WO2014139601A1

WO2014139601A1 - Heating device

Info

Publication number: WO2014139601A1
Application number: PCT/EP2013/074869
Authority: WO
Inventors: Jochen Hantschel
Original assignee: Refusol Gmbh
Priority date: 2013-03-12
Filing date: 2013-11-27
Publication date: 2014-09-18
Also published as: DE102013102465A1; EP2973931A1; JP2016516264A; US20160033169A1

Abstract

The invention relates to a heating device, in particular for heating at least one fluid, comprising at least one first heating resistor (12; 12a, 13a, 14a) and at least one supply electronics unit (20; 20a) that is provided in order to supply a current, which is provided by at least one first photovoltaic system (16; 16a, 17a, 18a), to at least the first heating resistor (12; 12a, 13a, 14a). The supply electronics unit (20; 20a) is provided in order to operate at least the first heating resistor (12; 12a, 13a, 14a) in a clocked manner at least in an operating mode. (Fig. 1)

Description

heater

State of the art

The invention relates to a heating device according to the preamble of claim 1. It has already been proposed to use photovoltaic systems for heating.

The object of the invention is in particular to provide a generic device with improved properties in terms of high efficiency and / or low cost. The object is achieved by the features of claim 1, while advantageous embodiments and modifications of the invention can be taken from the dependent claims.

Advantages of the invention

The invention is based on a heating device, in particular for heating at least one fluid, with at least one first heating resistor and at least one supply electronics, which is provided to supply at least the first heating resistor with electricity provided by at least one first photovoltaic system.

It is proposed that the supply electronics be provided to operate at least the first heating resistor clocked at least in one operating mode. A "fluid" is intended in particular to mean a liquid, a gas and / or a

preferably at least free-flowing, bulk material, in particular with particle sizes of not more than 5 cm, in particular not more than 3 cm, advantageously not more than 1 cm, preferably not more than 0.5 cm. Alternatively or additionally, it is conceivable that at least the first heating resistor is provided to a

Latency heat storage material, which is liquid, in particular in at least one operating condition, to heat. Furthermore, it is conceivable that the heating resistor to a heating of at least one solid, in particular in the form of at least one , -

Rock and / or mineral blocks, in particular for heat storage is provided. A "heating resistor" is to be understood in particular as meaning a unit which is intended to convert electrical energy into at least 70%, in particular at least 90%, advantageously at least 95%, preferably at least 99%, heat at least one electrical component, in particular a group of, preferably permanently, parallel and / or series-connected electrical components, in particular at least one of the electrical components is designed as, preferably a metallic, ohmic resistor, Alternatively or additionally it is conceivable in that the at least one of the electrical components is designed as a semiconductor component, in particular with a controllable resistor

Heating resistor surrounded by a, in particular metallic, preferably tubular, enveloping body, which is advantageously provided to a thermal contact, in particular by means of heat conduction and / or thermal radiation, between the

Heating resistor and the medium to be heated, in particular the fluid to produce. In particular, the heating resistor forms a snake heater. In particular, at least one electrically insulating, advantageously good heat-conducting, preferably ceramic, material is arranged between the electrical component and the enveloping body. In particular, at least one of the electrical components is wound around a ceramic carrier, which is inserted into an enveloping body delimiting the medium to be heated, wherein an air gap is maintained between the electrical component and the enveloping body, so that heat transfer essentially takes place by means of heat radiation , In particular, the

Heating device to a fluid container and / or a Fluidleitelement, in which the

Heating resistor protrudes or is penetrated by the heating resistor. Alternatively, it is conceivable that the heating resistor forms a wall of the fluid container and / or - leitelements. In particular, the supply electronics has at least one

Power interface, which is intended to be connected to the photovoltaic system. The supply electronics preferably have at least one control unit which is at least provided to control and / or regulate an operation of the heating resistor. A "photovoltaic system" is to be understood in particular as meaning a unit which is intended to convert light, in particular sunlight, directly into electrical energy, in particular a photovoltaic system only of photovoltaic cells, protective sheaths, carrier elements and / or connecting cables - -

educated. A "timed operation" is to be understood in particular as an operating mode in which the heating resistor repeats, in particular with a frequency of more than 100 Hz, in particular more than 1 kHz, advantageously more than 10 kHz, preferably more than 20 kHz, and / or A maximum frequency of 100 kHz, in particular a maximum of 60 kHz, advantageously a maximum of 40 kHz, in particular periodically, is connected to the photovoltaic system

