WO2020188587A1

WO2020188587A1 - A capital efficient concentrated photo-voltaic flexible hybrid system

Info

Publication number: WO2020188587A1
Application number: PCT/IN2020/050194
Authority: WO
Inventors: Mahesh Lakshminarayanan; Pardeep GARG; Prashant Kumar
Original assignee: Suncept Tech Private Limited
Priority date: 2019-03-19
Filing date: 2020-03-03
Publication date: 2020-09-24

Abstract

The embodiments herein provide a cost-effective, compact and scalable solar energy-based hybrid system for electricity generation. The system comprises a concentrator and a receiver. The concentrator receives radiation from sun and concentrate radiation onto the receiver. The receiver has at least one surface to receive concentrated radiation from the concentrator. A particular area of receiver is directed towards the solar radiation from the concentrator. A photo-voltaic element within receiver forms the particular area wherein radiation is concentrated. The photovoltaic element comprises several unit cells moduled in the receiver in a particular manner to realise flexibility for achieving higher operational currents or higher voltages while operating at a particular power level. The system uses active as well as passive cooling mechanisms in a combinational way to constrain cold water requirement and in turn hot water generation.

Description

A CAPITAL EFFICIENT CONCENTRATED PHOTO- VOLTAIC FLEXIBLE

HYBRID SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The embodiments herein claim the priority of the Indian Non-Provisional Patent Application (NPA) fded on March 19, 2019 with the serial number 201941010724 with the title,“A CAPITAL EFFICIENT CONCENTRATED PHOTO-VOLTAIC FLEXIBLE HYBRID SYSTEM”, and the contents of which are included in entirety as reference herein.

BACKGROUND

Technical Field

[0002] The embodiments herein are generally related to the field of solar energy. The embodiments herein are particularly related to solar energy based hybrid systems. The embodiments herein are more particularly related to concentrated solar energy based systems capable of generating either electricity or a combination of electricity and hot water in a hybrid manner. The embodiments herein are especially related to methods and systems for achieving flexibility in terms of interconnection possibilities among solar cells for achieving either higher voltage or higher current.

Description of the Related Art

[0003] With ever increasing population all over the world, a demand for energy requirements/consumption also increases heavily. The rapid increase in consumption of energy results in exhaustion of fossil fuels available on earth and endangers the accustomed climate through carbon dioxide released by burning these fuels. Thus, the use of fossil fuels needs to be replaced with a more sustainable and less destructive source of energy. The earth receives energy from the sun at several orders of magnitude of than needed for use by mankind’s current energy usage. Thus, solar energy is a sustainable source of energy for use in place of fossil fuels. The expense and inefficiency of current methods in capturing solar energy limits the ability of solar energy in replacing fossil fuels.

[0004] The photovoltaic (PV) cells used in conventional systems are quite expensive and constitute more than 50% of the total system cost. The concentration of direct normal irradiance (DNI) on the reduced area of PV cells possesses potential to lower the cost of associated PV cells and if the balance of system is inexpensive, there lies the potential of reducing the cost of electricity generation. This, however, results in overheating of cells which in turn causes the conversion efficiency of PV cells to decline. In order to overcome the issue of overheating of cells several cooling mechanisms are suggested in the art.

[0005] The conventional PV cells available in the market are typically above 100 cm2 in footprint area. Concentrating solar radiation on PV cells magnifies the current generation by a factor equal to concentration ratio. Overall economic optimizations suggest using concentration ratios above 10. At these concentration ratios, the magnitude of current generation could be significantly higher and fingers printed on such solar cells may not be adequately designed to carry such high currents. Further, the current flow path in the fingers of these conventional cells are quite significant (of the order of 10 cm) which results in significant resistive losses and cell efficiency upon concentration drops significantly.

[0006] Increase in finger density in such conventional cells when used for concentration applications can help in reducing the finger resistance. This helps in improving efficiency of these cells for concentration applications. However, finger densities typically practiced in these conventional cells result in ~5% radiation shading losses. Desired finger densities at concentration ratio of around 10 results in shading losses as high as 20%. This is a significant loss in radiation input to the solar cell and hence is not a feasible solution from economic optimization point of view. [0007] Upon concentration, critical parameter causing efficiency loss is high current flow path in these fingers before the current is evacuated to back side of the cell using external busbars. Any attempts made in the direction of reducing the current flow path will help arrest resistive losses and efficiency loss arising due to concentration can be minimized. One way of achieving the shorter current flow paths is to use small solar cells (< 5 cm²) and integrate them to form a solar receiver of required size.

[0008] Using small cells (< 5 cm²) offers one more advantage. The absolute amount of current generation can be minimized when all these small cells are used in series mode. Operation in series mode offer higher voltage which is desirable from the point of view of power evacuation for final end use. This not only makes handling higher amounts of power easier but also makes the power evacuation system more efficient. However, handling such small cells is cumbersome process from the point of view of establishing inter-cell connections and moduling. This results in significant cell wastage defeating the purpose of bringing the cost of electricity generation down.

[0009] One potential solution is to integrate these small cells on a thin and transparent substrate including but not limited to glue, tape or polymers such as but not limited to ethylene vinyl acetate (EVA). The common substrate is provided/moduled on the side facing solar radiation. This common substrate provides an ease in establishing inter-cell connections.

[0010] Another possible solution is to integrate these small cells on a removable substrate including but not limited to glue, tape or polymers such as but not limited to ethylene vinyl acetate (EVA). The common substrate is provided/moduled on the side facing solar radiation. This common substrate provides an ease in establishing inter-cell connections. Post establishment of inter-cell connections, this common substrate is removed. Another possible solution is to start with an integrated / pre-fabricated solar cell wafer on which unit cells of smaller size (< 5 cm²) are provided. These small unit cells are provided in such a way that while they are physically pre-integrated on the base cell material but electrically isolated. Yet another possibility is to immobilize the unit cells on a solar glass using a near-transparent or tape or polymers such as but not limited to ethylene vinyl acetate (EVA) before establishing interconnections among these unit cells. The obtained substrate post establishment of the interconnections is bonded to a heat sink for providing cooling to the unit cells.

