SYSTEMS AND METHODS OF GENERATING SOLAR ENERGY AND DRY COOLING

Abstract

Dry cooling systems and methods are provided including at least one plastic elongated tube formed at least partially of a semi-rigid material and having a flat wall portion, a reflective material attached to said flat wall portion of the tube to reflect solar radiation, and at least one fluid channel in thermal communication with the reflective material, the fluid channel adapted to allow flow of a heat transfer fluid. Thermal power plants are provided which include a dry cooling system, one or more pipes in fluid communication with the dry cooling system, and at least one heat exchanger in fluid communication with the one or more pipes.

Claims

1. A dry cooling system comprising: at least one elongated tube formed at least partially of a semi-rigid material and having a flat wall portion; a reflective material attached to said flat wall portion of the tube to reflect solar radiation; at least one fluid channel in thermal communication with the reflective material, the fluid channel adapted to allow flow of a heat transfer fluid.

2. The system of claim 1 wherein the at least one elongated tube is located in a support basin of water.

3. The system of claim 2 wherein the at least one elongated tube further comprises a central air conduit.

4. The system of claim 1 wherein the at least one elongated tube is incorporated into a heliostat assembly.

5. The system of claim 1 wherein the torsional load of the heliostat assembly is 5 mRad or lower.

6. The system of claim 1 wherein the at least one elongated tube further comprises a slideable pipe next to the reflector.

7. The system of claim 1 wherein the heat transfer fluid comprises one or more of thermal oil, water, molten salt, or supercritical CO2.

8. The system of claim 1 wherein the at least one elongated tube can be configured in a cooling track mode to cool the system.

9. The system of claim 1 wherein the semi-rigid material is plastic.

10. A thermal power plant comprising: a dry cooling system including at least one elongated tube formed at least partially of a semi-rigid material and having a flat wall portion, a reflective material attached to said flat wall portion of the tube to reflect solar radiation, and at least one fluid channel in thermal communication with the reflective material, the fluid channel adapted to allow flow of a heat transfer fluid; one or more pipes in fluid communication with the dry cooling system; and at least one heat exchanger in fluid communication with the one or more pipes; wherein water is routed through the at least one heat exchanger to the dry cooling system, the water is circulated in thermal communication with the reflective material, and the water is heated.

11. The power plant of claim 10 wherein the water gives up heat, the reflective material radiatively dumps the heat from the water, and the water is recirculated through the heat exchanger.

12. The power plant of claim 10 of claim 1 wherein the at least one elongated tube is located in a support basin of water.

13. A method of dry cooling, comprising: routing water through a heat exchanger; routing the water through one or more pipes to a dry cooling system including one or more solar reflectors; circulating the water in thermal communication with a reflective material of the one or more solar collectors such that the water is heated; circulating the heated water such that the heated water gives up heat and the reflective material radiatively dumps the heat from the water; and circulating the water such that the water is rerouted through the heat exchanger.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above-mentioned features and objects of the present disclosure will become more apparent with reference to the following description taken in conjunction with the accompanying drawings wherein like reference numerals denote like elements and in which:

[0021] FIG. 1 is a schematic of an exemplary embodiment of a hybrid geothermal and concentrated solar power plant in accordance with the present disclosure;

[0022] FIG. 2 is a schematic of an exemplary embodiment of a hybrid geothermal and concentrated solar power plant in accordance with the present disclosure;

[0023] FIG. 3 is a process flow diagram of an exemplary method of dry cooling in accordance with the present disclosure;

[0024] FIG. 4 is a perspective view of an exemplary embodiment of dry cooling system in accordance with the present disclosure;

[0025] FIG. 5 is a schematic of an exemplary embodiment of a thermal power plant in accordance with the present disclosure; and

[0026] FIG. 6 is a cross-sectional view of an exemplary embodiment of an elongated tube in accordance with the present disclosure.

DETAILED DESCRIPTION

[0027] In the following detailed description of exemplary embodiments of the disclosure, reference is made to the accompanying drawings in which like references indicate similar elements, and in which is shown by way of illustration specific embodiments in which disclosed systems and devices may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, functional, and other changes may be made without departing from the scope of the present disclosure. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. As used in the present disclosure, the term or shall be understood to be defined as a logical disjunction and shall not indicate an exclusive disjunction.

