Control strategy of offshore marine energy converters for improving reliability availability and cost effectiveness

High–energy density places in the sea are typically located some kilometres away from the shores. Harvesting energy from these sites is desirable but defiant. In these areas, one of the challenges is the harsh weather conditions, which may limit the maintenance accessibility of electrical generators. The nature of the marine resources (i.e. turbulence and wave spectrum) could create high-load patterns that may jeopardise the reliability and economic feasibility of entire projects. Thus, reliability of marine energy converters becomes a key challenge for engineers. Most marine energy devices are being designed to allow the usage of off–the–shelf electrical generators. At the cost of dismissing potential benefits of especially designed machines, developers are focusing their efforts in optimising the hydro-dynamic and aerodynamic performance of the devices. Stress-levels seen by the electrical machine are device dependant. The work here presented is focused on an oscillating water column (OWC). This is a system using a semi open chamber with one opening semi submerged under the sea and the other directed to a duct. The air pushed and sucked by the waves is forced to pass through an air turbine that extracts energy from the moving fluid. The turbine is then attached to an electrical generator for a final energy conversion. The key aspect of this work is to present a proposed methodology that could be used to extend the life of a machine. The methodology first consists on defining the life of a generator as a single variable phenomenon. Second, the methodology is assuming that a deterioration model can be used as a proxy for estimating the life of the generator. Third, the in–service load profile is calculated by modelling a generator in an OWC. Lastly, with the load profile and the life estimated from the generator, a power management technique is demonstrated

Technology Pathway Partnership Final Scientific Report

This report covers the scientific progress and results made in the development of high efficiency multijunction solar cells and the light concentrating non-imaging optics for the commercial generation of renewable solar energy. During the contract period the efficiency of the multijunction solar cell was raised from 36.5% to 40% in commercially available fully qualified cells. In addition significant strides were made in automating production process for these cells in order to meet the costs required to compete with commercial electricity. Concurrent with the cells effort Boeing also developed a non imaging optical systems to raise the light intensity at the photovoltaic cell to the rage of 800 to 900 suns. Solar module efficiencies greater than 30% were consistently demonstrated. The technology and its manufacturing were maturated to a projected price of < $0.015 per kWh and demonstrated by automated assembly in a robotic factory with a throughput of 2 MWh/yr. The technology was demonstrated in a 100 kW power plant erected at California State University Northridge, CA

Reliability Abstracts and Technical Reviews 1966

No abstract availabl

Managing the restoration of membranes in reverse osmosis desalination using a digital twin

This thesis studies degradation and restoration policies for a pressure vessel in a reverse osmosis (RO) desalination plant. In the study context, biofouling is the primary cause of the degradation of the RO membrane elements, amplified by seasonal algal blooms. This research developed a decision support system (DSS) for evaluating membrane restoration strategy. The engine of the DSS is a digital twin (DT), a virtual representation of wear (degradation) and restoration of membrane elements in a RO pressure vessel. The basis of the DT is a mathematical model that describes an RO pressure vessel as a novel multi-component system in which the hidden wear-states of individual elements (components) are quantified, and elements can be swapped or replaced. This contrasts with the contemporary presentation of a membrane system as a single system in the literature. The parameters of the model are estimated using statistical methods. The research approach is described in the context of a case study on the Carlsbad Desalination Plant in California. Results show a good fit between the observed and the modelled wear-states. Competing policies are compared based on risk, cost, downtime, and the number of stoppages. Projections indicate that a significant cost-saving can be achieved while not compromising the integrity of the plant. Alternative policies 11 and 12 showed better wear management than the current policy 10 of the maintenance company while reducing costs between $0.7 to$1.7 million for the next five years.The research in the thesis contributes toward maintenance modelling. New models of multivariate degradation and imperfect repair are presented. The research makes an important contribution to desalination and water treatment engineering, providing a unique membrane maintenance management approach currently absent from the literature. The thesis also contributes to the maintenance theory. It proposes a general approach for applying a decision support system (DSS) for maintenance requirements analysis, involving a digital twin (DT) for wear and repair projections when wear is stochastic, and repair effects are not immediately apparent. The essential elements of a DSS are discussed. This research encourages a dialogue between researchers of maintenance theory and modelling and practitioners of maintenance planning about decision support systems and digital twins that not only project the when but also evaluate the what in maintenance strategy. The presented concept of a DSS driven by a DT for maintenance requirement analysis has valuable practical implications, and the thesis, in discussing this concept, makes an essential contribution to the discussion about Industry 4.0, digital twins, and maintenance

Proceedings of the 36th International Workshop Statistical Modelling July 18-22, 2022 - Trieste, Italy

The 36th International Workshop on Statistical Modelling (IWSM) is the first one held in presence after a two year hiatus due to the COVID-19 pandemic. This edition was quite lively, with 60 oral presentations and 53 posters, covering a vast variety of topics. As usual, the extended abstracts of the papers are collected in the IWSM proceedings, but unlike the previous workshops, this year the proceedings will be not printed on paper, but it is only online. The workshop proudly maintains its almost unique feature of scheduling one plenary session for the whole week. This choice has always contributed to the stimulating atmosphere of the conference, combined with its informal character, encouraging the exchange of ideas and cross-fertilization among different areas as a distinguished tradition of the workshop, student participation has been strongly encouraged. This IWSM edition is particularly successful in this respect, as testified by the large number of students included in the program

Reliability Abstracts and Technical Reviews January-December 1968

No abstract availabl

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen

Cumulative index to NASA Tech Briefs, 1986-1990, volumes 10-14

Tech Briefs are short announcements of new technology derived from the R&D activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This cumulative index of Tech Briefs contains abstracts and four indexes (subject, personal author, originating center, and Tech Brief number) and covers the period 1986 to 1990. The abstract section is organized by the following subject categories: electronic components and circuits, electronic systems, physical sciences, materials, computer programs, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences