Eugen Rusu

An Evaluation of the Wind Energy in the North-West of the Black Sea

The objective of the present work is to evaluate the opportunity of the wind farms implementation in the north-western side of the Black Sea. An assessment of the wind energy potential was first carried out by analyzing eleven years of data. Both in situ measurements and model data coming from the European Centre for Medium-Range Weather Forecasts were considered at this level. Using a classical logarithmic transformation law, the wind speeds were translated to the height of 80 m where usually the wind turbines operate. The analysis of the in situ measurements indicates the Romanian coastal environment as being more energetic during the winter season, with an average wind speed at 80 m of about 9.7 m/s and a power density of 870W/m2. On the other hand, the analysis of the model dataset indicates that the Ukrainian nearshore is slightly more energetic during the winter season with an average wind speed of 7.5 m/s and a power density of 310W/m2. As a further step, the seasonal and spatial distributions of the wind energy were evaluated in terms of the power estimated to be delivered by the Siemens 2.3 wind turbine. Finally, the regional wind energy resources are compared with similar ones from locations in which offshore wind farms are known to operate or are expected to be developed in the near future. The main conclusion coming from the present work would be that the north-western side of the Black Sea represents a promising area for the wind energy extraction.

The Environmental Impact of a Wave Dragon Array Operating in the Black Sea

The present work describes a study related to the influence on the shoreline dynamics of a wave farm consisting of Wave Dragon devices operating in the western side of the Black Sea. Based on historical data analysis of the wave climate, the most relevant environmental conditions that could occur were defined, and for these cases, simulations with SWAN spectral phase averaged wave model were performed. Two situations were considered for the most representative patterns: model simulations without any wave energy converter and simulations considering a wave farm consisting of six Wave Dragon devices. Comparisons of the wave model outputs have been carried out in both geographical and spectral spaces. The results show that although a significant influence appears near the wave farm, this gradually decreases to the coast line level. In order to evaluate the influence of the wave farm on the longshore currents, a nearshore circulation modeling system was used. In relative terms, the longshore current velocities appear to be more sensitive to the presence of the wave farm than the significant wave height. Finally, the possible impact on the marine flora and fauna specific to the target area was also considered and discussed.

Assessment of the changes induced by a wave energy farm in the nearshore wave conditions

Starting from the observation that an important next stage in exploiting the ocean energy is to install large arrays of several identical devices in order to raise their overall electricity production, the present work has as objective to assess the local and coastal impact of a large wave farm that would operate in the Portuguese coastal environment. The target area is the Portuguese maritime pilot zone, Sao Pedro de Moel, which is located in the central part of the Portuguese continental nearshore. A generic wave farm was considered and various transmission situations were analyzed. The study started with the situation without wave farm (zero absorption) and subsequently different scenarios were considered by gradually increasing the conditions to the hypothetic case of the total absorption. For each case study, model simulations were performed covering the entire year 2009 using a wave prediction system based on Wave Watch 3, for the wave generation at the level of the entire North Atlantic Ocean, and on SWAN, for the coastal wave transformation. In this way, a comprehensive picture of the possible impact of the wave farm is provided. The results show that the presence of a wave farm operating offshore has a strong influence on the wave conditions immediately down wave. Although this influence is usually attenuated at the level of the coastline, it appears as obvious a general decrease in terms of significant wave height due to the wave farm, but also some other wave parameters are modified.

Evaluation of the Wind Energy Potential in the Coastal Environment of Two Enclosed Seas

The work presents a comprehensive picture of the wind energy potential in the coastal environment of the Black and the Caspian Seas. 10-year of data coming from the US National Centers for Environmental Prediction was considered as the main source. This dataset was subsequently compared with both in situ and remotely sensed measurements. The results show that the western side of the Black Sea has an enhanced wind power potential, especially in the vicinity of the Crimean Peninsula. As regards the Caspian Sea, the northeastern sector can be considered more energetic. A direct comparison of various wind parameters corresponding to the locations with higher potential in the two target areas considered was also carried out, in order to notice the similarities and the key features that could be taken into account in the development of an offshore wind project. Finally, it can be concluded that the coastal environments of the Black and the Caspian Seas can become in the near future promising locations for the wind energy extraction, as well as for the hybrid wind-wave energy farms that could play an important role also in the coastal protection.

Validation of Two Wave and Nearshore Current Models

This paper deals with three coastal applications of a 1D model system to represent the nearshore currents. In these applications, comparisons are made with the predictions from 2D and 3D models and field data. The system evaluated is the ISSM (the Interface for SWAN and Surf Models), which was developed as an attempt to develop a simple and reliable coastal circulation model. The nearshore circulation model SHORECIRC was considered as a reference. It is a quasi-3D model that uses REFDIF as wave driver, and combines a numerical solution for the depth-integrated 2D horizontal momentum balance equations with an analytical solution for the 3D current profiles. Three case studies were considered for comparing the models. The first is a plane beach treated as a 1D problem. The other two applications are 2D problems. The first application had mild bottom contours, while the second was characterized by strong bathymetric irregularities. Comparisons are performed between the results of the two models and with the in situ measurements. It was found that, when the angle between the direction of the wave advance and the normal to the shoreline was less than 15°, the 1D surf models can be used with confidence in coastal applications. For larger angles and more complex bathymetric conditions, 2D and 3D models are required.

