustainability mode or reduced carbon mode herein) of various embodiments, the electric heating elements are used both at the lower range of the firing rate to increase turndown and at the upper range of the firing rate to supplement the burners. In this regard, the sustainability mode uses more electricity and less fuel, thereby generally lowering the carbon dioxide emissions of the hybrid air heating system since the electricity powering the electric heating elements is assumed to be purchased from low carbon intensity sources.

[0043] In various embodiments, the control system of a hybrid air heating system sends a modulated signal to the electric heating elements corresponding to the desired firing rate of the electric heating elements and/or sends a modulated signal to the burners corresponding to the desired firing rate of the burners. In some embodiments, the modulated signal is a 4-20 milliamp (mA) signal, with 4 mA equal to a 0% firing rate and 20 mA equal to a 100% firing rate.

[0044] In various embodiments, it is desirable to have an overlap between the output capability of the electric heating elements and the burners. That is, it is desirable that the minimum output of the burners (based on the turndown rate) is lower than the maximum output of the electric heating elements (based on their rated capacity as a percentage of the overall output capacity of the hybrid heating system).

[0045] In various embodiments, the switchover point from electric heating elements to burners is predetermined and set between the minimum output of the burners and the maximum output of the electric heating elements. For example, in a hybrid heating system in which the minimum output of the burners is 10% and the maximum output of the electric heating elements is 20%, the switchover point may be set at 15%.

[0046] In some embodiments, the capabilities of the system controller that is controlling an industrial system/machine/process that requires heated air and the capabilities of the control system for a hybrid air heating system, as described herein, may be combined into a single system or controller.

[0047] FIG. 1 shows a block diagram of an example hybrid air heating control system in accordance with various embodiments. As depicted in FIG. 1, in some embodiments the example hybrid air heating control system comprises a hybrid heating system controller 100 and a hybrid heating system 110. In some embodiments, as described above, the hybrid heating system controller 100 is in communication with and receives signals from a system controller 120 for an industrial system/machine/process. As depicted in FIG. 1, in some embodiments the hybrid heating system 110 comprises one or more electric heating elements 112 and one or more burners 114. As depicted in FIG. 1, in some embodiments the hybrid heating system controller 100 comprises a controller or processing circuitry 102, memory circuitry 104, input/output circuitry 106, and communications circuitry 108. In some embodiments, the hybrid heating system controller 100 is configured to execute and perform the operations described herein.

[0048] Although components are described with respect to functional limitations, it should be understood that at least some of the implementations necessarily include the use of particular computing hardware. It should also be understood that in some embodiments certain of the components described herein include similar or common hardware. For example, in some embodiments two sets of circuitry both leverage use of the same processor(s), memory(ies), circuitry(ies), and/or the like to perform their associated functions such that duplicate hardware is not required for each set of circuitry.

[0049] Processing circuitry 102 may be embodied in a number of different ways. In various embodiments, the use of the terms processor or processing circuitry should be understood to include a single core processor, a multi-core processor, multiple processors internal to the hybrid heating system controller 100, and/or one or more remote or cloud processor(s) external to the hybrid heating system controller 100. In some example embodiments, processing circuitry 102 may include one or more processing devices configured to perform independently. Alternatively, or additionally, processing circuitry 102 may include one or more processor(s) configured in tandem via a bus to enable independent execution of operations, instructions, pipelining, and/or multithreading.

[0050] In an example embodiment, the processing circuitry 102 may be configured to execute instructions stored in the memory circuitry 104 or otherwise accessible to the processor. Alternatively, or additionally, the processing circuitry 102 may be configured to execute hard-coded functionality. As such, whether configured by hardware or software methods, or by a combination thereof, processing circuitry 102 may represent an entity (e.g., physically embodied in circuitry) capable of performing operations according to embodiments of the present disclosure while configured accordingly. Alternatively, or additionally, processing circuitry 102 may be embodied as an executor of software instructions, and the instructions may specifically configure the processing circuitry 102 to perform the various algorithms embodied in one or more operations described herein when such instructions are executed. In some embodiments, the processing circuitry 102 includes hardware, software, firmware, and/or a combination thereof that performs one or more operations described herein.

