CN118728673A - Ocean temperature difference energy and solar energy combined power generation system, offshore platform and power generation method - Google Patents

Abstract

The present invention discloses a combined power generation system of ocean temperature difference energy and solar energy, an offshore platform and a power generation method, and relates to the technical field of comprehensive utilization of ocean temperature difference energy and solar energy. The power generation system includes an N-stage Rankine cycle system, a warm seawater pump and a power generation device; each stage of the Rankine cycle system includes an evaporator and a solar collector, and the working fluid outlet end of the evaporator is connected to the working fluid inlet end of the solar collector; the seawater outlet end of the evaporator in the k-1-stage Rankine cycle system is connected to the seawater inlet end of the evaporator in the k-stage Rankine cycle system; the warm seawater pump is connected to the seawater inlet end of the evaporator of the 1-stage Rankine cycle system; the power generation device is connected to the working fluid outlet end of the solar collector; the evaporator is used to perform heat exchange between the supplied working fluid and the supplied warm seawater; the solar collector is used to heat the supplied working fluid; and the power generation device is used to generate electricity using the internal energy of the supplied working fluid. The present invention improves the heat utilization rate of the power generation system.

Description

Ocean temperature difference energy and solar energy combined power generation system, offshore platform and power generation method

Technical Field

The present invention relates to the technical field of comprehensive utilization of ocean temperature difference energy and solar energy, and in particular to an ocean temperature difference energy and solar energy combined power generation system, an offshore platform and a power generation method.

Background Art

Ocean temperature difference energy refers to the heat energy stored between the warm seawater on the surface heated by solar energy and the cold seawater at a depth of 800 to 1,000 meters. The most common way to use ocean temperature difference energy is to generate electricity. The basic principle is to use the warm seawater on the surface of the ocean to heat certain low-boiling-point working fluids and vaporize them to drive the expander and the generator to generate electricity; the working fluid steam at the outlet of the expander is condensed through heat exchange with the cold seawater at a depth of 800 to 1,000 meters, and is transported to the evaporator through the working fluid pump to complete a cycle.

Compared with traditional thermal power generation, the ocean thermal power generation system has low thermal-electric conversion efficiency and high marine engineering investment, because the temperature difference between the cold and hot sources is only about 20°C, resulting in high unit electricity costs and restricting the industrial development of ocean thermal energy development. Therefore, a power generation system jointly driven by ocean thermal energy and solar energy has emerged to combine the power generation advantages of the two energy sources.

However, the existing power generation system driven by the combined power of ocean temperature difference and solar energy has the problem of low utilization rate of heat in seawater, which needs to be solved urgently.

Summary of the invention

The main purpose of the present invention is to propose an ocean temperature difference energy and solar energy combined power generation system, aiming to solve the problem that the existing ocean temperature difference energy and solar energy combined power generation system has low utilization rate of heat in seawater.

To achieve the above-mentioned purpose, the ocean temperature difference energy and solar energy combined power generation system proposed in the present invention includes N-stage Rankine cycle systems, warm seawater pumps and power generation equipment, each stage of the Rankine cycle system at least includes an evaporator and a solar collector, the working fluid outlet end of the evaporator is connected to the working fluid inlet end of the solar collector; the seawater outlet end of the evaporator in the k-1-stage Rankine cycle system is connected to the seawater inlet end of the evaporator in the k-stage Rankine cycle system; 2≤k≤N; the warm seawater pump is connected to the seawater inlet end of the evaporator of the 1st stage Rankine cycle system; the power generation equipment is connected to the working fluid outlet end of the solar collector; the evaporator is used to perform heat exchange between the supplied working fluid and the supplied warm seawater; the solar collector is used to heat the supplied working fluid; and the power generation equipment is used to generate electricity using the internal energy of the supplied working fluid.

