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Currently, wind energy is one of the most important sources of renewable energy. Offshore locations for wind turbines are increasingly exploited because of their numerous advantages. However, offshore wind farms require high investment in maintenance service. Due to its complexity and special requirements, maintenance service is usually outsourced by wind farm owners. In this paper, we propose a novel approach to determine, quantify, and reduce the possible conflicts of interest between owners and maintenance suppliers. We created a complete techno-economic model to address this problem from an impartial point of view. An iterative process was developed to obtain statistical results that can help stakeholders negotiate the terms of the contract, in which the availability of the wind farm is the reference parameter by which to determine penalisations and incentives. Moreover, a multi-objective programming problem was addressed that maximises the profits of both parties without losing the alignment of their interests. The main scientific contribution of this paper is the maintenance analysis of offshore wind farms from two perspectives: that of the owner and the maintenance supplier. This analysis evaluates the conflicts of interest of both parties. In addition, we demonstrate that proper adjustment of some parameters, such as penalisation, incentives, and resources, and adequate control of availability can help reduce this conflict of interests. • Reliability of OWF analysis for owners and maintenance suppliers. • Consequences of outsourced maintenance for owners and maintenance suppliers. • Costs and profits analysis of OWF owners and maintenance suppliers. • A novel approach to reduce the conflict of interests between both parties. [ABSTRACT FROM AUTHOR]

Seasonal thermal energy storage can provide flexibility to smart energy systems and are characterised by low cost per unit energy capacity and varying applicability to different geographical and geological locations. This paper identifies applications and reviews modelling approaches for seasonal thermal energy storage technologies in the context of their integration in smart energy systems. An example district-scale smart energy system is outlined to analyse three potential smart applications for seasonal thermal energy storage: (i) utilisation of multiple renewable energy sources, (ii) integrating waste heat and cool, and (iii) electrical network balancing. The rest of the paper focuses on modelling methods for borehole thermal energy storage and aquifer thermal energy storage in energy system analysis. Energy system tools for planning and detailed design stages are reviewed. Gaps are identified for planning tools in control strategies and open code. TRNSYS is found to be the dominant detailed design tool used to model large-scale borehole thermal energy storage. Co-simulation methods involving detailed physics and power system tools are also reviewed, including studies using co-simulation of a detailed physics tool to represent borehole or aquifer thermal energy storage alongside an energy system tool. A gap exists in co-simulation of borehole or aquifer thermal energy storage models with energy system tools capable of simulating both electricity and heat. In conclusion, seasonal thermal energy storage can provide flexibility through different smart applications at different scales, and modelling approaches using co-simulation methods offer a promising avenue for capturing potential benefits of these smart applications. • Three smart applications of seasonal thermal energy storage are explored. • Integrating multiple energy sources, waste heat, and electricity network balancing. • Modelling STES using planning and detailed energy system tools is reviewed. • TRNSYS dominates studies in the detailed energy system modelling tools category. • Co-simulation methods can capture potential benefits of smart applications. [ABSTRACT FROM AUTHOR]

