Title:
Solar energy collector
Kind Code:
A1


Abstract:
A solar energy collector comprised of Fresnel lenses attached by support frames to a solar tracking drive. Each of the Fresnel lenses is continuously alined with the sun during a desired period of operation and are maintained at a focus distance from energy absorbers by the support frames and the solar tracking drive. The energy absorbers may be absorption conduit.



Inventors:
Johnson, Neldon P. (Salem, UT, US)
Application Number:
10/621933
Publication Date:
01/20/2005
Filing Date:
07/17/2003
Assignee:
JOHNSON NELDON P.
Primary Class:
Other Classes:
126/600, 126/652
International Classes:
F24J2/54; F24S20/20; F24S23/30; (IPC1-7): F24J2/08
View Patent Images:
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Primary Examiner:
COCKS, JOSIAH C
Attorney, Agent or Firm:
J. David Nelson (Sandy, UT, US)
Claims:
1. Apparatus for solar energy collection comprising: a) one or more Fresnel lenses, each Fresnel lens having a focal axis; b) one or more energy absorbers, each energy absorber having one or more internal absorption ducts for transferring solar energy absorbed by the energy absorber to an absorption liquid; c) one or more support frames, each support frame securing a respective Fresnel lens in a respective focus position for focusing solar energy passing the Fresnel lens on an absorption zone of an energy absorber; and d) one or more solar tracking drives affixed to the support frames for maintaining alinement of the focal axis of each of the Fresnel lenses with the sun and maintaining each of the Fresnel lenses in a respective focus position during a desired period of operation.

2. Apparatus as recited in claim 1 wherein the energy absorbers are absorption conduits.

3. Apparatus as recited in claim 1 further comprising an absorption liquid circulating system connected to the absorption ducts in each energy absorber.

4. Apparatus as recited in claim 2 wherein each absorption zone is comprised of an energy assimilator of high thermal conductivity material affixed to the absorption conduit.

5. Apparatus as recited in claim 4 wherein each energy assimilator is spherically shaped.

6. Apparatus as recited in claim 1 wherein the absorption zone of each energy absorber is encapsulated in an energy retaining capsule of material with a high solar radiation transmission rate and a low thermal conductivity rate.

7. Apparatus as recited in claim 6 wherein the energy retaining capsule is comprised of transparent material.

8. Apparatus as recited in claim 6 wherein the energy retaining capsule is spherically shaped.

9. Apparatus as recited in claim 7 wherein the transparent material is a borsilicate glass.

10. Apparatus as recited in claim 3 wherein the absorption liquid circulating system comprises an absorption liquid conduit system and one or more absorption liquid pumps.

11. Apparatus as recited in claim 3 wherein the absorption liquid is an oil.

12. Apparatus as recited in claim 3 further comprising an energy transfer system connected to the absorption liquid circulating system.

13. Apparatus as recited in claim 12 wherein the transfer liquid is water.

14. Apparatus as recited in claim 12 wherein the energy transfer system comprises an energy exchanger, a transfer liquid conduit system and one or more transfer liquid pumps, the energy exchanger being connected to the absorption liquid circulating system.

15. Apparatus as recited in claim 1 wherein the solar tracking drive comprises longitudinal pivot means, lateral pivot means and tracking control means.

16. Apparatus as recited in claim 1 wherein one or more of the Fresnel lenses have an elongated focus for an elongated absorption zone on the energy absorbers.

17. Apparatus as recited in claim 1 wherein one or more Fresnel lenses have longitudinal grooves with a linear distributed focus for a linear elongated absorption zone on the energy absorbers.

18. Apparatus as recited in claim 1 wherein one or more Fresnel lenses have oval grooves with a distributed focus for the absorption zones on the energy absorbers.

19. Apparatus as recited in claim 1 wherein the energy absorbers have absorption surfaces which are displaced radially from the focal point of the respective lenses for a distributed focus on the absorption zones of the energy absorbers.

20. Apparatus as recited in claim 2 wherein the absorption conduits comprise one or more pipes.

21. Apparatus as recited in claim 1 further comprising an energy retaining capsule with a high solar energy transmission rate and a low thermal conductivity rate encapsulating each absorption zone.

22. Apparatus as recited in claim 21 wherein the energy retaining capsule is spherical in shape.

23. Apparatus as recited in claim 21 wherein the capsule is made of borsilicate glass.

24. Apparatus as recited in claim 2 further comprising a respective energy retaining capsule encapsulating each absorption zone on each absorption conduit.

25. Apparatus as recited in claim 24 wherein the energy retaining capsule comprises a conduit coating with a high solar energy transmission rate and a low thermal conductivity rate.

26. Apparatus as recited in claim 25 wherein the conduit coating is made of borsilicate glass.

27. Apparatus as recited in claim 25 wherein the conduit coating is ceramic.

28. Apparatus as recited in claim 1 further comprising a respective absorption fin mounted in an interior absorption duct of one or more energy absorbers in the absorption zone.

29. Apparatus as recited in claim 1 wherein one or more of the energy absorbers comprise an energy assimilator affixed on an absorption liquid conduit.

30. Apparatus as recited in claim 29 wherein the absorption liquid conduits comprise one or more pipes.

31. Apparatus as recited in claim 30 further comprising an energy retaining capsule with a high solar energy transmission rate and a low thermal conductivity rate encapsulating each absorption zone.

32. Apparatus as recited in claim 31 wherein the energy retaining capsule is spherical in shape.

33. Apparatus as recited in claim 31 wherein the energy retaining capsule is hemispherical in shape.

34. Apparatus as recited in claim 31 wherein the energy retaining capsule is made of borsilicate glass.

35. Apparatus as recited in claim 1 further comprising a respective absorption fin mounted in an interior absorption duct of one or more energy absorbers at the absorption zone.

36. Apparatus as recited in claim 1 further comprising one or more secondary lenses affixed by a secondary lens frame to the support frame.

37. Apparatus as recited in claim 14 further comprising: a) steam turbine, the steam turbine having an output shaft; and b) rotary generator affixed to the output shaft of the steam turbine.

38. Apparatus for solar energy collection comprising: a) one or more Fresnel lenses for concentrating incident solar energy, each Fresnel lens having a focal axis; b) absorption means for absorbing solar energy concentrated by the Fresnel lenses and transferring the absorbed solar energy to an absorption liquid; c) support means for supporting each Fresnel lens in a respective focus position for focusing solar energy passing the Fresnel lens on the absorption means; and d) solar tracking means affixed to the support means for maintaining alinement of the focal axis of each of the Fresnel lenses with the sun and maintaining each of the Fresnel lenses in a respective focus position during a desired period of operation.

Description:

FIELD OF THE INVENTION

This invention is in the field of solar energy systems and in particular in the field of solar energy collectors which use lenses to concentrate solar radiation for use in heat exchange applications.

BACKGROUND OF THE INVENTION

The use of lenses to concentrate solar radiation on an absorbing device is known in the art. Solar concentrators utilizing Fresnel lenses have also been disclosed in the prior art. U.S. Pat. No. 5,915,376 to McLean discloses a solar heat collecting apparatus comprised of glass domes consisting of Fresnel lenses. Solar radiation entering the solar heat collecting apparatus is absorbed by an absorber plate, and transferred to a remote storage system by conventional heat transfer means.

U.S. Pat. No. 6,384,320 to Chen discloses a compound parabolic concentrator (CPC) which is mounted under a Fresnel lens that concentrates the intensity of solar radiation to five to ten times above normal level. The focused solar radiation is further concentrated twenty to fifty times by the CPC collector. The intensified solar radiation is focused onto the top of a stainless steel heat pipe or heat exchanger.

The use of Fresnel lenses for concentrating solar energy is disclosed in U.S. Pat. No. 6,399,874 to Olah, U.S. Pat. No. 6,299,317 to Gorthala, and U.S. Pat. Nos. 5,959,787 and 6,091,020 to Fairbanks. The devices disclosed in these patents provide for concentrating solar energy for photovoltaic cells.

It is an object of the present invention to provide a simplified, economical and efficient solar collector for heat transfer applications.

It is a further object of the present invention to provide a solar collector using a pipe for an energy absorber.

It is a further object of the present invention to provide a solar collector that is flexible as to the intensity, distribution and geometry of concentration of solar radiation on an energy absorber.

It is a further object of the present invention to provide a solar collector that incorporates an energy absorber with enhanced energy absorption efficiency.

It is a further object of the present invention to provide a solar collector that uses a pipe with an energy retaining capsule encapsulating the absorption zone as an energy absorber.

It is a further object of the present invention to provide a solar collector with a simple and economical solar tracking drive.

It is a further object of the present invention to provide a solar collector that is readily incorporated into a solar collector installation that is flexible as to size and geometry.

It is a further object of the present invention to provide a simple, economical and efficient solar collector installation.

It is a further object of the present invention to provide a solar collector installation that is simple and economical to operate and maintain.

It is a further object of the present invention to provide a solar collector installation that utilizes pipes as energy absorbers.

It is a further object of the present invention that provides a solar collector and energy extraction installation that is simple and economical to construct, operate and maintain.

