CN113983720B - Gain type molten salt energy storage system - Google Patents

Gain type molten salt energy storage system Download PDF

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Publication number
CN113983720B
CN113983720B CN202111305046.0A CN202111305046A CN113983720B CN 113983720 B CN113983720 B CN 113983720B CN 202111305046 A CN202111305046 A CN 202111305046A CN 113983720 B CN113983720 B CN 113983720B
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molten salt
temperature
ultra
high temperature
low
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CN113983720A (en
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王俊峰
金建祥
邓国梁
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Zhejiang State Energy Power Technology Co ltd
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Zhejiang State Energy Power Technology Co ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B30/00—Heat pumps
    • F25B30/02—Heat pumps of the compression type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01B—MACHINES OR ENGINES, IN GENERAL OR OF POSITIVE-DISPLACEMENT TYPE, e.g. STEAM ENGINES
    • F01B23/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
    • F01B23/08—Adaptations for driving, or combinations with, pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01B—MACHINES OR ENGINES, IN GENERAL OR OF POSITIVE-DISPLACEMENT TYPE, e.g. STEAM ENGINES
    • F01B25/00—Regulating, controlling, or safety means
    • F01B25/02—Regulating or controlling by varying working-fluid admission or exhaust, e.g. by varying pressure or quantity
    • F01B25/08—Final actuators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B35/00—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for
    • F04B35/008—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for the means being a fluid transmission link
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B35/00—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for
    • F04B35/04—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for the means being electric
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D20/0034—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D20/0034—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material
    • F28D2020/0047—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material using molten salts or liquid metals
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P80/00—Climate change mitigation technologies for sector-wide applications
    • Y02P80/10—Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

The invention provides a gain type molten salt energy storage system, which comprises an ultrahigh temperature heat pump system, a molten salt system and a low-quality heat recovery system; the ultra-high temperature heat pump system can generate high quality energy at high temperature of 550 ℃ and 900 ℃. The molten salt system includes: the system comprises a low-temperature molten salt tank, a molten salt pump and a high-temperature molten salt tank; the low-temperature molten salt tank is connected with a molten salt heater through a molten salt pump, and a low-temperature side outlet of the molten salt heater is connected with an inlet of the high-temperature molten salt tank; the low quality heat recovery system includes: the power generation island comprises a power generation island hot water storage tank, a water pump and a power generation island cold water storage tank. Therefore, the invention realizes the effective utilization of the expansion work of the compressed gas working medium by reasonably arranging the expansion machine, the heat regenerator, the cooler and other equipment, effectively improves the inlet temperature of the ultra-high temperature compressor, reduces the compression work of the ultra-high temperature compressor, effectively absorbs the energy of a low-quality heat source, and obviously improves the overall conversion efficiency.

Description

Gain type molten salt energy storage system
Technical Field
The invention relates to the technical field of energy storage, in particular to a gain type molten salt energy storage system.
Background
With the gradual improvement of the power generation proportion of intermittent new energy such as solar photovoltaic, wind power and the like, the proportion of adjustable power supplies such as thermal power and the like is reduced year by year, the safety and stability of the operation of a power grid are challenged more and more, and a large-scale, long-time and fast-response peak regulation means of a power grid level becomes an important guarantee for guaranteeing the safety and stability of the power grid and improving the consumption capacity of the new energy.
The existing mature large-scale and long-time peak regulation technology is only water pumping energy storage, but is limited by geographical conditions, the developable capacity of the water pumping energy storage is limited, and the requirement of a novel power system which mainly uses new energy in China on energy storage peak regulation in the future cannot be met, meanwhile, the investment cost of the water pumping energy storage is high, the construction period is long, the large-scale reservoir construction also has certain influence on ecological environment, besides the water pumping energy storage, the battery energy storage is developed rapidly, but the safety and environmental protection problems are not solved effectively all the time, the cost is high, the method is difficult to be used as a large-scale long-time energy storage peak regulation means of a power grid level, the compressed air energy storage which is researched and developed in recent years enters a demonstration stage, but the compressed air energy storage efficiency is relatively low, underground salt cavern gas storage is generally adopted, the requirement on geographical conditions is high, and the development scale is limited.
Along with the completion of the commercialization demonstration of the international and domestic solar thermal power generation technology, the safety, economy, stability and reliability of high-temperature molten salt heat storage power generation are fully verified, the molten salt is heated and stored by using a resistor in the valley power period, and the high-temperature molten salt is used for heating water to generate steam in the peak power period, so that the power generation of a steam turbine is pushed to become a feasible thermal energy storage peak regulation scheme, the large-scale long-term energy storage of a power grid level can be realized, and each technical link is fully verified, so that the development potential is high.
