Abstract:
The present invention relates to an electricity generation unit ( 100 ) equipped with:—at least one heat withdrawal chamber ( 23 ) for at least temporarily arranging a heat source ( 3 ) at least partially therein,—at least one shell ( 13 ) for delimiting the heat withdrawal chamber ( 23 ) from the surrounding environment thereof,—at least one thermoelectric converter ( 1 ) for converting heat into electrical energy. Provision is made for the thermoelectric converter ( 1 ) to be removable from the electricity generation unit ( 100 ), while the sleeve ( 13 ) of the working chamber can remain closed, unchanged.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter of the invention is an electricity generation unit for converting heat into electrical energy, according to the preamble of claim  1 . 
       PRIOR ART 
       [0002]    In some technical applications, a need exists to convert heat into electricity, for example to allow the process waste heat from internal combustion engines, foundries or rolling mills to be utilized. This can be achieved using thermoelectric generators (TEG), which contain thermoelectric converters. 
         [0003]    Thermoelectric generators of this type can be located, e.g. within a channel through which hot chemicals or heat-radiating products are transported, e.g. red-hot bottles, steel bars or other products that are manufactured or processed by casting processes or other thermal processes. 
         [0004]    This involves a number of disadvantages. These include:
       limited efficiency   varying localized temperature distributions to thermoelectric generators due to the varying distances from a heat source   soiling and corrosion on heat exchanging surfaces   diminishing efficiency with prolonged operation due to accumulated soiling   potential for localized thermal overloading   seals of water and power connections are located close to a hot heat source   costly maintenance due to poor accessibility of the thermoelectric generators while a device that generates waste heat is in operation       
 
         [0012]    Thus a need for an improved utilization of waste heat exists. 
       SUBJECT MATTER OF THE INVENTION 
       [0013]    In light of this background, a technical concept having the features of claim  1  is proposed. Additional advantageous embodiments are found in the remaining claims and in the following description. 
     
    
     
       FIGURES 
         [0014]    Details of the invention are specified in the following description and in the claims. These specifications are intended to clarify the invention. However, they are merely exemplary in nature. Of course, one or more of the described features may also be omitted, modified or enhanced within the scope of the invention as defined by the independent claims. The features of different embodiments may of course also be combined with one another. 
           [0015]    What is critical is that the concept of the invention must essentially be realized. When a feature is to be at least partially fulfilled, this includes cases in which said feature is also fully or substantially fully fulfilled. “Substantially” in this context means particularly that implementation allows the desired use to be achieved to a recognizable extent. This can mean, in particular, that a corresponding feature is at least 50%, 90%, 95% or 99% fulfilled. If a minimum quantity is indicated, more than said minimum quantity may, of course, also be used. When the number of a component is indicated as at least one, this also includes particularly embodiments having two, three or some other multiple of components. The same generally also applies when the indefinite article “a, an” is used. “A single” will be explicitly specified as such where necessary. 
           [0016]    A description in reference to an object may also be applied to the majority or the entirety of all other objects of the same type. Unless otherwise indicated, intervals include their end points. 
           [0017]    In the following, reference will be made to: 
           [0018]      FIG. 1A  a schematic longitudinal section of a steel rolling mill with two embodiments of an electricity generation unit  100  and  100 ′ 
           [0019]      FIG. 1B  an enlarged view of detail a) of  FIG. 1A   
           [0020]      FIG. 1C  an additional embodiment of an electricity generation unit  100 ″ 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0021]      FIGS. 1A and 1C  show a waste heat generation unit  200 . This may be a motor, for example, or as in this case, a rolling mill for producing or processing metal bars. 
         [0022]    Waste heat generation unit  200  has a heat source  3  or generates said heat source continuously. Heat source  3  is preferably a mass flow of gaseous, liquid and/or solid material, in this case red-hot, solid metal. Frequently this this is a mass flow which carries in it residual process heat that will be converted to electricity. Said mass flow may be a fluid flow, e.g. of heated water or hot waste gases from an internal combustion engine, or as in this case, a mass flow of a solid material. In the embodiment example, heat source  3  is red-hot rolled steel in or downstream of a rolling mill. 
