CN106481522B - A Closed Helium Turbine Tower Solar Thermal Power Generation System with Thermal Storage - Google Patents

Abstract

The invention provides a closed helium turbine tower type solar thermal power generation system with heat storage, which comprises: the system comprises a tower type solar heat collection system, a heat storage system and a power system, wherein the tower type solar heat collection system, the heat storage system and the power system form a first circulation system, the heat storage system and the power system form a second circulation system, the tower type solar heat collection system adopts helium as a heat absorption working medium, and the power system adopts helium as a power working medium. The invention realizes the improvement of the economy of the tower type solar energy system by combining the design of the high-efficiency helium gas heat absorber and the design of the novel heat storage system through the application of the high-temperature, high-efficiency and compact-structure closed helium gas wheel power system.

Description

A Closed Helium Turbine Tower Solar Thermal Power Generation System with Thermal Storage

technical field

The invention relates to a tower-type solar thermal power generation system device, in particular to a closed-type helium turbine tower-type solar thermal power generation system with heat storage.

Background technique

Solar energy resources are abundant, but the energy flow density is low, and concentrating solar power technology has emerged as the times require. Concentrating solar power generation system coupling energy storage technology can overcome the intermittent defect of solar radiation, realize continuous power generation and have basic load characteristics, making it obvious Superior to other renewable energy technologies, it has become the most popular research direction in the development and utilization of new energy and renewable energy. During the "Thirteenth Five-Year Plan" period, the scale of my country's solar power generation industry is expected to be greatly improved. According to the scale development indicators provided by the National Energy Administration, by the end of 2020, the installed capacity of solar energy will be 7% of the power structure, and the total installed capacity of solar thermal power generation is expected to reach 10 million kilowatts, accounting for about 6% of the total installed capacity of solar energy.

According to different concentrating methods, concentrating solar thermal power generation technology (CSP) mainly includes trough type, tower type, dish type and Fresnel type. The former two have entered the stage of commercial operation, and the latter two are in the demonstration and test stage. . The trough power generation technology is the most mature and widely commercialized, accounting for about 85% of the global commercial solar thermal power plants. This technology only tracks solar radiation one-dimensionally, has low concentration ratio, operating temperature is basically 50-400°C, and low thermal efficiency; compared with tower and dish systems, the wind resistance system is poor. The light concentration ratio of the disc system is as high as hundreds to thousands, and it can also make the heat exchange medium reach a high temperature, and its system can be operated independently. However, the power of the system is small, and it is mainly connected to the Stirling power generation device. The Fresnel system has high light-gathering efficiency, but low work efficiency, and is currently in the demonstration project stage. Tower-type thermal power generation systems usually use a large number of heliostats to concentrate solar radiation on the heat-collecting receiver at the top of the tower, so that the heat conversion working medium (steam, molten salt, air, etc.) can obtain high temperature, and drive the power system to generate electricity or enter Heat storage system releases heat. The heliostat adopts a dual-axis tracking method, the light concentration ratio can reach 150-2000 times, and the light concentration effect is high. Thermal power conversion efficiency is also suitable for large-scale power generation. However, the heliostat requires a high-precision tracking system, and the heat sink needs to reach a higher temperature, so the cost of the mirror field and the heat sink is high, resulting in high power generation costs. Compared with other systems, tower solar power generation technology has the most development potential. At present, the United States, Spain, India, South Africa, Mexico, Australia, China and other countries have invested a lot of research on solar tower systems, including conceptual design, component research, demonstration projects, etc., in order to improve the efficiency of solar tower power generation, reduce investment costs, and make Tower solar power generation technology can compete with current conventional power generation costs. The present invention relates to a new heat-exchanging working medium of tower solar energy, a new heat storage technology and a new power system, so the prior art of the tower solar thermal power generation system will be described in terms of these items.

1) Heat absorption and heat transfer working medium: The heat transfer working medium of tower solar heat absorber is diversified, which can be water/steam, molten salt, normal pressure air, pressurized air, supercritical steam and other gases. Currently, water/steam and molten salt are mainly used in commercial power plants, and other media are in the stage of demonstration, component research or conceptual design. Water/steam is a relatively mature heat-absorbing working fluid. The condensed water is sent to the heat absorber at the top of the tower, where it is heated, evaporated and even overheated in turn. The water pump at the top of the tower consumes less power. Saturated or superheated steam can directly drive sophisticated steam turbine units, or store heat in thermal storage systems. However, due to the high pressure corresponding to high-temperature steam, the current steam temperature range is 400-500°C and the pressure range is 5-12MPa. If the steam parameters develop towards the supercritical parameters of thermal power plants, the corresponding pressure will exceed 20MPa. The high-pressure environment requires that the thickness of the tube in the heat absorber be increased, and the stress of the tube is also increased accordingly, which will reduce the heat transfer coefficient of absorbing solar radiation heat to a certain extent, and limit the solar radiation flux. In addition, the superheated steam generated in the heat absorber has the problem of differential control of heat transfer coefficients in different regions. In comparison, saturated steam is more beneficial to the life of the heat absorbing plate and the control of heat absorption, so saturated steam is usually preferred in commercial units. At present, tower-type power stations in the world that use water/steam as heat-absorbing working medium mainly include EURELIOS in Italy, SUNSHINE in Japan, Solar One in the United States, CESA-1 in Spain, SPP-5 in Russia, and Badaling in China.

Molten salt has become the most potential and widely used heat transfer medium because of its high heat capacity density, high heat transfer coefficient and low price. As a heat-absorbing working medium, molten salt can also be used as a heat-storing working medium. At the same time, its operating system pressure is low, and the system works relatively safely. The design of the heat absorber is more compact, the manufacturing cost is reduced, and the heat loss is reduced. But the molten salt medium still has some obvious disadvantages: 1) The molten salt, as a heat-absorbing working fluid, flows in the entire pipeline. When there is no solar energy input at night, the molten salt in the pipeline of the heat absorber will dissipate after the temperature drops. Solidification, such as the melting point temperature of 40% KNO ₃ /60% NaNO ₃ binary salt commonly used now is 220°C, the system needs better heat preservation measures and additional heat tracing equipment to prevent the molten salt from solidifying; 3) If the system shuts down, use High-pressure nitrogen blows out the residual molten salt in the heat absorber to avoid solidification of the molten salt; 4) The corrosiveness of the high-temperature molten salt to the molten salt pump leads to hidden dangers in the safe operation of the system, and the high-temperature molten salt corrodes the heat exchange pipes of the heat absorber It also leads to a decrease in the efficiency of the collector, resulting in safety hazards and short running time; 5) It is not suitable for high-power tower solar power generation systems. The increase in tower height and the increase in circulating molten salt flow will lead to increased power consumption and cost of molten salt pumps. Molten salt pumps consume significantly more power than water pumps. The world's tower solar power plants that use molten salt as heat absorption and heat exchange medium mainly include MSEE and Solar Two in the United States, THEMIS in France, and Solar Tres in Spain. At present, the main research direction of molten salt as a heat exchange medium is to develop a new type of molten salt with low melting point and high reliability, in order to reduce system cost and improve system safety.

Air media has attracted much attention due to its low cost, high safety, and most importantly, the ability to achieve higher operating temperatures. When air is used as the heat-absorbing medium, it is divided into normal-pressure air and pressurized air. When normal-pressure air is used as the heat-absorbing medium, it is coupled with a steam turbine power generation system through an intermediate heat exchanger, such as the German test power station Jülich. Due to the use of low-pressure air and the low heat transfer capacity of the gas, the heat absorber is bulky, and the maximum temperature of the steam Rankine cycle unit is limited and the current material technology (generally not exceeding 625°C), so that the high temperature obtained by air exchange cannot be controlled. Take advantage of. When the heat-absorbing medium is high-pressure air, it is mainly coupled with an open gas turbine cycle or a combined cycle. This method can be fully based on the existing mature gas turbine unit technology. The technology is currently in the component research and conceptual design phase. Air heat absorbers mainly have volumetric and cavity structures. Laboratories such as the Weizmann Research Institute in Israel and the German Aerospace Center DLR have carried out research on various high-temperature air heat absorbers, and conducted in-depth studies on their heat transfer performance and flow characteristics. Research. Compared with liquid, the specific heat of air is small, and it is more difficult to transport high-flow high-temperature air to high altitudes. When the air delivery pressure is high and the volume flow is large, the proportion of self-consumption electricity of the system will increase, reducing the net power generation efficiency of the system.

2) Heat storage system: Although solar energy resources are inexhaustible, solar radiation energy is an unstable random natural energy source, and it is intermittent. In order to meet the continuous power load demand and avoid power system Frequent start and stop calls for an efficient heat storage system. When the solar radiation is insufficient or at night, the thermal storage system is activated to ensure the continuous operation of the power system.

Heat storage methods include sensible heat storage, latent heat storage and chemical reaction heat storage.

Sensible heat storage media include solid and liquid. Solid heat storage media include sand, refractory bricks, concrete, honeycomb ceramics, composite ceramics, etc., and liquid heat storage media are mainly molten salt. Due to the following characteristics of molten salt, it becomes The most widely used sensible heat storage medium: wide temperature range and relative thermal stability; molten salt has good thermal conductivity; low vapor pressure, especially mixed molten salt; large heat capacity; low viscosity and good chemical stability. At present, molten salt heat storage is basically used in commercial tower systems, and the heat storage time can be designed for up to 15 hours, realizing uninterrupted power supply of the power system.

Phase change heat storage can realize constant temperature heat storage and heat release, the output temperature and energy are stable, and the heat storage density is high, the heat storage per unit volume is significantly higher than sensible heat storage, and has great development potential. At present, the medium and low temperature heat storage using steam as the phase change medium has been realized, and the heat storage using the high temperature phase change medium is still in the research stage, and there is no report on its application in demonstration projects. At present, the most potential high-temperature heat storage phase change heat storage media mainly include high-temperature molten salt and metal alloys. The bottleneck in the application of high-temperature molten salt lies in the low thermal conductivity, which affects the charge and discharge rate of the heat storage system. Metal alloys have very high thermal conductivity, high heat storage density, high latent heat of phase change, and good thermal cycle stability. However, the obvious disadvantage is that liquid metal alloys are highly corrosive and require high requirements for corresponding container materials, and the research on metal alloy phase change materials in the field of heat storage is insufficient. The temperature and phase state of the heat storage material change with the charging and heating process of the system, and the corresponding physical parameters will also change, which will affect the heat storage and heat transfer performance of the system, but there is little relevant data accumulation. The research on the compatibility of high-temperature liquid metal alloys and container materials lacks system and regularity. The key to the further development of phase change heat storage technology is the research on the enhancement of thermophysical properties of phase change heat storage materials, and solving problems such as uneven heat transfer, cavitation, thermal stress, erosion and materials.

