Highly efficient architecture and control scheme for solid-state HVAC applications

Abstract

A system and method for controlling a heat exchanger including a plurality of thermoelectric coolers to provide conditioned air is provided. The method includes receiving system measurements indicative of one or more of the group consisting of a temperature on a receiving side of a first thermoelectric cooler, a temperature on a rejection side of the first thermoelectric cooler, a temperature on a receiving side of a second thermoelectric cooler, a temperature on a rejection side of the second thermoelectric cooler, an indication of a direction of airflow within the heat exchanger, and an indication of a relative humidity value. The method also includes selectively controlling two or more subsets of the thermoelectric coolers among the plurality of thermoelectric coolers based on the received system measurements, thereby enabling increased efficiency of the heat exchanger.

Description

[Technical Field]

[0001] Related Applications This application claims the benefit of Provisional Patent Application No. 63 / 385,677, filed December 1, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates generally to controlling air conditioning applications. [Background technology]

[0003] Traditional heating, ventilation, and air conditioning (HVAC) applications desire, target, and create significant temperature differences between conditioned and unconditioned spaces in order to provide acceptable performance and comfort to the user.

[0004] Creating large temperature differences between conditioned and unconditioned spaces using conventional integration methods generally puts solid-state heating and cooling systems at a disadvantage compared to conventional (e.g., vapor compression-based) heat pump systems.

[0005] Thermodynamically simplified, the greater the temperature difference created within a heat pump system, the lower the efficiency the heat pump system can achieve. Therefore, traditional solid-state heating and cooling implementation methods place any application of solid-state heat pump methods at a potential disadvantage relative to alternative technologies. Summary of the Invention

[0006] A system and method for controlling a heat exchanger including a plurality of thermoelectric coolers to provide conditioned air is provided. The method includes receiving system measurements indicative of one or more of the group consisting of a temperature on a receiving side of a first thermoelectric cooler, a temperature on a rejection side of the first thermoelectric cooler, a temperature on a receiving side of a second thermoelectric cooler, a temperature on a rejection side of the second thermoelectric cooler, an indication of a direction of airflow within the heat exchanger, and an indication of a relative humidity value. The method also includes selectively controlling two or more subsets of the thermoelectric coolers among the plurality of thermoelectric coolers based on the received system measurements, thereby enabling increased efficiency of the heat exchanger.

[0007] Solid-state heating and cooling systems can provide very high efficiency operation when device and system differentials are small. Also, because solid-state systems have the potential for 100% modulation from zero to full capacity, these types of systems can take advantage of the variable nature of demand in HVAC applications more effectively than fixed temperature differential systems. However, as temperature differentials, and therefore demand, increase, the efficiency of solid-state systems decreases if they are not efficiently integrated and managed.

[0008] In some embodiments, the indication of the direction of air flow within the heat exchanger includes one of parallel air flow and counter air flow.

[0009] In some embodiments, selectively controlling two or more subsets of thermoelectric coolers includes being able to provide equal power to two or more subsets of thermoelectric coolers when the indication of the direction of airflow within the heat exchanger includes opposing airflow.

[0010] In some embodiments, when the indication of the direction of airflow within the heat exchanger includes parallel airflow, selectively controlling the two or more subsets of thermoelectric coolers includes providing different powers to the two or more subsets of thermoelectric coolers.

[0011] In some embodiments, the system measurements further include an indication of airflow.

[0012] In some embodiments, selectively controlling two or more subsets of the thermoelectric coolers includes attempting to optimize a system-level efficiency of the heat exchangers.

[0013] In some embodiments, selectively controlling the two or more subsets of thermoelectric coolers includes providing an overall temperature difference by providing a smaller temperature difference across each of the two or more subsets of thermoelectric coolers.

[0014] In some embodiments, selectively controlling two or more subsets of the thermoelectric coolers includes adjusting the relative humidity on one or more of the heat rejection side and the receiving side.

[0015] In some embodiments, the heat exchanger includes multiple controllers for selectively controlling two or more subsets of the thermoelectric coolers.

[0016] In some embodiments, each subset of thermoelectric exchangers includes one or more different thermoelectric coolers from the plurality of thermoelectric coolers.

[0017] Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in conjunction with the accompanying drawing figures.

