EP2769093A1

EP2769093A1 - Solar thermal power plant and method for operating a solar thermal power plant

Info

Publication number: EP2769093A1
Application number: EP12702750.6A
Authority: EP
Inventors: Horst Schierack
Original assignee: Individual
Current assignee: Schierack Green Technology GmbH
Priority date: 2011-10-19
Filing date: 2012-01-20
Publication date: 2014-08-27
Also published as: WO2013056752A1; DE102011116338B4; DE102011116338A1

Abstract

The invention relates to a solar thermal power plant (1) comprising at least one solar collector (4) of a solar circuit (2) and comprising an expansion turbine (20) associated with a working circuit (3). The solar circuit (2) and the working circuit (3) are coupled to each other via at least one primary heat exchanger (6); the solar circuit (2) has a solar fluid, and the working circuit has a working fluid. The solar circuit (2) is associated with a primary heat accumulator (9) which has at least one primary heat accumulator tank (10) for the solar fluid of the solar circuit (2), said accumulator tank being connected in parallel to the primary heat exchanger (6) in particular. The invention further relates to a method for operating a solar thermal power plant (1).

Description

Solar thermal power plant and method for operating a solar thermal power plant

The invention relates to a solar thermal power plant having at least one solar collector of a solar circuit and an expansion turbine associated with a working cycle, wherein the solar circuit and the working circuit are coupled to each other via at least one primary heat exchanger and the solar circuit comprises a solar fluid and the working circuit has a working fluid. The invention further relates to a method for operating a solar thermal power plant.

Solar thermal power plants of the type mentioned are basically known from the prior art. They have several circuits, but at least the solar circuit and the working cycle. In the solar circuit, the solar fluid and in the working cycle, the working fluid is present, with no direct flow connection between the solar circuit and the working cycle is given, but only a heat coupling through the primary heat exchanger. Both fluids are usually circulated by means of a conveyor in the respective circuit. Both the solar circuit and the working circuit are preferably closed circuits, which means that the amount of fluid contained in the respective fluid ideally remains constant except for possible leakage losses. The solar fluid may be referred to as the first fluid and the working fluid as the second fluid. The solar fluid present in the solar circuit is heated by solar radiation in the solar collector in this, with its enthalpy, in particular the internal energy contained in it increases. Usually, therefore, the solar fluid in the region of the fluidically in the solar circuit following the solar collector primary heat exchanger to a higher temperature than the working fluid. By means of the primary heat exchanger can be transmitted due to the temperature difference heat from the solar fluid to the working fluid. Usually, the primary heat exchanger is designed as an evaporator or superheater, so that the working fluid in it is evaporated and / or overheated. The working fluid enters so far in gaseous state in the expansion turbine. In this, the total enthalpy of the gaseous working fluid is used to partially convert the thermal energy of the working fluid, in particular with an efficiency of about 75% to 80%, into mechanical energy. The expansion turbine is used, for example, for driving a generator and thus for generating electricity. The expansion turbine can basically be designed arbitrarily, in particular as a single-stage or multi-stage expansion turbine or steam turbine.

In known solar thermal power plants, a thermal oil or thermal oil is used as solar fluid in the solar circuit. In normal sunlight, the heat transfer oil of the solar circuit in the solar collector is heated up to about 420 ° C. This temperature is sufficient to heat the water used as working fluid in the working cycle to about 390 ° C, to evaporate and overheat. Subsequently, the water is supplied in the gaseous state of the expansion turbine. The running in the working cycle process can for example by means of Clausius-Rankine cycle process are described at least approximately. The working fluid is accordingly condensed alternately at low pressure and evaporated at high pressure. In the present application, absolute temperatures are given in degrees Celsius (° C) and temperature differences in Kelvin (K).

Usually, the known solar thermal power plants additionally have a fluidically separated from the working cycle and the solar circuit present storage circuit, in which, for example, salt water is used as storage fluid. When operating the solar thermal power plant can occur due to changing environmental conditions, strong fluctuations in the electric power generated. For this reason, the storage circuit is provided in order not to be used only to cover a peak load of the connected consumers, but also to be able to contribute at least partially to cover a medium load or a base load. If the solar radiation is sufficient, ie if it is greater than or equal to a design solar radiation, the storage fluid is heated to approximately 290 ° C. with a portion of the heat present in the solar circuit or in the solar fluid. As soon as the solar radiation is lower than the design sun radiation, for example in the case of cloud cover or at night, the temperature in the solar circuit can drop significantly, for example by more than 20 K.

Because the storage fluid has a lower temperature than the solar fluid, which is even smaller than the temperature required in the working cycle, must be at least partially Unterbre- chung the solar heat supply from the solar circuit, so when falling below the design sun radiation by the current solar radiation - despite the use of heat from the storage circuit - the working circuit to maintain the necessary for the expansion turbine saturated steam temperature of about 390 ° C additional external heat to be supplied. Accordingly, the temperature in the working cycle - starting from the 290 ° C in the storage cycle - with the help of external, especially fossil energy must be increased by 100K. In solar radiation below the design sun radiation known from the prior art solar thermal power plants work by means of this dual or hybrid heat supply maximum about eight hours until the temperature of the storage medium or the storage fluid and thus the efficiency of the solar thermal power plant have dropped so far that another Operation does not make sense. The known solar thermal power plants can hardly or only partially serve to cover the medium load and the base load, and this only with the supply of external heat or external energy.

It is an object of the invention to provide a solar thermal power plant, which does not have the disadvantage mentioned above, but an efficient operation at temporarily low or without solar radiation over a long period of, for example, more than eight hours, in particular without supply of external energy possible.

This is inventively achieved with a solar thermal power plant with the features of claim 1. It is intended that the solar circuit is associated with a primary heat accumulator having at least one, in particular connected parallel to the heat exchanger, primary heat storage tank for the solar fluid of the solar circuit. As already mentioned, known from the prior art solar thermal power plants via a (not mandatory) have a memory circuit which is fluidly separated from the solar circuit and the working cycle. For example, salt water is present as storage fluid in the known storage cycle. Alternatively, it is also known to use a heat storage tank with a storage medium, for example a salt or the like. By contrast, it should now be provided that the primary heat storage is assigned directly to the solar circuit and the primary heat storage tank for receiving and especially temporary storage of solar fluid is connected to the solar circuit. Preferably, the primary heat storage tank is fluidically parallel to the primary heat exchanger.

The solar circuit has in the primary flow direction in particular the following elements: The solar collector, an inlet switching valve, the primary heat exchanger, an outlet switching valve and a conveyor for conveying the solar fluid through the solar circuit. The inlet switching valve and the outlet switching valve each have at least three ports, wherein the solar collector, the primary heat exchanger and the primary heat storage tank are connected to the inlet switching valve or its terminals. On the other hand, the primary heat exchanger, the conveyor and in turn the primary heat storage tank are connected to the outlet switching valve or its connections. The primary heat storage tank is located so far between the inlet switching valve and the outlet switching valve. By means of the inlet switching valve and the outlet switching valve, the mass flows of the solar fluid through the respective connections are adjustable, preferably continuously. The setting can be controlled and / or regulated. Of course, however, another structural design of the solar thermal power plant can be realized.

The primary heat store or its primary heat storage tank has a storage volume which can preferably be completely filled with the solar fluid. The storage volume is in particular greater than the fluid volume of the solar fluid in the other areas of the solar thermal power plant. A large part of the solar fluid can therefore be located at any time in the primary heat storage and removed or supplied as needed. The primary heat storage or the primary heat storage tank is particularly preferably designed as a stratified charge storage. This means that the solar fluid is stratified during the intermediate storage in the primary heat store according to its temperature at different positions, in particular at different heights. This is made possible by the temperature-dependent density of the solar fluid. The stratification can be achieved for example by a suitable guidance of the solar fluid in the storage volume or the primary heat storage tank. Compared to the known solar thermal power plants deleted in this respect the absolute need to provide a separate storage circuit to allow operation at low solar radiation. Rather, the solar fluid is added directly held high temperature to be able to bridge even longer periods of low or no sunlight on the solar collector, in particular under constant maintenance of the rated power. The temperature of the stored solar fluid is in this case in particular higher than the critical temperature of the working fluid, which will be discussed in more detail below.

In the embodiment described, the advantage arises that the volumes required for storage are significantly lower than in the case of solar thermal power plants known from the prior art. For example, to bridge a period of 16 hours without solar radiation (in the sense of solar radiation corresponding to a minimum solar radiation, for example at night), a heat storage tank with a volume of 0.2 m ³ / kWh, during this period, also referred to as design period is to be able to constantly provide the rated power of the power plant (for example in the form of electric current). The known from the prior art solar thermal power plants, however, require a storage volume of 0.7 m ³ / kWh for a mere eight-hour bridging. For this, however, always, as already mentioned, the supply of external energy necessary. This is due, in particular, to the fact that a molten salt is often used as the storage medium, which always has to have a temperature above its solidification temperature, so that the operability of the solar thermal power plant is not adversely affected or damage from solidifying storage medium is prevented.

The large difference described above between the required storage volumes results in particular from the large one Temperature difference, which during a normal operation of the solar thermal power plant according to the invention, in which the solar radiation is greater than or equal to the design sun radiation, between the solar circuit and the working cycle - for example by appropriate choice of solar fluid and working fluid - be realized. This makes it possible, the stored heat in a storage operation, in which the present in the primary heat storage heat is used, even at - due to the removal of heat from the primary heat storage - significantly lower temperature of the solar fluid and thus lower temperature difference to operate the Working cycle.

The primary heat storage described here allows corresponding operation of the working cycle or the generation of electric power over a long period of time with little or no sunlight, with no supply of external heat is necessary and therefore not provided. This period depends exclusively on the intended storage volume and the cooling of the solar fluid stored in the primary heat storage tank by heat losses. With appropriate design of the solar thermal power plant or the primary heat storage so a continuous operation with the generation of electric power can be achieved, is periodically switched between normal operation and storage operation. It goes without saying that the solar radiation during normal operation for this purpose must be sufficient to the present in the primary heat storage or in the solar circuit solar fluid to a temperature bring, which corresponds to an amount of heat that is sufficient for the desired period of memory operation.

The solar collector of the solar thermal power plant according to the invention can be designed, for example, as a parabolic trough collector or have parabolic trough collectors, wherein an absorber line of the solar circuit runs along a focal line of a collector element, in particular a mirror, of the solar collector. Alternatively, the solar collector can of course be designed as a Fresnel mirror collector or as a paraboloid collector. The solar collector usually consists in this respect of the collector element and the absorber line, the latter part of the solar circuit or is connected to this, so that the absorber line is traversed by the solar fluid during operation of the power plant. The solar fluid absorbs corresponding solar heat via an inner surface of the absorber line. The collector element is designed, for example, as a mirror, in particular as a parabolic trough, Fresnel mirror or paraboloid mirror. Usually, the solar thermal power plant has a large number of solar collectors, which are combined in particular in at least one solar field.