Biobased products are complete or partial derivatives from naturally occurring/growing materials such as agricultural, plants, and forest materials and serve as an alternative to traditional product derivatives of petroleum. Technically, biobased product counterparts can replace almost every fossil resource-based industrial material. Adopting life cycle analysis and circular economy concepts has also accelerated the move towards biobased products. It meets the criteria for easy recycling and can facilitate the shift from linear fossil-based productions to a greener circular economy. In line with the Renewable and Sustainable Energy Reviews (RSER) policy, this Virtual Special Issue (VSI) published two types of articles, high-quality review papers and original research papers with a strong review component. After a rigorous peer-review process, 32 articles were accepted and published in this VSI. This editorial overview these articles and examines their contribution to the field. This RSER VSI has contributed with new insights on value-added biobased products from various bioresources to their applications, technical challenges and advancement in a sustainable manner. • VSI is focused on the recent development of biobased biorefineries. • Greener technologies offering biobased products. • Sustainable bioprocesses and bioproducts development from bioresources. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) is a viable technique to address food waste (FW) problems by converting FW into sustainable energy. Despite the advantages of the AD process, large-scale AD plants like in Germany and the USA have not been developed in Australia. Therefore, this paper aims to study the technological, economic, and environmental feasibility of sustainable energy production from household FW in Australia. In addition, this paper discusses the different waste to energy (WtE) technologies along with the operational parameters as well as the challenges in developing a biogas plant. The energy and economic potential analysis of the AD process indicates that the processing of 10% FW from Australian states and territories can generate 1.22 GWh to 35.4 GWh electricity which can subsequently earn AUD 0.54 million to AUD 15.7 million revenue per year. The greenhouse gas (GHG) emissions analysis indicates that conversion of the 10% of Australian FW has the potential to lower GHG emissions by 639,852 tonnes per annum. Hence, it can be said that FW plays a vital role as a promising source of sustainable energy and is capable of benefiting the country's economy significantly and reducing GHG emissions. • FW is a potential source of sustainable energy. • AD is a useful waste to energy process for producing clean energy. • Conversion of FW into energy can significantly lower GHG emissions. [ABSTRACT FROM AUTHOR]

The paper presents an enhanced scheme to control the dynamic response that can be delivered by distributed generation (DG) and renewable energy resource (RER) to be more reliable and stable than other electric systems. Robust Adaptive Emulated- Controller (RAEC) has been included to control and tune the adoption of controller parameters across a broad range of operating conditions. Some existing challenges related to high loading profiles that will be handled by new performance features. The objective of paper is to propose robust adaptive emulated-controller that is incorporated with high-speed fluctuations and dynamic energy systems. That can achieve an integrated system to reflect the enhanced structure and operation of electric systems, in addition to, Enhanced Mud Layers (EML) optimization will be applied to control and optimize the performance parameters. • A novel robust system is proposed to enhance the sustainable energy and renewables operation and dynamic performances. • The proposed technique supports the implications of energy resources for the sustainable communities and networks. • There are scenarios to consider the changes in the loading profiles, beside to the uncertain conditions. • The obtained results by the proposed technique have been appraised and examined. [ABSTRACT FROM AUTHOR]

As the discourse surrounding 100% renewable energy systems has evolved, several energy system modelling tools have been developed to demonstrate the technical feasibility and economic viability of fully sustainable, sector coupled energy systems. While the characteristics of these tools vary among each other, their purpose remains consistent in integrating renewable energy technologies into future energy systems. This paper examines two such energy system models, the LUT Energy System Transition model, an optimisation model, and the EnergyPLAN simulation tool, a simulation model, and develops cost-optimal scenarios under identical assumptions. This paper further analyses different novel modelling approaches used by modellers. Scenarios are developed using the LUT model for Sun Belt countries, for the case of Bolivia, to examine the effects of multi and single-node structuring, and the effects of overnight and energy transition scenarios are analysed. Results for all scenarios indicate a solar PV dominated energy system; however, limitations arise in the sector coupling capabilities in EnergyPLAN, leading it to have noticeably higher annualised costs compared to the single-node scenario from the LUT model despite similar primary levelised costs of electricity. Multi-nodal results reveal that for countries with rich solar resources, high transmission from regions of best solar resources adds little value compared to fully decentralised systems. Finally, compared to the overnight scenarios, transition scenarios demonstrate the impact of considering legacy energy systems in sustainable energy system analyses. • Direct comparison between two of the most widely used energy system models. • Reduction of spatial resolution in modelling does not necessarily lower costs. • High interregional interconnection shows little added value for Sun Belt countries. • Overnight scenarios undervalue annualised costs compared to transition scenarios. • Full LHV alignment compared to mixed LHV/HHV demonstrates minor result differences. [ABSTRACT FROM AUTHOR]

