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The aim of this work is to describe several experiences of STEMbach in different areas: engineering, economics, materials, etc. The STEMbach is a program carried out by high school students during their two years of study to obtain their High School Diploma (equivalent to A-levels), designed for both the Humanities and Sciences modalities, and created alongside the Galician strategy for digital education. It encourages the vocation of the scholars towards scientific and technological research and allows a connection directly with the college education. The STEM works explained in this work were developed between the University of A Coruña and several high schools located in the region of Galicia (North-West of Spain). Results were very constructive for promoting STEM careers.

The aim of this work is to describe several experiences of STEMbach in different areas: engineering, economics, materials, etc. The STEMbach is a program carried out by high school students during their two years of study to obtain their High School Diploma (equivalent to A-levels), designed for both the Humanities and Sciences modalities, and created alongside the Galician strategy for digital education. It encourages the vocation of the scholars towards scientific and technological research and allows a connection directly with the college education. The STEM works explained in this work were developed between the University of A Coruña and several high schools located in the region of Galicia (North-West of Spain). Results were very constructive for promoting STEM careers.

This study explores the pedagogical approach in the first-year Applied Physics course of Engineering degrees at the University of A Corufia. Employing a comprehensive strategy, educators developed simulations to address student weaknesses identified in pre-tests. The research aims to bridge gaps by outlining objectives, elucidating methodology, and presenting tools used. Utilizing a quasi-experimental design over eight academic years. the investigation incorporates computer simulations, pre-tests, post-tests, and final exams. The primary objective is to improve engineering education through innovative methods, focusing on core principles like friction. thermodynamics, fluid rotation, and electromagnetic forces. Outcomes are showcased through various assessments. including general satisfaction surveys and specific questionnaires. Emphasizing distinctiveness, marked by inventive pedagogy, rigorous data analysis, and a sustained cohort study, the study contributes to ongoing discussions on engineering education enhancement. Ultimately, it empowers students for practical applications. [ABSTRACT FROM AUTHOR]

The aim of the present paper is to propose a new methodology for the production and installation of green artificial reefs (GARs) in shallow waters, with special attention to the transport stages. The process includes both onshore (manufacturing, road transport and unload at port) and offshore (load at port, sea transport, positioning, and deployment tasks) stages. Two different types of truck were analysed for the road transport. Furthermore, three different options were considered for sea transport: a workboat powered by liquefied natural gas, a barge using diesel (0.1% sulphur) as fuel, and an electric specific design barge. A simulation tool called AGARDO (Automatic Green Artificial Reef Deploy Optimisation) was developed for such a purpose. An estuary located in Galicia (North-West of Spain), where 180 GAR units must be installed, has been considered as case study. AGARDO was used to obtain results concerning process total time, equivalent CO2 emissions and costs for different scenarios. Consequently, the use of the proposed methodology allows the decision-maker to select the best option in terms of costs, emissions and time. AGARDO can be easily adapted to other case studies, with different onshore and offshore options. [ABSTRACT FROM AUTHOR]

The aim of this paper is to examine the most relevant competitive factors of a shipyard. The method conducted interviews and questionnaires with multiple agents related to the company and analyzed several institutional, business, and academic documents. The case of study considered was the manufacturing center of Navantia, S.A. in the Ferrol estuary (A Coruña, North-West of Spain). The results indicate that the five most important competitive factors are the government and political support, the production organization, the product technology, manpower, and skills and knowledge. Thus, these five competitive factors are critical to analyze the competitiveness of a shipyard with the characteristics of the one studied for new uses of the ocean, such as offshore wind, wave energy, or aquaculture. [ABSTRACT FROM AUTHOR]

This paper defines a methodology for the economic feasibility analysis of a floating offshore wind farm composed of tensioned leg platforms, which are part of the EU ARCWIND research project. In this context, the phases and subphases of its life-cycle process are considered to deal with aspects such as bathymetry, characteristics of the platforms, distance from the farm to shore, distance from the farm to port and offshore wind speed. All the costs and other external parameters such as capital cost, electric tariff, interest rate, percentage of financing and corporate tax have been analysed to calculate the internal rate of return, net present value, discounted pay-back period and levelized cost of energy of the farm. This work studies a farm composed of TLP offshore wind platforms designed by CENTEC and located at Ribadeo in Spain. Results indicate the costs and the economic feasibility of this platform for deep waters. They indicate that the platform is economically feasible for the location selected. [ABSTRACT FROM AUTHOR]

