DE102015014874A1 - Activation of a latent heat storage - Google Patents

Abstract

The invention relates to an activation device for a latent heat accumulator (16) which can be coupled via a fluid circuit to an electrical component (11, 12, 14) in a motor vehicle. The activation device comprises a crystallization nucleus generator (36) which is designed as a function of a mechanical excitation to provide nucleation nuclei in a phase change material (33) of the latent heat accumulator present as a supercooled melt, and a drive element (31) which is designed to mechanically excite the crystallization nuclei generator in dependence on a control signal which can be provided by means of a control device (37) of the motor vehicle. Furthermore, the invention relates to a latent heat accumulator (16) with such an activation device and a method for activating such a latent heat accumulator.

Description

The invention relates to an activation device for a latent heat storage, which can be coupled via a fluid circuit with an electrical component in a motor vehicle. Furthermore, the invention relates to a latent heat storage with such an activation device. Moreover, the invention relates to a method for activating a latent heat accumulator, which can be coupled via a fluid circuit with an electrical component in a motor vehicle.

Motor vehicles, in particular electric vehicles or hybrid vehicles, may have an electrical energy store, which are preferably constructed from lithium-ion cells or nickel-metal hydride cells. The energy storage of the lithium-ion and nickel metal hydride technology sometimes have significant limitations in terms of their permitted charging currents and discharge currents or the still removable currents at the lower useful temperature range of the vehicle. Today, for the removal of energy and also the charging operation, use restrictions are therefore implemented via the energy management of the vehicle to ensure that the permitted operating limits of the energy storage cells are not violated. This not only means that the removable current is limited in the cold state, but also that today cells can be charged only very limited at low minus temperatures, as long as the memory is cold.

The former leads to clearly perceptible loss of dynamics when accelerating the vehicle and the restriction of comfort features, the latter leads to a significant loss of energy recovery potential from the drive train, because the memory must not be charged with the maximum recoverable by the electric machine power during recuperation. Only when the memory exceeds certain temperature limits, the operation is enabled with full energy saving options and full drive dynamics.

Today, primarily two heating methods are known. The standard case is the heating only by the current heat at working current with the temperature-controlled allowable current, which usually takes longer and depending on the size and mass of the energy storage longer than a typical driving cycle in most countries in the world. The colder the reservoir is, the less power is allowed or removed, the longer the warming up process by the operation itself. For more sophisticated and equipped vehicles and powertrains electrothermal heaters are known to heat the cooling water flowing through the energy storage. The former method only starts when the vehicle is being driven, resulting in large currents that become thermally relevant. The second method can also be started via a defined, programmed starting point by autonomous commissioning of the high-voltage system for advanced air conditioning, but costs valuable, stored energy from the energy storage, which then lacks the electrical range for the vehicle.

Also known are latent heat storage for use in buildings, in the industrial process waste heat storage and recovery, and in motor vehicles, where they have already been used to quickly use the still stored in the latent heat storage residual heat in internal combustion engine driven vehicles after engine start to heat the cooling water circuit so the combustor reaches operating temperature faster and releases clean exhaust gas and thus also provide for the interior heating of the vehicle. In the simplest case, isolated containers are known in which several liters of cooling water are stored in an evacuated double wall vessel. The insulation causes the contained cooling liquid to lose the contained heat only slowly and to maintain useful amounts of energy for up to 36 hours. A disadvantage is that the unwanted heat loss begins immediately after parking and cooling of the vehicle. Once cooled, a significantly larger amount of cooling water than normal must be heated. In addition, a lot of space must be provided for the insulated vessel, if possible in an area where the heat is generated. The best are spherical vessels that are difficult to accommodate in the vehicle. Also known, but more interesting for the named applications are latent heat storage, using a so-called phase change material (PCM). In this case, the phase transition of the material itself is used to use the accumulated energy for the aggregate state transition at the same temperature. By using appropriate media, the temperature at which the phase transition occurs can be predetermined. Parafins, fatty acids or salt hydrates may be suitable, possibly including some sugar alcohols. Either only the melt-solidification process is exploited, or the crystallization phase of salts. Usually, when the crystallization phase is used, substances are added to the media which allow nucleation above the melting temperature of the medium. When the transition from solid to liquid occurs, then, after the end of the heat supply, the medium enters through the propagating crystallization and solidification an exothermic process, the stored heat again. This energy can be used for a new heating cycle. With appropriate memory design can be so day and night fluctuations in temperature, for example, in buildings, with very reduced energy use very well balanced.

