DE102011014907B4 - Method for controlling a solar circuit - Google Patents

Abstract

Method for controlling a solar circuit (1) with a solar collector (16) and a solar fluid (20), by means of which a liquid medium (11) is heated in a store (12), comprising the following steps: A) determining a storage temperature (TSp ) of the liquid medium (11) in the memory (12) by means of a first temperature sensor (18); B) determining a flow temperature (TV) of the solar fluid (20) at the solar collector (16) by means of a second temperature sensor (19); C) comparing the storage temperature (TSp) with a first limit temperature (TG1) and a second limit temperature (TG2) by means of a control unit (17), wherein - a control program R1 is selected when the storage temperature (TSp) is greater than or equal to the first limit temperature ( TG1), - wherein control program R1 is a regulation of the flow temperature (TV) by controlling the volume or mass flow of the solar fluid (20) to a first flow temperature (TV, soll 1), which is the sum of the storage temperature (TSp) and a first Spreading value (ΔT1) is, - a control program R2 is selected when the storage temperature (TSp) is less than the first limit temperature (TG1) and greater than or equal to the second limit temperature (TG2), - where control program R2 a flow temperature (TV) by regulation of the volume or mass flow of the solar fluid (20) to a constant second flow temperature setpoint (TV, 2), and - a control program R3 is selected when the storage temperature (TSp) is less than the second limit temperature (TG2), - wherein control program R3 is a regulation of the flow temperature (TV) by controlling the volume or mass flow of the solar fluid (20) to a third flow set temperature (TV, soll3 ), which is the sum of the storage temperature (TSp) and a second spread value (ΔT2), wherein a desired storage temperature (TSp, soll) can be predetermined, the first limit temperature (TG1) is greater than or equal to the desired storage temperature (TSp, soll) and second limit temperature (TG2) is less than the desired storage temperature (TSp, soll).

Description

The invention relates to a method for controlling a solar circuit with a solar collector and a solar fluid, by means of which a liquid medium is heated in a memory, according to the preamble of claim 1.

The solar collector can be directly connected to the reservoir via a supply and a return, so that the solar fluid corresponds to the liquid medium in the memory, or the solar fluid is removed from the liquid medium and fed back to it. More often, however, it is provided that the solar collector is connected via the flow and return to a heat exchanger, through which the liquid medium is heated.

Such solar circuits are usually used to heat water in a domestic hot water tank in addition to a constantly available heat source. Whenever sufficient heating by means of the solar circuit can not be achieved, the constantly available heat source takes over the heating of the water. The latter is both more costly and less ecological due to the energy source, which is for example gas, oil or electricity. Therefore, the solar cycle should be used as well as possible.

For this purpose, different control methods are known in the art. By activation and deactivation of the pump in the solar circuit, the pump can be turned off in the simplest case, if the temperature difference between the collector and memory below a certain constant temperature difference and are turned on when the temperature difference between the collector and memory exceeds this. To turn it on, a slightly higher second temperature difference can be set so that the pump is not deactivated too frequently. With such a control, however, large losses occur in the frequent starting operations and the available solar energy is used insufficiently. Accordingly, the constantly available heat source frequently turns on.

More recent methods therefore employ controllable pumps, with the aid of which the mass flow through the solar thermal circuit can be regulated. In order to be able to carry out such a control, controlled variables must be introduced by means of which the pump speed or the mass flow or the volume flow is set. If the temperature difference is too low even at low pump speed or low mass flow or volume flow, the pump is also deactivated in this process.

For the control range at a sufficient flow temperature, for example, provides a control function referred to below as Match Flow, that the flow temperature by a constant temperature difference is higher than the storage temperature. If the supply temperature exceeds the storage temperature by more than the temperature difference, the pump speed is increased. On the other hand, if the flow temperature falls below the sum of the tank temperature and the temperature difference, the pump speed is reduced.

