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• Mechanisms to encourage clean energy in Spain from 2005 to the present are analyzed. • FiT and FiP mechanisms can be effective in promoting new renewable projects. • Experience suggests that excessive support can jeopardize the entire market. • A transitional retribution scheme has proven to be effective if correctly supervised. This research paper delves into the central mechanisms implemented in Spain to foster the adoption of clean energy projects. The study scrutinizes various mechanisms established from 2005 onwards, evaluating their efficacy in achieving the desired outcome of supporting clean energy project implementation. The aim is to comprehensively assess the associated costs, effectiveness, and attainment of renewable energy objectives stemming from implementing diverse support schemes. This paper explores the effectiveness of feed-in tariffs and feed-in premium mechanisms in promoting the integration of new renewable energy generation into the power system. However, the Spanish experience suggests that exhaustive planning control is imperative to prevent excessive support costs that could jeopardize the entire market and cause a significant rise in final energy costs. The research studies the support schemes and associated market distortion and presents the roadmap from regulated tariffs to a "total market" for wind and solar energy. The findings demonstrate that, under proper supervision and planning, a transitional retribution scheme effectively promotes renewable energy plant integration. Finally, the analysis examines the need to regulate the excess benefits that non-emitting power sources receive in a marginal price market, as this can lead to market imbalances and a substantial increase in final costs. These plans serve as a crucial tool in achieving the decarbonization objectives of the European Power System. [ABSTRACT FROM AUTHOR]

• Pioneer Spain: first country to include in grid code the synthetic inertia capability. • Synthetic inertial response of a PV inverter studied based on the Spanish grid code. • Analyzed the role of power plant controller in the dynamic response of the facility. • PV system able to contribute to frequency control providing an inertial response. As the large-scale integration of renewable energy grows, inertia in power systems is reduced, which causes the rate of change of frequency to increase and worsens the frequency nadir during disturbances. There is, therefore, an urgent need to accelerate the development of international standards and regulations that require solar PV systems and other renewable installations to also contribute to stability in the network by emulating inertia. Spain is a pioneer in this field: it is currently the only country that includes the synthetic inertia technical requirement in its grid code. In this context, the present paper analyzes the synthetic inertial response of a PV system model that forms part of an actual PV power plant in Spain under two scenarios, according to its grid code: i) when measurements are conducted at the power conversion PV system level and hence only its control algorithms are executed; and ii) when measurements are conducted at the power plant level and the power plant controller also influences the response of the entire installation. Among its aims, this paper seeks to thoroughly assess the response of an actual PV power conversion system that has the capability of actively contributing to frequency regulation in a network and to critically analyze the suitability of having a power plant controller when the PV facility contributes to power-frequency control by means of an inertial response. The results reveal, at the power conversion PV system level, that the inertia emulation module significantly reduces the response times of the installation to changes in frequency -by more than 68% in the worst case under frequency increases, and by 73% under frequency decreases, thus contributing to more rapid power-frequency regulation in the network. However, at the power plant level, the power plant controller disturbs the PV power conversion system's behavior and causes the opposite effect: response times increase -up to more than 7% in the most unfavorable case when the inertia module is enabled. [ABSTRACT FROM AUTHOR]

Decreasing greenhouse gas emissions plays a crucial role in the Europe energy transition and the production of hydrogen using electricity from renewable sources (green H 2) contributes significantly to this objective. As the renewable energy production capacity grows, the impact of green H 2 is likely to increase. In the case of the Iberian Electricity Market (MIBEL), no quantitative studies have so far tested the viability of the H 2 growth plans. This paper fills this gap through a novel mathematical programming model, which integrates H2 generation into the MIBEL. The model reveals a mismatch between the sustainability goals and the expansion plans of renewable and green H 2 for Spain and Portugal. [Display omitted] • Mathematical Programming to analyse green hydrogen production in the MIBEL. • Influence of the electricity market on hydrogen production and prices. • Generating green hydrogen is preferable to hydro pumping. • Green hydrogen integration might entail additional emissions. • MIBEL hydrogen strategy must be revised to achieve sustainability. [ABSTRACT FROM AUTHOR]

Wind power is one of the most important renewable energy sources worldwide. However, integrating these technologies in electricity markets faces challenges due to the intermittent wind speed, resulting in potential imbalances within power grids and subsequent inefficiencies. Traditional approaches for modeling the uncertainty simulate fixed wind power values in operational and planning models, which work well for the short term but are inadequate for medium-term decision-making due to lower forecasting accuracy and the inability to differentiate the imbalance risk faced in each simulated value. This paper proposes a novel methodology for incorporating wind energy imbalance risk into medium-term generation planning models. For this, we first simulate realistic wind power scenarios and perform a fitting distribution process to characterize the hourly wind power behavior. Then, we model the imbalance risk using quadratic-uncertainty cost functions for each simulated value. Subsequently, we conduct a temporal aggregation to reduce the computational burden, preserving the conceptual framework of the imbalance risk modeling. Finally, we propose a medium-term generation planning model that includes the imbalance risk model and the temporal aggregation strategy. Our approach is evaluated in a real-size case study formed by Spain, Portugal, and France's electricity markets, demonstrating accurate wind power imbalance risk modeling and lowered planning costs. • A new methodology to include wind energy imbalance risk in generation planning models. • Introducing a fitting process for modeling the distribution asymmetries of wind power. • Proposing a temporal aggregation method for efficient imbalance risk modeling. • The methodology is validated in Spanish, Portuguese, and French electricity markets. [ABSTRACT FROM AUTHOR]

