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In line with the decarbonization of the domestic sector to meet the 2050 climate neutrality targets, this paper describes the energy, economic, and environmental analysis of a set of different novel configurations of polygeneration installations to provide electricity, air conditioning, domestic hot water, and desalinated water for a building of 80 dwellings. All arrangements were designed to cover 100% of the five demands required in the building with renewable energy only, from photovoltaic (PV) and photovoltaic-thermal (PVT) panels and biomass backup boilers (BB). Electricity can be sold to or purchased from the grid without electrical storage with batteries. Additional electricity generation with thermoelectric generators (TEG) coupled to the PVTs, and the BB was explicitly analyzed. The choice of electrically or thermally activated technologies (heat pump, HP/single-effect absorption chiller, SEAC for cooling and multi-effect distillation, MED/reverse osmosis, RO for desalination) created four configurations from the basic structure based on solar and biomass sources. Thus, the paper has studied four designs in detail and applied them to three case studies corresponding to different locations in Spain. They were modeled with TRNSYS and included specific models for desalination technologies. Both structures provide important energy and CO2 savings concerning the conventional supply of the building demands. The novel life-cycle analysis approach further increases the lifetime CO2 savings for all configurations as well. The electric option (the combination of HP and RO for cooling and desalting) was, by far, the most attractive solution in terms of liability and lower investment required in the three case studies. [ABSTRACT FROM AUTHOR]

This paper shows a practice to raise the reliability of an electric power system by the installation of distributed generation, taking gasified biomass as fuel. To calculate the reliability index, a probabilistic load flow was used. This index is determined as the fault probability of the system. The resolution of this probabilistic load flow combines the method of cumulants and Gram–Charlier expansion. To achieve the reliability index, simulating a number of contingencies is required; the greater the number of simulated contingencies, the higher the accuracy of the index obtained. This probabilistic technique uses the random variables as starting information, so the two generators and loads are simulated as random variables. The generators of this distributed generation are biomass-fueled gas engines, commonly found in Spain. The simulations carried out on the IEEE 14-bus Test System, including three biomass generators, show that the inclusion of this type of generation improves the overall reliability indices of the electrical system. [ABSTRACT FROM AUTHOR]

Climate change motivated by human activities constitutes one of the main challenges of this century. To cut carbon emissions in order to mitigate carbon's dangerous effects, the current energy generation mix should be shifted to renewable sources. The main drawback of these technologies is their intermittency, which will require energy storage systems to be fully integrated into the generation mix, allowing them to be more controllable. In recent years, great progress to develop an effective and economically feasible energy storage systems, particularly motivated by the recent rise of demand for electric transportation, has been made. Lithium-ion (Li-ion) battery prices have fallen near 90% over the past decade, making possible the affordability of electric vehicles and transforming the economics of renewable energy. In this work, a study on storage capacity demand previously presented as conference paper is expanded, including a deep analysis of the Spanish generation mix, the evaluation of the energy storage requirements for different low-carbon and carbon-free scenarios in Mainland Spain, and the calculation of the CO2 emissions' reduction and the associated storage costs. [ABSTRACT FROM AUTHOR]

Biomass is a renewable energy source that, due to its strong seasonality, needs to be stored, handled, and managed under suitable conditions for its optimal use. Storage is therefore a key process in which biomass can lose many of its qualities as a fuel, but which can also serve to improve the condition of the resource. This paper presents results from a study to assess the effect of large‐scale storage on a range of different biomass resources that was carried out at an electricity generation plant located in southern Spain. It included a series of field tests carried out with different types of biomass resources, to observe the behavior of these products during storage and the changes in their main characteristics. Based on these results, recommendations have been proposed for the optimal storage management of each of the products. The testing program confirms that the initial moisture content of the biomass, particle size, and the leafy content are critical aspects to consider to avoid self‐ignition and dry matter losses. Biomass with high moisture content should therefore be stored in small stockpiles and should be consumed immediately. This is especially important in the case of olive leaves and pine prunings when they have a high initial moisture content. Stockpiles of drier biomass, such as dried olive pomace, fruit tree pruning or dried olive pruning can reach up to 1200 t and be stored for up to 6 months, under adequately controlled conditions. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

This study aims to quantify the climate change impact of pyrochar production from pulp and paper mill sludge and the subsequent utilisation in combined heat and power (CHP) plants for co-generation of heat and electricity using the environmental life cycle assessment (E-LCA) method. In the Pyrochar Scenario, in which the sludge is pyrolyzed into pyrochar, the authors have assumed that pyrochar would replace coal. In the Reference Scenario, sludge is incinerated with a subsequent low rate of energy recovery. A comprehensive sensitivity analysis was performed to determine the conditions in which the sludge pyrochar would offer the greatest climate-effect benefits. The parameters selected for the said analysis are the form of pyrochar (pellet or powder), fuels replaced by it in the CHP plant (solid waste and peat vis-à-vis coal), and the utilisation of the pyrochar fuel in another European country (Germany and Spain vis-à-vis Sweden). The results of this E-LCA clearly show that using pyrochar as a biofuel in CHP plants delivered a considerable reduction in greenhouse gas (GHG) emissions (−1.87 tonne CO2-eq per 2.8 tonne dry sludge). Contribution analysis reveals that the process accounting for the biggest share of the reduction is the pyrochar combustion (a negative contribution of 76%), which results in a displacement of coal-based fuels. The authors conclude that the utilisation of pyrochar in firing units would provide the highest reduction in GHG emissions, while recommending a comprehensive economic analysis in addition to climate effect assessment, before making a decision regarding the introduction of sludge pyrochar to the energy sector. [ABSTRACT FROM AUTHOR]

