Method for operating a solar installation

Method for operating a solar installation. The solar installation includes a solar field with direct evaporation accompanied by the generation of superheated live steam, a turbine for expanding the live steam, and a generator driven by the turbine for generating electrical energy. At least one valve is associated with the turbine by which the amount of live steam fed to the turbine is adjusted. The valve, or each valve, through which the amount of live steam fed to the turbine is adjusted such that an actual value of a live steam pressure occurring upstream of the turbine follows a reference value determined depending on a live steam temperature of the live steam upstream of the turbine.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to a method for operating a solar installation.

2. Description of the Related Art

In a solar installation, electrical energy is generated from solar energy. For this purpose, a working medium, particularly water, is evaporated in a solar field of the solar installation, and the evaporated working medium is fed to a turbine. The working medium is expanded in the turbine and energy obtained in this way is used to drive a generator of the solar installation. The generator generates electrical energy. The steam of the working medium which is generated in the solar field and fed to the turbine is also known as live steam.

SUMMARY OF THE INVENTION

One embodiment of the present invention is a method for operating a solar installation of the type mentioned above, wherein the solar field operates on the principle of direct evaporation, i.e., wherein the working medium is evaporated in a circuit in the solar field and is expanded in the turbine.

When a solar installation cannot be operated at full load but only at partial load, for example, due to shading of the solar field of the solar installation, it has not been possible to operate the solar installation at optimum efficiency.

There is a need for a solar installation that can be operated at optimum efficiency at both full load and partial load.

On this basis, one embodiment of the present invention provides a novel method for operating a solar installation.

According to one embodiment of the invention, the valve, or each valve, through which the amount of live steam fed to the turbine is adjusted or controlled such that an actual value of a live steam pressure occurring upstream of the turbine follows a reference value determined based at least in part on a live steam temperature of the live steam upstream of the turbine.

It is suggested by one embodiment of the present invention to control the valve, or each valve, through which the amount of live steam fed to the turbine is adjusted so that an actual value of the live steam pressure occurring upstream of the turbine follows the corresponding reference value, wherein this reference value is determined depending on the actual value of the live steam temperature upstream of the turbine. In this way, operation of the solar installation at optimum efficiency is also possible at partial load.

According to an advantageous further development, the live steam temperature is measured by a sensor, and the corresponding actual value is supplied to a controller that generates a reference value for the live steam pressure depending on the actual value of the live steam temperature and, depending on the reference value for the live steam pressure, determines a control variable for the valve, or each valve, such that the actual value of the live steam pressure follows the reference value for the live steam pressure. Operating the solar installation in this way by the controller allows a particularly simple and preferable efficiency-optimized operation of a solar installation.

The invention is further directed to a controller of a solar installation having elements for implementing the method according to the invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1shows a schematic section of a solar installation that comprises a solar field1, a turbine2, and a generator3. A working medium, particularly water, is evaporated in the solar field1of the solar installation. Live steam generated in the solar field1is supplied to the turbine2for expansion. When the live steam is expanded in the turbine2, energy is obtained by which the generator3can be driven for generating electrical energy.

In the illustrated embodiment, the solar field1of the solar installation comprises a preheater4, an evaporator5, and a superheater6. The working medium is preheated to an evaporation temperature in the preheater4. The actual evaporation of the working medium takes place in the evaporator5. The steam is superheated in the superheater6, and the superheater6supplies the live steam that is subsequently supplied to the turbine2for expansion.

The amount of live steam to be fed to the turbine2for expansion can be adjusted by at least one valve7. The valve7, or each valve7, can be an integral component part of the turbine2.

Within the meaning of the present invention, the valve7, or each valve7, by which the amount of live steam fed to the turbine2is adjusted for operating the solar installation is controlled such that an actual value pISTof a live steam pressure p occurring upstream of the turbine2follows a corresponding reference value pSOLL, which is determined depending on an actual value TISTof a live steam temperature T of the live steam upstream of the turbine2.

The valve7, or each valve7, is preferably controlled such that the actual value pISTof the live steam pressure p occurring directly upstream of the valve7or of each valve7follows the corresponding reference value pSOLLwhich, as was already mentioned, is determined depending on the actual value TISTof the live steam temperature of the live steam directly upstream of the valve7or each valve7.

A controller8is used to carry out the method according to one embodiment of the invention. The actual value TISTof the live steam temperature upstream of the turbine2or upstream of the valve7, or each valve7, is supplied to the controller8. This actual value TISTof the live steam temperature is determined by a sensor9. Depending on this actual value of the live steam temperature, the controller8determines a reference value pSOLLfor the live steam pressure of the live steam upstream of the turbine2or upstream of the valve7or each valve7, and depending on this reference value pSOLLfor the live steam pressure the controller8determines a control variable X for the valve7or each valve7such that the actual value pISTof the live steam pressure follows the reference value pSOLLfor the live steam pressure.

The determination of the reference value pSOLLfor the live steam pressure depending on the actual temperature TISTof the live steam temperature in the controller8is preferably carried out by a characteristic line11.FIG. 2shows an exemplary characteristic line11which is used for determining the reference value pSOLLfor the live steam pressure depending on the actual value TISTof the live steam temperature.

In the characteristic line11ofFIG. 2, a reference value for the live steam pressure pSOLLof approximately 30 bar is determined at an actual live steam temperature TISTof about 310° C. At a temperature TISTof the live steam of about 280° C., a reference value pSOLLfor the live steam pressure of about 19.5 bar is generated.

As was already mentioned, the controller8determines the control variable X for the valve7, or each valve7, depending on the reference value pSOLLfor the live steam pressure so that the actual value pISTof the live steam pressure follows the reference value pSOLLof the live steam pressure. For this purpose, the control variable X is preferably generated depending on a control deviation between the reference value pSOLLof the live steam pressure and the actual value pISTof the live steam pressure. According toFIG. 1, the actual value pISTof the live steam pressure is determined by a sensor10and is supplied to the controller8.

In accordance with one embodiment of the invention, it is possible to operate a solar installation with optimum efficiency at full load as well as at partial load. Accordingly, when less live steam is generated in the solar field1because of shading therein, the turbine2can be operated at optimal efficiency to generate a maximum of electrical energy by the generator3. The invention allows operation of the solar installation with an optimal combination of the available amount of live steam, the available enthalpy drop, and loading of the individual component groups of the solar installation.