WO2011092703A1

WO2011092703A1 - Mounting assembly

Info

Publication number: WO2011092703A1
Application number: PCT/IL2011/000105
Authority: WO
Inventors: Hagay Cafri
Original assignee: Heliofocus Ltd.
Priority date: 2010-01-30
Filing date: 2011-01-30
Publication date: 2011-08-04
Also published as: CN102812304B; IL221113A0; CN102812304A

Abstract

A solar receiver including a receiver housing, a window positioned within the housing for allowing solar radiation to penetrate therethrough, the housing is subjected to tensile stresses due to thermal expansion caused by solar heating thereof resulting from the solar radiation, a fluid inlet operative to allow a working fluid to flow therein, a solar radiation absorber surrounding at least a portion of the window and is operative to be heated by the solar radiation penetrating the window, a fluid outlet operative to allow the working fluid to egress the absorber and to flow out of the receiver, a mounting element provided to mount the window to the housing, the mounting element is at least partially formed of a material with a low coefficient of thermal expansion, thereby minimizing the tensile stresses applied by the housing on the window.

Description

MOUNTING ASSEMBLY

FIELD OF THE INVENTION The present invention relates generally to mounting assemblies and particularly to assemblies for mounting low tensile strength materials.

BACKGROUND OF THE INVENTION

A material with low tensile strength may be defined as a material that fails upon application of relatively low tensile stresses thereupon. The failure point is defined as the degree of Ultimate tensile strength (UTS).

SUMMARY OF THE INVENTION

There is thus provided in accordance with an embodiment of the invention a solar receiver including a receiver housing, a window positioned within the housing for allowing solar radiation to penetrate therethrough, the housing is subjected to tensile stresses due to thermal expansion caused by solar heating thereof resulting from the solar radiation, a fluid inlet operative to allow a working fluid to flow therein, a solar radiation absorber surrounding at least a portion of the window and is heated by the solar radiation penetrating the window, a fluid outlet operative to allow the working fluid to egress the absorber and to flow out of the receiver, a mounting element provided to mount the window to the housing, the mounting element is at least partially formed of a material with a low coefficient of thermal expansion, thereby rnmirnizing the tensile stresses applied by the housing on the window.

In accordance with an embodiment of the invention the solar heating is at a relatively high temperature of above 100°C. Alternatively, the solar heating is at a relatively high temperature of above 400°C. Moreover, the solar heating is at a relatively high temperature of above 600°C. Additionally, the solar heating is at a relatively high temperature of 1000°C or above.

In accordance with another embodiment of the invention the material with a low coefficient of thermal expansion has a linear coefficient of thermal expansion of less than 3 (10^-6/°C). Additionally, the material with a low coefficient of thermal expansion is formed of FeNi36.

In accordance with yet another embodiment of the invention the mounting element is formed with an inclined surface on a bottom portion thereof, the inclined surface is configured to apply a normal force on the window in an orientation apposite an orientation of the tensile stresses, thereby minimizing the tensile stresses applied by the housing on the window. Additionally, the housing is formed with a bottom portion which is threadably engaged with the housing for allowing readily access to the window. Furthermore, the solar receiver includes a deformable cord engaged with the housing and operative to press upon the window so as to prevent dislocation of the window from the housing.

There is thus provided in accordance with another embodiment of the invention a mounting assembly including a first element including a material with low tensile strength, a second element operative to be subjected to tensile stresses due to thermal expansion thereof, and a mounting element provided to mount the first element to the second element, the mounting element is formed with an inclined surface on a bottom portion thereof the inclined surface is configured to apply a normal force on the first element in an orientation apposite an orientation of the tensile stresses, thereby mimmizing the tensile stresses applied by the second element on the first element.

