ELECTRICALLY HEATED LATENT HEAT STORAGE SYSTEM WITH SHORT CHARGING TIMES

Description

[0001] The invention relates to a latent heat storage device which can be charged with electrically generated thermal energy in a short time, as well as to its use for heating electrically powered vehicles and to an operating method therefor.

[0002] The latent heat storage device according to the invention is designed according to the features of claim 1. Features of advantageous developments are the subject of subclaims. Document WO2011 / 072988 shows a vehicle with an electrically heatable latent heat storage device according to the preamble of claim 1.

[0003] The attached figures show: Fig. 1 a latent heat storage device in a passenger bus according to an embodiment of the invention; Fig. 2 a basic structure of a heat pump; Fig. 3 a relationship between heat storage capacity and working temperature of selected phase change materials; Fig. 4a graphical relationship between heat demand, discharge power and storage capacity; Fig. 5 a schematic representation of heat storage concepts according to an embodiment of the invention; Fig. 6 various memory module concepts according to an embodiment of the invention; Fig. 7 two sections of design variants of a latent heat storage device according to an embodiment of the invention; Fig. 8 a further embodiment of a latent heat storage device according to an embodiment of the invention; Fig. 9 Sections A, B and C from the Fig. 8 ; Fig. 10 Design variants of heat conducting structures for a latent heat storage device according to an embodiment of the invention; Fig. 11 a section of a heating element with a heating power varying in the z-direction of a latent heat storage device according to an embodiment of the invention; and Fig. 12a section of a heating element with a heating output varying in the x-direction of a latent heat storage device according to an embodiment of the invention.

[0004] One of the major challenges for urban public transport in the coming years is to achieve zero climate-damaging emissions. Advancing the development of everything from conventional to hybrid to fully electric city buses represents an important step toward achieving this goal.

[0005] Compared to conventional energy sources (e.g., diesel), the storage systems of fully electric vehicles have significantly limited energy resources due to their much lower energy density. If the energy available in the limited storage systems of electric buses is used not only for traction but also to operate auxiliary units, such as the passenger compartment heater, the range of these vehicles is significantly reduced.

[0006] A key problem here is the heating of the passenger compartment, as this requires a relatively high level of power.

[0007] Regarding the specific heating energy requirement of city buses related to the mileage, it is known from the state of the art that with decreasing outside temperature an increasing heating energy requirement can be expected and at outside temperatures of about -10°C a heating energy requirement at the level of the specific traction energy requirement of the vehicle.

[0008] If, in addition to realising the drive task of the fully electrically powered vehicle, one also wants to supply an electric heating system for heating the passenger compartment from an electrical energy storage device, this must have at least twice the storage capacity compared to the case where the energy storage device is only used to provide energy for the movement of the vehicle and for necessary auxiliary processes with low energy requirements.

[0009] The following application-specific system requirements and technical constraints speak against supplying electric heating systems for passenger compartment heating of electrically powered vehicles, and in particular of city buses, from traction energy storage systems integrated in these vehicles: Available space and weight reserves of vehicles or city buses for the integration of electrical energy storage technology Range reduction Cost situation for electrical energy storage systems Reduction of system efficiency through intermediate storage of electrical energy (storage and withdrawal process) before conversion into thermal energy

[0010] The solution according to the invention is based on the object of enabling the complete heating of an electrically powered vehicle, in particular the passenger compartment of a fully electric city bus, even at low outside temperatures, without having to draw energy from the traction energy storage for this purpose. State of the art - heating systems for city buses

[0011] For decades, heating systems for city buses have been designed to transport the abundant waste heat from the diesel engine to the passenger compartment. These conventional heating systems typically include an auxiliary fuel heater to preheat the engine and quickly achieve a comfortable passenger compartment temperature. The increasing focus on fully electric and thus emission-free city buses significantly increases the demands on the efficiency of heating systems.

[0012] There are currently electric and therefore potentially emission-free heating systems on the market, which can be divided into two basic categories: heat pump systems and PTC heaters.

[0013] In principle, other alternative heating concepts for city buses are also conceivable, which are already available for other applications. These include panel and infrared heating systems. Conventional solutions

[0014] A variety of fuel-fired heaters from various manufacturers are commercially available on the market. Depending on the medium to be heated, a distinction is made between air and water heaters, which are available in different power classes (air: 0.8–8.0 kW; water: 1.5–40 kW). While water heaters are always integrated into the cooling / heating water circuit and connected to the interior via heat exchangers, air heaters heat the passenger compartment locally and directly. One advantage of air heaters is their short start-up time. However, to cover the entire heat requirements of a bus, for example, and to ensure appropriate heat distribution, several air heaters are required in a vehicle.

[0015] In general, the advantage of fuel heating in fully electric buses is that no energy needs to be drawn from the battery. This decouples the vehicle's range from the influence of heating requirements. However, this approach contradicts the fundamental principle of electromobility, which demands zero local and global emissions, and, in conjunction with environmentally friendly fuels such as biodiesel, represents at best a temporary solution. Emission-free solutions Heat pumps

[0016] A heat pump enables the temperature level of a heat flow to be raised Q 0 a heat source with supply of electrical power P el. In Fig. 2 The basic structure of a heat pump is shown, namely the cycle of a compression heat pump. Fig. 2 is Q usable heat at high temperature level; Q0 heat for evaporation of the working fluid at low temperature level; and P< el electrical power.

[0017] The low-temperature heat Q0 supplied to the evaporator leads to the evaporation of the refrigerant (301→302) before it is drawn in by the compressor and compressed to a higher pressure (302→303). The cooling and condensation of the refrigerant at the condenser (303→304) leads to the release of the usable heat flow. Q at a high temperature level. The cycle then closes with the pressure reduction of the refrigerant at the throttle valve (304→301), which can then be evaporated again at a lower temperature level. The efficiency of a heat pump is characterized by the COP (coefficient of performance) and is the ratio of usable heat to electrical work.

[0018] Heat pump systems, typically air-to-air systems, are particularly suitable for urban use. They extract heat from the ambient air and deliver it to the passenger compartment at the desired temperature. In fully electric buses, the drive energy required to operate the compressor and fans is supplied by the traction battery (which results in a reduced range). At outside temperatures below -5°C, they can no longer fully cover the heating needs of a city bus due to reduced performance (evaporator icing) and efficiency. Consequently, an auxiliary heater is required, which is usually a fuel-fired heater. Electric resistance heaters (PTC heaters)

[0019] PTC heaters are electrical heating devices that convert electrical energy into thermal energy via a resistor (PTC resistor). Like fuel heaters, they can be divided into air and water heaters. Currently commercially available devices cover a power range of up to 20 kW at a supply voltage of up to 600 V with an efficiency of up to approximately 98%.