In addition to the generation of electricity, the solar thermal power plant described here can also - additionally or alternatively - be used for a multi-desalination plant or represent an energy supply of such. Desalinization systems require in addition to electrical energy (for pumps and the like) especially heat to evaporate the salt water taken from the sea and desalt it. Some of the heat can be added to the working fluid, for example after Expansion turbine, in particular in a condenser, are removed. For this purpose, it makes sense to increase the amount of heat available at this point. For this purpose, for example, the power plant can be adjusted so that sets for the working fluid after relaxing in the expansion turbine, a state that lies on the dew line or at least - lying in the wet steam area - as close as possible. The possible maximum temperature of the working fluid before entering the expansion turbine can alternatively also be increased by an appropriate choice of the working fluid. In this way, the salt water can be at least preheated. Further heating can be provided by means of a solar collector.

For example, it may also be provided that the primary heat accumulator has an insulation surrounding the primary heat storage tank at least in regions. The insulation at least partially prevents the heat of the stored in the primary heat storage tank solar fluid is delivered to an environment of the primary heat storage. In this case, the isolation can in principle be performed arbitrarily. However, it must be made of a material that is poor heat-conducting. Additionally or alternatively, a safety sheath is provided, which at least partially encloses the primary heat storage tank or at least one of the primary heat storage tanks, preferably all. The containment is designed in such a way that even in the event of a leak in one of the primary heat storage tanks, the safety of persons in the vicinity of the primary heat store is guaranteed. It thus prevents in particular a sudden deformation of the primary heat storage tank by the pressurized solar fluid or a sudden escape of the solar fluid.

Additionally or alternatively, it can be provided that the primary heat accumulator has a plurality of preferably fluidically connected, primary heat storage tanks, which are in cylindrical form and are arranged parallel to each other, wherein intermediate spaces between the primary heat storage tanks with a heat storage material, in particular magnesite, at least partially filled. With such an embodiment of the primary heat accumulator, a particularly high heat storage capacity per unit volume can be achieved. Due to the cylindrical shape, the primary heat storage tanks are also extremely resistant to pressure, so that the working circuit can be operated at a very high maximum temperature, which causes a high pressure of the solar fluid in order to prevent a change of state of aggregation. The cylindrical primary heat storage tanks are arranged, for example, fluidically parallel to each other. Of course, however, it can also be provided to switch the primary heat storage tanks one after the other in terms of flow or to arrange some of the primary heat storage tanks parallel to one another and others in turn one behind the other.

The conditional by the design and the parallel arrangement of the primary heat storage tanks gaps to optimize the heat storage capacity of the primary heat storage, at least partially filled with the heat storage material. The heat pump material is a material which has particularly good heat storage properties. For example, magnesite can be used. Alternatively or additionally, however, is also for example a latent heat storage material can be used which uses reversible thermodynamic state changes to store the heat. It is of course of particular advantage when the primary heat storage tanks together with the heat storage material are enveloped by the insulation described above and intermediate spaces between the insulation and the primary heat storage tanks are also filled with the heat storage material at least partially, in particular completely. Around the insulation, the safety cover can additionally be arranged. A development of the invention provides that at least one secondary heat exchanger is provided, via which the working cycle and / or the solar circuit is coupled to at least one secondary storage circuit having a secondary storage fluid. In addition to the primary heat storage so the secondary storage circuit should be present. In this the secondary storage fluid is provided. The secondary storage circuit is used for storing or buffering heat, in particular from the solar circuit. The secondary storage circuit is coupled via the at least one secondary heat exchanger with the solar circuit and / or the working cycle.

In a first, simple embodiment, there is only one secondary heat exchanger, by means of which heat can be transferred between the secondary storage cycle and the solar cycle. The secondary storage circuit is fluidically separated both from the solar circuit and the working circuit. The secondary storage fluid may be different from the solar fluid and / or the working fluid. The secondary storage fluid is preferably a heat storage fluid which has good heat storage properties. th, in particular a high heat capacity, has. For example, water, in particular salt water, or thermal oil is used as secondary storage fluid. During normal operation, ie in the case of solar radiation, which is greater than the design solar radiation, heat from the solar fluid can be supplied to the secondary storage circuit. In the storage operation, in contrast, a transfer of heat from the secondary storage fluid to the solar fluid by means of the secondary heat exchanger and then by means of the primary heat exchanger to the working fluid so that it can be brought to a temperature which is sufficient to operate the working cycle on.

In another embodiment, the secondary storage circuit may be associated with a plurality of heat exchangers, wherein at least one of the heat exchangers as described above between the solar circuit and the storage circuit and another of the heat exchanger is present as a secondary heat exchanger between the storage circuit and the working cycle. Here, too, a fluidic separation between the secondary storage circuit and the other circuits can be provided. As already stated, the secondary storage fluid of the secondary storage circuit can be heated with heat from the solar circuit during normal operation. In the storage operation, it is now provided, however, not first to heat the solar fluid of the solar circuit, but rather directly the working fluid of the working cycle using the stored heat in the secondary storage circuit.

Additionally or alternatively, the secondary storage fluid can be heated in other ways, for example by the Secondary storage circuit is connected to the solar collector of the solar circuit or at least one further solar collector. In this case, it is sufficient if only at least one secondary heat exchanger is present between the secondary storage circuit and the working cycle.

In the described embodiments, the heat stored in the secondary storage circuit is usually sufficient for a comparatively long period of time in order to continue to bring the working fluid to the desired temperature, thus to evaporate and preferably to overheat. Again, therefore, no supply of external energy, such as fossil energy or the like, necessary to operate the solar thermal power plant in the storage operation.

A further development of the invention provides that the secondary storage circuit is fluidically isolated from the solar circuit and the working circuit or is fluidically connected to the solar circuit. The former embodiment has already been briefly outlined above. If the secondary storage circuit is separated from both the solar circuit and the working circuit, then the secondary heat exchanger is preferably provided between the working circuit and the secondary storage circuit. In all the described embodiments, the secondary storage fluid may be different from the solar fluid and / or the working fluid. Alternatively, the secondary storage circuit can also be fluidically connected to the solar circuit, so be connected fluidically with this. In this case, the se- secondary storage fluid to the solar fluid. In such an embodiment, the working fluid of the working cycle can be heated both by means of the primary heat exchanger and by means of the secondary heat exchanger, in each case using heat from the solar circuit.

For example, in the described embodiments, the secondary heat exchanger is designed as an evaporator and the primary heat exchanger as a superheater. The amount of secondary storage fluid supplied to the secondary heat exchanger is thus set such that the working fluid merely evaporates but is not overheated. Accordingly, the amount of the solar fluid supplied to the primary heat exchanger is adjusted so that the working fluid evaporated by the secondary heat exchanger is overheated. Usually, the secondary heat exchanger and the primary heat exchanger in the working circuit are connected in series, so that the entire amount of the working fluid passes first the secondary heat exchanger and then the primary heat exchanger.

A development of the invention provides that the secondary storage circuit is connected to the solar collector of the solar circuit or to at least one further solar collector. It can be provided that the secondary storage fluid is not or only partially heated by heat transfer from the solar fluid. In this case, it makes sense to bring about the heating directly by solar radiation. For this purpose, the secondary storage circuit is connected to the solar collector and / or the further solar collector. In the former case, it can either be provided that the secondary storage circuit is fluidically connected to the solar circuit and insofar the Connection to the solar collector is present. Alternatively, however, the solar collector may also have a plurality of absorber lines, wherein one of the absorber lines is assigned to the solar circuit and a further one of the absorber lines is assigned to the secondary storage circuit. Accordingly, even with simultaneous connection of the secondary storage circuit and the solar circuit to the solar collector, the fluidic separation between the two circuits can be realized. In such an embodiment, it is of course possible that all solar panels of the solar cycle are connected to both the secondary storage circuit and to the solar circuit, to which they have several absorber lines. Subsequently, the mass flow through the absorber line of the secondary storage circuit and the absorber line of the solar circuit can be adjusted depending on the heat required for the respective circuit controlling and / or regulating. Alternatively or additionally, it is of course possible that the secondary storage circuit has a different from the solar collector of the solar circuit further solar collector and is connected thereto. In this case, it is not necessary to use solar panels with multiple absorber lines. The number of solar panels or other solar panels is selected according to the desired distribution of solar radiation to the secondary storage circuit and the solar circuit. A development of the invention provides that the secondary heat exchanger is a storage heat exchanger and / or the secondary storage circuit has a secondary heat storage. In this way, the amount of heat storable in the secondary storage cycle can be increased. Is the secondary heat exchanger as a storage heat exchanger, it is designed, for example, as a heat accumulator, which can be flowed through both by the fluid to be heated, in particular the working fluid of the working circuit, and the secondary storage fluid. In particular, the storage heat exchanger for this purpose has two separate heat exchangers, by means of which heat a storage medium can be removed or supplied. The storage medium is, for example, a salt, in particular a molten salt. For example, the storage medium is a salt mixture, in particular liquid salt mixture, of sodium nitrate and potassium nitrate. However, it is also possible to use other suitable substances. To this extent, the storage heat exchanger described above is preferably in the form of a heat storage tank arrangement, in particular a liquid salt tank arrangement, which has at least one heat storage tank, in particular a liquid salt tank. In such an embodiment, the secondary heat exchanger thus serves itself as a heat storage. Heat from heated fluid, in particular solar fluid of the solar circuit, is supplied to the storage medium via a first heat exchanger and heated accordingly. At the same time, heat is given off to the fluid to be heated, in particular working fluid of the working cycle.

Additionally or alternatively, the secondary storage circuit may have the secondary heat storage. This contains, for example, also a storage medium. The secondary heat accumulator can in principle have a heat storage tank, for example according to the above statements, in particular a liquid salt tank. The secondary heat accumulator has a heat exchanger, via which it or the storage medium present in it with the secondary storage circuit relationship way the secondary storage fluid is coupled heat transfer. Of course, the secondary heat accumulator can alternatively also be constructed analogously to the primary heat accumulator and thus have at least one secondary heat storage tank for the secondary accumulator fluid of the secondary accumulator circuit.

Basically, the storage medium of the secondary heat exchanger and the secondary heat storage can be chosen arbitrarily. For example, it is different from the solar fluid, the working fluid and / or the secondary storage fluid. The storage medium is, for example, a latent heat storage material or the like. It is preferably present as a phase change material. In particular salt, for example in the form of a molten salt, is used as the latent heat storage material. During normal operation, heat can now be supplied to the secondary heat exchanger or to the secondary heat storage tank from the solar circuit or the secondary storage circuit. In the storage operation, on the other hand, it is provided to remove heat from the storage heat exchanger or the secondary heat storage and to heat the solar fluid of the solar circuit and / or the working fluid of the working cycle and / or the secondary storage fluid of the secondary storage circuit and bring it to the desired temperature. In principle, therefore, the storage heat exchanger or the secondary heat storage can be assigned to any of the circuits or more of the circuits.

