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Wolf D.,Heliocentris Industry GmbH | Budt M.,Fraunhofer Institute for Environmental, Safety and Energy Technology
Applied Energy | Year: 2014

Most of the recent approaches on Adiabatic Compressed Air Energy Storage (A-CAES) aim at Thermal Energy Storage (TES) at high temperatures. High TES temperatures together with high pressures intrinsic to CAES are not easy to handle. In order to avoid this technical challenge, we introduce a low-temperature Adiabatic Compressed Air Energy Storage (LTA-CAES) plant. We select and design multistage radial compressors and expanders with single stages rotating with different speeds allowing for intermediate cooling and reheating of the air flow. The proposed LTA-CAES design shows roundtrip efficiencies in the range of 52-60%, slightly lower compared to those envisioned for high temperature A-CAES. However, it can be shown in an economic analysis that its fast start-up characteristics and wide-ranging part load ability overcompensates the lower cycle efficiencies with regard to plant profitability. © 2014 Elsevier Ltd. Source

Timar G.,Debrecen University | Timar G.,ETH Zurich | Blomer J.,Fraunhofer Institute for Environmental, Safety and Energy Technology | Kun F.,Debrecen University | And 2 more authors.
Physical Review Letters | Year: 2010

We present an experimental and theoretical study of the fragmentation of polymeric materials by impacting polypropylene particles of spherical shape against a hard wall. Experiments reveal a power law mass distribution of fragments with an exponent close to 1.2, which is significantly different from the known exponents of three-dimensional bulk materials. A 3D discrete element model is introduced which reproduces both the large permanent deformation of the polymer during impact and the novel value of the mass distribution exponent. We demonstrate that the dominance of shear in the crack formation and the plastic response of the material are the key features which give rise to the emergence of the novel universality class of fragmentation phenomena. © 2010 The American Physical Society. Source

Bretz K.,Fraunhofer Institute for Environmental, Safety and Energy Technology
Chemical Engineering and Technology | Year: 2015

Considering glycerol as an inexpensive alternative carbon source, the optimal glycerol concentration for succinic acid production with Anaerobiospirillum succiniciproducens was identified in shake-flask trials. The addition of a defined amount of glucose improved the growth and succinic acid productivity significantly. In fed-batch processes with glycerol as sole substrate, a maximum succinic acid concentration and product substrate yield were obtained. The addition of glucose led to a 2.5-fold increased succinic acid concentration whereas the product substrate yield remained nearly constant. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Bretz K.,Fraunhofer Institute for Environmental, Safety and Energy Technology | Kabasci S.,Fraunhofer Institute for Environmental, Safety and Energy Technology
Biotechnology and Bioengineering | Year: 2012

The aim of this work was the development of a feed-control for a succinic acid production fed-batch process. The performed batch trials indicated a correlation between succinic acid production and base consumption pH control. Based on the metabolism of Anaerobiospirillum succiniciproducens, a theoretical correlation between base consumption and glucose feed was established and proved in cultivation trials. With the established fed-batch process, the succinic acid yield could be increased to 0.875 (g/g glucose) in comparison to batch processes (0.60) with similar glucose concentrations. Additionally, the results indicate that the osmolarity of the medium has a significant influence on succinic acid production. © 2011 Wiley Periodicals, Inc. Source

Metz M.,Fraunhofer Institute for Environmental, Safety and Energy Technology | Doetsch C.,Fraunhofer Institute for Environmental, Safety and Energy Technology
Energy | Year: 2012

Due to the rapid increase of wind and photovoltaic generation, flexible storage applications become more important. Electric vehicles are supposed as one option to fill the gap between a fixed energy demand and a stochastic feed in from fluctuating energy sources. But the charging loads will also affect the grid load, since the transport sector contributes considerably to the total energy consumption today. This study examines the conflicting relationship between user mobility and grid support and introduces an approach to simulate large vehicle fleets on the basis of individual driving profiles.9744 driving profiles from the German mobility panel were used within this examination. 958 were classified as potential early adopters for electric vehicles. Those vehicles could provide grid support in 81% of the time, when charging spots are available at home and at work. We simulated the charging loads under the restrictions of the individual mobility for the scenario 2030. Uncoordinated charging will increase the load fluctuations, whereas coordinated charging loads allow load shifting without limiting the mobility. The additional electricity demand is moderate over the next two decades. © 2012 Elsevier Ltd. Source

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