AU2015201631B2 - Method of designing a concentrated solar cavity receiver - Google Patents
Method of designing a concentrated solar cavity receiver Download PDFInfo
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- AU2015201631B2 AU2015201631B2 AU2015201631A AU2015201631A AU2015201631B2 AU 2015201631 B2 AU2015201631 B2 AU 2015201631B2 AU 2015201631 A AU2015201631 A AU 2015201631A AU 2015201631 A AU2015201631 A AU 2015201631A AU 2015201631 B2 AU2015201631 B2 AU 2015201631B2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B10/00—Integration of renewable energy sources in buildings
- Y02B10/20—Solar thermal
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/40—Solar thermal energy, e.g. solar towers
- Y02E10/46—Conversion of thermal power into mechanical power, e.g. Rankine, Stirling or solar thermal engines
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Abstract
Abstract Described herein is a concentrated solar thermal cavity receiver and a method of designing a concentrated solar thermal cavity receiver. In one embodiment, a concentrated solar thermal cavity receiver comprises: A. a concave surface comprising a plurality of surfaces defining a cavity; and B. an aperture for receiving solar radiation onto said surfaces. A cross section of a plane orthogonal to the aperture comprises at least four surfaces abutting at obtuse angles and the plurality of surfaces are asymmetrical about at least two planes. Figure 1 Figure 2
Description
Method of designing a concentrated solar cavity receiver
Field [0001] The present invention relates to the field of concentrated solar thermal systems and in particular to a concentrated solar thermal cavity receiver and a method of designing thereof.
Background [0002] In a concentrating solar thermal system operating at temperatures where thermal radiation is significant, the efficiency of a cavity receiver is sensitive to the size of the aperture. The aperture in such a system is defined as the surface with the smallest area where both optical energy passes in and thermal radiation from the receiving surface passes out.
[0003] A larger aperture may allow in more solar energy, but will allow more thermal radiation losses. In systems operating at temperatures approaching 1000 degrees Celsius, the aperture size that results in optimum receiver efficiency may result in peak intensities larger than 1 MW/m2. Often receiver surface limitations mean that the intensity at the optimal aperture is too great. Therefore there is a need for an improved cavity receiver design which has improved efficiency and enhanced robustness against mechanical failure due to high peak surface temperatures.
[0004] Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
[0005] It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.
Summary of the Invention [0006] The present invention, in at least its preferred embodiments, addresses this problem by using an iterative process to design a cavity receiver with the objective of establishing the smallest cavity surface area which can receive all the flux without the cavity surface exceeding a predetermined maximum peak temperature during operation (e.g. on an annual basis).
2015201631 28 Feb 2020 [0007] Preferred embodiments of the present invention are intended for use in receiving concentrated solar thermal radiation from a field of heliostat devices, which are configured to direct light towards a central receiver tower containing the solar thermal receiver. However, it will be appreciated that the invention is applicable to other solar thermal systems such as prism based systems.
[0008] According to a first functional aspect of the present invention, there is provided a concentrated thermal solar cavity receiver comprising:
A. a concave surface defining a cavity; and
B. an aperture for receiving solar radiation onto said surface, wherein the concave surface comprises an aperture facing absorptive surface configured to limit the peak maximum expected temperature thereof to a designated value (i.e. target value) while maintaining an objective of minimising the surface area of the cavity.
[0009] According to a first structural aspect of the present invention, there is provided a concentrated solar thermal cavity receiver comprising:
A. a concave surface comprising a plurality of surfaces defining a cavity; and
B. an aperture for receiving solar radiation onto said surfaces, wherein a cross-section of a plane orthogonal to the aperture comprises at least four surfaces abutting at obtuse angles; and wherein the plurality of surfaces are asymmetrical about at least two planes.
[0010] Preferably, the ratio of the surface area of the cavity to the surface area of the aperture is greater than 2, more preferably greater than 3, even more preferably greater than 4 and yet even more preferably greater than 5. With the objective of establishing the smallest possible cavity surface area while achieving a designated target maximum peak temperature, the maximum ratio of the surface area of the cavity to the surface area of the aperture is preferably no more than 20 and even more preferably no more than 10. Naturally, the ability to minimise the cavity surface area will be dictated by the objective of achieving a designated target maximum peak expected temperature.
