SOLAR RECEIVER TYPE HEAT EXCHANGER, PARTICULARLY FOR CONCENTRATING SOLAR APPLICATION

Abstract

The invention relates to a solar receiver (1) comprising: - one or more inlet tubes (2) for heat transfer fluid; and - an external convergent section (5) located at the inlet; and - an internal divergent section (6) located inside the solar receiver; and - a rigid casing (8) which ensures the mechanical retention of the tubes and the minimization of optical and thermal losses; and - a neck (9) having a minimum diameter, and positioned between the external convergent section (5) and the internal divergent section (6); and - a conical section (10) located inside the solar receiver, characterized in that said tubes take a helical shape with variable diameter forming a cavity (11) into which the solar rays penetrate and characterized in that the size and number of said tubes (4) is different in the different sections of the solar receiver. Abstract figure: Fig. 1

Description

Title of the invention: SOLAR RECEIVER TYPE HEAT EXCHANGER, IN PARTICULAR FOR A CONCENTRATING SOLAR APPLICATION

[0001] The invention relates to the field of heat exchanger devices and systems of the solar receiver type, for a solar concentrator application. The invention relates more generally to a thermal absorber of the solar receiver type, intended to absorb the energy received from a solar concentrator to heat a fluid while minimizing thermal losses to the outside.

[0002] Solar energy production systems such as solar concentrators are currently being widely studied as converters of solar energy into other types of energy.

[0003] These converters can transform part of the solar rays into thermal energy by collecting the received solar energy and directing it in a concentrated manner onto the receiving surface of a component called the solar receiver.

[0004] By concentrating the flow of solar energy on a surface, it will be converted into thermal energy which can be used for thermal needs or to operate a thermodynamic machine which transforms part of the thermal energy into mechanical energy.

[0005] Several systems for converting solar energy into electrical and thermal energy exist, some are marketed as photovoltaic panels which allow solar energy to be transformed into electricity only, others like so-called solar thermal systems or so-called concentrated solar systems, allow solar energy to be transformed into thermal energy.

[0006] The so-called concentrated solar system or solar concentrator is a system with high potential for energy production applications from solar energy. Concentrated solar thermal technology consists of using solar radiation, the flow of solar energy, to heat a heat transfer fluid serving as a heat source in a thermodynamic cycle. This system makes it possible to reach relatively high temperatures at the solar receiver, which makes it possible to produce mechanical energy using thermodynamic machines with better efficiency compared to so-called photovoltaic panel systems. The mechanical energy can be transformed into electrical energy through an electric generator. The solar receiver is the component where the solar radiation, concentrated on its surface, is converted into sensible heat.The solar receiver is therefore this thermal absorber where solar radiation is absorbed by the walls then. dissipated by conduction in its internal structure. A transport fluid, also called a heat transfer fluid, circulates in the internal structure and heats up by heat exchange. This fluid can be air, water or any other type of liquid or gaseous fluid.

[0007] This technology of so-called solar concentrator systems promises the following advantages: - Use of renewable solar energy to produce electrical and thermal energy;

[0008] - Good solar electric and solar thermal conversion efficiency; - Low ground impact; - Silent system with little or no vibration or noise; - Low level of maintenance; - Ability to couple the system with thermal energy storage systems.

[0009] Solar receiver type heat exchangers exist on solar concentration applications and several types are proposed: - a rectangular surface solar receiver;

[0010] - a conical tube receiver; - a printed metal receiver; - a spherical receiver to minimize the energy re-emitted by radiation.

[0011] The interest of this invention application lies in the fact that a variable power solar receiver with high efficiency is proposed, while reducing the complexities of integration and manufacturing. The problems encountered with solar receivers are as follows:

[0012] Unfortunately, the architectures of the prior art are not optimized so as to minimize energy losses by radiation and convection, to minimize pressure losses in the fluid circulating inside the receiver and to maximize efficiency.

[0013] Furthermore, the rectangular surface solar receiver represents heat losses by radiation effect through the solar concentration surface as well as heat losses by natural convection.

