A method for regulating the supply water temperature of a centrifugal chiller in a distributed energy system

Abstract

The present invention discloses a method for regulating the water supply temperature of a centrifugal chiller in a distributed energy system. The distributed energy system includes an internal combustion engine, a lithium bromide chiller, and a centrifugal chiller. The distributed energy system is a primary constant flow system. The water supply temperature regulation method includes the following steps: determining whether the lithium bromide chiller can meet the user's cooling load demand by utilizing the internal combustion engine's waste heat. If not, starting the centrifugal chiller; calculating the maximum cooling capacity that a single lithium bromide chiller can generate when using the internal combustion engine's waste heat as input heat; determining the expected energy supply ratio of a single centrifugal chiller; determining the cold water supply set temperature of a single centrifugal chiller; and operating the centrifugal chiller according to the cold water supply set temperature of the single centrifugal chiller. The present invention enables the system to not deviate from the established operating strategy, improves the waste heat utilization rate and primary energy utilization rate, and reduces system energy consumption and carbon emissions.

Description

Technical Field

[0001] The present invention belongs to the field of energy technology, and more specifically, relates to a method for regulating the water supply temperature of a centrifugal chiller in a distributed energy system. Background Art

[0002] Distributed energy systems can integrate different local energy sources to simultaneously provide electricity, heat, cooling, and domestic hot water to surrounding users. This system primarily relies on internal combustion engines to meet user electricity loads, while lithium bromide units utilize the engine's waste heat for cooling. For areas with larger cooling loads, centrifugal chillers are typically deployed to meet additional cooling and heating demands. When these loads are high, lithium bromide units and centrifugal chillers operate together to meet user cooling and heating needs. Therefore, appropriate system operation strategies are required to ensure the orderly and efficient operation of the system. Determining heat by electricity and electricity by heat are common operational strategies. Internal combustion engines operate according to specified rules, guiding the operation of distributed energy systems.

[0003] However, in actual operation, distributed energy systems often deviate from established operating strategies, leading to problems such as decreased primary energy utilization and poor economic efficiency. Especially for a fixed-flow system, the cooling capacity of each unit is constrained by the water system, and the cooling capacity of each unit is directly related to the unit flow and the supply and return water temperature difference. When the lithium bromide unit cannot meet the user's cooling load, the centrifugal chiller is turned on to meet the shortfall. However, since the units are all operating at partial load after the addition of the unit, the system return water temperature drops, causing the lithium bromide unit to also reduce from full load to partial load operation, deviating from the established operating strategy and failing to fully utilize the waste heat. Summary of the Invention

[0004] To address the above-mentioned deficiencies or improvements in the prior art, the present invention provides a method for regulating the water supply temperature of a centrifugal chiller in a distributed energy system. The method aims to set the chilled water supply temperature of the centrifugal chiller based on the number of lithium bromide chillers and centrifugal chillers in operation, their rated flow rates, return water temperatures, and the chilled water supply temperature of the lithium bromide chiller, when both are in operation. This method ensures that the system does not deviate from its established operating strategy, improves waste heat utilization and primary energy utilization, and reduces system energy consumption and carbon emissions.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for regulating the water supply temperature of a centrifugal chiller in a distributed energy system is provided, wherein the distributed energy system includes an internal combustion engine, a lithium bromide chiller, and a centrifugal chiller, and the distributed energy system is a primary constant flow system;

[0006] The water supply temperature adjustment method comprises the following steps:

[0007] (S1) determining whether the lithium bromide chiller can meet the user's cooling load demand by utilizing the waste heat of the internal combustion engine; if not, starting the centrifugal chiller and proceeding to step (S2);

[0008] (S2) calculating the maximum cooling capacity that can be generated by a single lithium bromide chiller when the waste heat of the internal combustion engine is used as the heat input based on the relationship between the heat input and the operating efficiency;

[0009] (S3) obtaining the user's cooling load, the number of lithium bromide chillers and centrifugal chillers in operation, and determining the expected energy supply ratio of a single centrifugal chiller when each lithium bromide chiller is operated to generate the maximum cooling capacity;

[0010] (S4) obtaining the rated flow of the lithium bromide chiller, the rated flow of the centrifugal chiller, the return water temperature, and the chilled water supply set temperature of the lithium bromide chiller, and determining the chilled water supply set temperature of the single centrifugal chiller based on the expected energy supply ratio of the single centrifugal chiller and the relationship between the load distribution and the return water temperature and the supply water temperature;

[0011] (S5) operating the centrifugal chiller according to the chilled water supply set temperature of the single centrifugal chiller.