There is thus provided in accordance with yet another embodiment of the invention a mounting assembly including a first element including a material with low tensile strength, a second element operative to be subjected to tensile stresses due to thermal expansion thereof, and a mounting element provided to mount the first element to the second element, the mounting element is at least partially formed of a material with a low coefficient of thermal expansion, the mounting element is formed with an inclined surface on a bottom portion thereof, Ihe inclined surface is configured to apply a normal force on the first element in an orientation apposite an orientation of the tensile stresses, thereby minimizing the tensile stresses applied by the second element on the first element.

There is thus provided in accordance with still another embodiment of the invention a mounting assembly including a first element including a material with low tensile strength, a second element operative to be subjected to tensile stresses due to thermal expansion thereof, and a mounting element provided to mount the first element to the second element, the mounting element is at least partially formed of a material with a low coefficient of thermal expansion, thereby minimizing the tensile stresses applied by the second element on the first element.

In accordance with an embodiment of the invention the thermal expansion is caused by solar heating of the second element.

In accordance with another embodiment of the invention the solar heating is at a relatively high temperature of above 100°C. Alternatively, the solar heating is at a relatively high temperature of above 400°C. Moreover, the solar heating is at a relatively high temperature of above 600°C. Additionally, the solar heating is at a relatively high temperature of 1000°C or above.

In accordance with yet another embodiment of Ihe invention the material with a low coefficient of thermal expansion has a linear coefficient of thermal expansion of less than 3 (10^~6/°C). Additionally, the material with a low coefficient of themial expansion is formed of FeNi36.

There is thus provided in accordance with a further embodiment of the invention a method for mounting including providing a first element including a material with low tensile strength, providing a second element operative to be subjected to tensile stresses due to thermal expansion thereof and mounting the first element to tiie second element with a mounting element, the mounting element is formed with an inclined surface on a bottom portion thereof, the inclined surface is configured to apply a normal force on the first element in an orientation apposite an orientation of the tensile stresses, thereby minimizing the tensile stresses applied by the second element on the first element.

There is thus provided in accordance with yet a further embodiment of the invention a method for mounting including providing a first element including a material with low tensile strength, providing a second element operative to be subjected to tensile stresses due to thermal expansion thereof, and mounting the first element to the second element with a mounting element, the mounting element is at least partially formed of a material with a low coefficient of thermal expansion, the mounting element is formed with an inclined surface on a bottom portion thereof the inclined surface is configured to apply a normal force on the first element in an orientation apposite an orientation of the tensile stresses, thereby minimizing the tensile stresses applied by the second element on the first element.

There is thus provided in accordance with still a further embodiment of the invention a method for mounting including providing a first element including a material with low tensile strength, providing a second element operative to be subjected to tensile stresses due to thermal expansion thereof, and mounting the first element to the second element with a mounting element, the mounting element is at least partially formed of a material with a low coefficient of thermal expansion, thereby rninimizing the tensile stresses applied by the second element on the first element.

There is thus provided in accordance with another embodiment of the invention a solar receiver including a receiver housing, a window positioned within the housing for allowing solar radiation to penetrate therethrough, a fluid inlet operative to allow a working fluid to flow therein, a solar radiation absorber surrounding at least a portion of the window and is heated by the solar radiation penetrating the window, a fluid outlet operative to allow the working fluid to egress the absorber and to flow out of the receiver, the housing is formed with a bottom portion which is threadably engaged with the housing for allowing readily access to the window.

There is thus provided in accordance with yet another embodiment of the invention a solar receiver including a receiver housing, a window positioned within the housing for allowing solar radiation to penetrate therethrough, a fluid inlet operative to allow a working fluid to flow therein, a solar radiation absorber surrounding at least a portion of the window and is heated by the solar radiation penetrating the window, a fluid outlet operative to allow the working fluid to egress the absorber and to flow out of the receiver, a deformable cord engaged with the housing and operative to press upon the window so as to prevent dislocation of the window from the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which:

Fig. 1A and IB is a simplified pictorial illustration of a mounting assembly constructed and operative in accordance with an embodiment of the invention and a simplified sectional illustration taken along lines IB - IB in Fig. 1 A;

Fig. 2 is a simplified sectional illustration of a solar receiver comprising a mounting assembly constructed and operative in accordance with an embodiment of the invention; and

Fig. 3 is a simplified sectional illustration taken along lines III - III in Fig. 2. DETAILED DESCRIPTION OF THE PRESENT INVENTION

In the following description, various aspects of the present invention will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details presented herein. Furthermore, well known features may be omitted or simplified in order not to obscure the present invention.