         [0023]    A transport device  5  is preferably provided for transporting at least one heat-carrying mass flow. In the present case, said device comprises rollers of a rolling mill, which transport steel bars through or out of the rolling mill. In the case of fluidic heat-carrying mass flows however, pumps, impeller wheels or other flow machines may also be provided as the transport device. 
         [0024]    According to the invention, at least one electricity generation unit  100  is preferably provided for converting heat from heat source  3  into electrical energy. Said unit is preferably a thermoelectric generator or a device having at least one thermeoectric converter  1 . 
         [0025]    Waste heat generation unit  200 , heat source  3  and/or electricity generation unit  100  are preferably equipped with at least one heat withdrawal chamber  23 , or are at least partially arranged therein. Said chamber is understood to include a chamber region which is heated by a heat source  3  and in which electricity generation unit  100  directly or indirectly withdraws the thermal energy it requires from heat source  3 . Heat withdrawal chamber  23  can also encompass a plurality of chamber regions that are structurally delimited from one another. 
         [0026]    Preferably, at least one heat withdrawal chamber  23  is at least partially encompassed by a shell  13 . Shell  13  can be formed at least partially by a waste gas pipe of an engine, for example, or as in this case by a housing of a rolling mill or of the component parts thereof. Shell  13  serves particularly to shield heat source  3  from the area surrounding it. This serves to protect the surrounding area against the effects of excessive heat. At the same time, the shell prevents any loss of thermal energy. Shell  13  can be embodied as a device for conducting the heat-carrying mass flow, e.g. as pipes through which hot waste water flows. However, it may also be arranged, as in this embodiment example, spaced from the heat-carrying mass flow of heat source  3 . This is expedient particularly in the case of high-temperature heat sources  3 , as it protects shell  13  against excessive thermal loads. In some cases it is expedient for shell  13  to be hermetically sealed, however in cases such as the present case this is not mandatory. 
         [0027]    Heat withdrawal chamber  23  and/or shell  13  thereof can be components of electricity generation unit  100 . Heat withdrawal chamber  23  can also be a separate component between electricity generation unit  100  and waste heat generation unit  200 . In the present case, heat withdrawal chamber  23  is embodied as a component of waste heat generation unit  200 . 
         [0028]    An electricity generation unit  100  has at least one thermoelectric converter  1  for converting heat directly into electricity. This is understood, for example, as a component that is capable of converting heat directly into electrical voltage. In this case, this is preferably a plurality of Seebeck elements electrically connected in series. 
         [0029]    At least one thermoelectric converter  1  preferably has one or more thermoelectric elements  21 . These are understood particularly as Peltier and Seebeck elements. Preferably, one or more of such thermoelectric elements  21  are embodied as flat, annular disks. These are preferably stacked one on top of the other so as to multiply the amount of electrical voltage that can be tapped. This preferably results in a thermoelectric converter  1  in the form of a tubular structure having a cylindrical exterior at an outer diameter and a cylindrical interior at an inner diameter. 
         [0030]    At least one thermoelectric element  21  preferably has a warm side  15 . In the case of the annular disks, this corresponds to the outer side at the outer diameter of a thermoelectric element  21 . This is where the exchange of heat between heat source  3  and thermoelectric converter  1  or one or more thermoelectric elements  21  takes place. 
         [0031]    At least one thermoelectric element  21  preferably has at least one cold side  17 . In the case of the annular disks, cold side  17  corresponds to the inner side at the inner diameter of a thermoelectric element  21 . 
         [0032]    Cold side  17  is preferably cooled by a cooling fluid  19 , which flows through the hollow inner diameter of thermoelectric elements  21 , that is, through the annular disks. In this manner, the temperature on cold side  17  is preferably kept constant. Cooling fluid  19  is preferably circulated in a cooling fluid circuit or is provided via a continuously supplied cooling fluid flow. In the interest of clarity however, this is not illustrated here in detail. 
