HVAC SYSTEM, CONTROL METHOD FOR HVAC SYSTEM, AND COMPUTER-READABLE STORAGE MEDIUM

Description

PRIORITY CLAIM

This application claims benefit of Chinese Patent Application No. 202410338617.8, filed Mar. 22, 2024, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which in their entirety are herein incorporated by reference.

BACKGROUND

This application relates to the field of HVAC, in particular to an HVAC system, a control method for an HVAC system, and a computer-readable storage medium.

SUMMARY

This application aims to provide an HVAC system, a control method for an HVAC system, and a computer-readable storage medium, in order to at least address or alleviate some of the issues present in the prior art.

In one or more embodiments, the application provides an HVAC system, comprising a chiller/heat pump unit, an air handling unit and a controller. The chiller/heat pump unit provides working fluid. The air handling unit is provided with a heat exchanger, air is blown indoors after exchanging heat with the working fluid flowing through the heat exchanger, and the air handling unit adjusts the supply air temperature based on a temperature setpoint. The controller is configured to acquire an expected emission level of an energy source powering the HVAC system and adjust the temperature setpoint based on the expected emission level.

In one or more embodiments, the controller is configured to adjust the temperature setpoint in a manner that reduces the input power of the HVAC system when the expected emission level rises.

In one or more embodiments, when the expected emission level indicates that the energy source will become relatively dirtier, the temperature setpoint is increased for a period of time in cooling mode, and decreased for a period of time in heating mode.

In one or more embodiments, the controller is configured to adjust the temperature setpoint in a manner that increases the input power of the HVAC system when the expected emission level falls.

In one or more embodiments, when the expected emission level indicates that the energy source will become relatively cleaner, the temperature setpoint is decreased for a period of time in a cooling mode, and increased for a period of time in a heating mode.

In one or more embodiments, the magnitude of the rise/fall in the temperature setpoint exceeds the magnitude of change that is needed at the moment.

In one or more embodiments, the controller is also configured to acquire at least one parameter associated with thermal comfort, assess whether at least one parameter meets a preset constraint, and based on the assessment, decide whether to adjust the temperature setpoint based on the expected emission level.

In one or more embodiments, the application provides a control method for an HVAC system. The control method comprises the following steps: acquiring an expected emission level of an energy source powering the HVAC system; and adjusting a temperature setpoint based on the expected emission level.

In one or more embodiments, the control method further comprises: in response to the step of adjusting a temperature setpoint based on the expected emission level, adjusting a flow rate or supply temperature of working fluid.

In one or more embodiments, the air handling unit also comprises an external air inlet and a recirculated air inlet, a first damper is installed at the external air inlet, and a second damper is installed at the recirculated air inlet; and the control method further comprises the following step: in response to the step of adjusting a temperature setpoint based on the expected emission level, adjusting an opening degree of the first damper and/or the second damper.

In one or more embodiments, in the step of adjusting a temperature setpoint based on the expected emission level, the input power of the HVAC system is reduced when the expected emission level rises, and the input power of the HVAC system is increased when the expected emission level falls.

In one or more embodiments for the control method for an HVAC system, in the step of adjusting a temperature setpoint based on the expected emission level, when the expected emission level indicates that the energy source will become relatively dirtier, the temperature setpoint is increased for a period of time in cooling mode, and decreased for a period of time in heating mode; and when the expected emission level indicates that the energy source will become relatively cleaner, the temperature setpoint is decreased for a period of time in cooling mode, and increased for a period of time in heating mode.

In one or more embodiments for the control method for an HVAC system, in the step of adjusting a temperature setpoint based on the expected emission level, the magnitude of the rise/fall in the temperature setpoint exceeds the magnitude of change that is needed at the moment.

In one or more embodiments for the control method for an HVAC system, the control method further comprises: acquiring at least one parameter associated with thermal comfort, assessing whether at least one parameter meets a preset constraint, and based on the assessment, deciding whether to execute the step of adjusting a temperature setpoint based on the expected emission level.