SUMMARY OF THE INVENTION

The solar energy collector of the present invention uses one or more Fresnel lenses. Typically the Fresnel lens used for the present invention is a extruded or molded from a thin, lightweight plastic sheet with concentric grooves formed in one side of the lens. The grooves act as individual refracting surfaces, like small prisms when viewed in cross section, bending parallel rays in a very close approximation to a common focal length. Because the lens is thin, very little energy is lost by absorption.

For a preferred embodiment, the Fresnel lenses are mounted on a support frame above an absorption conduit which is typically a metal pipe. If the Fresnel lenses are designed for a point focus or a distributed focus on an absorption zone, the absorption conduit may have an energy absorber mounted on the conduit in the absorption zone which is enclosed in an energy retaining capsule with a high solar radiation transmission rate and a low thermal conductivity rate, thereby providing for transmission of the focused incident solar radiation to the absorption zone of the energy absorber while minimizing the loss of energy from the energy absorber to the surrounding air. An in-line or attached spherical energy absorber with a spherical energy retaining capsule or a hemispherical energy absorber with a hemispherical energy retaining capsule may be used. Alternatively, a spherical or hemispherical energy retaining capsule can simply be used to encapsulate an absorption zone on the absorption conduit. For a linear absorption zone, a cylindrical capsule is preferred on the absorption conduit. The absorbed energy is transferred to an absorption liquid flowing through the absorption conduit.

An absorption fin can also be incorporated inside the energy absorber which extends into the absorption duct and is in contact with the absorption zone, thereby assisting in the transfer of energy to the absorption liquid which flows through the energy absorber. The absorption fin would normally be made of high thermal conductivity material thereby rapidly transferring the energy of the incident solar radiation from the absorption zone to the absorption liquid. A preferred material for the absorption zone and absorption fins is tungsten due to its high thermal conductivity rate, its high melting point and its glass to metal sealing capabilities.

Each Fresnel lenses is mounted on a support frame which is attached to a solar tracking drive. The solar tracking drive continually aligns each Fresnel lenses with the sun, during a desired period of operation, thereby providing for continual point focus or distributed focus of the incident solar radiation on an absorption zone of the energy absorber. The absorption conduit, or other energy absorber, can be positioned so that the Fresnel lens top surface is separated from the absorption conduit top surface by a distance which is equal to the focal length of the lens, thereby providing for the incident solar radiation to be focused at a single point in the absorption zone of the energy absorber or can be positioned such that incident solar radiation is distributed on a larger area of the absorption zone. If the incident solar radiation is focused on a single point in the absorption zone of the energy absorber, substantially higher temperatures will be experienced at the focal point. Having the focal point coincident with the center of the energy absorber, rather than a point on the surface of the energy absorber, results in distribution of the energy and therefore substantially reduced temperatures. The focus of the incident solar radiation can be varied between the center of the absorption conduit and a point on the surface of the absorption conduit thereby varying the distribution of the focused solar radiation and thereby the maximum temperature experienced in the absorption zone.

Rather than a circular pattern of grooves, the Fresnel lenses may have longitudinal grooves which result in the incident solar radiation having a line focus rather than a single focal point. This offers an advantage of distributing the focused incident solar radiation over a larger area, thereby reducing the temperature of the absorption zone. The expanded absorption zone for embodiments utilizing a Fresnel lens with longitudinal grooves can be encapsulated in an energy retaining capsule with a high solar radiation transmission rate and low thermal conductivity rate such as glass. Other portions of the absorption conduit which do not receive focused incident solar radiation can be insulated or merely be covered with the energy retaining capsule material to reduce energy loss to the surrounding air. Similarly, Fresnel lenses with oval grooves may be used to provide for distribution of energy on the absorption zone as the lens will distribute the concentrated radiation on an expanded area rather than a single focus point. Further distribution of the energy can be accomplished, regardless of the pattern of grooving on the Fresnel lens, by positioning the Fresnel lenses so that the energy absorbers have absorption surfaces which are displaced radially from the focal point or focal line of the respective lenses. The extent of the distribution can be selected based upon the desired range of surface temperatures for the absorption zone.

The Fresnel lens itself is preferably constructed of an optically clear material. These materials include but are not limited to acrylic, glass, rigid vinyl, polycarbonate, polyethylene, polyester blends including PET and PETG respectively, poly IR, polystyrene, polyurethane, polypropylene, polyacrylonitrile, Kevlar, Nomex, rubber, germanium, silicon, zinc sulfide, quartz and other such materials. The inventor's preferred materials are polyester (PET or PETG) or a blend thereof.

