Gregorio Iglesias - Academia.edu (original) (raw)
Papers by Gregorio Iglesias
Coastal Engineering 2008 - Proceedings of the 31st International Conference, 2009
Abstract: Wave energy is a promising energy resource in many coastal regions. Its harnessing pose... more Abstract: Wave energy is a promising energy resource in many coastal regions. Its harnessing poses a technological challenge, and a number of wave energy converters based on different principles are currently under development. WaveCat™ is a floating ...
... Alberte Castro Ponte University of Santiago de Compostela, Spain Gregorio Iglesias University... more ... Alberte Castro Ponte University of Santiago de Compostela, Spain Gregorio Iglesias University of Santiago de Compostela, Spain Francisco Taveira Pinto University of Porto, Portugal Rodrigo Carballo University of Santiago de Compostela, Spain ...
OWC (Oscillating water column) wave power plants are widely used in ocean wave energy conversion.... more OWC (Oscillating water column) wave power plants are widely used in ocean wave energy conversion. It is universally accepted that for a good efficiency of the plant, the turbine and the chamber should match each other according to the wave climate site. In this work an alternative methodology is presented for
coupling the chamber and the turbine efficiently, carrying out a whole dimensional analysis of the OWC plant.
Basically, the wave data and the chamber geometry are the input data. The behaviour of the chamber is numerically simulated. From the numerical results, the optimum damping could be identified for every wave condition.
Once the optimum chamber damping is found, the objective is to determine which turbine matches this damping. Numerical results, based on the quasi-steady assumption, were used to simulate turbine performance under periodic conditions. The calculation of the diameter is based on the damping caused by the turbine on the OWC, whereas the rotational speed is fixed to maximize the turbine mean efficiency.
Furthermore, this methodology is worked out to compare the size and the rotational speed of different kinds of turbines. Finally, the influence of sea state changes on the parameters of the optimum turbine is also studied.
Energy Conversion and Management, 2015
ABSTRACT The wave energy resource is usually characterized by a significant variability throughou... more ABSTRACT The wave energy resource is usually characterized by a significant variability throughout the year. In estimating the power performance of a Wave Energy Converter (WEC) it is fundamental to take into account this variability; indeed, an estimate based on mean annual values may well result in a wrong decision making. In this work, a novel decision-aid tool, iWEDGE (intra-annual Wave Energy Diagram GEnerator) is developed and implemented to a coastal region of interest, the Death Coast (Spain), one of the regions in Europe with the largest wave resource. Following a comprehensive procedure, and based on deep water wave data and high-resolution numerical modelling, this tool provides the monthly high-resolution characterization matrices (or energy diagrams) for any location of interest. In other words, the information required for the accurate computation of the intra-annual performance of any WEC at any location within the region covered is made available. Finally, an application of iWEDGE to the site of a proposed wave farm is presented. The results obtained highlight the importance of the decision-aid tool herein provided for wave energy exploitation.
Tidal currents offer considerable potential for the generation of renewable energy. A study to as... more Tidal currents offer considerable potential for the generation of renewable energy. A study to assess the potential of a site for tidal energy extraction needs to be effective on providing information on the precise distribution of the tidal stream energy (Carballo et al., 2009) as well as detailed assessment of the sites potentially viable for installing Tidal Stream Turbines, i.e., TSTs (Xia et al., 2010a,b). The kinetic energy flux through a channel cross-section provides an indication of the available power. However, it must be considered that the cross-section of a real channel varies along its length, and vertically as result of the tide. The value of a tidal power potential prediction with a channel constant cross-section lacks accuracy, since it does not takes into account the spatial and temporal variability of the flow along and across the channel. The Faro-Olhão Inlet (Ria Formosa, Southern Portugal, Fig. 1) represents an attractive case study for implementing TSTs becaus...
The significant advances in the past years towards the consolidation of wave energy as a major re... more The significant advances in the past years towards the consolidation of wave energy as a major renewable warrant the investigation of the synergies between this novel resource and coastal defence. The aim of this work is to examine the effects of a wave farm operating nearshore on the beach through a case study, and, on this basis, establish its efficacy as a coastal protection scheme. A high-resolution nearshore wave propagation model is coupled to a morphodynamic model to assess the wave farm impacts on the beach. The wave farm is found to reduce the erosion significantly in the beach face. This is a bonus to be added to the primary role of the wave farm – and one which enhances its economic viability by leading to savings in conventional coastal defence measures.
The location of a wave farm and, in particular, its distance to the coast is one of the key aspec... more The location of a wave farm and, in particular, its distance to the coast is one of the key aspects in a wave energy project. The effects of the farm on the coast, which can be instrumental in mitigating storminduced erosion and thus contribute to coastal defence, are sometimes disregarded in selecting its location, possibly due to the inexistence of an ad hoc methodology. In this context, the objective of this work is to examine the influence of the farm-to-coast distance through a sensitivity analysis in a case study: Perranporth (UK). The impacts of a wave farm on the beach morphology are examined in four scenarios with different farm-to-coast distances using a high-resolution suite of numerical models. The results show that a wave farm closest to the beach offers the highest degree of coastal protection (up to 20% of beach erosion reduction). The downside of this enhanced coastal protection is that the wave resource available at this location would be slightly smaller (approx. 10%) than in the case of the wave farms further from the coast. More generally, we find that the farm-to-coast distance is a critical variable in determining the effectiveness of a wave farm for coastal defence.
Energy
In a tidal stream project the selection of the most appropriate device is of major importance. Th... more In a tidal stream project the selection of the most appropriate device is of major importance. The aim of this work is to investigate the difference between two tidal farms, one with floating TSTs (Tidal Stream Turbines), the other with bottom-fixed TSTs, in terms of annual performance and its monthly variability. This investigation is carried out considering real operational conditions in a case study: Ria de Ortigueira (NW Spain), a drowned river valleys which is one of the most promising sites for tidal stream energy exploitation in the Iberian Peninsula. A 3D, high-resolution, numerical model is applied to simulate the hydrodynamics of the ria during an entire year with either the floating or bottom-fixed TSTs, and, on these grounds, determine the most representative performance parameters. Significant differences emerge in the performance of both plants; these are due to a great extent to the vertical variation in the flow velocity, which is relevant at many sites of interest f...
Dyna (Medellin, Colombia)
To remain competitive both locally and globally companies must currently make great efforts to ad... more To remain competitive both locally and globally companies must currently make great efforts to adapt to changes in technology, business, and law. A new business culture is growing, based on a number of fundamental principles including research, development, and innovation. This culture also entails integrating management systems to prevent risks at work, protect the environment, and maintain quality, professional ethics, leadership, values, intellectual capital, continuous improvement, and social responsibility. People support this culture, workers being one of the main assets of companies. Human resources management will be the key to achieving sustainable development and business excellence.
This work is concerned with the impact of the extraction of energy from the flow by means of a ti... more This work is concerned with the impact of the extraction of energy from the flow by means of a tidal farm on the transient and residual flow in an estuary. The investigation is conducted through a case study. A 3D, high-resolution hydrodynamics model is implemented and successfully validated based on field data. The model is then applied to investigate the effects of the tidal farm in winter and summer scenarios. After analysing the impacts on the transient flow, the residual flow is considered; it is found that the farm does not alter the twolayer estuarine circulation drastically, but it does weaken the residual velocities over a large area, which could have consequences in terms of water quality and biological productivity.
Energy Conversion and Management, 2015
This is the first assessment of the wave energy resource in Peru, an emerging country with an inc... more This is the first assessment of the wave energy resource in Peru, an emerging country with an increasing energy demand and a high dependence on fossil fuels. On the basis of wave buoy measurements, we characterize the offshore wave energy resource and analyze its temporal variability, comparing the results with those obtained in previous works for other regions. A wave propagation numerical model (SWAN) is used to determine the nearshore spatial distribution of wave energy. A total of 357 offshore sea states, representing 90% of the wave energy and 94% of the time in an average year, were propagated. The wave energy in Peru presents a resource exceeding by more than seven times the total electric demand of the country. Because of the large amount of resource available and its low seasonal variation, wave energy must be considered in Peru as an alternative to conventional energy resources.
