HK1094917B - Extracting heat from an object - Google Patents

Description

Extracting heat from objects

Technical Field

The present invention relates to an assembly for extracting heat from an object.

The present invention relates generally to extracting heat from an object in situations where a high heat transfer rate is required to extract heat in a relatively confined space with low energy input.

Background

One such case is heat extraction from an array of photovoltaic cells in a concentrated solar radiation based power generation system, and by way of example, the invention is described below in the context of this application, but is not limited to this application.

Solar radiation based power generation systems typically include:

(a) a receiver comprising (i) a photovoltaic unit that converts solar energy to electrical energy, and (ii) circuitry for transferring the electrical energy output of the photovoltaic unit; and

(b) means for concentrating solar radiation onto photovoltaic cells of a receiver.

Although by no means exclusively, the present invention is particularly applicable to large scale solar radiation based power generation systems of the type described above, which are capable of producing a substantial amount of electrical power ready to be regulated to standard 3-phase 415 volt AC power of at least 20 kW.

Applications for such large-scale power generation systems include remote regional power supplies for isolated power grids, power connected to a backbone network, water pumping, telecommunications, crude oil pumping, water purification, and hydrogen generation.

A significant problem associated with the development of commercially viable solar radiation based power generation systems of the type described above is the ability to reject sufficient heat from the photovoltaic cell array to promote long term performance of the cell array material in the following situations:

(a) exposure to extremely high intensity solar radiation capable of generating high temperatures, i.e. temperatures well in excess of 1000 ℃;

(b) cycling between high and low intensities of solar radiation;

(c) temperature variations between different parts of the cell array; and

(d) different thermal expansion rates of the different materials comprising the array of cells and associated components.

In a large scale solar radiation based power generation system of the type described above, the photovoltaic cells are exposed to a solar radiation intensity of at least 200 times the solar brightness during optimal operating conditions. Furthermore, photovoltaic cells are subject to significant cycling between extremely high and low levels of solar radiation, and to variations in the intensity of the solar radiation across the surface of the receiver.

International application PCT/AU02/00402 in the name of the present applicant discloses a receiver for a solar radiation based power generation system comprising a plurality of unit modules electrically connected together. The international application discloses: each module includes a plurality of photovoltaic cells and a particular form of module for extracting heat from an array of photovoltaic cells.

Disclosure of Invention

It is an object of the present invention to provide an alternative heat extraction assembly for an array of cells that enables the array of cells to be cooled sufficiently to withstand prolonged exposure to extremely high intensity solar radiation, significant cycling between extremely high and low intensities of solar radiation, temperature variations between different parts of the module and receiver components, and different rates of thermal expansion of the different materials that make up the array of cells.

Broadly stated, the present invention provides a photovoltaic cell module for a receiver of a solar radiation based power generation system. The module includes an assembly for extracting heat from the photovoltaic cells. The heat extraction assembly includes a coolant chamber disposed behind and in thermal contact with the photovoltaic cells. The coolant chamber includes an inlet for coolant and an outlet for heated coolant. In the coolant chamber, the heat extraction assembly further comprises a plurality of beads, rods, bars or spheres of high thermal conductivity material in thermal contact with the photovoltaic cells and with each other and together having a large surface area for heat transfer and defining a three-dimensional labyrinth within the coolant chamber, the labyrinth being operable to conduct heat from the photovoltaic cell or cells therethrough to the coolant flowing through the labyrinth from the inlet to the outlet of the coolant chamber.

More specifically, according to the present invention there is provided a photovoltaic cell module for a receiver of a solar radiation based power generation system, the module comprising:

(a) one or more than one photovoltaic cell having an exposed surface for solar radiation;

(b) an electrical connection for transferring the electrical energy output of the photovoltaic cell or cells to an output circuit, an

(c) An assembly for extracting heat from the photovoltaic cell or cells, the assembly comprising (i) a housing disposed behind and in thermal contact with an exposed surface of the photovoltaic cell or cells, the housing comprising a base and a plurality of side walls extending from the base, wherein the base, side walls and the photovoltaic cell or cells define a coolant chamber and the housing comprises an inlet for supplying coolant into the chamber and an outlet for exhausting coolant from the chamber, and (ii) a coolant member located in the coolant chamber in heat transfer relationship with the photovoltaic cell or cells, the coolant member comprising a plurality of beads, rods, bars or spheres of a high thermal conductivity material in thermal contact and having a large surface area for heat transfer and defining a three-dimensional labyrinth, the labyrinth conducts heat away from the photovoltaic cell or cells therethrough via a substantial number of heat transfer paths formed by thermally connected beads, rods, bars or balls, and has a substantial number of coolant flow passages for coolant supplied to and flowing through the coolant chamber through the inlet and discharged from the coolant chamber through the outlet when the module is in use.