The alarming increase in the average temperature of the planet due to the massive emission of greenhouse gases has stimulated the introduction of electric vehicles (EV), given transport sector is responsible for more than 25% of the total global CO2 emissions. EV penetration will substantially increase electricity demand and, therefore, an optimization of the EV recharging scenario is needed to make full use of the existing electricity generation system without upgrading requirements. In this paper, a methodology based on the use of the temporal valleys in the daily electricity demand is developed for EV recharge, avoiding the peak demand hours to minimize the impact on the grid. The methodology assumes three different strategies for the recharge activities: home, public buildings, and electrical stations. It has been applied to the case of Spain in the year 2030, assuming three different scenarios for the growth of the total fleet: low, medium, and high. For each of them, three different levels for the EV penetration by the year 2030 are considered: 25%, 50%, and 75%, respectively. Only light electric vehicles (LEV), cars and motorcycles, are taken into account given the fact that batteries are not yet able to provide the full autonomy desired by heavy vehicles. Moreover, heavy vehicles have different travel uses that should be separately considered. Results for the fraction of the total recharge to be made in each of the different recharge modes are deduced with indication of the time intervals to be used in each of them. For the higher penetration scenario, 75% of the total park, an almost flat electricity demand curve is obtained. Studies are made for working days and for non-working days. [ABSTRACT FROM AUTHOR]

This paper presents an approach to determine the optimal daily generation scheduling based on the Spanish electricity market rules. The Spanish power system considers the pool-based daily market and the technical constraints resolution as two different and consecutive processes. After the daily market has been cleared, a centralized constraints resolution process is applied to this initial scheduling through the redispatch of previously matched energy. In this paper, an algorithm based on Benders decomposition, arranged in three levels, is proposed to solve the technical constraints solution process in order to define a preventive secure dispatch. The constraints resolution process includes a full ac network and security model. This method determines the active power committed to each generating unit so as to minimize the energy redispatch cost subject to dispatch, network, and security constraints. The solution also provides the reactive power output of the generating units, the value of the transformers taps, and the committed voltage control devices. The model has been tested in an actual example of the Spanish power system. Some relevant results are reported. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to review the literature focused on the energy/electricity-growth nexus, highlighting how the focus has shifted from aggregated energy/electricity consumption towards specific energy sources. Moreover, it aims to shed light on the relationships between different energy/electricity sources and economic growth. Empirically, the paper focuses on the analysis of interactions between electricity generation in Spain under both the Special Regime ( SR ) and the Ordinary Regime ( OR ), and their relationship with economic activity. Data for Spain is studied for a time span from January 2003 to January 2016. The Toda-Yamamoto causality test is carried out to check for causality relationships. Additionally, both short- and long-run effects are assessed by using the ARDL bounds test approach. Overall, the results reveal high internal consistency when comparing the ARDL results with the causality analysis. The substitution effect was detected between OR and SR. However, the negative effect of the SR on economic activity deserves special attention by energy policymakers. This paper argues that the main challenge of renewable sources for policymakers is their cost-effectiveness. [ABSTRACT FROM AUTHOR]

This paper describes the construction and analysis of a disaggregated input-output model and its extension to a social accounting matrix (SAM) for the Spanish economy in 2013. Our focus is the specific disaggregation of the electricity industry into the generating, transmission, distribution and marketing businesses, which were decoupled in 1997 under legislation prohibiting any single company from conducting more than one of them. The multi-sectoral framework also allows disaggregation of electricity generating by production technologies (wind, nuclear, conventional thermal, hydropower, solar and other technologies). To the best of our knowledge, this is the first paper in which this information is presented in a multi-sectoral framework for the Spanish economy, which is enormously dependent on the electricity industry. The structural analysis reveals the industry's role in Spain and the importance of its activities. None of the electricity generating businesses is a Rasmussen key sector, and generating and distribution are both capital-intensive activities. Meanwhile, conventional thermal and hydropower generating together make up more than 50% of total output in value terms, while nuclear power accounts for only around 7%. Finally, imports and exports of electricity are small, and almost all demand is covered by domestic production. [ABSTRACT FROM AUTHOR]

This work investigates integrating vegetation into solar chimney power plants (SCPPs) using numerical simulations of an SCPP prototype in Spain. A 2D axisymmetric computational fluid dynamics model with radiation heat transfer was employed to evaluate the impact of vegetation beneath the solar collector roof on system performance. Different SCPP configurations were analyzed: a standard design, one with a secondary collector roof, and another with secondary and tertiary collector roofs. Results indicate the secondary and tertiary roof configuration exhibited the highest annual electricity generation capacity of 34-80 kW. While introducing vegetation under the collector appears feasible, it is likely to reduce the overall energy output. In summary, simulations suggest that vegetation influences SCPP operation, decreasing power production, while incorporating multiple collector roofs enhances the generation capacity. [ABSTRACT FROM AUTHOR]

Spain must reduce its energy consumption by 23% and achieve 100% renewable energy in electricity generation by 2030. This paper presents the current energy scenario en Spain, and the outlooks for different renewable options, with special focus on photovoltaic (PV) solar energy. In 2012, Spain was the number two European country in terms of installed rewnewable energy power. Solar PV technology has the potential to meet Spain's future energy demand and its associated environmental challenges. This paper gives a review of solar energy economy at global scale for both PV and thermal power technologies. The Spanish energy scenario shows actual trends and progress made by solar power. Economic concepts of levelised cost of electricity and grid parity are presented. The financial analysis shows that PV electricity achieves grid parity at a plant profitability rate up to 7.26%. [ABSTRACT FROM AUTHOR]

Hydropower stands out for its fast response ability and flexible operation, playing a predominant role in the provision of regulation reserves. As hydro power is an energy-constrained generation technology, it needs to be protected against any possible deployment of the scheduled reserves. However, the few models that formulate a detailed hourly co-optimization of energy and regulation reserves, neglect infeasibilities that could be derived from the requested reserves in real-time. As the regulation reserve market is becoming increasingly important, hydro producers can no longer neglect such effect. This paper presents a stochastic optimization model to find the optimal hourly schedule of a set of hydraulically coupled hydropower plants to obtain the weekly operation that simultaneously maximizes the expected profit in both energy and regulation reserves markets. The model is formulated for a price-taker agent, and it considers a very detailed representation of the system including minimum–maximum water flows, net head dependency, and fractional water travel time. The main contribution is that the obtained solution protects a multi-reservoir system against risk of water and storage unavailability due to the uncertainty in real-time use of regulation-up and down reserves, respectively, and that the reserves deem the net head dependency. The paper presents a realistic case study where the proposed formulation has been tested successfully with real data from the Spanish electricity market. [ABSTRACT FROM AUTHOR]

