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The reduction of energy demand in buildings is one of the key challenges in contemporary construction. To this end, the application of structural and material partitioning solutions that provide a high level of thermal insulation and the employment of technical installations with high energy performance have become widespread. However, there are a number of other factors that can reduce energy demand. These include the optimal use of heat gains from solar radiation. An aspect that is often discussed in the literature is the overheating of buildings due to excessive heat gains from solar radiation. This article is a case study showing the impact of the orientation of a single-family passive house on its heating energy demand. The building under consideration is located in Central Europe. External climate parameters measured directly at the site during experimental examinations were used for the calculations. This paper adopts six calculation options, considering the different orientations of the glazed façade. As the simulations showed, the effect of solar radiation on the energy demand between two extreme options of glazing orientation, that is south and north-facing orientation, reached 4.7% of the annual energy demand for heating, while for the option corresponding to the actual location of the building and the option involving south-facing windows, the difference was 0.3%, respectively. [ABSTRACT FROM AUTHOR]

Renewable energy sources (RESs) and electricity demand are not evenly distributed geographically across Europe. Thus, harvesting the wind energy from the north and solar energy from the south and delivering them to the demand in central Europe is a more viable solution. However, the present High-voltage alternating current (HVAC) transmission grids have been sometimes congested; thus, High-voltage direct current (HVDC) provides another possibility along the existing HVAC infrastructure. In this paper, we propose a hybrid HVAC-HVDC grid, allowing a large penetration of concentrated RES in Europe and North Africa. More specifically, the HVDC network is constructed to transfer wind and hydro electricity from northwestern Europe and solar electricity from north Africa, while the HVAC network is used to distribute electricity within each country or among adjacent areas. To quantitatively evaluate the feasibility and relevant performances, multiple dimensions of indicators are designed. Employing several European energy scenarios up to 2050, the performances of the proposed HVAC-HVDC infrastructure are analyzed and compared. The calculation results show that compared with the pure HVAC grid, the integrated HVAC-HVDC grid can significantly reduce greenhouse gas emissions and pollutants, leading to a further reduction in the number of deaths from air pollution. In addition, the HVAC-HVDC grids can accommodate a higher penetration of RES without causing infeasible power flows. [ABSTRACT FROM AUTHOR]

Electricity markets are increasingly influenced by variable renewable energy such as wind and solar power, characterized by a pronounced weather-induced variability and imperfect predictability. As a result, the evaluation of the capacity value of variable renewable energy, i.e., its contribution to security of supply, gains importance. This paper develops a new methodology to endogenously determine the capacity value in large-scale investment and dispatch models for electricity markets. The framework allows balancing effects to be accounted for that arise due to the spatial distribution of generation capacities and interconnectors. The practical applicability of the methodology is shown with an application for wind power in Europe. We find that wind power can substantially contribute to security of supply in a decarbonized European electricity system in 2050, with regional capacity values ranging from 1-40%. Analyses that do not account for the temporal and spatial heterogeneity of the contribution of wind power to security of supply therefore lead to inefficient levels of dispatchable back-up capacity. Applying a wind power capacity value of 5% results in an overestimation of firm capacity requirements in Europe by 66 GW in 2050. This translates to additional firm capacity provision costs of 3.8 bn EUR per year in 2050, which represents an increase of 7%. [ABSTRACT FROM AUTHOR]

This paper is inspired of idea to investigate possibilities to use solar energy for water heating in Lithuania. Lithuania is somewhere between central and north Europe. So that's mean that geographical position is not as favorable as it is in Mediterranean region but as harsh as it is northern Europe. The investigation is interesting and actual because this paper presents the first steps investigate small thermosiphon solar thermal system. Thermosiphon solar thermal systems are more common in south but not in central or even in north of the Europe. The author made theoretical calculation how water temperature in the solar water heater depends on the time and compare calculated data with real measurements. [ABSTRACT FROM AUTHOR]

Future power production in Europe is expected to include large shares of variable wind and solar power production. Norway, with approximately half of the hydropower reservoir capacity in Europe, can contribute to balance the variability. The aim of this paper is to assess how such a role may impact the Norwegian hydropower system in terms of production pattern of the plants, changes in reservoir level and water values. The study uses a stochastic optimization and simulation model and analyses an eHighway2050 scenario combined with increases in the hydropower production capacities in Norway. The capacity increases from ca. 31 GW in the present system to 42 and 50 GW respectively. The study uses 75 years with stochastic wind, solar radiation, temperature and inflow data. The results show that the hydropower system is able to partly balance the variable production and significantly reduce the power prices for the analyzed case. The paper shows that some of the power plants utilize their increased capacity, while other plants do not due to hydrological constraints and model limitations. The paper discusses how the modelling can be further improved in order to quantify more of the potential impacts on the future power system. [ABSTRACT FROM AUTHOR]

