A carbon dioxide solar thermal power generation system and method equipped with phase change thermal storage

Abstract

This invention discloses a carbon dioxide solar thermal power generation system and method equipped with phase change thermal storage, including a concentrating solar collector system, a thermal storage and heat exchange system, a CO2 power generation system, and a photovoltaic power generation system. The concentrating solar collector system includes a collector; the thermal storage and heat exchange system includes a phase change thermal storage heater, a molten salt-CO2 heat exchanger, and a molten salt heat transfer tank. The phase change thermal storage heater is connected to the molten salt heat transfer tank via the molten salt-CO2 heat exchanger. The outlet of the molten salt heat transfer tank is divided into two paths: one connected to the phase change thermal storage heater, and the other connected to the collector. The collector is also connected to the phase change thermal storage heater. The CO2 power generation system is connected to the molten salt-CO2 heat exchanger, and the photovoltaic power generation system is connected to the phase change thermal storage heater. This invention uses phase change energy storage as the energy storage system for the CO2 solar thermal power generation system, which can significantly reduce the amount of thermal storage medium used. Phase change energy storage can be achieved using an electric heater, eliminating the need for stepped phase change energy storage.

Description

TECHNICAL FIELD

[0001] The present application relates to a power generation system, in particular to a carbon dioxide photo-thermal power generation system and method equipped with phase change heat storage. BACKGROUND

[0002] Under the background of energy shortage and environmental crisis, improving energy utilization is increasingly valued. Solar energy is a kind of inexhaustible clean energy. At the current stage, the technology of solar photovoltaic is relatively mature, and the price has been reduced a lot after years of development. At present, with the reduction of photovoltaic unit cost, the state has gradually begun to reduce or even cancel the subsidy. But the problem of photovoltaic power generation and energy storage has been difficult to solve. The relatively mature photovoltaic energy storage matching mode is still battery energy storage, but the cost of battery energy storage is always too high, and it is difficult to avoid accidents such as fire. For large-scale energy storage demand of power plants of this power level, various types of battery energy storage are currently difficult to promote. Photothermal power station has the inherent advantage of using cheap energy storage method to store energy, so this technology is strongly supported, but the cost of photothermal power generation system has been high, much higher than photovoltaic power generation. From the economic point of view, solar power generation is non-photovoltaic, but from the point of view of power grid fluctuation, a certain proportion of photothermal power station must be matched as a regulating power station. Therefore, the state and local governments encourage energy enterprises to promote photovoltaic power generation, and also introduce corresponding policies to match a certain proportion of photothermal power station, so that large photovoltaic is matched with small photothermal.

[0003] At the same time, photothermal power generation needs to realize heat and electricity conversion through heat cycle. Among many heat cycles, supercritical Brayton cycle is the most advantageous cycle form. New CO2 supercritical working medium has the inherent advantages of high energy density, high heat transfer efficiency, simple system, etc., which can greatly improve the heat and power conversion efficiency and reduce the equipment size, and has high economic efficiency. It is the best choice to replace the existing water vapor heat cycle system, and it is also the trend of future heat and electricity system development. Therefore, it is very suitable to apply supercritical CO2 cycle to photothermal power generation system. SUMMARY

[0004] In order to overcome the problems existing in the prior art, the purpose of the present application is to provide a carbon dioxide photothermal power generation system equipped with phase change heat storage and a method, to match the current large photovoltaic matched with small photothermal solar power generation.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] A carbon dioxide photothermal power generation system equipped with phase change heat storage, comprising a light collecting and heat collecting system, a heat storage and heat exchange system, a CO2 power generation system and a photovoltaic power generation system.

[0007] The light collecting and heat collecting system comprises a heat collector;

[0008] The heat storage and heat exchange system comprises a phase change heat storage heater, a molten salt-CO2 heat exchanger and a heat transfer molten salt storage tank, the outlet of the phase change heat storage heater is in communication with the heat transfer molten salt side inlet of the molten salt-CO2 heat exchanger, the heat transfer molten salt side outlet of the molten salt-CO2 heat exchanger is in communication with the inlet of the heat transfer molten salt storage tank, the outlet of the heat transfer molten salt storage tank is divided into two paths, one path is in communication with the inlet of the phase change heat storage heater, and the other path is in communication with the inlet of the collector, and the outlet of the collector is in communication with the inlet of the phase change heat storage heater.