[0014] Furthermore, the conical tube solar receiver has thermal losses by radiation due to its relatively large inlet surface and significant pressure losses due to the length of the tubes.

[0015] The 3D printed metallic solar receiver involves a complex technology, costly in time, and difficult to industrialize on a large scale.

[0016] In addition, the plate solar receiver requires specific insulation to reduce heat losses. This solar receiver also requires specific brazing at the level of the plates and at the level of the collectors on the fluid inlet and outlet.

[0017] Thus, one objective of the invention is to overcome the defects of the prior art, in particular to propose a solar receiver or thermal absorber solution, which can be industrialized on a large scale, having good energy efficiency while minimizing pressure losses at the level of the heat transfer fluid.

[0018] To achieve this objective, the invention proposes a solar receiver comprising: - one or more heat transfer fluid inlet tubes; and

[0019] - one or more heat transfer fluid outlet tubes; and

[0020] - one or more tubes for circulating a heat transfer fluid; and - an external convergent section located at the entrance of the solar flux; and

[0021] - an internal diverging section located inside the solar receiver; and

[0022] - an internal converging section located inside the solar receiver; and

[0023] - a rigid envelope which ensures the mechanical maintenance of the tubes and the minimization optical and thermal losses; and

[0024] - a neck having a minimum diameter, and positioned between the converging section external and the internal diverging section; and

[0025] - a conical section located inside the solar receiver, characterized in that said tubes take a helical shape with variable diameter forming a cavity into which the solar rays penetrate.

[0026] In order to reduce the pressure drop, it is better to have larger passage and heat exchange sections (of increasing size). However, a larger section implies more volume and a low heat exchange coefficient. This implies a loss of efficiency. In other words, an efficient solar receiver will have more pressure drop. Similarly, to reduce the heat loss in the heat transfer fluid, one of the ways will be to reduce the flow speed. One of the ways to reduce the pressure drop will be to distribute the flow in different tubes. To overcome this, the solar receiver is characterized by the fact that it is formed of one, two or more adjacent tubes thus forming a helical shape, said tubes can be of variable sections in the different sections of the solar receiver to have a good compromise between heat exchange efficiency, pressure drop and total volume.

[0027] The flow rate also depends on the volume flow rate which depends on the operating temperature. As the fluid heats up, the volume flow rate increases, and for a given section, the speed increases, which generates more pressure losses. In order to overcome this problem, the number of tubes can be increased as the flow heats up. A tube of a certain diameter can therefore be provided on the first converging section at the inlet, then the flow will be divided into two tubes in the diverging section and then divided into three or more tubes on the last part of the exchanger. Thus, the solar receiver is characterized in that the number of tubes carrying the heat transfer fluid can be different in each section of said solar receiver.

[0028] The efficiency of a solar receiver is defined by the amount of solar energy absorbed by the heat transfer fluid relative to the amount of solar energy received. A portion of this received solar energy is lost due to convective heat losses, radiative heat losses, and optical losses. Convective heat losses are often due to wind effects and buoyancy. Radiative heat losses are due to irradiation of the hot surface of the receiver, particularly the surface of the tubes, to the outside. Optical losses are due to reflection of the solar flux from the receiver to the environment and alignment errors between the solar concentrator and the solar receiver.

[0029] In order to minimize convective heat losses, the solar flux is converged on a part located inside the solar receiver, said solar receiver is positioned so that the heat exchange by convection is minimized. Thus the convective heat loss is limited because the part of the receiver which exchanges a lot of energy is relatively far from the ambient air which limits the exchanges by convention. Thus the solar receiver is characterized by the fact that the section where the surface of the tubes reaches a high temperature is located at the bottom of the solar receiver thus reducing the thermal losses and the convective heat losses.

[0030] In order to minimize radiative or radiation heat losses, the inlet sections and the neck have a smaller diameter than the maximum diameter inside the solar receiver. This maximum diameter is located at the intersection between the internal divergent and the internal convergent. At the neck, the passage section is reduced and consequently, radiative heat losses are reduced. Thus, the solar receiver is characterized in that it has a neck located between the external convergent part and the internal divergent part and making it possible to reduce radiative heat losses.