In this context, the DE 10 2008 034 857 A1 a method and an apparatus for operating a vehicle with a battery, comprising a plurality of parallel and / or serially interconnected, arranged in a housing individual cells, wherein the housing is flowed through by a Wärmeleitmedium and the heat transfer medium is conveyed within a first coolant circuit by a pump unit, wherein the first coolant circuit is coupled via a latent heat storage with a arranged in this phase transition material to a second coolant circuit, wherein in vehicle operation upon reaching a first predetermined temperature limit of the latent heat accumulator this is traversed by the coolant of the second coolant circuit until the latent heat accumulator cooled to a predetermined temperature value becomes.

Furthermore, from the DE 10 2011 105 366 A1 a cooling arrangement for an electrical energy storage, in particular a high-voltage battery, a vehicle, known with a first cooling circuit, in which a cooling medium can be conveyed through a cooling channel of the electrical energy storage, and which is thermally coupled via a latent heat storage with a second cooling circuit, wherein the second cooling circuit an air conditioning circuit of the vehicle is.

A disadvantage of such latent heat storage arrangements, however, is that a high self-discharge occurs when the latent heat storage is not consuming isolated.

It is therefore an object of the present invention to provide a device, a latent heat accumulator with such a device and a method for operating such a device, which allows a more efficient storage of heat energy in the latent heat storage.

This object is achieved by an activation device having the features of patent claim 1, a latent heat accumulator having the features of patent claim 5 and by a method having the features of patent claim 8. Advantageous developments of the present invention are the subject matter of the dependent claims.

The invention is based on an activation device for a latent heat accumulator, which can be coupled via a fluid circuit with an electrical component in a motor vehicle. Such an electrical component can be provided, for example, by power electronics in the form of a drive converter of the motor vehicle, by an electrical machine or by an electrical energy store of a motor vehicle, in particular in the form of a battery. According to the invention, the activation device is further developed by a nucleation generator which is designed to provide crystallization nuclei in a phase change material of the latent heat accumulator present as a supercooled melt as a function of a mechanical excitation, and a drive element which is designed as a function of one by means of a control device of the motor vehicle provide a controllable control signal to mechanically stimulate the seed generator.

The inventors have recognized that the possibilities of a phase change material, which can be coupled with an electrical component in a motor vehicle, are currently only insufficiently exhausted. In particular, the possibility that the phase change material may be present in a state of a supercooled melt - which is also referred to as a metastable state - is not exploited. It is therefore only the increased storage capacity of thermal energy during the phase transition from liquid to solid or solid liquid used, the further possibility of a delayed heat energy release, however, remains unused. This is particularly of great technical and economic interest, since in this way a complex insulation for long maintenance of the stored thermal energy can be made simpler and thereby additional costs and space and weight can be saved. Accordingly, during the transition from the phase change material from a temperature above its melting point to a temperature below the melting point, a crystallization process no longer takes place automatically; rather, this crystallization process is triggered by a corresponding external excitation. A suitable activation device for this purpose is provided by the invention.

In an advantageous development of the seed generator is designed as a standing under mechanical prestress, reversibly bendable spring element, in particular as spring steel plate.

In a further advantageous embodiment, the drive element is designed as an electromechanical actuator.

The drive element is preferably designed to change its length depending on the control signal.