A Fresnel lens can be formed or manufactured in a number of ways from the substrate materials identified above. This includes but is not limited to press thermalforming, roll thermalforming, casting, emboss extruding, injection molding, milling, lathing, or UV curing. Emboss extrusion is the preferred method of creating Fresnel lenses. Extruding allows for the creation of an inexpensive, thin, flat plastic sheet with an embossed Fresnel image imprinted on one side of the lens. The preferred materials, namely polyester (PET or PETG) can be utilized with or without protective additives. Protective additives may include ultraviolet light and antioxidant additives, both of which reduce yellowing and clouding of the Fresnel lens. These additives can be introduced into the resin prior to the extrusion process or during the extrusion process in a step referred to a co-extruding. A protective co-extruded cap layer is preferred, promoting longevity of the Fresnel lens.

Each Fresnel lens is secured in a focal position for focusing solar radiation passing the Fresnel lens on the absorption zone on the energy absorber by a support frame. A preferred embodiment consists of a lens retainer to which the perimeter of the lens is attached and secured on its perimeter and a pair of pivot brackets. A preferred embodiment of the solar tracking drive is comprised of a base frame, a base drive, a pivot rail, pivot bar, a pivot drive, a pivot drive plate, anchor pedestals and base bearings. Each of the support frames is pivotally attached to the base frame by base pivot bearings which pivotally attach the bottom of the pivot bracket, thereby providing for longitudinal pivoting of the support frames respectively. The longitudinal pivoting of the support frames is controlled by the pivot drive which varies the position of the pivot bar, which is pivotally attached to the pivot rail by a pivot bar bearing. The pivot rail is pivotally attached to the top of one of side of each of the solar collector support structures by top bearings.

Lateral pivoting of the solar collector support structures is accomplished by lateral rotation of the base frame which is controlled by the base drive and facilitated by base bearings. The number of anchor pedestals and base bearings can be varied as needed to provide for adequate support and reliability. By controlling the lateral pivoting and the longitudinal pivoting of the support frames the axis of each of the Fresnel lenses can be maintained in alignment with the sun during a desired period of operation thereby maintaining the focus of the incident solar radiation on the desired absorption zones of each of the energy absorbers. The base drive and the pivot drive can each be controlled by a sensor which continually adjusts the alignment of the axis of the Fresnel lenses to match the position of the sun in the sky during a desired period of operation. This allows the Fresnel lenses to be aligned with the incident solar radiation for the time of day and season of the year.

Depending upon the material used for the Fresnel lens and the thickness of the lens, the lens may be rigid or somewhat flexible. Because the solar collector will generally be used in an exterior, unprotected environment, the support frame and the solar tracking drive must be able to withstand wind loading, moisture and temperature variations. Further, because of the wind and other environmental conditions to which the lens will be subjected, it must be securely attached to the lens retainer. This can be accomplished by many attachment means known in the art including.

The Fresnel lens support frame as well as the solar tracking drive components, can be constructed from a variety of materials including, but not limited to, steel, aluminum or plastic. A preferred material for the support frames and the solar tracking drive is steel. A non-corrosive coating such as galvanizing, paint or powder coating, would be needed.

The base drive and the pivot drive, which comprise the drive means of preferred embodiments of the solar tracking drive, can be comprised of any of common drive mechanisms known in the art. These drive means will generally be composed of a combination of electric motors and gears. Chains and belts may also be used. The solar tracking can be accomplished through simple programming to a vary the longitudinal angle and the lateral angle based on the orientation of the solar collector, the longitude and latitude of the installation, the time of day, and the day of the year. Alternatively, a sensor can be used to continually align the axis of the Fresnel lenses with the incident solar radiation during a desired period or operation.

Many variations of geometry and grooving of the Fresnel lens may be used. As discussed above, longitudinal grooving will provide for distributed focus of the incident solar radiation on a absorption conduit. If a spot focus is desired, then the grooving will be circular. A rectangular or square lens is more practical and economical to manufacture and utilize and is more efficient for a normal application, since the grooving provides for the concentration of solar radiation incident to the corners of the lens on the absorption zone as well. One of the main advantages of the present invention is economy. One preferred embodiment utilizing rectangular lenses with longitudinal grooving, providing for a distributed focus on an absorption conduit, and a solar tracking drive which is actuated by a sensor can be very economical and very effective compared to other solar energy collection systems known in the art. Preferably, the longitudinal axis of the solar collector installation will be aligned in an east/west direction and the lateral axis will be aligned in a north/south direction.

