Patent Publication Number: US-2011073717-A1

Title: Aircraft with a hybrid energy supply

Description:
The present invention relates to an aircraft powered with a mixture of energy supplies. 
     Nearly all aircraft are propelled by means of internal combustion engines. They may be two or four-stroke piston engines for aircraft of low power, or more commonly turbomachines for aircraft of greater power. 
     Propulsion means of that kind make use of hydrocarbons, essentially gasoline or kerosene. Given the cost of hydrocarbons and the ever-increasing attention given to the problem of pollution, it would be advantageous to be able to reduce the consumption of hydrocarbons and in particular of kerosene. 
     For this purpose, proposals have been made on an experimental basis for propelling aircraft electrically. Under such circumstances, the energy source is taken either from storage batteries or possibly from a fuel cell, or else from solar panels disposed on the external structures of the aircraft, and the aircraft is propelled by an electric motor. 
     Nevertheless, given the present cost of solar collectors and their relatively low efficiency, applications are very limited for propelling aircraft by means of an electric motor. 
     Nevertheless, a large amount of work is presently being done to improve the efficiency of solar collectors and to reduce their costs. 
     An object of the present invention is to provide an aircraft with a mixture of energy sources that enables the consumption of hydrocarbon to be reduced compared with conventional solutions, when the speed of the aircraft is not too great, e.g. less than 300 kilometers per hour (km/h). 
     To achieve this object, the invention provides an aircraft with a hybrid power supply, the aircraft comprising:
         an external structure;   electrical equipment;   internal combustion propulsion means; and   means for feeding energy to the propulsion means;   the aircraft being characterized in that it further comprises:   a plurality of converters for directly converting light energy into electrical energy, which converters are disposed on at least a fraction of the outside surface of the external structure;   means for comparing the electrical energy produced by said converters with the instantaneous consumption of said electrical equipment;   means for recovering the excess electrical energy, if any; and   means for delivering to said propulsion means additional energy taken from said excess electrical energy, if any.       

     It can be understood that because of the provisions of the invention, the aircraft has an additional energy source constituted by the electrical energy produced by the converters for directly converting light energy into electrical energy. Such additional energy supply means are preferably used to satisfy the instantaneous consumption of the electrical equipment of the aircraft, with any surplus electrical energy being delivered to the propulsion means that are of the internal combustion type. 
     This optimizes overall management of the available energy, and in particular of the available electrical energy. 
     Another advantage of the invention is that it provides an emergency source of electrical energy in the event of failure of other means. 
     In a first embodiment of the invention, the aircraft is characterized in that the means for delivering the additional energy comprise at least one electric motor powered by said excess electrical energy if any, said electric motor co-operating with said propulsion means. 
     It can be understood that in this first embodiment, the additional excess energy produced by the converters for converting light energy into electrical energy serves to power an electric motor that co-operates with the propulsion means. 
     In a second embodiment, the aircraft is characterized in that said means for delivering additional energy comprise:
         a hydrogen-production assembly for producing hydrogen from water, said hydrogen-production assembly being fed with said excess electrical energy, if any; and   means for delivering the hydrogen to the heat energy production means.       

     It can be understood that in this second embodiment, the electrical energy serves to produce hydrogen from the available water and means are also provided for delivering the hydrogen to the internal combustion propulsion-producing means. 
     In this second embodiment, the aircraft is preferably characterized in that it comprises:
         means for condensing at least some of the exhaust gas from the propulsion means;   means for recovering liquid water from the condensate produced; and   means for feeding the hydrogen production assembly with the water obtained in this way.       

     Other characteristics and advantages of the invention appear better on reading the following description of various embodiments of the invention given as non-limiting examples. The description refers to the accompanying figures, in which: 
       FIG. 1  is a diagrammatic view of an aircraft fitted with light energy to electrical energy converters; 
       FIG. 2  is a diagram of the energy production device in a first embodiment; and 
       FIG. 3  is a diagram showing the second embodiment for supplying electrical energy. 
    
