Method for determining effective capacity of heat storage tank added to combined heat and power unit

Abstract

The present application belongs to the field of hot water tank heat measurement, discloses a kind of effective capacity determination method of hot water tank added in cogeneration unit, and the effective capacity of hot water tank can be accurately determined according to real working condition by step-by-step quantitative calculation of key parameters such as heat load, peak shaving duration, heat storage efficiency and supply and return water temperature difference.First, by quantifying the average heat load of the heating period and the typical peak shaving or peak duration, the heat storage demand can be closely matched with the actual operating load, avoiding the use of traditional estimation method with large safety factor, reducing the capacity configuration from the source. The present application introduces the heat loss parameter of the hot water tank, and includes the inevitable heat loss in the energy storage process into the calculation, so that the final effective daily heat storage is closer to the real available value, thereby avoiding the insufficient effective capacity caused by ignoring the loss and improving the sustainable heating capacity of the unit during peak shaving and peak period.

Description

Technical Field

[0001] This invention belongs to the field of hot water tank heat measurement, specifically relating to a method for determining the effective capacity of an additional hot water storage tank in a combined heat and power unit. Background Technology

[0002] Among various thermal storage technologies coupled with cogeneration units, the addition of hot water storage tanks offers advantages such as large storage capacity, long lifespan, high cost-effectiveness, and technological maturity, leading to its widespread application in engineering practice. The core equipment of water-based thermal storage technology is the inclined temperature transition layer storage tank. This tank operates based on the principle of stratification of hot and cold water at different temperatures due to density differences. Under low-disturbance conditions, the less dense hot water is at the top of the container, while the denser cold water is at the bottom. This interface forms a temperature gradient layer—the inclined temperature transition layer—facilitating the simultaneous storage of different working fluids at different temperatures. Specifically, the upper region of the storage tank contains the higher-temperature supply water, while the lower region contains the lower-temperature return water, creating a transition layer between the hot and cold water. During the thermal storage process, hot water enters the tank from the upper region, while the same mass of cold water is discharged from the bottom. During the heat release process, water flows in the opposite direction. Smoothly controlling the inflow and outflow of water is crucial for ensuring the reliable operation of the thermal storage device, preventing the mixing of the hot and cold water layers within the tank, and maintaining the stability of the transition layer.

[0003] The determination of the thermal storage tank capacity mainly considers factors such as the heating load on the heating network side, the peak-shaving / peak-loading capacity of the unit during the heating season, and the duration of peak-shaving / peak-loading. Since the maximum heat load on the heating network side lasts for a very short time, designing the thermal storage tank according to the maximum heat load would result in an oversized storage tank, leading to a certain amount of wasted capacity. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of capacity waste caused by the above-mentioned effective capacity calculation error and insufficient peak-shaving / peak-loading capacity of the unit, and to provide a method for determining the effective capacity of the hot water storage tank added to the cogeneration unit.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for determining the effective capacity of an additional hot water storage tank in a combined heat and power (CHP) unit, comprising the following steps: Obtain the average heat load and average duration of daily peak shaving or peak on the heating network side during the heating season. Based on the average heat load and average duration of daily peak shaving or peak on the heating network side during the heating season, calculate the total heat required daily on the heating network side to meet the peak shaving or peak operation requirements of the units. Obtain the heat loss of the hot water storage tank, calculate the heat storage efficiency of the hot water storage tank based on the heat loss, and calculate the effective daily heat storage capacity of the hot water storage tank based on the heat storage efficiency of the hot water storage tank and the total heat required by the heating network side each day. Obtain the supply and return water temperatures of the hot water storage tank, and infer the water quality based on the supply and return water temperatures of the hot water storage tank and the effective daily heat storage capacity of the hot water storage tank. The effective heat storage capacity of the hot water tank is calculated based on the quality of the water.

[0006] A further improvement of this invention is that the method for calculating the total daily heat required by the heating network to meet the peak-shaving or peak-operation requirements of the generating units is as follows:

[0007] in, This represents the total daily heat required by the heating network. This represents the average heat load on the heating network side during the heating season. This refers to the average duration of daily peak shaving or peak.