A latent heat storage device according to the invention has an activation device according to the invention and a phase change material which is designed to liquefy when its melting temperature is exceeded and to remain in a predeterminable temperature range below the melting temperature without a presence of crystallization nuclei in a metastable state of the supercooled melt.

In an advantageous development, the drive element is arranged outside the phase change material.

In a further advantageous embodiment, the latent heat accumulator has a housing in which the phase change material is arranged, wherein the crystallization nucleus generator is mechanically coupled to the drive element via the housing. Alternatively it can be provided that the crystallization nucleus generator is coupled via a magnetic coupling with the drive element. This results in a particularly advantageous power transmission, since the housing in this case does not have to be elastically deformable.

The invention is further based on a method for activating a latent heat accumulator, which can be coupled via a fluid circuit with an electrical component in a vehicle. According to the invention, the method is further developed by providing crystallization nuclei in a phase change material of the latent heat accumulator present as a supercooled melt as a function of a mechanical excitation of a crystallization nucleus generator, and mechanically exciting the crystallization nucleus generator in dependence on a control signal which can be provided by means of a control device of the motor vehicle.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention. The advantages and features and embodiments described for the activation device according to the invention and for the latent heat storage device according to the invention apply equally to the method according to the invention and vice versa. Consequently, corresponding device features and vice versa can be provided for device features. In the figures, like reference characters designate like or equivalent features and functions.

Showing:

1 in a simplified schematic representation of a latent heat storage with a single heat exchanger coil for coupling with a battery-powered electric vehicle;

2 in a simplified schematic representation of a latent heat storage with two heat exchanger coils for coupling with a battery-powered electric vehicle; and

3 in a simplified schematic representation of a preferred embodiment of a latent heat accumulator according to the invention.

The invention allows optimized operation with respect to the operating parameters of an electrochemical energy storage device for vehicles with alternative drive trains. Such vehicles contain energy storage devices, for example battery cells, which can be charged and discharged within certain temperature limits. The operating current at which they may be discharged or charged depends on the core temperature of the battery cells. The invention allows optimized operation to the effect that a latent heat storage is used to buffer waste heat at high loads without having to accept a further increase in temperature, and release this energy only when needed by the vehicle to preheat the energy storage release again. Thus, the temperature range with released high-current capacity and / or Hochstromentladefähigkeit can be achieved at the beginning of the drive cycle or even before the programmed departure, otherwise the memory would be too cold, as well as a greatly improved cooling in high load phases below the upper limit of the allowed temperature range allows ,

In the cooling circuit of an electric drive system, a heat exchanger can be introduced. This makes it possible to heat transfer from the cooling medium to a phase change material contained in the heat exchanger (Phase Change Material, PCM), the phase transition temperatures are such that the waste heat in the cooling system for the electric drive system in a normal driving cycle is sufficiently large to a phase transition of solid to ensure liquid. As long as the aggregate state transition takes place, that takes Phase change material on energy without the temperature of the same changes. Regardless of the state of aggregation and the thermal status of the phase change material, it can buffer load peaks until thermal saturation by either accelerating the energy input or changing the state of the aggregate state or simply increasing the temperature. The registered waste heat can also originate from the internal combustion engine of a hybrid vehicle.

For a meaningful use of the possibilities of the phase change material, the proposed use in the vehicle is particularly advantageous feasible if the recrystallization does not start immediately after the warm-up, but can be started on request. For this purpose, the phase change material must be free from crystallization nuclei. Thus, it remains in the passive phase after heating in its liquid state, even if a strong hypothermia takes place. An effect known from commercial pocket warmers is used to initiate the exothermic reaction of the aggregate state transition back into the crystallization phase only and exclusively at the request of the vehicle.