Reference is now made to Fig. 1A and IB, which is a simplified pictorial illustration of a mounting assembly constructed and operative in accordance with an embodiment of the invention and a simplified sectional illustration taken along lines IB - IB in Fig. 1A. As seen in Fig. 1 A, a mounting assembly 10 comprises a first element 12 mounted on a second element 14 via a mounting element 16. First element 12 and second element 14 may each be formed in any suitable configuration such as an annulus, as seen in Figs. 1A and IB, a cylinder, a dome, or a cuboid, for example. The first element 12 may be formed of any suitable material, typically a material with low tensile strength.

A material with low tensile strength may be defined as a material that fails upon application of relatively low tensile stresses thereupon. The failure point is defined as the degree of Ultimate tensile strength (UTS). For example, a material with low tensile strength may be defined as a material with a UTS of less than 150. Alternatively, a material with low tensile strength may be defined as a material with a UTS of less than 100. Alternatively, a material with low tensile strength may be defined as a material with a UTS of less than 50.

The second element 14 may be formed of any suitable material and may be arranged to be subjected to tensile stresses. The tensile stresses may be due to thermal pressure applied to the second element 14, which in turn thermally expands causing outwardly oriented, radial tensile stresses illustrated by arrows 20. The thermal pressure may be generated by any thermal energy source, such as solar energy, as will be further described in reference to Figs. 2 and 3.

The thermal energy source may be heat at a relatively high temperature, such as above 100 °C. The thermal energy source may be heat at a relatively high temperature, such as above 200 °C. The thermal energy source may be heat at a relatively high temperature, such as above 300 °C. The thermal energy source may be heat at a relatively high temperature, such as above 400 °C. The thermal energy source may be heat at a relatively high temperature, such as above 500 °C. The thermal energy source may be heat at a relatively high temperature, such as above 600 °C. The thermal energy source may be heat at a relatively high temperature, such as above 700 °C. The thermal energy source may be heat at a relatively high temperature, such as above 800 °C. The thermal energy source may be heat at a relatively high temperature, such as above 900 °C. The thermal energy source may be heat at a relatively high temperature, such as 1000 °C or above.

The mounting element 16 may be provided to minimize the tensile stresses applied to first element 12. The mounting element 16 may be formed in any suitable configuration and of any suitable material operative to minimize the tensile stresses applied to first element 12. As seen in Figs. 1A and IB, the mounting element 16 may be formed as a ring with an inclined surface 22 on a bottom portion 24 thereof. A generally downwardly oriented force, such as due to thermal pressure or any gravitational force illustrated by arrow 28, may be applied to first element 12. In turn, the first element 12 applies a downwardly oriented force illustrated by arrow 30 on the mounting element 16. The resultant normal force applied by the mounting element 16 on the first element 12 is partially upwardly oriented as illustrated by arrow 34 and partially inwardly oriented as illustrated by arrow 36. The inwardly oriented normal force 36 minimizes the outwardly oriented tensile stresses 20 applied to the first element 12.

Additionally or alternatively, the mounting element 16 may be formed of a material with a relatively low coefficient of thermal expansion so as to rninimize the tensile stresses applied by the thermally expanding second element 14 on the first element 12. The material with a relatively low coefficient of thermal expansion maybe any suitable material, such as FeNi36 which may be commercially available under the trade name INVAR®. Other materials with a relatively low coefficient of thermal expansion may be used, such as Fe-33Ni-4.5Co, and may be commercially available under the trade name I OVCO® , FeNi42 and FeMCo alloys, for example.

