Patent Application
20100162700
The invention relates to a method for operating a solar-thermal power plant in which a working fluid circulates in a circuit, with a solar steam generator based on direct evaporation and a steam turbine in which the working fluid is expanded while doing technical work on a relief path, with at least one intermediate superheater, which is heated means of working fluid removed from the circuit upstream of the intermediate superheater and which superheats working fluid by means of an intermediate superheater which can be fed downstream of the heating removal by flowing into the relief path.
Solar-thermal power plants represent an alternative to conventional power generation. A solar-thermal power plant utilizes solar radiation energy to produce electrical energy. It consists of a solar power plant part for absorption of the sun's energy and a second generally conventional power plant part.
The solar-thermal power plant in such cases comprises a solar array, meaning a concentration system with collectors. The concentrating collectors are the main component of the solar-thermal power plant. Known collectors in such cases are the parabolic trough collector, the fresnel collector, the solar tower and the paraboloid mirror. Parabolic trough collectors concentrate the sun's rays onto an absorber tube placed in the focus line. The sun's energy is absorbed there and passed on as heat to a heat carrier medium.
In such cases thermo oil, water, air or fused salt can be employed as the heat carrier medium.
The conventional power plant part generally comprises a steam turbine as well as a generator and a condenser with, by contrast to a conventional power plant, the heat input from the boiler being replaced by the heat input generated by the solar array.
Currently solar-thermal power plants are embodied with indirect evaporation, i.e. with heat exchangers being connected between the solar power plant part and the conventional power plant part, in order to transfer the energy generated in the solar array circuit from the heat carrier of a solar array circuit to a water-steam circuit of the conventional power plant part.
Direct evaporation represents an option for the future, in which the solar array circuit of the solar power plant part and the water-steam circuit of the conventional power station part form a common circuit, with the feed water being preheated in the solar array, evaporated and superheated and fed in this form to the conventional part. The solar power plant type is thus a solar steam generator.
The conventional power plant part cannot be operated to the optimum with the steam parameters obtained in a solar array with direct evaporation. The condensation of the steam via as large a pressure drop as possible is very restricted by the moisture arising during condensation in the turbine. To minimize the creation of moisture in the turbine when utilizing the greatest possible pressure drop, an intermediate superheating of the steam is necessary.
In a conventional steam power plant the intermediate superheating is undertaken by means of a heat exchanger in the boiler. With solar-thermal power plants with direct evaporation the intermediate superheating can be carried out in a separate solar array. However this version of intermediate superheating does not appear worthwhile since with an intermediate superheating in the solar array a very high pressure loss is to be expected.
The object of the invention which relates to the device is thus to specify a solar-thermal power plant with improved intermediate superheating. A further object is to specify a method for operating such a power plant installation.
This object is achieved in accordance with the invention by the features of the claims.
Further advantageous embodiments are claimed in the subclaims,
The inventive solar-thermal power plant installation comprises a working fluid circuit, a solar steam generator based on direct evaporation and a steam turbine, for condensing the working fluid on a relieving path, with at least one intermediate superheater, which is able to be heated up by working fluid able to be removed upstream of the intermediate superheater and is able to be superheated by the working fluid thereof, which can be fed downstream of the heating removal by following into the relief path. This enables the working fluid to be superheated without the very high loss of pressure to be expected on intermediate superheating in the solar array.
The intermediate superheater is heated by the steam removal before the relief path or by means of tapping off from the relief path of the turbine. Tapping off in context of this document means the removal of steam between two vane stages.
Preferably the intermediate superheater is a steam-steam-heat exchanger which is connected on the primary side into a fresh steam line. In this case fresh steam is removed ahead of the turbine and used for superheating of the cooled intermediate superheating steam.
It is further preferred for the steam-steam heat exchanger to be connected into a tapping-off point of the high-pressure part of the turbine. In this instance a removal of the higher-quality fresh steam is advantageously dispensed with.
In a preferred embodiment the intermediate superheating is undertaken via two steam-steam heat exchangers, of which one is connected on the primary side into a fresh steam line and another on the primary side into a tapping-off point of the high-pressure part. The respective proportion of intermediate superheating can be set as required.
It is advantageous to use the cooled steam of the primary side of the superheater for recuperative feed water preheating.
