CN112523981A - Direct expansion type solar thermal power generation system using biphenyl-diphenyl ether mixture - Google Patents

Direct expansion type solar thermal power generation system using biphenyl-diphenyl ether mixture Download PDF

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CN112523981A
CN112523981A CN202110084910.2A CN202110084910A CN112523981A CN 112523981 A CN112523981 A CN 112523981A CN 202110084910 A CN202110084910 A CN 202110084910A CN 112523981 A CN112523981 A CN 112523981A
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working medium
rankine cycle
biphenyl
storage tank
heat storage
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李晶
高广涛
裴刚
杨洪伦
李鹏程
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University of Science and Technology of China USTC
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University of Science and Technology of China USTC
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
    • F03G6/00—Devices for producing mechanical power from solar energy
    • F03G6/06—Devices for producing mechanical power from solar energy with solar energy concentrating means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
    • F01C13/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D15/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
    • F01D15/10—Adaptations for driving, or combinations with, electric generators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/006—Methods of steam generation characterised by form of heating method using solar heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S20/00—Solar heat collectors specially adapted for particular uses or environments
    • F24S20/20—Solar heat collectors for receiving concentrated solar energy, e.g. receivers for solar power plants
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S60/00—Arrangements for storing heat collected by solar heat collectors
    • F24S60/10—Arrangements for storing heat collected by solar heat collectors using latent heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S60/00—Arrangements for storing heat collected by solar heat collectors
    • F24S60/30—Arrangements for storing heat collected by solar heat collectors storing heat in liquids
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/40—Solar thermal energy, e.g. solar towers
    • Y02E10/46—Conversion of thermal power into mechanical power, e.g. Rankine, Stirling or solar thermal engines

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Energy (AREA)
  • Sustainable Development (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)

Abstract

The invention relates to a direct expansion type solar thermal power generation system using a biphenyl-biphenyl ether mixture, and belongs to the technical field of solar thermal power generation. Comprises a primary circulation loop and a secondary circulation loop. The working medium of the primary circulation loop is a biphenyl-diphenyl ether mixture, has the functions of solar energy collection and storage, heat energy release and top Rankine cycle power generation, and mainly comprises a solar heat collection field, a top Rankine cycle expander, a working medium pump, a valve, a high-temperature heat storage tank, a low-temperature heat storage tank and a phase-change material. Wherein the phase-change material is placed in the high-temperature heat storage tank. The secondary circulation loop has the function of bottom Rankine cycle power generation and mainly comprises a bottom Rankine cycle expander, a bottom Rankine cycle working medium pump, an evaporator, a condenser and a heat regenerator. The invention combines biphenyl-diphenyl ether mixture with high evaporation temperature and low evaporation pressure with cascade Rankine cycle, and utilizes phase change to store heat, thereby improving thermal power generation efficiency and heat storage capacity and having strong application potential.

Description

Direct expansion type solar thermal power generation system using biphenyl-diphenyl ether mixture
Technical Field
The invention belongs to the technical field of solar thermal power generation, and particularly relates to a direct expansion type solar thermal power generation system using a biphenyl-diphenyl ether mixture.
Background
The direct expansion type solar thermal power generation is an important light-gathering power generation technology. The water vapor is directly generated in the heat collection field and pushes the steam turbine to do work without intermediate heat exchange fluid. The water has large latent heat of vaporization, low cost, environmental protection and good safety, and is the only medium adopted by the current commercial direct expansion type light-gathering heat power generation system. However, this type of solar thermal power generation system has two challenges that need to be addressed: first, there is a lack of long-cycle, low-cost thermal storage solutions; secondly, the system has low heat-power conversion efficiency. The first problem is that the temperature and pressure of the high-temperature water tank are unstable in the heat release process, and in order to prevent the thermodynamic cycle from deviating from the design working condition seriously, the temperature drop of the high-temperature water tank is generally less than 50 ℃. If long-cycle heat storage is required, the high-pressure heat storage tank has a large volume and high cost, and the cycle fluctuation of the pressure can reduce the service life of the container. The second problem is that the saturation pressure of water rises sharply with the rise of temperature, and when the temperature is 270 ℃, the saturation pressure reaches 5.5 MPa, and at the moment, the technical requirements of the heat collecting pipe and the heat storage tank are high, and the manufacturing cost is high. If the temperature is further raised, the cost index of the system is raised, and the thermal efficiency of the system is raised relatively slowly. In particular, when the temperature is higher than 270 ℃, the saturation steam enthalpy of water is reduced along with the increase of the temperature, the humidity of the water vapor in the expansion process is increased, and the technical requirements of the wet steam turbine are increased. The design temperature of the already established direct expansion plant is not high as the design temperature of Planta Solar 10 and Planta Solar 20 is 250 ℃. Because the operation temperature is not high, compared with a concentrating thermal power generation system adopting molten salt and heat conducting oil, the efficiency of the direct expansion type solar thermal power generation system is lower.
If the heat conduction oil is adopted to replace a water medium, the problems that the pressure of a heat storage tank of the traditional direct expansion type solar thermal power generation system is high, and the steam temperature and the heat-power conversion efficiency are low can be theoretically solved. The heat conduction oil directly absorbs heat in the heat collection field and generates steam, the steam is used for driving thermodynamic cycle power generation, and the working principle of the steam is similar to that of a water medium. Because the boiling point of the heat conducting oil is high (such as more than 200 ℃), the saturated vapor pressure of the heat conducting oil is obviously lower than that of the water medium at the same temperature, and the saturated pressure can be maintained below 1MPa when the operation temperature is close to 400 ℃. Meanwhile, the heat conducting oil is generally benzene working medium and belongs to dry organic working medium, and the heat conducting oil cannot enter a gas-liquid two-phase region in the expansion process, so that the technical requirement of the expansion machine is low. It is worth noting that, despite the above advantages of thermal oil, direct expansion solar thermal power generation systems based on thermal oil have not been demonstrated or commercialized. The potential problems of the method are mainly that the heat conducting oil is low in specific heat and latent heat of vaporization and high in cost. At the same temperature, the specific heat of the heat conduction oil is less than 50% of that of water, and the latent heat of vaporization is less than 20% of that of water. In order to obtain a long-term heat storage capacity, the heat transfer oil is expensive. For example, assuming that the system design temperature is 370 ℃, in order to ensure that the thermodynamic cycle does not deviate from the design working condition seriously in the heat release and power generation process, the minimum temperature of the heat conducting oil of the high-temperature tank is 340 ℃, the thermodynamic cycle design efficiency is 31%, and the heat storage time is 12 hours. Based on the above assumptions, the mass of the heat transfer oil required by each kW system is about 170kg, and considering that the heat transfer oil needs to be replaced periodically, the heat storage cost is higher than 4000 yuan/kW. Therefore, the investment recovery period of the direct expansion type thermal power generation system cannot be shortened simply by replacing the water medium with the heat transfer oil.