A disadvantage of the match flow control is that the temperature difference is a compromise over the entire span of the storage tank temperature. Regardless of the height of the storage temperature, the increase in the flow temperature compared to the storage temperature has the same amount. As a result, the solar energy is used inefficient and the power consumption of the pump is increased. In addition, this regulation takes insufficient water withdrawals from the memory, which often heat the constantly available heat source must.

Another control function, which is referred to below as a double match flow control function, provides for a sufficient flow temperature, that is switched when falling below a defined upper tank temperature of a first constant temperature difference to a second constant temperature difference. Thus, when the upper storage tank temperature is undershot, the flow temperature is regulated to an upper storage tank temperature plus a temperature difference. If the upper storage tank temperature exceeds the upper storage setpoint temperature, the flow temperature is regulated to a lower storage tank temperature plus a second temperature difference.

A disadvantage is the double match flow control that a second temperature sensor is required. This must be located in the upper half of the memory. This increases the costs, error-prone and the computational effort. Nevertheless, the available heating capacity of the solar circuit is not used optimally. Above all, the constantly available heat source still frequently turns on, as the upper target storage temperature is reached too slowly.

In addition, a method is known in the prior art, in which for controlling a solar circuit, with a solar collector and a solar fluid by means of which a liquid medium is heated in a memory, first a storage temperature of the liquid medium in the memory by means of a first temperature sensor is determined. Furthermore, a flow temperature of the solar fluid at the solar collector by means of a second temperature sensor determined. Subsequently, a control unit compares the storage temperature with a first limit temperature. If the tank temperature is greater than or equal to the first limit temperature, a first control program is selected. The first control program corresponds to a regulation of the flow temperature by controlling the volume or mass flow of the solar fluid to a first flow target temperature, which is the sum of the storage temperature and a first spread value. However, if the storage temperature is less than the first limit temperature, a second control program is selected. This corresponds to a regulation of the flow temperature by controlling the volume or mass flow of the solar fluid to a constant second flow temperature setpoint.

Although this type of regulation ensures that the constantly available heat source does not have to be switched on unnecessarily often, the disadvantage here is that the solar system is operated inefficiently at low storage temperatures.

The invention has for its object to further increase the efficiency of the solar circuit in conjunction with the constantly available heat source. In particular, a connection of the constantly available heat source, for. As a gas or oil heating, are reduced to a minimum and as much heat from the solar circuit are loaded into the memory. The solution should be easy to implement, d. H. Above all, require low installation costs, work safely in a variety of installation situations and cause low costs.

This is achieved with the features of claim 1 according to the invention. Advantageous developments can be found in the dependent claims.

• A) Bestimmen einer Speichertemperatur des flüssigen Mediums im Speicher mittels eines ersten Temperatursensors;
• B) Bestimmen einer Vorlauftemperatur des Solarfluids am Solarkollektor mittels eines zweiten Temperatursensors;
• C) Vergleichen der Speichertemperatur mit einer ersten Grenztemperatur und einer zweiten Grenztemperatur mittels einer Regeleinheit, wobei
• – ein Regelprogramm R1 ausgewählt wird, wenn die Speichertemperatur größer oder gleich der ersten Grenztemperatur ist,
• – wobei Regelprogramm R1 einem Regeln der Vorlauftemperatur durch Regelung des Volumen- oder Massenstroms des Solarfluids auf eine erste Vorlaufsolltemperatur entspricht, welche die Summe der Speichertemperatur und einem ersten Spreizwert ist,
• – ein Regelprogramm R2 ausgewählt wird, wenn die Speichertemperatur kleiner als die erste Grenztemperatur und größer oder gleich der zweiten Grenztemperatur ist,
• – wobei Regelprogramm R2 einem Regeln der Vorlauftemperatur durch Regelung des Volumen- oder Massenstroms des Solarfluids auf eine konstante zweite Vorlaufsolltemperatur entspricht, und
• – ein Regelprogramm R3 gewählt wird, wenn die Speichertemperatur kleiner als die zweite Grenztemperatur ist,
• – wobei Regelprogramm R3 einem Regeln der Vorlauftemperatur durch Regelung des Volumen- oder Massenstroms des Solarfluids auf eine dritte Vorlaufsolltemperatur entspricht, welche die Summe der Speichertemperatur und einem zweiten Spreizwert ist.