The present invention is a simple, economical, compact, efficient heat sink (heat sink) based on a labyrinth of thermally conductive material and voids with optimized thermal conductivity ratios, located within a coolant chamber and capable of extracting substantial heat from the photovoltaic cell/cells. The labyrinth has: a large surface area for high heat transfer to the coolant; an optimized void space to facilitate sufficient coolant flow to remove the concentrated thermal energy from the photovoltaic cell/cells with low pressure drop of the coolant and thus low coolant pumping power required to circulate the coolant. In particular, the heat sink of the present invention achieves the necessary heat extraction from the photovoltaic cell/cells within the significant constraints of placing the heat sink entirely behind the overhanging cell area and thereby allowing the exposed receiver area to be entirely made up of the photovoltaic cell/cells. This spatial constraint does not conflict with heat sinks used in other non-solar applications and is a significant constraint in the case of solar radiation based power generation systems.

The applicant has found that the above-described unit modules, characterized by a substantial number of heat transfer paths formed by beads, rods, bars or balls in thermal contact and by a substantial number of coolant flow paths, are capable of extracting in an economical, efficient and reliable manner the significant heat generated by the incident concentrated solar radiation. In particular, the applicant has found that the labyrinth structure of the coolant chamber makes it possible to direct thermal energy gradually away from the photovoltaic cell or cells and from the beads, rods, bars or balls of high thermal conductivity material and thereafter to the coolant.

In this way, the unit module solves the following significant problems: most of the incident concentrated radiation on the photovoltaic cells of the receivers of large-scale solar radiation-based power generation systems is not converted into electricity but appears as heat, which generally substantially reduces their efficiency by increasing the operating temperature of the photovoltaic cells.

In particular, the applicant has found that the above-described unit modules make it possible to extract enough heat generated by incident concentrated solar radiation such that the temperature difference between the inlet coolant temperature and the front of the photovoltaic cells is less than 40 ℃, typically less than 30 ℃, more typically less than 25 ℃, and in recent test operations less than 20 ℃, and that this result can be achieved with a low pressure drop of the coolant across the coolant inlet and coolant outlet of the unit module, typically less than 100kPa, typically less than 60kPa, more typically less than 40 kPa. The low pressure drop is an important consideration as it means that it is possible to minimize the energy requirements for circulating the coolant through the module.

In a particular set of test operations, the applicant found that the above-described cell module was operable to maintain a temperature differential of 20.5 ℃ between the inlet coolant temperature and the front of the photovoltaic cell, and under these operating conditions, per cm²Heat of 30W of the exposed surface area of the cell was removed from the above cell module per cm²Electricity of 8.1W exposed cell surface area was generated by the module and, per cm²Heat from the exposed surface area 6W of the cell is reflected by the module as infrared radiation. Coolant flow path of module 23 forms coolantPart of a circuit. In general, the unit is such that each cm is incident and processed thereon²The total exposed surface area of the cell was 44.1W of power (in the form of heat, electricity, and infrared radiation). Typically, this level of energy density will produce temperatures of at least 600 ℃, and the unit will fail at these temperatures.

In addition, the applicant has found that the above-described unit modules can be manufactured relatively inexpensively and with consistent performance.

Preferably, the heat extraction element is located entirely behind, and does not extend laterally beyond, the exposed surface area of the photovoltaic cell or cells.

Preferably, the coolant member comprises beads, rods, bars or balls of a high thermal conductivity material thermally bonded together by sintering the beads, rods, bars or balls together. One advantage of sintering better than some other options for joining beads, rods or balls together is that there is direct contact between the beads, rods or balls, which optimizes heat transfer between the beads, rods or balls.

Preferably, the surface area for heat transfer provided by the beads, rods, bars or balls of high thermal conductivity material is at least 5 times, more preferably at least 10 times, the front surface area of the block of beads, rods, bars or balls of high thermal conductivity material in direct contact with the substrate. The coolant member is therefore a particularly effective heat transfer member.

Preferably, the coolant member at least substantially occupies the volume of the coolant chamber.

Preferably, the coolant inlet is located at one side wall of the housing or at the base of the housing adjacent that side wall, and the coolant outlet is located at the opposite side wall or at the base adjacent that side wall.