Photovoltaic system and the heating resistor is arranged, and advantageous to

Generation of the clocked operation is controlled by the control unit and in particular as a semiconductor switching element, preferably as a power MOSFET and / or power IGBT, alternatively as an electromechanical switching element, in particular as a relay is formed. Preferably, the supply electronics additionally has at least one operating mode in which the heating resistor is continuously connected to the photovoltaic system. In particular, the term "provided" should be understood to mean specially programmed, designed and / or equipped.Assuming that an object is intended for a specific function should in particular mean that the object fulfills this specific function in at least one application and / or operating state and / or In particular, high efficiency and / or low costs, in particular due to component savings, can be achieved.

Furthermore, it is proposed that the supply electronics be provided to at least the first heating resistor in at least one operating mode with a frequency between 1 kHz and 100 kHz, in particular with a frequency between 10 kHz and 70 kHz, advantageously with a frequency between 20 kHz and 50 kHz , preferably with a frequency between 30 kHz and 40 kHz to operate. In particular, high efficiency can be achieved. In particular, low

Switching losses at a substantially constant load for the

Photovoltaic system can be achieved. In particular, a low-cost and / or simple design with a low number of components can be achieved. Furthermore, it is proposed that the supply electronics be provided to adjust a duty cycle of the pulsed operation of at least the first heating resistor to set a drop across the heating resistor performance. Under a , ,

"Duty cycle of the clocked operation" should be understood in particular a duty cycle of a control signal, in particular a control voltage, with which the control unit, the switching element for connecting the heating resistor with the

Photovoltaic system controls. In particular, a simple control can be achieved.

Furthermore, it is proposed that the supply electronics be provided to vary a duty cycle of the clocked operation of at least the first heating resistor to optimize the falling across the first heating resistor performance.

In particular, the supply electronics has at least one voltage control loop, wherein the voltage control circuit is advantageously provided to implement a voltage difference between a predetermined setpoint voltage and a measured actual voltage in a duty cycle of the clocked operation. In particular, the

Supply electronics provided to change the target voltage and / or the duty cycle of the clocked operation at regular and / or irregular intervals in a variation step by a certain amount and a resulting

Comparing the output via the heating resistor with a value measured before the change, wherein the target voltage and / or the duty cycle is maintained, resulting in a higher power output. In particular, in one

Variation step increases the target voltage and / or reduces the duty cycle, if in the previous variation step by increasing the target voltage and / or

Reduction of the duty cycle could be achieved an increase in performance or by increasing the duty cycle and / or increasing the duty cycle no performance increase could be achieved. In particular, in one

Variation step reduces the target voltage and / or increases the duty cycle, if in the previous variation step by increasing the duty cycle and / or increasing the duty cycle performance could be achieved or by increasing the target voltage and / or reducing the duty cycle no performance improvement could be achieved. Advantageously, the control unit is provided to a variation of the desired voltage and / or the duty cycle

when the power output reaches a rated power of the heating resistor until the power output falls below the rated power again. In particular, a simple control can be achieved. Alternatively, embodiments are conceivable in which an ideal setpoint voltage and / or an ideal duty cycle at least based on , ,

measured voltage and current measured variables of the current of the photovoltaic system and / or other, a person skilled in the appearing suitable measured variables is calculated or in which an alternative, the expert appears to be suitable variation method is used. It is also proposed that the supply electronics have at least one buffering capacity allocated to the first heating resistor, which is provided to at least temporarily store energy of the photovoltaic system. In particular, the

Buffer capacity of at least one capacitor formed. In particular, a high efficiency can be achieved because in states in which the heating resistor is not connected to the photovoltaic system in the short term, energy supplied by the photovoltaic system can be used. In particular, a high energy yield can be achieved.