[0008] A further improvement of this invention is that, based on the heat storage efficiency of the hot water storage tank and the total daily heat required by the heating network, the method for calculating the effective daily heat storage capacity of the hot water storage tank is as follows:

[0009] in, To ensure the effective daily heat storage capacity of the hot water storage tank, This represents the total daily heat required by the heating network. The heat storage efficiency of the hot water storage tank.

[0010] A further improvement of this invention lies in the method of inferring the water quality based on the supply and return water temperatures of the hot water storage tank, combined with the effective daily heat storage capacity of the hot water storage tank, as follows:

[0011] in, For the quality of water, To ensure the effective daily heat storage capacity of the hot water storage tank, The specific heat capacity of water, This refers to the temperature difference between the supply water temperature and the return water temperature.

[0012] A further improvement of this invention is that the method for converting the effective heat storage capacity of the hot water storage tank based on the quality of the water is as follows:

[0013] in, The effective heat storage capacity of the hot water storage tank, For the quality of water, This is the density of water.

[0014] A further improvement of the present invention is that the average heat load on the heating network side during the heating season refers to the weighted average power of the combined heat and power units delivering heat to the heating network during the heating season.

[0015] A further improvement of the present invention is that the average duration of daily peak shaving or peak is the cumulative time within a single day required to activate the release of stored heat to meet the peak heat load.

[0016] A further improvement of this invention is that the hot water storage tank adopts a layered atmospheric pressure water heat storage structure.

[0017] A further improvement of this invention is that the supply water temperature and return water temperature of the hot water storage tank are collected separately.

[0018] A further improvement of the present invention is that the heat storage efficiency of the hot water storage tank is 95% to 99%.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention enables precise determination of the effective capacity of hot water storage tanks based on actual operating conditions through step-by-step quantitative calculations of key parameters such as heat load, peak-shaving duration, thermal storage efficiency, and supply and return water temperature difference. First, by quantifying the average heat load and typical peak-shaving or peak-load duration during the heating season, the thermal storage demand can be closely matched with the actual operating load, avoiding the use of traditional estimation methods based on empirical values ​​or excessively high safety factors, thus reducing the risk of over-configuration of capacity from the outset. Second, by introducing the heat loss parameter of the hot water storage tank, this invention incorporates the unavoidable heat loss during energy storage into the calculation, making the final effective daily heat storage closer to the actual usable value. This avoids insufficient effective capacity due to ignoring losses and improves the unit's sustainable heating capacity during peak-shaving and peak-load periods. Third, by inferring water quality from the supply and return water temperatures and the effective daily heat storage, this invention achieves a quantifiable mapping between heat demand and the geometric capacity of the hot water storage tank, transforming tank capacity design from fuzzy estimation to a verifiable physical calculation process. This method can accurately determine the actual required mass and volume of hot water to be stored, ensuring that peak-shaving demand is met while avoiding investment waste caused by constructing excessively large thermal storage tanks. Ultimately, the water quality is converted into effective thermal storage capacity, creating a closed-loop chain from load to heat, efficiency, water quality, and volume in the entire capacity calculation process, significantly improving the reliability of capacity design. In summary, this invention not only improves the accuracy of calculating the effective capacity of hot water storage tanks but also enables the thermal storage system to better meet the peak-shaving and peak-load operation requirements of the unit, avoiding cost waste due to excessive capacity and preventing insufficient capacity from affecting heating safety and peak-shaving capabilities, thus comprehensively improving the flexibility and economy of cogeneration unit operation. Attached Figure Description

[0020] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0021] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0022] Example 1: Step 1: Obtain the average heat load and average duration of daily peak shaving or peak operation on the heating network side during the heating season. Based on the average heat load and average duration of daily peak shaving or peak operation on the heating network side during the heating season, calculate the total heat required daily on the heating network side to meet the peak shaving or peak operation requirements of the units.

[0023] Specifically, the average heat load on the heating network side during the heating season refers to the weighted average power of the combined heat and power (CHP) units delivering heat to the heating network throughout the entire heating season. The average duration of daily peak shaving or peak load refers to the cumulative time within a single day that requires the release of stored heat to meet peak heat load requirements.