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Despite the relevant potential of offshore resource to substantially mitigate the effects of climate change through the generation of renewable electricity, the full exploitation of such wind resource currently remains incomplete. To promote offshore wind energy projects, it is crucial to engage in comprehensive planning processes that encompass technical, social, environmental, stakeholder, and political considerations. Within this framework, this paper presents a combined approach based on Geographical Information Systems (GIS) and Multi-Criteria Decision-Making (MCDM) methodology to optimize the selection of offshore wind farm locations. The proposed methodology includes annual net electricity production as a critical factor in the decision-making process, which has been previously optimized with regard to the wake effect. Subsequently, the determination of potential locations involves key criteria such as technical feasibility, environmental impact, economic viability, and power generation potential. This MCDM-GIS approach was applied and evaluated in a case study along the Spanish coastline, considering 92 initial alternatives. The results indicate that the offshore wind energy targets established for Spain in 2030 and 2050 should be reevaluated, as the optimal utilization of the available area represents only 16% of the total potential area. Based on the aforementioned criteria, a suitability map was generated by integrating all relevant map layers, including their respective buffer zones. [Display omitted] • Net electricity production criterion included in the alternative decision matrix. • GIS-MCDM synergy methodology at territorial level to optimize offshore wind sites. • Multi-criteria definition includes technical, environmental, and economic factors. • 92 potential offshore wind plant alternatives in a Spanish case study are considered. • Results give different ranking of alternatives depending on each MCDM approach. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper presents the impact of non-homogeneous deposits of dust on the performance of a PV array. The observations have been made in a 2-MW PV park in the southeast region of Spain. The results are that inhomogeneous dust leads to more significant consequences than the mere short-circuit current reduction resulting from transmittance losses. In particular, when the affected PV modules are part of a string together with other cleaned (or less dusty) ones, operation voltage losses arise. These voltage losses can be several times larger than the short-circuit ones, leading to power losses that can be much larger than what measurements suggest when the PV modules are considered separately. Significant hot-spot phenomena can also arise leading to cells exhibiting temperature differences of more than 20 degrees and thus representing a threat to the PV modules' lifetime. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract During the last two decades, a relevant development of renewable energy sources for electricity generation has been observed in Spain. Their diffusion has provoked deep changes that at times have been controversial. The large penetration of renewables under the recent economic conditions has affected power plants, triggering changes in the regulatory framework. In Spain, the use of Combined Cycles Gas Turbines (CCGTs) for complementing intermittent renewables is meant to ensure the security of supply. This paper aims toward a better understanding of the effects of renewables deployment and the modifications of the regulatory framework in terms of resource and capacity support schemes. Highlights • A relevant development of RES has been observed in the Spanish electricity system. • A substantial loss of generation was detected for Spanish CCGT. • National regulatory framework in the field of electricity changes continuously. • A clear regulatory position should be taken in order to re-order the electricity sector. [ABSTRACT FROM AUTHOR]

Abstract This research aims to analyse the impact of feed-in tariffs, feed-in premiums, and capacity payments on electricity generation by source. It also assesses their consequences for interactions between electricity sources, while considering the market price. Monthly data for Spain, from January of 2010 to February of 2017, and the Autoregressive Distributed Lag approach were used. The results reveal that both feed-in tariffs and feed-in premiums appear to contribute negatively to electricity production from wind. Capacity payments appear to encourage fuel and natural gas producers to bid low and increase electricity production from renewable resources. Highlights • This paper considers feed-in tariffs, feed-in premiums and capacity payments. • It uses monthly data and an autoregressive distributed lag approach. • The interactions between electricity sources are assessed, while studying the market price. • The feed-in system is found to contribute negatively to electricity generation from wind. • Capacity payments are found to decrease the uncertainty felt by controllable-source producers. [ABSTRACT FROM AUTHOR]

Highlights • Hourly-resolved model to investigate highly-renewable electricity generation in Spain. • Correlation analysis of time series to create 900 combinations used in simulations. • Transition paths evaluated based on security of supply, CO 2 emissions, and renewable share. • Short-term phase-out of nuclear and coal power plants proven to be feasible. Abstract Two alternative paths to achieve highly-renewable electricity generation in peninsular Spain are investigated in this paper. Every transition path comprises a description of the installed and decommissioned generation and storage capacities, from 2017 to 2030, as well as a hypothesis on the evolution of the electricity demand. The electricity mix for every hour within the transition path is determined through a dispatch algorithm that prioritizes electricity from renewable energy sources. The simulation is run for 900 different combinations of time series representing the hourly capacity factors of different technologies, as well as the electricity demand. This robust approach allows the evaluation of the transition paths based on the statistical distribution of several defined assessment criteria, such as security of supply, CO 2 emissions or renewable share in electricity generation. The feasibility of a Spanish power system with high renewable penetration is investigated not only in a future reference year but throughout the transition path. In particular, a progressive and simultaneous phase-out of nuclear and coal power plants in the short-term is proven to be feasible. Furthermore, the results sensitivity is analyzed including scenarios with a delayed nuclear phase-out, lower hydroelectricity generation due to more frequent and severe droughts caused by climate change and higher annual increment for the electricity demand. [ABSTRACT FROM AUTHOR]

