Hvac System with Improved Operation of a Single-Stage Compressor During a Peak Demand Response

The application is a continuation of U.S. patent application Ser. No. 18/760,343, filed Jul. 1, 2024, published as U.S. Patent Publication No. 20240353138, and entitled “HVAC SYSTEM WITH IMPROVED OPERATION OF A SINGLE-STAGE COMPRESSOR DURING A PEAK DEMAND RESPONSE,” and a continuation of U.S. patent application Ser. No. 17/654,342, filed Mar. 10, 2022, now U.S. Pat. No. 12,078,374 issued Sep. 3, 2024, and entitled “HVAC SYSTEM WITH IMPROVED OPERATION OF A SINGLE-STAGE COMPRESSOR DURING A PEAK DEMAND RESPONSE,” which are incorporated by reference in their entirety.

This disclosure relates generally to heating, ventilation, and air conditioning (HVAC) systems. More particularly, in certain embodiments, this disclosure relates to an HVAC system with improved operation of a single-stage compressor during a peak demand response.

Heating, ventilation, and air conditioning (HVAC) systems are used to regulate environmental conditions within an enclosed space. Air is cooled via heat transfer with refrigerant flowing through the HVAC system and returned to the enclosed space as conditioned air.

In some cases, HVAC systems may be required to operate under restricted operating requirements to reduce power consumption during times of peak electricity demand and/or decreased electricity supply, referred to in this disclosure as peak demand response times or demand response times. For example, a third party such as a utility provider may enforce certain operating restrictions upon HVAC systems during peak demand response times. A peak demand response time may correspond, for example, to a time period associated with high outdoor temperatures or any other time when electrical power consumption is expected (e.g., based on a forecast or projection) to be increased. Generally, the third party (e.g., a utility provider) provides a request, referred to herein as a demand response, which specifies an upper limit on power consumption by an HVAC system during a peak demand response time.

The system of this disclosure solves problems of previous HVAC systems by facilitating improved comfort during peak demand response times by intelligently operating (e.g., turning on and off on a specially determined schedule) a single-stage compressor of an HVAC system more efficiently and effectively than was previously possible. For example, when a demand response is upcoming, a controller of the HVAC system may determine an efficient operation schedule of on and off times for the compressor that improves user comfort during a demand response time while also meeting energy saving requirements. In certain embodiments, the systems and methods described in this disclosure may be integrated into a practical application of an HVAC controller that improves system performance and occupant comfort during peak demand response times by more effectively and efficiently operating the compressor. In certain embodiments, an operation schedule is determined by predicting indoor air temperatures for different possible operation schedules and selecting the operation schedule that most improves occupant comfort while also saving energy (e.g., by meeting comfort and/or energy-saving criteria).

Certain embodiments may include none, some, or all of the above technical advantages. One or more other technical advantages may be readily apparent to one skilled in the art from the figures, descriptions, and claims included herein.

In an embodiment, an HVAC system is configured to regulate a temperature of a space. The HVAC system includes a single-stage compressor configured to compress a refrigerant used to cool air provided to the space and a controller communicatively coupled to the single-stage compressor. The controller determines that a demand response time period is starting at a start time. The demand response time period is a future period of time during which a reduction in energy consumption by the HVAC system is requested. After determining that the demand response time period is starting at the start time, an operation schedule is determined indicating alternating portions of the demand response period during which the single-stage compressor is to be turned off and turned on. At or after the start time of the demand response time period, the controller begins operating the single-stage compressor according to the determined operation schedule.

Embodiments of the present disclosure and its advantages are best understood by referring toof the drawings, like numerals being used for like and corresponding parts of the various drawings.