One or more absorption liquid pumps typically circulate the absorption liquid through absorption liquid lines to the absorption conduit and back to an energy transfer device which can be one or more of a number of energy exchange devices which are known in the art. A variety of absorption liquids may be used for circulating through the absorption conduits, which include but are not limited to water, oil or salt. Absorption liquids preferred by the present inventor are heat transfer oil for lower temperatures and molten salt for higher temperature absorption liquid applications. Salt materials which work well for high temperature applications include sodium nitrate, sodium nitrite or potassium nitrate. Heat transfer oil can be synthetic, organic or a combination of synthetic and organic oil.

A preferred embodiment of an energy transfer system comprises the energy transfer device, transfer liquid circulation lines and transfer liquid pumps. Transfer liquid is circulated through the transfer liquid circulation lines by the transfer liquid pumps to the energy transfer device and back to an energy extraction device such as a steam turbine engine. Again, any number of liquids may be used for the transfer liquid but to eliminate the necessity of another heat exchange process at the energy extraction device, water is preferred. The steam turbine engine illustrated in FIG. 10 is disclosed in U.S. Pat. No. 6,533,539 to Johnson, the inventor of the present invention and provides for the flashing of heated water or other liquids from peripheral nozzles. The energy extracted by the energy extraction device, such as the steam turbine illustrated, can be used to drive a generator or other energy conversion device. Make up water can be supplied through a make up water line which is controlled by an automated valve or pump connected to a make up water supply.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal vertical cross section of an embodiment of a solar energy collector of the present invention.

FIG. 2 is a plan view of a Fresnel lens with longitudinal grooves for a solar collector with a linear absorption zone.

FIG. 3 is a side perspective view of a solar energy collector installation of the present invention with an absorption conduit having a spherical energy absorber in a spherical energy retaining capsule.

FIG. 4 is a side perspective view of a multiple solar energy collector installation of the present invention with support frames, absorption conduit, and solar tracking drive.

FIG. 5 is a perspective detail of an embodiment of a solar tracking drive of the present invention.

FIG. 6 is a perspective detail of an embodiment of a solar energy collector installation of the present invention with secondary lens, secondary lens frame and an in-line half spherical energy absorber with a half spherical energy retaining capsule.

FIG. 7 is a cutaway detail of an in-line half spherical energy absorber of the present invention with a half spherical energy retaining capsule.

FIG. 8 is a plan view cross section of an in-line half spherical energy absorber of the present invention with absorption fins and a half spherical energy retaining capsule.

FIG. 9 is a vertical cross section of an in-line half spherical energy absorber of the present invention with absorption fins and a half spherical energy retaining capsule.

FIG. 10 is an isometric illustration of an embodiment of the solar energy collector installation, energy exchange system, and turbine engine of the present invention.

DETAILED DESCRIPTION

Referring first to FIG. 1 a cross section of a Fresnel lens 3 and energy absorber 5 components of a solar energy collector 1 of the present invention. The energy absorber as shown is an absorption conduit 7 which has an internal absorption fin 9 extending into an absorption duct 10, which for an absorption conduit is merely the internal barrel of the pipe. The Fresnel lens axis 11 is aligned with the incident solar radiation 13. This results in the incident solar radiation being focused to a focal point 15 as is illustrated by the incident rays 17 and the focused rays 19. The energy absorber, which for the embodiment shown in FIG. 1, is an absorption conduit, will have an absorption zone 21 on the top surface of the absorption conduit. The absorption conduit will preferably be positioned so that the center 23 of the absorption conduit is aligned with the Fresnel lens axis. The absorption conduit, or other energy absorber, can be positioned so that the Fresnel lens top surface 25 is separated from the absorption conduit top surface 27 by a distance 29 which is equal to the focal length of the lens as shown in FIG. 1, thereby providing for the incident solar radiation to be focused at a single point in the absorption zone of the energy absorber or can be positioned such that incident solar radiation is distributed on a larger area of the absorption zone. If the incident solar radiation is focused on a single point in the absorption zone of the energy absorber, substantially higher temperatures will be experienced at the focal point. Having the focal point coincident with the center of the energy absorber, rather than a point on the surface of the energy absorber, results in substantially reduced temperatures. Of course the focus of the incident solar radiation can be varied between the center of the absorption conduit and a point on the surface of the absorption conduit thereby varying the distribution of the focused solar radiation and thereby the maximum temperature experienced in the absorption zone. An absorption fin 9 can also be incorporated inside the energy absorber which extends into the absorption duct 10 as shown FIG. 1 and shown in FIGS. 8 and 9 is in contact with the absorption zone, thereby assisting in the transfer of energy to the absorption liquid 33 which flows through the energy absorber. The absorption fin would normally be made of high thermal conductivity material thereby rapidly transferring the energy of the incident solar radiation from the absorption zone to the absorption liquid. An energy retaining capsule 35 can be used to encapsulate the absorption zone. The energy retaining capsule will be constructed of material with a high solar radiation transmission rate and a low thermal conductivity rate thereby providing for transmission of the focused incident solar radiation to the absorption zone of the energy absorber while minimizing the loss of energy from the energy absorber to the surrounding air 37.

