RU2210839C1 - Electrochemical thermomagnetic power- generating system - Google Patents

Abstract

FIELD: power generating systems built around fuel cells. SUBSTANCE: system has at least one unit of electrochemical fuel cells, fuel tank, fuel feed unit, unit for discharging products of chemical reaction, heat storage, automatic-control unit, and at least one thermomagnetic heat-to-electricity converter made in the form of balanced three-core distributed magnetic circuit . Built in two extreme cores carrying secondary windings are working inserts of magnetically soft material distinguished by high magnetization jump at magnetic transition temperature and low residual magnetization. Magnetic flux is built up in magnetic circuit by applying dc current generated by electrochemical fuel cells. Automatic-control unit functions to alternately supply concurrently generated heat flux at preset frequency to mentioned working inserts during their heating cycle up to magnetic transition temperature and when they are being cooled down below magnetic transition temperature by cold flow pumped from environment. Periodic opening of magnetic flux results in electromotive force induced in secondary windings. EFFECT: enhanced utilization of heat as well as specific and total output power. 1 cl, 2 dwg

Description

 The invention relates to electric systems based on fuel cells, in particular, based on the use of electrochemical energy converters and magnetothermal devices, with the aim of increasing the amount of electrical energy received, as well as increasing the specific output power of the installation.

 It is important that the electrochemical method of energy production in fuel cells exceeds the traditional fuel energy in environmental cleanliness by tens and hundreds of times, and in the specific energy characteristics of conventional chemical current sources by thousands of times.

 Currently, in a number of countries, based on the latest achievements of science and technology, intensive research is being conducted in the field of developing and creating highly efficient and economically competitive energy systems based on fuel cells.

 The most promising are considered to be electrochemical plants created on the basis of fuel cells, in which the heat associated with the generation of electric energy is used for heating or to start steam turbines, in order to obtain additional electricity, thus, most fully utilizing the thermal part of the chemical energy of the fuel.

 Known electric power systems containing at least one unit of electrochemical fuel cells, a storage system, supply, removal and distribution of reagents, channels for the removal of chemical reaction products, a turbine unit and a control and automatic control unit (see RU 2168806 C2, N 01 M 8/06, 06/10/2001). Efficiency of the best fuel cell power plants for electricity reaches from 50 to 70%. The rest of the chemical energy, comprising from 30 to 50%, during the oxidation-reduction process is converted into heat. Utilization of this heat for domestic purposes within the framework of traditionally used schemes, as a rule, is ineffective. Moreover, in the absence of consumers of associated heat, as is the case, for example, in mobile installations, it is necessary to spend part of the electrical energy produced by electrochemical converters to remove and remove the heat generated by them. The main task of electric power systems is to generate maximum electric energy per unit of spent fuel.

 In this regard, it seems interesting to consider an alternative electric power system, which is a combination of an electrochemical generator with a magnetothermal device. In such a system, the heat released by fuel cells is used to obtain an additional amount of electric energy by means of a magnetothermal generator producing alternating current in cyclic heating - cooling of the working fluid.

 The external magnetic field necessary for the operation of the generator is induced by the direct current produced by the fuel cells, and the working fluid itself, made of a soft magnetic material with a magnetization jump at the phase transition point, is selected from a number of conditions imposed on its magnetothermal properties. The main ones are low magnetic viscosity, high specific saturation magnetization, and negligible coercive force.

 This dependence is possessed by a number of well-known magnets, for example, those which undergo a first-order magnetic phase transition, which occurs under the influence of thermal energy, from the ferromagnetic to the paramagnetic state or from the antiferromagnetic to the ferromagnetic state and vice versa, as well as some rare-earth metals and their alloys with magnetic and magneto-orientation transitions.