In the prior art, a system using high-temperature waste heat exists, the patent application number is CN201420317097.4, the waste heat in industrial production is concentrated, the purpose of recycling the waste heat in the industry is achieved by using the principle of water/steam power generation, and the fused salt energy storage system for power peak regulation of a thermal power unit is also provided, the patent number is CN201810599639.4, the system can better use heat storage and heat release, and the problem of power deep peak regulation is solved by matching with the thermal power unit.
Because the electric-thermal conversion efficiency of the resistance heating mode is less than 1, the efficiency of converting heat into electricity by the steam turbine is generally only about 45 percent, the total conversion efficiency of electricity into electricity is lower than 45 percent, even if the efficiency of the steam turbine is further improved, the total efficiency is generally hardly over 50 percent, and compared with the efficiency of about 75 percent of pumped storage and the efficiency of about 60 percent of compressed air storage, the electric-thermal conversion efficiency of the resistance heating mode has serious restrictive short plates,
in view of the above, the prior art is obviously inconvenient and disadvantageous in practical use, and needs to be improved.
In order to solve the problem, the invention provides a gain type molten salt energy storage system, wherein a traditional mode of heating molten salt by using a resistor is replaced by a mode of heating molten salt by using an ultrahigh-temperature heat pump, the ultrahigh-temperature heat pump is a thermal circulation system, and low-quality energy in low-temperature environments such as waste heat of a power generation island, air and the like can be improved to high-quality energy with the temperature of 550 ℃ and the temperature of 900 ℃, so that the electric-thermal conversion efficiency which is more than 1 can be realized, the electric-thermal conversion efficiency can be matched with the current mature molten salt medium, the electric-to-electric conversion efficiency of 1.5 can be realized, and 60-70% of the electric-to-electric conversion efficiency can be realized by matching with a mature steam turbine, so that the high-temperature molten salt energy storage power generation becomes a peak regulation mode with strong competitiveness.
Disclosure of Invention
In view of the above drawbacks, the present invention aims to provide an enhanced molten salt energy storage system, which realizes effective utilization of expansion work of a compressed gas working medium by reasonably arranging an expander, a heat regenerator, a cooler, and other devices, effectively increases the inlet temperature of an ultra-high temperature compressor, reduces the compression work of the ultra-high temperature compressor, and effectively absorbs energy of a low-quality heat source.
In order to achieve the above object, the present invention provides a gain type molten salt energy storage system, which comprises an ultrahigh temperature heat pump system, a molten salt system and a low quality heat recovery system; the ultra-high temperature heat pump system includes: the system comprises a motor, an ultrahigh-temperature compressor, a molten salt heater, a heat regenerator, an expander, a heat absorber and a cooler; the motor is connected with the ultra-high temperature compressor, the output end of the ultra-high temperature compressor is connected with the heat regenerator through the molten salt heater, the output end of the heat regenerator is connected with the expander and the feed inlet of the ultra-high temperature compressor, and the output end of the expander is connected with the heat regenerator through the heat absorber; the molten salt system includes: a low-temperature molten salt tank, a molten salt pump and a high-temperature molten salt tank; the low-temperature molten salt tank is connected with a molten salt heater through a molten salt pump, and a low-temperature side outlet of the molten salt heater is connected with an inlet of the high-temperature molten salt tank; the low quality heat recovery system includes: the system comprises a power generation island hot water storage tank, a water pump and a power generation island cold water storage tank; the power generation island hot water storage tank is connected with a low-temperature side inlet of a heat absorber through a water pump, and a low-temperature side outlet of the heat absorber is connected with an inlet of a power generation island cold water storage tank.
According to the gain type molten salt energy storage system, the ultrahigh temperature heat pump system, the molten salt system and the low-quality heat recovery system are provided with a plurality of temperature sensors, and the temperature sensors comprise a first temperature sensor, a second temperature sensor, a third temperature sensor and a fourth temperature sensor; the first temperature sensor is connected with an outlet pipeline at the low-temperature side of the heat absorber; the second temperature sensor is connected with a low-temperature side outlet pipeline of the molten salt heater; a third temperature sensor connected with the temperature transmission system is arranged between the output end of the ultrahigh-temperature compressor and the molten salt heater; and a fourth temperature sensor is arranged between the cooler and the ultrahigh-temperature compressor.