Applied Ocean Research, 2014
Disturbances to load and unload operations caused by excessive vessel movements are a recurrent p... more Disturbances to load and unload operations caused by excessive vessel movements are a recurrent problem at many ports, among which the Exterior Port of Ferrol (NW Spain). The objective of this work is to investigate whether long waves (with periods above those of swell) may play a role in these movements, and if so, to characterize their effects on the different vessel movements. For this purpose the movements of a bulk carrier in the six degrees of freedom were recorded alongside the sea level oscillations inside and outside the port basin. Large rectilinear motions were measured, with values close to the safety limits for cargo handling operations. We analyze these movements in both the time and frequency domains and their correlation with the swell and long wave energy within two frequency bands: low frequency (LF) and very low frequency (VLF). We find that the vessel movements in the vertical plane (heave, pitch and roll) are mainly determined by the swell energy inside the port basin. On the contrary, the movements in the horizontal plane (sway, surge and yaw) are strongly correlated with the total wave energy in the system and, more importantly, with the ratio of LF band to total energy. These results highlight the relevance of long wave energy levels to cargo handling operations and, more generally, port management.
Journal of Renewable and Sustainable Energy, 2012
ABSTRACT Tenerife, the largest of the Canary Islands, aims to enhance the contribution of renewab... more ABSTRACT Tenerife, the largest of the Canary Islands, aims to enhance the contribution of renewable energies to its electricity demand. The objective of this work is twofold: (i) to assess the wind resources and (ii) to evaluate the energy that a specific wind turbine would produce at different locations across the island. Wind data from four meteorological stations covering a period of 91 years (1920–2011) are used. The annual and monthly distributions of wind velocity and power density are evaluated using the Weibull and Rayleigh distributions, and the prevailing wind directions are analyzed. The monthly energy generated by an ideal turbine is compared to that generated by a real turbine for the four study sites. (An ideal turbine extracts all the energy available in the wind, whereas a real turbine is subjected to Betz’ law.) The high availability and capacity factors obtained are indicative of the large wind resource in Tenerife and in particular at three of the four study sites.
Energy, 2014
During the last years the interest of supplying the energy needs by means of renewable energy sou... more During the last years the interest of supplying the energy needs by means of renewable energy sources has risen sharply. The objective of this work is to investigate the viability of the implementation of a tidal farm to fulfill the electricity demands of the Port of Ribadeo, which is located in a tide-driven estuary (Ria de Ribadeo, NW Spain). For this purpose a 3D hydrodynamic model of the estuary was implemented and successfully validated. Overall, Ria de Ribadeo presents a substantial tidal resource with annual energy densities close to 72.56 MWhm À2 . On these grounds, taking the Evopod tidal turbine as a reference, the viability and installation of a tidal farm are analyzed by means of four performance parameters (electric energy output, site-specific efficiency, capacity and availability factors), which are computed on a monthly basis according to the characteristics of the flow at the site. In addition, a momentum sink term was used to simulate the blockage effect caused by the turbine in the flow, and, therefore determine its performance with more accuracy. The results obtained prove that a tidal farm of 25 turbines with a rated power of 400 kW is capable of fulfilling the electricity needs of the port.
Coastal Engineering, 2014
The possibility of using wave farms for coastal defence warrants investigation because wave energ... more The possibility of using wave farms for coastal defence warrants investigation because wave energy is poised to become a major renewable in many countries over the next decades. The fundamental question in this regard is whether a wave farm can be used to reduce beach erosion under storm conditions. If the answer to this question is positive, then a wave farm can have coastal defence as a subsidiary function, in addition to its primary role of producing carbon-free energy. The objective of this work is to address this question by comparing the response of a beach in the face of a storm in two scenarios: with and without the wave farm. For this comparison a set of ad hoc impact indicators is developed: the bed level impact (BLI), beach face eroded area (FEA), non-dimensional erosion reduction (NER), and mean cumulative eroded area (CEA); and their values are determined by means of two coupled models: a high-resolution wave propagation model (SWAN) and a coastal processes model (XBeach). The study is conducted through a case study: Perranporth Beach (UK). Backed by a well-developed dune system, Perranporth has a bar between −5 m and −10 m. The results show that the wave farm reduces the eroded volume by as much as 50% and thus contributes effectively to coastal protection. This synergy between marine renewable energy and coastal defence may well contribute to improving the viability of wave farms through savings in conventional coastal protection.