In one or more embodiments for the control method for an HVAC system, at least one parameter comprises a difference between an actual temperature inside a building and a desired temperature inside the building; the preset constraint is that the difference is greater than the threshold; when the difference is greater than the threshold, the step of adjusting a temperature setpoint based on the expected emission level is not executed; and when the difference is less than the threshold, the step of adjusting a temperature setpoint based on the expected emission level is executed.

In one or more embodiments, the application provides a computer-readable storage medium storing a control program, wherein the control program, when executed by a processor, realizes the control method for an HVAC system in any of the above optional technical schemes.

The HVAC system, the control method for an HVAC system, and the computer-readable storage medium as described in this application enable more efficient use of electricity in HVAC systems.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of an air handling unit according to one or more embodiments of the application;

FIG. 2 illustrates a schematic diagram of the variation of MOER over time according to one or more embodiments of the application;

FIG. 3 illustrates a schematic diagram of an HVAC system operating in cooling mode according to one or more embodiments of the application;

FIG. 4 illustrates a schematic diagram of an HVAC system operating in heating mode according to one or more embodiments of the application;

FIG. 5 illustrates a schematic diagram of an HVAC system operating in cooling mode according to one or more embodiments of the application;

FIG. 6 illustrates a schematic diagram of a model predictive control system according to one or more embodiments of the application;

FIG. 7 illustrates a flowchart of a control process according to one or more embodiments of the application; and

FIG. 8 illustrates a flowchart of a control process according to one or more embodiments of the application.

Reference numerals: air handling unit 10, supply air handling unit 1, heat exchanger 12, supply fan 13, external air inlet 14, recirculated air inlet 15, first damper 16, second damper 17, temperature sensor 18, return air handling unit 2, return fan 23, outlet 24, passage 3, controller 19, model predictive control system 200.

DETAILED DESCRIPTION OF THE DISCLOSURE

First, it should be noted that the following will illustrate, by way of example, the composition, working principles, characteristics, and advantages of an HVAC system, a control method for an HVAC system, and a computer-readable storage medium according to this application. However, it should be understood that all descriptions are provided solely for illustrative purposes and should not be construed as imposing any limitations on this application.

Additionally, for any individual technical features described or implied in the embodiments mentioned herein, or any individual technical features shown or implied in the accompanying drawings, this application still allows for any combination or omission of these technical features (or their equivalents) without any technical barriers, thereby obtaining other embodiments of this application that may not be directly mentioned herein.

The main electrical energy consumption of buildings comes from HVAC systems running inside. Conventional HVAC control methods aim to reduce electricity usage by stabilizing the set temperature of the HVAC system within a specific range during working hours and turning off the HVAC system during non-working hours. However, reducing electricity consumption may not equate to the rational use of electricity.

An HVAC system according to some embodiments of the application is used in buildings and comprises a chiller/heat pump unit (not shown in the drawings) and an air handling unit 10. The chiller/heat pump unit provides working fluid, such as water or refrigerant. The air handling unit 10 is provided with a heat exchanger 12, air is blown indoors after exchanging heat with the working fluid flowing through the heat exchanger 12, and the air handling unit 10 adjusts the supply air temperature based on a temperature setpoint.

In some embodiments, as shown in FIG. 1, the air handling unit 10 comprises a supply air handling unit 1 and a return air handling unit 2, with a passage 3 positioned between the supply air handling unit 1 and the return air handling unit 2.

The supply air handling unit 1 is equipped with two heat exchangers 12 and a supply fan 13. Chilled water from the chiller unit flows through a coil of one of the heat exchangers 12, cooling the air to be treated. Hot water from the heat pump unit flows through a coil of the other heat exchanger 12, heating the air to be treated. Depending on whether the HVAC unit is operating in cooling mode or heating mode, either the chiller unit and its corresponding heat exchanger 12 or the heat pump unit and its corresponding heat exchanger 12 can be activated, while the other and its corresponding heat exchanger remain inactive. Of course, based on demand, both the chiller unit and heating unit, along with their respective heat exchangers 12, can also operate simultaneously. The return air handling unit 2 is equipped with a return fan 23. The air to be treated may be external air or a mixture of external air and recirculated air.

