Abstract:
An energy system for a processing or manufacturing facility is considered a cascading system, as it sequentially utilizes the output product or waste of higher energy processes as at least part of the input energy for lower energy processes. Multiple absorption chillers are incorporated throughout the system along the cascading process stages to step-down the energy in the output product of one stage to at or near the appropriate input energy level for a subsequent stage. Cooling capacity is created by the absorption chillers during each step-down phase for use elsewhere in the facility.

Description:
BACKGROUND 
       [0001]    The present invention relates to energy systems for processing and manufacturing facilities. 
         [0002]    Resource efficiency and conservation are important aspects of designing processing and manufacturing facilities. 
       SUMMARY 
       [0003]    The present invention provides an improved energy system for a processing or manufacturing facility. The system is considered a cascading system, as it sequentially utilizes the output product or waste of higher energy processes as at least part of the input energy for lower energy processes. Multiple absorption chillers are incorporated throughout the system along the cascading process stages to “step-down” the energy in the output product of one stage to at or near the appropriate input energy level for a subsequent stage. Cooling capacity is created by the absorption chillers during each step-down phase for use elsewhere in the facility. 
         [0004]    Additionally, the system is a fully balanced system in terms of water consumption. Fluid flow rates are determined for the entire system such that little or no excess water is used and/or wasted. The system is designed such that components in the system get precisely the amount of water needed for each specific operation. Therefore, water consumption, and the associated costs, are also reduced as compared to existing systems. 
         [0005]    In one embodiment, the invention provides an energy system for a facility. The energy system includes a first process stage resulting in an output fluid at a first temperature T 1 , a second process stage utilizing an input fluid at a second temperature T 2  lower than the first temperature T 1 , and a third process stage utilizing an input fluid at a third temperature T 3  lower than both the first and second temperatures T 1  and T 2 . The system further includes a first absorption chiller in fluid communication between the first process stage and the second process stage. The first absorption chiller is operable to reduce the temperature of the output fluid of the first process stage from the first temperature T 1  to the second temperature T 2  to provide the input fluid for the second process stage. The system also includes a second absorption chiller in fluid communication between the first absorption chiller and the third process stage. The second absorption chiller receives fluid at the second temperature T 2  from the first absorption chiller and is operable to further reduce the temperature of the fluid to the third temperature T 3  to provide the input fluid for the third process stage. 
         [0006]    No additional fluid is added to the output fluid in the system between the first process stage and the second process stage, or between the first process stage and the third process stage. Furthermore, no additional fluid is added to the output fluid in the second process stage. Additional fluid is added to the output fluid in the third process stage. 
         [0007]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic view of a first process stage of a cascading energy system embodying the invention. 
           [0009]      FIG. 2   a  is a schematic view of an absorption chilling section of the cascading energy system embodying the invention. 
           [0010]      FIG. 2   b  is a schematic view of a refrigeration system operating with heat exchange from the absorption chilling section of the cascading energy system embodying the invention. 
           [0011]      FIG. 3  is a schematic view of a second process stage of a cascading energy system embodying the invention. 
           [0012]      FIG. 4  is a schematic view of a third process stage of a cascading energy system embodying the invention. 
           [0013]      FIG. 5  is a schematic view of a fourth process stage of a cascading energy system embodying the invention. 
           [0014]      FIG. 6  is a schematic view of a fifth process stage of a cascading energy system embodying the invention. 
           [0015]      FIG. 7  is a schematic view of a sixth process stage of a cascading energy system embodying the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
         [0017]      FIGS. 1-7  together illustrate a cascading energy system  10  according to the present invention. Each figure schematically shows a different process stage or section of the overall system  10 . It should be noted that the illustrated process stages and sections are shown by way of example in relation to a food processing facility (e.g., a pork processing plant). However, other processing or manufacturing facilities can utilize components of the inventive energy system designed for use specifically with the specific processing and manufacturing stages of the particular facility. Those skilled in the art will understand that the illustrated embodiment includes detail, such as specific fluid temperatures, specific flow rates, and specific operations, that can vary according to the specific facility. 
