Abstract:
A system for recapturing electrical energy from a waste stream is disclosed. Further, features of the invention can be used to reduce the energy required for waste stream processing. Various energy sources are identified within the waste stream, and source-specific modules are provided for converting the various sources into electrical energy.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of an earlier filed co-pending application Ser. No. 60/147,304 filed Aug. 5, 1999 entitled SEPTIC BATTERY. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to systems for converting waste energy to electricity. More specifically, the present invention relates to an electrical generator for salvaging waste energy in a septic system. 
     Much of the electricity used today is generated from coal burning plants which are tolerated as a virtual necessity in modern life. However, such plants are thought to produce greenhouse gasses which are believed to have an undesirable effect on the global environment. Although vast resources are currently being spent on identifying and developing alternative energy source, such as wind and solar power, efforts to use energy more efficiently are also important. 
     In a household, or other dwelling, with a septic system, significant energy often escapes which could be recaptured and used. The lost energy has many forms. For example, septic systems are located below the dwelling elevation. Thus, one form of lost energy is due to the gravitational potential of the waste stream as it descends into the septic system. A variety of other sources all add to a significant loss of energy. Additionally, energy is usually required to process the waste stream into components that reduce the environmental impact of the waste. Thus, not only is energy lost in the waste stream, but additional energy must be expended to process the waste. 
     As non-renewable energy resources are slowly depleted, and the cost of energy rises, there is an increasing need to identify and salvage lost energy. Recapturing energy otherwise lost in a waste stream could reduce the costs of energy by providing for more efficient consumption, while potentially processing the waste stream to reduce its environmental impact. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention provides a system for recapturing energy in the form of electrical energy from a waste stream, while processing the waste stream to potentially reduce its environmental impact. Various energy sources are identified within the waste stream, and source-specific modules are provided for converting the various sources of energy into electricity. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an environmental diagram illustrating an environment of a septic battery in accordance with the an embodiment of the present invention. 
     FIG. 2 is a system block diagram of a septic battery in accordance with an embodiment of the present invention. 
     FIG. 3 is a system block diagram of a static module in accordance with an embodiment of the present invention. 
     FIG. 4 is a more detailed system block diagram of a static module in accordance with an embodiment of the present invention. 
     FIGS. 5 a  and  5   b  are system block diagrams of electro chemical cells in accordance with an embodiment of the present invention. 
     FIG. 6 is a system block diagram of a thermal module in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is an environmental diagram illustrating an environment of a septic battery in accordance with an embodiment of the invention. As used herein, “septic battery” refers to any system capable of providing electrical energy from a waste stream. FIG. 1 shows septic battery  10  coupled to battery bank  12 , which bank  12  is coupled to DC to AC converter  14 . Converter  14  is coupled to dwelling unit  16  and power grid  18 . Septic battery  10  is adapted to convert potential energy in a waste stream into electricity, as will be described in greater detail later in the specification. The electricity from septic battery  10  is stored in conventional battery bank  12 . 
     DC to AC converter  14  contains suitable circuitry to provide stored electricity to dwelling unit  16 , power grid  18 , or both. Preferably, converter  14  is addressable, via a telephone line, or RF link or the like, such that an electric utility can issue a command to converter  14  regarding the provision of electricity stored in battery bank  12 . Thus, a utility may command converter  14  to provide the converted electricity back to power grid  18  for provision to other utility customers. 
     FIG. 2 is a system block diagram of a septic battery in accordance with an embodiment of the present invention. Septic battery  10  includes septic tank  11 , inlet  20  and outlet  22 . Battery  10  receives a waste stream inflow via inlet  20 , and provides a waste stream outflow via outlet  22 . Between inlet  20 , and outlet  22 , battery  10  includes various modules, each of which is adapted to convert a different form of waste stream energy into electricity. Septic battery  10  can thus include static module  24 , electro-chemical cell  26 , biological cell  28 , and thermal cell  30 . Although the present invention is described with respect to all four cells, using fewer than all described cells is expressly contemplated. Static module  24  is shown coupled, through static to DC converter  32 , to current bus  34  to which electro-chemical cell  26 , biological cell  28  and thermal cell  30  are also coupled. Current bus  34  is coupled to battery bank  12  (shown in FIG. 1) such that electricity provided on current bus  34  is stored in battery bank  12 . 
