Energy storage type heat pump-cogeneration system

Abstract

The invention discloses an energy storage type heat pump-heat and power cogeneration system, and belongs to the technical field of energy storage. Comprising a heat pump cycle, a power generation cycle and a storage tank, and when electric energy is sufficient, the system operates in a reverse Rankine cycle heat pump mode; when the electric energy is in shortage, the system operates in a forward circulation discharge mode. According to the system, high electricity-electricity conversion efficiency can be achieved, residual energy can be converted into heat to be stored to achieve heat supply, and therefore ultrahigh energy utilization efficiency is achieved.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to an energy storage heat pump-combined heat and power system and an operating method thereof. Background Art

[0002] The utilization of renewable energy continues to rise year by year. However, current renewable energy generation, such as solar and wind power, suffers from intermittency and volatility, significantly impacting the safety and stability of power systems. Energy storage is a key technology for addressing the volatility and intermittency of renewable energy. Existing energy storage technologies primarily include pumped hydro, compressed air, and battery storage. Pumped hydro and compressed air storage are susceptible to geographical constraints, while battery storage technology is limited by processing technology, performance degradation, and cost.

[0003] Currently, research on heat pump energy storage systems in China is relatively limited, and research on their use in combined heat and power (CHP) is even more scarce. According to research, the efficiency of current heat pump energy storage systems generally ranges from 40% to 60%, meaning that only half of the energy is effectively utilized, while the other half is lost to the environment, resulting in waste. In light of this, the present invention proposes an energy storage heat pump-CHP system designed to recycle this lost heat for heating.

[0004] The energy storage heat pump-cogeneration system proposed in this invention consists of a heat engine cycle, a heat pump cycle, and a storage tank. During the energy storage cycle, electrical energy is consumed to drive a reverse power cycle, raising some of the heat energy below ambient temperature to a high temperature and storing it, thereby generating high-temperature and low-temperature heat energy relative to the ambient temperature. During the energy release cycle, this stored high-temperature and low-temperature heat energy is converted into mechanical energy through a forward power cycle, thereby driving power generation.

[0005] In today's context, traditional energy storage methods have low energy efficiency. However, this technology, through cogeneration, improves overall energy utilization, improves environmental quality, and promotes energy conservation and emission reduction. This method saves more fuel than generating electricity and heat separately. Furthermore, cogeneration improves energy efficiency by up to over 120%. Summary of the Invention

[0006] The purpose of the present invention is to propose an energy storage heat pump-combined heat and power system, which can realize stable electricity-to-electricity round-trip efficiency while converting the remaining energy into low-grade thermal energy for utilization, thereby ultimately achieving higher energy utilization efficiency.

[0007] The energy storage heat pump-heat and power combined supply system proposed in the present invention comprises three parts: a heat pump cycle, a power generation cycle and a storage tank; the heat pump cycle comprises a compressor / expander (1), a first three-way valve (3), a high-temperature heat exchanger 1 (4), a low-temperature heat exchanger (8), an HP regenerator (9), a throttle valve (10), a second three-way valve (11), a third three-way valve (13) and an HP / HE environment heat exchanger (12); the power generation cycle comprises a high-temperature heat exchanger 2 (2), a first three-way valve (3), a compressor / expander (1), an HE regenerator (15), a third three-way valve (13), an HE environment heat exchanger (12), a second three-way valve (11) and a pump (14); and the storage tank comprises a high-temperature heat storage tank 1 (5), a high-temperature heat storage tank 2 (6) and a low-temperature heat storage tank (7).

[0008] The port B of the compressor / expander (1) is connected to the port a of the first three-way valve (3); the port c of the first three-way valve (3) is connected to the port a of the second three-way valve (11) via a heat exchange channel of the high-temperature heat exchanger 1 (4), a heat exchange channel of the low-temperature heat exchanger (8), a heat exchange channel of the HP regenerator (9), and the throttle valve (10) in sequence; the port c of the second three-way valve (11) is connected to the port a of the third three-way valve (13) via a heat exchange channel of the HP / HE environment heat exchanger (12); the compressor / expander (1) Port A is connected to port C of the third three-way valve (13) via another heat exchange channel of the HP regenerator (9); port B of the third three-way valve (13) is connected to port A of the compressor / expander (1) via a heat exchange channel of the HE regenerator (15); port B of the second three-way valve (11) is connected to port B of the first three-way valve (3) via a pump (14), another heat exchange channel of the HE regenerator (15), and a heat exchange channel of the high-temperature heat exchanger 2 (2); another heat exchange channel of the HP / HE environmental heat exchanger (12) is connected to the environment. The inlet of another heat exchange channel of the high-temperature heat exchanger 2 (2), the high-temperature heat storage tank 1 (5), another heat exchange channel of the high-temperature heat exchanger 1 (4), the high-temperature heat storage tank 2 (6), and the outlet of another heat exchange channel of the high-temperature heat exchanger 2 (2) are connected in sequence to form a heat storage system; another heat exchange channel of the low-temperature heat exchanger (8), the low-temperature heat storage tank (7), and the heat user are connected to form a user direct heat use system.

