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New Absorber Manufacturing and Materials - Challenges for Absorber Design and Evaluation

: Hermann, M.; Koch, L.; Lauro, P. di; Bauch, M.

Volltext urn:nbn:de:0011-n-2210306 (1.3 MByte PDF)
MD5 Fingerprint: 16d8f820b5ccde131c311e327ca16d8b
Erstellt am: 28.11.2015

International Solar Energy Society -ISES-:
Rapid transition to a renewable energy world. ISES Solar World Congress 2011. DVD-ROM : 28 Aug - 2 Sep 2011, Kassel, Germany; conference proceedings
Freiburg: ISES, 2011
ISBN: 978-3-9814659-0-7
Solar World Congress (SWC) <30, 2011, Kassel>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer ISE ()
Solarthermie und Optik; Solarthermie; Solaranlagen; Thermische Solaranlagen

State-of-the-art solar thermal absorbers are mostly based on sheet-and-tube constructions. Laser welding, ultrasonic welding or soldering are common technologies to connect the absorber sheet with the fluid channels. For future absorbers both new manufacturing and materials are key issues for innovation and cost savings. PVT collectors for example need rigid, one-side-flat absorbers. If metals are used, potential alternative manufacturing technologies are in most cases based on sheet metal forming such as roll-bonding, hydroforming or deep-drawing. The main difference to state-of-the-art is that with these technologies absorber and channel form a union, i. e. the thermal bottleneck of a sheet-tube connection is not relevant anymore. Moreover, the number of channels does not have a big influence on the absorber costs, and there is much more flexibility regarding the geometry of both the channel paths and their cross sections. Fraunhofer ISE has been working on this topic together with industry as well as research partners for some years now (Hermann et al., 2010). Examples are the European project BIONICOL (aluminium roll-bond absorbers, Hermann et al., 2011), the German project STAHLABS (steel absorbers produced by roll cladding and hydroforming, Koch et al., 2011) and work done in direct contact with manufacturers willing to enter the solar thermal market. The question arising with the gained flexibility in design is how the channel pattern and the channel cross sections should look like with respect to high thermal efficiency as well as low pressure drop, taking the material and the sheet thickness into consideration. One example for work on channel patterns is the so-called FracTherm® algorithm (Hermann, 2005). But even if standard meander or harp patterns are used, it is still a challenge to design and assess absorbers within the framework of the boundary conditions given by the manufacturing technology and the material.