Multi-unit operation control method for distributed energy systems based on water flow distribution

Abstract

The present invention discloses a multi-unit operation control method for a distributed energy system based on water flow distribution. The method includes: obtaining the available waste heat in the flue gas and liner water generated by a single internal combustion engine; calculating the maximum cooling capacity or maximum heating capacity that can be generated by a single absorption cold and hot water unit when the available waste heat is used as input heat; determining the flow of a single absorption cold and hot water unit; calculating the expected energy supply ratio of a single heat pump; based on the flow of the single absorption cold and hot water unit and the expected energy supply ratio of the single heat pump, determining the flow of the single heat pump unit according to the relationship between load distribution and water flow distribution; and adjusting the water pumps corresponding to each unit according to the flow of the single absorption cold and hot water unit and the flow of the single heat pump unit. The method provided by the present invention enables the system to not deviate from the established operation 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 multi-unit operation control method of a distributed energy system based on water flow distribution. Background Art

[0002] Distributed energy systems can integrate diverse local energy sources to simultaneously provide electricity, heat, cooling, and domestic hot water to surrounding users. This system primarily utilizes internal combustion generators to meet user electricity loads, while absorption chillers utilize the generator's waste heat for cooling and heating. This achieves cascaded utilization of primary energy, improving the system's primary energy efficiency and reducing its carbon emissions. However, in operation, the cooling and heating capacity generated solely by waste heat from power generation often cannot match user cooling and heating loads. Therefore, systems often add chillers or heat pumps to meet additional cooling and heating loads. When cooling and heating loads are high, absorption chillers and heat pumps operate together to meet user cooling and heating needs. Numerous studies have focused on operational strategies for distributed energy systems integrated with heat pumps. One common strategy is to use electricity to determine heat output, with the generator operating according to the electricity load. When the waste heat generation fails to meet user cooling and heating needs, the heat pump is used to supplement the heat output. Alternatively, the heat pump's energy supply ratio can be pre-set to calculate the internal combustion generator's current power generation, which the internal combustion generator then operates at. Other operational strategies include operating the internal combustion generator at a stable maximum load. These operation strategies can play an optimized scheduling role in the operation of distributed energy systems.

[0003] However, in actual system operation, when multiple units are running simultaneously, the cooling / heating capacity of each unit is constrained by the water system. The cooling / heating capacity of each unit is directly related to the flow ratio of each unit. If the air conditioning water system cannot be effectively regulated, the system's operation will deviate from the established operation strategy, and the units will fail to operate according to the set load. In particular, under low-load conditions, the absorption chiller and heat pump units are both operating at partial load, and some of the waste heat from the internal combustion generator cannot be effectively utilized by the absorption chiller, and the system cannot achieve the operating goals of high efficiency, energy saving, and carbon reduction. Therefore, the existing technology still lacks a water flow distribution strategy for distributed energy systems. Summary of the Invention

[0004] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a multi-unit operation control method for a distributed energy system based on water flow distribution, the purpose of which is to determine the flow of the absorption cold and hot water unit and the heat pump unit according to the maximum available waste heat of the absorption cold and hot water unit and the user load, so that the system does not deviate from the established operation strategy, improve the waste heat utilization rate and primary energy utilization rate, and reduce the system energy consumption and carbon emissions.

[0005] To achieve the above objectives, according to one aspect of the present invention, a multi-unit operation control method of a distributed energy system based on water flow distribution is provided, wherein the distributed energy system includes an internal combustion engine, an absorption chiller and hot water unit, and a heat pump system;

[0006] The multi-unit operation control method comprises the following steps:

[0007] (S1) obtaining available waste heat from flue gas and liner water generated by a single internal combustion engine;

[0008] (S2) calculating the maximum cooling capacity or maximum heating capacity that can be generated by a single absorption chiller / hot water unit when the available waste heat is used as the input heat based on the relationship between the input heat and the operating efficiency; then determining the flow rate of the single absorption chiller / hot water unit by the ratio of the maximum cooling capacity to the rated cooling capacity, or determining the flow rate of the single absorption chiller / hot water unit by the ratio of the maximum heating capacity to the rated heating capacity;

