Patent Publication Number: US-10778121-B2

Title: Active cooling for a concentrated photovoltaic cell

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/233,685, filed Jan. 17, 2014, now U.S. Pat. No. 10,014,803, issued Jul. 3, 2018, which was a national phase entry under 35 U.S.C. § 371 of International Patent Application PCT/I132012/001415, filed Jul. 20, 2012, designating the United States of America and published in English as International Patent Publication WO 2013/014511 A1 on Jan. 31, 2013, which claims the benefit under Article 8 of the Patent Cooperation Treaty and under 35 U.S.C. § 119(e) to French Patent Application Serial No. 1156837, filed Jul. 26, 2011, the disclosure of each of which is hereby incorporated herein in its entirety by this reference. 
    
    
     BACKGROUND 
     In recent years, the development of renewable energy has increased due to concern over the availability of fossil energy sources as well as environmental concerns. Among the different kinds of renewable energy sources, solar energy is the most abundant. Accordingly, there has been intensive research on how to collect solar energy and transform it into electricity. Among the different techniques proposed, photovoltaic (PV) cells are well known in the art and have been extensively developed in order to increase their efficiency and lower their cost. 
     In particular, concentrated photovoltaic (CPV) cells are known to be cheaper to manufacture than a standard photovoltaic type system providing the same amount of power. This is due to the fact that concentrated photovoltaic cells use lenses to focus the solar light on a PV surface, which is smaller due to the light concentration. Accordingly, the area and material required is reduced. 
     At high concentration ratios of the solar light, for instance, more than 500 times, cooling of the photovoltaic cell is required. This is due to the fact that PV cells are less efficient at higher temperatures and due to the possibility of the PV cells being damaged by very high temperatures. 
     In order to cool down the PV cells, passive cooling, such as a heat dissipater, becomes complicated and, therefore, costly. As an alternative, it is known to use an active cooling solution in which some medium, like water or oil, is used for cooling down the cell. In this approach, the cooling medium is heated and either directly used, for instance, as hot water, or used to run a generator for electricity production. In the latter case, the efficiency of the electricity generation process is rather low. 
     More specifically, a typical CPV cell can be sized between 0.25 cm 2  and 1 cm 2 . Assuming a concentration ratio of 500, it can be estimated that about 5 to 18 watts are wasted in heat. This is roughly on the same order of magnitude of the energy transformed into electricity by the CPV cell. 
     DISCLOSURE 
     Accordingly, it would be an improvement in the art of concentrated photovoltaic cells if the generated heat could be transformed into electricity via a highly efficient process. 
     Such a problem is solved by the invention, as defined by the independent claims. 
     More specifically, the present invention may relate to a wasted heat harvesting device for harvesting electricity including: switching means configured to convey a magnetic field from a first region to at least a second region when the temperature of the switching means crosses a predetermined temperature. 
     As a result of such approach, a wasted heat harvesting device is capable of converting heat into electricity in an efficient manner. 
     In some embodiments, the wasted heat harvesting device can further include: magnetic means configured to generate the magnetic field; a magnetic flux conveyor configured to convey a magnetic flux generated by the switching of the switching means; and electricity-generating means configured to generate electricity from the magnetic flux. 
     This approach results in a wasted heat harvesting device capable of converting heat into electricity with a simple design. 
     In some embodiments, a first side of the magnetic flux conveyor can be connected to one pole of the magnetic means and the switching means can be placed between a second side of the magnetic flux conveyor and the other pole of the magnetic means. 
     With this approach, the magnetic field can generate a magnetic flux flowing through the magnetic flux conveyor. 
     In some embodiments, the switching means can be a magnetic alloy switch. 
     As a result of this approach, the switch can allow or prevent passage of the magnetic field. 
     In some embodiments, the electricity-generating means can include a coil wound around the magnetic flux conveyor. 
     As a result of this approach, electricity can be generated from the magnetic flux. 
