WO2016034308A1

WO2016034308A1 - Device for absorbing and storing thermal energy and corresponding production method

Info

Publication number: WO2016034308A1
Application number: PCT/EP2015/065312
Authority: WO
Inventors: Philipp Kohlrausch; Vikram Anil GODBOLE
Original assignee: Robert Bosch Gmbh
Priority date: 2014-09-04
Filing date: 2015-07-06
Publication date: 2016-03-10
Also published as: DE102014217704A1

Abstract

The invention relates to a device for absorbing and storing thermal energy, which device is in particular used in an energy store. The invention further relates to a method that produces the device or a part of the device. The device according to the invention comprises at least one extruded profiled element, which is composed of a metal foam. For this purpose, especially an aluminum foam has proven to be advantageous, wherein the invention should not be restricted to aluminum foam. Said metal foam has the characteristic that the pores located in the foam are filled with water. In order to prevent the water from flowing out, the surface of the extruded profiled element is covered with a protective layer.

Description

The invention relates to a device for receiving and storing heat energy and a corresponding production method

Heat energy, in particular for use in an energy storage.

State of the art

Both the loading and the discharge of batteries cause the generation of heat. This heat can turn negative

Have effects on the storage capacity of the battery, e.g. by lowering the capacity of the battery. In the worst case, irreversible events can also be started, e.g. Generation of gases that restrict or even endanger the use of the battery.

To dissipate the resulting heat from the battery, various heat couplings are known. In addition to an active cooling by corresponding cooling devices with coolant flows are just passive cooling elements of

Advantage that does not require an independent power supply. For this purpose, different materials are brought between the individual energy cells of the battery, which are thermally coupled to the energy cells. typical

Materials that allow for cooling and storage are various plastics, metals, potting compounds as well

Combinations / composites of plastics and ceramics or graphites and phase change materials (PCM).

A disadvantage of the typical Entwärmungsmaterialien is that it is usually optimized either to a high heat conduction or a high heat capacity are. In addition, some of the materials mentioned also lack the ability to process them at will, to make them into a desired shape for use in battery packs, or lack the stability to use them in portable battery packs.

With the present invention, a device is proposed which does not have these disadvantages. Thus, also battery packs can be made in different design for outdoor use, e.g. for the

Electric vehicle sector, in particular electric bicycles.

Disclosure of the invention

According to the present invention, a device for receiving and storing heat energy is described, which finds particular use in an energy storage. Furthermore, a method is described, which generates the device or a part of the device.

The device according to the invention consists of at least one

Extruded profile, which consists of an open-pored metal foam. For this purpose, especially an aluminum foam has proven to be advantageous, the invention should not be limited to aluminum foam. This metal foam has the property that the pores in the foam are filled with water. In order to prevent the water from flowing out, the surface of the extruded profile is covered with a protective layer.

With such a device which is easy to manufacture, a form of heat dissipation or storage of heat energy adapted individually to the desired use can be generated. By the combination of the metal,

In particular, the aluminum, with the water can be compared to the known materials also achieve higher levels of thermal conductivity and heat capacity. The pore size of the metal foam can be adjusted by the adjustment during extrusion such that the pore size, in particular the average pore size, is smaller than 1 cm in diameter. The size of the pores can be chosen to allow rapid filling with water or other suitable liquid, and yet be able to seal the outer pores to prevent leakage of the water.

Furthermore, the ratio of pores to the metal of the extruded profile can be selected such that the metal has only a volume fraction of 5 to 15%. In particular, a volume fraction of around 10% has proven to be particularly efficient.

Although the outflow of water through the protective layer is prevented, it can also be provided that the pores are selected to be so small that the water can not escape due to capillary action and / or surface tension.

The protective layer may additionally or optionally also have the function of electrical insulation.

As a protective layer, for example, paints or an epoxy resin can be used.

Of course, a plurality of individually manufactured extruded profiles can be interconnected, e.g. by being connected side by side with their oblong side to form a package. Both

Extruded profiles can generally be star-shaped, triangular or square shapes in cross-section.