The storage heat exchanger and / or the secondary heat storage may be analogous to the above statements, in particular to the primary heat storage, formed, for example, visibly the insulation, the security envelope and / or the storage medium used. In particular, it is provided to exchange the storage medium between a plurality of heat accumulators, that is, storage heat exchangers or secondary heat accumulators. For example, one of the heat storage is not or only partially heated storage medium removed during normal operation, heated with heat from the solar circuit and then fed to another of the heat storage. The storage medium can already be brought to the desired temperature by heating once. However, it may also be provided that the storage medium is circulated several times between the plurality of heat accumulators, wherein with each circulation, the temperature of the storage fluid is increased by supplying heat from the solar circuit or the secondary storage circuit. If the solar radiation now falls under the design sun radiation, the storage operation is carried out with the aid of the secondary storage fluid present in the secondary storage circuit. According to the above embodiments, the storage medium is heated to the heat storage or at least one of the heat storage. The heat contained in this heat is supplied by means of a heat exchanger, which is assigned to the storage heat exchanger or the secondary heat storage, either the secondary storage circuit or directly to the working cycle. The storage medium is fluidically separated from the fluid connected to the storage heat exchanger and the secondary heat storage circuits. So there is no fluid connection between the storage heat exchanger or the secondary heat storage and the circuits, which he assigned. In principle, the storage heat exchanger or the secondary heat accumulator can be used to receive heat from any of the circuits in normal operation and to output it to any of the circuits in the accumulator operation. It is of course particularly preferred if the storage heat exchanger or the secondary heat storage during normal operation with heat from the solar circuit or the secondary storage circuit fed and thus the storage medium in it is heated. In the storage mode, the heat stored with the aid of the storage medium should preferably be delivered directly to the working cycle.

A development of the invention provides that the primary heat exchanger is present downstream of the secondary heat exchanger in the working cycle. It may be provided that the amount of heat to be introduced into the working fluid of the working cycle is transmitted solely by means of the primary heat exchanger or solely by means of the secondary heat exchanger. Preferably, however, first a first amount of heat by means of the secondary heat exchanger and then a second amount of heat by means of the primary heat exchanger is introduced into the working fluid. In the first case, either the primary heat exchanger or the secondary heat exchanger operates both as an evaporator and as a superheater. In the latter case, the secondary heat exchanger is preferably designed as an evaporator and the primary heat exchanger as a superheater. In this case, the primary heat exchanger and the secondary heat exchanger are particularly advantageously controlled and / or regulated in such a way that the working fluid in the secondary heat exchanger is merely vaporized without overheating it while this is already being done vaporized fluid in the primary heat exchanger is subsequently overheated.

A development of the invention provides that in the solar circuit a bypass for fluidic bypass of the solar collector and / or a bypass return, on its one side between the primary heat exchanger and an outlet of the primary heat storage tank and on its other side to an inlet of the Primary heat storage tanks is connected, are provided. In this respect, the bypass branches, for example, on its one side between the conveyor and the solar collector and opens on its other side between the inlet switching valve and the primary heat exchanger. By contrast, the bypass return can, for example, branch off on one side between the primary heat exchanger and the outlet switching valve and open on its other side between the inlet switching valve and the primary heat storage tank. The bypass thus serves to bridge the solar collector, so that the solar fluid passing through the solar fluid is guided past the solar collector. By contrast, the bypass return makes it possible to remove the solar fluid present in the primary heat store in the direction of flow through the primary heat store or the primary heat storage tank. Together with the bypass, removal of the stored solar fluid is made possible without having to subsequently guide it through the solar collector, whereby under certain circumstances - if the solar radiation is too low or too small - heat stored in the solar fluid could be released to an environment of the solar collector. In that regard, maintaining the rated power even at low solar radiation is ensured by the bypass and the bypass return. A development of the invention provides that in the working circuit downstream of the expansion turbine, a condenser is provided, which is operated with the ambient air as the cooling medium or at least a portion of the downstream of the expansion turbine in the working fluid present heat at least one heating circuit supplies. In the flow direction, the working circuit has in particular the elements listed below: the primary heat exchanger, the expansion turbine, the condenser, and a condensate pump, the latter being essentially a conveying device for the condensed working fluid. In the expansion turbine, the previously under high pressure and high temperature working fluid is expanded and cooled. At the same time, the working fluid begins to change from its gaseous state present in front of the expansion turbine into a liquid state.

During the expansion, care must be taken that the vapor content or vapor mass fraction present at the outlet of the expansion turbine is still sufficiently high to ensure reliable operation of the expansion turbine. Downstream of the expansion turbine so preferably still a majority of the working fluid is present as steam. In order to convert the vaporous part of the working fluid back into the liquid state in order to be able to feed it again to the primary heat exchanger and / or the secondary heat exchanger for heating or vaporizing, the working fluid must therefore be further cooled. For this purpose, the condenser is provided, in which the cooling and, accordingly, a transfer to the liquid state takes place. The condenser is essentially a heat exchanger which operates, for example, with ambient air as the cooling medium. ben will. That is, both the working fluid and the ambient air are supplied to the condenser in separate fluid streams to heat the ambient air and, correspondingly, to cool and condense the working fluid. The use of the ambient air as a cooling medium eliminates expensive devices, which are sometimes required for other cooling media.

Alternatively, the condenser can also be used as a heat exchanger between the working fluid present in the working cycle and the heating circuit. In this respect, at least part of the heat still present in the working fluid is transferred to the heating circuit or the heating circuit fluid present in the latter. The heat can subsequently be supplied for any purpose via the heating circuit.

For example, it is provided that the heating circuit comprises a sun collector heating, at least one radiator of a living space and / or a cooler, wherein a heating fluid used in the heating circuit by means of the radiator cooled or the heating circuit via the, in particular a heat pump with training, cooler on another heating circuit is connected. Especially at low ambient temperatures in the vicinity of the solar thermal power plant, it may happen that after a period of little or no sunlight, the solar panel is covered with condensed water or even ice, so only after a comparatively long period of time with solar irradiation made an operability of solar thermal power plant is. For this reason, the solar panel heater is provided with which the solar panel otherwise not required heat can be supplied. Thus, the condensed water or ice present on the solar collector can be eliminated quickly and the operational readiness of the solar thermal power plant can be established or maintained. Alternatively or additionally, the heating circuit may comprise the radiator of the living space, so that the heating circuit is used for heating the living space (or another room). Likewise, it may be provided that the heating circuit has the radiator. In this case, the heating circuit or the heating fluid used therein can be brought to a lower temperature by means of the cooler, for example if the temperature present in the heating circuit is too high, but no heat has to be expended for operating the solar collector heater or the radiator.

Alternatively, the radiator may constitute a heat transfer connection between the heating circuit and another heating circuit. Thus, the further branching of the heat originally incurred at the condenser of the working cycle is possible. The cooler may in a further embodiment, the heat pump with form, so represent a part of the same. In this way, the further heating circuit is operable at a higher maximum temperature than the heating circuit itself.

A development of the invention provides that the critical temperature in the critical point of the solar fluid at least by a factor of 1, 5, preferably by at least a factor of 2, 2.5 or 3, is greater than the critical temperature in the critical point of Ar - Beitsfluids, or that the solar fluid is a thermal oil and the critical see temperature of the working fluid is at most 160 ° C. This means that the solar circuit can always be operated subcritically, that is, the solar fluid never exceeds its critical temperature and / or its critical pressure, which are in the critical point. Nevertheless, even in the subcritical operation of the solar circuit, the temperature of the solar fluid is sufficient to vaporize and possibly overheat the working fluid whose critical temperature is significantly lower. Even at low temperatures of the solar fluid after the solar collector and / or the Sekundärspeicherfluids in the secondary storage cycle so that contained in this enthalpy, in particular the internal energy sufficient to evaporate the working fluid in the primary heat exchanger and / or secondary heat exchanger and / or overheat and so in the expansion turbine usable. The available enthalpy of the solar fluid and / or the secondary storage fluid is correspondingly greater than the evaporation enthalpy of the working fluid necessary for the evaporation, which is necessary in order to convert it from a liquid to a gaseous state. The more clearly the critical temperature of the solar fluid exceeds the critical temperature of the working fluid, the more efficient the solar thermal power plant according to the invention operates. However, care must be taken to ensure that the working fluid has properties which permit its use in the working cycle without, for example, unrealistically high pressures being required before or in the primary heat exchanger or secondary heat exchanger. The solar thermal power plant presented here is suitable for any nominal power range, which can be represented by appropriate design. The rated power is preferably provided in the form of electric current, but other forms of energy, such as mechanical work, can be realized.

The factors mentioned refer to the critical temperatures with the unit degrees Celsius. In other units correspondingly other factors may arise, but these can be determined from the stated values. For example, in the unit Kelvin, the factor is at least 1.5; 1, 6; 1, 75 or 2.0. Alternatively or additionally, the boiling point temperature of the solar fluid in the unit Kelvin by a factor of at least 1, 3, for example at least 1.4; at least 1, 5 or at least 1, 6, greater than the boiling point temperature of the working fluid.

Due to the difference between the critical temperatures of the solar fluid and the working fluid or the low critical temperature of the working fluid of the working cycle can be operated at lower compared to known power plants temperatures. For example, the working fluid in the primary heat exchanger and / or the secondary heat exchanger is heated at a pressure of 60 bar to about 130 ° C, vaporized or superheated, and then fed to the expansion turbine. Even with a sharp drop in temperature in the solar circuit due to reduced solar radiation or in the secondary storage cycle by removing a large amount of heat, it is thus possible without falling below a rated power of the solar thermal power plant to produce further mechanical energy and corresponding electric current by means of the expansion turbine. With sufficient solar radiation, electricity is generated according to the nominal power. Due to the process is usually a minimum temperature of about 10 K between the solar fluid and the secondary storage fluid and the working fluid in the primary heat exchanger or the secondary heat exchanger necessary to transfer a sufficiently large amount of heat from the solar fluid or the secondary storage fluid to the working fluid and ensure during operation of the expansion turbine. Of course, under certain circumstances, however, an operation can also be carried out at a lower temperature difference. Alternatively, it can also be provided that the solar fluid is a thermal oil and the critical temperature of the working fluid is at most 160 ° C. Instead of the term "thermal oil", the term "thermal oil" can also be used. The above statements, in particular with regard to the structural design of the solar thermal power plant, remain valid in principle. The thermal oil may be, for example, a mineral oil or a synthetic oil. The former is a hydrocarbon and is made from petroleum. The latter is a synthetically produced oil, for example from the group of siloxanes, wherein in particular polymeric siloxanes are used. Examples of synthetic oils are silicone oils which are present, for example, as methylsiloxanes or phenylsiloxanes. Often, no critical point can be specified for thermal oil. In particular, thermal cracking occurs at many thermal oils above a certain temperature, at which the thermal oil or long-chain hydrocarbons contained therein are split into hydrocarbons with a shorter chain length. Nevertheless, to achieve the advantages described above, it is now provided to indicate the critical temperature of the working fluid absolute. This should not exceed 160 ° C, but can Of course, be less. In particular, the critical temperature of the working fluid is at most 150 ° C, 140 ° C, 120 ° C, 100 ° C, 80 ° C or 40 ° C.