According to the gain type molten salt energy storage system, a plurality of cooler regulating valves are arranged in a low-quality heat recovery system, and each cooler regulating valve comprises a first cooler regulating valve and a second cooler regulating valve; an inlet of a first cooler regulating valve is communicated with an outlet of the ultra-high temperature compressor, a heat absorber is connected with the cooler through a second cooler regulating valve, a high-temperature side outlet of the cooler is communicated with a rotor cooling inlet in the ultra-high temperature compressor, and the rotor cooling inlet of the ultra-high temperature compressor is positioned on the side surface of a cylinder body of the ultra-high temperature compressor and is communicated with a gap between the rotor of the ultra-high temperature compressor and a cylinder; and a pressure sensor is arranged on an inlet pipeline of the ultra-high temperature compressor.
According to the gain type molten salt energy storage system, a buffer pressure system is further arranged between the expansion machine and the heat absorber, and the pressure buffer system comprises: a buffer tank and a connecting valve; one end of the connecting valve is connected with the buffer tank, and the other end of the connecting valve is connected with an outlet pipeline of the expansion machine.
According to the gain type molten salt energy storage system, the same working medium as that in the ultra-high temperature heat pump system is filled in the buffer tank, and the working medium in the buffer tank is connected with the outlet pipeline of the expansion machine through the connecting valve; when the ultra-high temperature heat pump system needs to discharge working media, the working media in the outlet pipeline of the expansion machine enter the buffer tank through the connecting valve to be stored.
According to the gain type molten salt energy storage system, the working medium in the ultrahigh temperature heat pump system is any one or more of carbon dioxide, nitrogen, helium, argon and xenon;
the molten salt medium of the molten salt heater is heat conducting oil or water, and the heat absorption source of the heat absorber is air, geothermal or industrial waste gas;
when the working medium in the high-temperature heat pump system is liquid, the motor, the ultrahigh-temperature compressor and the expander are coaxially arranged and are connected by adopting a coupling; the left side and the right side of the motor are respectively connected with the ultra-high temperature compressor and the expander.
According to the gain type molten salt energy storage system, in the working state, the rotating speeds of the ultrahigh-temperature compressor and the expander are both 3000 rpm, the rotating speeds of the ultrahigh-temperature compressor and the expander in the standby state are both 500 rpm, the ultrahigh-temperature compressor is in the low-rotating-speed low-power-consumption heat standby state in the standby state, and the outlet temperature of the ultrahigh-temperature compressor is 550-900 ℃ in the working state and the standby state.
According to the gain type molten salt energy storage system, the molten salt heater is a printed circuit plate type heat exchanger or a shell-and-tube type heat exchanger.
An operation method of a gain type molten salt energy storage system comprises the following starting steps:
step 1), starting an ultrahigh temperature heat pump system when electricity is used in a valley, wherein the inlet pressure of an ultrahigh temperature compressor in the ultrahigh temperature heat pump system is normal pressure in an initial state, a bypass valve is fully opened, an expansion machine regulating valve is fully closed, and a motor takes electricity from a power grid to drive the rotating speed of the ultrahigh temperature compressor to rise to 3000 revolutions per minute;
step 2), the pressure buffer system is put into, the connecting valve is opened, gas working media in the buffer tank are injected into the ultrahigh temperature heat pump system, the temperature of the outlet of the ultrahigh temperature compressor is gradually increased until the temperature of the third temperature sensor reaches 550 ℃, the bypass valve is closed, and the expansion machine adjusting valve is opened;
step 3), putting the molten salt system into operation, starting the molten salt pump, monitoring the second temperature sensor and the pressure sensor, cooperatively adjusting the operating frequency and the opening of the connecting valve of the molten salt pump, gradually increasing the reading of the inlet pressure sensor of the ultrahigh-temperature compressor to a target value, and simultaneously enabling the temperature shown by the second temperature sensor to be within the range of 550-900 ℃;
step 4), when the operation of the step 3) is performed, the low-quality heat recovery system is put into use, the water pump is started, the operating frequency of the water pump is gradually increased, and meanwhile, the first temperature sensor is monitored until the index of the first temperature sensor is gradually increased to a target value;
and 5), cutting off the pressure buffering system and closing the connecting valve.
An operation method of a gain type molten salt energy storage system,
the shutdown steps are as follows:
step 1), the pressure buffer system is put into operation, the connecting valve is opened, and meanwhile, the expansion machine adjusting valve is rapidly adjusted to 40% of opening degree, so that the flow and the pressure of the ultra-high temperature heat pump system are rapidly reduced, rapid load reduction is realized,
step 2), cutting off the molten salt system, and cooperatively adjusting the operating frequency of the molten salt pump to ensure that the temperature indicated by the second temperature sensor is within the range of 550-900 ℃, and stopping the molten salt pump when the indication of the third temperature sensor is lower than 540 ℃;
step 3), gradually cutting off the low-quality heat recovery system while operating in the step 2), gradually reducing the operating frequency of the water pump, and closing the water pump when the reading of the pressure sensor reaches 0.1 MPa;
and 4), the ultra-high temperature heat pump system is in hot standby, the motor frequency reduction rate is operated, and the rotating speed of the ultra-high temperature compressor is reduced to 500 rpm.