[0051] In some embodiments, the processing circuitry 102 (and/or co-processor or any other processing circuitry assisting or otherwise associated with the processor) is/are in communication with the memory circuitry 104 via a bus for passing information among components of the hybrid heating system controller 100.

[0052] Memory or memory circuitry 104 may be non-transitory and may include, for example, one or more volatile and/or non-volatile memories. In some embodiments, the memory circuitry 104 includes or embodies an electronic storage device (e.g., a computer readable storage medium). In some embodiments, the memory circuitry 104 is configured to store information, data, content, applications, instructions, or the like, for enabling the hybrid heating system controller 100 to carry out various operations and/or functions in accordance with example embodiments of the present disclosure.

[0053] Input/output circuitry 106 may be included in the hybrid heating system controller 100. In some embodiments, input/output circuitry 106 may provide output to the user and/or receive input from a user. The input/output circuitry 106 may be in communication with the processing circuitry 102 to provide such functionality. The input/output circuitry 106 may comprise one or more user interface(s). In some embodiments, a user interface may include a display that comprises the interface(s) rendered as a web user interface, an application user interface, a user device, a backend system, or the like. In some embodiments, the input/output circuitry 106 also includes a keyboard, a mouse, a joystick, a touch screen, touch areas, soft keys a microphone, a speaker, or other input/output mechanisms. The processing circuitry 102 and/or input/output circuitry 106 may be configured to control one or more operations and/or functions of one or more user interface elements through computer program instructions (e.g., software and/or firmware) stored on a memory accessible to the processor (e.g., memory circuitry 104, and/or the like). In some embodiments, the input/output circuitry 106 includes or utilizes a user-facing application to provide input/output functionality to a computing device and/or other display associated with a user.

[0054] Communications circuitry 108 may be included in the hybrid heating system controller 100. The communications circuitry 108 may include any means such as a device or circuitry embodied in either hardware or a combination of hardware and software that is configured to receive and/or transmit data from/to a network and/or any other device, circuitry, or module in communication with the hybrid heating system controller 100. In some embodiments the communications circuitry 108 includes, for example, a network interface for enabling communications with a wired or wireless communications network. Additionally or alternatively, the communications circuitry 108 may include one or more network interface card(s), antenna(s), bus(es), switch(es), router(s), modem(s), and supporting hardware, firmware, and/or software, or any other device suitable for enabling communications via one or more communications network(s). In some embodiments, the communications circuitry 108 may include circuitry for interacting with an antenna(s) and/or other hardware or software to cause transmission of signals via the antenna(s) and/or to handle receipt of signals received via the antenna(s). In some embodiments, the communications circuitry 108 enables transmission to and/or receipt of data from a user device, one or more sensors, and/or other external computing device(s) in communication with the hybrid heating system controller 100.

[0055] In some embodiments, two or more of the sets of circuitry 102-108 are combinable. Alternatively, or additionally, one or more of the sets of circuitry 102-108 perform some or all of the operations and/or functionality described herein as being associated with another circuitry. In some embodiments, two or more of the sets of circuitry 102-108 are combined into a single module embodied in hardware, software, firmware, and/or a combination thereof.

[0056] While the description above provides an example hybrid heating system controller 100, it is noted that the scope of the present disclosure is not limited to the description above. In some examples, an example hybrid heating system controller 100 in accordance with the present disclosure may be in other forms. In some examples, an example hybrid heating system controller 100 may comprise one or more additional and/or alternative elements, and/or may be structured differently than that illustrated in FIG. 1.

[0057] Reference will now be made to FIGS. 2 and 4 which provide flowcharts illustrating example steps, processes, procedures, and/or operations in accordance with various embodiments of the present disclosure. Various methods described herein, including, for example, example methods as shown in FIGS. 2 and 4, may provide various technical benefits and improvements. It is noted that each block of the flowchart, and combinations of blocks in the flowchart, may be implemented by various means such as hardware, firmware, circuitry and/or other devices associated with execution of software including one or more computer program instructions. For example, one or more of the procedures described in FIGS. 2 and 4 may be embodied by computer program instructions, which may be stored by a non-transitory memory of an apparatus employing an embodiment of the present disclosure and executed by a processor in the apparatus. These computer program instructions may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage memory produce an article of manufacture, the execution of which implements the function specified in the flowchart block(s).

