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Along the last century there has been an unprecedented growth in both global food production and related socioecological impacts. The objective of this paper is to analyse the effects of long-term metabolic patterns of agrarian systems on land use and cover changes (LUCC). We have developed an Energy-Landscape Integrated Analysis (ELIA) of agroecosystems to measure the energy storage (E) and the information (I) represented by the complexity of internal energy cycles, in order to correlate both with the energy imprint in the landscape functional-structure (L) that sustains biodiversity. ELIA values are used to assess the agro-ecological landscape transitions in different case studies analysed in North America (Canada and USA) and Europe (Austria and Spain), demonstrating their sensitivity and robustness for case study comparisons on farm-driven environmental change. The results show two stages of the socio-metabolic transition: a first period (from 1830 to 1956) characterized by a non-significant decrease in energy reinvestment (E) and a decrease in energy redistribution (I); and a second period (from 1956 to 2000) with a significant loss of E·I optimal values and associated landscape patterns (L). To overcome the socioecological degradation that these trends implied requires a low external input strategy based on an innovative enhancement of cultural knowledge kept by rural populations, which may help to empower farm communities in the markets and in the public arena. Further research could help to reveal how and why different strategies of agroecosystem management lead to key turning points in the relationship between energy flows, landscape functioning and biodiversity. This research will be very useful for public policies aimed to promote more climate and socioecological resilience of agricultural landscapes and food systems worldwide. Unlabelled Image • An Energy-Landscape Integrated Analysis (ELIA) of agroecosystems is proposed. • ELIA relies on the complexity of internal energy cycles and land-use heterogeneity. • ELIA measures the energy reinvested, redistributed and imprinted in the landscape. • ELIA is used to assess long-term socioecological transitions in western agriculture. • Results recommend a low external inputs strategy for agroecosystems. [ABSTRACT FROM AUTHOR]

One promising technology to manage and store renewable electricity from wind or solar sources is Power to Gas (PtG). PtG combines H 2 from electrolysis –run by renewable electricity– with CO 2 to produce synthetic CH 4. A suitable option to get the required CO 2 streams is the integration with carbon capture technologies, in particular with oxy-fuel combustion. The application proposed in this study is a cogeneration system that combines PtG, oxyfuel boiler, wind energy and photovoltaic solar production to be applied in buildings. This paper describes the concept and analyses the influence of equipment dimensions varying the relative size and the proportion of the solar-wind installed power for two locations representative of North and South European countries. Show that higher solar and wind powers are required in the Northern region to satisfy coverage of thermal demand. It results in longer time displacement of energy storage towards cold months. Accordingly to the generation patterns of wind and solar energies, higher solar proportion results in longer energy storage periods. Therefore, solar resource is more suitable than wind power to exploit the potential of PtG technology, although the size of the overall systems increases. • An application of satisfying energy demand through Power to Gas is analysed. • The combination of solar PV, wind, oxyfuel boiler and energy storage is feasible. • North Europe countries need bigger systems achieving large energy storage. • Energy storage necessities for southern Europe countries are smaller than for Northern Europe. • Larger amounts of synthetic gas are stored with high PV power shares. [ABSTRACT FROM AUTHOR]

Highlights • Building internal mass (BaB) is preheated during the afternoon hours for evening heating. • Measured BaB efficiencies of 60–80% for insulated apartments. • Measured BaB efficiencies of 40–70% for low-insulation apartments. • Variable renewable energy as photovoltaic is appropriate for building as battery. • BaB thermal storage can be a viable option for consumers with small reductions in daytime electricity cost. Abstract To increase the penetration of photovoltaic renewable energy (PV RE) in the residential building sector energy mix, the mismatch between mid-day production and evening electrical energy demand must be bridged. The use of heat pumps for space heating of residential buildings creates an opportunity for energy flexible residential buildings that rely on low-cost thermal energy storage systems. This paper explores the 'building as battery' concept (BaB), i.e. the use of the structural thermal capacity as a heat storage medium in winter. In these systems the building internal mass is preheated during solar daytime hours (using a PV RE powered heat pump) and cooled by discharge into the room air after sunset, for space heating. This study presents measured and simulated performance of BaB systems used for thermal energy storage in living rooms of three different apartment buildings with variable thermal insulation levels, ranging from typical southern Europe 1980s construction to a insulated apartment (Passive House certified). To assist in interpreting the results and facilitate their integration in simplified simulation of BaB systems in smart grids the model parameters of a simplified Resistance-Capacitance model were found by fitting the experimental results. The results show that, for apartments with high thermal mass, thermal insulation is the key driver of BaB system thermal efficiency, with the highly insulated apartment reaching BaB efficiencies of 60–80%. For existing apartments with a low thermal insulation, the BaB approach is only effective when space heating is required right after sunset (just when PV RE powered heat pump charging finishes). [ABSTRACT FROM AUTHOR]

