Open Access

The present work deals with the integration of variable renewable energy sources, wind and solar energy into the European and US power grid. In contrast to other networks, such as the gas supply mains, the electricity network is practically not able to store energy. Generation and consumption therefore always have tobe balanced. Currently, the load curve is viewed as a rigid boundary condition, which must be followed by the generation system. The basic idea of the approach followed here is that weather-dependent generation causes a shift of focus of the electricity supply. At high shares of wind and solar generation, the role of the rigid boundary condition falls to the residual load, that is, the remaining load after subtraction of renewable generation. The goal is to include the weather dependence as well as the load curve in the design of the future electricity supply. After a brief introduction, the present work first turns to the underlying weather-, generation and load data, which form the starting point of the analysis. In addition, some basic concepts of energy economics are discussed, which are needed in the following. In the main part of the thesis, several algorithms are developed to determine the load flow in a network with a high share of wind and solar energy and to determine the backup supply needed at the same time. Minimization of the energy needed from controllable power plants, the capacity variable power plants, and the capacity of storing serve as guiding principles. In addition, the optimization problem of grid extensions is considered. It is shown that it can be formulated as a convex optimization problem. It turns out that with an optimized, international transmission network which is about four times the currently available transmission capacity, much of the potential savings in backup energy (about 40%) in Europe can be reached. In contrast, a twelvefold increase the transmission capacity would be necessary for a complete implementation of all possible savings in dispatchable power plants. The reduction of the dispatchable generation capacity and storage capacity, however, presents a greater challenge. Due to correlations in the generation of time series of individual countries, it may be reduced only with difficulty, and by only about 30%. In the following, the influence of the relative share of wind and solar energy is illuminated and examined the interplay with the line capacitance. A stronger transmission network tends to lead to a higher proportion of wind energy being better integrated. With increasing line capacity, the optimal mix in Europe therefore shifts from about 70% to 80% wind. Similar analyses are carried out for the US with comparable results. In addition, the cost of the overall system can be reduced. It is interesting at this point that the advantages for the network integration may outweigh higher production costs of individual technologies, so that it is more favourable from the viewpoint of the entire system to use the more expensive technologies. Finally, attention is given to the flexibility of the dispatchable power plants. Starting from a Fourier-like decomposition of the load curve as it was a few years ago, when hardly renewable generation capacity was present, capacities of different flexibility classes of dispatchable power plant are calculated. For this purpose, it is assumed that the power plant park is able to follow the load curve without significant surplusses or deficits. From this examination, it is derived what capacity must at least be available without having to resort to a detailed database of existing power plants. Assuming a strong European cooperation, with a stronger international transmission network, the dispatchable power capacity can be significantly reduced while maintaining security of supply and generating relatively small surplusses in dispatchable power plants.

The transition to a future electricity system based primarily on wind and solar PV is examined for all regions in the contiguous US. We present optimized pathways for the build-up of wind and solar power for least backup energy needs as well as for least cost obtained with a simplified, lightweight model based on long-term high resolution weather-determined generation data. In the absence of storage, the pathway which achieves the best match of generation and load, thus resulting in the least backup energy requirements, generally favors a combination of both technologies, with a wind/solar PV (photovoltaics) energy mix of about 80/20 in a fully renewable scenario. The least cost development is seen to start with 100% of the technology with the lowest average generation costs first, but with increasing renewable installations, economically unfavorable excess generation pushes it toward the minimal backup pathway. Surplus generation and the entailed costs can be reduced significantly by combining wind and solar power, and/or absorbing excess generation, for example with storage or transmission, or by coupling the electricity system to other energy sectors.

We introduce a top-down stylized model to analyse the impact of a transition to a European power system based only on wind and solar power. Wind and solar power generation is calculated from high-resolution weather data and based on the country specific electricity demand alone, we introduce a model of the conventional power system that facilitates simple spatio-temporal modelling of its macroscopic behavior without direct reference to the underlying technological, economical, and political development in the system. Using this model, we find that wind and solar power generation can replace conventional power generation and power capacity to a large degree if power transmission across the continent is made possible.

Acute kidney injury is associated with mortality in COVID-19 patients. However, host cell changes underlying infection of renal cells with SARS-CoV-2 remain unknown and prevent understanding of the molecular mechanisms that may contribute to renal pathology. Here, we carried out quantitative translatome and whole-cell proteomics analyses of primary renal proximal and distal tubular epithelial cells derived from human donors infected with SARS-CoV-2 or MERS-CoV to disseminate virus and cell type–specific changes over time. Our findings revealed shared pathways modified upon infection with both viruses, as well as SARS-CoV-2-specific host cell modulation driving key changes in innate immune activation and cellular protein quality control. Notably, MERS-CoV infection–induced specific changes in mitochondrial biology that were not observed in response to SARS-CoV-2 infection. Furthermore, we identified extensive modulation in pathways associated with kidney failure that changed in a virus- and cell type–specific manner. In summary, we provide an overview of the effects of SARS-CoV-2 or MERS-CoV infection on primary renal epithelial cells revealing key pathways that may be essential for viral replication.