[0009] The heat storage system can be equipped with a liquid-driven flow device as needed.

[0010] The working principle of the system of the present invention in the process of storing and discharging electricity is described below. Figure 1 The triangle arrows represent the heat pump cycle, and the dovetail arrows represent the power generation cycle. Both the charging and discharging cycles use transcritical CO2 as the circulating working fluid and thermal oil as the heat storage medium.

[0011] When the electric energy is sufficient, the system operates in the heat pump mode of the reverse Rankine cycle; at this time, the first three-way valve (3) ports a and c are opened and port b is closed, the second three-way valve (11) ports a and c are opened and port b is closed, and the third three-way valve (13) ports a and c are opened and port b is closed; the electric energy drives the compressor / expander (1) to operate, at this time the compressor / expander (1) acts as a compressor, and the HP / HE environmental heat exchanger (12) acts as an HP environmental heat exchanger; the low-temperature and low-pressure carbon dioxide working fluid absorbs the energy to be stored in the HP environmental heat exchanger to a normal temperature and low-pressure state, and after leaving the HP environmental heat exchanger, the working fluid enters the HP regenerator (9) to perform heat exchange with the low-temperature working fluid discharged from the high-temperature heat exchanger 1 (4) and the low-temperature heat exchanger (8) to a superheated state, and then enters The working fluid enters the compressor and is compressed into a high-temperature and high-pressure gas; the working fluid leaves the compressor and enters the high-temperature heat exchanger 1 (4) and the low-temperature heat exchanger (8) in turn, where it performs countercurrent heat exchange with the heat storage medium fluid, that is, the working fluid releases heat and the temperature decreases, while the heat storage medium fluid absorbs heat and the temperature increases; the heat released by the working fluid in the high-temperature heat exchanger 1 (4) is absorbed and stored by the heat storage medium fluid to drive the positive heat engine cycle, and the heat released in the low-temperature heat exchanger (8) is used for heating; thereafter, the high-temperature working fluid enters the HP regenerator (9) and performs heat exchange with the low-temperature working fluid to become a normal temperature and high-pressure state, and then passes through the throttle valve (10) to become a low-temperature and low-pressure state, and then enters the HP ambient heat exchanger (12) to absorb the energy to be stored, completing a closed cycle;

[0012] When there is a power shortage, the system operates in a forward cycle discharge mode; at this time, the first three-way valve (3) has ports a and b open and port c closed, the second three-way valve (11) has ports b and c open and port a closed, and the third three-way valve (13) has ports a and b open and port c closed; the compressor / expander (1) acts as an expander, and the HP / HE environment heat exchanger (12) acts as an HE environment heat exchanger; the normal temperature and low pressure carbon dioxide working fluid absorbs low temperature cold energy in the HE environment heat exchanger to a low temperature and low pressure state, and then the working fluid is pressurized by the pump (14) and enters the HE regenerator (15), and in the HE regenerator (15) and the high-temperature working fluid discharged from the expander for heat exchange, and then enters the high-temperature heat exchanger 2 (2) to perform countercurrent heat exchange with the heat storage medium fluid, that is, the temperature of the heat storage medium fluid gradually decreases as it releases heat, and the temperature of the working fluid gradually increases as it absorbs heat; the high-temperature and high-pressure working fluid enters the expander, driving the impeller to rotate at high speed to generate electricity, and the temperature and pressure of the working fluid decrease in this process; the normal temperature and pressure working fluid discharged from the expander enters the HE regenerator (15) and exchanges heat with the low-temperature working fluid discharged from the HE environmental heat exchanger, and then returns to the HE environmental heat exchanger to release heat energy again, completing a closed cycle.

[0013] The device completes the charging and discharging processes through reverse and forward cycles, respectively, enabling the storage and retrieval of electrical energy, and also incorporates a heat recovery process to improve cycle efficiency. High-quality thermal energy is used for power generation, achieving highly efficient electricity-to-electricity conversion, while low-quality thermal energy is used for heating, achieving cogeneration.

