HEATING SYSTEM WITH HEAT ACCUMULATOR ARRANGEMENT FOR HYBRID OR ELECTRIC VEHICLES, AND METHOD THERETO

Abstract

The invent inn relates to a heating system (10) for a hybrid or electric vehicle (50) comprising at least one electric machine (12) operable in the generator mode, at least one heat accumulator arrangement (32), al least one electric heating device (30) associated with the heat accumulator arrangement (32), and a switching arrangement (26), wherein the switching arrangement (26) is designed to optionally couple the at least one electric machine (12) with the at least one electric heating device (30) and or an electric energy accumulator (28), when the at least one electric machine (12) operates in the generator mode during a braking process, wherein al least one heat accumulator arrangement (32) has a latent heat accumulator agent (34) for heal storage, comprising at least one sugar alcohol which comprises at least one compound selected from the group consisting of erythritol, threitol, xylitol, mannitol, and dulcitol. With such a heating system (10), heat for heating can be stored well. The invention also relates to a method for accumulating heat and healing with such a heating system (10).

Claims

1. A heating system (10) for a hybrid or electric vehicle (50) comprising at least one electric machine (12) operable in the generator mode, at least one heat accumulator arrangement (32), at least one electric heating device (30) associated with the heat accumulator at (32), and a switching arrangement (26), wherein the switching arrangement (26) is designed to optionally couple the at least one electric machine (12) with the at least one electric heating device (30) and/or an electric energy accumulator (28), when the at least one electric, machine (12) operates in the generator mode during a braking process, characterized in that: the heat accumulator arrangement (32) has a latent heat accumulator agent (34) for heat storage, comprising at least one sugar alcohol which comprises at least one compound selected from the group consisting of erythritol, threitol, xylitol, mannitol, and dulcitol.

2. The heating system (10) according to claim 1, characterized in that the latent heat accumulator agent (34) comprises substantially erythritol,

3. The heating system (10) according to claim 1, characterized in that the latent heat accumulator agent (34) comprises a mixture of two or more sugar alcohols with compounds from the group consisting of erythritol, threitol, xylitol, mannitol, and dulcitol.

4. The heating system (10) according to claim 1, characterized in that the at least one electric heating device (30) is designed to heat the latent heat accumulator agent (34) to a maximum temperature in the range from 121 degrees Celsius to 200 degrees Celsius.

5. The heating system (10) according to one of the claim 1, characterized in that the latent heat accumulator agent (34) comprises as a supercooling inhibitor an inorganic salt selected from phosphates, sulfates, pyrophosphates, silver salts, inorganic acids, or silver halides.

6. The heating system (10) according to claim 1, characterized in, that at least one heat accumulator arrangement (32) is designed to be positionable directly behind the driver's seat (52) or on, and particularly on top of, a wheelhouse (60).

7. The heating system (10) according to claim 6, characterized in, that at least one heat accumulator arrangement (32) for the positioning behind the driver's seat (52) has a height of maximally 181 centimeters, a width of maximally 42 centimeters, and a depth of maximally 83 centimeters, or for the positioning on, and particularly on top of, a wheelhouse (60), it has a height of maximally 135 centimeters, a width of maximally 99 centimeters, and a depth of maximally 83 centimeters.

8. The, heating system (10) according to claim 1, characterized in that the at least one heat accumulator arrangement (32) is designed to directly convey heat stored in the heat accumulator arrangement by means of an air conveyor device to the air to be heated for the vehicle interior provided for vehicle occupants.

9. The heating system (10) according to claim 1, characterized in that at least one heat exchanger arrangement (38) for, conveying heat stored in the heat accumulator arrangement (32) to a medium to be heated, particularly heating water of a heating circuit for heating the air of the vehicle interior provided for vehicle occupants, is associated with the at least one heat accumulator arrangement (32).

10. The heat accumulator arrangement (32) for a heating system (10) according to claim 2, characterized in that the heat accumulator arrangement (32) for accumulating heat has a latent heat accumulator agent (34), comprising substantially erythritol.

11. A hybrid or electric vehicle (50) particularly a hybrid or electric bus, with a heating system (10), the heating system (10) comprising at least one electric machine (12) operable in the generator mode, at least one heat accumulator arrangement (32), at least one electric heating, device (30) associated with the heat accumulator arrangement (32), and a switching arrangement (26) wherein the switching arrangement (26) is designed to optionally couple the at least one electric machine (12) with the at least one electric heating device (30) and/or an electric energy accumulator (28), when the at least one electric machine (12) operates in the generator mode during a braking process, characterized in that: the heat accumulator arrangement (32) has a latent heat accumulator agent (34) for heat storage, comprising at least one sugar alcohol which comprises at least one compound selected from the group consisting of erythritol, threitol, xylitol, mannitol, and dulcitol.