[0020] In a fully electric city bus, the traction battery supplies the electrical power to operate the PTC heater, which converts it into heat. Depending on the heater, this heat is either released directly into the air in the passenger compartment or into a conventional heating circuit. In the latter case, the heat is ultimately transferred to the interior via convectors. Since the corresponding piping is primarily installed beneath the vehicle floor, electric water heaters result in significant heat losses to the environment, as confirmed by the results of a heating performance assessment on a city bus.

[0021] Between the provision of electrical energy at the charging point and its use in the heating system of an electrically powered, battery-powered vehicle, the energy must currently be temporarily stored in the traction battery. The resulting energy losses can reach a magnitude of up to 10%, depending on the energy storage capacity, the storage technology used, and the required charging currents. All electric heating systems currently available on the market are subject to this circumstance, which is detrimental to system efficiency. Alternative solutions Infrared heating elements

[0022] In addition to convective heat, which is released by heaters into the ambient air, transported by the air, and then passed on to passengers, it is also possible to warm bodies using radiant heat (infrared / IR radiation). This radiation is divided into three ranges based on its wavelength: IR-A radiation (0.78–1.4 µm), IR-B radiation (1.4–3 µm), and IR-C radiation (3–1,000 µm). Unlike other types of radiation, IR-C radiation is harmless to human health. Hot bodies emit a certain proportion of their energy in the form of IR radiation. When this radiation hits a body, it is partially adsorbed, and its energy is converted into heat. This heats the body, e.g., a human body. An important difference from convective heat distribution is that heat radiation spreads purely via electromagnetic waves.Heating of the surrounding air is not necessary, so a body can be warmed despite cool ambient air.

[0023] Technical devices that emit IR radiation (IR radiators) are divided into low-temperature radiators with a maximum surface temperature of 120 °C and high-temperature radiators. Due to the acute risk of burns, the latter are not suitable for use in areas accessible to humans. Their main application is in hall heating systems, where they are installed several meters above the ground, preventing human contact.

[0024] In contrast, low-temperature radiators, despite their high surface temperatures, can also be used in places accessible to humans. This is because the well-insulated surfaces and the exclusive use of "dry heat" prevent burns even at temperatures around 100 °C.

[0025] Low-temperature radiators emit exclusively long-wave IR-C radiation. Today, low-temperature radiators are primarily heated using gas or electrical energy. The conversion efficiency is calculated as the ratio of the amount of energy emitted as thermal radiation by the device to the input energy—e.g., electrical energy. The remaining energy is usually dissipated into the environment in the form of convection heat. The radiation component of an IR radiator increases with its temperature. Therefore, high-temperature radiators, depending on their design, have very high efficiencies of around 90%. Low-temperature radiators, on the other hand, generate IR radiation with efficiencies of a maximum of 60–70%. Surface heating

[0026] One form of low-temperature radiant heating is surface heating. A distinction is made between electric and hot water surface heating. Depending on the design, specific heat output densities of up to 350 W / m² can be achieved. Integration into a bus structure, for example, can take place in the floor area or in the side walls. The corresponding total surface area for an 18 m² bus is approximately 128 m². From a practical point of view, however, only a fraction of this area can be used for heating elements. The use of a heat pump in conjunction with hot water surface heating appears to be particularly interesting. The advantage here is the combination of the heat pump's low energy requirement with the ability to achieve a comparable level of thermal comfort to conventional heating systems at lower interior temperatures thanks to the low-temperature radiant heat.With a heat output of 20 kW to be introduced and a maximum specific heat output density of the surface heating of 350 W / m 2<, this results in a required area of ​​57 m 2< .

[0027] Seat heaters are used to directly heat the seat surface and backrest of vehicle seats, for example. They usually consist of heating mats that are either incorporated into the upholstery or seat cover, or glued between them. Wires are incorporated into these mats and heat up when electrically powered. The resulting heat is transferred directly to the person sitting on it via the seat. Convective heat distribution via the air is therefore not necessary. However, a large portion of the heat energy enters the seat and is therefore no longer directly available to warm the passenger. However, it is possible to achieve targeted conduction of the heat energy towards the passenger through intensive insulation.

[0028] The seat heating is regulated via built-in sensors and control units. This allows the energy output to be adjusted as needed. The sensors also monitor the response of the heating mat, thus eliminating health risks from burns on overly hot seats or electrical short circuits from broken heating elements.

[0029] For example, seat heaters for air conditioning the driver's workplace are already widespread in buses. This technology is also already standard in the passenger car sector. However, heating passenger seats on buses using heating mats is not currently common.

[0030] Depending on requirements, seat heaters are typically equipped with a heating output of 40–100 W per seat. However, no figures are currently available on the potential energy consumption of seat heaters for passenger seats. Model-based calculations of the energy consumption of electric cars assume that seat heaters are used for approximately 10% of the driving time. However, this information is not necessarily transferable to buses. Latent heat storage

[0031] Latent heat storage, or storage and storage systems using phase change materials (PCM), store a large portion of the heat in the form of the energy required for a phase transition of the storage material used. Advantages over water include higher specific storage densities and the ability to store a comparable amount of heat in a narrower temperature range tailored to the application. This reduces heat loss to the environment. Commercial latent heat storage systems for buses are not currently available. Latent heat storage systems are known, for example, from the publications DE 10 2012 002 952 A1, DE 10 2009058 842 A1, DE 10 2006043 525 A1, EP 0 424 700 A1 and DE 10 2006 037 760 A1. Materials

[0032] For the use of PCM in heating systems for electric buses, Fig. 3 especially paraffins and salt hydrates. Fig. 3provides an overview of the specific heat storage capacities of various materials and storage types in relation to the relevant temperature ranges. Table 1 provides an overview of the properties of both material classes. PCMs generally exhibit good heat capacity but poor thermal conductivity. The thermal conductivity can be increased by up to a factor of 100, for example, by combining graphite and PCM in a matrix to create a hybrid storage material. Table 1: Properties of suitable PCM materials Paraffins Salt hydrates T application in °C 0 - 400 0 - 140 T melting in °C 2 - 164 7 - 117 h melt in kJ / kg 40 - 340 100 - 210 cp in kJ / (kg*K) 2,0 - 2,9 1,6 - 2,6 Advantages inert, non-toxic, non-corrosive, non-separating, cycle-stable Cost, high density, non-flammable Disadvantages large volume change (10%) during phase transition solid → liquid, flammable, costs, poor heat transfer separate during the melting process (technical solutions available), poor heat transfer, corrosive Prototypical latent heat storage