Energy, 2014
The paper combines hydrographic surveying techniques with numerical modelling to evaluate the spa... more The paper combines hydrographic surveying techniques with numerical modelling to evaluate the spatial and temporal distributions of tidal power in a confined channel located in Portugal (Faro Channel in the Ria Formosa). The channel is characterised by strong currents with depth-averaged velocities exceeding 2 m s À1 . The model was successfully validated against harmonic analysis data and in situ flow measurements acquired with an Acoustic Doppler Current Profiler (ADCP). Annual estimates of power and energy output were derived, considering spatial and temporal variations in flow velocities and in power density both across and along the channel. The study confirms the relevance of integrating field information with numerical models to achieve a better estimation of tidal power potential through the water column. The accuracy of both bathymetric and tidal elevation data contributes greatly to validating the model; whereas validating the model results with 3D velocity patterns obtained using boat-mounted ADCPs allows peak velocity distributions along the water column and the spatial variation of velocity through different cross-sections to be considered, further assisting in the dynamic placement of tidal energy conversion devices adapted to different resource scenarios. The methodology can be readily adapted and applied to any other inlet, tidal channel, or estuarine mouth.
Energy, 2014
Tidal currents represent a promising energy source for electrical supply in Europe; however, nowa... more Tidal currents represent a promising energy source for electrical supply in Europe; however, nowadays there still exist important aspects to address regarding their exploitation prior to becoming a fullyfledged renewable energy. The accurate assessment of the available resource and the development of TECs (Tidal Energy Converters) are challenges which have been partially solved, but it is necessary to go further in the investigation of other aspects such as the impacts on the estuarine circulation. In this work, the impacts caused on the estuarine circulation in Ria de Ortigueira by the operation of two different tidal stream plants, one composed of floating and the other of bottom-fixed TSTs (Tidal Stream Turbines), were analysed by means of a three-dimensional model. Prior to using the model for assessing the impacts, it was validated based on field data at two measuring stations. Then, the tidal farms were implemented in the model as a momentum sink. The results show that there are no significant differences between the impacts caused on the general circulation by floating and bottom-fixed TSTs with slight reductions of the flow being apparent up to some km away the plant. Then again, strong differences were found in the vicinity of the plant.
Coastal Engineering 2008 - Proceedings of the 31st International Conference, 2009
Abstract: Wave energy is a promising energy resource in many coastal regions. Its harnessing pose... more Abstract: Wave energy is a promising energy resource in many coastal regions. Its harnessing poses a technological challenge, and a number of wave energy converters based on different principles are currently under development. WaveCat™ is a floating ...
... Alberte Castro Ponte University of Santiago de Compostela, Spain Gregorio Iglesias University... more ... Alberte Castro Ponte University of Santiago de Compostela, Spain Gregorio Iglesias University of Santiago de Compostela, Spain Francisco Taveira Pinto University of Porto, Portugal Rodrigo Carballo University of Santiago de Compostela, Spain ...
OWC (Oscillating water column) wave power plants are widely used in ocean wave energy conversion.... more OWC (Oscillating water column) wave power plants are widely used in ocean wave energy conversion. It is universally accepted that for a good efficiency of the plant, the turbine and the chamber should match each other according to the wave climate site. In this work an alternative methodology is presented for
coupling the chamber and the turbine efficiently, carrying out a whole dimensional analysis of the OWC plant.
Basically, the wave data and the chamber geometry are the input data. The behaviour of the chamber is numerically simulated. From the numerical results, the optimum damping could be identified for every wave condition.
Once the optimum chamber damping is found, the objective is to determine which turbine matches this damping. Numerical results, based on the quasi-steady assumption, were used to simulate turbine performance under periodic conditions. The calculation of the diameter is based on the damping caused by the turbine on the OWC, whereas the rotational speed is fixed to maximize the turbine mean efficiency.
Furthermore, this methodology is worked out to compare the size and the rotational speed of different kinds of turbines. Finally, the influence of sea state changes on the parameters of the optimum turbine is also studied.