         [0018]    Referring to  FIG. 1 , a first process stage  14  is illustrated as a rendering stage, in which waste animal tissue (e.g., pork) is converted into stable, value-added materials in a manner typical of that manufacturing process. Water from a well  18  is provided to a boiler system  22  at line  26 . Natural gas is supplied at line  30  to heat the water in the boiler  22  to generate steam at line  34 , as is well known. The steam at line  34  is used in a rendering station  38  to carry out the rending process. Water from the well  18  at a temperature of about 55 degrees Fahrenheit is also provided to the rendering station  38  for use therein at line  42 . The well water is provided to the rendering station  38  at a flow rate of between about 700 to about 1,050 gallons per minute, and in the illustrated embodiment at a flow rate of about 712 gallons per minute for a lower capacity system and about 1,045 gallons per minute for a higher capacity system. These flow rates are much lower than conventional flow rates to rendering operations of about 1,500 gallons per minute for lower capacity systems and about 2,200 gallons per minute for higher capacity systems. Optionally, potable ambient-temperature water may be supplied to the rendering station  38  at line  46  from a wastewater treatment stage (see  FIG. 5 ), as discussed further below. 
         [0019]    As a result of the rendering operation at the rendering station  38 , condensate returns to the boiler system  22  at line  50 . Additionally, the rendering operation results in output fluid or waste fluid in the form of water at a temperature T 1  of about 200 degrees Fahrenheit at line  54 . The output fluid maintains the flow rate of between about 700 to about 1,050 gallons per minute, and in the illustrated embodiment, a flow rate of about 712 gallons per minute for a lower capacity system and about 1,045 gallons per minute for a higher capacity system. In other embodiments, the output fluid could be steam or other gas/liquid combinations. As a byproduct of the high energy rendering operation, the output fluid is at a lower energy (i.e., a lower temperature) than the input fluid (i.e., steam) to the rendering operation. However, the cascading energy system  10  will make use of the output fluid from the rendering stage as at least a portion of the input fluid for one or more subsequent, lower energy operations. The output fluid can be collected in one or more surge tanks  58  to accommodate pressure changes in the system and until needed for the next section of the energy system  10 . In the illustrated embodiment, three to six 75,000 gallon surge tanks can be used depending on system requirements and capacity. Line  62  provides fluid communication for the output fluid between the surge tanks  58  and the next sections  66   a  and  66   b  (see  FIGS. 2   a  and  2   b ) of the energy system  10 . 
         [0020]    The fluid flow rate of the output fluid from the surge tanks  58  can be regulated to between about 500 to about 750 gallons per minute depending on system requirements and capacity. For a lower capacity system, the flow rate can be about 504 gallons per minute, while for a higher capacity system, the flow rate can be about 740 gallons per minute. Conventional rendering operations typically result in much higher output flow rates (e.g., about 1,500 gallons per minute for lower capacity systems and about 2,200 gallons per minute for higher capacity systems) of waste water at about 140 degrees Fahrenheit, much of which is simply dumped to a wastewater treatment stage or a sewer without being used further. In these conventional systems, the 1,500 to 2,200 gallons per minute flow rate is what is provided from the well or water source, and is at least about double that necessary with the present invention. The additional water results in a smaller temperature increase in the output water, which is why the conventional waste water exiting the rendering stage is only at about 140 degrees Fahrenheit. Therefore, with the energy system  10  of the present invention, more of the waste heat is retained for subsequent use. As will be further understood from the description below, the energy system  10  is a balanced system in terms of water consumption, such that little or none of this initial output fluid is wasted. 
         [0021]      FIG. 2   a  illustrates the absorption chilling or energy step-down section  66   a  of the energy system  10 . The 200 degree Fahrenheit water in line  62  enters one or more absorption chillers  70 . A cooling tower  74  is coupled to the absorption chiller  70 . The cooling tower  74  receives water at about 101 degrees Fahrenheit from the chiller  70  at line  78  and returns cooler water at about 85 degrees Fahrenheit to the chiller  70  at line  82 . The heat from the 200 degree Fahrenheit output fluid from the rendering stage  14  is used by the chiller  70  and is output from the chiller at a lower-energy, stepped-down temperature of about 177 degrees Fahrenheit in line  86 . 
         [0022]    The illustrated chiller  70  is a conventional lithium-bromide type absorption chiller. Water enters the chiller  70  at about 60 degrees Fahrenheit in line  90  and exits the chiller  70  at about 50 degrees Fahrenheit in line  94 . The 50 degree water is used in the facility&#39;s ammonia refrigeration system  66   b , as shown in  FIG. 2   b . Specifically, the 50 degree water runs through a heat exchange condenser  96  to remove heat from the ammonia in the refrigeration system  66   b . The condenser  96  can range in capacity from about 770 tons to about 915 tons, which can be obtained using various combinations of shell-in-tube heat exchangers available from a variety of manufacturers, including Teknotherm, Inc. of Seattle, Wash. under model numbers beginning with “SCC-”. At times where the ambient air temperature is warmer than 45 degrees Fahrenheit (e.g., non-winter months), the 50 degree water from the chiller  70  greatly improves the efficiency of the refrigeration system  66   b  due largely to lower system pressure requirements, with a minor savings from not running energy-consuming components. The remainder of the system  66   b  includes an ammonia evaporative condenser  98 , an ammonia compressor  100 , an ammonia evaporator  102 , and an expansion valve  104 , and is conventional and understood by those skilled in the art such that it need not be discussed in further detail. The 50 degree water can be used to remove heat from the ammonia refrigerant and thereby provide improved cooling capacity to the facility (e.g., to provide air conditioning, refrigeration, or other cooling functionality) via the refrigeration system  66   b . Of course, other refrigeration systems can be substituted for the specific ammonia-based system  66   b  illustrated. 
         [0023]    The 200 degree Fahrenheit water in line  62  enters the one or more absorption chillers  70  at a flow rate of between about 450 to about 700 gallons per minute depending on system requirements and capacity. For example, a lower capacity system might use a 285 ton absorption chiller receiving water at about 472 gallons per minute and a higher capacity system might use a 457 ton chiller receiving water at about 692 gallons per minute. These flow rates result from the output fluid from the surge tanks  58  being blended with other 200 degree Fahrenheit water provided from microturbines  228  and  240  (and possibly from turbine  252 ) at a lower relative flow rate (e.g., 425 to 650 gallons per minute), as discussed below with respect to an electricity generation stage  224  (see  FIG. 6 ) and the electricity generation stage  248  (see  FIG. 7 ). Suitable absorption chillers  70  are available from Carrier/Sanyo under model numbers TSA-16LJ-32 (285 ton) and TSA-16LJ-52 (457 ton). The absorption chillers  70  are constant flow devices, such that the flow rate is not changed by virtue of the fluid passing through the chillers  70  (i.e., any pressure losses in the chillers  70  are negligible relative to the overall system flow rate). 
         [0024]    Referring again to  FIG. 2   a , a portion of the 177 degree Fahrenheit water exiting the chiller  70  at line  86  is diverted at line  108  into a second absorption chiller or chillers  112 , which operates in the same manner as the first chiller  70  (with a cooling tower  74  and lines  78  and  82 , and communicating with the lines  90  and  94 ) to reduce the energy in the 177 degree Fahrenheit water to a stepped-down temperature of about 167 degrees Fahrenheit exiting the chiller  112  at line  116 . The portion of the 177 degree Fahrenheit water entering the chillers  112  enters at a flow rate of between about 375 to about 625 gallons per minute depending on system requirements and capacity. For example, a lower capacity system might use a 100 ton absorption chiller receiving water at about 396 gallons per minute and a higher capacity system might use a 173 ton chiller receiving water at about 613 gallons per minute. Suitable absorption chillers  112  are available from Carrier/Sanyo under model numbers TSA-16LJ-14 (100 ton) and TSA-16LJ-24 (173 ton). The absorption chillers  112  are constant flow devices, such that the flow rate is not changed by virtue of the fluid passing through the chillers  112 . 
         [0025]    The portion of the 177 degree Fahrenheit water exiting the first chiller  70  and that does not get diverted to the second chiller  112  continues in line  86  to a second process stage  120 , which in the illustrated embodiment, is an equipment (e.g., knife) sterilization stage or operation illustrated in  FIG. 3 . This non-diverted water in line  86  has a flow rate of between about 75 and 80 gallons per minute depending on system requirements. The lower capacity system would have a flow rate of about 76 gallons per minute (472 gpm−396 gpm=76 gpm) and the higher capacity system would have a flow rate of about 79 gallons per minute (692 gpm−613 gpm=79 gpm). It is combined with water at a similar flow rate from line  86 ′ (discussed below) to achieve a total combined flow rate into the second process stage  120  of between about 150 and 160 gallons per minute depending on system requirements. The lower capacity system would have a flow rate of about 152 gallons per minute into the second process stage  120  and the higher capacity system would have a flow rate of about 158 gallons per minute into the second process stage  120 . Optionally, and as shown in  FIG. 2   a , a winter bypass line  124  can be included in which some or all of the 200 degree Fahrenheit output water from the rendering stage  14  bypasses the chillers  70  and  112 , can be utilized in the facility&#39;s heating system (e.g., a radiant heating system), and can then proceed to the second process stage  120 . Running the 200 degree water through a radiant heating system can result in output water at or about 177 degrees Fahrenheit. 
