Heat supply system integrated with heat pump and peak shaving operation method

Abstract

The application discloses a heat supply system integrated with a heat pump and a peak regulation operation method, and the heat supply system comprises a combined heat and power unit, heat users, primary / secondary heat network supply and return water pipelines, a heat exchange station and a heat pump system. The operation mode of the system is as follows: according to modeling of the heat supply system, steam extraction amounts of the combined heat and power unit under different peak regulation requirements are calculated, and the peak regulation requirements are achieved by adjusting the steam extraction amounts; the heat pump is integrated, the primary heat network return water temperature can be effectively reduced, the excess electric load can be utilized, and the flexibility of the combined heat and power unit is improved; the application can increase the heat and power operation domain of the combined heat and power unit without changing the pipeline network operation mode, adding a heat storage device and other modules, has small modification to the original system, is low in investment cost, and has higher feasibility.

Description

Technical Field

[0001] This invention relates to the field of combined heat and power (CHP) district heating technology, specifically to a heating system with an integrated heat pump and a peak-shaving operation method. Background Technology

[0002] With the continuous development of urbanization, the scale of urban centralized heating is constantly expanding and the heating load is increasing. At present, the centralized heating system still mainly relies on coal-fired power plants for heating. However, the strong thermoelectric coupling of cogeneration units and the "heat-determined power generation" operation mode have significantly reduced their power generation load regulation capacity during the heating season, which is not conducive to the development of low-carbon energy.

[0003] The main measures to improve the flexibility of thermal power plants include: upgrading the generating units themselves, electrothermal conversion, and adding thermal storage equipment. Upgrading the generating units themselves will have a significant impact on their performance, adding thermal storage equipment will increase system costs, and electrothermal conversion methods have the problem of inefficient utilization of high-grade energy. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide an integrated heat pump heating system and a peak-shaving operation method. This system comprises a primary heating network, a secondary heating network, and a heat pump system. It requires minimal modification to existing systems and has low investment costs. During operation, utilizing the thermal inertia of the heating system, under a given heat load and peak-shaving maintenance time, when the required electrical load increases, the amount of steam extracted from the cogeneration unit into the primary heat exchanger is increased; when the required electrical load decreases, the amount of steam extracted from the cogeneration unit into the primary heat exchanger is decreased.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A heating system with an integrated heat pump, characterized in that it comprises a primary heating network system, a heat pump system, and a secondary heating network system connected in sequence.

[0007] The primary heating network system includes a primary heat exchanger 1, a primary heating network water supply pipeline 2, a secondary heat exchanger 7, an evaporator 8, and a primary heating network return water pipeline 3;

[0008] The heat pump system includes an evaporator 8, a compressor 9, a condenser 10, and an expansion valve 11;

[0009] The secondary heating network system includes a secondary heat exchange station heat exchanger 7, a condenser 10, a secondary heating network water supply pipeline 4, heat users 6, and a secondary heating network return water pipeline 5.

[0010] The hot side inlet of the first heat exchanger 1 is connected to the steam extraction port of the intermediate pressure cylinder of the cogeneration unit; the hot side outlet of the first heat exchanger 1 is connected to the deaerator inlet of the cogeneration unit.

[0011] The cold-side outlet of the first heat exchanger 1 is connected to the hot-side inlet of the second heat exchanger 7 via the primary heating network water supply pipeline 2; the hot-side outlet of the second heat exchanger 7 is connected to the hot-side inlet of the evaporator 8; and the hot-side outlet of the evaporator 8 is connected to the cold-side inlet of the first heat exchanger 1 via the primary heating network return water pipeline 3.

[0012] The cold-side outlet of the evaporator 8 is connected to the inlet of the compressor 9; the outlet of the compressor 9 is connected to the hot-side inlet of the condenser 10; the hot-side outlet of the condenser 10 is connected to the inlet of the expansion valve 11; and the outlet of the expansion valve 11 is connected to the cold-side inlet of the evaporator 8.