The appearance of the SARS-CoV-2 pandemic on the world stage has implemented changes in all social activities and, therefore, in teaching at all educational levels. On the one hand, it is argued that the closure of centers and virtual teaching minimizes the risk of contagion and, on the other, this closure implies a reduction in social interactions in the population at ages in which social skills are lower developing. In addition, it is necessary to guarantee that all children and adolescents have access to the necessary means for distance education. This article analyzes the impact of the COVID-19 pandemic during the second, third and fourth waves in Galicia (northwestern region of Spain), where the centers were kept open with strict security protocols, with the aim of evaluating whether the measure of the center closure is a proportionate measure or not. The results obtained show that, at all educational levels, the incidence of infections has been low, as has the appearance of outbreaks of infections related to educational centers, so the damage caused by this measure can be considered uncompensated, with greater health security. [ABSTRACT FROM AUTHOR]

Light emitting diode (LED) and compact fluorescent light (CFL) lamps are widely used because they are associated with low energy consumption and a reduced environmental impact. In the present paper, a study of the real consumption of these devices has been carried out. To do this, the active, reactive, distortion and apparent power and electrical efficiency for various lamps have been measured and calculated. The distortions produced in the network provoke the consumed energy to be in the order of 50–75% higher than that which appears in the commercial characteristics. This situation means that for its operation, it is necessary to generate and distribute an amount of energy much higher than that which is declared as the consumption of these lamps, and so far, this amount of energy is neither quantified nor invoiced. Additionally, groups of lamps have also been studied to check whether, when working together on the same network, there is a compensation phenomenon that reduces the negative effects of individual lamps. We have found that this compensation effect does not occur for the type of devices evaluated. [ABSTRACT FROM AUTHOR]

The goal of this work is to carry out an economic analysis of a novel floating offshore wind structure, of which the main material is concrete: the SATH® platform. It takes a step forward in floating marine wind energy research, in which traditional platforms are mainly composed of steel. The technique to calculate the costs of the platform and the economic parameters to decide if the farm is economically feasible are explained in the paper. This case study analyzes a possible farm of 500 MW located in Portugal and several scenarios considering different electric tariffs and capital costs (Scenario 1: electric tariff of 50 €/MWh and 6% of capital cost; Scenario 2: electric tariff of 50 €/MWh and 8% of capital cost; Scenario 3: electric tariff of 150 €/MWh and 6% of capital cost; Scenario 4: electric tariff of 150 €/MWh and 8% of capital cost). Results show the economic feasibility of a farm with the characteristics of Scenarios 3 and 4. This work is significant in order to provide a new approach to analyzing traditional floating offshore wind structures, which can represent a path towards the future of floating offshore renewable energy technologies. [ABSTRACT FROM AUTHOR]

In the present work, a numerical model was developed to analyze a commercial diesel engine. The adequacy of this model was validated using experimental results. This model was employed to study several pre-injection strategies. Particularly, the pre-injection rate, duration and starting instant were analyzed in the ranges 5% to 25%, 1° to 5° and −22° to −18°, respectively. The effect on consumption and emissions of NOx, CO, and HC wereas evaluated. Since some of these configurations have opposite effects on consumption and/or emissions, it is necessary to develop a formal tool to characterize the most appropriate injection pattern. To this end, a multiple-criteria decision making approach was employed. It was found that the injection duration must remain as low as possible due to significant reductions in NOx. The most appropriate injection pattern resulted 1° pre-injection duration, 20% pre-injection rate, and −19° pre-injection starting instant. This configuration leads to increments of 6.7% in consumption, 3.47% in CO, and 3.83% in HC but reduces NOx by 34.67% in comparison with the case without pre-injection. [ABSTRACT FROM AUTHOR]