The invention relates to a method for controlling a solar circuit with a solar collector and a solar fluid, by means of which a liquid medium is heated in a store, comprising the following steps:

• A) determining a storage temperature of the liquid medium in the memory by means of a first temperature sensor;
• B) determining a flow temperature of the solar fluid at the solar collector by means of a second temperature sensor;
• C) comparing the storage temperature with a first limit temperature and a second limit temperature by means of a control unit, wherein
• A control program R1 is selected if the storage temperature is greater than or equal to the first limit temperature,
• Wherein control program R1 corresponds to a regulation of the flow temperature by regulation of the volume or mass flow of the solar fluid to a first desired flow temperature, which is the sum of the storage temperature and a first spread value,
• A control program R2 is selected if the storage temperature is less than the first limit temperature and greater than or equal to the second limit temperature,
• - wherein control program R2 corresponds to a regulation of the flow temperature by controlling the volume or mass flow of the solar fluid to a constant second flow temperature setpoint, and
• A control program R3 is selected if the storage temperature is less than the second limit temperature,
• - Where control program R3 corresponds to a regulation of the flow temperature by controlling the volume or mass flow of the solar fluid to a third flow temperature, which is the sum of the storage temperature and a second spread value.

In this case, the first limit temperature is greater than or equal to a predefinable desired storage temperature, the second limit temperature is less than the desired storage temperature.

Since a liquid medium of different temperature stratifies in a store, with cold liquid medium at the bottom and warm liquid medium at the top, at least the return from the store to the solar collector should be located near the bottom of the store. The same applies to the measuring position of the first temperature sensor.

A best possible determination of the flow temperature takes place at the output of the solar collector, but still in the insolation area of the sun. So even with deactivated solar fluid flow, a flow temperature can be determined.

Depending on the temperature of the liquid medium in the memory of one of the three control programs is activated according to the method. In this case, at a low temperature, ie at a storage temperature which is less than the second limit temperature, regulated to a defined, preferably minimal, more preferably between 7 Kelvin to 11 Kelvin temperature spread between flow temperature and storage temperature (control program R3). For example, it is not to be expected that the storage tank temperature can be heated up to a hot water temperature. This is the case in particular when only a small amount of solar radiation hits the solar collector or when there are very low outside temperatures. The advantage here is that despite the low solar radiation as much heat in the Memory is charged, or the liquid medium is heated as much as possible. With such a defined temperature spread, the losses of the solar circuit are very low and the efficiency is accordingly high.

The control to a desired flow temperature is carried out in each case by adjusting the volume or mass flow of the solar fluid. In particular, this can be implemented via a rotational speed of a pump. If the flow temperature is higher than the desired flow temperature, the speed would be increased, and if the supply temperature drops below the supply temperature by the flow temperature, the speed would be reduced. If the flow temperature does not reach the set flow temperature even if the speed continues to drop, the speed will eventually be zero revolutions per minute. If the pump speed drops below a certain pump speed, however, the solar circuit becomes inefficient. Therefore, the pump should be deactivated beforehand until the flow temperature is sufficient again to enable the pump again with a speed above this pump speed.

Control program R2 has the main goal of ensuring that sufficient solar radiation ensures that the constantly available heat source is switched on as rarely as possible. It is activated when the temperature of the liquid medium in the store is near a target temperature and it can be expected that this target temperature can be achieved by means of the solar cycle. In this temperature range, short-term efficiency losses of the solar circuit are accepted, but these are significantly lower than possible losses due to the addition of the constantly available heat source.

By means of the control program R1, as much heat as possible is again charged into the storage tank when the temperature of the liquid medium is already high, by controlling the temperature spread between the flow temperature and the storage temperature to a defined, preferably minimum, more preferably between 7 and 11 Kelvin. An addition of the constantly available heat source is not expected in this temperature range of the liquid medium. Therefore, the process selects in this temperature range control program R1 with the highest possible efficiency for the solar cycle.