The invention has the beneficial technical effects that: the invention aims to solve the problem of low efficiency of high-temperature molten salt thermal energy storage power generation, and provides a gain type molten salt energy storage system.
Drawings
FIG. 1 is a system flow diagram of the present invention;
fig. 2 is a schematic view of a conventional heat pump system represented by an air conditioner;
fig. 3 is a simplified flow diagram of a conventional thermodynamic cycle.
In the figure, 1 electric motor, 2 ultra-high temperature compressor, 3 molten salt heater, 4 heat regenerator, 5 expander, 6 heat absorber, 7 cooler, 8 bypass valve, 9 expander regulating valve, 10 first temperature sensor;
11 low-temperature molten salt tank, 12 molten salt pump, 13 second temperature sensor, 14 high-temperature molten salt tank, 15 buffer tank and 16 connecting valve;
17 power generation island hot water storage tank, 18 water pump, 19 power generation island cold water storage tank, 20 third temperature sensor, 21 fourth temperature sensor, 22 pressure sensor, 23 first cooler regulating valve and 24 second cooler regulating valve;
25 ordinary compressors, 26 turbines, 27 pressure reducing valves, 28 radiators, 29 safety shut-off valves and 30 rotating speed regulating valves.
Detailed Description
For purposes of promoting a better understanding of the objects, aspects and advantages of the present invention, reference will now be made in detail to the present invention, which is to be read in connection with the accompanying drawings and examples, wherein the specific examples are set forth to illustrate, but are not to be construed as limiting,
referring to fig. 1-3, the invention provides a gain-type molten salt energy storage system based on the large-scale and long-time peak shaving requirements of a power grid level, and aims at the problem of low efficiency of traditional resistance heating molten salt heat energy storage power generation, so as to realize the significant improvement of the overall electricity-electricity conversion efficiency.
As shown in fig. 1, the gain-type molten salt energy storage system includes an ultra-high temperature heat pump system, a molten salt system, a low-quality heat recovery system, and a pressure buffer system.
The ultra-high temperature heat pump system adopts gases which can stably run at high temperature such as carbon dioxide, air, nitrogen, helium, argon, xenon and the like as circulating working media, and comprises the following components: the system comprises a motor 1, an ultrahigh-temperature compressor 2, a molten salt heater 3, a heat regenerator 4, an expander 5, a heat absorber 6, a cooler 7, a bypass valve 8, an expander regulating valve 9, a first cooler regulating valve 23, a second cooler regulating valve 24 and a first temperature sensor 10.
Motor 1, ultra-high temperature compressor 2 and 5 coaxial arrangements of expander adopt the coupling joint, and motor 1 is located the intermediate position, and the side is ultra-high temperature compressor 2 and expander 5 respectively about motor 1, and three above-mentioned equipment are coaxial directly to be connected and realize 5 work of expansion direct drive ultra-high temperature compressor 2 of expander, and need not to convert 5 work of expansion of expander into electric energy and redrive ultra-high temperature compressor 2, have reduced the energy conversion link, reduce the loss, have improved system efficiency.
The outlet of the ultrahigh-temperature compressor 2 is communicated with the inlet of the high-temperature side of the molten salt heater 3, the outlet of the high-temperature side of the molten salt heater 3 is communicated with the inlet of the high-temperature side of the heat regenerator 4, the outlet of the high-temperature side of the heat regenerator 4 is communicated with the inlet of the expansion machine regulating valve 9, the outlet of the expansion machine regulating valve 9 is communicated with the inlet of the expansion machine 5, the outlet of the expansion machine 5 is communicated with the inlet of the high-temperature side of the heat absorber 6, the outlet of the high-temperature side of the heat absorber 6 is communicated with the inlet of the low-temperature side of the heat regenerator 4, the outlet of the low-temperature side of the heat regenerator 4 is communicated with the inlet of the ultrahigh-temperature compressor 2, and a complete thermodynamic cycle system is formed. A first temperature sensor 10 is connected to the low temperature side outlet pipe of the heat absorber 6 to measure the low temperature side outlet temperature of the heat absorber 6.
An inlet of the bypass valve 8 is communicated with a high-temperature side outlet pipeline of the molten salt heater 3, an outlet of the bypass valve 8 is communicated with an inlet pipeline of the ultra-high temperature compressor 2, and a bypass of the ultra-high temperature compressor 2 is formed.