To mitigate the effects of climate change, energy systems are becoming increasingly reliant on renewable energy sources. Since these energy sources are typically dependent on the prevailing weather, renewable energy systems are susceptible to shortages during certain weather conditions. As renewable sources become larger contributors to the energy mix, the risks associated with these shortages, referred to as energy droughts, increase. Techniques are therefore required that can help policymakers to understand and mitigate the impacts associated with energy droughts. In this paper, two standardised indices are introduced to monitor droughts in renewable energy systems. The indices incorporate energy demand and renewable energy production, and constitute analogues to the standardised precipitation index (SPI) and standardised precipitation evapotranspiration index (SPEI), two indices regularly employed operationally to monitor meteorological droughts. The indices are straightforward to construct, can be defined on any timescale, and facilitate comparisons between regions with different climates and installed capacities. We demonstrate how the standardised energy indices proposed herein can be used to define renewable energy droughts, and illustrate the practical utility of these indices in an application to reconstructed time series of electricity demand and wind and solar power generation across Europe. [ABSTRACT FROM AUTHOR]

The EU has undertaken a thorough reform of its energy model. Current EU 2050 climate commitment sets an 80–95% GHG reduction goal. To reach this goal, the EU must make continued progress towards a low-carbon society. Renewable energy sources and electric vehicle play an important role for a gradual transition. The power grid faces a challenging future due to intermittency and the non-dispatchable nature of wind and solar energy production, but flexibility needs can migrate from generation to load, with the expansion of demand-side resources and storage technologies. A novel grid technique is presented and evaluated in this paper for the optimal integrated operation of renewable resources and electric vehicle to increase penetration of renewable energy. It is proposed a distribute control system to manage a charge and discharge strategy to support mismatching between load and renewable generation thru V2G technology. Demand response, peak saving and ancillary services are introduced to keep a reliable power quality, stable frequency and flatten load profile. Image 1 • Europe 2050 low-carbon scenario based on RES and energy efficiency is reviewed. • The effects of high renewable and efficient electricity system are assessed. • A smart charging strategy for EV is presented to provide grid services. • Demand response and EV storage are analyzed to match with non-dispatchable resources. • The impact of proposed charging strategy on electric load curve is evaluated. [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]

With the technological advance in electricity generation techniques and the prevailing need for sustainable development of countries, the massive use of alternative energies has been in force for the last 15 years, with clear goals towards 2020 for sustainable development. At the regulatory level, Colombia cannot be left behind in the regulation, and progress has already been made on the subject with law 1715 of 2014 and several decrees of incentives in the promotion of renewable energies. The objective of this paper is to show the state of the art on the way in which the net balance and residential energy self-consumption by DER is handled by several tax regulations in different countries of Europe; moreover, it will also go into detail about the advantages offered by using a selected methodology to consider fair charges of support for the use of the electrical network by generators distributed from photovoltaic solar energy, all this as a contribution to advances already made in this field. This is provided from a network planning approach, in which a long-term methodology is selected that efficiently integrates the distributed generation into the interconnected system and allows transition periods in its implementation to avoid disruption of network operators (ORs). Likewise, this analysis is supported by the simulated operation of a system with DER together with the changes in load flows due to decongestion and surplus injection that the electric system has in the scenario of massive use of these resources. [ABSTRACT FROM AUTHOR]

Renewable energy in Middle East and North Africa (MENA) region, particular solar energy, can be connected to Europe to provide the Northern neighbouring countries with electricity. To achieve this long term objective, it is necessary to understand the local domestic consumption of electricity in the MENA region as the main consumer of energy. The understanding of current and future trends could help to provide a complete picture of the energy situation in MENA region and the feasibility of exporting energy to Europe. For this reason, this paper investigates the domestic energy use and occupants’ energy behaviour in Libya. The aim of this study is to evaluate the effect of domestic energy consumption and householders’ awareness, attitudes and behaviour on the overall energy consumption in Libya and how this could affect the peak demand, capacity, future trends and government energy budget. The paper also investigates the sustainability aspect of consumer products and the awareness and attitude of consumers towards consumption and demand. A comprehensive survey has been conducted to evaluate several aspects of domestic energy demand and characteristics in Libya. The findings have indicated that there is a significant increase in energy demands in the household sector in Libya and it is significant to have a clear strategy to reduce carbon emission and energy use by improving occupants’ behaviour as well as utilising other sustainable measures. Minor adjustment in householders’ energy consumption behaviour and the technology used to generate energy could provide significant financial savings and contribute significantly to the reduction in carbon emission and energy consumption. This will allow significant benefit to the local economy and the energy sector in Libya but at the same time could provide sustainable energy resources for Europe on the long term. [ABSTRACT FROM AUTHOR]

Renewable energy is a focal point of discussion in the European Union, as clean production technologies contribute to all three aims of energy policy (security, competitiveness, and sustainability). This paper focuses on an empirical assessment of feed-in tariff and quota obligation policies, as well as their policy design elements, applied to solar photovoltaic energy in the European Union over the period 2000–2014. The results indicate that only feed-in tariff policy has significant impacts in terms of installed photovoltaic capacity. However, its main policy design elements (tariff size and contract duration) have a positive but not significant influence on the development of this clean production technology. Policy-makers should consider the importance of reducing regulatory uncertainty about these parameters. [ABSTRACT FROM AUTHOR]