This paper evaluates the net effect of renewable energy policy in Spain from 2002 to 2017 and calculates its cost-effectiveness in terms of CO 2 emission reductions in the production of electricity. Our conclusions indicate that although the phasing out of Feed-in Tariffs reduced the regulatory costs, it also limited renewable participation in the electricity market, leading to an increased electricity price and higher emissions. According to our results, the joint effect of (i) the value of avoided emissions due to renewable energy participation and (ii) the merit order effect was able to compensate for the regulatory costs (subsidies) up until 2010, while the sign of the net effect was reversed from 2011 to 2017. Finally, we find that the economic implications of emission reductions are highly dependent on how the social cost of carbon is measured. [ABSTRACT FROM AUTHOR]

Abstract: This paper contributes a critical view of the development of grid-connected photovoltaic systems (GCPVS) in Spain during the period 1998–2008 by looking into the different actions that were intended to promote this technology. The Spanish photovoltaic (PV) sector has undergone bullish development in the recent years, but its underlying factors still lack systematic identification and analysis. Accordingly, this paper collects and presents detailed data for describing this evolution. It also makes a special case of the particular promotion of PV systems on roof and goes further to analyze how these actions have affected GCPVS evolution as well as the magnitude of their impact on its performance. The exponential growth of installed cumulative PV power at the end of this period, which largely exceeded the target set for 2008, is canvassed by building an analogy with feedback control systems. In this approach, market response or the PV power attained is considered as the system output, while the different regulation changes are regarded as control actions aimed at enabling GCPVS to hit the energy target. Such an analysis allows determining the most significant delays and control actions that explain the system''s performance. Hence, this study suggests an alternative framework to support the formulation and assessment of energy policy as it puts the emphasis not only on the evolution of the system per se but rather on the performance of the system against the energy target. In this regard, it might contribute to enhance the promotion mechanisms of green technologies. [Copyright &y& Elsevier]

Abstract: The use of biomass resources for power generation offers numerous benefits of interest for political decision-makers: fuel security, rural and industrial development, ecological benefits. In Spain, policy instruments have been used since 1980 to stimulate biomass power generation. However, the diffusion outcome by 2007 was very disappointing: only 525MW. This paper argues that two factors lie at the core of this: the conceptualization of biomass resources by political decision-makers in the instruments used, and the desire that policy instruments be in line with market liberalization principles. These generated a persistent economic obstacle for biomass power generation, and impeded the development of markets for the supply of biomass resources. The policy learning regarding the heterogeneity of biomass resources, and the investors’ expectations on risks, profitability and resource markets was very slow among political decision-makers. The paper contributes to the understanding of diffusion outcomes by proposing to analyse diffusion by means of five indicators: types of resources, technologies, developers, motivations to invest and project sizes. Besides, the paper shows the usefulness of investigating policy instruments in terms of their risk and profitability characteristics. This enables a better understanding of the diffusion patterns and outcomes. [Copyright &y& Elsevier]

The aim of this paper is to present a feasibility analysis of the application of fuel cells for a combined heat and power system with grid connection in the tertiary sector. Although the analysis considers Spanish data, the methodology proposed is developed to be applicable at the EU level. The current legislative framework is analysed in order to establish the suitability of the payment scheme considered for the sale of surplus electricity from these systems. The paper also establishes criteria for the optimal design of distributed generation systems based on fuel cells from a technical, economic and environmental point of view, presenting the strategies that should be implemented to promote the future implantation of these systems and their progressive introduction to the market. [Copyright &y& Elsevier]

The main objective of the work described in this paper is to offer a new method of prediction of wind speeds, whilst aware that the method develops predictions in time-scales that can vary from a few minutes to an hour. This is needed because wind energy generation is increasing its participation in energy distribution and has to compete with other energy sources that are not so variable in terms of generated active power. It is important to consider that active power demand can vary quite rapidly and different sources of electricity generation must be available. In the case of wind energy, wind speed predictions are an important tool to help producers make the best decisions when selling the energy produced. These decisions are crucial in the electricity market, because of the economic benefits for producers and consequently their profitability, depends on them. The algorithm presented in this paper is based on an artificial neural network and two types of wind data have been used to test the algorithm. In the first, data was collected from a not very windy area; in the second data was collected from a real wind farm located in Navarre (North of Spain), and the values vary from very low to high speeds. Although the algorithm was not tested with typical wind speed values measured on offshore wind farm applications, it can be concluded from the first set of results presented in this paper that the algorithm is valid for estimating average speed values. Finally, a generic algorithm for the active power generation of a wind farm is presented. [Copyright &y& Elsevier]

• First-ever study to relate future Spanish environmental policies with EVs penetration. • The paper presents a novel methodology to reach a sustainable urban transport sector. • The limit power emissivity to hold a zero CO 2 emissions introduction of EVs is calculated. • A 100% renewable system will ensure a 77% CO 2 emissions reduction in Spain by 2040 due to EVs. Electric Vehicles (EVs) appear as an environmental solution for transport sector since they emit zero emissions while driving. Nonetheless, the carbon intensity (CI) of the energy sources involved in the electricity generation system could seriously compromise this solution. Hence, this study proposes a methodology to verify the sustainability of the sector by the introduction of EVs. By means of the "Well-to-Wheel" tool, it compares emissions generated by two fleets: one based on internal combustion engine vehicles (ICEVs) and another one that also contemplates different EVs penetration levels. This methodology develops an iterative process on the contribution of renewable sources to the electricity generation system until a certain level of emissions reduction is achieved. The needed evolution of the CI for the electricity system is therefore deduced. The methodology has been applied to Spain by the mid-term future, given these country policies for both a high penetration of EVs and a progressive introduction of renewable sources in its electricity system. Results indicate that the current Spanish electricity mix allows for a reduction in CO 2 emissions by the introduction of EVs, but a 100% renewable system will be needed for reductions up to 74 million tons per year. This research is a first-ever study to relate the forecasted Spanish environmental policies, in terms of urban transport and configuration of the power system, with a sustainable introduction of EVs in the urban fleet. Hence, this paper would be very helpful for policy makers on evaluation of the requirements for a transport fleet electrification. [ABSTRACT FROM AUTHOR]