As described above, prior to the present disclosure, there was a lack of tools for improving comfort in a conditioned space in response to a demand response (i.e., a request for decreased HVAC energy consumption). This disclosure recognizes that temperature in a space (e.g., a home, office, or other building) that is serviced by an HVAC system with a single-stage compressor can be maintained at more comfortable levels than was formerly achieved by more efficiently and effectively staging the operations of the compressor. In this way, effective cooling is still provided during the peak demand response time, while still satisfying the energy-saving requirements of the demand response. Turning off a compressor corresponds to stopping or preventing operation of the compressor of the HVAC system, such that the HVAC system does not provide cooling to a corresponding space and such that the energy consumption of the HVAC system is negligible. Likewise, turning on a compressor corresponds to starting or allowing operation of the compressor, such that the HVAC system can provide cooling to the space. For example, when a compressor is turned on, the HVAC system may provide cooling based on a predefined setpoint temperature.

shows an example HVAC systemconfigured to operate according to a specially determined operation schedulein response to a demand response(abbreviated as “DR” in). A controllerof the HVAC systemmay determine the operation schedule, which indicates times during which the compressoris turned off and on during a demand response time, such that user comfort can be maintained while still achieving the decrease in energy consumption indicated by the demand response. A demand responsegenerally indicates an upper limit on power consumption by the HVAC systemduring a future period of time (e.g., demand response timeof).

The HVAC systemconditions air for delivery to a conditioned space (e.g., all or a portion of a room, a house, an office building, a warehouse, or the like). In some embodiments, the HVAC systemis a rooftop unit (RTU) that is positioned on the roof of a building and the conditioned air is delivered to the interior of the building. In other embodiments, portion(s) of the systemmay be located within the building and portion(s) outside the building. The HVAC systemmay include one or more heating elements, not shown for convenience and clarity. The HVAC systemmay be configured as shown inor in any other suitable configuration. For example, the HVAC systemmay include additional components or may omit one or more components shown in.

The HVAC systemincludes a working-fluid conduit subsystem, at least one condensing unit, an expansion valve, an evaporator, a blower, and one or more thermostats. The working-fluid conduit subsystemfacilitates the movement of a working fluid (e.g., a refrigerant) through a cooling cycle such that the working fluid flows as illustrated by the dashed arrows in. The working fluid may be any acceptable working fluid including, but not limited to hydroflurocarbons (e.g. R-A) or any other suitable type of refrigerant.

The condensing unitincludes a single-stage compressor, a condenser, and a fan. In some embodiments, the condensing unitis an outdoor unit while other components of systemmay be located indoors. The compressoris coupled to the working-fluid conduit subsystemand compresses (i.e., increases the pressure of) the working fluid. The compressoris in signal communication with the controllerusing wired and/or wireless connection. The controllerprovides commands and/or signals to control operation of the compressorand/or receive signals from the compressorcorresponding to a status of the compressor. For example, the controllermay provide signals to turn the compressoron or off based on the operation schedule, which indicates when the single-stage compressorturns on and off during a demand response time.

The condenseris configured to facilitate movement of the working fluid through the working-fluid conduit subsystem. The condenseris generally located downstream of the compressorand is configured to remove heat from the working fluid. The fanis configured to move airacross the condenser. For example, the fanmay be configured to blow outside air through the condenserto help cool the working fluid flowing therethrough. The fanmay be in communication with the controller(e.g., via wired and/or wireless communication) to receive control signals for turning the fanon and off and/or adjusting a speed of the fan. The compressed, cooled working fluid flows from the condensertoward the expansion valve. The fanmay be turned on and off along with the compressorbased on the operation schedule.

The expansion valveis coupled to the working-fluid conduit subsystemdownstream of the condenserand is configured to remove pressure from the working fluid. In this way, the working fluid is delivered to the evaporator. In general, the expansion valvemay be a valve such as an expansion valve or a flow control valve (e.g., a thermostatic expansion valve (TXV)) or any other suitable valve for removing pressure from the working fluid while, optionally, providing control of the rate of flow of the working fluid. The expansion valvemay be in communication with the controller(e.g., via wired and/or wireless communication) to receive control signals for opening and/or closing associated valves and/or to provide flow measurement signals corresponding to the rate of working fluid flow through the working-fluid conduit subsystem.