Compared with the traditional heat pump system represented by an air conditioner (as shown in fig. 2), the invention has the following significant differences:
(1) after a working medium in the traditional heat pump system passes through a common compressor 25, the working medium is connected with a heat absorber 6 through a heat radiator 28 and a pressure reducing valve 27, the outlet temperature of the common compressor 25 is usually lower and is generally less than 50 ℃, while the outlet temperature of the ultra-high temperature compressor 2 in the invention is obviously improved and can reach 550-900 ℃. (2) The traditional heat pump system realizes pressure relief through an expansion valve, and expansion work is not utilized, but the expansion machine 5 is arranged to absorb the expansion work in the invention, so that the power consumption of the system can be greatly reduced; (3) the inlet of the common compressor 25 in the traditional heat pump system is connected with the heat absorber 6, the temperature is close to the room temperature, while the inlet temperature of the ultra-high temperature compressor 2 in the invention is in the range of 200-400 ℃, and necessary measures are required to improve the inlet temperature of the common compressor 25 as much as possible.
In a conventional thermodynamic cycle system (as shown in fig. 3), a working medium is compressed by a common compressor 25, enters a molten salt heater 3, works through a turbine 26, and enters a cooler 7. The invention has the following significant differences with the traditional thermodynamic cycle system:
(1) the common compressor 25 in the traditional thermodynamic cycle system is the highest point of system pressure but not the highest point of temperature, but the highest point of the system pressure and temperature of the ultrahigh-temperature compressor 2 in the invention, how to cool the common compressor 25 is the key problem to be solved; (2) in the conventional thermodynamic cycle system, the steam turbine 26 is used to drive the generator, and since the steam turbine 26 has the risk of overspeed during operation, a safety shut-off valve 29 and a speed regulating valve 30 are required to be arranged at the inlet of the steam turbine 26 to ensure the safety of the steam turbine 26. The expander 5 of the invention assists the motor 1 to drive the ultra-high temperature compressor 2, and the problem of over-rotation speed of the expander 5 does not exist.
Aiming at the problems caused by the difference, the invention uses the heat of the outlet part flow of the ultra-high temperature compressor 2 to heat the inlet working medium of the ultra-high temperature compressor 2 by arranging the cooler 7, improves the inlet temperature of the ultra-high temperature compressor 2 and forms the working medium which can be used for cooling the rotor of the ultra-high temperature compressor 2 at the same time, realizes the cooling of the rotor of the ultra-high temperature compressor 2 under the ultra-high temperature condition, reduces the material requirement of the rotor of the ultra-high temperature compressor 2, weakens the high temperature damage of the rotor, saves the cost and prolongs the service life of the equipment.
Meanwhile, the heat regenerator 4 is arranged, and the residual heat after the heat absorption of the molten salt heater 3 is partially used for heating the inlet working medium of the ultra-high temperature compressor 2, so that the inlet temperature of the ultra-high temperature compressor 2 is increased, the compression power consumption of the ultra-high temperature compressor 2 is reduced under the condition of ensuring that the outlet temperature of the compressor is unchanged, and the equipment manufacturing difficulty and cost are obviously reduced; on the other hand, the inlet temperature of the expansion machine 5 is reduced, which is beneficial to realizing the lower outlet temperature of the expansion machine 5 and the heat absorber 6 to realize the full absorption of low-quality heat.
Meanwhile, the expansion machine 5 is arranged to replace an expansion valve in the traditional heat pump, so that the further utilization of the expansion work of the high-pressure compressed gas is realized, the power of the motor 1 is effectively reduced, and the overall efficiency of the system is improved.
In addition, only 1 regulating valve is arranged at the inlet end of the expansion machine 5, a safety shut-off valve 29 and a rotating speed regulating valve 30 are omitted, the number of equipment is reduced, the cost is reduced, meanwhile, the regulating valve only completes 40% -60% flow regulation and does not participate in low flow regulation, the diameter of the throat part of the valve is obviously larger than that of the rotating speed regulating valve 30 in the traditional thermodynamic cycle, the pressure loss is greatly reduced, and the system efficiency is improved.
The inlet of the first cooler regulating valve 23 is connected with the outlet of the ultra-high temperature compressor 2, the outlet of the first cooler regulating valve 23 is connected with the inlet of the high-temperature side of the cooler 7, the outlet of the high-temperature side of the cooler 7 is communicated with the cooling inlet of the rotor of the ultra-high temperature compressor 2, the fourth temperature sensor 21 is arranged, the cooling inlet of the rotor of the ultra-high temperature compressor 2 is positioned on the side surface of the cylinder body of the ultra-high temperature compressor 2, and the inlet of the rotor of the ultra-high temperature compressor 2 is communicated with the gap of the cylinder. The inlet of the second cooler regulating valve 24 is communicated with the low-temperature side outlet of the heat absorber 6, the outlet of the second cooler regulating valve 24 is communicated with the low-temperature side inlet of the cooler 7, and the low-temperature side outlet of the cooler 7 is communicated with the inlet of the ultra-high temperature compressor 2. When the inlet temperature of the ultra-high temperature compressor 2 is increased, a working medium which can be used for cooling the rotor of the ultra-high temperature compressor 2 is formed, and the rotor cooling of the ultra-high temperature compressor 2 under the ultra-high temperature condition is realized.