[0011] Within the structural aspect, the plurality of surfaces comprises aperture facing absorptive surfaces. Said absorptive surfaces face the aperture and are configured to limit the maximum peak expected temperature thereof.
[0012] Preferably, the absorptive surface forms part of a plurality of tubes (or vice versa), said tubes carrying a working fluid.
2015201631 28 Feb 2020 [0013] The cavity receiver of the present invention provides a balance between the required surface area of the cavity and the maximum annual receiver surface temperature to enable both high receiver efficiency and high reliability of the receiver material.
[0014] There are costs associated with having large areas of receiver and cavity wall area. The cavity surface area is typically filled with white insulation to avoid extreme temperatures and redirect energy optically to the receiver. Ideally the cavity surface should be completely covered (preferably at least 80%, more preferably at least 90% covered) in absorptive receiver surface in order to minimise the temperature of the cavity surface for thermal loss purposes as thermal loss by radiation increases with the fourth power of temperature.
[0015] In the case of a receiver designed to receive solar energy into a fluid that travels behind the receiver surface and increases in temperature, where the fluid containment material (working fluid) has a temperature limitation, the intensity capacity of the fluid containment material is dependent on the fluid temperature, and therefore the order in which the fluid travels through receiver elements.
[0016] The receiver of the present invention has a number of advantages. The high ratio of the aperture facing absorptive surface to the aperture converts to a relatively small receiver with lower thermal losses, with the reduction in re-radiation resulting in improved efficiencies, while the configuration of the absorptive surfaces enables the annual maximum expected temperature kept below sustainable operating limits for the materials of construction. Through being able to balance the expected annual maximum temperature of the aperture facing absorptive surface, the annual peak maximum expected temperature of any portion of the aperture facing absorptive surface may be reduced and the variation in annual peak temperature between portions of the aperture facing absorptive surfaces may also be reduced. By reducing the variation of annual peak maximum expected temperatures across the absorptive surfaces, material and mechanical failure due to stress fractures and/or corrosion may be reduced. As a result, compared to conventional receivers, more cost effective material and/or extended operational life may be achieved.
[0017] Further improvements in the material life may be achieved through further balancing variations of annual peak temperature across the absorptive surfaces with variations of temperatures (temperature gradients along the absorptive surface) at a particular time. This may be achieved through specifying a maximum temperature gradient,
2015201631 28 Feb 2020 as a design constraint in the modelling of the aperture facing absorptive surface temperature.
[0018] Other design constraints which promote extending the material life may be included, such as a maximum temperature gradient across the pipe wall and/or the maximum temperature gradient from the front (aperture facing side) to the back of the pipe.
[0019] The cavity may further comprise aperture facing reflective surfaces. Preferably, the aperture facing reflective surfaces are no more than 30% (and preferably at least 70% absorptive surfaces), more preferably no more than 20% (and preferably at least 80% absorptive surfaces), and even no more than 10% (and preferably at least 90% absorptive surfaces), of the total surface area of the cavity. A reduction in aperture facing reflective surface area enables the aperture facing absorptive surface area to be maximised thereby enabling the maximum expected temperature of the receiver to be reduced.
[0020] Within the context of the present invention, the configuration of the aperture facing absorptive surfaces to limit the maximum expected temperature thereof relates to controlling solar irradiance (heat in) with the heat transfer properties of the aperture facing surfaces (heat out). Through controlling heat flow at each point of the internal cavity, excessive variations in annual peak temperatures over the cavity surface may be avoided. By control of the heat that the aperture facing absorptive surfaces receives (heat in) and dissipates (heat out) the maximum expected temperature may be kept below a designated value, thereby enabling the receiver to work efficiently (reduced energy loss from aperture) and effectively (extended life of absorptive surface materials).
[0021] Preferably, the variation in annual peak temperature over the aperture facing surfaces (planar or curved) is no more than 200°C and preferably no more than 120°C. Within each surface component, the variation in peak temperature over the aperture facing surface component is no more than 120°C, preferably no more than 50°C and even more preferably no more than 25°C. The typical peak temperature is in the range of 800°C to 1400°C and more preferably 900°C to 1200°C and even more preferably 950°C to 1100°C.
