Featured Publications Q1-2024

Sustainable Energy & Fuels | 2024 | Advance Article | 05 April 2024

T. Cholewa, B. Steinbach, C. Heim, F. Nestler, T. Nanba, R. Güttel and O. Salem

The production of ammonia (NH3) with green hydrogen is expected to play an important role in the global energy transition. To make this process more efficient, experiments were carried out with ruthenium- and iron-based catalysts. Pressures between 10 and 80 bar and temperatures of 350 to 450 °C were used. The data enabeld the development of kinetic models that allow the precise prediction of the synthesis process . These models could be used in the future to further optimize ammonia synthesis and make it available for industrial production.

iScience | Volume 26, Issue 12 | December 2023 | 108432

Andreas Velte-Schäfer, Eric Laurenz, Gerrit Füldner

Thermally driven heat pumps and chillers use waste heat as heat source. In applications with a waste heat source and with  a need for cooling, thermally driven chillers can cleverly combine these two heat flows. Examples of this include data centers and the use of waste heat from power electronics to cool process gas flows in electrolysis. For the quick -but precise analysis of the potential of this technology a simple calculation method for efficiency and cooling capacity is required. In the calculation methods available to date, the closely coupled heat and mass transfer processes in adsorption chillers are described with a system of transient differential equations. In the paper we develop a radically simplified approach that reduces this calculation to an algebraic system of equations. This enables significantly faster calculations, which is very advantageous for both prediction and model validation. The newly developed method could also be used in established tools for process planning, which was previously not possible. The paper is the result of more than a decade of research and represents an important milestone in model development

Energy Technology | Volume 11, Issue 12 | December 2023 | 2300460

Dennis Wöhrle, Bruno Burger, Oliver Ambacher

The use of wide-bandgap (WBG) power devices made of gallium nitride (GaN) or silicon carbide (SiC) offers numerous advantages over silicon devices, which are highlighted in the article. However, the state-of-the-art power module packaging technology has too high power and gate loop stray inductances to fully leverage the capabilities of WBG power semiconductors. In the article, a novel power module design comprising a 650 V, 300 A half-bridge with integrated DC-link and gate drivers is proposed to overcome the limitations associated with state-of-the-art power module packaging. The investigations include a finite element analysis of the parasitic elements and a subsequent double-pulse test simulation. The results promise outstanding electrical performance of the novel power module design.

ACS Energy Letters | 9, 3, 908-910 | February 8, 2024

Ershuai Jiang, Mathias List, Armin Jamali, and Uli Würfel

When connecting organic solar cells to a module in series, efficient structuring using lasers is essential in order to minimize the inactive area as much as possible. In the meantime, there are a number of interesting applications that require only low electrical power but high voltages of a few hundred to a few thousand volts. These include, in particular, so-called dielectric elastomer actuators, but also applications such as electro-aerodynamic propulsion. 

The article reports on the development of organic solar modules, which consist of 1640 laser-structured, series-connected cells on an area of 3.6 x 3.7 cm². Under 100 klux warm white LED light, an open-circuit voltage (V_OC) of 1256.6 V and a power conversion efficiency (PCE) of 19.7% could be achieved with the organic absorber material PV-X plus, while a V_OC of 1739.5 V and a PCE of 6.4% could be achieved with PM6:GS-ISO. These values are considerably higher than anything previously reported in the literature for these small areas. The work was carried out in cooperation with the University of Freiburg in the framework of the DFG funded excellence cluster livMatS.