This paper analyses the energy and economic performance of roof and/or façades Building Integrated flat-plate PhotoVoltaic and Thermal (BIPVT) collectors for residential applications. Aim of the analysis is to assess the active and passive effects due to the building integration of solar technologies on the building energy consumptions. In particular, a comparison among innovative building-plant system configurations, based on BIPVT collectors for the simultaneous production of electricity, thermal energy, and domestic hot water, is carried out. The simulation models of the proposed system layouts are designed and implemented in TRNSYS simulation environment for the dynamic assessment of their energy and economic performance. By means of the developed simulation model, the occurring summer and winter building passive energy effects due to the PVT building integration are also analysed. Several case studies are developed by modelling a representative multi-storey residential building and by taking into account different European climates. For such case studies a suitable energy parametric analysis is performed by varying the thermal resistances and capacitances of the building envelope. By the simulation results interesting design and economic feasibility guidelines are obtained. In particular, by varying the weather location and the building-plant configuration, the adoption of BIPVT panels produces a decrease of the primary energy demands from 67% to 89%. The passive effects of the BIPVT system in both the winter and summer season are also assessed for all the investigated climate zones. The calculated economic profitability resulted slightly better for roof BIPVT panels than for roof and façade applications. For the investigated case studies, the pay back periods appear quite long, varying from 11 years for South European weather zones to 20 for North European ones. [ABSTRACT FROM AUTHOR]

Abstract: Sizing of stand-alone photovoltaic systems (SAPVS) requires knowledge of their reliability. Because of primary influence of the solar irradiance and meteorological conditions, simulations are the best way to compute an accurate reliability for a given location and fixed sizing parameters. These studies have been developed for more than two decades, but have had a narrow geographical applicability. In this paper, we perform a complete (in time and space) simulation of a standard SAPVS in Europe using 23year radiation data corresponding to almost 2300 geographical points. At each point, the tilt angle that maximizes the energy reaching the PV array in December is estimated and the relation among sizing parameters and reliability is computed for wide ranges of values. Finally, multilayer perceptrons are trained for both computations, allowing (after their training) simple and fast estimations of the sizing parameters of this type of plants for any location in Europe. The procedure presented in this paper, although focused particularly in Europe, can be easily extended to almost any other region in the world. [Copyright &y& Elsevier]

Abstract: In the last few years the solar-powered air-conditioning systems have been in intensive development and more often are considered as the viable application for the thermal solar systems in the regions of southern Europe. This is mainly due to the increasing higher electrical consumption in many countries (especially in Spain) which is moving from the winter to summer months due to expanding usage of cooling systems in this period of the year. In this paper we will analyze the behaviour of the solar-assisted air-conditioning system installed in the CIESOL building. This system consists mainly of flat-plate solar collectors and the simple effect LiBr–H2O absorption chiller. Different operation modes were analyzed. Coefficient of performance (COP) at various generator, absorber, condenser and evaporator temperatures is investigated and experimental results show that in practice it is easy to obtain values of about 0.6. The main goal of this paper is to describe the characteristics of the developing building and the solar-assisted air-conditioning system. Another useful purpose is to find the optimum conditions and operation parameters for the solar system through analyzing various systems'' operation strategies. [Copyright &y& Elsevier]

The paper aims to address the potential of low-carbon and renewable hydrogen in decarbonizing the European energy system; specifically, reducing emissions by 55% in 2030 compared to 1990, and targeting net-zero emissions by 2050. The methodology relies on a cost-optimization modelling approach using three models complementarily: a detailed European TIMES-type model (MIRET-EU); an aggregated model for the European energy system, allowing endogenous cost reductions based on technology deployment in a dynamic programming formulation for investment strategies (Integrate Europe); and a dedicated model for assessing hydrogen import options for Europe (HyPE). Two policy-relevant scenarios have been developed: Technology Diversification (TD) and Renewable Push (RP). Both lead to climate neutrality in Europe in 2050 but the RP scenario differs by setting new reinforced targets for renewable technologies in Europe. Results show that hydrogen production would increase sharply in the coming decades, exceeding 30 million tons (Mt) by 2030 and more than 100 Mt by 2050 in both scenarios. Polyvalence of hydrogen in decarbonizing the European energy system for certain hard-to-abate energy uses in transport and industry is also observed. European hydrogen production relies on a diverse mix including both renewable and low-carbon technologies. It is complemented by hydrogen imports from neighboring regions, that represent between 10 and 15% of total demand in 2050. Access to existing cross-border pipelines is a critical advantage compared to maritime transport. Notably, there are considerable cost reductions due to technology deployment for solar power and hydrogen production by electrolyzers. • European hydrogen demand could exceed 100 million tons per year by 2050. • 15% of H 2 needed to reach carbon neutrality could be imported from outside Europe. • More than half of H 2 is used for transport, the rest is dominated by industry. • 1800 GW of solar and wind power is needed for the roll-out of renewable hydrogen. • Resilience of natural gas in European energy transition by 2050 with uptake of CCS. [ABSTRACT FROM AUTHOR]