[0009] The CO2 power generation system is connected with the molten salt-CO2 heat exchanger.

[0010] The photovoltaic power generation system is connected with the phase change heat storage heater.

[0011] Further, the outlet of the heat transfer molten salt storage tank is in communication with the inlet of the heat transfer molten salt pump, the outlet of the heat transfer molten salt pump is divided into two paths, one path is in communication with the inlet of the phase change heat storage heater, and the other path is in communication with the inlet of the collector.

[0012] Further, the CO2 power generation system comprises a CO2 turbine, a high-temperature regenerator, a low-temperature regenerator, a pre-cooler, a main compressor and a re-compressor, the outlet of the CO2 turbine is in communication with the low-pressure side inlet of the high-temperature regenerator, the low-pressure side outlet of the high-temperature regenerator is in communication with the low-pressure side inlet of the low-temperature regenerator, the low-pressure side outlet of the low-temperature regenerator is divided into two paths, one path is in communication with the CO2 side inlet of the pre-cooler, the CO2 side outlet of the pre-cooler is in communication with the high-pressure side inlet of the low-temperature regenerator through the main compressor, the high-pressure side outlet of the low-temperature regenerator is in communication with the high-pressure side inlet of the high-temperature regenerator, the other path of the low-pressure side outlet of the low-temperature regenerator is in communication with the high-pressure side inlet of the high-temperature regenerator through the re-compressor, the high-pressure side outlet of the high-temperature regenerator is in communication with the CO2 inlet of the molten salt-CO2 heat exchanger, and the CO2 outlet of the molten salt-CO2 heat exchanger is in communication with the inlet of the CO2 turbine.

[0013] Further, the phase change heat storage heater comprises an electric heating unit and a phase change heat storage unit connected in series, and the photovoltaic power generation system is connected with the electric heating unit.

[0014] Further, the heating temperature in the collector is 50℃ higher than the phase change temperature of the heat transfer molten salt.

[0015] Further, a mirror field system is arranged on one side of the collector.

[0016] A method based on the carbon dioxide photo-thermal power generation system with phase change heat storage as described above, when the photovoltaic power generation system generates sufficient power during the day, the solar energy is converted into heat energy by the mirror field and the heat collector and is transferred to the heat transfer molten salt, the heat transfer molten salt further heats the phase change heat storage heater, the phase change heat storage heater consumes the excess power of the photovoltaic power generation system and converts the power into heat energy, heats the phase change heat storage heater, and the heating object is selected according to the temperature of the heating unit in the phase change heat storage heater, when the heating unit reaches the designed temperature, the other heating unit is switched, and at this time, the CO2 power generation system does not work.

[0017] Further, when the photovoltaic power generation system stops generating power at night, the communication between the heat transfer molten salt and the heat collector is disconnected, the heat transfer molten salt releases heat in the molten salt-CO2 heat exchanger, and the heat transfer molten salt gradually heats the CO2 in the molten salt-CO2 heat exchanger by the heat of the phase change heat storage heater, and the CO2 power generation system starts to work.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] The CO2 photo-thermal power generation system and method of the present application is a power generation system for large photovoltaic and small photo-thermal design, which can consume photovoltaic solar energy abandoned light power, and is characterized in that a phase change heat storage heater is provided, and mainly uses phase change energy storage as the energy storage system of the CO2 power generation system. Due to the characteristics of the CO2 photo-thermal power generation system, after heat recovery, the temperature of the molten salt into the tower is very high, and the heat storage temperature difference of the molten salt is small, so if the conventional sensible heat storage is used, the storage of the molten salt will be very large. However, the phase change heat storage has constant temperature during heat release, and the energy storage density is much larger than that of the sensible heat storage, so the amount of heat storage medium can be greatly reduced. In addition, the photo-thermal power generation and energy storage system is matched with the photovoltaic power station, and the phase change energy storage can realize heat storage by using an electric heater. When the electric heating converts the electric energy into heat energy, there is no need for a high heat transfer temperature difference to realize energy transmission, and there is no need for step phase change energy storage.