Offshore wind energy is recognised globally as a viable alternative to finite energy sources. However, large cost reductions are still needed, particularly in the Operations & Maintenance (O&M) phase, which currently accounts for about 30% of the cost of offshore wind. For large component replacements, a jack-up vessel is often leased from the spot market, resulting in high costs and low utilisation. These costs can be lowered when multiple wind farm service providers would share the resources needed to employ jack-up vessels. In this paper, we analyse two types of resource sharing, as an alternative to each service provider leasing its own vessel: (i) vessel purchasing and sharing and (ii) the combined use of vessel and harbour sharing. We design a simulation model and include stochastic processes such as weather patterns and component failures. Results show that cost benefits up to 45% can be achieved compared to a leasing policy, depending on the number of wind farm service providers involved and on the geographical distance between offshore wind farms. Moreover, it is shown that the jack-up vessel should not be fully utilised to minimise costs. The performance benefits of harbour sharing in addition to vessel sharing are generally small, but become more significant if the network faces considerable congestion. Results are illustrated using a case study based on a setting in the Western North Sea. • Three policies are studied for the deployment of jack-up vessels for o_shore wind farm maintenance. • Collaboratively purchasing and sharing a jack-up vessel outperforms individually leasing it. • Adding harbour facility sharing among operators only leads to slightly further cost reductions. • Operators should not focus on high jack-up utilisation as this results in unnecessarily high costs. • Yearly cost and the best coalition size are particularly sensitive to the replacement time and failure rate of the gearbox. [ABSTRACT FROM AUTHOR]

Abstract The implementation of waste to energy technology such as the production of biogas from animal waste has been considered as one of the best means to achieve sustainable energy development goals in many developing countries including Indonesia. In the past several years, the rapid increment in the number of animal husbandries in Indonesia could potentially provide a considerable amount of feedstock for the generation of biogas. Therefore, this article is aimed at highlighting the potential application of waste to energy technology via the production of biogas from animal waste as an alternative source of power generation in Indonesia. Here, Indonesia's energy mix and several issues regarding waste management is comprehensively reviewed. Additionally, this article also discusses the current status in Indonesia's energy generation from new and renewable resources, especially from waste. Hence, several key technologies on how to utilize waste for power generation are presented. Based on the analyses, numerous opportunities could be explored in terms of turning animal waste to energy by biogas production in Indonesia. It is estimated that about 9597.4 Mm3/year of biogas could potentially be generated from animal waste in Indonesia. This large amount of biogas production could be utilized to generate electric power up to 1.7 × 106 KWh/year. Finally, this paper also highlights several main challenges faced in the implementation of large-scale biogas production in Indonesia. Graphical abstract fx1 Highlights • Current issues in Indonesia's high-energy demand and waste management. • Recent development in waste to energy technologies in Indonesia. • Biogas production from organic waste as a promising renewable energy source. • The potential of biogas from animal waste for electricity generation in Indonesia. • Future prospects and challenges for large-scale biogas production in Indonesia. [ABSTRACT FROM AUTHOR]

Abstract As investments and policies that promote renewable energy (RE) projects in electricity systems are most often grounded on the goal of reducing emissions of greenhouse gases, and actual investment and policy decisions are shaped by the estimates of the accrued emissions savings, it is crucial that these estimates are as accurate as possible. In this paper we compare different econometric models that estimate the amount of carbon abated due to RE in terms of their results and their inherent methodological benefits and drawbacks. Specifically, we use the British, French and Spanish grids as case studies for the application of a selection of econometric models and compare the resulting CO2 abatement estimates. We find that, across the three markets, estimates can vary substantially across the different models – this can lead to an over or underestimation of the emissions abated by RE. Overall, our results highlight the need for choosing econometric specifications that lead to results that are congruent with the operational framework of the examined power systems. Highlights • We compare three econometric models to estimate marginal emissions factors (MEF) in power systems. • Focus on CO2 reductions due to renewable electricity generation – wind and solar. • We use the British, French and Spanish grids as case studies. • In each country MEF estimates vary substantially according to the model that is used. [ABSTRACT FROM AUTHOR]