In order to solve the above problems, the present invention provides a direct expansion type solar thermal power generation system using a biphenyl-diphenyl ether mixture. The system is expected to obtain saturated vapor at the temperature of 400 ℃, so that the thermodynamic cycle efficiency is greatly improved, and meanwhile, the heat storage cost of the system is reduced by the scheme of combining sensible heat storage and latent heat storage.
Disclosure of Invention
In order to overcome the problem that the saturated steam temperature of water in a conventional direct expansion type solar thermal power generation system is low (<280 ℃) and the pressure of a heat storage water tank is high (>4MPa), the invention provides a direct expansion type solar thermal power generation system using a biphenyl-diphenyl ether mixture. The system comprises a primary circulation loop and a secondary circulation loop, and the structure of the system is shown in figure 1.
The direct expansion type solar thermal power generation system using the biphenyl-biphenyl ether mixture comprises a primary circulation loop and a secondary circulation loop;
the primary circulation loop comprises a solar heat collection field 1, a high-temperature heat storage tank 2, a top Rankine cycle expander 4, a low-temperature heat storage tank 7, a first working medium pump 8 and a second working medium pump 9; the phase-change material 3 is filled in the high-temperature heat storage tank 2, the volume of the phase-change material 3 accounts for 10-80% of the volume of the high-temperature heat storage tank 2, and the phase-change temperature of the phase-change material 3 is 250-400 ℃; the working medium in the primary circulation loop is a biphenyl-biphenyl ether mixture;
the secondary circulation loop comprises a bottom Rankine cycle expander 10, a heat regenerator 20, a condenser 21, a third working medium pump 22, a first evaporator 6 and a second evaporator 5; the working medium in the secondary circulation loop is a bottom Rankine cycle working medium, and the bottom Rankine cycle working medium is a working medium with the boiling point lower than 200 ℃;
the first evaporator 6 and the second evaporator 5 are identical in structure and respectively comprise a top Rankine cycle working medium side and a bottom Rankine cycle working medium side which are parallel, and the two sides of the heat regenerator 20 are both bottom Rankine cycle working media;
the working temperature of the biphenyl-diphenyl ether mixture in the high-temperature heat storage tank 2 is 250-400 ℃, and the working temperature of the biphenyl-diphenyl ether mixture in the low-temperature heat storage tank 7 is 30-240 ℃;
the gaseous mass fraction of the biphenyl-diphenyl ether mixture at the outlet of the solar heat collection field 1 is 5-95%;
the high-temperature heat storage tank 2 and the low-temperature heat storage tank 7 form a double-tank heat conduction oil heat storage unit;
the solar thermal power generation system has 4 working modes which are respectively as follows:
in a solar heat collection power generation mode, a solar heat collection field 1, a high-temperature heat storage tank 2, a top Rankine cycle expansion machine 4, a low-temperature heat storage tank 7, a first working medium pump 8, a second working medium pump 9, a bottom Rankine cycle expansion machine 10, a heat regenerator 20, a condenser 21, a third working medium pump 22, a first evaporator 6 and a second evaporator 5 participate in work;
in a primary heat release power generation mode, the high-temperature heat storage tank 2, the top Rankine cycle expander 4, the second working medium pump 9, the bottom Rankine cycle expander 10, the heat regenerator 20, the condenser 21, the third working medium pump 22, the first evaporator 6 and the second evaporator 5 participate in work;
in the secondary heat release power generation mode, the high-temperature heat storage tank 2, the top Rankine cycle expander 4, the low-temperature heat storage tank 7, the second working medium pump 9, the bottom Rankine cycle expander 10, the heat regenerator 20, the condenser 21, the third working medium pump 22, the first evaporator 6 and the second evaporator 5 participate in working;
and in the three-level heat release power generation mode, the high-temperature heat storage tank 2, the low-temperature heat storage tank 7, the bottom Rankine cycle expander 10, the heat regenerator 20, the condenser 21, the third working medium pump 22, the first evaporator 6 and the second evaporator 5 participate in working.
The technical scheme for further limiting is as follows:
the specific connection relationship between the primary circulation loop and the secondary circulation loop is as follows:
the bottom outlet of the high-temperature heat storage tank 2 is communicated with the outlet of the top Rankine cycle expansion machine 4 through one side of a three-way pipe, and the other side of the high-temperature heat storage tank is sequentially connected with a fourth valve 14, one side of the top Rankine cycle working medium of the first evaporator 6, a seventh valve 17 and the top inlet of the low-temperature heat storage tank 7 in series; an outlet at one side of the top of the high-temperature heat storage tank 2 is communicated with an inlet of the top Rankine cycle expander 4 through a first valve 11; the outlet at the bottom of the low-temperature heat storage tank 7 is communicated with the inlet of the solar heat collection field 1 through a first working medium pump 8 and an eighth valve 18 which are connected in series, the outlet of the solar heat collection field 1 is communicated with the inlet at the other side of the top of the high-temperature heat storage tank 2, and a ninth valve 19 is connected in parallel between the inlet of the eighth valve 18 and the outlet of the solar heat collection field 1; a sixth valve 16 and a second working medium pump 9 are connected in parallel between an inlet of the seventh valve 17 and an outlet of the first working medium pump 8, the sixth valve 16 and the second working medium pump 9 are connected in series, and an outlet of the second working medium pump 9 and an outlet of the first working medium pump 8 are connected in parallel;
the outlet of the top Rankine cycle expansion machine 4 is sequentially connected with a third valve 13, the top Rankine cycle working medium side of the second evaporator 5 and a fifth valve 15 in series, and the outlet of the fifth valve 15 is respectively communicated with the inlet of the top Rankine cycle working medium side of the first evaporator 6 and the outlet of the fourth valve 14 through a three-way pipe;
the inlet of the bottom Rankine cycle expansion machine 10 is sequentially connected with one side of the bottom Rankine cycle working medium of the second evaporator 5, one side of the bottom Rankine cycle working medium of the first evaporator 6, one side of the heat regenerator 20 and the outlet of the third working medium pump 22 in series, and the outlet of the bottom Rankine cycle expansion machine 10 is sequentially connected with the other side of the heat regenerator 20, one side of the condenser 21 and the inlet of the third working medium pump 22 in series;
and an outlet at one side of the Rankine cycle working medium at the top of the second evaporator 5 is connected with an inlet of a second working medium pump 9 in parallel.
