WO2011024176A1

WO2011024176A1 - Solar receiver

Info

Publication number: WO2011024176A1
Application number: PCT/IL2010/000709
Authority: WO
Inventors: Hagay Cafri
Original assignee: Heliofocus Ltd.
Priority date: 2009-08-31
Filing date: 2010-08-30
Publication date: 2011-03-03

Abstract

A solar receiver is provided, comprising a receiver housing, a window positioned within the housing and configured to allow solar radiation to penetrate therethrough, a receiver volume defined between the receiver housing and the window, a fluid inlet operative to allow a fluid to flow therethrough into the receiver volume, a fluid outlet operative to allow the fluid to flow therethrough out of the receiver volume, and a solar radiation absorber disposed within the receiver volume. The solar radiation absorber surrounds at least a portion of the window so as to be heated by the solar radiation penetrating therethrough, and is configured for heating the fluid within the receiver volume. The solar radiation absoτber defines therein a helical fluid channel between the fluid inlet and outlet for flow of the fluid therethrough.

Description

SOLAR RECEIVER

FIELD OF THE INVENTION

The present invention relates generally to solar energy systems and more particularly to solar receivers within solar energy systems.

BACKGROUND OF THE INVENTION

Solar thermal energy systems harness solar energy for thermal energy. A known method for converting solar energy to thermal energy is by heating a working fluid employing solar radiation and transferring the heated working fluid to a thermal energy consumption system or apparatus. In solar energy systems one device known in the art for heating the working fluid is a solar receiver. Such a receiver utilizes solar radiation which impinges upon a solar radiation absorber within the solar receiver. The working fluid is heated by the absorber, and thereafter the working fluid transfers the heat to a thermal energy consumption system or apparatus.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided a solar receiver comprising:

• a receiver housing;

• a window positioned within the receiver housing and configured to allow solar radiation to penetrate therethrough;

• a receiver volume defined between the receiver housing and the window;

• a fluid inlet operative to allow a fluid to flow therethrough into the receiver volume;

• a fluid outlet operative to allow the fluid to flow therethrough out of the receiver volume;

• a solar radiation absorber disposed within the receiver volume surrounding at least a portion of the window so as to be heated by the solar radiation penetrating therethrough, the solar radiation absorber being configured for heating the fluid within the receiver volume and defining therein a helical fluid channel between the fluid inlet and outlet for flow of the fluid therethrough. The absorber may comprise walls, which may be made of an insulating material, arranged in a helical configuration defining therebetween the fluid channel. The absorber may comprise a base, which may be made of an insulating material, carrying the walls protruding therefrom, for example, toward the window.

The window may be mounted to the housing by a deformable cord pressed between the window and the housing.

The solar receiver may further comprise a mounting element formed with an inclined surface configured to press upon the cord.

The solar receiver may further comprise a cover engaged with the helical fluid channel. The cover may be formed of a perforated material.

According to another aspect of the present invention, there is provided a solar receiver system comprising a solar receiver and a thermal energy consumption apparatus, the solar receiver comprising:

• a receiver housing;

• a receiver volume defined between the receiver housing and the window;

• a fluid outlet operative to allow the fluid to flow therethrough out of the receiver volume; and

• a solar radiation absorber disposed within the receiver volume surrounding at least a portion of the window so as to be heated by the solar radiation penetrating therethrough, the solar radiation absorber being configured for heating the fluid within the receiver volume and defining therein a helical fluid channel between the fluid inlet and outlet for flow of the fluid therethrough; the thermal energy consumption apparatus being configured to receive the heated fluid flowing out of the fluid outlet so as to utilize thermal energy within said heated fluid.

The absorber may comprise walls, which may be made of an insulating material, arranged in a helical configuration defining therebetween the fluid channel. The absorber may comprise a base, which may be made of an insulating material, carrying the walls protruding therefrom, for example toward the window.

The window may be mounted to the housing by a deformable cord pressed between the window and the receiver housing.

The solar receiver system may comprise a plurality of the solar receivers.