Each groove 38 of the Fresnel lens is a small piece of an aspherical surface 39. The tilt 41 of each surface is varied with distance 42 from the center 43 of the lens to provide for focus of the incident solar radiation at the focal point of the lens. The cross section shown in FIG. 1 could be illustrative of a Fresnel lens with circular grooves which will provide for focusing of the incident solar radiation to a single focal point or could be illustrative of a Fresnel lens with longitudinal grooves as shown in FIG. 2.

The Fresnel lens of FIG. 2 with longitudinal grooves 44 results in the incident solar radiation being focused in a line rather than a single focal point. This offers an advantage of distributing the focused incident solar radiation over a larger area, thereby reducing the temperature of the absorption zone. The expanded absorption zone for embodiments utilizing a Fresnel lens with longitudinal grooves can be encapsulated in an energy retaining capsule with a high solar radiation transmission rate and low thermal conductivity rate such as glass. Similarly, a Fresnel lens with oval grooves provides for distributed focus and distribution of the concentrated energy on the energy absorber. Also, if the Fresnel lens is positioned so that the energy absorbers have absorption surfaces which are displaced radially from the focal point or focal line of the respective lenses, the larger absorption zone may be encapsulated. Other portions of the absorption conduit which do not receive focused incident solar radiation can be insulated or merely be covered with the energy retaining capsule material to reduce energy loss to the surrounding air.

A cement coating can be placed on the absorption zone to increase the absorption rate of the focused incident solar radiation. Alternatively, an energy assimilator of high thermal conductivity material can be placed on the absorption conduit or other energy absorber. Further the energy assimilator can be thermally connected to an absorption fin extending into the absorption duct, thereby increasing the energy transfer rate to the absorption liquid.

Material selection for the absorption zone of the energy absorber or energy assimilator placed on the energy absorber in the absorption zone will be selected based upon anticipated maximum temperatures and desired absorption and thermal conductivity rates. Materials that can be used include stainless steel, carbon steel, tungsten, titanium, molybdenum, rhenium, niobium, platinum, copper and other metals and non-metallic materials. A preferred material for the absorption zone and absorption fins is tungsten due to its high thermal conductivity rate, its high melting point and its glass to metal sealing capabilities.

The energy retaining capsule 35, whether it is spherically shaped as indicated on FIG. 1 and FIG. 3, hemispherically shaped as indicated on FIG. 6 or tubularly shaped for an absorption conduit, the capsule can be made from a number of materials including soda lime glass, borsilicate glass or quartz. Borsilicate glass is a preferred material because of its inherent impact strength and its lower thermal conductivity rate. While a spherical or hemispherical shape is preferred for a point focus due to a higher solar radiation transmission rate and a higher absorption rate, other shapes can be used, depending upon the energy distribution desired on the absorption zone. For a linear absorption zone, a cylindrical capsule is preferred on the absorption conduit.

It is preferred for the retaining capsule material to be bonded or hermetically sealed to the absorption zone or to the absorption conduit. This generally increases energy retention by the absorption conduit or other form of energy absorber. Alternatively a space may be provided between the energy absorber and the energy retaining capsule, whether the energy retaining capsule is spherically shaped, hemispherically shaped or cylindrically shaped, which may be air evacuated, thereby providing a vacuum space separating the energy retaining capsule from the energy absorber, thereby further enhancing the energy retention of the energy retaining capsule.

The Fresnel lens itself is preferably constructed of an optically clear material. These materials include but are not limited to acrylic, glass, rigid vinyl, polycarbonate, polyethylene, polyester blends including PET and PETG respectively, poly IR, polystyrene, polyurethane, polypropylene, polyacrylonitrile, Kevlar, Nomex, rubber, germanium, silicon, zinc sulfide, quartz and other such materials. The inventor's preferred materials are polyester (PET or PETG) or a blend thereof.

A Fresnel lens can be formed or manufactured in a number of ways from the substrate materials identified above. This includes but is not limited to press thermalforming, roll thermalforming, casting, emboss extruding, injection molding, milling, lathing, or UV curing. Emboss extrusion is the preferred method of creating Fresnel lenses. Extruding allows for the creation of an inexpensive, thin, flat plastic sheet with an embossed Fresnel image imprinted on one side of the lens. The preferred materials, namely polyester (PET or PETG) can be utilized with or without protective additives. Protective additives may include ultraviolet light and antioxidant additives, both of which reduce yellowing and clouding of the Fresnel lens. These additives can be introduced into the resin prior to the extrusion process or during the extrusion process in a step referred to a co-extruding. A protective co-extruded cap layer is preferred, promoting longevity of the Fresnel lens.