Wave Energy Assessments in the Coastal Environment of Portugal Continental

The potential for wave energy extraction can be obtained from the analysis of the wave climate which can be determined with numerical models. The wave energy devices can be deployed in offshore, nearshore and shoreline. From this reason, it is important to be able to assess properly the spatial distribution of the wave energy in various locations from the offshore to the coastline in a specific area. The methodology proposed here considers a SWAN based wave model system focusing in the Portuguese continental coastal environment from deep water towards the nearshore. An analysis of the average and high energetic conditions was first performed for a ten-year period, between 1994 and 2003, considering the most relevant in situ measurements available in the Portuguese nearshore. In this way both the average and high energetic conditions corresponding to the Portuguese continental costal environment have been properly defined. For the most relevant average wave conditions, SWAN simulations were performed in some medium resolution areas covering the northern and central parts of Portugal continental, which are traditionally considered richer in wave power resources. The present work allows the identification of some locations in the continental coastal environment of Portugal with greater potential from the point of view of wave power resources. An important observation is related to the fact that the wave power depends on the product between the energy density spectrum and the group velocity of waves. This means that, although the significant wave height is a relevant parameter when assessing the wave power in a specific site, a location having in general higher wave heights is not necessarily also the richest in wave power.Copyright

Efficiency assessments for some state of the art wind turbines in the coastal environments of the Black and the Caspian seas

The main objective of the present work is to assess the wind energy resources in the Black and in the Caspian seas. Additionally, the electric power expected to be provided by various state of the art technologies was also evaluated. For this reason, several reference points were considered in the coastal environments of the two areas targeted. In order to assess the wind potential in these locations, 12 year of data coming from the US National Centers for Environmental Prediction were processed and analyzed. From the analysis of the wind power density (corresponding to a height of 80 m), it was possible to evaluate the spatial and seasonal distributions of the wind resources, and also to identify some hot spot areas. Since the regions located near the shoreline are under the influence of the diurnal/nocturnal fluctuations, a special attention was paid to this aspect. This is especially due to the fact that the power output of a wind farm project is supposed to be significantly influenced by such variations. In the second part of the work, several offshore wind turbines were considered and their performances were evaluated in relationship with the local wind patterns. Based on these results, we can conclude that important variations may occur between the diurnal and the nocturnal intervals, in terms of both wind velocity and direction, while on a regional scale the northern parts of the Black and the Caspian seas seem to present more consistent wind energy potential. Moreover, this potential is comparable with that from the locations where such offshore wind farms already successfully operate.

Modeling Waves in Open Coastal Areas and Harbors with Phase-Resolving and Phase-Averaged Models

ABSTRACT Rusu, E. and Guedes Soares, C., 2013. Modeling waves in open coastal areas and harbors with phase-resolving and phase-averaged models. A wave-prediction system based on spectral models was validated against in situ measurements in the Portuguese continental nearshore and is now operational. As a final extension of this system, the present article describes the implementation and validation of high-resolution wave models. In this connection, the objective of the present work was to evaluate the performance of such models in different coastal environments. The first target was an open coastal area located in the central part of the Portugal continental. An evaluation of the two state-of-the-art phase-resolving wave models, REFDIF1 and FUNWAVE, was carried out, and the results are compared with those from a field experiment. The second target area was the port of Leixões in the north of the Portuguese continental coast. A high-resolution SWAN computational domain that included the harbor area, was implemented and connected to the modeling system that provides ocean forcing. To provide a more realistic picture of the wave conditions inside the harbor area, the FUNWAVE model was also coupled to the wave-prediction system. Comparisons between the results provided by the two wave models provide a better image of the reliability and limitations of both models at the entrance and inside the harbor area.

A multi-parameter data-assimilation approach for wave prediction in coastal areas

ABSTRACT This work describes an approach based on the successive correction method for assimilating in situ measurements in the high-resolution computational domain of a wave-modelling system based on the spectrum concept. Its objective is to improve the wave predictions in the nearshore and in the vicinity of the harbours. The coastal environment targeted is the western side of the Black Sea, but similar approaches can be developed for any nearshore area where in situ wave measurements are available. A wave modelling system based on the simulating waves nearshore (SWAN) model was implemented for the entire sea basin. On the western side, a higher-resolution computational domain was nested in the large area. Wave measurements from the Gloria drilling unit were considered for the assimilation procedure. For several boundary points of the last computational domain, corrections of the main wave parameters were performed which take into account the measured values. In this case, only the significant wave height and peak period were assimilated, but the wave direction and the directional spreading can be also assimilated as a further computational step. Considering these corrected values, parametric boundary conditions are used to force the model. As a result, the wave-prediction system becomes more reliable.

Assessment of the potential for developing combined wind-wave projects in the European nearshore:

The objective of this work is to assess the synergy of the marine resources in the vicinity of several European offshore sites, in order to analyze the viability of the combined wind-wave renewable projects. The reference sites considered for evaluation are located in the vicinity of the European coasts, being already taken into account for various marine projects. As a first step, based on the dataset provided by the European Center for Medium-Range Weather Forecasts for the 10-year interval 2005–2014, it was possible to analyze the joint seasonal distribution of the offshore resources. In the second part of the paper, based on the technical characteristics of various offshore wind turbines and wave energy converters, it was possible to identify the performances of some systems for wind and wave energy conversion. Finally, it can be also highlighted that the results presented in the present work can be considered interesting and useful, since they provide some insights regarding the potential of some operational European sites to support colocated wind-wave projects.