[0033] As part of a study, various PCM storage prototypes were built for the commercial vehicle sector and tested for their discharge performance. The concept investigated always assumed conventional vehicles powered by an internal combustion engine and the resulting waste heat. In particular, the prototypes were not designed for the application of "heating a bus interior." The storage capacities of the prototypes range between 0.14 and 8.33 kWh. Charging times and performances were not investigated. The discharge times and performances are too low for interior heating. One exception is a storage type that was specifically developed for high discharge performance and enables discharge performances of up to 15 kW. However, with a very low storage capacity of 0.14 kWh, it is almost completely discharged after just 100 seconds.However, the study fundamentally demonstrates the feasibility of a heating concept based on latent heat storage for use in fully electric buses. Commercial latent heat storage

[0034] PCM is already finding increasing use in stationary applications. A distinction is made between passive and active systems. Passive systems, such as PCM in plasterboard as wall cladding in buildings, serve to reduce the energy required for room air conditioning by increasing the thermally active storage mass of the walls. In connection with use as the sole heating system for mobile applications, only active systems are of interest, as these can be charged and discharged in a targeted manner, i.e. using a control or regulation system. Corresponding storage systems are already available on the market as modular storage systems using phase change materials with different melting points and a usable heat quantity of 10 - 12 kWh. The charging and discharging of these storage systems always takes place via a heat transfer fluid. Opportunity charging - especially for electric buses

[0035] Wherever the transport capacity required for regular inner-city and commuter traffic does not exceed the feasible level of modern scheduled buses, these will continue to form the backbone of municipal transport operations. As a result of the ongoing urbanization of our conurbations, inner-city traffic areas and suburban outskirts in particular are exposed to increasing environmental pollution due to the associated increase in traffic density. A growing number of battery bus projects with various recharging concepts are being implemented worldwide. These pilot projects primarily serve to provide operating companies, vehicle and component manufacturers with insights into the reliability of new technologies and different recharging and operating concepts under real-world operating conditions.Of course, operational availability of the respective overall system at least at the level of a conventional diesel bus operation is an indispensable prerequisite for examining a future substitution of the conventional and operationally proven drive technology with alternative, locally emission-free drive technology. Principle of energetic decoupling

[0036] More than 10 years ago, a concept for fully electric bus operation based on the "docking principle" was developed at one of the applicant's institutes. In this case, an energy storage unit integrated into the vehicle acts as the sole energy source, absorbing energy from rapid charging stations installed at specific points along the way and releasing it as needed to propel the vehicle and supply electrical auxiliary systems.

[0037] From a current perspective, three charging concepts are being considered for recharging a vehicle's energy storage system. Firstly, rapid charging at the end of the line, typically lasting a few minutes and with a power of 250 kW, can provide the energy required for the subsequent line cycle.

[0038] With the energy storage technologies currently available, it may still be useful to install additional charging points at one or more stops (where the vehicle can dock for recharging, hence the term "docking principle").

[0039] This makes longer routes possible with acceptable depths of discharge of the vehicle energy storage system from a service life perspective.

[0040] Experience has shown that a waiting time of more than 15 seconds is only available at selected stops; recharging of the energy storage system, which is currently implemented here with realistic recharging capacities of up to 700 kW, is referred to as pulse charging.

[0041] Since the recharging concepts mentioned utilize available downtime during scheduled line stops, they are generally referred to as opportunity charging.

[0042] If the energy is recharged exclusively outside of regular operating hours, this is called overnight charging.

[0043] In particular, the sufficient cooling of the energy storage elements during recharging processes at high ambient temperatures represents a challenge in the implementation of the docking principle. For this purpose, for example, a specially designed air conditioning system is suitable, which in a realization form created by the applicant has a coolant storage as a special feature.

[0044] This takes into account the special concept of a point-by-point energy supply based on the docking principle. During the recharging process of the traction battery at the end of the line, the cooling medium in the system is simultaneously recooled using energy from the charging station. This allows sufficient cooling energy to be charged to the refrigerant storage tank for the subsequent line cycle, without the need to draw energy from the traction battery for this purpose.

[0045] In the sense of the task, the principle of energetic decoupling of battery cooling from driving operation is transferred by the inventive solution to the auxiliary process of the driver's workplace and passenger compartment heating of the vehicle, which is necessary for many applications, especially for city buses.

[0046] The replacement of conventional heating systems based on the combustion of fuels with electric heating systems that can be operated with electrical energy from public supply networks will further increase the attractiveness of fully electric bus operation based on the docking principle. Description of the invention

[0047] The solution underlying the invention takes advantage of the benefits of so-called opportunity charging, particularly for urban buses. This involves recharging energy from on-board charging infrastructure connected to a public energy grid at terminal stops or during longer stops en route, within a few minutes of charging. The charging power required by the battery (or available based on its current charge level) is often lower than the charging power available on the system. "Excess"—that is, unused or unavailable—electrical charging power can thus be used for other tasks (e.g., charging thermal storage systems).

[0048] The inventive approach is therefore based on shifting the - indirect - heating energy supply from the traction battery to the charging infrastructure.

[0049] The inventive solution therefore creates a novel, fast-charging, and modular heat storage heater using latent heat storage materials. To avoid unnecessary heat loss associated with conventional systems, it is positioned in or in close proximity to the passenger compartment.

[0050] At the end points of the line, the innovative heating system is charged with energy from the stationary energy supply network at the same time as or simultaneously with the recharging of the vehicle energy storage system in the shortest time available.

[0051] The stored heat is then evenly distributed to the passenger compartment until it is recharged again.

[0052] In addition to this primary charging concept, recharging while driving is also possible through the direct use of recuperation energy.

[0053] To ensure energy-efficient, demand-based operation of the storage heater, appropriate energy and storage management, including a methodology for determining the state of charge, is required. Two variants are planned for the implementation of the storage heater: one with direct and one with indirect heat input into the passenger compartment.

[0054] The problems described in the state of the art of known systems for emission-free heating of passenger compartments of fully electric city buses can be solved with a fast-charging, efficient, modular latent heat storage heating system, as shown schematically in Fig. 1 shown, can be solved. The Fig. 1 shows a systematic connection of a fast-charging heat storage heater. In particular, the Fig. 1 a latent heat storage device in a passenger bus according to an embodiment of the invention.

