Patent Application
20210066526
This invention related to the area of CPV (Concentrating Photovoltaics); it is a concentrating photovoltaic technology that generates electricity from sunlight. Contrary to conventional photovoltaic systems, it uses lenses and curved mirrors to focus sunlight onto small, but highly efficient, solar cells; preferably, multi-junction (MJ) solar cells. In addition, CPV systems often use solar trackers and sometimes a cooling system to further increase their efficiency.
Ongoing research and development are rapidly improving their competitiveness in the utility-scale segment and in areas of high insolation. This sort of solar technology can be thus used in smaller areas.
Systems using high-concentration photovoltaics (HCPV) especially have the potential to become competitive in the near future. They possess the highest efficiency of all existing PV technologies, and a smaller photovoltaic array also reduces the balance of system costs.
The author of this invention tried to solve the problems of cooling photovoltaic cells in HCPV in his US Patent Application No. 20060169315.
U.S. Pat. No. 9,437,766 describes a method for operating a photovoltaic thermal hybrid system having a hybrid solar receiver with a photovoltaic module, operatively coupled to the system to deliver an electrical output power for a power user, a thermal collector distinct from the photovoltaic module, wherein the photovoltaic module and/or the thermal collector are movably mounted in the system, a collector thermal storage thermally connected to the thermal collector to store heat collected at the thermal collector, and a positioning mechanism adapted to move the photovoltaic module and/or the thermal collector.
The method includes instructing the positioning mechanism to move the photovoltaic module and/or the thermal collector to change a ratio of an intensity of radiation received at the photovoltaic module to an intensity of radiation received at the thermal collector.
There are some articles, which describe application of heat pipes for cooling photovoltaic cells in HCPV:
Some technical solutions of this invention are based on the theory of two-phase thermosiphons developed in this book.
The main technical solutions of the invention include following elements:
a two-phase thermosiphon intended to cool photovoltaic cells being installed on the external end butt of a plug sealing the lower section of the two-phase thermosiphon;
the lower section of the two-phase thermosiphon is divided onto three sub-sections: a distal rigid sub-section from a pipe, a middle sub-section designed as a flexible bellows and a proximal rigid sub-section;
the proximal rigid sub-section of the lower section of the two-phase thermosiphon is in fluid communication via a 3-way connector with two inclined upper sections of the two-phase thermosiphon; these inclined upper sections are designed as two inclined pipes; the proximal ends of these inclined upper sections are sealed and supported by two supporting units installed on two posts;
a bushing, which is fastened on the rigid distal sub-section of the lower section of the two-phase thermosiphon; this bushing is joined by truss struts with a supporting structure of a parabolic dish-shaped mirror. This supporting structure, in turn, is joined with a tracking manipulator.
The tracking manipulator provides orientation of the axis of the parabolic dish-shaped mirror and, therefore, of the axis of the rigid distal sub-section of the lower section of the two-phase thermosiphon towards the sun.
The tracking manipulator can operate on the base of celestial tracking algorithm or with application of optical detectors, which determine direction of the axis of the parabolic dish-shaped mirror regarding the sun.
The tracking manipulator is joined with a supporting structure of the parabolic dish-shaped mirror at a certain point.
The tracking manipulator comprises in general two mechanisms of mutually perpendicular displacements in the horizontal plane and a mechanism of vertical displacement; an arm of the tracking manipulator, which is joined with the supporting structure of the parabolic dish-shaped mirror at a certain spot, causes by combination of these three displacements a desired azimuthal and altitude parameters of the axis of the parabolic dish-shaped mirror (these displacements depend as well on geometric and mechanical characteristics of the bellows).
The outer surface of the bellows can be protected by a braid.
The photovoltaic cells are preferably multi-junction (MJ) photovoltaic cells.
An optical unit, which provides uniform illumination of the photovoltaic cells by concentrated solar radiation, can be installed below the distal low section of the two-phase thermosiphon.
Such optical units are described, for example in: Nguyen Xuan Tien and Seoyong Shin
“A Novel Concentration Photovoltaic (CPV) System with the Improvement of Irradiance Uniformity and the Capturing of Diffuse Solar Radiation”. The article is published in Applied Sciences 6(9):251. September 2016.
The distal sub-section of the lower section of the two-phase thermosiphon can be designed as a pipe, which is terminated with a truncated cone or a truncated pyramid. It allows to increase significantly the area of the external end butt of the plug, which seals the distal sub-section of the lower section of the two-phase thermosiphon, regarding the areas of the cross-sections of other sub-sections of the two-phase thermosiphon.