[0012] Preferably, the maximum cooling capacity Q in step (S2) AC.MAX Calculated by the following formula:

[0013] Q AC.MAX =Q smoke.input ×eff smoke +Q water.input ×eff water (2)

[0014] Among them, Q smoke.input The available waste heat of the internal combustion engine flue gas; Q water.input The available waste heat of the cylinder jacket water of the internal combustion engine; eff smoke and eff water They are the flue gas cooling efficiency and hot water cooling efficiency of the lithium bromide unit respectively.

[0015] Preferably, the expected energy supply ratio Fac of a single centrifugal chiller in step (S3) is EC Calculated by the following formula:

[0016]

[0017] Among them, Q user Q is the user's cooling load; AC.MAX is the maximum cooling capacity of the lithium bromide unit, num EC is the number of centrifugal chillers in operation, numAC The number of centrifugal chillers and lithium bromide units in operation.

[0018] Preferably, the cold water supply setting temperature T of a single centrifugal chiller in step (S4) is EC.supply Calculated by the following formula:

[0019]

[0020] Among them, T return is the return water temperature of the centrifugal chiller and lithium bromide chiller, F AC is the rated flow of the lithium bromide unit, F EC is the rated flow of the centrifugal chiller, T AC.supply Set the temperature of the cold water supply to the lithium bromide unit, num EC is the number of centrifugal chillers in operation, num AC is the number of centrifugal chillers and lithium bromide chillers in operation, Fac EC is the expected energy supply ratio of a single centrifugal chiller.

[0021] Preferably, the water supply temperature adjustment method also includes: when the internal combustion engine of the distributed energy system is not running but there is a cooling load, only the centrifugal refrigeration unit is turned on to meet the system cooling load, and the set temperature of the centrifugal refrigeration unit when it is running is the conventional water supply set temperature, and the conventional water supply set temperature is 5-7°C.

[0022] Preferably, the step (S1) further includes: determining whether the lithium bromide chiller can meet the user's cooling load demand by utilizing the waste heat of the internal combustion engine. If so, the lithium bromide chiller operates alone according to the conventional water supply set temperature, which is 5-7°C.

[0023] Preferably, the internal combustion engine is connected to the lithium bromide chiller, the lithium bromide chiller and the centrifugal chiller are connected in parallel, and both the lithium bromide chiller and the centrifugal chiller are connected to the user side.

[0024] In general, the above technical solutions conceived by the present invention can achieve at least the following beneficial effects compared with the prior art.

[0025] (1) For a single constant flow system, the load ratio of the lithium bromide chiller and the centrifugal chiller depends on their flow rates and the set water supply temperature. If the loads borne by each unit cannot be reasonably distributed, and each unit distributes the cooling load according to its rated flow rate ratio, the lithium bromide chiller cannot operate according to the available waste heat, and the waste heat is not fully utilized, resulting in problems such as reduced system operating efficiency and increased carbon emissions. To solve this problem, the present invention proposes a distributed energy centrifugal chiller water supply temperature adjustment method. When the lithium bromide chiller and the centrifugal chiller are operated simultaneously, the cold water supply set temperature of the centrifugal chiller is adjusted according to the number of lithium bromide chillers and centrifugal chillers that are turned on, the rated flow rate, the return water temperature, and the cold water supply set temperature of the lithium bromide chiller. This method changes the water supply set temperature of the centrifugal chiller and the proportion of cooling and heating loads borne by each unit in the constant flow system, thereby ensuring that the lithium bromide unit fully utilizes the waste heat generated by the internal combustion engine, reducing system energy consumption, improving system energy utilization efficiency, and reducing carbon emissions.

[0026] (2) The present invention can provide a reference for improving the primary energy utilization rate of the distributed energy system throughout the year and reducing the system energy consumption and carbon emissions, which is conducive to enhancing the energy-saving and carbon-reduction effects of the distributed energy system and providing a theoretical basis for the further utilization of the distributed energy system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural diagram of the distributed energy system in the present invention;

[0028] Figure 2 This is a flow chart of a method for regulating the water supply temperature of a centrifugal chiller in a distributed energy system provided by the present invention;

[0029] In all drawings, the same reference numerals are used to denote the same equipment or structure, where: 1 - internal combustion engine, 2 - power grid, 3 - lithium bromide chiller, 4 - centrifugal chiller, 5 - controller, 6 - user. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0031] The distributed energy system in the present invention, such as Figure 1 As shown, the system includes:

[0032] The internal combustion engine 1 is electrically connected to the centrifugal chiller 4 and the user 6, and is used to drive the centrifugal chiller 4 and meet the electrical load of the user 6. It is also connected to the lithium bromide unit 3 to provide waste heat for the lithium bromide unit.

[0033] The power grid 2 is electrically connected to the centrifugal chiller 4 and the user 6, and is used to drive the centrifugal chiller 4 and meet the electrical load of the user 6;

[0034] The lithium bromide chiller 3 is connected to the internal combustion engine 1 and is used to absorb the waste heat generated by the internal combustion engine 1, including high-temperature flue gas and jacket water. It is also connected to the user 6 to provide cooling load to the user 6.

