NDT of Composites Based on Active Infrared Thermography and Ultrasound Testing

Composite materials, such as glass and carbon reinforced ones, are characterized by inhomogeneous structure that requires non destructive testing based on uncommon evaluation methods. The presented approach is based on the active infrared thermography, supported by the A-scan ultrasound testing. The heat wave propagation induced by halogen or xenon bulbs, due to the differences in thermal conductivity, reveals material structure and anomalies. In our previous work we have developed several signal processing and depth evaluation methods, but the real engineering approach requires additional approval testing methods such as the A-scan ultrasound is. The A-scan ultrasound, based on the low frequency probe, enables approval of anomalies located by infrared thermography. The active infrared thermography, as a full field method, enables evaluation of the whole scanned area. The A-scan, as a point-wise method, does not provide the image of whole area of interest. By combining these two methods, robust and reliable approach to analysis of composite structure is enabled.

Energy Decarbonisation and Primary Energy in the 21st Century

This paper emphasizes the role of primary sources of energy, primarily oil and gas in the future (so-called “energy mix”) with the expected trends in the future. The changes expected by the oil and gas sector in the 21st century have been underlined due to energy decarbonisation. There are intense discussions about the oil and gas future due to the effects of climate change and the announcement that oil is in the final phase of exploitation due to the high depletion of fields around the world. How are the big oil companies responding to these challenges and what are the trends of global energy consumption? In the 21st century, it is necessary to take in account all types of energy with the growth of renewable sources. In the meantime, natural gas is imposed as a bridge between fossil and decarbonised energy, and the trends in the gas segment in the world and in the Republic of Croatia will be emphasized as well. In addition, the new Croatian energy strategy must be aligned with changes in the oil and gas sector, as well as exploration and production of hydrocarbons. Carbon-free energy is still a long way, but the low-carbon energy period has begun.

Transhumanism — Robotics Interactions

Thinking wrong that the humanistic ideal has already been realized, transhumanism is promoting the liberation of man by progressive overcoming of his own biological boundaries in order to improve his physical and mental abilities, as well as his life extension. From interaction between biomimetic robotics and transhumanism augmented man was born. But a smart management application is still missing, that one for a future society, in which men and supermen will live together and which would allow technological improvement to everyone and halt the accelerated process of deepening socio-economic inequalities. That's the reason why the transhumanism is often experienced as an opponent and competitor to humanism, same as the new technology development which is often perceived as the goal in itself - as a phenomenon which is not in the service of the real needs of social development. Consequently, It is urgent to move from simple thinking (speculations, preferences and beliefs) to the complex one: proposing hypotheses and solutions, creating relationships and observing interactions, seeking criteria, relying on verified facts and self-correction practices.

Trends in Hydropower

With a global focus on reducing carbon dioxide emissions, hydro power has come to the fore as an effective means of balancing other forms of electricity production from renewable sources (wind, photovoltaics and biomass). The role of hydropower in the modern mix of energy has led to favorable climatic conditions for development in the construction of new plants and upgrading with the renovation of existing hydroelectric power plants. Especially reversible hydropower plants with modern equipment with the so-called variable speed technology have a special role, which enables stability in the primary and secondary energy regulation system. A noteworthy trend is the construction of new facilities with low falls with the installation of highly efficient Kaplan and Tubular turbines. The already built projects in the fifth and sixth decades of the previous century, especially in northern Europe, are rapidly revamped and prepared for use in the next 40 to 50 years. Modern and sustainable approach to designing and preparing documentation for the construction of new or renewable power plants requires the use of modern information technology with 3D design and BIM (Building information Modeling) approach. In this way, young generations of engineers and consultants are easier to communicate with each other and reduce the possibility of errors in all phases of project realization. Key to the realization is the contracting of projects, the big dilemma whether to have EPC (Engineering, Procurement, and Construction) contracts (turnkey) a responsibility in one place or to deal with separate lots and engage their employees to control realization in order to minimize risk. Special attention is given to model research and development of turbines with reciprocal tests both on the model and prototype turbines.

How COVID-19 lockdown has impacted demand curves of Croatia and surrounding countries

Electrical energy is a specific commodity because it can’t be stored in significant quantities, so accurate day-ahead forecasting of total consumption plays a crucial role in stable operation of the whole power system. In order to maintain the adequacy, power generation and electricity consumption have to be constantly in a balance. Electricity demand curve is very sensitive and vulnerable to a lot of different factors that can be categorized in several main groups that include social, stochastic and weather dependent factors. In condition of global pandemic caused by COVID 19, prediction of total consumption is even more challenging task. New restrictive rules, that completely changed behavior of consumers, their daily routine and habits, have been adopted in most of the European countries. Hence, this lockdown restrictive measures affected the volume of electricity consumption and the shape of demand curves as well. This paper analyzes some of the cases with very variable electricity load, due to volatile households’ behavior, on cases of Croatia and countries in the region. Additionally, results are compared with the electricity load of Italy and Sweden whose economy and industry are well developed. Consumption of Sweden was interesting to observe because of its totally different approach of mitigating corona virus, without lockdown restrictions.