The evaporatoris generally any heat exchanger configured to provide heat transfer between air flowing through (or across) the evaporator(i.e., airflowcontacting an outer surface of one or more coils of the evaporator) and working fluid passing through the interior of the evaporator. The evaporatormay include one or more circuits of coils. The evaporatoris fluidically connected to the compressor, such that working fluid generally flows from the evaporatorto the condensing unitwhen the HVAC systemis operating to provide cooling.

A portion of the HVAC systemis configured to move airflowprovided by the bloweracross the evaporatorand out of the duct sub-systemas conditioned airflow. Return air, which may be air returning from the building, fresh air from outside, or some combination, is pulled into a return duct. A suction side of the blowerpulls the return air. The blowerdischarges airflowinto a ductsuch that airflowcrosses the evaporatoror heating elements (not shown) to produce conditioned airflow. The bloweris any mechanism for providing airflowthrough the HVAC system. For example, the blowermay be a constant-speed or variable-speed circulation blower or fan. Examples of a variable-speed blower include, but are not limited to, belt-drive blowers controlled by inverters, direct-drive blowers with electronic commuted motors (ECM), or any other suitable type of blower.

The HVAC systemincludes one or more sensors,in signal communication with the controller(e.g., via wired and/or wireless connection). Sensoris positioned and configured to measure an indoor air temperature. Sensoris positioned and configured to measure an occupancyof the space serviced by the HVAC system. For example, an occupancy sensormay be a motion sensor or the like. In some cases, occupancymay be determined using known positions of occupants of the space. For example, geofencing may be used to determine occupancy based on the locations of mobile devices operated by occupants of the space. The HVAC systemmay include one or more further sensors (not shown for conciseness), such as sensors for measuring air humidity and/or any other properties of a conditioned space (e.g. a room of the conditioned space). Sensors,and/or any other sensors may be positioned anywhere within the conditioned space, the HVAC system, and/or the surrounding environment.

The thermostatmay be located within the conditioned space (e.g. a room or building) serviced by the HVAC system. The controllermay be separate from or integrated within the thermostat. The thermostatis configured to allow a user to input a desired temperature or temperature setpointfor the conditioned space. In some embodiments, the thermostatincludes a user interface and display for displaying information related to the operation and/or status of the HVAC system. For example, the user interface may display operational, diagnostic, and/or status messages and provide a visual interface that allows at least one of an installer, a user, a support entity, and a service provider to perform actions with respect to the HVAC system. For example, the user interface may provide for display of messages related to the status and/or operation of the HVAC system(e.g., whether the HVAC systemis being operated for a demand responseaccording to an operation scheduledetermined by the controller). The thermostatmay further be configured to monitor a historical power consumption of the HVAC system, which may be used to generate the home model, as described further below.

The thermostat(and/or controller) may be in communication with a utility provider or other third party tasked with overseeing and/or regulating energy consumption by the HVAC systems. For example, a utility provider or third party may be a company or organization that distributes energy to homes and businesses. In situations in which energy demand is anticipated to exceed supply, a demand responsemay be transmitted to HVAC system. As described above, the demand responseindicates a prescribed reduction in energy consumption (e.g., a percent reduction in energy consumption from a baseline or average value) or a maximum energy consumption (e.g., a maximum permitted energy consumption per time) during the future period of time during which a decrease in energy consumption is needed.

The controlleris communicatively coupled (e.g., via wired and/or wireless connection) to components of the HVAC systemand configured to control their operation. The controllergenerally determines that a demand responsehas been received and that a time period (e.g., time periodof) is upcoming during which a reduction in energy consumption by the HVAC systemis requested. The controllerthen determines an operation scheduleindicating alternating portions of the demand response period during which the single-stage compressoris to be turned off and turned on. The operation scheduleindicates the distribution of on and off times of single-stage compressorover the time interval of the demand response. For example, the operation schedulemay indicate period of times during the demand response time during which the compressoris on or off (see, e.g., alternating on times-and off times-during time periodof). In some cases, the operation schedulemay indicate an alternative energy-saving setpoint at which to operate the HVAC system(e.g., comfort setpointof). For example, if the HVAC systemis cooling an occupied space, the setpointmay be “setback” to a higher temperature for cooling mode operation.