3) Power system: The current concentrating solar technology is mainly equipped with a mature steam turbine as the power system. Due to the characteristics of the high-temperature heat transfer medium it can provide, the tower solar system can be equipped with a high-temperature and high-efficiency power system based on Brayton cycle or combined cycle. . At present, the steam temperature of the steam turbine power plant equipped in commercial applications is basically in the subcritical range, and the steam parameters can be developed to supercritical and ultra-supercritical parameters, but limited to the current material and process level, the efficiency of the steam turbine Rankine cycle system is further improved. The space is small, and the system cost is high, and the equipment size is large.

Brayton cycles include open and closed cycles. When air is used as the heat-absorbing medium, the high-pressure air is directly heated to about 1000°C to drive the gas turbine, and then the steam Rankine cycle is used as the bottom cycle to realize cascade utilization of heat energy and improve thermal efficiency. This power cycle is based on the open Brayton + Langen Ken's combined cycle. At present, the application of this power system at home and abroad is still in the research stage.

The application of the power system based on the closed Brayton cycle to the tower solar system is basically in the conceptual design stage. The working medium of the power system based on the closed Brayton cycle can be diversified, including air, helium, supercritical CO ₂ and other inert gas mixtures. At present, the most extensively researched closed Brayton cycle working medium is supercritical CO ₂ . The air closed cycle was applied to tower solar thermal power generation system in the 1980s. A detailed conceptual design was proposed, but there was no follow-up test. Compared with the steam Rankine cycle and the open gas turbine Brayton cycle, the power system based on the closed Brayton cycle has obvious advantages: 1) The cycle efficiency is high, for example, the SCO ₂ working fluid can reach 45% at a temperature of 600 °C The thermal power conversion efficiency of the power system is high, and the thermal power conversion efficiency of the helium working medium is as high as 45-48% when the temperature is 850 °C; 2) Small size and compact layout. Taking helium as an example, the power system occupies only 1/5 of the steam turbine power system at the same power level; 3) It can ensure the efficient operation of the system under both basic load and variable load conditions: various load adjustment methods, And it can maintain the efficient operation of the unit without deviating from the design working point; 4) The cooling source of the cooling system of the device can be either air-cooled or water-cooled, that is, it meets the anhydrous operation condition.

U.S. Patent US7685820 "Supercritical carbon dioxide concentrating solar power generation system device" proposes to replace the steam turbine device in the tower solar power system with a supercritical carbon dioxide turbine, and the molten salt is still used as a heat absorption, heat exchange and heat storage medium to ensure the compression The carbon dioxide parameters at the inlet of the machine are slightly higher than the supercritical state, that is, 7.38MPa, 30.98°C. The Chinese patent family of this patent is 200710306179.3. The follow-up Chinese patent 201010277740.1 also proposed a supercritical carbon dioxide solar thermal power generation system with heat storage. The difference is that the lowest temperature of carbon dioxide in the cycle is lower than the critical point, that is, the compressor is replaced by a carbon dioxide booster liquid pump to achieve transcritical compression. , to further improve cycle efficiency. The supercritical carbon dioxide power plant has high efficiency and compact device, but its working environment is high, reaching about 20MPa, and the design maturity of supercritical carbon dioxide impeller machinery is low, and the control system is relatively complicated. It is still in the experimental stage of components and systems. A recent Chinese patent 201510068135.6 proposes a tower-type solar thermal power generation method and system using a closed-loop Brayton cycle. The water vapor cycle is different from the high-pressure and high-temperature steam of the traditional steam Rankine cycle. Instead, it uses low-pressure, high-temperature steam to drive the steam turbine to do work. At the same time, it couples the gas turbine device and the bottom Rankine cycle, and uses the high-temperature exhaust gas of the gas turbine cycle to heat and enter the heat absorption. The water in front of the condenser is evaporated into water vapor; the bottom Rankine cycle is used as the cold source of the condenser to further use the waste heat to realize the cascade utilization of heat and improve the cycle efficiency. This cycle intends to make full use of the advantage of less power consumption of the water pump and the cascaded utilization of heat, but it is difficult to realize, and the high-temperature and low-pressure water vapor (700-1500°C) has poor workability and low density (resulting in large equipment size), while still There is a problem of water vapor corrosion, and the material requirements are high.

The key issue facing the widespread commercialization of tower-type solar power generation systems is to reduce investment costs and make them competitive with traditional power generation costs. The reduction of investment costs mainly focuses on increasing the installed capacity of the system, optimizing the design of the mirror field and heat absorber, developing an efficient and economical heat storage system, and supporting an economical and efficient thermal power conversion system. Statistics in the past have shown that the order of system cost impact factors is slightly different under different heat-absorbing working fluids. For example, when using molten salt heat exchange medium, the order is to increase the system power, optimize the size and structure design of the heliostat, adopt advanced mirror field design, Advanced heat storage system; when using steam heat exchange medium, increase the system power, optimize the size and structure design of heliostats, use supercritical steam, advanced heat storage, mirror field; use atmospheric air heat exchange medium in order to increase Large system power, optimized size and structural design of heliostats, advanced heat storage, improved performance of heat absorbers, and advanced mirror field design.

The purpose of the present invention is to make full use of the high concentration ratio of tower solar energy, seek a heat transfer gas that is beneficial to the design of a high-temperature heat absorber-a new heat-exchange working medium, and match a power system with high efficiency and great power amplification potential-based on a closed Brayton cycle , while coupling a new high-efficiency heat storage system - high temperature phase change heat storage, to improve the power generation efficiency of the tower solar power generation system and reduce the cost of power generation.

Contents of the invention

In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a closed helium turbine tower solar thermal power generation system with heat storage, in order to power The application of the system, combined with the design of the high-efficiency helium heat absorber and the design of the new heat storage system, realizes the improvement of the economy of the tower solar system.