With this arrangement, preferably the coolant member is shaped such that the coolant chamber comprises a manifold (manifold) extending along said inlet side wall in fluid communication with the coolant inlet and a manifold extending along said outlet side wall in fluid communication with the coolant outlet. Applicants have found in testing work that this arrangement of inlet and outlet manifolds ensures that the pressure drop experienced via any flow path parallel to the plane of the photovoltaic cell or cells is substantially equal to facilitate uniform cooling throughout the entire area of the heat sink. This is a significant problem where the heat extraction component is located entirely behind and does not extend laterally beyond the exposed surface area of the photovoltaic cell or cells. Uniform cooling is not an issue where the heat sink extends laterally beyond the device being cooled.

Preferably, the housing includes a weir (weir) extending upwardly from the base within the inlet sidewall and defining a barrier to coolant flow from the coolant inlet through the coolant chamber.

Preferably, the housing includes a weir extending upwardly from the base within the outlet sidewall and defining a barrier to coolant flow from the coolant chamber to the coolant outlet.

Applicants have found in testing work that the weir improves the distribution of coolant through the coolant chamber, thereby minimizing temperature variations within the chamber and increasing the overall thermal conductivity of the heat extraction assembly. In particular, the weir on the inlet side causes the coolant to flow, preferably from the inlet side away from the substrate and towards the plane of the photovoltaic cell or cells and thereafter parallel to the cell/cells towards the weir on the outlet side. A weir on the outlet side preferably directs the flow of heated coolant away from the unit/units toward the base and away from the housing. The net result is that the weir concentrates the coolant flow in the upper portion of the coolant chamber where the greatest high level of heat extraction is required.

Preferably, the beads, rods, bars or balls of high thermal conductivity material have a major dimension of 0.8-2.0 mm.

More preferably, the beads, rods, bars or balls of high thermal conductivity material have a major dimension of 0.8-1.4 mm.

The test work carried out by the applicant was based on the use of a cylindrical rod of diameter 1.2mm and length 1.3 mm. These rods were formed by cutting wires having a diameter of 1.2 mm.

Preferably, the packing density of the beads, rods, bars or balls of high thermal conductivity material decreases with increasing distance from the substrate. This feature facilitates heat transfer away from the photovoltaic cell or cells.

Preferably, the coolant flow passage occupies between 20% and 30% of the volume of the coolant component.

It should be noted that in any given case, a balance needs to be struck between the volume occupied by the beads, rods, bars or balls of high thermal conductivity material (i.e. the heat sink capacity of the coolant member), the amount of surface area provided by the beads, rods, bars or balls for heat transfer (i.e. the capacity of the coolant member to transfer heat to the coolant), and the void space available for coolant to flow through the coolant member (i.e. the volume of the coolant member through which coolant is allowed to flow). The volume and surface area and void space of the beads, rods, bars or balls are interrelated and can have a competitive effect on each other, which needs to be taken into account for different situations when designing the coolant component for a given situation.

Preferably, the coolant member acts as a heat sink.

The coolant member may be formed of any suitable high thermal conductivity material.

Preferably, the high thermal conductivity material is copper or a copper alloy.

Preferably, the copper or copper alloy is resistant to corrosion and/or erosion by the coolant.

Preferably, the cell module comprises a substrate on which the photovoltaic cell or cells are mounted and the housing is mounted to the substrate.

Preferably, the substrate is formed from or comprises one or more layers of an electrical insulator material.

Preferably, the substrate is formed from a material having a high thermal conductivity.

One suitable material for the substrate is aluminum nitride. Such ceramic materials are electrical insulators and have a high thermal conductivity.

Preferably, the substrate comprises a metallised layer disposed between the photovoltaic cell or cells and the electrical insulator layer or layers.

Preferably, the substrate comprises a metallised layer interposed between the electrical insulator layer or layers and the coolant means.

According to the present invention, there is provided a method of manufacturing the above photovoltaic cell module, the method comprising:

(a) forming the coolant component by: providing a predetermined mass of a plurality of beads, rods, bars or balls of a high thermal conductivity material into a mold of a predetermined shape, thereafter heating the beads, rods, bars or balls of a high thermal conductivity material and sintering the beads, rods, bars or balls together to form a coolant component;

(b) placing a coolant component in the housing; and

(c) a photovoltaic unit or a plurality of photovoltaic units is mounted to the housing.

According to the present invention, there is provided a method of manufacturing the above photovoltaic cell module, the method comprising:

(a) forming the coolant component by: providing a predetermined mass of a plurality of beads, rods, bars or balls of a high thermal conductivity material into the housing, thereafter heating the beads, rods, bars or balls of a high thermal conductivity material and sintering the beads, rods, bars or balls together to form a coolant component within the housing; and

(b) the photovoltaic cell or cells are mounted to the housing, for example, by soldering or sintering the substrate to the housing.

Preferably, the above method comprises: grinding the surface of the coolant member forming a contact surface with the substrate to increase the surface area of contact between the beads, rods, bars or balls of high thermal conductivity material and the substrate.