     In some embodiments, the magnetic flux conveyor can be any of iron type, ferromagnetic alloy, such as Fe or Fe—P or FeSi or Ni/Fe 45/55. 
     With this approach, the magnetic flux can be conveyed efficiently. 
     In some embodiments, the magnetic means can be any of SmCo 5 , Sm 2 Co 15 , Nd 2 Fe 14 B or Ba ferritis. 
     As a result of this approach, the magnetic field can be efficiently realized. 
     In some embodiments, the switching means can be made of Gd 5 (Si x Ge 1-x ) 4 . 
     As a result of such approach, the switching of the magnetic flux can be realized in an efficient manner. 
     The present invention may further relate to a wasted heat harvesting system including: at least two wasted heat harvesting devices according to any of the previous embodiments, each of the at least two wasted heat harvesting devices including a device power output for outputting electricity generated by the electricity-generating means. 
     With this approach, multiple wasted heat harvesting devices can operate in conjunction. 
     In some embodiments, the at least two device power outputs can be connected in parallel or in series to each other. 
     As a result of this approach, multiple wasted heat harvesting devices operating at the same frequency can operate in conjunction. 
     In some embodiments, the connection of the at least two device power outputs can be connected to an AC/DC converter and the output of the AC/DC converter can be connected to a power output of the wasted heat harvesting system. 
     With this approach, the power output of the wasted heat harvesting system can be connected to a second power output of a similar wasted heat harvesting system. 
     In some embodiments, the connection of the at least two device power outputs can be connected to an AC/AC converter and the output of the AC/AC converter can be connected to a power output of the wasted heat harvesting system. 
     As a result of such approach, the power output of the wasted heat harvesting system can be connected to a second power output of a similar wasted heat harvesting system. 
     In some embodiments, each of the at least two device power outputs can be connected to an AC/DC converter. 
     With this approach, multiple wasted heat harvesting devices not operating at the same frequency can operate in conjunction. 
     In some embodiments, the output of the AC/DC converters can be connected in series or in parallel to each other and the resulting connection can be connected to a power output of the wasted heat harvesting system. 
     This approach results with multiple wasted heat harvesting devices not operating at the same frequency being able to operate in conjunction. 
     In some embodiments, each of the at least two device power outputs can be connected to an AC/AC converter. 
     With this approach, multiple wasted heat harvesting devices not operating at the same frequency can operate in conjunction. 
     In some embodiments, the output of the AC/AC converters can be connected in series or in parallel to each other and the resulting connection can be connected to a power output of the wasted heat harvesting system. 
     As a result of such approach, multiple wasted heat harvesting devices not operating at the same frequency can operate in conjunction. 
     The present invention may further relate to a modular wasted heat harvesting system comprising at least two wasted heat harvesting systems according to any of the previous embodiments. 
     The present invention may further relate to a photovoltaic cell including a wasted heat harvesting device and/or a wasted heat harvesting system and/or a modular wasted heat harvesting system according to any of the previous embodiments. 
     As a result of this approach, heat generated by sunlight on the photovoltaic cell can be efficiently converted into electricity. 
     The present invention may further relate to a solar module comprising a plurality of photovoltaic solar cells, in particular, concentrated photovoltaic solar cells, further comprising at least one wasted heat harvesting device configured to transform heat into electricity configured and arranged such that at least one of the photovoltaic solar cells is furthermore cooled by the transformation of heat into electricity. 
     This approach results in the solar module being able to efficiently operate because of the cooling of the cells and the generated heat additionally being converted into electricity. 
     The present invention may further relate to a method for realizing a wasted heat harvesting device including the steps of: a first deposition step of depositing a metal layer on a substrate; a second deposition step of depositing a magnetic alloy on the substrate; a third deposition step of depositing a ferromagnetic seed material on the substrate; a fourth deposition step of depositing a metal layer on the substrate; and a fifth deposition step of depositing a magnetic material on the substrate. 