Return air entering the return air handling unit 2 partially exits through an outlet 24, while the other part is recirculated through the passage 3 and enters the supply air handling unit 1 via a recirculated air inlet 15. External air entering from an external air inlet 14 mixes with recirculated air entering from the recirculated air inlet 15 and passes through the heat exchanger 12 before being delivered indoors. Here, “indoors” refers to the interior of a building.

A first damper 16 is installed at the external air inlet 14, and a second damper 17 is installed at the recirculated air inlet 15. By adjusting the opening degree of the first damper 16 and the opening degree of the second damper 17, the ratio of external air to recirculated air entering the supply air handling unit 1 can be adjusted.

The supply air temperature should meet the temperature setpoint. The supply air temperature can be monitored using a temperature sensor 18.

It should be understood that the chiller/heat pump unit and the air handling unit 10 can be located either inside or outside the building.

It should be understood that the positions of the heat exchangers 12, fans, and inlets and outlets in the air handling unit 10 are not limited to the configurations shown in the figure. The specific form of the air handling unit 10 can vary widely; for example, it may be a dedicated outdoor air system (DOAS), an air handling unit 10 with variable air volume (VAV) units, or an air handling unit 10 with fan coil units (FCUs). Standalone VAV units or FCUs also fall within the scope of the air handling unit 10 described in this application.

The HVAC system in some embodiments of the application further comprises a controller 19 configured to acquire an expected emission level of an energy source powering the HVAC system and adjust the temperature setpoint based on the expected emission level.

To provide electricity, energy must be consumed, which can come from fossil fuels or renewable clean energy sources such as wind, solar, and nuclear power. Generally, when the proportion of clean energy in the energy consumed for electricity generation is high, the emission level is relatively low; conversely, when the proportion of clean energy is low, the emission level is relatively high.

The expected emission level refers to a prediction of the emission level of the energy source used to power the HVAC system over a future period. The duration of this “future period” may vary and is not specifically restricted. In some embodiments, the future period refers to the next half hour. In some embodiments, the future period may refer to the next 10 minutes.

The expected emission level can be used to guide electricity usage timing. When the expected emission level rises, it is desirable to reduce electricity consumption (or input power) appropriately; conversely, when the expected emission level falls, electricity consumption (or input power) can be increased accordingly. This approach allows for the shifting of the cooling/heating load of the HVAC system.

By adjusting the supply air temperature setpoint, the electricity consumption of the HVAC system can be modified. For instance, in cooling mode, when the temperature setpoint rises, the demand for the working fluid flow rate in the chiller unit can be reduced, or the supply temperature of the working fluid can be increased to enhance the working efficiency of the chiller unit, thereby reducing the electricity consumption of the chiller unit.

According to the HVAC system in some embodiments of the application, the supply air temperature setpoint in the air handling unit 10 can be adjusted in real time based on the expected emission level, thereby achieving the goal of reducing emissions.

For example, if the predicted time period t shows a decrease in the proportion of clean energy compared to the current situation, resulting in an increase in the expected emission level, the temperature setpoint can be adjusted to reduce the demand for the working fluid in the chiller/heat pump unit. This reduction in electricity consumption during the time period t will subsequently lower emissions. Conversely, if the predicted time period t indicates an increase in the proportion of clean energy, leading to a decrease in the expected emission level, the temperature setpoint can be adjusted to obtain more cooling/heating energy. The cooling/heating energy can be stored in building materials (e.g., the walls of the building) and released during periods when the proportion of clean energy decreases, thus utilizing the thermal inertia of the building to meet the thermal comfort needs of its occupants.