The molten salt system includes: a low-temperature molten salt tank 11, a molten salt pump 12, a second temperature sensor 13 and a high-temperature molten salt tank 14. The outlet of the low-temperature molten salt tank 11 is connected with the inlet of a molten salt pump 12, the outlet of the molten salt pump 12 is connected with the inlet of the low-temperature side of a molten salt heater 3, and the outlet of the low-temperature side of the molten salt heater 3 is connected with the inlet of a high-temperature molten salt tank 14 to form a complete molten salt system. The second temperature sensor 13 is located at the outlet pipeline at the low-temperature side of the molten salt heater 3 and is used for measuring the outlet temperature at the low-temperature side of the molten salt heater 3.
The low quality heat recovery system includes: a power generation island hot water storage tank 17, a water pump 18 and a power generation island cold water storage tank 19. An outlet of a hot water storage tank 17 of the power generation island is connected with an inlet of a water pump 18, an outlet of the water pump 18 is connected with an inlet of a low-temperature side of a heat absorber 6, and an outlet of the low-temperature side of the heat absorber 6 is connected with an inlet of a cold water storage tank 19 of the power generation island, so that a complete low-quality heat recovery system is formed.
The pressure buffer system includes: a buffer tank 15 and a connecting valve 16. The connecting valve 16 is connected to the buffer tank 15 at one end and to the outlet pipe of the expander 5 at the other end. When the ultra-high temperature heat pump system needs to supplement working media, the working media in the buffer tank 15 enter an outlet pipeline of the expansion machine 5 through the connecting valve 16; when the ultra-high temperature heat pump system needs to discharge working media, the working media in the outlet pipeline of the expansion machine 5 enter the buffer tank 15 through the connecting valve 16 to be stored.
The gain type molten salt energy storage system starting scheme is as follows:
1) and starting the ultrahigh temperature heat pump system when the electricity is used in a valley. In the initial state, the inlet pressure of the ultra-high temperature compressor 2 in the ultra-high temperature heat pump system is normal pressure, the bypass valve 8 is fully opened, the expansion machine adjusting valve 9 is fully closed, and the motor 1 of the expansion machine 5 takes electricity from a power grid to drive the rotation speed of the ultra-high temperature compressor 2 to rise to 3000 revolutions per minute.
2) The pressure buffer system is put into operation. And (3) opening the connecting valve 16, injecting the gas working medium in the buffer tank 15 into the ultrahigh temperature heat pump system, gradually increasing the outlet temperature of the ultrahigh temperature compressor 2 until the temperature of the third temperature sensor 20 reaches 550 ℃, closing the bypass valve 8, and opening the expander regulating valve 9.
3) And (5) putting a molten salt system. Starting the molten salt pump 12, monitoring the second temperature sensor 13 and the pressure sensor 22, cooperatively adjusting the operating frequency of the molten salt pump 12 and the opening degree of the connecting valve 16, gradually increasing the reading of the pressure sensor 22 at the inlet of the ultra-high temperature compressor 2 to a target value, and simultaneously increasing the temperature shown by the second temperature sensor 13 within the range of 550-900 ℃.
4) And (4) putting the low-quality heat recovery system into operation in the step (3), starting the water pump 18, gradually increasing the running frequency of the water pump 18, and simultaneously monitoring the first temperature sensor 10 until the reading of the first temperature sensor 10 is gradually increased to the target value.
5) The pressure buffer system is cut off and the connecting valve 16 is closed.
Through the scheme, the motor 1 gets electricity from a power grid, drives the ultrahigh-temperature compressor 2 to rotate, and compresses the working medium to a high-temperature state. The high-temperature working medium heats the molten salt, stores heat in a molten salt medium, recovers expansion work through the expander 5, further cools, enters the heat absorber 6 to absorb heat from low-temperature waste heat and heat up, is preheated through the heat regenerator 4, enters the inlet of the ultrahigh-temperature compressor 2, and is circulated to prepare the high-temperature molten salt.
The shutdown scheme of the gain type molten salt energy storage system is as follows:
1) and (3) the pressure buffer system is put into operation, the connecting valve 16 is opened, and meanwhile, the expansion machine regulating valve 9 is quickly regulated to 40% of opening degree, so that the flow and the pressure in the ultrahigh-temperature heat pump system are quickly reduced, and the quick load reduction is realized.