[0058] As described above and as will be appreciated based on this disclosure, embodiments of the present disclosure may be configured as methods, mobile devices, backend network devices, and the like. Accordingly, embodiments may comprise various means including entirely of hardware or any combination of software and hardware. Furthermore, embodiments may take the form of a computer program product on at least one non-transitory computer-readable storage medium having computer-readable program instructions (e.g., computer software) embodied in the storage medium. Similarly, embodiments may take the form of a computer program code stored on at least one non-transitory computer-readable storage medium. Any suitable computer-readable storage medium may be utilized including non-transitory hard disks, CD-ROMs, flash memory, optical storage devices, or magnetic storage devices.

[0059] FIGS. 2 and 3 provide, respectively, a flowchart and graph illustrating an example method of controlling a hybrid air heating system in accordance with example embodiments of the present disclosure. Specifically, FIGS. 2 and 3 illustrate an economy mode of operation of an example hybrid air heating system in which the electric heating elements are used exclusively to increase turndown. In the example method, as illustrated in the graph 300 of FIG. 3, the predetermined switchover point is 15% (illustrated by the long-long-short dash line), the minimum burner output is 10% (illustrated by the short-short-long dash line), and the maximum electric heating element output is 20% (illustrated by the long dash line).

[0060] FIG. 2 illustrates an example method 200. At step/operation 202, a processor (such as, but not limited to, the processing circuitry 102 of the example hybrid heating system controller 100 described above in connection with FIG. 1) receives a signal from, for example, a system controller processor (such as, but not limited to, the system controller 120 described above in connection with FIG. 1) indicating a desired firing rate (from 0-100%) of a hybrid air heating system. The signal from the system controller may be any suitable type of signal, such as an analog signal ranging from 4 to 20 mA as described above. It should be evident to one of ordinary skill in the art that other switchover points may be used.

[0061] Step/operation 204 illustrates what happens when the requested firing rate is in the lower range of the firing rate (i.e., from 0% up to the predetermined switchover point (15% in this example)). At step/operation 204, the processor ensures that the burner is disabled (in some embodiments, this involves reducing the analog control voltage to the burner to 4 mA) and a scaled signal is sent to the electric heating element to modulate the output of the electric heating element to correspond with the requested firing rate. For example, with an electric heating element that has a maximum output of 20% (as a percentage of the total output of the hybrid air heating system), the processing element will send a signal to the electric heating element to scale its output from 0 to 75% (i.e., at 75% output, the electric heating element will produce the correct output for a system firing rate of 15%. The signal from the processor to the electric heating element may be any suitable type of signal, such as an analog signal ranging from 4 to 20 mA. This output of only the electric heating element from 0-15% firing rate is illustrated by the solid line in FIG. 3. Again, it should be evident to those of ordinary skill in the art that other switching percentages may be used.

[0062] Step/operation 206 illustrates what happens when a signal is received for a requested firing rate that is above the switchover point up to 100% firing rate. At step/operation 206, the processor ensures that the electric heating element is disabled (in some embodiments, this involves reducing the analog control voltage to the electric heating element to 4 mA). Because the burner has been off prior to this point, a signal is sent to the burner to light/re-light the burner.

[0063] Most burner codes require a pre-ignition air purge prior to lighting or relighting a burner to ensure combustible gases are removed before ignition. This may be problematic for temperature stability in hybrid systems where the burner is expected to be lit and extinguished during regular operation because the pre-ignition purge introduces both increased heat load (though the cold air injected as part of the purge) and a time delay (on the order of 30 seconds to many minutes, depending on the system) between when there is a call for more heat and when that call is met. In various embodiments of the disclosure, the output of the electric heating element may be temporarily increased to compensate for this air purge, as described further below in relation to FIG. 6.