In order to achieve the above purpose and other related purposes, the present invention provides a closed helium turbine tower solar thermal power generation system with heat storage, comprising: a tower solar heat collection system, a heat storage system and a power system, the tower The solar heat collection system, the heat storage system and the power system form the first circulation system, the heat storage system and the power system form the second circulation system, and the tower solar heat collection system uses helium as the Endothermic working fluid, the power system uses helium as the power working fluid.

As a preferred solution of the closed helium turbine tower solar thermal power generation system with heat storage of the present invention, when the solar radiation is sufficient, the tower solar heat collection system is coupled with the heat storage system and the power system, and the heat storage system It works decoupled from the power system. After the helium absorbs heat from the tower solar collector system, part of the high-temperature helium directly drives the power system, and the other part directly enters the heat storage system. The low-temperature helium after passing through the power system and the heat storage system The exothermic low-temperature helium is combined and sent back to the tower solar heat collection system to form the first circulation system.

As a preferred solution of the closed helium turbine tower solar thermal power generation system with heat storage of the present invention, when the solar radiation is insufficient, the tower solar heat collection system and the power system are decoupled, and the heat storage system and the power system Coupled work, and the heat storage system is used as a heat source. After the helium exchanges heat with the heat storage medium in the heat storage system, the high temperature helium drives the power system, and then the low temperature helium is sent back to the heat storage system to form the second circulation system.

As a preferred solution of the closed-type helium turbine tower solar thermal power generation system with heat storage of the present invention, the action switching between the coupling work and the decoupling work is realized by the opening and closing of the valve.

As a preferred solution of the closed helium turbine tower solar thermal power generation system with heat storage of the present invention, the first circulation system uses helium as the heat transfer medium, and uses helium as the tower solar heat collector The endothermic working fluid of the system, and helium is used as the power working fluid of the power system.

As a preferred solution of the closed-type helium turbine tower solar thermal power generation system with thermal storage in the present invention, the second circulation system uses helium as the heat transfer medium, and uses helium as the heat absorption system of the thermal storage system. Thermal working medium, and helium is used as the power working medium of the power system.

As a preferred solution of the closed helium turbine tower solar thermal power generation system with heat storage of the present invention, the first circulation system uses helium as the heat transfer medium, and uses helium as the tower solar heat collector The heat-absorbing working fluid of the system adopts high-temperature phase-change materials as the heat-storage working medium of the heat storage system.

Preferably, the high-temperature phase-change material includes a high-temperature molten salt, and its melting point temperature is not lower than 750°C.

As a preferred solution of the closed-type helium turbine tower solar thermal power generation system with heat storage of the present invention, the heat storage system also includes a circulation fan for providing pressure head for the cooled helium, and returning to Tower type solar heat collection system realizes circulation.

As a preferred solution of the closed helium turbine tower solar thermal power generation system with heat storage of the present invention, the power system adopts a closed cycle helium turbine system.

As a preferred solution of the closed helium turbine tower solar thermal power generation system with heat storage of the present invention, the helium turbine system is based on closed cycle work, including helium turbine, regenerator, precooling device, low-pressure compressor, intercooler, high-pressure compressor and motor, the inlet of the helium turbine is connected with the tower solar heat collection system and heat storage system, and the motor is connected with the helium turbine The first outlet is connected, the second outlet and the third outlet of the helium turbine are respectively connected with the first inlet of the high-pressure compressor and the first inlet of the regenerator, the first outlet of the high-pressure compressor and The second outlet is respectively connected to the second inlet of the regenerator and the first inlet of the low-pressure compressor, the inlet of the intercooler is connected to the outlet of the low-pressure compressor, and the outlet of the intercooler is connected to the outlet of the low-pressure compressor. The second inlet of the high-pressure compressor is connected, the first outlet of the regenerator is connected with the inlet of the precooler, the outlet is connected with the tower solar heat collection system and the heat storage system, and the precooler The outlet of is connected with the second inlet of the low-pressure compressor.

Preferably, the precooler and the intercooler at least cool the temperature of the helium to below 30°C.

Preferably, the cooling source of the cooler includes one of air and water.

Preferably, the cooler is a low-temperature waste heat recovery device to realize cascaded utilization of heat.

Preferably, the design pressure of the power system is not less than the load pressure of the power system when the solar radiation is sufficient, and is proportional to the helium flow rate of the first circulation system or the second circulation system.

Preferably, the design pressure of the heat storage circuit in the heat storage system is not less than the working pressure of the power system circuit when the heat storage system is used as a heat source for exothermic heat.

Preferably, the thermal storage capacity of the thermal storage system is sufficient to ensure that the thermal storage system and the power system are coupled to work when the solar radiation is insufficient.

As mentioned above, the closed-type helium turbine tower solar thermal power generation system with heat storage of the present invention has the following beneficial effects:

Helium is used as the heat-absorbing working medium, which can realize an efficient and compact heat-absorbing device design. Helium is an inert gas with good compatibility with materials, higher system operation safety, and higher working temperature of heat transfer medium. Helium has good thermal properties, the specific heat capacity is about 2.4 times that of water vapor, and 4.7 times that of air; the thermal conductivity is about 5.6 times that of air, and the kinematic viscosity of helium is small. When the temperature is the same and the resistance coefficient is equal, the flow velocity of air in the pipeline is allowed to vary within the range of 25-45m/s, while the allowable value of the flow velocity of helium is 55-100m/s, which will help to enhance heat transfer. Therefore, the designed heat absorber has small temperature difference, small pressure loss, small heat loss and compact structure.