[0018] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate several aspects of the disclosure and, together with the description, serve to explain the principles of the disclosure. [Brief explanation of the drawings]

[0019] [Figure 1] 1 illustrates a heat exchanger including multiple thermoelectric coolers thermodynamically configured in a series orientation in a counterflow source / sink mass flow configuration. [Figure 2] 1 shows a heat exchanger with parallel airflow. [Figure 3] 1 shows a heat exchanger with counter-airflow. [Figure 4A] An example is shown in which heat exchanger series sub-delta modules can all be optimized to function as primaries. [Figure 4B] An example is shown in which a heat exchanger series sub-delta module can be optimized to function as a full primary. [Figure 5A] An example is shown in which a heat exchanger series sub-delta module can be optimized to function as a master / slave configuration. [Figure 5B] An example is shown in which a heat exchanger series sub-delta module can be optimized to function as a master / slave configuration. [Figure 6] 1 shows an example of capacity and efficiency optimization curves. [Figure 7] The capacity curves associated with the example of FIG. 6 are shown. [Figure 8] The COP curves associated with the example of FIG. 6 are shown. [Figure 9] The V / I curves associated with the example of FIG. 6 are shown. DETAILED DESCRIPTION OF THE INVENTION

[0020] The embodiments described below present the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode for practicing the embodiments. Upon reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the present disclosure and will recognize applications of these concepts not specifically addressed herein. It is understood that these concepts and applications are within the scope of this disclosure and the appended claims.

[0021] Solid-state heating and cooling systems can provide very high efficiency operation when device and system differentials are small. Also, because solid-state systems have the potential for 100% modulation from zero to full capacity, these types of systems can take advantage of the variable nature of demand in HVAC applications more effectively than fixed temperature differential systems. However, as temperature differentials, and therefore demand, increase, the efficiency of solid-state systems decreases if they are not efficiently integrated and managed.

[0022] To take advantage of the potential for higher efficiencies achievable with solid-state-based systems at lower temperature differentials and overcome their reduced capacity, the entire system must be designed to take advantage of the thermodynamic properties of the solid-state materials and components used to pump heat from source to sink when operating at a higher-efficiency operating point. This includes the temperature-dependent properties of the solid-state materials themselves, as well as lower efficiencies at higher temperature differentials and capacities, along with internal system parasitics and methods for regulating and controlling the system. To be effective, the system must optimize and manage a multivariable set of mutually incompatible areas, including, but not limited to: 1. Heat pump selection 2. Capacity optimization 3. Efficiency (COP) optimization 4.Heat flux 5. Heat Transfer 6. Heat Transport 7.Thermal resistance 8. System Configuration 9. Control / Power

[0023] Fundamentally, to be effective, a system must manage multiple elements of physical characteristics, functionality, capabilities, and control. This includes (but is not limited to) heat pump characteristics, internal parasitics, heat transfer efficiency / capacity, system regulation / control, and power conversion / supply. Due to the unique operating characteristics and intrinsic properties of typical solid-state heat pumps and the materials used to create them, implementing a solid-state solution in a HAVC application is best achieved by dividing the overall system delta into smaller, manageable sub-delta segments managed and supplied by separate physical modules. The number of sub-delta modules is a function of the desired efficiency, capacity, dimensional constraints, and economics of the system / market demand. Unfortunately, in real-world applications, each sub-delta module will operate not only at different absolute receiving and rejecting temperatures, but also at different temperature differentials between the two sides, so dividing the overall delta, by itself, is only marginally effective in improving system performance. Operating in this suboptimal state significantly impairs overall system performance and may produce much less power than desired.

[0024] When solid-state systems are properly utilized in system-level implementations, the effective operating temperatures of individual heat exchangers are critical to performance and modeling requirements. For a system to achieve maximum efficiency, internal parasitics must be minimized, starting with the solid substrate utilized and continuing through heat transport, power conversion, and control to the overall system architecture. The key system-level metric is generally considered to be the thermal resistance of the system from source to heat pump and from heat pump to sink. While the total thermal resistance of a system from source to sink can be calculated and measured, these two metrics must be considered separately to effectively characterize the system's transport efficiency, as contact resistance, internal efficiency losses of heat transport mechanisms, and the inherent temperature discontinuity between the source and sink sides of a heat pump device can have a significant impact on performance when considered in its entirety.

[0025] The first step in optimizing a system divided into sub-delta modules for maximum capacity and efficiency is to configure the system architecture so that the system source / sink interfaces for the separate modules are thermodynamically configured in a series orientation with a counter-current source / sink mass flow configuration (Figure 1).