Energy Conversion and Management, 2015
ABSTRACT The wave energy resource is usually characterized by a significant variability throughou... more ABSTRACT The wave energy resource is usually characterized by a significant variability throughout the year. In estimating the power performance of a Wave Energy Converter (WEC) it is fundamental to take into account this variability; indeed, an estimate based on mean annual values may well result in a wrong decision making. In this work, a novel decision-aid tool, iWEDGE (intra-annual Wave Energy Diagram GEnerator) is developed and implemented to a coastal region of interest, the Death Coast (Spain), one of the regions in Europe with the largest wave resource. Following a comprehensive procedure, and based on deep water wave data and high-resolution numerical modelling, this tool provides the monthly high-resolution characterization matrices (or energy diagrams) for any location of interest. In other words, the information required for the accurate computation of the intra-annual performance of any WEC at any location within the region covered is made available. Finally, an application of iWEDGE to the site of a proposed wave farm is presented. The results obtained highlight the importance of the decision-aid tool herein provided for wave energy exploitation.
Tidal currents offer considerable potential for the generation of renewable energy. A study to as... more Tidal currents offer considerable potential for the generation of renewable energy. A study to assess the potential of a site for tidal energy extraction needs to be effective on providing information on the precise distribution of the tidal stream energy (Carballo et al., 2009) as well as detailed assessment of the sites potentially viable for installing Tidal Stream Turbines, i.e., TSTs (Xia et al., 2010a,b). The kinetic energy flux through a channel cross-section provides an indication of the available power. However, it must be considered that the cross-section of a real channel varies along its length, and vertically as result of the tide. The value of a tidal power potential prediction with a channel constant cross-section lacks accuracy, since it does not takes into account the spatial and temporal variability of the flow along and across the channel. The Faro-Olhão Inlet (Ria Formosa, Southern Portugal, Fig. 1) represents an attractive case study for implementing TSTs becaus...
The significant advances in the past years towards the consolidation of wave energy as a major re... more The significant advances in the past years towards the consolidation of wave energy as a major renewable warrant the investigation of the synergies between this novel resource and coastal defence. The aim of this work is to examine the effects of a wave farm operating nearshore on the beach through a case study, and, on this basis, establish its efficacy as a coastal protection scheme. A high-resolution nearshore wave propagation model is coupled to a morphodynamic model to assess the wave farm impacts on the beach. The wave farm is found to reduce the erosion significantly in the beach face. This is a bonus to be added to the primary role of the wave farm – and one which enhances its economic viability by leading to savings in conventional coastal defence measures.
The location of a wave farm and, in particular, its distance to the coast is one of the key aspec... more The location of a wave farm and, in particular, its distance to the coast is one of the key aspects in a wave energy project. The effects of the farm on the coast, which can be instrumental in mitigating storminduced erosion and thus contribute to coastal defence, are sometimes disregarded in selecting its location, possibly due to the inexistence of an ad hoc methodology. In this context, the objective of this work is to examine the influence of the farm-to-coast distance through a sensitivity analysis in a case study: Perranporth (UK). The impacts of a wave farm on the beach morphology are examined in four scenarios with different farm-to-coast distances using a high-resolution suite of numerical models. The results show that a wave farm closest to the beach offers the highest degree of coastal protection (up to 20% of beach erosion reduction). The downside of this enhanced coastal protection is that the wave resource available at this location would be slightly smaller (approx. 10%) than in the case of the wave farms further from the coast. More generally, we find that the farm-to-coast distance is a critical variable in determining the effectiveness of a wave farm for coastal defence.
Energy
In a tidal stream project the selection of the most appropriate device is of major importance. Th... more In a tidal stream project the selection of the most appropriate device is of major importance. The aim of this work is to investigate the difference between two tidal farms, one with floating TSTs (Tidal Stream Turbines), the other with bottom-fixed TSTs, in terms of annual performance and its monthly variability. This investigation is carried out considering real operational conditions in a case study: Ria de Ortigueira (NW Spain), a drowned river valleys which is one of the most promising sites for tidal stream energy exploitation in the Iberian Peninsula. A 3D, high-resolution, numerical model is applied to simulate the hydrodynamics of the ria during an entire year with either the floating or bottom-fixed TSTs, and, on these grounds, determine the most representative performance parameters. Significant differences emerge in the performance of both plants; these are due to a great extent to the vertical variation in the flow velocity, which is relevant at many sites of interest f...