[0009] (S3) obtaining the user's cooling load or heating load, as well as the number of heat pumps and absorption chillers that are turned on, and calculating the expected energy supply ratio of a single heat pump;

[0010] (S4) determining the flow rate of the single heat pump unit based on the flow rate of the single absorption hot and cold water unit and the expected energy supply ratio of the single heat pump according to the relationship between load distribution and water flow distribution;

[0011] (S5) adjusting the water pumps corresponding to the units according to the flow rate of the single absorption hot and cold water unit and the flow rate of the single heat pump unit.

[0012] Preferably, the step (S1) includes: obtaining the temperature and flow of the flue gas and the liner water generated by the internal combustion engine, and calculating the available waste heat in the flue gas and the liner water of a single internal combustion engine according to a heat formula.

[0013] Preferably, the heat formula is:

[0014] Q smoke.input =Cp smoke ×m smoke ×(T smoke.in -T smoke.out ) (1)

[0015] Q water.input =Cp water ×m water ×(T water.in -T water.out ) (2)

[0016] Among them, Q smoke.input and Q water.input are the available waste heat in the flue gas and liner water generated by the internal combustion engine; Cpsmoke and Cp water are the specific heat capacities of flue gas and hot water respectively; m smoke and m water are the mass flow rates of flue gas and jacket water respectively; T smoke.in 、T smoke.out 、T water.in and T water.out are the temperatures of flue gas and hot water entering and leaving the absorption chiller / water unit, respectively.

[0017] Preferably, the maximum cooling capacity or the maximum heating capacity in step (S2) is obtained by the following formula:

[0018] Q AC.MAX =Q smoke.input ×eff smoke +Q water.input ×eff water (4)

[0019] Among them, eff smoke and eff water are the cooling efficiency or heating efficiency of the flue gas and jacket water of a single absorption chiller / hot water unit, Q smoke.input and Q water.input are the available waste heat in the flue gas and liner water generated by the internal combustion engine, Q AC.MAX It is the maximum cooling capacity or heating capacity of a single absorption chiller or hot water unit.

[0020] Preferably, the flow rate F of a single absorption hot and cold water unit in step (S2) AC It is expressed by the following formula:

[0021]

[0022] Among them, F rated is the rated flow of a single absorption hot and cold water unit, Q AC.MAX Q is the maximum cooling capacity or maximum heating capacity of a single absorption chiller / hot water unit. rated F is the rated cooling capacity or heating capacity of a single absorption chiller or hot water unit; AC.min This is the minimum flow rate allowed for a single absorption hot and cold water unit.

[0023] Preferably, the expected energy supply ratio Fac of a single heat pump in step (S3) is HP Calculated by the following formula:

[0024]

[0025] Among them, Q user is the user's cooling load or heating load; num HP and num ACThese are the number of heat pump units and absorption hot and cold water units that are in operation.

[0026] Preferably, the flow rate F of a single heat pump unit in step (S4) HP Calculated by the following formula:

[0027]

[0028] Among them, num HP and num AC are the number of heat pump units and absorption hot and cold water units that are turned on, respectively. HP is the expected energy supply ratio of a single heat pump, F AC is the flow rate of a single absorption hot and cold water unit, F HP，min This is the minimum flow rate allowed for a single heat pump.

[0029] Preferably, the internal combustion engine is connected to the absorption cold and hot water unit, the absorption cold and hot water unit and the heat pump system are connected in parallel, and the heat pump system is connected to the user side.

[0030] In general, the above technical solutions conceived by the present invention can achieve at least the following beneficial effects compared with the prior art.