[0031] In order to minimize optical losses, the solar rays are converged inside the solar receiver and encapsulated so that the output radiative flux is minimized. To do this, the solar receiver takes the form of a convergent, divergent then convergent, seen from the solar flux entry zone. The solar rays which reach the external convergent zone are reflected inside the solar receiver. Similarly, the solar rays which reach the internal convergent zone are reflected and diffuse inside the solar receiver and arrive at the internal diverging zone. The reflection of the solar rays inside the solar receiver makes it possible to minimize optical losses.Thus the solar receiver is characterized in that the optical losses are minimized due to the fact that the solar rays which are reflected on the tubes in the internal diverging section and in the internal converging section, are trapped inside the cavity forming the internal volume of said solar receiver.

[0032] In particular, the invention is valid for any type of solar concentrator comprising a solar receiver. This proposed invention is furthermore valid for any type of application requiring the use of a solar receiver.

[0033] Advantageously, the invention makes it possible to have a solar receiver with a low pressure loss by varying the sizes of the tubes, which is a very important criterion, particularly in the case of a solar concentrator type application. In addition, this makes it possible to increase the overall efficiency of the system formed by the solar concentrator and the solar receiver.

[0034] Furthermore, a solar receiver with a counter-current heat exchange architecture makes it possible to improve the efficiency of the recuperator. In the case of a counter-current type exchange, the heat transfer fluid enters through the external converging section and exits from the side of the internal conical section, thus the solar receiver is characterized by a counter-current type heat exchange between the heat transfer fluid and the solar flux, where the heat transfer fluid enters through the external converging section and exits from the side of the internal conical section.

[0035] According to a variant, the number and / or the section of the first circulation tubes is different from those of the second and / or third circulation tubes. This makes it possible to modulate between efficiency and pressure loss within each section.

[0036] According to a variant, the solar receiver comprises at least one inlet and at least one outlet, said solar receiver also comprises a modular architecture so that said inlet and said outlet can be arranged at different locations in the functional volume of the heat receiver.

[0037] This allows the inlets / outlets to be arranged at any location within the functional volume of the heat receiver, or to change them according to said functional volume of the solar receiver. Thus, the exchanger is adaptable to different configurations of solar concentrators.

[0038] The solar receiver comprises a rigid casing which ensures the mechanical maintenance of the tubes and the minimization of optical and thermal losses. Thus the solar fluxes which leak through the tubes and the inter-distances between the tubes, are converged again on the other surface of the tubes through the rigid casing.

[0039] According to a variant, the solar receiver has a composite structure comprising aluminum or other type of materials in a first section, copper or other type of materials in a second section with heat transfers of less than 600°C, and metal or steel alloys in a section with thermal stresses of more than 650°C.

[0040] This makes it possible to adapt the type of materials to increase the heat exchange performance and minimize the mass of the solar receiver.

[0041] According to a variant, the solar receiver is connectable to at least three circuits of different fluids.

[0042] Advantageously, in the context of the solar concentrator, having an exchange with a third (or even a fourth) working fluid makes it possible to operate several types of thermodynamic machines and makes it possible to increase the overall efficiency of thermal recovery. More generally, this makes it possible to ensure thermal exchanges with other fluids and to recover a maximum of energy.

[0043] According to one variant, the solar receiver can be connected to an organic Rankine cycle machine or to a turbogenerator type machine operating according to a Brayton cycle.

[0044] According to a variant, the solar receiver is connectable to a turbogenerator operating according to a thermodynamic cycle with cooled compression and intermediate reheating with recuperator. This thermodynamic cycle is called in English "Intercooled Recuperative Reheat Gas Turbine". In this case, the solar receiver ensures the function of the first and second combustion chambers. Thus, the solar receiver is characterized in that it comprises at least one inlet and at least one outlet so that said inlet and said outlet can be arranged so as to ensure the function of primary reheating and secondary reheating of a Brayton type thermodynamic cycle with intermediate reheating.