The optimal utilization of solar energy requires a thorough characterization of the solar resource. The most accurate way is to measure that resource in situ. However accurate measurements are not a common commodity, especially over longer time spans. To circumvent the lack of ground based measurements, models can be applied to estimate solar irradiance components. A fundamental component is clear sky irradiance. In particular, clear sky irradiance is used as the normalization function in models that convert meteorological satellite images into irradiance, or in models that decompose global irradiance into diffuse/direct fraction. It is therefore important to evaluate and validate clear sky irradiance models. This paper presents the results of a validation of hourly clear sky models spanning up to eight years. The validation relies on high quality measurements at 22 locations in Europe and around the Mediterranean region. Seven models are evaluated. They were selected on the basis of their published performance, their simplicity of use, and/or their computational speed; two different sources of the aerosol load are used as input to the models. The three best models show a low bias and a standard deviation ranging from ±3% to ±5%. The standard deviation of the bias across the 22 locations is of the same order of magnitude. The observed bias patterns can be largely traced to inaccuracies inherent to the sources aerosol optical depth. No particular seasonal effects are noted. A consistent limitation across all selected models, even if their direct irradiance performance can be judged satisfactory based on the standard deviation metric, is that they tend to fall short of observations for a given clear sky global clearness index value. [ABSTRACT FROM AUTHOR]

The built environment in communities is responsible for at least 40% of the entire energy consumption in the EU. This environment is closely analyzed under the national and European strategies aiming to increase sustainability in the communities through energy efficiency actions and the use of renewable energy sources. Once these European objectives are met, optimistic scenarios show that the solar-thermal (ST) systems will be able to provide from 3.6% of the amount of the thermal energy demand in 2020, up to 15% in 2030, and 47% in 2050. The EU energy strategy demands that by 2030 all new buildings should be able to entirely cover the energy amount needed for heating / cooling and domestic hot water (DHW) by using ST systems, whereas the old buildings will have to cover at least 50% of the amount needed for heating / cooling and DHW by using ST systems. This paper proposes a novel methodology to design optimized ST systems implemented at district level, while developing various implementation scenarios; a comparative analysis of individual projects (e.g.: for one apartment blocks), groups of multi-family houses (2, 5, 10 apartment blocks) up to districts (25 and 50 apartment blocks) allows for the optimal sizing of the feasible and affordable ST arrays, also making use of the already existent complementary infrastructure for DHW. A case study (Taberei District - Odorheiu Secuiesc Town, Harghita County) validates the methodology and outlines that district DHW production, entirely based on ST systems, supports the lower initial investment and payback time. [ABSTRACT FROM AUTHOR]

The production of thermal and electrical energy is related to the emission of greenhouse gases, which are believed to cause climatic changes. The activities of the international community show an increase of ecological awareness. In the Central European countries the share of renewable energy in overall energy production is relatively small. One sector where some progress can be made is agriculture. This paper presents simulation results of CO 2 reduction potential by replacing conventional heating system for a poultry house with a hybrid solar–wind system. Heat requirement for 2400 birds was calculated. Simple models for solar collector, wind turbine and heat storage tank are presented. The system is modelled in a Matlab/Simulink environment and various system configurations are analysed for climatic conditions typical for Central Europe. The solar collector area was varied between 0 and 80 m 2 , wind turbine diameter was varied in the range of 0–20 m and 1 to 4 heat storage tanks. Apart from percentage of CO 2 emission reduction two other indicators are introduced: renewable energy utilisation ratio and weighted CO 2 emission reduction — renewable energy utilisation coefficient. The results show that larger systems provide higher CO 2 reduction but the energy utilisation ratio decreases. [ABSTRACT FROM AUTHOR]

This paper compares the daily solar irradiation available at surface estimated by the MERRA (Modern-Era Retrospective Analysis for Research and Applications) re-analysis of the NASA and the ERA-Interim re-analysis of the European Center for Medium-range Weather Forecasts (ECMWF) against qualified ground measurements made in stations located in Europe, Africa and Atlantic Ocean. Using the clearness index, also known as atmospheric transmissivity or transmittance, this study evidences that the re-analyses often predict clear sky conditions while actual conditions are cloudy. The opposite is also true though less pronounced: actual clear sky conditions are predicted as cloudy. This overestimation of occurrence of clear sky conditions leads to an overestimation of the irradiation and clearness index by MERRA. The overall overestimation is less pronounced for ERA-Interim because the overestimation observed in clear sky conditions is counter-balanced by underestimation in cloudy conditions. The squared correlation coefficient for clearness index ranges between 0.38 and 0.53, showing that a very large part of the variability in irradiation is not captured by the re-analyses. Within an irradiation homogeneous area, the variability of the bias, root mean square error and correlation coefficient are surprisingly large. MERRA and ERA-Interim should only be used in solar energy with proper understanding of the limitations and uncertainties. In regions where clouds are rare, e.g. North Africa, MERRA or ERA-Interim may be used to provide a gross estimate of monthly or yearly irradiation. Satellite-derived data sets offer less uncertainty and should be preferred. [ABSTRACT FROM AUTHOR]

This paper contributes to the development of renewable energy innovation metrics through an exploration of innovation patterns across the European countries in 2010. The identified localized innovation capabilities describe the health of the wind, solar and bioenergy sectors, highlighting a concentrated RES innovation activity within four countries: Germany, France, United Kingdom and Denmark. The association of technological capabilities along the innovation composite indicators allows the extraction of useful insights of the role of environmental policies on employment and technological change. Briefly, the corporate research investment per patent is lower for wind energy (EUR 0.61 million) and higher for PV and biofuels (approximately EUR 1 million). Important lever of innovation capabilities across Europe is identified within public support to deployment, which provides significant insights in terms of economic efficiency of generation technologies; the investigation finds job ratios which are higher for wind and lower for PV technology. As the evolution of the market drives the patterns of innovation activities for all selected technologies, considerable financial consequences are identified in the context of delocalization of clean technology manufacturers. [ABSTRACT FROM AUTHOR]