[0011] Cooling is accomplished by flowing suitable cooling media such as water in the heat sink that gets activated intermittently or continuously based on temperature. The cooling media in turn gets heated up which caters to multiple applications such as water purification, power generation, cogeneration and direct utility as hot water.

[0012] Hence, there is a need for a cost-effective, less area intensive and scalable solar energy based system capable of generating both electricity with or without hot water in a flexible manner. There is also a need for a solar energy-based system that uses active as well as passive cooling mechanisms in a combinational way to constrain cold water requirement and in turn hot water generation. Further, there is a need for a solar energy-based system wherein the cooling media operates in open or closed loops. Further, there is a need for designing a cost-effective concentration-based solar energy system which is able to dissipate surplus heat to the ambience without involving any cooling liquid such as water.

[0013] The above-mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

OBJECTS OF THE EMBODIMENTS HEREIN

[0014] The primary object of the embodiments herein is to provide a cost-effective, compact, and scalable solar energy based system and method for electricity generation.

[0015] The primary object of the embodiments herein is to provide a cost-effective, compact, and scalable solar energy based system and method capable of generating both electricity and hot water in a hybrid manner. [0016] Another object of the embodiments herein is to provide a solar energy based system and method that uses a concentrator for reducing the requirement of photo-voltaic cells (PV cells) by concentrating solar radiation on PV cells.

[0017] Yet another object of the embodiments herein is to provide a solar energy based system and method that uses a concentrator built in a cost effective way along with a tracker to maximize energy input the system such as but not limited to parabolic reflector built with linear mirror strips powered by a single axis tracker.

[0018] Yet another object of the embodiments herein is to provide a solar energy based system and method that uses unit cells with each unit cell being smaller than 5 cm² for minimizing current flow path and facilitating a quick evacuation of the current to external busbar from current carrying fingers on the unit cells.

[0019] Yet another object of the embodiments herein is to provide a solar energy based system and method that immobilizes these unit cells on a substrate before establishing interconnections among the unit cells in order to minimize wastage occurred during establishing these interconnections otherwise.

[0020] Yet another object of the embodiments herein is to provide a solar energy based system and method that uses a thin, a transparent and a common substrate including but not limited to glue, tape or polymers such as but not limited to ethylene vinyl acetate (EVA) provided on the side facing solar radiation.

[0021] Yet another object of the embodiments herein is to provide a solar energy based system and method that uses a common removable substrate including but not limited to metal/tape provided on the side facing solar radiation.

[0022] Yet another object of the embodiments herein is to provide a solar energy based system and method that firstly fixes the sun facing side of unit cells on a near-transparent glass using adhesives such as but not limited to glue, tape and polymers such as but not limited to ethylene vinyl acetate (EVA) and secondly fixes the other side of unit cells to a heat sink for providing a cooling mechanism, after establishing electrical interconnections amongst the unit cells.

[0023] Yet another object of the embodiments herein is to provide a solar energy based system and method that addresses the problem of overheating of cells due to the concentration of direct normal irradiance (DNI) on the reduced area of PV cells which causes the conversion efficiency of the PV cells to decline.

[0024] Yet another object of the embodiments herein is to provide a solar energy based system and method that ensures uniformity in radiation received across the cell surface through use of planar reflecting or refracting surfaces of variable widths.

[0025] Yet another object of the embodiments herein is to provide a solar energy based system and method that uses water as a cooling media operated in an open loop.

[0026] These and other objects and advantages of the embodiments herein will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY

[0027] The various embodiments herein provide a concentrated photovoltaic system. The system comprises a concentrator and a receiver. The concentrator comprises a group of reflecting or refracting planar surfaces of differing dimensions forming a near parabolic geometry for achieving near uniform radiation and confining focused radiation to a particular part of the receiver. The receiver comprises a photovoltaic element and a heat sink. While the photo-voltaic element is configured for generating electricity, the heat sink is configured for removing excess heat of the radiation. The photovoltaic element is configured for forming a particular part of the receiver that receives a near uniform radiation. The photovoltaic element further comprises a plurality of unit cells each having an area of less than 5 cm² and each having a first side and a second side. The first side is configured for receiving solar radiation and the second side is configured for providing power evacuation connections. The first side of the unit cell is physically bonded on to a common substrate and the second side of unit cell is physically bonded to the heat sink after establishing electrical inter-connections amongst the unit cell for removing excess heat of radiation through a cooling media circuit.

[0028] According to one embodiment herein, the first side of the unit cell is physically bonded on to a common and a near-transparent substrate before establishing inter-connections. The first side of the unit cell is physically bonded on to a removable substrate before establishing inter-connections on the second side. The plurality of the unit cells are connected in a pre-defined configuration in order to be physically integrated but electrically isolated before bonding to the common substrate. The unit cells are of metal-wrapped-through types and are connected in a series mode to achieve higher voltage and in a parallel mode to achieve higher current.

[0029] According to one embodiment herein, the unit cells further comprise a plurality of fingers for carrying current. The plurality of fingers is laser-grooved onto the unit cells. The unit cells are the thin film back-contact-cells made of poly-silicon or mono silicon. The unit cells are configured for deploying passivated emitter and rear cell (PERC).

[0030] According to one embodiment herein, the system further comprises a cooling media circuit configured for circulating a cooling media. The circulation of the cooling media results in generation of heated water which in turn is useful as hot water or for one or more applications requiring heat. The cooling media circuit is configured for exchanging heat with the ambience using evaporative cooling mechanism. The cooling media circuit is further configured for operating in a closed loop. The receiver further comprises a metallic base channel facilitating cooling media flow. [0031] According to one embodiment herein, a parabolic reflector is used as a concentrator and the parabolic reflector further comprises a plurality of planar mirror strips spaced with each other for lowering wind stresses.

[0032] According to one embodiment herein, the first side is physically bonded to the common substrate using transparent adhesive while the second side is physically bonded to the heat sink using transparent or opaque adhesives. The adhesives used for physical bonding are made from natural or synthetic polymers with elastic properties.