This paper proposes the first application of a split-range control technique on a concentrating solar collector to improve an absorption plant production. Solar absorption plants have solar power availability in phase with cooling demand under design conditions. Thus, it is a powerful cooling technology in the context of renewable energy and energy efficiency. These plants need control systems to cope with solar irradiance intermittency, reject irradiation disturbances, manage fossil fuels backup systems and dump closed-loop thermal-hydraulic oscillations. In this work, control techniques are proposed and simulated in an absorption plant in Spain. The plant consists of a concentrating Fresnel solar collector connected to an absorption chiller. The objectives are to operate with 100% renewable solar energy and avoid safety defocus events while reducing temperature oscillations and control actuators effort. Firstly, the current available plant controllers are defined, then two modifications are proposed. The first modification is a split-range controller capable of manipulating both flow and defocus of the Fresnel collector, the second modification is a PI controller to substitute the original chiller on-off controller. The results compare, through validated models, the different control systems and indicate that using both proposed controllers reduces 94% of the sum of actuators effort and 43% of the integral of absolute set-point tracking error compared to the plant's factory pre-set controllers. The suggested controllers increase 66% of energy production and 63% of exergy production. Besides, the split-range technique can be extended to any concentrating solar collector control. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights • The paper describes a methodology to obtain an Urban Energy Sustainability Index (UESI). • This methodology can evaluate the global energy performance for any city. • UESI works through the measurement of 12 clearly-defined indicators and targets. • UESI is also a tool for designing effective actions towards energy-sustainable cities. • The index has been applied successfully to two Spanish cities (Malaga and Barcelona). Abstract The aim of the paper is to propose a methodology for evaluating the energy sustainability of a city based on the characterization of the energy end-use, energy systems and flows, as well as other intrinsically related concepts, such as the quality of air and the energy efficiency in transport and buildings. As a result, an Urban Energy Sustainability Index (UESI) has been proposed to measure the energy sustainability of the cities. Several indicators have been proposed to be used to build the index. These indicators have been grouped into three types depending on their influence on energy urban sustainability: basic, instrumental and complementary. For each indicator, an analysis has been done and as a result an expression for estimating it has been proposed. The value of the index is obtained from the combination of these indicators using the weighted average method. The proposed index can be used as an operational tool to improve the sustainability of cities. It also aims to have an international application as it is related to the global sustainability objectives defined by internationally recognized organizations. The proposed methodology has been used for two different Spanish cities, Barcelona and Malaga. The results show that it covers most of the issues related to the use of energy and sustainability in the cities and that it can also be applied to others cities. [ABSTRACT FROM AUTHOR]

Countries worldwide have set national targets for energy production from renewable sources. Yet, while many governments are committed to more renewable energy, obtaining permission to site installations is becoming increasingly difficult. With large tracts of land for renewables becoming intensely contested, countries seeking to meet their renewables targets are directing attention also towards tapping the potential in the urban environment through smaller-scale facilities. These entail other challenges, and countries are seeking ways to overcome them. The focus of this paper is on one, still evolving, type of renewable energy technology: small-scale wind turbines (SSWT). The paper presents a review of current but limited international academic knowledge on the land-regulation aspects of siting SSWT in countries that already have experience with such installations, including the USA, UK and New Zealand. The paper also reports on a comparative analysis of the land-related regulations and practices in two selected Mediterranean jurisdictions – Spain (Catalonia) and Israel. The approach of this study is exploratory, relying on analysis of legal and policy documents complemented by field work through in-depth interviews with key-stakeholders in both jurisdictions. The overall aim of this study is to examine different approaches of planning systems to new technologies. The findings show that despite their shared objective factors, the two jurisdictions have adopted almost opposite approach to regulating SSWTs. The findings, therefore, suggest that the incorporation of an unknown technology within the city requires a change of mindset both among the officials and among the city residents. A more effective regulatory framework might therefore entails a combination of strategic thinking, an experimental approach and the capacity to learn from cross-national comparative experiences. [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]

The increased penetration of renewable energy sources (RESs) as an effective mechanism to reduce carbon emissions leads to an increased weather dependency for power and energy systems. This has created dynamic operation and degradation phenomena, which affect the lifetime estimation of the assets operated with RESs. For the reliable and efficient operation of RES it is crucial to monitor the health of its constituent components and feature selection is a crucial step for building robust and accurate health monitoring approaches. In this context, this paper presents a probabilistic feature selection approach, which probabilistically weights and selects features through a heuristic and iterative process for an improved asset lifetime estimation. Power transformers are key power grid assets and they are used to demonstrate the validity and impact of the proposed approach. The approach is tested on two different photovoltaic power plants operated in Spain and Australia. Results consistently show that the proposed feature-selection approach reduces the prediction error and consistently selects relevant features. The approach has been applied to transformer lifetime estimation, but it can be generally applied to assist in the lifetime estimation of other components operated in RESs. Part of the studies presented here as well as source codes are all open-source under the GitHub repository https://github.com/iramirezg/FeatureSelection. • Probabilistic feature selection approach for improved asset lifetime estimation. • Integration of environmental features for improved renewable-operated asset lifetime. • Systematic and robust feature weighting methodology. • Improved transformer lifetime estimation including sensor and environmental data. • Validated on two real photovoltaic power plant case studies. [ABSTRACT FROM AUTHOR]