Abstract During recent decades with the power system restructuring process, centralized energy sources are being replaced with decentralized ones. This phenomenon has resulted in a novel concept in electric power systems, particularly in distribution systems, known as Distributed Generation (DG). On one hand, utilizing DG is important for secure power generation and reducing power losses. On the other hand, widespread use of such technologies introduces new challenges to power systems such as their optimal location, protection devices' settings, voltage regulation, and Power Quality (PQ) issues. Another key point which needs to be considered relates to specific DG technologies based on Renewable Energy Sources (RESs), such as wind and solar, due to their uncertain power generation. In this regard, this paper provides a comprehensive review of different types of DG and investigates the newly emerging challenges arising in the presence of DG in electrical grids. Highlights • Proposing a comprehensive review on Distributed Generations (DGs). • Investigating the impact of DGs on the protection of distribution systems. • Reviewing the voltage regulation methods in the presence of DGs. [ABSTRACT FROM AUTHOR]

Abstract This review brings to the fore the fast-growing and significant phenomenon of community and private sector renewable energy partnerships, which constitute a fundamental building block of the global renewable energy transformation. This paper theoretizes on this issue by identifying six archetypes of local community–private sector renewable energy partnerships, namely knowledge sharing, private finance, local consumption, land seeking, community employment, and lease architypes. These archetypes are discussed with relation to key variables influencing partnership formation and perpetuation as part of the wider discussion regarding renewable energy partnerships between local communities and the private sector and the role they play in energy transition to a low-carbon society. Highlights • Community-private partnerships are key drivers of renewable energy transition. • This study identifies community-private partnership archetypes in renewable energy. • The different archetypes are characterized by varying involvement of the actors. • The study characterizes variables that influence the partnership archetypes choice. [ABSTRACT FROM AUTHOR]

Abstract The depletion of fossil fuels and the environmental concerns associated with their extraction and utilisation have heightened the need for alternative sustainable energy resources. Microwave-assisted pyrolysis (MAP) of biomass is one of the promising sustainable methods for the production of bio-oil and value-added chemicals. This conversion technique has been widely studied at lab-scale and has demonstrated good potential in producing bio-oils of high quality. The main objective of this review paper is to examine the main parameters that affect MAP yields, whilst assessing the options for optimising the identified parameters for maximum bio-oil production. The results show that factors such as pyrolysis temperature, microwave power, microwave absorbent type and catalysis greatly influence the bio-oil yield. Pyrolysis holding time, feedstock particle size, purging gas type and flowrate also affect the bio-oil yield, though to a lesser extent. It is also established that the MAP technique is highly scalable and has several environmental benefits. The review concludes that the interdependence of various factors must be studied in detail in order to optimise bio-oil yield. There is therefore a need to develop an optimised pilot scale MAP system in a bid to determine the techno-economic viability of upscaling the technology for commercialisation. The use of Response Surface Methodology (RSM) via the Central Composite Design (CCD) approach is recommended for the optimisation of MAP systems because it takes into account the interaction between the variables that affect bio-oil yield. This review could be used to guide future research related to the design, simulation, fabrication and operation of pilot scale MAP reactors. Highlights • Parameters affecting bio-oil yield in MAP of lignocellulosic biomass are reviewed. • Environmental impacts of MAP systems are reviewed. • The RSM via CCD approach is recommended for optimisation of MAP systems. • Upscaling of optimised MAP systems for bio-oil production is recommended. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Abstract As more renewable energy is developed, energy storage is increasingly important and attractive, especially grid-scale electrical energy storage; hence, finding and implementing cost-effective and sustainable energy storage and conversion systems is vital. Batteries of various types and sizes are considered one of the most suitable approaches to store energy and extensive research exists for different technologies and applications of batteries; however, environmental impacts of large-scale battery use remain a major challenge that requires further study. In this paper, batteries from various aspects including design features, advantages, disadvantages, and environmental impacts are assessed. This review reaffirms that batteries are efficient, convenient, reliable and easy-to-use energy storage systems (ESSs). It also confirms that battery shelf life and use life are limited; a large amount and wide range of raw materials, including metals and non-metals, are used to produce batteries; and, the battery industry can generate considerable amounts of environmental pollutants (e.g., hazardous waste, greenhouse gas emissions and toxic gases) during different processes such as mining, manufacturing, use, transportation, collection, storage, treatment, disposal and recycling. Battery use at a large scale or grid-scale (>50 MW), which is widely anticipated, will have significant social and environmental impacts; hence, it must be compared carefully with alternatives in terms of sustainability, while focusing on research to quantify externalities and reduce risk. Alternatives such as pumped hydro and compressed air energy storage must be encouraged because of their low environmental impact compared to different types of batteries. Highlights • Review of batteries from various aspects such as design features, advantages, disadvantages, and environmental impacts. • Study of the share of batteries in the use of raw materials and the depletion of natural resources. • Study of the role of batteries in causing the environmental pollutants, greenhouse gas (GHG) emissions, and harmful effects on public health. [ABSTRACT FROM AUTHOR]