[0033] According to one embodiment herein, the system further comprises a tracking mechanism configured for providing a tracking force. The tracking mechanism comprises one or more linear or rotary type actuators. The tracking mechanism is either single axis or dual axis. The longitudinal axis of the near-parabolic reflector and the receiver are arranged with a constant tilt from the horizontal powered by the single axis tracking mechanism. The tracker motion is either pre-programmed or is based on real-time-position of the sun.

[0034] According to one embodiment herein, the water flow is effected through free or forced circulative mechanisms. The cooling media circulation is of continuous or intermittent type. The cooling media circulation is regulated based on one or more pre-defined parameters of the cooling media or intensity of solar insolation.

[0035] According to one embodiment herein, a method for generating electricity and hot water in a hybrid manner using solar energy. The method comprises the steps of receiving radiation on a receiver from the sun using a concentrator. The concentrator is designed to achieve a line focus on the receiver. The method also comprises converting the concentrated radiation into electricity and heat using a photovoltaic element. The method further comprises circulating a cooling media through a cooling media circuit provided in the system. The circulation of cooling media results in generation of heated water which in turn is useful as hot water or for one or more applications requiring heat. [0036] According to one embodiment herein, the method further comprises the step of removing the excess heat of radiation using a heat sink provided in the receiver.

[0037] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating the preferred embodiments and numerous specific details thereof, are given by way of an illustration and not of a limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The other objects, features, and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

[0039] FIG. 1 illustrates a block diagram of a concentrated photovoltaic system, according to an embodiment herein.

[0040] FIG. 2 illustrates a schematic representation of a concentrator and a receiver arrangement in which the focal axis is parallel to the horizontal, and the receiver has a degree of freedom in the longitudinal direction, according to one embodiment herein.

[0041] FIG. 3 illustrates a schematic representation of a concentrator and a receiver arrangement in which the focal axis is not parallel to the horizontal, according to one embodiment herein.

[0042] FIG. 4 illustrates a side view of a receiver mounted at focal plane in between two physically separated parabolic surfaces, according to one embodiment herein. [0043] FIG. 5A illustrates a side view of a side view of a concentrator mounted with a number of linear mirror strips used to approximate a parabolic geometry, according to one embodiment herein.

[0044] FIG. 5B illustrates a side view of a concentrator mounted with linear mirror strips of variable width used to approximate a parabolic geometry, according to one embodiment herein.

[0045] FIG. 6A illustrates a side view of a concentrator with refracting surface designed as an arc, according to one embodiment herein.

[0046] FIG. 6B illustrates a side view of a concentrator mounted with a plurality of linear lens strips of variable width used to approximate a parabolic geometry and the receiver placed horizontally below, according to one embodiment herein.

[0047] FIG. 7A and 7B illustrate a side view of a concentrator designed to obtain a point-focus or area-focus on the receiver respectively, according to one embodiment herein.

[0048] FIG. 8A illustrates a block diagram of a receiver comprising a photovoltaic element and a heat sink, according to one embodiment herein.

[0049] FIG. 8B illustrates a block diagram of a receiver comprising a protective element in front of a photovoltaic element to provide weather proofing to the receiver, according to one embodiment herein.

[0050] FIG. 9A illustrates a perspective view of a receiver for a line focus concentrator, according to one embodiment herein.

[0051] FIG. 9B illustrates a side view of a receiver for a line focus concentrator, according to one embodiment herein.

[0052] FIG. 9C illustrates a top side view of a receiver for a line focus concentrator, according to one embodiment herein. [0053] FIG. 10A illustrates a block diagram of a receiver comprising a protective element in front of the first side of the photovoltaic elements, according to one embodiment herein.

[0054] FIG. 10B illustrates a block diagram of a receiver comprising a heat sink on the second side of the photovoltaic elements, according to one embodiment herein.

[0055] FIG. IOC illustrates a block diagram of a heat sink comprising a cooling circuit in thermal communication with the photovoltaic element, according to one embodiment herein.

[0056] FIG. 10D illustrates a block diagram of a heat sink comprising a cooling circuit in an open loop, according to one embodiment herein.

[0057] FIG. 10E illustrates a block diagram of a heat sink comprising a cooling circuit in a closed loop, according to one embodiment herein.

[0058] FIG. 11A illustrates a block diagram of a photovoltaic element comprising a plurality of unit cells, according to one embodiment herein.

[0059] FIG. 1 IB illustrates a side view of a unit cell with two sides and an evacuation layout laid on both the sides of the unit cell, according to one embodiment herein.

[0060] FIG. l lC illustrates a side view of a unit cell with two sides and an evacuation layout laid only on the second side of the unit cell, according to one embodiment herein.

[0061] FIG. 12A illustrates a side view of the unit cells indicating a bonding of the first side of the unit cells to a common and a near transparent substrate, according to one embodiment herein.

[0062] FIG. 12B illustrates an assembled view of a substrate obtained after completion of a first step of moduling, according to one embodiment herein. [0063] FIG. 12C illustrates an assembled view of a substrate obtained with the evacuation layout and the heat sink post a second step of the moduling, according to an embodiment herein

[0064] Although the specific features of the embodiments herein are shown in separate drawings, it is done for convenience only as each feature may be combined with any or all of the other features in accordance with the herein.

DETAILED DESCRIPTION OF THE EMBODIMENTS HEREIN

[0065] In the following detailed description, a reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments herein are described in sufficient detail to enable those skilled in the art to practice the embodiments herein and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments herein. The following detailed description is therefore not to be taken in a limiting sense.

[0066] The various embodiments herein provide a concentrated photovoltaic system. The system comprises a concentrator and a receiver. The concentrator is configured to receive radiation from the sun and concentrate the radiation onto the receiver. The receiver is configured to have at least one surface for receiving concentrated radiation from the concentrator. The concentrator comprises a group of reflecting or refracting planar surfaces of differing dimensions forming a near parabolic geometry for achieving a near uniform radiation and confining focused radiation to a particular part of the receiver. The system also comprises a photovoltaic element and a heat sink. The photovoltaic element is configured for generating electricity and the heat sink is configured for removing excess heat of the radiation. The photovoltaic element is configured for forming the particular part of the receiver receiving the near uniform radiation. The photovoltaic element further comprises a plurality of unit cells each having an area of less than 5 cm² and each having a first side and a second side. The first side is configured for receiving solar radiation and the second side is configured for providing power evacuation connections. The first side of the unit cells is physically bonded on to a common substrate and the second side of unit cells is physically bonded to the heat sink after establishing electrical inter-connections amongst the unit cells for removing excess heat of radiation through a cooling media circuit.