[0020] When the power generation system generates power, during the day when the photovoltaic power generation system generates sufficient power, the solar energy is converted into heat energy and is transferred to the heat transfer molten salt, the heat transfer molten salt heats the phase change material in the phase change heat storage heater, and at the same time, the excess power of the photovoltaic power generation system is also used to heat the phase change material in the phase change heat storage heater, thereby avoiding the problem of abandoned light. In the present application, when the electric heating converts the electric energy into heat energy, there is no need for a high heat transfer temperature difference to realize energy transmission, and there is no need for step phase change energy storage.

[0021] Further, at night, the heat in the phase change material is further used to heat the CO2 power generation system through the heat transfer molten salt, thereby realizing the complementation of the photovoltaic power generation system. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The figure is a structural schematic diagram of the system of the present application.

[0023] In the diagram, 1 is the solar collector, 2 is the mirror field system, 3 is the phase change thermal energy storage heater, 4 is the molten salt-CO2 heat exchanger, 5 is the heat transfer molten salt storage tank, 6 is the heat transfer molten salt pump, 7 is the CO2 turbine, 8 is the high-temperature regenerator, 9 is the low-temperature regenerator, 10 is the precooler, 11 is the main compressor, 12 is the recompressor, and 13 is the photovoltaic power generation system. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings:

[0025] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0026] like Figure 1 As shown, a CO2 solar thermal power generation system with a large photovoltaic ratio and equipped with phase change thermal storage includes a concentrating solar collector system, a thermal storage and heat exchange system, a CO2 power generation system, and a photovoltaic power generation system.

[0027] The concentrating solar thermal system includes: a solar collector 1 and a mirror field system 2; the mirror field system 2 is located on one side of the solar collector 1.

[0028] The heat storage and heat exchange system includes: a phase change heat storage heater 3, a molten salt-CO2 heat exchanger 4, a heat transfer molten salt storage tank 5, and a heat transfer molten salt pump 6. The outlet of the phase change heat storage heater 3 is connected to the heat transfer molten salt side inlet of the molten salt-CO2 heat exchanger 4. The heat transfer molten salt side outlet of the molten salt-CO2 heat exchanger 4 is connected to the inlet of the heat transfer molten salt storage tank 5. The outlet of the heat transfer molten salt storage tank 5 is connected to the inlet of the heat transfer molten salt pump 6. The outlet of the heat transfer molten salt pump 6 is divided into two paths: one path is connected to the inlet of the phase change heat storage heater 3, and the other path is connected to the inlet of the collector 1. The outlet of the collector 1 is connected to the inlet of the phase change heat storage heater 3.

[0029] The CO2 power generation system comprises a CO2 turbine 7, a high-temperature regenerator 8, a low-temperature regenerator 9, a pre-cooler 10, a main compressor 11 and a re-compressor 12, the outlet of the CO2 turbine 7 is communicated with the low-pressure side inlet of the high-temperature regenerator 8, the low-pressure side outlet of the high-temperature regenerator 8 is communicated with the low-pressure side inlet of the low-temperature regenerator 9, the low-pressure side outlet of the low-temperature regenerator 9 is divided into two paths, one path is communicated with the CO2 side inlet of the pre-cooler 10, the CO2 side outlet of the pre-cooler 10 is communicated with the inlet of the main compressor 11, the outlet of the main compressor 11 is communicated with the high-pressure side inlet of the low-temperature regenerator 9, the high-pressure side outlet of the low-temperature regenerator 9 is communicated with the high-pressure side inlet of the high-temperature regenerator 8, the low-pressure side outlet of the low-temperature regenerator 9 is divided into another path which is communicated with the inlet of the re-compressor 12, the outlet of the re-compressor 12 is communicated with the high-pressure side inlet of the high-temperature regenerator 8, the high-pressure side outlet of the high-temperature regenerator 8 is communicated with the CO2 inlet of the molten salt-CO2 heat exchanger 4, the CO2 outlet of the molten salt-CO2 heat exchanger 4 is communicated with the inlet of the CO2 turbine 7;

[0030] The phase change heat storage heater 3 comprises an electric heating unit and a phase change heat storage unit connected in series;

[0031] The photovoltaic power generation system 13 is connected with the electric heating unit in the phase change heat storage heater 3 through a cable;

[0032] A method of a large photovoltaic proportion CO2 photo-thermal power generation system equipped with phase change heat storage is provided.