When other conditions are the same, the pressure loss of helium in the pipeline is 2.2 times smaller than that of air, and the heat storage circuit requires less fan power consumption.

The use of high-temperature phase-change materials as the heat storage medium can keep the temperature stable during the charging and discharging process, thereby ensuring the stable operation of the power system when the heat storage system is started.

The use of high-temperature phase-change materials with a melting point temperature not lower than 750°C ensures the high efficiency of the power system for starting the heat storage system.

The helium closed-type Brayton cycle is adopted. When the turbine inlet temperature reaches a high temperature range above 850°C, its thermal power conversion efficiency reaches 45% and above, which has obvious advantages compared with the steam Rankine cycle.

The closed Brayton cycle of helium is adopted, and the maximum pressure of the system cycle is obviously lower than that of the steam Rankine cycle and the supercritical carbon dioxide cycle, which improves the safety of the system and reduces the material and process manufacturing requirements of pipelines and equipment.

In short, the excellent physical properties of the new heat exchange medium helium ensure the feasibility of designing an efficient and compact heat absorber, and at the same time, the existing air heat absorber design and test experience can be fully used for reference. The efficient and economical heat storage system overcomes the intermittent defect of solar radiation, meets the continuous power load demand, avoids the frequent start and stop of the power system, and maintains the efficient operation of the power system. The helium turbine power system based on the closed cycle ensures high heat-to-power conversion efficiency under design conditions and a wide range of variable conditions. Finally, the overall efficiency and economy of the system can be improved.

Description of drawings

Fig. 1 is a schematic diagram showing the architecture of a closed helium turbine tower solar thermal power generation system with heat storage in the present invention.

Fig. 2 is a schematic structural diagram of an embodiment of a closed helium turbine tower solar thermal power generation system with heat storage of the present invention.

Fig. 3 is a graph showing the relationship between the efficiency of the power system and the cycle pressure ratio in the first cycle system under different split ratios.

Fig. 4 is a graph showing the relationship between the power of the heat storage circuit circulation fan and the split rate in the first circulation system.

Fig. 5 is a graph showing the relationship between the efficiency of the power system in the first circulation system and the circulation pressure ratio under different split ratios under the influence of the power of the heat storage branch circuit circulation fan.

Component designation description

10 tower solar heat collection system

101 mirror field

102 heat sink

20 heat storage system

201 High temperature heat storage tank

202 circulation fan

30 power system

301 Helium Turbine

302 motor

303 high pressure compressor

304 Low Pressure Compressor

305 Intercooler

306 Regenerator

307 precooler

Detailed ways

Embodiments of the present invention are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes, and various modifications or changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention.

Please refer to Figure 1 to Figure 5. It should be noted that the diagrams provided in this embodiment are only schematically illustrating the basic idea of the present invention, so that only the components related to the present invention are shown in the diagrams rather than the number, shape and Dimensional drawing, the type, quantity and proportion of each component can be changed arbitrarily during actual implementation, and the component layout type may also be more complicated.

As shown in Figure 1, the present invention provides a closed helium turbine tower solar thermal power generation system with heat storage, including: a tower solar heat collection system 10, a heat storage system 20 and a power system 30, the tower The solar heat collection system 10, the heat storage system 20 and the power system 30 form a first circulation system, the heat storage system 20 and the power system 30 form a second circulation system, and the tower solar heat collection The system 10 uses helium as the endothermic working fluid, and the power system 30 uses helium as the power working fluid.

As an example, when the solar radiation is sufficient, the tower type solar thermal collection system 10 is coupled with the heat storage system 20 and the power system 30 to work, the heat storage system 20 and the power system 30 are decoupled, and helium is absorbed from the tower type solar heat collection system 10 After heating, part of the high-temperature helium directly drives the power system 30, and the other part directly enters the heat storage system 20, and the low-temperature helium after passing through the power system 30 is combined with the low-temperature helium released from the heat storage system 20, and then sent back to the tower The solar heat collection system 10 constitutes a first circulation system. When the solar radiation is insufficient, the tower solar heat collection system 10 and the power system 30 work decoupled, the heat storage system 20 and the power system 30 work coupled, and the heat storage system 20 is used as a heat source, and the helium in the heat storage system 20 is combined with the heat storage After heat exchange by the medium, the high-temperature helium drives the power system 30, and then the low-temperature helium is sent back to the heat storage system 20 to form a second circulation system.

Specifically, the closed-type helium turbine tower solar thermal power generation system with heat storage includes two working cycle processes within 24 hours, as shown in Figure 1:

1) When the solar radiation is sufficient during the day, the helium gas absorbs the solar radiant heat through the heat absorber of the tower solar heat collection system 10, making its temperature reach 850°C or even higher, a part of the high-temperature helium directly drives the power system 30, and the other part directly After entering the heat storage system 20, the low-temperature helium gas after passing through the power system 30 and the low-temperature helium gas exothermic through the heat storage system 20 merge and then enter the heat absorber to absorb heat. The above-mentioned components and processes constitute the first circulation system.

2) When the solar radiation is insufficient, including rainy weather and at night, the heat storage system 20 enters the heat release mode, and the helium gas exchanges heat with the heat storage medium in the heat storage system 20 to obtain a high temperature to drive the power system, and then returns to the heat storage system 20 To absorb heat, the above-mentioned components and processes constitute the second circulation system.

In the first working cycle system, the flow ratio of helium entering the power system 30 and entering the heat storage system 20 affects the thermal power conversion efficiency of the system and the heat capacity of the heat storage system, which can be optimally determined based on the principle of high efficiency and economy.

As an example, the action switching between the coupling work and the decoupling work is realized by the opening and closing of the valve.