In one embodiment, the power generation system further includes a cold seawater pump; each stage of the Rankine cycle system further includes a condenser; the seawater outlet end of the condenser in the k-th stage Rankine cycle system is connected to the seawater inlet end of the condenser in the k-1-th stage Rankine cycle system; 2≤k≤N; the cold seawater pump is connected to the seawater inlet end of the condenser of the N-th stage Rankine cycle system; the working fluid inlet end of the condenser is connected to the power generation equipment, and the working fluid outlet end of the condenser is connected to the working fluid inlet end of the evaporator; the condenser is used to perform heat exchange between the working fluid used by the power generation equipment in the power generation process and the supplied cold seawater.

In one embodiment, the power generation system also includes a mixing container, and the seawater inlet end of the mixing container is respectively connected to the evaporator of the N-stage Rankine cycle system and the condenser of the 1st-stage Rankine cycle system; the mixing container is used to receive and mix the warm seawater from the evaporator of the N-stage Rankine cycle system and the cold seawater from the condenser of the 1st-stage Rankine cycle system, and discharge the mixed seawater into the seawater stratosphere.

In one embodiment, the power generation equipment includes an expander and a generator; the working fluid outlet end of the solar collector is connected to the inlet end of the expander; the outlet end of the expander is connected to the condenser; the driving end of the expander is transmission-connected to the generator; each stage of the Rankine cycle system also includes a working fluid pump, the inlet end of the working fluid pump is connected to the working fluid outlet end of the condenser, and the outlet end of the working fluid pump is connected to the working fluid inlet end of the evaporator.

The present invention also provides an offshore platform, comprising the above-mentioned ocean temperature difference energy and solar energy combined power generation system.

The present invention also proposes a power generation method, which is applied to the above-mentioned power generation system combining ocean temperature difference energy and solar energy, wherein the evaporator is filled with high-pressure liquid working fluid, and the power generation method comprises:

The evaporator allows the high-pressure liquid working medium to exchange heat with warm seawater, so that the high-pressure liquid working medium is converted into a subcritical high-pressure gaseous working medium, and the subcritical high-pressure gaseous working medium is transported to the solar collector;

The solar collector heats the high-pressure gaseous working medium in the subcritical state to the supercritical state, and transmits the high-pressure gaseous working medium in the supercritical state to the expander of the Rankine cycle system;

The high-pressure gaseous working fluid in the supercritical state expands and performs work inside the expander, driving the transmission part of the expander to drive the generator to generate electricity.

In one embodiment, the method for generating electricity further comprises:

The high-pressure gaseous working medium in the supercritical state expands and does work inside the expander and becomes exhaust steam in the subcritical state;

The outlet end of the expander delivers the exhaust steam to the condenser of the Rankine cycle system;

The condenser exchanges heat between the exhaust steam and cold seawater to obtain condensed liquid working fluid.

In one embodiment, the method for generating electricity further comprises:

The working fluid pump of the Rankine cycle system pressurizes the condensed liquid working fluid to obtain high-pressure liquid working fluid, and pumps the high-pressure liquid working fluid into the evaporator.

In one embodiment, the high-pressure liquid working fluid is an organic working fluid.

In one embodiment, the method for generating electricity further comprises:

The warm seawater pump sequentially pumps the warm seawater through the evaporator of each stage of the Rankine cycle system, so that the warm seawater exchanges heat with the evaporator of each stage of the Rankine cycle system;

The cold seawater pump of the Rankine cycle system sequentially pumps the cold seawater through the condenser of each stage of the Rankine cycle system, so that the cold seawater exchanges heat with the condenser of each stage of the Rankine cycle system; wherein the initial temperature of the warm seawater is ≥25°C, and the initial temperature of the cold seawater is ≤7°C;

The mixing container of the power generation system receives and mixes warm seawater from the evaporator of the Nth-stage Rankine cycle system and cold seawater from the condenser of the first-stage Rankine cycle system, and discharges the mixed seawater into the seawater stratosphere.