According to a further aspect of the present invention, there is provided a method for heating a fluid, the method comprising:

• providing a solar receiver comprising a fluid inlet, a fluid outlet, a solar absorber configured to be heated by solar radiation impinging thereupon and being formed with a helical fluid channel allowing a fluid to flow therethrough between the fluid inlet and outlet along a helical path, and a window disposed so as to allow solar radiation to impinge upon the solar absorber;

• exposing the solar absorber to solar radiation via the window, thereby heating the solar absorber;

• introducing the fluid into the solar receiver via the fluid inlet so as to be in contact with the solar absorber;

• causing the fluid to flow along the helical path, wherein the fluid is heated by the heated solar absorber; and

• causing the fluid to exit the solar receiver via the fluid outlet.

According to a still further aspect of the present invention, there is provided a method for exploiting thermal energy, the method comprising:

• providing a thermal energy consumption apparatus configured to exploit thermal energy within heated fluid; - A -

• causing the fluid to flow along the helical path, wherein the fluid is heated by the heated solar absorber;

• causing the fluid to exit the solar receiver via the fluid outlet and enter the thermal energy consumption apparatus; and

• operating the thermal energy consumption apparatus to exploit the thermal energy within the heated fluid.

According to a further aspect of the present invention, there is provided a solar radiation absorber of a solar receiver comprising:

• an annular base; and

• at least a pair of walls protruding from the base and defining therebetween a helical fluid channel for fluid flow therein.

The solar receiver may further comprise a window being mounted to the housing by a deformable cord pressed between the window and 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. 1 is a simplified pictorial illustration of a solar receiver constructed and operative in accordance with an embodiment of the present invention;

Fig. 2 is a simplified sectional illustration taken along lines II - II in Fig. 1; Fig. 3 is a simplified sectional illustration taken along lines HI - HI in Fig. 1; Fig. 4 is a simplified sectional illustration taken along lines IV - IV in Fig. 1; Fig. 5 is a simplified pictorial illustration of a single solar radiation absorber element of a solar absorber shown in Fig. 4;

Fig. 6 is a simplified illustration of another embodiment of elements shown in Fig. 4;

Fig. 7 is a simplified pictorial illustration of a single solar radiation absorber element of a solar absorber shown in Fig. 6; and

Fig. 8 is a simplified operational illustration of the solar receiver of Figs. 1-7.

DETAILED DESCRIPTION

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.

As seen in Fig. 1, a solar receiver 100 comprises a receiver housing 102 formed of stainless steel or any other 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.

As seen in Fig. 2, main portion 104 is engaged with top portion 108 by any suitable means, such as by welding, for example. 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 engaging main portion 104 with 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 (Fig. 4), 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.

As seen in the inset in Fig. 2, central inlet conduit portion 148 defines on a bottom portion thereof a peripheral protrusion 170 which presses upon a central radiation shield enclosure 172 of a radiation shield assembly 174 at an inclined surface 178 thereof. Protrusion 170 may be formed of stainless steel or any other suitable material. Enclosure 172 may be provided for thermal insulation of a high-temperature fluid flowing through radiation shield assembly 174, as will be further described hereinbelow with reference to Fig. 8. Enclosure 172 may be formed of a ceramic material or any other suitable material. A ridge 180, defined by enclosure 172, is seated on a peripheral ring support 182 formed of stainless steel or any other suitable material.

Enclosure 172 defines an annular recess 188 in a middle portion 190 thereof. A radiation shield 192 is seated within recess 188 and may be formed of any suitable material, such as ceramics or metals adopted to withstand relatively high temperatures. Radiation shield 192 may be formed of tubes, pins or any perforated structure, for example, so as to allow fluid to flow therethrough.

An annular insulating element 198 may be provided to surround peripheral protrusion 170 and a portion of enclosure 172 and may be connected to peripheral protrusion 170 and ring support 182 via screws 200 inserted therein or by any other suitable means.

Radiation shield 192 may be provided so as to shield the inlet conduit assembly 140 from solar radiation entering receiver 100 via a window 222 while allowing the fluid to flow from inlet conduit 142 via perforation in the radiation shield 192 on to window 222. It is noted that the radiation shield 192 may be replaced by any other suitable means for shielding the inlet conduit assembly 140 from solar radiation impinging thereon. Alternatively, the radiation shield 192 may be obviated.

Window 222 is disposed within receiver 100, and defines therebetween a receiver volume 224. Window 222 is designed so as to allow solar radiation to impinge thereon and penetrate therethrough, as will be further described hereinbelow with reference to Fig. 8.