[0013] The hot-side outlet of the heat user 6 is split into two branches via the secondary heating network return water pipeline 5. One branch is connected to the cold-side inlet of the condenser 10, and the other branch is connected to the cold-side inlet of the heat exchanger 7 in the secondary heat exchange station. The cold-side outlet of the condenser 10 is connected to the hot-side inlet of the heat user 6 via the secondary heating network water supply pipeline 4. The cold-side outlet of the heat exchanger 7 in the secondary heat exchange station is connected to the hot-side inlet of the heat user 6 via the secondary heating network water supply pipeline 4.

[0014] Preferably, in the integrated heat pump heating system that utilizes system thermal inertia for peak shaving, the refrigerant used in the heat pump system is R134a.

[0015] Preferably, the integrated heat pump heating system utilizing system thermal inertia for peak shaving has the following design conditions: the primary heating network has a heating temperature of 130℃ and a return water temperature of 40℃; the secondary heating network has a heating temperature of 60℃ and a return water temperature of 45℃.

[0016] The peak-shaving operation method of the integrated heat pump heating system utilizes the thermal inertia of the heating system. Under a given heat load and peak-shaving maintenance time, when the required electrical load increases, the amount of steam extracted from the cogeneration unit into the first-station heat exchanger 1 is increased; when the required electrical load decreases, the amount of steam extracted from the cogeneration unit into the first-station heat exchanger 1 is decreased.

[0017] Preferably, the steam extraction rate of the cogeneration unit entering the first heat exchanger 1 is calculated based on modeling, including the following steps:

[0018] Step 1: Establish a system model that considers the thermal inertia of the heating system, including a combined heat and power unit model, and dynamic models of the heating network, heat pumps, and heat users.

[0019] Step 2: Specify the indoor temperature range required by heat user 6 in the heating system: 18-24℃;

[0020] Step 3: Using the system model established in Step 1 and the indoor temperature range given in Step 2, calculate the time that can be used to maintain the indoor temperature requirements of heat users under different steam extraction rates of cogeneration units.

[0021] Step 4: Calculate the required steam extraction volume of the cogeneration unit under different outdoor temperatures using the following formula;

[0022] q v ·V(T z -T w ) = D h ·Δh

[0023] Where: q v The volumetric heat capacity index for building heating, w / (m³) 3 ·℃); V is the building volume, m 3 ;T z The average indoor temperature of the building, in °C; T w D represents the outdoor temperature in °C. h Δh represents the steam extraction rate of the cogeneration unit, in kg / s; Δh represents the enthalpy difference between the steam extraction for heating and the return water of the cogeneration unit, in kJ / kg.

[0024] Step 5: Repeat Step 3 under different outdoor temperatures to calculate the time that the combined heat and power unit can maintain the indoor temperature required by the heat user under different steam extraction rates at different outdoor temperatures.

[0025] Step 6: Using the cogeneration unit model established in Step 1, calculate the electrical power of the cogeneration unit under different steam extraction rates;

[0026] Step 7: Based on the peak shaving requirements, using the time required to maintain the indoor temperature of the heat users calculated in Step 5 and the electrical power calculated in Step 6, select the steam extraction rate that meets the peak shaving requirements for both the maintenance time and the electrical load.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) The present invention provides a heating system with an integrated heat pump. By integrating the heat pump, the return water temperature of the primary heating network can be effectively reduced, and excess electrical load can be utilized to improve the flexibility of the cogeneration unit.

[0029] (2) The present invention utilizes the thermal inertia and heat storage capacity of the heating system itself during the peak shaving process, requiring minimal modification to the existing system and saving costs.

[0030] (3) The peak shaving process of the present invention does not affect the indoor temperature requirements of heat users, and can effectively maintain the thermal stability of the indoor temperature of heat users.