The method provides that a storage target temperature can be specified. This applies in particular to the height of the memory in which the first temperature sensor is arranged. This adaptation allows, for example, homeowners to adjust the desired store temperature to their needs. The storage target temperature should be slightly above a desired hot water temperature. Such a predefinable desired storage temperature can represent important information for the control unit of the solar circuit. In fact, the method is ideally also designed for this desired storage temperature in order to achieve the highest possible efficiency by preventing frequent connection of the constantly available heat source. In particular, the limit temperatures are designed for the desired storage temperature.

Thus, the method provides that the first limit temperature is greater than or equal to the storage target temperature. Particularly preferably, the first limit temperature corresponds to the desired storage temperature. This could be, for example, 50 ° C. Above this first limit temperature, control program R1 is activated and the constantly available heat source is deactivated. The solar circuit now loads as much heat as possible into the storage tank, while at the same time providing high efficiency for the solar cycle.

Furthermore, it is provided that the second limit temperature is less than the desired storage temperature. It is preferable to have a second limit temperature that is half the first limit temperature plus / minus 5 Kelvin. For example, this could be 25 ± 5 ° C when the first limit temperature is 50 ° C. Above such a second limit temperature, it can be assumed that the heat to be supplied can be reached by means of the solar circuit for reaching the desired storage temperature. By means of the control program R2, a connection of the constantly available heat source is prevented.

Between the two limit temperatures regulating program R2 controls according to the invention to a constant second flow temperature. This is preferably greater than the desired storage temperature. Thus, the storage tank temperature is charged as fast as possible above the storage target temperature and the constantly available heat source is not activated.

An embodiment of the method provides that the first spread value is constant. It is preferably between 7 Kelvin and 11 Kelvin. The ideal first spread value can vary slightly depending on the solar cycle and could be determined. In particular, this can be influenced by heat losses in the flow and return. The determination could be carried out individually at each solar circuit or else a standardized first spread value could be determined by means of previous tests. A standardized first spread value may then serve as a default that allows operation of the solar loop and does not necessarily require individual adjustment by an installer.

Unlike a constant first spread value, the ideal first spread value could have a dependency on the store temperature. Accordingly, the first spread value could then be a function dependent on the storage temperature. Such a first spread value function preferably moves in a temperature range from 7 Kelvin to 11 Kelvin. In particular, as the storage temperature rises, the first spread value could increase in order to delay stagnation of the storage temperature, for which purpose the solar circuit is specifically operated with a somewhat lower efficiency.

The second spread value could also be constant and preferably between 7 Kelvin and 11 Kelvin. This should also be determined. This could be done individually at each solar circuit or it could be determined by means of previous attempts a standardized second spread value.

Unlike a constant second spread value, the ideal second spread value could have a dependency on the store temperature. Accordingly, the second spread value could then be a function dependent on the storage temperature, which preferably lies in a temperature range from 7 Kelvin to 11 Kelvin.

There is also the possibility that the second spread value corresponds to the first spread value. As a result, the investigation effort is very low and only pretend a spread value.

Furthermore, a variant provides that the first spread value is specified. This makes it possible that an installer of a solar circuit can set the first spread individually. Thus, a maximum efficiency of the control program R1 is achieved for each individual solar circuit.

Likewise, the second spread value could be specified. This makes it possible for an installer of a solar circuit to set the second spread value individually. Thus, a maximum efficiency of the control program R3 is achieved for each individual solar circuit.

The drawings illustrate embodiments of the invention and show in FIG

1 a diagram of a method according to the invention for controlling the flow temperature as a function of the storage temperature with constant spread values;

2 a diagram of a method according to the invention for controlling the flow temperature in dependence on the storage temperature with spread values dependent on the storage temperature;

3 a solar circuit with heat exchanger; and

4 a solar circuit without heat exchanger.