The technical solution of the present invention adopts a combined power generation system of ocean temperature difference energy and solar energy, including N-stage Rankine cycle systems, warm seawater pumps and power generation equipment. Each stage of the Rankine cycle system at least includes an evaporator and a solar collector. The working fluid outlet end of the evaporator is connected to the working fluid inlet end of the solar collector; the seawater outlet end of the evaporator in the k-1-stage Rankine cycle system is connected to the seawater inlet end of the evaporator in the k-stage Rankine cycle system; 2≤k≤N; the warm seawater pump is connected to the seawater inlet end of the evaporator of the 1st stage Rankine cycle system; the power generation equipment is connected to the working fluid outlet end of the solar collector; the evaporator is used to perform heat exchange between the supplied working fluid and the supplied warm seawater; the solar collector is used to heat the supplied working fluid; and the power generation equipment is used to generate electricity using the internal energy of the supplied working fluid.

The technical solution of the present invention is provided with a multi-stage Rankine cycle system, and the evaporators of each stage of the Rankine cycle system are connected to each other. The warm seawater after heat exchange in the previous stage evaporator can be used to heat the working medium of the next stage evaporator, thereby further extracting heat from the warm seawater; because the evaporators of each stage of the Rankine cycle system are connected to each other, only a single warm seawater pump is needed to achieve the pumping effect of the multi-stage evaporators, reducing the energy consumption of extracting seawater. Overall, the technical solution of the present invention can improve the absorption of heat in seawater, while improving the power generation capacity and reducing the energy consumption of extracting surface warm seawater.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

FIG1 is a schematic structural diagram of an embodiment of an ocean temperature difference energy and solar energy combined power generation system provided by the present invention;

FIG. 2 is a schematic flow chart of an embodiment of a power generation method provided by the present invention.

Description of Figure Numbers:

1. Rankine cycle system; 11. Evaporator; 12. Solar collector; 13. Condenser; 14. Working fluid pump; 2. Warm seawater pump; 3. Power generation equipment; 31. Expander; 32. Generator; 4. Cold seawater pump.

The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and/or" or "and/or" appears in the full text, its meaning includes three parallel schemes. Taking "A and/or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Ocean temperature difference energy refers to the heat energy stored between the warm seawater on the surface heated by solar energy and the cold seawater at a depth of 800 to 1,000 meters. The most common way to use ocean temperature difference energy is to generate electricity. The basic principle is to use the warm seawater on the surface of the ocean to heat certain low-boiling-point working fluids and vaporize them to drive the expander and the generator to generate electricity; the working fluid steam at the outlet of the expander is condensed through heat exchange with the cold seawater at a depth of 800 to 1,000 meters, and is transported to the evaporator through the working fluid pump to complete a cycle.

Compared with traditional thermal power generation, the ocean thermal power generation system has low thermal-electric conversion efficiency and high marine engineering investment, because the temperature difference between the cold and hot sources is only about 20°C, resulting in high unit electricity costs and restricting the industrial development of ocean thermal energy development. Therefore, a power generation system jointly driven by ocean thermal energy and solar energy has emerged to combine the power generation advantages of the two energy sources.

However, the existing power generation system driven by the combined power of ocean temperature difference and solar energy has the problem of low utilization rate of heat in seawater, which needs to be solved urgently.

In order to solve the above problems, the present invention proposes a combined power generation system of ocean temperature difference energy and solar energy.

Please refer to Figure 1. In one embodiment of the present invention, the ocean temperature difference energy and solar energy combined power generation system includes N-stage Rankine cycle systems 1, warm seawater pumps 2 and power generation equipment 3; each stage of the Rankine cycle system 1 includes at least an evaporator 11 and a solar collector 12, and the working fluid outlet end of the evaporator 11 is connected to the working fluid inlet end of the solar collector 12; the seawater outlet end of the evaporator 11 in the k-1-th stage Rankine cycle system 1 is connected to the seawater inlet end of the evaporator 11 in the k-th stage Rankine cycle system 1; 2≤k≤N; the warm seawater pump 2 is connected to the seawater inlet end of the evaporator 11 of the first stage Rankine cycle system 1; the power generation equipment 3 is connected to the working fluid outlet end of the solar collector 12; the evaporator 11 is used to perform heat exchange between the supplied working fluid and the supplied warm seawater; the solar collector 12 is used to heat the supplied working fluid; the power generation equipment 3 is used to generate electricity using the internal energy of the supplied working fluid.