A further development of the invention provides that the solar fluid present in the solar cycle and / or the secondary storage fluid present in the secondary storage circuit is water or a thermal oil and / or the working fluid present in the working cycle is water or a hydrocarbon, in particular an alkane , preferably propane or butane, or carbon dioxide, ammonia or a mixture of these substances. In principle, the solar fluid, the working fluid and the secondary storage fluid can be chosen arbitrarily. Particularly preferably, the solar fluid is liquid at realizable pressures, for example at about 75 to 100 bar, and the temperatures present in the solar circuit. A phase change of the solar fluid in the solar cycle from liquid to gaseous state is disadvantageous because under some circumstances the entire solar cycle is destabilized. In the liquid state, by contrast, the maximum amount of heat can be transported from the solar collector to the primary heat exchanger and / or secondary heat exchanger by means of the solar fluid, so that the efficiency of the solar thermal power plant remains optimal in this area.

At the same time, the working fluid present in the working cycle, as already described above, should have such a low critical temperature that reliable operation of the working cycle is ensured even at low temperatures in the solar circuit or the secondary storage circuit. Suitable fluids can be found, for example, in the substance group of the Koh Hydrocarbons, especially the alkanes. Preferably, the working fluid is propane or butane. Alternatively, however, carbon dioxide, ammonia or a mixture of the substances mentioned can be used as the working fluid. Of course, both in the solar fluid and in the working fluid impurities and the like may be present, which, however, not or only slightly affect the essential properties. The critical point of water is reached at a critical temperature T _c = 374.12 ° C and a critical pressure p _c = 22.12 MPa. The critical points of propane, butane, carbon dioxide and ammonia are at T _c = 96.9 ° C and p _c = 4.2 MPa; T _c = 152.01 ° C and p _c = 3.776 MPa; T _c = 31 ° C and p _c = 7.38 MPa and T _c = 132.4X and p _c = 11, 3 MPa. It becomes clear that the critical temperatures of the substances specified for the working fluid are at least a factor of 1.5, but in some cases considerably more, than the critical temperature of the water. For example, a factor of 2; 2.5; 3 or more ago.

Specifically, the critical temperature of the working fluid is at most 40 ° C, 80 ° C, 100 ° C, 120 ° C, 140 ° C, 150 ° C or 160 ° C (these values and all values therebetween as well as the above temperatures for the specifically including specific substances). By contrast, the critical temperature of the solar fluid is, for example, at least 150 ° C., 200 ° C., 250 ° C., 300 ° C., 350 ° C. or 375 ° C., again these, the values lying between them and the critical temperatures mentioned for the including concrete substances. In this case, preferably at least said factor between the critical temperatures of the two fluids should be present. Additionally, the working fluid may include an admixture having, for example, a higher condensation temperature and / or a higher condensation pressure. In this way, the stated values of the working fluid can be influenced in the direction of a higher temperature or a higher pressure. Thus, it becomes possible to increase the temperature and / or the pressure upstream of the expansion turbine and still achieve after relaxing in this one state in the wet steam region, in particular on the dew line. Accordingly, if the structure of the power plant is otherwise unchanged after the expansion turbine, there is likewise a higher temperature or a higher pressure. This increases the residual heat present at this time, which can be supplied via the capacitor to other destinations. For example, the heat thus available in the seawater desalination plant described above can be used for evaporation and thus for desalinating seawater. The electrical power also generated may serve to operate other facilities of the seawater desalination plant, for example, pumps, controllers, and the like. The admixture is preferably also an alkane, especially ethane.

The solar thermal power plant has the fluids differing by the named factor additionally or alternatively to the primary heat store. To this extent, they are a further unique feature of the solar thermal power plant presented here, which means significant advantages over the power plants known from the prior art. The invention further relates to a method for operating a solar thermal power plant, in particular a power plant according to the foregoing, wherein the solar thermal power plant has at least one solar collector of a solar circuit and an expansion turbine associated with a working cycle, wherein the solar circuit and the working circuit coupled together via at least one primary heat exchanger and in the solar circuit a solar fluid and in the working cycle a working fluid is used. It is provided that the solar cycle a primary heat accumulator is assigned, which has at least one, in particular parallel to the primary heat exchanger connected, primary heat storage tank for the solar fluid of the solar circuit.

For operating the solar thermal power plant, the solar fluid in the solar circuit and the working fluid are circulated in the working circuit, for which purpose the pump and in the working circuit the condensate pump are provided in the solar circuit. In the primary heat exchanger, the heat or enthalpy present in the solar fluid after the solar collector is used to evaporate the working fluid by introducing at least the evaporation enthalpy and / or in particular to overheat by supplying additional heat. The solar thermal power plant used in this case can be developed according to the above statements. A development of the invention provides that at least one secondary heat exchanger is provided, via which the working cycle and / or the solar circuit with at least one secondary storage circuit having a secondary storage fluid can be disposed. In normal operation, and at a solar radiation which is smaller than the design sun radiation, a storage operation is performed, wherein in normal operation, the working fluid of the working circuit evaporated and superheated only with the secondary heat exchanger and in the Storage operation with the secondary heat exchanger only evaporated and with the primary heat exchanger only superheated. In addition to the primary heat exchanger already described above so the secondary heat exchanger is provided, which ensures a thermal coupling with the secondary storage circuit.

The solar thermal power plant or the primary heat exchanger and the secondary heat exchanger are now operated depending on the instantaneous solar radiation. In the normal operation, the secondary heat exchanger or the amount of secondary storage fluid supplied to it is adjusted such that the amount of heat transferred to the working fluid is sufficient to vaporize it and subsequently to overheat it. In normal operation, the secondary heat exchanger therefore serves as a combined evaporator and superheater. In contrast, the primary heat exchanger is not or only slightly acted upon by the solar fluid of the solar circuit, so that the working fluid in it no further heat is supplied. The working cycle is operated in this respect only with heat from the secondary storage circuit. However, it may well be provided that the secondary storage circuit is connected fluidically to the solar circuit or is part of this. If the solar thermal power plant is to be operated in the storage mode, then the secondary heat exchanger or the throughput of the secondary storage fluid supplied to it is set in such a way that the heat transferred to the working fluid only evaporates it. In the storage operation, therefore, no overheating of the working fluid should take place in the secondary heat exchanger. This is provided in the primary heat exchanger, which is present in the working circuit downstream of the secondary heat exchanger. The primary heat exchanger or the throughput of the solar fluid supplied to it is accordingly set in such a way that the already evaporated working fluid supplied to it is overheated.

A further development of the invention provides that in normal operation the solar circuit is operated exclusively for charging the first primary heat accumulator. According to the above explanations, the evaporation and overheating of the working fluid in normal operation should be carried out exclusively by means of the secondary heat exchanger. Accordingly, if the solar circuit and the secondary storage circuit are not fluidly connected, the heat present in the solar circuit is not required for the evaporation and / or overheating of the working fluid. Accordingly, it is fed to the primary heat storage or used to charge it. In this way, in the normal operation, a particularly fast charging of the first heat accumulator can be ensured, so that it is preferably fully charged in a storage operation following the normal operation.

In the method described can analogously to the solar thermal power plant according to the above explanations provided hen that the critical temperature in the critical point of the solar fluid at least by a factor of 1, 5, preferably by at least a factor of 3, is greater than the critical temperature in the critical point of the working fluid, or that as a solar fluid, a thermal oil is used and the critical temperature of the working fluid is at least 160 ° C.

A development of the invention provides that the solar thermal power plant is adjusted such that the solar fluid used in the solar cycle has a maximum temperature, in particular in or immediately after the solar collector, which is lower than its critical temperature, and / or that in Working fluid used in the working cycle has a maximum temperature, in particular in or immediately after the primary heat exchanger and / or secondary heat exchanger, which is greater than its critical temperature. The setting of the solar thermal power plant takes place in particular by adjusting the respective fluid flow rate at the conveying means of the solar circuit and / or at the condensate pump of the working circuit and / or a conveying means of the secondary storage circuit and the inlet switching valve and the Auslassschaltventils. The setting can be done controlling and / or regulating. The maximum temperature of the solar fluid is usually in or immediately after the solar collector, in which the solar thermal energy is introduced into the solar fluid. This maximum temperature should always be below the critical temperature of the solar fluid so that the solar fluid is always in liquid form. This means, of course, that the pressure of the solar fluid in the solar circuit must be selected to be correspondingly high. For example, the maximum temperature of the solar fluid is at least 10% to 30%, for example about 15% to 20%, low. ger as the critical temperature, the indicated values are based on the latter.

The working fluid present in the working cycle usually has its maximum temperature in or immediately after the primary heat exchanger and / or the secondary heat exchanger, in which heat is transferred from the solar fluid or the secondary storage fluid to the working fluid. This should be done in such a way that the working fluid has a maximum temperature which is greater than the critical temperature of the working fluid. In that regard, in particular in the primary heat exchanger overheating of the working fluid should be made. As already stated above for the solar fluid, of course, the pressure of the working fluid must be selected such that it is also greater than or equal to the critical pressure. Accordingly, it can also be provided correspondingly that the solar thermal power plant is additionally adjusted in such a way that the solar fluid used in the solar circuit is present under a pressure which is less than the critical pressure of its critical point, and / or the working fluid used in the working cycle under a pressure greater than the critical pressure of its critical point.

In a particular embodiment of the invention, it is provided that the maximum temperature and the pressure of the solar fluid are selected so that they lie on the boiling line of the solar fluid. At least, however, no change of state of aggregation should take place. The solar fluid is so far always completely in liquid form and not, not even partially, as a gas. If the condition, then Temperature and pressure, the solar fluid is disposed on or at least near the boiling line, this can absorb a maximum amount of heat in the solar collector and transport in the direction of the heat exchanger. In this respect, optimal efficiency is realized with such a choice of maximum temperature and pressure in the solar circuit.