Additionally, the material with a relatively low coefficient of thermal expansion may be defined as a material with a linear coefficient of thermal expansion of less than 6 (10^-6/°C). The material with a relatively low coefficient of thermal expansion may be defined as a material with a linear coefficient of thermal expansion of less than 5 (10^_6/°C). The material with a relatively low coefficient of thermal expansion may be defined as a material with a linear coefficient of thermal expansion of less than 4 (10^_6/°C). The material with a relatively low coefficient of thermal expansion may be defined as a material with a linear coefficient of thermal expansion of less than 3 (10^-6/°C). The material with a relatively low coefficient of thermal expansion may be defined as a material with a linear coefficient of thermal expansion of Iess than 2 (10^"6/°C).

In the following Figs. 2 and 3 an embodiment of the mounting assembly 10 is describes. It is appreciated that this embodiment is provided as non-limiting example and the mounting assembly 10 may be realized in many other ways.

Reference is now made to Fig. 2, which is a simplified sectional illustration of a solar receiver comprising a mounting assembly constructed and operative in accordance with an embodiment of the invention. As seen in Fig. 2, a solar receiver 100 comprises a receiver housing 102 formed of any suitable material. Housing 102 may be configured of a generally cylindrical main portion 104 formed with a top portion 108 and a bottom portion 110. Housing 102 may be shaped in any suitable form. In an embodiment of the present invention top portion 108 and main portion 104 may be formed of stainless steel and bottom portion 110 may be formed of iron.

Main portion 104 is engaged with top portion 108 by any suitable means, such as by a peripheral protrusion 116, protruding from main portion 104, mounted to a peripheral protrusion 118, protruding from top portion 108, by screws 120. An O-ring 122 may be disposed between protrusions 116 and 118. O-ring 122 is provided to ensure the engagement of respective main portion 104 with top portion 108 is a tight sealed engagement. Any other means for sealing main portion 104 to top portion 108 may be employed.

Main portion 104 is engaged with bottom portion 110 by any suitable means, such as by a peripheral protrusion 126, protruding from main portion 104, mounted to a peripheral protrusion 128, protruding from bottom portion 110, by screws 130. An O- ring 136 may be disposed between protrusions 126 and 128. O-ring 136 is provided to ensure the engagement of respective main portion 104 with bottom portion 110 is a tight sealed engagement. Any other means for sealing main portion 104 to bottom portion 110 may be employed.

An inlet conduit housing 138 of an inlet conduit assembly 140 protrudes from top portion 108. An inlet conduit 142 is formed of a generally cylindrical portion 144 which is partially disposed within inlet conduit housing 138. A generally central inlet conduit portion 148 is disposed within main portion 104 and is connected to cylindrical portion 144 by a generally angular portion 150. Inlet conduit 142 may be formed of stainless steel or any other suitable material.

Inlet conduit 142 may be formed in any suitable configuration, such as in a generally cylindrical confrguration, for example.

Central inlet conduit portion 148 defines oh a bottom portion thereof a peripheral protrusion 170 which presses upon a central radiation shield enclosure 172 of a radiation shield assembly 174.

Radiation shield assembly 174 may be provided so as to shield the inlet conduit assembly 140 from solar radiation entering receiver 100 via a window 222 while allowing a working fluid to flow from inlet conduit 142 via perforation 224 formed in the radiation shield assembly 174 on to window 222.

It is noted that the radiation shield assembly 174 may be obviated.

Window 222 is disposed within receiver 100. Window 222 is designed to allow solar radiation to impinge thereon and penetrate therethrough. Window 222 may be shaped, e.g., as a portion of a paraboloid of revolution, as a portion of a hyperbolic paraboloid or as any suitable geometric configuration defining a streamlined contour wherein there is no profile transition from one geometric shape to the other. The streamlined contour rriinimizes turbulent flow of the working fluid flowing along the window 222 and minimizes reflection losses of mcorriing solar radiation therethrough. Additionalry, the streamlined contour obviates tensile stresses on the window 222 caused e.g., by profile transitions, and allows for increased accuracy in production thereof.