[0031] (1) The internal combustion generator operates according to the electric load required by the user, and the waste heat generated is supplied to the absorption chiller and hot water unit to generate cold water or hot water to meet the cooling and heating needs of the building. The insufficient cooling and heating needs are provided by the heat pump unit. When the absorption chiller and hot water unit and the heat pump unit are running at the same time, if the flow of each unit cannot be reasonably distributed, the system operation will deviate from the established optimization scheduling plan, and each unit will operate at a partial load condition, resulting in incomplete utilization of the waste heat of the absorption chiller and hot water unit, causing problems such as decreased system operating efficiency, reduced economy, and increased carbon emissions. In order to solve this problem, the control method of the present invention proposes a distributed energy system multi-unit operation control method based on water flow distribution. When the absorption chiller and hot water unit and the heat pump unit are running at the same time, the flow of each absorption unit is determined according to the current maximum available waste heat of the absorption chiller, and then the flow of each heat pump unit is determined according to the number of absorption units turned on, the number of heat pump units turned on, and the user load. By changing the cooling and heating loads borne by each unit through flow distribution, it is ensured that the absorption cooling and hot water units can fully utilize the waste heat generated by the internal combustion generator, improve the energy utilization efficiency and economy of the system, reduce the system energy consumption and carbon emissions; ensure that the system does not deviate from the established operating strategy, and improve the utilization rate of waste heat and primary energy.

[0032] (2) The present invention can improve the waste heat utilization efficiency and primary energy utilization rate of the distributed energy system throughout the year, reduce the system energy consumption and carbon emissions, and provide a reference for the operation control of the distributed energy system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram of the distributed energy system in the present invention;

[0034] Figure 2 This is a flow chart of a multi-unit operation control method for a distributed energy system based on water flow distribution provided by the present invention;

[0035] In all the drawings, the same reference numerals are used to denote the same equipment or structures, where: 1 - internal combustion generator, 2 - power grid, 3 - absorption chiller / hot water unit, 4 - heat pump, 5 - user. DETAILED DESCRIPTION

[0036] 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.

[0037] The structure of the distributed energy system in the present invention is as follows Figure 1 As shown, the distributed energy system includes: an internal combustion engine 1, electrically connected to a heat pump 4 and a user 5, for driving the heat pump 4 and meeting the electrical load of the user 5;

[0038] The power grid 2 is electrically connected to the heat pump 4 and the user 5, and is used to drive the heat pump 4 and meet the electrical load of the user 5;

[0039] The absorption type hot and cold water unit 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, and is connected to the user 5 to provide cooling / heating load to the user 5;

[0040] The heat pump 4 is connected to the user 5 and is used to provide cooling / heating load to the user 5;

[0041] The power supply demand of the user 5 and the heat pump 4 is first met by the internal combustion engine 1, and the shortfall is provided by the power grid 2;

[0042] The absorption type hot and cold water unit 3 is connected to the internal combustion generator 1 and can absorb the waste heat generated by the internal combustion engine 1 to perform cooling and heating;

[0043] The absorption cold and hot water unit 3 and the heat pump 4 are both connected to the user 5 through water pipes and provide cold / hot water to provide the user 5 with cold and hot loads. The cold / hot water is heated / cooled by the user and then returns to the absorption cold and hot water unit 3 and the heat pump 4. The flow rates of the absorption cold and hot water unit 3 and the heat pump 4 respectively depend on the flow rate setting values of the corresponding water pumps of each device.

[0044] The multi-unit operation control method of the distributed energy system of the present invention is as follows: Figure 2 As shown, the following steps are included:

[0045] (S1) Obtaining available waste heat from flue gas and liner water generated by a single internal combustion engine.

[0046] Wherein, the step (S1) includes: obtaining the temperature and flow of the flue gas and cylinder jacket water generated by the internal combustion engine, and calculating the available waste heat in the flue gas and cylinder jacket water of a single internal combustion engine according to the heat formula.