The repowering of already installed wind farms is considered one of the most promising and cost-effective short-term strategies to scale-up wind capacity. In this study, we apply Markowitz's mean-variance (MV) portfolio optimization theory to explore alternative repowering actions in Spain. The efficient portfolios – a direct outcome of the MV optimization – offer optimal repowering alternatives to current wind farm generation mixes. They deliver the highest possible average power output (yield) for a given level of supply risk. Different repowering scenarios are considered in this paper that range from a full restructuring of the existing wind generation mix to restricting by certain amounts the percentage of down-/uprating of each reference region. Results show that, depending on the configuration of the MV portfolio optimization problem, hourly fluctuations in the aggregate power supply can be reduced as much as 12–31%, while retaining the current level of energy productivity. In addition, for the level of energy supply risk experienced with the existing portfolio of Spanish wind farms; we can derive more efficient mixes that boost-up productivity by 16–55%. This work aims at providing valuable insight for energy policy-making in the direction of optimally repowering future renewable generation. [ABSTRACT FROM AUTHOR]

The rapid expansion of photovoltaics within the global energy market requires increasing use of land, a limited resource where different uses compete. In this respect, photovoltaic systems that combine electricity generation with land use for crops are becoming increasingly important. This article proposes an analytical model validated in an operating bifacial photovoltaic plant during the summer months. This analytical model considers view factors and heat transfer calculations, as well as an electrical model of the photovoltaic modules. A study was carried out on a commercial solar power plant (11.24 MWp) in Seville, southern Spain, where different vegetal species were planted in two strings, and string performance was monitored. Nine crop species with different irrigation and light requirements, offering different albedo parameters and thermal characteristics. The results show advantages from the point of view of module temperature and power gain. This paper provides regressions for the characterisation of the photovoltaic agricultural plant, with R2 higher than 85%, both for module temperature and energy exported in the string with crops. [Display omitted] [ABSTRACT FROM AUTHOR]

On the path towards the decarbonization of the electricity supply, flexibility and demand response have become key factors to enhance the integration of distributed energy resources, shifting the consumption from peak hours to off-peak hours, optimizing the grid usage and maximizing the share of renewables. Despite the technical viability of flexible services, the reduction of greenhouse gas emissions has not been proven. Traditionally, emissions are calculated on a yearly average timescale, not providing any information about peak hours' environmental impact. Furthermore, peak-hours' environmental impacts are not always greater than on the base load, depending on the resources used for those time periods. This paper formulates a general methodology to assess the potential environmental impact of peak-hourly generation profiles, through attributional life cycle assessment. This methodology was applied to five different countries under the INVADE H2020 Project. Evaluation results demonstrate that countries like Spain and Bulgaria could benefit from implementing demand response activities considering environmental aspects, enhancing potential greenhouse gas reductions by up to 21% in peak hours. [ABSTRACT FROM AUTHOR]

Proper planning for the dimensions of an electricity production and transmission system requires the availability of medium- and long-term electricity demand projections that are sufficiently reliable. Generally, these projections are directly linked to the estimated growth for the whole real GDP (gross domestic product), although an in-depth historical evolution of this demand, as that given in this article, advises the explicit consideration of several determinants. The aim of this paper is to present an alternative analysis of the demand for electricity based on a simple growth rate decomposition scheme that allows the key factors behind this evolution to be identified. It is possible, taking this scheme as a starting point, to develop a long-term forecasting model to obtain projections of electricity demand given the expected evolution of the key factors. The proposed methodology is illustrated using Spain as a case study to obtain demand projections till 2030. [ABSTRACT FROM AUTHOR]

Costs for High Concentrator Photovoltaic (HCPV) power plants dropped dramatically during 2013 and are expected to continue to fall in the next few years. Moreover, when viewed from the perspective of life cycle cost, HCPV becomes even more competitive than other renewable technologies in some geographical areas. Consequently, an analysis of the economic feasibility of the HCPV systems in future scenarios is necessary for comparison with other electricity generation technologies. One of the methods commonly used for the economic feasibility analysis in electricity generation projects is the levelised cost of electricity (LCOE). In this paper a cost analysis of electricity generation of HCPV technology in Spain by using the LCOE has been carried out. The results obtained in this LCOE analysis show that in 2020 the LCOE will be able to reach values for HCPV systems from 0.035 to 0.080 €/kW h, lower than LCOE for conventional PV systems, in some geographical areas of Spain. The results obtained in this analysis have been shown in innovative maps. [ABSTRACT FROM AUTHOR]

At the end of January 2012, the Spanish government suspended the economic incentives for electricity generation facilities using renewable energy sources, including wind energy plants. Spain maintains a high level of energy dependence that can only be reduced by applying measures to increase energy efficiency and using massive amounts of renewable sources. In addition, the target assumed by Spain, i.e., to have at least 20% of the primary energy to be supplied by renewable sources by 2020, has not yet been reached. In Spain, wind farms, a number of which have been in commercial operation for over 15 years, offer a broad market appropriate for repowering. The use of more efficient wind turbines by means of repowering provides benefits to the electricity sector as a whole by optimizing the use of natural resources and facilitating the grid integration of the energy generated. This paper analyses existing wind farms to quantify and characterize the market suitable for repowering. We discuss whether repowering is a valid alternative from the point of view of feasibility to enable the continuation of the integration of wind energy in the Spanish energy mix and whether this feasibility is sufficient when the energy generated is charged at the electricity market price in terms of grid parity. The results support that repowering is a profitable alternative and is often even better than the construction of new wind farms under certain conditions. [ABSTRACT FROM AUTHOR]

