METHODS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of and priority to U.S. Provisional Patent Application No. 62/445,638 filed January 12, 2017, which is hereby incorporated in its entirety.

BACKGROUND

[0002] Solar thermal power plants, also called concentrating solar power plants, concentrate sunlight to heat a fluid and use thermal energy of the heated fluid to drive electricity-generating turbines or engines. As the thermal energy of the fluid is converted to electricity, the fluid temperature decreases, and the fluid is reheated using concentrated light. There are four general heating types for solar thermal power plants, namely parabolic troughs, compact linear Fresnel reflectors, power towers, and dish-engines (also called dish Stirling). These heating types differ according to the apparatus and methods used for concentrating sunlight. The discussions henceforth pertain to solar thermal power plants that employ parabolic troughs, also called parabolic reflectors. Parabolic reflectors, in the context of solar thermal power plants, operate by having a concave parabolic reflective surface and a pipe positioned at the focal point of the parabolic surface, extending into the longitudinal direction of the parabolic reflector. The pipe is called the receiver or a heating pipe henceforth. Fluid inside the heating pipe is called the working fluid or heat transfer fluid (HTF). This fluid is, for example, oil, water (or steam), or molten salt. The properties of the fluid influence the operating temperatures of the solar thermal power plant.

[0003] Currently-installed high-temperature parabolic reflector (trough) loops rely on continuous flow to inhibit freezing of the (working) fluid. They are rarely drained, but when they are drained they require manual purging of low-spots in the loop, typically between solar collector assemblies and at crossover piping. This draining method is acceptable only for very rare occurrences, and it is not suitable for frequent draining of the solar collector assemblies and associated pipes and/or hoses. [0004] Oil-based parabolic reflector (trough) systems that operate below 400 °C use a vacuum truck to evacuate the fluid loop. Fluid that is left in low spots in the loop is neglected, because the oil may be liquid at ambient conditions. Molten salt systems require manual draining of salt in low spots in the loop into containment vessels each time the loop is drained.

[0005] Conventional draining techniques are slow, require personnel engagement, and present a notable risk to the personnel involved. Consequently, they are not suitable for frequent loop draining procedures.

BRIEF SUMMARY OF THE INVENTION

[0006] Applicant has developed self-draining solar collector systems that can be drained gravitationally into a manifold without the need for collection vessels at intermediate points, such as in between solar collector assemblies. In particular embodiments, the self-draining solar collector systems include multiple unique piping connections that are configured to gravitationally drain to a manifold when one or more solar collector assemblies of the systems are oriented in respective draining positions. Certain embodiments of the featured systems may be drained automatically and gravitationally from a control room or with manual opening of a valve. As a result, personnel exposure to the high temperature fluids is minimized or eliminated during draining.

[0007] In an aspect, a self-draining solar collector system includes one or more solar collector assemblies, a manifold connecting assembly, and a crossover connecting assembly. In an embodiment of this aspect, each solar collector assembly includes a collector support subsystem, one or more heating pipes, and one or more parabolic reflectors. In an embodiment of this aspect, the one or more parabolic reflectors and the one or more heating pipes of each solar collector assembly are configured to rotate with respect to the collector support subsystem of the solar collector assembly. In an embodiment of this aspect, the manifold connecting assembly connects the one or more heating pipes of each of the one or more of solar collector assemblies to a manifold disposed at a lower elevation than the one or more heating pipes of the one or more solar collector assemblies when the one or more solar collector assemblies are oriented in respective draining positions. In an embodiment of this aspect, the manifold connecting assembly is configured to have a downward slope toward the manifold to allow fluid within the one or more heating pipes of the one or more solar collector assemblies to gravitationally drain into the manifold when the one or more solar collector assemblies are oriented in their respective draining positions. In an embodiment of this aspect, the crossover connecting assembly connects the one or more heating pipes of each of the one or more solar collector assemblies to a crossover pipe disposed at a higher elevation than the one or more heating pipes of the one or more solar collector assemblies when the one or more solar collector assemblies are oriented in their respective draining positions. In an embodiment of this aspect, the crossover connecting assembly is configured to have a downward slope toward the one or more heating pipes of the one or more solar collector assemblies to allow fluid within the crossover pipe to gravitationally drain into the one or more heating pipes of the one or more solar collector assemblies when the one or more solar collector assemblies are oriented in their respective draining positions.

[0008] In an embodiment, for example, the crossover connecting assembly has a different structural configuration than the manifold connecting assembly.

[0009] In an embodiment, for example, the crossover connecting assembly includes (a) a crossover end pipe and (b) a flexible crossover hose connected between the crossover end pipe and the crossover pipe. In an embodiment, for example, the crossover connecting assembly further includes a crossover flexible expansion hose connected between the crossover end pipe and the one or more heating pipes of the one or more solar collector assemblies.

[0010] In an embodiment, for example, the manifold connecting assembly includes a flexible manifold hose connected between the manifold and the one or more heating pipes of the one or more solar collector assemblies.

[0011] In an embodiment, for example, the manifold connecting assembly includes (a) a rotary joint connected to the manifold and (b) a flexible manifold hose connected between the rotary joint and the one or more heating pipes of the one or more solar collector assemblies. [0012] In an embodiment, for example, the crossover connecting assembly includes (a) one or more crossover spherical joint connectors connected to the crossover pipe and (b) a spherical joint crossover end pipe connected between the one or more crossover spherical joint connectors and the one or more heating pipes of the one or more solar collector assemblies.

[0013] In an embodiment, for example, the manifold connecting assembly includes

(a) one or more manifold spherical joint connectors connected to the manifold and

(b) a manifold end pipe connected between the one or more manifold spherical joint connectors and the one or more heating pipes of the plurality of solar collector assemblies.