The internal end butt of the distal plug can be covered with a capillary coating in order to ensure uniform wetting of the internal end butt of the distal plug and to achieve higher heat transfer characteristics.
The upper inclined sections of the two-phase thermosiphon can be provided with external fins in order to enhance dissipation of heat released on the photovoltaic cells and passed from the lower section of the two-phase thermosiphon into these inclined upper sections.
In addition, several fans can be installed on the fins of the inclined upper sections in order to improve heat transfer from the fins to the surrounding air. Diameters of the inclined upper sections of the two-phase thermosiphon can be increased in order to increase heat transfer to the surrounding air.
In another version of design of the two-phase thermosiphon, its lower section is the same as in the first version, and its upper section comprises a first pipe with a concave axis.
A second pipe with a concave axis having smaller diameter than the first pipe, is situated in the internal space of the first pipe (the first and second pipes are positioned coaxially); the terminal sections of the second pipe are protruded regarding the ends of the first pipe, and the ends of the first pipe are sealed with the proximal sub-sections of the second pipe with application of two annular plugs. In such a way, such first and second pipes play a role of an upper section of the two-phase thermosiphon.
The first pipe of the upper section of the two-phase thermosiphon can be provided with two sub-sections of additional bellows; these additional bellows are intended to compensate thermal tensions between the first and second pipes of the upper section of the two-phase thermosiphon.
In such a way, this second pipe can be applied for cooling and condensation of vapors of a working medium of the two-phase thermosiphon by the cooling medium, which flows in this second pipe. Cooling and condensation processes occur on the external surface of the second pipe.
It should be noted that this second version of the concentrating photovoltaic module can be realized with further heat dissipation to the surroundings from the cooling medium.
This can be performed by a pump, which circulates the cooling medium via the second pipe; in addition, the cooling medium circulates via a radiator, which is provided with a fan causing forced convection of the surrounding air around external fins of this radiator.
In both version of the two-phase thermosiphon the upper sub-section of its lower section can be joined with a cross-bar; the terminal sections of this cross-bar are joined, in turn, with the posts used for supporting the proximal sub-sections of the upper section of the two-phase thermosiphon.
The lower section of the two-phase thermosiphon is joined with a supporting structure of a parabolic dish-shaped mirror. This supporting structure is joined, in turn, with a tracking manipulator shown schematically.
In such a way, a photovoltaic receiver of the proposed photovoltaic module is positioned on the external end butt of the distal plug and the focal spot of the parabolic dish-shaped mirror is mostly overlapped by the photovoltaic cells of this photovoltaic receiver.
The upper sections of the two-phase thermosiphon are provided with external fins, which serve for heat dissipation by forced convection. This forced convection caused by fans installed on the external fins.
The external end butt of the plug, which seals the two-phase thermosiphon's lower section, serves for installation of photovoltaic cells. In addition, there is an optical unit arranged below the photovoltaic cells, which ensures uniform illumination of the photovoltaic cells by concentrated solar radiation obtained from a parabolic dish-shaped mirror.
There is a bushing, which is fastened on the distal sub-section of the lower section of the two-phase thermosiphon and serves, in turn, for installation of the parabolic dish-shaped mirror; this parabolic dish-shaped mirror is joined with a tracking manipulator (shown schematically).
The upper section of the two-phase thermosiphon comprises a first pipe having concave axis, and a second pipe of smaller diameter; the second pipe has concave axis too and is situated coaxially in the internal space of the first pipe; the terminal sections of this second pipe are protruded from the first pipe and the ends of the first pipe are sealed with the proximal sub-sections of the second pipe.
In such a way, this second pipe can be applied for cooling and condensation of vapors of working medium of the two-phase thermosiphon by a cooling medium, which flows in this second pipe.
In addition, there is a pump, radiator and fan; they serve for chilling the cooling medium. These units are shown schematically.
The upper sections of the two-phase thermosiphon are provided with external fins, which serve for heat dissipation by forced convection. This forced convection is caused by fans installed on the external fins.
In such a way, the concentrating photovoltaic module comprises: a two-phase thermosiphon 100 with its lower section including, in turn, an upper rigid sub-section 101, bellows 103, a distal rigid sub-section 119, which is terminated with a conical member 117; this conical member 117 is sealed by plug 116; photovoltaic cells 109 are fastened on the external end butt of this plug 116 and its internal end butt is covered with a capillary coating 118.