         [0026]    Referring again to  FIG. 3 , the 177 degree Fahrenheit water in line  86  is the input fluid for the equipment sterilization stage  120  at a temperature T 2  of about 177 degrees Fahrenheit. The input fluid enters a surge tank  128  before being provided by line  132  to a booster water heater  136 . The surge tank  128  (e.g., a 65,000 gallon surge tank) regulates the flow rate of the input fluid to a rate suitable for the booster water heater  136 . In the illustrated embodiment, fluid exiting the surge tank  128  enters the booster water heater  136  at a maximum rate of about 225 gallons per minute. 
         [0027]    The illustrated booster water heater  136  is provided with a natural gas supply  140  to heat the 177 degree Fahrenheit water to about 180 degrees Fahrenheit. Because the input water at 177 degrees Fahrenheit is so close to the 180 degree Fahrenheit temperature requirement for the sterilization stage  120 , the lower energy consumption booster water heater  136  can be used instead of a larger, higher energy consuming boiler. In conventional systems, well water or water at about 140 degrees Fahrenheit must be heated to 180 degrees Fahrenheit for the sterilization stage, thereby requiring a boiler and the use of more energy. In the event that the water in line  86  is coming from the facility&#39;s heating system due to winter bypass, the booster water heater  136  may not be required, as the water in line  86  may be at about 180 degrees Fahrenheit. 
         [0028]    The 180 degree Fahrenheit water is provided by line  144  to one or more knife or other equipment sterilizers  148  for an equipment sterilization operation. The water used for the equipment sterilization process is then sent in line  152  to another process stage of the energy system  10 , and in the illustrated embodiment, to a wastewater treatment stage to be discussed further below. Alternatively, the water used in the equipment sterilization process can be sent through line  152  to a sewer.  FIG. 3  also illustrates yet another optional winter bypass line  156  through which 177 degree Fahrenheit water from line  86  can bypass the equipment sterilization stage  120 , be used in the facility&#39;s heating system, and then proceed to another process stage, such as a third process stage  160  in the form of a sanitation stage (see  FIG. 4 ) that utilizes input fluid at a temperature T 3  of about 167 degrees Fahrenheit. The use of the water in the heating system cools the 177 degree Fahrenheit water in the winter bypass 156 to about 167 degrees Fahrenheit for input to the sanitation stage  160 . In an alternative embodiment, the winter bypass line  156  could communicate directly with the 200 degree Fahrenheit water from winter bypass line  124 . This could result in lower water consumption as less of the 200 degree Fahrenheit water is required to achieve a temperature of about 167 degrees Fahrenheit for input to the sanitation stage  160 . 
         [0029]    Referring to  FIG. 4 , 167 degree Fahrenheit input fluid enters the sanitation stage  160  at line  116  is combined with water at a similar flow rate from line  116 ′ (discussed below) to achieve a total combined flow rate of between about 325 gallons per minute and 600 gallons per minute depending on system requirements. Some of the flow from the combined lines  116  and  116 ′ is diverted off for cooling microturbines  228  and  240  as discussed below with respect to an electricity generation stage  224  (see  FIG. 6 ), and optionally for cooling turbine  252  discussed below with respect to electricity generation stage  248  (see  FIG. 7 ), which accounts for the decrease in flow rate from the combined flow rates of lines  116  and  116 ′. The lower capacity system would have a flow rate of about 352 gallons per minute into the sanitation stage  160  and the higher capacity system would have a flow rate of about 582 gallons per minute into the sanitation stage  160 . 
         [0030]    The input fluid to the sanitation stage  160  passes through one or more surge tanks  164 , and enters line  168  where it is mixed with cold well water from line  172  at about 55 degrees Fahrenheit and flowing at a rate of about 100 to about 200 gallons per minute to cool the 167 degree Fahrenheit input fluid to about 140 degrees Fahrenheit. In the illustrated embodiment, two to four 75,000 gallon surge tanks  164  can be used depending on system requirements and capacity. The surge tanks  164  in combination with the supply of well water from line  172  cooperate to regulate the pressure of the input fluid to a value suitable for the sanitation process or processes  176 . In the illustrated embodiment, pressure requirements for fluid used in the sanitation process  176  can range from about 80 to about 300 pounds per square inch. The water balance of the system  10  is maintained as only the required amount/flow of well water is added to achieve the output needed for the sanitation process  176 . 