[0014] In an embodiment, for example, the one or more solar collector assemblies include a plurality of solar collector assemblies, the self-draining solar collector system further includes one or more shared connecting assemblies connecting the one or more heating pipes of adjacent ones of the plurality of solar collector assemblies such that the one or more heating pipes of the plurality of solar collector assemblies are connected in series. In an embodiment, for example, each shared connecting assembly is configured to allow fluid within the one or more heating pipes of the plurality of solar collector assemblies to drain into the manifold when the plurality of solar collector assemblies are oriented in respective draining positions.

[0015] In an embodiment, for example, each of the one or more the shared connecting assemblies is capable of being changed between a normal operating mode and a draining operating mode. In an embodiment, for example, each of the one or more shared connecting assemblies includes (a) a shared pipe and (b) first and second flexible shared hoses each having proximal and distal ends. Proximal ends of each of the first and second flexible shared hoses are connected to respective ends of the shared pipe, and distal ends of each of the first and second flexible shared hoses are connected to respective heating pipes of the plurality solar collector assemblies. In an embodiment, for example, each of the one or more shared connecting assemblies further include a clamping subsystem configured to (a) secure the shared pipe of the shared connecting assembly to a pipe support having a fixed position with respect to the one or more heating pipes of the plurality of solar collector assemblies, in the normal operating mode of the shared connecting assembly and (b) secure each of the first and second shared flexible hoses of the shared connecting assembly to respective rotation supports, in the draining operating mode of the shared connecting assembly. In an embodiment, for example, each of the one or more shared connecting assemblies further include a mode changing subsystem configured to change the operating mode of the shared connecting assembly between its normal operating mode and its draining operating mode.

[0016] In an embodiment, for example, the one or more shared connecting assemblies include one or more shared spherical joint connectors and first and second spherical joint shared pipes each having proximal and distal ends. Proximal ends of each of the first and second spherical joint shared pipes are connected to the one or more shared spherical joint connectors, and distal ends of each of the first and second spherical joint shared pipes are connected to respective heating pipes of the plurality of solar collector assemblies. In an embodiment, for example, the one or more shared spherical joint connectors are collinear with the rotational axes of the parabolic reflectors of each of the plurality of solar collector assemblies.

[0017] In an embodiment, for example, the one or more of solar collector assemblies further include a tracking subsystem configured to rotate the one or more parabolic reflectors and the one or more heating pipes of the solar collector assembly with respect to the collector support subsystem of the solar collector assembly, to track an incident light source and reflect light from the incident light source onto the one or more heating pipes of the one or more solar collector assemblies.

[0018] In another aspect, a self-draining solar collector system includes a plurality of solar collector assemblies and one or more shared connecting assemblies. In an embodiment of this aspect, each solar collector assembly includes a collector support subsystem, one or more heating pipes, and one or more parabolic reflectors. In an embodiment of this aspect, the one or more parabolic reflectors and the one or more heating pipes of each solar collector assembly are configured to rotate with respect to the collector support subsystem of the solar collector assembly. In an embodiment of this aspect, the one or more shared connecting assemblies connect the one or more heating pipes of adjacent ones of the plurality of solar collector assemblies such that the one or more heating pipes of the plurality of solar collector assemblies are connected in series. In an embodiment of this aspect, each shared connecting assembly is capable of being changed between a normal operating mode and a draining operating mode. In an embodiment of this aspect, each shared connecting assembly is configured to allow fluid within the one or more heating pipes of the plurality of solar collector assemblies to drain into a manifold when the plurality of solar collector assemblies are oriented in respective draining positions and each shared connected assembly is operating in its draining operating mode.

[0019] In an embodiment, for example, each of one or more shared connecting assemblies may include a shared pipe and first and second flexible shared hoses each having proximal and distal ends. In an embodiment, proximal ends of each of the first and second flexible shared hoses are connected to respective ends of the shared pipe, and distal ends of each of the first and second flexible shared hoses are connected to respective heating pipes of the plurality of solar collector assemblies.

[0020] In an embodiment, for example, each of the plurality of shared connecting assemblies may further include a clamping subsystem configured to (a) secure the shared pipe to a pipe support having a fixed position with respect to the one or more heating pipes of the plurality of collector assemblies, in the normal operating mode of the shared connecting assembly, and (b) secure each of the first and second shared flexible hoses to respective rotation supports, in the draining operating mode of the shared connecting assembly.

[0021] In an embodiment, for example, each of the one or more shared connecting assemblies may further include a mode changing subsystem configured to change the operating mode of the shared connecting assembly between its normal operating mode and its draining operating mode.

[0022] In another aspect, a method for operating a self-draining solar collector system includes the steps of: (a1 ) rotating one or more parabolic reflectors and respective heating pipes of each of one or more solar collector assemblies to track an incident light source, (b1 ) rotating the one or more parabolic reflectors and respective heating pipes of each of the one or more of solar collector assemblies to respective draining positions such that a manifold is at a lower elevation and a crossover pipe is at a higher elevation than the one or more heating pipes of the one or more solar collector assemblies, and (c1 ) opening a purge valve in the crossover pipe. In an embodiment, for example, the method may be executed at least once per day as a method for maintaining a self-draining solar collector system. In an embodiment, for example, step (a1 ) may include rotating the one or more parabolic reflectors and respective heating pipes of each of the one or more solar collector assemblies independently of the one or more parabolic reflectors and the respective heating pipes of each other one of the one or more solar collector assemblies. In an embodiment, for example, the method further includes, after step (a1 ) but before step (b1 ), changing an operating mode of a shared connecting assembly connected between the one or more heating pipes of a first one of the one or more solar collector assemblies and the one or more heating pipes of a second one of the one or more solar collector assemblies from a normal operating mode to a draining operating mode. In an embodiment, for example, the step of changing the operating mode of the shared connecting assembly includes (a2) freeing a shared pipe of the shared connecting assembly from a pipe support having a fixed position with respect to the one or more heating pipes of the one or more solar collector assemblies, and (b2) securing each of first and second shared flexible hoses of the shared connecting assembly to respective rotation supports of the plurality of solar collector assemblies.

[0023] In yet another aspect, a self-draining solar collector system includes (a) one or more solar collector assemblies, (b) a manifold connecting assembly, and (c) a crossover connecting assembly. In an embodiment of this aspect, each solar collector assembly includes a collector support subsystem, one or more heating pipes, and one or more parabolic reflectors. In an embodiment of this aspect, the one or more parabolic reflectors and the one or more heating pipes of each solar collector assembly are configured to rotate with respect to the collector support subsystem of the solar collector assembly. In an embodiment of this aspect, the manifold connecting assembly connects the one or more heating pipes of each of the plurality of solar collector assemblies to a manifold disposed at a lower elevation than rotational axes of the one or more parabolic reflectors of the one or more solar collector assemblies. In an embodiment of this aspect, the crossover connecting assembly connects the one or more heating pipes of each of the one or more solar collector assemblies to a crossover pipe disposed at a higher elevation than rotational axes of the one or more parabolic reflectors of the one or more solar collector assemblies. In an embodiment of this aspect, the crossover connecting assembly has a different structural configuration than the manifold connecting assembly.

[0024] In an embodiment, for example, the crossover connecting assembly includes (a) a crossover end pipe and (b) a flexible crossover hose connected between the crossover end pipe and the crossover pipe. In an embodiment, for example, the crossover connecting assembly further includes a crossover flexible expansion hose connected between the crossover end pipe and the one or more solar collector assemblies.

[0025] In an embodiment, for example, the manifold connecting assembly includes a flexible manifold hose connected between the manifold and the one or more solar collector assemblies.

[0026] In an embodiment, for example, the manifold connecting assembly includes (a) a rotary joint connected to the manifold and (b) a flexible crossover hose connected between the rotary joint and the one or more heating pipes of the one or more solar collector assemblies.

[0027] In an embodiment, for example, the crossover connecting assembly includes (a) one or more crossover spherical joint connectors connected to the crossover pipe and (b) a spherical joint crossover end pipe connected between the one or more crossover spherical joint connectors and the one or more solar collector assemblies.

[0028] In an embodiment, for example, the manifold connecting assembly includes

(a) one or more manifold spherical joint connectors connected to the manifold and

(b) a manifold end pipe connected between the one or more manifold spherical joint connectors and the plurality of solar collector assemblies.

[0029] In an embodiment, for example, the one or more solar collector assemblies include a plurality of solar collector assemblies, and the self-draining solar collector system further includes one or more shared connecting assemblies connecting the one or more heating pipes of adjacent ones of the plurality of solar collector assemblies such that the one or more heating pipes of the plurality of solar collector assemblies are connected in series. In an embodiment, each of the one or more shared connecting assemblies has a different structural configuration than each of the manifold connecting assembly and the crossover connecting assembly.

[0030] In an embodiment, for example, each of the one or more shared connecting assemblies include a shared pipe and first and second flexible shared hoses each having proximal and distal ends. In an embodiment, proximal ends of each of the first and second flexible shared hoses are connected to respective ends of the shared pipe, and distal ends of each of the first and second flexible shared hoses are connected to respective heating pipes of the plurality of solar collector assemblies.

[0031] In an embodiment, for example, each of the one or more shared connecting assemblies include one or more shared spherical joint connectors and first and second spherical joint shared pipes each having proximal and distal ends. In an embodiment, proximal ends of each of the first and second spherical joint shared pipes may be connected to the one or more shared spherical joint connectors, and distal ends of each of the first and second spherical joint shared pipes may be connected respective heating pipes of the plurality of solar collector assemblies. In an embodiment, for example, the one or more shared spherical joint connectors are collinear with rotational axes of the parabolic reflectors of each of the plurality of solar collector assemblies.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1A shows a self-draining solar collector system in a normal operating mode, according to an embodiment.

[0033] FIG. 1 B shows the FIG. 1 A self-draining solar collector system in a draining operating mode.

[0034] FIG. 2 illustrates a portion of a solar collector assembly of the system of FIG. 1 A. [0035] FIG. 3A shows a flexible hose manifold connecting assembly during a normal operating mode, according to an embodiment.

[0036] FIG. 3B shows the FIG. 3A flexible hose manifold connecting assembly in a draining operating mode.

[0037] FIG. 4A shows a spherical joint manifold connecting assembly in a normal operating mode, according to an embodiment.

[0038] FIG. 4B shows the FIG. 4A spherical joint manifold connecting assembly in a draining operating mode.

[0039] FIG. 5A shows a flexible hose crossover connecting assembly during a normal operating mode, according to an embodiment.

[0040] FIG. 5B shows the FIG. 5A flexible hose crossover connecting assembly in a draining operating mode.

[0041] FIG. 6A shows a spherical joint crossover connecting assembly in a normal operating mode, according to an embodiment.

[0042] FIG. 6B shows the FIG. 6A spherical joint crossover connecting assembly in a draining operating mode.

[0043] FIG. 7A shows a flexible hose shared connecting assembly during a normal operating mode, according to an embodiment.

[0044] FIG. 7B shows the FIG. 7A flexible hose shared connecting assembly in a draining operating mode.

[0045] FIG. 8A shows a spherical joint shared connecting assembly in a normal operating mode, according to an embodiment.

[0046] FIG. 8B shows the FIG. 8A spherical joint shared connecting assembly in a draining operating mode.

[0047] FIG. 9 illustrates a flexible hose connecting assembly including a flexible hose and a rotary joint connector, according to an embodiment. [0048] FIG. 10 illustrates a spherical joint connecting assembly including an end pipe and a plurality of spherical joint connectors.

[0049] FIG. 11 illustrates another spherical joint connecting assembly including three pipes and three spherical joint connectors.

[0050] FIG. 12 shows a flow chart of a method of operating a self-draining solar collector system, according to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0051] In general the terms and phrases used herein have their art-recognized meaning, which can be found by reference to standard texts, journal references and contexts known to those skilled in the art.