1 shows a diagram of a method according to the invention for controlling a flow temperature of a solar circuit. On the abscissa for this purpose, a storage temperature T _Sp and on the Ordninate a flow temperature T _{V is} plotted. A dashed line running at 45 degrees through the intersection of the storage temperature T _Sp and the flow temperature T _V marks the state in which the storage temperature T _{Sp is} equal to the flow temperature T _V. Above this dashed line runs a _{desired flow temperature} T _{V, soll} , which is composed of three sections T _{V, soll1} , T _{V, soll2} and T _{V, soll3} . The limits between these three _{desired flow temperatures} T _{V, soll1} , T _{V, soll2} and T _{V, soll3} result from two limit temperatures T _G1 and T _G2 , wherein in the illustrated _{embodiment of} the method the first limit temperature T _G1 corresponds to a _desired storage temperature T _{Sp, soll} , The first limit temperature T _G1 forms the boundary between T _{V, soll1} and T _{V, soll2 ,} and the second limit temperature T _G2 that between T _{V, soll2} and T _{V, soll3} .

_According to the invention, it is provided that the first _{desired flow temperature} T _{V, soll1} is above the 45 degree line by a first spread value ΔT ₁ , ie it lies above this first spread value ΔT ₁ above the storage temperature T _Sp . According to the illustration shown, the first _{flow target temperature} T _{V, soll1 runs} parallel to the 45 degree line and thus the first spread ΔT _{1 is} constant. In order to regulate the flow temperature T _V to the first _desired flow temperature T _{V , soll1} , the method selects a control program R1 at a storage temperature T _Sp which is higher than or equal to the first limit temperature T _G1 .

Furthermore, the second _{flow target temperature} T _{V, soll2 is} a constant value which is above the 45 degree line, ie it is above the storage temperature T _Sp . In particular, the second _{desired flow temperature} T _{V, soll2 is} the sum of the _desired storage _temperature T _{Sp, soll} and the first spread value ΔT ₁ . In order to regulate the flow temperature T _V to the second _desired flow temperature T _{V , soll2} , the method selects at a storage temperature T _Sp which is higher than or equal to the second limit temperature T _G2 and lower than the first limit temperature T _G1 , a Control program R2 off.

At a storage temperature T _Sp below the second limit temperature T _{G2, it} is provided that the third _{setpoint target} temperature T _{V, soll3} is above the 45 degree line by a second spread value ΔT ₂ , ie, it lies above the second spread value ΔT ₂ above the storage temperature T _Sp . According to the illustration shown, the third _{flow target temperature} T _{V, soll3 runs} parallel to the 45 degree line and thus the third spread ΔT _{3 is} constant. In order to regulate the flow temperature T _V to the third _desired flow temperature T _{V , soll3} , the method selects a control program R3 at a storage temperature T _Sp which is lower than the second limit temperature T _G2 .

The _process regulates the flow temperature T _V, for example, such that it regulates the volume or mass flow of a solar fluid flowing through a solar collector to these flow _target temperatures T _{V, soll1} , T _{V, soll2} and T _{V, soll3} .

Another diagram illustrates in 2 also an inventive method for controlling a flow temperature T _{V of} a solar circuit. On the abscissa for this purpose, a storage temperature T _Sp and on the Ordninate a flow temperature T _{V is} plotted. A dashed line running at 45 degrees through the intersection of the storage temperature T _Sp and the flow temperature T _V marks the state in which the storage temperature T _{Sp is} equal to the flow temperature T _V. Above this dashed line runs a _{desired flow temperature} T _{V, soll} , which is composed of three sections T _{V, soll1} , T _{V, soll2} and T _{V, soll3} . The limits between these three _{desired flow temperatures} T _{V, soll1} , T _{V, soll2} and T _{V, soll3} are given by two limit temperatures T _G1 and T _G2 . According to the embodiment of the method shown, between the two limit temperatures T _G1 , T _{G2 there is} a desired storage temperature T _{Sp, soll} . The first limit temperature T _G1 forms the boundary between T _{V, soll1} and T _{V, soll2} , and the second limit temperature T _G2 that between T _{V, soll2} and T _{V, soll3} .