[0055] The thermally active material used in the latent heat storage system, which can be designed, for example, in the form of a homogeneously filled volume or in the form of disc and / or plate-shaped storage modules, is charged by means of electrical energy, which is primarily provided at charging stations at the end of the line or, if necessary, additionally via recuperation.

[0056] Phase change materials (PCM) are used as thermal storage materials. PCMs have a high specific heat storage density and can store heat with a small temperature difference of the

[0057] Storage material (or release). Through the phase transition that occurs, e.g., from solid to liquid, a large portion of the heat is stored in the form of the enthalpy of fusion required for this process. This process is isothermal.

[0058] In an initial study, the fundamental feasibility of heat storage heating was demonstrated. The basis for this study is a simulation tool developed by the applicant for calculating the annual air conditioning requirements of a bus with a temporal resolution of 5 minutes. An initial estimate of the required storage capacity was made depending on the discharge power, the desired degree of fulfillment of the heat demand, and the cycle length between two charging processes. Fig. 4 shows the degree of fulfillment of the heat demand depending on the discharge power and the storage capacity (12 m city bus, cycle length: 1 h, Central Europe). Fig. 4 It can be seen that a capacity of 10 kWh with a discharge power of 10 kW and a cycle length of 1h is sufficient to cover over 90% of the expected heat demand.

[0059] Fig. 5 shows a schematic representation of heat storage heating concepts ( Fig. 5A: direct, Fig. 5B : indirect). In the Fig. 5A direct heating of a passenger compartment by the latent heat storage is shown. Fig. 5B Indirect heating of a passenger compartment by the latent heat storage is shown. Fig. 5 The described heat storage heating technology can be implemented with at least two different system concepts.

[0060] In the direct heat input version, the storage material of the latent heat storage system is housed in individual modules that can be variably arranged in the passenger compartment. The discharge behavior and discharge performance result from the interaction of the thermal boundary conditions in the bus (temperature, air flow), the design of the storage system's heat exchanger structures, and the heat transport within the storage system itself. Various options are available to enable the discharge performance to be adapted to the heating requirements.

[0061] If the storage system is constructed from several separately rechargeable modules, the amount of heat stored and thus the discharge power can be adjusted depending on various factors, such as the expected number of passengers (waste heat) and the outside temperature.

[0062] In addition, the heat transfer between the storage modules and the surrounding air can be influenced by varying the air velocity.

[0063] Another option is the use of PCMs with different melting temperatures in different modules, which enables modules with different discharge power levels.

[0064] The indirect variant consists of two or three storage modules through which water flows to discharge the stored heat, releasing it to the passenger compartment via conventional convectors. The discharge capacity can be adjusted to the heating demand by varying the pump speed and the resulting flow rate.

[0065] Lamellar PCM packs with integrated heating elements and sensors form the basic building block for the modules of the indirect variant. Various concepts for the schematic design of corresponding storage modules (direct variant) are described in Fig. 6 shown. Fig. 6 shows a functionally integrated design, namely lamellar PCM packings. Fig. 6A a side wall module. Fig. 6B shows a seating module. Fast charging capability of the PCM heat storage as an advantageous embodiment of the invention

[0066] The solution according to the invention enables the complete heating of the passenger compartment of a fully electric city bus even at low outside temperatures without having to draw energy from the traction energy storage system for this purpose and has the following advantages over the known state of the art: The thermal energy storage system can be fully charged within a few minutes. This requires charging rates of approximately 10 h -1<. The charging rate is defined as the ratio of the applied heat output to the heat storage capacity of the thermal energy storage system. The heat required to completely melt the PCM used as a heat storage material is supplied by heating elements (rods, mesh structures, surface heating elements, etc.) integrated into the storage mass.Complete melting of the material within minutes and simultaneous protection against local overheating, which would otherwise result in the destruction of the storage properties, is achieved by application-appropriate integration of the heating elements integrated into the storage mass in terms of their geometric arrangement and heating output. For example, a large number of heating elements are distributed essentially evenly over the volume of the PCM acting as the storage medium. In this way, a high electrical charging output acting over a short time is spread as homogeneously as possible over the storage volume, thus avoiding local overheating in particular. The density differences in the material associated with melting and re-solidification can be used to determine the state of charge of the thermal energy storage device.

[0067] Fig. 7shows possible design variants of the fast-charging PCM heat storage system as schematic cross-sectional views. Fig. 7 An example of indirect discharge is shown above, while in the Fig. 7 An example of direct discharge is shown below. Advantages of the invention

[0068] The application of the invention leads to an increase in efficiency compared to currently available electrical heating systems for electrically powered vehicles and in particular for electrically powered buses in local public transport and decouples the energy supply for heating the passenger compartment from the traction battery.

[0069] This results in an increased vehicle range and a reduction in the required battery capacity, resulting in lower acquisition and operating costs compared to alternative, emission-free, electric heating systems. In particular, the following system advantages have been identified compared to battery-powered electric storage systems: More cost-effective solution Low-wear solution Flexible geometric design to utilize existing space and weight reserves Increased system efficiency through direct energy conversion

[0070] The widespread use of fast-charging latent heat storage heaters in fully electric commercial vehicles, such as city buses, while simultaneously using renewable energy for their operation, makes a decisive contribution to reducing local (inner-city) and global CO2 emissions. This addresses the following goals in particular: "Consistently drive forward the expansion of electromobility and create the conditions for rapid market penetration." Reducing costs for electric vehicles. Increasing the efficiency of high-performance electrical ancillary units. Increasing the range of electric vehicles. Establishing a comprehensive energy and thermal management system for electric vehicles.

[0071] Charging, loading, or charging the latent heat storage device within the meaning of this document means that the latent heat storage device absorbs thermal energy via the electrically active heating elements. Thus, during charging, loading, or charging of the latent heat storage device, heat is supplied from the heating elements or from the at least one heating element into the phase-change material. Discharging the latent heat storage device within the meaning of this document means that the latent heat storage device releases thermal energy, for example, to its surroundings or to a heat transfer fluid.