According to the present invention, there is provided a method of manufacturing the above photovoltaic cell module, the method comprising forming the coolant member by: providing a predetermined mass of a plurality of beads, rods, bars or balls of a high thermal conductivity material into the housing and placing a substrate on the housing, thereafter heating the beads, rods, bars or balls of a high thermal conductivity material and sintering the beads, rods, bars or balls together to form a coolant component within the housing and bonding the coolant component to the housing and substrate. One advantage of this method is that there is a better heat-conducting connection between the base plate and the coolant part than is achieved with a soldered connection.

According to the present invention there is also provided a system for generating electricity from solar radiation, the system comprising:

(a) a receiver comprising a plurality of photovoltaic cells for converting solar energy into electrical energy, and circuitry for transferring the electrical energy output of the photovoltaic cells; and

(b) means for concentrating solar radiation onto the receiver; and is

The system is characterized in that the receiver comprises: a plurality of the photovoltaic cell modules described above, an electrical circuit comprising the photovoltaic cells of each of the cell modules, and a coolant circuit comprising the heat extraction assembly of each of the modules.

Preferably, the coolant, when in use, maintains the photovoltaic cells at a temperature not exceeding 80 ℃.

More preferably, the coolant, when in use, maintains the photovoltaic cells at a temperature not exceeding 70 ℃.

It is particularly preferred that the coolant, when in use, maintains the photovoltaic cells at a temperature not exceeding 60 ℃.

More particularly preferably, the coolant maintains the photovoltaic cells at a temperature not exceeding 40 ℃ when in use.

Preferably, the receiver comprises a frame supporting the modules in an array of modules.

Preferably, the support frame supports the modules such that the photovoltaic cells form an at least substantially continuous surface exposed to the reflected concentrated solar radiation.

The surface may be flat, curved or stepped in a fresnel fashion.

Preferably, the support frame includes a coolant flow path that supplies coolant to a coolant inlet of the module and removes coolant from a coolant outlet of the module.

Preferably, the coolant is water.

Preferably, the water inlet temperature is as cold as reasonably available.

Typically, the water inlet temperature is in the range of 10-30 ℃.

Typically, the water outlet temperature is in the range of 20-40 ℃.

Preferably, said means for concentrating solar radiation onto the receiver is a dish reflector (dish reflector) comprising an array of mirrors for reflecting solar radiation incident on the mirrors towards the photovoltaic cells.

Preferably, the surface area of the specular surface of the dish reflector exposed to solar radiation is substantially greater than the surface area of the photovoltaic cell exposed to reflected solar radiation.

Drawings

The invention will be further described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a preferred embodiment of a system for generating electricity from solar radiation according to the present invention;

FIG. 2 is a front view of a receiver of the system shown in FIG. 1, illustrating an exposed surface area of a photovoltaic cell of the receiver;

FIG. 3 is a perspective view, partially in section, of the receiver with elements removed to more clearly show the coolant circuit forming part of the receiver;

FIG. 4 is an exploded perspective view of one embodiment of a photovoltaic cell module forming the receiver portion according to the present invention;

FIG. 5 is a plan view of a housing of the unit module shown in FIG. 4;

FIG. 6 is a cross-section along line 5-5 of FIG. 5;

FIG. 7 is a perspective view of another embodiment of a housing of a photovoltaic cell module according to the present invention;

FIG. 8 is a top view of the housing shown in FIG. 7; and

fig. 9 is a top view of another embodiment of a housing of a photovoltaic cell module according to the present invention.

Detailed Description

The solar radiation based power generation system shown in fig. 1 comprises a parabolic array of mirrors 3 which reflect solar radiation incident on the mirrors towards a plurality of photovoltaic cells 5.

The unit 5 forms part of a solar radiation receiver, generally identified by the numeral 7.

The general arrangement of the receiver 7 is shown in figures 2 and 3.

Figures 1 to 3 are the same as figures 1 to 3 of international application PCT/AU02/00402 and the disclosure in that international application is incorporated herein by cross-reference.

The surface area of mirror 3 exposed to solar radiation is substantially greater than the surface area of photovoltaic cell 5 exposed to reflected solar radiation.

The photovoltaic unit 5 converts the reflected solar radiation into DC electrical energy.

The receiver 7 includes circuitry (not shown) for the electrical energy output of the photovoltaic cells.

Mirror 3 is mounted to frame 9. The mirror and the frame define a dish reflector.

A series of arms 11 extend from the frame 9 to the receiver 7 and position the receiver as shown in figure 1.