In some embodiments, the prediction of emission levels is performed by inputting the grid carbon emission index (MOER) provided by a third-party data supplier.

FIG. 2 illustrates a schematic diagram of the variation of MOER over time. It is understood that throughout the day and across different seasons, the grid will rely as much as possible on renewable or green energy (clean energy) but will also depend to some extent on fossil fuels (dirty energy). For instance, wind, nuclear, or solar energy, as renewable or green energy sources, can be used as substitutes for fossil fuels. However, the proportion of clean energy will vary depending on the availability of wind, nuclear, and solar energy. As shown in FIG. 2, emissions at point X, representing midnight, are relatively high. Emissions at point Y, representing noon the next day, are lower. Emissions at point Z rise again.

As shown by the dashed line I in FIG. 2, this curve varies based on different dates, seasons, or weather conditions. In other words, the curve does not simply exhibit periodic changes throughout different time periods of a single day.

As shown in FIG. 3, the MOER variation line 40 indicates a “dirty” peak at point 42. The temperature setpoint variation line 48 rises to point 49 to reduce the use of relatively dirty energy. As it passes through point 42, the temperature setpoint is controlled to decrease at point 50 to help restore the temperature inside the building. When the temperature setpoint is lowered, the magnitude of change in the temperature setpoint can be made to exceed the magnitude of change that is needed at the moment. When the MOER returns to its normal value at point 43, the temperature setpoint returns to the actually required level at point 51. In this way, the overall emissions of the HVAC system can be reduced. Although the reduction may not be significant, over time, even a small reduction in emissions is valuable.

It should be understood that there is thermal inertia in HVAC systems, or in buildings, so the interior of the building will not immediately become overheated even if the temperature setpoint is increased at point 49. Furthermore, the magnitude of the increase at point 49 does not need to be significant.

It should be understood that FIG. 3 illustrates a schematic diagram of an HVAC system operating in cooling mode. Meanwhile, the power variation line 44 decreases at point 46 to coincide with the peak 42.

FIG. 4 illustrates a schematic diagram of an HVAC system operating in heating mode. When the peak 42 occurs, the temperature setpoint variation line 48 drops to point 60 and then rises at point 62. When the MOER returns to its normal level at point 43, or when the temperature inside the building becomes unacceptable, the temperature setpoint increases to point 62 to quickly restore the temperature of the building. Subsequently, the temperature setpoint decreases from point 62 to the actually required level at point 63 after a period of time.

Additionally, it can be observed that the power variation line 44 decreases at point 46 to coincide with the peak 42 and increases at point 64.

FIG. 5 illustrates a possible scenario. In this scenario, the MOER variation line 40 exhibits a prolonged peak 42. The temperature setpoint variation line 48 rises at point 149 for a period of time, then decreases at point 150, and oscillates between points 149 and 150 until it returns to the actual required level at point 151. In this way, when a prolonged peak is anticipated and the temperature inside the building remains acceptable, there is no significant decline in thermal comfort.

It should be understood that FIG. 5 depicts operation in cooling mode, but the same scenario can also occur in heating mode.

FIG. 6 illustrates a schematic diagram of a model predictive control system. Output information 202 enters the controller 19 of the HVAC system. A predictor 204 receives MOER information 206. The predictor 204 also receives the output information 202 and is capable of predicting carbon emissions and indoor temperatures that will be experienced in the building. Input information 216 may be a reference temperature of the building. An optimizer 208 is provided with a cost function 210 and constraints 212. The constraints 212 may be, for example, limitations on the range and duration of temperature deviations from the desired temperature. The model predictive control system 200 also provides a building site or model 214.

Although the model predictive control system 200 is depicted as separate from the controller 19 here, it can certainly be integrated into the controller 19.

The model predictive control system 200 is capable of calculating carbon emission savings based on the method and device of this application. As an example, the predicted emissions per British Thermal Unit (BTU) of energy can be combined with the reduced BTUs during each emission reduction event to derive the carbon emission savings achieved by the method of this application. Such savings can be reported to various organizations that recognize carbon emission savings. While the basic algorithm for calculating carbon emission savings has been mentioned above, more sophisticated algorithms can also be developed.