The solar heat collection field 1 is one of a parabolic groove type heat collection field, a linear Fresnel heat collection field and a tower type heat collection field.
The phase change material 3 is an inorganic salt phase change material, and the inorganic salt phase change material is one of potassium hydroxide inorganic salt, lithium chloride-potassium chloride binary mixed inorganic salt and lithium chloride-sodium chloride-potassium chloride ternary mixed inorganic salt.
The bottom Rankine cycle working medium is toluene, benzene, pentane or water.
The structural formula of biphenyl in the biphenyl-biphenyl ether mixture is C12H10The concentration of biphenyl in the biphenyl-biphenyl ether mixture was 26.5%; the structural formula of the diphenyl ether is C12H10The concentration of diphenyl ether in the O, biphenyl-diphenyl ether mixture was 73.5%.
The top Rankine cycle expander 4 and the bottom Rankine cycle expander 10 are both one of a steam turbine or a screw expander.
Compared with the prior art, the invention has the beneficial technical effects that:
1. the biphenyl-biphenyl ether mixture is simultaneously used as a working medium of a solar heat collection field, a heat storage working medium and a thermodynamic cycle working medium for the first time. The biphenyl-biphenyl ether mixture is also called as Daiheng, is a eutectic mixture of 73.5 percent of biphenyl ether and 26.5 percent of biphenyl, and is a widely used high-quality heat conduction oil. Its main advantages include: (1) excellent thermal stability. The thermal stability of the biphenyl-biphenyl ether mixture is incomparable with other heat carriers, can be applied to gas-liquid two-phase occasions without causing component concentration imbalance, can be used at 400 ℃, and has the service life of 6-10 years. (2) Lower vapor pressure. The vapor pressure of the biphenyl-biphenyl ether mixture at high temperatures is considerably lower compared to water. The saturated vapor pressure at 400 ℃ is about 1 MPa. (3) The liquid phase has lower viscosity, which is beneficial to reducing the power consumption of the heat collection field. (4) The safety is better, the fuel range is not included, and the explosion limit range of steam is very small. (5) Has no corrosion to equipment.
The prior literature indicates that the technical scheme of the biphenyl-biphenyl ether mixture as a solar heat transfer medium and a heat storage medium is reported. Biphenyl-biphenyl ether mixtures are widely used solar heat transfer and storage media in solar power stations that are currently being built. The technical scheme of using biphenyl-biphenyl ether mixture as thermodynamic cycle working medium is also reported. As in a patent document of 2017, biphenyl-diphenyl ether mixtures were also used for working fluids of high temperature organic Rankine cycles (WO 2017199170a1, Cogenerative organic Rankine cycle system). However, the technical scheme of using the biphenyl-biphenyl ether mixture as the working medium of the solar heat collection field, the heat storage working medium and the thermodynamic cycle working medium has not been reported yet.
Compared with a direct expansion type solar thermal power generation system adopting water, the system provided by the invention can obtain the saturated steam temperature close to 400 ℃, the heat-power conversion efficiency is greatly improved, and the design pressure of the heat storage tank is obviously reduced.
2. The double-tank heat conduction oil heat storage unit based on the high-temperature heat storage tank 2 and the low-temperature heat storage tank 7 is combined with the overlapping Rankine cycle, and is innovatively applied to the technical field of direct expansion type solar thermal power generation. The double-tank heat conduction oil heat storage unit is common in a solar thermal power generation system, but the heat conduction oil is only a heat transfer and heat storage medium and is not a thermodynamic cycle working medium. The double-tank water heat storage unit is also reported in a direct expansion type solar thermal power generation system, for example, in the invention application CN201710608229.7, but the heat collection, heat storage and thermodynamic cycle working medium is water. According to the technical scheme, the double-tank heat conduction oil heat storage unit is combined with the cascade Rankine cycle, and heat conduction oil steam in the heat storage tank directly enters the top Rankine cycle to do work, so that no report is found.
The innovative combination can effectively deal with the unstable problem of solar energy. When the sun irradiates in the daytime, the liquid biphenyl-diphenyl ether mixture in the low-temperature heat storage tank 7 is pressurized by the first working medium pump 8, enters the solar heat collection field 1, and then flows into the high-temperature heat storage tank 2. The flow of the first working medium pump 8 can be changed according to the change of the solar radiation intensity, so that the temperature and the pressure of the high-temperature heat storage tank 2 are stable, and the stability of the cascade Rankine cycle power generation is further ensured. At night or on cloudy days, the high-temperature thermal storage tank 2 can flow back to the low-temperature thermal storage tank 7 through the first evaporator 6 and the second evaporator 5, and the released sensible heat can be used for heating the bottom Rankine cycle.