It should be noted that the Rankine cycle is a thermodynamic cycle that is used to convert thermal energy into mechanical energy, and then into electrical energy through a generator. In the Rankine cycle, four major processes are usually included: isobaric heating, isentropic expansion, isobaric condensation, and isentropic compression. Compared with the Brayton cycle, the Rankine cycle can effectively reduce the energy consumption of working fluid transportation by using liquid working fluid and lower compression pressure.

Among them, the interconnection method between each component can be connected by an insulated pipe. For example, the warm seawater pump 2 is connected to the evaporator 11 through an insulated pipe, the evaporator 11 is connected to the solar collector 12 through an insulated pipe, and the solar collector 12 is connected to the power generation equipment 3 through an insulated pipe.

The technical solution of the present invention is provided with a multi-stage Rankine cycle system 1, and the evaporators 11 of each stage of the Rankine cycle system 1 are connected to each other. The warm seawater after heat exchange in the upper stage evaporator 11 can be used to heat the working medium of the lower stage evaporator 11, thereby further extracting heat from the warm seawater; because the evaporators 11 of each stage of the Rankine cycle system 1 are connected to each other, only a single warm seawater pump 2 is needed to achieve the pumping effect of the multi-stage evaporators 11, thereby reducing the energy consumption of extracting seawater. Overall, the technical solution of the present invention can improve the absorption of heat in seawater, while improving the power generation capacity and reducing the energy consumption of extracting surface warm seawater.

For ease of understanding, illustratively, an N-stage Rankine cycle system 1 can be set as a three-stage Rankine cycle system 1. Then, in the process of pumping warm seawater, the warm seawater pump 2 sequentially pumps the warm seawater from the ocean surface to the evaporator 11 of the first-stage Rankine cycle system 1, the evaporator 11 of the second-stage Rankine cycle system 1, and the evaporator 11 of the third-stage Rankine cycle system 1, so that the warm seawater sequentially exchanges heat with the working fluid inside the evaporator 11 of each stage of the Rankine cycle system 1, thereby improving the utilization rate of the heat of the warm seawater.

As a preferred embodiment, the N-stage Rankine cycle system 1 can be set as a 2-stage Rankine cycle system 1 or a 3-stage Rankine cycle system 1, so as to make full use of the heat in the warm seawater while avoiding the problem of reduced heating effect on the working medium after the warm seawater undergoes heat exchange with the working medium in the multi-stage evaporator 11, thereby ensuring heating efficiency. Of course, the N-stage Rankine cycle system 1 can also be set as a Rankine cycle system 1 with more stages, and the number of stages of the Rankine cycle system 1 is not limited here.

Furthermore, since the existing power generation system combining ocean temperature difference energy and solar energy has low utilization rate of not only the heat of warm seawater but also the coldness of cold seawater, in order to solve the above problems, in an embodiment of the present invention, please refer to FIG1 , the power generation system further includes a cold seawater pump 4; each Rankine cycle system 1 further includes a condenser 13; the seawater outlet end of the condenser 13 in the k-th Rankine cycle system 1 is connected to the seawater inlet end of the condenser 13 in the k-1th Rankine cycle system 1; 2≤k≤N; the cold seawater pump 4 is connected to the seawater inlet end of the condenser 13 in the N-th Rankine cycle system 1; the working fluid inlet end of the condenser 13 is connected to the power generation equipment 3, and the working fluid outlet end of the condenser 13 is connected to the working fluid inlet end of the evaporator 11; the condenser 13 is used to heat exchange the working fluid used by the power generation equipment 3 during the power generation process with the supplied cold seawater.

Thus, in this embodiment, by connecting the condensers 13 of each stage of the Rankine cycle system 1 to each other, the cold seawater after heat exchange in the condenser 13 in the k-th stage Rankine cycle system 1 can be used as the condensing medium for the condenser 13 in the k-1-th stage Rankine cycle system 1, thereby further extracting the coldness in the cold seawater; since the condensers 13 of each stage of the Rankine cycle system 1 are connected to each other, only a single cold seawater pump 4 is needed to achieve the pumping effect of the multi-stage evaporator 11, thereby reducing the energy consumption of extracting seawater.