[0035] A centrifugal chiller 4 is connected to a user 6 and is used to provide cooling load to the user 6;

[0036] The controller 5 is connected to the internal combustion engine 1, the lithium bromide chiller 3, and the centrifugal chiller 4, and is used to calculate the water supply temperature setting value of the centrifugal chiller according to the received operating status of the chiller.

[0037] The power supply demand of the user 6 and the centrifugal chiller is first met by the internal combustion engine 1 , and the insufficient part is provided by the power grid 2 .

[0038] The lithium bromide chiller 3 is connected to the internal combustion engine 1 and can absorb the waste heat generated by the internal combustion engine 1 for cooling. The set water supply temperature of the chiller is set according to the rated working conditions, usually 5-7°C.

[0039] The lithium bromide chiller 3 and the centrifugal chiller 4 are both connected to the user 6 through water pipes and provide cold water to the user 6 to provide cold and hot loads. The cold water is heated by the user and then returns to the lithium bromide chiller 3 and the centrifugal chiller 4.

[0040] That is, the internal combustion engine is connected to the lithium bromide chiller, the lithium bromide chiller and the centrifugal chiller are connected in parallel, and both the lithium bromide chiller and the centrifugal chiller are connected to the user side.

[0041] The centrifugal chiller 4 is used to meet the cooling load of some users that cannot be met by the lithium bromide chiller 3. The water supply temperature adjustment method of the centrifugal chiller in the distributed energy system provided by the present invention is as follows: Figure 2 As shown, the following steps are included; wherein, the distributed energy system includes an internal combustion engine, a lithium bromide chiller and a centrifugal chiller, and the distributed energy system is a primary constant flow system;

[0042] The water supply temperature adjustment method comprises the following steps:

[0043] (S1) When the system is running, it is first determined whether the internal combustion engine is running. If not, only the centrifugal chiller is turned on when there is a cooling load. The set temperature of the centrifugal chiller during operation is the normal water supply set temperature, which is 5-7°C. If so, the set temperature of the lithium bromide chiller is set according to the rated operating conditions, typically 5-7°C, which uses the waste heat of the internal combustion engine for cooling.

[0044] Then determine whether the lithium bromide chiller can meet the user's cooling load demand by utilizing the waste heat of the internal combustion engine. If so, the lithium bromide chiller is operated alone according to the conventional water supply set temperature, which is 5-7°C. If not, start the centrifugal chiller and enter step (S2).

[0045] (S2) Calculating the maximum cooling capacity that can be generated by a single lithium bromide chiller when the waste heat of the internal combustion engine is used as the input heat based on the relationship between the input heat and the operating efficiency.

[0046] The maximum cooling capacity Q AC.MAX Calculated by the following formula:

[0047] Q AC.MAX =Q smoke.input ×eff smoke +Q water.input ×eff water (2)

[0048] Among them, Q smoke.input The available waste heat of the internal combustion engine flue gas; Q water.input The available waste heat of the cylinder jacket water of the internal combustion engine; eff smoke and eff water They are the flue gas cooling efficiency and hot water cooling efficiency of the lithium bromide unit respectively.

[0049] (S3) Obtaining the user's cooling load, the number of lithium bromide chillers and centrifugal chillers in operation, and determining the expected energy supply ratio of a single centrifugal chiller when each lithium bromide chiller is operated to generate the maximum cooling capacity.

[0050] Expected energy supply ratio of a single centrifugal chiller Fac EC Calculated by the following formula:

[0051]

[0052] Among them, Q user Q is the user's cooling load; AC.MAX is the maximum cooling capacity of the lithium bromide unit, num EC is the number of centrifugal chillers in operation, num AC The number of centrifugal chillers and lithium bromide units in operation.

[0053] (S4) Obtain the rated flow of the lithium bromide chiller, the rated flow of the centrifugal chiller, the return water temperature, and the cold water supply set temperature of the lithium bromide chiller, and determine the cold water supply set temperature of the single centrifugal chiller based on the expected energy supply ratio of the single centrifugal chiller and the relationship between the load distribution and the return water temperature and the supply water temperature.

[0054] The cold water supply setting temperature T of a single centrifugal chiller EC.supply Calculated by the following formula:

[0055]

[0056] Among them, T return is the return water temperature of the centrifugal chiller and lithium bromide chiller, F AC is the rated flow of the lithium bromide unit, F EC is the rated flow of the centrifugal chiller, T AC.supply Set the temperature of the cold water supply to the lithium bromide unit, num EC is the number of centrifugal chillers in operation, num AC is the number of centrifugal chillers and lithium bromide chillers in operation, Fac EC is the expected energy supply ratio of a single centrifugal chiller.