Referring now to FIG. 3 and FIG. 4, a preferred embodiment of a solar energy collection apparatus of the present invention is shown. Referring to FIG. 3 the Fresnel lens 3 is secured in a focal position 45 for focusing solar radiation passing the Fresnel lens on the absorption zone on the energy absorber by a support frame 47. For this embodiment the support frame consists of a lens retainer 49 to which the perimeter 51 of the lens is attached and secured on its perimeter and a pair of pivot brackets 53.

Referring to FIG. 4 and FIG. 5, a preferred embodiment of the solar tracking drive is comprised of a longitudinal pivot means, a lateral pivot means and a tracking control means. A preferred embodiment of the lateral pivot means comprises a base frame 55, a base drive 57, anchor pedestals 67 and base bearings 69. Lateral pivoting 83 of the solar collector support structures is accomplished by lateral rotation 85 of the base frame 55 through a lateral angle which is controlled by the base drive 57 and facilitated by base bearings 69. The number of anchor pedestals and base bearings can be varied as needed to provide for adequate support and reliability.

A preferred embodiment of the longitudinal pivot means comprises a pivot rail 59, pivot bar 61, a pivot drive 63, a pivot drive plate 65, base pivot bearings 71, pivot bar bearing 77, and top bearings 81. Each of the support frames is pivotally attached to the base frame by the base pivot bearings 71 which pivotally attach the bottom 73 of the pivot bracket, thereby providing for longitudinal pivoting 75 of the support frames respectively through a longitudinal angle. The longitudinal pivoting of the support frames is controlled by the pivot drive 63 which varies the position of the pivot bar 61, which is pivotally attached to the pivot rail by a pivot bar bearing 77. The pivot rail is pivotally attached to the top of one of side 79 of each of the solar collector support structures by top bearings 81.

A tracking control means controls the lateral pivoting 83 and the longitudinal pivoting 75 of the support frames so that the axis 11 of each of the Fresnel lenses is maintained in alignment with the sun during a desired period of operation thereby maintaining the focus of the incident solar radiation on the desired absorption zones of each of the energy absorbers. For a preferred embodiment, the tracking control means consists of a sensor which controls the base drive and the pivot drive, thereby continually adjusting the alignment of the axis of the Fresnel lenses to match the position of the sun in the sky during a desired period of operation. An alternative embodiment of the tracking control means is a simple computer which controls the base drive and the pivot drive and continually positions the support frames, during a desired period of operation, based upon the physical orientation of the solar collector installation, the date, the time of day, and the longitude and latitude of the installation. This allows the Fresnel lenses to be continually aligned with the incident solar radiation.

Referring to FIG. 4, preferably, the longitudinal axis 109 of the solar collector installation will be aligned in an east/west direction and the lateral axis 111 will be aligned in a north/south direction.

Referring now to FIG. 6 and also FIG. 7, an in-line energy absorber 87 which has a hemispherical absorption zone which is encapsulated by a hemispherical shaped energy capturing capsule 89. The energy absorber is affixed in line in the absorption conduit 7 with the connection to the conduit 90, typically by flanged or mechanical joint connections. For some embodiments an optional secondary lens 91 is affixed between the Fresnel lens and the energy absorber by a secondary lens frame 93 which is affixed to the opposing pivot brackets 53 of the Fresnel lens support frame.

Referring now to FIG. 8 and FIG. 9, an embodiment of a hemispherical shaped energy absorber 87 with absorption fins 9 inserted in the flow path 97 of the absorption is shown. The absorption fins facilitate the transfer of energy from the energy absorber to the absorption liquid 33. The energy absorber is encapsulated by an energy capturing capsule 101 of one of the preferred materials described above.

Depending upon the material used for the Fresnel lens and the thickness of the lens, the lens may be rigid or somewhat flexible. Because the solar collector will generally be used in an exterior, unprotected environment, the support frame 47 and the solar tracking drive must be able to withstand wind loading, moisture and temperature variations. Further, because of the wind and other environmental conditions to which the lens will be subjected, it must be securely attached to the lens retainer 49. This can be accomplished by many attachment means known in the art including, but not limited to, springs, wire, bungee cords, plastic strips or ties, glue, screws, clamps or slidable inserts. A preferred attachment means is springs. Springs allow for thermal expansion, wind loads, hail stones or any other type of contraction or expansion that the Fresnel lens may encounter. Referring to FIG. 2, spring receptacles 103, which, in the case of a lens formed by extrusion, may be extruded out during the extrusion process or they may be punched or drilled in the perimeter 105 of the lens. Spring grommets 107 may be inserted into the spring receptacles if needed for added strength and durability. One end of the spring is inserted in the spring receptacle and the other end is attached to the lens retainer or other point on the support frame.