[0033] The heat transfer molten salt flows through and exchanges heat outside the phase change heat storage heater 3.

[0034] The heat transfer molten salt needs to be high-temperature molten salt, the heating temperature of the heat transfer molten salt in the heat collector 1 is at least 50℃ higher than the phase change temperature, the temperature of the phase change heat storage heater 3 needs to be monitored during operation, and the temperature of the phase change heat storage heater 3 needs to be ensured to be lower than the decomposition temperature of the heat transfer molten salt.

[0035] When the photovoltaic power generation system generates sufficient power during the day, the light and heat collecting system and the heat storage system in the photo-thermal system work simultaneously, and the solar energy is converted into heat energy by the mirror field and the heat collector 1 and is transmitted to the heat transfer molten salt, which in turn heats the phase change heat storage heater 3. At the same time, the phase change heat storage heater 3 consumes the excess power of the photovoltaic power generation system 13 and converts it into heat energy to heat the phase change heat storage heater 3. When the phase change heat storage heater 3 is heated by electricity, the heating object is selected according to the temperature of the heating unit in the phase change heat storage heater 3. When the heating unit in the phase change heat storage heater 3 reaches the design temperature, the heating of the heating unit is stopped to avoid the decomposition of the heat transfer molten salt, and the heating of other units is started. At this time, the communication between the heat transfer molten salt and the molten salt-CO2 heat exchanger 4 is disconnected, and the CO2 power generation system does not work. The phase change heat storage heater 3 itself has multiple independent heating unit arrays, and each unit contains an electric heater and a phase change heat storage medium. The heat transfer molten salt does not distinguish these heating units and always flows through them, but the electric heating distinguishes these independent heating units according to the temperature, and stops heating when the temperature reaches the design temperature.

[0036] At night, when the photovoltaic power generation system stops generating power, the communication between the heat transfer molten salt and the heat collector 1 is disconnected, and the communication between the heat transfer molten salt and the molten salt-CO2 heat exchanger 4 is restored. The heat transfer molten salt gradually heats the CO2 in the molten salt-CO2 heat exchanger 4 with the heat of the phase change heat storage heater 3, and the CO2 power generation system starts to work.

[0037] The system is a power generation system that can consume photovoltaic solar energy and abandoned light power, which is specially designed for large photovoltaic and small photo-thermal. The system is characterized by being equipped with a phase change heat storage heater, mainly using phase change energy storage as a CO2 photo-thermal power generation system energy storage system. Due to the characteristics of the CO2 photo-thermal power generation system, after the heat recovery, the temperature of the molten salt entering the tower is very high, and the heat storage temperature difference of the molten salt is small. If conventional sensible heat storage is used, the storage of the molten salt will be very large. However, the phase change heat storage has a constant temperature during heat release, and the energy storage density is much higher than that of sensible heat storage, so the amount of heat storage medium can be greatly reduced. In addition, the photo-thermal power generation and energy storage system is matched with the photovoltaic power station, and the phase change energy storage can use an electric heater to achieve heat storage. When the electric heater converts electrical energy into heat energy, there is no need for a high heat transfer temperature difference to achieve energy transmission, and there is no need for step phase change energy storage.