[0072] Heat capacity can be defined as the heat energy that a phase-change material can absorb per kilogram within a temperature range of ± 7.5 °K around the melting temperature of the phase-change material. If a melting temperature range exists, the specified temperature range of ± 7.5 °K preferably includes this melting temperature range. The difference between a highest temperature and a lowest temperature within the melting temperature range is typically no more than 15 °K or no more than 10 °K. Embodiments of the invention

[0073] In a first embodiment, an electrically heatable latent heat storage device is provided with a phase-change material (PCM) as the storage medium. A plurality of electrically active heating elements are distributed substantially uniformly within the volume of the PCM. Alternatively or additionally, at least one electrically active heating element is provided, with a plurality of heat-conducting structures distributed substantially uniformly within the volume of the PCM. The ratio of the heating power of the heating elements or of the heating element to the heat storage capacity of the phase-change material can be at least 5 h -1<.

[0074] The specified ratio can, for example, be a maximum of 15 h -1<. The claimed ratio reflects a rapid charging capacity of the latent heat storage device. On the other hand, the uniform distribution of the heating elements or heat-conducting structures in the phase-change material allows the heating of the phase-change material to be as uniform as possible, thus avoiding local overheating of the phase-change material despite the high power of the heating elements.

[0075] A uniform distribution of the heating elements and / or the heat-conducting structures can be achieved, for example, by ensuring that adjacent heating elements and / or adjacent heat-conducting structures are equally spaced from one another, at least in one spatial direction of the latent heat storage device. The heating elements and / or heat-conducting structures can, for example, form a two- or three-dimensional grid. Without a uniform arrangement of the heat-conducting structures and / or heating elements in the phase-change material, a wedge-shaped or wave-shaped melting front could form when the phase-change material is heated by the heating element. This would counteract the inventive objective of rapid charging capability.

[0076] Depending on the dimensions of the latent heat storage device, at least 5, at least 10, at least 15, or at least 20 heating elements can be arranged within the volume of the phase change material. Furthermore, at least 5, at least 10, at least 15, or at least 20 heat conduction structures can be provided per heating element.

[0077] The heat-conducting structures can be connected to the at least one heating element. Alternatively, the heat-conducting structures can also form disjoint units spaced from the heating element and not connected to the heating element. The heat-conducting structures can promote homogeneous melting of the phase-change material in the latent heat storage device. To promote heat exchange, adjacent heat-conducting structures can be connected to one another via thermal bridges. The heat-conducting structures can be aligned parallel to one another. Furthermore, the heat-conducting structures can be arranged substantially perpendicular to the at least one heating element.

[0078] The heat-conducting structures are preferably made of a thermally conductive metal, such as steel, aluminum, or copper, and can be configured, for example, as rods or plates. The wall thickness of the plates and / or the radius or diameter of the rods can be, for example, a maximum of 5 mm. The wall thickness and / or the radius or diameter can be at least 0.1 mm. A longitudinal direction of the heat-conducting structures can be aligned parallel to the force of gravity.

[0079] In a further embodiment, adjacent heating elements can be connected to each other, for example via thermal bridges. Alternatively, the heating elements can also form disjoint, spaced-apart units.

[0080] When reference is made to "one heating element" below, this also means "a plurality of heating elements" and vice versa. A heating element in the sense of this document can be defined in particular as Heating wire with or without insulation; and / or surface heating element, e.g. a surface heating element made of heating wire and insulating sheath (e.g. silicone or polyimide such as Kapton); and / or heating rod located in a tube equipped with thermally conductive structures that is in contact with the PCM; and / or heating cartridge, heater, heating coil, heating conductor, heating tape, heating sleeve or heating mat Different types of heating elements can be integrated into a single latent heat storage device. Further design options for the heating element are known to those skilled in the art.

[0081] To heat the phase-change material as quickly as possible, it is advantageous if the surface area of ​​the heating elements (hereinafter referred to as the heating element surface) is relatively large compared to the amount of phase-change material to be heated. For example, the ratio of the heating element surface area to the heat storage capacity of the latent heat storage device is at least 2 cm² / Wh. For an effective systemic heat storage capacity of the entire system in Wh / kg or Wh / l—and also due to the costs of larger heating element surfaces—this ratio can be a maximum of 20 cm² / Wh.

[0082] In a further development, the average heat output density of the heating elements or of the heating element is at least 0.25 W / cm 2 < or at least 0.5 W / cm 2 < or at least 0.75 W / cm 2 < . The average heat output density can have a maximum value of 2.5 W / cm 2 < or 2.25 W / cm 2 < or 2 W / cm 2 < or 1.75 W / cm 2 <. The heat output density can be independent of the choice of phase change material. The average heat output density is the power that is emitted on average per area by the heating element or by the heating elements. It is therefore possible that the spatial distribution of the heat output of the heating elements varies (see below).

[0083] In one embodiment, at least the effective parts of the heating elements or the heating element, i.e., the heat-emitting parts, are completely covered with the phase-change material, regardless of the physical state of the phase-change material. The effective parts of the heating elements are typically the parts of the heating elements through which current flows. If parts of the heating element are not in contact with the phase-change material, i.e., are not completely covered by it, unacceptably high temperatures can arise at these parts of the heating element due to reduced heat transfer from the heating element to the air. This can lead to the phase-change material being destroyed or decomposed at the triple interface of air / heating element / phase-change material.

[0084] Liquid (warm) phase change material generally has a lower density than solid (cold) phase change material. This causes liquid phase change material to be transported upwards. In order to achieve the most uniform temperature possible within the phase change material, it can be advantageous to vary the heating power of the heating element by expanding the heating element. In one development, the heating element is designed such that the heating power of the heating element decreases upwards over a height of the latent heat storage device. The heating element can also be configured such that the heating power of the heating element increases outwards in a direction perpendicular to gravity. Thus, to achieve a homogeneous temperature in the phase change material, heat dissipation by the latent heat storage device to its surroundings can be taken into account.In an outer edge area of ​​the latent heat storage, the heating output of the heating element in the horizontal direction can be higher than in the middle of the phase change material.

[0085] It can be advantageous if the heat-conducting structures partially protrude from the phase-change material, at least when the phase-change material is in a solid state. Depending on the dimensions of the latent heat storage device, the heat-conducting structures can protrude from the phase-change material to a height of at least 0.5 cm and / or at most 2 cm. This allows so-called "target melting points" to be created on the phase-change material surface.

[0086] When the phase-change material liquefies due to heating by the at least one heating element, the parts of the heat-conducting structures that previously protruded from the phase-change material can subsequently be completely covered by the phase-change material due to a reduction in density or an increase in volume of the heat-conducting structures. It can be provided that a longitudinal section of the heat-conducting structures is triangular, quadrangular, rectangular, square, or trapezoidal and / or has a convex or concave shape that tapers upwards.