In some embodiments, the controllerdetermines the operation scheduleusing a home model. The home modelgenerally allows predicted indoor temperature(s)and/or predicted occupancyto be determined for the space serviced by HVAC systemfor different possible operation scenarios. For instance, the home modelmay allow different operation scenariosto be proactively tested and refined to further improve occupant comfort via determination of predicted indoor temperature(s)and/or predicted occupancy. The operation scenariosare different on and off timings/schedules for the single-stage compressor. A predicted indoor temperaturemay be determined (e.g., as a temperature over time, as shown for temperatureof) for each operation scenario.

The home modelmay also account for a temperature forecast, the current indoor temperature, and/or an occupancyof the space serviced by the HVAC system. For example, the home modelmay be used to determine predicted indoor air temperatureas a function of one or more of outdoor air temperature (e.g., using a temperature forecast), compressor on/off status (e.g., from the operation scenario), occupancy (e.g., using a measured occupancyand/or predicted occupancy), and a length of the demand response time period. The operation scheduleis the operation scenariowith the best performance (e.g., the operation scenariofor which the predicted indoor air temperatureis less than a threshold comfort value (e.g., temperature difference thresholdof). In some cases, the operation scheduleis determined as the operation scenariowith a predicted indoor air temperaturethat is less than the threshold comfort value (e.g., temperature difference thresholdof) and with an energy consumption that is less than a predefined energy consumption (e.g., energy consumption thresholdof).

The home modelmay be determined, for example, based at least in part on historical power consumption of the HVAC systemand historical indoor temperatures achieved by the HVAC system. For example, historical information about power consumption by the HVAC systemmay be used to generate the home modeland subsequently determines predicted indoor temperaturesfor a given operation scenario. The home modelmay provide predicted indoor temperatureand/or predicted occupancyas a function of run time (e.g., as indicated in operation schedule). One or more rounds of iteration may be used to test and/or adjust the operation scenariosto determine the operation schedulethat maintains the predicted indoor temperature(s)in a target range (see, e.g., the maintenance of temperaturebelow the comfort temperature value/setpointusing operation scheduleand thresholds,of). Examples of home modelsand their development are described in U.S. Pat. No. 10,612,804, entitled “Operating an HVAC system to reach target temperature efficiently”; U.S. Pat. No. 10,612,808, entitled “Operating an HVAC system based on predicted indoor air temperature”; U.S. Pat. No. 10,830,474, entitled “Systems and methods of predicting energy usage”; and U.S. Pat. No. 11,067,305, entitled “Method and system for heating auto-setback”, each of which is incorporated herein in its entirety.

Once the operation scheduleis determined, controllercauses the compressorto operate according to the operation schedule. For example, the controllermay send signals at the start time of the demand response causing the compressorto turn on and off according to the operation schedule. During the demand response time, the controllermay override operation according to the temperature setpoint, such that the HVAC systemis not operated according to the temperature setpointduring at least a portion of the demand response time period. Instead, the controllermay give preference to turning on and off the compressoraccording to the operation schedule

In some cases, the controller, while operating the compressoraccording to the operation schedule, may determine that the indoor air temperaturebecomes greater than a predefined maximum temperature (e.g., the comfort temperature setpointof) and increase cooling to bring the indoor air temperaturebelow this level. For example, after determining that the indoor air temperatureis greater than the predefined maximum temperature, the controllermay cause the single-stage compressorto turn on at least until the indoor air temperaturebecomes less than the predefined maximum temperature. In this way, the demand responsemay be briefly paused to ensure that the space remains comfortable for occupants.

In some embodiments, the operation schedulemay be adjusted based at least in part on occupancyof the space cooled by the HVAC systemand or a predicted occupancydetermined by the home model. Occupancies,may be “occupied” if one or more people are in the space (or predicted to be in the space) or “unoccupied” if no one is in the space (or no one is predicted to be in the space). An occupancy sensormay be used to determine the occupancy. Historical values of the occupancymay be used by the home modelto determine the predicted occupancy, which may indicate that a space is likely to be occupied during certain portions of the day and unoccupied during other portions of the day. If the space serviced by the HVAC systembecomes unoccupied during the demand response time or is predicted to be unoccupied during the demand response time, the operation schedulemay be adjusted to cause compressorto shut off at least when the serviced space is unoccupied.