Similarly, for ease of understanding, the above-mentioned N-stage Rankine cycle system 1 is continued to be explained in the case of being set as a 3-stage Rankine cycle system 1: in the process of pumping cold seawater, the cold seawater pump 4 sequentially pumps the cold seawater on the ocean surface to the condenser 13 of the 3rd-stage Rankine cycle system 1, the condenser 13 of the 2nd-stage Rankine cycle system 1, and the condenser 13 of the 1st-stage Rankine cycle system 1, so that the cold seawater sequentially exchanges heat with the working medium inside the condenser 13 of each stage of the Rankine cycle system 1, thereby improving the utilization rate of the heat of the cold seawater.

Furthermore, in order to avoid the problem that the warm seawater after heat exchange and the cold seawater after cold exchange are directly discharged without treatment, which affects the current seawater temperature and leads to the inability to effectively utilize the ocean temperature difference energy, in an embodiment of the present invention, the power generation system also includes a mixing container, and the seawater inlet end of the mixing container is respectively connected to the evaporator 11 of the N-stage Rankine cycle system 1 and the condenser 13 of the first-stage Rankine cycle system 1; the mixing container is used to receive and mix the warm seawater from the evaporator 11 of the N-stage Rankine cycle system 1 and the cold seawater from the condenser 13 of the first-stage Rankine cycle system 1, and discharge the mixed seawater into the seawater stratosphere.

It should be noted that the seawater stratosphere refers to the seawater layer with the same temperature as the mixed seawater. Seawater layers at different depths have different temperatures due to the different degrees of solar radiation received. Generally, the deeper the seawater layer, the lower its temperature. Therefore, discharging the mixed seawater into the seawater stratosphere can effectively avoid the discharged seawater from affecting the temperature of the seawater layer, ensuring the effective extraction of ocean temperature difference energy.

In this way, by providing a mixing container, the warm seawater from the evaporator 11 of the Nth-stage Rankine cycle system 1 and the cold seawater from the condenser 13 of the first-stage Rankine cycle system 1 are received and mixed with a mixed solution, and the mixed seawater is discharged into the seawater stratosphere, thereby avoiding the temperature influence of the discharged seawater on a small sea area, and further avoiding the temperature influence of the discharged seawater on the extracted warm seawater/cold seawater, thereby preventing the utilization of the ocean temperature difference energy from being affected.

Further, in an embodiment of the present invention, please refer to Figure 1, the power generation equipment 3 includes an expander 31 and a generator 32; the working fluid outlet end of the solar collector 12 is connected to the inlet end of the expander 31; the outlet end of the expander 31 is connected to the condenser 13; the driving end of the expander 31 is transmission-connected to the generator 32; each stage of the Rankine cycle system 1 also includes a working fluid pump 14, the inlet end of the working fluid pump 14 is connected to the working fluid outlet end of the condenser 13, and the outlet end of the working fluid pump 14 is connected to the working fluid inlet end of the evaporator 11.

As mentioned above, the Rankine cycle generally includes four major processes: isobaric heating, isentropic expansion, isobaric condensation, and isentropic compression. In this embodiment, the working fluid first undergoes heat exchange in the evaporator 11 and the solar collector 12 to complete the isobaric heating process. The working fluid then expands and works in the expander 31 to complete the isentropic expansion process. After that, the working fluid undergoes heat exchange in the condenser 13 to complete the isobaric condensation process. Finally, the working fluid is transported and compressed by the working fluid pump 14 to complete the isentropic compression process. In this way, the power generation system combining ocean temperature difference energy and solar energy of the present invention realizes a complete Rankine cycle.