[0022] The heat transfer properties of the aperture facing absorptive surfaces are preferably influenced by a heat transfer fluid. In one embodiment, the aperture facing absorptive surfaces form part of a plurality of tubes/pipes through which a heat transfer fluid or working fluid flow. Suitable working fluids include molten salts or metal, water or other rankine cycle fluid, gases, gaseous mixtures, gaseous mixtures undergoing endothermic
2015201631 28 Feb 2020 chemical reactions. In an alternative embodiment, the heat transfer fluid may flow through a series of channels in a monolithic structure. Within the above arrangements the portions of the aperture facing absorptive surfaces having the highest irradiance levels can be matched to areas in which the internal pipe surfaces (inner surface) have greatest cooling effect, thereby minimising the peak maximum expected temperature of that portion of the aperture facing (pipe outer surface) absorptive surface.
[0023] The configuration of the cavity may be influenced by a compromise between manufacturing cost and receiver efficiency. In some embodiments, curved surfaces may be advantageously used. In alternative embodiments a plurality of planar surfaces may be advantageously used.
[0024] The number of planar surfaces is preferably at least 8, more preferably at least 12, even more preferably at least 20, yet even more preferably at least 40 and most preferably at least 60. The greater the number of planar surfaces the greater the design flexibility to balance the solar irradiance with the heat transfer properties of the aperture facing absorptive surfaces. The planar surfaces may be contiguous or non-contiguous. Having at least some non-contiguous planar surfaces enables greater design freedom for the heat balance to achieve peak maximum expected temperatures below a desired maximum value (as well as meeting the design objective of minimising the cavity surface area).
[0025] The nature of the irradiance profile passing through the aperture and the design criteria to keep the aperture facing surface temperature below one or more specified maximum surface temperatures will typically result in an irregular aperture facing surface configuration. The aperture facing surface configuration is preferably asymmetrical about at least two planes (e.g. x-y, x-z plane), and more preferably about all three planes. These structural limitations are a direct consequence of a cavity surface which meets the design objective of a designated maximum peak temperature and a minimised cavity surface area.
[0026] Preferably, the aperture facing surface configuration comprises no more than two, more preferably no more than one and even more preferably no abutting surfaces (in a plane orthogonal to the aperture) with right angles (90°) and/or angles less than 90°. The avoidance of too many right or acute angles promotes aperture facing surface temperature profiles with reduced temperature gradients as well as minimising the cavity surface area.
[0027] The configuration of the aperture facing surfaces (either planar and/or curved) preferably comprises a plurality of aperture facing surfaces which abut at angles of at least
2015201631 28 Feb 2020
90°, more preferably at angles of at least 95°, even more preferably at angles of at least 110° and yet even more preferably at angles of at least 120°. In some embodiments there is 2 or more, preferably 4 and more preferably 16 or more abutting aperture facing surfaces which have obtuse joining angles (i.e. >90° and less than 180°). The number of aperture facing surfaces meeting these criteria is determined through counting the number of angles meeting these criteria in a cross-section, along an orthogonal plane to the plane of the aperture. For example, Figure 2 comprises 5 obtuse angles.
[0028] Preferably there is no abutting aperture facing surfaces with an angle of 270° or more.
[0029] The embodiments in which the aperture facing surfaces comprise curved surfaces, the determination of obtuse or acute angles will be determined at points of change between curves comprising a different arc.
[0030] In some embodiments the receiver further comprises external (non-aperture facing) absorptive surfaces adjacent to the aperture and external to the cavity. The external absorptive surfaces serve to capture regions of the solar image that fall outside the aperture. While good control and calibration of the heliostats minimises the portion of sunlight which is directed outside the aperture, the use of both internal (aperture facing) and external absorptive surfaces enable the aperture size to be minimised whilst maximising the output of the solar concentrating devices (e.g. heliostats).
[0031] According to a second aspect of the present invention, there is provided a system to concentrate solar energy comprising:
a. a solar concentrating device; and
b. a concentrated solar cavity receiver according to all embodiments of the first aspect (functional and/or structural) of the present invention, wherein the solar concentrating device concentrates solar radiation through the aperture of the receiver and wherein the configuration of the aperture facing absorptive surface is such that the distribution of solar irradiance upon the aperture facing absorptive surface combined with the distribution of heat flux removed from the aperture facing absorptive surface acts to limit the peak maximum expected temperature of the aperture facing absorptive surface to below a designated value, while maintaining an objective of minimising the surface area of the cavity.