The system further comprises:

(a) a support assembly 13 supporting the dish reflector and receiver relative to the ground and for tracking the movement of the sun; and

(b) a tracking system (not shown) that moves the dish reflector and receiver as needed to track the sun.

The receiver 7 also comprises a coolant circuit. The coolant loop cools the photovoltaic units 5 of the receiver 7 with a coolant, preferably water, in order to minimize the operating temperature and maximize the performance (including the operating life) of the photovoltaic units 5.

The receiver 7 is tailored to include the coolant circuit.

Fig. 2 and 3 show the elements of the receiver in relation to the coolant circuit. It should be noted that for the sake of clarity many other elements of the receiver 7, such as elements constituting the circuitry of the receiver 7, are not included in the figure.

Referring to fig. 2 and 3, the receptacle 7 comprises a substantially box-like structure defined by an assembly of hollow columns 15.

The receiver 7 also comprises a solar flux modulator, generally indicated by the numeral 19, which extends from a lower wall 99 (as seen in figure 3) of the box-like structure. The solar flux modulator 19 comprises four panels 21 extending from the lower wall 99 and converging towards each other. Solar flux modulator 19 also includes a mirror 91 mounted to the inwardly facing side of panel 21.

Receiver 7 also includes an array of 1536 closely packed rectangular photovoltaic cells 5 mounted to 64 square modules 23. The array of cells 5 is best seen in fig. 2. The term "tightly packed" means that the exposed surface area of the photovoltaic cells 5 constitutes 98% of the total exposed area of the array. Each module comprises 24 photovoltaic cells 5. The photovoltaic cells 5 are mounted on each module 23 such that the exposed surface of the array is a continuous surface. It should be noted that the heat extraction assembly 71 described below makes it possible to provide such a tightly packed receiver with up to 100% of the photovoltaic cells 5.

The module 23 is mounted to the lower wall 99 of the box-like structure of the receiver 7 so that the exposed surface area of the combined array of photovoltaic cells 5 is a continuous plane.

As described in more detail below, each module 23 includes a coolant flow path. The coolant flow path is an integral part of each module 23. The coolant flow path allows coolant to be in thermal contact with the photovoltaic cell 5 and to draw heat from the cell 5 so that the front of the cell 5 is maintained at a temperature of no more than 80 ℃, preferably no more than 60 ℃, more preferably no more than 40 ℃.

As noted above, in certain test runs, applicants have found that the above-described cell module is operable to maintain a 20.5 deg.C temperature difference between the inlet coolant temperature and the front of the photovoltaic cell, andand, under these working conditions, per cm²Heat of 30W of the unit exposed surface area was removed from the unit module per cm²Electricity of 8.1W exposed cell surface area was generated by the module and per cm²The heat of the unit exposed surface area 6W is reflected by the module as infrared radiation. The coolant flow paths of the modules 23 form part of the coolant circuit. In general, the unit is such that each cm is incident and processed thereon²The total exposed surface area of the cell was 44.1W of power (in the form of heat, electricity, and infrared radiation). Typically, this level of energy density will produce temperatures of at least 600 ℃, and the unit will fail at these temperatures.

The coolant circuit also comprises the above-mentioned hollow column 15.

Furthermore, the coolant circuit comprises a series of parallel coolant channels 17, which form part of the lower wall 99 of the box-like structure. As shown in fig. 3, both ends of the passage 17 are connected to the pair of lower horizontal posts 15, which are opposite, respectively. The lower column 15 defines an upstream header that distributes coolant to the channels 17 and a downstream header that collects coolant from the channels 17. The module 23 is mounted to the lower surface of the channel 17 and is in fluid communication with the channel such that coolant flows through the channel 17 and through the coolant flow passages of the module 23 and back into the channel 17, thereby cooling the photovoltaic cells 5.

The coolant circuit also includes a coolant inlet 61 and a coolant outlet 63. The inlet 61 and the outlet 63 are located in the upper wall of the box-like structure. As shown in fig. 3, the inlet 61 is connected to the adjacent upper horizontal column 15, and the outlet 63 is connected to the adjacent upper horizontal column 15.

In use, coolant supplied from a source (not shown) flows through the inlet 61 into the upper horizontal column 15 connected to the inlet 61 and then flows along the vertical column 15 connected to the upper horizontal column 15. The coolant then flows into the upstream lower header 15 and, as described above, along the coolant flow paths of the channels 17 and modules 23 and into the downstream lower header 15. The coolant then flows upwardly through the vertical column 15 connected to the downstream lower header 15 and into the upper horizontal column 15. The coolant is then discharged from the receiver 17 through the outlet 63.

Fig. 4 to 6 illustrate the basic configuration of one embodiment of each module 23.

As described above, each module 23 includes an array of 24 closely packed photovoltaic cells 5.

