Featured Publications Q3-2024

Impact of filler size and shape on performance of thermal energy storage

Division Heat and Buildings

© 2024 The Authors. Published by Elsevier Ltd.

Journal of Energy Storage | Volume 98, Part B | 20 September 2024 | 113157

Julius Weiss, Tatvakumar Arvindbhai Bhanderi, Thomas Fluri

 

Stratified high temperature thermal energy storage (TES) systems with filler materials present significant potential for cost reduction compared to the conventional two-tank storage systems. This study introduces a new numerical model for TES systems that accounts for mixing effects at the inlet, which are often neglected in similar models.

The model was experimentally validated using a setup based on similarity theory, demonstrating comparable conditions between water-based and molten salt-based TES systems. A comprehensive parameter study was conducted, varying both the size and shape of the filler materials.

The results indicate that for filler sizes above 1 cm in diameter the filler shape plays a crucial role in TES performance. Smaller fillers generally achieve better storage performance, while larger fillers lead to a deterioration in thermal stratification.

This study enhances the understanding of the dynamic behavior of TES systems and identifies key design parameters. Further validation with molten salt-based systems is planned in future work.

Tailoring perovskite crystallization and interfacial passivation in efficient, fully textured perovskite silicon tandem solar cells

Division Photovoltaics

© 2024 The Author(s). Published by Elsevier Inc.

Joule | 19 July 2024

Oussama Er-raji, Mohamed A.A. Mahmoud, Oliver Fischer, Alexandra J. Ramadan, Dmitry Bogachuk, Alexander Reinholdt, Angelika Schmitt, Bhushan P. Kore, Thomas William Gries, Artem Musiienko, Oliver Schultz-Wittmann, Martin Bivour, Martin Hermle, Martin C. Schubert, Juliane Borchert, Stefan W. Glunz, Patricia S.C. Schulze

 

As silicon solar cells are approaching their theoretical efficiency limit, perovskite silicon tandem solar cells promise to be a strong candidate to further raise the efficiency potential with only a little additional production costs.

Nevertheless, perovskite absorbers deposited on industry-compatible textured silicon with large pyramid size (>1 μm) often suffer from a high grain boundary defect density and poor interfacial passivation at the perovskite/electron transport layer (C60) junction. We tackle both loss mechanisms by introducing a multi-functional additive (urea), which simultaneously regulates the perovskite crystallization as well as passivates the perovskite/C60 interface.

Together with an optimization of functional layers, a fully-textured perovskite silicon tandem solar cell with 30% power conversion efficiency was produced. This approach is of high relevance for the industrialization of tandem solar cells.

Inductive loops in impedance spectra of PEM water electrolyzers

Division Hydrogen Technologies

© 2024 The Authors. Published by Elsevier B.V.

Journal of Power Sources | Volume 622 | 1 December 2024 | 235375

Debora Brinker, Niklas Hensle, Jerónimo Horstmann de la Viña, Irene Franzetti, Lena V. Bühre, Umesh Anirudh Andaluri, Charlotte Menke, Tom Smolinka, André Weber

 

Electrochemical impedance spectroscopy (EIS) is an established electrochemical characterization method.

In several applications like batteries and fuel cells the low-frequency inductive feature is widely discussed. However, for PEM water electrolysis cells the so-called “inductive loop” is not discussed and the physio-chemical process behind it is yet not known.

With the present work we can encircle the origin of the inductive loop using variations of the catalyst layer and membrane thickness, reference electrode measurements and material interventions to purposely increase diffusion related resistances. The impedance measurements are analyzed with the Distribution of Relaxation Time (DRT) method and subsequent equivalent circuit modeling (ECM). We provide process hypotheses and can relate the inductive loop with a membrane (electrolyte) effect.

Revealing the Local pH Value Changes of Acidic Aqueous Zinc Ion Batteries with a Manganese Dioxide Electrode during Cycling

Division Power Solutions

© 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited

Journal of The Electrochemical Society | Volume 167 | Number 2 | 30 January 2020

Christian Friedrich Bischoff, Oliver Sebastian Fitz, Jordan Burns, Manuel Bauer, Harald Gentischer, Kai Peter Birke, Hans-Martin Henning and Daniel Biro

 

Zinc-ion batteries (ZIB) are considered a promising battery technology for stationary applications. Due to the high level of safety due to the use of a water-based electrolyte and the high cost reduction potential due to the use of highly available and environmentally friendly materials, they represent an interesting alternative to lithium-ion batteries. Nevertheless, the reaction mechanism of the ZIB cell chemistry in a water-based electrolyte environment has still not been definitively clarified. 

At Fraunhofer ISE, we are investigating a promising variant of ZIB with the material combination zinc at the anode and manganese dioxide at the cathode in acidic electrolytes. In this publication, a pH indicator has been added to the water-based electrolyte as an innovative research approach. In transparent experimental cells, the electrochemical processes in the battery cell could be investigated locally during the charging/discharging of the battery (in-operando). Using electrolyte variations and supplemented by local pH measurements using small pH sensors, the electrochemical processes could be quantified and conclusions about the reaction mechanism could be drawn. This work represents an important basis in the literature on ZIB as well as for the following research work at Fraunhofer ISE in research projects with industry participation. The work has already been cited over 100 times since publication.