_According to the invention, it is provided that the first _{desired flow temperature} T _{V, soll1} is above the 45 degree line by a first spread value ΔT ₁ , ie it lies above this first spread value ΔT ₁ above the storage temperature T _Sp . According to the illustration shown, the first _{flow target temperature} T _{V, soll1} does not run parallel to the 45 degree line and thus the first spread ΔT _{1 is} not constant. Rather, the first set flow temperature T _{V, soll1} approaches asymptotically to a temperature which is parallel above the 45 degree line. The first spread value .DELTA.T ₁ thus decreases with increasing storage temperature T _Sp . He could, however, just as well increase (not shown). Ideally, the first spread value ΔT ₁ in the control range of the storage temperature T _{Sp is} between 7 and 11 Kelvin. In order to regulate the flow temperature T _V to the first _desired flow temperature T _{V , soll1} , the method selects a control program R1 at a storage temperature T _Sp which is higher than or equal to the first limit temperature T _G1 .

Furthermore, the second _{flow target temperature} T _{V, soll2 is} a constant value which is above the 45 degree line, ie it is above the storage _temperature T _Sp . In order to regulate the flow temperature T _V to the second _desired flow temperature T _{V , soll2} , the method selects at a storage temperature T _Sp which is higher than or equal to the second limit temperature T _G2 and lower than the first limit temperature T _G1 , a Control program R2 off.

At a storage temperature T _Sp below the second limit temperature T _{G2, it} is provided that the third _{setpoint target} temperature T _{V, soll3} is above the 45 degree line by a second spread value ΔT ₂ , ie, it lies above the second spread value ΔT ₂ above the storage temperature T _Sp . According to the illustration shown, the third _{flow target temperature} T _{V, soll3 is} not parallel to the 45 degree line and thus the second spread value ΔT _{2 is} not constant. Ideally, the second spread value ΔT ₂ in the control range of the storage temperature T _{Sp is} between 7 and 11 Kelvin. In order to regulate the flow temperature T _V to the third _desired flow temperature T _{V , soll3} , the method selects a control program R3 at a storage temperature T _Sp which is lower than the second limit temperature T _G2 .

The _process regulates the flow temperature T _V, for example, such that it regulates the volume or mass flow of a solar fluid flowing through a solar collector to these flow _target temperatures T _{V, soll1} , T _{V, soll2} and T _{V, soll3} .

3 shows a solar cycle 1 consisting of a solar collector 16 and a heat exchanger 13 that have a lead 14 and a return 15 are connected. Here is the heat exchanger 13 in a store 12 arranged. By means of a return 15 arranged controllable pump 10 becomes a solar fluid 20 through the solar circuit 1 pumped. This takes in the solar collector 16 Heat up and pass it over the heat exchanger 13 to one in the store 12 located liquid medium 11 from. For regulating the solar circuit 1 is a control unit 17 provided with a first temperature sensor 18 In the storage room 12 , a second temperature sensor 19 in the exit area of the solar collector 16 and the pump 10 connected is. Thus, a storage temperature of the liquid medium 11 In the storage room 12 by means of the first temperature sensor 18 and a flow temperature of the solar fluid 20 by means of the second temperature sensor 19 determinable. The control unit 17 can now regulate the flow temperature to a temperature dependent on the storage temperature feed temperature by changing the speed of the pump 10 regulates.

According to 4 there is a solar cycle 1 from a solar collector 16 , as well as from a preliminary 14 and a return 15 both in one store 12 lead. By means of a return 15 arranged controllable pump 10 becomes a solar fluid 20 through the solar circuit 1 pumped, with the solar fluid 20 one out of memory 10 withdrawn liquid medium 11 equivalent. The solar fluid 20 takes in the solar collector 16 Heat up and then over the flow 14 back to the store 12 directed. For regulating the solar circuit 1 is a control unit 17 provided with a first temperature sensor 18 In the storage room 12 , a second temperature sensor 19 in the exit area of the solar collector 16 and the pump 10 connected is. Thus, a storage temperature of the liquid medium 11 In the storage room 12 by means of the first temperature sensor 18 and a flow temperature of the solar fluid 20 by means of the second temperature sensor 19 determinable. The control unit 17 can now regulate the flow temperature to a temperature dependent on the storage temperature feed temperature by changing the speed of the pump 10 regulates.