It is noted that window 222 may be shaped in any suitable conical-like or frusto-conical-like configuration or a geometric configuration defining a sfreamlined contour wherein there is a profile transition from one geometric shape to the other or any other suitable form so as to allow solar radiation to impinge thereupon and working fluid to flow therearound. Window 222 may be formed of any suitable material able to withstand relatively high temperatures and admit solar radiation therein. For example, window 222 may be formed of fused quartz. These materials may be materials with relatively low tensile strength.

A solar radiation absorber 230 is disposed around and along an internal surface 232 of window 222. Solar radiation absorber 230 may be configured in any suitable configuration for allowing solar radiation to be absorbed therein so as to heat an incoming working fluid entering via inlet assembly 140.

A circumferential seal 240 is disposed underneath window 222. Seal 240 may be formed of any suitable material, such as graphite, for example.

Window 222 may be mounted to housing 102 by any suitable means. In accordance with an embodiment of the invention the window 222, which may be defined as the first element 12 of mounting assembly 10 in Figs. 1A and IB, may be mounted to bottom portion 110 of housing 102 by a ring 244. The bottom portion 110 may be defined as second element 14 and the ring 244 may be defined as the mounting element 16. Ring 244 may be formed of any suitable material, as described hereinabove in reference to Figs. 1 A and 1 B. For example, ring 244 may be formed of a material with a relatively low coefficient of thermal expansion, such as FeNi36. The ring 244 may be formed in any suitable configuration such as with an inclined bottom surface 246.

During operation of the receiver 100 solar radiation impinges thereupon at relatively high temperatures, such as in the range of 400 -1000 °C. The receiver 100 may be subjected to the relatively high temperatures for relatively long periods of time, such as every day of the year.

Bottom portion 110 and a window cooling flange 248 of a window cooling system 250 thermally expand causing outwardly oriented, radial tensile stresses, illustrated by arrows 252, which apply tensile stresses on window 222.

The ring 244 is provided to rninimize the tensile stresses applied to the window 222. The incline orientation of bottom surface 246 is configured to apply a normal force on seal 240 and window 222 in an orientation, illustrated by arrow 253, apposite an orientation of tensile stresses 252, thereby reducing the tensile stresses applied to the window 222. Additionally, the relatively low coefficient of thermal expansion material forming ring 244 prevents additional application of tensile stresses upon window 222.

Cooling flange 248 may be formed of any suitable material, preferably a material with a relatively high resistance to corrosion, such as stainless steal, for example, so as prevent corrosion due to a cooling fluid flowing within an annular cooling fluid channel 254 formed within cooling flange 248. Cooling flange 248 is secured to bottom portion 110 by any suitable means, such as by screws 255. A seal 256 may be disposed intermediate cooling flange 248 and bottom portion 110. Seal 256 may be formed of any suitable material, such as graphite, for example.

Screws 255 threadably engage the bottom portion 110 with the main portion

104 of the housing 102. Unscrewing of screws 255 provides for relatively easy and readily removal of bottom portion 110 from main portion 104 thereby allowing easy access to window 222 and absorber 230 without necessitating disassembling of housing 102.

A bulkhead clamp 260 overlies a portion of cooling flange 248 and is engaged thereto by any suitable means, such as by screws 262. Mounting element 260 is formed with an inclined surface 266 for pressing upon a cord 270 which in tum presses upon window 222 so as to ensure that window 222 is tightly engaged with bottom portion 110 via seal 240, ring 244 and cooling flange 248 and is thus not displaced from bottom portion 110.

Cord 270 may be configured with a rectangular cross section 272 formed of any suitable deformable material so as to allow the cord 270 to be pressed between window 222, seal 240, mounting element 244 and cooling flange 248. For example, the deformable material may be a ceramic material, for example, and may be a Square Braid CeraTex Ceramic Fiber Rope commercially available at Ceramic Fiber.Net of Mineral Seal Corp. 1832 S. Research Loop Tucson, AZ, USA. A plurality of bulkhead clamps 260 may be annually arranged around cord 270.