 The attractiveness of such a magnetothermal generator is that it directly converts thermal energy into alternating electric current energy, and the generator’s efficiency is directly related to the magnetic and thermophysical properties of the soft magnetic material used as the working fluid. In particular, the working material should possess in the vicinity of the Curie point Tc - as large a magnetization jump as possible, while the magnetic phase transition should occur as narrow as possible in the temperature range. As a result, during a magnetic transformation in a working material placed, for example, in an inductor, under the influence of a thermal pulse in a short time (less than a millisecond), the stored magnetic energy is released, which is proportional to the square of the magnetization jump, which is converted into alternating electric current by means of electromagnetic induction. Since the change in the magnitude of the magnetization (a jump in the magnetization in the vicinity of the point Tc) that occurs under the influence of a heat pulse, in some magnets, for example, in gadolinium, dysprosium, holmium, as well as in intermetallic alloys prepared on their basis, it can reach a very large values, respectively, and the magnitude of the EMF induced in the coil can reach high values.

 The magnetic relaxation times in the aforementioned magnets with a low content of foreign impurity, as noted above, are ≤1ms, which is significantly less than the practical times that are typical for the heating – cooling cycle of the working fluid, which makes it possible to realize the frequency the pump released during the phase transition stored in the inductance coil of magnetic energy, with its direct conversion to alternating current. Thus, it can be argued that if we use a soft magnetic material with a low magnetic viscosity, a large magnetization jump, and a narrow temperature region in the vicinity of which a magnetic phase transition is used as the working medium considered below the electric energy generator, then such a generator should have a high efficiency and high specific power output.

 The technical result of the invention is the most complete utilization of thermal energy released during the operation of fuel cells, obtaining additional amounts of electric energy, increasing the fuel efficiency, and accordingly increasing the specific and total output power of the electric power system.

 The technical result is achieved by the fact that the electric power system contains at least one unit of electrochemical fuel cells, a system for storing, supplying, discharging and distributing reagents, channels for discharging chemical reaction products and a control and automatic control unit, the system is equipped with at least one a DC to AC converter, based on a magnetothermal device, which is a symmetrically branched magnetic circuit containing the main magnetic circuit made of magnetically soft material with high magnetic permeability and three magnetically soft cores with high saturation magnetization, in the two outermost of which are inserts from a working fluid with a large magnetization jump from temperature, low magnetic viscosity and a narrow temperature interval, in the vicinity of the Curie point Tc, in which this transition takes place. The magnetic circuit contains one primary and two secondary windings, while the primary excitation winding is supplied with direct current produced by the fuel cells, while the heat generated by them is alternately switched to the soft magnetic inserts mentioned above. The latter are made in the form of close-packed assemblies, assembled from thin-walled work elements, for example, lamellar type, with a three-dimensional relief deposited on their surface, with the aim of intensifying heat and mass transfer and performing alternating heating and cooling for short times, and heating is carried out by the heat flow generated by fuel cells , followed by cooling of the working inserts due to the reverse flow, for example, air pumped by the compressor from the environment.

 Thus, the combination of an electrochemical fuel cell with a magnetothermal machine into a single energy-generating system leads to the creation of a new class of electric machines in which the direct current electric energy produced by fuel cells is directly used to excite a magnetic field in a magnetothermal machine, and the heat generated along the way, used in the heating cycle - cooling the working fluid, induces an alternating electric current in the circuit.

 Below in Fig.1 is a schematic diagram of the proposed electric power system, illustrating the principle of its operation. It combines an electrochemical generator containing a battery of fuel cells 1, a fuel tank 2, a fuel supply unit 3, a chemical product removal unit 4, a control and automatic control unit 5, a heat collector 6 with a magnetothermal device 7 made in the form of a symmetrically branched magnetic circuit, powered by direct current produced by fuel cells.

 The magnetic circuit consists of a main magnetic circuit 8 made of soft magnetic steel, two extreme cores 9 with high magnetic permeability and saturation magnetization, located in the secondary winding circuit 10 and containing working inserts 11 made of soft magnetic material and having the above magnetic properties, as well as central core 12 with a primary winding 13 connected to a direct current network produced by fuel cells 1. Soft magnetic inserts 11 have a length along the direction magnetic flux sufficient to substantially complete opening of the magnetic circuit when heated above the Tg, and the cross section of the working insert body provides short-circuited magnetic circuit as it cools below Tc. They are made of thin plate elements 16 with spherical recesses 17 deposited on their surface, made in the form of holes, with a given step and form a close-packed three-dimensional lattice, touching each other by means of many points formed by convexities on their surface, as shown in FIG. 2. The three-dimensional relief deposited on the working plates provides a significant increase in heat and mass transfer and at the same time the necessary mechanical stiffness of the magnetically soft insert, which is under the cyclic influence of the temperature difference and pressure exerted by the coolant flow.

 The electric power system operates as follows. In the initial state, the direct current generated by the battery of fuel cells 1 is supplied to the primary winding 13 of the static magnetothermal generator 7, as a result of which a magnetic flux Φ is induced in the central core, which closes by means of the magnetic circuit 8 through the outer cores 9 containing working inserts 11 made in the form the above assemblies and alternately in a ferromagnetic state. The heat flux accompanying the operation of the fuel cells from the heat collector 6 is periodically supplied to the right and left branches of the magnetic circuit containing the above soft magnetic inserts 11 and, passing through many parallel channels 13 (see a fragment of FIG. 2), heats them alternately, transferring from the initial ferromagnetic to the paramagnetic state. Thus, when the heat flux is supplied to the right branch of the magnetic circuit, transferring the working fluid of the corresponding insert 11 to the paramagnetic state, it opens due to a multiple increase in the magnetic resistance and almost the entire magnetic flux Φ closes through the left insert in the ferromagnetic state, as a result whereby a voltage is induced in the coil 10 of the left branch of a symmetrically branched magnetic circuit. The reverse movement of the cold stream, for example, the air pumped by the compressor 14, supplied from the alternating current network, produced by the magnetothermal generator and supplied from the distribution manifold 15 alternately to the right and left inserts, restores the magnetic conductivity of the right working insert 11, while the heat flux automatically switched from the right branch to the left one with a predetermined frequency, it heats up now the working medium of the left insert, thereby short-circuiting the magnetic flux through the right branch, inducing the voltage in the coil 10 belonging to the right branch. Thus, in synchronism with the clock frequency of the heat flux alternation, the magnetic flux is periodically opened in the right and left branches of the magnetic circuit, as a result of which EMF of a different sign is induced on the windings of the coils 10, due to the fact that while one of them has a magnetic the flow increases to its full value Ф, on another coil the flow at this time, accordingly, decreases almost to zero.

 This system principle of the controlled process of the joint work of an electrochemical generator assembled on the basis of fuel cells and a static magnetothermal machine, made in the form of a symmetrically branched magnetic circuit, with magnetically soft inserts embedded in it, having the magnetothermal properties described above, can be implemented in constructions of arbitrary scale and various destination, from portable and mobile to stationary household and industrial power plants.

 In conclusion, we note that the magneto-thermal machine described above is a completely autonomous source of electric energy in the case of supplying a magnetic circuit with a permanent magnet (a permanent magnet is installed instead of a central core with a primary winding) and using natural sources of thermal energy for heating working inserts, for example, solar radiation.

Claims (1)

 An electrochemical magnetothermal energy generating system comprising at least one block of electrochemical fuel cells, a fuel tank, a fuel supply unit, a unit for removing chemical reaction products, a heat collector and an automatic control unit, characterized in that it is provided with at least one magnetothermal a converter of thermal energy into electrical energy, made in the form of a symmetric branched magnetic circuit with three cores made of thin electrically isolated soft magnetic material with high magnetic permeability, in the two extremes with secondary windings are embedded working inserts of soft magnetic material with a large magnetization jump at the Curie point temperature and low remanence, and a direct current is applied to the primary winding on the central core to excite magnetic flux in a symmetrical branched magnetic circuit produced by electrochemical fuel cells, and the automatic control unit provides pop Alternating supply of the heat flux generated by them at a predetermined frequency to the indicated working inserts in the cycle of their heating to the temperature of the Curie point and cooling to a temperature below the Curie point with a cold flow pumped from the environment, providing periodic opening of the magnetic flux in the outer cores, resulting in secondary windings induced EMF of different signs, and these working inserts are made in the form of tightly packed assemblies of thin plate elements with a three-dimensional relief on their surface Surfaces in contact with each other at points formed by convexities of a three-dimensional relief and forming a multitude of parallel channels for intensifying heat transfer.

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