The European Commission and EU Member States have recently promoted legislation (under the REPower EU Plan) to accelerate renewable energy projects by allowing the elimination or reduction of environmental assessment and public participation in the approval procedure. To avoid adverse effects on the environment, these regulations propose the exclusion of certain areas (identified through available information on protected and/or environmentally sensitive areas) from the procedure. This paper aims to evaluate whether such measures are effective to avoid damage to biodiversity from the implementation of photovoltaic energy. To this end, we studied the distribution and abundance of a threatened bird species, the Black-bellied Sandgrouse, at two geographic scales: i) regional: Andalusia (southern Spain); ii) local: Campo de Tabernas (an excellent example of the semi-arid ecosystems of southeastern Spain) and evaluated the quality of the information that Administrations have on the species by comparing it with own censuses. We also assessed the effectiveness of the environmental impact procedure for photovoltaic plants planned in Campo de Tabernas. Data from the regional Administration reveal that Andalusian protected areas cover a minimal part (17.7%) of the species' range. Moreover, neither the regional nor the national Administration have reliable and updated information on the distribution of the species in Campo de Tabernas (only 17% of the current distribution area is known). The wrong choices made by developers about where to locate the photovoltaic plants together with wrong decisions of the regional Administration (with land-use planning competences, including the planning of power plant locations) have led to the loss of 630 ha of the species' range in Campo de Tabernas. Public participation of experts prevents, through allegations to the projects, an important part of the impact on the species. Policy implications: the information that the Administrations have on this species does not allow them to make proper decisions on where to apply renewable acceleration. Obtaining complete and updated information on the distribution of endangered species to elaborate detailed wildlife sensitivity areas is essential and urgent before implementing measures to accelerate renewables. • The new EU renewable acceleration directives are analysed here for the first time. • A threatened species becomes locally extinct due to solar power plants' poor planning. • Involving experts in EIA procedure greatly reduces the impact on a threatened species. • The design of renewable go-to areas demands specific research on threatened species. • Current EU legislation to accelerate renewables will negatively affect biodiversity. [ABSTRACT FROM AUTHOR]

Agriculture is one of the most energy intensive activities within the European Union. The common absence of electric infrastructure in these rural settings has led to the need for in situ generation in many cases. The existing excess pressures in large pressurised irrigation networks makes the generation of micro hydropower here a possible alternative renewable energy source. Pump-as-turbines have been proposed as a cost-effective technology for such purposes, taking advantage of the excess pressure in pipe networks to produce energy. This paper presents a methodology for the design of a plant for micro hydropower generation in an agricultural farm and outlines the predicted benefits of the installation. These predicted benefits were also compared with the measured performance of the plant for the 2019 irrigation season. The main aim of the plant was to replace a diesel generator that supplied energy to the farm. The excess pressure found in the pipe network varied between 0m and almost 60m. The nominal power of the pump-as-turbine was selected to supply the maximum energy requirements of the farm. The predicted operation time of the plant was estimated at up to 3199 h concentrated between April and September. An annual savings of approximately €2950 and 11 t eCO 2 were also estimated. The measured results showed an actual operation time of 2443 h between May and September, as in April the monitoring system was not operational. For this operation time, the savings were €2258 and 8.4 t eCO 2. Considering the April theoretical irrigation time obtained, the savings raised up to approximately €2434 and 9.1 teCO 2. The return on investment of the installation was computed to be recovered in less than ten years. • Real pilot PAT installation operating during an entire irrigation season. • Electricity was brought to remote places with no access to grid connection. • Diesel energy source was fully replaced by micro hydropower technology. • Solar and micro hydro hybrid solution was used for self-consumption. • More than 9 tCO 2 and €2400 were saved during the 2019 irrigation season. [ABSTRACT FROM AUTHOR]

This paper presents a model for optimizing the life cycle economic and environmental impacts of a hybrid renewable energy and battery storage system – as energy supply technologies (EST) for off-grid farms. Micro-hydropower and photovoltaics represent the primary renewable energy (RE) sources, with batteries and a diesel generator considered as possible back-up systems. A modified Non-dominated Sorting Genetic Algorithm II (NSGA-II) was developed and applied to a case study farm in Southern Spain and provided different EST solutions to optimize a design based on economic (life cycle costing or LCC) and environmental (life cycle assessment or LCA) constraints. The results highlighted that cases with a strong dependence on batteries could achieve minimum costs and lower impacts for climate change and energy resources (non-renewable fuels). In contrast, the optimal system for minimizing the consumption of material resources (metals/minerals) resulted in higher fuel use, which was up to 25% more expensive. The optimal EST solutions used up to 37% of the total energy generated; however, the results were sensitive to energy production-demand distributions. This methodology can help identify the most cost-effective solutions with the lower environmental impacts for decarbonizing the agricultural sector. [Display omitted] [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]