Depending on the steam parameters a steam separator can be useful in the circuit ahead of the intermediate superheater, in order to move with the largest possible steam content into the steam-steam heat exchanger on the cold secondary side of the intermediate superheater.
In such cases it is further useful for the condensate to be introduced at a suitable point from the steam separator back into the working fluid circuit.
In an advantageous embodiment the solar-thermal power plant system includes a generator for electrical energy generation.
A good increase in efficiency with acceptable constructional outlay is produced if at least two turbines are provided in the relief path, for example a combined high and medium-pressure turbine at the start and a low-pressure turbine at the end of the relief path, with working fluid being subjected to intermediate superheating after the first turbine section in a steam-steam heat exchanger and subsequently being directed to the low-pressure turbine section.
For larger power plant outputs in particular at least three turbines, a high-pressure turbine, a medium-pressure turbine and at least one low-pressure turbine are advantageous in the relief path. One of the options offered by this configuration is an especially flexible design of the intermediate superheating. The working fluid can be removed after the high-pressure turbine and/or after the medium-pressure turbine and subjected to an intermediate superheating in a steam-steam heat exchanger, before it flows into the subsequent downstream turbine. The low-pressure part turbines can always be embodied as single or multi flow. It is also possible to provide a number of low-pressure turbine sections connected to the regenerative intermediate superheating according to the invention.
Especially advantageously the thermo-solar power plant installation comprises parabolic trough collectors, which are technologically highly mature and have the highest concentration factor for linear-concentrating systems, which makes higher process temperatures possible.
In an alternate embodiment fresnel collectors are used. An advantage of fresnel collectors over parabolic trough collectors lies in the tubing and the resulting, comparatively low pressure losses. A further advantage of fresnel collectors are the largely standardized components compared to parabolic trough collectors, which can be manufactures without technological know-how. Fresnel collectors can therefore be procured and maintained at low cost.
A further advantageous alternate embodiment uses a solar tower for direct solar evaporation, which allows the highest process temperatures.
Because of its very high specific thermal capacity or its high specific evaporation enthalpy and its ease of handling, water is a very good heat carrier and thus very suitable as a working fluid.
In relation to the method the object is achieved by a method for operating a solar-thermal power plant system, in which a working fluid circulates in a circuit, with a solar steam generator based on direct evaporation and a steam turbine, in which the working fluid is condensed on a relief path while supplying technical work, with at least one intermediate superheater, which is heated by means of working fluid removed from the circuit upstream of the intermediate superheater and is superheated by means of the working fluid thereof, which is fed downstream of the heating removal by flowing into the relief path.
The method makes use of the facility described The advantages of the device are thus also produced for the method.
Further advantages, features and details of the invention emerge from the description given below of preferred exemplary embodiments and drawings as well as from further subclaims.
The invention is explained in further detail on the basis of the drawings.
These show simplified and not-to-scale drawings in the following figures:
The same parts are provided with the same reference symbols in all figures.
In the exemplary embodiment of
The fresh steam is cooled off in this case far enough to enable it to be used for recuperative feed water preheating at the corresponding point in the feed water system (injection point 13). Before the intermediate superheating, should this be necessary because of the steam parameters, a steam separator 14 can also be built into the circuit 9, in order to move with as high a steam content as possible into the steam-steam heat exchanger 12 on the cold intermediate superheater side. The condensate from the steam separator 14 is introduced at a suitable point (injection point 15) back into the feed water circuit 9. The temperature of the hot intermediate superheating steam is produced by the temperature difference of the steam-steam heat exchanger 12 and the saturated steam temperature of the removed steam at the removal point 11 at the pressure predetermined by the solar array 2 and the pressure loss of the steam-steam heat exchanger 12.
In an embodiment shown in
All the above-mentioned arrangements of the intermediate superheating by means of heat exchangers are likewise conceivable in any combination with the supplementary firing explained here (fossil, biomass, H2).
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 013 852.2 | Mar 2007 | DE | national |
This application is the US National Stage of International Application No. PCT/EP2008/053205, filed Mar. 18, 2008 and claims the benefit thereof. The International Application claims the benefits of German application No. 10 2007 013 852.2 DE filed Mar. 20, 2007, both of the applications are incorporated by reference herein in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2008/053205 | 3/18/2008 | WO | 00 | 3/3/2010 |