[0052] Referring to the drawings, like numerals indicate like elements and the same number appearing in more than one drawing refers to the same element. In addition, hereinafter, the following definitions apply:

[0053] The term "fluid" includes fluid that is within the heating pipes of the solar collector assemblies. The "fluid" is also known in the art as a "working fluid" or "heat transfer fluid (HTF)." The fluid may be in the liquid phase. The fluid is, for example, water, steam, oil, or molten salt. "Molten salt" refers to a salt that is in a liquid phase, and is typically, but not necessarily, at temperatures above room temperature. "Salt" refers to any ionic chemical compound. Non-restrictive examples of molten salts include sodium nitrate, potassium nitrate, calcium nitrate and various combinations thereof.

[0054] The term "gravitationally," in the context of a fluid flowing or being drained, includes a fluid moving (flowing or draining) under the influence of gravity. The term "drain" or "drained" includes fluid flowing out the system, wherein the system in question is a solar collector assembly, for example.

[0055] The term "substantially elevated above" refers to a majority of the length of pipes and/or hoses of a connecting assembly being elevated above an item or items in question, such as a heating pipe. [0056] The term "downward slope" as used in the context of piping or an assembly, such as the manifold connecting assembly and the crossover connecting assembly, being configured to have a downward slope refers to said assembly being configured such that fluid contained in said assembly flows downward (i.e., to a lower elevation with respect to the ground). An assembly which is configured to have a downward slope may have one or more portions (e.g., pipe or hose) that are perpendicular to the ground level while still allowing a fluid contained in said assembly to flow downward. An assembly which is configured to have a downward slope may have one or more portions (e.g., pipe or hose) oriented at an angle (i.e., not parallel) with respect to the ground level. An assembly which is configured to have a downward slope may allow a fluid to drain from said assembly with negligible or no pooling of said fluid at any region within the assembly.

[0057] The term "normal operating mode," in the context of a self-draining solar collector system and its constituent elements, refers to an operating mode where the self-draining solar collector system is intended to transport, circulate and/or heat a fluid, such as a working fluid or heat transfer fluid. In certain embodiments, normal operating mode refers to an operating mode for power generation via using a concentrating solar power system.

[0058] The term "draining operating mode," in the context of a self-draining solar collector system and its constituent elements, refers to an operating mode where the self-draining solar collector system is intended to be partially or fully drained, for example, via the transfer, removal and/or storage of a heat transfer material, such as working fluid or heat transfer fluid.

[0059] The term "draining position," in the context of a solar collector assembly and its constituent elements, refers to a configuration of the solar collector assembly during draining operating mode, such as a configuration wherein one or more parabolic reflectors and respective heating pipe(s) are rotated to respective draining positions wherein a manifold is at a lower elevation and a crossover pipe is at a higher elevation than the one or more heating pipes of a solar collector assemblies.

[0060] Without wishing to be bound by any particular theory, there may be discussion herein of beliefs or understandings of underlying principles relating to the devices and methods disclosed herein. It is recognized that regardless of the ultimate correctness of any mechanistic explanation or hypothesis, an embodiment of the invention can nonetheless be operative and useful.

[0061] This invention provides self-draining solar collector systems, including solar collector assemblies with parabolic reflectors, that can be drained gravitationally into a manifold without the need for collection vessels at intermediate points, such as in between solar collector assemblies. This invention further provides methods for gravitationally draining a self-draining solar collector system. In an embodiment, the manifold includes pipes for supply (e.g., cold) and return (e.g., hot) HTF. The solar collector systems may be drained automatically and gravitationally from a control room or with manual opening of a valve (e.g., a purge valve) located at each crossover pipe, in particular embodiments. As a result, personnel exposure to the high temperature fluids is minimized or eliminated during draining. Use of certain embodiments of the self-draining solar collector systems helps reduce operational costs of a solar thermal power plant, which employs parabolic reflectors and high temperature fluids, while also potentially making frequent draining of the solar collector assemblies economically viable.

[0062] Frequent draining may be advantageous for solar thermal power plants that use high-temperature fluids, such as molten salt, to reduce heat loss during periods of inactivity. Periods of inactivity may occur due to weather related events, seasonal shutdowns, maintenance events, or night.

[0063] Certain embodiments of the self-draining solar collector systems include connecting assemblies with pipes and/or flexible hoses and spherical and/or rotary joint connectors. However, the connection assemblies of the present systems are not limited to the particular illustrated embodiments. For example, spherical joint connectors (e.g., 312, 422, or 532 of FIGs. 4, 6, and 8) may be interchangeably replaced with rotary joint connectors (e.g., 308 and 409) or other similar connectors or joints known in the art, and vice versa, to the extent not inconsistent with the function or performance of the respective joint connector(s). Additionally, the illustrated pipe, hose, and connecting assemblies could also be modified to include various combinations of components mentioned herein and/or known in the art, such as various combinations of pipes, flexible hoses, bellows connectors, spherical or ball joint connectors, and rotary connectors.

[0064] In certain embodiments of the self-drawing solar collector systems, the following three distinct locations have different structural configurations of pipes and/or hoses: (1 ) the manifold (i.e., manifold connecting assembly), (2) in between adjacent solar collector assemblies or parabolic reflectors (i.e., shared connecting assembly), and (3) at the crossover (i.e., crossover connecting assembly). Fluid (e.g., HTF) may be drained from the system of solar collector assemblies gravitationally in certain embodiments. Gravitational draining is achieved because the crossover pipe is located at an elevation higher than the heating pipe(s) of the solar collector assemblies and the manifold is located at an elevation lower than the heating pipe(s) of the solar collector assemblies, at least when the solar collector assemblies are oriented in respective draining positions. Additionally, particular embodiments of the self-draining solar collector systems disclosed herein minimize fluid pooling (i.e., collection of fluid) in the pipes and/or hoses during draining, including in the manifold, shared, and crossover connecting assemblies.