Each module 23 comprises a base plate on which the units 5 are mounted, generally identified by the numeral 27. The substrate comprises a central layer (not shown) of ceramic material and an outer metallised layer (not shown) on the opposite face of the layer of ceramic material.

Each module 23 also includes a glass cover 37 mounted on the exposed surface of the array of photovoltaic cells 5. The glass cover 37 may be formed to optimize the transmission of useful wavelengths of solar radiation and to minimize the transmission of unwanted wavelengths of solar radiation.

Each module 23 also includes an assembly 71 that facilitates heat extraction from the photovoltaic cells 5. The assembly 71 is formed of a high thermal conductivity material. The preferred material is copper.

The module 71 is located entirely behind the exposed surface of the photovoltaic unit 5 and therefore has a smaller cross-sectional area than it.

The assembly 71 includes a housing 79 and a coolant component 35 located within the housing.

The housing 79 includes a base 85 and sidewalls 87 extending from the base. The base plate 27 is mounted on the housing 79 such that the base 85, side walls 87 and base plate 27 define a coolant chamber.

The housing 79 further includes an inlet 91 for supplying coolant, such as water, into the coolant chamber and an outlet 93 for discharging coolant from the chamber. The inlet 91 is in the form of a circular hole in the base 85 at one corner of the housing 79. The outlets 93 are in the form of circular holes in the base 85 at diametrically opposite corners of the housing 79.

The coolant member 35 is shaped so as to substantially occupy the volume of the coolant chamber. The upper surface 75 of the coolant member is formed as a flat surface and contacts the substrate 27.

The coolant member 35 comprises a plurality of beads, rods, bars or balls of a high thermal conductivity material that are sintered and thereby thermally connected together and form a porous block having a large surface area and a large volume for heat transfer. The beads, rods or balls form a substantial number of continuous heat transfer paths extending through the coolant member 35. The block of beads, rods or balls is a porous rather than a solid block and there are spaces between the sintered beads, rods or balls. These spaces define a substantial number, typically at least 1000, of continuous coolant flow passages extending through the coolant member 35. In general, the coolant member 35 takes the form of a labyrinth defined by sintered beads, rods, bars or balls and coolant flow passages in the spaces between the sintered beads, rods, bars or balls.

The arrangement is such that, in use, coolant supplied under pressure through the coolant inlet 91 flows through the said basic number of coolant flow passages in the coolant member 35 and is discharged from the coolant chamber through the coolant outlet 93. This arrangement is such that the substantial number of heat transfer paths conduct heat away from the front of the unit 5 and the heat conducted through the paths is transferred to the coolant flowing through the substantial number of coolant flow passages.

In any given case, factors such as the shape and size of the beads, rods or balls, the packing density of the beads, rods or balls, the volume occupied by the beads, rods or balls, the heat transfer characteristics of the heat transfer paths formed by the sintered beads, rods or balls, and the volumetric flow rate of the coolant through the coolant flow passages are selected with a view to achieving a target extraction rate of heat from the modules 23.

The opposite end walls 95 of the coolant member 35 adjacent the coolant inlet 91 and the coolant outlet 93 are tapered downwardly such that the end walls 95, the base 85, and the side walls 87 define inlet and outlet manifolds 45 that are in fluid communication with the coolant inlet and outlet and extend along the side walls 87 so that coolant can be supplied to and received from the entirety of the side walls 95 of the coolant member 35.

Each module 23 also comprises electrical connections (not shown) which form part of the electrical circuit of the receiver 7 and which electrically connect the photovoltaic cells 5 into said electrical circuit. The electrical connection is provided extending from the outer metallization layer of the substrate 27 and through one of two hollow sleeves 83 extending from a base 85 of the housing 79.

As is apparent from the above, the coolant inlet 91, the coolant manifold 45, the coolant flow passages in the coolant member 35, and the coolant outlet 93 define the coolant flow path of each module 23.

As described above, the configuration of coolant member 35 makes it possible to achieve a high level of heat transfer, which is required to maintain photovoltaic unit 5 at a temperature not exceeding 60 ℃, and to accommodate the substantially different thermal expansions of coolant member 35 and substrate 27 that would otherwise cause structural failure of module 23.

The embodiment of the module 23 shown in fig. 7 and 8 is the basic construction shown in fig. 4 to 6, and like reference numerals are used to describe like parts.

In addition, the module 23 includes two ridges 101 that extend from the base 85 within and parallel to the inlet and outlet manifolds 45. The ridges 101 form a barrier or weir to the flow of coolant to and from the inlet and outlet manifolds 45. In summary, the ridges 101 improve the distribution of coolant through the coolant chamber and thereby minimize temperature variations within the chamber and increase the overall thermal conductivity of the heat extraction assembly 71. More specifically, the coolant is forced to flow through the inlet ridges 101 to flow through the lower coolant flow passages within the coolant member 35, and then through the outlet ridges 101 to flow from the lower coolant flow passages into the outlet manifold 45. Thus, the ridges 101 increase the coolant path length through the lower coolant flow passage as compared to the coolant path length through the upper coolant flow passage. The ridges 101 promote greater coolant flow through the upper flow passage and this is an advantage in optimizing heat transfer from the coolant member 35.

The embodiment of the module 23 shown in fig. 9 is the basic configuration shown in fig. 7 and 8, and like reference numerals are used to describe like parts. The main difference between the embodiments is that the inlet 91 and the outlet 93 take the form of a slit instead of a circular opening. In certain circumstances, the use of slots has been found to be beneficial in improving the distribution of coolant through the coolant chamber.

There are many options for manufacturing the module 23 shown in the figures.

One option includes separately forming the coolant member 35, thereafter disposing the coolant member in the housing 79, and thereafter disposing the substrate 27 on the housing/coolant member. In this option, the coolant component may be formed by forming in a suitable mould and comprises sintering together a mass of high thermal conductivity beads, rods, bars or balls. Also, in this option, the substrate 27 may be welded to the exposed edges of the side walls 87 of the housing 79 and the exposed front face of the coolant member 35.

Another option includes placing a large number of beads, rods, bars or balls of high thermal conductivity material directly within the housing 79 and sintering these materials in situ within the housing, and thereafter sintering the base plate 27 to the assembly of the housing 79 and the coolant component 35.

Many modifications may be made to the preferred embodiment described above, while remaining within the spirit and scope of the invention.

For example, while the preferred embodiment includes 1536 photovoltaic cells 5 mounted to 64 modules 23 in 24 units per module, the invention is not so limited and extends to any suitable number and size of photovoltaic cells and modules.

By way of further example, although the photovoltaic cells are mounted such that the exposed surface of the array of cells is a flat surface, the invention is not so limited and extends to any suitably shaped surface, such as curved or stepped surfaces.

By way of further example, although the preferred embodiment includes a receiver coolant loop forming part of the receiver support frame, the invention is not so limited and extends to arrangements in which the coolant loop is not part of the receiver structural frame.

By way of further example, although the preferred embodiment includes dish reflectors in the form of an array of parabolic arrays of mirrored surfaces 3, the invention is not so limited and extends to any suitable means of concentrating solar radiation onto a receiver. One such suitable device is a series of heliostats (heliostats) arranged to concentrate solar radiation onto a receiver.

By way of further example, although the preferred embodiment of the receiver is constructed from extruded elements, the invention is not so limited and the receiver is manufactured by any suitable means.

By way of further example, although the preferred embodiment of the coolant member 35 comprises a plurality of beads, rods, bars or balls of high thermal conductivity material that are sintered and thereby in thermal contact, the invention is not so limited and the beads, rods, bars or balls may be thermally connected together in any suitable manner. Other options include ultrasonic welding, resistance welding, and plasma treatment.

By way of further example, although the preferred embodiments are described in the context of extracting heat from an array of photovoltaic cells contacted by concentrated solar radiation, the invention is not so limited and extends to extracting heat originating from any intense source of radiation.

Claims (22)

1. A photovoltaic cell module for a solar radiation based power generation system, the module comprising:

(a) one or more than one photovoltaic cell having an exposed surface for solar radiation;

(b) an electrical connection for transferring the electrical energy output of the photovoltaic cell or cells to an output circuit, an

(c) An assembly for extracting heat from the photovoltaic cell or cells, the assembly comprising (i) a housing disposed behind and in thermal contact with an exposed surface of the photovoltaic cell or cells, the housing comprising a base and a plurality of side walls extending from the base, wherein the base, side walls and photovoltaic cell or cells define a coolant chamber and the housing comprises an inlet for supplying coolant into the chamber and an outlet for exhausting coolant from the chamber, and (ii) a coolant member located in the coolant chamber in heat transfer relationship with the photovoltaic cell or cells, the coolant member comprising a plurality of beads, rods, bars or spheres of high thermal conductivity material in thermal contact and having a large surface area for heat transfer and defining a three-dimensional labyrinth, the labyrinth conducts heat away from the photovoltaic cell or cells therethrough via a substantial number of heat transfer paths formed by thermally connected beads, rods, bars or balls, and has a substantial number of coolant flow passages for coolant provided to and flowing through the coolant chamber through the inlet and discharged from the coolant chamber through the outlet when the module is in use.