[0028] Exemplary embodiments of the presently disclosed invention include a thermal power plant 30, illustrated in FIG. 5 and associated dry cooling methods, shown in FIG. 3, wherein heat from the power plant is transferred to the the cooling water 22 (or other heat transfer fluid) (step 110)), which is routed through a heat exchanger 32 to provide cooling to the power plant 30. Then the cooling water 22 is routed through one or more pipes 34 to a CSP reflector field (step 120), said collector field configured to provide a heat boost to the thermal power plant and also to allow for circulation of water in direct thermal communication with one or more of the reflector elements of the CSP array (step 130). This heated water which is routed into direct thermal communication with one or more CSP reflectors gives up heat which is radiatively dumped by the reflector and the water returned to ambient or close to ambient. At that point the water is recirculated to the power plant (step 140) to perform its cooling function once again and the cycle is repeated, with no net loss of water through evaporation. This process is illustrated by the flow diagram in FIG. 5.

[0029] Referring to FIG. 1, exemplary embodiments of a dry cooling system 10 comprise an elongated tube 12, made at least partially of a flexible or semi-rigid material such as plastic, with a flat wall portion 14, which is a section built into a wall of the tube or attached to the wall of the tube, and a reflective material 16 attached to the flat wall portion 14 of the tube 12 to reflect solar radiation. The elongated tube 12 may have an axis of rotation oriented generally parallel to a surface of a supporting body of liquid 18. The elongated tube may be elastically or plastically deformed by application of a torque along its length, so as to bring flat-surface normal vectors at each end of the tube largely into alignment with each other. The dry cooling system 10 may further comprise one or more individual sections that are coupled together through either rigid or flexible couplings, mid-span. Liquid ballast may or may not be used in various embodiments of this invention. In exemplary embodiments, the inner portion of the tube defines a reservoir containing fluid facilitating ballast, the fluid having a top surface generally parallel to the surface of a support body of liquid.

[0030] In the case of a floating tube structure mounting system for a CSP reflector, to move too high of a volume of water (or other heat transfer fluid 22) into thermal communication with the reflector section, the tube would lose buoyancy and sink into the water support. Moreover, the increased mass within the tube itself would lead to asymmetric loading on the mechanical system, and cause mis-aiming of the reflector element itself.

[0031] CSP reflectors are typically glass mirrors, but they can also be other types of reflectors, for example, polymer reflectors. Importantly, most reflectors (both glass mirror and polymer reflectors) possess certain inherent qualities that can be exploited for use in the present invention. Reflectors by their nature are typically composed of a volume of material that is largely transparent in the solar spectrum, with a layer at the bottom that is reflective in the solar spectrum. This means that the reflector will not absorb the majority of solar radiation impingent on it. However, if one looks at the black-body radiation spectrum of the earth, the glass, or other visibly transparent material of most reflectors is opaque and will emit non-negligible amounts of energy in the IR spectrum.

[0032] In exemplary embodiments, heat can be transferred from the cooling water to the mirror through conduction, convection, or radiation, and the primary mode of ultimate heat rejection is when the heat is vented through radiation from the reflector. This effect can work throughout the day and night.

[0033] Importantly, to achieve this end, it is critical that the function of the mirror in its use as a solar concentrator not be compromised. For this reason, the temperature gradient of the fluid within the tube must be managed so as not to cause bending or warping of the mirror which would interfere with its function as a CSP reflector. Further, in order not to interfere with the reflector's primary function of reflecting light onto a target, no additional materials or assemblies can be introduced in front of the reflector, the reflector must remain exposed to ambient air.

[0034] In the case of a line focus reflector system, such as a Linear Reflector System (LFR) or parabolic trough system, the reflector system will have actuators at periodic distances along their length, with spacing at intervals between the actuators. Between these actuators, the reflector systems experience torsion. Adding a volume of water to the reflector system, whether it be in a plastic tube, or as a water jacket of some form, mounted on a scaffold consisting of traditional steel and concrete construction, will change the torsion characteristics of the reflector system. There exists an upper limit of practical application of this additional torsional load. As a general rule, a torsion of more than 5 mRad is not acceptable without adversely affecting the performance of the reflector system. Accordingly, embodiments of this invention are generally characterized as configurations where the net torque T, of the water conduit system on the linear reflector system is less than or equal to 0.005*G*J.sub.T/1. Where G is the modulus of rigidity of the reflector mounting system, J.sub.T is the torsional constant for the cross section of the reflector mounting system, and 1 is one half the distance between the most closely spaced actuators of the reflector mounting system.