Furthermore, it is proposed that the supply electronics be provided to measure, in particular only, a voltage above the buffer capacity for determining a power output via the heating resistor. In particular, the supply electronics has at least one voltage sensor which measures a voltage drop across the buffer capacity. In particular, the control unit is provided, depending on at least one voltage measurement, in particular a voltage curve over the buffer capacity, in particular only while the heating resistor is connected to the photovoltaic system, the known duty cycle of the clocked operation and an at least substantially known size of the ohmic resistance of the heating resistor to calculate a power output in the heating resistor. In particular, it is possible to achieve a saving in terms of component, a low measuring outlay and / or a high level of efficiency. Alternatively, it is conceivable that the supply electronics is provided, in particular only, to measure a current through the heating resistor.

Advantageously, the supply electronics is provided to the duty cycle of the clocked operation, at least in response to a mean above the

Buffer capacity applied voltage, in particular as a function of a calculated over this power output of the heating resistor to select. A "medium voltage" is intended in particular to mean, in particular averaged, averaged over a period in which the heating resistor is connected to the photovoltaic system, , ,

Tension to be understood. In particular, improved measurement accuracy can be achieved. In particular, a component savings, in particular at least a saving of a current sensor for measuring a current through the heating resistor, can be achieved. Advantageously, the heating resistor is connected directly to a buffer capacity of

Supply electronics connected. The fact that the heating resistor is "directly" connected to the buffer capacitor, should be understood in particular that the heating resistor, at least in a state in which it is connected to the photovoltaic system, only about at least substantially pure resistive elements, in particular only electrical connecting lines and / or switching elements, in

Row is connected to the buffer capacity. In particular, high efficiency and / or high component savings can be achieved since, in particular, additional converter stages are dispensed with.

Advantageously, the buffer capacity is intended to be connected directly to the photovoltaic system. In particular, between the power interface for connection of the photovoltaic system and the buffer capacity only at least in

Essentially pure resistive elements, in particular only electrical

Connecting lines and / or switching elements, connected in series to the buffer capacity. It can be particularly high efficiency and / or high

Component savings can be achieved, since in particular is dispensed with additional converter stages.

Furthermore, it is proposed that the supply electronics be provided to vary a frequency of the clocked operation in at least one operating mode.

In particular, the supply electronics are provided to vary the frequency of the clocked operation as a function of a power obtainable from the photovoltaic system. In particular, the supply electronics is provided, in an operating state in which a power output via the heating resistor corresponds to a maximum of 50%, in particular a maximum of 30%, advantageously not more than 20%, preferably not more than 10% of a rated power of the heating resistor, for outputs above 50% of Rated power usual frequency of clocked operation to reduce, in particular, advantageously staggered, halve, third and / or quarter. In particular, high efficiency can be achieved, since in particular switching losses , ,

can be reduced. Furthermore, it is proposed that the supply electronics be provided for a frequency of the clocked operation in a range having a width of at least 1 kHz, in particular at least 3 kHz, advantageously at least 8 kHz, and / or in a range with a width of at most 20 kHz , Advantageously, a maximum of 13 kHz, in particular periodically and / or linearly, alternatively by leaps and bounds, to change, in order to reduce a, in particular radiated and / or retransmitted into the photovoltaic system, harmonic spectrum.

Furthermore, it is proposed that the supply electronics have at least one sensor unit which is provided to examine a frequency of a current taken from the photovoltaic system in order to conclude arcing typical behavior. In particular, the sensor unit is formed by the voltage sensor provided for determining the power, wherein the control electronics are in particular provided to filter out a current frequency of the clocked operation from the measured signal of the voltage sensor. Alternatively, it is conceivable that the

Supply electronics, an additional sensor, in particular a current sensor for measuring a current across the Leistungsschnittselle has, in order to achieve improved measurement accuracy. In particular, a frequency between 10 kHz and 30 kHz, which differs from a frequency of the clocked operation, a on

arc typical behavior out, in which, in particular designed as connectors, connection contacts of the photovoltaic system, in particular the

Photovoltaic cells, arcs occur. In particular, the supply electronics are provided, upon detection of arc-type behavior, at least in the short term, to interrupt operation of the heating resistor in order to extinguish the arc and / or to output at least a warning message. In particular, the supply electronics are provided to set an operation until completion of maintenance measures, at least in the case of repeated occurrence of arc-type behavior. In particular, it can be a high security and / or a long life of the connected

Photovoltaic system can be achieved.