The controllerincludes a processor, memory, and input/output (I/O) interface. The processorcomprises one or more processors operably coupled to the memory. The processoris any electronic circuitry including, but not limited to, state machines, one or more central processing unit (CPU) chips, logic units, cores (e.g. a multi-core processor), field-programmable gate array (FPGAs), application specific integrated circuits (ASICs), or digital signal processors (DSPs) that communicatively couples to memoryand controls the operation of HVAC system. The processormay be a programmable logic device, a microcontroller, a microprocessor, or any suitable combination of the preceding. The processoris communicatively coupled to and in signal communication with the memory. The one or more processors are configured to process data and may be implemented in hardware or software. For example, the processormay be 8-bit, 16-bit, 32-bit, 64-bit or of any other suitable architecture. The processormay include an arithmetic logic unit (ALU) for performing arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that fetches instructions from memoryand executes them by directing the coordinated operations of the ALU, registers, and other components. The processor may include other hardware and software that operates to process information, control the HVAC system, and perform any of the functions described herein (e.g., with respect to). The processoris not limited to a single processing device and may encompass multiple processing devices.

The memorycomprises one or more disks, tape drives, or solid-state drives, and may be used as an over-flow data storage device, to store programs when such programs are selected for execution, and to store instructions and data that are read during program execution. The memorymay be volatile or non-volatile and may comprise ROM, RAM, ternary content-addressable memory (TCAM), dynamic random-access memory (DRAM), and static random-access memory (SRAM). The memoryis operable to store any suitable set of instructions, logic, rules, and/or code for executing the functions described in this disclosure with respect to. The memorymay store the temperature forecast, operation scenarios, indoor temperatures, occupancies, the home model, predicted indoor temperatures, predicted occupancies, and operation schedules.

The I/O interfaceis configured to communicate data and signals with other devices. For example, the I/O interfacemay be configured to communicate electrical signals with the other components of the HVAC systems. The I/O interfacemay send signals that cause the operation scheduleto be implemented by the compressor. The I/O interfacemay use any suitable type communication protocol. The I/O interfacemay comprise ports and/or terminals for establishing signal communications between the controllerand other devices. The I/O interfacemay be configured to enable wired and/or wireless communications.

Connections between various components of the HVAC systemand between components of systemmay be wired or wireless. For example, conventional cable and contacts may be used to couple the thermostatto the controllerand various components of the HVAC system, including, the compressor, the expansion valve, the blower, and/or sensor(s),. In some embodiments, a wireless connection is employed to provide at least some of the connections between components of the HVAC system. In some embodiments, a data bus couples various components of the HVAC systemtogether such that data is communicated there between. In a typical embodiment, the data bus may include, for example, any combination of hardware, software embedded in a computer readable medium, or encoded logic incorporated in hardware or otherwise stored (e.g., firmware) to couple components of HVAC systemto each other.

As an example and not by way of limitation, the data bus may include an Accelerated Graphics Port (AGP) or other graphics bus, a Controller Area Network (CAN) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT) interconnect, an INFINIBAND interconnect, a low-pin-count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a serial advanced technology attachment (SATA) bus, a Video Electronics Standards Association local (VLB) bus, or any other suitable bus or a combination of two or more of these. In various embodiments, the data bus may include any number, type, or configuration of data buses, where appropriate. In certain embodiments, one or more data buses (which may each include an address bus and a data bus) may couple the controllerto other components of the HVAC system.

In an example operation of the system, the compressorof the HVAC systemis initially turned on and allowed to facilitate cooling of the space based on the temperature setpoint. A demand responseis then received indicating that a decrease in energy consumption is needed during an upcoming period of time. An operation scheduleis then determined for turning the compressoron and off during the demand response time of the demand response, and the compressoris operated according to the operation schedule.

shows a plotillustrating an example temperaturethat may be achieved during a demand responseusing the improved operation schedulecompared to a temperatureachieved using a conventional approach. The example operation scheduledesignates alternating off times-and on times-for the compressorduring the time periodof the demand response.