[0031] (4) This invention can effectively increase the operating range of cogeneration units and improve the new energy absorption capacity of heating systems. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a heating system using an integrated heat pump.

[0033] Figure 2 This figure shows the maximum electrical power and the maximum duration of maintaining the required indoor temperature for heat users under different steam extraction rates during peak-shaving operation of an integrated heat pump heating system, based on a specific calculation example.

[0034] Figure 3 This is a comparison diagram of the thermal power operation domain of a cogeneration unit before and after the integration of a heat pump under different heat loads. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0036] like Figure 1 As shown, the present invention provides a heating system integrating a heat pump, comprising a primary heating network system, a heat pump system, and a secondary heating network system connected in sequence:

[0037] The primary heating network system includes a primary heat exchanger 1, a primary heating network water supply pipeline 2, a secondary heat exchanger 7, an evaporator 8, and a primary heating network return water pipeline 3.

[0038] The heat pump system includes an evaporator 8, a compressor 9, a condenser 10, and an expansion valve 11.

[0039] The secondary heating network system includes a secondary heat exchange station heat exchanger 7, a condenser 10, a secondary heating network water supply pipeline 4, heat users 6, and a secondary heating network return water pipeline 5.

[0040] The hot side inlet of the first heat exchanger 1 is connected to the steam extraction port of the intermediate pressure cylinder of the cogeneration unit; the hot side outlet of the first heat exchanger 1 is connected to the deaerator inlet of the cogeneration unit.

[0041] The cold-side outlet of the first heat exchanger 1 is connected to the hot-side inlet of the second heat exchanger 7 via the primary heating network water supply pipeline 2; the hot-side outlet of the second heat exchanger 7 is connected to the hot-side inlet of the evaporator 8; the hot-side outlet of the evaporator 8 is connected to the cold-side inlet of the first heat exchanger 1 via the primary heating network return water pipeline 3.

[0042] The cold-side outlet of evaporator 8 is connected to the inlet of compressor 9; the outlet of compressor 9 is connected to the hot-side inlet of condenser 10; the hot-side outlet of condenser 10 is connected to the inlet of expansion valve 11; and the outlet of expansion valve 11 is connected to the cold-side inlet of evaporator 8.

[0043] The hot-side outlet of heat user 6 is split into two branches via the secondary heating network return water pipeline 5. One branch is connected to the cold-side inlet of condenser 10, and the other branch is connected to the cold-side inlet of heat exchanger 7 in the secondary heat exchange station. The cold-side outlet of condenser 10 is connected to the hot-side inlet of heat user 6 via the secondary heating network water supply pipeline 4. The cold-side outlet of heat exchanger 7 in the secondary heat exchange station is connected to the hot-side inlet of heat user 6 via the secondary heating network water supply pipeline 4.

[0044] In a preferred embodiment of the present invention, the refrigerant used in the heat pump system is R134a, which is non-toxic, non-flammable, and chemically stable.

[0045] As a preferred embodiment of the present invention, under the following design conditions: the heating temperature of the primary heating network is 130°C, and the return water temperature of the primary heating network is 40°C. The selection of a supply water temperature of 130°C will not affect the pipe insulation material, and the selection of a return water temperature of 40°C can ensure the optimal operation of the heat pump; the heating temperature of the secondary heating network is 60°C, and the return water temperature of the secondary heating network is 45°C. The 15°C temperature difference between the supply and return water will not cause the heating network flow to be too large, thus reducing the heating network circulation operation cost.

[0046] This invention is illustrated using a specific cogeneration unit as an example. Table 1 shows a comparison of system parameters before and after the integrated heat pump heating system. It can be seen that the system can effectively reduce the return water temperature of the primary network.