12. The hybrid or electric vehicle (50) according to claim 11, characterized in that at least one heat accumulator arrangement (32) of the heating system (10) is, arranged behind the driver's seat (52) or on, and particularly on top of, a wheelhouse (60).

13. A method for accumulating heat and releasing stored heat with a heating system (10) integrated in a hybrid or electric vehicle (50), comprising the steps: a) of converting (100) kinetic energy during braking of the hybrid or electric vehicle (50) into electric energy by means of at least one electric,machine (12) operated as a generator; b) of converting (120) the electric energy into heat by means of an at least one heating device (30) associated with an at least one heat, accumulator arrangement (32) of the heating system (10), characterized by the further steps c) of storing (130) heat converted according to step b) in an latent heat accumulator agent (34) of an at least one heat accumulator arrangement (3) of the heating system (10) by storing it as sensible heat and/or as latent heat through phase transformation in the at least one sugar, alcohol, comprising at least one compound selected from the group consisting of erythritol, threitol, mannitol, and dulcitol; and d) of releasing (150), if necessary, sensible and/or latent heat stored in the intent accumulator agent (34) in the at least one heat accumulator arrangement (32) for heating air for or in the vehicle interior provided for vehicle occupants.

14. The method according to claim 13, characterized in that the latent heat accumulator agent (34) comprises substantially erythritol, and the conversion (120) of electric energy into heat in step b) stops automatically, when a predefined temperature of the latent heat accumulator agent in the range from 121 degrees Celsius to 200 degrees Celsius is exceeded.

15. The method according to claim 13, characterized in that step d) (150) is executed only when the temperature of the air in the vehicle interior provided for vehicle occupants lies below or undercuts a predefined target temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Embodiments of the invention shall be described using the drawings,

[0029] FIG. 1 shows a block diagram of an embodiment of the heating system according to the invention;

[0030] FIG. 2 shows a schematic depiction of an embodiment of a hybrid or electric vehicle as a bus with an installed heating system according to the invention; and

[0031] FIG. 3 shows a flowchart of an embodiment of a method for accumulating heat and releasing stored heat with a heating system according to the invention installed in a hybrid or electric vehicle.

DETAILED DESCRIPTION OF THE INVENTION

[0032] All drawings are to be understood as schematic. For the purpose of increased clarity of the depiction, drawings to scale were foregone.

[0033] FIG. 1 shows a block diagram of an embodiment of the heating system 10 according to the invention in a hybrid or electric vehicle. By means of a shaft 14, the electric machine 12 is connected to at least one wheel 16 of the hybrid, or electric vehicle. During the braking process of the hybrid or electric vehicle, a torque is applied to the electric machine 12 via the shaft 14, wherein the electric machine 12, provided with a rotor 18 and a stator 20, converts in the generator mode the kinetic energy into electric energy. This recuperation into electric energy during braking according to the principle of the eddy current brake is a technology known for hybrid or electric vehicles. In this embodiment, the electric machine 12 can also be used as a drive motor of the hybrid or electric vehicle. However, electric machines 12, which are only used in the generator mode during the braking process, are also conceivable. Furthermore, embodiments are conceivable which contain a plurality of electric machines 12, for example, one for each wheel of the hybrid or electric vehicle. In the design as a hybrid vehicle, an internal-combustion engine 22 with a switchable clutch 24 can be coupled to the drive train. In a design as an electric vehicle, the internal-combustion engine 22 plus clutch 24 is omitted.

[0034] The electric energy generated by the electric machine 12 in the generator mode during the braking process is conducted to the switching arrangement 26 via an electric line. The switching arrangement 26 contains conventional switching elements, with which the, electric machine ::12 operating in the generator mode is optionally electrically connected to or coupled with either the electric energy accumulator 28 or the electric heating device 30. Circuits, in which the electric energy generated by the electric machine 12 is optionally simultaneously distributed partly to the electric energy accumulator 28 and partly top the electric heating device 30, are also conceivable. In this embodiment, the switching arrangement 26 contains a priority switching for coupling the electric machine 12 with the electric energy accumulator 28 prior to coupling the electric machine 12 with the electric heating device 30. Only when a state of charge of, for example, 85% of the maximum value of the electric energy accumulator 28 is reached or exceeded, the electric machine 12 operating in the generator mode during the braking process is coupled with the heating device 30. The electric energy accumulator 28 is, but not limited to, a lithium-ion battery usually provided for the electric drive.