Particularly advantageous are the inventive devices in use in energy storage, in which by the thermal coupling between

Device and energy cell, a removal and storage of heat is possible. The storage of heat can also be used to keep the energy cell at a desired temperature, for example when used outdoors in winter. In the inventive production of an aforementioned extruded profile is by means of an extrusion of a metal foam

Molded extruded profile. The pores of the metal foam are then at least partially filled with water, e.g. by applying a negative pressure to one side of the extruded profile and thus absorbing the water through the interconnected pores of the metal foam. Subsequently, a protective layer is applied to the surface of the extruded profile, which acts electrically insulating and / or retains the water in the pores.

Another advantage of using the combination of metal foam and water described lies in the utilization of the heat of vaporization of the water. If, in a particularly critical case, a cell heats up to a critical temperature (about 140 ° C with Li-Ion batteries) (in this case, it is referred to as thermal runaway), the neighboring cells can also be prevented from attacking Heat the critical temperature and prevent known "critical runaway propagation" by removing the heat from the system by evaporating the water.

Should the water evaporate in the metal show profiles, it will escape into the free volume of the battery pack as steam. The protective layer should be carried out accordingly. In this case, it is advantageous to provide a pressure relief valve in the housing of the battery pack. Through this valve, the water vapor can be released to the environment and the temperature in the battery can be reduced. Optionally, it can be provided here that e.g. is informed by means of a suitable sensor of the user about the evaporation of the water, so that a regeneration of the system, e.g. by adding water. Alternatively, this regeneration may also be automatic, e.g. by means of a supply of water or the recovery of the evaporated water.

Further advantages will become apparent from the following description of

Embodiments or from the dependent claims. Brief description of the drawings

In the figure 1 is a schematic close-up of the pores of a

Metal foam shown. Figures 2a to c show a single

inventive extruded profile and devices from

composite extruded profiles. With the flowchart of Figure 3, the production of an extruded profile according to the invention is shown schematically.

embodiment

For the absorption and storage of heat, metals with their high thermal conductivities and heat capacities are suitable. Due to their mass and cost, however, the use of massive metal blocks for the dissipation and storage of heat only makes limited sense.

Instead, metal foams are known with which large volumes can be realized with low material usage and high stability. However, since in such metal foams just a smaller volume fraction of the metal is present, the pores present in the metal can be filled with a liquid, which also have relatively good thermal conductivities and heat capacities in order to achieve the desired effect.

In the following embodiment, the invention with reference to a

Aluminum foam presented, which is soaked in water. In addition, other metals are conceivable, which are processable as foam and has correspondingly good thermal conductivities or heat capacities.

FIG. 1 shows a close-up of an open-pore aluminum foam. Such metal foams can be produced or processed by various processes and should not explicitly be the subject of this invention. As can be clearly seen in the close-up, the aluminum foam forms a grid Aluminum webs between which pores have formed, which are in particular interconnected. With the use of such an aluminum foam, the production of an extruded profile 10 is possible by means of an extrusion process, as shown in Figure 2a. During the processing of the aluminum foam, the pores can be adjusted such that they can form pore sizes of> 1 μηι up to several centimeters, so that the metal foam can have a pore volume of up to 95%.

For the above invention, a (mean) pore size of less than one centimeter in diameter is provided, so that a volume fraction of the

Aluminum on aluminum foam from 5 to 15% results. This has become a

Aluminum content of 10% by volume proved to be particularly advantageous. The pore size can also be chosen such that the pores retain the water due to capillary action and / or surface tension, without further covering of the pores being necessary.

To keep the water in the pores and / or around the surface of the

Extruded profile 10 to electrically isolate, a protective layer is provided. This protective layer may consist of paints or an epoxy resin.

The individual extruded profiles can be cut into the desired length and combined with other extruded profiles to form a composite 20 or 30, as shown in FIGS. 2b and 2c. When using star-shaped

Extruded profiles, as shown by the example of FIG. 2a, can do so

Through holes are created, through which further cooling, e.g. by air or other coolant is possible. In addition, however, other cross-sectional profiles such as triangles, crosses, diamonds or other rectangles are possible.