Window cooling system 250 may be provided so as to cool window 222 during impingement of solar radiation thereon. Window cooling system 250 may comprise an inlet cooling fluid conduit 302 operative to allow a cooling fluid, typically water, to flow merewithin and within annular cooling fluid channel 254. Cooling fluid exits fluid channel 254 via a cooling fluid outlet 320. An O-ring 350 may be provided intermediate cooling flange 248 and ring 244 so as to ensure a cooling fluid flowing within the window cooling system 250 is sealed therein.

It is appreciated that window 222 may be cooled by any suitable means. Alternatively, cooling system 250 may be obviated.

A plurality of annular thermal insulating elements 390 may be disposed within receiver 100. Thermal insulating elements 390 may be formed of a ceramic material or any other suitable insulating material and are provided to prevent solar radiation emission onto housing 102. It is appreciated that thermal insulating elements 390 may be configured in any suitable manner, such as in the form of a single element, for example.

An outlet conduit housing 400 of an outlet conduit assembly 410 protrudes from top portion 108. An outlet conduit 420 is formed of a generally cylindrical portion which is partially disposed within outlet conduit housing 400 and partially disposed within top portion 108. Outlet conduit housing 400 and outlet conduit 420 may be formed of stainless steel or any other suitable material. Outlet conduit assembly 410 is provided for egress of the working fluid from receiver 100.

It is appreciated that the solar receiver 100 may be incorporated in solar thermal systems such as on-axis tracking solar thermal systems, or off-axis tracking solar thermal systems. The on-axis tracking solar system is known in the art as a solar system wherein the target, e.g. a solar receiver, is always kept on a center-line formed between a solar reflector (or reflectors) and the sun, therefore the target (e.g. solar receiver) location continuously changes to follow the sun movement. Examples of on- axis tracking solar systems include parabolic dish reflectors/concentrators and Fresnel lens concentrators. In off-axis tracking solar systems the target (e.g. solar receiver) may be stationary or move, but generally not kept in the center-line formed between the reflector (or reflectors) and the sun. Examples of off-axis tracking solar systems include central solar receivers such as solar towers.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described herein above. Rather the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove as well as variations and modifications which would occur to persons skilled in the art upon reading the specifications and which are not in the prior art.

Claims

1. A solar receiver comprising:

a receiver housing;

a window positioned within said housing for allowing solar radiation to penetrate therethrough,

said housing being subjected to tensile stresses due to thermal expansion caused by solar heating thereof resulting from said solar radiation;

a fluid inlet operative to allow a working fluid to flow therein;

a solar radiation absorber surrounding at least a portion of said window and operative to be heated by said solar radiation penetrating said window;

a fluid outlet operative to allow said working fluid to egress said absorber and to flow out of said receiver,

a mounting element provided to mount said window to said housing, said mounting element being at least partially formed of a material with a low coefficient of thermal expansion, thereby rranirnizing said tensile stresses applied by said housing on said window.

2. A solar receiver according to claim 1 wherein said solar heating is at a relatively high temperature of above 100°C.

3. A solar receiver according to claim 1 wherein said solar heating is at a relatively high temperature of above 400°C.

4. A solar receiver according to claim 1 wherein said solar heating is at a relatively high temperature of above 600°C.

5. A solar receiver according to claim 1 wherein said solar heating is at a relatively high temperature of 1000°C or above.

6. A solar receiver according to any one of claims 1 -5 wherein said material with a low coefficient of thermal expansion has a linear coefficient of thermal expansion of

Iess than 3 (10^"6/°C).

7. A solar receiver according to any one of claims 1 -6 wherein said material with a low coefficient of thermal expansion is formed of FeNi36.

8. A solar receiver according to any one of claims 1-7 wherein said mounting element is formed with an inclined surface on a bottom portion thereof, said inclined surface being configured to apply a normal force on said window in an orientation apposite an orientation of said tensile stresses, thereby mininiizing said tensile stresses applied by said housing on said window.