[0026] Without this configuration, the first heat rejection (sink) stage has the smallest temperature difference between its hot and cold sides, with each subsequent stage having a larger difference governed by an increasing heat rejection temperature. This results from the pumped heat load being combined with the work done by the system and co-rejected to the ambient through the heat rejection exchanger. This condition is exacerbated when combined with a higher absolute temperature average, causing each subsequent downstream sink stage to operate due to preheating of the stage from the output of the upstream module. Due to this different average operating temperature, each stage has distinctly different material properties, operating, and control optimization curves. In fact, if improperly implemented, this basic configuration has a high potential to adversely affect overall system performance, increase the performance differential(s) of individual downstream sub-delta module(s), minimize or even negate targeted potential performance improvements by excluding the potential impact of downstream module(s) on system capacity, and degrade upstream module(s) by significantly reducing the heat absorption capacity on the receiving (source) side of the system (Figure 2). Sub-delta splitting is generally considered desirable in modeling, but if not properly considered in conjunction with the overall system architecture and operating parameters, the effects of non-optimization can be more harmful than helpful.

[0027] When implemented in the described series / counterflow configuration, the sub-delta system is now loaded from high to low (hottest to coldest) on the source side and low to high (coldest to hottest) on the sink side. Doing this now allows the individual sub-delta modules to operate at similar differential but different absolute temperature averages (Figure 3). This allows the system to potentially pump the greatest amount of energy from the system consuming the least amount of energy.

[0028] However, there is at least one more important factor. Each sub-delta system must be operated and controlled at a different point of optimization, independent and interdependent on the other sub-delta modules in series. This method of controlling the various sub-delta modules is the final major contributor to optimal system-level performance. Series sub-delta modules can be optimized to function either as an all-primary (FIGS. 4A and 4B), as a master / slave (primary, secondary, tertiary, etc.) (FIGS. 5A and 5B), or as a mixture of both configurations. In some embodiments, relative humidity is used as one of the input variables. In some embodiments, the system adjusts the relative humidity on the heat rejection side and / or the receiving side. In some embodiments, the heat exchanger is controlled to intentionally induce water condensation at specific locations within the heat exchanger. This can be used to protect some systems within the heat exchanger or to aid in water removal. In some embodiments, the humidity on the heat rejection side is increased. This may come from water captured or otherwise provided from the receiving side. This increase in humidity on the heat rejection side can increase the heat transfer capacity of the heat rejection side.

[0029] In an all-primary configuration, all sub-delta modules receive demand control signals and individually optimize for maximum efficiency while communicating with the appropriate sub-delta modules that share the overall load in separate subnetworks (Figure 3). In a master-slave configuration, the primary (master) sub-delta module interfaces with the demand control via a direct interface (wireless, WAN, direct wire, etc.) and optimizes its own operating point based on the current demand signal and environmental conditions. In a dynamic loop, the primary then initiates control commands on a separate local network that drive lateral / upstream / downstream sub-delta modules as a dedicated function of their position in the network and the optimized conditions determined from the demand signal and environmental conditions (Figure 5).

[0030] In any control system, aiming for maximum efficiency and performance, the end result of this system is to provide an optimal system operating point based on demand and available sensor feedback. In the case of a thermoelectric system, each configuration exhibits a predictable performance envelope of capacity and efficiency (COP) based on the operating temperature differential and power input. Therefore, each individual sub-stage module must be able to determine the optimal operating conditions for its own contribution based not only on overall demand, but also on the individual modules operating in conjunction with it in the same thermal circuit.

[0031] A specific example of this capacity and efficiency optimization curve can be seen in Figure 6. This curve is a function of the heat pump device(s) used, the associated capacity curve (Figure 7), COP curve (Figure 8), V / I curve (Figure 9), and the resulting temperature difference created by the heat transport system and internal parasitic elements for a given load. It is a fundamental and inherent property of the complete system architecture. Using this resulting inherent characterization, the control system can optimize each sub-delta module(s) based on the demand and steady-state operating conditions of the other modules in the thermal circuit. In this way, overall system performance can be maximized for the best possible outcome at any system operating condition.

[0032] Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present disclosure, and all such improvements and modifications are considered to be within the scope of the concepts disclosed herein and the following claims.