According to the invention an actuator can be controlled by a control unit in the vehicle, if a programmed departure time is known in the vehicle, or if the customer communicates with the vehicle, for example by means of remote control. The actuator preferably bends a spring steel plate installed in the interior of the heat exchanger with a bias voltage. This process liberates nuclei and initiates crystallization and initiates the exothermic reaction. The coolant contained in the heat exchanger is brought by the heat output of the phase change material to temperature and is thus available for heating the energy storage and, if desired, for heating the interior of the vehicle. The cooling system then needs to pump the warmed coolant into the energy storage unit where it heats the battery cells by means of a pump. Preferably used as a location for the heat exchanger sealed cavities of the body, which are available anyway. In the underbody and in the Schwellerbereich thereby otherwise cold vehicle parts in the foot area are brought to pleasant temperatures. When the reservoir is depleted and the PCM is completely in its fixed aggregation, the next charge cycle may begin by again using waste heat from the duty cycle to reflow the phase change material.

A strong isolation can be dispensed with, because the liquefied phase change material keeps the energy stored even with strong hypothermia. However, it can be used in order to use as much of the waste heat as possible and not have to use parts thereof for the heating of the phase change material itself.

It can also be provided embodiments in which the cooling water path can bypass the heat exchanger with the phase change material by means of a bypass, which is always useful when there are high outside temperatures anyway. For this purpose, a controller can evaluate season and position data and / or track temperature profiles to assess the respective cooling potential in the potential Abstellpause and accordingly operate in the operating phase, the valves so that the cooling water does not flow through the heat exchanger, if no heat is to be stored or the store is already loaded. Thus, only as much cooling water is heated in the cycle as necessary and the operating temperature is reached very quickly.

It may further be provided to use the energy in the latent heat storage to warm the interior of a commercial vehicle cab when the vehicle has a steering break and park with the burner turned off.

Furthermore, embodiments are conceivable in which the entire latent heat storage module is removable as a module and can then be used on a standardized connection for "off car use", for example for heating drinking water. The advantage would be an effective use of waste heat, which fizzles in the garage today by cooling down ineffective. Also conceivable are applications in which an exchange module is heated by solar thermal or geothermal energy during the day in order to be able to use it at the next departure.

In a first arrangement as shown in FIG 1 is a drive converter in the form of power electronics 11 with an electric machine 12 , a cooler 13 , an electrochemical storage in the form of a battery 14 and a latent heat storage 16 thermally coupled across a fluid circuit. The fluid circuit is in this case by a pump 15 driven. In this first arrangement, the latent heat storage 16 equipped with a single heat exchanger coil.

The pump 15 promotes the liquid in the liquid circuit from a drain of the battery 14 to a branching point Y11, where the fluid circuit to an inlet of the power electronics 11 and an adjustable throttle valve 112 branched. The fluid circulation continues from an outflow of power electronics 11 to an inflow of the electric machine 12 and from a drain of the electric machine 12 to a branch point Y12. Via an adjustable throttle valve 103 From there, the fluid circuit continues to lead to an inflow of the radiator 13 , and further from a drain of the radiator 13 to a branch point Y14. The liquid circuit leads from the branch point Y14 to an inlet of the battery 14 and the expiry of the battery 14 back to the pump 15 , At the branch point Y14 also leads to a lapse of the latent heat storage 16 , wherein an inlet of the latent heat storage 16 via an adjustable throttle valve 106 is connected to a branch point Y13. Between the branch point Y11 and the branch point Y13 is the variable throttle valve 112 connected. Between the branch point Y12 and the branch point Y13 is a non-adjustable throttle valve 110 connected.

By means of throttle valves 103 . 106 . 110 . 112 , each with only a single fluid circuit between the components power electronics 11 with electric machine 12 , Cooler 13 and latent heat storage 16 and the battery 14 Energy is exchanged in the form of heat. Thus, with skillful interconnection of the components of the cooling circuit for charging and for removing the heat energy one and the same coil can be used in the heat exchanger.

A second arrangement with a latent heat storage 16 with two heat exchange filaments is in the 2 shown. Unlike the first Anrodnung is instead of the cooler 13 each a first cooler 13a and a separate second cooler 13b available. Furthermore, instead of the pump 15 in each case a first pump 15a and a second pump 15b provided for the respective liquid circuit, so that both fluid circuits are independently operable.