[0067] According to one embodiment herein, the first side of the unit cells is physically bonded on to a common and a near-transparent substrate before establishing inter-connections. The first side of the unit cells is physically bonded on to a removable substrate before establishing inter-connections on the second side. The unit cells are connected in a pre-defined configuration in order to be physically integrated but electrically isolated before bonding to the common substrate. The unit cells are of metal -wrapped-through types and are connected in a series mode to achieve higher voltage and in parallel mode to achieve higher current.

[0068] According to one embodiment herein, the unit cells further comprise a plurality of fingers for carrying current. The plurality of fingers is laser-grooved onto the unit cells. The unit cells can be the thin film back-contact-cells made of poly-silicon or mono silicon. The unit cells can be configured for deploying passivated Emitter and rear cell (PERC).

[0069] According to one embodiment herein, the system further comprises a cooling media circuit configured for circulating a cooling media. The circulation of the cooling media results in generation of heated water which in turn is useful as hot water or for one or more applications requiring heat. The cooling media circuit is configured for exchanging heat with the ambience using evaporative cooling mechanism. The cooling media circuit is further configured for operating in a closed loop. The receiver further comprises a metallic base channel facilitating cooling media flow. [0070] According to one embodiment herein, the concentrator is of parabolic reflector type and the parabolic reflector comprises a plurality of planar mirror strips spaced with each other for lowering wind stresses.

[0071] According to one embodiment herein, the first side is physically bonded to the common substrate using transparent adhesive while the second side is physically bonded to the heat sink using transparent or opaque adhesives. The adhesives used for physical bonding are made from natural or synthetic polymers with elastic properties.

[0072] According to one embodiment herein, the system further comprises a tracking mechanism configured for providing a tracking force. The tracking mechanism comprises one or more linear or rotary type actuators. The tracking mechanism is either single axis or dual axis. The longitudinal axis of the near-parabolic reflector and the receiver are arranged with a constant tilt from the horizontal powered by the single axis tracking mechanism. The tracker motion is either pre-programmed or is based on real-time-position of the sun.

[0073] According to one embodiment herein, the water flow is effected through free or forced circulative mechanisms. The cooling media circulation is of continuous or intermittent type. The cooling media circulation is regulated based on one or more pre-defined parameters of the cooling media or intensity of solar insolation.

[0074] According to one embodiment herein, a method for generating electricity and hot water in a hybrid manner using solar energy. The method comprises the steps of receiving radiation on a receiver from the sun using a concentrator. The concentrator is designed to achieve a line focus on the receiver. The method also comprises converting the concentrated radiation into electricity and heat using a photovoltaic element. The method further comprises circulating a cooling media through a cooling media circuit provided in the system. The circulation of cooling media results in generation of heated water which in turn is used as hot water or for one or more applications requiring heat. [0075] According to one embodiment herein, the method further comprises the step of removing the excess heat generated from the radiation using a heat sink provided in the receiver.

[0076] The various embodiments herein provide a cost-effective, compact, and scalable solar energy based system for electricity generation. The system can also be operated in a hybrid manner by generating hot water along with electricity. The system comprises a concentrator and a receiver. The concentrator is configured to receive radiation from the sun and concentrate the radiation onto the receiver. The receiver is configured to have at least one surface to receive concentrated radiation from the concentrator. A particular area of the receiver is directed towards the solar radiation from the concentrator. A photo-voltaic element within the receiver forms the particular area wherein the radiation is concentrated.

[0077] FIG. 1 illustrates a concentrator, according to one embodiment herein. With respect to FIG. 1 , the concentrator is designed as an arc from a near-parabolic arc 101 extruded geometrically (parabolic trough) onto which reflective material 102 is disposed to reflect solar radiation onto the receiver 104 wherein a line focus 103 is achieved. The plane along the focal axis where the radiation is concentrated is termed as focal plane 105 and the direction along the focal axis is termed as the longitudinal direction. The length of the concentrator (parabolic trough) 102 is defined in the longitudinal direction and the width is defined along a direction perpendicular to the longitudinal direction in the plane of the aperture area. The sun’s radiation is focused on the focal plane 105. The receiver 104 is placed in a manner to lie at or below or above the focal plane 105 to collect the concentrated radiation. The longitudinal axes of the receiver 104 and the collector 102 are configured to be parallel to each other.

[0078] According to one embodiment herein, the receiver 104 and the concentrator 102 are connected in such a way that the receiver gets one degree of freedom in its longitudinal direction while being rigid in the direction perpendicular to it as shown in FIG. 2. The assembly is mounted on a main shaft which supports the weight of the assembly. The direction of degree of freedom is depicted using reference numeral 106. The shaft is configured to track the direction of the sun using a tracking mechanism. The tracking mechanism is of single axis type or dual axis type. In case of dual-axis tracking, the solar radiation is always perpendicular to concentrator and hence also to the plane of the photo-voltaic elements in the receiver.

[0079] According to one embodiment herein, the focal axis is not parallel to the horizontal in order to make lower angle with the incident radiation as shown in FIG. 3. This is particularly important for upper latitudes in the Northern-hemisphere where the sun remains for majority of the year in south.

[0080] According to one embodiment herein, a continuous reflecting surface 101 is used to approximate an arc of a near-parabolic geometry as shown in FIG. 4. While a continuous surface provides concentration ratios up to 100, such high concentration ratios are unsuitable for photovoltaic applications. The concentrator is also configured to have two physically separated parabolic surfaces 101-A and 101-B with the receiver 104 mounted at focal plane in between the two physically separated parabolic surfaces.

