Hvac System, Control Method for Hvac System, and Computer-Readable Storage Medium

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.

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.

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.

Reference numerals: air handling unit, supply air handling unit, heat exchanger, supply fan, external air inlet, recirculated air inlet, first damper, second damper, temperature sensor, return air handling unit, return fan, outlet, passage, controller, model predictive control system.

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. The chiller/heat pump unit provides working fluid, such as water or refrigerant. The air handling unitis 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 unitadjusts the supply air temperature based on a temperature setpoint.

In some embodiments, as shown in, the air handling unitcomprises a supply air handling unitand a return air handling unit, with a passagepositioned between the supply air handling unitand the return air handling unit.

The supply air handling unitis equipped with two heat exchangersand a supply fan. Chilled water from the chiller unit flows through a coil of one of the heat exchangers, cooling the air to be treated. Hot water from the heat pump unit flows through a coil of the other heat exchanger, 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 exchangeror the heat pump unit and its corresponding heat exchangercan 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, can also operate simultaneously. The return air handling unitis equipped with a return fan. 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 unitpartially exits through an outlet, while the other part is recirculated through the passageand enters the supply air handling unitvia a recirculated air inlet. External air entering from an external air inletmixes with recirculated air entering from the recirculated air inletand passes through the heat exchangerbefore being delivered indoors. Here, “indoors” refers to the interior of a building.

A first damperis installed at the external air inlet, and a second damperis installed at the recirculated air inlet. By adjusting the opening degree of the first damperand the opening degree of the second damper, the ratio of external air to recirculated air entering the supply air handling unitcan be adjusted.

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

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

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

The HVAC system in some embodiments of the application further comprises a controllerconfigured 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 unitcan 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.

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, 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, 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, the MOER variation lineindicates a “dirty” peak at point. The temperature setpoint variation linerises to pointto reduce the use of relatively dirty energy. As it passes through point, the temperature setpoint is controlled to decrease at pointto 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, the temperature setpoint returns to the actually required level at point. 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. Furthermore, the magnitude of the increase at pointdoes not need to be significant.

It should be understood thatillustrates a schematic diagram of an HVAC system operating in cooling mode. Meanwhile, the power variation linedecreases at pointto coincide with the peak.

illustrates a schematic diagram of an HVAC system operating in heating mode. When the peakoccurs, the temperature setpoint variation linedrops to pointand then rises at point. When the MOER returns to its normal level at point, or when the temperature inside the building becomes unacceptable, the temperature setpoint increases to pointto quickly restore the temperature of the building. Subsequently, the temperature setpoint decreases from pointto the actually required level at pointafter a period of time.

Additionally, it can be observed that the power variation linedecreases at pointto coincide with the peakand increases at point.

illustrates a possible scenario. In this scenario, the MOER variation lineexhibits a prolonged peak. The temperature setpoint variation linerises at pointfor a period of time, then decreases at point, and oscillates between pointsanduntil it returns to the actual required level at point. 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 thatdepicts operation in cooling mode, but the same scenario can also occur in heating mode.

illustrates a schematic diagram of a model predictive control system. Output informationenters the controllerof the HVAC system. A predictorreceives MOER information. The predictoralso receives the output informationand is capable of predicting carbon emissions and indoor temperatures that will be experienced in the building. Input informationmay be a reference temperature of the building. An optimizeris provided with a cost functionand constraints. The constraintsmay be, for example, limitations on the range and duration of temperature deviations from the desired temperature. The model predictive control systemalso provides a building site or model.