Abstract: Biomass-fueled Organic Rankine Cycle power plants in a cogeneration topping layout have been operated in Central Europe since 2000. These plants are usually integrated into a district heating system and located near to the villages whose thermal and electric energy demands are to be covered. In this paper, a technical and economic feasibility assessment of this kind of plants is presented. The energy performance has been analyzed in different scenarios. Four different typical organic fluids (two silicone oils, toluene and isopentane), subcritical and supercritical cycles and the inclusion of a recuperator have been considered. Thermal and electric energy are sold to a nearby village at competitive market prices. Spanish market prices have been used as a reference. No subsidies have been considered in the case of electricity, so that the Spanish average power pool market price has been considered. The size of the plant, the cost of biomass and the annual operation schedule have been considered for the economical analysis. According to the technical analysis, hexamethyldisiloxane (HMDSO) in recuperative cycles has turned out to be the best choice in both the subcritical and the supercritical layouts, due to its favorable global behavior (harmfulness, reliability and efficiency). The economic assessment shows a lower profitability in the case of supercritical cycles because of the fact that the increase in electric efficiency implies a decrease in the amount of produced useful heat, which is the main source of cash inflow. The size of the plant can be established according to the cost of fuel in order to achieve a similar profitability (i.e. a 1 MWe plant fueled with biomass priced at 5.5 €/MWhth has a similar internal rate of return than a 2 MWe plant fueled with biomass priced at 15.5 €/MWhth). In order to obtain a 5% internal rate of return with subcritical recuperative plants, the annual operation time must be 2750 h in the case of a 2 MWe plant fueled with biomass priced at 5.5 €/MWhth and 5500 h in the case of a 1 MWe plant fueled with biomass priced at 15.5 €/MWhth. [Copyright &y& Elsevier]

Abstract: The cut-off of any subsidy or feed-in tariff that incentives the installation of new renewable energy systems which are close to the grid parity, is a reality in most of the European countries, but in the recent years the grid parity has worsened because of the global economic crisis. In the case of Spain, in addition to the economic problems, the photovoltaic sector has been dramatically damaged through a changeable regulatory framework, an excessive bureaucracy and the inclusion of additional fees or possible back-up tolls that are very prejudicial for the deployment of this sector. Nowadays, the current Spanish legislation mentions the possibility of self-consumption (totally or partially) of the electricity generated by PV or any renewable energy systems but, up to the date of this work, the law that regulates the administrative, technical and economic conditions for the net-metering of the electrical energy produced within the consumer׳s network, is still under a draft stage. In this paper it is analyzed the case of the University of Jaen, where it has been identified and simulated several PV systems on the roofs and parking lots of the University Campus, and considering the current electrical tariffs (hourly defined for the case of high power and high voltage consumers), it has been done a cost and economic analysis. As a result, it has been obtained an average Levelised Cost of Energy around 0.125€kWh−1, a discount payback time of 17.5 years or less, a positive Net Present Value and a nominal Internal Rate of Return of 8.48% in the worst case. Beyond that, it has been carried out a sensitivity analysis of the factors that have more influence in the profitability of these systems, like the initial investment cost, the PV electricity yield, additional taxes and the variations in the electricity price market. [Copyright &y& Elsevier]

Abstract: This paper reviews the production and consumption of traditional and renewable energy in Spain over the past two decades. It also presents an overview on the development of renewable energy, such as solar (photovoltaic and photothermal), wind, biomass, hydropower, marine and geothermal energies in Spain. A brief overview of the legislation regulating renewable energy in Spain is offered. It was shown that the installed renewable energy of 32,472MW represented 11.6% of the country׳s primary energy consumption. Furthermore, the installed renewable energy average of electric power in Spain was 0.7kW per capita and 59kW/km2. Wind energy continues to experience a good growth rate, and does not seem to be affected by regulations, which has made it the most sustainable renewable energy in Spain. Finally, an analysis of energy production and consumption, renewable and non-renewable energy by province is made. The data indicates that highly populated and industrialised provinces made more efficient use of their energy from an electrical consumption viewpoint. This uneven growth was not motivated solely by the existence or lack of renewable energy resources but by the autonomous community or province in their socio-economic context. [Copyright &y& Elsevier]

We apply an index decomposition analysis to investigate the main drivers of CO2 emissions in the electricity generation sector in Spain over the period 1991–2017. We quantify the impact of five different effects: carbonization, transformation, fossil intensity, electricity intensity, and production effects. Four subperiods are identified. The relevance of the drivers changed over these subperiods. The fossil intensity, electricity intensity, and production effects played an important role in the increase in emissions during the first half of the period, and particularly from 1999 to 2005. In contrast, the carbonization and fossil intensity effects were the dominant drivers of emissions reductions between 2006 and 2010. The research allows an assessment of the impact of different measures on emissions by considering their influence on the different effects, and suggests which sets of measures could be more effective in reducing emissions. [ABSTRACT FROM AUTHOR]

Abstract: The capacity expansion planning problem of the renewable energy industry involves decisions regarding the optimal mix of different plant types, locations where each plant should be built, and capacity expansion decisions over the planning horizon for each plant. The aim of this paper is to develop a goal programming model, based on a multi-source multi-sink network, in order to locate five renewable energy plants for electric generation in five places located in the autonomous region of Cantabria, in the north of Spain. As different types of plants can be placed in each location, the goal is to locate one plant in each place, maximizing the number of plants that are matched with comparable locations, in a way that the total deviations from goals are minimized. [Copyright &y& Elsevier]

Abstract: Climate change, added to security of supply concerns, has been leading many countries to strongly support the development of electric vehicles (EVs) not only as a cleaner and more energy efficient source of transportation but also as a flexible electricity storage option. However, the massive deployment of EVs will impose important challenges to power systems operation. In this context, this paper investigates the impact of EVs with V2G capability to power system operation. Since this impact depends on the power system considered and on the number (and type) of EVs, different scenarios for renewable energy sources (RES) generation and EV penetration are studied. A detailed analysis of the impact of EVs the Spanish power system – demand, generation, use of flexible units (pumped storage) and power reserve, and energy curtailment – is performed. For this purpose, a mid-term operation model that computes generation dispatch and simulates hourly power system operation is used. The advantage of this model is that it includes EVs in the unit commitment and represents in detail mobility and connection patterns, which allows the estimation of more realistic results. [Copyright &y& Elsevier]