[0081] According to one embodiment herein, a number of linear mirror strips are used to approximate a parabolic geometry as shown in FIG. 5A. This configuration is particularly important when concentration ratios are below 30 as using linear mirror strips can be more cost effective. Advantage of linear mirror strips over that of the continuous reflector is that uniform intensity radiation is achieved on the receiver which is one of the key features required by concentrated photovoltaic systems. Additionally, a gap of less than 1cm is provided between any and all linear mirror strips to minimize wind load on the reflector. This provides significant structural advantage over the continuous reflector. [0082] According to one embodiment herein, linear mirror strips of variable width are used to approximate a parabolic geometry in the concentrator wherein the receiver is placed horizontally as shown in FIG. 5B. Linear mirror strips of the same width as that of the photo voltaic element in the receiver cause sub-optimal collection of reflected radiation whereas linear mirror strips of width smaller than that of the photo-voltaic element in the receiver cause non-uniform radiation intensity on the receiver leading to electrical performance issues. To overcome this problem, the linear mirror strips decrease in width as one moves away from the vertex of the parabola.

[0083] According to one embodiment herein, the concentrator is designed as an arc from an approximate parabolic geometrically extruded to form a surface onto which refractive material such as Fresnel lens is disposed to refract solar radiation onto the receiver as shown in FIG. 6A. According to one embodiment herein, the receiver and the concentrator are connected in such a way that the receiver or concentrator gets one degree of freedom in its longitudinal direction while being rigid in the direction perpendicular to it. The assembly is mounted on a main shaft which supports the weight of the assembly. The shaft is configured to track the direction of the sun using a tracking mechanism that uses either a single axis type or dual axis type of tracking mechanism.

[0084] According to one embodiment herein, Fresnel lens with linear lens strips of variable width are used to approximate a parabolic geometry in the concentrators wherein the receiver is placed horizontally below as shown in FIG. 6B. Linear lens strips of the same width as that of the photo-voltaic element in the receiver cause sub-optimal collection of refracted radiation whereas linear lens strips of width smaller than that of the photo-voltaic element in the receiver cause non-uniform radiation intensity on the receiver leading to electrical performance issues. To overcome this problem, the linear lens strips in the Fresnel lens are decreased in width in the longitudinal direction as one moves away from the vertex of the parabola.

[0085] According to one embodiment herein, the concentrator is designed to obtain a point focus on the receiver as shown in FIG. 7A. The geometry of the concentrator is approximated by a three-dimensional paraboloidal shape 110. Such a concentrator is configured to track the direction of sun using a tracking mechanism that uses a dual axis type of tracking. With such a tracking mechanism, the sun radiation is always perpendicular to concentrator and hence the plane of the photo-voltaic elements in the receiver. The concentrator is fabricated out of single or many curved continuous surfaces. The concentrator is also configured to employ a number of linear mirror fragments.

[0086] According to one embodiment herein, the concentrator is designed to obtain a point focus on the receiver as shown in FIG. 7B. The geometry of the concentrator is approximated by a three-dimensional paraboloidal shape which is reflecting in nature. Such a concentrator is configured to track the direction of sun using a tracking mechanism that uses a dual axis type of tracking. With such a tracking mechanism, the sun radiation is always perpendicular to concentrator and hence the plane of the photo-voltaic elements in the receiver. The concentrator is fabricated out of single or many curved continuous surfaces. The concentrator is also designed to employ a number of linear mirror fragments.

[0087] According to one embodiment herein, the concentrator is designed to obtain a point focus on the receiver using a refractive surface such as but not limited to Fresnel lens 111. Such a concentrator is configured to track the direction of sun using a tracking mechanism that uses a dual axis type of tracking. With such a tracking mechanism, the sun radiation is always perpendicular to concentrator and hence the plane of the photo-voltaic elements in the receiver. The concentrator is designed or configured to employ either a single Fresnel lens and a single PV element or a number of Fresnel lenses and those many numbers of PV elements spaced apart from each other.

[0088] According to one embodiment herein, the receiver 104 comprises of a photo voltaic element 112 and a heat sink 113 as shown in FIG. 8A. While the photo-voltaic element 112 facilitates generation of electricity and the heat sink 113 helps maintain the temperature of photovoltaic element 112.

[0089] According to one embodiment herein, the receiver 104 also comprises a protective element 114 in front of photo-voltaic element 112 for providing weather proofing to the receiver as shown in FIG. 8B.

[0090] According to one embodiment herein, the geometry of the receiver 104 is determined by the geometry of the concentrator 101. In case of line focus concentrators, the receiver 104 typically runs long with relatively a narrow footprint along the width (as shown in FIG. 9A). In case of point or area focus reflectors for example, 700A and 700B, the shape of geometry is mostly square or a rectangle with ratio between the sides of the rectangle being not more than 2 (as shown in FIG. 9B). When multiple Fresnel refractive surfaces are used to concentrate radiation, then only a part of receiver is designed/configured to contain photo voltaic elements spaced at the center of the Fresnel refractive surfaces.

[0091] According to one embodiment herein, the photo-voltaic element 112 further comprises of two sides, namely, a first side 115 and a second side 116. While the first side 115 is always directed to face sun and designed to provide the means for maximum absorption of solar radiation, the second side 116 which is always opposite to the first side 115 and designed to provide the means for power evacuation by having connections (solder pads) for drawing power. [0092] According to one embodiment herein, the receiver 104 is further designed to comprise a protective element 114 in front of the first side 115 of the photo-voltaic element 112 to provide humidity and weather protection as shown in FIG. 10A. The protective element is made of completely or near transparent material such as but not limited to glass, acrylic, quarts, etc. The protective element is provided with anti-reflecting coating to enhance the transmittivity of the protective element 114. The protective element 114 is also be tempered to provide additional mechanical strength to the protective element 114.

[0093] According to one embodiment herein, the protective element 114 and the first side 115 of the photo-voltaic element 112 are bonded together using liquid adhesives or hot- melt adhesives. Such adhesives include but not limited to natural or synthetic polymers with elastic properties. These adhesives are designed to be near transparent for ensuring maximum radiation input to the cell.

[0094] According to one embodiment herein, the protective element 114 and the first side 115 of the photo-voltaic elements 112 are bonded together using a solid substrate which doesn’t require heat conditioning for bonding. The solid substrate further comprises two surfaces, and both of which have the adhesive properties such as but not limited to dual-side tape. While the one side is bonded to the protective element 114, the other side is bonded to the photo-voltaic element 112. These solid substrate based adhesives are designed to be near transparent for ensuring maximum radiation input to the cell.