Renewable energy sources (RES) can play a significant role in economic growth. This article examines the development of the wind energy market in the EU. The applicable regulations, directives, and legal acts are reviewed, and the State's role in the development of the renewable energy market is discussed. The analyses were carried out based on the available literature and Eurostat data. The authors of the paper used basic statistics to summarize the changes in wind energy and make a prognosis. The data analysis uses the Autoregressive Integrated Moving Average Method (ARIMA). The survey found that the highest average wind cumulative installed capacities were in Germany (31026 MW), Spain (18602 MW), United Kingdom (7894 MW) and France (6108 MW). Our analysis indicates that the biggest average annual installed wind capacity was in Germany (2952.6 MW), Spain (1224.5 MW) and the United Kingdom (1363.8 MW). These same countries achieved the highest average wind gross electricity production in the years 2004–17: Germany (50.9 TWh), Spain (39.3 TWh) and United Kingdom (18.9 TWh). The study finds that wind cumulative installed capacity will increase in most countries of the EU. • The European Union onshore wind energy market seems to be stable. • Wind power plays an important role as a source of energy supply. • The most important wind gross electricity producers in the EU are: Germany and Spain. • The highest increase of wind cumulative installed capacity in 2022 will be in Croatia. [ABSTRACT FROM AUTHOR]

Hydrokinetic energy has been mainly studied in areas where the principal driver of the current is the tide. However, in certain areas river discharges play also a principal role. The exploitation of the hydrokinetic resource in such areas has its own peculiarities, dictated by the combined influence of the two driving agents. The objective of this paper is to investigate the exploitation of hydrokinetic energy in the Miño Estuary, the largest estuary in NW Spain and N Portugal, with a focus on the site-specific performance of hydrokinetic energy converters (HECs) and its intra-annual variability. A state-of-the-art hydrodynamics numerical model is implemented and successfully validated based on field data. A third-generation HEC—to be more specific, the new Smart Freestream Turbine (SFT)—is considered, and its performance at the location with the greatest potential is assessed by means of: (i) site-specific efficiency, (ii) availability factor, and (iii) capacity factor. We find that, whereas the site-specific efficiency does not vary significantly, the availability and capacity factors do experience substantial intra-annual (seasonal) variability. In summer and autumn, river discharges are low, and the tide dominates the hydrokinetic resource. In contrast, during winter and spring, the river discharges significantly contribute to the resource, leading to a considerable increase in the availability and capacity factors. More generally, the results imply that in areas subject to combined fluvial and tidal influences the performance of HECs may depart significantly from that in tide-dominated areas, and this departure must be carefully weighed in assessing a project. • Hydrokinetic resource under influence of tide and river discharges is investigated. • River discharges induce a pronounced seasonal variability in the hydrokinetic resource. • The hydrokinetic resource is controlled to a large extent by the hydrological regime. • River discharges lead to a considerable increase in the performance during winter. [ABSTRACT FROM AUTHOR]

• Energy Communities analysis and review in Europe and, more specifically, in Spain. • Promoting energy poverty reduction and cooperation through Energy Communities. • Real case study focused on reducing energy poverty in the city of Getafe (Spain). • Selection of public buildings to implement energy community in two neighborhoods. • Significant electricity bill reductions for energy poverty households. Advancements in renewable energy technologies, a growing awareness of the need for sustainable energy solutions, and the emergence of new business models in the energy sector, have contributed to the growth of Energy Communities. Public entities can find in energy communities today an opportunity to tackle energy poverty, to increase the cooperation among citizens and to empower them to be a more active player within the energy sector. This paper analyzes energy communities in Europe and focuses specifically on Spain; considering the three beneficial aspects previously mentioned. It aims to obtain ground truth about the applications of these new citizens' arrangements. A citizen-led initiative at the city of Getafe (Madrid, Spain) is included and discussed in detail. This case study focused on reducing energy poverty of its participants. An energy community was designed and implemented as a collective PV solar self-consumption infrastructure. The roofs of various public buildings in the two case study neighborhoods were selected for locating the PV installations. Real metered data were used to evaluate the solution. A public building was selected for the energy community, considering generation on roof and dwellings proximity. The results provided that out of the 77% PV generations could be used to contribute to the demand of 100 residences; while the resulting 23% would provide approximately 60% of the energy demand of the public building. The setting up of the Energy Community not only had the technical part but also included workshops seminars and information sessions, to ensure that people prone to benefit and maximize its impact. [ABSTRACT FROM AUTHOR]

Marine renewable energies can play a key role by reducing the dependency on fossil fuels and, therefore, mitigating climate change. Among them, it is expected that wave energy will experience rapid growth in the upcoming decades. Thus, it is important to know how wave climate will change and how suitable the wave energy converters (WECs) will be to the new wave conditions. This paper aims to evaluate the capability of four different WECs—a WaveRoller type device (WRTD), Atargis, AquaBuoy and RM5—to extract wave energy on the Northwest coast of Spain (NWCS). The analysis was performed using the high-resolution wave data obtained from the Simulating Waves Nearshore (SWAN) model over the near future winters (2026–2045). The energy output (P E), the power load factor (ε), the normalized capture width (NC w) and the operational time (OT) were analyzed. According to these parameters, among the devices that work for intermediate-deep waters, Atargis would be the best option (P E = 1400 ± 56 kW, ε = 55.4 ± 2.2%, NC w = 35.5 ± 4.1% and OT = 84.5 ± 3.3%). The WRTD would also be a good option for shallow nearshore areas with P E = 427 ± 248 kW, ε = 12.8 ± 7.4%, NC w = 48.9 ± 9.6% and OT = 88.7 ± 18.9%. A combination of Atargis and WRTDs is proposed to make up the future wave energy farms on the NWCS. • Dynamical downscaling using SWAN to simulate near-shore wave conditions. • Wave energy converters suitability is analyzed in the context of climate change. • Atargis is the most suitable device to future sea conditions in intermediate waters. • WaveRoller type devices can constitute future wave farms for shallow waters. [ABSTRACT FROM AUTHOR]