By the two-part production of the composite by first the extruded profile 10 is produced and then these extruded profiles are cut, the composites thus produced can be adapted to the desired shape. Thus, the composite can be used as a cell holder for energy cells of a battery to dissipate the waste heat generated during the charging or discharging of the energy cells and possibly save. For this purpose, both the blanks of the extruded profiles as Their cross-sections may also be adapted to the energy cells in order to be able to record them positively and thus with good thermal coupling. A particularly good thermal coupling between the extruded profile or composite is achieved when the energy cell is substantially largely enclosed.

To produce the extruded profiles according to the invention, a method can be used, which is shown schematically as a flowchart in FIG. Thereafter, in a step 100, the extruded profile 10 is made of a metal foam, e.g. Aluminum foam made. Since the production of such

Extruded profiles, also by means of metal foam, is to be regarded industrially as standard, shall not be discussed further here. Subsequently, optional extrusion profiles can be cut to size and joined together to form a composite. In step 120, the single extruded profile or the composite is soaked with water, so that the pores, which are in the metal foam, can at least partially fill with water. If the pores can not be filled alone, it is also possible to work with negative pressure, e.g. by applying the negative pressure to a side or surface of the extruded profile, thus achieving a suction effect. Since the pores in the metal foam are not only on the surface but branch out through the entire extruded profile and are connected to each other, thus the water can be sucked into the pores. With step 130, the surface of the extruded profile or of the composite is provided with a protective layer. This protective layer can serve as electrical insulation of the metal of the extruded profile. Additionally or optionally, this protective layer can also close the pores on the surface, so that the water can no longer flow out. The latter can be quite useful, even if the pores would automatically retain the water due to capillary action and / or surface tension, as this prevents evaporation. If the extruded profiles are individually, i. in the originally prepared or already cut state, with which water has been soaked, in a further optional step 140 the connection to a composite can be carried out.

Claims

claims

Anspruch [en] A device for receiving and storing heat energy, wherein the device has at least one extruded profile (10) which consists at least partially of a metal foam, in particular of aluminum, with pores, wherein the pores are at least partially filled with water, the surface of the Extruded profile is covered with a protective layer that prevents leakage of water from the pores.

2. Apparatus according to claim 1, characterized in that the

especially average pore size <1 cm in diameter.

3. Device according to one of the preceding claims, characterized

characterized in that the pore size is selected such that the metal on the extruded profile is a volume fraction of 5 to 15%, in particular 10%.

4. Device according to one of the preceding claims, characterized

characterized in that the pore size is selected such that the water is not discharged due to capillary action and / or surface tension.

5. Device according to one of the preceding claims, characterized

characterized in that the protective layer forms an electrical insulation.

6. Device according to one of the preceding claims, characterized

characterized in that the protective layer of a paint or a

Epoxy resin exists.

7. Device according to one of the preceding claims, characterized

in that a plurality of extruded profiles are joined together via their oblong sides to form a unit (20, 30).

8. Energy storage with at least one energy cell, wherein the energy cell is at least partially enclosed by a device according to one of claims 1 to 7, wherein the heat output of the energy cell is transferred to the device during loading or unloading.

9. Energy storage with at least one energy cell, wherein the energy cell is at least partially enclosed by a device according to one of claims 1 to 7, which is enclosed by a closed, waterproof housing, which is provided with a pressure relief valve.

10. A method for producing an extruded profile for use in a device according to one of claims 1 to 7, wherein

• by means of an extrusion of voided metal foam, in particular an aluminum foam, a

Extruded profile (10) is formed (100), and

• the pores of the metal foam are at least partially filled with water (120), and

• the surface of the extruded profile with a protective layer

is closed (130).

11. A method for producing an extruded profile according to claim 9, characterized in that the filling of the pores takes place by means of negative pressure.