WO2013057043A1

WO2013057043A1 - Solar receiver tube assembly with suited receiver tube per working temperature and use of the receiver tube assembly

Info

Publication number: WO2013057043A1
Application number: PCT/EP2012/070242
Authority: WO
Inventors: Hagai Aran; Eli Lipman
Original assignee: Siemens Aktiengesellschaft; Siemens Concentrated Solar Power Ltd.
Priority date: 2011-10-21
Filing date: 2012-10-12
Publication date: 2013-04-25
Also published as: JP2014531012A; AU2012325054A1; IL231897A0; AU2012325054B2; CN203310150U; EP2745059A1; CL2014000966A1; CN103062945A; BR112014009105A2; US20140360489A1; ZA201402168B

Abstract

A solar receiver tube assembly (1) is provided with at least one first solar receiver tube (101) with a first selective absorptive coating; at least one second solar receiver tube (102) with a second selective absorptive coating, wherein values of at least one optical characteristic of the first selective coating and the second selective coating differs from each other while an operating the solar receiver tube assembly. The optical characteristics are preferably alpha and epsilon.

Description

SOLAR RECEIVER TUBE ASSEMBLY WITH SUITED RECEIVER TUBE PER WORKING TEMPERATURE AND USE OF THE RECEIVER TUBE ASSEMBLY

BACKGROUND OF THE INVENTION

1. Field of the Invention This invention relates to a solar receiver tube assembly and a use of the receiver tube assembly.

2. Description of the Related Art A solar field comprises loops with receiver tubes for absorb^¬ ing solar energy and transferring absorbed energy to a heat transfer fluid which is located in the receiver tubes. One loop or more than one loop is a solar receiver tube assembly. A receiver tube comprises a selective absorptive coating. The selective coating set point is a tradeoff between maximum ab^¬ sorption and minimal radiation. It is the nature of the se^¬ lective coating that enlarging the absorption percentage (designated by a) will increase the radiation (designated by ε) . It is also in the nature of the selective coating that while the absorption is indifferent with the working tempera^¬ ture, the emissivity is higher as the temperature is higher. In the current state of the art all the receivers along the loop have the same design.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an optimized so^¬ lar receiver tube assembly. A further object of the invention is a use of the solar re^¬ ceiver tube assembly. These objects are achieved by the invention specified in the claims .

A solar receiver tube assembly is provided with at least one first solar receiver tube with a first selective absorptive coating; at least one second solar receiver tube with a sec^¬ ond selective absorptive coating, wherein values of at least one optical characteristic of the first selective coating and the second selective coating differs from each other while an operating the solar receiver tube assembly. The optical char- acteristics are preferably a and ε . The idea is to improve the effectiveness of the receiver tubes along the receiver assembly .

The advantage is by gaining more energy from the loop and the solar field as a whole especially at the area where the tem^¬ perature is low and the threshold between absorption and sup^¬ pression can be shifted to higher wave length and gain more energy. This will become more effective when working in higher temperature HTF for example molten salt or DSG.

In a preferred embodiment the first receiver tube and the second receiver tube are components of a single loop of the solar receiver tube assembly. By this, within a loop different solar receiver tubes are used. Alternatively, same kinds of receiver tubes with same selective absorptive coatings are used, whereas while the operating the complete system the values of the optical characteristics are different. Concerning a different embodiment the first receiver tube is a component of a first loop of the solar receiver tube assem^¬ bly and the second receiver tube is a component of a second loop of the solar receiver tube assembly and the first loop and the second loop are different from each other. There are at least two loops.

Finally the solar receiver tube assembly is used in a power plant for converting solar energy into electrical energy.

BIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention are produced from the description of an exemplary embodiment with refer- ence to the drawings. The drawings are schematic.

Figure 1 and figure 2 show partial views of different solar receiver tube assemblies. DETAILED DESCRIPTION OF THE INVENTION

Example 1 :

More than one type of solar receiver tubes with different set point are installed on different locations along one single loop 100 of the solar receiver tube assembly 1 (figure 1) . There are at least one first solar receiver tube 101 with a first selective absorptive coating and at least one second solar receiver tube 102 with a second selective absorptive coating.

Values of at least one optical characteristic of the first selective coating and the second selective coating differ from each other while an operating the solar receiver tube assembly. The set point for lower temperature associated with the beginning of the loop might have higher a and higher ε and the receiver associated with the end of the loop and higher temperature will be design with lower ε and lower a .

Example 2 :

The result concerning example 1 is possible with different loops 200 and 300 for different temperature. For instance, this is suggested for direct steam generation (DSG) . In this case different loops will be equipped with different solar receiver tubes.

In view of the invention there are at least two possibilities to gain the different values of the optical characteristics:

- Using solar receiver tubes with different solar absorptive coatings . - Development of a special coating, using thermal sensitive layers, that is changing it's optical characteristic accord^¬ ing it's temperature. In this case the entire loop or the en^¬ tire field will be equipped with the same receiver tubes but the optic behaviour of the selective coatings will be effect by the temperature of the receiver tubes.

Claims

Patent claims

1. Solar receiver tube assembly (1) with

- at least one first solar receiver tube (101) with a first selective absorptive coating;

- at least one second solar receiver tube (102) with a second selective absorptive coating, wherein

- values of at least one optical characteristic of the first selective coating and the second selective coating differs from each other while an operating the solar receiver tube assembly ( 1 ) .

2. Solar receiver tube assembly according to claim 1, wherein the first receiver tube and the second receiver tube are com- ponents of a single loop (100) of the solar receiver tube as^¬ sembly ( 1 ) .

3. Solar receiver tube assembly according to claim 1, wherein the first receiver tube is a component of a first loop (200) of the solar receiver tube assembly (1) and the second re^¬ ceiver tube is a component of a second loop of the solar re^¬ ceiver tube assembly (1) and the first loop (200) and the second loop (300) are different from each other.

4. Use of the solar receiver tube assembly (1) according to one of the claims 1 to 3 in a power plant for converting so^¬ lar energy into electrical energy.