Multi-stage peak shaving system coupling deep geothermal energy storage with combined heat and power

Abstract

The present invention relates to the technical field of flexibility retrofitting for combined heat and power (CHP) units, and specifically relates to a multi-stage peak shaving system coupling deep geothermal energy storage with CHP. On the basis of long-term geothermal energy storage by aquifer thermal energy storage (ATES) units and hot well / cold well (HW / CW) pairs, combined with electric heat pump (EHP) units, the waste heat recovery of CHP units is realized, thereby improving the wind-solar power accommodation capacity of a power grid and the CHP peak shaving response speed; and integrating the EHP units with two-stage plate heat exchangers (HX1 / HX2) for coordinated heat storage and supply operation achieves three-stage deep peak shaving for CHP, thereby improving the CHP power generation peak shaving depth and expanding the CHP heat supply range. Overall, the wind-solar curtailment rate and the system operation cost are reduced, thereby achieving the applicability to large-scale high-penetration wind-solar power accommodation and deep peak shaving operation scenarios of CHP units.

Description

A deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system Technical fields:

[0001] This invention relates to the field of peak-shaving flexibility retrofitting technology for cogeneration units, specifically a deep geothermal energy storage coupled cogeneration multi-stage peak-shaving system. Background technology:

[0002] In the "heat-driven power generation" operation mode, the peak-shaving flexibility of combined heat and power (CHP) units is constrained by the heat-power decoupling capability, and they face many challenges in terms of renewable energy consumption, deep peak shaving, response speed, and multi-energy system synergistic optimization.

[0003] In terms of renewable energy consumption, the heating load under this model directly determines the power generation output. Especially during the winter heating season in northern China, the minimum output of thermal power units is significantly limited by the principle of "heat-driven power generation," resulting in insufficient peak-shaving capacity and difficulty in effectively coping with the fluctuations in new energy power generation. When wind and solar power generation is large, the units cannot quickly reduce their power generation output due to the constraints of heating demand, thus causing wind and solar curtailment.

[0004] Deep peak shaving also faces challenges. Currently, deep peak shaving requires the unit load rate to be reduced to below 30%, but low-load operation brings a series of problems: First, energy efficiency drops significantly, and equipment wear intensifies; second, combustion is unstable, which can easily lead to boiler coking, flameout, and other difficulties in stable combustion; third, when the load changes rapidly, the temperature difference between the cylinder and the rotor increases, which may shorten the equipment life; finally, when the load drops to the critical value, the amount of steam extracted decreases, which may not be able to meet the needs of the heating network, requiring reliance on thermal storage or backup heat sources.

[0005] In terms of response speed, traditional cogeneration units have a slow load regulation rate, making it difficult to match the rapid fluctuations of new energy sources. A CHP unit typically takes tens of minutes to rise from minimum load to full load (compared to about 30-60 minutes for a traditional coal-fired unit), while the power fluctuation cycle of wind and solar power can be as short as minutes (such as solar "ramp-up" events). Furthermore, the thermal inertia of hot water pipe networks causes heating regulation to be slower than electric regulation; the electric-heat-gas system requires coordinated response, which traditional decentralized control modes cannot meet the demands of rapid regulation. Therefore, it is necessary to improve response capabilities through control system optimization and flexibility upgrades.

[0006] Multi-energy system synergistic optimization also presents challenges. Although various technologies such as thermal storage tanks, electric boilers, and main steam auxiliary heating can be integrated, the system coupling is complex. At the same time, it is necessary to comprehensively optimize power peak regulation, heat supply and demand, economic efficiency, and environmental protection, and face the trade-off between renewable energy consumption and unit life loss (frequent load changes will shorten equipment life).