Abstract: Successful technological innovation frameworks are based on synergistic packages of technology-push and demand-pull measures. As the massive deployment of premature renewable energy technologies risks becoming very expensive, the debate on the optimal trajectory of renewable technologies should explicitly consider the balance between deployment incentives and R&D efforts. This paper explores this balance regarding wind and PV technology support in Europe. Based on rather conservative estimates, we calculate future deployment costs and compare these figures to the current public investments in PV and wind R&D. We find that, today, for each Euro spent on R&D to develop future technologies, 35 to 41 Euros are spent on the deployment of existing technologies. Furthermore, private PV and wind technology companies tend to underinvest in R&D for various reasons. In an alternative scenario, we assess the optimal R&D efforts for the PV and wind sectors based on a 7% R&D-to-sales benchmark that is typical for engineering sectors. If public R&D efforts would increase according to this benchmark, and hence compensate for the private underinvestments in R&D, pull/push ratios between 6 and 8 could be achieved. This leads us to conclude that the current balance between deployment and R&D is far from optimal. [Copyright &y& Elsevier]

• The yield inside PV greenhouses was estimated on 14 species. • The evaluation identified the suitable crops inside four PV greenhouse types. • A PV cover ratio of 25% is compatible to all crops, with limited yield reduction. • A PV cover ratio of 50% is sustainable to medium and low light demanding crops. • Structures with 100% PV cover support only crops with optimal DLI < 10 mol m−2 d−1. The integration of the photovoltaic (PV) energy in the greenhouse farm has raised concerns on the agricultural sustainability of this specific agrosystem in terms of crop planning and management, due to the shading cast by the PV panels on the canopy. The PV greenhouse (PVG) can be classified on the basis of the PV cover ratio (PV R), that is the ratio of the projected area of PV panels to the ground and the total greenhouse area. In this paper, we estimated the yield of 14 greenhouse horticultural and floricultural crops inside four commercial PVG types spread in southern Europe, with PV R ranging from 25 to 100%. The aim of the work is to identify the PVG types suitable for the cultivation of the considered species, based on the best trade-off between PV shading and crop production. The daily light integral (DLI) was used to compare the light scenarios inside the PVGs to the crop light requirements, and estimate the potential yield. The structures with a PV R of 25% were compatible with the cultivation of all considered species, including the high light demanding ones (tomato, cucumber, sweet pepper), with an estimated negligible or limited yield reduction (below 25%). The medium light species (such as asparagus) with an optimal DLI lower than 17 mol m−2 d−1 and low light crops can be cultivated inside PVGs with a PV R up to 60%. Only low light demanding floricultural species with an optimal DLI lower than 10 mol m−2 d−1, such as poinsettia, kalanchoe and dracaena, were compatible inside PVGs with a PV R up to 100%. Innovative cropping systems should be considered to overcome the penalizing light scenarios of the PVGs with high PV R , also implementing LED supplementary lighting. This paper contributes to identify the sustainable PVG types for the chosen species and the alternative crop managements in terms of transplantation period and precision agriculture techniques, aimed at increasing the crop productivity and adaptability inside the PVG agrosystems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Detailed assessment of Organic Rankine Cycles is presented. • Mixture working fluids achieves higher thermodynamic efficiency. • Biomass and solar energy are still rarely adopted as ORC's heat resources. • USA and Europe have major share in ORC systems. • Studies for reducing the levelized cost of electricity is needed to be carried out. This paper presents state-of-the-art review on organic Rankine cycle (ORC) by assessing the working fluids, thermal resources, cooling utilities, and commercial status with future aspects. It is found that the mixture working fluids achieve higher thermodynamic efficiency. However, the difficulty in obtaining the optimum composition and components limits their applications. The thermal resources with different temperature ranges and cooling utilities are then assessed to investigate their effects on the thermodynamic performance of ORC. The low-temperature ORC utilizing waste heat and geothermal heat is dominant, while biomass and solar energy are still rarely adopted as ORC's heat resources. From the commercial perspective, the USA and Europe are the leaders in conversion of low-grade waste heat into useful power using ORC. Furthermore, the main challenges of ORC are: (a) selection of appropriate working fluid with suitable expander, and (b) reducing the specific cost of the small-scale ORC system to compete with the renewable energy. Finally, several future research directions are identified such as: (1) overall performance of the ORC system including its thermodynamic efficiency, stability and safety needs to be investigated with experimental studies; (2) a general methodology should be developed for the selection of working fluids; (3) studies for reducing the net present cost and levelized cost of electricity with techno-economic optimization are needed to be carried out. This study benchmarks the recent progress on ORC technology and presents an insight into the scientific problems that need to be explored to nexus low-grade heat to power in the future. [ABSTRACT FROM AUTHOR]