The first cooling circuit is here to the first pump 15a , the power electronics 11 , the electric machine 12 , the first cooler 13a as well as to the latent heat storage 16 coupled. The second cooling circuit is to the second pump 15b , to the latent heat storage 16 , to the second radiator 13b as well as to the battery 14 coupled. A drain of the first pump 15a is with an inflow of power electronics 11 coupled. A process of power electronics 11 is about the electric machine 12 coupled to a branch point Y22. The branch point Y22 is via an adjustable throttle valve 103a with an inlet of the first radiator 13a coupled. An inlet of the first pump 15a is coupled to a branch point Y21, which also includes a drain of the first radiator 13b and a lapse of latent heat storage 16 is coupled. An inlet of the latent heat accumulator 16 is coupled to the branch point Y22.

A drain of the second pump 15b is coupled to a branch point Y23, which with an inlet of the latent heat storage 16 is coupled. A process of the latent heat storage 16 is via an adjustable throttle valve 106b coupled to a branch point Y24. The branch point Y24 is with an inlet of the battery 14 coupled, a drain of the battery 14 is with an inlet of the second pump 15b coupled. The branch point Y23 is further via an adjustable throttle valve 103b over the second cooler 13b , ie via its inlet and its outlet, coupled to the branching point Y24. Like in the 2 can be clearly seen, are the respective fluid circuits through the first pump 15a and the second pump 15b formed as separate fluid circuits whose cooling medium is not in direct contact with each other and thermally only by means of the latent heat storage 16 is coupled. In this arrangement with two heat exchange filaments, one heat exchange filament can be used for charging to the liquid state and the other heat exchange filament for extraction.

Based on 3 a preferred embodiment of a latent heat accumulator according to the invention is explained in more detail, which in one of the arrangements according to the 1 or the 2 as latent heat storage 16 with a heat exchanger coil or with two heat exchanger coils (in 3 not shown) is used. The latent heat storage 16 includes a drive element 31 , which is preferably designed as a variable-length actuator. The drive element 31 is about an actuator 34 . 35 mechanically with a phase change release 36 which is within a phase change material 33 is arranged, mechanically coupled. The phase change trigger 36 serves as a nucleation generator for the phase change material 33 in a state of supercooled melt. The phase change material 33 and the phase change trigger 36 are inside a housing 38 arranged, the housing 38 an elastic housing part 32 has, on which the actuating element 34 . 35 is suspended. In the illustration according to the 3 the actuating element is once in rest position ( 34 ) and once in a controlled state ( 35 ). the drive element 31 can be from a control device 37 be controlled by a motor vehicle. Thus, depending on the interconnection of the latent heat storage 16 in an embodiment with a single heat exchanger coil in a cooling circuit or with two separate heat exchanger coils in two separate cooling circuits, namely one for the battery 14 and one for the power electronics 11 and the electric machine 12 , the respective cooling circuits each have the components, pumps, valves and radiators already shown.

The triggering mechanism for triggering the energy delivery may be designed such that the drive element 31 is designed as an electromagnet which exerts force on a ferromagnetic metal rod, which with the crystallization trigger in the form of the phase change trigger 36 connected is. Another possibility may be an expression such that a mechanical connection between the crystallization trigger and the outer wall of the housing 38 consists, which is designed to be elastic at the actuating point and a fixedly mounted actuating lever - in accordance with the actuating element 34 . 35 - Has on the outside, to which any length change actuator as a drive element 31 attacks, which causes a deformation of the outer wall in such a manner that is actuated in the interior of the crystallization trigger.

The embodiments are only illustrative of the invention and are not limiting for these. In particular, the specific embodiments of drive element 31 and phase change triggers 36 can be arbitrarily designed without departing from the spirit of the invention.