[0014] The present invention has the following advantages:

[0015] 1. During the construction phase of the system, considering that a certain amount of waste heat will inevitably be generated during the circulation process, in order to effectively utilize this waste heat resource, the present invention provides a heat recovery device during the circulation process, which can reintroduce the generated waste heat into the circulation process, thereby improving the circulation efficiency and achieving energy-saving effects.

[0016] 2. The system proposed in this invention is based on the transcritical CO2 Rankine cycle and operates at a lower temperature, avoiding the high cost problem caused by high temperature and high pressure. CO2 is used as the circulating working fluid, which is non-toxic, stable and easy to obtain. It has a high thermal conductivity and specific heat capacity in the critical state. CO2 is almost incompressible near the critical point.

[0017] When the compressor (1) operates near the critical point, the compression power consumption can be effectively reduced, thereby improving the cycle efficiency.

[0018] 3. This invention proposes an energy storage heat pump combined heat and power system. This system utilizes a heat pump cycle to store electricity when sufficient electricity is available and to export it during peak hours. In terms of efficiency, this heat pump combined heat and power system maintains approximately 40% electricity-to-electricity conversion efficiency while converting excess energy into low-grade thermal energy for utilization, ultimately achieving an energy utilization efficiency of up to 120%.

[0019] 4. The present invention has two major application scenarios. On the one hand, it can effectively absorb the volatility of renewable energy such as wind energy and solar energy, store the fluctuating renewable energy using energy storage technology, and convert it into stable and adjustable electricity; on the other hand, if this technology is promoted in northern my country, it can also convert renewable energy that is not converted into electricity and part of the heat energy absorbed from the environment into low-grade energy for heating, thereby realizing a zero-carbon and clean supply of heat energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the overall structure of the present invention

[0021] The figure shows:

[0022] Compression / expansion machine (1) First three-way valve (3)

[0023] High temperature heat exchanger 1(4) Low temperature heat exchanger(8)

[0024] HP regenerator (9) Throttle valve (10)

[0025] Second three-way valve (11) HP / HE environment heat exchanger (12)

[0026] Third three-way valve (13) High temperature heat storage tank 1 (5)

[0027] High temperature heat storage tank 2 (6) Low temperature heat storage tank (7)

[0028] High temperature heat exchanger 2 (2) HE regenerator (15)

[0029] Pumps (14) DETAILED DESCRIPTION

[0030] This invention proposes an energy storage heat pump-combined heat and power system and its operating method. This system uses reverse and forward cycles to complete the charging and discharging processes, respectively, to store and utilize electrical energy. This system also incorporates a heat recovery process to improve cycle efficiency. High-quality thermal energy is used for power generation, achieving highly efficient electricity conversion, while low-quality thermal energy is used for heating, achieving combined heat and power generation.

[0031] This embodiment provides an energy storage heat pump-heat and power combined supply system, such as Figure 1 As shown, the device consists of three parts: a heat pump circuit, a power generation circuit, and a storage tank. The heat pump circuit consists of a compressor / expander (1), a high-temperature heat exchanger 1 (4), a low-temperature heat exchanger (8), an HP regenerator (9), a throttle valve (10), and an HP / HE environment heat exchanger (12); the power generation circuit consists of a high-temperature heat exchanger 2 (2), a compressor / expander (1), an HE regenerator (15), an HP / HE environment heat exchanger (12), and a pump (14). The operating method of the device includes a charging step and a discharging step.

[0032] The charging process of this embodiment is as follows Figure 1As shown by the triangular arrows: the photovoltaic power, wind power or grid valley power to be absorbed drives the compressor / expander (1) to operate. At this time, the compressor / expander (1) acts as a compressor and the HP / HE environmental heat exchanger acts as an HP environmental heat exchanger. The low-temperature and low-pressure carbon dioxide working fluid absorbs the energy to be stored in the HP environmental heat exchanger to a normal temperature and low pressure state. After leaving the HP environmental heat exchanger, the working fluid enters the HP regenerator (9) and exchanges heat with the low-temperature working fluid discharged from the high-temperature heat exchanger 1 (4) and the low-temperature heat exchanger (8) to a superheated state. Then, it enters the compressor / expander (1) and is compressed into a high-temperature and high-pressure gas. The working fluid leaves the compressor (1) and enters the high-temperature heat exchanger 1 (4) and the low-temperature heat exchanger (8) in turn, where it performs countercurrent heat exchange with the heat storage medium fluid, that is, the working fluid releases heat and the temperature decreases, while the heat storage medium fluid absorbs heat and the temperature increases. The heat released by the working fluid in the high-temperature heat exchanger 1 (4) is absorbed by the heat storage medium fluid and stored to drive the positive heat engine cycle, while the heat released in the low-temperature heat exchanger (8) is used for heating. Afterwards, the high-temperature working fluid enters the HP regenerator (9) to exchange heat with the low-temperature working fluid and changes to a normal temperature and high pressure state. It then passes through the throttle valve (10) to a low temperature and low pressure state and then enters the HP ambient heat exchanger to absorb the energy to be stored, completing a closed cycle.