Abstract: High altitude winds are considered to be, together with solar energy, the most promising renewable energy source in the future. Till date, there are no yet solutions available on the market but various concepts for utilizing high altitude winds are under research and are expected to be fully operational within next few years. In this paper, the potential of high altitude wind energy will be investigated for the SEE (Southeast Europe) region and mapped using available data and technologies. The data available from NCEP/DOE analysis will be used in terms of obtaining the high altitude wind speeds for the span of 30 years, from 1980 to 2010, which are then processed for easier visualization. The obtained data is plotted against the available geographic data which could limit the positioning of the system (settlements, traffic…). The result of this work will display the “optimal” locations for these kinds of facilities for the Southeast Europe region. Such map could be beneficial for all future plans of utilizing this high altitude winds as a power source. [Copyright &y& Elsevier]

Although methods of using renewable energy are knows all over the world (biomass, solar, wind, geothermal and hydro), so far only a relatively small fraction of the technical and economic potential of renewable energy is being used today. Investments in renewable energy and energy efficiency represent an important solution for environment and for economic crisis that Europe and the world at large are facing today. This paper presents the evaluation of renewable energy potential use for an independent house. The house uses a system comprising photovoltaic panels and solar panels. When there is surplus of electricity supplied from panels, this extra energy is stored in batteries to be used during not producing periods. We also use a solar thermal collector for thermal energy. The energy required for the home is used for household's appliances, for heating and for domestic hot water. Local real weather data are used in the modelling. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a universal model of luminous efficacy for direct solar radiation on a horizontal surface. The model is applicable to all sky conditions and is based on data obtained from satellites and available via web servers. Solar radiation data from 10 locations in Europe and North Africa has been used to obtain four functions for luminous efficacy (K) against the sole independent variable solar altitude (α). Additionally cloud amount (C) was been used to obtain four other functions. All were used to accurately estimate illuminance for the 10 originating locations; for four locations based on satellite data; and for a further four based on measured data. A statistical assessment showed that three models performed best, namely, K against 1/α, K against sin α, and K against C/α. Comparison between results from the proposed models, and those produced using three previously published models, indicate that the former produce more accurate estimates of luminous efficacy. The satellite based approach makes daylight data available in locations remote from current measurement sites. [ABSTRACT FROM AUTHOR]

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 explores the capabilities of a combination of the reduced data set ISCCP-B2 from the Meteosat satellites and the recently developed method Heliosat-2 to assess the daily mean of the surface solar irradiance at any geographical site in Europe and Africa. Firstly, we discuss the implementation of the method Heliosat-2. Secondly, B2-derived irradiances are compared to coincident measurements made in meteorological networks for 90 stations from 1994 to 1997. Bias is less than 1Wm−2 for the whole set. Larger bias may be observed at individual sites, ranging from −15 to +32Wm−2. For the whole set, the root mean square difference is 35Wm−2 (17%) for daily mean irradiance and 25Wm−2 (12%) for monthly mean irradiance. These accuracies are close to those of similar data sets of irradiance, such as Medias and NASA Surface Radiation Budget. It is concluded that B2 data can be used in a reliable way to produce long-term time-series of irradiance for Europe, Africa and the Atlantic Ocean. [Copyright &y& Elsevier]

In April 2001 the new European Standard EN 12975:2000: “Thermal solar systems and components––Solar Collectors” was established. With the publication of this European standard all national standards, related to the same topic, have to be withdrawn by the nations of the European Community. Now only one standard for testing solar collectors is valid throughout Europe.This European Standard specifies test methods for validating the durability, reliability and safety requirements for liquid heating collectors. The standard also includes two alternative test methods for the thermal performance characterization for liquid heating collectors. Apart from the well-known test method under steady-state conditions according to ISO 9806-1, ISO 9806-3 and ASHRAE 93-77 the EN 12975 permits a quasi-dynamic test method for the thermal performance characterization of solar thermal collectors.This paper presents the improved approach to outdoor performance testing of solar thermal collectors under quasi-dynamic test conditions. The test requirements and collector theory are closely connected to those long agreed on for steady-state testing, as described in the ISO and ASHRAE standards mentioned above. The most important effects for the all day performance of the collector are taken into account. The test method covers most collector designs on the market today (except ICS type). Only some correction terms are added to the basic collector models of the present steady-state test methods. Still this limited change will allow test data to be collected and used from whole days.An important fact is that the collector model used for the parameter identification is written so that the error in collector output power is minimized. Therefore an accurate long-term prediction of the collector performance can be an integral part of the test method, where the same collector model and parameters are used for both testing and prediction. [Copyright &y& Elsevier]

This paper concerns the application of the first European example of a roof mounted, multi-operational ventilated photovoltaic and solar air collector, development of a detailed simulation methodology for such a system, and gives a brief outline of monitored findings after six months of operation. The aim for this simulation development was to provide a method that can aid future system design and optimize performance in line with energy requirements for specific buildings. This work is discussed in relation to two key investigations into the simulation of building integrated hybrid PV thermal collectors. [Copyright &y& Elsevier]