The invention makes it possible to store in the operating phase of a drive system waste heat accumulated so that it is not lost unused, but only when needed and controlled by the vehicle is released when very low ambient temperatures prevail, under which the energy storage is subject to operational restrictions. As a result, the release can be saved for a later time and is available even after a longer service life, if retained by insulation heat would be lost long ago. Furthermore, in very hot environmental conditions, the invention allows to produce, at least for a limited time, a temperature rise limit similar to a cooling effect when the storage was previously discharged. For this purpose used temperature profiles, location and time data are available in the vehicle anyway. The invention thus makes it possible to expand the range of use of the energy storage without temperature-limited operating parameters or to use larger parts of a driving cycle even under climatically harsh conditions without any limitation of the operating parameters. This results in advantages over the prior art in terms of economy and energy consumption, ease of use and electrical range in electrically or hybrid-powered vehicles. If the latent heat storage designed as a removable exchange module, the energy can also be used outside the vehicle, for example in a household, for example, to heat drinking water or to heat the house itself.

Thus, as shown above, such as a latent heat storage 16 can be used with aktuatorgetriggerter energy delivery for operating parameter influencing electrochemical energy storage, for example, the battery 12 in a motor vehicle in an optimal temperature range to bring.

LIST OF REFERENCE NUMBERS

11

power electronics

12

electric machine

13

cooler

13a

first cooler

13b

second cooler

14

battery

15

pump

15a

first pump

15b

second pump

16

Latent heat storage

31

driving element

32

elastic housing part

33

Phase change material

34, 35

actuator

36

Phase change triggers

37

control device

38

casing

103, 103a, 103b

throttle valve

106, 106b

throttle valve

110

throttle valve

112

throttle valve

Y11, Y12, Y13, Y14

branching point

Y21, Y22, Y23, Y24

branching point

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008034857 A1 [0006]
• DE 102011105366 A1 [0007]

Claims (8)

Activation device for a latent heat store ( 16 ), which via a fluid circuit with an electrical component ( 11 . 12 . 14 ) can be coupled in a motor vehicle, characterized by - a crystallization germ generator ( 36 ), which is designed, depending on a mechanical excitation, nuclei in a phase change material present as supercooled melt ( 33 ) provide the latent heat storage, and - a drive element ( 31 ), which is designed, depending on a by means of a control device ( 37 ) of the motor vehicle to be provided mechanically stimulate the seed generator. Activation device according to claim 1, characterized in that the crystallization germ generator ( 36 ) is formed as a standing under mechanical prestress, reversibly bendable spring element, in particular as spring steel plate. Activation device according to one of the preceding claims, characterized in that the drive element ( 31 ) is designed as an electromechanical actuator. Activation device according to one of the preceding claims, characterized in that the drive element ( 31 ) is adapted to change its length in response to the control signal. Latent heat storage ( 16 ) with an activation device according to one of the preceding claims, characterized by - a phase change material ( 33 ), which is designed to liquefy when its melting temperature is exceeded and to remain in a predeterminable temperature range below the melting temperature without the presence of crystallization nuclei in a metastable state of the supercooled melt. Latent heat store according to claim 5, characterized in that the drive element ( 31 ) outside the phase change material ( 33 ) is arranged. Latent heat store according to claim 5 or 6, characterized by - a housing ( 38 ), in which the phase change material ( 33 ), wherein the nucleation generator ( 36 ) via the housing mechanically with the drive element ( 31 ) is coupled. Method for activating a latent heat accumulator ( 16 ), which via a fluid circuit with an electrical component ( 11 . 12 . 14 ) can be coupled in a motor vehicle, characterized by providing crystallization nuclei in a phase change material present as a supercooled melt ( 33 ) of the latent heat storage ( 16 ) as a function of a mechanical excitation of a nucleation generator ( 36 ), and - mechanical stimulation of the seed generator in dependence on a by means of a control device ( 37 ) of the motor vehicle available control signal.

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