[0035] The electric heating device 30 is associated with a heat accumulator arrangement 32. For accumulating heat, the heat accumulator arrangement 32 contains a latent heat accumulator agent 34. The electric heating device this case, the electric heating device 30 is located directly in the latent heat accumulator agent 34. For heating the latent heat accumulator agent 34, the electric heating device 30 comprises one or more FTC heating elements. The electric heating device 30 can also comprise, for example, one or more electric heating rods embedded in the latent heat accumulator agent 34. The latent heat accumulator agent 34 contains exclusively or almost exclusively the sugar alcohol erythritol The other sugar alcohols threitol, xylitol, mannitol, and dulcitol and mixtures of these sugar alcohols, such as the eutectic mixture of mannitol and dulcitol with the molar mixture ratio of 50 to 50, are also conceivable as latent heat accumulator agent 34. The melting points, densities, and enthalpies of fusion of the compounds threitol, xylitol, erythritol, mannitol, and dulcitol and the eutectic mixture of mannitol and dulcitol with the molar mixture ratio of 50 to 50 are listed in the following table.

TABLE-US-00001 TABLE Melting point Density Enthalpy of fusion Substance ( C.) (kg/dm.sup.3) (kJ/kg) (kJ/dm.sup.3) Threitol (T) 71 1.46 223 326 Xylitol (X) 94 1.52 240 365 Erythritol(E) 120 1.46 334 488 Mannitol (M) 167 1.50 306 459 Dulcitol (D) 189 1.50 358 537 M/D 50:50 153 1.50 282 423

[0036] In a particular embodiment of the latent heat accumulator agent 34, an inorganic salt selected from phosphates, sulfates, pyrophosphates, silver salts, inorganic acids, or silver halides can be added to the erythritol as supercooling inhibitor in, small quantities of, for example, 1% by weight proportion. Such supercooling inhibitors for the sugar alcohols erythritol, mannitol, and dulcitol are listed in EP 0 754 744 B1.

[0037] The electric heating device 30 is designed to be able to heat the latent heat accumulator agent 34, which almost exclusively comprises erythritol, above the melting point of approximately 120 degrees Celsius, and so it becomes liquid. When the predefined maximum temperature in the range from 121 degrees Celsius to 200 degrees Celsius for the latent heat accumulator agent 34 is reached or exceeded, for example, 130 degrees Celsius, the energy supply of electric energy to the electric heating device 30 is stopped. If the electric energy is available from the electric machine 12 during the braking process, it is once again fed to the electric, heating device 30 if the latent heat accumulator agent 34 cools down below a predefined temperature value, such as 124 degrees Celsius.

[0038] Except for a small portion of its outer surface, the latent heat accumulator agent 34 is encased by a heat insulation layer 36. The heat insulation layer 36 consists of, but is not limited to, an inner and outer layer made of a solid material with little heat conduction, tier example, a ceramic, and an air or vacuum gap in between. A heat exchanger arrangement 38 is connected to or associated with the heat accumulator arrangement 32 and is in direct heat-conducting connection with the small portion of the outer surface of the latent heat accumulator agent 34 not insulated in said manner. The heat exchanger arrangement 38 is designed, for example, in the manner of a plate heat exchanger. A medium to be heated, in this case heating water of a heating circuit, can flow through the heat exchanger arrangement 38. If necessary, latent heat and/or sensible heat stored in the latent heat accumulator agent 34 can be released in the heat exchanger arrangement 38 to the medium to be heated. If the temperature of the air of the vehicle interior for the vehicle occupants to be heated lies below a predefined value, the heat transfer of heat stored in the heat accumulator arrangement 32 to the medium to be heated is switched on and is used for heating the air of or for the vehicle interior. The medium to be heated, for example, can also be directly the air provided for the vehicle interior to be heated, which is blown beforehand by means of an air conveyor device, for example, a radial blower, through a heat exchanger arrangement 38 designed for such purpose and located on the heat accumulator arrangement 32. Such a heat exchanger arrangement 38 has, for example, ribs which are made of a material with good heat conduction, and which are in thermal communication with the latent heat accumulator agent 34.