As an example, the first circulation system uses helium as the heat transfer medium, uses helium as the heat absorbing working medium of the tower solar collector system 10 , and uses helium as the power working medium of the power system 30 .

As an example, the second circulation system uses helium as the heat transfer fluid, helium as the heat absorption fluid of the heat storage system 20 , and helium as the power fluid of the power system 30 .

As an example, the first circulation system uses helium as the heat transfer working medium, uses helium as the endothermic working medium of the tower solar heat collection system 10, and uses a high-temperature phase change material as the heat storage working medium of the heat storage system 20 . Preferably, the high-temperature phase-change material includes a high-temperature molten salt, and its melting point temperature is not lower than 750°C.

As shown in FIG. 2 , as an example, the heat storage system 20 also includes a circulation fan, which is used to provide a pressure head for the cooled helium, and return it to the tower solar heat collection system 10 to realize circulation. Preferably, the design pressure of the heat storage circuit of the heat storage system 20 is not less than the working pressure of the circuit of the power system 30 when the heat storage system 20 is used as a heat source for exothermic heat. Preferably, the heat storage capacity of the heat storage system 20 is sufficient to ensure that the heat storage system 20 and the power system 30 are coupled to work when the solar radiation is insufficient. Specifically, the heat storage capacity of the heat storage system 20 is to ensure that the power system 30 maintains high-efficiency work during the heat release period, and the size and cost of the heat storage system 20 are considered to be finally determined.

As an example, the power system 30 adopts a closed cycle helium gas turbine system.

As shown in Figure 2, the helium gas turbine system works based on a closed cycle, including a helium gas turbine, a regenerator, a precooler, a low-pressure compressor, an intercooler, a high-pressure compressor, and an electric motor. The inlet of the turbine is connected with the tower type solar heat collection system 10 and the thermal storage system 20, the motor is connected with the first outlet of the helium turbine, the second outlet of the helium turbine and the third The outlets are respectively connected to the first inlet of the high-pressure compressor and the first inlet of the regenerator, and the first outlet and the second outlet of the high-pressure compressor are respectively connected to the second inlet of the regenerator and the low-pressure regenerator. The first inlet of the compressor is connected, the inlet of the intercooler is connected with the outlet of the low-pressure compressor, the outlet of the intercooler is connected with the second inlet of the high-pressure compressor, and the first The outlet is connected to the inlet of the precooler, the outlet is connected to the tower solar heat collection system 10 and the heat storage system 20, and the outlet of the precooler is connected to the second inlet of the low pressure compressor.

Preferably, the precooler and the intercooler at least cool the temperature of the helium to below 30°C.

Preferably, the pressure ratio of the compressor is determined by a stable temperature (such as 850° C.) provided by the heat absorber and performance optimization calculations of various components in the power system 30 .

Preferably, the cooling source of the cooler includes one of air and water. In addition, the cooler can also be a low-temperature waste heat recovery device to realize cascaded utilization of heat.

Preferably, the design pressure of the power system 30 is not less than the load pressure of the power system 30 when the solar radiation is sufficient, and the helium flow rate of the first circulation system or the second circulation system is proportional to the relationship.

As shown in Figure 2, the working process of the power system 30 is:

1) High-temperature and high-pressure helium gas enters the helium gas turbine and expands to do work, driving the generator to generate electricity;

2) After expansion, helium enters the low-pressure side of the regenerator to recover part of the heat;

3) Then enter the precooler to cool;

4) After cooling, the helium enters the low-pressure compressor and is compressed to a certain pressure;

5) Then enter the intercooler to cool again;

6) After cooling, helium enters the high-pressure compressor to continue compression and boosting;

7) High-pressure helium enters the high-pressure side of the regenerator to heat up;

8) Finally, it enters the heat absorber to absorb solar radiation energy or enters the heat storage system 20 to absorb the heat release of the heat storage medium, prepares for entering the turbine to do work, and completes a cycle.

The closed helium turbine tower solar thermal power generation system with heat storage of this embodiment will be further described below.

As shown in FIG. 1 , the closed-type helium turbine tower-type solar thermal power generation system with heat storage in this embodiment includes a tower-type solar heat collection system 10 , a heat storage system 20 and a power system 30 .

As shown in Figure 2, the tower type solar heat collection system 10 mainly includes a mirror field 101 and a heat absorber 102, the heat storage system 20 includes a high temperature heat storage tank 201 and a circulating fan 202, and the thermal work conversion system mainly includes a helium ventilation system. Flat 301, helium regenerator 306, precooler 307, helium low pressure compressor 304, intercooler 305, helium high pressure compressor 303 and motor 302.

When the solar radiation is sufficient during the day, valve c is closed, and valves a and b are opened. The heat storage process of the heat storage system and the working process of the power system start at the same time, and affect each other due to different flow distribution.

The heat absorber 102 heats the heat-absorbing working fluid. After the temperature is stabilized, a part of the working fluid directly enters the power system to drive the turbine 301, drives the generator 302 to generate electricity, and the other part of the high-temperature working fluid enters the heat storage system. The working medium entering the power system is expanded by the turbine and releases waste heat through the low-pressure side of the regenerator 306, then enters the precooler 307 for cooling, and then enters the low-pressure compressor 304 for compression, and the high-pressure working medium enters the intercooler 305 to be cooled again, and then Enter the high-pressure compressor 303 for further compression. At this time, the pressure of the working medium is the maximum pressure of the cycle. The high-pressure working medium enters the regenerator 306 to absorb the waste heat of the working medium on the low-pressure side, and then releases heat from the heat storage circuit to the helium of the heat storage medium. Converge back to the heat absorber 102 to absorb solar radiant heat, completing a cycle. The working medium entering the heat storage system relies on the pressure head provided by the circulating fan 202 to overcome the pressure loss generated by the pipeline and the heat storage system, and forms a pressure balance with the working medium from the power system.