     FIG. 3 is a system block diagram of static module  24  in accordance with an embodiment of the present invention. Static module generally includes drip initiator  36  and conversion module  38 . As shown in FIG. 3, static module  24  can include an inflow static module and an outflow static module. Static module  24  is used to convert gravitational kinetic energy in the waste stream directly into electricity. Preferably, static module  24  also includes a nitrogen vent to release nitrogen that is generated when the gravitational kinetic energy of the waste stream is converted to electricity. The static module proximate inlet  20  includes a plurality of drip initiators. The first drip initiator includes a sludge drip initiator, while the second drip initiator is configured to drip liquid (septic effluent). 
     FIG. 4 is a more detailed system block diagram of static module  24  in accordance with an embodiment of the invention. Drip initiator  36  is shown having a cylindrical sidewall  40  and endcaps  42 . An inlet (not shown) receives the waste stream, portions of which exit either sidewall  40  or endcaps  42 . Sidewall  40  includes effluent apertures  44  which are adapted to create effluent droplets from the waste stream. Conversion module  38  preferably includes first cylinder  46 , second cylinder  48 , third cylinder  50  and fourth cylinder  52 , all of which are preferably conductive. First cylinder  46  is disposed above second cylinder  48  in vertical alignment with one of apertures  44 . Third cylinder  50  is disposed above fourth cylinder  52  in vertical alignment with the other aperture  44 . Thus, an effluent droplet emanating from one of apertures  44  will fall through either cylinders  46 ,  48  or  50 ,  52 . As can be seen, first cylinder  46  is electrically coupled to fourth cylinder  52 , while second cylinder  48  is electrically coupled to third cylinder  50 . 
     In operation, effluent droplets emerge from apertures  44  and fall through one of the sets of vertically oriented cylinders. As the effluent droplet passes through the cylinders, and lands in the lowest cylinder, an electric potential is developed between lines  54  and  56 . Lines  54  and  56  are coupled to static to DC converter  32 , and thus to current bus  34  for storage within battery bank  12 . 
     FIG. 4 also shows endcaps  42  which each contain sludge apertures  58  and  60 . While apertures  44  are adapted to provide effluent droplets, apertures  58  and  60  are adapted to provide droplets of sludge. A conversion module (not shown) similar to module  38  is used to convert energy in falling sludge to electricity. Aperture  60  will provide droplets of non-floating sludge and aperture  58  will provide droplets of floating sludge. Additionally, while the static module near the inlet includes drip initiators for effluent, floating sludge and non-floating sludge, the static module near the outlet of battery  10  preferably includes only an effluent drip initiator. 
     FIGS. 5A and 5B are system block diagrams of electro-chemical cells  26  and  27 , respectively, in accordance with an embodiment of the invention, and like components are numbered similarly. Cell  26  is an anaerobic electrochemical cell and preferably includes waste stream inlet  62 A and waste stream outlet  64 A. Cell  26  is disposed within septic tank  11  within or above the waste stream. Disposed within electrochemical cell  26  are cathodes  70 A, anodes  72 A and ion-selective membrane  74 A. Cathodes  70 A and anodes  72 A are operably coupled to battery bank  12  (shown in FIG. 1) such that electricity developed upon the electrodes  70 A,  72 A is stored within battery bank  12 . 
     Electrochemical cell  27  is an aerobic cell operating in accordance with known fuel cell technology. Cell  27  is disposed near outlet  22  of septic tank  11 . Cell  27  is similar to cell  26  except that cell  27  includes air inlet  66  and air outlet  68 . In a known manner, cell  27  combines oxygen received via inlet  66  with the waste stream entering through port  62 B. Waste entering cell  27 , having traveled through biological cell  28  and/or electrochemical cell  26 . 
