22 nd International Expert Meeting Power Engineering 2013 Stephan Thaler, MSc “Energy saving through the use of biomimetic architecture”

Content Motivation Introduction Models: Vascular tissues Abstraction & Simulation Application & Measurement Results & Conclusion

Aim of this work: -is to optimize the pipework system in the absorber plate of a solar thermal collector in relation to a lower decrease in pressure - inspired by nature Motivation Fig.: Photography and design of a GeoTec solar panel GSE The other parts of the collector like the housing, the insulation, and the transparent cove should be the same as in the common flat plate collectors to be able to use the existing production equipment and maintain the production line.

Introduction Statement: Optimization of the flow structure – lead to a reduction of the pressure loss and a reduction of the energy loss Answer: The best way that the nature found to extract resources from the environment and distribute them to the whole organism is to fill the area with a network of tubes: Vascular system Fig.: Venation of leaves [3], Tracheal system in wings [4], Vascular system, Veins [5] We try to find different natural channel structures and highlight the characteristics of the individual examples. We want to use a combination of the most promising properties for our pipework structure. We decided to take a closer look at the leaf vein structure, the vein structure of insect wings and the vascular system in animals.

Vascular tissues in leaves Models with Dichotomous-pattern: Leaves of Ginkgo tree and Maidenhair fern Fig.: Ginkgo leaf venation [8] Fig.: Maidenhair fern venation [9] Fig.: CAD design Ginkgo Fig.: CAD design Maidenhair fern -ramified structure ( implies efficient space use ) - regular and smooth vein forking ( may lead to a uniform flow characterisation )

Vascular tissues in insect wings Models of order of Palaeoptera: Wings of Mayfly and Dragonfly Fig.: Photography of the mayfly wing [13]Fig.: CAD design mayfly Fig.: CAD design dragonflyFig.: Photography of dragonfly wing [14] - well definite fluting system Fig.: Photography of a mayfly [11]Fig.: Photography of a dragonfly [12]

Vascular system in mammals Fig.: Photography of the structure in the manatee tail [17]Fig.: Blood vessel [16] Rules: The sum of the cubes of R1 of outgoing pipes must at least equal the cube of radius R0. Comparing the diameter of different vessel types shows a mathematical regularity. Fig.: Plot with double logarithmic scale [19] Tab.: Diameter and quantity of vessels [18]

Abstraction & Simulation Simulation of connection areas The new pipework structure should: - reduce the area of high back pressure - reduce the occurrence of turbulence and counter-flow - use the advantages of branching structures To achieve this, the connection was optimized following the example of leaf vein structures. Fig.: Abstraction of leaf vein structure and wing venation to pipework structure

Abstraction & Simulation Simulation of the whole pipework structure of the optimized collector: Result: pressure loss reduction of 16% Reference model: pressure loss of Pa Optimized model: pressure loss of Pa Improvement in pressure drop of Pa means that we can expect an improvement by about 16 %. Fig.: Plot of first biomimetic optimized pipework structure

Application & Measurement Reference model: An absorber of a conventional collector (taken from current production) Optimized model: The copper pipes are cut and shaped and connected by brazing Measurement: Hydraulic measuring arrangement which corresponds to a conventional solar system Fig.: Preparation of pipework structure Fig.: Design of measuring arrangement

Results Measurements at defined flow: read out the differential pressure The result of our measurement shows us the expected reduction in the pressure loss of about 15% due to the optimization of the channel structure. These results confirm our initial assumptions and the performed simulations. Fig.: Plot of the results of the final differential pressure measurement The outcome of the simulations shows that geometry of flow structure influences flow behaviour. By employing a ramified structure we can achieve a minor flow redirection. This leads to a minor leakage of pressure and flow losses. As shown in our example, even small changes lead to measurable improvements.

Bibliography [1] [2] [3] [4] [5] [6]Helmut Tributsch, Lecture Biomimetic in Energy systems, Chapter 4, FH Kärnten, 2011 [7]François G. Feugier, Models of Vascular Pattern Formation in Leaves, University of Paris, 2006 [8] [9] [10]Herbert Oertel jr., Bioströmungsmechanik, Universität Karlsruhe, 2008 [11] [12] [13]Spektrum Bionik: Vorbild Natur in Leben und Technik, Wissen Media Verlag GmbH, Gütersloh/München, 2008 [14] [15]Michael LaBarbera, Principles of Design of Fluid transport systems in zoology, Science Magazine, 1990 [16] [17]Sentinel A. Rommel, Heather Caplan, Vascular adaptations for heat conservation in the tail of Florida manatees, Anatomical Society of Great Britain and Ireland, 2003 [18]Robert F. Schmidt, Florian Lang, Gerhard Thews, Physiologie des Menschen, Rhein/Schneider, 1980 [19]Ingo Rechenberg, Von Bäumen und Adern: Optimierung in der Natur, TU Berlin, 2000