     As a result of this approach, it is possible to realize a wasted heat harvesting device with a reduced number of steps and with technology compatible with photovoltaic cell manufacturing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in more detail, by way of example, hereinafter using advantageous embodiments and with reference to the drawings. The described embodiments are only possible configurations in which the individual features may, however, as described above, be implemented independently of each other or may be omitted. Equal elements illustrated in the drawings are provided with equal reference numerals. Parts of the description related to equal elements illustrated in the different drawings may be left out. In the drawings: 
         FIG. 1A  is a schematic drawing of a wasted heat harvesting device according to an embodiment of the present invention; 
         FIG. 1B  is a schematic drawing of the operation of the wasted heat harvesting device of  FIG. 1A ; 
         FIGS. 2 to 7  are schematic drawings of a method for realizing a wasted heat harvesting device of  FIG. 1A ; 
         FIGS. 8A and 8B  are schematic drawings of a wasted heat harvesting device according to further embodiments of the present invention; 
         FIG. 9A  is a schematic drawing of a wasted heat harvesting system in accordance with a further embodiment of the present invention; and 
         FIGS. 9B, 10A, 10B, and 11  are schematic drawings of modular wasted heat harvesting systems in accordance with further embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     As can be seen in  FIG. 1A , a wasted heat harvesting device  1000  in accordance with an embodiment of the present invention comprises a magnet  1100  including south pole  1101  and north pole  1102 , a ferromagnet  1400 , a switch  1200  and a coil  1300 . The two ends of the coil  1300  act as a power output  1500  of the wasted heat harvesting device. 
     As can be seen in  FIG. 1B , when the switch  1200  switches from the open position of  FIG. 1A  to the closed position of  FIG. 1B , a magnetic flux Φ  1600  is generated by the magnetic field of magnet  1100  being redirected through the ferromagnet  1400 . The magnetic flux  1600  induces a current A  1700  in coil  1300 . The current  1700  can be collected at power output  1500 , for instance, to power a load  1900  resulting in a voltage drop V  1800 . 
     In other words, the magnetic field is conveyed from a first region outside the coil  1300  to a second region inside the coil  1300  by the switch  1200 . 
     Symmetrically, when the switch moves from the closed position of  FIG. 1B  to the open position of  FIG. 1A , an opposite magnetic flux is generated, resulting in an opposite induced current. Accordingly, by the opening and closing of the switch  1200 , an AC current is generated at the power output  1500 . 
     More specifically, the switch  1200  is a magnetic switch alloy that switches on and off depending on its temperature. The wasted heat harvesting device is placed in thermal contact with a CPV cell. When the CPV cell is exposed to sunlight, its temperature will rise. As the temperature rises above a first predefined temperature, the switch  1200  closes. This causes the temperature to drop. As the temperature drops below a second predefined temperature, the switch opens. After a certain time, the CPV cell temperature will start rising again because of solar irradiation and the temperature will increase again, leading to a new cycle. 
     In this manner, the CPV cell can be cooled actively. That is, thermal energy is converted to electricity in order to cool the cell, instead of passively dissipating the thermal energy. 
     Although the above embodiment has been described with a first and a second predetermined temperature so as to indicate a hysteresis of the magnetic switch alloy, the present invention is not limited to this. Alternatively, the magnetic switch alloy could have a substantially negligible hysteresis and the first and second predetermined temperatures could substantially correspond to a single threshold temperature. 
     For instance, the material of the magnetic switch alloy could be Gd 5 (Si x Ge 1-x ) 4 . When using this material, the first and second predetermined switching temperatures can be set, for instance, between 40° C. and 80° C., according to the composition of the switching alloy. 
     Although the embodiment has been described with reference to a coil  1300  and a ferromagnet  1400 , the present invention is not limited to this. Alternatively, the present invention could be realized even without a ferromagnet, but only using a geometry that allows a magnetic field to be at least partially re-directed, or conveyed, from a first region to a second region, based on a change in temperature. The magnetic flux generated by such change can then be converted into electrical energy. The conversion to electrical energy can be done via the coil but also via any other means that allows a magnetic flux to be converted into electricity, such as a straight piece of conductor. 