Dyna (Medellin, Colombia)
To remain competitive both locally and globally companies must currently make great efforts to ad... more To remain competitive both locally and globally companies must currently make great efforts to adapt to changes in technology, business, and law. A new business culture is growing, based on a number of fundamental principles including research, development, and innovation. This culture also entails integrating management systems to prevent risks at work, protect the environment, and maintain quality, professional ethics, leadership, values, intellectual capital, continuous improvement, and social responsibility. People support this culture, workers being one of the main assets of companies. Human resources management will be the key to achieving sustainable development and business excellence.
This work is concerned with the impact of the extraction of energy from the flow by means of a ti... more This work is concerned with the impact of the extraction of energy from the flow by means of a tidal farm on the transient and residual flow in an estuary. The investigation is conducted through a case study. A 3D, high-resolution hydrodynamics model is implemented and successfully validated based on field data. The model is then applied to investigate the effects of the tidal farm in winter and summer scenarios. After analysing the impacts on the transient flow, the residual flow is considered; it is found that the farm does not alter the twolayer estuarine circulation drastically, but it does weaken the residual velocities over a large area, which could have consequences in terms of water quality and biological productivity.
Energy Conversion and Management, 2015
This is the first assessment of the wave energy resource in Peru, an emerging country with an inc... more This is the first assessment of the wave energy resource in Peru, an emerging country with an increasing energy demand and a high dependence on fossil fuels. On the basis of wave buoy measurements, we characterize the offshore wave energy resource and analyze its temporal variability, comparing the results with those obtained in previous works for other regions. A wave propagation numerical model (SWAN) is used to determine the nearshore spatial distribution of wave energy. A total of 357 offshore sea states, representing 90% of the wave energy and 94% of the time in an average year, were propagated. The wave energy in Peru presents a resource exceeding by more than seven times the total electric demand of the country. Because of the large amount of resource available and its low seasonal variation, wave energy must be considered in Peru as an alternative to conventional energy resources.
Applied Ocean Research, 2014
Disturbances to load and unload operations caused by excessive vessel movements are a recurrent p... more Disturbances to load and unload operations caused by excessive vessel movements are a recurrent problem at many ports, among which the Exterior Port of Ferrol (NW Spain). The objective of this work is to investigate whether long waves (with periods above those of swell) may play a role in these movements, and if so, to characterize their effects on the different vessel movements. For this purpose the movements of a bulk carrier in the six degrees of freedom were recorded alongside the sea level oscillations inside and outside the port basin. Large rectilinear motions were measured, with values close to the safety limits for cargo handling operations. We analyze these movements in both the time and frequency domains and their correlation with the swell and long wave energy within two frequency bands: low frequency (LF) and very low frequency (VLF). We find that the vessel movements in the vertical plane (heave, pitch and roll) are mainly determined by the swell energy inside the port basin. On the contrary, the movements in the horizontal plane (sway, surge and yaw) are strongly correlated with the total wave energy in the system and, more importantly, with the ratio of LF band to total energy. These results highlight the relevance of long wave energy levels to cargo handling operations and, more generally, port management.
Journal of Renewable and Sustainable Energy, 2012
ABSTRACT Tenerife, the largest of the Canary Islands, aims to enhance the contribution of renewab... more ABSTRACT Tenerife, the largest of the Canary Islands, aims to enhance the contribution of renewable energies to its electricity demand. The objective of this work is twofold: (i) to assess the wind resources and (ii) to evaluate the energy that a specific wind turbine would produce at different locations across the island. Wind data from four meteorological stations covering a period of 91 years (1920–2011) are used. The annual and monthly distributions of wind velocity and power density are evaluated using the Weibull and Rayleigh distributions, and the prevailing wind directions are analyzed. The monthly energy generated by an ideal turbine is compared to that generated by a real turbine for the four study sites. (An ideal turbine extracts all the energy available in the wind, whereas a real turbine is subjected to Betz’ law.) The high availability and capacity factors obtained are indicative of the large wind resource in Tenerife and in particular at three of the four study sites.