[0047] The caloric formula is:

[0048] Q smoke.input =Cp smoke ×m smoke ×(T smoke.in -T smoke.out ) (1)

[0049] Q water.input =Cp water ×m water ×(T water.in -T water.out ) (2)

[0050] Among them, Q smoke.input and Q water.input are the available waste heat in the flue gas and liner water generated by the internal combustion engine; Cp smoke and Cp water are the specific heat capacities of flue gas and hot water respectively; m smoke and m water are the mass flow rates of flue gas and jacket water respectively; T smoke.in 、T smoke.out ; are the temperatures T of flue gas entering and leaving the absorption chiller and hot water unit respectively water.in and T water.out These are the temperatures of hot water entering and leaving the absorption chiller / water unit, respectively.

[0051] (S2) calculating the maximum cooling capacity or maximum heating capacity that can be generated by a single absorption chiller / hot water unit when the available waste heat is used as the input heat based on the relationship between the input heat and the operating efficiency; and then determining the flow rate of the single absorption chiller / hot water unit by the ratio of the maximum cooling capacity to the rated cooling capacity, or determining the flow rate of the single absorption chiller / hot water unit by the ratio of the maximum heating capacity to the rated heating capacity.

[0052] The maximum cooling capacity or maximum heating capacity is obtained by the following formula:

[0053] Q AC.MAX =Q smoke.input ×eff smoke +Qwater.input ×eff water (4)

[0054] Among them, eff smoke and eff water are the cooling efficiency or heating efficiency of the flue gas and jacket water of a single absorption chiller / hot water unit, Q smoke.input and Q water.input are the available waste heat in the flue gas and liner water generated by the internal combustion engine, Q AC.MAX It is the maximum cooling capacity or heating capacity of a single absorption chiller or hot water unit.

[0055] Flow rate F of a single absorption hot and cold water unit AC It is expressed by the following formula:

[0056]

[0057] Among them, F rated is the rated flow of a single absorption hot and cold water unit, Q AC.MAX Q is the maximum cooling capacity or maximum heating capacity of a single absorption chiller / hot water unit. rated F is the rated cooling capacity or heating capacity of a single absorption chiller or hot water unit; AC.min This is the minimum flow rate allowed for a single absorption hot and cold water unit.

[0058] (S3) Obtain the user's cooling load or heating load, as well as the number of heat pumps and absorption chillers that are turned on, and calculate the expected energy supply ratio of a single heat pump.

[0059] Expected energy supply ratio of a single heat pump Fac HP Calculated by the following formula:

[0060]

[0061] Among them, Q user is the user's cooling load or heating load; num HP and num AC These are the number of heat pump units and absorption hot and cold water units that are in operation.

[0062] (S4) Based on the flow rate of the single absorption hot and cold water unit and the expected energy supply ratio of the single heat pump, the flow rate of the single heat pump unit is determined according to the relationship between load distribution and water flow distribution.

[0063] Flow rate F of a single heat pump unit HP Calculated by the following formula:

[0064]

[0065] Among them, num HP and numAC are the number of heat pump units and absorption hot and cold water units that are turned on, Fac HP is the expected energy supply ratio of a single heat pump, F AC is the flow rate of a single absorption hot and cold water unit, F HP，min This is the minimum flow rate allowed for a single heat pump.

[0066] (S5) adjusting the water pumps corresponding to the units according to the flow rate of the single absorption hot and cold water unit and the flow rate of the single heat pump unit.

[0067] Therefore, compared with the existing technology, the present invention can determine the flow of the absorption cold and hot water unit and the heat pump unit according to the maximum available waste heat of the absorption cold and hot water unit and the user load, so that the absorption cold and hot water unit and the heat pump unit can 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.