[0033] The discharge process of this embodiment is as follows Figure 1 As shown by the dovetail arrows: the compressor / expander (1) acts as an expander, and the HP / HE ambient heat exchanger acts as an HE ambient heat exchanger. The normal temperature and low pressure carbon dioxide working fluid absorbs low temperature cold energy in the HE ambient heat exchanger to a low temperature and low pressure state. The working fluid is then pressurized by the pump (14) and enters the HE regenerator (15) to exchange heat with the high temperature working fluid discharged from the expander, and then enters the high temperature heat exchanger 2 (2) to perform countercurrent heat exchange with the heat storage medium fluid, that is, the temperature of the heat storage medium fluid gradually decreases as it releases heat, and the temperature of the working fluid gradually increases as it absorbs heat. The high temperature and high pressure working fluid enters the expander, driving the impeller to rotate at high speed to generate electricity, and the temperature and pressure of the working fluid decrease during this process. The normal temperature and pressure working fluid discharged from the expander enters the HE regenerator (15) to exchange heat with the low temperature working fluid discharged from the HE ambient heat exchanger, and then returns to the HE ambient heat exchanger (12) to release heat energy again, completing a closed cycle.

[0034] In this embodiment, the system's electric-to-electric round-trip efficiency can be stabilized at around 40%, while the energy utilization efficiency can reach a maximum of over 120%. This embodiment proposes the use of transcritical CO2 as a working fluid. Compared to argon, helium, nitrogen, etc., CO2 is more stable and readily available, and has a higher thermal conductivity and specific heat capacity in the critical state. CO2 is almost incompressible near the critical point. When the compressor operates near the critical point, it can effectively reduce compression power consumption, thereby improving cycle efficiency.

Claims

1. An energy storage heat pump-combined heat and power system, characterized in that: The system includes three parts: a heat pump cycle, a power generation cycle and a storage tank; the heat pump cycle includes a compressor / expander (1), a first three-way valve (3), a high-temperature heat exchanger 1 (4), a low-temperature heat exchanger (8), an HP regenerator (9), a throttle valve (10), a second three-way valve (11), a third three-way valve (13) and an HP / HE environment heat exchanger (12); the power generation cycle includes a high-temperature heat exchanger 2 (2), a first three-way valve (3), a compressor / expander (1), an HE regenerator (15), a third three-way valve (13), an HP / HE environment heat exchanger (12), a second three-way valve (11) and a pump (14); the storage tank includes a high-temperature heat storage tank 1 (5), a high-temperature heat storage tank 2 (6) and a low-temperature heat storage tank (7); The B port of the compressor / expander (1) is connected to the a port of the first three-way valve (3); the c port of the first three-way valve (3) is connected to the a port of the second three-way valve (11) via a heat exchange channel of the high-temperature heat exchanger 1 (4), a heat exchange channel of the low-temperature heat exchanger (8), a heat exchange channel of the HP regenerator (9), and the throttle valve (10) in sequence; the c port of the second three-way valve (11) is connected to the a port of the third three-way valve (13) via a heat exchange channel of the HP / HE environment heat exchanger (12); the A port of the compressor / expander (1) is connected to the c port of the third three-way valve (13) via another heat exchange channel of the HP regenerator (9); the b port of the third three-way valve (13) is connected to the b port of the third three-way valve (13) via a heat exchange channel of the HE regenerator (15). The port A of the compression / expansion machine (1) is connected; the port b of the second three-way valve (11) is connected to the port b of the first three-way valve (3) via the pump (14), another heat exchange channel of the HE regenerator (15), and a heat exchange channel of the high-temperature heat exchanger 2 (2); the other heat exchange channel of the HP / HE environmental heat exchanger (12) is connected to the environment; the inlet of the other heat exchange channel of the high-temperature heat exchanger 2 (2), the high-temperature heat storage tank 1 (5), another heat exchange channel of the high-temperature heat exchanger 1 (4), the high-temperature heat storage tank 2 (6), and the outlet of the other heat exchange channel of the high-temperature heat exchanger 2 (2) are connected in sequence to form a heat storage system; the other heat exchange channel of the low-temperature heat exchanger (8), the low-temperature heat storage tank (7), and the heat user are connected to form a user direct heat use system.