Abstract: This paper deals with the potential of power generation resources for hydrogen production and electric grid load balancing in large scale management scenarios like the Spanish power system; much of which is currently underutilized and could deliver substantial amounts of energy, with great advantages for the reliability of the system at the same time. In this context, the production of hydrogen by electrolysis using the power grid mix is a promising option as an alternative to other operational procedures or exporting the electricity. Power generation can be controlled by the disposability of the installations and their utilization ratios; thus, we analyze the forms of generation to shape the power load curves, by using the regulation with hydrogen and getting a balance of efficiency, economy and ease of operations. To estimate hydrogen production we use the characteristic curves of electrolyzers, where the interest is that it applies to variable operations with time: i.e. the ‘surplus energy’ during over-generation periods is electrolyzed into hydrogen, which can be reconverted into electricity for ‘peak shaving’ or other uses. We establish a ‘critical ratio’, which determines the power generation for given demands, to fulfill the needs of the electric grid according to the curve profiles and the regulation with hydrogen; this ratio depends of many variables which are investigated for reaching an adequate balance: the energy gap of the generation and load curves, the capacity factor of the electrolyzers with regard to their maximum power inputs and the shape of daily generation curves. The resulting scenario is good enough for the transition of power system, as it admits 42% of energy from decarbonated sources, at the same time that shortens the payback period of fossil fuel utilities and generates hydrogen for other uses; economically, we obtain a positive cash-flow of the project after the third year, while the net incomes are 1863 M€ in the whole period; environmentally, it reduces the emissions from 236 to 210  per MWhe, while we can fuel three millions of hydrogen vehicles, with a net reduction of 4  and local air pollutants. After ordinary thermal installations are amortized, the management with hydrogen at large scales would permit the deployment of the power systems based in renewable sources, doing away with all CO2 emitting technologies which are substituted by wind, solar, hydro or nuclear. [Copyright &y& Elsevier]

Abstract: As fossil fuels are not only a limited resource, but also contribute to global warming, a transition towards a more sustainable energy supply is urgently needed. Therefore, today''s environmental policies are largely devoted to fostering the development and implementation of renewable energy technologies. One important aspect of this transition is the increased use of biomass to generate renewable energy. Agricultural residues are produced in huge amounts worldwide, and most of this residue is composed of biomass that can be used for energy generation. Consequently, converting this residue into energy can increase the value of waste materials and reduce the environmental impact of waste disposal. This paper analyses the situation of biomass energy resources in Andalusia, an autonomous community in the south of Spain. More specifically, biomass is the renewable source which most contributes to Andalusian energy infrastructure. The residual biomass produced in the olive sector is the result of the large quantity of olive groves and olive oil manufacturers that generate byproducts with a potentially high energy content. The generation of agricultural and industrial residues from the olive sector produced in Andalusia is an important source of different types of residual biomass that are suitable for thermal and electric energy since they reduce the negative environmental effects of emissions from fossil fuels, such as the production of carbon dioxide. [Copyright &y& Elsevier]

Abstract: Solar thermal electricity technologies are attractive alternatives to produce electricity by means of a renewable source. One of these technologies is parabolic trough collectors. In Spain, the sale of solar electricity to the national grid is primed. There are three main parameters that affect the behaviour of these plants: area of solar collector field, capacity of thermal storage tanks and power of the auxiliary system. In this paper, a simplified model of the plant is used to optimize the size of its components that produces the maximum yearly profit. The use of traditional methods of optimization is not possible and genetic algorithms have been used. An important feature of the model is that the minimum level of the electricity production of the block of power can be fixed. Once the optimization has been performed, the traditional parameters that characterize the dimension of the plant are analysed (the solar multiple and the capacity factor). For a gross power of 50 MW, the optimum collector area varies between 583,000 m2 and 749,860 m2 with a thermal storage between 6.55 h and 13.46 h respectively. The economic benefit is always higher than 19.30 M€ per year and the cost of the electricity produced is about 18.5 c€/kWh. [Copyright &y& Elsevier]

Abstract: This paper describes a simulation model that reproduces the performance of parabolic trough solar thermal power plants with a thermal storage system. The aim of this model is to facilitate the prediction of the electricity output of these plants during the various stages of their planning, design, construction and operation. Model results for a 50MWe power plant are presented and compared to real data from an equivalent power plant currently operated by the ACS Industrial Group in Spain. [Copyright &y& Elsevier]

Energy projections made by the World Energy Council, the International Energy Agency (IEA) and the US Energy Information Administration give similar pictures of the dominant role of fossil fuel in the future primary energy global demand and the necessity of incorporating CCS Technologies as part of the portfolio of solutions to reach the target world emission reduction in the coming years. Without CCS, CO2 emission levels by 2050 are expected to increase by 70%. One of the most relevant initiatives for the deployment of CCS technologies is promoted by the Spanish Government through the institution Fundacion Ciudad de la Energia (CIUDEN). CIUDEN is developing a complete programme focusing on the development of CCT and CCS technologies in Europe. CIUDEN's CO2 capture programme includes the construction and operation of a Technology Development Plant (TDP) in NW Spain (El Bierzo). The construction of the installation started in November 2008 and incorporates the following technologies: fuel preparation system, pulverised coal boiler (20 MWth), circulating fluidized bed boiler (30 MWth), biomass gasifier (3 MWth), flue gas cleaning train for NOx, dust and SOx and CO2 processing unit. This paper describes CIUDEN's TDP for CO2 capture, focusing on the particularities of the installation and design, and especially on the PC unit and equipment required for its operation. The experimental programme currently under way is also described. Results are expected to be an extraordinary advance in the development and strengthening of CCT and CCS technologies, particularly oxycombustion. [ABSTRACT FROM AUTHOR]