[0065] The manifold connecting assembly has a general downward slope toward the manifold pipes and no fluid-containing pipe or hose of the manifold connecting assembly is substantially elevated above the heating pipe(s) during draining operating mode, thereby allowing fluid to drain from the heating pipes gravitationally without pooling. Significant pooling of fluid within the pipes and/or hoses of the crossover connecting assembly is also prevented because no fluid-containing pipes or hoses are substantially elevated above the crossover pipe during draining operating mode, and there is a general downward slope of the crossover connecting assembly from each crossover pipe to the respective heating pipe(s) of each respective solar collecting assembly. Also, during draining operating mode, no fluid- containing pipes and/or hoses of the shared connecting assemblies are substantially elevated above or below the heating pipes, or the rotational axes of the parabolic reflectors, of the respective solar collector assemblies (i.e., on either side of the shared connecting assembly). In some embodiments, while in a normal operating mode, any two parabolic reflectors, with respective heating pipe(s), or solar collector assemblies may rotate independently about a rotation axis to track incident light (e.g., sunlight). Certain embodiments of the systems provided herein also allow one or more of the pipes and/or hoses of the shared connecting assemblies to rotate together with the parabolic reflectors, with respective heating pipe(s), or solar collector assemblies, instead of being fixed to a pylon (i.e., an upright fixed and stationary support structure), to achieve a draining operating mode.

[0066] In some embodiments, where a connection is made between a crossover pipe and a solar collector assembly that is farthest from the manifold (i.e., "last solar collector assembly"), the flexible pipe is connected to the parabolic reflector at a location that is on the opposite side of the rotational axis from the heating pipe. It rotates through a path that opposes the path of the heating pipe, and is connected to the crossover connecting assembly at a location above the rotational axis of the parabolic reflector.

[0067] FIGs. 1A and 1 B illustrate a self-draining solar collector system 100, which is one possible embodiment of the self-draining solar collector systems featured herein. Self-draining solar collector system 100 has at least the following two operating modes: a normal operating mode and a draining operating mode. FIG. 1A illustrates self-draining solar collector system 100 in its normal operating mode, and FIG. 1 B illustrates self-draining solar collector system 100 in its draining operating mode. Self-draining solar collector system includes one or more solar collector assemblies 102. Each solar collector assembly 102 includes one or more parabolic reflectors 113, one or more tracking subsystems 108, one or more heating pipes

112, and one or more collector support subsystems 110 for each parabolic reflector

113. Each parabolic reflector 113 includes components such as (1 ) reflective elements that assist in reflecting incident light; (2) structural support elements for the parabolic reflector, including, for example, tubes, pipes, and cables; and (3) structural support elements for the respective heating pipe(s) such as structural support elements 202 (see FIG. 2). As a parabolic reflector 113 is rotated with respect to its respective collector support subsystem 110, components of the parabolic reflector 113 will rotate with the parabolic reflector 113. Each collector support subsystem 110 includes components that are fixed or stationary, such as pylons. The connecting assembly on each end of each solar collector assembly 102 may be a manifold connecting assembly 114, a shared connecting assembly 116, or a crossover connecting assembly 118.

[0068] Self-draining solar collector system 100 includes of one or more rows 101 of solar collector assemblies 102, which include one or more solar collector assemblies 102, one or more shared connecting assemblies 116, a crossover connecting assembly 118, and a manifold connecting assembly 114. Rows 101 (e.g., 101 (1 ) and 101 (2)), illustrated in FIGs. 1A and 1 B, are connected to a crossover pipe 128 on one side and to a manifold 121 on the other side. In the illustrated embodiments, manifold 121 includes first and second manifold pipes 122, 124 and first and second manifold connecting pipes 123, 125. Each shared connecting assembly 116 connects the heating pipe(s) 112 of two respective adjacent solar collector assemblies 102 (e.g., a first and a second solar collector assembly 501 (1 ) and 501 (2), as shown in FIGs. 7-8), such that heating pipes 112 of solar collector assemblies 102 are connected in series. Each manifold connecting assembly 114 connects heating pipe(s) 112 of each solar collector assembly 102 of a respective row 101 to manifold 121. Each crossover connecting assembly 118 connects heating pipe(s) 112 of each solar collector assembly 102 of a respective row 101 to crossover pipe 128.

[0069] In the example of FIGs. 1A and 1 B, the illustrated self-draining collector system 100 includes two rows 101 of solar collector assemblies 102, each row 101 having two solar collector assemblies 102, each solar collector assembly 102 including two parabolic reflectors 113 and one heating pipe 112. A tracking subsystem 108, for example located between each parabolic reflector 113 as part of each solar collector assembly 102, helps to rotate its respective parabolic reflector and heating pipe(s) about a rotation axis 120 to track incident light 204 (i.e., sunlight) to maximize the flux of incident light 204 onto parabolic reflectors 113 as the orientation of the source of incident light 204 (e.g., sun) changes with respect to the location of the solar collector assembly 102. (See FIG. 2). Rotation axis 120 is parallel, but not necessarily collinear, with the heating pipe 112. The rotating components (i.e., the respective one or more parabolic reflectors and respective one or more heating pipes) of each solar collector assembly 102 may rotate independently from the rotating components of each other solar collector assembly 102 in normal operating mode to track a source of incident light 204.

[0070] In normal operating mode, in the embodiment illustrated in FIG. 1A, fluid (e.g., molten salt) may flow within the pipes and/or hoses of solar collector system 100 in a loop arrangement as follows: from manifold 121 into first row of solar collector assemblies 101 (1 ) via manifold connecting assembly 114(1 ), through heating pipes 112 and shared connecting assembly 116(1 ) of first row 101 (1 ) of solar collector assemblies, into crossover pipe 128 via crossover connecting assembly 118(1 ), then into second row of solar collector assemblies 101 (2) via crossover connecting assembly 118(2), through heating pipes 112 and shared connecting assembly 116(2) of second row of solar collector assemblies 101 (2), and back into manifold 121 through manifold connecting assembly 114(2). In other embodiments, the fluid may flow in an arrangement that involves any other number of manifold pipes, manifold connecting pipes, manifold connecting assemblies, heating pipes, solar collector assemblies, parabolic reflectors, shared connecting assemblies, crossover connecting assemblies, and crossover pipes.