Floating offshore wind energy could be one alternative in exploiting ocean wind energy resources when there is high depth as, for instance, in Spain. Therefore, in order to develop this type of offshore energy, floating offshore platforms are needed. The aim of this article is to characterise the importance of the non-direct cost which is implied in the manufacturing of a floating platform. For this purpose, an activity-based costing method will be used. It will distribute direct labour, material and activity costs of the platform taking into account that they are constructed in a shipyard. The methodology has been applied to three different floating offshore wind platforms: semisubmersible, spar and tension leg platform. It introduces a new study concept into the manufacturing process of shipyards: activity costs. In this sense, some results indicate that activity costs are of great importance, representing more than 40% of the total costs. [ABSTRACT FROM AUTHOR]

This paper develops a methodology to determine the installation costs of a floating wind farm installed offshore, the value of which depends on the type of floating offshore wind platform installed. In this context, several costs in the installation process have been defined: installation of the offshore wind generators, installation of the floating offshore wind substructures, installation of the anchoring and mooring, installation of the electric systems and the commissioning or start up of the floating offshore wind farm. Furthermore, several installation scenarios have been taken into consideration regarding the shipyard surface and draught, the number of lifts, the transport, the mooring strategy and the substation configuration. The method, tested for the region of Galicia and for three sorts of floating substructures: spar, semisubmersible and tensioned leg, allows to compare different alternatives of installing a floating offshore and the most important aspects of the costs proposed. It can be useful for investors who decide to use this type of offshore renewable energy in the future. [ABSTRACT FROM AUTHOR]

This article discusses the state of the art for driving technologies of anchor handling winches for offshore operations. These systems are necessary for anchor handling operations associated with installation of many types of moored floating offshore structures. To perform these operations, it is necessary to use specialized vessels known as AHT (Anchor Handling Tug) or AHTS (Anchor Handling Tug Supply) vessel, which incorporate specific equipment such as towing winches, but with higher performance than conventional tugs both in size and in technical performance. There are nowadays two main options for driving the Anchor Handling/Towing winches: hydraulic with low or high pressure motors, and electrical with AC motors driven by Variable Frequency Drives. Additionally, a new technology is appearing in the industrial sector which is starting to be applied in the marine sector, and in some cases for anchor handing winches: the permanent magnet motor. The aim of this paper is to discuss these driving technologies and their importance in the future of this part of the marine sector. [ABSTRACT FROM AUTHOR]

The aim of this paper is to determine the main costs and the feasibility of repowering wind farms. For this purpose, two study methods, which depend on legal and wind turbines issues, have been considered. They will provide nine alternatives, whose study will be developed. The methodology has been applied to the particular case of Galicia (North-West of Spain), where there is a good onshore wind resource. Calculations indicate the costs, the Net Present Value (NPV), the Internal Rate of Return (IRR), and the Pay-Back Period of these alternatives. In addition, a sensitivity study has analyzed the main variables of dependence in repowering wind farms. Results show that repowering can be a new alternative for onshore wind farms in areas where old wind turbines are currently installed. [ABSTRACT FROM AUTHOR]

The objective of this work is to establish a framework for the development of an economic analysis tool for floating offshore wind platforms built in concrete. The operation and usefulness of the beta version of a software, called Arcwind, is explained. It calculates the main economic aspects of offshore wind platforms built in concrete considering different locations in the European Atlantic Arc. This software allows the user to select different input parameters such as: the type of platform, the installation area of the farm, its specific location and in this way create different analysis scenarios. This paper analyzes the case study to install TELWIND® offshore concrete floating platforms in the Canary Islands, in Spain. The software provides data on the main economic parameters of the farm, such as Levelized Cost Of Energy (LCOE), Net Present Value (NPV), Internal Rate of Return (IRR), Pay-Back Period (PBP), as well as the main costs: cost of conception and definition, cost of design and development, cost of manufacturing, cost of installation, cost of operation and cost of dismantling. Using these parameters, a first analysis of the viability of this type of floating technology built on concrete is shown. [ABSTRACT FROM AUTHOR]