[0087] The thermal conduction structures described above enable controlled, preferential expansion of the phase-change material upon heating by the heating elements and / or thermal conduction structures. Furthermore, the thermal conduction structures can prevent high local pressure gradients.

[0088] The latent heat storage device can comprise a measuring device for determining a density and / or a volume and / or a fill level and / or a temperature of the phase change material and / or an internal pressure in the latent heat storage device. The measuring device can be designed to determine a quantity of heat stored by the latent heat storage device based on the density and / or the volume and / or the fill level and / or the temperature of the phase change material and / or an internal pressure in the latent heat storage device. In principle, it is sufficient to determine the quantity of heat stored in the phase change material if only the density or one of the other mentioned measured variables of the phase material is measured. However, the accuracy of the measurement can be increased by means of additional volume, pressure, fill level, and temperature measurements. The determination of the quantity of heat stored can, for example,transmitted to a display device connected to the measuring device, e.g. via a radio connection between the measuring device and the display device.

[0089] In one embodiment, the latent heat storage device has a housing in which the phase-change material is arranged, wherein the housing is designed to be fluid-tight. Fluid-tightness should in particular mean that it is airtight, watertight, and / or phase-change material-tight. This can prevent any gaseous phase-change material from escaping from the housing. To further prevent a chemical reaction between liquid and / or gaseous phase-change material and the air contained in the housing, the housing can be designed to be vacuum-tight. The housing can be configured, for example, as a metallic housing or as a plastic shell.

[0090] The phase-change material can have a melting temperature of at least 50 °C and / or at most 120 °C. At such melting temperatures, the latent heat storage device can be used, for example, as a heater in rooms occupied by people. The phase-change material can have an enthalpy of fusion of at least 100, at least 200, or at least 300 kJ / kg. The phase-change material is preferably electrically non-conductive, as this eliminates the need for additional electrical insulation measures.

[0091] A preferred phase-change material is paraffin. For the physical properties of paraffins, such as enthalpy of fusion h melting , melting temperature T melting , and specific heat capacity cp, please refer to Table 1 above. Paraffin is electrically non-conductive and also has the advantage of effectively damping shocks and mechanical vibrations in both the solid and liquid states.

[0092] In a further embodiment, the latent heat storage comprises a plurality of separately rechargeable storage modules (see above explanations on page 19 and Figures 1 , 5 and 6 ). For example, at least two of the separately rechargeable modules each have different phase-change materials, each with different melting temperatures. In one embodiment, a storage module comprises a plurality of PCM cells, which are connected to one another, for example. A PCM cell typically comprises phase-change material, one or more heating elements, and a housing for the phase-change material.

[0093] The latent heat storage device is typically designed such that the heat dissipation of the latent heat storage device to its surroundings, for example a passenger compartment and / or vehicle interior of a vehicle, is at least 1 kW or at least 3 kW or at least 5 kW when an at least partially liquid phase change material is present. The heat storage capacity of the latent heat storage device can be at least 0.25 kWh or at least 0.5 kWh or at least 0.75 kWh or at least 1 kWh. The specific heat capacity of the phase change material defined above is preferably greater than 1.5 kJ / kg or greater than 2.0 kJ / kg. For a phase change material with a specific heat capacity of 64 Wh / kg, a heat storage capacity of the latent heat storage device of at least 0.25 kWh results in a mass of phase change material of at least 3.9 kg.

[0094] In one embodiment, the latent heat accumulator has at least one fluid pipe for a heat transfer fluid to dissipate the heat from the latent heat accumulator. The fluid pipe can be designed, for example, as a heat pipe. Typically, the fluid pipe runs through the phase change material so that heat exchange between the phase change material and the heat transfer fluid takes place efficiently in the fluid pipe. In one embodiment, the phase change material is surrounded by a heat exchanger. In one embodiment, the latent heat accumulator is surrounded by a heat-insulating layer. The above-mentioned housing of the latent heat accumulator can also be provided with a heat-insulating layer or have such a heat-insulating layer as a casing or consist of such a heat-insulating layer.

[0095] Furthermore, the invention provides a heating system with the latent heat accumulator of the type described above. In one embodiment, the heating system comprises a latent heat accumulator of the type described above, a fluid circuit, and at least one radiator or at least one convector. The radiator or convector can be connected, for example, via a heating flow and a heating downstream line to the aforementioned fluid pipe of the latent heat accumulator. A pump can be provided to convey the heat transfer fluid. Water, for example, can be used as the heat transfer fluid.

[0096] In another embodiment, the heating system comprises the latent heat storage device and at least one heat pipe. For further details and the functionality of the heat pipe, please refer to the following publication: DE 10 2009 058 842 A1.

[0097] Furthermore, the invention provides a vehicle with the latent heat storage device of the type described above. Vehicles within the meaning of the present specification are understood in particular to be motor vehicles that have a traction battery for driving the vehicle. This includes, on the one hand, purely electrically powered vehicles, but also hybrid vehicles. Furthermore, a motor vehicle with many seats for transporting people (bus) is particularly suitable as a vehicle. The latent heat storage device is preferably designed to heat a passenger compartment and / or the vehicle interior of the vehicle. The latent heat storage device can be arranged in the passenger compartment, in the vehicle interior, or in the immediate vicinity of the passenger compartment and / or the vehicle interior.

[0098] In electrically powered vehicles, braking energy can often be converted into electrical energy using an electric generator, i.e., recuperated. In particular, the vehicle is designed such that the heating element of the latent heat storage system is powered by recuperation energy generated during braking.

[0099] The invention further proposes the use of an electrically heatable latent heat storage device for heating passenger compartments and / or vehicle interiors of electrically powered vehicles. Charging of the storage device preferably takes place at a charging station for electric vehicles.

[0100] Furthermore, the invention provides a method for charging an electrically heatable latent heat storage device of the type described above.

[0101] Accordingly, charging, e.g., electrical charging, of the latent heat storage device preferably occurs simultaneously with the charging of the traction battery of an electrically powered vehicle. Alternatively, the latent heat storage device can be charged more frequently than the traction battery. This allows the latent heat storage device to be kept relatively small. Furthermore, depending on the capacity of a charging station, the traction battery and the latent heat storage device can be charged alternately during a charging process.

[0102] In a further development, the latent heat storage device is electrically charged at a charging station for electrically powered vehicles. To charge the latent heat storage device, at least some of the electrical power is drawn from the charging station, which is not required or cannot be required by the battery charging process taking place at the same time.