About 20% of the final energy consumed in Europe is used in buildings. The active and passive use of solar energy is an approach to reduce the fossil energy consumption and the greenhouse gas emissions originated by buildings. Consideration of solar energy technologies in urban planning demands accurate information of the available solar resources. This can be achieved by the use of remote sensing data from geostationary satellites which show a very high spatial and a sufficient temporal resolution compared to ground station data. This paper gives a brief introduction to the HELIOSAT method applied to derive surface solar irradiance from satellite images and shows examples of applications: The use of daylight in buildings, the generation of correlated time series of solar irradiance and temperature as input data for simulations of solar energy systems and a short-term forecast of solar irradiance which can be used in intelligent building control techniques. Finally an outlook is given on potential improvements expected from the next generation of European meteorological satellites Meteosat Second Generation (MSG). [Copyright &y& Elsevier]

The paper presents a strategic approach to assess the importance of space solar power for securing the increasing energy demand of Europe. Based on European particularities, like its high and increasing energy import dependence and the strong engagement to significantly reduce its emission of greenhouse gases (GHG), the effort of the recently created European Network on Space Solar Power, lead by the European Space Agency (ESA), are described. [Copyright &y& Elsevier]

Dish-Stirling systems have demonstrated the highest efficiency of any solar power generation system by converting nearly 30% of direct-normal incident solar radiation into electricity after accounting for parasitic power losses [1]. These high-performance, solar power systems have been in development for two decades with the primary focus in recent years on reducing the capital and operating costs of systems. Even though the systems currently cost about $10,000 US/kW installed, major cost reduction will occur with mass production and further development of the systems. Substantial progress has been made to improve reliability thereby reducing the operating and maintenance costs of the systems. As capital costs drop to about $3000 US/kW, promising market opportunities appear to be developing in green power and distributed generation markets in the southwestern United States and in Europe. In this paper, we review the current status of four Dish-Stirling systems that are being developed for commercial markets and present system specifications and review system performance and cost data. We also review the economics, capital cost, operating and maintenance costs, and the emerging markets for Dish-Stirling systems. [ABSTRACT FROM AUTHOR]

Solar and wind energy are expected to play a key role in creating a climate-neutral Europe by 2050 and decarbonizing energy production in general, albeit requiring significant deployment. This presupposes that the population accepts such energy sources, thus necessitates understanding how people perceive energy systems. Unlike the abundant literature about wind energy, social acceptance of solar energy has received less attention, especially concerning large solar installations. Opinion polls indicate that solar energy enjoys a high level of socio-political acceptance and is preferred to other renewables, although it is unclear whether this acceptance persists as the technology is deployed on a large scale. This paper helps close this gap by describing the results of a representative survey (n = 601) conducted using a between-subject design to examine how attitudes of the public towards solar energy vary based on the size of installations, how the latter compare to attitudes towards wind energy, and what the role of affect is in the former. Results reveal that the stronger preference for solar power decreases to a similar level as that for wind energy when comparing installation of similar sizes, highlighting that solar energy installations may not easily be scaled up. The study also shows that affect plays an important role in forming people's attitudes towards wind and solar, especially concerning large-scale installations. This underlines the need for policymakers and project developers, who aim to deploy renewables on a large scale, to attend to the affective component of decision-making. • Between-subject design survey with a representative sample (n = 601). • Positive attitudes towards solar energy are mediated by installation size. • Solar parks are less positively perceived than rooftop PV installations. • When comparing installations of similar sizes, solar is not more popular than wind energy. • Large installations evoke stronger emotions, which in turn influence attitudes. [ABSTRACT FROM AUTHOR]

The number of large-scale solar thermal installations has increased rapidly in Europe in recent years, with 70 % of these systems operating with flat-plate solar collectors. Since these systems cannot be easily switched on and off but directly depend on the solar radiation, they have to be combined with other technologies or integrated in large energy systems. In order to most efficiently integrate and operate solar systems, it is of great importance to consider their expected energy yield to better schedule heat production, storage and distribution. To do so the availability of accurate forecasting methods for the future solar energy yield are essential. Currently available forecasting methods do not meet three important practical requirements: simple implementation, automatic adaption to seasonal changes and wide applicability. For these reasons, a simple and adaptive forecasting method is presented in this paper, which allows to accurately forecast the solar heat production of flat-plate collector systems considering weather forecasts. The method is based on a modified collector efficiency model where the parameters are continuously redetermined to specifically consider the influence of the time of the day. In order to show the wide applicability the method is extensively tested with measurement data of various flat-plate collector systems covering different applications (below 200 ° Celsius), sizes and orientations. The results show that the method can forecast the solar yield very accurately with a Mean Absolute Range Normalized Error (MARNE) of about 5 % using real weather forecasts as inputs and outperforms common forecasting methods by being nearly twice as accurate. • Self-learning approach with only very few parameters to be determined. • Automatically considers seasonal changes and pollution of collector fields. • Simple regarding its mathematical structure and straightforward to implement. • Experimental long-term validation with data from various collector systems. • Superior to state-of-the-art forecasting methods regarding accuracy. [ABSTRACT FROM AUTHOR]

This paper describes solar thermal technologies for the solution of long term Europe`s energy problem with better reliability. A short overview about solar energy is explained with a basic energy analysis. This report also includes some evaluations and discussions of solar energy systems in the following pages. The general purpose of the article is to understand how efficiently solar thermal systems generates energy, and solve the Europe`s increasing energy demand in our century. [ABSTRACT FROM AUTHOR]

