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Research Papers

Solar Concentrating Systems Using Small Mirror Arrays

[+] Author and Article Information
Joachim Göttsche1

Solar-Institut Jülich/Aachen, University of Applied Sciences, Solar -Institut Jülich Heinrich-Mussmann-Str. 5 Juelich, NRW 52428 Germany

Bernhard Hoffschmidt, Stefan Schmitz, Markus Sauerborn

Solar-Institut Jülich/Aachen, University of Applied Sciences, Solar -Institut Jülich Heinrich-Mussmann-Str. 5 Juelich, NRW 52428 Germany

Reiner Buck, Edgar Teufel

German Aerospace Center (DLR), Pfaffenwaldring 38-40 Stuttgart, 70569 Germany

Kathrin Badstübner, David Ifland, Christian Rebholz

Fraunhofer Institute for Reliability and Microintegration (Fraunhofer-IZM), Argelsrieder Feld 6 Oberpfaffenhofen, D-82234 Germany

1

Corresponding author.

J. Sol. Energy Eng 132(1), 011003 (Nov 09, 2009) (4 pages) doi:10.1115/1.4000332 History: Received August 22, 2008; Revised May 28, 2009; Published November 09, 2009

Abstract

The cost of solar tower power plants is dominated by the heliostat field making up roughly 50% of investment costs. Classical heliostat design is dominated by mirrors brought into position by steel structures and drives that guarantee high accuracies under wind loads and thermal stress situations. A large fraction of costs is caused by the stiffness requirements of the steel structure, typically resulting in $∼20 kg/m2$ steel per mirror area. The typical cost figure of heliostats (figure mentioned by Solucar at Solar Paces Conference, Seville, 2006) is currently in the area of $150 €/m2$ caused by the increasing price of the necessary raw materials. An interesting option to reduce costs lies in a heliostat design where all moving parts are protected from wind loads. In this way, drives and mechanical layout may be kept less robust, thereby reducing material input and costs. In order to keep the heliostat at an appropriate size, small mirrors (around $10×10 cm2$) have to be used, which are placed in a box with a transparent cover. Innovative drive systems are developed in order to obtain a cost-effective design. A $0.5×0.5 m2$ demonstration unit will be constructed. Tests of the unit are carried out with a high-precision artificial sun unit that imitates the sun’s path with an accuracy of less than 0.5 mrad and creates a beam of parallel light with a divergence of less than 4 mrad.

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Figures

Figure 1

Schematic view of the minimirror array (5)

Figure 2

Design study of the mirror array

Figure 3

General mechanical buildup

Figure 4

Mechanical buildup of the demonstrator

Figure 5

Assembly of the drive system

Figure 6

Reflection efficiency as a function of box orientation

Figure 7

Performance of all configurations (21.3. 12:00)

Figure 8

Annual performance of all configurations

Figure 9

Daily performance of the MMA and the reference heliostat

Errata

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