[0103] With the proposed method and the proposed use of the latent heat storage device, the latent heat storage device can be cyclically charged and discharged. A cycle duration is typically at least 0.5 and / or at most 2 hours. This makes the proposed latent heat storage device, its use, and the proposed method particularly suitable for electrically powered city buses or regular-service buses that incorporate the proposed latent heat storage device for heating the passenger compartment and / or vehicle interior.

[0104] The invention is described below with reference to the attached Figures 5-12 further explained.

[0105] The Figure 5 shows a schematic representation of heat storage concepts according to embodiments of the invention. In both cases, the latent heat storage devices are designed for heating a passenger compartment and / or vehicle interior. Fig. 5 left ( Fig. 5A) it can be seen that the latent heat storage, which is shown as a fast-charging PCM storage element, releases its stored heat directly to the passenger compartment. Fig. 5 right ( Fig. 5B ) there is also a heating circuit by means of which the heat stored in the latent heat storage is transferred into the passenger compartment.

[0106] The Fig. 6 shows two possible modules of a latent heat storage system of the Fig. 5 left. The latent heat storage can be Fig. 6 according to as a side wall module ( Fig. 6A ) or as a seating module ( Fig. 6B ). However, the invention is limited to the Fig. 6 shown embodiments are not limited.

[0107] The properties of the latent heat storage of the Figures 5 and 6 are made with reference to the Figures 7-11 described in more detail.

[0108] The Figure 7shows two sections of embodiments of a latent heat storage device 100, 100'. The latent heat storage device 100, 100' has a plurality of electrical heating elements 101 embedded in a phase change material 104. Regardless of the phase of the phase change material 104, the electrical heating element 101, in particular the parts of the heating elements 101 through which current flows, are completely covered with the phase change material 104. The heating elements 101 form a regular grid within the phase change material 104, with adjacent heating elements 101 being equally spaced from one another at least in one spatial direction. As shown in the above figure and the lower figure of the Fig. 7As can be seen, the distance between adjacent heating elements 101 in the x-direction differs from the distance between adjacent heating elements 101 in the y-direction. The heating elements 101 are designed as heating rods and extend in the z-direction parallel to an extension of the latent heat storage device 100, 100' in the z-direction.

[0109] The latent heat storage device 100' has a fluid-tight housing 105 so that the phase-change material 104 cannot escape from the housing 105 during heating by the electrically active heating elements 101. The latent heat storage device 100' can release heat energy directly into its surroundings, see FIG. Figure 5 left.

[0110] In contrast to the latent heat storage device 100', the latent heat storage device 100 has thermal insulation 102, which also functions as a fluid-tight shell. The thermal insulation minimizes heat loss from the latent heat storage device 100 to its surroundings. Instead, fluid tubes 106 filled with a heat transfer fluid 103 are provided in the latent heat storage device 100. The heat transfer fluid 103 can be a liquid or a gas. In the illustrated embodiment, the heat transfer fluid 103 is water. Thermal energy stored in the phase change material 104 of the latent heat storage device can be dissipated through the heat transfer fluid 103. The fluid tubes 106 are, for example, part of a heating circuit and are connected to at least one collector or at least one radiator. The heat transfer fluid 103 can be pumped through the heating circuit by means of a pump (see FIG. Fig. 5 right).

[0111] The Figure 8shows an isometric view of a latent heat storage 10. The Figure 9 shows sections A, B and C of the latent heat storage device 10 of Figure 8.

[0112] The latent heat storage 10 of the Figures 8 and 9 differs from the latent heat storage 100' of the Fig. 7 (below) only in that instead of a plurality of rod-shaped heating elements 101, a single plate-shaped heating element 6 is provided. In addition, a plurality of heat-conducting structures 5 are embedded in the phase change material 7. The heat-conducting structures 5 are spaced from the heating element 6 and form a regular grid within the phase change material 7. Alternatively, the heat-conducting structures can also be connected to the heating element, for example, a direct connection of the heat-conducting structures 5 to the heating element 6 or an indirect connection of the heat-conducting structures 5 to the heating element 6 via metallic thermal bridges being possible.

[0113] The phase change material 7 is located in the Figures 8 and 9 in its solid state. In section A of the Fig. 9 It can be seen that the heat-conducting structures 5 partially protrude from a surface 3 of the phase-change material 7. This creates "predetermined melting points." Sections A and C indicate the course of a melting front 4. The heat-conducting structures are arranged parallel to the course of the melting front 4 in the phase-change material. The heat-conducting structures are designed as metal plates and serve to improve heat conduction in the latent heat storage device 10. Furthermore, the heat-conducting structures serve to reduce the temperature gradient in the phase-change material, at least in the z-direction. This makes it possible to homogenize the melting front 4 and improve heat conduction in the phase-change material.

[0114] While in the Figures 8 and 9only one heating element is shown, in further embodiments several heating elements 6 can also be provided.

[0115] In the Fig. 10 Various embodiments of heat conducting structures 5, 5', 5" with a plate-shaped heating element 6, 6', 6" are shown. The heat conducting structures 5, 5', 5" are particularly suitable for use in the Fig. 8 shown latent heat storage 10. The heat conducting structures 5, 5', 5" of the Fig. 10 (a), (b) and (c) In a longitudinal section, they have a rectangular shape, a triangular shape, or a concave shape tapering upwards. By adjusting or varying the shape of the heat-conducting structures, the course of the melting front 4 can be influenced.

[0116] The Fig. 11shows a section of a plate-shaped heating element 6 with a spatially varying heating power. The heating power of the heating element 6 decreases stepwise in the z-direction from a lower partial region 65 to an upper partial region 61. Due to the spatially varying heating power, a surface temperature of the heating element 6 can be kept at a constant value. The heating element 6 is preferably used in the latent heat storage device 10 described above. Alternatively or additionally, it can be provided that the heating element 6 is designed such that a heating power increases outwards in a horizontal x-direction perpendicular to gravity. Such an arrangement is described in the Fig. 12 shown.

[0117] The Fig. 12shows a section of a heating element with a heating output of a latent heat accumulator 10 with partial regions 66 and 67 that varies in the x-direction. In order to compensate for heat losses at the edges of the latent heat accumulator 10, the heating output of the heating element 6 increases step by step in the x-direction from a central region 66 to an edge region 67. The latent heat accumulators 100, 100', 10 of Figures 7, 8 and 9 have further similarities: The phase change material of the latent heat accumulators 100, 100' and 10 is paraffin in the exemplary embodiments shown, with a melting temperature in the range 50 °C - 120 °C depending on the application.