[0045] This makes it possible to transform part of the recovered energy into mechanical or electrical work and consequently to increase the overall efficiency of the system.

[0046] According to one variant, the solar receiver is used to heat only a working fluid to produce hot thermal energy.

[0047] Thus the solar receiver is characterized by its capacity to heat at least one working fluid for at least one thermal cycle or a thermodynamic machine.

[0048] Another object of the invention relates to a solar concentrator comprising at least one thermodynamic machine equipped with at least one solar receiver according to the invention.

[0049] Another object of the invention relates to a solar receiver characterized in its capacity to use at least two working fluids for at least two different thermodynamic cycles and several circulation flows of the working fluids.

[0050] The invention further relates to a method of manufacturing a solar receiver for a solar concentrator according to the invention, characterized in that it comprises the following steps: - making said first windings of heat transfer tubes at the level of the external convergent, by winding one or more adjacent tubes, on a first specimen having the shape of the external convergent, and

[0051] - making said windings of heat transfer tubes at the level of the internal divergent, by winding a tube or several adjacent tubes, on a specimen having the shape of the internally divergent, and

[0052] - making said windings of heat transfer tubes at the level of the internal convergent, by winding one or more adjacent tubes, on a specimen having the shape of the internal convergent, and - create a counter-current heat exchange architecture by coupling the heat transfer fluid inlet on the external convergent side of the solar receiver and positioning the outlet at the conical section, and

[0053] - weld the tubes at the different sections, and

[0054] - make a rigid envelope all around the tubes.

[0055] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: - [Fig.l] schematically illustrates a perspective view in transparency in space of a solar receiver for a solar concentrator according to a preferred embodiment of the invention; - [Fig.2] illustrates a perspective view of the solar receiver of [Fig.l] from another viewing angle; - [Fig.3] illustrates a view of the solar receiver according to another embodiment, comprising two inputs and two outputs; - [Fig.4] schematically illustrates a view of the solar receiver of [Fig.3] from another viewing angle; - [Fig.5] illustrates a functional diagram of a heating circuit comprising a solar receiver according to another preferred embodiment of the invention; - [Fig.6] illustrates a functional diagram of an organic Rankine cycle comprising a solar receiver according to another preferred embodiment of the invention;

[0056] - [Fig.7] illustrates a functional diagram of a heating cycle comprising a solar receiver, said heating cycle is coupled to an organic Rankine cycle; - [Fig.8] illustrates a functional diagram of a Brayton-type thermodynamic cycle comprising a solar receiver providing the combustion chamber function, said thermodynamic cycle may optionally comprise a combustion chamber and / or a heat recovery unit; - [Fig.9] illustrates a functional diagram of a thermodynamic cycle of a turbogenerator with cooled compression, recovery and intermediate reheating, in English "Intercooled Recuperative Reheat Gas Turbine", using the solar receiver with or without the combustion chambers;

[0057] - [Fig. 10] illustrates a functional diagram of the thermodynamic cycle of [Fig.9] with a Rankine loop using the same solar receiver to preheat the two fluids of the two thermodynamic machines;

[0058] In what follows, the embodiments described relate more particularly to an implementation of the solar receiver for a solar concentrator application. However, any implementation in a different context, in particular for heat exchanger applications, is also covered by the present invention.

[0059] Elements designated by the same numerical references in the different figures are identical.