A control method for an HVAC system in some embodiments of the application comprises the following steps: acquiring an expected emission level of an energy source powering the HVAC system; and adjusting a temperature setpoint based on the expected emission level.

FIG. 7 illustrates a flowchart of a control process in cooling mode. When the expected emission level indicates that the energy source will become relatively dirtier, the temperature setpoint is increased for a period of time; and when the expected emission level indicates that the energy source will become relatively cleaner, the temperature setpoint is decreased for a period of time.

To determine whether the expected emission level indicates that the energy source will become relatively dirtier, or relatively cleaner, one approach is to compare the current emission level with the expected emission level. Alternatively, this assessment can be made by examining whether the MOER curve contains “dirty” peaks or “clean” peaks.

Similar to the control method in cooling mode, in heating mode, when the expected emission level indicates that the energy source will become relatively dirtier, the temperature setpoint is decreased for a period of time; and when the expected emission level indicates that the energy source will become relatively cleaner, the temperature setpoint is increased for a period of time.

In some embodiments, the control method further comprises: acquiring at least one parameter associated with thermal comfort, assessing whether at least one parameter meets a preset constraint, and based on the assessment, deciding whether to execute the step of “adjusting a temperature setpoint based on the expected emission level”.

Referring to FIG. 8, when at least one parameter does not meet the preset constraint, the temperature setpoint is adjusted in an emission reduction mode, which is based on the expected emission level. Conversely, when at least one parameter meets the preset constraint, the temperature setpoint is adjusted in a normal mode, which is based on the actual temperature demand within the building.

In some embodiments, at least one parameter comprises a difference between an actual temperature inside a building and a desired temperature inside the building; the preset constraint is that the difference is greater than the threshold; when the difference is greater than the threshold, the step of “adjusting a temperature setpoint based on the expected emission level” is not executed; and when the difference is less than the threshold, the step of “adjusting a temperature setpoint based on the expected emission level” is executed.

In some embodiments, in response to the step of “adjusting a temperature setpoint based on the expected emission level”, a flow rate or supply temperature of working fluid is adjusted. Specifically, when the supply air temperature setpoint in the air handling unit 10 changes, the flow rate or temperature of the working fluid provided by the chiller/heat pump unit will also change accordingly. Since the electricity consumption of the chiller/heat pump unit is often significant, adjusting the demand for the working fluid allows for a rapid response to achieve the desired changes in electricity consumption, aligning as closely as possible with “dirty” peaks or “clean” peaks.

In some embodiments, in response to the step of “adjusting a temperature setpoint based on the expected emission level”, an opening degree of the first damper 16 and/or the second damper 17 is adjusted. By adjusting the opening degree of the first damper and/or the second damper 17, the proportion of recirculated air in the air to be treated can be increased when necessary, thereby helping to maintain thermal comfort within the building.

It should be understood that the action of “adjusting a temperature setpoint based on the expected emission level” is not limited to adjusting the temperature of the working fluid or the opening degree of the first damper 16 and/or the second damper 17. For example, it may also involve adjusting a supply fan 13 or a return fan 23, etc.

In some embodiments, in the step of “adjusting a temperature setpoint based on the expected emission level”, the input power of the HVAC system is reduced when the expected emission level rises, and the input power of the HVAC system is increased when the expected emission level falls.

In some embodiments, in the step of “adjusting a temperature setpoint based on the expected emission level”, the magnitude of the rise/fall in the temperature setpoint exceeds the magnitude of change that is needed at the moment.

A computer-readable storage medium according to one or more embodiments of the application stores a control program, and the control program, when executed by a processor, realizes the control method for an HVAC system described in some of the aforementioned embodiments.

The above are merely exemplary embodiments of the application, and are not intended to limit the application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the application should be included in the scope of protection of the application.