[0047] Table 1 Comparison of primary network return water temperature parameters of heating systems before and after integrated heat pump

[0048]

[0049] like Figure 1 As shown, the present invention discloses a peak-shaving operation method for an integrated heat pump heating system. Utilizing the thermal inertia of the heating system, under a given heat load and peak-shaving maintenance time, when the required electrical load increases, the amount of steam extracted from the cogeneration unit into the first-station heat exchanger 1 is increased; when the required electrical load decreases, the amount of steam extracted from the cogeneration unit into the first-station heat exchanger 1 is decreased.

[0050] The calculation of the steam extraction rate entering the first heat exchanger 1 of the cogeneration unit based on modeling includes the following steps:

[0051] Step 1: Establish a system model that considers the thermal inertia of the heating system, including a combined heat and power unit model, and dynamic models of the heating network, heat pumps, and heat users.

[0052] Step 2: Specify the indoor temperature range required by heat user 6 in the heating system: 18-24℃;

[0053] Step 3: Using the system model established in Step 1 and the indoor temperature range given in Step 2, calculate the time that can be used to maintain the indoor temperature requirements of heat users under different steam extraction rates of cogeneration units.

[0054] Step 4: Calculate the required steam extraction volume of the cogeneration unit under different outdoor temperatures using the following formula;

[0055] q v ·V(T z -T w ) = D h ·Δh

[0056] Where: q v The volumetric heat capacity index for building heating, w / (m³) 3 ·℃); V is the building volume, m 3 ;T z The average indoor temperature of the building, in °C; T w D represents the outdoor temperature in °C. h Δh represents the steam extraction rate of the cogeneration unit, in kg / s; Δh represents the enthalpy difference between the steam extraction for heating and the return water of the cogeneration unit, in kJ / kg.

[0057] Step 5: Repeat Step 3 under different outdoor temperatures to calculate the time that the combined heat and power unit can maintain the indoor temperature required by the heat user under different steam extraction rates at different outdoor temperatures.

[0058] Step 6: Using the cogeneration unit model established in Step 1, calculate the electrical power of the cogeneration unit under different steam extraction rates;

[0059] Step 7: Based on the peak shaving requirements, using the time required to maintain the indoor temperature of the heat users calculated in Step 5 and the electrical power calculated in Step 6, select the steam extraction rate that meets the peak shaving requirements for both the maintenance time and the electrical load.

[0060] This invention uses a specific heating system as an example for illustration, describing the time it takes for the integrated heat pump heating system to maintain the indoor temperature required by heat users under different steam extraction rates, and the maximum electrical power of the combined heat and power unit, such as... Figure 2 As shown. A comparison of the heating systems before and after the integration of the heat pump, and a comparison of the cogeneration unit's heat and power operation domain diagram. Figure 3 As shown, the integrated heat pump heating system of the present invention can improve the flexibility of cogeneration units and enhance peak-shaving capabilities.

[0061] This invention integrates a heat pump, which can effectively reduce the return water temperature of the primary heating network and utilize excess electrical load, thereby improving the flexibility of the cogeneration unit. This invention can increase the thermal and power operating range of the cogeneration unit without changing the pipeline network operation mode, adding heat storage devices and other modules, requiring minimal modification to the original system, with low investment costs and high feasibility.