2015201631 28 Feb 2020 [0032] The designated value of the maximum expected peak temperature of the aperture facing absorptive surface may be dependent upon the materials of construction and the required replacement life of the receiver. Typically, the designated value of the maximum peak temperature is below 1100°C, more preferably below 1050°C, even more preferably below 1000°C and yet even more preferably below 950°C. The designated value of the maximum peak temperature is typically at least 800°C. The cavity surface may have more than one portion of the cavity surface each with a different designated value for the maximum expected peak temperature. The different designated values may relate to different material of constructions or different rates of material degradation (e.g. curved surfaces).
[0033] As the distribution of solar irradiance is dependent upon the geographic location of the receiver, each cavity receiver design may be customised to a solar irradiance profile of that specific geographic location, which is preferably an annual solar irradiance profile.
Aperture [0034] The size and position of the aperture will be optimised with the layout of the solar concentrating device (e.g. heliostat field, dish, Fresnel lens). Preferably, the aperture diameter is such that the peak intensity is greater than 0.6 MW/m2, more preferably greater than 0.8 MW/m2 and most preferably greater than 1 MW/m2.
Materials of constructions [0035] The cavity receiver is typically constructed using high temperature alloys, including stainless steels, silicon carbide and ceramics.
Design methodology [0036] According to a third aspect of the present invention, there is provided a method for designing a concentrated solar cavity receiver comprising the steps of:
A. selecting a cavity receiver surface geometry adjacent an aperture, the surface geometry comprising a plurality of mesh elements, each mesh element comprising an aperture facing surface;
B. determining a maximum expected irradiance on each of the mesh elements;
C. Using the location of each mesh element within the surface geometry and the intensity data thereof to calculate the aperture facing surface
2015201631 28 Feb 2020 temperature of each of the mesh elements (Tmesh,) to compare against a target maximum aperture facing surface temperature of each of the mesh elements(T meshmax,);
D. adjusting:
I. the size and/or orientation of the aperture;
ii. the configuration of the mesh elements; and/or
Hi. the composition of the mesh elements;
to thereby meet or approach the criteria of Tmeshmax, > Tmesh,; and
E. repeating steps B to D until said criteria is satisfied.
[0037] Preferably, the method is used to design the concentrated solar thermal cavity receivers of the first and second aspect of the present invention.
[0038] Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.
STEP A • Selecting a cavity receiver surface geometry adjacent an aperture, the surface geometry comprising a plurality of mesh elements, each mesh element comprising an aperture facing surface.
[0039] The selected cavity receiver surface geometry is preferably hemispherical, as it represents the minimum surface area of a cavity for a given aperture diameter. Preferably the hemispherical geometry is approximated using triangular mesh elements. However, in other embodiments, the hemispherical geometry is approximated using other geometric shapes.
[0040] The aperture facing surface of the mesh element is equivalent to the internal surface of the cavity which is exposed to the solar irradiance.
Step B
Determining a maximum expected irradiance on each of the mesh elements.
2015201631 28 Feb 2020
Preferably, a ray trace is performed using a plurality of sun positions to determine a maximum expected irradiance on each of the mesh elements from any one of the sun positions. The ray traces are preferably performed at intervals over the whole year (e.g. 12 ray traces over the year) to ensure the maximum expected radiance on each of the mesh elements is accurately known. A variety of solar flux calculation software packages may be used for this purpose, including those reviewed in Garcia et al, Solar Energy, volume 82, issue 3, pages 189-197.
[0041] The maximum expected irradiance on each of the mesh elements may also be determined through other techniques including convolution, projection and cone optics methods.
Step C
Using the location of each mesh element within the surface geometry and the intensity data thereof to calculate the aperture facing surface temperature of each of the mesh elements (Tmesh,) to compare against a target maximum aperture facing surface temperature of each of the mesh elements(Tmeshmaxj);
[0042] The calculation of the Tmeshjis determined by performing a heat balance over each of the mesh elements. A heat balance is then performed on the mesh elements through using a number of parameters including the maximum irradiance on each of the mesh elements; the temperature versus enthalpy curve of the working fluid; the heat transfer coefficient of the mesh elements, the inlet and outlet temperature of the working fluid; and the working fluid flow rate. A heat balance of this nature may be readily performed by mechanical and chemical engineers working within this field.
