The paper presents the numerical model of a supply vessel-load-crane-offshore vessel system for simulation of heave motion and dynamic analysis of the system during critical phases of the handling operation: taking the load off from and lowering it to a moving base. The model enables extreme forces in elements and deflection of the structure to be determined. Different operating and emergency conditions can be simulated (e.g. horizontal motion of a supply vessel). The elaborated software can be applied also for determination of derated load charts and ultimate crane capacity (sequence of failure).

Underwater steel structures require periodic maintenance. In the case of vessels, anti-corrosion works are carried out in the shipyard, where very good conditions for applying organic protective coatings can be provided. Very good surface preparation can be obtained by the use of abrasive blasting. The well-prepared metal surface is free from impurities (particularly inorganic salts). Suitable conditions for the application and renovation of coatings are also ensured (creating appropriate climatic conditions, drying the air, setting the appropriate air temperature). However, there are underwater constructions that cannot be transferred above the water level and, therefore, their conservation against corrosion can take place only under the surface of the water, which significantly hinders the execution of renovation works. In this work, protective coatings for underwater application were tested. The application of coatings on selected steel surfaces over and under the water was carried out. Physico-mechanical and electrochemical tests were carried out in order to assess the quality of the obtained corrosion protection. The possible difficulties faced when applying coatings in marine conditions were discussed.

Offshore wind power is a relatively new sector of the economy with a tremendous potential for development. Its main advantage is foreseeable production and a high capacity factor, estimated at 50% (with prospects to increase to 60%), which makes it the most efficient energy source of all renewable energy technologies. In the Baltic Sea Region, Poland has the largest potential for the development of offshore wind energy. This has been reflected in plans by investors interested in offshore investments within the Polish marine areas. European energy and climate strategies, which define principles and objectives for the transformation of the European energy sector in line with the principle of sustainable development, underline the importance of offshore wind in the effort to achieve climate neutrality of the EU economy and contribute to energy security in Europe. Decision-makers in Poland endeavor to create conditions favorable to the development of the offshore wind sector. The article presents European and Polish conditions for the development of the offshore wind energy. To assess threats and opportunities for the development of the technology in Poland, the article examines whether the offshore wind potential has been included in strategic policy papers related to the development of the Polish energy sector, as well as how the state intends to support the development of the technology. A particular emphasis has been put on the latest draft of the Energy Policy of Poland until 2040 due to the crucial role of the document, since it sets directions for the development of the Polish energy sector for the next 20 years.

The purpose of the article is to present perspectives for the development of offshore wind farms in the leading, in this respect, country in the EU and in the world – Great Britain. Wind power plays a remarkable role in the process of ensuring energy security for Europe since in 2016 the produced wind energy met 10.4% of the European electricity demand while in 2017 it was already around 11.6%. The article analyses the capacity of wind farms, support systems offered by this country and the criteria related to the location of offshore wind farms. The research has been based on the analysis of legal acts, regulations, literature on the subject, information from websites. The article shows that in recent years, the production of energy at sea has been developing very rapidly, and the leading, in this matter, British offshore energy sector is character-ised by strong governmental support.

The peculiarity of offshore cranes, i. e. cranes based on ships or drilling platforms, is not only a significant motion of their base, but also the taut-slack phenomenon. Under some circumstances a rope can temporarily go completely slack, while a moment later, the force in the rope can increase to nominal or even higher value. Periodic occurrence of such phenomena can be damaging to the supporting structure of the crane and its driver. In the paper, mathematical models of offshore cranes that allow for analysis of the taut-slack phenomenon are presented. Results of numerical calculations show that the method of load stabilization proposed by the authors in their earlier works can eliminate this problem.

In offshore pedestal cranes one may distinguish three components of considerable length: a pedestal, a boom and a frame present in some designs. It is often necessary in dynamical analyses to take into account their flexibility. A convenient and efficient method for modelling them is the rigid finite element method in a modified form. The rigid finite element method allows us to take into account the flexibility of the beam system in selected directions while introducing a relatively small number of additional degrees of freedom to the system. This paper presents a method for modelling the pedestal, the frame and the boom of an offshore column crane, treating each of these components in a slightly different way. A custom approach is applied to the pedestal, using rigid finite elements of variable length. Results of sample numeric computations are included.

This paper presents the concept of the modelling methodology of a payload-vessel system allowing for a comprehensive investigation of mutual interactions of the system dynamics for lifting in the air. The proposed model consists of six degrees of freedom (6-DoF) vessel and three degrees of freedom (3-DoF) lifting model that can replace the industrial practice based on a simplified approach adopted for light lifts. Utilising the response amplitude operators (RAOs) processing methodology provides the ability to incorporate the excitation functions at the vessel crane tip as a kinematic and analyse a wide spectrum of lifted object weights on a basis of regular wave excitation. The analytical model is presented in detail and its solution in a form of numerical simulation results are provided and discussed within the article. The proposed model exposes the disadvantages of the models encountered in engineering practice and literature and proposes a novel approach enabling efficient studies addressing a lack of access to reliable modelling tools in terms of coupled models for offshore lifting operations planning..

A theoretical approach was applied to investigate the impact of nonlinear standing waves underneath a horizontal deck. A solution was achieved by applying a boundary element method. The model was applied to predict impact pressure underneath a deck. The results show that the wave impact is a very complex momentary process. The influence of initial boundary conditions, wave parameters and deck clearance on impact pressure are analysed. The analysis shows that purely sinusoidal waves of very small amplitude may cause an impact pressure several orders of magnitude higher than a pressure arising from typical applications of a linear wave theory. The analysis shows that all these non-intuitive outcomes arise from the complexity of a wave impact process and its enormous sensitivity to initial conditions what indicates serious difficulties in a reliable prediction of a wave impact for complex wave fields or other structures. Laboratory experiments were conducted to validate theoretical results.