     The materials of cathodes  70 A,  70 B, anodes  72 A,  72 B and membrane  74 A,  74 B are preferably selected to be ion selective such that they are optimally configured to convert a specific ion into electricity for storage within bank  12 . For example, if biological cell  28  is configured to provide hydrogen sulfide gas as an end product, reducing cell  26  can include an iron electrode such that cell  26  can reduce the hydrogen sulfide into hydrogen and ferric sulfide, to thereby generate electricity. Further, conventional fuel-cell technology can be employed to create electrochemical cell  27 , which can convert the hydrogen back to water. 
     Referring to FIG. 2, battery  10  preferably includes biological cell  28  which is known in the art. Thus, cell  28  includes a mass of bacteria which are selected to digest portions of the waste stream and provide an output, such as methane, hydrogen sulfide, and heat. In the embodiment shown in FIG. 2, electrochemical cell  26  is shown disposed upstream of biological cell  28 . In such embodiment, cell  26  is preferably selected to provide an output which is digestible by biological cell  38 . In other embodiments, the positions of electrochemical cell  26  and biological cell  28  can be reversed, such that the output of biological cell  28  provides an input to cell  26  that is specifically processable by cell  26 . For example, biological cell  28  can be adapted to digest the raw waste stream into methane, hydrogen sulfide, and heat, while electro-chemical cell  26  can be adapted to convert sulfurous ions into electrical energy. Some known fuel cells convert such substances as methane or propane gas into carbon dioxide, and water, while providing electricity in the process (cell  27 ). 
     FIG. 6 is a system block diagram of thermal module  30  in accordance with an embodiment of the present invention. In embodiments where thermal module  30  is employed, septic tank  11  is preferably thermally insulated except for portions proximate thermoelectric module  76 . Thermoelectric module  76  operates according to known principles, and is often used as a chilling element for coolers. For example, U.S. Pat. No. 5,099,649 to Zorn teaches the use of a thermoelectric element for cooling an automotive glove compartment. 
     Traditionally, electric currents are applied to such elements to create a temperature gradient across the thermoelectric element. However, in thermal module  30 , a temperature gradient is applied to thermoelectric module  76 . As a result, module  76  provides an electric current through lines  78 . Lines  78  are operably coupled to battery bank  12  such that the electricity created by module  76  is stored within bank  12 . Heat sinks  80  are operably coupled to the hot side of thermoelectric module  76 , while heat sinks  82  are operably coupled to the cold side of thermoelectric module  76 . Because the temperature within septic tank  11  is higher than the temperature outside of tank  11 , heat will flow through thermoelectric module  76  thus generating electricity. Heat sinks  80 ,  82  can take any appropriate form to increase surface area to thereby increase thermal conduction through thermoelectric module  76  and thus raise efficiency. As an illustrative example, a 1250 gallon septic tank having a thermoelectric conversion efficiency of about 5% should produce approximately 2 Kilowatts when subjected to a 15 degree Fahrenheit temperature gradient. Efficiencies will vary with specific heat sink configurations, and selection of thermoelectric module  76 , and the above example is provided for illustration only. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, although the invention has been described with respect to electrical power generation, embodiments of the invention may be useful to measure the efficacy of the septic system. Further, although all modules are shown connected to a single current bus, it is expressly contemplated that such modules can be connected individually to the battery bank  12 , such that electricity can be measure from each individual module, potentially providing enhanced septic system diagnostics. For example, the electricity generated from thermal module  30  may be indicative of temperature within septic tank  11 , while the energy generated by electro-chemical cell  26  may be indicative of ion concentration or presence. Additionally, a solar cell could be provided in conjunction with the septic battery to add additional electricity, or to power communication electronics which may be used in conjunction with addressing DC to AC converter  14 . Finally, although embodiments of the present invention have been described with respect to all four modules, the invention can be practiced with fewer than four such modules, as well as with various modules duplicated as desired. Thus, various electrochemical cells may be used and tailored to a variety of ions, while various biological cells can be used and tailored to various waste streams. Further still, although the various modules have been described as separate modules, such description is provided for clarity. It is contemplated that various modules can share components. For example, an iron electrode of an electrochemical cell can double as a heat sink for the thermal module.