[0071] In draining operating mode, parabolic reflectors 113 and heating pipes 112 of each solar collector assembly 102 are rotated to respective draining positions whereby crossover pipe 128 is at a higher elevation than heating pipes 112 and shared connecting assemblies 116, and whereby manifold 121 (i.e., manifold pipes 122, 124) are at a lower elevation than heating pipes 112 and shared connecting assemblies 116. Consequently, manifold connecting assemblies 114 are configured to have a downward slope toward manifold 121 in the draining operating mode to allow fluid within heating pipes 112 to gravitationally drain into manifold 112. Additionally, crossover connecting assemblies 118 are configured to have a downward slope toward heating pipes 112 in the draining operating mode to allow fluid within crossover pipe 128 to drain into heating pipes 112. Additionally, shared connecting assemblies 116 are configured in the draining operating mode to allow fluid within heating pipe(s) 112 of one respective solar collector assembly 102 to drain into heating pipe(s) 112 of another respective solar collector assembly 102, such that fluid within heating pipes 112 drains into manifold 112. [0072] For example, the parabolic reflectors are rotated, about their rotation axis 120, to a substantially horizontal draining position as illustrated in FIG. 1 B, to achieve the aforementioned relative elevation conditions. In draining operating mode, a purge valve 126, located along crossover pipe 128, is opened to allow fluid (i.e., liquid such as molten salt) to flow gravitationally from crossover pipe 128 toward manifold 121. Purge valve 126 may be opened manually or automatically, for example from a control room. Manifold 121 is directly or indirectly connected, for example, to a solar thermal power plant (not shown). For the purpose of clarity in discussion and illustration, a solar collector assembly 102 that is closest to the manifold 121 is referred to as an initial solar collector assembly 104, and a solar collector assembly 102 that is farthest from the manifold 121 (and closest to the crossover pipe 128) is referred to as a last solar collector assembly 106. The number of solar collector assemblies 102 in each row 101 , as well as the number of rows 101 in self-draining solar collector system 100, may vary without departing from the scope hereof.

[0073] Manifold, shared, and crossover connecting assemblies (114, 116, and 118, respectively) may have a variety of configurations without departing from the scope hereof. For example, FIGs. 2-11 illustrate some possible embodiments of these assemblies including pipes, flexible hoses, rotary joint, and/or spherical joint connectors, as discussed below. It should be appreciated, however, that the manifold, shared, and crossover connecting assemblies of the present self-draining solar collector systems are not limited to these particular embodiments.

[0074] FIG. 2 illustrates a part of one possible embodiment of a solar collector assembly 102. In the illustrated embodiment, heating pipe support elements 202 support heating pipe 112 in its position relative to the parabolic reflector(s) 113. Parabolic reflectors 113 are shown in a normal operating mode. Incident light 204 is reflected by each parabolic reflector 113 toward its respective heating pipe 112. A source of incident light may be the sun, and the incident light may be sunlight. Reflected light 206 heats the fluid (e.g., molten salt) within heating pipe 112.

[0075] FIGs. 3A, 3B, 4A, and 4B illustrate several exemplary embodiments of manifold connecting assembly 114. For the purpose of example, FIGs. 3A and 3B as well as FIGs. 4A and 4B show a portion of an initial solar collector assembly 104 connected via a manifold connecting assembly 114 to manifold 121 via a first or second manifold connecting pipe 123 or 125, which is connected to first or second manifold pipe 122 or 124. FIGs. 3A and 4A illustrate a normal operating mode, and FIGs. 3B and 4B illustrate a draining operating mode when solar collector assemblies 102 are disposed in respective draining positions.

[0076] FIGs. 3A and 3B illustrate a flexible hose manifold connecting assembly 300, which is an embodiment of manifold connecting assembly 114. Flexible hose manifold connecting assembly 300 includes a flexible manifold hose 302, whose distal end 306 is connected to a heating pipe 112 and whose proximal end 304 is connected to a manifold connecting pipe (e.g., 123). In an embodiment, the connection between the proximal end of a flexible manifold hose 302 and manifold connecting pipe (e.g., 123) may include a rotary joint 308. FIG. 3B illustrates flexible hose manifold connecting assembly 300 where the initial solar collector assembly 104 is in a draining operating mode instead of a normal operating mode. In draining operating mode, fluid (e.g., liquid, molten salt) may flow gravitationally from the heating pipe 112 of the initial solar collector assembly 104 to manifold 121 (i.e., manifold and manifold connecting pipe(s)), which is located at a lower elevation than heating pipe 112 and rotation axis 120, via flexible hose manifold connecting assembly 300.

[0077] FIGs. 4A and 4B illustrate a spherical joint manifold connecting assembly 310, which is another embodiment of a manifold connecting assembly 114. Spherical joint manifold connecting assembly 310, as illustrated in FIGs. 4A and 4B, includes a manifold end pipe 317, and manifold end pipe 317 includes a first and second manifold end pipe 314, 316 and a plurality (e.g., three) of manifold spherical joint connectors 312. In the illustrated example, a proximal end 318 of manifold end pipe 317 is connected to a second manifold connecting pipe 125, which itself is connected to a second manifold pipe 124, and a distal end 320 of manifold end pipe 317 is connected to heating pipe 112 of a first solar collecting assembly 104. FIG. 4A shows spherical joint manifold connecting assembly 310 embodiment in a normal operating mode, and FIG. 4B shows the same in a draining operating mode. In draining operating mode, fluid (e.g., liquid, molten salt) may flow gravitationally from the heating pipe 112 of the initial solar collector assembly 104 to the manifold 121 (i.e., manifold and manifold connecting pipe(s)), which is located at a lower elevation than heating pipe 112 and rotation axis 120, via spherical joint manifold connecting assembly 310.

[0078] FIGs. 5A, 5B, 6A, and 6B illustrate several exemplary embodiments of a portion of a last solar collector assembly 106 connected via a crossover connecting assembly 118 to crossover pipe 128. FIGs. 5A and 6A illustrate a normal operating mode, and FIGs. 5B and 6B illustrate a draining operating mode where solar collector assemblies 102 are disposed in their respective draining positions.