Maintenance of Filter at The Gas Turbine Compressor Intake and Electric Transformer Connector Based on Operational Reliability

The article analyzes the operational reliability of filter on the gas turbine compressor intake and the operational reliability of electric transformer connector. Empirical data (statistical sample) were collected to determine the failure density function f (t), the hazard function λ (t), and the expected value of mean time to failure MTTF. The numerical model was created in the Minitab 19 software tool. The Anderson-Darling test was used to accept or reject the hypothesis.

Dynamic Stability Enhancement Through the Application of Stabilizers of Electromechanical Oscillations

Power system dynamic stability is one of key issues system engineers face. Oscillations that regularly occur in the system, limit the transmission capability of the network. The need to study the stability of power systems has been increasingly growing along with the development of power systems and their grouping into large interconnections. The focus of this paper is determining the dynamic stability of a synchronous generator, and thus the power system, by applying the general theory of stability of dynamic systems. Furthermore, the procedure for the initial adjustment of the parameters of a conventional (IEEE3 type PSS1A) stabilizer of electromechanical oscillations is briefly described based on the frequency response analysis of a linear generator model also known as the Heffron-Phillips generator model.

Influence of Composition of Power Plant Fleets and Ownership of Transmission and Distribution Networks to Incumbent Company’s Business Success in Some Former Socialist EU Countries

By joining the EU, companies from eastern countries, which until then had largely operated in regulated circumstances, had to adapt to the open market. Liberalization and deregulation were imposed on them as new mantras, in contrast to ensuring the supply at all costs and addressing social issues. How these companies flourished in new circumstances is a legitimate topic for managerial research. This article researches the impact of the "hard assets" composition, that those companies operated, on their expected business success after a multi-year adjustment period. Positivistic research philosophy, "case study", and the deduction approach are used. The data were collected mainly from secondary sources. 3 research goals were selected with 3 relevant research questions. An attempt was made to respond to them on the example of 7 Central European countries and 11 companies, direct successors of original incumbents. The property is grouped into 3 groups: classical power plants (nuclear, hydro, coal), renewable power plants (wind, solar, bio mass) and lines (transmission and distribution). Criteria for success are selected according to usual praxis, but also adjusted to accessible data, predominantly from the company's annual financial statements. Contrary to the developed intuition, and based on cases of companies analyzed, there was no significant correlation between the selected criteria of success and the observed asset classes, serving as independent variables. The biggest problem in the research was access to data. This paper is an extraction from an MBA dissertation.

On the Future of Fission and Solar Energy

Our attitudes towards the risks of climate change must be reconsidered. We must recognise that the consequences will be huge and inevitable if we do not act now. Better to accept a few false alarms rather than be unprepared for a climate catastrophe. An outstanding example is the calculation by groups from Germany and the UK in 2009 (1) of the allowable emissions of CO2 before a 2°C increase in global temperature is exceeded. This leaves very little time, only 4 to 8 years, for mitigation measures. Nuclear fission now presents a formidable fleet of some 450 reactors benefitting from over 50 years of operational experience. Throughout decades of development, they reached outstanding safety standards, exceeding those of most renewable sources. However, the threat of climate change is calling this perspective into question as nuclear technology requires long-term stability of institutions. The future of nuclear fission will be determined after the expiration of the next decade with the development of hydro, solar and wind energy as replacements. For Croatia, in view of future climate insecurity, we cannot recommend the construction of a nuclear power plant built to operate from 2043 to 2083 (2) as a replacement for the outgoing NE Krško plant. Instead, we should intensify the development of our renewable resources.

Multicriterial analyses and selection of the best option for revitalization and development of the southern part of Croatian 400 kV network and connection to the power system of Bosnia and Herzegovina

The southern wing of the Croatian transmission network was constructed for 220 kV in the early 1960’s, with additional 400 kV reinforcement at the end of 1970’s. Its route of more than 200 km is quite demanding due to extreme climate, environmental specifics and related costs. However, operational experience during more than 50 years has been quite positive. Nowadays, at the end of its lifetime it is again extremely important to analyze and select the best option for network revitalization and development to serve the network users for the next 50 years, but in very different conditions of technological development, more restrictive environmental requirements, electricity market conditions and large scale RES integration. Moreover, special attention should be given to the potential opportunity and need to use this revitalization also for new interconnection to the power system of Bosnia and Herzegovina (BiH). Five main options have been initially selected as topology candidates for problem resolving. Detailed methodology and criteria for the selection of optimal option (revitalization and development scenario and topology) were developed and approved by all involved stakeholders. For selected option, based on comprehensive analyses and approved methodology , for further detailed analyses ( system reliability, technical design, investment, economics /CBA/ and environmental analyses) have been prepared, including assessment of its impact on transmission tariffs of each country. Sensitivity analyses to the most uncertain variables (investment costs and CO2 prices) were also performed. The environmental and social assessment was very demanding due to the complex governance structure and three legal frameworks to be respected (two countries, along with two entities in BiH). The Project impact was evaluated with respect to: air quality, water quality, waste management, noise, biological diversity, electromagnetic field, social measures and protected areas. This paper presents above mentioned analyses, findings and recommendations, as the most comprehensive analytical approach to the transmission line development that’s ever been applied in this region.