Patent Number: 062326791
Section: description

BEST MODE FOR CARRYING OUT THE INVENTION Referring now to the Figure, an illustrative embodiment of the invention is shown in a heating and electricity generating system 10. The heating and electricity generating system 10 comprises a generator 20 for generating electricity, a pump 30 for pressurizing liquified working fluid, a pump 40 for circulating engine coolant, an oil fired heater 50, a turbine 60 for driving generator 20 through shaft 62 and a condenser 70 for liquefying the working fluid. A control 80 receives power from generator 20 through conductor 28 and supplies power to power consumers through conductor 88. Control 80 also controls pump 30, pump 40 and oil fired heater 50 through means indicated by dashed lines 82, 84 and 86 respectively. It will be appreciated as the description proceeds that the invention may be implemented in different embodiments. Referring now to FIG. 1, the heating and electricity generating system 10 comprises a generator 20 which can be any of many known designs. The preferred generator design is a high speed generator with a permanently magnetized armature and electronic commutation of the stator coils. This design is known to have the advantages of small size and high efficiency. The pump 30 may be of any known design but is preferably a piston or gerotor type pump powered by an electric motor. The pump 40 is preferably a centrifugal pump powered by an electric motor designed to provide a flow of several gallons per minute of engine coolant. The oil fired heater 50 may be of any conventional design. A preferred design uses an oil burner of the catalytic type commonly used in room heaters. Means such as fire tubes are provide to transfer heat from the combustion gases produced by the oil burner of heater 50 to the liquified working fluid. The turbine 60 is preferably a radial inlet centrifugal turbine but may be of any known design suitable for converting pressurized working fluid provided by oil fired heater 50 to mechanical energy. Computer codes are available from many sources for computing the exact shape of a suitable turbine rotor and housing depending on the working fluid, operating temperatures and power rating. The turbine rotor is preferably made by an inexpensive process such as casting and is preferably made of an inexpensive metal such as a steel. Condenser 70 receives spent working fluid from turbine 60 and cools it to liquify it and transfers the heat it receives to engine coolant provided by pump 40. Condenser 70 may be of any design known to be suitable by those skilled in the design of heat exchangers. Control 80 operates to control power to the coils in generator 20 if required which would be required if generator 20 is of the type having a rotor comprising permanent magnets. Control 80 also operates to convert the power it receives from generator 20 to a desired form such as 120 volt 60 Hertz ac or 12 volt dc and deliver that power through electrical conductors 88. Control 80 also receives from a switch 90 located in the vehicle cabin a signal turning the heating and electricity generating system 10 on or off. Control 80 also indicates to pumps 30 and 40 and oil fired heater 50 by means indicated by dashed lines 82, 84 and 86 respectively that they should turn on or off. Heating and electricity generating system 10 is a sealed system filled with a working fluid. The working fluid is selected to have the desirable properties of low sound velocity in the vapor, high heat of vaporization, a suitable condensation temperature at the operating pressures, a high critical temperature, a low freezing temperature, a low viscosity and a high film heat conductivity. An optimum working fluid has not been identified but decane and is believed to be suitable. A primary consideration is that the low temperature of the cycle is likely to be the temperature of a hot engine and the working fluid must have a low vapor pressure at these high temperatures so it can be condensed in condenser 70. The operation of the heating and electricity generating system 10 of this invention will now be described with reference to FIG. 1. In operation of the system, when the truck operator closes switch 90, control 80 initiates operation of the heating and electricity generating system 10 by providing power or otherwise controlling pump 30, pump 40, and oil fired heater 50 to begin operating. Pump 30 pumps any liquid working fluid in condenser 70 through fluid conduit 32 into oil fired heater 50. Pump 40 circulates engine coolant through condenser 70 for withdrawing heat from the working fluid and causing it to condense to a liquid. Oil fired heater 50 burns diesel fuel from the main fuel supply of the truck to heat and vaporize and thereby pressurize the working fluid. Preferably, the working fluid vapor is then superheated by oil fired heater 50. The superheated working fluid vapor is conducted by conduit 52 to the inlet of turbine 60 where it causes turbine 60 to turn shaft 62 and the armature of electric generator 20. The spent working fluid vapor (with any entrained liquid) is conducted by fluid conductor 62 to condenser 70 where the spent working fluid condenses to a liquid and the heat it contains is transferred to the engine coolant. Heat in the coolant is carried to the heater core in the passenger compartment in cold weather to heat the passenger compartment and in warm weather it is sent directly to the engine block which operates as a large heat sink. Generator 20 generates electrica power which is supplied through conductor 28, control 80 and conductor 88 for use by the electrical appliances in the truck cabin. An advantage the heating and electricity generating system 10 is that it is acoustically quiet because all of the components when combined as described hereinabove are not noisy. More particularly, the pump 30 is quiet by virtue of its small size. Pump 40 is also quiet by virtue of being a centrifugal pump of small size and low pressure. Oil fired heaters of the catalytic type are commercially available in designs that are acoustically quiet. Turbine 60 is also inherently quiet. Therefore the cogeneration system described hereinabove can be installed in such as the engine compartment of a truck or elsewhere outside the truck cabin and will not generate objectionable sound even when the truck is parked and the operator is sleeping. By comparison, other low cost cogeneration plants are undesirably noisy without sound insulation means. A particular example of a cogeneration plant that is undesirably noisy comprises a Diesel engine driving an electric generator. A second advantage of the heating and electricity generating system 10 is that it minimizes pollution. Catalytic heaters produce sufficiently low amounts of objectionable gases that they are commonly sold for use inside residences. A third advantage of the heating and electricity generating system 10 is that all components are likely to last for the lifetime of the truck without maintenance. Gerotor pumps are used as oil pumps in engines and last the lifetime of the engine. Centrifugal pumps can be designed to last far longer than required. Oil fired heaters are simple and reliable. Turbines on fluid bearings have no wear except at the bearings which can be designed to provide the desired lifetime. Although the description of this invention has been given with reference to a particular embodiment, it is not to be construed in a limiting sense. Many variations and modifications will now occur to those skilled in the art. For a definition of the invention reference is made to the appended claims.