[0064] Step/operation 208 illustrates what happens while the requested firing rate is in the upper range of the firing rate (i.e., from the predetermined switchover point (15% in this example) up to 100%). At step/operation 208, the processor continues to ensure that the electric heating element is disabled (in some embodiments, this involves reducing the analog control voltage to the electric heating element to 4 mA) and sends a signal to the burner to modulate the output of the burners to correspond with the requested firing rate. In various embodiments, the burners are used exclusively from the switchover point up to 100% firing rate (with a small overlap as the switchover occurs). This output of only the burners from 15-100% firing rate is illustrated by the short dash line in FIG. 3.

[0065] Step/operation 210 illustrates what happens when a signal is received to reduce the requested firing rate from one that is above the switchover point to one that is below the switchover point. At step/operation 210, the processor ensures that the burner is disabled (in some embodiments, this involves reducing the analog control voltage to the burner to 4 mA) and prepares to send a scaled signal to the electric heating element (e.g., an analog signal ranging from 4 to 20 mA). In some embodiments, there may be another air purge after the burner is extinguished in which case the output of the electric heating element may be temporarily increased to compensate for this air purge, as described further below in relation to FIG. 6.

[0066] If the requested firing rate remains below the switchover point, the method 200 returns to step/operation 204 to modulate the output of the electric heating element until the requested firing rate changes.

[0067] As seen in FIG. 3, the total system output illustrated by the short-long dash line is based on the output of only the electric heating element from 0-15% firing rate and only the burner from 15-100% firing rate (with a small overlap as the switchover occurs). In some embodiments, the method 200 repeats for the duration of the process heat demand.

[0068] FIGS. 4 and 5 provide, respectively, a flowchart and graph illustrating an example method of controlling a hybrid air heating system in accordance with example embodiments of the present disclosure. Specifically, FIGS. 4 and 5 illustrate a sustainability mode of operation of an example hybrid air heating system in which the electric heating elements are used both at the lower range of the firing rate to increase turndown and at the upper range of the firing rate to supplement the burners. In the example method, as illustrated in the graph 500 of FIG. 5, the predetermined switchover point is 15% (illustrated by the long-long-short dash line), the minimum burner output is 10% (illustrated by the short-short-long dash line), and the maximum electric heating element output is 20% (illustrated by the long dash line).

[0069] FIG. 4 illustrates an example method 400. At step/operation 402, the processor receives a signal from, for example, a system controller processor (such as, but not limited to, the system controller 120 described above in connection with FIG. 1) indicating a desired firing rate (from 0-100%) of a hybrid air heating system. The signal from the system controller may be any suitable type of signal, such as an analog signal ranging from 4 to 20 mA as described above.

[0070] Step/operation 404 illustrates what happens when the requested firing rate is in the lower range of the firing rate (i.e., from 0% up to the predetermined switchover point (15% in this example)). At step/operation 404, the processor ensures that the burner is disabled (in some embodiments, this involves reducing the analog control voltage to the burner to 4 mA) and a scaled signal is sent to the electric heating element to modulate the output of the electric heating element to correspond with the requested firing rate. For example, with an electric heating element that has a maximum output of 20% (as a percentage of the total output of the hybrid air heating system), the processing element will send a signal to the electric heating element to scale its output from 0 to 75% (i.e., at 75% output, the electric heating element will produce the correct output for a system firing rate of 15%. The signal from the processor to the electric heating element may be any suitable type of signal, such as an analog signal ranging from 4 to 20 mA. This output of only the electric heating element from 0-15% firing rate is illustrated by the solid line in FIG. 5.

[0071] Step/operation 406 illustrates what happens when a signal is received for a requested firing rate that is above the switchover point up to 100% firing rate. At step/operation 406, the processor ensures that the electric heating element is disabled (in some embodiments, this involves reducing the analog control voltage to the electric heating element to 4 mA). Because the burner has been off prior to this point, a signal is sent to the burner to light/re-light the burner. In various embodiments of the disclosure, an air purge is performed prior to lighting/re-lighting the burner, in which case the output of the electric heating element may be temporarily increased to compensate for this air purge, as described further below in relation to FIG. 6.