In this work, a numerical model was developed to analyze the performance and emissions of a marine diesel engine, the Wärtsilä 6L 46. This model was validated using experimental measurements and was employed to analyze several pre-injection parameters such as pre-injection rate, duration, and starting instant. The modification of these parameters may lead to opposite effects on consumption and/or emissions of nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC). According to this, the main goal of the present work is to employ a multiple-criteria decision-making (MCDM) approach to characterize the most appropriate injection pattern. Since determining the criteria weights significantly influences the overall result of a MCDM problem, a subjective weighting method was compared with four objective weighting methods: entropy, CRITIC (CRiteria Importance Through Intercriteria Correlation), variance, and standard deviation. The results showed the importance of subjectivism over objectivism in MCDM analyses. The CRITIC, variance, and standard deviation methods assigned more importance to NOx emissions and provided similar results. Nevertheless, the entropy method assigned more importance to consumption and provided a different injection pattern. [ABSTRACT FROM AUTHOR]

The employer (owner) of the project wants to obtain the maximum profit for the money invested and the consultant (contractor) will try to give less for that money. The regulation of their relationship is based on the contractual agreement, which in the energy sector is mainly based on the engineering, procurement, and construction (EPC) model. The objective of this work was to evaluate which factors should be included in the drafting of contracts, to minimize problems between the parties, and thus minimize execution costs and optimize operation and maintenance costs. Information and data on the integration of operability and maintainability criteria in contracts for 158 projects, with a total contract value of close to €40,000M, were analyzed. Several of those projects corresponded to wind, solar, and hydroelectric plants. The information collected the perception of the agents involved, and was classified according to the experience of the agents consulted in the operation and maintenance areas. Finally, the proposed criteria were prioritized. In general, the owner is willing to introduce these criteria in his contracts if they reduce the operation and maintenance cost by around 1–5%, while the contractor is interested in increasing his probability to be selected by 1–3%. [ABSTRACT FROM AUTHOR]

A technique to analyse the economic viability of offshore farms composed of wave energy converters is proposed. Firstly, the inputs, whose value will be considered afterwards in the economic step, was calculated using geographic information software. Secondly, the energy produced by each wave converter was calculated. Then the economic factors were computed. Finally, the restriction that considers the depth of the region (bathymetry) was put together with the economic outputs, whose value depends on the floating Wave Energy Converter (WEC). The method proposed was applied to the Cantabric and Atlantic coasts in the north of Spain, a region with a good offshore wave energy resource. In addition, three representative WECs were studied: Pelamis, AquaBuoy and Wave Dragon; and five options for electric tariffs were analysed. Results show the Wave Energy Converter that has the best results regarding its LCOE (Levelized Cost of Energy), IRR (Internal Rate of Return) and NPV (Net Present Value), and which area is best for the development of a wave farm. [ABSTRACT FROM AUTHOR]

This work analyzes NOx reduction in a marine diesel engine using ammonia injection directly into the cylinder and compares this procedure with water injection. A numerical model based on the so-called inert species method was applied. It was verified that ammonia injection can provide almost 80% NOx reduction for the conditions analyzed. Furthermore, it was found that the effectiveness of the chemical effect using ammonia is extremely dependent on the injection timing. The optimum NOx reduction was obtained when ammonia is injected during the expansion stroke, while the optimum injection timing using water is near top dead center. Chemical, thermal, and dilution effects of both ammonia and water injection were compared. The chemical effect was dominant in the case of ammonia injection. On the other hand, water injection reduces NOx through dilution and, more significantly, through a thermal effect. [ABSTRACT FROM AUTHOR]

This paper assesses the economic feasibility of offshore wind farms installed in deep waters considering their internal rate of return (IRR), net present value (NPV), and levelized cost of energy (LCOE). The method proposed has three phases: geographic phase, economic phase, and restrictions phase. The purpose of the geographic step is to obtain the input values, which will be used in the economic phase. Then, the economic parameters are calculated considering the inputs provided previously. Finally, the bathymetric restriction is added to the economic maps. The case study focused on the Cantabric and North-Atlantic coasts of Spain, areas that have not been studied previously in economic terms regarding floating offshore wind technology. Moreover, several alternatives have been considered, taking into account the type of floating offshore wind structure and the electric tariff. Results indicate which is the best floating offshore wind structure with respect to LCOE, IRR, and NPV, and where is the best location for the connection of a floating offshore wind farm in the region selected. [ABSTRACT FROM AUTHOR]