It is advantageously proposed that the supply electronics at least one

Temperature sensor has. Preferably, the temperature sensor is at least in the vicinity of the medium to be heated, advantageously enclosed by this, arranged.

In particular, the temperature sensor is integrated in an envelope of the heating resistor. - -

Alternatively or additionally, a separate arrangement of the temperature sensor is conceivable. In particular, improved safety can be achieved. In particular, the supply electronics are provided to at least reduce and / or adjust an operation of at least the first heating resistor when a limit temperature is exceeded by the temperature sensor. In particular, improved safety can be achieved. In particular, a high level of comfort can be achieved.

Furthermore, it is proposed that the heater at least one

Fluid transport unit, which is intended to pass a fluid to be heated to the heating resistor and which is controlled and / or powered by the supply electronics, in particular in dependence on the temperature sensor. In particular, the fluid transport unit is provided to supply a fluid to the heating resistor. In particular, the fluid transport unit is intended to force a movement of a fluid. In particular, the fluid transport unit has at least one pump, a fan and / or a screw conveyor. In particular, the supply electronics are provided to regulate a delivery rate of the fluid transport unit such that a temperature measured by the temperature sensor is at least substantially kept constant and / or corresponds to a predetermined value, in particular by an operator. In particular, the supply electronics has at least one

Voltage converter and / or frequency converter, which is intended to convert the energy provided by the photovoltaic system in a form required by the fluid transport unit. Alternatively, it is conceivable that the fluid transport unit is supplied via a separate mains connection, wherein the fluid transport unit preferably has at least one control interface via which the control unit of the

Supply electronics can set a delivery rate and / or speed. In particular, a high quality can be achieved.

It is also proposed that the supply electronics has a control unit which is provided to monitor at least one functional unit of a control unit which controls the clocked operation of at least one heating resistor.

In particular, the control unit has at least one separate temperature sensor and is intended to provide a connection between the heating resistor and the

Photovoltaic system when exceeding a threshold temperature, preferably redundant to interrupt. Overheating can be caused in particular by a malfunction of the - -

Control unit, a malfunction of a first sensor and / or a malfunction of a switching element caused. In particular, the control unit has a separate switching element connected in series between the heating resistor and the

Power interface is switched. In particular, the control unit and the control unit each have at least one communication input in order to carry out at least one check of a functioning of the control unit. Preferably, the control unit is provided via the communication inputs a

Operational efficiency of the control unit. In particular, the control unit and control unit are jointly provided to allow a flow of current through the heating resistor only if a functionality of both units has been ensured. In particular, a high degree of safety can be achieved, in particular with regard to overheating and / or consequential damage.

Furthermore, it is proposed that control electronics of the supply electronics be provided to be supplied by the photovoltaic system. In particular, the supply electronics have at least one voltage and / or frequency converter, which is provided to convert energy provided by the photovoltaic system into a form required by the control electronics, in particular at least the control unit, the control unit, and / or the at least one sensor , In particular, a high degree of self-sufficiency can be achieved. In particular, a high level of efficiency can be achieved since the control electronics are only active, in particular, when sufficient energy is available.

drawings

Further advantages emerge from the following description of the drawing. In the drawings, two embodiments of the invention are shown. The drawings, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

Show it:

Fig. 1 shows a heating device according to the invention for generating a

Fluid flow of constant temperature, - -

Fig. 2 shows an exemplary sequence of a clocked operation and

Fig. 3 shows an alternative heating device according to the invention for connection to a plurality of photovoltaic systems.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS FIG. 1 shows a system 1 1 with a heating device 10 and a first one

Photovoltaic system 16. The heating device 10 is provided for heating and drying of a fluid formed as a bulk material and has a first heating resistor 12 and a supply electronics 20, which is provided to supply the first heating resistor 12 provided by the first photovoltaic system 16 current. The supply electronics 20 is provided to operate the first heating resistor 12 clocked in different operating modes.