The innovative combination can also improve the heat storage capacity of the heat conduction oil. Compared with a conventional double-tank heat conduction oil unit for driving a steam Rankine cycle, the double-tank heat conduction oil unit has higher heat storage capacity under the same heat storage tank volume. The water working medium is a typical wet working medium, the latent heat of vaporization is large, and the latent heat of vaporization still is 1400kJ/kg at 310 ℃. To ensure the efficiency of the cycle, the evaporation temperature of the water is high. The physical properties of water make it difficult to lower the temperature of the cryogenic tank in the dual-tank conduction oil unit, because most of the heat needs to be used for water evaporation, and the temperature of oil is higher than the evaporation temperature of water during evaporation. For an operating double-tank heat conduction oil solar thermal power station, the temperature of a low-temperature tank is usually higher than 280 ℃, and the temperature difference of heat conduction oil of a high-temperature tank and a low-temperature tank is about 100 ℃. In contrast, the biphenyl-diphenyl ether mixture and the working medium of the bottom Rankine cycle in the invention have obviously low latent heat of vaporization, and the working medium at the inlet of the expansion machine does not need to be in an overheat state, so that even if the bottom Rankine cycle adopts the water working medium, the evaporation temperature of water is lower than that of water of the conventional solar thermal power station. This allows the temperature of the low-temperature thermal storage tank 7 to be reduced to 100 c or less, so that the temperature difference between the high-temperature thermal storage tank 2 and the low-temperature thermal storage tank 7 reaches 250 c or more. This significantly increased temperature difference is favorable on the one hand for reducing the flow of the biphenyl-biphenyl ether mixture in the solar thermal collection field 1 and for reducing the power consumption of the first working medium pump 8. On the other hand, because the temperature difference between the high-temperature heat storage tank 2 and the low-temperature heat storage tank 7 is large (such as more than 250 ℃), the sensible heat released by the biphenyl-diphenyl ether mixture per unit mass is large and is 1-2 times higher than that of the conventional double-tank heat conduction oil technology, and the heat storage capacity of the system is greatly improved.
3. The high-temperature heat storage tank 2 and the low-temperature heat storage tank 7 are organically combined with a phase-change material, and the method is innovatively applied to the technical field of direct expansion type solar thermal power generation. The heat storage unit of heat conduction oil is combined with phase change material, the technical scheme for indirect solar thermal power generation system is reported. However, the technical scheme of combining the two is not reported, and the technical scheme is used for a direct expansion type solar thermal power generation system. In the technical scheme of the invention, the double-tank heat conduction oil unit and the phase change material work cooperatively, so that respective defects are respectively made up. As described above, if the entire cascade rankine cycle is driven by the heat transfer oil during the heat release process, the temperature and pressure will decrease rapidly with the increase of the heat release amount due to the low specific heat of the heat transfer oil, and the operation parameters of the vapor will decrease accordingly, so that it is not easy for the entire cascade rankine cycle to operate stably. Although the conduction oil can flow into the low-temperature heat storage tank 7 from the high-temperature heat storage tank 2 to drive the bottom Rankine cycle to stably generate electricity, the efficiency of the single bottom Rankine cycle is lower than that of the entire cascade Rankine cycle. The phase-change material 3 can solve the problem, the heat-power conversion efficiency of the system in the heat release process is improved, and the cascade Rankine cycle efficient power generation is maintained. In the heat release process of the phase-change material, the temperature is relatively constant, the heat storage density per unit mass is high, and the material (such as composite salt) is cheaper than heat conduction oil. However, the phase-change material has the defects of low heat conductivity coefficient, and solid media can be attached to the heat exchange surface in the heat release process, so that the heat transfer resistance is increased. This deficiency of the phase change material can be compensated by the thermal oil. When the thermal resistance of the phase change unit is increased and the heat release power is reduced, the heat conduction oil flows from the high-temperature heat storage tank 2 to the low-temperature heat storage tank 7 through the first evaporator 6, the released sensible heat is provided for the bottom Rankine cycle, the flow of the heat conduction oil is adjusted according to the heat release rate of the phase change material 3, the smaller the heat release rate of the phase change material 3 is, the larger the flow of the heat conduction oil is, and therefore the fact that the whole cascade Rankine cycle always keeps higher power output is guaranteed.
Based on the organic combination of the double-tank heat conduction oil heat storage unit of the high-temperature heat storage tank 2 and the low-temperature heat storage tank 7 and the phase-change material 3, the system provided by the invention has a unique three-level heat release and power generation mode, which is respectively as follows: the method comprises the following steps of (I) driving a cascade Rankine cycle by means of heat released by a phase change material 3; secondly, driving a cascade Rankine cycle by virtue of the latent heat of phase change of the phase change material 3 and the sensible heat of the heat conduction oil; and (III) driving the bottom Rankine cycle by means of sensible heat of the conduction oil. Meanwhile, a direct expansion type solar thermal power generation system with the three-stage heat release power generation mode is not reported.
The unique heat release power generation mode effectively improves the heat storage power generation capacity of the system, can reduce the usage amount and cost of heat conduction oil, and overcomes the defect of heat storage of a single phase change material.
Drawings
FIG. 1 is a schematic view of the structure of the present invention.
Fig. 2 is a flow chart of a solar heat collection power generation mode.
Fig. 3 is a flow chart of a first stage heat and power generation mode.
Fig. 4 is a flow chart of the second stage heat and power generation mode.
Fig. 5 is a flow chart of the third stage heat-release power generation mode.
Fig. 6 is a graph of saturation temperature versus entropy for biphenyl-biphenyl ether mixtures.
Sequence numbers in FIGS. 1-5: the solar heat collection system comprises a solar heat collection field 1, a high-temperature heat storage tank 2, a phase-change material 3, a top Rankine cycle expander 4, a second evaporator 5, a first evaporator 6, a low-temperature heat storage tank 7, a first working medium pump 8, a second working medium pump 9, a bottom Rankine cycle expander 10, a first valve 11, a second valve 12, a third valve 13, a fourth valve 14, a fifth valve 15, a sixth valve 16, a seventh valve 17, an eighth valve 18, a ninth valve 19, a heat regenerator 20, a condenser 21 and a third working medium pump 22.
Detailed Description
The invention will now be further described by way of example with reference to the accompanying drawings.
Referring to fig. 1, a direct expansion type solar thermal power generation system using a biphenyl-biphenyl ether mixture includes a primary circulation loop and a secondary circulation loop.