[0072] Step/operation 408 illustrates what happens while the requested firing rate is in the lower portion of the upper range of the firing rate (i.e., from the predetermined switchover point (15% in this example) up to a second predetermined threshold value (35% in this example) that is the sum of the first threshold value (15% in this example) plus the maximum electric heat energy output (20% in this example). At step/operation 208, the sends a signal to the burner to modulate the output of the burners at a fixed value of 15% (i.e., the switchover value) and sends a signal to the electric heating elements to modulate the output of the electric heating elements between 0% and its maximum output such that the sum of the output of the electric heating elements and the output of the burners corresponds with the requested firing rate. In FIG. 5, between a firing rate of 15% and a firing rate of 35%, the fixed output of the burners at 15% (illustrated by the short dash line) and the variable output of the electric heating elements from 0% to 20% (illustrated by the solid line) is seen.

[0073] Step/operation 410 illustrates what happens while the requested firing rate is in the upper portion of the upper range of the firing rate (i.e., from the second predetermined threshold value (35% in this example) up to 100%. At step/operation 410, the processor sends a signal to the electric heating element to modulate the output of the electric heating elements at a fixed value of its maximum output (20% in this example) and sends a signal to the burners to modulate the output of the burners between 15% (the switchover value) and its maximum output such that the sum of the output of the electric heating elements and the output of the burners corresponds with the requested firing rate. In FIG. 5, between a firing rate of 35% and a firing rate of 100%, the fixed output of the electric heating elements at 20% (illustrated by the solid line) and the variable output of the burners from 15% to 100% (illustrated by the short dash line) is seen.

[0074] As seen in FIG. 5, the total system power (illustrated by the short-long dash line) may exceed 100% as a percentage of combustion power because (starting at a 35% system firing rate) the output of the electric heating elements (20% in this example) is added to the output of the burners. In various other embodiments, the controller may reduce the requested output of the burners accordingly to keep the total system power from exceeding 100% as a percentage of combustion power.

[0075] As seen in FIG. 4, the requested firing rate may vary between the lower portion of the upper range (step/operation 408) and the upper portion of the upper range (step/operation 410), and the controller would vary the modulation of the electric heating elements and the burners accordingly.

[0076] Step/operation 412 illustrates what happens when a signal is received to reduce the requested firing rate from one that is above the switchover point to one that is below the switchover point. At step/operation 412, the processor ensures that the burner is disabled (in some embodiments, this involves reducing the analog control voltage to the burner to 4 mA) and prepares to send a scaled signal to the electric heating element (e.g., an analog signal ranging from 4 to 20 mA). In some embodiments, there may be another air purge after the burner is extinguished in which case the output of the electric heating element may be temporarily increased to compensate for this air purge, as described further below in relation to FIG. 6.

[0077] If the requested firing rate remains below the switchover point, the method 400 returns to step/operation 404 to modulate the output of the electric heating element until the requested firing rate changes.

[0078] As seen in FIG. 5, the total system output illustrated by the short-long dash line is based on the output of only the electric heating element from 0-15% firing rate and a combination of the output of the electric heating elements and the output of the burner from 15-100% firing rate. In some embodiments, the method 400 repeats as long as the industrial system/machine/process calls for heat from the hybrid controller.

[0079] Referring now to FIG. 6, a graph 600 is illustrated. The graph 600 illustrates an example control method in which the output of the electric heating element is temporarily increased to compensate for an air purge before lighting and/or after extinguishing the burners. In the example method, as illustrated in the graph 600 of FIG. 6, the predetermined switchover point is 15% (illustrated by the long-long-short dash line), the minimum burner output is 10% (illustrated by the short-short-long dash line), the maximum electric heating element output is 20% (illustrated by the long dash line), the output of the electric heating elements is illustrated by the solid line, and the output of the burners is illustrated by the short dash line. As seen in FIG. 6, the output of the electric heating elements is increased to the maximum output during the air purge (as indicated on the x-axis) to compensate for the lower temperature air being introduced.