     The material and dimensions of the switch  1200  are chosen based on the thermal mass of the CPV cell on which the wasted heat harvesting device  1000  is matched. More specifically, the thermal mass of the heat harvesting device  1000  is matched to the thermal mass of the CPV cell to be cooled. The term “matching” in this context means that, for instance, the heat harvesting device  1000  on the cell backside is, e.g., a 1.5 mm wide ring that is 200 μm thick. In this case, the physical mass of the ferromagnetic material is comparable, i.e., matched, to the mass of the cell. 
     As can be seen in  FIG. 2 , a process for realizing a wasted heat harvesting device  1000  includes a deposition step S 1  of depositing a metal layer on a substrate  100 , thereby obtaining intermediate wasted heat harvesting device  1001 . The deposition of the metal layer results in first and second coil segments  1301  and  1302 , respectively. 
     More specifically,  FIG. 2  represents from top to bottom, a top view of substrate  100 , a section view of substrate  100  along the line A-A′, and three section views of substrate  100  along the lines B-B′, C-C′ and D-D′. 
     As can be seen in the section view along line A-A′, the deposited metal layer could have a thickness T 1  in the range of 100 μm to 200 μm, with a preferred value of 150 μm. The metal could be any iron-based material or any other material that enables high magnetic flux. 
     Moreover, in this particular example, the length of the first and second coil segments  1301  and  1302  along direction Y, on the top view, is longer than the length of those elements along direction X. However, the present invention is not limited to this. Alternatively, the dimensions of the first coil segment  1301  and second coil segment  1302  could be different between each other as long as the chosen dimensions allow the realization of a coil. 
     As can be seen in  FIG. 3 , the process for realizing a wasted heat harvesting device  1000  further includes a deposition step S 2  of depositing a magnetic alloy on a substrate  100 , thereby obtaining intermediate wasted heat harvesting device  1002 . The deposition of the magnetic alloy results in switch  1201 . 
     More specifically,  FIG. 3  represents, from top to bottom, a top view of substrate  100 , a section view of substrate  100  along the line A-A′, and three section views of substrate  100  along the lines B-B′, C-C′ and D-D′. 
     As can be seen in the section view along line A-A′, the deposited magnetic alloy layer could have a thickness T 2  in the range of 100 μm to 300 μm, with a preferred value of 200 μm. The metal could be any of Gd 5 (Si x Ge 1-x ) 4  as described above or any other thermomagnetic material with the capability of switching the magnetic performance at a defined temperature. 
     As can be seen in  FIG. 4 , the process for realizing a wasted heat harvesting device  1000  further includes a deposition step S 3  of depositing a ferromagnetic seed material on a substrate  100 , thereby obtaining intermediate wasted heat harvesting device  1003 . This deposition of the ferromagnetic material results in ferromagnetic seed layer  1401 . 
     More specifically,  FIG. 4  represents, from top to bottom, a top view of substrate  100 , a section view of substrate  100  along the line A-A′, and three section views of substrate  100  along the lines B-B′, C-C′ and D-D′. 
     The purpose of the ferromagnetic seed layer  1401  is to realize a base for the subsequent quicker deposition of a ferromagnetic thick layer  1402 . 
     As can be seen in the section view along line A-A′, the deposited ferromagnetic layer could have a thickness T 3  in the range of 100 μm to 200 μm, with a preferred value of 150 μm. The material could be any of iron type, ferromagnetic alloy, such as Fe or Fe—P or FeSi or Ni/Fe 45/55. The advantage of such material is that it has excellent ferromagnetic performance. 