Abstract The offshore renewable energy sector has challenging requirements related to the physical simulation of the ocean environment for the purpose of evaluating energy generating technologies. In this paper the demands of the wave and tidal energy sectors are considered, with measurement and characterisation of the environment explored and replication of these conditions described. This review examines the process of advanced ocean environment replication from the sea to the tank, and rather than an exhaustive overview of all approaches it follows the rationale behind projects led, or strongly connected to, the late Professor Ian Bryden. This gives an element of commonality to the motivations behind marine data acquisition programmes and the facilities constructed to take advantage of the resulting datasets and findings. This review presents a decade of flagship research, conducted in the United Kingdom, at the interfaces between physical oceanography, engineering simulation tools and industrial applications in the area of offshore renewable energy. Wave and tidal datasets are presented, with particular emphasis on the novel tidal measurement techniques developed for tidal energy characterisation in the Fall of Warness, Orkney, UK. Non-parametric wave spectra characterisation methodologies are applied to the European Marine Energy Centre's (EMEC) Billia Croo wave test site, giving complex and highly realistic site-specific directional inputs for simulation of wave energy sites and converters. Finally, the processes of recreating the resulting wave, tidal, and combined wave-current conditions in the FloWave Ocean Energy Research Facility are presented. The common motivations across measurement, characterisation, and test tank are discussed with conclusions drawn on the strengths, gaps and challenges associated with detailed site replication. Highlights • State-of-the-art review of ocean measurement, analysis, and replication techniques. • Decade of flagship research presented, led by the late Professor Ian Bryden. • Novel measurement techniques presented for tidal site characterisation. • Advanced ocean replication methodologies described, with recent results presented. [ABSTRACT FROM AUTHOR]

Abstract Offshore wind is a source of clean, renewable energy of great potential value to the power industry in the context of a low carbon society. Rapid development of offshore wind energy depends on a good understanding of technical issues related to offshore wind turbines, which is spurring ongoing research and development programmes. Foundations of offshore wind turbines present one of the main challenges in offshore wind turbine design. This paper reviews the present state of knowledge concerning geotechnical and structural issues affecting foundation types under consideration for the support structures of offshore wind turbines, and provides recommendations for future research and development. Highlights • Reviews the technology development and designs of offshore wind turbine foundations. • Discusses geotechnical and structural issues affecting the foundations. • Provides recommendations for future R&D to improve the effectiveness of different designs. [ABSTRACT FROM AUTHOR]