Energy, 2014
During the last years the interest of supplying the energy needs by means of renewable energy sou... more During the last years the interest of supplying the energy needs by means of renewable energy sources has risen sharply. The objective of this work is to investigate the viability of the implementation of a tidal farm to fulfill the electricity demands of the Port of Ribadeo, which is located in a tide-driven estuary (Ria de Ribadeo, NW Spain). For this purpose a 3D hydrodynamic model of the estuary was implemented and successfully validated. Overall, Ria de Ribadeo presents a substantial tidal resource with annual energy densities close to 72.56 MWhm À2 . On these grounds, taking the Evopod tidal turbine as a reference, the viability and installation of a tidal farm are analyzed by means of four performance parameters (electric energy output, site-specific efficiency, capacity and availability factors), which are computed on a monthly basis according to the characteristics of the flow at the site. In addition, a momentum sink term was used to simulate the blockage effect caused by the turbine in the flow, and, therefore determine its performance with more accuracy. The results obtained prove that a tidal farm of 25 turbines with a rated power of 400 kW is capable of fulfilling the electricity needs of the port.
Coastal Engineering, 2014
The possibility of using wave farms for coastal defence warrants investigation because wave energ... more The possibility of using wave farms for coastal defence warrants investigation because wave energy is poised to become a major renewable in many countries over the next decades. The fundamental question in this regard is whether a wave farm can be used to reduce beach erosion under storm conditions. If the answer to this question is positive, then a wave farm can have coastal defence as a subsidiary function, in addition to its primary role of producing carbon-free energy. The objective of this work is to address this question by comparing the response of a beach in the face of a storm in two scenarios: with and without the wave farm. For this comparison a set of ad hoc impact indicators is developed: the bed level impact (BLI), beach face eroded area (FEA), non-dimensional erosion reduction (NER), and mean cumulative eroded area (CEA); and their values are determined by means of two coupled models: a high-resolution wave propagation model (SWAN) and a coastal processes model (XBeach). The study is conducted through a case study: Perranporth Beach (UK). Backed by a well-developed dune system, Perranporth has a bar between −5 m and −10 m. The results show that the wave farm reduces the eroded volume by as much as 50% and thus contributes effectively to coastal protection. This synergy between marine renewable energy and coastal defence may well contribute to improving the viability of wave farms through savings in conventional coastal protection.
Energy, 2014
The paper combines hydrographic surveying techniques with numerical modelling to evaluate the spa... more The paper combines hydrographic surveying techniques with numerical modelling to evaluate the spatial and temporal distributions of tidal power in a confined channel located in Portugal (Faro Channel in the Ria Formosa). The channel is characterised by strong currents with depth-averaged velocities exceeding 2 m s À1 . The model was successfully validated against harmonic analysis data and in situ flow measurements acquired with an Acoustic Doppler Current Profiler (ADCP). Annual estimates of power and energy output were derived, considering spatial and temporal variations in flow velocities and in power density both across and along the channel. The study confirms the relevance of integrating field information with numerical models to achieve a better estimation of tidal power potential through the water column. The accuracy of both bathymetric and tidal elevation data contributes greatly to validating the model; whereas validating the model results with 3D velocity patterns obtained using boat-mounted ADCPs allows peak velocity distributions along the water column and the spatial variation of velocity through different cross-sections to be considered, further assisting in the dynamic placement of tidal energy conversion devices adapted to different resource scenarios. The methodology can be readily adapted and applied to any other inlet, tidal channel, or estuarine mouth.
Energy, 2014
Tidal currents represent a promising energy source for electrical supply in Europe; however, nowa... more Tidal currents represent a promising energy source for electrical supply in Europe; however, nowadays there still exist important aspects to address regarding their exploitation prior to becoming a fullyfledged renewable energy. The accurate assessment of the available resource and the development of TECs (Tidal Energy Converters) are challenges which have been partially solved, but it is necessary to go further in the investigation of other aspects such as the impacts on the estuarine circulation. In this work, the impacts caused on the estuarine circulation in Ria de Ortigueira by the operation of two different tidal stream plants, one composed of floating and the other of bottom-fixed TSTs (Tidal Stream Turbines), were analysed by means of a three-dimensional model. Prior to using the model for assessing the impacts, it was validated based on field data at two measuring stations. Then, the tidal farms were implemented in the model as a momentum sink. The results show that there are no significant differences between the impacts caused on the general circulation by floating and bottom-fixed TSTs with slight reductions of the flow being apparent up to some km away the plant. Then again, strong differences were found in the vicinity of the plant.