     In the particular example of  FIG. 4 , the position of the ferromagnetic seed layer  1401  in the present embodiment consists of an outer circle close to the peripheral substrate  100 , an inner circle and two connecting arms between the inner and outer circles. However, the present invention is not limited to this and more examples will be provided below. Generally speaking, the ferromagnetic material should be deposited so that it can be connected at least on one side to the subsequently deposited magnet and so that it can be connected on at least one side to the magnetic switch alloy. In this embodiment, as can be seen in the section taken along line A-A′, the ferromagnetic seed layer  1401  is deposited on a region overlapping first and second coil segments  1301  and  1302  but not in a region overlapping switch  1200 . 
     As can be seen in  FIG. 5 , the process for realizing a wasted heat harvesting device  1000  further includes a deposition step S 4  of depositing a ferromagnetic material on a substrate  100 , thereby obtaining intermediate wasted heat harvesting device  1004 . This deposition of the ferromagnetic material results in ferromagnetic thick layer  1402 . 
     More specifically,  FIG. 5  represents, from top to bottom, a top view of substrate  100 , a section view of substrate  100  along the line A-A′, and three section views of substrate  100  along the lines B-B′, C-C′ and D-D′. 
     The ferromagnetic thick layer  1402  is deposited over ferromagnetic seed layer  1401 . The combination of the two layers results in ferromagnet  1400 . 
     As can be seen in the section view along line A-A′, the deposited ferromagnetic layer could have a thickness T 4  in the range of 100 μm to 200 μm, with a preferred value of 150 μm. The metal could be the same as the ferromagnetic seed layer  1401 , or a different one. The advantage of using a different material is that a ferromagnetic seed could be chosen so as to secure good mechanical and thermal contact to the cell backside surface. 
     Although  FIGS. 4 and 5  and steps S 3  and S 4  have been defined in order to realize a ferromagnet  1400 , the ferromagnet  1400  could be realized in a single deposition step or in more than two deposition steps. The advantage of using more than one deposition step is that seed layer deposition may secure a better mechanical and thermal contact compared to a single step process. 
     As can be seen in  FIG. 6 , a process for realizing a wasted heat harvesting device  1000  includes a deposition step S 5  of depositing a metal layer on a substrate  100 , thereby obtaining intermediate wasted heat harvesting device  1005 . The deposition of the metal layer results in a third coil segment  1303 . 
     More specifically,  FIG. 6  represents, from top to bottom, a top view of substrate  100 , a section view of substrate  100  along the line A-A′, and three section views of substrate  100  along the lines C-C′, E-E′ and D-D′. 
     As can be seen in the section view along line D-D′, the deposited metal layer could have a thickness T 5  in the range of 100 μm to 200 μm, with a preferred value of 150 μm. The metal could be the same one used for first and second coil segments  1301  and  1302  ( FIG. 2 ). 
     Third coil segment  1303  is deposited so that it creates a connection between one end of first coil segment  1301  and an end of second coil segment  1302 . In this manner, a coil structure  1300  wound around ferromagnet  1400  is achieved. 
     As can be seen in  FIG. 7 , the process for realizing a wasted heat harvesting device  1000  further includes a deposition step S 6  of depositing a magnetic material on a substrate  100 , thereby obtaining wasted heat harvesting device  1000 . This deposition of the magnetic material results in magnet  1100 . Alternatively or in addition, the magnet  1100  can be realized through deposition or assembly of a finished permanent magnet. The deposition may require an activation of the magnet  1100  through annealing and magnetization. 
     More specifically,  FIG. 7  represents, from top to bottom, a top view of substrate  100  and a section view of substrate  100  along the line F-F′. 
     As can be seen in the section view along line F-F′, the deposited magnetic layer could have a thickness T 6  in the range of 100 μm to 300 μm, with a preferred value of 200 μm. The magnetic material could be any of SmCo 5 , Sm 2 Co 15 , Nd 2 Fe 14 B or Ba ferritis. The advantage of such materials is that they are all very strong permanent magnet materials. 