[0057] (S5) operating the centrifugal chiller according to the chilled water supply set temperature of the single centrifugal chiller.

[0058] Therefore, compared with the prior art, the present invention can adjust the cold water supply set temperature of the centrifugal chiller according to the number of lithium bromide chillers and centrifugal chillers in operation at the same time, the rated flow rate, the return water temperature and the cold water supply set temperature of the lithium bromide chiller, so that the lithium bromide chiller and the centrifugal chiller reach the set operating state of each unit, so that the system does not deviate from the established operating strategy, improve the system waste heat utilization rate and primary energy utilization rate, reduce the system energy consumption and carbon emissions, and provide a reference for operation control in distributed energy systems.

[0059] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for regulating the water supply temperature of a centrifugal chiller in a distributed energy system, characterized in that: The distributed energy system includes an internal combustion engine, a lithium bromide chiller and a centrifugal chiller, and the distributed energy system is a primary constant flow system; The water supply temperature adjustment method comprises the following steps: (S1) determining whether the lithium bromide chiller can meet the user's cooling load demand by utilizing the waste heat of the internal combustion engine; if not, starting the centrifugal chiller and proceeding to step (S2); (S2) calculating the maximum cooling capacity that can be generated by a single lithium bromide chiller when the waste heat of the internal combustion engine is used as the heat input based on the relationship between the heat input and the operating efficiency; (S3) obtaining the user's cooling load, the number of lithium bromide chillers and centrifugal chillers in operation, and determining the expected energy supply ratio of a single centrifugal chiller when each lithium bromide chiller is operated to generate the maximum cooling capacity; (S4) obtaining the rated flow of the lithium bromide chiller, the rated flow of the centrifugal chiller, the return water temperature, and the chilled water supply set temperature of the lithium bromide chiller, and determining the chilled water supply set temperature of the single centrifugal chiller based on the expected energy supply ratio of the single centrifugal chiller and the relationship between the load distribution and the return water temperature and the supply water temperature; (S5) operating the centrifugal chiller according to the chilled water supply set temperature of the single centrifugal chiller.

2. The water supply temperature adjustment method according to claim 1, characterized in that: The maximum cooling capacity Q in step (S2) AC.MAX Calculated by the following formula: Q AC.MAX =Q smoke.input ×eff smoke +Q water.input ×eff water (2) Among them, Q smoke.input The available waste heat of the internal combustion engine flue gas; Q water.input The available waste heat of the cylinder jacket water of the internal combustion engine; eff smoke and eff water They are the flue gas cooling efficiency and hot water cooling efficiency of the lithium bromide unit respectively.

3. The water supply temperature adjustment method according to claim 1, characterized in that: The expected energy supply ratio Fac of a single centrifugal chiller in step (S3) EC Calculated by the following formula: Among them, Q user Q is the user's cooling load; AC.MAX is the maximum cooling capacity of the lithium bromide unit, num EC is the number of centrifugal chillers in operation, num AC The number of centrifugal chillers and lithium bromide units in operation.

4. The water supply temperature adjustment method according to any one of claims 1 to 3, characterized in that: The cold water supply setting temperature T of a single centrifugal chiller in step (S4) EC.supply Calculated by the following formula: Among them, T return is the return water temperature of the centrifugal chiller and lithium bromide chiller, F AC is the rated flow of the lithium bromide unit, F EC is the rated flow of the centrifugal chiller, T AC.supply Set the temperature of the cold water supply to the lithium bromide unit, num EC is the number of centrifugal chillers in operation, num AC is the number of centrifugal chillers and lithium bromide chillers in operation, Fac EC is the expected energy supply ratio of a single centrifugal chiller.

5. The water supply temperature adjustment method according to any one of claims 1 to 3, characterized in that: The water supply temperature adjustment method also includes: when the internal combustion engine of the distributed energy system is not running but there is a cooling load, only the centrifugal refrigeration unit is turned on to meet the system cooling load, and the set temperature of the centrifugal refrigeration unit when running is the conventional water supply set temperature, and the conventional water supply set temperature is 5-7°C.

6. The water supply temperature adjustment method according to any one of claims 1 to 3, characterized in that: The step (S1) also includes: determining whether the lithium bromide chiller can meet the user's cooling load demand by utilizing the waste heat of the internal combustion engine. If so, the lithium bromide chiller operates alone according to the conventional water supply set temperature, which is 5-7°C.

7. The water supply temperature adjustment method according to any one of claims 1 to 3, characterized in that: The internal combustion engine is connected to the lithium bromide chiller, the lithium bromide chiller and the centrifugal chiller are connected in parallel, and both the lithium bromide chiller and the centrifugal chiller are connected to the user side.

Images