[0007] Therefore, the core of the peak-shaving flexibility transformation of cogeneration units lies in breaking the bottleneck of "heat and electricity decoupling" and realizing the transformation from "heat-driven power generation" to "electricity-heat interaction" mode through thermal / electric storage technology, unit equipment transformation and multi-energy synergistic optimization. Summary of the Invention:

[0008] The purpose of this invention is to provide a deep geothermal energy storage coupled with a multi-stage cogeneration (CHP) peak-shaving system. By combining an aquifer energy storage unit (ATES) with an electric heat pump unit (EHP) and a primary / secondary plate heat exchanger (HX1 / HX2), deep peak-shaving of the CHP system is achieved. This system not only effectively reduces the curtailment rate of wind and solar power generation but also significantly improves the deep peak-shaving capability of the CHP system.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A deep geothermal energy storage coupled with cogeneration and multi-stage peak-shaving system includes a cogeneration unit, an electric heat pump unit, an aquifer energy storage unit, a primary plate heat exchanger, a secondary plate heat exchanger, a power grid, and a heating network.

[0011] The condenser of the cogeneration unit is connected to the evaporator of the electric heat pump unit; the cogeneration unit is connected to both the power grid and the heating network; the primary condenser of the electric heat pump unit is connected to the heating network, and the secondary condenser of the electric heat pump unit is connected to the primary plate heat exchanger; the hot well group of the aquifer energy storage unit is connected to the secondary plate heat exchanger, and the cold well group of the aquifer energy storage unit is connected to the primary plate heat exchanger; the primary plate heat exchanger is connected to both the secondary condenser of the electric heat pump unit and the cold well group of the aquifer energy storage unit; the secondary plate heat exchanger is connected to the cogeneration unit, the primary plate heat exchanger, and the hot well group of the aquifer energy storage unit; the power grid is simultaneously connected to the cogeneration unit, the wind and solar power plant, and the electric heat pump unit; the heating network is simultaneously connected to the primary condenser, the primary plate heat exchanger, and the secondary plate heat exchanger of the cogeneration unit and the electric heat pump unit.

[0012] The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system described above further includes:

[0013] The condenser of the cogeneration unit is connected to the evaporator of the electric heat pump unit, providing low-temperature waste heat resources for the electric heat pump unit; the cogeneration unit is connected to the power grid and the heating network respectively, providing both electricity and heat.

[0014] The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system described above further includes:

[0015] The electric heat pump unit includes one set of evaporators and two sets of condensers. The evaporators are connected to the condensers of the cogeneration unit to recover the condensing heat of the cogeneration unit. The primary condenser is connected to the heating network to provide a primary peak-shaving heat source. The secondary condenser is connected to the primary heat exchanger to provide a secondary peak-shaving heat source and a heat source for the aquifer energy storage unit. The electric heat pump unit is connected to the power grid to absorb the excess wind and solar power generated by the grid and convert it into heat, thereby realizing the heat storage of the aquifer energy storage unit, the absorption of wind and solar power, and the peak-shaving of the cogeneration unit.

[0016] The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system described above further includes:

[0017] The aquifer energy storage unit includes a group of hot wells and a group of cold wells; the hot well group is connected to a secondary plate heat exchanger to provide a three-stage peak-shaving heat source and a heat storage channel; the cold well group is connected to a primary plate heat exchanger to provide a heat storage source.

[0018] The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system described above further includes:

[0019] The primary plate heat exchanger is connected to the secondary condenser of the electric heat pump unit and the cold well group respectively; through heat exchange with the electric heat pump unit, it provides a heat source for geothermal energy storage of the cold well group and peak shaving of the heating network.

[0020] The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system described above further includes:

[0021] The secondary plate heat exchanger is connected to the cogeneration unit, the primary plate heat exchanger, and the hot well group, respectively. During the heat storage period, it provides a heat source for the aquifer energy storage unit through heat exchange with the cogeneration unit. During the heating period, it provides a peak-shaving heat source for the heating network through heat exchange with the hot well group.

[0022] The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system described above further includes:

[0023] The power grid is connected to the combined heat and power (CHP) unit, the wind and solar power plant, and the electric heat pump unit, respectively, to supply power to the CHP unit and the wind and solar power plant, and to provide power to the electric heat pump unit.

[0024] The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system described above further includes:

[0025] The heating network is simultaneously connected to the primary condenser, primary plate heat exchanger, and secondary plate heat exchanger of the combined heat and power unit and the electric heat pump unit, providing a basic heat source and a tertiary peak-shaving heat source for user loads.