[0039] FIG. 2 shows a schematic depiction of an embodiment of a hybrid, or electric vehicle 50 as a hybrid or electric bus with an installed heating system 10 according to the invention. A driver is also shown schematically on the driver's seat 52. The heating system 10 corresponds to the one described for FIG. 1. Of all the individual components of the heating system 10, such as electric machine, electric heating device, and switching arrangement, only the accumulator arrangement 32 is shown in FIG. 2 individually from the outside. The heat accumulator arrangement 32 is positioned directly behind the driver's seat 52. In this case, it has a width of 40 centimeters, a height of 80 centimeters, and, a depth of 80 centimeters, but it is not limited to these dimensions. The installation space, in which the heat accumulator arrangement 32 is installed, is located in the otherwise unused space behind the driver's seat 52. Due to the good heat accumulator properties of the latent heat accumulator agent according to the invention, comprising at least one sugar alcohol, which comprises at least one compound selected from the group consisting of erythritol, threitol, xylitol mannitol, and dulcitol, the volume of the installation space behind the, driver's seat 52 is adequate for a sufficient heat accumulation. Particularly suitable alternative positions for at least one or further heat accumulator arrangement(s) 32 of the heating system 10 according to the invention are, for example, the installation space 54 shown dashed under one or more passenger seats 56 and/or the installation space 58 on or above a wheelhouse 60 of the hybrid or electric vehicle 50 designed as a hybrid or electric bus. Usually, these installations spaces are also not obstructed and offer sufficient space for heat accumulator arrangements 32 according to the invention with a sufficient heat accumulator capacity. The hybrid or electric vehicle 50 designed as a hybrid or electric bus can be purely an electric vehicle or a hybrid vehicle. Both variations are possible for FIG. 2.

[0040] FIG. 3 shows a flowchart of an embodiment of a method for accumulating heat and releasing stored heat with a heating system according to the invention installed in a hybrid or electric vehicle. In the first step 100, the kinetic energy during the braking of the hybrid or electric vehicle is converted into electric energy by means of an electric machine operated as a generator of the heating system according to the invention in step 120, this electric energy is subsequently completely or partly converted into heat by means of an electric heating device associated with the heat accumulator arrangement of the heating system, when, yes, beforehand during the automatic test 110, the state of charge of the electric energy accumulator of the hybrid or electric vehicle lies above or exceeds a predefined threshold value of, for example 80% of the maximum value, or only the portion of the electric energy generated in the first step 100 which is associated with the portion lying above a further predefined threshold value of the charging current generated during the braking of the hybrid or electric vehicle by means of the at least one electric machine operated as a generator. This predefined further threshold value orients itself by the maximum value of the charging current permissible first the electric energy accumulator. This maximum value depends particularly on the type, size, and the state of charge of the respective electric energy accumulator. Said threshold value can accordingly also be, adjusted temperature-dependently to the temperature of the electric energy accumulator because the maximum value of the permissible charging current for electric energy accumulators is temperature-dependent.

[0041] Otherwise, in case of no, the electric energy generated in step 100 through conversion, or the portion of said electric energy not to be converted further into heat, is fed to the electric energy accumulator. The electric heating device is, for example, a PTC heating element.

[0042] The electric energy converted into heat in, step 120 is stored in step 130 in the latent heat accumulator agent of the beat accumulator arrangement of the heating system as sensible heat and/or as latent heat through phase transition. The latent heat accumulator agent comprises predominantly at least one sugar alcohol which comprises at least one compound selected from the group consisting of erythritol, threitol, mannitol, and dulcitol. In this embodiment, the latent heat accumulator agent consists exclusively or almost exclusively of erythritol. In an optional variation of the method, it stops automatically prior to step 120, when a predefined temperature of the latent heat accumulator agent in the range from 121 degrees Celsius to 200 degrees Celsius, for example, 140 degrees Celsius, exceeded. If the latent heat accumulator agent subsequently cools down again, for example, to below 130 degrees Celsius, the method starts up again.

[0043] After step 130, test 140 verifies, whether yes, there is demand for the release of heat from the heat accumulator arrangement stored in the latent heat accumulator agent for heating air fir or in the vehicle interior provided for vehicle occupants, and the air in said vehicle interior lies below a predefined target temperature, for example, of 22 degrees Celsius, or whether no there is no demand or the target temperature has not yet been undercut. In case of a positive test 140, i.e. yes, the sensible and/or latent heat stored in the heat accumulator arrangement in the latent heat accumulator agent is released in the final step 150 for heating air for or in the vehicle interior provided for vehicle occupants. This is achieved, for example, by means of a subsequently activated heat exchanger arrangement.

[0044] The heating system according to the invention, with which the method, according to the invention can be executed, is usable for hybrid or electric vehicles, particularly advantageously in buses. The heat accumulation in the heat accumulator arrangement with the latent heat accumulator agent according to the invention, which advantageously is inexpensive, readily available and only slightly or not at all toxic for humans, is particularly effective and suitable. The operating temperatures of the heat accumulator arrangement are sufficiently low for a not particularly elaborately heat-insulated positioning in the vehicle interior provided for vehicle occupants,