• 2050 low-carbon economy pledge and Spanish photovoltaic investment plan. • Photovoltaic spatial allocations minimising unpredictable variability. • Impact of wind energy investments on the optimal photovoltaic spatial allocation. • Allocation of photovoltaic and wind investments minimising supply–demand mismatch. • Assessment of the current photovoltaic investments in Spain. After a period of stagnation that lasted until approximately 2018, Spain has established an ambitious investment program in photovoltaics, derived from the pledge to switch to a carbon-free energy system by 2050, the sustained cost decreases of the technology, and the excellent irradiance values over its territory. This paper implements an additional criterion for the spatial allocation of these investments based on minimising the energy variability generated because of weather intermittency. The analysis is based on hourly data for the years 2005–2020 (inclusive), in various locations homogeneously spread throughout Spain. Subtracting the deterministic daily and annual irradiance cycles to estimate the variability of the random component is discussed. Failing to do that yields significantly higher and distorted values for solar energy variability, resulting in low investment proportions when combined with other energies, like wind. The first results show that a straightforward, equally-weighted allocation of investments is suboptimal. It is also shown that investing in low-irradiance locations contributes to reducing overall variability. Secondly, the study analyses overall power variability minimisation conditional on a given wind investment weight. It is found that the impact is significant spatially, and that proportions of wind energy above 10% increase aggregated variability across all levels of aggregated power generated. Nevertheless, investment proportions in wind energy below 10% reduce the overall combined variability significantly due to the negative correlation between wind and solar irradiation. The third point addressed is the minimisation of the mismatches between renewable energy supply and aggregate electricity demand. The optimal proportion for solar and wind investments becomes close to 50% in this case. However, this proportion tilts towards solar investments if variability minimisation is also considered. Finally, the current spatial distribution of photovoltaic investments in Spain is analysed, and it is shown that there is room for improvement. It is also found that the current ratio between wind and photovoltaic energy may not be optimal, and that it would be advisable to increase proportionally more photovoltaic energy. [ABSTRACT FROM AUTHOR]

Abstract: The most widespread support system for renewable-energy-sourced electricity (RES-E) is the feed-in tariff (FIT). FITs can be divided into fixed-FIT and premium systems. The latter type may also include a cap and floor option, turning it into a variable premium system. The cap value (upper limit) aims to avoid windfall profits for the RES-E investor if the electricity price rises quickly, while the floor value (lower limit) ensures minimum revenue, reducing the risk caused by low electricity prices. This paper examines the performance of the variable premium system as established in Spain (hourly-based) and investigates the possibility of alternative novel designs. For this purpose, an analysis was undertaken of the cap & floor system established in Spain based on real market data over a three year period and its performance compared to the fixed premium system (no cap & floor limitations) and two novel cap & floor designs (monthly- and yearly-based). Two other novel alternatives were also considered: daily- and weekly-based. It is shown that the hourly-based cap & floor system did not result in a reduction of the overall RES-E revenue compared to the fixed premium system over the three year period, though revenue was more evenly distributed from year-to-year. The paper concludes that variable premium systems should be based on monthly or yearly cap & floor mechanism as opposed to an hourly one. [Copyright &y& Elsevier]

• Application of the ampacity control system is necessary for wind energy integration. • DLR application reduced the time in which wind farms were out of service by 4100 h in 44 months. • DLR application increased the energy supplied by wind farms by 70.9 GWh in 44 months. • DLR application saved more than 7800 t of CO 2 in 44 months. The total renewable wind energy capacity of Spain currently accounts for more than 20% of the total installed energy capacity, which makes integration into the grid challenging for wind farm owners as well as Distribution System Operator (DSO). Electrical companies require new techniques to integrate renewable energies safety and with low investment costs. Dynamic line rating (DLR) is one of these techniques, and is used by DSOs to maximise the capacity of existing infrastructure. This paper presents a successful case of DLR application by a DSO over several years to reduce the time that wind farms were out of service due to an excess of electrical energy generated. Over the period from January 2015 to September 2018, the application of the DLR technique prevented 4,100 hours of out-of-service time, increasing the energy supplied by the wind farms by 70.9 GWh and by extension saving 7,800 tons of CO2. [ABSTRACT FROM AUTHOR]