[0043] In some embodiments, there may be more than one Tmeshmaxi. For example, if a portion of the aperture facing surface is exposed to a relative high irradiance, an alternative to (or in addition to) using the flow pattern of the working fluid to reduce the temperature of the mesh elements, a higher grade material of construction may be employed which enables a localised Tmeshmaxi to be set which may be higher than a standard Tmeshmaxi. In the case of the external surfaces adjacent to aperture, the localised Tmeshmax, may be lower than the standard Tmeshmaxi.
Steps D & E
2015201631 28 Feb 2020 [0044] In an iterative process, one or more parameters are adjusted which impact upon (i) the maximum design temperature of the aperture facing surface of the mesh element (Tmeshmaxj) or the maximum temperature reached by the aperture facing surface of each mesh element (Tmesh,).
[0045] The design criteria of Tmeshmaxj > Tmeshimay also be met through:
I. adjusting the size and/or orientation of the aperture;
ii. adjusting the configuration of the mesh elements; and/or ill. adjusting of the composition of the mesh elements;
[0046] Through adjusting one or more of these parameters, the initially selected design, including the surface geometry may be changed such that the criteria of Tmeshmaxj > Tmeshj is approached or met.
[0047] In a preferred embodiment, the mesh element further comprises an inner surface, the inner surface in communication with a working fluid. Within this embodiment, step D further comprises the options of adjusting:
i. the type of working fluid;
ii. the flowrate of the working fluid;
ill. the composition of the working fluid; and/or iv. the flow pattern of the working fluid.
[0048] Through knowing the maximum expected irradiance of each of the mesh elements, a flow pattern may be chosen to reduce the maximum aperture facing surface temperature of a mesh element. Preferably, the flow pattern is chosen to reduce the maximum temperature of the mesh element(s) with highest aperture facing surface temperature. This assists in reducing the thermal stresses across the receiver.
[0049] Preferrably, the flow pattern is chosen such that the inlet of the working fluid is proximate to the mesh elements with the highest temperature (in the absence of a working fluid), such that the effect of the inlet of the working fluid reduces the temperature of the mesh elements, such that the target maximum aperture facing surface temperature is greater than the expected aperture facing surface temperature of the mesh elements (i.e. Tmeshmaxj > Tmeshj).
[0050] The methodology preferably further comprises the step of transforming the selected geometric surface into a geometric surface comprising a plurality of pipes having designated lengths and diameters, thereby producing a receiver pipe layout configuration.
2015201631 28 Feb 2020 [0051] Preferably, the receiver pipe layout configuration is transformed to take into account manufacturing process constraints. For example, constraints may be placed upon pipe length, pipe diameter, pipe curvature, pipe thickness, pipe material composition and pipe supports.
[0052] Preferably, the geometric surface temperature is recalculated according to steps B to E. More preferably, the aperture facing surface temperature is recalculated according to steps B to E.
[0053] In a preferred embodiment, transformation of the receiver pipe layout configuration is an iterative process with the effects of the transformation on the temperature profile of each of the mesh elements (Tmesh,).
[0054] The methodology of the present invention results in a desired receiver shape (driven by maximum peak temperature constraints and an objective to minimise cavity surface area) that can approximated by real manufacturing processes, pipe routing methods etc. to give an manufacturable receiver shape which provided enhanced efficiency.
Definitions [0055] Irradiance is the power of electromagnetic radiation per unit area (radiative flux) incident on a surface. Radiant emittance or radiant exitance is the power per unit area radiated by a surface. The SI units for all of these quantities are watts per square meter (W/m2). Irradiance may also be referred to as radiant flux density or intensity.
[0056] The peak maximum expected temperature relates to the temperature calculated through the design process using a heat balance of the absorptive surface and based upon the irradiance profile of a specified geographic location.
[0057] The cavity surface area is defined as the surface area facing the aperture.
[0058] For convenience the term “annual” has been used as a default time period for which a peak maximum expected temperature is determined. The term “annual” may be appropriately replaced with the term “designated time period”.