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 minimizes turbulent flow of the fluid flowing along the window 222 and minimizes reflection losses of incoming solar radiation therethrough. Additionally, 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 streamlined contour wherein there is a profile transition from one geometric shape to the other. Additionally, window 222 may be shaped in any other suitable form so as to allow solar radiation to impinge thereupon and fluid to flow therearound. Window 222 may be formed of any suitable material able to withstand relatively high temperatures, typically above ambient temperature, for example, and admit solar radiation therein. For example, window 222 may be formed of fused quartz.

A solar radiation absorber 230 is disposed around and along at least a portion of an internal surface 232 of window 222.

Underlying absorber 230 may be disposed an annular insulating element 240 surrounding window 222 at a base portion 244 of window 222. Insulating element 240 may be formed of a ceramic material or any other suitable material and is provided to prevent solar radiation emission into bottom portion 110 of housing 102. Insulating element 240 may be adhered to bottom portion 110 by any suitable means such as by screws 246 (Fig. 3).

Window 222 may be mounted onto housing 102 by any suitable means. As seen in the inset in Fig. 2 a circumferential seal 250 is engaged with window 222 and is supported by bottom portion 110 of housing 102. A mounting element 260 overlies a portion of bottom portion 110 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 turn presses upon window 222 and bottom portion 110 thereby ensuring window 222 is tightly engaged with seal 250 and bottom portion 110 and is not displaced therefrom.

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 and bottom portion 110. 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 mounting elements 260 may be annually arranged around cord 270, as seen in Fig. 3.

A window cooling system 300 may be provided so as to cool window 222 during impingement of solar radiation thereon. As seen in the inset in Fig. 2, window cooling system 300 may comprise an inlet cooling fluid conduit 302 operative to allow a fluid, typically water, to flow therewithin and within an annular cooling fluid conduit 306 underlying bottom portion 110 of housing 102. Cooling fluid exits fluid channel 306 via a cooling fluid outlet 320 (Fig. 3).

It is appreciated that window 222 may be cooled by any suitable means or alternatively, the cooling system 300 may not be provided.

Receiver 100 may include an annular focusing element 340, which may be attached thereto by any suitable means. As seen in Fig. 2, focusing element 340 is mounted to housing 102 via an annular bracket 342 which is attached to bottom portion HO by any suitable means, such as by screws (not shown) attaching brackets 342 to focusing element 340 on a bottom portion 346 thereof and screws (not shown) attaching brackets 342 to bottom portion 110 on a top portion 348 thereof.

Focusing element 340 is operative to guide solar radiation to penetrate window 222 and prevent the solar radiation from impinging upon bottom portion 110 of housing 102. Focusing element 340 may be formed of a ceramic material or any other suitable material. It is appreciated that any other focusing functionality may be employed to guide solar radiation to window 222, such as optical elements, for example. Alternatively, focusing element 340 may not be provided.

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.

A support assembly 392 may be disposed around annular thermal insulating elements 390 so as to prevent displacement of the elements 390 within housing 102. Support assembly 392 may be formed in any suitable manner such as with a plurality of horizontal bars 394 inserted within a plurality of longitudinal bars 396. It is appreciated that any other supporting means may be provided to prevent displacement of the elements 390 within housing 102. Alternatively, support assembly 392 may not be provided.

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 (Fig. 4). 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 a fluid from receiver 100.

A plurality of thermal insulating elements 430 may be disposed around and along an outer surface 432 of outlet conduit 420 and is provided to prevent heating of receiver housing top portion 108 by a relatively high temperature fluid flowing through outlet conduit 420. Thermal insulating elements 430 may be formed of a ceramic material or any other suitable material. Outlet conduit 420 is in fluid communication with an outlet fluid chamber 440 defined by the vacancy formed between insulating element 198, absorber 230 and insulating elements 390.

Outlet conduit housing 400 may include a first flange 443 protruding therefrom. First flange 443 may be mounted onto a second flange 444 protruding from top portion 108 via screws 446 inserted therein. First flange 443 is provided as an interface with a solar energy system component, such as a turbine or any other thermal energy consumption apparatus (not shown).