9. A solar receiver according to any one of claims 1-8 wherein said housing is formed with a bottom portion which is threadably engaged with said housing for allowing readily access to said window.

10. A solar receiver according to any one of claims 1-9 and comprising a deformable cord engaged with said housing and operative to press upon said window so as to prevent dislocation of said window from said housing.

11. A mounting assembly comprising:

a first element comprising a material with low tensile strength;

a second element operative to be subjected to tensile stresses due to thermal expansion thereof; and a mounting element provided to mount said first element to said second element, said mounting element being formed with an inclined surface on a bottom portion thereof said inclined surface being configured to apply a normal force on said first element in an orientation apposite an orientation of said tensile stresses, thereby minimizing said tensile stresses applied by said second element on said first element.

12. A mounting assembly comprising:

a first element comprising a material with low tensile strength;

a second element operative to be subjected to tensile stresses due to thermal expansion thereof; and

a mounting element provided to mount said first element to said second element,

said mounting element being at least partially formed of a material with a low coefficient of thermal expansion,

said mounting element being formed with an inclined surface on a bottom portion thereof said inclined surface being configured to apply a normal force on said first element in an orientation apposite an orientation of said tensile stresses, thereby minimizing said tensile stresses applied by said second element on said first element.

13. A mounting assembly comprising:

a first element comprising a material with low tensile strength;

a mounting element provided to mount said first element to said second element, said mounting element being at least partially formed of a material with a low coefficient of thermal expansion, thereby miriimizing said tensile stresses applied by said second element on said first element.

14. A mounting assembly according to any one of claims 11-13 wherein said thermal expansion is caused by solar heating of said second element.

15. A mounting assembly according to claim 14 wherein said solar heating is at a relatively high temperature of above 100°C.

16. A mounting assembly to claim 14 wherein said solar heating is at a relatively high temperature of above 400°C.

17. A mounting assembly according to claim 14 wherein said solar heating is at a relatively high temperature of above 600°C.

18. A mounting assembly according to claim 14 wherein said solar heating is at a relatively high temperature of 1000°C or above.

19. A mounting assembly according to any one of claims 11, 12, 14-18 wherein said material with a low coefficient of thermal expansion has a linear coefficient of thermal expansion of less than 3 (10^_6/°C).

20. A mounting assembly according to any one of claims 11, 12, 14-19 wherein said material with a low coefficient of thermal expansion is formed of FeNi36.

21. A method for mounting comprising:

providing a first element comprising a material with low tensile strength;

providing a second element operative to be subjected to tensile stresses due to thermal expansion thereof; and

mounting said first element to said second element with a mounting element, said mounting element being formed with an inclined surface on a bottom portion thereof, said inclined surface being configured to apply a normal force on said first element in an orientation apposite an orientation of said tensile stresses, thereby minimizing said tensile stresses applied by said second element on said first element.

22. A method for mounting comprising:

providing a first element comprising a material with low tensile strength;

mounting said first element to said second element with a mounting element, said mounting element being at least partially formed of a material with a low coefficient of thermal expansion,

said mounting element being formed with an inclined surface on a bottom portion thereof, said inclined surface being configured to apply a normal force on said first element in an orientation apposite an orientation of said tensile stresses, thereby minimizing said tensile stresses applied by said second element on said first element.

23. A method for mounting comprising:

providing a first element comprising a material with low tensile strength;

mounting said first element to said second element with a mounting element, said mounting element being at least partially formed of a material with a low coefficient of thermal expansion, thereby rnininiizing said tensile stresses applied by said second element on said first element.

24. A solar receiver comprising:

a receiver housing;

a fluid inlet operative to allow a working fluid to flow therein;

said housing being formed with a bottom portion which is threadably engaged with said housing for allowing readily access to said window.

25. A solar receiver comprising:

a receiver housing;

a fluid inlet operative to allow a working fluid to flow therein;

a deformable cord engaged with said housing and operative to press upon said window so as to prevent dislocation of said window from said housing.