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Abstract The main aim of this study was to analyse scientific and energy production, funding, collaboration among countries and most cited papers on the renewable energies topic through bibliometric and social network study of articles included in the Web of Science database. 12,167 papers were recovered from 2007 to 2016. Wind power is the energy from which a greater number of articles have been published (n = 3,930), followed by solar energy (n = 2,570) and ocean energy (n = 1,565). The United States leads the world production of articles (n = 2,320), followed by China (n = 1,629), the United Kingdom (n = 1007), Germany (n = 730) and Spain (n = 729). China is the leading country in financed works (80%), followed by South Korea (77%), Spain (61%) and the United States (59%). An important level of international collaboration has been identified, notably popping up the triangle made by United States, China and the European Union. Highlights • Scientific study based in the analysis of the energy production, funding and collaboration among countries. • Wind power is the energy from which a greater number of articles have been published. • The United States leads the world production of articles. • China is the leading country in financed works. • The triangle made by United States, China and the European Union have the most important level of collaboration. [ABSTRACT FROM AUTHOR]

This paper aims at presenting and describing a dimensioning methodology for energy storage systems (ESS), in particular for one based on flywheels, applied for the specific application of reducing power oscillation in a wave energy conversion (WEC) plant. The dimensioning methodology takes into account the efficiency maps of the storage technology as well as the effect of the filtering control techniques. The methodology is applied to the case study of a WEC plant in operation in Spain, using real power generation profiles delivered into the electric grid. The paper firstly describes the calculation procedure of the efficiency maps for the particular technology of flywheels, although it could be extended to other storage technologies. Then, the influence of using future data values in the dimensioning process and the control of the ESS operation is analysed in depth. A moving average filter (MAF) is defined to compensate for power oscillations, studying the difference between considering prediction and not doing so. It is concluded that a filtering control using future values based on a number of samples equivalent to a 4-min time order provides an important reduction in the energy storage requirements for a power generation plant. Finally, and based on the selection of storage modules previously defined, the efficiency maps, and the MAF used for delivering the power into the grid, an optimal operation strategy is suggested for the storage modules, based on a stepped switching technique. The selection of four flywheel energy storage system (FESS) modules achieves a reduction of 50% in power oscillations, covering 85% of the frequency excursions at the grid. [ABSTRACT FROM AUTHOR]

• An enhanced Hybrid Intelligent System is proposed to predict the energy generated by a solar thermal system. • Supervised (neural networks) and unsupervised learning (clustering) are combined an applied to a real-world case study. • Best regression results are obtained when applying a Multilayer Perceptron trained with the Bayesian Regularization and Levenberg-Marquardt algorithms to k-means clustered datasets. There is wide acknowledgement that solar energy is a promising and renewable source of electricity. However, complementary sources are sometimes required, due to its limited capacity, in order to satisfy user demand. A Hybrid Intelligent System (HIS) is proposed in this paper to optimize the range of possible solar energy and power grid combinations. It is designed to predict the energy generated by any given solar thermal system. To do so, the novel HIS is based on local models that implement both supervised learning (artificial neural networks) and unsupervised learning (clustering). These techniques are combined and applied to a real-world installation located in Spain. Alternative models are compared and validated in this case study with data from a whole year. With an optimum parameter fit, the proposed system managed to calculate the solar energy produced by the panel with an error that was lower than 10−4 in 86% of cases. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present a methodology for dimensioning an energy storage system (ESS) to the generation data measured in an operating wave energy generation plant connected to the electric grid in the north of Spain. The selection criterion for the ESS is the compliance of the power injected into the grid with a specific active-power ramp-rate limit. Due to its electrical characteristics, supercapacitor (SC) technology is especially suitable for this application. The ESS dimensioning methodology is based on a mathematical model, which takes into account the power generation system, the chosen ramp-rate limit, the ESS efficiency maps and electrical characteristics. It allows one to evaluate the number of storage cabinets required to satisfy the needs described, considering a compromise between the number of units, which means cost, and the reliability of the storage system to ensure the grid codes compliance. Power and energy parameters for the ESS are obtained from the calculations and some tips regarding the most efficient operation of the SC cabinets, based on a stepped switching strategy, are also given. Finally, some conclusions about the technology selection will be updated after the detailed analysis accomplished. [ABSTRACT FROM AUTHOR]

Renewable energies play an important role as a solution to the challenge of satisfying the growing global energy demand without jeopardizing the achievements in the fight against climate change. Given this panorama, different countries, including Spain, have developed policies to promote renewable energies. One of the technologies that benefit from these policies is photovoltaics. In Spain, the number of grid-connected photovoltaic installations has increased significantly in recent years. It is interesting to analyze the panorama of these facilities and identify the trends in their design criteria. In this line, in this work, the projects of 70 grid-connected photovoltaic installations distributed across Spain were analyzed. For that purpose, benchmarking techniques were applied, facilitating the systematization of information, the intercomparison of plants and the identification of trends and efficient solutions. A set of characteristic indicators of each installation was defined, and a statistical analysis of them was developed. Likewise, a tool was developed that allows the designers of this type of photovoltaic plant to compare the design parameters chosen for their installations with those of the surrounding area. Therefore, this work provides knowledge about the current panorama of photovoltaic implementation applicable to its future advance. [ABSTRACT FROM AUTHOR]