Inlet conduit housing 138 may include a first flange 450 protruding therefrom.

First flange 450 may be mounted onto a second flange 454 protruding from top portion 108 via screws 456 inserted therein. First flange 450 is provided as an interface with a solar energy system component, such as a compressor or any fluid containing device

(not shown).

It is noted that first flange 443 and first flange 450 may not be provided.

A bellows (not shown) may be disposed about inlet conduit 142 and is provided to absorb the thermal expansion of inlet conduit 142 during heating thereof by a relatively high-temperature fluid flowing therein. Additionally, a bellows (not shown) may be disposed about outlet conduit 420 and is provided to absorb the thermal expansion of outlet conduit 420 during heating thereof by relatively high-temperature fluid flowing thereout.

The bellows may be formed of any suitable material, such as, e.g., stainless steel or a suitable elastomeric material and may be engaged with inlet conduit 142 and/or outlet conduit 420 by any suitable means such as by use of clamps (not shown).

As seen in Fig. 4, solar radiation absorber 230 comprises a plurality of solar radiation absorber elements 534. As seen in Fig. 5, each absorber element 534 may comprise a base configured as a generally longitudinal portion 540 defining a plurality of fluid channels 544 thereon by walls 546 being carried by and extending from an upper surface 548 of longitudinal portion 540. On a bottom portion 550 of absorber element 534 is formed a fluid ingress 554 for allowing fluid to be introduced into absorber element 534, flow within fluid channels 544 and thereafter exit the absorber element 534 via a fluid egress 556 defined at a top portion 557 of absorber element 534.

Longitudinal portion 540 and walls 546 may be formed of any suitable material, such as an insulating material, for example, such as a material formed of

Vitreous Aluminosilicate Fibers which may be commercially available under the trade name of GEMCOLITE® of Refractory Specialties, Inc. of 230 W. California Avenue Sebring, OH, USA. An additional layer 558 may be disposed upon upper surface 548 of longitudinal portion 540, Layer 558 may be formed of any suitable material, such as a perforated material formed of silicon carbide, for example, so as to allow solar radiation to penetrate therein and thus heat fluid entering absorber elements 534 via ingress 554, as will be further described with reference to Fig. 8 hereinbelow.

Absorber elements 534 are annually arranged around internal surface 232 of window 222 defining an annular array 560. As seen in Fig. 4, the walls 546 of each absorber element 534 are aligned therebetween so as to form a continuous fluid channel within array 560 thus defining a helical fluid channel 566.

The helical fluid channel 566 is provided for guiding a fluid entering ingress 554 to flow within the absorber 230 in a helical motion.

The fluid channels 544 may be covered by a cover 570, as shown in Figs. 6 and 7. Cover 570 is provided to prevent the fluid from flowing out of the fluid channel 544 while allowing solar radiation to penetrate therein and thus heat fluid flowing within fluid channel 544. Cover 570 may be formed of any suitable material, such as a perforated material formed of silicon carbide, for example. Cover 570 may not be provided, as seen in the embodiment shown in Figs. 4 and 5.

It is appreciated that the plurality of absorber elements 534 may be replaced by a single conical structure surrounding window 222 and defining annular array 560.

As seen in Fig. 8, a fluid, typically a working fluid, such as air, for example, is introduced into the receiver volume 224 via inlet conduit 142 of receiver 100. Fluid may flow in the receiver 100 following compression within a compressor or any fluid containing device (not shown).

The fluid flows from inlet conduit 142 via radiation shield 192 on to the internal surface 232 of window 222. At window base 244 the fluid expands into absorber 230.

It is noted that the incoming fluid from inlet conduit 142 flows via radiation shield 192 initially to the internal surface 232 of window 222 prior to flowing into the absorber 230 due to the decrease of the surface area of the fluid flow from the radiation shield 192 to a top portion 600 of window 222. As seen in the inset in Fig. 2, the surface area of the radiation shield 192 is substantially larger than the surface area defined by the surface area between a bottom portion 604 of enclosure 172 and top portion 600. This area is designated by reference numeral 610. The difference in the surface areas is illustrated by the difference in a radius 612 of the radiation shield surface area and a radius 614 of surface area 610. Thus, as the surface area of the fluid flow decreases from the radiation shield surface area to surface area 610, the velocity of the fluid consequentially increases, thereby urging the fluid to flow along internal surface 232 of window 222 from top portion 600 to base portion 244 thereof. At base portion 244 the velocity of the fluid decreases thus allowing the fluid to expand into absorber 230. The initial flow of the fluid along window 222 provides for cooling of the window 222, which is subjected to relatively high temperatures due to admission of solar radiation therethrough.