[0079] FIGs. 5A and 5B illustrate a flexible hose crossover connecting assembly 400, which is an embodiment of a crossover connecting assembly 118. Flexible hose crossover connecting assembly 400 includes a flexible crossover hose assembly 405, whose distal end 410 is connected to a heating pipe 112 and whose proximal end 408 is connected to crossover pipe 128. The flexible crossover hose assembly 405 includes a flexible crossover hose 402, a crossover end pipe 406, and a flexible expansion hose 404. In an embodiment, the connection between the proximal end 408 of a flexible crossover hose assembly 405 and a crossover pipe 128 includes a rotary joint 409. FIG. 5B illustrates flexible crossover hose assembly 405 where the last solar collector assembly 106 is in a draining operating mode instead of a normal operating mode. In draining operating mode, fluid (e.g., molten salt) may flow gravitationally from the crossover pipe 128 to heating pipe 112 via the crossover connecting assembly 118, wherein the crossover pipe 128 is positioned at a higher elevation than the heating pipe 112. At least one purge valve 126 is located along the crossover pipe 128, and draining of fluid during the draining operating mode is modulated automatically or manually via the purge valve 126. In draining operating mode, fluid (e.g., liquid, molten salt) may flow gravitationally from crossover pipe 128, which is located at a higher elevation than heating pipe 112 and rotation axis 120, via flexible hose crossover connecting assembly 400 to heating pipe 112 of last solar collector assembly 106.

[0080] FIGs. 6A and 6B illustrate a spherical joint crossover connecting assembly 420, which is another embodiment of crossover connecting assembly 118. Spherical joint crossover connecting assembly 420, as illustrated in FIGs. 6A and 6B, includes a spherical joint crossover end pipe 427, which further includes a first and second crossover end pipe 424, 426 and a plurality (e.g., three) of crossover spherical joint connectors 422. In the illustrated example, the proximal end 428 of the crossover end pipe 427 is connected to crossover pipe 128, and distal end 430 of crossover end pipe 427 is connected to a heating pipe 112 of a last solar collector assembly 106. FIG. 6A shows the spherical joint crossover connecting assembly 420 embodiment in a normal operating mode, and FIG. 6B shows the same in a draining operating mode. In draining operating mode, fluid (e.g., molten salt) may flow gravitationally from the crossover pipe 128 to heating pipe 112 via crossover connecting assembly 118, wherein the crossover pipe 128 is positioned at a higher elevation than heating pipe 112. At least one purge valve 126 is located along the crossover pipe 128, and draining of fluid during the draining operating mode is modulated automatically or manually via purge valve 126. In draining operating mode, fluid (e.g., liquid, molten salt) may flow gravitationally from crossover pipe 128, which is located at a higher elevation than heating pipe 112 and rotation axis 120, via spherical joint crossover connecting assembly 420 to heating pipe 112 of last solar collector assembly 106.

[0081] FIGs. 7A, 7B, 8A, and 8B illustrate several exemplary embodiments of a shared connecting assembly 116, which connects heating pipes 112 of any two adjacent solar collector assemblies 102, for example, a first solar collector assembly 501 (1 ) and a second collector assembly 501 (2). In a different exemplary embodiment, first and second solar collector assemblies 501 (1 ) and 501 (2) are the initial solar collector assembly 104 and last solar collector assembly 106. FIGs. 7A and 8A show a normal operating mode, and FIGs. 7B and 8B show a draining operating mode where solar collector assemblies 102 are disposed in their respective draining configurations.

[0082] FIGs.7A and 7B illustrate a flexible hose shared connecting assembly 500, which is an exemplary embodiment of a shared connecting assembly 116, capable of being changed between a normal operating mode and a draining operating mode. Flexible hose shared connecting assembly 500 includes a first shared flexible hose 502 and a second shared flexible hose 504, with both shared flexible hoses 502, 504 connected to a shared pipe 506 at their proximal ends 508, 512. The distal ends 510, 514 of the first and second shared flexible hoses 502, 504 are each connected to the respective heating pipe(s) 112 of first and second solar collector assemblies 501 (1 ) and 501 (2), respectively. In an embodiment of a flexible hose shared collector assembly 500, during normal operating mode, as illustrated in FIG. 7A, shared pipe 506 is connected or secured to a pipe support 518 via a clamping subsystem 516, which may include one or more clamps. During normal operating mode, the parabolic reflector(s) and heating pipe(s) of the first solar collector assembly may be rotated independently of the parabolic reflector(s) and heating pipes(s) of the second solar collector assembly about rotation axis 120. In an embodiment of a flexible hose shared collector assembly 500, during draining operating mode, as illustrated in FIG. 7B, shared pipe 506 is freed from pipe support 518, and the first and second shared flexible hoses 502, 504 are connected or secured to the first and second rotation supports 520, 521 , respectively, via clamping subsystem 516. The arrangement of clamps and clamping subsystem is optionally modulated by a mode changing subsystem (not shown) to change shared connecting assembly 116 between its normal and draining operating modes, such by using electric motors, magnetic actuators, and/or pneumatic controls.

[0083] FIGs. 8A and 8B illustrate a spherical joint shared connecting assembly 530, which is an exemplary embodiment of shared connecting assembly 116. Spherical joint shared connecting assembly 530 includes a first and a second spherical joint shared pipes 537, 545 that are connected to each other at their respective proximal ends 538, 546. First and second spherical joint shared pipes 537, 545 each may include one or more pipes (e.g., first shared pipes 534, 536 and second shared pipes 542, 544) and one or more shared spherical joint connectors 532. The first and second spherical joint shared pipes are each connected at their distal ends 540, 548 to a respective heating pipe 112 of each of the first and second solar collector assemblies 501 (1 ) and 501 (2). For example, first and second solar collector assemblies 501 (1 ) and 501 (2) may be initial solar collector assembly 104 and last solar collector assembly 106, respectively. FIG. 8A shows a spherical joint shared connecting assembly during normal operating mode and FIG. 8B shows the same during draining operating mode. In an embodiment of the spherical joint shared connecting assembly, illustrated in FIGs. 8A and 8B, the parabolic reflectors and heating pipes of each solar collector assembly may be rotated independently of the parabolic reflectors and heating pipes of other solar collector assemblies about rotation axis 120. The rotation axis 120 is collinear with the proximal ends of the first and second spherical joint shared pipes and with shared spherical joint connectors 532.