The primary circulation loop comprises a solar heat collection field 1, a high-temperature heat storage tank 2, a top Rankine cycle expander 4, a low-temperature heat storage tank 7, a first working medium pump 8 and a second working medium pump 9. The phase-change material 3 is filled in the high-temperature heat storage tank 2, the volume of the phase-change material 3 accounts for 50% of the volume of the high-temperature heat storage tank 2, the phase-change material is potassium hydroxide, and the phase-change temperature is 360 ℃. The working medium in the primary circulation loop is a biphenyl-biphenyl ether mixture. The structural formula of biphenyl in the biphenyl-biphenyl ether mixture is C12H10The concentration of biphenyl in the biphenyl-biphenyl ether mixture was 26.5%; the structural formula of the diphenyl ether is C12H10The concentration of diphenyl ether in the O, biphenyl-diphenyl ether mixture was 73.5%.
The secondary circulation loop comprises a bottom Rankine cycle expander 10, a heat regenerator 20, a condenser 21, a third working medium pump 22, a first evaporator 6 and a second evaporator 5; the working medium in the secondary circulation loop is bottom Rankine cycle working medium, the bottom Rankine cycle working medium is toluene, and the boiling point is 110.6 ℃.
The first evaporator 6 and the second evaporator 5 are identical in structure and respectively comprise a top Rankine cycle working medium side and a bottom Rankine cycle working medium side which are parallel, and the two sides of the heat regenerator 20 are both bottom Rankine cycle working media.
The working temperature of the biphenyl-diphenyl ether mixture in the high-temperature heat storage tank 2 is 350 ℃, and the working temperature of the biphenyl-diphenyl ether mixture in the low-temperature heat storage tank 7 is 90 ℃.
The gaseous mass fraction of the biphenyl-diphenyl ether mixture at the outlet of the solar heat collection field 1 is 50%.
The high-temperature heat storage tank 2 and the low-temperature heat storage tank 7 form a double-tank heat conduction oil heat storage unit.
Both the top rankine cycle expander 4 and the bottom rankine cycle expander 10 are steam turbines.
The solar heat collection field 1 is a parabolic trough type heat collection field.
The specific connection relationship between the primary circulation loop and the secondary circulation loop is as follows:
the bottom outlet of the high-temperature heat storage tank 2 is communicated with the outlet of the top Rankine cycle expansion machine 4 through one side of a three-way pipe, and the other side of the high-temperature heat storage tank is sequentially connected with a fourth valve 14, one side of the top Rankine cycle working medium of the first evaporator 6, a seventh valve 17 and the top inlet of the low-temperature heat storage tank 7 in series; an outlet at one side of the top of the high-temperature heat storage tank 2 is communicated with an inlet of the top Rankine cycle expander 4 through a first valve 11; the outlet at the bottom of the low-temperature heat storage tank 7 is communicated with the inlet of the solar heat collection field 1 through a first working medium pump 8 and an eighth valve 18 which are connected in series, the outlet of the solar heat collection field 1 is communicated with the inlet at the other side of the top of the high-temperature heat storage tank 2, and a ninth valve 19 is connected in parallel between the inlet of the eighth valve 18 and the outlet of the solar heat collection field 1; a sixth valve 16 and a second working medium pump 9 are connected in parallel between the inlet of the seventh valve 17 and the outlet of the first working medium pump 8, the sixth valve 16 and the second working medium pump 9 are connected in series, and the outlet of the second working medium pump 9 and the outlet of the first working medium pump 8 are connected in parallel.
The outlet of the top Rankine cycle expansion machine 4 is sequentially connected with a third valve 13, the top Rankine cycle working medium side of the second evaporator 5 and a fifth valve 15 in series, and the outlet of the fifth valve 15 is respectively communicated with the inlet of the top Rankine cycle working medium side of the first evaporator 6 and the outlet of the fourth valve 14 through a three-way pipe.
The inlet of the bottom Rankine cycle expander 10 is sequentially connected with one side of the bottom Rankine cycle working medium of the second evaporator 5, one side of the bottom Rankine cycle working medium of the first evaporator 6, one side of the heat regenerator 20 and the outlet of the third working medium pump 22 in series, and the outlet of the bottom Rankine cycle expander 10 is sequentially connected with the other side of the heat regenerator 20, one side of the condenser 21 and the inlet of the third working medium pump 22 in series.
And an outlet at one side of the Rankine cycle working medium at the top of the second evaporator 5 is connected with an inlet of a second working medium pump 9 in parallel.
The solar thermal power generation system mainly has 4 working modes, namely a solar heat collection power generation mode and a three-stage heat release power generation mode, and the specific working principle is described as follows:
(1) the solar heat collection power generation mode is shown in figure 2, and the flow of the mode is indicated by a black solid line. In a solar heat collection power generation mode, a solar heat collection field 1, a high-temperature heat storage tank 2, a top Rankine cycle expansion machine 4, a low-temperature heat storage tank 7, a first working medium pump 8, a second working medium pump 9, a bottom Rankine cycle expansion machine 10, a heat regenerator 20, a condenser 21, a third working medium pump 22, a first evaporator 6 and a second evaporator 5 participate in work.