The present invention also provides an offshore platform, including the above-mentioned ocean temperature difference energy and solar energy combined power generation system. The specific structure of the ocean temperature difference energy and solar energy combined power generation system refers to the above-mentioned embodiment. Since the offshore platform adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

Among them, the offshore platform can be an ocean power station, an offshore oil platform, an offshore aquaculture platform, etc., which will not be elaborated here.

The present invention also proposes a power generation method, which is applied to the above-mentioned ocean temperature difference energy and solar energy combined power generation system. The evaporator 11 is filled with high-pressure liquid working fluid. Please refer to FIG. 2. The power generation method includes steps S10 to S30:

Step S10, the evaporator 11 performs heat exchange between the high-pressure liquid working medium and the warm seawater to convert the high-pressure liquid working medium into a subcritical high-pressure gaseous working medium, and the subcritical high-pressure gaseous working medium is transported to the solar collector 12;

It should be noted that the subcritical state refers to a state in which the temperature and pressure of the working fluid are lower than its critical point. In the subcritical state, the working fluid can exist in the liquid phase and the gas phase.

Step S20, the solar collector 12 heats the high-pressure gaseous working medium in the subcritical state to a supercritical state, and transports the high-pressure gaseous working medium in the supercritical state to the expander 31 of the Rankine cycle system 1;

It should be noted that the supercritical state means that the temperature and pressure of the working fluid exceed its critical point. In this state, the working fluid no longer has a clear distinction between liquid and gas, but is in a supercritical state between liquid and gas.

In step S30, the high-pressure gaseous working medium in the supercritical state expands inside the expander 31 to perform work, driving the transmission part of the expander 31 to drive the generator 32 to generate electricity.

In this embodiment, by utilizing the secondary heating of the evaporator 11 and the solar collector 12, the original high-pressure liquid working medium is converted into a high-pressure gaseous working medium in a supercritical state, thereby realizing a supercritical Rankine cycle. Compared with the existing subcritical Rankine cycle, the supercritical Rankine cycle of the present invention can have a good temperature match with the warm seawater and the solar collector 12 as a heat source because its evaporation heat exchange process does not pass through the two-phase region; through the supercritical Rankine cycle, the heat exchange loss between the warm seawater and the working medium, and between the solar collector 12 and the working medium is reduced, the thermoelectric conversion efficiency is improved, the amount of seawater required under the condition of the same power generation is reduced, and the energy consumption of extracting seawater is reduced, which is conducive to improving the overall efficiency of the ocean temperature difference energy power generation system.

Furthermore, in an embodiment of the present invention, the power generation method further includes steps A40 to A60:

Step A40, the high-pressure gaseous working medium in the supercritical state expands and does work inside the expander 31 to become exhaust steam in the subcritical state;

It should be noted that exhaust steam refers to a gaseous working fluid in a low-pressure, medium-temperature state.

Step A50, the outlet end of the expander 31 transports the exhaust steam to the condenser 13 of the Rankine cycle system 1;

In step A60, the condenser 13 performs heat exchange between the exhaust steam and the cold seawater to obtain a condensed liquid working medium.

In this embodiment, the exhaust steam in the subcritical state is heat exchanged with cold seawater in the condenser 13 to achieve condensation of the exhaust steam, obtain condensed liquid working fluid, and complete the condensation process in the supercritical Rankine cycle.

In an embodiment of the present invention, the power generation method further includes step A70:

In step A70 , the working medium pump 14 of the Rankine cycle system 1 pressurizes the condensed liquid working medium to obtain high-pressure liquid working medium, and pumps the high-pressure liquid working medium 14 to the evaporator 11 .

In this embodiment, the condensed liquid working medium is pressurized by the working medium pump 14 to obtain high-pressure liquid working medium, and the high-pressure liquid working medium is pumped to the evaporator 11 by the working medium pump 14, thereby completing the pressurization process in the supercritical Rankine cycle.

Furthermore, in order to solve the problem that water and other working fluids have a high critical point and are not convenient to be used in a system based on ocean temperature difference energy for power generation, in an embodiment of the present invention, the high-pressure liquid working fluid is an organic working fluid. Since organic working fluids usually have a lower critical temperature and pressure, they can be vaporized and liquefied under the condition of a low-temperature heat source, thereby effectively converting thermal energy into mechanical energy or electrical energy.