LIST OF REFERENCE NUMBERS

1

Solar circuit

10

pump

11

liquid medium

12

Storage

13

heat exchangers

14

leader

15

returns

16

solar collector

17

control unit

18

first temperature sensor

19

second temperature sensor

20

solar fluid

T _Sp

storage temperature

T _V

flow temperature

T _{Sp, shall}

Cylinder temperature

T _{V , shall}

Flow temperature

T _{V, soll1}

first flow temperature setpoint

T _{V, soll2}

second flow setpoint temperature

T _{V, soll3}

third flow setpoint temperature

T _G1

first limit temperature

T _G2

second limit temperature

ΔT ₁

first spread value

ΔT ₂

second spread value

Claims (7)

Method for controlling a solar cycle ( 1 ) with a solar collector ( 16 ) and a solar fluid ( 20 ), by means of which a liquid medium ( 11 ) in a memory ( 12 ), comprising the following steps: A) determining a storage temperature (T _Sp ) of the liquid medium ( 11 ) In the storage room ( 12 ) by means of a first temperature sensor ( 18 ); B) determining a flow temperature (T _V ) of the solar fluid ( 20 ) at the solar collector ( 16 ) by means of a second temperature sensor ( 19 ); C) comparing the storage temperature (T _Sp ) with a first limit temperature (T _G1 ) and a second limit temperature (T _G2 ) by means of a control unit ( 17 ), wherein - a control program R1 is selected when the storage temperature (T _Sp ) is greater than or equal to the first limit temperature (T _G1 ), - wherein control program R1 is controlling the flow temperature (T _V ) by controlling the volume or mass flow of the solar fluid ( 20 ) to a first desired flow temperature (T _{V, soll 1 )} , which is the sum of the storage temperature (T _Sp ) and a first spread value (.DELTA.T ₁ ), - a control program R2 is selected when the storage temperature (T _Sp ) is less than that is the first limit temperature (T _G1 ) and greater than or equal to the second limit temperature (T _G2 ), - wherein control program R2 a regulation of the flow temperature (T _V ) by controlling the volume or mass flow of the solar fluid ( 20 ) to a constant second flow temperature setpoint (T _{V, 2} ), and - a control program R3 is selected when the temperature of the reservoir (T _Sp ) is less than the second temperature limit (T _G2 ), - wherein control program R3 is controlled according to flow temperature ( T _V ) by controlling the volume or mass flow of the solar fluid ( 20 ) to a third _{desired flow temperature} (T _{V, soll3} ), which is the sum of the storage _temperature (T _Sp ) and a second spread value (.DELTA.T ₂ ), wherein a storage target temperature (T _{Sp, soll} ) can be predetermined, the first limit temperature (T _G1 ) is greater than or equal to the desired store temperature (T _{Sp, soll} ) and the second limit temperature (T _G2 ) is less than the desired store temperature (T _{Sp, soll} ). A method according to claim 1, characterized in that the second _{flow temperature setpoint} (T _{V, soll2} ) is greater than the _{desired storage temperature} (T _{Sp, soll} ). Method according to one of the preceding claims, characterized in that the first spread value (ΔT ₁ ) is constant. Method according to one of the preceding claims, characterized in that the second spread value (ΔT ₂ ) is constant. Method according to one of the preceding claims, characterized in that the second spread value (ΔT ₂ ) corresponds to the first spread value (ΔT ₁ ). Method according to one of the preceding claims, characterized in that the first spread value (ΔT ₁ ) is specified. Method according to one of the preceding claims, characterized in that the second spread value (ΔT ₂ ) is specified.

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