The system of the present invention generally operates in a solar thermal collection power generation mode. Under the condition of sufficient solar irradiation, solar heat collection, heat storage and thermodynamic cycle power generation are simultaneously carried out. The first working medium pump 8, the second working medium pump 9 and the third working medium pump 22 are operated. The second valve 12, the fourth valve 14, the seventh valve 17 and the ninth valve 19 are in a closed state, and the remaining valves are in an open state. Under the action of the first working medium pump 8 and the second working medium pump 9, the liquid biphenyl-biphenyl ether mixture enters the solar heat collection field 1 from outlets on one side of the Rankine cycle working medium at the tops of the low-temperature heat storage tank 7 and the first evaporator 6. The flow of the first working medium pump 8 can be adjusted according to the intensity of solar radiation, and the aim is to ensure the stable temperature and pressure of the biphenyl-diphenyl ether mixture in the high-temperature heat storage tank 2 and fully collect solar energy. Under normal conditions, the biphenyl-diphenyl ether mixture at the outlet of the solar heat collection field 1 is in a gas-liquid two-phase state. And part of the gaseous biphenyl-biphenyl ether mixture at the outlet of the solar heat collection field 1 enters the top Rankine cycle expander 4 through the high-temperature heat storage tank 2, part of the gaseous biphenyl-biphenyl ether mixture is condensed into liquid in the high-temperature heat storage tank 2, and the released heat is transferred to the phase-change material 3. The high-temperature and high-pressure gaseous biphenyl-biphenyl ether mixture enters the top Rankine cycle expander 4 to do work, and then enters one side of the top Rankine cycle working medium of the second evaporator 5 through the third valve 13 to be partially condensed. And the partially condensed biphenyl-biphenyl ether mixture enters the top Rankine cycle working medium side of the first evaporator 6 through a fifth valve 15 and is further condensed into a liquid state. The liquid biphenyl-biphenyl ether mixture enters the second working medium pump 9 through a sixth valve 16. The liquid biphenyl-diphenyl ether mixture in the low-temperature heat storage tank 7 is pressurized by the first working medium pump 8, the working medium at the outlet of the first working medium pump 8 is mixed with the working medium at the outlet of the second working medium pump 9, and then the mixture enters the solar heat collection field 1 through the eighth valve 18. For the bottom Rankine cycle, high-temperature and high-pressure bottom Rankine cycle working medium methylbenzene enters a bottom Rankine cycle expansion machine 10 to do work, gas methylbenzene after acting enters a heat regenerator 20 to be primarily cooled, cooled working medium methylbenzene enters a condenser 21 to be condensed into liquid, liquid working medium methylbenzene enters a third working medium pump 22 to be pressurized, the pressurized liquid working medium methylbenzene enters the heat regenerator 20 to be primarily heated, the heated working medium methylbenzene sequentially passes through one side of the bottom Rankine cycle working medium of a first evaporator 6 and one side of the bottom Rankine cycle working medium of a second evaporator 5 to absorb heat and evaporate, and the high-temperature and high-pressure working medium methylbenzene enters the bottom Rankine cycle expansion machine 10 to do work. The bottom Rankine cycle working medium toluene is different from a biphenyl-diphenyl ether mixture, and the boiling point of the bottom Rankine cycle working medium toluene is lower.
Under normal conditions, when the solar heat collection and power generation mode is finished in the evening, the phase-change material in the high-temperature heat storage tank 2 is changed into liquid, and meanwhile, most of the biphenyl-diphenyl ether mixture in the low-temperature heat storage tank 7 is heated and transferred into the high-temperature heat storage tank 2 through the solar heat collection field 1 to prepare for heat release and power generation.
(2) The first stage heat-generation and power-generation mode is shown in fig. 3, and the flow of the mode is indicated by a solid black line. In a primary heat release power generation mode, the high-temperature heat storage tank 2, the top Rankine cycle expander 4, the second working medium pump 9, the bottom Rankine cycle expander 10, the heat regenerator 20, the condenser 21, the third working medium pump 22, the first evaporator 6 and the second evaporator 5 participate in work. In the first-stage heat release power generation mode, the heat required by the cascade Rankine cycle is obtained through the latent heat of phase change of the phase change material. As the initial stage of heat release is realized, most of the phase-change material is in a liquid state, the thermal resistance with the wall surface is small, and the rate of heat release of the phase-change material is large at the given temperature of the biphenyl-diphenyl ether mixture, so that the requirement of the whole cascade Rankine cycle can be met. In the mode, the solar heat collection field 1, the low-temperature heat storage tank 7 and the first working medium pump 8 do not work. The high-temperature and high-pressure gaseous biphenyl-biphenyl ether mixture enters the top Rankine cycle expander 4 to do work, and then enters one side of the top Rankine cycle working medium of the second evaporator 5 through the third valve 13 to be partially condensed. And the partially condensed biphenyl-biphenyl ether mixture enters the top Rankine cycle working medium side of the first evaporator 6 through a fifth valve 15 and is further condensed into a liquid state. The liquid biphenyl-biphenyl ether mixture enters the second working medium pump 9 through a sixth valve 16. The biphenyl-biphenyl ether mixture at the outlet of the second working medium pump 9 returns to the high-temperature heat storage tank 2 again through the ninth valve 19, and the liquid biphenyl-biphenyl ether mixture absorbs heat from the phase-change material 3 and evaporates. For the bottom Rankine cycle, high-temperature and high-pressure bottom Rankine cycle working medium methylbenzene enters a bottom Rankine cycle expansion machine 10 to do work, the gas working medium methylbenzene after acting enters a heat regenerator 20 to be primarily cooled, the cooled working medium methylbenzene enters a condenser 21 to be condensed into a liquid state, the liquid working medium methylbenzene enters a third working medium pump 22 to be pressurized, the pressurized liquid working medium methylbenzene enters the heat regenerator 20 to be primarily heated, the heated working medium methylbenzene sequentially passes through one side of the bottom Rankine cycle working medium of a first evaporator 6 and one side of a main Rankine cycle working medium of a second evaporator 5 to absorb heat and evaporate, and the high-temperature and high-pressure working medium methylbenzene enters the bottom Rankine cycle. The bottom Rankine cycle working medium toluene is different from a biphenyl-diphenyl ether mixture, and the boiling point of the bottom Rankine cycle working medium toluene is lower.