This paper addresses the economic and environmental effects of three scenarios of change for the electricity sector in Spain, in line with the European Union targets: (1) to address the low trade with the rest of Europe, increasing the integration with the European network; (2) to enhance environmental sustainability, increasing the use of renewable energy sources, while decreasing the use of brown energy sources; and (3) increasing the competitiveness of the Spanish electricity sector. To this end, we develop a computable general equilibrium model, with 72 productive sectors, eleven of which are energy sectors, where electricity is disaggregated into five production technologies and transmission, distribution, commercialization, and related activities. The model is calibrated on a previously developed input-output table with this detailed disaggregation for Spain for 2013. Our results suggest potential improvements in production and trade, and reductions in CO 2 emissions in scenario 2 are also observed. • We address the effects of three policy scenarios for electricity sector in Spain. • We analyze the effects of increasing trade, renewables, and competitiveness. • We construct and disaggregate a computable general equilibrium (CGE) model. • CGE distinguishes the businesses of the sector and the production technologies. • We found improvements in production and trade and reductions in CO 2 emissions. [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 Recent electricity management systems such as Smart Grids and Virtual Power Plants help to better integrate distributed generation renewable resources (RDG), such as photovoltaic, small hydro or micro wind in electricity markets. In this context, an important increase of small-scale power generation technologies is expected in Spain by 2020, according to the Spanish Action Plan for Renewable Energy. This paper analyses the environmental and economic impacts of the massive integration of RDG in Spain for 2020 by using an Input-Output approach. The induced production and employment effects in every sector due to new RDG project investments as well as the CO 2 reductions attributed to a decline in conventional electricity consumption are estimated. The results indicate that investments in RDG based on photovoltaic and small-hydro have the greatest impact on employment generation. The RDG investments will lead to a decrease in emissions of 21.67% in 2020 compared with 2013. The RDG technologies become an alternative to reach a sustainable economic growth in Spain. In future research, a multi-regional input-output model and the study of the links between energy consumption, standard of living and consumption patterns will aid to delve deeper into the relationship between economic growth and the environmental impacts of small-scale renewable technologies. Highlights • RDG will be over half of total installed electricity generation capacity in 2020. • The impact of RDG deployment is quantified on Spanish economy in 2020. • The IO methodology is used to study the environmental and economic impacts. • Photovoltaic and small-hydro have the highest impact on employment generation. • RDG becomes an alternative to reach a sustainable economic growth in Spain. [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]

Incentives have played a major role in wind power development in Spain, having allowed the country to reach top worldwide positions in terms of wind power penetration but having also contributed to a structural cost-revenue unbalance. Feed-in tariff and premium schemes had been in force in Spain since the inception of wind power until the adoption of an auction-based support framework in 2016. So far, auctions have resulted in no incentives being allocated to any new wind farm. The present paper analyses the historical evolution of wind power support schemes in Spain and assesses the long run impact of the newly adopted policies on the future evolution of wind capacity and system costs through a behavioral stochastic System Dynamics model. Results show that the current lack of incentives will entail limited wind capacity growth, below the goal set in Spain's Renewable Energy Plan 2011–2020. Incentive levels required to meet specific goals in terms of capacity growth and system costs are computed and discussed. [ABSTRACT FROM AUTHOR]

This paper evaluates a parametric analysis towards compliance with the nZEB standard, which in Spain is defined by the latest update of the Technical Building Code. This regulation is critically assessed regarding its ability to promote the concept of cost optimization, promote renewable energy sources and minimize primary energy consumption in the residential sector. To this end, a virtual building was defined and multiple designs were evaluated using DesignBuilder software. A set of 170 alternative scenarios was established and parametrically evaluated for five cities representing the five climatic zones of inland Spain (Bilbao, Burgos, Seville, Madrid and Almeria). The results were evaluated focusing on cost-cost effectiveness and primary energy consumption values for the different scenarios, evaluating them in relation to the minimum requirements set by the regulation. The great potential of photovoltaic energy is highlighted, which allows negative values to be obtained for the two Equivalent Uniform Annual Costs due to the cost avoided through self-consumption. This fact makes the optimal designs tend to electrification, specifically through air and ground source heat pumps. It is worth mentioning that the new Code has only established a minimum target for renewable self-consumption in the residential sector, which should be reinforced in future updates. [ABSTRACT FROM AUTHOR]

• Self-consumption in residential sector is studied under Spanish regulatory framework. • An average-day model versus a whole-year model is benchmarked. • Scheduling household appliances is analysed in a residential building. • Ex-ante and ex-post renewable energy sharing is investigated. Studies on self-consumption in residential use are constantly evolving, and society claims new solutions in response to changes to new paradigms. This paper aims to optimise the sizing of a self-consumption installation for collective self-consumption in a residential building under the Spanish regulatory framework. The study considers the current price volatility in the retail electricity Spanish market and focuses on the techno-economic analysis of self-consumption in a building consisting of 12 dwellings using photovoltaic energy and the possible support of a storage system. The three aspects analysed are the sizing of the self-consumption facility, the use of smart appliances to shift their consumption to more cost-effective times and the sharing of the renewable energy generated by the facility among the consumers participating in the collective self-consumption. This study employs two models, an average-day model and a whole-year model. The techno-economic analysis yields that between the two self-consumption modalities for residential consumption, the modality with surplus simplified compensation is more profitable than the one without surpluses. Finally, the study focuses on sharing the total renewable energy generated among the participants. The results indicate that both ex-ante and ex-post dynamic sharing brings few benefits. [ABSTRACT FROM AUTHOR]

