@misc{LehmannMartinMannigeletal., author = {Lehmann, Mario and Martin, Frank and Mannigel, Kerstin and Kaltschmidt, Kristin and Sack, Ulrich and Anderer, Ursula}, title = {Three-dimensional scaffold-free fusion culture: the way to enhanced chondrogenesis of in vitro propagated human articular chondrocytes}, series = {European Journal of Histochemistry}, volume = {57}, journal = {European Journal of Histochemistry}, number = {4}, issn = {2038-8306}, doi = {10.4081/ejh.2013.e31}, pages = {205 -- 215}, language = {en} } @misc{MartinLehmannSchlaegeretal., author = {Martin, Frank and Lehmann, Mario and Schl{\"a}ger, Peter and Sack, Ulrich and Anderer, Ursula}, title = {Differentiation capacity of chondrocytes in microtissues depends on TGF-ß subtyp}, series = {Journal of biochips \& tissue chips : JBTC}, volume = {S2}, journal = {Journal of biochips \& tissue chips : JBTC}, number = {002}, issn = {2153-0777}, doi = {10.4172/2153-0777.S2-002}, pages = {11}, language = {en} } @misc{MartinLehmannSacketal., author = {Martin, Frank and Lehmann, Mario and Sack, Ulrich and Anderer, Ursula}, title = {In vitro development of personalized cartilage microtissues uncovers an individualized differentiation capacity of human chondrocytes}, series = {Experimental Biology and Medicine}, volume = {242}, journal = {Experimental Biology and Medicine}, number = {18}, issn = {1535-3702}, doi = {10.1177/1535370217728498}, pages = {1746 -- 1756}, language = {en} } @incollection{MartinLehmannAnderer, author = {Martin, Frank and Lehmann, Mario and Anderer, Ursula}, title = {Generation of scaffold free 3-D cartilage-like microtissues from human chondrocytes}, series = {Medical Advancements in Aging and Regenerative Technologies: Clinical Tools and Applications}, booktitle = {Medical Advancements in Aging and Regenerative Technologies: Clinical Tools and Applications}, editor = {Daskalaki, Adriani}, publisher = {IGI Global}, address = {Hershey, PA, USA}, isbn = {978-1-4666-2506-8}, pages = {169 -- 194}, language = {en} } @misc{BergHimmelbergLehmannetal., author = {Berg, Heinz Peter and Himmelberg, Axel and Lehmann, Mario and D{\"u}ckershoff, Roland and Neumann, Mathias}, title = {The Turbo-Fuel-Cell 1.0 - family concept - Compact Micro Gas Turbine (MGT) - Solid Oxide Fuel Cell (SOFC) energy converters in the 100 - 500 kW electrical power range for the future}, series = {IOP conference series : Materials Science and Engineering}, volume = {297}, journal = {IOP conference series : Materials Science and Engineering}, issn = {1757-899X}, doi = {doi:10.1088/1757-899X/297/1/012004}, pages = {15}, abstract = {The "Turbo-Fuel-Cell-Technology" has been described as a MGT-SOFC hybrid system consisting of a recuperated micro gas turbine (MGT) process with an embedded solid oxide fuel cell (SOFC) subsystem. SOFC stacks are connected to "SOFC stack grapes" and are equipped with the so called HEXAR-Module. This module is composed of a high-temperature heat exchanger (HEX), an afterburner (A) and a steam reformer (R). The MGT-concept is based on a generator driven directly by the turbomachine and a recuperator, which returns the exhaust heat to the pressurized compressor outlet air. This provides the necessary base for a highly effective, pure MGT process and the "MGT-SOFC-high-efficiency process". This paper describes the concept and the thermodynamic background of a highly effective and compact design of the "Turbo-Fuel-Cell 1.0-Family" in the electrical performance class from 100 to 500kW. The technological state of the system is shown and a rating of the system with comparative parameters is discussed. It becomes visible that all necessary basic technologies should be available and that the technology (for stationary applications) can have the "entry into services (E.I.S.)" in the next 10 years. The MGT-SOFC performance map under different operation conditions is discussed. This article also provides an overview of the research on MGT-SOFC-Systems and the scenario of an energy supply network and a mobile energy conversion of the future introduction.}, language = {en} } @misc{BergKleisslHimmelbergetal., author = {Berg, Heinz Peter and Kleissl, Marko and Himmelberg, Axel and Lehmann, Mario and Prechavut, Nontavut and Vorpahl, Michael}, title = {Heat balancing of direct reforming fuel cells in MGT-SOFC hybrid systems}, series = {9th Thai Society of Mechanical Engineers, International Conference on Mechanical Engineering (TSME-ICoME 2018) 11-14 December 2018, Phuket, Thailand}, journal = {9th Thai Society of Mechanical Engineers, International Conference on Mechanical Engineering (TSME-ICoME 2018) 11-14 December 2018, Phuket, Thailand}, editor = {Prukvilailert, Monchai}, edition = {1. Auflage}, publisher = {IOP Publishing/IOP Science}, address = {Bristol}, issn = {1757-899X}, doi = {10.1088/1757-899X/501/1/012007}, pages = {50 -- 60}, abstract = {Solid oxide fuel cells convert chemical energy in electrical energy and are highly suitable for the conversion of hydrocarbon based fuels and products from PowerToGas conversions. Embedded in a micro gas turbine-cycle instead of the combustion chamber the heat energy of the injected fuel, released in the SOFC-Stack, can additionally converted into work and by a turbine-generator into electricity. In a compact system, SOFC stacks are designed to realize a direct steam-reforming process inside. In such direct-reforming fuel cell systems the SOFC operating temperature due to the heat demand for reforming, can be reduced to a value in the range of the outlet temperature of the downstream flow (650°C). If the cycle uses a recuperating system, the operating conditions of the SOFC can be realized without additional high-temperature heat exchanger systems. The system with an uncooled turbine, described in [1], just can reach the operating temperature with an additional high-temperature heat exchange. The system described in this publication does not require an additional high-temperature heat exchanger, because the X-value, as the ratio between the exchanged heat quantity and the required amount of heat to complete the MGT-cycle [2] due to the referring process, is nearly zero and can be realized via the inner container wall (of the MLC). The cycle is completed (between the SOFC and the turbine entry) by the heat input of an afterburner. Here the unreacted fuel of the SOFC fuel-stream is used to provide the necessary heat energy for the downstream turbo-generator-system.