Biomass can help reaching climate goals in many sectors. In electricity generation it can complement variable renewables or, if coupled with carbon capture and storage (CCS), also provide negative emissions. This paper adds to the existing literature by focusing on the cost-efficiency of balancing variable renewables with biomass and by providing an indication on acceptance of these technologies. A dynamic optimization model is used to analyse the role of biomass in the European electricity system pending different emission targets for 2050. The results are compared with survey data on investment preferences for biomass technologies, and wind and solar power. The formulation of the emission target greatly influences the cost-efficient use of biomass, with more concentrated use observed, if bioenergy with CCS is allowed. This indicates that a Europe-wide emission target could be more cost-efficient than separate national targets. Both governmental and nongovernmental actors tend to be negative towards investing in biomass technologies, although with greater variation if combined with CCS, indicating possible challenges for implementation. Their attitudes towards wind and solar power are much more positive in all countries, supporting the continuation of the existing trend of an increasing share of variable renewables in the European electricity system. • Formulation of the emission target greatly influence biomass use and distribution. • Europe-wide emission targets may be preferred when negative emissions are required. • Negative emissions combined with natural gas are cost-efficient variation management. • Preferences to invest in bio-based technologies are low in all countries. • Non-governmental actors strongly oppose bioenergy with carbon capture and storage. [ABSTRACT FROM AUTHOR]

This paper presents an environmental sustainability assessment of residential user-scale energy systems, named solar home systems, encompassing their construction, operation, and end of life. The methodology adopted is composed of three steps, namely a design phase, a simulation of the solar home systems' performance and a life cycle assessment. The analysis aims to point out the main advantages, features, and challenges of lithium-ion batteries, considered as a benchmark, compared with other innovative devices. As the environmental sustainability of these systems is affected by the solar radiation intensity during the year, a sensitivity analysis is performed varying the latitude of the installation site in Europe. For each site, both isolated and grid-connected solar home systems have been compared considering also the national electricity mix. A general overview of the results shows that, regardless of the installation site, solid state nickel cobalt manganese and nickel cobalt aluminium lithium-ion batteries are the most suitable choices in terms of sustainability. Remarkably, other novel devices, like sodium-ion batteries, are already competitive with them and have great potential. With these batteries, the solar home systems' eco-profile is generally advantageous compared to the energy mix, especially in on-grid configurations, with some exceptions. [ABSTRACT FROM AUTHOR]

• First power system study considering regional differences in cost of capital. • System design is significantly affected compared to homogeneous reference. • Levelized costs of wind power decrease. • Levelized costs of solar photovoltaic increase. • Levelized costs of electricity are unevenly distributed across Europe. In order to reduce greenhouse gas emissions of the power sector, high shares of renewable power sources need to be integrated into existing systems. This will require vast amounts of investments. Cost of the capital needed for these investments are unevenly distributed among European regions. They show a clear North-South and West-East divide, which has not exhibited significant signs of narrowing in recent years. Power system studies investigating a continent-wide European power system, however, usually assume homogeneous cost of capital. The objective of this paper is to investigate how regional differences in cost of capital affect the result of these studies with respect to the optimal power system design. Our analysis is based on power system optimization with inhomogeneous cost of capital in Europe. We find that assuming homogeneous cost of capital leads to estimates on the levelized costs of electricity in a highly renewable European power system, which are too conservative. The optimal system design is significantly affected compared to an inhomogeneous scenario. In particular, we show that inhomogeneous cost of capital favors overall wind power deployment in the case of Europe, while the investment in solar power decreases. [ABSTRACT FROM AUTHOR]

Reanalysis data such as MERRA and MERRA-2 are commonly used to derive solar and wind power generation time series, and to estimate their resource potentials. However, the spatial resolution of the reanalysis data (0.5° latitude x 0.625° longitude for MERRA-2) is not sufficient for small-scale energy system models (e.g. states and cities), nor for siting potential projects. This paper uses the MERRA-2 reanalysis data in combination with additional data sources for land-use, topography, and protected areas, in order to obtain accurate global resource potential maps with a spatial resolution of 15 arcseconds. We also generate time series for individual cells of the rasters and identify the best locations for future wind and solar projects. The results are validated against measured hourly generation data of wind and photovoltaic power plants in Europe. [ABSTRACT FROM AUTHOR]

Besides continuous implementation of concentrating solar power plants (CSP) in Europe, which stipulate cost reduction by mass production effects, further R&D activities are necessary to achieve the cost competitiveness to fossil power generation. The European Concentrated Solar Thermal Roadmap (ECOSTAR) study that was conducted by European research institutes in the field of CSP intends to stipulate the direction for R&D activities in the context of cost reduction. This paper gives an overview about the methodology and the results for one of the seven different CSP system concepts that are currently under promotion worldwide and considered within ECOSTAR. The technology presented here is the parabolic trough with direct steam generation (DSG), which may be considered as an evolution of the existing parabolic systems with thermal oil as heat transfer fluid. The methodology is explained using this exemplary system, and the technical improvements are evaluated according to their cost-reduction potential using a common approach, based on an annual performance model. Research priorities are given based on the results. The simultaneous implementation of three measures is required in order to achieve the cost-reduction target: Technical improvement by R&D, upscaling of the unit size, and mass production of the equipment. [ABSTRACT FROM AUTHOR]