This study is a first attempt to evaluate how the major efforts made by several European cities in the frame of the Covenant of Mayors (CoM) initiative can impact the air pollution levels in the participating cities. CoM is by no mean one of the major cities initiatives aimed at mitigating climate change, supporting local authorities in the implementation of their climate action plans. Energy savings measures reported in the CoM cities' action plans have been analysed from the air quality perspective in order to find quantitative relations in the way local authorities deal with mitigation and how these practices are expected to have consequences on the air quality at urban level and finally positively impacting the citizens' health. In the paper, the air quality 2713 energy saving measures proposed by 146 cities located in 23 countries in the frame of the CoM are selected and their co-benefits for air quality and public health estimated by means of SHERPA, a fast modelling tool that mimics the behaviour of a full physically-based Chemical Transport Model. Besides evaluating the overall benefits of this subset of mitigation measures for the air quality, the study also investigates the relevance of some factors such as the implementation sector, the city size and the pollution levels in achieving the highest possible co-benefits. The results presented refer to the special field covered by the study, i.e. energy saving measures and are not automatically referable to other types of measures. Nevertheless, they clearly show how climate mitigation and air quality policies are deeply interconnected at the urban level. [ABSTRACT FROM AUTHOR]

Abstract: With the rising prices of the retail electricity and the decreasing cost of the PV technology, grid parity with commercial electricity will soon become a reality in Europe. This fact, together with less attractive PV feed-in-tariffs in the near future and incentives to promote self-consumption suggest, that new operation modes for the PV Distributed Generation should be explored; differently from the traditional approach which is only based on maximizing the exported electricity to the grid. The smart metering is experiencing a growth in Europe and the United States but the possibilities of its use are still uncertain, in our system we propose their use to manage the storage and to allow the user to know their electrical power and energy balances. The ADSM has many benefits studied previously but also it has important challenges, in this paper we can observe and ADSM implementation example where we propose a solution to these challenges. In this paper we study the effects of the Active Demand-Side Management (ADSM) and storage systems in the amount of consumed local electrical energy. It has been developed on a prototype of a self-sufficient solar house called “MagicBox” equipped with grid connection, PV generation, lead–acid batteries, controllable appliances and smart metering. We carried out simulations for long-time experiments (yearly studies) and real measures for short and mid-time experiments (daily and weekly studies). Results show the relationship between the electricity flows and the storage capacity, which is not linear and becomes an important design criterion. [Copyright &y& Elsevier]

Pumped hydro energy storage (PHS) currently is the only electricity grid storage technology with substantial deployment throughout the world, representing over 99% of storage capacity, but other storage technologies such as batteries are increasingly finding application. In Europe, the implementation of storage systems is expected to increase because of the integration of intermittent, nondispatchable renewable energy sources. Nevertheless, there is no overview available of the power and energy ratings of large-scale stationary storage at the supranational level. In the absence of officially collected statistics on energy capacity, publicly available information is collected from storage owners, freely accessible databases, scientific articles, reports, brochures and government websites. The status of PHS and other large-scale storage technologies in the EU-28 countries, supplemented by Norway and Switzerland, is presented. First, this paper defines a measure of energy storage capacity, to allow comparison of pumped hydro storage plants with other storage technologies. Next, a set of technical parameters of current large-scale storage plants is presented, as well as an overview of planned storage projects. The estimate of PHS power ratings in the EU-28 exceeds previous estimates, with a total of 160 plants and 45.283 GW rated power in turbine mode and a full cycle storage capacity of 602 GWh. When adding Norway and Switzerland, a total of 188 operational PHS plants is shown with 1313 GWh. The data is used to obtain EU-wide discharge curves and national indicators of utilization and significance. [ABSTRACT FROM AUTHOR]

This paper provides a revision of the latest studies on the topic methanation, a multi-stage process where water is first converted into hydrogen in an electrolyzer, which subsequently reacts with carbon dioxide to produce methane. The present and future of the most common water electrolysis technologies is addressed. Critical issues to take into consideration when selecting a carbon dioxide source are evaluated. Chemical and biological approaches, together with photocatalytic configurations are discussed, analyzing pros and cons in all the cases. This paper also highlights the extensive work being done in the development of catalysts capable of selectively converting carbon dioxide into methane, as well as the different reactor configurations that can be used with this aim in any of the available methanation modalities. Relevant power-to-methane plants in Europe have been identified and assessed regarding their location, year of commissioning, capacity, technology for electrolysis and methanation type. Finally, cost issues are analyzed, highlighting economic perspectives of the power-to-methane technologies for the next decades. This document reviews all the key elements associated with the methanation process, revealing which aspects can pave the way for the large-scale implementation of this power generation model. In this sense, the gradual cost reduction of the equipment involved and the continuous increase in the efficiency of the processes are revealed as crucial aspects that can lead to a general implementation of the methanation concept on the way to a low carbon economy. • The latest studies on Power to Methane (PtM) processes are reviewed. • Methanation systems will facilitate the transition to a low-carbon economy. • Flexible operation of PEMEC electrolyzers makes them the best option for PtM plants. • Chemical methanation have the greatest potential to be implemented on a large scale. • Biological methanation is a promising pathway for future energy storage. [ABSTRACT FROM AUTHOR]