The events that took place on April 10,2010 on the Gulf of Mexico began an international debate on minimizing and materializing the risk of dangerous occurrences and accidents during the exploitation of offshore energy resources. In the aftermath of this event to ensure safe operation in European maritime areas, the European Union decided to introduce regulations throughout the entire EU. On June 12, 2013, Directive 2013/30/EU of the European Parliament and of the Council on safety of offshore oil and gas operations and amending Directive 2004/35/EC was issued. The main aim of the Directive is to reduce the occurrence of major accidents relating to offshore oil and gas operations and limits their consequences. The article is a review of provision of Directive 2013/30/UE with particular regard to requirements at the national level. What is more, the paper indicates solutions which must be introduced by July 19, 2018 in offshore companies. The incorporated solutions must include the protection of the marine environment against pollutions (especially oil spills), establish minimum conditions for safe offshore exploration and the production of oil and gas and improve the response mechanism in the eventof an accident. The paper also presents accidents which take place in oil and gas fields which are a background of necessary improvements of safety during offshore operations.

This article, as far as possible based on the available literature, empirical measurements, and data from mesoscale models describes and compares expected wind conditions within the Baltic Sea area. This article refers to aspects related to the design and assessment of wind farm wind resources, based on the author’s previous experience related to onshore wind energy. The consecutive chapters of this publication are going to describe the present state and the presumptions relating to the development of wind energy within the Baltic Sea area. Subsequently, the potential of the sea was assessed using mesoscale models and empirical data from the Fino 2 mast that is located approximately 200 kilometers away from the majority of areas indicated in the Polish marine spatial development plan draft of Poland for offshore wind farm development (Maritime Office in Gdynia 2018). In the chapter describing mesoscale models, the author focused his attention on the GEOS5.12.4 model as the source of Modern-Era Retrospective Analysis for Research and Application 2 data, also known as MERRA2 (Administration National Aeronautics and Space Agency, 28), which, starting from February 2016, replaced MERRA data (Thogersen et al. 2016) and have gained a wide scope of applications in the assessment of pre-investment and operational productivity due to a remarkable level of correlation with in-situ data. Model-specific data has been obtained for eight locations, which largely overlap with the locations of the currently existing offshore wind farms within the Baltic Sea area. A significant part of this publication is going to be devoted to the description of the previously mentioned Fino 2 mast and to the analysis of data recorded until the end of 2014 by using the said mast (Federal Maritime and Hydrographic Agency 2018). The analysis has been carried out by means using scripts made in the VBA programming language, making it easier to work with large chunks of data. Measurements from the Fino 2 mast, together with long-term mesoscale model-specific measurements can be used, to some extent, for the preliminary assessment of wind farm energy yield in the areas designated for the development of renewable energy in the Polish exclusive maritime economic zone (Maritime Office in Gdynia 2018). In the final part of this article, pieces of information on the forecasted Baltic Sea wind conditions, especially within the exclusive economic zone of Poland, are going to be summarized. A major focus is going to be put on the differences between offshore and onshore wind energy sources, as well as on further aspects, which should be examined in order to optimize the offshore wind power development.

The high temperature and thermal radiation caused by generator fire accidents on the offshore platform lead to the destruction of equipment and facilities and threaten the structural safety of the offshore platform. Based on the background of a crude oil generator fire accident on an offshore platform, KFX software was used to conduct a numerical simulation of the fire process and explore the spatial-temporal variation characteristics of smoke, temperature and heat radiation within the scope of the fire room. The influence ranges of 12.5 kW/m2, 25 kW/m2 and 35 kW/m2 were obtained according to the thermal radiation criterion. Researchers examined the temperature variation and heat flow at the room’s ceiling and floor near the primary steel support. The results show that: 1) The surface temperatures of partial steel supports exceed 550°C, and the heat flux of partial steel supports exceeds 37.5 kW/m2. 2) In the ignition position, the maximum temperature at the ceiling reaches 2299°C when t = 24 s, and the maximum temperature at the flooring reaches 701°C when t = 79 s. The heat radiation flux at the ceiling and flooring both exceeds 25 kW/m2. The maximum temperature of partial crude oil generators can reach 1299°C. 3) The heat radiation flux of partial generators can reach 105 kW/m2, and the heat radiation flux at the adjacent point of partial generators never exceeds 20 kW/m2. The above research results can provide a reference for checking the response time of flame detectors and the strength of the supporting structure.

This paper reviews latest developments of substructures for offshore wind turbines focusing on investigations and applications of hybrid foundations. Model tests and numerical analyses were used to simulate the loading of hybrid piles in sand. The results of pile-soil interaction were investigated to confirm the changes in soil stiffness around the hybrid monopile head. The mechanism and factors affecting the change in lateral stiffness of the hybrid foundation were explained by analysing p–y curves for M+H loading conditions in sand. Based on this research, a new shape of p–y curves for hybrid monopiles was established and a method for determining key parameters was proposed. The effectiveness of new p–y curves was verified by comparing back-calculated results with those from numerical simulations. The conducted tests confirmed that the hybrid monopile displacement is 30–50% smaller when compared to a standard monopile with similar dimensions. The gained experiences can be useful for designers and researchers to enhance the design of foundations for offshore wind turbines.