         [0033]    An electricity generation unit  100 , a waste heat generation unit  200  and/or a heat withdrawal chamber  23  have at least one heat withdrawal channel  11 . Said channel penetrates at least partially into heat withdrawal chamber  23  at least at one passage opening. At least sections of said channel preferably extend linearly. Said section is preferably spaced from shell  13  and/or aligned at an angle relative thereto. 
         [0034]    At least sections of heat withdrawal channel  11  are preferably tubular in shape. Such a tube can be circular, oval or even rectangular in cross-section. Heat withdrawal channel  11  preferably enters heat withdrawal chamber  23  in such a way that fluid or hot material cannot exit heat withdrawal chamber  23  at the common boundary region. This can be ensured, for example, by welding heat withdrawal channel  11  to heat withdrawal chamber  23  along their common boundaries. 
         [0035]    Heat withdrawal channel  11  preferably has a wall  51 . Said wall is preferably made of a thermally resistant material. This can be pipes made of stainless steel or titanium, for example. The material is preferably highly thermally conductive. For high temperature applications, however, lower thermal conductivity may be preferable. Wall  51  is provided for preventing direct contact between the hot material in the heat withdrawal chamber and a heat withdrawal fluid  50  located in heat withdrawal channel  11  and/or a thermoelectric converter  1 . It also serves as a fluid conducting device when a heat withdrawal fluid  50  is flowing through heat withdrawal channel  11 . 
         [0036]    Heat withdrawal channel  11  preferably penetrates heat withdrawal chamber  23  in such a way that at least one entry point  60  and at least one exit point  61  are created. A thermoelectric converter  1  arranged between these two positions is thereby accessible from two sides. A heat withdrawal fluid  50  flowing through heat withdrawal channel  11  can thus enter at entry point  60  and can be withdrawn from heat withdrawal chamber  23  at exit point  61 . 
         [0037]    If a thermoelectric converter  1  inside a heat withdrawal channel  11  is located within heat withdrawal chamber  23 , at least one end of heat withdrawal channel  11  preferably essentially does not project beyond shell  13  of heat withdrawal chamber  23 . This improves the accessibility of thermoelectric converter  1  located inside heat withdrawal channel  11 . 
         [0038]    If one or more thermoelectric converters  1  inside a heat withdrawal channel  11  are located within heat withdrawal chamber  23 , they preferably take up at least 50% of the distance between entry point  60  and exit point  61 , preferably at least 80%, preferably substantially entirely. 
         [0039]    If one or more thermoelectric converters  1  inside a heat withdrawal channel  11  are located within heat withdrawal chamber  23 , they preferably take up at least 30% of the area of the open cross-section of heat withdrawal channel  11 , preferably at least 50%, preferably no more than 95%. 
         [0040]    When a thermoelectric converter  1  is located within a heat withdrawal chamber  23 , this does not mean that it comes into direct contact with the medium or the heat source  3  located there. Rather, it means that said converter is located within the shell  13  of heat withdrawal chamber  23 , which is embodied as closed. Said converter always remains separated from heat withdrawal chamber  23  by wall  51  of heat withdrawal channel  11 . 
         [0041]    In this connection, it can be expedient to provide spacers  12 , which keep a thermoelectric converter  1  that is arranged inside heat withdrawal channel  11  spaced from wall  51  of heat channel  11 . Said spacers can be strip-type fixed members arranged along thermoelectric converter  1  or along heat withdrawal channel  11 . They may also be nubs that keep thermoelectric converters  11  spaced in relation to wall  51  at points. It is further conceivable for at least one spacer  12  to be embodied as a film, ring or pipe which keeps thermoelectric converter  1  spaced from heat withdrawal channel  11 . Spacers  12  can be embodied as a film-type insulating material, e.g. glass wool or a silicon coating, but may also be made of the material of wall  51 . In the present example, said spacer is a fixed member made of metal and arranged along the tubular heat withdrawal channel  23 . In the present case, this is a weld seam in the form of a bead. 