[0038] The above specific embodiments further illustrate the purpose, technical solutions and advantages of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of carbon dioxide photo-thermal power generation equipped with phase change heat storage, characterized by, The method adopts a carbon dioxide photo-thermal power generation system equipped with phase change heat storage, which comprises a light collecting and heat collecting system, a heat storage and heat exchange system, a CO2 power generation system and a photovoltaic power generation system; The light collecting and heat collecting system comprises a heat collector (1). The heat storage and heat exchange system comprises a phase change heat storage heater (3), a molten salt-CO2 heat exchanger (4) and a heat transfer molten salt storage tank (5), the outlet of the phase change heat storage heater (3) is in communication with the heat transfer molten salt side inlet of the molten salt-CO2 heat exchanger (4), the heat transfer molten salt side outlet of the molten salt-CO2 heat exchanger (4) is in communication with the inlet of the heat transfer molten salt storage tank (5), the outlet of the heat transfer molten salt storage tank (5) is divided into two paths, one path is in communication with the inlet of the phase change heat storage heater (3), and the other path is in communication with the inlet of the heat collector (1), and the outlet of the heat collector (1) is in communication with the inlet of the phase change heat storage heater (3). The CO2 power generation system is connected with the molten salt-CO2 heat exchanger (4). The photovoltaic power generation system is connected with the phase change heat storage heater (3). During the day when the photovoltaic power generation system (13) generates sufficient electricity, solar energy is converted into heat energy by the mirror field and the heat collector (1) and is transferred to the heat transfer molten salt, the heat transfer molten salt further heats the phase change heat storage heater (3), the phase change heat storage heater (3) consumes the excess electricity of the photovoltaic power generation system (13) and converts the electricity into heat energy to heat the phase change heat storage heater (3), and the heating object is selected according to the temperature of the heating unit in the phase change heat storage heater (3), when the heating unit reaches the designed temperature, the other heating unit is switched, and at this time, the CO2 power generation system does not work. At night when the photovoltaic power generation system (13) stops generating electricity, the communication between the heat transfer molten salt and the heat collector (1) is disconnected, the heat transfer molten salt releases heat in the molten salt-CO2 heat exchanger (4), and the heat transfer molten salt gradually heats the CO2 in the molten salt-CO2 heat exchanger (4) by the heat of the phase change heat storage heater (3), and the CO2 power generation system starts to work.

2. The method for generating solar thermal power from carbon dioxide equipped with phase change thermal storage according to claim 1, characterized in that, The outlet of the heat transfer molten salt storage tank (5) is in communication with the inlet of the heat transfer molten salt pump (6), the outlet of the heat transfer molten salt pump (6) is divided into two paths, one path is in communication with the inlet of the phase change heat storage heater (3), and the other path is in communication with the inlet of the heat collector (1). The outlet of the heat transfer molten salt storage tank (5) is in communication with the inlet of the heat transfer molten salt pump (6), the outlet of the heat transfer molten salt pump (6) is divided into two paths, one path is in communication with the inlet of the phase change heat storage heater (3), and the other path is in communication with the inlet of the heat collector (1).

3. A method for generating solar thermal power from carbon dioxide equipped with phase change thermal storage according to claim 1, characterized in that, The CO2 power generation system comprises a CO2 turbine (7), a high-temperature regenerator (8), a low-temperature regenerator (9), a precooler (10), a main compressor (11) and a re-compressor (12), the outlet of the CO2 turbine (7) is communicated with the low-pressure side inlet of the high-temperature regenerator (8), the low-pressure side outlet of the high-temperature regenerator (8) is communicated with the low-pressure side inlet of the low-temperature regenerator (9), the low-pressure side outlet of the low-temperature regenerator (9) is divided into two paths, one path is communicated with the CO2 side inlet of the precooler (10), the CO2 side outlet of the precooler (10) is communicated with the high-pressure side inlet of the low-temperature regenerator (9) through the main compressor (11), the high-pressure side outlet of the low-temperature regenerator (9) is communicated with the high-pressure side inlet of the high-temperature regenerator (8), the low-pressure side outlet of the low-temperature regenerator (9) is communicated with the high-pressure side inlet of the high-temperature regenerator (8) through the re-compressor (12), the high-pressure side outlet of the high-temperature regenerator (8) is communicated with the CO2 inlet of the molten salt-CO2 heat exchanger (4), and the CO2 outlet of the molten salt-CO2 heat exchanger (4) is communicated with the inlet of the CO2 turbine (7).

4. A method for generating solar thermal power from carbon dioxide equipped with phase change thermal storage according to claim 1, characterized in that, The phase change heat storage heater (3) comprises an electric heating unit and a phase change heat storage unit connected in series; and the photovoltaic power generation system (13) is connected with the electric heating unit.

5. A method for generating solar thermal power from carbon dioxide equipped with phase change thermal storage according to claim 1, characterized in that, The heating temperature in the heat collector (1) is 50°C higher than the phase change temperature of the heat transfer molten salt.

6. A method for generating solar thermal power from carbon dioxide equipped with phase change thermal storage according to claim 1, characterized in that, The heat collector (1) is provided with a mirror field system (2) on one side.

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