Claims

1. 1. A method of controlling a heat exchanger comprising a plurality of thermoelectric coolers to provide conditioned air, the method comprising: the temperature of the receiving side of the first thermoelectric cooler; and the temperature of the heat rejection side of the first thermoelectric cooler; the temperature of the receiving side of the second thermoelectric cooler; and the temperature of the heat rejection side of the second thermoelectric cooler; and an indication of the direction of air flow within the heat exchanger; Display of relative humidity value and receiving a system measurement indicative of one or more of the group consisting of: selectively controlling two or more subsets of thermoelectric coolers among the plurality of thermoelectric coolers based on the received system measurements; The method comprising:

2. The method of claim 1 , wherein the indication of the direction of the airflow within the heat exchanger comprises one of parallel airflow and counter-current airflow.

3. 3. The method of claim 2, wherein selectively controlling two or more subsets of the thermoelectric coolers comprises being able to provide equal power by two or more subsets of the thermoelectric coolers when the indication of the direction of the airflow within the heat exchanger includes opposing airflow.

4. 3. The method of claim 2, wherein selectively controlling two or more subsets of the thermoelectric coolers comprises providing different powers to two or more subsets of the thermoelectric coolers when the indication of the direction of the air flow within the heat exchanger comprises parallel air flow.

5. The method of claim 1 , wherein the system measurements further include an indication of airflow.

6. The method of claim 1 , wherein selectively controlling two or more subsets of the thermoelectric coolers comprises attempting to optimize a system-level efficiency of the heat exchangers.

7. 10. The method of claim 1, wherein selectively controlling two or more subsets of the thermoelectric coolers comprises providing an overall temperature difference by providing a smaller temperature difference across each of the two or more subsets of thermoelectric coolers.

8. The method of claim 1 , wherein selectively controlling two or more subsets of the thermoelectric coolers comprises adjusting the relative humidity on one or more of the heat rejection side and the receiving side.

9. The method of claim 1 , wherein the heat exchanger comprises a plurality of controllers for selectively controlling two or more subsets of the thermoelectric coolers.

10. The method of claim 1 , wherein each subset of thermoelectric exchangers includes one or more different thermoelectric coolers from the plurality of thermoelectric coolers.

11. 1. A controller for controlling a heat exchanger comprising a plurality of thermoelectric coolers to provide conditioned air, the controller comprising: the temperature of the receiving side of the first thermoelectric cooler; and the temperature of the heat rejection side of the first thermoelectric cooler; the temperature of the receiving side of the second thermoelectric cooler; and the temperature of the heat rejection side of the second thermoelectric cooler; and an indication of the direction of air flow within the heat exchanger; Display of relative humidity value and receiving a system measurement indicative of one or more of the group consisting of: selectively controlling two or more subsets of thermoelectric coolers among the plurality of thermoelectric coolers based on the received system measurements; The controller may perform the following steps:

12. The controller of claim 11 , wherein the indication of the direction of the airflow within the heat exchanger includes one of parallel airflow and counter airflow.

13. 13. The controller of claim 12, wherein selectively controlling two or more subsets of the thermoelectric coolers comprises enabling two or more subsets of the thermoelectric coolers to provide equal power when the indication of the direction of the airflow within the heat exchanger comprises opposing airflow.

14. 13. The controller of claim 12, wherein selectively controlling two or more subsets of the thermoelectric coolers comprises providing different power to two or more subsets of the thermoelectric coolers when the indication of the direction of the airflow within the heat exchanger comprises parallel airflow.

15. The controller of claim 11 , wherein the system measurements further include an indication of airflow.

16. The controller of claim 11 , wherein selectively controlling two or more subsets of the thermoelectric coolers comprises attempting to optimize a system level efficiency of the heat exchangers.

17. 12. The controller of claim 11, wherein selectively controlling two or more subsets of the thermoelectric coolers comprises providing an overall temperature difference by providing a smaller temperature difference across each of the two or more subsets of thermoelectric coolers.

18. The controller of claim 11 , wherein selectively controlling two or more subsets of the thermoelectric coolers comprises adjusting the relative humidity on one or more of the heat rejection side and the receiving side.

19. The controller of claim 11 , wherein the heat exchanger comprises a plurality of controllers for selectively controlling two or more subsets of the thermoelectric coolers.

20. The controller of claim 11 , wherein each subset of thermoelectric exchangers includes one or more different thermoelectric coolers from the plurality of thermoelectric coolers.

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