[0060] With reference to [Fig. 1], there is shown schematically a solar receiver (1) according to a first embodiment of the present invention. This solar receiver (1) comprising: - one or more heat transfer fluid inlet tubes (2); and

[0061] - one or more heat transfer fluid outlet tubes (3); and

[0062] - one or more tubes (4) for circulating a heat transfer fluid; and - an external convergent section (5) formed by the tubes (4) and located at the entrance of the solar flux; and

[0063] - an internal divergent section (6) formed by the tubes (4) and located inside the solar receiver (1); and

[0064] - an internal convergent section (7) formed by the tubes (4) and located inside the solar receiver (1); and

[0065] - a rigid envelope (8) which ensures the mechanical maintenance of the tubes (4) and the mini implementation of optical and thermal losses; and

[0066] - a neck (9) formed by the tubes (4) and having a minimum diameter, and positioned between the external converging section (5) and the internal diverging section (6); and

[0067] - a conical section (10) formed by the tubes (4) and located inside the solar receiver (1), characterized in that said tubes (4) take a helical shape with variable diameter forming a cavity (11) into which the solar rays penetrate.

[0068] The solar rays enter through the external converging section (5) and pass through the neck (9) to arrive inside the solar receiver (1) where they are reflected on the conical section (10). A part of the reflected solar rays ends up on the tubes (4) of the internal diverging section (6) and a part on the tubes (4) of the internal converging section (7). A part of the reflected solar rays exits through the neck (9) towards the outside of the solar receiver (1).

[0069] The solar receiver (1) is a heat exchanger between the solar flux and the heat transfer fluid circulating inside the tubes (4) (heat transfer fluid and solar rays are not shown in the diagrams). The heat transfer fluid can be water or an organic fluid or another liquid, or air or another gas.

[0070] The challenges for solar receivers are presented below:

[0071] The first challenge is to have a high efficiency of exchanges between the hot source (the solar rays on the external surfaces of the tubes (4) and which have the effect of increasing the temperature of the surface), and the cold source (the heat transfer fluid circulating inside the tubes (4)); this efficiency of heat exchange is represented by an overall heat exchange coefficient (H [W / (m2.K)]).

[0072] To achieve high efficiency, it is preferable to have high exchange coefficients and a counter-current type heat exchange architecture. With a counter-current type heat exchanger, the outlet temperature of the cold fluid can exceed the outlet temperature of the hot fluid, which is not possible in the case of an exchanger with a co-current type thermal architecture.

[0073] The second challenge is to have a low pressure drop. This is a very important criterion, particularly in the case of heating applications and applications for the production of mechanical and electrical energy. Minimizing pressure drops increases the net mechanical power generated and consequently the overall efficiency of the system.

[0074] To minimize pressure losses, it is interesting to adapt the sections of the tubes (4) in the solar receiver (1). Indeed, the more the fluid (case of a gas) cools and the more the density decreases and the more the sections can be reduced to optimize the volume. Similarly; the more the fluid heats up, the more the volume flow increases and the more the passage sections must be increased. This is not possible with plate solar receivers (possible with 3D printed solar receivers but this is not currently industrializable on a large scale and the manufacturing technique is expensive).

[0075] The third challenge is that the heat exchanges at the walls must be controlled: If the tubes (4) are external, there will be significant heat exchanges at the walls and this complicates the thermal insulation of the solar receiver. Indeed, the internal temperature of the receiver can exceed 1000°C if the technology of said solar receiver is used for a turbogenerator type application for example. Similarly, in the case of the turbogenerator, the inlet of the solar receiver can reach temperatures above 750°C. If the collector is external, the surface temperature will be high and the heat losses will be significant.

[0076] To minimize heat losses at the walls, it is advantageous for the hot exchange surface in contact with the exterior to be insulated. Consequently, it will be advantageous to have a casing (8) which thermally insulates the tubes (4).

[0077] With reference to [Fig.3], the solar receiver of [Fig.l] and [Fig.2] is shown according to another variant. This solar receiver of [Fig.3] comprises two inputs 2' and 2” and two outputs 3' and 3”. Said inputs and outputs of the solar receiver have an impact on the volume and the physical architecture of said solar receiver. If the inputs / outputs are difficult to "move", one will be constrained by the design and by the integration of the machine.

[0078] It is interesting to have a modular design where the inputs / outputs can be placed anywhere in the functional volume of the solar receiver (1).