Turning to Fig. 8, solar radiation, designated by reference numeral 630, is admitted into absorber 230 via window 222 typically following concentration by a concentrator 634 of the solar energy system. It is noted that concentrator 634 is not shown to scale. Solar radiation 630 passes window 222 and thereafter penetrates absorber elements 534, typically via perforations of layer 558 (Fig. 5). The solar radiation absorbed within absorber elements 534 is emitted as heat to the fluid flowing within the absorber 230, thereby heating the fluid therein.

The expanded fluid enters the absorber 230 via any one of the absorber elements 534 at ingress 554 and flows into fluid channel 544. The fluid progresses to flow along helical fluid channel 566 and thereafter flows out of absorber 230 via an egress 556 of another absorber element 534. Flow of the fluid within helical fluid channels 566 allows for the fluid to flow within absorber 230 along a relatively long fluid path thus increasing the exposure of the fluid to heat emitted from the absorber 230. Additionally, flow of the fluid within helical fluid channels 566 increases adherence of the fluid flowing within the absorber 230 to the helical fluid channels 566, thus minimizing the interface of the fluid flowing within the absorber 230 with a fluid flowing simultaneously along window 222. The cover 570 (Figs. 6 and 7) may be additionally provided for minimizing the interface of the fluid flowing within the absorber 230 with a fluid flowing simultaneously along window 222.

Heated fluid flows from absorber 230 to outlet fluid chamber 440 and exits the receiver volume 224 via outlet conduit 420. Thereafter heated fluid may be introduced into a turbine or any other thermal energy consumption apparatus (not shown).

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

CLAIMS:

1. A solar receiver comprising.

• a receiver housing;

• a window positioned within said receiver housing and configured to allow solar radiation to penetrate therethrough;

• a receiver volume defined between said receiver housing and said window;

• a fluid outlet operative to allow said fluid to flow therethrough out of the receiver volume; and

• a solar radiation absorber disposed within said receiver volume surrounding at least a portion of said window so as to be heated by said solar radiation penetrating therethrough, said solar radiation absorber being configured for heating said fluid within the receiver volume and defining therein a helical fluid channel between said fluid inlet and outlet for flow of said fluid therethrough.

2. A solar receiver according to Claim 1, wherein said absorber comprises walls arranged in a helical configuration defining therebetween said fluid channel.

3. A solar receiver according to Claim 2, wherein said absorber comprises a base carrying said walls protruding therefrom toward said window.

4. A solar receiver according to Claim 3, wherein a layer formed of a perforated material is disposed upon said base.

5. A solar receiver according to any one of Claims 3 and 4, wherein said base is formed of an insulating material.

6. A solar receiver according to any one of Claims 2 through 5, wherein said walls are formed of an insulating material.

7. A solar receiver according to any one of the preceding claims, wherein said window is mounted to said housing by a deformable cord pressed between said window and said housing.

8. A solar receiver according to Claim 7, further comprising a mounting element formed with an inclined surface configured to press upon said cord.

9. A solar receiver according to any one of the preceding claims, further comprising a cover engaged with said helical fluid channel.

10. A solar receiver according to Claim 9, wherein said cover is formed of a perforated material.

11. A solar receiver system comprising a solar receiver and a thermal energy consumption apparatus, the solar receiver comprising:

• a receiver housing;

• a receiver volume defined between said receiver housing and said window; • a fluid inlet operative to allow a fluid to flow therethrough into the receiver volume;

• a solar radiation absorber disposed within said receiver volume surrounding at least a portion of said window so as to be heated by said solar radiation penetrating therethrough, said solar radiation absorber being configured for heating said fluid within the receiver volume and defining therein a helical fluid channel between said fluid inlet and outlet for flow of said fluid therethrough, said thermal energy consumption apparatus being configured to receive the heated fluid flowing out of said fluid outlet so as to utilize thermal energy within said heated fluid.