[0118] A measuring device (not shown) for determining the density, volume, and temperature of the phase-change material is present in the phase-change material 104, 7. The measuring device is designed to determine the amount of heat stored by the latent heat storage device 100, 100', 10 based on the density, volume, and temperature of the phase-change material 104, 7. Optionally, the measuring device can alternatively or additionally be designed to measure a fill level of the phase-change material and / or an internal pressure in the latent heat storage device to determine the amount of heat stored by the latent heat storage device 100, 100', and 10.

[0119] The latent heat storage device 100, 100', 10 is designed such that a ratio of heating power of the heating elements 101, 6 to a heat storage capacity of the latent heat storage device 100, 100', 10, in particular of the phase change material 104, 7, 10 h -1 <. A heating power density of the heating elements 101, 6 is 1 W / cm 2 <, while a ratio of a specific heating surface of the heating elements 101, 6 to a heat storage capacity of the latent heat storage device 100, 100', 10 is, for example, 10 cm 2 < / Wh. The latent heat storage device 100, 100', 10 is particularly suitable for heating a passenger compartment or vehicle interior, such as in the Figures 1 , 5 and 6 indicated.

[0120] Further possible uses of the latent heat storage devices 100, 100', 10 are evident from the above explanations. Furthermore, the electrically heatable latent heat storage devices 100, 100', 10 can be used to carry out the methods described above for charging an electrically heatable latent heat storage device. List of reference symbols:

[0121] 1Airtight cell envelope 2Expansion direction of phase change material 3Surface of the phase change material 4Course of the melting front 5Heat conducting structure 5'Heat conducting structure 5"Heat conducting structure 6Electric surface heating element 6'Electric surface heating element 6"Electric surface heating element 7Phase change material 10Latent heat storage 61Heating element section 62Heating element section 63Heating element section 64Heating element section 65Heating element section 66Heating element section 67Heating element section 100Latent heat storage 100'Latent heat storage 101Heating element 102Heat insulation 103Heat transfer fluid 104Phase change material 105Housing 106Fluid pipe 201Outside temperature 202Inside temperature 18 °C 20310 kWh heating output bound in PCM per driving cycle in the city 204Charging strategy 205Fast charging at the final stop in approx.6 minutes 206Charging by recuperation 301Status point 302Status point 303Status point 304Status point 305Condenser 306Throttle valve 307Evaporator 308Compressor 401Fast-charging PCM storage element 402Electrical energy 403Thermal energy 404Passenger compartment 405Pump.

Claims

1. Vehicle with an electrically heatable latent heat accumulator (100, 100', 10) with a phase-change material (PCM) (104, 7) as storage medium to heat a passenger compartment and / or a vehicle interior, the latent heat accumulator having a fluidly sealed housing in which the PCM is arranged, characterized in that a plurality of electrically effective heating elements (101) are essentially uniformly distributed throughout the volume of the PCM (104, 7) and / or that at least one electrically effective heating element (6) is provided and a plurality of thermal conductivity structures (5) are essentially distributed uniformly throughout the volume of the PCM (104, 7), characterised in that a ratio of the heating output of the heating elements (101) or of the heating element to a heat accumulator capacity of the phase-change material (104) is at least 5 h-1, wherein the effective parts of the heating elements (101) or of the heating element (6) are completely covered by the phase-change material (104, 7) independently of the aggregate state of the phase-change material (104, 7).

2. Vehicle (100, 100', 10) according to claim 1, characterised in that the ratio of a specific heating surface of the heating elements (101) or of the heating element (6) to a heat accumulator capacity of the latent heat accumulator is at least 2 cm2 / Wh.

3. Vehicle according to one of the preceding claims, characterised in that at least 0.25 W / cm2 is a mean heating output density of the heating elements (101) or of the heating element (6).

4. Vehicle (100, 100', 10) according to one of the preceding claims, characterised in that the thermal conductivity structures (5) partially protrude from the phase-change material (104, 7) at least when the phase-change material (104, 7) is in a solid aggregate state.

5. Vehicle (100, 100', 10) according to one of the preceding claims, characterised in that a respective longitudinal section of the thermal conductivity structures (5) is triangular, quadrangular, rectangular, square, trapezoidal and / or has a convex or concave shape tapering upwards.

6. Vehicle (100, 100', 10) according to one of the preceding claims, comprising a measuring device to determine a density and / or a volume and / or a fill level and / or a temperature of the phase-change material (104, 7) and / or an interior pressure in the latent heat accumulator (100, 100', 10), with the measuring device being configured to determine the amount of heat stored by the latent heat accumulator (100, 100', 10) on the basis of the density and / or the volume and / or the fill level and / or the temperature of the phase-change material (104, 7) and / or the interior pressure of the latent heat accumulator (100, 100', 10).

7. Vehicle (100, 100', 10) according to one of the preceding claims with the heating elements (101) or the heating element (6) being configured such that the heating output of the heating elements (101) or of the heating element (6) decreases upwards over a height of the latent heat accumulator.

8. Vehicle (100, 100', 10) according to one of the preceding claims with the heating elements (101) or the heating element (6) being configured such that the heating output increases outwards in one direction perpendicular to gravity.

9. Vehicle (100, 100', 10) according to one of the preceding claims, characterised in that it comprises a plurality of separately chargeable memory modules.

10. Vehicle (100, 100', 10) according to claim 9, characterised in that at least two of the separately chargeable modules each have different phase-change materials with different melting temperatures each.

11. Vehicle (100, 100', 10) according to one of the preceding claims, characterised in that it has at least one heat transfer fluid pipe (106) for a heat transfer fluid to discharge the latent heat accumulator.

12. Use of an electrically heatable latent heat accumulator (100, 100', 10) in the vehicle according to one of claims 1-11 to heat passenger compartments and / or vehicle interiors, wherein the vehicle is an electrically powered vehicle.

13. Use of a latent heat accumulator in the vehicle according to claim 12, characterised in that the memory is charged at a charging station for electric vehicles.

14. Method for charging an electrically heatable latent heat accumulator (100, 100', 10) in a vehicle according to one of claims 1-11, characterised in that the latent heat accumulator is charged at the same time as the traction battery of an electrically powered vehicle is charged.

15. Method according to claim 14, characterised in that the electric charging of the latent heat accumulator (100, 100', 10) occurs at a charging station for electrically powered vehicles, with at least part of the electrical output required to electrically charge the latent heat accumulator at the charging station being taken from the battery charging occuring at the same time and is not required or cannot be required.