(3) The second stage heat-generation and power-generation mode is shown in fig. 4, and the flow of the mode is indicated by a solid black line. In the two-stage heat release power generation mode, the high-temperature heat storage tank 2, the top Rankine cycle expander 4, the low-temperature heat storage tank 7, the second working medium pump 9, the bottom Rankine cycle expander 10, the heat regenerator 20, the condenser 21, the third working medium pump 22, the first evaporator 6 and the second evaporator 5 participate in working. Under the second-stage heat release power generation mode, a large proportion of phase change materials are solidified, the heat transfer resistance with the wall surface is increased, the heat release rate of the phase change materials is low at a given temperature of the biphenyl-diphenyl ether mixture, and the requirement of the whole cascade Rankine cycle is difficult to meet. At this time, the sensible heat of the biphenyl-diphenyl ether mixture in the high-temperature heat storage tank 2 is required to be supplemented. The liquid biphenyl-diphenyl ether mixture in the high-temperature heat storage tank 2 flows into the low-temperature heat storage tank 7 through the fourth valve 14, the first evaporator 6 and the seventh valve 17, and the released sensible heat is used for primarily heating the bottom Rankine cycle working medium toluene. The high-temperature and high-pressure gaseous biphenyl-biphenyl ether mixture enters the top Rankine cycle expander 4 to do work, and then enters one side of the top Rankine cycle working medium of the second evaporator 5 through the third valve 13 to be condensed. The condensed biphenyl-biphenyl ether mixture enters a second working medium pump 9. The biphenyl-biphenyl ether mixture at the outlet of the second working medium pump 9 returns to the high-temperature heat storage tank 2 again through the ninth valve 19, and the liquid biphenyl-biphenyl ether mixture absorbs heat from the phase-change material 3 and evaporates. For the bottom rankine cycle, the operation mode and the operating temperature, pressure and flow rate are the same as in the first stage exothermic power generation mode, so the power output of the bottom rankine cycle expander 10 is also kept constant. In the second stage heat-release power generation mode, the operating temperature, pressure and flow of the top Rankine cycle are lower than those in the first stage heat-release power generation mode. Although the power output of the top rankine cycle expander 4 is reduced in the second stage exothermic power generation mode compared to the first stage exothermic power generation mode, the entire cascade rankine cycle still maintains a higher power output because the bottom rankine cycle expander is still operating at rated operating conditions.
(4) The third stage heat-generation power generation mode is shown in fig. 5, and the flow of the mode is indicated by a solid black line. And in the three-level heat release power generation mode, the high-temperature heat storage tank 2, the low-temperature heat storage tank 7, the bottom Rankine cycle expander 10, the heat regenerator 20, the condenser 21, the third working medium pump 22, the first evaporator 6 and the second evaporator 5 participate in working. Under the third-stage heat release power generation mode, most of the phase change materials are solidified, and the phase change latent heat is fully utilized. At this time, the power generation needs to be carried out completely depending on the sensible heat of the biphenyl-biphenyl ether mixture in the high-temperature heat storage tank 2. The liquid biphenyl-biphenyl ether mixture in the high-temperature heat storage tank 2 sequentially flows into the low-temperature heat storage tank 7 through the second valve 12, the top Rankine cycle working medium side of the second evaporator 5, the fifth valve 15, the top Rankine cycle working medium side of the first evaporator 6 and the seventh valve 17, and the released sensible heat is used for driving the bottom Rankine cycle to generate power. The working mode and the operation temperature, the pressure and the flow of the bottom Rankine cycle are the same as those of the first-stage heat release power generation mode.
Figure 648113DEST_PATH_IMAGE002
Referring to table 1 and fig. 6, the biphenyl-biphenyl ether mixture is a dry working medium, and no liquid drop is generated in the expansion process, thereby being beneficial to improving the efficiency of the expander and reducing the technical difficulty of the expander. Table 1 shows the thermodynamic cycle parameters for each stage in the three-stage heat release mode. Assuming that the bottom Rankine cycle working medium is toluene (Teluene, boiling point 110.6 ℃, critical temperature 318.6 ℃), the design efficiency of the top Rankine cycle expansion machine 4 and the bottom Rankine cycle expansion machine 10 is 85%, the design efficiency of the first working medium pump 8, the second working medium 9 and the bottom Rankine cycle working medium pump 22 is 75%, the phase change material is potassium hydroxide, and the melting point is 360 ℃. This phase transition temperature is advantageous to ensure that the biphenyl-diphenyl ether mixture is below the maximum safe operating temperature (400 ℃) and to increase the lifetime. The operation parameters of the top Rankine cycle expansion machine 4 in the heat collection power generation mode are the same as those in the first-stage heat release mode. The bottom rankine cycle is always in design condition. As can be seen from the table, in the first-stage heat release mode, although the temperature of the high-temperature heat storage tank 2 is only 350 ℃, the thermal efficiency of the cascade rankine cycle is higher than that of the conventional two-tank conduction oil system, and the conduction oil of the latter operates at a temperature of about 400 ℃. The main reason is that the biphenyl-biphenyl ether mixture of the present invention is in a gaseous state rather than a liquid state after leaving the high temperature thermal storage tank 2, thereby increasing the average endothermic temperature of the cascade rankine cycle. If the temperature of the high-temperature heat storage tank 2 is raised to 400 ℃, the efficiency of the cascade rankine cycle is expected to be further improved.

Claims (7)

1. Utilize direct expansion formula solar thermal power generation system of biphenyl-diphenyl ether mixture, its characterized in that: comprises a primary circulation loop and a secondary circulation loop;
the primary circulation loop comprises a solar heat collection field (1), a high-temperature heat storage tank (2), a top Rankine cycle expansion machine (4), a low-temperature heat storage tank (7), a first working medium pump (8) and a second working medium pump (9); the phase-change material (3) is filled in the high-temperature heat storage tank (2), the volume of the phase-change material (3) accounts for 10% -80% of the volume of the high-temperature heat storage tank (2), and the phase-change temperature of the phase-change material (3) is 250-400 ℃; the working medium in the primary circulation loop is a biphenyl-biphenyl ether mixture;
the secondary circulation loop comprises a bottom Rankine cycle expansion machine (10), a heat regenerator (20), a condenser (21), a third working medium pump (22), a first evaporator (6) and a second evaporator (5); the working medium in the secondary circulation loop is a bottom Rankine cycle working medium, and the bottom Rankine cycle working medium is a working medium with the boiling point lower than 200 ℃; the first evaporator (6) and the second evaporator (5) are identical in structure and respectively comprise a top Rankine cycle working medium side and a bottom Rankine cycle working medium side which are parallel, and the two sides of the heat regenerator (20) are both bottom Rankine cycle working media; the working temperature of the biphenyl-diphenyl ether mixture in the high-temperature heat storage tank (2) is 250-400 ℃, and the working temperature of the biphenyl-diphenyl ether mixture in the low-temperature heat storage tank (7) is 30-240 ℃;
the gaseous mass fraction of the biphenyl-diphenyl ether mixture at the outlet of the solar heat collection field (1) is 5-95%;
the high-temperature heat storage tank (2) and the low-temperature heat storage tank (7) form a double-tank heat conduction oil heat storage unit;
the solar thermal power generation system has 4 working modes which are respectively as follows:
in a solar heat collection power generation mode, a solar heat collection field (1), a high-temperature heat storage tank (2), a top Rankine cycle expansion machine (4), a low-temperature heat storage tank (7), a first working medium pump (8), a second working medium pump (9), a bottom Rankine cycle expansion machine (10), a heat regenerator (20), a condenser (21), a third working medium pump (22), a first evaporator (6) and a second evaporator (5) participate in work;
in a primary heat release power generation mode, a high-temperature heat storage tank (2), a top Rankine cycle expansion machine (4), a second working medium pump (9), a bottom Rankine cycle expansion machine (10), a heat regenerator (20), a condenser (21), a third working medium pump (22), a first evaporator (6) and a second evaporator (5) participate in work;
in a two-stage heat release power generation mode, a high-temperature heat storage tank (2), a top Rankine cycle expansion machine (4), a low-temperature heat storage tank (7), a second working medium pump (9), a bottom Rankine cycle expansion machine (10), a heat regenerator (20), a condenser (21), a third working medium pump (22), a first evaporator (6) and a second evaporator (5) participate in working;
and in a three-level heat release power generation mode, the high-temperature heat storage tank (2), the low-temperature heat storage tank (7), the bottom Rankine cycle expander (10), the heat regenerator (20), the condenser (21), the third working medium pump (22), the first evaporator (6) and the second evaporator (5) participate in work.