         [0031]    The 140 degree Fahrenheit water is then used in a sanitation process or processes  176  to sanitize various equipment and features within the facility. Output fluid from the sanitation process  176  travels through line  180  to another process stage of the energy system  10 , and in the illustrated embodiment, to the wastewater treatment stage to be discussed further below. Alternatively, the water used in the sanitation process can be sent through line  180  to a sewer. 
         [0032]      FIG. 5  illustrates a fourth process stage  184  in the form of a wastewater treatment stage. Wastewater from both the equipment sterilization stage  120  and the sanitation stage  160  is provided to the wastewater treatment stage  184  at line  188 . The wastewater can enter line  192  and flow to a wastewater pre-treatment operation  196  in which methane gas is produced as a byproduct from the digester and exits the pre-treatment operation  196  via line  200 . The pre-treated wastewater passes through line  204  to a second wastewater treatment operation  208 . Output from the second wastewater treatment operation  208  can be separated into potable water, which can exit via line  46  in communication with the rendering stage  14 , greywater, which can exit via line  212  for use in facility toilets, irrigation, and the like, and remaining waste, which can exit via line  216  for disposal or further processing. The wastewater treatment stage  184  can include a bypass line  220  such that wastewater from line  188  bypasses the pre-treatment operation  196  and flows directly to the second wastewater treatment operation  208 . 
         [0033]      FIG. 6  illustrates a fifth process stage  224 , which in the illustrated embodiment is an electricity generation stage. One or more microturbines  228  receive the methane gas from line  200  coming from the wastewater treatment stage  184 . Suitable microturbines  228  are available from Capstone under model numbers CR65 and CR65-ICHP (65 kW). The methane gas provides the energy source for the microturbines  228  to generate electricity that is output at line  232  for the facility&#39;s electrical system. Water from lines  116  and  116 ′ (see also  FIG. 2   a ) at temperature T 3  of 167 degrees Fahrenheit is also provided/diverted to the microturbines  228  for cooling. This diverted cooling water can have a flow rate ranging from about 425 to about 650 gallons per minute depending on system capacity. The lower capacity system would have a flow rate of about 440 gallons per minute (396 gpm+396 gpm−352 gpm=440 gpm) and the higher capacity system would have a flow rate of about 644 gallons per minute (613 gpm+613 gpm−582 gpm=644 gpm). As will be described further below, only a portion of the water diverted from lines  116 ,  116 ′ is diverted to the microturbines  128 . The flow rate to the microturbines  128  ranges from about 150 to about 200 gallons per minute, and in the illustrated embodiment is about 167 gallons per minute. The flow rate of the heated water exiting the microturbine  228  remains the same as the flow rate of the cooling water entering the microturbine  228 . The 167 degree Fahrenheit water is heated via heat exchange with the microturbines  228  to about 200 degrees Fahrenheit and exits the microturbines  228  at line  236 , where it then returns to the absorption section  66   a  by fluid communication with line  62 . 
         [0034]    The illustrated electricity generation stage  224  further includes a second microturbine or microturbines  240  powered by a natural gas supply  244  to generate electricity that is output to line  232  for the facility&#39;s electrical system. Suitable microturbines  240  are available from Capstone under model numbers C65 and C65-ICHP (65 kW). As with the microturbines  228 , the microturbines  240  can be cooled by water provided/diverted from lines  116 ,  116 ′ at the temperature T 3  of about 167 degrees Fahrenheit. The flow rate of cooling water to the microturbines  240  ranges from about 250 to about 500 gallons per minute, with the lower capacity system having a flow rate of about 273 gallons per minute (440 gpm−167 gpm=273 gpm) and the higher capacity system having a flow rate of about 477 gallons per minute (644 gpm−167 gpm=477 gpm). The flow rate of the heated water exiting the microturbine  240  remains the same as the flow rate of the cooling water entering the microturbine  240 . The cooling fluid is heated via heat exchange with the microturbines  240  to about 200 degrees Fahrenheit and exits the microturbines  240  at line  236 , combining with the heated cooling fluid exiting the microturbine  128 , where it then returns to the absorption section  66   a  by fluid communication with lines  62 ,  62 ′, thereby providing an additional or alternate source of high-energy output or waste fluid for the energy cascading system  10 . As shown in  FIG. 2   a , lines  62  and  62 ′ are connected by a header or manifold for communication therebetween. 