A development of the invention provides that the maximum temperature of the working fluid is chosen so that the working fluid after the expansion turbine occupies a state in its wet steam region and at least a certain vapor content, in particular between 0.75 and 1, 0, has. The vapor content may also be referred to as the vapor mass fraction and indicates the distribution of the fluid in the wet steam region to its liquid and gaseous phases. At a vapor content of 0 or 0%, the working fluid is accordingly present only in liquid form, with a vapor content of 1 or 100% exclusively in gaseous form. To ensure effective operation of the solar thermal power plant or its working cycle, the state of the working fluid after the expansion turbine must be in the wet steam region of the working fluid. In this way it is ensured that the maximum proportion of the thermal energy contained in the working fluid is converted into mechanical energy in the expansion turbine.

Immediately before the expansion turbine, the working fluid is exclusively in the gaseous state; the state is therefore so far on the dew point of the working fluid or even when the working fluid was overheated in the heat exchanger, at higher temperature and / or higher pressure. While relaxing of the working fluid in the expansion turbine, the instantaneous state shifts in the direction of the dew-line or into the wet-steam area. However, in order to ensure a high efficiency of the expansion turbine, the steam content must not drop too much. In particular, the steam content should always be greater than the specific steam content, this being, for example, between 0.75 and 1.0 (including these values). Preferably, the determined vapor content is greater than or equal to 0.9, that is less than 1.0.

Finally, it may additionally or alternatively be provided that an inlet switching valve and an outlet switching valve of the primary heat accumulator of the solar circuit are adjusted so that the temperature of the working fluid remains constant immediately after the primary heat exchanger regardless of solar radiation to the solar collector at least over a certain period. The setting can be done controlling and / or regulating. On the inlet switching valve and the outlet switching valve and the primary heat storage has already been discussed above. The primary heat accumulator has the primary heat storage tank connected fluidically to the solar circuit. If there is sufficient solar irradiation on the solar collector (at least the design solar irradiation correspondingly), the solar fluid present in the primary heat storage tank is heated. If the solar radiation is below the design solar irradiation or is completely eliminated, the already heated solar fluid present in the primary heat accumulator is removed, transferred to the working fluid for operating the solar circuit and thus used for the constant delivery of the rated output. In addition, the heat present in the secondary storage circuit can also be used. In particular, no ex- Energy, such as fossil energy supplied to ensure the operation of the work cycle and the output of the rated power.

The working cycle can thus be operated with the stored heat in the primary heat storage or the solar fluid and / or the secondary storage circuit at least over the specific period of time - which can also be referred to as design period - under delivery of constant rated power, wherein the working fluid after the primary heat exchanger and / or the secondary heat exchanger always at least approximately the same temperature has or does not fall below. For this purpose, the inlet switching valve and the outlet switching valve, which determine the inflow and outflow of the solar fluid from the primary heat storage are to be adjusted such that the exiting from the primary heat exchanger working fluid has a substantially constant temperature, regardless of the current solar radiation on the Solar collector, ie both in normal operation and in storage operation. Such operation of the working cycle and the constant output of the rated power are made possible in particular by the primary heat accumulator, by means of the secondary accumulator circuit and / or by the ratio of the critical temperature and the solar fluid and the working fluid to each other. If the primary heat store has a plurality of primary heat storage tanks, the solar thermal power plant can be operated particularly advantageously in the storage operation. It is provided that only at least one of the primary heat storage tanks serves to store the heated during normal operation solar fluid. This primary heat storage tank is referred to below as a source tank. At least one of the primary heat storage tanks, however, is emptied during normal operation or is already in an empty form, so that it is at least partially, preferably completely, empty at the beginning of operation. This primary heat storage tank is referred to below as a target tank or "swap tank." Ideally, there are just as many source tanks as target tanks, to remove only the source tank of solar fluid and only to the target tank, the primary heat storage corresponding actuators, in particular control valves on By means of the latter, the solar fluid supplied to the primary heat accumulator can be distributed in a targeted manner to the primary heat storage tanks, thus in particular fed to a specific one of the primary heat storage tanks.

At the beginning of the storage operation so the source tank is filled with heated solar fluid while the target tank is empty. During the storage operation, the source tank is now used to use the solar fluid to operate the working cycle while maintaining the constant rated power. Subsequently, however, the solar fluid is no longer returned to the source tank, but rather introduced into the target tank. Thus, cooling of the still existing in the source tank solar fluid is avoided by the recycled solar fluid. Accordingly, there is always solar fluid at high temperature, namely almost ideally during normal operation reached temperature, available. Of course, the temporary storage and the heat losses occurring during this process can result in a slight temperature drop in the source tank. However, this is significantly lower than a temperature drop caused by the return of the solar fluid into the source tank.

It is particularly advantageous if, during normal operation, the solar fluid is taken from the target tank (filled after storage operation) and, after heating in the solar collector, is supplied to the source tank (empty after storage operation). In this way, only already heated solar fluid at a correspondingly high temperature is present in the source tank. In a storage operation immediately following normal operation, this makes it possible to use high-temperature solar fluid and correspondingly extremely efficient heating of the working fluid in the primary heat exchanger. In the described procedure, the primary heat storage tanks used as source tanks in the first normal operation or storage operation are used in the subsequent storage operation or normal operation as destination tank and vice versa. In that regard, there is an alternating use of the primary heat storage tanks as a source tank and as a target tank. Accordingly, all of the primary heat storage tanks are at least temporarily used as swap tanks or swap tanks because emptying the swelling tank causes a pressure drop and a filling of the target tank causes a pressure increase, these primary heat storage tanks preferably have a pressure equalizing means respective Primary heat storage tank balanced, so that the pressure can be kept substantially constant. For example, in each case at least one source tank and at least one target tank via at least one pressure equalization line or Pendellei- direction fluidly connected to each other. In this case, the respective volume not filled with the solar fluid in the source tank and / or the target tank is preferably filled with a filler. For example, as the filler, a gaseous agent which is advantageously substantially inert to the solar fluid can be used under the conditions prevailing in the solar cycle. In particular, nitrogen is used as the filler. The pressure equalization line is now connected to the source tank and the target tank, that only the filler, but not the solar fluid, can be exchanged between it for pressure equalization. Alternatively, the internal volume of the respective primary heat storage tank can be variable.

It should be pointed out that the division into source tank and target tank described here is essentially possible only on the basis of the above-described reduction of the necessary storage volumes of the primary heat store, which is significant in comparison with the prior art. For the known power plants, such an approach is hardly feasible because the space required for the corresponding heat storage would simply be too large.

The invention will be explained in more detail below with reference to the exemplary embodiments illustrated in the drawing, without the invention being restricted. Show it: 1 shows a schematic representation of a solar thermal power plant in a first embodiment,

2 shows the solar thermal power plant in a second embodiment, wherein a heating circuit is provided in addition to a solar circuit and a working cycle,

FIG. 3 shows a schematic detail of the heating circuit, which in particular has a solar panel heater 31,

4 shows the solar thermal power plant in a third embodiment, in which a secondary storage circuit is provided,

Figure 5 shows the solar thermal power plant in a fourth embodiment, which also has the secondary storage circuit, and

Figure 6 shows the solar thermal power plant in a fifth embodiment.

FIG. 1 shows a schematic representation of a solar thermal power plant 1 in a first embodiment, which essentially has a solar circuit 2 and a working circuit 3. The solar circuit 2 comprises at least one solar collector 4, an inlet switching valve 5, a primary heat exchanger 6, an outlet switching valve 7 and a conveyor 8 (seen in a main flow direction during normal operation of the solar thermal power plant 1). In addition, the solar circuit 2 is a primary heat accumulator 9 with at least one primary märwärmespeichertank 10 assigned. Between the individual elements line sections 11 to 17 are provided to produce a respective flow connection. In addition, there are a bypass 18 and a bypass return 19. To the inlet switching valve 5, the solar collector 4, the primary heat exchanger 6 and the primary heat storage tank 10 via the respective line section 11, 12 and 16 are connected. On the outlet switching valve 7, however, the primary heat exchanger 6, the conveyor 8 and also the primary heat storage tank 10 via the line sections 13, 14 and 17 are fluidly connected. On the outlet switching valve 7 side facing away from the conveyor 8 is connected via the line section 15 of the solar collector 4 fluidically. Thus, the primary heat accumulator 9 is arranged substantially parallel to the primary heat exchanger 6 in the solar circuit 2. The primary heat storage tank 10 or its storage volume is fluidically connected directly to the solar circuit 2. In that regard, it serves for the intermediate storage of at least part of the solar fluid present in the solar circuit 2. Preferably, the primary heat storage tank 10 can accommodate a volume of the solar fluid, which corresponds to a multiple of the present in the other areas of the solar circuit 2 volume of the solar fluid.

The working cycle 3 consists of the primary heat exchanger 6, an expansion turbine 20, a condenser 21 and a condensate pump 22. These elements are in turn fluidly connected to each other via line sections 23 to 26. The expansion turbine 20 and an output shaft 27 of the expansion turbine 20 is, for example, to a generator 28 for Generation of electricity connected. The expansion turbine 20 is preferably designed as a steam turbine. It can be formed in one or more stages with the series connection of several expansion turbine stages. The upstream - so upstream in the flow direction - expansion turbine stage is so far, for example, as a high-pressure turbine stage, the downstream downstream designed as a medium-pressure turbine stage and a low-pressure turbine stage. Needless to say, however, the medium-pressure turbine stage can be omitted, so that only the high-pressure turbine stage and the low-pressure turbine stage are present. Likewise, there may be a plurality of high-pressure turbine stages and / or a plurality of intermediate-pressure turbine stages and / or a plurality of low-pressure turbine stages. The respective flow direction is indicated in FIG. 1 in the respective line section 11 to 17 or 23 to 26, in each case by an arrow.

The embodiment shown here is directed to solar thermal power plants 1 with any nominal power. In particular, both small rated power up to 2 MW, average rated power of 2 MW to 5 MW, as well as large power ratings of more than 5 MW can be realized. It consists of the two thermally coupled circuits, namely the solar circuit 2, in which the solar fluid is present, and the working circuit 3, which operates with a working fluid. With the aid of the two circuits 2 and 3, the solar thermal heat of the solar collector 4, which is in particular part of a solar field, received in an absorber tube of the solar fluid of the solar circuit 2 and heated and either the integrated into the solar circuit 2 primary heat accumulator 9 or the primary heat exchanger. 6 supplied in which the solar fluid of the solar circuit 2 with the working fluid of the working group run 3 is thermally coupled. The absorber tube is for example part of a parabolic trough of the solar collector 4 or passes through it in or in the region of its focal line. The solar field has at least the solar collector 4, but preferably has a plurality of solar panels 4. Their absorber tubes can either be connected in parallel flow or in series. Of course, it is also possible that some of the solar panels 4 parallel and again other of the solar panels 4 are connected in series. Due to the temperature difference between the solar fluid in the primary heat exchanger 6 is transferred in this heat from the solar fluid to the working fluid to its evaporation and preferably overheating. Subsequently, the vaporized and in particular superheated working fluid is supplied to the expansion turbine 20 for the purposes of stress relief, wherein mechanical energy is released, which is then converted in the generator 28 into electrical energy, for example for feeding into a power grid. The relaxed, at least partially gaseous working fluid is condensed in a, for example, air or water cooled condenser 21 and supplied again by the condensate pump 22 to the primary heat exchanger 6 on the side of the working cycle 3. Then the evaporation and preferably overheating process of the working fluid begins again.