2. The direct expansion solar thermal power generation system using biphenyl-biphenyl ether mixture according to claim 1, characterized in that: the specific connection relationship between the primary circulation loop and the secondary circulation loop is as follows:
the bottom outlet of the high-temperature heat storage tank (2) is communicated with the outlet of the top Rankine cycle expansion machine (4) through one side of a three-way pipe, and the other side of the high-temperature heat storage tank is sequentially connected with a fourth valve (14), one side of the top Rankine cycle working medium of the first evaporator (6), a seventh valve (17) and the top inlet of the low-temperature heat storage tank (7) in series; an outlet at one side of the top of the high-temperature heat storage tank (2) is communicated with an inlet of a top Rankine cycle expansion machine (4) through a first valve (11); the bottom outlet of the low-temperature heat storage tank (7) is communicated with the inlet of the solar heat collection field (1) through a first working medium pump (8) and an eighth valve (18) which are connected in series, the outlet of the solar heat collection field (1) is communicated with the inlet of the other side of the top of the high-temperature heat storage tank (2), and a ninth valve (19) is connected in parallel between the inlet of the eighth valve (18) and the outlet of the solar heat collection field (1); a sixth valve (16) and a second working medium pump (9) are connected in parallel between an inlet of the seventh valve (17) and an outlet of the first working medium pump (8), the sixth valve (16) and the second working medium pump (9) are connected in series, and an outlet of the second working medium pump (9) is connected in parallel with an outlet of the first working medium pump (8);
the outlet of the top Rankine cycle expansion machine (4) is sequentially connected with a third valve (13), one side of the top Rankine cycle working medium of the second evaporator (5) and a fifth valve (15) in series, and the outlet of the fifth valve (15) is respectively communicated with the inlet of one side of the top Rankine cycle working medium of the first evaporator (6) and the outlet of the fourth valve (14) through a three-way pipe;
the inlet of the bottom Rankine cycle expansion machine (10) is sequentially connected with one side of a bottom Rankine cycle working medium of the second evaporator (5), one side of the bottom Rankine cycle working medium of the first evaporator (6), one side of the heat regenerator (20) and the outlet of the third working medium pump (22) in series, and the outlet of the bottom Rankine cycle expansion machine (10) is sequentially connected with the other side of the heat regenerator (20), one side of the condenser (21) and the inlet of the third working medium pump (22) in series;
an outlet at one side of the Rankine cycle working medium at the top of the second evaporator (5) is connected with an inlet of a second working medium pump (9) in parallel.
3. The direct expansion solar thermal power generation system using biphenyl-biphenyl ether mixture according to claim 1, characterized in that: the solar heat collection field (1) is one of a parabolic groove type heat collection field, a linear Fresnel heat collection field and a tower type heat collection field.
4. The direct expansion solar thermal power generation system using biphenyl-biphenyl ether mixture according to claim 1, characterized in that: the phase change material (3) is an inorganic salt phase change material, and the inorganic salt phase change material is one of potassium hydroxide inorganic salt, lithium chloride-potassium chloride binary mixed inorganic salt and lithium chloride-sodium chloride-potassium chloride ternary mixed inorganic salt.
5. The direct expansion solar thermal power generation system using biphenyl-biphenyl ether mixture according to claim 1, characterized in that: the bottom Rankine cycle working medium is toluene, benzene, pentane or water.
6. The direct expansion solar thermal power generation system using biphenyl-biphenyl ether mixture according to claim 1, characterized in that: the structural formula of biphenyl in the biphenyl-biphenyl ether mixture is C12H10The concentration of biphenyl in the biphenyl-biphenyl ether mixture was 26.5%; the structural formula of the diphenyl ether is C12H10The concentration of diphenyl ether in the O, biphenyl-diphenyl ether mixture was 73.5%.
7. The direct expansion solar thermal power generation system using biphenyl-biphenyl ether mixture according to claim 1, characterized in that: the top Rankine cycle expander (4) and the bottom Rankine cycle expander (10) are both one of a steam turbine or a screw expander.
CN202110084910.2A 2021-01-21 2021-01-21 Direct expansion type solar thermal power generation system using biphenyl-diphenyl ether mixture Pending CN112523981A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114439714A (en) * 2022-02-28 2022-05-06 中国科学技术大学 Tower type solar thermal power generation system adopting biphenyl and diphenyl ether mixture circulating working medium

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114439714A (en) * 2022-02-28 2022-05-06 中国科学技术大学 Tower type solar thermal power generation system adopting biphenyl and diphenyl ether mixture circulating working medium
CN114439714B (en) * 2022-02-28 2024-05-10 中国科学技术大学 Tower type solar thermal power generation system adopting biphenyl and biphenyl ether mixture circulating working medium

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