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Temperature has a significant influence on the behavior of batteries and their lifetime. There are several studies in literature that investigate the aging behavior under electrical load, but are limited to homogeneous, constant temperatures. This article presents an approach to quantifying cyclic aging of lithium-ion cells that takes into account complex thermal boundary conditions. It not only considers different temperature levels but also spatial and transient temperature gradients that can occur despite-or even due to-the use of thermal management systems. Capacity fade and impedance rise are used as measured quantities for degradation and correlated with the temperature boundary conditions during the aging process. The concept and definition of an equivalent aging temperature (EAT) is introduced to relate the degradation caused by spatial and temporal temperature inhomogeneities to similar degradation caused by a homogeneous steady temperature during electrical cycling. The results show an increased degradation at both lower and higher temperatures, which can be very well described by two superimposed exponential functions. These correlations also apply to cells that are cycled under the influence of spatial temperature gradients, both steady and transient. Only cells that are exposed to transient, but spatially homogeneous temperature conditions show a significantly different aging behavior. The concluding result is a correlation between temperature and aging rate, which is expressed as degradation per equivalent full cycle (EFC). This enables both temperature-dependent modeling of the aging behavior and its prediction.

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The development of a low-carbon technique to produce hydrogen from fossils would be of great importance during the transition to a long-term sustainable energy system. Methane decarbonisation, the well-known transformation of methane into hydrogen and solid carbon, is a potential candidate in this regard. At the Institute for Advanced Sustainability Studies (IASS), a new alternative technology for methane decarbonisation applying liquid metal technology was proposed and an ambitious programme was set up in collaboration with the Karlsruhe Institute of Technology (KIT). The comprehensive programme included the following: conceptual design of a liquid metal bubble column reactor and material testing, process engineering incorporating carbon separation and hydrogen purification, and a socioeconomic analysis. In the present paper, an overview of the programme along with some of the results, are presented. Results from the experimental campaigns show that the liquid metal reactor design works effectively in producing hydrogen and carbon separation. Other aspects of the technology such as socio-economics, environmental impact, and scalability also seem to be favourable making methane decarbonisation based on liquid metal technology a potential candidate for CO2-free hydrogen production.

Alongside electrical loads, it is known that temperature has a strong influence on battery behavior and lifetime. Investigations have mainly been performed at homogeneous temperatures and non-homogeneous conditions in single cells have at best been simulated. This publication presents the development of a methodology and experimental setup to investigate the influence of thermal boundary conditions during the operation of lithium-ion cells. In particular, spatially inhomogeneous and transient thermal boundary conditions and periodical electrical cycles were superimposed in different combinations. This required a thorough design of the thermal boundary conditions applied to the cells. Unlike in other contributions that rely on placing cells in a climatic chamber to control ambient air temperature, here the cell surfaces and tabs were directly connected to individual cooling and heating plates. This improves the control of the cells' internal temperature, even with high currents accompanied by strong internal heat dissipation. The aging process over a large number of electrical cycles is presented by means of discharge capacity and impedance spectra determined in repeated intermediate characterizations. The influence of spatial temperature gradients and temporal temperature changes on the cyclic degradation is revealed. It appears that the overall temperature level is indeed a decisive parameter for capacity fade during cyclic aging, while the intensity of a temperature gradient is not as essential. Furthermore, temperature changes can have a substantial impact and potentially lead to stronger degradation than spatial inhomogeneities.

Results of a recent photovoltaic energy life cycle study are presented. The focus lies on the energy payback time (EPBT) and the CO 2 emission rate achievable with state-of-the-art industrial production chains for conventional monocrystalline and multicrystalline silicon modules. The data have been provided by European manufacturers and represent the processes in their European-primarily German-production sites. The analysis covers all steps from metal grade silicon refinement down to assembled modules as shipped to the customer. Balance of system contributions have not been included in the analysis and in the result figures, both for EPBT and CO 2 emissions. The resulting EPBT values for the modules only are 1.09 and 0.93 years for monocrystalline and multicrystalline silicon, respectively, both under southern European conditions. CO 2 emission rates strongly depend on the scenario considered, ranging from 18 g/kWh in southern Europe to 60 g/kWh in northern Germany under worst-case conditions for useful lifetime and degradation.

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