         [0035]    Referring now to  FIG. 7 , the illustrated energy system  10  can optionally include another electricity generation process stage  248 , which can be separate from the electricity generation process stage  224  or can be combined with the electricity generation process stage  224 . The electricity generation stage  248  includes one or more gas turbines  252  powered by a natural gas supply  256  to generate electricity that is output at line  260  for the facility&#39;s electrical system. While the gas turbine  252  may likely be cooled by cooling water from an independent source, one skilled in the art would understand how it could alternatively be cooled by cooling water at the temperature T 3  of about 167 degrees Fahrenheit from lines  116 ,  116 ′ (as shown in  FIGS. 7 and 2   a ). If cooled with the water from lines  116 ,  116 ′, the flow rates of the cooling water provided to the microturbines  128  and  240 , and the total amount and flow of water in the system  10 , would likely need to be increased from those listed above to include sufficient cooling flow to the turbine  252 . The flow rates described above for the microturbines  128  and  240  have been determined assuming that the turbine  252  would be cooled by an independent cooling source so as not to be a part of system  10 . However, if the system  10  is designed as shown in  FIGS. 7 and 2   a , the cooling fluid to the turbine  252  is heated via heat exchange with the turbine  252  to about 200 degrees Fahrenheit and exits the turbine  252  at line  264 , where it then returns to the absorption section  66   a  by fluid communication with line  62 ′. It is to be understood that the heated cooling fluid in line  264  coming from the turbine  252  is about at the first temperature T 1  (about the same temperature as the output fluid from the rending stage  14 ), thereby providing an additional or alternate source of high-energy output or waste fluid for the energy cascading system  10 . 
         [0036]    Referring again to  FIG. 2   a , the absorption chiller  70 ′ is included in the absorption section  66   a  and is essentially a duplication of the absorption chiller  70  (with a cooling tower  74  and lines  78  and  82 , and communicating with the lines  90  and  94 ) to reduce the energy in the 200 degree Fahrenheit water to a stepped-down temperature of about 177 degrees Fahrenheit exiting the chiller  70 ′ at line  86 ′ that communicates with line  86 . Together, lines  86  and  86 ′ provide the 177 degree Fahrenheit water of temperature T 2  to the equipment sterilization stage  120  and to the chillers  112 ,  112 ′. Depending on the capacity of the chiller  70 , the absorption chiller  70 ′, as shown in  FIG. 2   a , could be eliminated such that only absorption chiller  70  is needed. In such an embodiment, the 200 degree Fahrenheit water line  264  exiting the electricity generation stage  248  is fed directly to line  62  for input into the chiller  70 . 
         [0037]      FIG. 2   a  also illustrates an absorption chiller  112 ′ that is essentially a duplication of the absorption chiller  112  (with a cooling tower  74  and lines  78  and  82 , and communicating with the lines  90  and  94 ) to reduce the energy in the 177 degree Fahrenheit water entering at line  108 ′ to a stepped-down temperature of about 167 degrees Fahrenheit exiting the chiller  112 ′ at line  116 ′. Line  116 ′ provides the 167 degree Fahrenheit water of temperature T 3  to the sanitation stage  160 , the electricity generation stage  224 , and optionally to the electricity generation stage  248  as described above. Depending on the system capacities, the absorption chiller  112 ′ may be eliminated in favor or using only the chiller  112 . The duplication of chillers  70 ,  70 ′ and  112 ,  112 ′ provides increased and redundant system capacity that facilitates system maintenance. Stages of the system  10  can be shut down for maintenance without requiring shut down of the entire system  10 . 
         [0038]    Those skilled in the art will understand that modifications to the illustrated embodiment can be made without departing from the scope of the invention. For example, it is understood that while each of the rendering stage  14 , the electricity generation stage  224 , and the electricity generation stage  248  can together provide the source of high-energy water at the first temperature T 1 , other embodiments may include fewer or more stages to provide the source of high-energy water used in the cascading energy system  10 . Furthermore, the number of stages utilizing input fluid at each of the second temperature T 2  and the third temperature T 3  can vary from the illustrated embodiment. Furthermore, and as mentioned above, the specific processes described with respect to each stage and the specific water temperatures and flow rates set forth in the above description of the illustrated embodiment are by way of example only, and can vary depending upon the specific facility in which the energy system  10  is utilized. 
         [0039]    In addition, the system can be utilized in facilities in which the initial output or waste fluid is steam instead of hot water. Steam absorption chillers can be used in place of or in combination with the illustrated water absorption chillers  70 ,  70 ′,  112 ,  112 ′ to vary the number of energy step-down phases as appropriate for the particular system. 
         [0040]    Various features and advantages of the invention are set forth in the following claims.