Furthermore, in an embodiment of the present invention, the power generation method further includes steps B40 to B60:

Step B40, the warm seawater pump 2 sequentially pumps the warm seawater through the evaporator 11 of each stage of the Rankine cycle system 1, so that the warm seawater exchanges heat with the evaporator 11 of each stage of the Rankine cycle system 1;

Step B50, the cold seawater pump 4 of the Rankine cycle system 1 sequentially pumps the cold seawater through the condenser 13 of each stage of the Rankine cycle system 1, so that the cold seawater exchanges heat with the condenser 13 of each stage of the Rankine cycle system 1; wherein the initial temperature of the warm seawater is ≥25°C, and the initial temperature of the cold seawater is ≤7°C;

Step B60, the mixing container of the power generation system receives and mixes the warm seawater from the evaporator 11 of the Nth stage Rankine cycle system 1 and the cold seawater from the condenser 13 of the first stage Rankine cycle system 1, and discharges the mixed seawater into the seawater stratosphere.

In this embodiment, the warm seawater pump 2 is used to sequentially pump the warm seawater through the evaporator 11 of each stage of the Rankine cycle system 1, thereby achieving heat exchange of the working medium in the evaporator 11 of each stage of the Rankine cycle system 1; the cold seawater pump 4 is used to sequentially pump the cold seawater through the condenser 13 of each stage of the Rankine cycle system 1, thereby achieving heat exchange of the used working medium in the condenser 13 of each stage of the Rankine cycle system 1; the warm seawater from the evaporator 11 of the Nth stage Rankine cycle system 1 and the cold seawater from the condenser 13 of the first stage Rankine cycle system 1 are received and mixed by using a mixing container, and the mixed seawater is discharged into the seawater stratosphere, thereby avoiding the discharged seawater from affecting the temperature of the extracted warm seawater/cold seawater, thereby preventing the utilization of the ocean temperature difference energy from being affected.

In addition, it should be noted that in order to make full use of the ocean temperature difference energy, it is necessary to ensure that there is a certain degree of temperature difference between cold seawater and warm seawater. As an optional implementation, in this embodiment, the initial temperature of warm seawater is set to ≥25°C, and the initial temperature of cold seawater is set to ≤7°C, so as to ensure that the temperature difference between cold seawater and warm seawater is above 18°C, thereby effectively utilizing the ocean temperature difference energy. Furthermore, the temperature difference between cold seawater and warm seawater is preferably maintained above 20°C, which can be achieved by deploying the power generation system in different sea areas or increasing the extraction depth of cold seawater. For example, the surface and shallow water temperatures are both above 25°C, the deep water temperature is below 5°C, and the surface and deep water temperature difference reaches 20°C to 24°C, which is an area rich in ocean temperature difference energy resources.

The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly/indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims (10)

1. A power generation system combining ocean thermal energy and solar energy, comprising:

The system comprises an N-stage Rankine cycle system, wherein each stage of Rankine cycle system at least comprises an evaporator and a solar heat collector, and a working medium outlet end of the evaporator is communicated with a working medium inlet end of the solar heat collector; the seawater outlet end of the evaporator in the Rankine cycle system at the k-1 stage is communicated with the seawater inlet end of the evaporator in the Rankine cycle system at the k stage; k is more than or equal to 2 and less than or equal to N;

The warm sea water pump is communicated with the sea water inlet end of the evaporator of the Rankine cycle system of the 1 st stage;

The power generation equipment is connected with the working medium outlet end of the solar heat collector;

The evaporator is used for carrying out heat exchange on the supplied working medium and the supplied warm seawater; the solar heat collector is used for heating the supplied working medium; the power generation equipment is used for generating power by utilizing the internal energy of the fed working medium.

