SYSTEMS FOR COST-EFFECTIVE CONCENTRATION AND UTILIZATION OF SOLAR ENERGY

• US 20100263709A1
• Filed: 04/15/2009
• Published: 10/21/2010
• Est. Priority Date: 04/15/2009
• Status: Active Grant

• Current Assignee: Richard Norman
• Original Assignee: Richard Norman
• Inventors: Norman, Richard, Dauphin, Philippe, de St. Croix, Frederick
• Granted Patent: US 9,995,507 B2
• Time in Patent Office: Days
• US Class Current: 136/246
• CPC Class Codes: F24S 20/20 Solar heat collectors for receiving concentrated solar energy, e.g. receivers for solar power plants
• CPC Class Codes: F24S 2020/18 having a particular shape, e.g. prismatic, pyramidal
• CPC Class Codes: F24S 23/12 Light guides
• CPC Class Codes: F24S 23/71 with parabolic reflective surfaces with cylindro-parabolic reflective surfaces F24S23/74
• CPC Class Codes: F24S 23/74 with trough-shaped or cylindro-parabolic reflective surfaces
• CPC Class Codes: F24S 23/745 flexible
• CPC Class Codes: F24S 25/12 using posts in combination with upper profiles
• CPC Class Codes: F24S 25/13 Profile arrangements, e.g. trusses F24S25/12 takes precedence
• CPC Class Codes: F24S 25/16 Arrangement of interconnected standing structures; Standing structures having separate supporting portions for adjacent modules
• CPC Class Codes: F24S 30/45 with two rotation axes
• CPC Class Codes: F24S 30/452 Vertical primary axis
• CPC Class Codes: H01L 31/0547 comprising light concentrating means of the reflecting type, e.g. parabolic mirrors, concentrators using total internal reflection
• CPC Class Codes: Y02B 10/20 Solar thermal
• CPC Class Codes: Y02B 10/70 Hybrid systems, e.g. uninterruptible or back-up power supplies integrating renewable energies
• CPC Class Codes: Y02E 10/40 Solar thermal energy, e.g. solar towers
• CPC Class Codes: Y02E 10/47 Mountings or tracking
• CPC Class Codes: Y02E 10/52 PV systems with concentrators

Abstract

The present invention is primarily directed to cost-effective systems for using large reflective elements that track the sun on two axes to concentrate solar energy onto a receiver that can convert the sun'"'"'s optical energy to a form usable for extensive displacement of combustion of fossil fuels. The structures of the tracker frame, tracking mechanism and tracker supports are co-optimized with the optical elements and the receiver for high efficiency, low cost, and ease of assembly, making moderate and large-scale implementations cost-competitive with fossil fuels for peak power, and, with suitable storage, for base-load power and dispatchable peaking power in sunny locations. Improvement to small-tracker two-axis systems and one-axis tracking systems that focus in two dimensions are also included, as are improvements in systems for space-based solar power.

Claims

1. An elongated curved mirror for use in a two-axis solar concentrator, the mirror having a flat reflective flexible substrate shaped to be substantially cylindrically curved in one direction about a widthwise axis, wherein said substrate is supported at least at its lengthwise ends by a substantially continuous mechanical support.

2. The mirror as defined in claim 1, wherein said substrate comprises a planar glass sheet mirror element.

3. The mirror as defined in claim 2, wherein said mirror element is retained using a sleeve member having a substantially parabolic groove for receiving each lengthwise edge of said planar glass sheet mirror element.

4. The mirror as defined in claim 1, wherein said mechanical support comprises one or more sheets folded or pivoted on a hinge about at least one curved fold line or curved hinge line.

5. The mirror as defined in claim 4, wherein said reflective substrate is not brittle and is integral with said sheets.

6. The mirror as defined in claim 5, wherein said mirror is made from a single sheet having folded sides and correspondingly curved lengthwise sides.

7. The mirror as defined in claim 1, wherein said reflective surface is supported by said mechanical support along an entire length of said reflective surface.