The especial characteristics of the Spanish electricity industry hinder the effective competition, in spite of the liberalization process developed. The high concentration in this industry facilitates the possible exercise of market power with the following negative consequences on electricity prices. Likewise, the high energy dependency and the greater participation of renewable energies would have an important impact on prices too. The aim of this paper is to analyze the effects of the liberalization of the Spanish electricity industry on the competition by means of an economic and institutional approach and, by extension, study other factors that have an impact on the household electricity prices. [ABSTRACT FROM AUTHOR]

Renewable energies play a fundamental role within the current political and social framework for minimizing the impacts of climate change. The ocean has a vast potential for generating energy and therefore, the marine renewable energies are included in the Sustainable Development Goals (SDGs). These energies include wave, tidal, marine currents, ocean thermal, and osmotic. Moreover, it can also be included wind, solar, geothermal and biomass powers, which their main use is onshore, but in the near future their use at sea may be considered. The manuscript starts with a state-of-the-art review of the abovementioned marine renewable energy resources worldwide. The paper continues with a case study focused on the Spanish coast, divided into six regions: (I) Cantabrian, (II) Galician, (III) South Atlantic, (IV) Canary Islands, (V) Southern Mediterranean, and (VI) Northern Mediterranean. The results show that: (1) areas I and II are suitable for offshore wind, wave and biomass; (2) areas III and V are suitable for offshore wind, marine current and offshore solar; area IV is suitable for offshore wind, ocean wave and offshore solar; (3) and area VI is suitable for offshore wind, osmotic and offshore solar. This analysis can help politicians and technicians to plan the use of these resources in Spain. [ABSTRACT FROM AUTHOR]

Abstract: This paper provides an economic valuation of RES-E promoted by the Spanish feed-in system. First, supported RES-E is evaluated in terms of CO2 emissions avoided when they are introduced in the Spanish electricity market instead of other potential polluting energy sources. And secondly, these positive environmental externalities of supported RES-E are compared with the funds they received from the Spanish feed-in system, in order to estimate the economic balance of this support system. The estimate for 2011 shows that approximately 10% of premiums paid to promote RES-E could be explained, from an economic point of view, by the monetary value of CO2 emissions avoided by not using alternative energy sources, as coal and combined cycle. Furthermore, the economic evaluation of National Energy Commission (CNE [Spanish acronym]) proposal that links the energy sources responsible for CO2 emissions to finance the support system of RES-E, confirms that the monetary value of CO2 emissions avoided when using promoted RES-E is nearly 70% of the revenues from the sale of allowances allocated to polluting technologies in the last National Plan of Emission Allowances in 2011. Promotion of RES-E over the use of fossil energy sources, must take into account not only the costs of their implementation, but also the overall balance of their use. [Copyright &y& Elsevier]

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Abstract: One of the characteristics of the Spanish energy system is its high degree of dependence on imports. In 2005, the Spanish government approved the new Renewable Energy Plan in the following sectors: Windpower, Hydroelectric, Solar Thermal, Solar Thermo-electric, Photovoltaic, Biomass, Biogas and Biofuels. The aim of the Plan is to make it possible to reach the target of 12% of primary energy being met from renewable sources by 2010. When selecting one from various Renewable Energy investment projects different groups of decision-makers become involved in the process. Decision-making has to take into consideration several conflicting objectives because of the increasingly complex social, economic, technological, and environmental factors that are present. Traditional single-criterion decision-making is no longer able to handle these problems. The Compromise Ranking method, also known as the VIKOR method, introduces the Multi-criteria ranking index based on the particular measure of “closeness” to the “ideal” solution. In this paper, we apply the method in the selection of a Renewable Energy project corresponding to the Renewable Energy Plan launched by the Spanish Government. The method is combined with the Analytical Hierarchy Process method for weighting the importance of the different criteria, which allows decision-makers to assign these values based on their preferences. The results show that the Biomass plant option (Co-combustion in a conventional power plant) is the best choice, followed by the Wind power and Solar Thermo-electric alternatives. [ABSTRACT FROM AUTHOR]

• Fiscal policies can be potential tools to boost renewables. • Electricity self-generation is implemented and evaluated. • Removal taxes to renewables achieves price competitiveness. The sustainability of the environment implies a dire need to redesign electricity systems. The aim of this paper is to evaluate the role of alternative fiscal incentives to promote renewable electricity. To this end, a disaggregated, electricity-related Computable General Equilibrium model is developed, taking the current structure of the (renewable and non-renewable) electricity sector into account. The Computable General Equilibrium model developed presents at least two advantages: the changes are analyzed from a global perspective (including impacts on prices), and second, rebound effects are accounted for. The fiscal measures examine three scenarios of change in line with the decarbonization processes of economies. Specifically, the scenarios assess: (1) a 100% decrease in renewable electricity taxes; (2) a 23% increase in taxes paid by the non-renewable electricity sector; and, (3) both together. In addition, these fiscal measures are evaluated assuming improvements in electricity self-generation. The case study is the Spanish economy for 2016. The Computable General Equilibrium model is calibrated on a symmetric input–output table, constructed from supply and use tables. These tables disaggregate the energy and electricity sectors. Results reveal the role and strength of fiscal policy in boosting the production of electricity generation technologies using green energy resources, and reducing the production of electricity generated from brown sources. However, results suggest that these effects are limited to the energy chain sectors, with insignificant effects in the whole economy. This study also provides better information and guidance to politicians and decision-makers who wish to promote renewables, and the need to have a clear understanding of the influence price competitiveness has on the economy. Moreover, the results of this study have implications for rebound effects when electricity self-generation is implemented. [ABSTRACT FROM AUTHOR]