Optimal siting of wind farms based on a pre-assessment of the spatiotemporal variability of wind resources is considered a suitable method for reducing fluctuations in the delivered output. In this study, we explore the potential for balancing wind energy generation in the Iberian Peninsula using Principal Component Analysis (PCA). This technique permits the discovery of possibly new promising locations for wind power harvesting and an evaluation of the existing wind farm network in terms of reliability in energy generation. Data input to the PCA consists of hourly wind capacity factor in a 5-km spatial resolution grid covering the entire peninsula. These data are derived from an equivalent wind farm power curve fed by modeled wind speed data from 80 m above ground level. PCA reveals three significant balancing patterns prevailing over the IP, where half of the currently operating wind farms in Spain are placed. Hence, among the many constituents of the existing wind farm network, these spots offer the best opportunity for stable power supply. The paper concludes by making proposals on an optimum wind capacity allocation based on the idea of equally distributing installed power between positive/negative dipoles emerging from balancing principal components. [ABSTRACT FROM AUTHOR]

Offshore wind energy generation has experienced an important growth in the last five years, reaching currently an installed capacity of almost 8000 MW. The most important references in this type of technology are Denmark, Holland, Sweden, Germany and United Kingdom. In Spain, previsions for technology, have been set at around 750 MW of installed power during the period 2011–2020. However, Spanish coastal features, social opposition to installations near the coast and lack of a stable regulatory environment guaranteeing the investments are factors which are restraining the development of this technology. This paper presents a brief review of the state of the art of offshore wind technology and it describes the most frequently used types of turbines, transmission systems and support structures in Europe. It also presents the current situation and the expected growth of offshore wind power facilities, introducing the characteristics of the operational – and under construction – windfarms. Finally, it analyses particular problems and solutions for its development in Spain which can be extrapolated to countries with similar circumstances. [ABSTRACT FROM AUTHOR]

• Evaluation of the most recent Spanish grid code requirements. • A new tool to speed up the commissioning of new solar PV power plants is presented. • The accuracy of the aggregated PV power plant dynamic model proposed is demonstrated. • The aggregated model is shown to be ten times faster than the detailed equivalent. • The aggregated solar PV power plant simulation model approved by the Spanish TSO. Renewable energy and, in particular, solar PV power, will play a crucial role in achieving net-zero emissions scenarios over the coming decades. Increasing the share of renewables in countries' energy mixes is therefore a major challenge that must be urgently addressed. Within this context, the present work proposes an innovative tool that may accelerate the commissioning process of new solar PV power plants, in the form of an aggregated simulation model to assess a power plant's responses under the technical requirements established in the Spanish grid code. Our analyses, based on the comparison of the proposed model with a detailed model -both representing the same installation, show, from a quantitative and qualitative viewpoint, the accuracy and usefulness of the dynamic simulation model proposed. The aggregated model is shown to be ten times faster than the detailed equivalent, while the errors encountered in the simulation responses of both models are below 0.1% in all cases. It must also be noted that the present paper has allowed for the introduction, in the most recent version of the Spanish grid code and following approval of the Spanish Transmission System Operator (TSO), Red Eléctrica de España (REE), of this new and advantageous PV power plant model. Finally, it is worth mentioning that this study could form the basis for encouraging other countries to also adopt this model in their grid codes as a new tool to help integrate PV power into power grids. [Display omitted] [ABSTRACT FROM AUTHOR]

The evaluation and comparative analyses of energy conversion technologies are carried out with well-established concepts, like the concept of efficiency. Today, however, new technologies based on renewable energy sources challenge conventional approaches. Accounting for fuel diversity and other inequalities can ensure that comparative analyses result in trustworthy results. This paper aims to address this issue by updating conventional efficiency for more accurate comparative evaluations of fossil fuel energy systems. Specifically, the concept of total efficiency is introduced to account for extraction, processing and transportation of fossil fuels, aspects that are not currently considered in the conventional definition of efficiency. The total efficiency is determined by studying the environmental impacts of these processes and quantifying their energy requirements in terms of additional fossil fuel use. Two case studies in Spain are presented to demonstrate the impact of using the developed method on efficiency estimates. The total efficiency is found to be lower than the convectional efficiency by 21–25% to up to 41%, in the most unfavorable cases. This shows the significant impact of the preparation steps of fossil fuels and represents a fairer comparison between fossil fuels and renewable conversion processes. • Introducing total efficiency for more accurate comparative evaluations of energy systems. • Total efficiency accounts for extraction, processing, and transportation of fossil fuels. • The developed method links environmental impacts to additional fuel input. • Fuel processing decreases the efficiencies of fossil power plants significantly. • Updated tools, like total efficiency, are necessary to achieve future energy sustainability. [ABSTRACT FROM AUTHOR]

In 2012, Spain obtained 68.5 TWh of its electricity (25% of the total) from renewable energy sources excluding large hydroelectric power (RES-E). Subsidies, through feed-in-tariffs, for various forms of RES-E ranged from 40.2 €/MWh to 321.1 €/MWh and totaled 6.1 billion E, an amount that has motivated substantial criticism. This paper examines the effects of RES-E on the market price of electricity considering the merit order effect in Spain's power auction system. The M5P algorithm developed by Quinlan (1992) is used to calculate changes in the settling price in daily power auctions. Also, the value of emissions of CO 2 , NO x , and SO x avoided through RES-E is calculated. They are valued at $10/t, $478/t, and $1460/t, respectively. Results of the analysis show that, in 2012, RES-E caused an estimated 3.1 B€ savings in electricity expenditures due to market effects and a 0.7 B€ saving in emission costs. When subtracted from the total subsidy a net cost of RES-E of 2.3 B€ is derived. Wind, biomass, and small hydroelectric had negative net costs (i.e., net benefits) while photovoltaic and solar-thermal power had net costs. Alternative scenarios in which the production of gas-fired and coal-fired electric power are individually curtailed by 30% in comparison to the baseline scenario, while RES-E is held at the 2012 level, yielded a net cost decrease of about 300 M€ for gas curtailment and a net cost increase of about 300 M€ for coal curtailment. [ABSTRACT FROM AUTHOR]