8. The mirror as defined in claim 1, wherein said mirror is a parabolic cylinder.

9. The mirror as defined in claim 1, wherein said substantially continuous mechanical support is adapted to adjust a shape of said reflective substrate for adjusting a focal distance and/or a focal spot shape of said mirror.

10. The mirror as defined in claim 1, further comprising a mounting base for mounting said mirror to a frame.

11. The mirror as defined in claim 1, wherein a plurality of said mirrors are mounted to a frame with their directions of curvatures rotated slightly relative to one another so that their foci substantially maximally overlap.

13. The concentrator as defined in claim 11, wherein said frame comprises:

a plurality of substantially identical curved rails for supporting said mirrors;

a plurality of substantially identical ribs for supporting said rails; and

a truss extending across said concentrator substantially orthogonal to said ribs and adapted to support said ribs in a substantially curved arrangement in a direction of said truss, said truss being supported by said two-axis mounting.

12. A two-axis solar concentrator that directs and concentrates sunlight directly and/or indirectly via a secondary concentrator onto a receiver with a concentration greater than 500 suns, the concentrator comprising:

a plurality of mirrors, each one of said mirrors having a flat reflective flexible substrate shaped to be substantially cylindrically curved in one direction about a widthwise axis, wherein said substrate is supported at least at its lengthwise ends by a substantially continuous mechanical support, and a mounting base;

a frame supporting said mounting base of said mirrors to focus light onto said receiver with focal spots of said mirrors substantially overlapping; and

a two-axis mounting for supporting and orienting said frame with respect to the earth.

14. The concentrator as defined in claim 12, further comprising a receiver mounting, said receiver mounting comprising:

three legs attached to said frame to provide a tripod support for said receiver, wherein two of said three legs are pivotally mounted to said frame to rotate about an axis, and another of said legs being detachable from said frame and/or said receiver to allow said two legs to pivot with said receiver toward said frame to facilitate access to said receiver for servicing.

15. The concentrator as defined in claim 12, wherein said concentration at least 2000 suns, said mirrors having substantially a paraboloid of translation shape with a width of at least 500 mm, and an aperture of said frame being at most 7.2 m on a side.

16. A concentrated solar photovoltaic receiver comprising:

a plurality of electrically conductive heat exchange tubes arranged side by side and in electrically insulated groups; and

a plurality of photovoltaic cells having a backplane and a front surface, said backplane having a first electrical contact and said front surface having a second electrical contact, in operation, at a potential with respect to said first electrical contact, said cells being mounted with said backplane in good thermal contact with at least one of said tubes, and said cells being electrically connected in series such that said groups of tubes are, in operation, at different electrical potential with respect to one another.

17. The receiver as defined in claim 16, wherein said groups each have a single tube, and a number of said cells are arrange electrically in parallel on each of said tubes.

18. The receiver as defined in claim 16, wherein said cells connected in series overlap with said first electrical contact of one cell touching said second electrical contact of another cell, preferably with said cells extending across said tubes in a substantially sawtooth manner.

19. The receiver as defined in claim 16, wherein said cells are characterized by a light conversion enhancement structure comprising one or more of:

a raised, substantially triangularly shaped raised profile on cell contacts provided on said front surface to increase light reaching a photoreceptive body of said cell that is otherwise lost to said cell contacts; and

an off-axis silicon layer sliced from a silicon ingot at an angle such that the lattice constant of the silicon ingot divided by the cosine of said angle is substantially equal to the lattice constant of a material of a non-silicon junction of the cell to allow junction materials that are lattice matched to each other but not to silicon to be used in a multi-junction cell able to convert more light than a single junction cell.

20. A photovoltaic cell adapted to receive light at a front surface, said cell being characterized by a light absorption enhancement structure comprising one or more of:

a raised, substantially triangularly shaped raised profile on cell contacts provided on said front surface to increase light reaching a photoreceptive body of said cell that is otherwise lost to said cell contacts; and

an off-axis silicon layer sliced from a silicon ingot at an angle such that the lattice constant of the silicon ingot divided by the cosine of said angle is substantially equal to the lattice constant of a material of a non-silicon junction of the cell to allow junction materials that are lattice matched to each other but not to silicon to be used in a multi-junction cell able to absorb more light than a single junction cell.