The supply electronics 20 has a first heating resistor 12 associated buffer capacity 22, which is intended to temporarily store energy of the photovoltaic system 16. The supply electronics 20 has a first

Power interface 36 which is connected to the photovoltaic system 16. The buffer capacity 22 is intended to be connected directly to the photovoltaic system 16. The buffer capacity 22 is directly with the

Power interface 36 connected. The heating resistor 12 is connected directly to the buffer capacity 22 of the supply electronics 20. The supply electronics 20 further comprises an insulation measuring unit 25, which is provided to determine whether the photovoltaic system 16 is operated in earthed or floating configuration. The isolation unit 25 is between the poles of

Power interface 36 switched. The insulation measuring unit 25 has a

Voltage divider, which operates in a first state by voltage bisecting and asymmetrically dividing in a second state, wherein a voltage at the center tap of the voltage divider is measured via a high resistance to ground potential. If too low bleeder resistances are detected by measurement in both states, a warning message is output.

The supply electronics 20 has a control unit 40 which controls and regulates an operation of the heating resistor 12. The supply electronics 20 has a first, as - -

Semiconductor switching element trained, switching element 42 which is arranged in series with the heating resistor 12 and the buffer capacitor 22 and the photovoltaic system 16. The power electronics 20 has a freewheeling diode 32, which is provided to occur when disconnecting the connection to the photovoltaic system 16, by possibly.

existing self-inductances of the heating resistor 12 and its

Connecting lines generated to derive voltages and currents. The

Supply electronics 20 has a voltage sensor 26, which measures a voltage U _P across the buffer capacitor 22.

The supply electronics 20 has a control unit 45, which is provided to monitor at least one functioning of the control unit 40. The

Control unit 45 has a first temperature sensor 49. The temperature sensor 49 is provided to detect a temperature of the fluid in a vicinity of the

Heating resistor 12 to measure. The control unit 45 is provided at

Exceeding a limit temperature by the first temperature sensor 49, which is arranged in a vicinity of the first heating resistor 12, to set an operation of the first heating resistor 12. The control unit 45 has a second one

Switching element 46, which is intended to provide a connection between the

Heating resistor 12 and the photovoltaic system 16 and the buffer capacity 22 to interrupt. The second switching element 46 is arranged in series with the heating resistor 12 and the buffer capacitor 22 or the photovoltaic system 16. Provides the

Control unit 45 a functionality of the control unit 40 and by means of the first temperature sensor 49 determines a temperature below the threshold temperature, the control unit 45 causes a switching of the second switching element 46, so that this does not preclude a connection of the heating resistor 12 with the photovoltaic system 16. The second switching element 46 is designed as a relay, but could alternatively be designed as a semiconductor switching element. Furthermore, it is alternatively conceivable that the second switching element is provided to interrupt a control signal U _{s of} the first switching element.

The control unit 40 has a second temperature sensor 41. Furthermore, the heating device 10, a fluid transport unit 50, which is intended to pass a fluid to be heated to the heating resistor 12 and by the

Supply electronics 20 is controlled and supplied. A delivery rate of - -

Fluid transport unit 50 is controlled by the control unit 40 such that one of the second temperature sensor 41, seen in the transport direction behind the

Heating resistor 12 is arranged, measured temperature constant on a

predetermined value remains. The fluid transport unit 50 has a drive unit 52 designed as a screw conveyor for transporting the fluid. The

Supply electronics 20 has a voltage converter 54, which is provided to supply the drive unit 52 of the photovoltaic system 16. The

Control electronics, so the control unit 40, the control unit 45, the

Temperature sensors 41, 49 and the voltage sensor 26, via a

Voltage converter 21 of the supply electronics 20 powered by the photovoltaic system 16. In an alternative embodiment, it is conceivable that the drive unit is designed as a conveyor belt and the heating resistor as, for example, arranged above the conveyor belt radiant heater. But also embodiments as a water heater for liquids, especially water, are conceivable. If the control unit 40 determines that the control unit 45 is functional, the control unit 40 generates a control signal U _s for driving the first switching element 42. A duty cycle t / T of the control signal U _s is determined iteratively.