[0095] According to one embodiment herein, the receiver 104 further comprises a heat sink 113 on the second side 116 of the photo-voltaic elements 112, that performs the dual purpose of removing excess heat in the photo-voltaic elements 112 but also designed for providing weather protection as shown in FIG. 10B. The heat sink 113 need not be transparent but is designed to offer low heat transfer resistance. The heat sink includes but not limited to a metallic substrate to keep the temperature differential between the photo-voltaic element 112 and the metallic substrate as low as possible.

[0096] According to one embodiment herein, the heat sink 113 and the second side 116 of the photo-voltaic element 12 are bonded together using liquid adhesives or hot-melt adhesives. Such adhesives include but not limited to natural or synthetic polymers with elastic properties. These adhesives need not be transparent for ensuring maximum radiation input to the cell but designed to offer low heat transfer resistance to keep temperature of photovoltaic elements as low as possible.

[0097] According to one embodiment herein, the heat sink 113 and the second side 116 of the photo-voltaic elements 112 are bonded together using a solid substrate which doesn’t require heat conditioning for bonding. The solid substrate further comprises two surfaces, both of which have the adhesive properties such as but not limited to dual-side tape. While the one side is bonded to the protective element 114, the other side is bonded to the photo-voltaic element 112. These solid substrate based adhesives are desined/configured to transparent or near transparent. These adhesives are configured to offer low heat transfer resistance to keep temperature of PV elements 112 as low as possible.

[0098] According to one embodiment herein, the heat sink 113 comprises a cooling circuit 117 which is in thermal communication with the photo-voltaic element as shown in FIG. IOC. The cooling circuit 117 further comprises a cooling media (not shown) in liquid or gaseous phase such as but not limited to water or air.

[0099] According to one embodiment herein, the heat sink 113 comprises of flow channels (not shown) facilitating the circulation of the cooling media. The system is configured to have a single or many flow channels. When multiple flow channels are provided, direction of flow is designed to either be parallel type or counter flow type. [00100] According to one embodiment herein, the cooling circuit is an open loop wherein the cooling media once heated in the heat sink is utilized for some down-stream heat application while fresh cooling media is supplied to the heat sink 113 for further cycling as shown in FIG. 10D.

[00101] According to one embodiment herein, the cooling circuit 117 is a closed loop wherein the cooling media first receives heat from the heat sink 113 and second dissipates received heat to a down-stream heat application or to the ambience as shown in FIG. 10E.

[00102] According to one embodiment herein, the cooling circuit 117 is a semi -open loop and wherein a latent heat of evaporation of a part of the cooling media is used to cool the other part of the cooling media. When water is used as a cooling media, the cooling media is cooled to wet-bulb temperature, as in a cooling tower and the electrical conversion efficiency of the system is enhanced.

[00103] According to one embodiment herein, the cooling circuit 117 comprises a cooling media pump facilitating circulation of cooling media in the cooling circuit. The flow of the cooling media is thus actively regulated in cooling circuit 117.

[00104] According to one embodiment herein, the system is configured to facilitate the flow of the cooling media in the cooling circuit 117 in a passive way. This configuration is sometimes referred to as pump-less configuration.

[00105] According to one embodiment herein, the system is configured to have a flow management scheme that is based on steady supply of cooling media in the cooling circuit 117. This scheme is mostly applicable wherein the temperature to which cooling media gets heated up to is of less importance.

[00106] According to one embodiment herein, the system is configured to have a flow management scheme that is based on intermittent supply of cooling media from the cooling circuit 117. A batch of the cooling media is allowed to receive heat from the heat sink 113 till the batch of the cooling media is heated to a certain set-temperature after which a fresh batch of the cooling media is circulated to the cooling circuit 117.

[00107] According to one embodiment herein, the system is configured to have a flow management scheme that provides a variable supply of cooling media regulated based on pre defined parameters such as the solar insolation received at any instant or the incoming or outgoing cooling media temperature. Such a system comprises a variable flow device to regulate the flow magnitude. This scheme has the potential of maintaining the temperature of the photo-voltaic element as well as the cooling media at near steady levels.

[00108] According to one embodiment herein, the system is configured to have a plurality of fins at optimized locations on the receiver to exchange heat passively with ambient air.

[00109] According to one embodiment herein, the system is configured to have a hot water tank and a cold water tank, the cold water circulating through the water channels is supplied from the cold water tank and gets heated to the temperatures to meet the hot water requirements for household or industrial use. Hot water so generated is stored in the hot water tank.

[00110] According to one embodiment herein, the system comprises the photo-voltaic element 112 which is unitized into a number of unit cells 120 as shown in FIG. 11A. When the power evacuation architecture employed within the PV element 112 is efficient, then the magnitude of current generation gets amplified by a factor equal to concentration ratio under standard operating conditions. As an example, the smallest size 121 standardly available in the photovoltaic market is 156 mm x 156 mm and can be used as a unit cell that is configured to generate short-circuit current of ~ 7 Amps under standard test conditions. Theoretically and ideally, at a concentration ratio of ~ 15, the current magnitude in 121 is as high as 100 Amps. However, in practice, such high magnitudes of current cause significant heating issues demanding higher finger density. To match heat losses in both the cases, one has to provide significantly higher finger densities that are as many as times concentration ratio. This results in significantly higher shading losses due to higher finger densities and hamper electric conversion efficiency significantly.

[00111] Further, the power evacuation system to be configured for handling and processing 100 Amps as against the one designed for the current magnitude of 7 Amps is significantly unmatched and increases the cost of balance of system.

[00112] The concentration of radiation on the photo-voltaic elements 112 results in amplification of current magnitude.