2. The power generation system of claim 1, wherein the power generation system further comprises a chilled sea water pump; each stage of the rankine cycle system also comprises a condenser;

The seawater outlet end of the condenser in the Rankine cycle system at the k stage is communicated with the seawater inlet end of the condenser in the Rankine cycle system at the k-1 stage; k is more than or equal to 2 and less than or equal to N;

the cold sea water pump is communicated with the sea water inlet end of the condenser of the Rankine cycle system of the nth stage;

The working medium inlet end of the condenser is connected with the power generation equipment, and the working medium outlet end of the condenser is communicated with the working medium inlet end of the evaporator; the condenser is used for carrying out heat exchange on working media used by the power generation equipment in the power generation process and the supplied cold sea water.

3. The power generation system of claim 2, further comprising a mixing vessel having a seawater inlet port in communication with the evaporator of the rankine cycle system at stage N and the condenser of the rankine cycle system at stage 1, respectively;

The mixing container is used for receiving and mixing warm seawater from the evaporator of the Rankine cycle system at the N level and cold seawater from the condenser of the Rankine cycle system at the 1 level, and discharging the mixed seawater to a seawater stratosphere.

4. The power generation system of claim 2, wherein the power generation device comprises an expander and a generator; the working medium outlet end of the solar heat collector is communicated with the inlet end of the expander; the outlet end of the expander is communicated with the condenser; the driving end of the expander is in transmission connection with the generator;

Each stage of Rankine cycle system further comprises a working medium pump, wherein the inlet end of the working medium pump is communicated with the working medium outlet end of the condenser, and the outlet end of the working medium pump is communicated with the working medium inlet end of the evaporator.

5. An offshore platform comprising a power generation system combining ocean thermal energy and solar energy as claimed in any one of claims 1 to 4.

6. A power generation method, characterized in that it is applied to the power generation system of the combination of ocean thermal energy and solar energy as defined in any one of claims 1 to 4, the inside of the evaporator is filled with high-pressure liquid working medium, the power generation method comprises:

The evaporator enables the high-pressure liquid working medium to exchange heat with the warm seawater so as to enable the high-pressure liquid working medium to be changed into a high-pressure gaseous working medium in a subcritical state, and the high-pressure gaseous working medium in the subcritical state is conveyed into the solar heat collector;

The solar heat collector heats the high-pressure gaseous working medium in the subcritical state to a supercritical state, and conveys the high-pressure gaseous working medium in the supercritical state to an expander of the Rankine cycle system;

the high-pressure gaseous working medium in the supercritical state expands in the expander to do work and drives the transmission part of the expander to drive the generator to generate electricity.

7. The power generation method according to claim 6, wherein the power generation method further comprises:

the high-pressure gaseous working medium in the supercritical state is changed into exhaust steam in the subcritical state after expansion work is done in the expander;

the exhaust steam is conveyed to a condenser of the Rankine cycle system by the outlet end of the expander;

And the condenser enables the exhaust steam and the cold sea water to perform heat exchange to obtain a condensed liquid working medium.

8. The power generation method according to claim 7, wherein the power generation method further comprises:

And the working medium pump of the Rankine cycle system pressurizes the condensed liquid working medium to obtain the high-pressure liquid working medium, and pumps the high-pressure liquid working medium into the evaporator.

9. The power generation method of claim 6, wherein the high-pressure liquid working medium is an organic working medium.

10. The power generation method according to claim 6, wherein the power generation method further comprises:

the warm sea water pump pumps the warm sea water through the evaporator of each stage of the Rankine cycle system in sequence so as to enable the warm sea water to exchange heat with the evaporator of each stage of the Rankine cycle system;

the cold sea water pump of the Rankine cycle system pumps cold sea water through the condenser of each stage of the Rankine cycle system in sequence so that the cold sea water exchanges heat with the condenser of each stage of the Rankine cycle system; wherein the initial temperature of the warm seawater is more than or equal to 25 ℃, and the initial temperature of the cold seawater is less than or equal to 7 ℃;

The mixing container of the power generation system receives and mixes warm seawater from the evaporator of the Rankine cycle system at the N level and cold seawater from the condenser of the Rankine cycle system at the 1 level, and discharges the mixed seawater to a seawater stratosphere.