[0079] The choice of materials is essential. The type of materials has an impact on the heat exchange coefficient. However, certain types of materials, such as copper or aluminum, have very high thermal conductivity or thermal transmission coefficients, but poor high temperature resistance characteristics. Similarly, some materials are lighter than others and allow the total mass of the solar receiver to be reduced. Of course, materials other than aluminum and copper can be used.

[0080] Having a design of a solar receiver where the type of materials can be adapted makes it possible to increase the thermal exchange performance and to minimize the mass of the solar receiver.

[0081] The invention further proposes to couple the solar receiver with a thermal loop. With reference to [Fig.5], a thermal loop is presented using the solar receiver R (1). This loop comprises, in addition to the solar receiver R (1), a circulation pump P, a heat exchanger HE and a thermal energy storage tank T. The circulation pump P circulates a heat transfer fluid which enters the solar receiver R (1) to be heated. The heated heat transfer fluid enters the heat exchanger HE or it can exchange with another fluid, depending on the target application. The remaining energy is stored in the tank T. A three-way valve V allows the heat transfer fluid to bypass the solar receiver, in certain life situations in particular when solar energy is not available (night, cloudy weather, etc.). In this case, the heat transfer fluid passes through the pump P through the collector C.

[0082] With reference to [Fig.6], the diagram of a Rankine loop (or ORC ball for "Organic Rankine Cycle" in English) is shown using a solar receiver R (1) as a boiler or evaporator. In this case, the circuit uses a pump Po, which pressurizes the organic fluid, which is in this architecture the heat transfer fluid. This heat transfer fluid passes into the solar receiver R (1) to be heated before entering the expansion machine E (in English "Expander"). The invention further proposes to couple the solar receiver R (1) with an organic Rankine cycle machine RK. The boiler for the ORC loop is in this case the solar receiver R (1). This saves a heat exchanger.

[0083] Referring to [Fig.7], the diagram of an energy storage loop coupled to a Rankine loop RK is shown. The components are identical to the components shown in Figures 5 and 6. At the heat exchanger HE, the fluid from the Rankine loop enters the cold section B to be evaporated.

[0084] With reference to [Fig.8], the diagram of a micro-turbine or turbogenerator cycle using the solar receiver R (1) instead of a combustion chamber CC is shown. The turbogenerator cycle comprises a compressor C, a turbine Tu, an electric machine EMG and the solar receiver R (1). The working fluid, in particular the pressurized air at the outlet of the compressor, enters the solar receiver R (1) to be preheated before re-entering the turbine Tu. The solar receiver R (1) is used instead of the combustion chamber or in series with the combustion chamber CC. In the case where the solar receiver R (1) is placed in series, this makes it possible to reduce the quantity of fuel injected into said combustion chamber CC, and this makes it possible to improve the overall efficiency of the system.The micro-turbine can also include a heat recovery unit G, allowing the energy to be recovered at the turbine outlet to preheat the air upstream of the solar receiver R (1). The use of the heat recovery unit G makes it possible to increase the thermodynamic efficiency of the cycle. The solar receiver R (1) described contains a path for the fluid FL. In the case of the turbogenerator application, this first fluid Fl is pressurized air at the outlet of the compressor C. This pressurized fluid circulates in tubes (4) ( [Fig.l]).

[0085] With reference to [Fig.9], the diagram of a micro-turbine cycle with cooled compression with intermediate heating and recuperator (in English "IRReGT" or "Intercooled Recuperative Reheat Gas Turbine") is shown where the double-flow solar receiver (variants of figures 3 and 4) is used instead of the combustion chambers (CCI and CC2) or in series with the combustion chambers (CCI and CC2). The cycle comprises at least one compressor (C1, C2), at least one turbine (Tul, Tu2), a double-flow solar receiver R for heating the working fluid at the outlet of the recuperator G and at the outlet of the first expansion turbine Tul, said heat recuperator G makes it possible to recover the energy at the outlet of the turbine Tu2 to preheat the working fluid at the inlet of the solar receiver R. The solar receiver can operate in single mode without the combustion chambers or in series with combustion chambers (CCI, CC2).

