DE10210634A1 - Device to thermally control electrochemical energy converters such as fuel cells and batteries uses Peltier element in region of converter where heat flow occurs - Google Patents

Abstract

A device for thermally controlling an electrochemical energy converter (1) comprises locating a Peltier element (4) in a region of the converter where a heat flow occurs and providing a current or voltage to this element. An Independent claim is also included for a process for the above which selects the direction of application of the current or voltage to minimize the heat flow.

Description

The invention relates to a device and a method for Temperature control of electrochemical energy converters.

Basically, it is from the general state of the art known that electrochemical energy converters, ie For example, fuel cells, batteries, electrolysis and like their ideal efficiency in comparatively small Have temperature windows. The location of these temperature windows In addition, can still from the current operating conditions depend on the electrochemical energy converter, so that the Temperature control, so the cooling and / or heating of Such electrochemical energy converters according to the general State of the art is of relatively great importance.

From EP 1 081 779 A1 latent heat storage are known, which can be used in fuel cell systems. In The above-mentioned document are manifold applications described for these latent heat storage, which is based on direct all components of a fuel cell system, which from a liquid starting material a hydrogen-rich Supply gas for operating a PEM fuel cell. There are both for the components of the gas generating system and for the fuel cell or the fuel cell stack itself such latent heat storage proposed to excess To absorb heat, to buffer it and to increase it Heat requirement back to the respective component.

Due to the principle, however, have such latent heat storage some disadvantages. In particular, these are in the size of the Latent heat storage itself and thus in the amount of storable thermal energy very limited. Is the Latent heat storage, for example, "full", so is the other Absorption of heat is no longer possible, causing the Heat dissipation from the respective component, such as the Fuel cell stack is obstructed. On the other hand, a Such latent heat storage does not provide heat when in it stored heat is already used up when the Fuel cell would need heat right now.

All in all, with such a structure Latent heat storage, which passive heating and / or cooling the represent respective components, relatively cumbersome and due to the limited sizes and memory contents rather suitable for cold start applications or the like, as for a temperature control of the fuel cell itself in virtually all their operating phases.

Furthermore, the general state of the art knows so-called thermoelectric modules or Peltier elements. such Peltier elements are made of ceramic materials, Semiconductor materials or according to the latest developments in this Range also from correspondingly conductive polymers produced. The basic principle of such thermoelectric elements is always the same. By applying a voltage or a Current flow is achieved, that is one side of the Peltier element cools down while the other side heated. Usually, such Peltier elements are therefore in Range of chillers and the like used since one by the so-called Peltier effect is able to with such thermoelectric modules through a heat transfer the applied voltage or the current caused thereby a heat transport against a temperature gradient realsieren.

As an example of such a Peltier element here is the called Peltier element described by WO 00/74149 A1 become.

It is now an object of the present invention, the Performance of electrochemical energy converters by a suitable temperature control in virtually all operating conditions increase.

According to the invention this object is achieved by a device for Tempering resolved by electrochemical energy converters, at which at least part of the areas of the electrochemical Energy converter, in which heat conduction to the energy converter towards or away from the energy converter, Peltier elements, to which a current and / or voltage can be applied.

In addition, the above object is achieved by the invention a method for the temperature control of electrochemical Energy converters solved, in which at least in part of the Areas of the electrochemical energy converter in which Heat conduction to the energy converter out or away from the energy converter takes place, Peltier elements are used in which one Current and / or a voltage depending on Operating state of the electrochemical energy converter controlled or is regulated.

Depending on in which direction the electric current flow in reaches the area of the Peltier elements, the through the Peltier elements transported heat, and here predominantly the heat conduction plays a role and of convection processes can be influenced. So can for example, in an operating phase of the electrochemical Energy converter, if generated by this excess process heat is, by an appropriate admission of the Peltier elements with electricity and / or a reinforced voltage Heat removal from the field of electrochemical energy converter in the environment, to coolers, coolants or the like will be realized. The resulting process heat will be so discharged to the outside stronger than in a pure heat conduction, since reinforced by the Peltier elements of heat transport and possibly also maintained against a temperature gradient becomes.

If, however, of the electrochemical energy converter no generates sufficient amount of heat, so that this heating would require the ideal operating conditions and therefore its to achieve ideal performance, eg. At minimum Power extraction, in the starting case or the like, it can by a reversal of the direction of voltage and / or current opposite effect of the Peltier elements can be achieved. The outflow of resulting heat to the outside then becomes hindered and ambient heat is generated by the Peltier element in the passed electrochemical energy converter.

By the device according to the invention and / or the inventive method can thus be an active thermal management for the be achieved electrochemical energy converter, which ensures that the electrochemical energy converter, For example, a fuel cell, a battery, a Accumulator or the like, over the at least approximately largest Part of his service life in the area of his ideal Operating temperature moves and thus the best possible Achieved efficiency.