Abstract: Assessing the correct operation of PV grid-connected systems (PVGCS) is paramount not only for mere energy and profitability concerns but also for safety reasons. Intended to this purpose, the IEC 62446 standard is open to some tests to be required in some circumstances, in addition to those stated in this document. Our work proposes a procedure to carry out quality checks in PVGCS complying with this standard and dealing with some tests not mentioned in it – namely, PV generator peak power measurement, inverter response and earth electrode measurement – so that the verification of the system gets more comprehensive. This procedure was carried out in six PV plants sited in different locations with a Mediterranean climate in Spain. The most remarkable results of this experimental campaign may be summarized as follows: an excellent on-site behavior of the inverters, in general very good figures for the isolation and earth electrode resistance and a scarcely relevant existence of hot spots. On the down side, some figures for the peak power of the tested PV generators well below their nominal value were found. The procedure described in this paper has proved to be a useful tool to assist in the verification of a PVGCS after installation and for subsequent re-inspection or maintenance. [Copyright &y& Elsevier]

Abstract: A steady state security margin for a particular operating point can be defined as the distance from this initial point to the secure operating limits of the system. Four of the most used steady state security margins are the power flow feasibility margin, the contingency feasibility margin, the load margin to voltage collapse, and the total transfer capability between system areas. This is the second part of a two part paper. Part I has proposed a novel framework of a general model able to formulate, compute and improve any steady state security margin. In Part II the performance of the general model is validated by solving a variety of practical situations in modern real power systems. Actual examples of the Spanish power system will be used for this purpose. The same computation and improvement algorithms outlined in Part I have been applied for the four security margins considered in the study, outlining the convenience of defining a general framework valid for the four of them. The general model is used here in Part II to compute and improve: (a) the power flow feasibility margin (assessing the influence of the reactive power generation limits in the Spanish power system), (b) the contingency feasibility margin (assessing the influence of transmission and generation capacity in maintaining a correct voltage profile), (c) the load margin to voltage collapse (assessing the location and quantity of loads that must be shed in order to be far away from voltage collapse) and (d) the total transfer capability (assessing the export import pattern of electric power between different areas of the Spanish system). [ABSTRACT FROM AUTHOR]

Abstract: The future commercial production of electricity based on thermonuclear fusion requires the development of a number of research projects in addition to ITER, mostly related to the development of long-term technologies needed for future fusion reactors. Among the priority areas identified in the framework of international fusion research programmes, it is projected to build a specific research centre for fusion technologies in Spain. The so-called National Centre for Fusion Technologies, TechnoFusión, will be equipped with a large number of top facilities for the fusion technological development. The research activities will be focused primarily on several areas, including the implementation of advanced manufacturing technologies, the evaluation of radiation effects on low activation structural and functional materials, the in-beam and out-beam characterization of materials, the development of robotics and automated systems for remote handling, studies of liquid metal technologies and computer simulation. Currently no similar facilities to TechnoFusión exist, so it will provide more realistic tests than those available in other facilities up today, helping in the fast track to DEMO and IFMIF. The present document summarizes a review of the different facilities to be included in TechnoFusión, with special emphasis on those proposed for remote handling (RH) applications. The paper will review the technical specifications concerning the RH facility, the analysis of the mock-up components and tests to be performed, and the relevance of the RH lab capabilities, particularly the required equipment under irradiation conditions. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we assess the potential for the generation of electricity in Spain from agro-industrial residues. The industries considered are olive-oil mills, rice mills, wineries, dairy plants, breweries and wood, meat and nut processing plants. The methodology used is based on statistical data, and is integrated into a Geographical Information System (GIS) from which geo-referenced results are obtained. The waste-to-electricity technologies analyzed are: grate firing followed by steam turbine, co-firing in coal power plants and anaerobic digestion plus internal combustion engine. The combined potential for the agro-industrial residues in Spain is estimated at 2625ktoe/year of primary energy (1.85% of the primary-energy consumption in Spain in 2008). Olive mill and wood processing residues have the largest energy potentials. Comparisons are presented with (partial) results from other studies. Considering only profitable plants, grate-firing followed by steam-turbine cycle is the conversion option with the largest potential, totaling 653MWe and an electrical generation of 4.57TWh (1.44% of the gross electrical generation in Spain in 2008). A complete sensitivity analysis is done to investigate the influence of the different economic parameters. A reduction by 50% of the investment costs of grate firing would increase profitable power to 1102MWe (and production to 7.70TWh). [Copyright &y& Elsevier]

Abstract: Trigeneration systems, also known as Combined Heat, Cooling and Power (CHCP) systems, are interesting alternatives to supply different energy services in urban districts and in large buildings, particularly in warm areas such as Mediterranean countries. These systems can provide substantial benefits from economic, energetic, and environmental viewpoints, since the cogenerated heat can be used for heating in winter as well as cooling in summer with an absorption refrigerator. This paper develops an optimization model using Mixed Integer Linear Programming (MILP) to determine the type, number and capacity of equipment in CHCP systems installed in the tertiary sector as well as to establish the optimal operation mode for the different plant components on an hour-by-hour basis throughout the year. The objective function to be minimized is the annual total cost. The optimization model considers the legal constraints imposed to feed the surplus autogenerated electricity into the grid at a regulated feed-in tariff. The optimization model is applied to design a system providing energy services for a hospital located in the city of Zaragoza (Spain). The effects of the financial market conditions and energy prices in the optimal structure of the system are analyzed. [Copyright &y& Elsevier]

Abstract: This paper presents an application of probabilistic methodologies to evaluate the reserve requirements of generating systems with a large penetration of renewable energy sources. The idea is to investigate the behavior of reliability indices, including those from the well-being analysis, when the major portion of the renewable sources comes from wind power and other intermittent sources. A new simulation process to address operating reserve adequacy is introduced, and the correspondent reliability indices are observed. Case studies on the Portuguese and Spanish generating systems are presented and discussed. [Copyright &y& Elsevier]