         [0042]    This results in one or more intermediate spaces  55  formed between wall  51  and at least one thermoelectric converter  1 . Said spaces facilitate the removal of the thermoelectric converter from heat withdrawal channel  11 . This is important since the dimensions of the two components can change substantially as a result of extreme temperature fluctuations, and therefore the thermoelectric converter could otherwise become stuck in heat withdrawal channel  11 . Furthermore, an intermediate space  55  that is filled with air or with an insulating material protects thermoelectric converter  1  from becoming overloaded by extremely high temperatures. 
         [0043]    An entry point  60  and an exit point  60  can be located opposite one another at the same height relative to a direction of movement B of heat source  3 , as in electricity generation unit  100 ′. 
         [0044]    However the distance between entry point  60  and an exit point  60  can also have at least one directional component along direction of movement B, so that entry point and exit point are located at different heights from one another relative to a direction of movement B of heat source  3 , as in electricity generation units  100  and  100 ″. 
         [0045]    When a heat withdrawal fluid  50  is flowing through heat withdrawal channel  11 , it can be expedient in most cases to alternatively or additionally arrange thermoelectric converter  1  outside of heat withdrawal chamber  23 , in order to optimize utilization of the available flow cross-section within heat withdrawal channel  11 . 
         [0046]    When a thermoelectric converter  1  is arranged inside heat withdrawal channel  11  but outside of heat withdrawal chamber  23 , at least one of the two ends of heat withdrawal channel  11  preferably extends beyond shell  13  of heat withdrawal chamber  23 , in order to further convey a heat withdrawal fluid  50 . 
         [0047]    When a thermoelectric converter  1  is arranged inside heat withdrawal channel  11  but outside of heat withdrawal chamber  23 , preferably at least one, but more preferably a plurality of thermoelectric converters  1  are arranged in a converter module  10 . The cross-section of this converter module  10  is preferably enlarged in relation to the cross-section of the remaining heat withdrawal channel  11 . This allows compensation for the cross-section that is blocked by thermoelectric converter  1 , so that the flow rate remains constant. It can also be provided that the cross-sectional area of the available inner open flow cross-section in converter module  10  is greater than the open flow cross-section in the remainder of heat withdrawal channel  11 . As a result, the flow rate of heat withdrawal fluid  50  within converter module  10  is reduced. This is advantageous for a heat exchange between heat withdrawal fluid  50  and thermoelectric converters  1 . 
         [0048]    In some cases, converter module  10  is a container having a plurality of pipes which are open to the exterior but which do not allow the contents of the container to pass to the exterior, as in the case of electricity generation units  100  and  100 ″. Rod-like thermoelectric modules are then introduced into the pipes. Said modules can also be removed from the pipes without opening the container. This is important particularly in systems that involve radioactive, aggressive or hot media. 
         [0049]    Heat withdrawal channel  11  preferably has at least one fluid infeed device  44 . Said device may simply be one end of a pipeline. However, it may also be a valve or a more complex type of fluid supply device. 
         [0050]    Heat withdrawal channel  11  preferably has at least one fluid withdrawal device  45 . It can have the same configuration as fluid infeed device  44 . 
         [0051]    In embodiments or operating states in which a fluid return device is not provided or is not in operation, and heat channel  11  is thus an open system, the desired volumetric flow rate for a heat withdrawal fluid  50  can preferably be adjusted by adjusting the degree of opening of fluid infeed device  44  and/or fluid withdrawal device  45 . 
         [0052]    Preferably however, heat withdrawal channel  11  has at least one fluid return device  46 . Said device is expediently a channel section that connects the beginning and end of heat withdrawal channel  11  to form a closed loop. However, it may also be a throttle valve or the like, particularly when combined with the fluid infeed or withdrawal device. 
         [0053]    A heat withdrawal fluid  50  may be transported within heat withdrawal channel  11  by means of natural convection, since a localized temperature increase in a heat withdrawal fluid  50  by means of heat source  3  will result in a tendency of heat withdrawal fluid  50  to rise. This is particularly effective for embodiments in which at least sections of a heat withdrawal channel  11  are arranged along and/or parallel to the alignment and/or direction of movement B of a heat source  3  in heat withdrawal chamber  23 . 
         [0054]    For some applications, it may be expedient to feed a heat withdrawal fluid  50  into heat withdrawal channel  11  via a fluid infeed device  44 . In some cases, once the heat withdrawal fluid has flowed through heat withdrawal chamber  23  and following a heat exchange with a thermoelectric converter  1 , it may be expedient to withdraw said fluid from heat withdrawal channel  11  via a fluid withdrawal device  45 . This flow movement can be implemented without additional drive means, solely by means of the natural tendency of hot media to rise. 
         [0055]    For certain applications it may be expedient to arrange a fluid pumping device  7  in heat withdrawal channel  11 , at fluid infeed device  44  and/or at fluid withdrawal device  45 . Such a fluid pumping device  7  allows the volume of heat withdrawal fluid  50  that is pumped to be influenced. An overheating of wall  51  of heat withdrawal channel  11  within the heat withdrawal chamber and/or an overheating of thermoelectric converter  1 , for example, can thereby be prevented. When the thermal load on heat withdrawal fluid  50  is lower, the flow rate can be correspondingly reduced in order to increase the transfer of heat between heat withdrawal chamber  23  and heat withdrawal fluid  50  and/or between heat withdrawal fluid  50  and thermoelectric converter  1 . 
         [0056]    Furthermore, when a fluid pumping device  7  is used, fluid can flow through heat withdrawal channel  11  in two different directions. 
         [0057]    Particularly in cases in which shell  13  is exposed to high thermal loads, this can be advantageous for operating the section of heat withdrawal channel  11  that is located within heat withdrawal chamber  23  in the manner of a direct-current heat exchanger. This is understood to mean that heat withdrawal fluid  50  flows in the same direction in which a heat source  3  is moving within heat withdrawal chamber  23 . The hottest point in heat withdrawal channel  11  is thereby cooled by the coolest possible heat withdrawal fluid  50 . 
         [0058]    If the temperature of heat source  3  is significantly lower than the melting point, which is the most favourable operating point for thermoelectric converter  1 , this lends itself to operation in the manner of a countercurrent heat exchanger. This means that the direction of flow of heat withdrawal fluid  50  is directed at least in sections substantially opposite the direction of movement of heat source  3  within heat withdrawal chamber  23 . This includes movements in which, in a vector analysis, the directional fraction opposite the direction of movement of heat source  3  is at least as great as its directional fraction perpendicular to said direction of movement. 
         [0059]    The flow direction of fluid pumping device  7  is preferably reversible, particularly if the temperature of the available heat source fluctuates substantially. 
         [0060]    For some applications, to achieve better accessibility it can be expedient to arrange a heat withdrawal channel  11  and/or the thermoelectric converters  1  arranged therein vertically. The thermoelectric converters  1  can then be removed using a crane, for example. In the case of electricity generation unit  100 ′ shown in  FIG. 1 , however, a horizontal arrangement is preferred, in order to achieve a uniform thermal load of thermoelectric converters  1  over their entire length. 
         [0061]    When a thermoelectric converter  1  is located outside of a heat withdrawal chamber  23 , and if a heat source  3  has a direction of movement or flow within heat withdrawal chamber  23 , at least sections of least one heat withdrawal channel  11  are preferably arranged along this direction of movement B. This includes pathways that are angled in relation to said direction of movement, particularly if the angle in relation to the direction of movement is smaller than 45°. 
         [0062]    When at least sections of a heat withdrawal channel  11  are arranged along a direction of movement of a heat source  3 , it is expedient, particularly with embodiments that utilize natural convection for transporting heat withdrawal fluid  50 , for the distance between the heat withdrawal channel and heat source  3  to decrease in the direction of movement of heat source  3 , and/or for the height of heat withdrawal channel  11  to drop in this direction. Both permit the heated fluid to ascend toward the warmer withdrawal point. For applications in which the temperature of the withdrawan heat withdrawal fluid  50  would be undesirably high, the aforementioned angling of heat withdrawal channel  11  can also be reversed. The fluid withdrawal point is thereby moved to a cooler zone. 
         [0063]    The invention thus enables thermoelectric elements and thermoelectric generators that are used, e.g., in the chemicals and metallurgical industries to be replaced without interrupting the main industrial process. 
       Particularly Preferred Features 
       [0064]    Particularly preferred is an electricity generation unit  100  for withdrawing heat from at least one heat withdrawal chamber  23  in which a heat source  3  is at least temporarily at least partially arranged, wherein heat withdrawal chamber  23  has at least one shell  13  for delimiting heat withdrawal chamber  23  from the area surrounding it, and electricity generation unit  100  is equipped with at least one thermoelectric converter  1  for converting heat into electrical energy. It is also expedient for thermoelectric converter  1  to be removable from electricity generation unit  100  while shell  13  of operating chamber  23  remains closed. This facilitates maintenance of the thermoelectric generators. 
         [0065]    Particularly preferred is an electricity generation unit  100  in which at least one thermoelectric converter  1  is arranged inside a heat withdrawal channel  11 , at least sections of which are in turn arranged within heat withdrawal chamber  23 . This increases efficiency. 
         [0066]    Particularly preferred is an electricity generation unit  100  in which heat withdrawal channel  11  penetrates heat withdrawal chamber  23  at least at one point and/or in which the main direction of extension of said channel intersects at least in sections with the shell of heat withdrawal chamber  23  and/or is aligned running up to the heat source. This results in a larger surface for heat exchange. 
         [0067]    Particularly preferred is an electricity generation unit  100  in which at least one heat withdrawal channel  11  has at least one wall  51  which delimits the interior of heat withdrawal channel  11  at least partially in relation to heat withdrawal chamber  23 , in which at least one thermoelectric converter  1  is arranged at least partially inside heat withdrawal channel  11  and at least partially within heat withdrawal chamber  23 , in which thermoelectric converter  1  is arranged at least partially spaced from wall  51 , and in which thermoelectric converter  1  is arranged concentrically and/or parallel in relation to wall  51 . A uniform temperature application and easy removal are thereby achieved. 
         [0068]    Particularly preferred is an electricity generation unit  100  in which at least one thermoelectric converter  1  or at least one wall  51  of a heat withdrawal channel  11  are held spaced from one another by means of one or more spacers  12 . This facilitates withdrawal even in the case of temperature and size fluctuations. 
         [0069]    Particularly preferred is an electricity generation unit  100  in which at least one spacer  12  is mounted on thermoelectric converter  1 , on wall  51  or separately from both. Depending on the intended use, one of these options is particularly easy to install. 
         [0070]    Particularly preferred is an electricity generation unit  100  in which an intermediate space  55  is provided between a thermoelectric converter  1  and a wall  51  of a heat withdrawal chamber  23  to facilitate a removal of thermoelectric converter  1  from heat withdrawal chamber  23 . 
         [0071]    Particularly preferred is an electricity generation unit  100  in which at least one thermoelectric converter  1  is located outside of a heat withdrawal chamber  23  to allow thermoelectric converter  1  to be removed without intervention into heat withdrawal chamber  23 , in which at least one heat withdrawal channel  11  is filled at least partially with a heat withdrawal fluid  50  and in which a transfer of heat from a heat source  3  to thermoelectric converter  1  is based on a flow of heat withdrawal fluid  50  along heat withdrawal channel  11 . This increases efficiency. 
         [0072]    Particularly preferred is an electricity generation unit  100  in which a plurality of thermoelectric converters  1  are arranged in a converter module  10  and in which converter module  10  is located outside of a heat withdrawal chamber  23 . This facilitates maintenance and assembly.