FIELD OF INVENTION
The present invention relates to solar energy devices and systems, and in particular, relates to a solar trough system dug or otherwise formed in the earth or ground.
BACKGROUND OF THE INVENTION
Existing parabolic solar trough systems include a plurality of parabolic solar troughs that focus the sun's heat into a heat-transfer fluid that flows through receivers of the solar troughs. The heated fluid may then be used to generate steam for conventional electricity producing steam turbines, heat water in hot water storage tanks, and the like. Such systems operate automatically at high efficiency and can be competitive with fossil fuel.
The parabolic solar troughs of current systems have parabolic light collectors, which track the sun along one axis. The parabolic light collectors include mirrors that are supported high above the earth's surface by complex aluminum space frames or torsion boxes, which are time-consuming and expensive to manufacture. The above-the-earth parabolic light collectors are also subject to damaging wind and weather loads.
The parabolic light collector must always be focusing the sun's heat on the receiver as the light collectors track the sun, therefore, the alignment between the light collector and the receiver must be precisely maintained. Because the receivers of current parabolic troughs are constructed to rotate with their corresponding above-the-earth parabolic light collectors, the system parasitic loads are higher due to increased pressure losses in the flexible couplings between troughs.
Accordingly, a parabolic solar trough system is needed that is less expensive and faster to manufacture and which also allows fixed couplings for less pressure loss than current parabolic solar trough systems.
SUMMARY OF INVENTION
Disclosed herein is a solar trough comprising a light receiver for transporting a fluid to be heated by the solar trough; at least one rail partially or fully disposed in a trench, a parabolic light collector for focusing sun-light on the light receiver slidably mounted on the at least one rail, and a drive unit for rotating the parabolic light collector within the trench.
Further disclosed herein is a solar trough system comprising a plurality of solar troughs.
Also disclosed herein is a method for making a solar trough. The method comprises forming a trench in a ground area, laying at least one rail in the trench, slidably mounting a parabolic light collector on the at least one rail, coupling a drive unit to the parabolic light collector for rotating the parabolic light collector within the trench, and locating a light receiver at a focal point of the parabolic light collector, the light receiver for transporting a fluid to be heated by the solar trough.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of an embodiment of an in-ground parabolic solar trough.
FIG. 2 is a sectional view through line 2-2 of FIG. 1.
FIG. 3 is a sectional view through line 3-3 of FIG. 1.
FIG. 4 is a sectional view through line 4-4 of FIG. 1.
FIG. 5 is an enlarged sectional view through a central most one of the rails.
FIG. 6 is a perspective view of an embodiment of the parabolic light collector.
FIG. 7 is a perspective view of an embodiment of the motor of a drive unit.
FIG. 8 is a perspective view of an embodiment of a solar trough system.
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1 and 2 collectively illustrate an embodiment of an in-ground parabolic solar trough 100, according to the present disclosure. The in-ground parabolic solar trough 100 generally includes an elongated trench dug 110 or otherwise formed in the earth or ground G, a plurality of rails 120 lining the surface of or otherwise disposed in the trench 110, a parabolic light collector 130 slidably mounted on the rails 120, a drive unit 140 for rotating the parabolic light collector 130 within the trench 110, and a light receiver 150 disposed at a focal point FP of the parabolic light collector 130.
As shown in FIG. 2, the trench 110 formed in the earth or ground should have a contour which is suitable for securely supporting the rails 120 and which may correspond with the outer contour of the rails 120. In one embodiment, the contour of the trench 110 is half- or semi-cylindrical in shape. In other embodiments, however, the contour of the trench 110 may be other suitable shapes, depending upon the outer contour or construction of the rails 120. The trench 110 may be formed to a length L of about 100 meters, a width W of about 3.5 meters and a depth D of about 3.5 meters. The trench 110 may also be formed to other length, width, and/or depth dimensions, if desired.
Each rail 120 disposed within the trench 110 may have a generally curved shape which is adapted for slidaby mounting the parabolic light collector 130. For example, as collectively shown in FIGS. 2 and 3, each rail 120 has a semi-circular curved in shape, with an I-shape transverse cross-section formed by a vertical web 121, a horizontal outer flange 122 disposed at an outer end 1210 of the vertical web 121, and a horizontal inner flange 123 disposed at an inner end 121i of the vertical web 121. The rails, in other embodiments, may be constructed in other suitable shapes that allow for easy construction and proper movement and focus of the parabolic light collector 130. Each rail 120 is transversely positioned in the trench 110 and securely anchored therein by elongated fasteners 160 (FIG. 3). The rails 120 are evenly spaced from one another along the length of the trench 110 from a marginal first end 112 to a marginal second end 114 thereof.
The parabolic light collector 130 is slidably mounted on the rails 120, as collectively shown in FIGS. 2 and 3. In one embodiment, the parabolic light collector 130 includes an array 131 of elongated light concentrators 132. As shown in FIG. 3, each light concentrator 132 of the array 131 extends between the first and second ends 112, 114 of the trench 110, and is slidably coupled to the rails 120. Each light concentrator 132, in one embodiment, includes an elongated riser 133, a plurality of mirror segments 134 fixedly mounted to an elongated front wall 133FW of the riser 133 and a plurality of attaching clips 135 fixedly mounted to an elongated back wall 133BW of the riser 133 for slidably coupling the riser 133 to the inner flanges 123 of the rails 120. The mirror segments 134 form a parabolic-shaped reflector surface RS having a focal point F which is coaxial with a longitudinal axis LA of the receiver 150. The number of mirror segments 134 used in the light concentrator 132, is a function of the sidewall length LM of each mirror segment 134, the manufacturing cost of the solar trough 100, and the performance desired from the solar trough 100. The mirror segments 134 may have any suitable sidewall length LM. For example, in one embodiment, the sidewall length LM of each mirror segment 134 may be about 0.5 meters.