The solar fluid of the solar circuit 2 which cools down when heat is released to the working fluid is fed back via the conveying device 8, in particular a pump, to the solar collector 4 or its absorber tube for renewed absorption of solar heat. The presented here solar thermal power plant is here both for the direct power generation during the day, so with sufficient sunlight (which is greater than or equal to a design sun radiation) on the solar panel 4, as well as for the storage of heat generated during the day for night operation or storage operation by means of the primary heat accumulator 9.

In the solar thermal power plant 1 presented here, for example, in the solar circuit 2 and the working circuit 3, fluids, namely solar fluid and working fluid, are used which reach their respective boiling point at different temperatures and pressures. The solar circuit 2 and the primary storage 9, for example, work with water or thermal oil as a solar fluid whose temperature is after the solar collector 4 290 ° C at about 75 bar. Thus, the state of the solar fluid is below its critical point (T _c = 374.12 ° C and p _c = 22.12 MPa for water). Preferably, the solar fluid after the solar collector 4 is in a state that lies on the boiling line of the solar fluid. In this state, the solar fluid can absorb its maximum amount of heat. For this reason, it can also be used simultaneously as storage fluid in the primary heat accumulator 9. As already stated, thermal oil can also be used as the solar fluid instead of the water.

The working cycle 3 operates, for example, with an alkane, for example propane, as the working fluid which is heated by heat supply and preferably overheating in the primary heat exchanger 6, for example at a temperature of 130 ° C. and a pressure of 60 bar, ie in particular in a supercritical state. the expansion turbine 20 is supplied. Due to the considerable temperature difference between see the fluids of the two circuits 2 and 3 of 160 K is a continuous heat transfer from the solar fluid of the solar circuit 2 causes the working fluid of the working circuit 3, which turns out to be largely stable even with reduced solar radiation with concomitant drop in temperature at the solar collector 4.

The performance of the solar thermal power plant 1 is designed so that both the heat for direct power generation by means of the expansion turbine 20, as well as the required amount of solar heat for night operation, in which the solar radiation is below the design sun radiation is taken during the day in normal operation. The heat is absorbed by the circulating in the solar circuit 2 at pressures of about 75 bar to about 125 bar solar fluid in the solar collector 4, wherein it heats up to about 290 ° C. During normal operation, ie in particular during the daytime, the amount of heat absorbed in this way is transferred to a specific part (for example to one third) on the working cycle 3 working with the working fluid for direct generation of mechanical energy with subsequent conversion into electrical energy. The remaining part of the amount of heat absorbed by the solar collector 4 is stored at the given pressure of the solar fluid in the primary heat accumulator 9 for operation at low solar radiation, ie a storage operation, in particular night operation. The solar fluid in the solar circuit 2 including the primary heat accumulator 9 incorporated therein absorbs at the aforementioned pressure and the aforementioned temperature the highest thermal storable amount of heat that is substantially greater than that Amount of heat required to evaporate and overheat the working fluid in the working cycle 3 during low sunshine storage operation to maintain the performance of the solar thermal power plant 1. If the solar radiation falls below the design sun radiation, the system switches from normal operation to storage operation. The heat required to maintain the (rated) power of the solar thermal power plant 1 is now taken from the primary heat accumulator 9, wherein the extracted solar fluid at the beginning (at previously fully charged primary heat accumulator 9) has a temperature of about 290 ° C.

The extracted solar fluid is fed to the primary heat exchanger 6 for evaporation and preferably overheating of the working fluid to further about 130 ° C. The vaporized or superheated working fluid is supplied in a gaseous state to the expansion turbine 20 at supercritical pressure and supercritical temperature. As already described above, the mechanical energy generated is converted into electrical energy. The amount of heat transferred from the primary heat accumulator 9 to the working cycle 3 during the storage operation at low solar irradiation has - due to the cooling of the solar fluid contained in the solar circuit 2 - a steady reduction in the temperature difference between the primary heat accumulator 9 and working cycle 3 necessary for the heat transfer. However, only about 80% of the available at the initial temperature difference of, for example 160 K and usable amount of heat transferred to the working cycle 3 during operation at low solar radiation at full power plant performance, so that the process-related necessary minimum temperature difference of about 10 K between the solar fluid of the primary heat accumulator 9 and the vaporized or superheated working fluid is not exceeded even while maintaining full power plant rated power. In this way, both a daytime operation or normal operation and a nighttime operation or storage operation without supply of external heat between sunset on a first day and sunrise on a second day following the first day, ie over a period of, for example, more than eight hours guaranteed , The period of time which should be bridgeable with the memory operation can be referred to as the design period.

This means that the solar thermal power plant is about 1 g load capacity and not, as well known power plants, which rely on renewable energies, is only suitable for covering peak loads. By the storage operation is ensured even without supply of external energy that over the design period - on which in particular the primary heat accumulator 9 or its storage volume is tuned - constant, the rated power of the solar thermal power plant 1 is achieved. Accordingly, the solar thermal power plant 1 presented here is largely weather-independent, which means a good predictability of the electrical power generated and, accordingly, the presence of the base load capacity. When cloudy and associated reduced solar radiation, the temperature of the solar fluid in the solar circuit 2 drops. This reduces the temperature difference to the ar- Beitsfluid in the working cycle 3, the temperature of the process for maintaining the evaporation ungs and especially the overheating process at about 130 ° C should be kept constant. The height of the drop in temperature in the solar circuit 2 corresponds to the reduction of the temperature difference to the working cycle 3. As soon as the initial temperature difference of 160 K (in normal operation, ie at a solar radiation that is greater than or equal to the design sun radiation) is reduced by more than 150 K. , which would be below the procedural necessary minimum temperature difference of about 10 K result, the solar thermal power plant to maintain power generation with full rated power to the storage operation, ie an operation taking out stored in the primary heat storage 9 solar fluid to. Alternatively, of course, the switching to the memory operation already at a lower reduction of the temperature difference, ie already at a higher temperature of the solar fluid, or take place only at a greater reduction.

In the operation of the solar thermal power plant 1, this is preferably set such that the solar fluid used in the solar circuit 2 has a maximum temperature which is lower than its critical temperature. Alternatively or additionally, the adjustment can be made such that the working fluid used in the working cycle 3 has a maximum temperature that is greater than its critical temperature. The same applies with regard to the critical pressure of the two fluids. Particularly preferably, the maximum temperature and the pressure of the solar fluid should lie on the boiling line of the solar fluid. The solar thermal power plant 1 is set in such a way that, independently of a solar irradiation tion on the solar collector 4, the temperature of the working fluid immediately after passing through the primary heat exchanger 6 at least over a certain period of time, the design period remains constant. If this can not be ensured, the temperature of the solar fluid should always be at least high enough, even when solar fluid is removed from the primary heat accumulator 9, that evaporation and / or overheating of the working fluid in the primary heat exchanger 6 and thus operation of the working cycle 3 or its expansion turbine 20 always, so regardless of the solar radiation to the solar collector 4, in particular while maintaining the rated power of the solar thermal power plant 1, is possible.

In conclusion, it should be pointed out that the solar thermal power plant 1 can, in principle, be designed for operation at any suitable temperature, in spite of the temperatures given above purely by way of example. The solar circuit 2 can therefore also be operated at a different temperature of 290 ° C (at then correspondingly adapted pressure) and the working cycle 3 at a temperature deviating from 130 ° C temperature. As explained, in the solar thermal power plant 1 presented here during the design period, the supply of external energy is not necessary. On the basis of the above explanations, it becomes clear that the bridging over of the design period is also possible in particular because of the primary heat accumulator 9, which serves for the direct intermediate storage of the solar fluid. In the primary heat storage 9, therefore, no heat exchanger is included, which transfers heat from the solar fluid to a (heat) storage medium during normal operation. The heat is removed from the storage medium and supplied to the solar fluid for carrying out the storage operation. Rather, the entire storage volume of the primary heat store 9 or its primary heat storage tank 10 can be flowed through by the solar fluid. The primary heat accumulator 9 in this case has a storage volume which is sufficiently large and is tuned in particular to the design period.

The advantages achieved by the primary heat accumulator 9 can be further improved by the appropriate choice of solar fluid and working fluid. In particular, the critical temperature in the critical point of the solar fluid - in degrees Celsius - at least by a factor of 1, 5 should be greater than the critical temperature in the critical point of the working fluid. However, the critical temperature of the solar fluid is preferably significantly greater, for example by at least a factor of 3, than the critical temperature of the working fluid. On an absolute scale with the unit Kelvin, factors of at least 1.5 exist; for example, at least 1, 6; at least 1, 75 or at least 2.0. Alternatively or additionally, the boiling point temperatures of the two fluids differ - on an absolute scale with the unit Kelvin - by factors of at least 1.3; for example, at least 1, 4; at least 1, 5 or at least 1, 6. The boiling point temperature of the working fluid is, for example, at least 100 K lower than that of the solar fluid. 2 shows a second embodiment of the solar thermal power plant 1. This corresponds in principle to the already presented with reference to FIG 1 embodiment, so far reference is made to the above statements. In addition to that already described solar thermal power plant 1 here is a heating circuit 29 is provided, in which a heating fluid is used. The heating fluid passes through the condenser 21 and serves as a coolant for the working fluid. In the condenser 21, in this respect downstream of the expansion turbine 20, heat still contained in the working fluid is transferred to the heating fluid of the heating circuit 29, and thus the working fluid is cooled. The heating circuit 29 has a circulating pump 30 with which the heating fluid is circulated through the heating circuit 29. The heating circuit 29 comprises, for example, a solar collector heater 31. The solar collector heater 31 serves to heat the solar collector 4 or a reflector (not shown) of the solar collector 4. The mass flow of the heating fluid flowing through the solar collector heater 31 can be controlled and / or regulated by means of a cross section adjustment member 32 become. Parallel to the solar panel heater 31 and the Querschnittsverstellglied 32 is in the heating circuit 29, a radiator 33, the mass flow rate by means of a further Querschnittsverstellglieds 34 is also adjustable. The Querschnittsverstell- member 34 is preferably formed automatically, so opens when there is a certain pressure in the condenser 21. In this way, the distribution of the heating fluid to the solar panel heater 31 and the radiator 33 can be adjusted solely by means of Querschnittsverstellglieds 32. If a large mass flow is to flow through the solar collector heater 31, the cross-section adjustment member 32 is opened, with the cross-section adjustment member 34 automatically closing at the same time. When the cross-section adjustment member 32 is closed, on the other hand, the transverse opening Schnittverstellglied 34, because by the circulation pump 30, the pressure present in the condenser 21 increases.