2) The molten salt system is cut off. The operation frequency of the molten salt pump 12 is cooperatively adjusted so that the temperature indicated by the second temperature sensor 13 is within the range of 550 ℃ and 900 ℃, and when the temperature indicated by the third temperature sensor 20 is lower than 540 ℃, the molten salt pump 12 is stopped.
3) And (3) gradually cutting off the low-quality heat recovery system while operating in the step (2), gradually reducing the operating frequency of the water pump 18, and turning off the water pump 18 when the reading of the pressure sensor 22 reaches 0.1 MPa.
4) And the ultra-high temperature heat pump system is in hot standby. The motor 1 operates at a lower frequency, so that the rotating speed of the ultrahigh-temperature compressor 2 is reduced to 500 rpm.
Through the scheme, the gain type molten salt energy storage system is shut down by quickly reducing the load, and meanwhile, the ultrahigh-temperature compressor 2 in the system is in a low-rotating-speed low-power-consumption hot standby state, so that the system can be quickly started.
The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it should be understood that various changes and modifications can be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (7)

1. A gain type molten salt energy storage system is characterized by comprising an ultrahigh temperature heat pump system, a molten salt system and a low-quality heat recovery system;
the ultra-high temperature heat pump system includes: the system comprises a motor (1), an ultrahigh-temperature compressor (2), a molten salt heater (3), a heat regenerator (4), an expander (5), a heat absorber (6) and a cooler (7);
the motor (1) is connected with the ultrahigh-temperature compressor (2), the output end of the ultrahigh-temperature compressor (2) is connected with the heat regenerator (4) through the molten salt heater (3), the output end of the heat regenerator (4) is connected with the expander (5) and the feed inlet of the ultrahigh-temperature compressor (2), and the output end of the expander (5) is connected with the heat regenerator (4) through the heat absorber (6);
the molten salt system includes: a low-temperature molten salt tank (11), a molten salt pump (12) and a high-temperature molten salt tank (14);
the low-temperature molten salt tank (11) is connected with the molten salt heater (3) through a molten salt pump (12), and the low-temperature side outlet of the molten salt heater (3) is connected with the inlet of the high-temperature molten salt tank (14);
the low quality heat recovery system includes: a power generation island hot water storage tank (17), a water pump (18) and a power generation island cold water storage tank (19);
the power generation island hot water storage tank (17) is connected with a low-temperature side inlet of a heat absorber through a water pump (18), and a low-temperature side outlet of the heat absorber (6) is connected with an inlet of a power generation island cold water storage tank (19);
a plurality of temperature sensors are arranged in the ultrahigh temperature heat pump system, the molten salt system and the low-quality heat recovery system, and the temperature sensors comprise a first temperature sensor (10), a second temperature sensor (13), a third temperature sensor (20) and a fourth temperature sensor (21);
the first temperature sensor (10) is connected with a low-temperature side outlet pipeline of the heat absorber (6);
the second temperature sensor (13) is connected with a low-temperature side outlet pipeline of the molten salt heater (3);
a third temperature sensor (20) connected with a temperature transfer system is arranged between the output end of the ultra-high temperature compressor (2) and the molten salt heater (3);
a fourth temperature sensor (21) is arranged between the cooler (7) and the ultrahigh-temperature compressor (2);
a plurality of cooler regulating valves are arranged in the low-quality heat recovery system, and each cooler regulating valve comprises a first cooler regulating valve (23) and a second cooler regulating valve (24);
an inlet of a first cooler regulating valve (23) is communicated with an outlet of the ultra-high temperature compressor (2), a heat absorber (6) is connected with a cooler (7) through a second cooler regulating valve (24), a high-temperature side outlet of the cooler (7) is communicated with a rotor cooling inlet inside the ultra-high temperature compressor (2), and the rotor cooling inlet of the ultra-high temperature compressor (2) is positioned on the side surface of a cylinder body of the ultra-high temperature compressor (2) and is communicated with a gap between the rotor of the ultra-high temperature compressor (2) and a cylinder; a pressure sensor (22) is arranged on an inlet pipeline of the ultra-high temperature compressor (2);
under the working state and the standby state, the outlet temperature of the ultra-high temperature compressor (2) is 550-;
still be equipped with buffer pressure system between expander (5) and heat absorber (6), pressure buffer system includes: a buffer tank (15) and a connecting valve (16);
one end of the connecting valve (16) is connected with the buffer tank (15), and the other end is connected with an outlet pipeline of the expansion machine (5).