The risers 133 of the light concentrators 132 are connected to one another, thus forming the parabolic light collector 130, as shown in FIG. 6. Each riser 133 may have a hollow, box-like structure including the earlier mentioned elongated front and back walls 133FW, 133BW, a pair of elongated end walls 133EW and a pair of side walls 133SW. Links 136 may be used for connecting the risers 133 to one another. The links 136 may connect the end walls 133EW and/or the side walls 133SW of the risers 133 to one another. The ends of the links 136 may be pivotally or fixedly fastened to end walls 133EW and/or the side walls 133SW of the risers 133 by rivets or other suitable fasteners. In other embodiments, the risers 133 may be connected to one another by mounting all the risers 133 on a thin sheet of metal or plastic (not shown). The height HC of the riser 133 of the central-most light concentrator 132, is constant from end wall to end wall 133EW, however, the height HV of the risers 133 of the other light concentrators 132, moving away from the central-most light concentrator 132, increases from end wall to end wall 133EW. As shown in FIG. 2, this arrangement angles the mirror segments 134 so that they form the parabolic-shaped reflector surface RS having the focal point F.
Referring to FIG. 5 bearing surface(s) of each attaching clip 135 slidingly engage corresponding bearing surface(s) of the inner flange 123 of the corresponding rail 120. The bearing surfaces of the clips and/or the inner flange may be lined, coated, and or impregnated with a layer 170 of low friction material that reduces the friction between the bearing surfaces(s) of the attaching clips 135 and the rails 120, thereby allowing the light concentrators 132 to slide easily on the rails 120 when the parabolic light collector 130 is rotated.
Referring again to FIG. 1, the receiver 150 extends the length of the trench 110 along the focal point F of the parabolic light collector 130 and carries a heat transfer fluid. The receiver 150 may be affixed to the surface of the ground or earth at each end of the trench 110 with one or more clamps or bearings (not shown), which allow for axial movement of the receiver 150 due to thermal expansion. The fluid F may be an organic or synthetic oil, water, a solution of water and antifreeze, or molten ionic or nitrate salt. The receiver 150 may be conventionally constructed as a glass encased absorbent-coated tube. In other embodiments, the receiver 150 may comprise a simple tube without any type of cover or coating. The fluid is circulated through the receiver 150 by a pump (not shown). After being heated by the parabolic light collector 130, the fluid is delivered to a heat exchanger (not shown) where it may be used to heat a hot water storage tank (not shown), create steam for process heating, or heat water in a steam generator (not shown) to turn a steam turbine (not shown) and generate electric power.
As collectively shown in FIGS. 1 and 4, the drive unit 140 in one embodiment, is disposed on the ground adjacent to a generally central area of the solar trough 100 and drives the parabolic light collector 130 so that it may track the sun continuously during the day. In one embodiment, as shown in FIG. 7, the drive unit 140 may include a motor 141 with first and second opposing drive-shafts 1421, 1422.
Referring collectively to FIGS. 4 and 6, the drive unit 140 further includes a cable winding spool 1431, 1432 attached to each of the drive-shafts 1421, 1422. A first pulley 1441 is rotatively disposed on a first end of one of the rails 120 at the generally central area of the solar trough 100, a second pulley 1442 is rotatively disposed on a second end of this rail 120, a third upper pulley 1443 is rotatively disposed between the rail 120 and the motor 141, and a fourth lower pulley 1444 is rotatively disposed between the rail 120 and the motor 141. A first yoke 1451 is connected to a first end of the parabolic light collector 130 at a generally central location thereof and a second yoke 1452 is connected to a second end of the parabolic light collector 130 at a generally central location thereof. A first cable 1461 has a first end attached to the first yoke 1451 and a second end attached to the first spool 1431 and a second cable 1462 has a first end attached to the second yoke 1452 and a second end attached to the second spool 1432. Starting at the first yoke 1451 and moving toward the first spool 1431, the first cable 1461 extends to the first pulley 1441, rides over a top of the first pulley 1441, extends about a first above-ground portion ABP1 of the rail 120 on the motor side thereof, rides under the bottom of the third upper pulley 1443, and then extends to the first spool 1431. Starting at the second yoke 1452 and moving toward the second spool 1432, the second cable 1462 extends to the second pulley 1442, rides over a top of the second pulley 1442, extends about a second above-ground ABP2 portion of the rail 120 on a remote side of the rail 120 opposite the motor 141 and about an in-ground portion IGP of the rail 120, rides over a top of the fourth lower pulley 1444, and then extends to the second spool 1432. The first and second cables 1461, 1462 maintain tension on the solar trough 100 as the motor 141 rotates the parabolic light collector 130. As shown in FIG. 5, the first and second cables 1461, 1462 may be guided about the rails 120 by the attaching clips 135.
Referring to FIG. 8, an array of the solar troughs 100 of the present disclosure may be arranged in parallel rows to form a solar trough system 200. The receivers 150 of the solar troughs 100 are serially connected to one another to form a single circuit. The trenches 110 of the solar troughs in each row may be separate and discrete from one another. Alternatively, the solar troughs 100 in each row may use one very elongated continuous trench 110.
Although the invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.
Patent Grant
8490620