[0086] With reference to [Fig.9], the solar receiver described can contain two paths:

[0087] - A path of a first fluid Fl: In the case of the turbogenerator application, This first fluid Fl is pressurized air at the outlet of compressor C2. This pressurized fluid circulates in tubes 2' (figures 3 and 4).

[0088] - A path of a second fluid F2: in the case of the turbogenerator application, This fluid corresponds to the hot gases leaving the Tu2 turbine. This pressurized fluid circulates in 2” tubes (figures 3 and 4).

[0089] With reference to [Fig. 10], the diagram of a combined turbogenerator cycle with a Rankine RK cycle using a multi-flow and multi-solar receiver is presented. working fluids. The solar receiver is used as a boiler for the Rankine cycle and as combustion chambers for the turbogenerator. The solar receiver is characterized by its ability to use at least two working fluids from two different thermodynamic cycles and several working fluid circulation flows.

[0090] With reference to [Fig. 10], the solar receiver described contains three paths:

[0091] - A path of a first fluid FL This first fluid Fl is for example air pressurized at the outlet of compressor C2.

[0092] - A path of a second fluid F2. This second fluid F2 is for example the hot gases at the outlet of the Tu2 turbine.

[0093] - A path of a third fluid F3. This third fluid F3 is a fluid of type water or ethanol or an organic fluid compatible with the Rankine cycle.

[0094] So finally, this solar receiver can be used to exchange with several fluids, we can therefore imagine having an architecture which combines both a Rankine RK cycle (ORC type for example) with a turbogenerator cycle (IRReGT type for example). In this case, the solar receiver will serve both as an evaporator boiler for the Rankine RK cycle and as combustion chambers for the turbogenerator cycle.

[0095] The different fluids F1, F2 and F3 can be collected to escape at the outlet of the solar receiver. The inlets and outlets of the solar receiver are on opposite sides ( [Fig.l]).

[0096] The total number of tubes (4) in each section is variable. The diameter defining the surface area of ​​the fluid passage in the tubes (4) in each section of the receiver (1) is also variable. The number of tubes (4) and the section of the tubes (4) can be adapted according to the characteristics of the fluid (temperature reached) at each section. This is an important parameter which allows us to optimize the solar receiver (1) and minimize the pressure losses in the tubes (4).

[0097] The materials in each section can also be adapted. For example, aluminum, which has good heat exchange characteristics and is not heavy, can be used in the first external convergent section (5). Copper can be used in the internal divergent section (6), knowing that copper has good heat transfer coefficients but begins to lose its mechanical strength characteristics at temperatures above 700°C. Finally, inconel or steel can be used in the internal convergent section (7) where there are high thermal constraints. This is an interesting characteristic allowing the optimization of heat exchanges and the weight of the solar receiver.

[0098] The length of the tubes (4) is variable and depends on the thermal exchanges.

[0099] As for the preferred manufacturing method, specimens of convergent, divergent shapes can be made, then tubes can be wound, spaced apart a certain distance around these specimens to form the external convergent, the internal divergent and the internal convergent.

[0100] Then, the tubes can be welded to the different sections between the convergent and the divergent.

[0101] The tubes can also be coupled using a brazing process.

[0102] Then we create a counter-current heat exchange architecture by coupling the heat transfer fluid inlet on the side of the external convergent (5) and positioning the outlet at the level of the conical section (10).

[0103] Then a rigid envelope (8) is made all around the tubes.

[0104] The technical advantages of the invention are in particular the following: - Improving the efficiency of the solar receiver by proposing a counter-current heat exchange; - Reduce heat loss to the exterior via walls and external surfaces; - Offer a modular and adaptable design depending on the application; - Allow to modify the positions of the solar receiver inputs / outputs; - Allow to modify the number of tubes (4) and the passage sections of the tubes (4) in each stage of the solar receiver; - Allow to modify the section of the tubes (4) in each passage in each stage of the solar receiver (1); - Allow to modify the materials in each passage section; - Allow to modify the number of passages (round trip) in the solar receiver; - Allow to use different type of working fluid (Air-Air / Air-Water / Air-ORC / Water-Water / Water-ORC or any other possible combination); - Allow the use of multiple working fluids, for example, using the solar receiver for a turbogenerator type application and preheating another ORC type fluid for a Rankine RK loop.