The supply electronics 20 determines from the voltage U _P measured during a connection phase t of an overall interval T by the voltage sensor 26 via the buffer capacitor 22 a mean voltage U _M (FIG. 2). One above the

Heating resistor 12 dropping power P is then calculated by the control unit 40 after

P = (U _M ² / R) * (t / T) where R corresponds to the ohmic resistance of the heating resistor 12. The

Supply electronics 20 is provided for setting an over the

Heating resistor 12 dropping power P to adjust a duty ratio t / T of the clocked operation of the first heating resistor 12. The duty ratio t / T of the clocked operation is hereby indirectly by varying a target voltage of a voltage regulator, which is provided to one of the buffer capacitor 22 and / or the

Power interface 36 to regulate applied voltage to a desired voltage varies to maximize the decaying power P. Should an available power be the - -

Exceed rated power, the duty cycle t / T is reduced so far, so that at maximum possible duty cycle, the rated power is reached. The duty cycle t / T is thus selected as a function of a mean voltage U _M applied across the buffer capacitor 22. The supply electronics 20 are provided to operate the heating resistor 12 in an operating mode in which a power obtainable from the photovoltaic system 16 is at least 10% of a rated power of the heating resistor 12, with a frequency varying between 30 kHz and 50 kHz. In operating modes where the available power falls below 10% of rated power, the

Supply electronics 20 provided to operate the heating resistor 12 clocked with a frequency varying between 15 kHz and 25 kHz frequency. In one

Operating mode in which a consumable power is about 100% of the rated power, the supply electronics 20 is provided to operate the heating resistor 12 continuously. The voltage sensor 26 is used by the power electronics 20 to a

Frequency of the photovoltaic system 16 taken to investigate current. Here, the signal of the voltage sensor 26 is adjusted by filtering the current frequency of the clocked operation. If dominant frequencies in the range between 10 kHz and 30 kHz are still to be found, a photovoltaic system 16 characteristic of the arc is closed and an operation of the heating resistor 12 is interrupted for a few seconds.

FIG. 3 shows a further exemplary embodiment of the invention. The following descriptions and the drawings are essentially limited to the differences between the exemplary embodiments, wherein, with regard to identically named components, in particular with regard to components having the same reference numerals, in principle also to the drawings and / or the description of the other embodiments, in particular FIGS to 2, can be referenced. To distinguish the embodiments of the letter a is added to the reference numerals of the embodiment in Figure 3. FIG. 3 shows a system 11a having a heating device 10a and a first, a second and a third photovoltaic system 16a, 17a, 18a. The heater 10 a is as - -

Hot water boiler formed and has to heat water a first

Heating resistor 12a, a second heating resistor 13a and a third heating resistor 14a. The heating device 10a has a supply electronics 20a, which is provided to supply the heating resistors 12a, 13a, 14a respectively with supplied current and voltage of exactly one of the photovoltaic systems 16a, 17a, 18a. The supply electronics 20a is intended to operate the heating resistors 12a, 13a, 14a clocked in several operating modes.

For each of the heating resistors 12a, 13a, 14a, the supply electronics 20a has a separate buffer capacity 22a, 23a, 24a to which it is directly connected. Furthermore, the supply electronics 20a three power interfaces 36a, 37a, 38a, which are each intended to be connected to one of the photovoltaic systems 16a, 17a, 18a and each directly with an associated the

Buffer capacitors 22a, 23a, 24a are connected, so that the buffer capacitances 22a, 23a, 24a energy of each associated photovoltaic system 16a, 17a, 18a

Caching. The power interfaces 36a, 37a, 38a have a common contact. The supply electronics 20a has voltage sensors 26a, 27a, 28a assigned to the respective buffer capacities 22a, 23a, 24a.