This paper uses a method to analyze the economic influence of the size of floating offshore wind farms. The economic aspects analyzed, LCOE (Levelized Cost Of Energy) and costs, depend on the number of floating offshore wind turbines, which establishes the effect of the size of the farm. This influence has been carried out for a map in a specific location. Regarding the case study, 18 alternatives have been considered taking into account the total power of the farm and the types of floating platforms. These aspects have been studied for the location of Galicia (Spain). Results indicate how LCOE and costs vary when the size of the floating offshore wind farm is increased for the studied kinds of offshore structures. Results are useful for planning an offshore wind farm in deep waters in future investments. [ABSTRACT FROM AUTHOR]

This paper develops a methodology to determine the economic feasibility of implementing offshore wave energy farms on the Portuguese continental coast. This methodology follows several phases: the geographic phase, the energy phase, the economic phase, and the restrictions phase. First, in the geographic phase, the height and the period of the waves, the bathymetry, the distance from the farm to the shore, from farm to shipyard, and from farm to port, are calculated. In the energy phase the energy produced by each wave energy converter is determined, and in the economic phase, the parameters calculated in the previous phases are used as input to find the economic parameters. Finally, in the restrictions phase, a limitation by the bathymetry will be added to the economic maps, whose value will be different depending on the floating offshore wave energy converter (WEC). In this study, three wave energy converters have been considered, Pelamis, AquaBuOY, and Wave Dragon, and several scenarios for electric tariffs have been taken into account. The results obtained indicate what the best WEC is for this study in terms of its levelized cost of energy (LCOE), internal rate of return (IRR), and net present value (NPV), and where the best area is to install wave energy farms. [ABSTRACT FROM AUTHOR]

Abstract The present paper proposes a Computational Fluid Dynamics model to analyze the operation cycle and exhaust gas composition in a four-stroke marine diesel engine, the Wärtsilä 6L 46. Once validated, the numerical model was employed to study the influence of several pre-injection parameters such as pre-injection rate, duration, starting instant and number of pre-injections. The purpose is to reduce consumption and emissions, especially nitrogen oxides, due to the current increasingly restrictive legislation. It was found that the fuel injection is a critical factor influencing combustion and emission characteristics. Important nitrogen oxides emission reductions were obtained for the parameters analyzed. Particularly, a 31.9% nitrogen oxides reduction was obtained using 20% pilot injection, 65.7% advancing 4° the pre-injection start angle, 20.1% shorting 4° the pre-injection duration and 36.7% using 4 pre-injections. A slight increment of hydrocarbons, carbon monoxide and consumption was obtained, lower than 5% for almost all the cases analyzed, and a negligible effect on carbon dioxide emissions. Highlights • A CFD model was developed and validated using experimental data at different loads. • Several NOx reduction mechanisms were compared. • The effect of pre-injection rate, duration, starting instant and number was evaluated. • NOx, CO, HC and CO2 emissions as well as consumption were analyzed. [ABSTRACT FROM AUTHOR]

The aim of this work is to develop a software to calculate the economic parameters so as to determine the feasibility of a floating offshore renewable farm in a selected location. The software can calculate the economic parameters of several types of offshore renewable energies, as follows: one renewable energy (floating offshore wind-WindFloat, tension leg platform (TLP), and spar; floating wave energy-Pelamis and AquaBuoy), hybrid offshore wind and wave systems (Wave Dragon and W2Power), and combined offshore wind and waves with different systems (independent arrays, peripherally distributed arrays, uniformly distributed arrays, and non-uniformly distributed arrays). The user can select several inputs, such as the location, configuration of the farm, type of floating offshore platform, type of power of the farm, life-cycle of the farm, electric tariff, capital cost, corporate tax, steel cost, percentage of financing, or interest and capacity of the shipyard. The case study is focused on the Galicia region (NW of Spain). The results indicate the economic feasibility of a farm of floating offshore renewable energy in a particular location in terms of its costs, levelized cost of energy (LCOE), internal rate of return (IRR), net present value (NPV), and discounted pay-back period. The tool allows for establishing conclusions about the dependence of the offshore wind resource parameters, the main distances (farm-shore, farm-shipyard, and farm-port), the parameters of the waves, and the bathymetry of the area selected., Competing Interests: The authors declare no conflicts of interest