[00113] According to one embodiment herein, the system comprises the photo-voltaic element 112 which is unitized into a number of unit cells. A power evacuation architecture 124 is provided on at least the second side 123 of the unit cells 120. The power architecture is provided on the first side 121 of the unit cells 120. In case, the power evacuation architecture 124 employed within the photo-voltaic element 112 is efficient, then the magnitude of current generation gets amplified by a factor equal to concentration ratio. As an example, the smallest size standardly available in the photo-voltaic market is 156 mm x 156 mm and is here onwards referred as a template cell. The template cell 121 (also referred to as unit cell) is configured to generate short-circuit current of ~ 6 Amps under standard test conditions. However, at a concentration ratio of - 15, the short circuit current magnitude in the template cell 121 is as high as 90 Amps provided evacuation resistance is small enough. In practice, such high magnitudes of current in 156 mm x 156 mm cause significant heating issues due to inadequate finger density on the first side of the photo-voltaic element 112 designed for one sun applications. [00114] Potential solution to make the conventional cells workable for concentration applications is to provide a significant boost in finger density on the first side of the photo voltaic element in order to minimize evacuation resistance. This boost in finger density is as high as concentration ratio. Such finger densities result in significantly higher shading losses and hamper overall conversion efficiency between solar insolation received and electrical units generated.

[00115] When looked at the problem closely, it turns out that finger resistance minimization is realized either by having more number of fingers or thicker fingers or by having fingers run for smaller lengths. While having more number of fingers or thicker fingers is well understood, the case of having fingers run for smaller lengths is least explored. The case of having fingers run for smaller lengths basically demands cells of smaller cell dimension along the fingers. This leads to usage of many unit cells. The dimensions of the unit cells are chosen in such a manner that they minimize the length of the fingers that connect to the nearest busbar which evacuate current from the fingers and which run in a direction perpendicular to that of the fingers. Such a dimension works out to an area less than 5 sq cm per unit cell, in which case the current carried out of the unit cell by the bus bar is less than 2 Amps.

[00116] According to one embodiment herein, the photo-voltaic element 112 comprises of a number of unit cells 120 physically separated in order to incur acceptable levels of evacuation resistance as shown in FIG. 11A. These unit cells 120 in one embodiment is of mono or poly silicon type.

[00117] According to one embodiment herein, a unit cell 121 has two sides, a first side 122 and a second side 123 as shown in FIG. 1 IB and 11C. While the first side 122 has or does not have an evacuation layout 124 printed on it, the second side 123 forms at least a part of the evacuation layout 124. The evacuation layout 124 is referred to as such as but not limited to fingers, busbars, solder pads, etc. [00118] While the strategy of going for unitized approach helps to prevent drop in conversion efficiencies at concentration ratios of the order of 10 or higher, it becomes practically difficult to implement unless accompanied by a moduling approach that accommodates integration of such unitized cells on substrates that also act as heat sink.

[00119] While unitization offers benefits in terms of short evacuation paths and the flexibility to arrange the cells as per current and voltage requirements of the end user, it increases the complexity of the process of interconnections as the cells have to be physically immobilized on a substrate before establishing interconnections on the second side of the unit cells.

[00120] According to one embodiment herein, the relative positioning of unit cell 121 is fixed by bonding the first side 122 of the unit cells 120 to a common and a near transparent substrate 125 as shown in FIG. 12A. Bonding on a common substrate 125 provides an array of the unit cells 120 forming the photovoltaic element 112 immobilized on a single substrate providing an ease in the moduling.

[00121] According to one embodiment herein, the unit cells 120 are physically separated and bonded on to a common and removable substrate 125 i.e. their relative positioning of is fixed. Bonding on to a removable substrate 125 provides an immobilized array of the unit cells which are then easily handled for establishing the interconnections on the second side of the unit cells. Post establishing the interconnections or laying out the power evacuation layout 124 the common and the removable substrate 125 is removed.

[00122] According to one embodiment herein, the unit cells 120 are physically separated and their relative positioning is fixed by bonding the first side 122 of the unit cells to a composite substrate 126 comprising of a protective element 127 and a bonding element 128 as shown in FIG. 12B and 12C. The protective element 127 and the bonding element 128 are designed to be near transparent. The bonding element 128 becomes an interface between the protective element 127 and the unit cells 120 forming the photovoltaic element 112. This is akin to a situation of achieving moduling in two steps namely, a first step and a second step. While the first step involves bonding of the first side 122 of the unit cells 120 to the composite substrate 126, the second step involves establishing the interconnections or laying of the power evacuation layout 124 on the second side 123 of the unit cells 120 along with bonding the obtained substrate 130 after first step to the heat sink 113 using a bonding element 129.

[00123] According to one embodiment herein, the unit cells 120 are not physically separated and their relative positioning is fixed to start with.

[00124] Further, once the moduling process is properly established, one need not limit size of the unit cells to ones obtained to maintain similar levels of evacuation resistance across the one-sun and the concentrated technologies. It is possible to obtain even smaller sizes and minimize shading losses further. This approach also leads to system configurations wherein instead of large current levels associated with concentrated systems, large voltage levels are achieved which are easier to handle by the power accessories and more efficient to transport as well. As an example, the template cell when is cut into unit cells of 1cm² area, the accumulative open circuit voltage in series mode at 15 concentration ratios would be around -135 V arresting the current to below one Amps. On the other hand, the parent template cell, even at one sun would offer roughly 0.60 V of open circuit voltage and current of - 6 Amps. Thus, the ease realized in the moduling process by breaking into two parts provides an added advantage of being able to achieve higher voltage levels as compared to higher current levels making the balance of system related to power evacuation more efficient and economically more friendly.

[00125] This ease in moduling provides the flexibility of using any solar cell material. In one example embodiment, the unit cells are of mono or poly crystalline type. The unit cells are thin film cells. These cells have screen-printed fingers or laser-grooved fingers. These unit cells are also metal-wrapper through type to avoid establishing any external contact from the side of cell that receives solar radiation. These cells contain anti-reflecting coating on the side receiving solar radiation.

[00126] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments herein.

[00127] It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications.

[00128] The various embodiments herein provide a cost-effective, compact, and scalable solar energy based system and method capable of generating both electricity and hot water in a hybrid manner. The system and method uses a concentrator built in a cost effective way along with a tracker to maximize energy input. The moduling in the system provides the flexibility of using any solar cell material such for the unit cells such as mono or poly crystalline type. The system and method addresses the problem of overheating of cells due to the concentration of direct normal irradiance (DNI) on the reduced area of PV cells which causes the conversion efficiency of the PV cells to decline. Further, the solar energy based system and method ensures uniformity in radiation received across the cell surface through use of planar reflecting or refracting surfaces of variable widths. [00129] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such as specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.