FIG. 3 shows a schematic detail view of the heating circuit 29. In contrast to the heating circuit 29 described with reference to FIG. 2, to the description of which reference is made in principle, the cooler 33 is designed as an evaporator in a heat exchanger whose further constituent is a compressor 36 and a capacitor 37 are. By means of the heat pump, heat is transferred from the heating circuit 29 to a further heating circuit 35, wherein the temperature after the heat pump in the further heating circuit 35 may be higher than the temperature in the heating circuit 29. The throughput through the heat pump can be adjusted via a throttle element 38 or be constantly elected. The further heating circuit 35 has a flow side 39 and a return side 40, wherein the fluid of the further heating circuit 35 and the flow side thereof, for example, a radiator of a living room is supplied. Subsequently, the fluid reaches the return side 40 and is correspondingly re-supplied to the condenser 37 of the heat pump. The fluid can in principle be chosen arbitrarily. However, water is particularly preferably used.

In the embodiments of the solar thermal power plant 1 described above, it may of course be provided that in addition to the primary heat accumulator 9 or instead of this primary heat accumulator 9 there is a storage circuit with a storage fluid, which is fluidly separated from the solar circuit 2 and the working circuit 3. Additionally or alternatively, a further heat storage tank may be provided, containing a storage medium, which is preferably different from the solar fluid, the working fluid and / or the storage fluid.

4 shows a third embodiment of the solar thermal power plant 1. This corresponds in essential parts of the embodiment described with reference to FIG 1, so reference is made in this respect to the above statements. The solar thermal power plant 1 has in the embodiment described here via a secondary heat exchanger 41, which is present in the working circuit 3 in terms of flow in front of the primary heat exchanger 6. At the same time, it is usually arranged downstream of the condensate pump 22, that is to say therefore in the flow direction of the working cycle 3 between the condensate pump 22 and the primary heat exchanger 6. Via the secondary heat exchanger 41, a secondary storage cycle 42 is coupled to the working cycle 3 to transfer heat. However, there is neither a flow connection between the secondary storage circuit 42 and the solar circuit 2 nor the secondary storage circuit 42 and the working circuit 3 before.

In the secondary storage circuit 42, a secondary storage fluid is provided, which is circulated by means of a conveyor 43. The secondary storage circuit 42 also has a solar collector 44 associated therewith. It may be a different from the solar panel 4 solar collector 44, which is assigned to the same or a different solar field than the solar panel 4. However, it may alternatively be provided that the solar panels 4 and 44 represent the same solar collector 4/44. In this case, for example, the solar collector 4/44 a plurality of absorber lines, wherein at least one the absorber lines to the solar circuit 2 and at least one further of the absorber lines is assigned to the secondary storage circuit 42. If in the following of the solar panels 4 and 44 is mentioned, so that both the separate design of the solar panels and the corresponding absorber line of the solar panel 4/44 is meant.

It can readily be seen that the secondary storage fluid of the secondary storage circuit 42 can be heated by means of the solar radiation, that is to say that solar heat is absorbed in the solar collector 44 when there is sufficient solar radiation. In terms of flow, following the solar collector 44, the secondary storage fluid is supplied to the secondary heat exchanger 41. Accordingly, with a sufficiently large temperature difference between the secondary storage fluid and the working fluid, heat can be transferred from the secondary storage fluid to the working fluid. The thus already heated in the secondary heat exchanger 41 working fluid then flows through the primary heat exchanger 6 and can be further heated in this with appropriate control of the solar thermal power plant 1. Particularly preferably, the secondary heat exchanger 41 is designed as a storage heat exchanger. This means that the secondary heat exchanger 41 not only serves to transfer heat from the secondary storage circuit 42 into the working circuit 3, but additionally intends to store heat temporarily. This should be sufficient to continue the working cycle 3 at least over a certain period, in particular the design period, during which the solar thermal power plant 1 continues to reach its rated power. in principle For example, the secondary heat exchanger 41 present as a storage heat exchanger has two integrated heat exchangers. With the aid of a first one of the heat exchangers, heat can be transferred from the secondary storage circuit 42 to a storage medium provided in the secondary heat exchanger 41. The second of the heat exchangers serves to remove heat from the storage medium and to supply the working cycle 3. The thermal coupling of secondary storage circuit 42 and working cycle 3 is achieved only indirectly via the storage medium. The storage medium can in principle be chosen arbitrarily. For example, it is a salt, in particular a liquid salt or a liquid salt mixture. The latter is preferably composed of sodium nitrate and potassium nitrate. However, it is also possible to use other suitable substances, for example a latent heat storage material, as the storage medium. The secondary heat exchanger 41 is present for example as a heat storage tank arrangement with at least one heat storage tank. In the heat storage tank, the storage medium is arranged. The size of the secondary heat exchanger 41 or the amount of the storage medium is particularly dependent on the length of the design period and the rated power. The longer the former is, the more storage medium has to be expended in order to be able to temporarily store the quantity of heat required for complete bridging in the secondary heat exchanger 41. Alternatively, the secondary heat exchanger 41 can also serve as a normal heat exchanger between the secondary storage circuit 42 and the working cycle 3, ie have no or only low heat storage capacity. In this case is preferred in the secondary storage circuit 42, a secondary heat accumulator provided, which is present for example fluidically between the solar collector 44 and the secondary heat exchanger 41. The secondary heat storage has analogous to the above statements regarding the storage heat exchanger on the storage medium, in which a certain amount of heat is cacheable. Of course, however, a secondary storage circuit 42 without dedicated heat storage can be realized, so that it has only a small heat capacity for intermediate storage of solar heat.

As already stated above, in the case of solar radiation which corresponds to or exceeds the design solar irradiation, normal operation should be carried out and, with solar radiation which is smaller than the design solar irradiation, a storage operation should be carried out. In principle, two different operating modes of the solar thermal power plant 1 can now be realized.

In a first operating mode, the working fluid of the working cycle 3 is vaporized exclusively in the normal operation with the secondary heat exchanger 41 and also superheated, for which purpose the solar heat absorbed via the solar collector 44 is expended. Via the primary heat exchanger 9, no additional heat is supplied to the working fluid. Accordingly, the primary heat exchanger 6 is not or only slightly acted upon by solar fluid, for which purpose, for example, the inlet switching valve 5 and the outlet switching valve 7 are set accordingly. The solar circuit 2 is operated exclusively to charge the primary heat accumulator 9 so that it is preferably fully charged when switching from normal operation to storage operation. must be changed. This means that the solar collector 44 must be designed such that the solar heat absorbed by it is sufficient to both vaporize and overheat the working fluid at the desired throughput. Accordingly, the secondary heat exchanger 41 is configured in the normal operation as an evaporator / superheater.

In the storage operation, by contrast, the solar thermal power plant 1 is to be set such that the working fluid only evaporates with the aid of the secondary heat exchanger 41 and is only superheated in the primary heat exchanger 6 following this flow technology. Accordingly, the secondary heat exchanger 41 operates only as an evaporator and the primary heat exchanger 6 only as a superheater, which receives the already evaporated fluid from the secondary heat exchanger 41, superheated and then the expansion turbine 20 provides.

In particular, in this mode, it may happen that the reached in the working cycle after the primary heat exchanger 6 temperature of the working fluid and thus the pressure in the storage operation are lower than during normal operation. However, this is unproblematic with an appropriate design of the solar thermal power plant 1. In particular, it is provided that the expansion turbine 20 - as described above - has several expansion turbine stages, which are designed for different input pressures due to their fluidic series connection. In this case, the output pressure of the upstream expansion turbine stage usually corresponds to the inlet pressure of the expansion turbine stage immediately following in the direction of flow. Lie now during normal operation and the storage operation different pressures of the working fluid after the primary heat exchanger 6 and thus before the expansion turbine 20 before, the working fluid is respectively fed directly to that expansion turbine stage, which is evidently designed for the pressure of the working fluid its input pressure.

At a high first pressure, which is present during normal operation, so the working fluid of the first expansion turbine stage is supplied, which is designed for the highest input pressure. The rated output is usually exceeded. At a second pressure, which is lower than the first pressure and, for example, during the storage operation is present, however, the working fluid is fed to one of the first expansion turbine stage fluidly downstream expansion turbine stage. In this case, this expansion turbine stage is selected such that its design inlet pressure essentially corresponds to the prevailing pressure of the working fluid. Thus, even at lower pressure of the working fluid, the solar thermal power plant 1 can be operated at its rated power. It is still no supply of external energy necessary. Alternatively, of course, differently designed expansion turbines 20 can be used for normal operation and storage operation. For example, during normal operation, the working fluid is supplied to a high-pressure expansion turbine and during the storage operation to a low-pressure expansion turbine, the latter permitting operation of the solar thermal power plant 1 at its rated power. In normal operation, on the other hand, as already mentioned above, the nominal power is usually even exceeded. In a second mode of operation, it may be provided that the secondary heat exchanger 41 is used only for evaporation and the primary heat exchanger 6 only for overheating of the working fluid both in normal operation and during storage operation. Accordingly, in this second operating mode in normal operation, the solar fluid must be used not only for charging the primary heat accumulator 9, but also for operating the primary heat exchanger 6.

FIG. 5 shows a fourth embodiment of the solar thermal power plant 1. Here too, reference should firstly be made to the above explanations. In contrast to the embodiment of the solar thermal power plant 1 described with reference to FIG. 4, it is now provided that the secondary storage circuit 42 and hence the secondary heat exchanger 41 are fluidically connected to the solar circuit 2. The secondary storage fluid thus corresponds to the solar fluid. In order to divide the solar fluid to the primary heat exchanger 6 and the secondary heat exchanger 41, switching valves 45 and 46 are provided. An output of the switching valve 45 and the switching valve 46 is connected to the primary heat exchanger 6 and the secondary heat exchanger 41, respectively. Further connections of the switching valves 45 and 46 are connected to further regions of the solar circuit 2, for example the switching valve 45 to the line section 12 and the switching valve 46 to the line section 13. By means of the switching valves 45 and 46, accordingly, the mass flow of the solar fluid through the primary heat exchanger 6 and the secondary heat exchanger 41 are divided.

