Search

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]

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]

Copyright of DYNA - Ingeniería e Industria is the property of Publicaciones Dyna SL and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

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]

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]

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]

• 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]

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]

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]

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]

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]

[Display omitted] • A novel genetic algorithm-based seasonal fractional grey model is proposed. • Monthly electricity generation is forecasted since the Covid-19 lockdown started. • Seasonal grey and machine learning models are used for forecasting. • The selected countries are France, Germany, Spain, Turkey, and the UK. • The share of renewables in total electricity generation is forecasted. Balances in the energy sector have changed since the implementation of the Covid-19 pandemic lockdown in Europe. This paper analyses how the lockdown affected electricity generation in European countries and how it will reshape future energy generation. Monthly electricity generation from total renewables and non-renewables in France, Germany, Spain, Turkey, and the UK from January 2017 to September 2020 were evaluated and compared. Four seasonal grey prediction models and three machine learning methods were used for forecasting; the quarterly results are presented to the end of 2021. Additionally, the share of electricity generation from renewables in total electricity generation from 2017 to 2021 for the selected countries was compared. Electricity generation from total non-renewables in the second quarter of 2020 for France, Germany, Spain, and the UK decreased by 21%–25% compared to the same period of 2019; the decline in Turkey was approximately 11%. Additionally, electricity generation from non-renewables in the third quarter of 2020 for all countries, except Turkey, decreased compared to the same period of the previous year. All grey prediction models and support vector machine method forecast that the share of renewables in total electricity generation will increase continuously in France, Germany, Spain, and the UK to the end of 2021. The forecasting methods provided by this study open new avenues for research on the impact of the Covid-19 pandemic on the future of the energy sector. [ABSTRACT FROM AUTHOR]

Olive sector residues could contribute to increased use of renewable energies, especially in those areas where the olive crop is produced. This paper determines the maximum amount of electrical and thermal energy which could be obtained in Andalusia from olive sector residues, and the economic value that could be obtained from these energy uses. For this, the current data on installed power and electrical and thermal generation are compared with the calculated potential data which would be obtained at full capacity. The results show there is a 69.23% wastage of olive sector residues for energy purposes. Thus, using the resources at full capacity, 3.9 million tons of biomass per year could be obtained for energy purposes. Currently, only 2 million tons of biomass are used for energy purposes. This wastage translates into a below potential generation of electrical and thermal energy. The full use of these residues would allow 83.9% and 64.9% higher generation of electrical and thermal energy, respectively. The results obtained also show that the economic value of olive sector biomass is higher than the market price value, with the average values for each use being 248.20 €/t for domestic thermal use, 165.04 €/t for electrical use and 139.50 €/t for industrial thermal use. Thus, it is considered feasible that the olive sector biomass could be used to a greater degree than at present. In this sense, it is recommended that more electricity generation plants and thermal-generating systems be put into operation. • There is a 69.2% wastage of olive sector residues that could be used for energy purposes. • The full use of olive by-products would account for 6.2% of renewable electricity. • The full use of olive by-products would account for 26.7% of thermal generation. • Better use of residues would promote the start-up of 55 and 1762 electricity and thermal plants, respectively. • The economic value of olive sector biomass allows the value chain to be covered. [ABSTRACT FROM AUTHOR]

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

• Optimal design approach for carbon-neural residential communities is outlined. • The design approach is applied to residential communities in Barcelona, Spain. • Energy efficiency measures combined with wind turbines are found to provide cost-effective options. This paper investigates the optimal retrofit solutions for residential communities to be carbon neutral in Barcelona, Spain. In particular, three different sizes for the residential communities are considered depending on the number of housing units: small, medium, and large. First, the best cost-effective energy efficiency measures (EEMs) have been determined and applied to all the buildings of the communities, in order to reduce their overall energy demand. The retrofit optimization results demonstrate that combinations of passive and active strategies would achieve source energy use saving and electrical peak demand savings up to 57% and 29%, respectively. Then, a variety of renewable energy generation systems has been explored to determine the optimal grid-connected technologies for meeting the electricity demands while achieving annual carbon neutral conditions for the residential buildings. The analysis shows that wind turbines can reduce the cost of electricity generation up to 21.5% compared to the current utility prices (LCOE value as 0.247 €/kWh) and electricity sell back policies. The results indicate that for PV systems to compete with wind turbines, their capital costs need to be lower by at least 40% compared to the current level costs. [ABSTRACT FROM AUTHOR]

Spain has become one of the leading countries in the world in promoting electricity generation from renewable energy sources (RES), due to their positive socioeconomic and environmental impacts, through highly favorable regulatory frameworks and public incentives set by Spanish governments mainly during the first decade of 2000s, i.e., Royal Decree (RD) 2818/1998, RD 436/2004 and RD 661/2007. Conversely, the highly favorable regime applicable to RES, and specifically to solar power plants during the 1998–2008 promotion period turned into an extremely unfavorable scenario during the 2008–2020 cost-containment stage, characterized by the dismantling of the previous promotion schemes so as to reduce the skyrocketing electricity system tariff deficit, in which regulations such as RD 1578/2008, Royal Decree Law (RDL) 6/2009, RDL 14/2010, RDL 1/2012, Law 15/2012, RDL 9/2013, Law 24/2013 and RD 413/2014 stood out. Nonetheless, the Spanish renewable sector, and especially the solar power sector, has shown great dynamism in its energy policy in the period 1998–2020. This academic contribution provides a comprehensive review of the energy policy evolution for the whole solar power sector in Spain, specifically both solar photovoltaic (PV) and concentrating solar power (CSP) plants, over the last 23 years. Thus, considering both the boom in the solar power sector as well as the solar sector's bust, a survey of the different legislation in force during the 1998–2020 period, as well as of the existing academic literature dealing with this issue, is conducted to first contextualize and describe, and then carefully assess, the last 23 years of solar energy policy in Spain. In brief, the decisive role of the Spanish government in developing the RES sector, and especially the solar power sector, in recent years has been noted. In this vein, a good planning of the energy development model, the regulatory stability, the simplicity and agility of the corresponding administrative process, the appropriate design of support mechanisms, as well as security and predictability of support levels in the mid and long term, play an important role in providing certainty to all the stakeholders. During the 1998–2008 promotion stage, even with a stable, quite favorable and easily predictable RES support mechanism in place, the Spanish solar system behaved as an open-loop system without any control structure detecting and reacting to problematic situations. The fact that the Spanish government was compelled to implement ex-post measures during the period 2008–2020, seriously jeopardizing the viability of the power plants in operation, as well as compromising the legal–economic stability of the renewable energy sector, clearly indicated a malfunctioning of the energy policy control mechanism. In essence, it is hoped that the lessons extracted from this 23-year comprehensive review of the Spanish solar power sector pathway could be quite useful for other countries either in the initial development stage or fully immersed in the promotion of solar power sector or any other renewable technology. [ABSTRACT FROM AUTHOR]