Bushing 104 is installed on the distal rigid sub-section 119 of the lower section of the two-phase thermosiphon 100; this bushing 104 serves for installation of a parabolic dish-shaped mirror 102; a supporting structure 120 of the parabolic dish-shaped mirror is joined with bushing 104 by truss struts 105.
A tracking manipulator 110 is joined with the supporting structure 120 of the parabolic dish-shaped mirror 102 at a certain point of the supporting structure 120.
There is an optical unit 108 arranged below the lower section of the two-phase thermosiphon 100; this optical unit 108 provides uniform illumination of the photovoltaic cells by concentrated solar radiation obtained from the parabolic dish-shaped mirror 102.
An upper rigid sub-section 101 of the lower section of the two-phase thermosiphon 100 is joined by cross-bar 115 with posts 112; it provides mechanical rigidity to the upper rigid sub-section 101 of the lower section of the two-phase thermosiphon 100.
There are two inclined upper sections 106 of the two-phase thermosiphon 100, these upper inclined sections 106 are in fluid communication with the lower section of the two-phase thermosiphon 100 via a metal 3-way connector 121.
The proximal sub-sections of the upper sections are sealed with plugs 113; these proximal sub-sections are supported by supporting members 114 installed on posts 112.
The external surface of the upper sections of the two-phase thermosiphon are provided with fins 107 and fans 111 for enhancement of forced convection from these fins 107 to the environment.
It comprises the lower sub-section 119 of the lower section of the two-phase thermosiphon 100; bushing 104 is installed on this lower sub-section 119.
The lower rigid sub-section 119 is terminated at its distal part with a truncated cone 117, which is sealed with plug 116. The photovoltaic cells 109 are installed on the external end butt of of plug 116; its internal end butt is covered with the capillary coating 118.
The optical unit 108 is arranged below the photovoltaic cells 109.
Bushing 104 is joined with the truss strut 105.
The protruded terminal sections of the internal pipe 209 are sealed by plugs 213, which are provided with openings serving for passage of a cooling medium.
The protruded terminal sections of the second pipe 209 are supported by supporting members 212 installed on posts 217.
In such a way, this second pipe 209 of smaller diameter can be applied for cooling and condensation of vapors of working medium of the two-phase thermosiphon 200 by the cooling medium, which flows in this second pipe 209.
The first pipe 207 is provided with two bellows 208 in order to diminish tensions caused by temperatures' difference between the first pipe 207 and the second pipe 209.
In addition, there is pump 215, radiator 214 and fan 216; they serve for chilling the cooling medium. These units are shown schematically.
The lower section of the two-phase thermosiphon 200 comprises an upper rigid sub-section 201, bellows 203, a distal rigid sub-section 206, which is terminated with a truncated conical member 224; this truncated conical member is sealed by plug 222; photovoltaic cells 218 are fastened on the external end butt of this plug 222 and its internal end butt is provided with a capillary coating 223.
Bushing 204 is installed on the distal rigid sub-section 206 of the lower section of the two-phase thermosiphon 200; this bushing 204 serves for installation of a parabolic dish-shaped mirror 202 and its supporting structure 221, which is joined with bushing 204 by truss struts 205.
A tracking manipulator 210 is joined with the supporting structure 221 of the parabolic dish-shaped mirror 202 at a certain point of this supporting structure 221.
There is an optical unit 219 arranged below the conical member 224; this optical unit 219 provides uniform illumination of the photovoltaic cells 218.
The upper sub-section 201 of the lower section of the two-phase thermosiphon 200 is joined by cross-bar 220 with posts 217; this provides mechanical rigidity to the upper sub-section 201 of this lower section.
It comprises the lower sub-section of the lower section of the two-phase thermosiphon 200; bushing 204 is installed on this lower sub-section 206.
The lower sub-section 206 is terminated at its distal part with the truncated conical member 224, which is sealed with plug 222. The photovoltaic cells 218 are installed on the external end butt of plug 222; its internal end butt is provided with the capillary coating 223.
The optical unit 219 is arranged below the conical member 224 and the photovoltaic cells 218; this optical unit 219 provides uniform illumination of the photovoltaic cells 218.
Bushing 204 is joined with the truss strut 205.