In a particularly favorable embodiment of the Device according to the invention, the current and / or the voltage comes to the Peltier elements from the energy converter itself.

In the operating phase of the electrochemical energy converter Although this means a certain loss of performance, this is However, in relation to the increase in performance, which by the improved dissipation of the resulting heat can be achieved to put. Overall, with appropriate interpretation certainly be achieved that this for the operation of the Peltier elements needed no excessive power component Performance represents, which by the inventive Device achieved benefits reduced. Even at a standstill of the electrochemical energy converter can be used for the Peltier Elements needed energy are taken from this. Therefore is only a minimum operation of the energy converter or a minimum power extraction from the energy converter necessary. This can then be achieved, however, that the heat flow by the appropriate current flow at the Peltier elements is hindered, so that the resulting process heat in the electrochemical energy converter remains. In addition, by the Peltier elements heat from outside the electrochemical Energy converter transported in these. The electrochemical Energy converter thus remains even in the absence of Performance requirement or removal tempered and can at a the required service immediately or at least very quickly.

The fact that the current or voltage from the Energy converter itself is taken, is not an independent sensor, for example, a measurement of the temperature in the energy converter, necessary because the fed into or out of the energy converter this extracted power in general with the Operating condition and the operating temperature will be related.

Further advantageous embodiments of the invention will become apparent from the other dependent claims and with reference to the drawing illustrated embodiment.

The sole attached figure shows a schematic Representation of a fuel cell stack as an example of a electrochemical energy converter.

In the following hereunder with reference to the drawings Embodiment shown are all descriptions of Inventive device and the invention Always use a fuel cell stack as an example related to an electrochemical energy converter. This should be the Designs, however, not on a fuel cell stack limit. With a comparable structure and a Comparable mode of operation would also be active thermal management for other electrochemical energy converters, such as Batteries, accumulators and the like, conceivable.

In the single attached figure, a schematically illustrated fuel cell stack 1 can be seen. The fuel cell stack 1 consists of a plurality of individual fuel cells, which are combined in the fuel cell stack 1 and have common supply lines 2 for the supply and removal of fuel, air, coolant or the like. The fuel cell stack 1 can also be taken from an electrical power, which is indicated here via the schematically indicated electrical lines 3 . It is now to be expected that the fuel cell stack 1 by thermal conduction through its outer surface or its housing corresponds to the environment, apart from the heat transfer and Konvektionsvorgängen, which caused by the supply and discharge of supplies and / or the coolant are and can be influenced only partially targeted. The heat conduction, for example by the above-mentioned housing of the fuel cell stack 1 to the environment and vice versa, is used in the concept shown here for active thermal management. This is made possible by the use of a plurality of Peltier elements 4 , only a few of which have been provided with reference numerals which cover the fuel cell stack 1 or its housing at least in a part of the areas in which heat conduction to the fuel cell stack 1 or from the Fuel cell stack 1 away takes place.

The Peltier elements 4 are interconnected electrically, which is not shown here. A voltage is applied to the Peltier elements 4 , so that a current flow takes place. This voltage or the current flow is controlled or regulated in accordance with the operating state of the fuel cell stack 1 by a control and / or regulation electronics, which is referred to below as a control unit 5 in principle.

As output variables for the control, or as feedback in a control, for example, data from temperature sensors could be used here. However, it is simpler and with less effort with regard to the components used if the current converted in the control unit 5 or the voltage processed there is taken directly from the energy converter, that is to say the fuel cell stack 1 itself, as is done by the guidance of the electrical lines in FIG the single attached figure is indicated. It is simply assumed that a relationship between the operating temperature and the operating conditions, which in the extracted power (U, i), or in the case of a battery in parallel to this also in the injected power represent.

The Peltier elements 4 should, in order to cover a comparatively large area with as little cost and interconnection as possible, be thin and predominantly flat. Such a design of Peltier elements 4 can be seen for example in the commercial tiling thermoelectric modules, for example, the HZ-20 from Hi-Z (www.hi-z.com), which has an extension of 7.5 × 7.5 cm at a thickness of about 5 mm.

In addition to this one example, which is not to be understood as limiting, other thermoelectric modules or Peltier elements 4 are of course also conceivable, whereby these should, if possible, be designed as thin, flat elements, preferably with a thickness of less than 10 mm. The space required and the weight caused by the use of the Peltier elements 4 can thus be kept within limits. Recent developments in this area show that even thin-film Peltier elements can be produced, in particular conductive polymers, eg. B. doped polyamide or the like. Of course, such Peltier elements 4 which could possibly be processed into films would also be useful for covering the fuel cell stack 1 .

If a corresponding electric power (U, i) is emitted from the fuel cell stack 1 , then process heat will also be produced as waste heat in the fuel cell stack 1 . The same applies when charging and discharging batteries, as another example of electrochemical energy converters. This process heat will heat up the fuel cell stack 1 , so that after a certain period of operation it reaches a temperature which is above the operating temperature which is meaningful for it. At such high temperatures, however, damage can then occur in the electrolyte, for example, phase changes or decomposition, which affect the fuel cell stack 1 in its performance and can damage it beyond. By using the Peltier elements 4 can now be achieved, however, that the resulting process heat can be ideally dissipated by heat conduction, since the Peltier elements 4 via a corresponding current flow, which in the present embodiment by the control unit 5 from that of the fuel cell stack 1 supplied power is switched so that the dissipation of process heat is favored. Excessive heating of the fuel cell stack 1 can be avoided by this active dissipation of emerging process heat.

In the case of a lack of process heat in the fuel cell stack 1 , the opposite effect can be achieved by reversing the flow of current through the control unit 5 , so that the process heat arising in the fuel cell stack 1 is prevented from flowing off by the Peltier elements 4 on the one hand and heat from the environment through the other Peltier elements 4 , if necessary, even against the temperature gradient, is transported into the fuel cell stack 1 . This can be useful, especially at very low temperatures, since damage to or blockage of the fuel cell stack, for example due to freezing or the like, can be avoided. The fuel cell stack 1 can also, if no power requirement is placed on him, heated by a small minimum operation for acting on the Peltier elements 4 with the resulting current or at least maintained at operating temperature, on the one hand, a small amount of heat in the fuel cell stack 1 is formed and on the other hand hinders the outflow of heat through the Peltier elements 4 and an inflow of ambient heat is favored. Depending on the time period over which no power requirement will be directed to the fuel cell stack 1 , the minimum operation can also be throttled to the extent that only a temperature protecting the fuel cell stack 1 from frost is maintained therein.

Of course, it would now also be conceivable to operate the fuel cell stack 1 in combination with a known from the above-mentioned prior art latent heat storage. If one or more of the Peltier elements 4 are now mounted in the heat-conducting contact region or the transition between the fuel cell stack 1 and the latent heat storage device, not shown here, then the heat exchange between the latent heat storage device can take place via the current flow or the voltage across the Peltier element 4 and the fuel cell stack 1 are actively influenced by the Peltier element 4 , so that a well-known from the prior art latent heat storage, despite a limited construction volume and thus a limited energy content, meaningful in the realized via the Peltier elements 4 active thermal management for the fuel cell stack 1 can be included.

Claims (11)

1. An apparatus for controlling the temperature of electrochemical energy converters, characterized in that at least a portion of the areas of the electrochemical energy converter ( 1 ), in which heat conduction to the energy converter ( 1 ) takes place away or away from the energy converter, Peltier elements ( 4 ), to which a current (i) and / or a voltage (U) can be applied. 2. Device according to claim 1, characterized in that the current (i) and / or the voltage (U) to the Peltier elements ( 4 ) in dependence of the operating state of the energy converter ( 1 ) is controlled. 3. A device according to claim 2, characterized in that the current (i) and / or the voltage (U) to the Peltier elements ( 4 ) from the energy converter ( 1 ) originates. 4. Apparatus according to claim 1, 2 or 3, characterized in that the energy converter ( 1 ) is designed as at least one fuel cell, preferably as a PEM fuel cell. 5. Device according to one of claims 1 to 4, characterized in that the Peltier elements ( 4 ) are arranged at least on a part of the surface of a housing of the energy converter ( 1 ). 6. Apparatus according to claim 5, characterized in that the Peltier elements ( 4 ) are formed thin and predominantly flat. 7. Device according to one of claims 1 to 6, characterized in that at least a part of the Peltier elements ( 4 ) are arranged in a heat-conducting contact region between the energy converter ( 1 ) and a latent heat storage. 8. A method for controlling the temperature of electrochemical energy converters, characterized in that Peltier elements ( 4 ) at least in a part of the areas of the electrochemical energy converter ( 1 ), in which heat conduction takes place to the energy converter or away from the energy converter, are used a current (i) and / or a voltage (U) is controlled or regulated at the Peltier elements ( 4 ) as a function of the operating state of the energy converter ( 1 ). 9. The method according to claim 8, characterized in that the direction of the current (i) and / or the voltage (U) at the Peltier elements ( 4 ) is selected with an excess of process heat so that a removal of the process heat by heat conduction is favored, while in a lack of process heat, the direction of the current (i) and / or the voltage (U) at the Peltier elements ( 4 ) is selected so that the dissipation of process heat by conduction is avoided or at least hindered. 10. The method according to claim 8 or 9, characterized in that the current ( 1 ) and / or the voltage (U) at the Peltier elements ( 4 ) from the energy converter ( 1 ) is removed. 11. The method according to claim 10, characterized in that the energy converter ( 1 ) continues to operate even in the absence of a power requirement, that the current (i) and / or the voltage (U) to the Peltier elements ( 4 ) from the Energy converter ( 1 ) can be removed.