[0080] In various embodiments, the additional heat transfer required during the air purge is calculated using the equation {dot over (Q)}={dot over (m)}.sub.purge*C.sub.p*(T.sub.setpointT.sub.purge air), where {dot over (Q)} is the heat transfer rate, {dot over (m)}.sub.purge is the mass flow rate of the purge air based on the design of the burner, C.sub.p is the specific heat of the purge air, T.sub.setpoint is the setpoint of the chamber in which the burners reside, and T.sub.purge air is the temperature of the incoming purge air (typically ambient air).

[0081] Operations and processes described herein support combinations of means for performing the specified functions and combinations of operations for performing the specified functions. It will be understood that one or more operations, and combinations of operations, may be implemented by special purpose hardware-based computer systems which perform the specified functions, or combinations of special purpose hardware and computer instructions.

[0082] In some example embodiments, certain ones of the operations herein may be modified or further amplified as described below. Moreover, in some embodiments additional optional operations may also be included. It should be appreciated that each of the modifications, optional additions or amplifications described herein may be included with the operations herein either alone or in combination with any others among the features described herein.

[0083] The foregoing method and process descriptions are provided merely as illustrative examples and are not intended to require or imply that the steps of the various embodiments must be performed in the order presented. As will be appreciated by one of skill in the art the order of steps in the foregoing embodiments may be performed in any order. Words such as thereafter, then, next, and similar words are not intended to limit the order of the steps; these words are simply used to guide the reader through the description of the methods. Further, any reference to claim elements in the singular, for example, using the articles a, an or the, is not to be construed as limiting the element to the singular and may, in some instances, be construed in the plural.

[0084] While various embodiments in accordance with the principles disclosed herein have been shown and described above, modifications thereof may be made by one skilled in the art without departing from the teachings of the disclosure. The embodiments described herein are representative only and are not intended to be limiting. Many variations, combinations, and modifications are possible and are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Accordingly, the scope of protection is not limited by the description set out above, but is defined by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present disclosure. Furthermore, any advantages and features described above may relate to specific embodiments but shall not limit the application of such issued claims to processes and structures accomplishing any or all of the above advantages or having any or all of the above features.

[0085] In addition, the section headings used herein are provided for consistency with the suggestions under 37 C.F.R. 1.77 or to otherwise provide organizational cues. These headings shall not limit or characterize the disclosure set out in any claims that may issue from this disclosure. For instance, a description of a technology in the Background is not to be construed as an admission that certain technology is prior art to any disclosure in this disclosure. Neither is the Summary to be considered as a limiting characterization of the disclosure set forth in issued claims. Furthermore, any reference in this disclosure to disclosure or embodiment in the singular should not be used to argue that there is only a single point of novelty in this disclosure. Multiple embodiments of the present disclosure may be set forth according to the limitations of the multiple claims issuing from this disclosure, and such claims accordingly define the disclosure, and their equivalents, which are protected thereby. In all instances, the scope of the claims shall be considered on their own merits in light of this disclosure but should not be constrained by the headings set forth herein.

[0086] Also, systems, subsystems, apparatuses, techniques, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other devices or components shown or discussed as coupled to, or in communication with, each other may be indirectly coupled through some intermediate device or component, whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the scope disclosed herein.

[0087] Many modifications and other embodiments of the disclosure set forth herein will come to mind to one skilled in the art to which these embodiments pertain having the benefit of teachings presented in the foregoing descriptions and the associated figures. Although the figures only show certain components of the apparatuses and systems described herein, various other components may be used in conjunction with the components and structures disclosed herein. Therefore, it is to be understood that the disclosure is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. For example, the various elements or components may be combined, rearranged, or integrated in another system or certain features may be omitted or not implemented. Moreover, the steps in any method described above may not necessarily occur in the order depicted in the accompanying drawings, and in some cases one or more of the steps depicted may occur substantially simultaneously, or additional steps may be involved. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.