Serbia

Bearing in mind the multiple effects of hydrogen in steels the specific mechanism of hydrogen embrittlement (HE) is active depending on the experimental conditions and numerous factors which can be grouped as environmental mechanical and material influences. A large number of contemporary studies and models about hydrogen environment assisted cracking and HE in steels are presented in the form of critical review in this paper. This critical review represent the necessary background for the development of a multiscale structural integrity model based on correlation between simultaneously active HE micro-mechanisms: the hydrogen-enhanced localized plasticity (HELP) and the hydrogen-enhanced decohesion (HEDE) - (HELP+HEDE) and macro-mechanical response of material unevenly enriched with hydrogen during service of boiler tubes in thermal fossil fuel power plant. Several different experimental methods and techniques were used to determine the boiler tube failure mechanism and afterwards also the viable HE mechanisms in the investigated ferritic-pearlitic low carbon steel grade 20 - St.20 (equivalent to AISI 1020). That represent a background for the development of a structural integrity model based on the correlation of material macro-mechanical properties to scanning electron microscopy fractography analysis of fracture surfaces of Charpy specimens in the presence of confirmed and simultaneously active HE micro-mechanisms (HELP+HEDE) in steel. The aim of this paper is to show how to implement what we have learned from theoretical HE models into the field to provide industry with valuable data and practical structural integrity model.

Optimal design and performance analysis of renewable energy system to serve the cruise ship main and auxiliary power in Stockholm Sweden is presented in this paper. The goal is to integrate renewable energy systems in small and large ships for greener and sustainable marine transport. The power load for the cruise ship was determined and modeling and simulation analysis was used to investigate the daily and annual performance of the power system architectures including the efficiency and capacity factors of the energy conversion systems. The total electrical power generated from the solar PV PEM fuel cell and Diesel generator; the cost of electricity; and the greenhouse gas and particulate matter PM emissions were determined. The proposed renewable energy system offers a good penetration of renewable energy system (13.83%) and greenhouse gas and particulate emissions reduction (9.84% emissions reduction compared to baseline system using Diesel engines). The integration of renewable and clean power systems such as solar PV and PEM fuel cell (high electrical efficiency) is very attractive solution for onboard ship power generation. They are economically viable (reduce the cost of Diesel fuel) cleaner than the conventional gas turbine and internal combustion engines and reduce the dependency on fossil fuel.

This study evaluated the economic feasibility of producing hydrogen from natural gas via thermal degradation in a plasma reactor. Plasma pyrolysis where natural gas passes through the space between electrodes and serves as the working medium enables high hydrogen yields without emitting carbon monoxide or carbon dioxide. Instead the primary products are hydrogen and solid carbon. Unlike conventional methods this approach requires no catalysts addressing a major technological limitation. A thermodynamic equilibrium model based on Gibbs free energy minimization was used to analyze the process over a temperature range of 500–2500 K. The results indicate an optimal temperature of approximately 1500 K which achieved a 99.5% methane conversion by mass. Considering the capital and operating costs and profit margins the hydrogen production cost was estimated at 3.49 EUR/kg. The sensitivity analysis revealed that the price of solid carbon had the most significant impact which potentially raised the hydrogen cost to 4.53 EUR/kg or reduced it to 1.70 EUR/kg.