Search results for: Thilo Krause
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Chemistry – A European Journal > 24 > 23 > n/a - n/a
A hydroxymethylation of alkynes with carbon dioxide and hydrogen was achieved without producing any salt waste. In a sequential procedure, terminal alkynes are carboxylated followed by hydrogenation of the carboxylate salts formed as intermediates. The gorge symbolizes the gap in pKa at which the two reaction steps usually operate. The key to bridging this gap was to identify a base that, under carefully...
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Chemistry – A European Journal > 24 > 23 > 6019 - 6024
A copper(I) catalyst enables the insertion of carbon dioxide into alkyne C−H bonds by using a suitable organic base with which hydrogenation of the resulting carboxylate salt with regeneration of the base becomes thermodynamically feasible. In the presence of catalytic copper(I) chloride/4,7‐diphenyl‐1,10‐phenanthroline, polymer‐bound triphenylphosphine, and 2,2,6,6‐tetramethylpiperidine as the base,...
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Journal of Applied Crystallography > 50 > 3 > 673 - 680
Coherent X‐ray diffraction imaging at symmetric hhh Bragg reflections was used to resolve the structure of GaAs/In0.15Ga0.85As/GaAs core–shell–shell nanowires grown on a silicon (111) substrate. Diffraction amplitudes in the vicinity of GaAs 111 and GaAs 333 reflections were used to reconstruct the lost phase information. It is demonstrated that the structure of the core–shell–shell nanowire can be...
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Higher shares of electricity generation from renewable energy sources and market liberalization is increasing uncertainty in power systems operation. At the same time, operation is becoming more flexible with improved control systems and new technology such as phase shifting transformers (PSTs) and high voltage direct current connections (HVDC). Previous studies have shown that the use of corrective...
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Angewandte Chemie International Edition > 55 > 47 > 14752 - 14755
A system consisting of catalytic amounts of [(p‐cym)RuCl2]2/PEt3⋅HBF4, K2CO3 as the base, and NMP as the solvent efficiently mediates the ortho‐C−H arylation of benzoic acids with aryl bromides at 100 °C. Replacing the phosphine ligand with the amino acid dl‐pipecolinic acid enables the analogous transformation with aryl chlorides. The key advantage of this broadly applicable transformation is the...
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Angewandte Chemie > 128 > 47 > 14972 - 14975
A system consisting of catalytic amounts of [(p‐cym)RuCl2]2/PEt3⋅HBF4, K2CO3 as the base, and NMP as the solvent efficiently mediates the ortho‐C−H arylation of benzoic acids with aryl bromides at 100 °C. Replacing the phosphine ligand with the amino acid dl‐pipecolinic acid enables the analogous transformation with aryl chlorides. The key advantage of this broadly applicable transformation is the...
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Forecast uncertainty related to the power production from renewables frequently leads to significant changes between the scheduled and the actual power injections. Larger and more frequent fluctuations in the power production require new approaches to handle congestion and ensure system security. In this paper, we investigate how different strategies for reserve activation influence the cost of integrating...
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IEEE Transactions on Power Systems > 2017 > 32 > 2 > 1626 - 1637
Higher shares of electricity generation from renewable energy sources and market liberalization is increasing uncertainty in power systems operation. At the same time, operation is becoming more flexible with improved control systems and new technology such as phase shifting transformers (PSTs) and high voltage direct current connections (HVDC). Previous studies have shown that the use of corrective...
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This paper presents a variety of different Security Constrained Optimal Power Flow formulations addressing four power system operation and planning problems: (a) forecast uncertainty of Renewable Energy Sources (RES) in-feed and load, (b) security criteria based on contingency risk, (c) corrective control offered through High Voltage Direct Current (HVDC) lines and flexible demand, (d) operation of...
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This note is a response to the discussion on the session “Managing uncertainty in power systems” by O. Alizadeh Mousavi and R. Cherkaoui [1] from the IREP Symposium 2013.
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In this paper, uncertainties from wind power in-feed are taken into account in a DC security-constrained optimal power flow (SCOPF) by formulating probabilistic constraints. The deviations from the wind power forecast are represented as Gaussian random variables and an analytical reformulation of the constraints is proposed, which is exact for the Gaussian distribution. The resulting formulation has...
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In this paper, an analytical approach is developed to address network planning questions for meshed AC networks. First, relationships are derived to compare the effectiveness of expansion measures, such as the building of long lines in the form of overlay grids, or local reinforcements along the transmission path in the existing grid. Results show that overlay networks are preferable, transferring...
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This paper derives a method for HVDC line placement in order to maximize social welfare. Assuming linear generator costs, it shows that for N congestions, there exist exactly N +1 marginal generators. It then demonstrates that HVDC lines connecting a high-cost with a low-cost marginal generator lead to the maximization of social welfare. The method poses an upper bound on the line installation costs,...
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Various trends in power systems increase the need for network investments on the transmission level. In this paper we compare different investment criteria and transmission technologies to determine where and how the network should be reinforced. We deploy an agent-based model taking explicitly into account that generation companies might behave strategically by submitting bids to the marketplace...
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Considering aging power system infrastructures in conjunction with increased electricity trading activities, there is a strong need for future investments in electricity grids. Technological progress has made available a number of different investment alternatives, ranging e.g. from “standard” reinforcements of existing transmission capacities to the installation of Flexible AC Transmission Systems...
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This paper describes an approach to model interconnected national energy systems using the concept of energy hubs. Each country is modeled as an energy hub, characterized by the national generation infrastructures for heat and electricity, the demand for heat and electricity as well as properties detailing mobility demand. Countries are interconnected via electricity and gas networks, i.e. it is possible...
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In this paper a model for maximizing exergy efficiency in multi-carrier energy systems is introduced. Based on modeling concepts developed in the project “Vision of Future Energy Network”, e.g. the Energy Hub concept, exergy is modeled in the context of energy systems that involve multiple energy carriers such as electricity, natural gas and heat. In the context of this integrated consideration of...