This embodiment is particularly advantageous when the secondary heat exchanger 41 as a storage heat exchanger according to the above embodiments is formed. In this case, during normal operation, the solar fluid heated in the solar collector 4 or 44 can be used for charging the primary heat accumulator 9, for operating the primary heat exchanger 6 and / or for operating the secondary heat exchanger 41. Preferably, the primary heat exchanger 6 has a lower heat capacity than the secondary heat exchanger 41 present, for example, as a storage heat exchanger. In that regard, even during a charging of the secondary heat exchanger 41 during which possibly the heat transferred to the working fluid is insufficient to evaporate it completely or to overheat it in that the solar fluid is divided between the primary heat exchanger 6 and the secondary heat exchanger 41 in such a way that the heat required for complete evaporation or superheating can be supplied to the working fluid by means of the primary heat exchanger 6.

The division of the solar fluid to the primary heat exchanger 6 and the secondary heat exchanger 41 is preferably set controlling and / or regulating. The division is in particular dependent on the state of charge of the secondary heat exchanger 41. At the beginning of the charging of the secondary heat exchanger 41, therefore, a comparatively large amount of heat is supplied to the working fluid by means of the primary heat exchanger 6. Until a quasi-stationary state in which as much heat is supplied to the secondary heat exchanger 41 during normal operation as it delivers to the working fluid, the amount of heat released from the primary heat exchanger 6 to the working fluid is steadily reduced. In the embodiment shown here, the secondary heat exchanger 41 is preferably designed such that the heat stored in it during the storage operation over the entire design period is sufficient to completely vaporize the working fluid of the working cycle 3 supplied to it without solar fluid of the solar circuit 2 being there is supplied. In the storage operation, the switching valves 45 and 46 are thus adjusted so that the entire circulated and in particular the primary heat accumulator 9 taken solar fluid is the primary heat exchanger 6 is supplied. The primary heat accumulator 9 is thus designed so that it can supply heat in the accumulator operation over the entire design period, which is sufficient to overheat the supplied by the secondary heat exchanger 41 working fluid by means of the primary heat exchanger 6.

FIG. 6 shows a fifth embodiment of the solar thermal power plant, which is basically based on that described with reference to FIG. In that regard, reference is made to the above statements. Here it can be clearly seen that the secondary heat exchanger 41 consists of two heat exchangers 47 and 48, which are arranged in a heat storage tank 49. In the heat storage tank 49 is the storage medium, which is in heat transfer communication with the secondary storage circuit 42 and the heat exchanger 48 in heat transfer communication with the working circuit 3 via the heat exchanger 47.

The difference between the embodiment shown here and that described with reference to FIG. technical interconnection of the solar circuit 2, for which line sections 50 to 61 are used. The inlet switching valve 5 is in fluid communication with the solar collector 4 via the line section 50 and via the line section 51 with a switching valve 62. In addition, a flow connection to the primary heat accumulator 9 or the primary heat storage tank 10 is established via the line section 58. The switching valve 62 is connected via the line section 52 with the primary heat exchanger 6, which in turn is on the side facing away from the switching valve 62 via the line section 53 in flow communication with a switching valve 63.

About the line section 57, the switching valves 61 and 62 directly, so not via the primary heat exchanger 6, connected to each other. Via the line section 54, the switching valve 63 is connected to the conveyor 8, which in turn is connected via the line section 55 with a switching valve 64. The switching valve 64 is in fluid communication with the solar collector 4 via the line section 56 and with the outlet switching valve 7 via the line section 61. Throttle elements 65 are provided in some of the pipe sections 50 to 61, but these are optional. The switching valves 62 to 64 may be provided as well as the inlet switching valve 5 and the outlet switching valve 7 for continuously adjusting the mass flow flowing therethrough. Accordingly, the solar fluid can be guided in each case with the desired mass flow into the line section connected to the respective switching valve.

During normal operation of the solar thermal power plant 1, the solar fluid flows from the solar collector 4 through the pipeline. sections 51 and 52 to the primary heat exchanger 6, further through the line sections 53 and 54 to the conveyor 8 and finally through the line sections 55 and 56 again to the solar collector 4. In addition, it may be provided for charging the primary heat accumulator 9, a part of heated solar fluid, which is adjustable in particular by means of the inlet switching valve 5, to lead through the line section 58 to the primary heat accumulator 9. A corresponding amount of not yet heated solar fluid is removed from the primary heat accumulator 9 and passed through the line sections 59 and 60 to the switching valve 63, from where it in turn passes through the line section 54 to the conveyor 8.

During the storage operation, it is provided to shut down the solar collector 4 together with the line sections 50 and 56, so that it is no longer permeated by the solar fluid. Rather, the solar fluid should be taken from the primary heat accumulator 9 via the line section 58 and fed via the inlet switching valve and the line sections 51 and 52 to the primary heat exchanger 6. Subsequently, the solar fluid flows through the line sections 53 and 54 to the conveyor 8, from which it passes through the line sections 55, 61 and 59 in turn into the primary heat accumulator 9. Of course, both in the normal operation and in the storage operation, it can be provided to pass at least part of the solar fluid through the line section 65 past the primary heat exchanger 6. Of course, in the embodiment of the solar thermal power plant 1 described here, the secondary heat exchanger 41 can also be fluidly connected to the solar circuit 2, as described with reference to FIG. He is preferably provided parallel to the primary heat exchanger 6 in the solar circuit 2.

Particularly in the embodiments of the solar thermal power plant 1 described with reference to FIGS. 4 to 6, it is provided that water is used as the solar fluid and as the working fluid. If the secondary storage circuit 42 is fluidly separated from the solar circuit 2 and the working circuit 3, thermal oil can be used as secondary storage fluid or, alternatively, also water. The embodiments of Figures 4 to 6 of the solar thermal power plant 1 can of course be equipped with the heating circuit 29 according to Figures 2 and 3, even if this is not explicitly shown.

Claims

claims

1 . Solar thermal power plant (1), comprising at least one solar collector (4) of a solar circuit (2) and an expansion turbine (20) associated with a working circuit (3), wherein the solar circuit (2) and the working circuit (3) via at least one primary heat exchanger ( 6) are coupled together and the solar circuit (2) comprises a solar fluid and the working circuit a working fluid, characterized in that the solar circuit (2) is associated with a primary heat accumulator (9), the at least one, in particular parallel to the primary heat exchanger (6 ), primary heat storage tank (10) for the solar fluid of the solar circuit (2).

2. Solar thermal power plant according to claim 1, characterized in that at least one secondary heat exchanger (41) is provided, via which the working circuit (3) and / or the solar circuit (2) with at least one secondary storage fluid having a secondary storage circuit (42) is coupled.

3. Solar thermal power plant according to one of the preceding claims, characterized in that the secondary storage circuit (42) is fluidically separated from the solar circuit (2) and the working circuit (3) or fluidly connected to the solar circuit (2).

4. Solar thermal power plant according to one of the preceding claims, characterized in that the secondary storage circuit (42) to the solar collector (4) of the solar circuit (2) or at least one further solar collector (44) is connected.

5. Solar thermal power plant according to one of the preceding claims, characterized in that the secondary heat exchanger (41) is a storage heat exchanger and / or the secondary storage circuit (42) has a secondary heat storage.

6. Solar thermal power plant according to one of the preceding claims, characterized in that the primary heat exchanger (6) downstream of the secondary heat exchanger (41) in the working circuit (3) is present.

7. Solar thermal power plant according to one of the preceding claims, characterized in that in the solar circuit

(2) a bypass (18) for fluidic bypass of the solar collector (4) and / or a bypass return (19) on one side between the primary heat exchanger (6) and an outlet of the primary heat storage tank (10) and on its other Side is connected to an inlet of the primary heat storage tank (10) are provided.

8. Solar thermal power plant according to one of the preceding claims, characterized in that in the working cycle

(3) downstream of the expansion turbine (20) there is provided a condenser (21) which is operated with the ambient air as the cooling medium or at least supplies a portion of the heat present in the working fluid downstream of the expansion turbine (20) to at least one heating circuit (35).

9. Solar thermal power plant according to one of the preceding claims, characterized in that the critical temperature in the critical point of the solar fluid at least by a factor of 1, 5, preferably by at least a factor of 2, 2.5 or 3, is greater as the critical temperature at the critical point of the working fluid or that the solar fluid is a thermal oil and the critical temperature of the working fluid is at most 160 ° C.

10. Solar thermal power plant according to one of the preceding claims, characterized in that in the solar circuit (2) present solar fluid and / or in the secondary storage circuit (42) present secondary storage fluid water or a thermal oil and / or present in the working cycle (3) Working fluid is water or a hydrocarbon, in particular an alkane, preferably propane or butane, or carbon dioxide, ammonia or a mixture of these substances.

11. A method for operating a solar thermal power plant (1), in particular according to one or more of the preceding claims, wherein the solar thermal power plant (1) at least one solar collector (4) of a solar circuit (2) and a working cycle (3) associated Expansion turbine (20), wherein the solar circuit (2) and the working circuit (3) via at least one primary heat exchanger (6) are coupled together and in the solar circuit (2) a solar fluid and in the working circuit (3) a working fluid is used , In that the solar circuit (2) a primary heat accumulator (9) is associated with at least one, in particular parallel to the primary heat exchanger (6) connected primary heat storage tank (10) for the solar fluid of the solar circuit (2).

12. The method according to claim 11, characterized in that at least one secondary heat exchanger (41) is provided, via which the working circuit (3) and / or the solar circuit (2) is coupled to at least one secondary storage fluid having a secondary storage fluid (42), wherein at a design sun radiation corresponding or exceeding solar radiation normal operation and at a solar radiation that is smaller than the design sun radiation, a storage operation is performed, wherein in normal operation, the working fluid of the working cycle (3) evaporated and superheated only with the secondary heat exchanger (41) and only evaporated in the storage operation with the secondary heat exchanger (42) and only superheated with the primary heat exchanger (6).

13. The method according to any one of the preceding claims, characterized in that in the normal operation of the solar circuit (2) is operated exclusively for charging the primary heat accumulator (9).

14. The method according to any one of the preceding claims, characterized in that the solar thermal power plant (1) is set such that the solar fluid used in the solar circuit (2) has a maximum temperature, in particular in or immediately after the solar collector (4), the lower is as its critical temperature, and / or that the working fluid used in the working circuit (3) has a maximum temperature, in particular in or immediately after the primary heat exchanger (6) and / or the secondary heat exchanger (41), which is greater than its critical temperature.

15. The method according to any one of the preceding claims, characterized in that the maximum temperature of the Arbeitsflu- ids is chosen so that the working fluid after the expansion turbine ne (20) assumes a state in its wet steam region and has at least one specific vapor content, in particular between 0.75 and 1.0.