[0035] Turning to FIG. 2, in the case of point focus reflectors, such as heliostats for a power tower configuration, the bending moment is a closer descriptor and limiter of practical application. The 5 mRad rule of thumb is equally applicable, so accordingly, embodiments of the present invention are generally characterized as configurations in which the volume and distribution of water routed through a reflector system impart a net load on a reflector system less than or equal to 0.005*6*E*I/L.sup.3. Where E is the modulus of elasticity of the reflector mounting structure, I is the area moment of inertia of the reflector mounting system, and L is the distance from the nearest actuator to the end of the reflector.

[0036] The functional relationships described above are for idealized beam configurations, but it should be noted that even in the case of more complicated designs that reduce the volume of materials used in construction and require more detailed analytical approaches, the basic nature of the invention remains: specifically that the net imparted torsion or torque on the CSP reflector system cannot cause the reflector system to be affected by more than 5 mRador else it ceases to serve as both an effective CSP reflector and a heat radiator.

[0037] Whatever conduit may be used to move the water behind the reflector system, it will undergo temperature cycling as hot water is moved into it, then cooled and moved out. This will lead to thermal cycling and associated thermal expansion and contraction. Importantly, this thermal expansion and contraction cannot be allowed to bend, break, or warp the glass. One approach is to use a flexible material for the conduit, another is to allow thermal coupling of the conduit to the reflector, but to prevent mechanical coupling. As illustrated in FIG. 6, this can be achieved by placing a pipe 24 next to the reflector 26 but allowing the pipe to slide next to the reflector when it changes dimension due to temperature cycling or for any reason. At the interface, the use of a heat conducting paste 28, or gel or other similar substance can be used to ensure good heat transfer between the conduit and the reflector.

[0038] Also, it is possible to limit the temperature gradient to a certain maximum amount, In practical terms, a maximum delta T of 75 C. is sufficient to ensure that less than 5 mRad of angular inaccuracy is imparted, in both the case of plastic and metal supports.

[0039] As shown in FIG. 4, large basins or reservoirs 20 can be configured and used to store hot water during the day and use the cooling capability of the reflectors at night. Embodiments of the present disclosure include a support basin 20 for supporting elongated tubes with reflectors mounted on them. This support basin 20 can be covered as a water bed, or partially open. In both cases, it can be configured so that water is circulated from the basin into the pipes to cool the water. In this way, each basin can be used as a water reservoir. This effectively stores cooling capacity for the system.

[0040] In general, CSP reflectors have a stow mode for high winds and other reasons. The water conduit system consistent with this invention does not interfere with the function of the reflector being put into stow mode, remaining in stow mode, or coming out of stow mode. Alternatively, the performance of the radiant cooling will be best, when the reflector is pointed at the portion of the sky with the least incoming IR radiation, so a cooling track mode can be substituted for stow mode or any other mode wherein the tracking of the sun is not immediately needed. The cooling track mode can be used to maximize cooling by using one or more sensors to determine the optimal direction to point for maximum cooling.

[0041] In the case of tubes configured to float on water to mount reflectors, filling the inner chamber completely would cause these tubes to be submerged and not function. So the present disclosure includes additional internal geometry (such as a central conduit containing air which does not interfere with the thermal communication of the hot water with the reflector) to facilitate floatation and/or a bottom sheet on top of the body of supporting water, on top of which, all the tubes sit, which that facilitates floatation from outside to tubes themselves.

[0042] While the apparatus, systems, and methods have been described in terms of what are presently considered to be the most practical and preferred embodiments, it is to be understood that the disclosure need not be limited to the disclosed embodiments. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the claims, the scope of which should be accorded the broadest interpretation to encompass all such modifications and similar structures. The present disclosure includes any and all embodiments of the following claims.

[0043] Thus, it is seen that dry cooling systems and methods and solar concentrating power plants are provided. It should be understood that any of the foregoing configurations and specialized components or chemical compounds may be interchangeably used with any of the systems of the preceding embodiments. Although illustrative embodiments are described hereinabove, it will be evident to one skilled in the art that various changes and modifications may be made therein without departing from the disclosure. It is intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the disclosure.