2. The cell module defined in claim 1 wherein the heat extraction element is located entirely behind, and does not extend laterally beyond, the exposed surface area of the photovoltaic cell or cells.

3. The cell module defined in claim 1 or claim 2 wherein the surface area for heat transfer provided by the beads, bars, rods or balls of high thermal conductivity material is at least 5 times the front surface area of the block of beads, bars, rods or balls of high thermal conductivity material in direct contact with the substrate.

4. The cell module defined in claim 1 wherein the coolant member at least substantially occupies the volume of the coolant chamber.

5. The cell module defined in claim 1 wherein the coolant inlet is located at one side wall of the housing or at the base of the housing adjacent that side wall and the coolant outlet is located at the opposite side wall or at the base adjacent that side wall.

6. The cell module defined in claim 5 wherein the coolant member is shaped so that the coolant chamber includes a manifold extending along the inlet side wall in fluid communication with the coolant inlet and a manifold extending along the outlet side wall in fluid communication with the coolant outlet.

7. A unit module as claimed in claim 5 or claim 6 in which the housing includes a weir extending upwardly from the base within the inlet side wall and defining a barrier to the flow of coolant from the coolant inlet through the coolant chamber.

8. The cell module defined in claim 5 wherein the housing includes a weir that extends upwardly from the base within the outlet side wall and defines a barrier to the flow of coolant from the coolant chamber to the coolant outlet.

9. The cell module defined in claim 1 wherein the beads, rods, bars or balls of high thermal conductivity material have a major dimension of 0.8-2.0 mm.

10. The cell module defined in claim 1 wherein the beads, rods, bars or balls of high thermal conductivity material have a major dimension of 0.8-1.4 mm.

11. The unit module as set forth in claim 1, wherein the packing density of the beads, rods, bars or balls of the high thermal conductivity material is decreased as the distance from the substrate is increased.

12. The cell module defined in claim 1 wherein the coolant flow passages occupy between 20% and 30% of the volume of the coolant component.

13. The cell module defined in claim 1 includes a substrate on which the photovoltaic cell or cells are mounted and to which the housing is mounted.

14. The cell module defined in claim 13 wherein the substrate is formed from or includes one or more layers of electrical insulator material.

15. The cell module defined in claim 13 or claim 14 wherein the substrate is formed from a material having a high thermal conductivity.

16. The cell module defined in claim 14 wherein the substrate comprises a metallised layer interposed between the photovoltaic cell or cells and the electrical insulator layer or layers.

17. A unit module as claimed in claim 14 or claim 16 wherein the substrate comprises a metallised layer interposed between the electrical insulator layer or layers and the coolant means.

18. A method of manufacturing the photovoltaic cell module defined in claim 1, the method comprising:

(a) forming a coolant component by: providing a predetermined mass of a plurality of beads, rods, bars or balls of a high thermal conductivity material into a predetermined shaped mold and thereafter heating and sintering the beads, rods, bars or balls of the high thermal conductivity material together to form a coolant component;

(b) placing a coolant component in the housing; and

(c) a photovoltaic unit or a plurality of photovoltaic units is mounted to the housing.

19. A method of manufacturing the photovoltaic cell module defined in claim 1, the method comprising:

(a) forming a coolant component by: providing a predetermined mass of a plurality of beads, rods, bars or balls of a high thermal conductivity material into a housing and thereafter heating and sintering the beads, rods, bars or balls of the high thermal conductivity material together to form a coolant component within the housing; and

(b) the photovoltaic cell or cells are mounted to the housing, for example, by soldering or sintering the substrate to the housing.

20. A method as claimed in claim 18 or claim 19, comprising abrading the surface of the coolant member forming the contact surface with the substrate to increase the surface area of contact between the beads, rods, bars or balls of high thermal conductivity material and the substrate.

21. A method of manufacturing the photovoltaic cell module defined in claim 1, comprising forming the coolant member by: providing a predetermined mass of a plurality of beads, rods, bars or balls of a high thermal conductivity material into a housing and placing a substrate over the housing, and then heating and sintering the beads, rods, bars or balls of the high thermal conductivity material together to form a coolant component within the housing and bonding the coolant component to the housing and the substrate.

22. A system for generating electricity from solar radiation, the system comprising:

(a) a receiver comprising a plurality of photovoltaic cells for converting solar energy to electrical energy and circuitry for transferring the electrical energy output of the photovoltaic cells; and

(b) means for concentrating solar radiation onto the receiver; and is

The system is characterized in that the receiver comprises: a plurality of the photovoltaic cell modules of claim 1; a circuit including the photovoltaic cells of each module; and a coolant loop including the heat extraction assembly of each module.