• Impacts of distributed generation on a non-residential building are studied. • A transformer anti-aging protection system is proposed. • Real electricity and weather data are used to perform the simulations. • Results show that the proposed system successfully limits transformer aging. • An economic analysis for the proposed system is presented. The increase of distributed generation units in low voltage distribution grids, stimulated by different mechanisms (mostly economic), like the Energy Performance of Buildings Directive in Europe and the associated nearly-Zero Energy Building concept, stresses in-depth research on the possible impacts that such generation may impose on fundamental grid equipment such as distribution transformers. Taking this into consideration, this paper has two main objectives: i) to analyze the impacts of distributed generation on a non-residential building supplied by a dedicated distribution transformer when this building is converted to a nearly-Zero Energy Building; and ii) to develop a Transformer Anti-Aging Protection System (TAAPS) that mitigates existing negative impacts in order to reduce transformer aging. The present study is based on 1-year, 1-min resolution, real electricity demand and weather data and uses the standard IEC 60076-7 (Loading Guide For Oil-immersed Power Transformers) to model the transformer aging. The collected results show that the introduction of distributed generation increases transformer aging and that the proposed protection system (TAAPS) fulfills its objectives preventing the excessive aging. An economic analysis, related with the proposed system, is also provided in this paper. [ABSTRACT FROM AUTHOR]

Abstract: The increase in PV (photovoltaic) capacities in Germany had since 2011 on some days already significant impacts on spot market prices at the German electricity exchange. The core objective of this paper is to investigate the possible effects of a further uptake of PV on the prices in electricity markets. We analyze two major effects: (i) the direct impact of PV at specific times of the year when PV shifts the supply curve of conventional electricity virtually out of the market, leading to temporarily very low market prices close to Zero; (ii) the indirect impact of PV (and wind) on the costs at which fossil capacities are offered at times when renewable energy sources are scarce. The major effects of these developments on the electricity markets will be: (i) a much higher price volatility from hour-to-hour and day-to-day; (ii) higher prices for electricity from fossil capacities and storage technologies for balancing the intermittent renewable generation; and (iii) growth of balancing markets and intensified competition at the level of decentralized balancing organizations. [Copyright &y& Elsevier]

Abstract: This paper analyses the hybrid solar and hydro (SHE) system as a unique technological concept of the sustainable energy system that can provide continuous electric power and energy supply to its consumers and the possibilities of its implementation in Europe and areas with similar climate. The sustainability of such system is based on solar photovoltaic (PV) and hydroelectric (HE) energy as renewable energy sources (RES). For the purpose of connecting all relevant values into one integral SHE system, a mathematical model was developed for selecting the optimal size of the PV power plant as the key element for estimating the technological feasibility of the overall solution. Sensitivity analysis (parameter analysis) was made for the model, where local climate parameters were varied: solar radiation, air temperature, reservoir volume, total head, precipitation, evaporation and natural water inflow. It has been established that, apart from total head (which is to be expected), solar radiation, hydro accumulation size and natural water inflow have the biggest effect on the calculated power of the PV power plant. The obtained results clearly show a wide range of implementation of the new energy source (SHE system), i.e. from relatively cold climates to those abundant in solar energy, but also with relatively small quantity of water, because it only recirculates within the system. All this points to the necessity for further development of hybrid systems (RES+HE systems) and to the fact that they could play an important role in achieving climate objectives. [Copyright &y& Elsevier]

Abstract: This paper reviews the development of latent heat thermal energy storage systems studied detailing various phase change materials (PCMs) investigated over the last three decades, the heat transfer and enhancement techniques employed in PCMs to effectively charge and discharge latent heat energy and the formulation of the phase change problem. It also examines the geometry and configurations of PCM containers and a series of numerical and experimental tests undertaken to assess the effects of parameters such as the inlet temperature and the mass flow rate of the heat transfer fluid (HTF). It is concluded that most of the phase change problems have been carried out at temperature ranges between 0°C and 60°C suitable for domestic heating applications. In terms of problem formulation, the common approach has been the use of enthalpy formulation. Heat transfer in the phase change problem was previously formulated using pure conduction approach but the problem has moved to a different level of complexity with added convection in the melt being accounted for. There is no standard method (such as British Standards or EU standards) developed to test for PCMs, making it difficult for comparison to be made to assess the suitability of PCMs to particular applications. A unified platform such as British Standards, EU standards needs to be developed to ensure same or similar procedure and analysis (performance curves) to allow comparison and knowledge gained from one test to be applied to another. [Copyright &y& Elsevier]