[0059] The term “concentrated” in the context of the solar receiver relates to the field of concentrated solar thermal power systems wherein solar radiation is concentrated or focussed from a wide area onto a smaller area at the receiver, typically using an array of reflective mirrors.
2015201631 28 Feb 2020 [0060] Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.
[0061] Throughout this specification, use of the term Optical’ in the sense of Optical radiation’ or the like is used to refer to electromagnetic radiation in one or more of the visible, ultraviolet or infrared frequency spectra.
[0062] Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the disclosure, and form different embodiments, as would be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.
Brief Description of the Figures [0063] Preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:
Figure 1 is an isometric diagram of a cavity receiver according to the present invention;
Figure 2 is the cavity receiver of Figure 1 from a side profile (z-y plane);
Figure 3 is a graph of solar irradiance of at an unspecified location;
Figure 4 is a computer generated image of a hemispherical shape of the initial cavity receiver surface geometry (with calculated aperture facing surface temperature) used in the receiver design methodology of the present invention; Figure 5 is the computer generated image of Figure 1 further adapted through an iteration of the design methodology and with incorporation of the flow of a working fluid below the surface;
Figure 6 is a computer generated image of Figure 5 further adapted through further iterations of the design methodology of the present invention;
Figure 7 is a computer generated image of Figure 6 further adapted through transforming the mesh elements to planar surfaces (half of the receiver surface shown);
Figure 8 is a computer generated image of Figure 7 further adapted to transform the planar surfaces into planar surfaces each comprising a plurality of tubes;
2015201631 28 Feb 2020
Figure 9 is a computer generated image of Figure 7 comprising an external surface temperature profile; and
Figure 10 is a computer generated image of the aperture facing surface temperature profile of the receiver.
Detailed description [0064] With reference to Figure 1, there is illustrated an isometric view of one half of a cavity receiver 10, which comprises a side wall zone 20, a high flux zone 30 and a roof zone 40. The side wall zone comprises an aperture (not shown). The receiver further comprises a preheating zone 50 which is located adjacent the aperture and in the same plane thereof [0065] Each of the zones comprise of a plurality of curved parallel tubes 60. The use of curved tubes enables a reduction in the number of tube connection points, thereby reducing the number of potential failure points. The degree of curvature is preferably limited to an extent at which the induced mechanical stresses increase the risk of mechanical failure of the curved tubes.
[0066] As indicated in Figure 2, the configuration of the tubing is such that the aperture facing surface is symmetrical about the z-y plane only.
[0067] In alternative embodiments, the zones comprise a plurality of planar segments. The tubes are capable of carrying a working fluid, which is distributed through an arrangement of manifolds 70. The inlet 80 of the working fluid is preferably located in the area which receives the highest irradiance (i.e. high flux zone).
[0068] The tubes are preferably made from a high temperature alloy material which is able to withstand the designated operating temperature. The zone may be made from differing grade materials depending upon the expected maximum peak temperature the zone operate under. From example, the pre-heater zone may be produced from a lower grade (i.e. lower maximum temperature rating) alloy and the high flux zone may be produced from a high grade alloy to ensure that all the tubes have similar operating lives.
[0069] The receiver is attached to a support frame (not shown) and placed upon a tower with the aperture directed towards a heliostat field.
[0070] The size of the aperture will be dependent upon the size of the heliostat field; the solar irradiance for the chosen location, the functionality of the receiver and the constraints placed upon the receiver design. Figure 3 illustrates solar irradiance variations with time of
2015201631 28 Feb 2020 day and at times over the year, with maximum irradiance exceeding 1000 W/m2 during summer. The heliostat field preferably concentrates the irradiance passing through the aperture by a factor of at least 500, more preferably at least 800 and most preferably at least 1000.
[0071] The methodology of creating a cavity receiver which most efficiently performs with specific design constraints at a given location is iterative in nature. As such, the methodology is preferably performed using algorithms implemented by computer driven software.
[0072] The starting point for the first iteration is preferably a hemispherical shape 200 (Figure 4) made up of a plurality of mesh elements having a surface 210. The mesh elements are preferably in contact with a working fluid flowing through a defined pathway.