[0068] 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 multi-unit operation control method for a distributed energy system based on water flow distribution, characterized in that; The distributed energy system includes an internal combustion engine, an absorption hot and cold water unit and a heat pump system; The multi-unit operation control method comprises the following steps: (S1) obtaining available waste heat from flue gas and liner water generated by a single internal combustion engine; (S2) calculating the maximum cooling capacity or maximum heating capacity that can be generated by a single absorption chiller / hot water unit when the available waste heat is used as the input heat based on the relationship between the input heat and the operating efficiency; then determining the flow rate of the single absorption chiller / hot water unit by the ratio of the maximum cooling capacity to the rated cooling capacity, or determining the flow rate of the single absorption chiller / hot water unit by the ratio of the maximum heating capacity to the rated heating capacity; (S3) obtaining the user's cooling load or heating load, as well as the number of heat pumps and absorption chillers that are turned on, and calculating the expected energy supply ratio of a single heat pump; (S4) determining the flow rate of the single heat pump unit based on the flow rate of the single absorption hot and cold water unit and the expected energy supply ratio of the single heat pump according to the relationship between load distribution and water flow distribution; (S5) adjusting the water pumps corresponding to the units according to the flow rate of the single absorption hot and cold water unit and the flow rate of the single heat pump unit.

2. The multi-unit operation control method according to claim 1, characterized in that: The step (S1) includes: obtaining the temperature and flow of the flue gas and the cylinder jacket water generated by the internal combustion engine, and calculating the available waste heat in the flue gas and the cylinder jacket water of a single internal combustion engine according to a heat formula.

3. The multi-unit operation control method according to claim 2, characterized in that: The caloric formula is: Q smoke.input =Cp smoke ×m smoke ×(T smoke.in -T smoke.out ) (1) Q water.input =Cp water ×m water ×(T water.in -T water.out ) (2) Among them, Q smoke.input and Q water.input are the available waste heat in the flue gas and liner water generated by the internal combustion engine; Cp smoke and Cp water are the specific heat capacities of flue gas and hot water respectively; m smoke and m water are the mass flow rates of flue gas and jacket water respectively; T smoke.in 、T smoke.out 、T water.in and T water.out are the temperatures of flue gas and hot water entering and leaving the absorption chiller / water unit, respectively.

4. The multi-unit operation control method according to claim 1, characterized in that: The maximum cooling capacity or the maximum heating capacity in step (S2) is obtained by the following formula: Q AC.MAX =Q smoke.input ×eff smoke +Q water.input ×eff water (4) Among them, eff smoke and eff water are the cooling efficiency or heating efficiency of the flue gas and jacket water of a single absorption chiller / hot water unit, Q smoke.input and Q water.input are the available waste heat in the flue gas and liner water generated by the internal combustion engine, Q AC.MAX It is the maximum cooling capacity or heating capacity of a single absorption chiller or hot water unit.

5. The multi-unit operation control method according to claim 1, characterized in that: The flow rate F of a single absorption hot and cold water unit in step (S2) AC It is expressed by the following formula: Among them, F rated is the rated flow of a single absorption hot and cold water unit, Q AC.MAX Q is the maximum cooling capacity or maximum heating capacity of a single absorption chiller / hot water unit. rated F is the rated cooling capacity or heating capacity of a single absorption chiller or hot water unit; AC.min This is the minimum flow rate allowed for a single absorption hot and cold water unit.

6. The multi-unit operation control method according to claim 1, characterized in that: The expected energy supply ratio Fac of a single heat pump in step (S3) HP Calculated by the following formula: Among them, Q user is the user's cooling load or heating load; num HP and num Ac These are the number of heat pump units and absorption hot and cold water units that are in operation.

7. The multi-unit operation control method according to claim 1, characterized in that: The flow rate F of a single heat pump unit in step (S4) HP Calculated by the following formula: Among them, num HP and num AC are the number of heat pump units and absorption hot and cold water units that are turned on, Fac HP is the expected energy supply ratio of a single heat pump, F AC is the flow rate of a single absorption hot and cold water unit, F HP，min This is the minimum flow rate allowed for a single heat pump.

8. The multi-unit operation control method according to claim 1, characterized in that: The internal combustion engine is connected to the absorption type cold and hot water unit, the absorption type cold and hot water unit and the heat pump system are connected in parallel, and the heat pump system is connected to the user side.

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