[00130] It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications. However, all such modifications are deemed to be within the scope of the claims.

Claims

CLAIMS What is claimed is:

1. A concentrated photovoltaic solar energy system, the system comprises:

A concentrator and a receiver configured wherein the concentrator is designed to achieve a line of focus on the receiver, and wherein the concentrator comprises a group of reflecting or refracting planar surfaces of mutually different dimensions forming a near parabolic geometry for achieving a near uniform radiation and confining focused radiation to a particular area or a portion of the receiver; and

a photovoltaic element and a heat sink provided in the receiver, and wherein the photovoltaic element is configured for generating electricity and wherein the heat sink is configured for removing an excess heat of the radiation, and wherein the photovoltaic element is configured for forming the particular area or the portion of the receiver for receiving the near uniform radiation, and wherein the photovoltaic element comprises a plurality of unit cells and wherein each of unit cell has a first side and a second side, and wherein the first side of unit cell is configured for receiving solar radiation and the second side of unit cell is configured for providing power evacuation connections, and wherein the first side of the unit cells is physically bonded on to a common substrate and the second side of unit cells is physically bonded to the heat sink after establishing electrical inter-connections amongst the unit cells for removing excess heat of radiation through a cooling media circuit.

2. The system according to claim 1, wherein the first side of the unit cells are physically bonded on to a common and a near-transparent substrate before establishing inter connections, and wherein the first side of the unit cells are physically bonded on to a removable substrate before establishing inter-connections on the second side, and wherein the unit cells are connected in a pre-defmed configuration to be physically integrated but electrically isolated before bonding to the common substrate, and wherein the unit cells are of metal-wrapped-through type and are connected in a series mode to achieve higher voltage and in parallel mode to achieve higher current.

3. The system according to claim 1, wherein the unit cells further comprise a plurality of fingers for carrying current, and wherein the plurality of fingers are laser-grooved onto the unit cells, and wherein the unit cells are the thin film back-contact-cells made of poly-silicon or mono silicon, and wherein the unit cells are configured for deploying passivated emitter and rear cell.

4. The system according to claim 1, wherein the unit cell occupies an area of less than 5 cm².

5. The system according to claim 1, wherein the cooling media circuit is configured for circulating a cooling media, and wherein the circulation of cooling media results in generation of hot water, and wherein the cooling media circuit is configured for exchanging heat with the ambient atmosphere through an evaporative cooling mechanism, and wherein the cooling media circuit is operated in a closed loop, and wherein the receiver further comprises a metallic base channel facilitating cooling media flow.

6. The system according to claim 1, wherein the concentrator provides a continuous and a single reflecting or refractive surface or provides a reflecting or refractive surface made of discrete elements.

7. The system according to claim 1, wherein the parabolic reflector is employed as a concentrator and comprises a plurality of planar mirror strips separated from each other.

8. The system according to claim 1, wherein the first side of the unit cell is physically bonded to the common substrate using transparent adhesive while the second side of the unit cell is physically bonded to the heat sink with transparent or opaque adhesives, and wherein the transparent or opaque adhesives used for physical bonding are made from natural or synthetic polymers with elastic properties.

9. The system according to claim 1, further comprises a tracking mechanism configured for providing a tracking force, and wherein the tracking mechanism comprises one or more linear or rotary type actuators, and wherein the tracking mechanism is mounted on single axis or dual axis, and wherein the longitudinal axis of the near-parabolic reflector and the receiver are arranged with a constant tilt from the horizontal, and wherein the tracker motion is either pre-programmed or is based on real-time-position of the sun.

10. The system according to claim 1, wherein the cooling media flow is achieved through free or forced circulative mechanisms, and wherein the cooling media is circulated continuously or intermittently, and wherein the cooling media circulation is regulated based on one or more pre -defined parameters of the cooling media or intensity of solar insolation.

11. A method for generating electricity and hot water in a hybrid manner using solar energy, the method comprising the steps of:

receiving radiation from the sun at a receiver using a concentrator; converting the concentrated radiation into electricity and heat with a photovoltaic element wherein the photovoltaic element further comprises a plurality of unit cells each having a first side and a second side; and circulating a cooling media through a cooling media circuit for generating hot water.

12. The method according to claim 11, further comprises the step of removing the excess heat generated from the radiation using a heat sink provided in the receiver.

13. The method according to claim 11, further comprises the step of physically bonding the first side of the unit cells on to a common and a near-transparent substrate before establishing inter-connections, and wherein the first side of the unit cells are physically bonded on to a removable substrate before establishing inter-connections on the second side, and wherein the unit cells are connected in a pre-defined configuration to be physically integrated but electrically isolated before bonding to the common substrate, and wherein the unit cells are of metal-wrapped-through type and are connected in a series mode to achieve higher voltage and in parallel mode to achieve higher current.

14. The method according to claim 11, further comprises the step of physically bonding the first side of the unit cell to the common substrate using transparent adhesive while physically bonding the second side of the unit cell to the heat sink with transparent or opaque adhesives, and wherein the transparent or opaque adhesives used for physical bonding are made from natural or synthetic polymers with elastic properties.

15. The method according to claim 11, further comprises the step of providing a tracking force using a tracking mechanism, and wherein the tracking mechanism comprises one or more linear or rotary type actuators, and wherein the tracking mechanism is mounted on single axis or dual axis, and wherein the longitudinal axis of the near-parabolic reflector and the receiver are arranged with a constant tilt from the horizontal, and wherein the tracker motion is either pre-programmed or is based on real-time-position of the sun.

16. The method according to claim 11, further comprises the step of achieving the flow of cooling media through free or forced circulative mechanisms, and wherein the cooling media is circulated continuously or intermittently, and wherein the cooling media circulation is regulated based on one or more pre-defined parameters of the cooling media or intensity of solar insolation.

17. The method according to claim 11, further comprises the step of employing a parabolic reflector as a concentrator, and wherein the parabolic reflector comprises a plurality of planar mirror strips separated from each other.