[0024] The method for calculating the total daily heat requirement on the heating network side is as follows:

[0025] in, This represents the total daily heat required by the heating network, expressed in GJ. The average heat load on the heating network side during the heating season is expressed in MW; T is the average duration of daily peak or peak load, expressed in hours; 3.6 is the unit conversion factor.

[0026] Step 2: Obtain the heat loss information of the hot water storage tank and calculate its heat storage efficiency based on this loss. Then, based on the heat storage efficiency of the hot water storage tank and the total daily heat required by the heating network, calculate the effective daily heat storage capacity of the hot water storage tank.

[0027] The hot water storage tank adopts a layered, atmospheric pressure water heat storage structure, which effectively reduces heat loss and thus improves heat storage efficiency. The heat storage efficiency of hot water storage tanks is typically between 95% and 99%, and the specific value can be determined based on factors such as the insulation material, structural design, and environmental conditions.

[0028] The method for calculating the effective daily heat storage capacity of a hot water storage tank is as follows:

[0029] in, The effective daily heat storage capacity of the hot water storage tank is expressed in GJ. This represents the total daily heat required by the heating network, expressed in GJ. The heat storage efficiency of the hot water storage tank is dimensionless.

[0030] Step 3: Obtain the supply and return water temperatures of the hot water storage tank. Based on the supply and return water temperatures of the hot water storage tank, and combined with the effective daily heat storage capacity of the hot water storage tank, deduce the required water quality.

[0031] The supply and return water temperatures of the hot water storage tank can be obtained by separately collecting the temperatures of the supply and return water pipes of the tank. Based on these two temperature values, the temperature difference can be calculated, and combined with the specific heat capacity of water and the effective daily heat storage capacity, the required mass of water can be deduced.

[0032] The method for back-calculating the mass of water is as follows:

[0033] in, The mass of water is expressed in kg. The effective daily heat storage capacity of the hot water storage tank is expressed in GJ. Specific heat capacity of water, expressed in kJ / (kg·℃); The temperature difference between the supply water temperature and the return water temperature is expressed in °C; 1000 is the unit conversion factor.

[0034] Step 4: Based on the quality of the water, convert it into the effective heat storage capacity of the hot water storage tank.

[0035] The relationship between the mass and volume of water is converted through the density of water, thereby determining the effective heat storage capacity required for the hot water storage tank.

[0036] The method for converting the effective heat storage capacity of a hot water storage tank is as follows:

[0037] in, The effective heat storage capacity of the hot water tank is expressed in cubic meters. The mass of water is expressed in kilograms. This is the density of water, expressed in kilograms per cubic meter.

[0038] By following the steps above, the effective capacity required for adding a hot water storage tank to a combined heat and power (CHP) unit can be accurately calculated, providing reliable thermal storage support for peak shaving or peak operation of the CHP unit, thereby improving energy utilization efficiency and meeting the heating demand during peak heat load periods.

[0039] Example 2: A 600MW-class combined heat and power unit has an average heat load of 318MW during the heating season and an average daily peak shaving duration of 3 hours. Calculate the total heat required daily by the heating network:

[0040] Assuming a heat storage efficiency of 98%, the effective daily heat storage capacity of the heat storage tank can be obtained:

[0041] The supply and return water temperatures of the heating network are 97℃ and 50℃ respectively, therefore t 47℃ C Taking 4.2 kJ / (kg℃), the mass of water in the thermal storage tank is obtained:

[0042] Further obtain the effective capacity of the thermal storage tank V m 3 :

[0043] This embodiment verifies that the effective capacity determination method can yield a clear, quantifiable, and realistic hot water storage tank capacity result by substituting typical operating parameters of a 600MW-class cogeneration unit. First, based on the unit's average heat load and average daily peak-shaving duration during the heating season, the total daily heat requirement of the heating network is calculated to be approximately 3434.4 GJ, indicating a high demand for heat shifting during peak-shaving operation. Then, by considering the 98% heat storage efficiency of the storage tank and incorporating heat loss factors into the quantification process, the effective daily heat storage capacity is increased to 3504.5 GJ, ensuring that the energy storage scale reflects the actual available heat rather than a nominal value.