[0105] - Allow the exchanger to be produced with several types of process such as welding normal, laser welding or brazing.

Claims

Claims

1. Solar receiver (1) comprising: - one or more inlet tubes (2) for heat transfer fluid; and - one or more outlet tubes (3) for heat transfer fluid; and - one or more circulation tubes (4) for a heat transfer fluid; and - an external convergent section (5) located at the inlet of the solar flux; and - an internal divergent section (6) located inside the solar receiver; and - an internal convergent section located inside the solar receiver (7); and - a rigid casing (8) which ensures the mechanical maintenance of the circulation tubes (5) and the minimization of optical and thermal losses; and - a neck (9) having a minimal diameter, and positioned between the external convergent section (5) and the internal divergent section (6);and - a conical section (10) located inside the solar receiver, characterized in that said tubes take a helical shape with variable diameter forming a cavity (11) into which the solar rays penetrate.;

2. Solar receiver (1) according to claim 1, characterized in that it is formed of one, two or more adjacent tubes (4, 4', 4”) thus forming a helical shape, said tubes (4, 4', 4”) can be of variable sections in the different sections (5, 6, 7, 10) of the solar receiver (1) to have a good compromise between heat exchange efficiency, pressure loss and total volume.

3. Solar receiver (1) according to claims 1 and 2 characterized in that the number of tubes (4) transporting the heat transfer fluid can be different in each section of said solar receiver (1).

4. Solar receiver (1) according to any one of claims 1 to 3 characterized in that the conical section (10) located inside the solar receiver where the surface of the tubes (4) reaches a high temperature is located inside the solar receiver (1) thus reducing heat losses and convective heat losses.

5. Solar receiver (1) according to any one of claims 1 to 4 characterized in that it has a neck (9) located between the external converging part (5) and the internal diverging part (6) and making it possible to reduce radiative heat losses.

6. Solar receiver (1) according to any one of claims 1 to 5 characterized in that the optical losses are minimized because the solar rays which are reflected on the tubes (4) in the internal diverging section (6) and the internal converging section (7), are trapped inside the cavity (11) forming the internal volume of said solar receiver (1).

7. Solar receiver (1) according to any one of claims 1 to 6, characterized by a counter-current type heat exchange between the heat transfer fluid and the solar flux, where the heat transfer fluid enters through the external converging section (2) and exits from the side of the internal conical-shaped section (9).

8. Solar receiver according to any one of claims 1 to 7, characterized in its capacity to heat at least one working fluid for at least one thermal cycle or thermodynamic machine.

9. Solar receiver according to any one of claims 1 to 8, characterized in that it comprises at least one inlet and at least one outlet so that said inlet and said outlet can be arranged so as to ensure the primary heating and secondary heating function of a Brayton type thermodynamic cycle with intermediate heating.

10. A method of manufacturing a solar receiver for a solar concentrator according to any one of claims 1 to 9, characterized in that it comprises the following steps: - producing said first windings of heat-transfer tubes (4) at the external convergent (5), by winding one or more adjacent tubes, on a first specimen having the shape of the external convergent (5), and - producing said windings of heat-transfer tubes at the internal divergent (6), by winding one or more adjacent tubes, on a specimen having the shape of the internal divergent (6), and - producing said windings of heat-transfer tubes at the internal convergent (7), by winding one or more adjacent tubes, on a specimen having the shape of the internal convergent (7),and - create a counter-current heat exchange architecture by coupling the heat transfer fluid inlet on the side of the external convergent (5) of the solar receiver and positioning the outlet at the level of the conical section (10), and - weld the tubes at the level of the different sections, and, - create a rigid envelope all around the tubes.

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