     In the particular example of  FIG. 7 , the position of the magnet  1100  in the present embodiment is between the outer circle of ferromagnetic material  1400 , close to the peripheral substrate  100  and the inner circle of ferromagnetic material  1400 . However, the present invention is not limited to this, and more examples will be provided below. Generally speaking, the magnet should be deposited so that it can be connected at least on one side to the ferromagnetic material  1400  and on the other side to the ferromagnetic material  1400  or to the switch  1200 . 
     Although in the above examples the thicknesses T 1 , T 2 , T 3 , T 4 , T 5  and T 6  have been pictured as being different, the present invention is not limited by this graphical representation, which has only been employed so as to clarify the various thicknesses. More specifically, the thicknesses could all be the same, or some of them could be the same. 
     Although in the above examples the term “deposition” has been employed for the steps S 1 , S 2 , S 3 , S 4 , S 5  and S 6 , this term is to be intended in the general meaning of realizing a layer. Accordingly, in order to deposit the described layers, a CVD, PVD, plasma deposition, nanoprinting, screen printing, or any other deposition technique could be used. 
     The deposition of any of the layers could be followed by one or more annealing steps. 
       FIGS. 8A and 8B  represent alternative embodiments of wasted heat harvesting devices  1106  and  1107 . More generally, any physical implementation of the wasted heat harvesting device  1000  according to  FIG. 1A  can be realized. 
     In general, a typical size of the wasted heat harvesting devices  1000 ,  1106  and  1107  is in the range of 5.5 mm by 5.5 mm. This is the typical cell size used in the terrestrial CPV cell industry. 
       FIG. 9A  illustrates a wasted heat harvesting system  2000  according to a further embodiment of the present invention. The wasted heat harvesting system  2000  could be attached to the backside of a CPV cell. In the case that the CPV cell is realized on a germanium substrate, the wasted heat harvesting system  2000  could be realized or applied on the underside of the germanium substrate before or after the realization of the CPV cell. 
     The wasted heat harvesting system  2000  includes a plurality of wasted heat harvesting devices  1000 . Each wasted heat harvesting device  1000  includes at least magnet  1100 , ferromagnetic material  1400 , switch  1200  and coil  1300 . The power output  1500  of the coil  1300  of each of the wasted heat harvesting devices  1000  produces AC current. Accordingly, when a plurality of wasted heat harvesting devices  1000  is to be connected together on a wasted heat harvesting system  2000 , different options are available. 
     For instance, the multiple power outputs  1500  could all be connected to each other in series, in parallel or in groups of parallel and series connections. In the following, four embodiments of the present invention will be described in which the connections of the multiple power outputs  1500  within a wasted heat harvesting system  2000  are described in conjunction with the connections of multiple power outputs  2500  of a plurality of wasted heat harvesting systems  2000 . 
       FIG. 9B  illustrates a modular wasted heat harvesting system  3000  composed by two wasted heat harvesting systems  2000 , each having a power output  2500 . Each of the two wasted heat harvesting systems  2000  includes a plurality of wasted heat harvesting devices  1000 , each having a power output  1500 . 
     In  FIG. 9B , the multiple power outputs  1500  are connected in parallel to each other and this parallel connection is input into AC/DC converter  2100 . In this manner, a wasted heat harvesting system  2000  would output a DC current on the power output  2500 . In this case, it is assumed that the different wasted heat harvesting devices  1000  of the wasted heat harvesting system  2000  are operating with the same frequency. This might be the case if the wasted heat harvesting devices are, for instance, in close proximity to each other. 
     Additionally, a second wasted heat harvesting system  2000  is realized in the same manner as described above. The two power outputs  2500  of the two wasted heat harvesting systems  2000  are connected to each other in parallel so as to realize a modular wasted heat harvesting system  3000 . This may be used in the case where the two wasted heat harvesting systems  2000  are placed in different regions having different temperatures, which would cause the operation of the plurality of wasted heat harvesting devices  1000  in each of the wasted heat harvesting systems  2000  to not be in phase with the remaining wasted heat harvesting devices. 