The composition of urban districts - residential, commercial, or 'mixed' topologies - can have drastically different energy load profiles and peak demands, leading to altered optimal District Multi-Energy System (D-MES) designs. Although demand-influenced differences in D-MES designs are generally understood, there is a research gap of how the interplay of various storage technologies differs between topologies. In this paper, we investigate the extent of D-MES reliance on storage technologies over various district topologies in central Europe. The core of this analysis relies on a multi-objective MILP optimization model utilized in an uncertainty analysis framework. Optimal D-MES results show distributions of designs which vary depending on uncertain parameters. For district energy planners, main findings show that mixed districts are the most promising case for D-MES planning due to a diversified demand type balance leading to lower costs and emissions. Residential districts typified by high peaks demonstrate larger storage requirements. All three storage technologies are key components of low emissions D-MES, enabling increased sector-coupling and renewable self-consumption. Such districts utilize power-to-hydrogen seasonally while batteries are relied upon for short-term load management. The most influential parameters for power-to-hydrogen installation are mainly attributed to competing technologies on the electric (batteries) and thermal (ASHPs) sectors. • Interplay of urban district topology and reliance on energy storage technologies. • Multi-objective optimization of multi-energy systems for costs and CO₂ emissions. • Consideration of thermal storage, electric li-ion batteries, and power-to-hydrogen. • Mixed district topologies provide demand-side balance, reducing storage requirements. • Power-to-hydrogen highly sensitive to competing storages' techno-economic inputs. [ABSTRACT FROM AUTHOR]

As the share of variable renewable energies in the power system increases, so does the need for flexibility options. These include, inter alia, energy storage, network optimization and expansion, and demand side management. In this paper, a broad sensitivity analysis is carried out to assess the potential role of innovative electrical energy storage technologies in comparison to well-established ones. The innovative technologies considered include compressed heat energy storage, adiabatic compressed air energy storage, power-to-heat-to-power storage, and reversible solid oxide fuel cells storage. To this aim, the cost-optimizing energy system model REMix has been applied to analyze the impact of main techno-economic parameters of electrical energy storages on their role in the future European power supply system. Two main studies have been calculated. The first one deals with a cost sensitivity analysis on a generic storage technology. Among the main findings is that – beside cost – the ratio between photovoltaics and wind power potentials in a particular region have a relevant impact on the capacity as well as on the energy to power ratio of the installed storages. In addition, a strong competition has been observed between energy storages and gas turbines. The second scenario evaluates the competition between well-established and innovative energy storage technologies. The results show that while some of the regions – namely southern Europe, alpine regions and Scandinavia – mainly rely on pumped hydro storage, in most of Central European regions and United Kingdom the cost optimal solution consists of a mix of pumped hydro storage (totaling 64.2 TWh/y of discharged energy in Europe), hydrogen underground storage (45.1 TWh/y) and batteries (27.1 TWh/y), with an additional small share of power-to-heat-to-power storages (0.1 TWh/y). In line with earlier studies, hydrogen storage is found mostly in regions with high wind power supply, while the distribution of batteries is more spread overall in Europe. The model results underline the high sensitivity of the economic efficiency of storage facilities to the investment costs and their components. [ABSTRACT FROM AUTHOR]

• Automatic Frequency Restoration Reserve market description. • Operating strategy for a generation pool comprising a Battery Energy Storage Systems (BESS) • Bidding strategy to derive optimal bids and to evaluate economic feasibility. • BESS market participation not economic feasible in 2019 but possibly in 2025. In continental Europe, automatic Frequency Restoration Reserve (aFRR) is one of three control reserve services to counteract imbalances in the electrical grid. The market is dominated by a few operators of conventional power plants since the auction design is complex and new players face various entrance barriers. In order to stabilize the electrical grid in the future, renewable generation technologies need to enter the market. To encourage operators (and traders) of renewable generation facilities to enter the market, this paper presents a bidding strategy based on an optimization approach for deriving an optimal bid and for estimating the revenue potential on this market. The focus is on the participation of Battery Energy Storage Systems (BESS) either in standalone mode or in conjunction with a virtual power plant (VPP). An in-depth cost breakdown and battery ageing model support the derivation of earning potentials. With current costs of containerized BESS, an operation is not economically viable. However, with a predicted cost breakdown for the year 2025 and a pooled operation, profits can be generated. But even for the reduced-cost scenario, profits were found to be lower than on the Frequency Control Reserve (FCR) market. [ABSTRACT FROM AUTHOR]