}, language = {en} } @misc{DueckershoffBergHimmelbergetal., author = {D{\"u}ckershoff, Roland and Berg, Heinz Peter and Himmelberg, Axel and Lehmann, Mario and Kleissl, Marko}, title = {Influence on the Electrical Efficiency of a Hybrid MGT-SOFC-System by μ-fogging in a-Two-Staged Compressor System}, series = {IOP Conference Series: Materials Science and Engineering}, journal = {IOP Conference Series: Materials Science and Engineering}, editor = {Ashton, Anete}, edition = {1. Auflage}, publisher = {IOP Science}, address = {Bristol}, issn = {1757-899X}, doi = {10.1088/1757-899X/886/1/012041}, pages = {1 -- 8}, abstract = {Hybrid combinations of solid oxide fuel cell and recuperated micro gas turbines can convert the chemical energy of hydrocarbon-based fuels in electrical energy with high electrical efficiency. With an integrated and improved cycle management, more than 70\% of the energy content of the fuel could be converted. Therefore, the systems are highly suitable for the Power-To-Gas conversion. In particular, a pressure charging of the SOFC fuel cell leads to an increase in stack performance. By a downstream turbo set, after residual fuels are intentionally oxidized with an afterburner, additional electrical energy can be gained from the expansion of the hot exhaust gas stream and the overall efficiency can be increased. In order to increase the electrical efficiency of the system, it is proposed, to ensure the required compression of the process air in particular by a-two-staged turbo compressor with an intermediate cooling system. By thus achievable reduction of the dissipation of the compressor and by targeted condensation of finest drops in front of the second compressor stage affected by intermediate cooling, an increase in efficiency of the system is possible. This is achieved by targeted cooling of the process air behind a low pressure compression, so that it is saturated over 100\% relative air humidity. As a result, a slightly supersaturated airflow is available for the second compressor stage, which enters the compressor after heat removal via an intermediate cooling having a small number of microdroplets. Therefore, the condensed water evaporates again by the heat of compression in the second stage and the compressed flow ultimately enters the recuperation at a lower temperature than during normal compression. Thus, more heat can be recovered within the recuperation system. Therefore, the electrical energy of the system can be produced having higher efficiency, because the heat dissipation of the overall system decreases. In this article it is presented, how such a process is thermodynamically modelled and how a technical realization can be built after optimization by simulations. Finally, in this study, the process-influencing factors are analyzed to show the highest possible electrical yield of such a system.}, language = {en} } @inproceedings{BergDueckershoffLehmannetal., author = {Berg, Heinz Peter and D{\"u}ckershoff, Roland and Lehmann, Mario and Prechavut, Nontavut}, title = {Micro Turbo-Fuel-Cell-Technology : Hybrid compact turbo machinery technology and thermodynamic aspects regarding design parameters of a high efficient MGT-SOFC-system}, series = {12th European Conference on Turbomachinery Fluid dynamics \& Thermodynamics}, booktitle = {12th European Conference on Turbomachinery Fluid dynamics \& Thermodynamics}, doi = {10.29008/ETC2017-266}, pages = {1 -- 12}, abstract = {The improvement of decentralised energy supply systems has received an important role in the recent years. One option is the combination of SOFC with recuperated MGT. Here, a new strategy for selecting the system parameters, such as the operating temperature of the SOFC, turbine inlet temperature and the pressure ratio of the hybrid system, is presented. By introducing the heat ratio between the heat required to increase the process gas to the SOFC operating temperature and the heat required to raise the SOCF exhaust gas to the TIT, it was found that high efficiency (approx. 68\%) is realisable in a compact hybrid system today. Analysis also shows that the HEX-technology is needed to improve the system effectiveness. Also, high recirculation rates with lower TIT can be considered as the future development direction. In addition, a sample configuration of an oil-free MGT rotor unit with high speed foil bearings is presented.}, language = {en} } @inproceedings{LehmannMartinScholkaetal., author = {Lehmann, Mario and Martin, Frank and Scholka, Jenny and Petto, Carola and Wittenburg, Gretel and Sack, Ulrich and Anderer, Ursula}, title = {Human chondrocytes and dental pulp stem cells enhance their chondrogenic differentiation potential via a two-step fusion culture technique}, series = {Tissue Engineering, Part A, Vol. 21, Suppl. 1}, booktitle = {Tissue Engineering, Part A, Vol. 21, Suppl. 1}, doi = {10.1089/ten.tea.2015.5000.abstracts}, pages = {S-268 -- S-269}, language = {en} } @inproceedings{LehmannVossMartinetal., author = {Lehmann, Mario and Voß, Fr{\"a}nzi and Martin, Frank and Schl{\"a}ger, Peter and Anderer, Ursula}, title = {Chondrogenic microtissues in the lab \& for the clinic}, series = {3D cell culture 2016, book of abstracts, DECHEMA Biotechnologie}, booktitle = {3D cell culture 2016, book of abstracts, DECHEMA Biotechnologie}, publisher = {DECHEMA e.V.}, address = {Frankfurt am Main}, isbn = {978-3-89746-182-6}, pages = {52 -- 53}, language = {en} }