When the solar radiation is insufficient or at night, the heat absorber stops heating the heat-absorbing working medium, the valves a and b are closed, and the valve c is opened, and the heat release of the heat storage system directly drives the power system to do work. The heat storage medium of the high-temperature heat storage system releases latent heat to heat the working medium, and then drives the turbine 301 to drive the generator 302 to generate electricity. After the working medium expands through the turbine, it releases waste heat through the low-pressure side of the regenerator 306, and then enters the precooler 307 for cooling. , and then enter the low-pressure compressor 304 for compression, the high-pressure working medium enters the intercooler 305 to be cooled again, and then enters the high-pressure compressor 303 for further compression. The device 306 absorbs the waste heat of the low-pressure side heat transfer medium, and then returns to the heat storage system to be heated continuously, completing a cycle.

In the working process, the heat-absorbing medium and the heat-transfer medium are both helium. The thermal power conversion system uses helium as the power cycle working fluid.

The heat storage system adopts latent heat storage, and the heat storage medium is a high temperature phase change material, which can be selected but not limited to high temperature phase change molten salt,

And the melting temperature is at least 750°C.

When the heat storage system is storing heat, the high-temperature helium continuously releases heat to heat the heat storage medium, and stores the heat in the form of latent heat.

When the heat storage system is used as an exothermic heat source, it can stably release the phase change latent heat of the heat storage medium, and heat the helium gas, the working medium of the power system, to reach a temperature close to the high temperature melting point of the phase change material.

The cooler and precooler in the power system reduce the temperature of helium to 30°C and below.

The ratio of the helium flow rate entering the power system to the helium flow rate entering the heat storage system affects the thermal power conversion efficiency of the cycle system and the selection of the optimal design pressure of the cycle.

The maximum design pressure of the power system cycle is determined comprehensively by the design requirements of the components and the compactness and economy of the system. For example, if the design load is 50MWe, the pressure is about 2.5-3.5MPa.

The actual pressure of the power system cycle is determined by the actual power level and is proportional to the flow rate of the working medium in the closed cycle.

The design pressure of the heat storage circuit of the heat storage system is determined by the design pressure of the power system.

The pressure head of the fan in the heat storage circuit of the heat storage system must be sufficient to overcome the helium pressure loss caused by the pipeline and the heat storage system.

The invention implements the modeling calculation of the system cycle to determine the optimal ratio of the helium flow entering the power system and the helium flow entering the heat storage system in the first cycle system, as well as the optimal design pressure ratio of the power system. The efficiencies mentioned above all refer to heat-to-electricity conversion efficiencies. In the η _{cycle1+cycle2,} cycle2 can maintain the power system to work for 14 hours with heat storage capacity to estimate the total system efficiency, wherein cycle1 and cycle2 correspond to the first cycle system and the second cycle system in FIG. 1 respectively.

Table 1 below gives the performance parameters of the system at different split rates when the pressure ratio of the fixed cycle is 2.86.

Table 1 The performance parameters of the system under fixed cycle pressure ratio

On the one hand, the performance prediction can comprehensively consider the system economy and the heat storage system cost to determine the final design parameters of the system. On the other hand, it also reflects the thermal power conversion efficiency of the closed helium turbine tower solar thermal power generation system with heat storage. advantages, and suitable for large-scale.

Figure 3 below shows how the system efficiency varies with the cycle pressure ratio when the flow rate of helium gas entering the power system is different from the flow rate of helium gas entering the heat storage system (referred to as split rate). Among them, the loop system efficiency of the first circulation system in Figure 5 takes into account the influence of the heat storage branch loop fan power, so it is lower than the loop power system efficiency of the first circulation system, and the fan power decreases with the increase of the split rate, as shown in Figure 4 shown.

As mentioned above, the closed-type helium turbine tower solar thermal power generation system with heat storage of the present invention has the following beneficial effects:

Helium is used as the heat-absorbing working medium, which can realize an efficient and compact heat-absorbing device design. Helium is an inert gas with good compatibility with materials, higher system operation safety, and higher working temperature of heat transfer medium. Helium has good thermal properties, the specific heat capacity is about 2.4 times that of water vapor, and 4.7 times that of air; the thermal conductivity is about 5.6 times that of air, and the kinematic viscosity of helium is small. When the temperature is the same and the resistance coefficient is equal, the flow velocity of air in the pipeline is allowed to vary within the range of 25-45m/s, while the allowable value of the flow velocity of helium is 55-100m/s, which will help to enhance heat transfer. Therefore, the designed heat absorber has small temperature difference, small pressure loss, small heat loss and compact structure.

When other conditions are the same, the pressure loss of helium in the pipeline is 2.2 times smaller than that of air, and the heat storage circuit requires less fan power consumption.

Using high-temperature phase-change materials as the heat storage medium can keep the temperature stable during the charging and discharging process, thereby ensuring stable operation of the power system 30 when the heat storage system 20 is started.

The use of high-temperature phase-change materials with a melting point temperature not lower than 750° C. ensures the high efficiency of the power system 30 for starting the heat storage system 20 .

The helium closed-type Brayton cycle is adopted. When the turbine inlet temperature reaches a high temperature range above 850°C, its thermal power conversion efficiency reaches 45% and above, which has obvious advantages compared with the steam Rankine cycle.

