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

Patent metadata

Field	Value
Publication number	US-9765759-B2
Application number	US-201214113055-A
Country	US
Kind code	B2
Filing date	Apr 19, 2012
Priority date	Apr 19, 2011
Publication date	Sep 19, 2017
Grant date	Sep 19, 2017

Abstract

To operate solar thermal technology economically, a cheap heat transfer fluid is used. To either completely spare or significantly reduce the energy-intensive auxiliary heating at night, a water tank is simply installed in the plant without a threat to the environment. With the water tank, the salt HTF is thinned by adding water when the solar heating is not in operation.

First claim

The invention claimed is:

1. A solar thermal power station using a water-free or water-containing salt as a heat transfer fluid (HTF), comprising:
a first circuit containing the HTF;
a second circuit containing steam to drive generators; and a heat exchanger connecting the first and second circuits,
where the first circuit comprises:
a solar field comprising mirror geometries and conduits in which the HTF flows;
a first conduit for heated HTF which leads from the solar field to the heat exchanger;
a heated HTF reservoir arranged along the first conduit;
a second conduit for cooled HTF which leads from the heat exchanger to the solar field;
a cooled HTF reservoir arranged along the second conduit;
a third conduit for introducing a diluent to the HTF;
a plurality of pumps including a first pump coupled to the heated HTF reservoir or the cooled HTF reservoir and configured to pump the HTF and diluent into the heated HTF reservoir or cooled HTF reservoir;
a plurality of flow valves; and
wherein the plurality of flow valves and pumps are controllable to operate the solar thermal power station in the following modes:
an energy generation mode in which the flow valves are controlled to pass a flow of HTF through the solar field, the first conduit, the heated HTF reservoir, the heat exchanger, the second conduit, the cooled HTF reservoir, and back into the solar field; and
a decoupled mode in which the flow valves are controlled to (a) route the HTF through a decoupled circuit that passes through the solar field but is decoupled from the heat exchanger such that the HTF routed through the decoupled circuit bypasses the heat exchanger, and (b) couple the third conduit to the decoupled circuit to supply diluent to the HTF in the decoupled circuit, the diluent reducing a melting point of the HTF; and
wherein during a transition from the decoupled mode to the energy generation mode, the flow valves and the first pump are controlled to pump the HTF and diluent into the heated HTF reservoir or cooled HTF reservoir to rapidly depressurize the HTF and diluent to vaporize and separate the diluent from the HTF.

2. The power station as claimed in claim 1 , wherein water is used as the diluent.

3. The power station as claimed in claim 1 ,
wherein the conduits, pumps, and/or cooled and heated HTF reservoirs are made of stainless steel.

4. The power station as claimed in claim 3 , wherein the conduits, pumps, and/or cooled and heated HTF reservoirs are made of high carbon stainless steel.

5. The power station as claimed in claim 1 ,
wherein inner surfaces of the conduits, pumps, and/or cooled and heated HTF tanks reservoirs are treated with a corrosion-inhibiting coating.

6. The power station as claimed in claim 1 , wherein
the HTF is a water-containing or water-free salt having one or more cations selected from the group consisting of alkali metal cations and alkaline earth metal cations, and
the HTF has one or more anions selected from the group consisting of nitrates, (hydrogen)carbonates, fluorides, chlorides, (hydrogen)sulfates, bromides, iodides and hydroxides.

7. The power station as claimed in claim 1 ,
wherein an over-pressure valve and/or a vapor separator with an associated vapor condenser are provided on at least one of the cooled HTF reservoir or the heated HTF reservoir.

8. The power station as claimed in claim 1 , wherein the heated HTF reservoir comprises a hot salt HTF tank,
the first conduit leads from the solar field to the heat exchanger via the hot salt HTF tank,
the hot salt HTF tank has an over-pressure valve, a vapor separator and an associated vapor condenser, and
the vapor separator removes the diluent from the hot salt HTF tank.

9. The power station as claimed in claim 1 , wherein
the diluent is water,
the HTF is water-free when driving the generators, and
the HTF is water-containing overnight.

10. A method of operating a solar thermal power station, comprising:
operating the solar thermal power station in an energy generation mode during a day time period, including:
heating a salt heat transfer fluid (HTF) using mirrors in a solar field, to thereby produce hot HTF;
transferring the hot HTF to a heat exchanger;
removing heat from the hot HTF in the heat exchanger to produce a cold HTF and to generate electricity;
transferring cold HTF from the heat exchanger to the solar field;

operating the solar thermal power station in a decoupled mode during a reduced solar energy period in which the temperature of the HTF decreases, including:
adding a diluent to the HTF to thereby reduce a melting point of the HTF and to maintain the HTF at a temperature above the melting point of the HTF;
decoupling the solar field from the heat exchanger, such that the HTF does not run from the solar field to the heat exchanger; and

transitioning the solar thermal power station from the decoupled mode to the energy generation mode, including delivering the HTF and diluent to a vaporization tank and rapidly depressurizing the HTF and diluent, causing rapid vaporization of the diluent.

11. The method as claimed in claim 10 , wherein the diluent is added continuously when the temperature of the HTF decreases by dropwise addition, spraying in, introduction of mist and/or introduction of a jet.

12. The method as claimed in claim 10 , wherein the solar field is decoupled from the heat exchanger overnight or during maintenance work.

13. The method as claimed in claim 12 , wherein for transitioning the solar thermal power station from the decoupled mode to the energy generation mode, the HTF is heated to significantly above the melting point of the HTF before the solar field is re-coupled to the heat exchanger, and after the HTF is heated to significantly above the melting point of the HTF, the HTF is suddenly depressurized in the vaporization tank.

14. The method as claimed in claim 10 , wherein the solar field is decoupled from the heat exchanger when the diluent is added.

15. The method as claimed in claim 10 , wherein
the diluent is water,
the HTF is water-free when driving the generators, and
the HTF is water-containing overnight.

16. The method of claim 10 , wherein, during operation of the solar thermal power station in the energy generation mode, the vaporization tank operates as a thermal reservoir for the hot HTF.

17. The method of claim 16 , wherein, operation of the solar thermal power station in the decoupled mode includes pulping heated HTF remaining in the thermal reservoir through the heat exchanger and into a cold HTF reservoir.

Assignees

• Gröppel Peter
• Heilmann Pascal
• Müller-Elvers Christian
• Mürau Peter
• Übler Matthias
• Siemens Ag

Inventors

• Gröppel Peter
• Heilmann Pascal
• Müller-Elvers Christian
• Mürau Peter
• Übler Matthias

Classifications

• Y02E10/41

  Cross-Sectional Technologies · mapped topic

• F03G6/005 Primary

  Binary cycle plants where the fluid from the solar collector heats the working fluid via a heat exchanger · CPC title

• F03G6/067 Primary

  Binary cycle plants where the fluid from the solar collector heats the working fluid via a heat exchanger · CPC title

• F01K25/08

  using special vapours · CPC title

• F01K13/02

  Controlling, e.g. stopping or starting · CPC title