[0073] The heat balance is used to determine the maximum peak temperature that each of the mesh elements will experience over a time period of operation, which will be typically a year. As indicated by the temperature profile of the mesh elements, there is a region of mesh elements with a peak temperature approaching 1150°C. In the current example, the maximum peak temperature of any mesh element is no more than 950°C.
[0074] A design parameter is adjusted with the objective of maintaining the maximum peak temperature of each of the mesh elements below 950°C. In the current example, this is achieved through adjusting the configuration of the mesh elements by increasing the distance between the aperture and the mesh elements with the peak temperatures above 950°C.
[0075] A further heat balance is performed on the amended receiver design (Figure 5). The updated temperature profile indicates that all mesh elements now have a peak maximum expected temperature of less than 1000°C.
[0076] Further iterations are performed until a design which satisfies the design constraints is achieved (Figure 6).
[0077] The mesh elements are then transformed into a manufacturable form, which in this example consists of a plurality of planar components (Figure 7). The size, shape and configuration constraints may be placed upon these planar components to match the manufacturing constraints thereof. In this particular embodiment, a roof component is arranged non-contiguously.
2015201631 28 Feb 2020 [0078] The planar components are then further transformed to comprise of a plurality of parallel tubes (Figure 8). Once again design constraints upon the pipe parameters (e.g. diameter, wall thickness) may be made to enable the resultant design to meet manufacturing, supply, HSE and/or other external constraints.
[0079] The temperature profile of the external (aperture non-facing) surfaces (Figure 9) and aperture facing surfaces (Figure 10) are then recalculated to validate that the selected design still satisfied the selected design criteria of maintaining the maximum peak temperatures of the aperture facing surfaces below 950°C. As indicated by the temperature profile in Figure 10, the criteria has been met, with the maximum temperature about 938°C. Additionally, the variation in the annual peak maximum expected temperature over the aperture facing surfaces is about 100°C indicating that thermal stresses due to annual peak maximum surface temperatures are relatively evenly distributed over the internal cavity, thereby reducing the risk of mechanical failure due to localised “hot spots”.
[0080] If the temperature profile of the resultant manufacturable design does not meet the criteria, the process may be repeated from the start or at an intermediate point in the process. One option would be to reduce Tmeshmaxi, such that the increase in surface temperature due to the transformation of the mesh elements to manufacturing elements can be taken into account.
[0081] The methodologies described herein are, in some embodiments, performable by one or more processors that accept computer-readable (also called machine-readable) code containing a set of instructions that when executed by one or more of the processors carry out at least one of the methods described herein. Any processor capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken are included. Thus, one example is a typical processing system that includes one or more processors. Each processor may include one or more of a CPU, a graphics processing unit, and a programmable DSP unit. The processing system further may include a memory subsystem including main RAM and/or a static RAM, and/or ROM. A bus subsystem may be included for communicating between the components. The processing system further may be a distributed processing system with processors coupled by a network. If the processing system requires a display, such a display may be included, e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT) display. If manual data entry is required, the processing system also includes an input device such as one or more of an alphanumeric input unit such as a keyboard, a pointing control device such as a mouse, and so forth. The term
2015201631 28 Feb 2020 memory unit as used herein, if clear from the context and unless explicitly stated otherwise, also encompasses a storage system such as a disk drive unit. The processing system in some configurations may include a sound output device, and a network interface device. The memory subsystem thus includes a computer-readable carrier medium that carries computer-readable code (e.g., software) including a set of instructions to cause performing, when executed by one or more processors, one of more of the methods described herein. Note that when the method includes several elements, e.g., several steps, no ordering of such elements is implied, unless specifically stated. The software may reside in the hard disk, or may also reside, completely or at least partially, within the RAM and/or within the processor during execution thereof by the computer system. Thus, the memory and the processor also constitute computer-readable carrier medium carrying computer-readable code.
[0082] It will also be understood that the invention is not limited to any particular implementation or programming technique and that the invention may be implemented using any appropriate techniques for implementing the functionality described herein. The invention is not limited to any particular programming language or operating system.
[0083] Thus, while there has been described what are believed to be the preferred embodiments of the disclosure, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the disclosure, and it is intended to claim all such changes and modifications as fall within the scope of the disclosure. Functionality may be added or deleted from the block diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present disclosure.