     Although the power outputs  1500  of the multiple wasted heat harvesting devices  1000  of each of the two wasted heat harvesting systems  2000  are illustrated as being connected in parallel to each other, they might be connected in series instead. 
     Similarly, although the power outputs  2500  of the two wasted heat harvesting systems  2000  are illustrated as being connected in parallel to each other, they might be connected in series instead. 
     In  FIG. 10A , the multiple power outputs  1500  are connected in parallel to each other and this parallel connection is input into AC/AC converter  2200 . In this manner, a wasted heat harvesting system  2000  would output an AC current on the power output  2500 . In this case, it is assumed that the different wasted heat harvesting devices  1000  of the wasted heat harvesting system  2000  are operating with the same frequency. This might be the case if the wasted heat harvesting devices are, for instance, in close proximity to each other. 
     Additionally, a second wasted heat harvesting system  2000  is realized in the same manner as described above. The two power outputs  2500  of the two wasted heat harvesting systems  2000  are connected to each other in parallel so as to realize a modular wasted heat harvesting system  3000  ( FIG. 9B ). This may be used in the case where the two wasted heat harvesting systems  2000  are placed in different regions having different temperatures, which would cause the operation of the plurality of wasted heat harvesting devices  1000  in each of the wasted heat harvesting systems  2000  to not be in phase with the remaining wasted heat harvesting devices. In this case, if the frequency of operation of the two wasted heat harvesting systems  2000  is not the same, the frequency of the AC current being output at power outputs  2500  can be aligned, via a connection  3011  between the AC/AC converters  2200 . In this manner, the operation of the wasted heat harvesting systems  2000  can be phased, so as to provide a stable output  3500  of modular wasted heat harvesting systems  3010 . 
     In  FIG. 10B , a modular wasted heat harvesting system  3020  is illustrated, wherein each of the multiple power outputs  1500  is connected to an AC/DC converter  2101 . In this manner, a wasted heat harvesting system  2000  would output a DC current on the power output  2500 . In this case, it is assumed that the different wasted heat harvesting devices  1000  of the wasted heat harvesting system  2000  are not operating with the same frequency. 
     In  FIG. 11 , each of the multiple power outputs  1500  is connected to an AC/AC converter  2201 . In this manner, a wasted heat harvesting system  2000  would output an AC current on the power output  2500 . In this case, it is assumed that the different wasted heat harvesting devices  1000  of the wasted heat harvesting system  2000  are not operating with the same frequency. In order to guarantee an efficient combination of the multiple AC currents being generated, a phase information is shared among the plurality of AC/AC converters  2201  via connection  3031 . 
     Any combination of the wasted heat harvesting device  1000 , wasted heat harvesting system  2000 , and modular wasted heat harvesting system  3000 , can be mounted on the back surface of a CPV cell, or, more generally, a PV cell. For instance, it could be mounted directly on the cell. Alternatively, or in addition, it could be mounted onto a heat-sink. 
     Still alternatively, or in addition, any combination of the wasted heat harvesting device  1000 , wasted heat harvesting system  2000 , and modular wasted heat harvesting system  3000 , could be realized directly on the back of the PV or CPV cell. 
     Although the present invention has been described with reference to the cooling of a concentrated photovoltaic cell, the present invention is not limited to this and could be used for cooling of any semiconductor substrate. 
     Still in addition, the present invention could be realized on a thin film, either semiconductor, metallic, or plastic, or any other material, and could be employed as an active cooling capable of generating current through the wasted heat in an application other than semiconductors, for instance, for powering engine management systems, or any surfaces exposed to the sun, like black painted surfaces, or motor engines, for instance, in cars, etc. 
     While the above was described with respect to one or more various embodiments, a person skilled in the art will appreciate the features described herein with respect to one or more embodiments that can be combined together without departing from the scope of the present invention as defined by the claims.