[0084] FIGs. 9, 10, and 11 show exemplary embodiments of connecting assemblies. FIG. 9 illustrates an exemplary flexible hose connecting assembly 600, which includes a flexible hose (e.g., 302) and a rotary connector (e.g., 308). Similar flexible hose connecting assemblies may be used for the manifold, shared, or crossover connecting assemblies 114, 116, 118. FIG. 10 illustrates an exemplary spherical joint connecting assembly 610, including a single end pipe (e.g., 314) and a plurality of spherical joint connectors (e.g., 312, 422). FIG. 11 illustrates another example spherical joint connecting assembly 620, including multiple pipes and three spherical joint connectors (e.g., 312 or 422). Similar spherical joint connecting assemblies may be used for the manifold, shared, or crossover connecting assemblies 114, 116, 118.

[0085] FIG. 12 illustrates a method 1200 for operating a self-draining solar collector system. In step 1202, one or more parabolic reflectors and respective heating pipes of each of one or more solar collector assemblies are rotated to track an incident light source. In one example of step 1202, parabolic reflectors 113, and their respective heating pipe(s) 112, are rotated about their rotation axis 120, with respect to stationary components of collector support subsystems 110, to track an incident light source, as part of the normal operating mode of self-draining solar collector system 100. In step 1204, parabolic reflectors and respective heating pipe(s) are rotated to respective draining positions such that a manifold is at a lower elevation and a crossover pipe is at a higher elevation than the heating pipes of the solar collector assemblies. In one example of step 1204, parabolic reflectors 113, and their respective heating pipe(s) 112, are rotated about their rotation axis 120, with respect to stationary components of collector support subsystems 110, to their respective draining positions as part of the draining operating mode of self-draining solar collector system 100. In step 1206, a purge valve in a crossover pipe is opened. In one example of step 1206, purge valve 126 is opened (e.g., manually or automatically) to initiate draining. Method 1200 is executed once per day in certain embodiments, such as to prevent heat loss during the night. STATEMENTS REGARDING VARIATIONS

[0086] All references throughout this application, for example patent documents including issued or granted patents or equivalents; patent application publications; and non-patent literature documents or other source material; are hereby incorporated by reference herein in their entireties, as though individually incorporated by reference, to the extent each reference is at least partially not inconsistent with the disclosure in this application (for example, a reference that is partially inconsistent is incorporated by reference except for the partially inconsistent portion of the reference).

[0087] Having now fully described the present invention in some detail by way of illustration and examples for purposes of clarity of understanding, it will be clear to one of ordinary skill in the art that the same can be performed by modifying or changing the invention within a wide and equivalent range of conditions, formulations and other parameters without affecting the scope of the invention or any specific embodiment thereof, and that such modifications or changes are intended to be encompassed within the scope of the appended claims.

[0088] The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments, exemplary embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims. The specific embodiments provided herein are examples of useful embodiments of the present invention and it will be apparent to one skilled in the art that the present invention may be carried out using a large number of variations of the devices, device components, methods steps set forth in the present description. Methods and devices useful for the present methods can include a large number of optional composition and processing elements and steps. [0089] When a group of substituents is disclosed herein, it is understood that all individual members of that group and all subgroups are disclosed separately. When a Markush group or other grouping is used herein, all individual members of the group and all combinations and subcombinations possible of the group are intended to be individually included in the disclosure.

[0090] It must be noted that as used herein and in the appended claims, the singular forms "a", "an", and "the" include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to "a heating pipe" includes a plurality of such heating pipes and equivalents thereof known to those skilled in the art, and so forth. As well, the terms "a" (or "an"), "one or more" and "at least one" can be used interchangeably herein. It is also to be noted that the terms "comprising", "including", and "having" can be used interchangeably. The expression "of any of claims XX- YY" (wherein XX and YY refer to claim numbers) is intended to provide a multiple dependent claim in the alternative form, and in some embodiments is interchangeable with the expression "as in any one of claims XX- YY."

[0091] Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described. Nothing herein is to be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention.

[0092] When a group of substituents is disclosed herein, it is understood that all individual members of that group and all subgroups, are disclosed separately. When a Markush group or other grouping is used herein, all individual members of the group and all combinations and subcombinations possible of the group are intended to be individually included in the disclosure. For example, when a device is set forth disclosing a range of materials, device components, and/or device configurations, the description is intended to include specific reference of each combination and/or variation corresponding to the disclosed range.

[0093] Every combination of components described or exemplified herein can be used to practice the invention, unless otherwise stated. [0094] Whenever a range is given in the specification, for example, a temperature range, a time range, or a composition or concentration range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure. As used herein, ranges specifically include the values provided as endpoint values of the range. For example, a range of 1 to 100 specifically includes the end point values of 1 and 1 00. It will be understood that any subranges or individual values in a range or subrange that are included in the description herein can be excluded from the claims herein.

[0095] As used herein, "comprising" is synonymous with "including," "containing," or "characterized by," and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, "consisting of" excludes any element, step, or ingredient not specified in the claim element. As used herein, "consisting essentially of" does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. In each instance herein any of the terms "comprising", "consisting essentially of" and "consisting of" may be replaced with either of the other two terms.

[0096] One of ordinary skill in the art will appreciate that device elements and combinations of components other than those specifically exemplified can be employed in the practice of the invention without resort to undue experimentation. All art-known functional equivalents, of any such materials and methods are intended to be included in this invention. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.