Claims

1. A peak-shaving operation method for an integrated heat pump heating system, wherein the integrated heat pump heating system comprises a primary heating network system, a heat pump system, and a secondary heating network system connected in sequence: The primary heating network system includes a primary heat exchanger (1), a primary heating network water supply pipeline (2), a secondary heat exchanger (7), an evaporator (8), and a primary heating network return water pipeline (3). The heat pump system includes an evaporator (8), a compressor (9), a condenser (10), and an expansion valve (11). The secondary heating network system includes a secondary heat exchange station heat exchanger (7), a condenser (10), a secondary heating network water supply pipeline (4), heat users (6), and a secondary heating network return water pipeline (5). The inlet end of the first heat exchanger (1) is connected to the steam extraction port of the intermediate pressure cylinder of the cogeneration unit; the outlet end of the first heat exchanger (1) is connected to the deaerator inlet of the cogeneration unit. The cold-side outlet of the first heat exchanger (1) is connected to the hot-side inlet of the second heat exchanger (7) via the primary heat network water supply pipeline (2); the hot-side outlet of the second heat exchanger (7) is connected to the hot-side inlet of the evaporator (8); the hot-side outlet of the evaporator (8) is connected to the cold-side inlet of the first heat exchanger (1) via the primary heat network return water pipeline (3); The cold side outlet of the evaporator (8) is connected to the inlet of the compressor (9); the outlet of the compressor (9) is connected to the hot side inlet of the condenser (10); the hot side outlet of the condenser (10) is connected to the inlet of the expansion valve (11); and the outlet of the expansion valve (11) is connected to the cold side inlet of the evaporator (8). The heat user (6) outlet on the hot side is split into two paths via the secondary heating network return water pipe (5). One path is connected to the cold side inlet of the condenser (10); the other path is connected to the cold side inlet of the heat exchanger (7) of the secondary heat exchange station. The cold side outlet of the condenser (10) is connected to the heat user (6) outlet on the hot side via the secondary heating network water supply pipe (4). The cold side outlet of the heat exchanger (7) of the secondary heat exchange station is connected to the heat user (6) outlet on the hot side via the secondary heating network water supply pipe (4). Its features are: The peak-shaving operation method is as follows: Utilizing the thermal inertia of the heating system, under a given heat load and peak-shaving maintenance time, when the required electrical load increases, the amount of steam extracted from the cogeneration unit into the first station heat exchanger (1) is increased; when the required electrical load decreases, the amount of steam extracted from the cogeneration unit into the first station heat exchanger (1) is decreased. The steam extraction rate of the cogeneration unit entering the first heat exchanger (1) is controlled based on the modeling calculation, including the following steps: Step 1: Establish a system model that takes into account the thermal inertia of the heating system, including a combined heat and power unit model, and dynamic models of the heating network, heat pumps and heat users (6); Step 2: Given the indoor temperature range required by the heat users (6) in the heating system; Step 3: Using the system model established in Step 1 and the indoor temperature range given in Step 2, calculate the time that can be used to maintain the indoor temperature requirements of heat users under different steam extraction rates of cogeneration units. Step 4: Calculate the required steam extraction volume of the cogeneration unit under different outdoor temperatures using the following formula; in: q v The volumetric heat capacity index for building heating, w / (m³) 3 ·°C); V For the volume of the building, m 3 ; T z The average indoor temperature of the building, in °C; T w Outdoor temperature, °C; D h The steam extraction rate of the combined heat and power unit is expressed in kg / s. △h The enthalpy difference between the steam extraction for heating and the return water of the cogeneration unit, in kJ / kg; Step 5: Repeat Step 3 under different outdoor temperatures to calculate the time that the combined heat and power unit can maintain the indoor temperature required by the heat user under different steam extraction rates at different outdoor temperatures. Step 6: Using the cogeneration unit model established in Step 1, calculate the electrical power of the cogeneration unit under different steam extraction rates; Step 7: Based on the peak shaving requirements, using the time required to maintain the indoor temperature of the heat users calculated in Step 5 and the electrical power calculated in Step 6, select the steam extraction rate that meets the peak shaving requirements for both the maintenance time and the electrical load.

2. The peak-shaving operation method of an integrated heat pump heating system according to claim 1, characterized in that: The indoor temperature range required by heat users (6) in the given heating system is 18-24℃.

3. The peak-shaving operation method of an integrated heat pump heating system according to claim 1, characterized in that: The refrigerant used in the heat pump system is R134a.

4. The peak-shaving operation method of an integrated heat pump heating system according to claim 1, characterized in that: Under the design conditions: the heating temperature of the primary heating network is 130℃, and the return water temperature of the primary heating network is 40℃; the heating temperature of the secondary heating network is 60℃, and the return water temperature of the secondary heating network is 45℃.

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