Claims (10)
- Claims1. A concentrated solar thermal cavity receiver comprising:A. a concave surface comprising a plurality of surfaces defining a cavity; andB. an aperture for receiving solar radiation onto said surfaces, wherein a cross-section of a plane orthogonal to the aperture comprises at least four surfaces abutting at obtuse angles; and wherein the plurality of surfaces are asymmetrical about at least two planes.
- 2. The receiver according to claim 1, wherein the plurality of surfaces comprises planar surfaces.
- 3. The receiver according to any one of the preceding claims, wherein the concave surface comprises an aperture facing absorptive surface wherein the absorptive surface forms part of a plurality of tubes, said tubes carrying a working fluid.
- 4. The receiver according to any one of the preceding claims, wherein at least some of the plurality of surfaces are non-contiguous.
- 5. The receiver according to any one of the preceding claims, wherein the cavity comprises at least 20 absorptive planar surfaces.
- 6. The receiver according to any one of the preceding claims, wherein the receiver further comprises external absorptive surfaces adjacent to the aperture and external to the cavity.
- 7. The receiver according to claim 3, wherein a variation in peak temperature over the aperture facing surface is no more than 200°C.
- 8. The receiver according to any one of claims 3 to claim 7, wherein the aperture facing absorptive surface comprises at least 80% of the concave surface defining the cavity.
- 9. The receiver according to any one of the preceding claims, wherein the surfaces are configured to limit the peak maximum expected temperature thereof below a designated value, while maintaining an objective of minimising the surface area of the cavity.2015201631 28 Feb 2020
- 10. A system to concentrate solar energy comprising:a. a solar concentrating device; andb. a concentrated solar thermal cavity receiver according to any one of the preceding claims, wherein the solar concentrating device concentrates solar radiation through the aperture of the receiver and wherein the configuration of the aperture facing absorptive surface is such that the distribution of solar irradiance upon the aperture facing absorptive surface combined with the distribution of heat flux removed from the aperture facing absorptive surface acts to limit the peak maximum expected temperature of the aperture facing absorptive surface below a designated value, while maintaining an objective of minimising the surface area of the cavity.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2015201631A AU2015201631B2 (en) | 2014-04-04 | 2015-03-30 | Method of designing a concentrated solar cavity receiver |
| AU2020203987A AU2020203987A1 (en) | 2014-04-04 | 2020-06-15 | Method of designing a concentrated solar cavity receiver |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2014901217 | 2014-04-04 | ||
| AU2014901217A AU2014901217A0 (en) | 2014-04-04 | Method of designing a concentrated solar cavity receiver | |
| AU2015201631A AU2015201631B2 (en) | 2014-04-04 | 2015-03-30 | Method of designing a concentrated solar cavity receiver |
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| AU2020203987A Division AU2020203987A1 (en) | 2014-04-04 | 2020-06-15 | Method of designing a concentrated solar cavity receiver |
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| AU2020203987A Abandoned AU2020203987A1 (en) | 2014-04-04 | 2020-06-15 | Method of designing a concentrated solar cavity receiver |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5797387A (en) * | 1995-09-27 | 1998-08-25 | Deutsche Forschungsanstalt Fur Luft-Und Raumfahrt E.V. | Absorber |
| WO2013146541A1 (en) * | 2012-03-28 | 2013-10-03 | 三菱重工業株式会社 | Method for producing mirror structure, mirror structure, light collection device provided with same, heat collection facility, and solar thermal generator facility |
-
2015
- 2015-03-30 AU AU2015201631A patent/AU2015201631B2/en active Active
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2020
- 2020-06-15 AU AU2020203987A patent/AU2020203987A1/en not_active Abandoned
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5797387A (en) * | 1995-09-27 | 1998-08-25 | Deutsche Forschungsanstalt Fur Luft-Und Raumfahrt E.V. | Absorber |
| WO2013146541A1 (en) * | 2012-03-28 | 2013-10-03 | 三菱重工業株式会社 | Method for producing mirror structure, mirror structure, light collection device provided with same, heat collection facility, and solar thermal generator facility |
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| AU2020203987A1 (en) | 2020-07-02 |
| AU2015201631A1 (en) | 2015-10-22 |
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