In the conventional approach, an increased comfort setpointis used during time period, such that the temperatureincreases from the initial setpointuntil it exceeds the comfort setpointand the compressorneeds to turn on for a relatively long period of time to bring the temperature back below the comfort setpoint. In the example of, temperaturenever reaches the comfortable range below comfort setpointduring the demand response time, such that the space is uncomfortably warm during the majority of the demand response time.

In the new approach of this disclosure using the operation schedule, the temperatureincreases a relatively small amount during each off time-and decreases during each on time-when cooling is provided to the space. In this way, temperatureis maintained in a more comfortable range while still satisfying energy consumption requirements of the demand response.

is a plotillustrating how the temperature differencebetween the indoor temperatureand the original setpointvaries with the on time of the compressorduring each fifteen-minute period of the demand response timeof. As the on time increases (from zero minutes per fifteen-minute interval to eleven minutes per fifteen-minute interval), the temperature differencedecreases. A decreased temperature differencecorresponds to improved comfort in the space serviced by the HVAC system. At on times of four minutes and greater, the temperature differenceis less than a comfort threshold valuecorresponding to adequate comfort in the space.

Plotofalso shows the percentage power usageof the HVAC systemat different on times. A percentage power usageof 100% corresponds to the scenario in which the compressoris turned on for the entire fifteen-minute interval. The percentage power usageincreases with the length of the on time. At on times of seven minutes and less, the percentage power usageis less than a threshold valuecorresponding to a maximum power usage allowed for the demand response. Accordingly, on times of four minutes and seven minutes both satisfy the energy-saving requirements of the demand response(i.e., by keeping percentage power usagebelow threshold) and maintain comfort in the space (e.g., by maintaining the temperature differencebelow threshold). As such, an operation schedulemay be determined based on the plotin which the on times-are between about four minutes and seven minutes of each fifteen-minute interval of the demand response time.

is a flowchart of an example methodof operating the system of. Steps of methodmay be implemented using the processor, memory, and I/O interfaceof the controller. In some cases, one or more steps may be performed by other components of the system(e.g., by the thermostat). Methodmay begin at stepwhere it is determined whether the start time of a demand responseis upcoming. If a demand response time (e.g., timeof) is upcoming, the controllerproceeds to step. Otherwise, the controllerwaits until a demand responseis received indicating an upcoming demand response time.

At step, the controllerreceives temperature forecast. The temperature forecastmay include predicted future outdoor air temperatures for the location in which the HVAC systemis operated. The temperature forecastmay be obtained from a weather forecast for the location of the HVAC system.

At step, the controllerdetermines predicted indoor air temperature and/or predicted occupancy for one or more operation scenarios. For example, the home modelofmay be used to determine values of the predicted indoor air temperatureover time for the predicted outdoor air temperatures indicated by the temperature forecastwhen the compressoris turned on and off according to the operation scenarios.

At step, the controllerdetermines the operation schedulebased on information from step. For example, the determined operation schedulemay be the operation scenariofor which the predicted indoor air temperatureis less than a comfort threshold value and the energy consumption is less than a predefined energy consumption threshold. For instance, referring to the example of, the determined operation schedulemay have an on time that satisfies both temperature difference thresholdand energy consumption threshold.

At step, the controlleroperates the compressoraccording to the operation schedulefrom step. The controllercauses the compressorto turn off and on during the different periods of time determined at step.

Modifications, additions, or omissions may be made to methoddepicted in. Methodmay include more, fewer, or other steps. For example, steps may be performed in parallel or in any suitable order. While at times discussed as the controllerperforming the steps, any suitable components (e.g., thermostat) of the systemmay perform one or more steps of the method.

While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, 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 items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate 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 spirit and scope disclosed herein.

To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants note that they do not intend any of the appended claims to invoke 35 U.S.C. § 112 (f) as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.