The closed Brayton cycle of helium is adopted, and the maximum pressure of the system cycle is obviously lower than that of the steam Rankine cycle and the supercritical carbon dioxide cycle, which improves the safety of the system and reduces the material and process manufacturing requirements of pipelines and equipment.

In short, the excellent physical properties of the new heat exchange medium helium ensure the feasibility of designing an efficient and compact heat absorber, and at the same time, the existing air heat absorber design and test experience can be fully used for reference. The efficient and economical heat storage system 20 overcomes the intermittent defect of solar radiation, meets the continuous power load demand, avoids frequent start and stop of the power system 30 , and maintains the high-efficiency operation of the power system 30 . The helium turbine power system 30 based on a closed cycle ensures high heat-to-power conversion efficiency in the design working condition and a wide range of variable working conditions. Finally, the overall efficiency and economy of the system can be improved.

Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial application value.

The above-mentioned embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed in the present invention should still be covered by the claims of the present invention.

Claims (12)

1. A closed helium turbine tower solar thermal power generation system with heat storage, comprising: the system comprises a tower type solar heat collection system, a heat storage system and a power system, wherein the tower type solar heat collection system, the heat storage system and the power system form a first circulation system, the heat storage system and the power system form a second circulation system, the tower type solar heat collection system adopts helium as a heat absorption working medium, and the power system adopts helium as a power working medium; the first circulation system adopts helium as a heat transfer working medium, helium as a heat absorption working medium of the tower type solar heat collection system and a high-temperature phase change material as a heat storage working medium of the heat storage system; the power system adopts a closed circulation helium turbine system; when the solar radiation is sufficient, the tower type solar heat collection system is coupled with the heat storage system and the power system, the heat storage system and the power system are decoupled, after helium absorbs heat from the tower type solar heat collection system, one part of high-temperature helium directly drives the power system, the other part of the high-temperature helium directly enters the heat storage system, and the low-temperature helium after passing through the power system is converged with the low-temperature helium after passing through the heat storage system and then returned to the tower type solar heat collection system to form a first circulating system; when the solar radiation is insufficient, the tower type solar heat collection system and the power system are decoupled, the heat storage system and the power system are coupled, the heat storage system is used as a heat source, after helium exchanges heat with a heat storage medium in the heat storage system, high-temperature helium drives the power system, and then low-temperature helium is returned to the heat storage system to form a second circulation system; the helium turbine system works based on closed circulation and comprises a helium turbine, a heat regenerator, a precooler, a low-pressure compressor, an intercooler, a high-pressure compressor and a motor, wherein an inlet of the helium turbine is connected with the tower type solar heat collection system and the heat storage system, the motor is connected with a first outlet of the helium turbine, a second outlet and a third outlet of the helium turbine are respectively connected with a first inlet of the high-pressure compressor and a first inlet of the heat regenerator, a first outlet and a second outlet of the high-pressure compressor are respectively connected with a second inlet of the heat regenerator and a first inlet of the low-pressure compressor, an inlet of the intercooler is connected with an outlet of the low-pressure compressor, an outlet of the intercooler is connected with a second inlet of the high-pressure compressor, a first outlet of the heat regenerator is connected with an inlet of the precooler, an outlet of the precooler is connected with the tower type solar heat collection system and the heat storage system, and an outlet of the precooler is connected with a second inlet of the low-pressure compressor.

2. The closed helium turbine tower solar thermal power system with heat storage of claim 1, wherein: the action switching of the coupling work and the decoupling work is realized by the opening and closing of the valve.

3. The closed helium turbine tower solar thermal power system with heat storage of claim 1, wherein: the first circulation system adopts helium as a heat transfer working medium, helium as a heat absorption working medium of the tower type solar heat collection system and helium as a power working medium of the power system.

4. The closed helium turbine tower solar thermal power system with heat storage of claim 1, wherein: the second circulation system adopts helium as a heat transfer working medium, helium as a heat absorption working medium of the heat storage system and helium as a power working medium of the power system.

5. The closed helium turbine tower solar thermal power system with heat storage of claim 1, wherein: the high-temperature phase change material comprises high-temperature molten salt, and the melting point temperature of the high-temperature molten salt is not lower than 750 ℃.

6. The closed helium turbine tower solar thermal power system with heat storage of claim 1, wherein: the heat storage system further comprises a circulating fan, wherein the circulating fan is used for providing a pressure head for the cooled helium gas and sending the pressure head back to the tower type solar heat collection system to realize circulation.

7. The closed helium turbine tower solar thermal power system with heat storage of claim 1, wherein: the precooler and the intercooler cool at least helium gas to a temperature below 30 ℃.

8. The closed helium turbine tower solar thermal power system with heat storage of claim 1, wherein: the cooling source of the intercooler comprises one of the atmosphere and water.

9. The closed helium turbine tower solar thermal power system with heat storage of claim 1, wherein: the intercooler is a low-temperature waste heat recovery device so as to realize gradient utilization of heat.

10. The closed helium turbine tower solar thermal power system with heat storage of claim 1, wherein: the pressure of the power system design is not less than the load pressure of the power system when the solar radiation is sufficient, and the load pressure is determined in direct proportion to the helium flow of the first circulation system or the second circulation system.

11. The closed helium turbine tower solar thermal power system with heat storage of claim 1, wherein: the design pressure of the heat storage system is not less than the working pressure of the power system loop when the heat storage system is used as a heat release heat source.

12. The closed helium turbine tower solar thermal power system with heat storage of claim 1, wherein: the heat storage capacity of the heat storage system is long enough to ensure the coupling work of the heat storage system and the power system when the solar radiation is insufficient.