[0044] Under the conditions of a supply and return water temperature difference of 47℃ and a specific heat capacity of 4.2 kJ / (kg·℃), the mass of water required to store the aforementioned effective heat can be calculated by reverse deduction to be approximately 17753 t. This result directly gives the actual demand for the thermal storage medium, and further conversion yields an effective volume of approximately 17753 m³ for the hot water storage tank. This result demonstrates that this method can transform heat load demand, thermal storage efficiency, and hydraulic parameters into a definite physical capacity, ensuring the accuracy and engineering feasibility of the thermal storage tank configuration. The final effective capacity scale indicates that the unit requires approximately 17,800 cubic meters of hot water storage tank to meet daily peak-shaving demand during peak-shaving operation, thus providing a reliable basis for the design, investment decisions, and operation planning of the thermal storage system.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for determining the effective capacity of an additional hot water storage tank in a combined heat and power (CHP) unit, characterized in that, Includes the following steps: Obtain the average heat load and average duration of daily peak shaving or peak on the heating network side during the heating season. Based on the average heat load and average duration of daily peak shaving or peak on the heating network side during the heating season, calculate the total heat required daily on the heating network side to meet the peak shaving or peak operation requirements of the units. Obtain the heat loss of the hot water storage tank, calculate the heat storage efficiency of the hot water storage tank based on the heat loss, and calculate the effective daily heat storage capacity of the hot water storage tank based on the heat storage efficiency of the hot water storage tank and the total heat required by the heating network side each day. Obtain the supply and return water temperatures of the hot water storage tank, and infer the water quality based on the supply and return water temperatures of the hot water storage tank and the effective daily heat storage capacity of the hot water storage tank. The effective heat storage capacity of the hot water tank is calculated based on the quality of the water.

2. The method for determining the effective capacity of an additional hot water storage tank in a combined heat and power unit according to claim 1, characterized in that, The method for calculating the total daily heat required by the heating network to meet the peak-shaving or peak-load operation needs of the generating units is as follows: in, This represents the total daily heat required by the heating network. This represents the average heat load on the heating network side during the heating season. This refers to the average duration of daily peak shaving or peak.

3. The method for determining the effective capacity of an additional hot water storage tank in a combined heat and power unit according to claim 1, characterized in that, Based on the heat storage efficiency of the hot water storage tank and the total daily heat required by the heating network, the effective daily heat storage capacity of the hot water storage tank is calculated as follows: in, To ensure the effective daily heat storage capacity of the hot water storage tank, This represents the total daily heat required by the heating network. The heat storage efficiency of the hot water storage tank.

4. The method for determining the effective capacity of an additional hot water storage tank in a combined heat and power unit according to claim 1, characterized in that, The method for inferring water quality based on the supply and return water temperatures of the hot water storage tank, combined with the effective daily heat storage capacity of the tank, is as follows: in, For the quality of water, To ensure the effective daily heat storage capacity of the hot water storage tank, The specific heat capacity of water, This refers to the temperature difference between the supply water temperature and the return water temperature.

5. The method for determining the effective capacity of an additional hot water storage tank in a combined heat and power unit according to claim 1, characterized in that, The method for converting the effective heat storage capacity of a hot water storage tank based on the water quality is as follows: in, The effective heat storage capacity of the hot water storage tank, For the quality of water, This is the density of water.

6. The method for determining the effective capacity of an additional hot water storage tank in a combined heat and power unit according to claim 1, characterized in that, The average heat load on the heating network side during the heating season refers to the weighted average power of the combined heat and power units delivering heat to the heating network during the heating season.

7. The method for determining the effective capacity of an additional hot water storage tank in a combined heat and power unit according to claim 1, characterized in that, The average duration of daily peak shaving or peak is the cumulative time within a single day required to activate the release of stored heat to meet peak heat load.

8. The method for determining the effective capacity of an additional hot water storage tank in a combined heat and power unit according to claim 1, characterized in that, The hot water storage tank adopts a layered atmospheric pressure water heat storage structure.

9. The method for determining the effective capacity of an additional hot water storage tank in a combined heat and power unit according to claim 1, characterized in that, The supply and return water temperatures of the hot water storage tank were collected separately to obtain the supply and return water temperatures of the hot water tank.

10. The method for determining the effective capacity of an additional hot water storage tank in a combined heat and power unit according to claim 3, characterized in that, The heat storage efficiency of hot water storage tanks is 95% to 99%.

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