[0026] The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system described above further includes:

[0027] It also includes control valves, which are connected to the inlet and outlet pipelines of the cogeneration unit, the electric heat pump unit, the primary plate heat exchanger, and the secondary plate heat exchanger. The control valves achieve different operating modes of the system by switching on / off states.

[0028] Compared with the prior art, the advantages of this invention are as follows:

[0029] 1) Significantly enhanced thermal storage and peak-shaving capabilities: Utilizing underground aquifer ATES for efficient thermal storage, while simultaneously achieving close coupling between CHP, EHP, and two-stage plate heat exchangers. This innovative approach not only successfully implemented multiple operating models and three-stage deep peak shaving, but also significantly increased the thermal storage capacity of ATES and further enhanced the peak-shaving range of CHP.

[0030] 2) Significantly increased wind and solar power absorption capacity: Through the ingenious coupling of EHP and CHP, the system can effectively absorb wind and solar power and recover the low-temperature condensation heat generated by CHP. This measure not only significantly improves the operating energy efficiency of CHP, but also effectively increases the overall absorption capacity of the system for wind and solar power, thereby greatly reducing the wind and solar power curtailment rate.

[0031] 3) A qualitative leap in peak shaving response speed: The synergistic operation of EHP and the two-stage plate heat exchanger enables EHP to rapidly absorb wind and solar power. This not only improves the electrothermal conversion efficiency but also significantly shortens the peak shaving response time and effectively reduces the thermal inertia effect during the CHP peak shaving process. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 is a schematic diagram of a deep geothermal energy storage coupled cogeneration multi-stage peak shaving system in an embodiment of the present invention.

[0034] Figure 2 is a simulation result diagram of the deep geothermal energy storage coupled cogeneration multi-stage peak shaving system in the embodiment of the present invention.

[0035] In the diagram: 1. Combined heat and power unit; 2. Electric heat pump unit; 3. Aquifer energy storage unit; 4. Primary plate heat exchanger; 5. Secondary plate heat exchanger; 6. Power grid; 7. Heating network; v1~v13, control valves. Detailed implementation method:

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0037] Example:

[0038] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, in the embodiments of this utility model are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those explicitly listed, but may include those not explicitly listed.

[0039] In the description of this utility model, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0040] Figure 1 is a schematic diagram of the deep geothermal energy storage coupled with cogeneration multi-stage peak shaving system in an embodiment of the present invention; Figure 2 is a simulation result diagram of the deep geothermal energy storage coupled with cogeneration multi-stage peak shaving system in an embodiment of the present invention. As shown in Figures 1 and 2...

[0041] The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system provided by this invention is shown in Figure 1. The system mainly consists of a water-containing cogeneration unit (CHP) 1, an electric heat pump unit (EHP) 2, an energy storage unit (ATES) 3, a primary plate heat exchanger (HX1) 4, a secondary plate heat exchanger (HX2) 5, a power grid (PG) 6, a heating network (HG) 7, and control valves (v1 to v13), etc.

[0042] The condenser 11 of the cogeneration unit 1 is connected to the evaporator 21 of the EHP to provide low-temperature waste heat resources for the EHP; it is also connected to the power grid 6 and the heating network 7 respectively, providing both electricity and heat.

[0043] The electric heat pump unit 2 includes one evaporator 21 and two condensers (22 / 23); the evaporator 21 is connected to the CHP condenser 11 to recover the heat of CHP condensation; the first-stage condenser 22 is connected to the heating network 6 to provide a first-stage peak-shaving heat source; the second-stage condenser 23 is connected to the first-stage heat exchanger 4 to provide a second-stage peak-shaving heat source and a heat source for ATES thermal storage; the EHP is connected to the power grid 6 to absorb the excess wind and solar power generated by the power grid 6 and convert it into heat, thereby realizing ATES thermal storage, wind and solar power absorption and CHP peak shaving.

[0044] The layered energy storage unit 3 includes a group of hot wells 31 and a group of cold wells 32; the group of hot wells 31 is connected to the secondary plate heat exchanger 5, providing a third-stage peak-shaving heat source and a heat storage channel; the group of cold wells 32 is connected to the primary plate heat exchanger 4, providing a heat storage water source.

[0045] The primary plate heat exchanger 4 is connected to the EHP secondary condenser 23, the heating network 7, the secondary plate heat exchanger 5, and the cold well group 32, respectively. Through heat exchange with the EHP secondary condenser 23, it provides a heat source for geothermal energy storage in the cold well group 32 and peak shaving in the heating network 7.

[0046] The secondary plate heat exchanger 5 is connected to the cogeneration unit 1, the primary plate heat exchanger 4, and the hot well group 31 respectively; during the heat storage period, it provides a heat source for ATES through heat exchange with CHP; during the heating period, it provides a third-level peak-shaving heat source for the heating network 7 through heat exchange with the hot well group 31.

[0047] Power grid 6 is also connected to cogeneration unit 1, wind and solar power plant, and electric heat pump unit 2, which respectively transmit power to CHP and wind and solar power plant to provide power for EHP.

[0048] Heating network 7 is also connected to cogeneration unit 1, EHP's primary condenser 22, primary plate heat exchanger 4, and secondary plate heat exchanger 5, providing basic heat source and tertiary peak-shaving heat source for user loads.

[0049] The control valves (v1~v13) are connected to the inlet and outlet pipelines of equipment such as the cogeneration unit 1, the electric heat pump unit 2, the primary plate heat exchanger 4, and the secondary plate heat exchanger 5. By switching the switch status, the system can operate in five modes: ATES heat storage, power consumption, primary peak shaving, secondary peak shaving, and tertiary peak shaving.

[0050] 1) ATES thermal storage operation mode

[0051] The CHP operates at maximum power output, transferring excess cogeneration heat to a secondary plate heat exchanger 5 to heat geothermal water from the ATES cold well cluster 32, thus achieving ATES thermal storage and providing heat reserves for peak shaving. The valve on / off status is shown in the table below:

[0052] 2) Power Consumption Operation Mode

[0053] Grid 6 transmits excess power from wind and solar power plants, which EHP rapidly absorbs. EHP utilizes grid power to recover waste heat from CHP condenser 11, transferring this heat to geothermal water from ATES cold well cluster 32 via EHP's second condenser 23 and primary plate heat exchanger 4. Finally, the heat is injected into hot well cluster 31 to achieve ATES thermal storage, providing heat reserves for peak shaving. Valve on / off states are shown in the table below.

[0054] 3) Level 1 peak shaving operation mode

[0055] CHP reduces power generation and heat supply simultaneously. Grid 6 prioritizes providing a channel for excess power generated by wind and solar power plants. EHP utilizes the wind and solar power from the grid to recover waste heat from CHP condenser 11, and provides first-level peak-shaving heat to heating network 7 through the first set of condensers 22 of EHP, reducing the heating and power generation output of CHP, and enabling rapid response to absorption and peak-shaving operation. The valve switching status is shown in the table below:

[0056] 4) Level 2 peak shaving operation mode

[0057] CHP continues to reduce power generation while simultaneously decreasing heat supply. Grid 6 prioritizes increasing the capacity of excess power channels from wind and solar power plants. EHP utilizes grid wind and solar power to recover waste heat from CHP condenser 11. Through the first set of condensers 22 and the second set of condensers 23 of EHP, it simultaneously provides two levels of peak-shaving heat to heating network 7, further reducing CHP's heating and power generation output and improving its peak-shaving operation range. The valve switching status is shown in the table below:

[0058] 5) Level 3 Peak Shaving Operation Mode

[0059] CHP minimizes power generation while reducing heat supply. Grid 6 maximizes the transmission of excess power from wind and solar power plants. EHP utilizes the grid's wind and solar power to recover waste heat from CHP condenser 11. Heat is simultaneously supplied through EHP's first set of condensers 22, second set of condensers 23, and ATES thermal storage combined with primary / secondary plate heat exchangers 4 / 5, providing three levels of peak-shaving heat to heating network 7. This minimizes CHP's heating and power generation output, maximizing the depth of peak-shaving operation. Valve on / off states are shown in the table below.