12. A solar receiver system according to Claim 11, wherein said absorber comprises walls arranged in a helical configuration defining therebetween said fluid channel.

13. A solar receiver system according to Claim 12, wherein said absorber comprises a base carrying said walls protruding therefrom toward said window.

14. A solar receiver system according to Claim 13, wherein a layer formed of a perforated material is disposed upon said base.

15. A solar receiver system according to any one of Claims 13 and 14, wherein said base is formed of an insulating material.

16. A solar receiver system according to any one of Claims 12 through 15, wherein said walls are formed of an insulating material.

17. A solar receiver system according to any one of Claims 11 through 16, wherein said window is mounted to said housing by a deformable cord pressed between said window and said housing.

18. A solar receiver system according to Claim 17 further comprising a mounting element formed with an inclined surface configured to press upon said cord.

19. A solar receiver system according to any one of Claims 11 through 18, further comprising a cover engaged with said helical fluid channel.

20. A solar receiver system according to Claim 19, wherein said cover is formed of a perforated material.

21. A solar receiver system according to any one of Claims 11 through 20, comprising a plurality of said solar receivers.

22. A method for heating a fluid, the method comprising:

• providing a solar receiver comprising a fluid inlet, a fluid outlet, a solar absorber configured to be heated by solar radiation impinging thereupon and being formed with a helical fluid channel allowing a fluid to flow therethrough between said fluid inlet and outlet along a helical path, and a window disposed so as to allow solar radiation to impinge upon said solar absorber;

• exposing said solar absorber to solar radiation via said window, thereby heating the solar absorber;

• introducing said fluid into said solar receiver via the fluid inlet so as to be in contact with the solar absorber;

• causing said fluid to flow along said helical path, wherein said fluid is heated by the heated solar absorber; and

• causing said fluid to exit said solar receiver via the fluid outlet.

23. A method for exploiting thermal energy, the method comprising:

• providing a thermal energy consumption apparatus configured to exploit thermal energy within heated fluid;

• causing said fluid to flow along said helical path, wherein said fluid is heated by the heated solar absorber;

• causing said fluid to exit said solar receiver via the fluid outlet and enter the thermal energy consumption apparatus; and

• operating said thermal energy consumption apparatus to exploit the thermal energy within the heated fluid.

24. A solar radiation absorber of a solar receiver comprising:

• an annular base; and • at least a pair of walls protruding from said base and defining therebetween a helical fluid channel for fluid flow therein.

25. A solar receiver according to Claim 3, wherein said base is formed of an insulating material.

26. A solar receiver according to Claim 2, wherein said walls are formed of an insulating material.

27. A solar receiver according to Claim 1, wherein said window is mounted to said housing by a deformable cord pressed between said window and said housing.

28. A solar receiver according to Claim 27, further comprising a mounting element formed with an inclined surface configured to press upon said cord.

29. A solar receiver according to Claim 1, further comprising a cover engaged with said helical fluid channel.

30. A solar receiver according to Claim 29 wherein said cover is formed of a perforated material.

31. A solar receiver system according to Claim 13, wherein said base is formed of an insulating material.

32. A solar receiver system according to Claim 12, wherein said walls are formed of an insulating material.

33. A solar receiver system according to Claim 11, wherein said window is mounted to said housing by a deformable cord pressed between said window and said housing.

34. A solar receiver system according to Claim 33, further comprising a mounting element formed with an inclined surface configured to press upon said cord.

35. A solar receiver system according to Claim 11, further comprising a cover engaged with said helical fluid channel.

36. A solar receiver system according to Claim 35 wherein said cover is formed of a perforated material.

37. A solar receiver system according to Claim 11, comprising a plurality of said solar receivers.

38. A solar receiver comprising:

• a receiver housing;

• a window positioned within said housing and configured to allow solar radiation to penetrate therethrough;

• a solar radiation absorber disposed within said receiver volume surrounding at least a portion of said window so as to be heated by said solar radiation penetrating therethrough, said solar radiation absorber being configured for heating said fluid within the receiver volume,

said window being mounted to said housing by a deformable cord pressed between said window and said housing.

39. A solar receiver according to Claim 38, further comprising a mounting element formed with an inclined surface configured to press upon said cord.