    
     In  FIG. 1 , there can be seen in highly diagrammatic manner the external structure of an aircraft  10  having a fuselage  12 , wings  14  and  16 , and tail planes  18  and  20 . Each of these component elements of the external structure of the aircraft  10  is fitted with converters for converting light energy into electrical energy and given respective references  22 ,  24 ,  26 ,  28 , and  30 . Naturally,  FIG. 1  is given purely by way of example and the zones that are covered with light energy to electrical energy converters should be adapted to the particular outside structure of the aircraft. 
     With reference initially to  FIG. 2 , there follows a description of a first embodiment of the invention for supplying additional electrical energy to the propulsion means of the aircraft. 
     This figure shows a solar panel, e.g. the panel  24  of  FIG. 1 , which panel is connected to an electricity manager device  32 . The electricity manager device receives a control signal C that is representative at all times of the electrical energy requirements of the electrical equipment  34  of the aircraft at all times. The circuits of the manager device  32  include means for comparing the amount of electrical energy being delivered instantaneously by the set of solar panels with the signal C that is representative of the needs of the electrical equipment of the aircraft. If these needs exist, then at least a fraction of the electrical energy produced by the solar panels  24  etc. is transmitted to the electrical equipment of the aircraft. Surplus electrical energy is transmitted to an electronics unit  36  for managing electric motor means that are given overall reference  38  and that are coupled either to the low pressure shaft, or to the high pressure shaft of the propulsion means of the aircraft when the aircraft is propelled by a turbomachine. The electronics unit  36  controls the power supply to the electrical machine  38  that is preferably constituted by the electrical starter motor or by a generator capable of operating as a motor and that is available on all aircraft propulsion means. 
     It can thus be understood that the invention enables the manager device  32  to cause the electrical energy produced by the solar panels such as  24  to be devoted primarily to the electrical equipment  34  of the aircraft. Part of this electrical energy may be transmitted to the electrical equipment  34  and part of it to the electronics unit  36 , depending on the instantaneous requirements for electrical energy of the electrical equipment of the aircraft. If the device  32  detects any excess electrical energy, it is used to power the electric motor  38  via the electronics unit, thus serving either to deliver energy to the internal combustion engines  40  of the aircraft, or to save on the mechanical power taken off from these engines  40  in order to be transformed into electrical power. 
     It should be emphasized that since the electric motor means already exist, even if they are not always reversible, they enable the invention to be implemented without installing additional equipment. 
     With reference now to  FIG. 3 , there follows a description of a second embodiment of the invention. In this second embodiment, any surplus electrical energy produced by the solar sensors is used for hydrolyzing water so as to produce hydrogen, for mixing with the fuel. In  FIG. 3 , there can be seen a light energy to electrical energy converter  24  that is connected to an electricity manager circuit  32  having exactly the same function as that described with reference to  FIG. 2 . 
     The electrical energy in excess over the requirements of the electrical equipment of the aircraft is used in a hydrolyzer  44  that is fed with water. The hydrogen produced by the hydrolyzer  44  is stored in a tank  46 . The standard fuel, e.g. kerosene, is stored in a tank  48 . The hydrogen stored in the tank  46  and the fuel stored in the tank  48  are fed to a fuel regulator circuit  50  that acts as a function of the availability of hydrogen to define the optimal hydrogen/fuel mixture for use in feeding to the engine  40  of the aircraft. 
     Preferably, the water used for feeding the hydrolyzer  44  is recovered from the exhaust gas from the engine  40 . To do this, a cooling circuit  52  cools the exhaust gas and delivers the cooled fraction of the exhaust gas via a pipe  54  while the non-recycled fraction is discharged by a pipe  56 . The cooled exhaust gas feeding the pipe  54  is taken to a circuit  60  for separating water and carbon dioxide. The mixture of carbon dioxide and nitrogen is discharged from the separator  60  by a pipe  62 , while the water separated from the remainder of the exhaust gas is taken by a pipe  64  to the hydrolyzer  44 . 
     It can be understood that this second embodiment of the invention presents all of the advantages of the first, since the production of electrical energy by the solar collectors is managed by the circuit  32  to power the electrical equipment of the aircraft as a priority, and it is only the excess portion, if any, that is used for powering the hydrolyzer and thus for producing hydrogen that then constitutes a portion of the fuel for the engine  40 . In addition, it should be added that in the preferred embodiment of the invention as described with reference to  FIG. 3 , the water used in the hydrolyzer is recovered from the exhaust gas of the internal combustion engine  40 . Nevertheless, it would not go beyond the ambit of the invention if an independent source of water were used, although that does not constitute the best solution.