In order to avoid noise developments, the heating resistors 12a, 13a, 14a are operated at the same frequency. To set over the heating resistors 12a, 13a, 14a sloping performances duty cycles of the clocked operations of the heating resistors 12a, 13a, 14a are varied separately in order to achieve a maximization of the falling over the respective heating resistors 12a, 13a, 14a performances. The heating resistors 12a, 13a, 14a serve to heat fluid or solid in a single container. The supply electronics 20a has a control unit 45a, which is provided to monitor at least one functioning of a control unit 40a, which controls the timed operation of the heating resistors 12a, 13a, 14a.

The control unit 40a has a first temperature sensor 41a. The first

Temperature sensor 41 a is used to monitor a temperature of the fluid and / or the solid in the container. The control unit 40a is provided at

Exceeding a first limit temperature by the first temperature sensor 41 a - -

to discontinue or at least reduce operation of the heating resistors 12a, 13a, 14a. The control unit 45a has a second temperature sensor 49a. The second temperature sensor 49a also serves to monitor a temperature of the fluid and / or the solid in the container. The control unit 45a is provided to set an operation of the heating resistors 12a, 13a, 14a by the second temperature sensor 49a when a second threshold temperature slightly higher than the first threshold temperature is exceeded.

The supply electronics 20a has a first, a third and a fifth switching element 42a, 43a, 44a, each with exactly one of the heating resistors 12a, 13a, 14a and exactly one of the buffer capacitors 22a, 23a, 24a or exactly one of

Photovoltaic systems 16a, 17a, 18a are arranged in series. The first, third and fifth switching elements 42a, 43a, 44a are each formed as a MOSFET or IGBT. The first, third and fifth switching elements 42a, 43a, 44a are driven by the control unit 40a with clocked control signals with frequencies between 15 kHz and 50 kHz to operate the heating resistors 12a, 13a, 14a clocked. Each of the heating resistors 12a, 13a, 14a is connected in parallel with a freewheeling diode 32a, 33a, 34a.

The control unit 45a further comprises three switching elements 46a, 47a, 48a, each of which is provided to prevent operation of the heating resistors 12a, 13a, 14a upon overheating, detected by the second temperature sensor 49a or detection of malfunction of the control unit 40a. The second, fourth and sixth

Switching elements 46a, 47a, 48a are respectively arranged in series with exactly one of the heating resistors 12a, 13a, 14a and exactly one of the buffer capacitors 22a, 23a, 24a or precisely one of the photovoltaic systems 16a, 17a, 18a.

Alternatively, embodiments with different numbers of heating resistors and / or photovoltaic systems are conceivable. Furthermore, it is conceivable that the control unit has only a single switching element, which is arranged in series with all the heating resistors and each of the first, third and fifth switching elements.

Furthermore, embodiments are conceivable in which a plurality of heating resistors can optionally be connected in series with one another according to an available power, and this selection in series connected heating resistors to one or more in parallel - -

switched photovoltaic systems are connected, which, in particular due to lower switching losses, increased efficiency can be achieved.

- -

reference numeral

10 heating device

1 1 system

12 heating resistor

13 heating resistor

14 heating resistor

16 photovoltaic system

17 photovoltaic system

18 photovoltaic system

20 supply electronics

21 voltage transformers

22 buffer capacity

23 buffer capacity

24 buffer capacity

25 insulation measuring unit

26 voltage sensor

27 voltage sensor

28 voltage sensor

32 freewheeling diode

33 freewheeling diode

34 freewheeling diode

36 Performance interface

37 Performance interface

38 Performance interface

40 control unit

41 temperature sensor

42 switching element

43 switching element

44 switching element

45 control unit - -

46 switching element

47 switching element

48 switching element

49 temperature sensor

50 fluid transport unit

52 drive unit

54 voltage transformers

T total interval

U _M mean stress

Up voltage

U _s control signal

t connection phase

Claims

claims

Heating device, in particular for heating at least one fluid, with at least one first heating resistor (12; 12a, 13a, 14a) and at least one supply electronics (20; 20a), which is provided to at least the first heating resistor (12; 12a, 13a, 14a) with at least a first one

16a, 17a, 18a), characterized in that the supply electronics (20; 20a) is provided to operate at least the first heating resistor (12; 12a, 13a, 14a) at least in an operating mode in a clocked manner ,

Heating device according to claim 1, characterized in that the

Supply electronics (20; 20a) is provided to operate at least the first heating resistor (12; 12a, 13a, 14a) in at least one operating mode with a frequency between 1 kHz and 100 kHz.

