Zdenko Šimić

Small wind off-grid system optimization regarding wind turbine power curve

Paper is presenting results from modeling of small hybrid off-grid system. The system is built from solar photo voltaic, wind, and diesel power sources. Realistic data were used regarding predicted solar global radiation, wind speeds, and load. Simulation was performed with HOMER micropower optimization tool. Special focus was put on the estimation of how wind turbine power curve can influence cost of energy and amount of electrical energy produced from the available wind. Keeping the rest of system unchanged five different wind turbine power curves was evaluated. System configuration is changed only regarding optimal number of some components (i.e., photovoltaic power, battery and charger/inverter capacity). Results are showing the influence of wind turbine power curve both on the cost of energy and optimal system configuration.

Prediction of the time-dependent failure rate for normally operating components taking into account the operational history

Abstract The prediction of the time-dependent failure rate has been studied, taking into account the operational history of a component used in applications such as system modeling in a probabilistic safety analysis in order to evaluate the impact of equipment aging and maintenance strategies on the risk measures considered. We have selected a time-dependent model for the failure rate which is based on the Weibull distribution and the principles of proportional age reduction by equipment overhauls. Estimation of the parameters that determine the failure rate is considered, including the definition of the operational history model and likelihood function for the Bayesian analysis of parameters for normally operating repairable components. The operational history is provided as a time axis with defined times of overhauls and failures. An example for demonstration is described with prediction of the future behavior for seven different operational histories.

Small wind turbine power curve comparison

This paper focus is on the small wind turbines resource potential estimation. Assessment is done for seven selected small wind turbines and one measured set of wind speed data with the micropower optimization modeling tool HOMER. Goal was to investigate how estimated energy production and economical parameters are sensitive to the selection of small wind turbine. Selected turbines have similar rated power, but different blades diameter and aerodynamic characteristics. Energy production was quantified for one year with hourly resolution. Results from all different wind turbines were compared on the power production base, and on the economical base. Two sensitivity cases related to the wind speed and installation lifetime were also simulated. Results are showing significant importance of the small wind turbine selection for the both total energy production and economical feasibility. This makes small wind turbine characteristics such as reliability and power curves testing very important.

Integrated approach to energy security and critical infrastructure in Croatia

The paper presents the concept and first results of the electrical engineering work package of the ongoing project “Energy security and critical infrastructure”, supported by the Croatian energy company HEP and Croatian Ministry of Defense. Participating institutions are from academic and private sector from multiple areas of science, including sociology, technology and policy planning. Work presented in the paper identifies critical infrastructures of interest, and demonstrates model based on complex network theory and probabilistic security analysis. The Croatian electrical power system risk is analyzed in order to indentify critical nodes and determine the optimal distribution of resources for risk reduction. There is potential to further improve this primarily deterministic and probabilistic analysis with use of multi-agent systems.

Uncertainty Analysis of Method-Based Operating Event Groups Ranking

Safe operation and industrial improvements are coming from the technology development and operational experience (OE) feedback. A long life span for many industrial facilities makes OE very important. Proper assessment and understanding of OE remains a challenge because of organization system relations, complexity, and number of OE events acquired. One way to improve OE events understanding is to focus their investigation and analyze in detail the most important. The OE ranking method is developed to select the most important events based on the basic event parameters and the analytical hierarchy process applied at the level of event groups. This paper investigates further how uncertainty in the model affects ranking results. An analysis was performed on the set of the two databases from the 20 years of nuclear power plants in France and Germany. From all uncertainties the presented analysis selected ranking indexes as the most relevant for consideration. Here the presented analysis of uncertainty clearly shows that considering uncertainty is important for all results, especially for event groups ranked closely and next to the most important one. Together with the previously performed sensitivity analysis, uncertainty assessment provides additional insights and a better judgment of the event groups’ importance in further detailed investigation.

Application of ASTEC, MELCOR, and MAAP Computer Codes for Thermal Hydraulic Analysis of a PWR Containment Equipped with the PCFV and PAR Systems

The integrity of the containment will be challenged during a severe accident due to pressurization caused by the accumulation of steam and other gases and possible ignition of hydrogen and carbon monoxide. Installation of a passive filtered venting system and passive autocatalytic recombiners allows control of the pressure, radioactive releases, and concentration of flammable gases. Thermal hydraulic analysis of the containment equipped with dedicated passive safety systems after a hypothetical station blackout event is performed for a two-loop pressurized water reactor NPP with three integral severe accident codes: ASTEC, MELCOR, and MAAP. MELCOR and MAAP are two major US codes for severe accident analyses, and the ASTEC code is the European code, joint property of Institut de Radioprotection et de Surete Nucleaire (IRSN, France) and Gesellschaft fur Anlagen und Reaktorsicherheit (GRS, Germany). Codes’ overall characteristics, physics models, and the analysis results are compared herein. Despite considerable differences between the codes’ modelling features, the general trends of the NPP behaviour are found to be similar, although discrepancies related to simulation of the processes in the containment cavity are also observed and discussed in the paper.

Forecasting prices of electricity on HUPX

The development of new simulation techniques by using Artificial Intelligence (AI) has become an improved tool to better forecast energy prices. This paper demonstrates building and validating a short term model for Hungarian day ahead power market — HUPX electricity price forecasting. This models takes into account multiple sources of information; the data set used is a table of historical hourly loads, electricity prices and other regional informations. Paper is discussing the application of intelligent systems to short term electricity prices forecasting and outlining proposed research direction.

Prediction of time dependent standby failure rates for periodically tested components taking into account the operational history

Abstract The prediction of time dependent standby failure rates was studied, taking into account the operational history of a component. These studies are important for applications such as system modeling in probabilistic safety analysis to evaluate the impact of equipment aging and maintenance strategies on the risk measures (e. g. reactor core damage frequency) considered. The time dependent model for the standby failure rate is defined based on the Weibull distribution and the principles of proportional age reduction by equipment overhauls. The parameters which determine the standby failure rate are estimated, including the definition of the operational history model and likelihood function for Bayesian analysis of parameters for periodically tested standby repairable components. The operational history is provided as time axis with defined times of overhauls, surveillance tests and failures. Assessment of time dependent unavailability due to the failure of periodically tested standby components is described. As an example, the prediction of the future behavior of components for seven different operational histories is described.

Sun trajectory modeling for specific location using PV measured data

In order to research the PV module characterization it was necessary to develop the Prototype PV characterization station. Among other possibilities derived from the measured results of Prototype PV characterization station it is also possible to model the Sun trajectory at installation location. Such measured results can be used to model Sun trajectory. Also, the Sun trajectory generated using presented model is verified with conventional analytical model Sun trajectory. Some conclusions for new approach are presented and discussed.

Computing the Top Event Uncertainty with Binary Decision Diagrams

This paper is discussing uncertainty quantification for the PSA model represented by BDD. First, it is discussed about uncertainty quantification of PSA model with BDD. Second, it is investigated about the difference in the quantified top event uncertainty between common partial uncertainty quantification approach and BDD approach.