2. The energy storage heat pump-cogeneration system according to claim 1, characterized in that: The operating modes include the following: When the electric energy is sufficient, the system operates in the heat pump mode of the reverse Rankine cycle; at this time, the first three-way valve (3) has ports a and c opened and port b closed, the second three-way valve (11) has ports a and c opened and port b closed, and the third three-way valve (13) has ports a and c opened and port b closed; the electric energy drives the compressor / expander (1) to operate, at this time the compressor / expander (1) acts as a compressor, and the HP / HE environmental heat exchanger (12) acts as an HP environmental heat exchanger; the low-temperature and low-pressure carbon dioxide working fluid absorbs the energy to be stored in the HP environmental heat exchanger to a normal temperature and low-pressure state, and after leaving the HP environmental heat exchanger, enters the HP regenerator (9) to perform heat exchange with the low-temperature working fluid discharged from the high-temperature heat exchanger 1 (4) and the low-temperature heat exchanger (8) to an overheated state, Then it enters the compressor and is compressed into a high-temperature and high-pressure gas; the working fluid leaves the compressor and enters the high-temperature heat exchanger 1 (4) and the low-temperature heat exchanger (8) in turn, where it performs countercurrent heat exchange with the heat storage medium fluid, that is, the working fluid releases heat and the temperature decreases, while the heat storage medium fluid absorbs heat and the temperature increases; the heat released by the working fluid in the high-temperature heat exchanger 1 (4) is absorbed and stored by the heat storage medium fluid to drive the positive heat engine cycle, and the heat released in the low-temperature heat exchanger (8) is used for heating; thereafter, the high-temperature working fluid enters the HP regenerator (9) and performs heat exchange with the low-temperature working fluid to become a normal temperature and high-pressure state, and then passes through the throttle valve (10) to become a low-temperature and low-pressure state, and then enters the HP ambient heat exchanger to absorb the energy to be stored, completing a closed cycle; When there is a power shortage, the system operates in a forward cycle discharge mode; at this time, the first three-way valve (3) has ports a and b open and port c closed, the second three-way valve (11) has ports b and c open and port a closed, and the third three-way valve (13) has ports a and b open and port c closed; the compressor / expander (1) acts as an expander, and the HP / HE environment heat exchanger (12) acts as an HE environment heat exchanger; the normal temperature and low pressure carbon dioxide working fluid absorbs low temperature cold energy in the HE environment heat exchanger to a low temperature and low pressure state, and then the working fluid is pressurized by the pump (14) and enters the HE regenerator (15), and in the HE regenerator (15) and the high-temperature working fluid discharged from the expander for heat exchange, and then enters the high-temperature heat exchanger 2 (2) to perform countercurrent heat exchange with the heat storage medium fluid, that is, the temperature of the heat storage medium fluid gradually decreases as it releases heat, and the temperature of the working fluid gradually increases as it absorbs heat; the high-temperature and high-pressure working fluid enters the expander, driving the impeller to rotate at high speed to generate electricity, and the temperature and pressure of the working fluid decrease in this process; the normal temperature and pressure working fluid discharged from the expander enters the HE regenerator (15) and exchanges heat with the low-temperature working fluid discharged from the HE environmental heat exchanger, and then returns to the HE environmental heat exchanger to release heat energy again, completing a closed cycle.

3. The energy storage heat pump-cogeneration system according to claim 2, characterized in that: Both the charging and discharging cycles use transcritical CO2 as the circulating working fluid and thermal oil as the heat storage medium.

4. The energy storage heat pump-cogeneration system according to claim 2, characterized in that: The charging and discharging processes are completed through reverse and forward cycles respectively, realizing the storage and use of electric energy, and the heat recovery process is added to improve the cycle efficiency; high-grade thermal energy is used for power generation to achieve high-efficiency electricity-to-electricity conversion, while low-grade thermal energy is used for heating to achieve cogeneration of heat and power.

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