[0060] It should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0061] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0062] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0063] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A deep geothermal energy storage coupled with cogeneration and multi-stage peak-shaving system, characterized in that: The system includes a combined heat and power (CHP) unit, an electric heat pump unit, an aquifer energy storage unit, a primary plate heat exchanger, a secondary plate heat exchanger, a power grid, and a heating network. The condenser of the CHP unit is connected to the evaporator of the electric heat pump unit. The CHP unit is connected to both the power grid and the heating network. The primary condenser of the electric heat pump unit is connected to the heating network, and the secondary condenser of the electric heat pump unit is connected to the primary plate heat exchanger. The thermal well group of the aquifer energy storage unit is connected to the secondary plate heat exchanger. The cold well group of the unit is connected to the primary plate heat exchanger; the primary plate heat exchanger is connected to the secondary condenser of the electric heat pump unit and the cold well group of the aquifer energy storage unit; the secondary plate heat exchanger is connected to the hot well group of the cogeneration unit, the primary plate heat exchanger and the aquifer energy storage unit; the power grid is simultaneously connected to the cogeneration unit, the wind and solar power plant and the electric heat pump unit; the heating network is simultaneously connected to the primary condenser, the primary plate heat exchanger and the secondary plate heat exchanger of the cogeneration unit and the electric heat pump unit.

2. The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system according to claim 1, characterized in that: The condenser of the cogeneration unit is connected to the evaporator of the electric heat pump unit, providing low-temperature waste heat resources for the electric heat pump unit; the cogeneration unit is connected to the power grid and the heating network respectively, providing both electricity and heat.

3. The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system according to claim 1, characterized in that: The electric heat pump unit includes one set of evaporators and two sets of condensers. The evaporators are connected to the condensers of the cogeneration unit to recover the condensing heat of the cogeneration unit. The primary condenser is connected to the heating network to provide a primary peak-shaving heat source. The secondary condenser is connected to the primary heat exchanger to provide a secondary peak-shaving heat source and a heat source for the aquifer energy storage unit. The electric heat pump unit is connected to the power grid to absorb the excess wind and solar power generated by the grid and convert it into heat, thereby realizing the heat storage of the aquifer energy storage unit, the absorption of wind and solar power, and the peak-shaving of the cogeneration unit.

4. The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system according to claim 1, characterized in that: The aquifer energy storage unit includes a group of hot wells and a group of cold wells; the hot well group is connected to a secondary plate heat exchanger to provide a three-stage peak-shaving heat source and a heat storage channel; the cold well group is connected to a primary plate heat exchanger to provide a heat storage source.

5. The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system according to claim 1, characterized in that: The primary plate heat exchanger is connected to the secondary condenser of the electric heat pump unit and the cold well group respectively; through heat exchange with the electric heat pump unit, it provides a heat source for geothermal energy storage of the cold well group and peak shaving of the heating network.

6. The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system according to claim 1, characterized in that: The secondary plate heat exchanger is connected to the cogeneration unit, the primary plate heat exchanger, and the hot well group, respectively. During the heat storage period, it provides a heat source for the aquifer energy storage unit through heat exchange with the cogeneration unit. During the heating period, it provides a peak-shaving heat source for the heating network through heat exchange with the hot well group.

7. The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system according to claim 1, characterized in that: The power grid is connected to the combined heat and power (CHP) unit, the wind and solar power plant, and the electric heat pump unit, respectively, to supply power to the CHP unit and the wind and solar power plant, and to provide power to the electric heat pump unit.

8. The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system according to claim 1, characterized in that: The heating network is simultaneously connected to the primary condenser, primary plate heat exchanger, and secondary plate heat exchanger of the combined heat and power unit and the electric heat pump unit, providing a basic heat source and a tertiary peak-shaving heat source for user loads.

9. The deep geothermal energy storage coupled with cogeneration multi-stage peak-shaving system according to claim 1, characterized in that: It also includes control valves, which are connected to the inlet and outlet pipelines of the cogeneration unit, the electric heat pump unit, the primary plate heat exchanger, and the secondary plate heat exchanger. The control valves achieve different operating modes of the system by switching on / off states.

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