2. The gain type molten salt energy storage system according to claim 1, characterized in that the same working medium as that in the ultra-high temperature heat pump system is filled in the buffer tank (15), and the working medium in the buffer tank (15) is connected with an outlet pipeline of the expansion machine (5) through a connecting valve (16); when the ultra-high temperature heat pump system needs to discharge working media, the working media in the outlet pipeline of the expansion machine (5) enter the buffer tank (15) through the connecting valve (16) to be stored.
3. The gain type molten salt energy storage system according to claim 2, wherein the working medium in the ultra-high temperature heat pump system is any one or more of carbon dioxide, nitrogen, helium, argon and xenon;
the molten salt medium of the molten salt heater (3) is heat conduction oil or water, and the heat absorption source of the heat absorber (6) is air, geothermal or industrial waste gas;
when the working medium in the high-temperature heat pump system is liquid, the motor (1), the ultrahigh-temperature compressor (2) and the expander (5) are coaxially arranged and are connected by adopting a coupling; the left side and the right side of the motor (1) are respectively connected with the ultra-high temperature compressor (2) and the expander (5).
4. The gain type molten salt energy storage system according to claim 1, characterized in that in the working state, the rotation speeds of the ultra-high temperature compressor (2) and the expander (5) are both 3000 rpm, the rotation speeds of the ultra-high temperature compressor (2) and the expander (5) in the standby state are both 500 rpm, and the ultra-high temperature compressor (2) is in the low-rotation-speed low-power-consumption hot standby state in the standby state.
5. The gain-type molten salt energy storage system according to claim 1, characterized in that the molten salt heater (3) is a printed circuit plate heat exchanger or a shell-and-tube heat exchanger.
6. A method of operating a gain-type molten salt energy storage system as claimed in any one of claims 1 to 5 wherein the start-up steps are as follows:
1) when electricity is used in a valley, the ultra-high temperature heat pump system is started, the inlet pressure of the ultra-high temperature compressor (2) in the ultra-high temperature heat pump system in an initial state is normal pressure, the bypass valve (8) is fully opened, the expansion machine regulating valve (9) is fully closed, and the motor (1) takes electricity from a power grid to drive the rotation speed of the ultra-high temperature compressor (2) to rise to 3000 revolutions per minute;
2) the pressure buffer system is put into, the connecting valve (16) is opened, gas working medium in the buffer tank (15) is injected into the ultra-high temperature heat pump system, the temperature of the outlet of the ultra-high temperature compressor (2) is gradually increased until the temperature of the third temperature sensor (20) reaches 550 ℃, the bypass valve (8) is closed, and the expansion machine adjusting valve (9) is opened;
3) the molten salt system is put into, the molten salt pump (12) is started, the second temperature sensor (13) and the pressure sensor (22) are monitored, the operating frequency of the molten salt pump (12) and the opening degree of the connecting valve (16) are cooperatively adjusted, the reading of the inlet pressure sensor (22) of the ultrahigh-temperature compressor (2) is gradually increased to a target value, and meanwhile, the temperature shown by the second temperature sensor (13) is within the range of 550-900 ℃;
4) while operating in the step 3), putting the low-quality heat recovery system into operation, starting the water pump (18), gradually increasing the operating frequency of the water pump (18), and simultaneously monitoring the first temperature sensor (10) until the indication of the first temperature sensor (10) is gradually increased to a target value;
5) the pressure buffer system is switched off and the connecting valve (16) is closed.
7. A method of operating a gain-type molten salt energy storage system as claimed in any one of claims 1 to 5,
the shutdown steps are as follows:
1) the pressure buffer system is put into operation, the connecting valve (16) is opened, and meanwhile, the expansion machine adjusting valve (9) is rapidly adjusted to 40% of opening degree, so that the flow and the pressure of the ultra-high temperature heat pump system are rapidly reduced, and rapid load reduction is realized;
2) cutting off the molten salt system, and cooperatively adjusting the operating frequency of the molten salt pump (12) so that the temperature indicated by the second temperature sensor (13) is in the range of 550-900 ℃, and stopping the molten salt pump (12) when the indication of the third temperature sensor (20) is lower than 540 ℃;
3) when the operation of the step (2) is carried out, the low-quality heat recovery system is cut off step by step, the running frequency of the water pump (18) is reduced step by step, and when the reading of the pressure sensor (22) reaches 0.1MPa, the water pump (18) is closed;
4) the ultra-high temperature heat pump system is in hot standby, the motor (1) operates at a low frequency, and the rotating speed of the ultra-high temperature compressor (2) is reduced to 500 rpm.
CN202111305046.0A 2021-11-05 2021-11-05 Gain type molten salt energy storage system Active CN113983720B (en)

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