From mid-2007 to September 2008, the Spanish PV sector experienced an investment boom, which led to a ten-fold increase in solar PV deployment. The concern of the government about the large increase in the associated support costs through a feed-in tariff led to the implementation of several cost-containment regulations. These included a cap on the electricity generation being eligible for support, a grid access charge, a generation charge, a shortening of the support period and the updating of tariffs below the consumer price index. The aim of this paper is to analyze the impact of those cost-containment mechanisms on the profitability of solar PV plants in Spain. The results show that these measures have had a moderate impact on the profitability of those plants, which is still relatively high, with internal rates of return which are always above 7% in all the simulated cases. However, their impact is mediated by different features of the plant, including the levels of the initial investment (upfront costs), borrowing and operation and maintenance (O&M) costs. It is also mediated by policy variables (such as changes in the tariff-updating method and the level of the grid-connection charges) and by other variables, e.g., the interest rates of loans. The specific impact of each of the cost-containment measures has also been analyzed. Our findings show that the generation charge has the greatest impact, followed by the change in the tariff-updating mechanism, the generation cap, the shortening of the support period and the grid access charge. [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: An analysis of scientific publications on solar energy was conducted to determine whether public interest in the subject is mirrored by more intense research in the area. To this end, the research published by Spain and Germany, the two EU countries with the highest installed photovoltaic capacity, was analyzed based on Web of Science data. The results show that: solar output has risen substantially; solar research has a greater impact (measured in terms of citations) than publications on other renewables such as wind power; scientific production on solar energy is high in Germany and Spain, which together account for 51% of the total in the EU-27; the pattern of topics researched in the two countries is very similar; and their international collaboration is more intense than the world average and higher than in countries such as the USA, China or Japan. Collaboration between them is likewise intense. The main conclusion is the divergence in Germany and Spain between solar energy demand/output growth, being exponential, and the growth of research papers on the subject, which is linear. [Copyright &y& Elsevier]

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]

• A systematic literature-approach to classify retrofitting is proposed. • An overview of Spain's previous guidelines on residential retrofits is presented. • A review of financial and subsidies mechanisms in Spain to renovate buildings is introduced. • A literature-based matrix on retrofitting actions is presented. • A classification of energy efficiency strategies for retrofitting is proposed. The building sector is responsible for more than 40% of final energy consumption in Europe; consequently, retrofitting existing buildings can significantly contribute to mitigate greenhouse emissions. Nevertheless, although the European Union has introduced relevant policy instruments, up to now the annual retrofit rates are considerably low with an average of 0.2% at European level. Understanding the past would support the success of the new strategies, such as the recent ones launched through the New Green Deal, which reinforces the importance of renovating existing buildings stock, as the main aim of the renovation wave. As a starting point for assessing the main challenges to allocate the Recovery funds, this paper provides a review of Spain's relevant literature to clearly define the characterization of the existing building stock, which actions have been typically considered under the scope of retrofits, and which strategies have been implemented until now, considering both, private and public initiatives and public financial schemes. The present work has a strong focus on energy-related strategies, although other interrelated actions are mentioned, such as accessibility measures and interior refurbishment of dwellings. Differences and similarities within these approaches are presented through the analysis of 27 relevant references of retrofitting actions and 52 references of financial mechanisms. As in Spain 93% of multifamily buildings were constructed prior to the national transposition of the first Energy Performance Building Directive (EPBD), and therefore are in need of deep energy renovations, the retrofitting of multifamily buildings topic has been widely addressed, even though often in a disjointed manner. The study suggests that although historically there have been several recommended strategies, few are conceived as integral actions, only 15% of the intervention packages refer passive and active energy-related measures and renewable energy incorporation. Furthermore, considering the antiquity of the building stock and the advantage of addressing the topic through clusters, only 63% of the resources directly refer these actions to specific clusters among the six distinctive periods, although in most cases focusing their recommendations on buildings constructed before 1980 where the worst energy performance buildings are concentrated. Concerning public financial and funding instruments, the research illustrates that there has been a substantial increment of programs over the last years promoting energy-related measures, renewable energy and other complementary aspects such as accessibility and interior renovations, mainly for older clusters. Nevertheless, the funds constitute only 8% of the necessary declared investments, which along with the dispersion between the different procedures and the complexity of the processes, have significantly reduced the global impact of these actions without generating robust and oriented market dynamics. Despite the several resources found, both financial instruments and guidelines tend to describe in more detail strategies related to heating demand and consumption and not delve into other relevant actions for warmer climates, fact associated both to the dynamics coming from other countries, and to a vision of the past in which people do not consume refrigeration. This clear focus on heating loads rather than cooling could present limitations for warmer regions in the near climate-change future. [ABSTRACT FROM AUTHOR]