Heating device according to one of the preceding claims, characterized in that the supply electronics (20; 20a) are provided for setting a power drop across the heating resistor (12; 12a, 13a, 14a) to a duty ratio of the clocked operation of at least the first heating resistor (12 ; 12a, 13a, 14a).

Heating device according to claim 3, characterized in that the

Supply electronics (20; 20a) is provided to vary a duty cycle of the pulsed operation of at least the first heating resistor (12; 12a, 13a, 14a) to optimize the power dropped across the first heating resistor (12; 12a, 13a, 14a).

5. Heating device according to one of the preceding claims, characterized in that the supply electronics (20; 20a) at least one of the first heating resistor (12; 12a, 13a, 14a) associated buffer capacity (22; 22a, 23a, 24a), provided for this purpose is, at least temporarily store energy of the photovoltaic system (16; 16a, 17a, 18a).

6. Heating device according to claim 5, characterized in that the

Supply electronics (20; 20a) are provided for determining a power drop across the heating resistor (12; 12a, 13a, 14a)

Measure voltage across the buffering capacitance (22; 22a, 23a, 24a).

7. Heating device according to claims 4 and 6, characterized in that the supply electronics (20; 20a) is provided to the duty ratio of the clocked operation, at least in response to a mean over the buffer capacity (22; 22a, 23a, 24a) voltage applied select.

8. Heating device at least according to claim 5, characterized in that the heating resistor (12; 12a, 13a, 14a) is connected directly to a buffer capacitance (22; 22a, 23a, 24a) of the supply electronics (20; 20a).

9. Heating device at least according to claim 5, characterized in that the buffer capacity (22; 22a, 23a, 24a) is intended to be connected directly to the photovoltaic system (16; 16a, 17a, 18a).

10. Heating device according to one of the preceding claims, characterized

characterized in that the supply electronics (20; 20a) is provided to vary a frequency of the pulsed operation.

1 1. Heating device according to claim 10, characterized in that the

Supply electronics (20; 20a) is provided to vary the frequency of the clocked operation as a function of a power available from the photovoltaic system (16; 16a, 17a, 18a).

12. Heating device according to one of the preceding claims, characterized in that the supply electronics (20; 20a) has at least one sensor unit which is provided to examine a frequency of the photovoltaic system (16; 16a, 17a, 18a) taken current close to arc typical behavior.

13. Heating device according to one of the preceding claims, characterized

characterized in that the supply electronics (20; 20a) has at least one temperature sensor (41, 49; 41a, 49a).

14. Heating device according to claim 13, characterized in that the

Supply electronics (20; 20a) is provided to at least reduce the operation of at least the first heating resistor (12; 12a, 13a, 14a) when a limit temperature is exceeded by the temperature sensor (49; 41a; 49a).

15. A heating device at least according to claim 13, characterized by a fluid transport unit (50) which is intended to pass a fluid to be heated to the heating resistor (12) and by the

Supply electronics (20) controlled and / or powered.

16. Heating device according to one of the preceding claims, characterized

characterized in that the supply electronics (20; 20a) has a control unit (45; 45a) which is provided for at least one functional unit of a control unit (40; 40a) which monitors the clocked operation of at least one heating resistor (12; 12a, 13a). 14a) controls, monitor.

17. Heating device according to one of the preceding claims, characterized

characterized in that control electronics of the supply electronics (20; 20a) are provided to be supplied by the photovoltaic system (16; 16a, 17a, 18a). Method for operating a heating device (10; 10a) according to one of the preceding claims.

System comprising a photovoltaic system (16; 16a, 17a, 18a) and a heating device (10; 10a) according to one of the preceding claims.