21. The cell as defined in claim 20, wherein said structure comprises said substantially triangularly shaped raised profile on said cell contacts, and a conductive footer supports a tall core of a higher melting-point material that is surrounded by a reflective material of a lower melting point, and wherein the amount of the lower melting material is such that when liquid its surface tension will pull it into a substantially triangular cross-section bounded by the footer and the core.

22. A solar tower system comprising a large number of two axis heliostats each directing sunlight onto a tower receiver, the system being characterized by a plurality of receiver towers cooperating with said heliostats by one or more of:

at least some of said heliostats are controlled to change from directing sunlight from one of said receiver towers to another of said receiver towers as a function of a position of the sun so as to maximize an amount of light reflected from said at least some of said heliostats reaching said receiver;

at least some of said heliostats have a field-adjustable focus to allow them to focus tightly when being switched from directing sunlight from one receiver tower to another; and

at least some of said heliostats located near a base of one of said receiver towers reflect light across one side of said one of said receiver towers to reach another of said receiver towers, wherein said at least some are within the azimuthal angular range of heliostats focusing on said receiver tower.

23. The system as defined in claim 22, wherein an improved mean-to-peak solar concentration ratio at said receiver tower is achieved.

24. The system as defined in claim 22, wherein at least one of said receiver towers comprises two receivers, a first one for converting light to heat, and a second one for converting light to photoelectric power, with a mechanism to switch said first and said second receivers during operation.

25. A system for supporting densely-packed two-axis trackers, comprising a substantially rectilinear array of poles or lattice towers, with said poles or lattice towers interconnected by trusses substantially parallel to the rows and columns of said substantially rectilinear array, wherein each of said two-axis trackers is supported at one end by a first one of said trusses, and at its other end by a second one of said trusses that is substantially parallel to and adjacent to said first one of said trusses, in a manner that allows said tracker to rotate relative to said first and second trusses.

26. A method for controlling photovoltaic power generated by a parking lot canopy structure providing shade within a parking lot area located in a location exposed to insolation, the method comprising:

connecting a plurality of motor vehicles each having a rechargeable battery to a source of photovoltaic power generated by said structure;

automatically assessing in accordance with predetermined logic an availability of excess power generated from said structure that is not required to supply an adjacent building or power grid;

switching power to said motor vehicles as a function of said assessing.

27. A system for supporting a row of an even number of curved mirror structures, that each focus sunlight in two dimensions, on top of a single pole or lattice tower, at a height that is within 2% of the width of the aperture of said mirror structures from the height of the center of gravity of said mirror structures, without requiring a gap in or between said mirror structures for said pole or lattice tower to pass through when tracking the sun through a range of altitudes.

28. The system as defined in claim 27, wherein said mirror structures are supported by an axle that runs through or near the mutual center of gravity of said mirror structures.

29. A system for concentrating solar energy in two dimensions onto a receiver, wherein said system comprises a primary concentrator that concentrates said solar energy substantially only in a first dimension and is rotated substantially only in that dimension to track the sun in said first dimension, said receiver being adapted to track the sun in a second dimension.

30. The system as defined in claim 29, wherein said receiver is rotatable in said second dimension and comprises a secondary concentrator that concentrates said solar energy in said second dimension.

31. The system as defined in claim 29, comprising multiple secondary concentrators that rotate to track the angle of the sun in said second dimension.

32. The system as defined in claim 29, wherein said primary concentrator is a parabolic trough reflector, said receiver comprising a number of receivers spaced out along said trough reflector.

33. A system for concentrating solar energy in one dimension comprising a set of parabolic trough mirror that all focus onto a common substantially linear focus, wherein each of said parabolic troughs has an adjustable focal length to match elevation.