Referring to FIGS. 3, 4 and 5, pivot bearings can be any variations known in the art. Pivot bearings can be manufactured from a number of types of commonly used material including, but not limited to, steel, graphite, plastic or ceramic. A preferred pivot bearing is a steel metal sleeve bearing. The base bearings 69 can also be steel metal sleeve bearings or a ceramic pipe, tube or sleeve bearing can be used as a heat barrier. Base frame bearings can be used as a thermal barrier between the support frame and the absorption conduit.

The Fresnel lens support frame 47 as well as the solar tracking drive components, can be constructed from a variety of materials including, but not limited to, steel, aluminum or plastic. A preferred material for the support frames and the solar tracking drive is steel. A non-corrosive coating such as galvanizing, paint or powder coating, would be needed.

Referring to FIG. 5, the base drive 57 and the pivot drive 63, which comprise the drive means of the solar tracking drive can be comprised of any of common drive mechanisms known in the art. These drive means may be comprised of a combination of electric motors and gears or may be pneumatically or hydraulically actuated. If the base drive and the pivot drive are pneumatically or hydraulically actuated, solar tracking will ordinarily be accomplished through the use of pneumatic or hydraulic cylinders. Chains and belts may also be used with electric motor drives.

The solar tracking can be accomplished through simple programming to a varied longitudinal angle 75 and the lateral angle 83 based on the longitude and latitude of the installation, the time of day, and the day of the year. Alternatively, the sensor can be used to continually align the axis of the Fresnel lenses with the incident solar radiation during a desired period or operation.

Many variations of geometry and grooving of the Fresnel lens may be used. As discussed above, longitudinal grooving as shown in FIG. 2 will provide for distributed focus of the incident solar radiation on a absorption conduit. If spot focus is desired so the solar energy can be concentrated to energy absorbers such as shown in FIGS. 6, 7, 8 and 9, then the grooving will be circular. A rectangular or square lens is more practical and economical to manufacture and utilize and is more efficient for a normal application, since the grooving provides for the concentration of solar radiation incident to the corners of the lens on the absorption zone as well.

One of the main advantages of the present invention is economy. One preferred embodiment utilizing rectangular lenses with longitudinal grooving, providing for a distributed focus on an absorption conduit, and a solar tracking drive which is actuated by a sensor can be very economical and very effective compared to other solar energy collection systems known in the art.

Referring now to FIG. 10, a schematic of an energy production system 113 utilizing the solar energy collector 1 of the present invention shown. The incident solar radiation 17 focused on the absorption conduit 7 by one or more solar collectors, each utilizing a Fresnel lens 3 and a support frame (not shown) and being positioned by a solar tracking drive (not shown). One or more absorption liquid pumps 115 circulate the absorption liquid 33 through absorption liquids lines 117 to the absorption conduit and back to an energy transfer device 119 which can be one or more of a number of energy exchange devices which are known in the art.

A variety of absorption liquids may be used for circulating through the absorption conduits, which include but are not limited to water, oil or salt. Absorption liquids preferred by the present inventor are heat transfer oil for lower temperatures and molten salt for higher temperature absorption liquid applications. Salt materials which work well for high temperature applications include sodium nitrate, sodium nitrite or potassium nitrate. Heat transfer oil can be synthetic, organic or a combination of synthetic and organic oil.

Transfer liquid 121 is circulated through transfer liquid circulation lines 123 by transfer liquid pumps 125 through the energy transfer device 119 and back to an energy extraction device 127 such as the steam turbine engine 129 illustrated in FIG. 10. Again, any number of liquids may be used for the transfer liquid but to eliminate the necessity of another heat exchange process at the energy extraction device, water is preferred. A preferred steam turbine engine for incorporation with the solar collector installation of the present invention as illustrated in FIG. 10 is disclosed in U.S. Pat. No. 6,533,539 to Johnson, the inventor of the present invention and provides for the flashing of heated water or other liquids from peripheral nozzles. The energy extracted by the energy extraction device, such as the steam turbine illustrated, can be used to drive a generator or other energy conversion device. Make up water 131 can be supplied through a make up water line 133 which is controlled by an automated valve or pump 135 connected to a make up water supply 137.

Other objects, features and advantages of the present invention will become apparent from the preceding detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention. Therefore, the foregoing is intended to be merely illustrative of the invention and the invention is limited only by the following claims.