Abstract Although passive building envelope systems dominate contemporary building design, active building envelope (ABE) research, development, and deployment are rapidly growing and present many new ways to address building energy efficiency at the façade level. This paper presents a comprehensive review on the state-of-art-research on ABEs for improving building energy efficiency. First, a clarified concept of ABE is put forward based on two conditions: The ability of lowering cooling/heating loads in buildings, and performing energy transformation as the key judging factors. Second, four major categories of ABEs, namely air-based, water-based, solid-based and kinetic façades, are discussed in terms of their system structural and functional features as well as system performance. In addition, a statistical analysis is performed for a better understanding of current research focus, general trends, as well as research methods. It is found that technical research on ABEs has dramatically increased but the ratio of ABE to general façade studies remains stable. In terms of research methods and approaches, numerical simulations are dominant. Some specific comments on limitations of current ABE studies and general suggestions for the future studies are discussed. Future work suggests the need for contributions from a wide range of scientists, engineers, and architects in the building industry and beyond to push forward building energy efficiency. Highlights • A new and effective definition of active building envelope is proposed. • Research tendency, distributions and study methods offer a clear map of active building envelopes. • A state-of-the-art review and discussion is presented for active building envelopes. • Outlooks and recommendations for active envelopes can facilitate its further development. [ABSTRACT FROM AUTHOR]

Abstract 1.1 billion of the world's population still does not have access to electricity in the 21st century. Most of that population resides in the rural communities in developing countries in South Asia, Latin America and Sub-Saharan Africa. Access to electricity can eliminate existing problems related to health, education, social life, economy and the environment, and can increase the income of underserved communities. Most of the yet to be energized regions are in remote, isolated areas, that cannot be serviced through the central grid. While decentralized diesel generators can potentially be installed in these areas, they have a poor effect on climate change mitigation. Clean renewable energy alternatives for off-grid systems are being deployed to reduce the non-electrification rate in the world, and The United Nation Foundation's 2030 Agenda has the objective of universal access to electricity by 2030. While there has been some progress towards that goal, the challenges are countless. If no changes in models, policies and practices are made, the universal access objective will not be achieved, especially in Sub-Saharan Africa that has a level of electrification projection of 30% by 2030. To determine the necessary changes, this paper reviews the rural electrification initiatives in eight developing countries, from Asia to Sub-Saharan Africa to Latin America, and aims to provide an assessment of their success and to discuss the lessons that can be learned and applied on future initiatives. Highlights • Different approaches to first-access systems have been studied. • The role of policy-making and its impact on project success is highlighted with real examples. • Experiences of different countries and different regions have been compared. • Lessons learned from these experiences are shared and keys parameters for more effective project development have been shared. • The research direction of this field and possible future work are documented. [ABSTRACT FROM AUTHOR]

Abstract The purpose of this paper is to highlight the most demanding aspects of grid interconnection of marine energy installations while at the same time providing an updated overview and comparative analysis of the connection requirements of eight European Grid Codes. Therefore, the major issues related to marine energy installations will be summarized as well as the requirements of this type of generation. Besides, the extent to which current Grid Codes include marine energy technologies will be analysed jointly with the need of harmonization of different Grid Codes into a generalised European grid code. Apart from this, several future trends of marine energy technology and its interconnection will be provided for the final discussion. Highlights • Capacity limits and critical power quality issues where not originally planned. • Impacts: limited dispatchability, electrical grid stress, high penetration effects. • Long submarine cables reduce precise voltage or reactive power control capability. • European Grid codes compared: only in UK and Germany offshore treated separately. • ENTSO-E effort for harmonization by setting common requirements for grid connection. [ABSTRACT FROM AUTHOR]

Abstract Studies of the production and use of biomass of perennial plants as energy feedstock have been conducted by Polish researchers for over 20 years. One genus of particular interest is Salix spp. L., which occurs naturally in the temperate zone. Experiments concerning the productivity of willow have been conducted mainly on small-scale experimental fields, but there have been studies conducted on large-scale, experimental and commercial plantations. An analysis of the scientific literature found that the mean willow biomass yield was 8.5 Mg ha−1 y−1 d.m. The mean productivity on small-scale experimental fields (11.4 Mg ha−1 y−1 d.m.) was much higher than on large-scale fields (5.7 Mg ha−1 y−1 d.m.), by 4.5, 7.2 and 7.5 Mg ha−1 y−1 d.m. for biennial, triennial and quadrennial harvest cycles, respectively. Meanwhile, when the optimum yield-generating agents were applied (such as cultivar/clone, fertilisation rate or planting density) higher yields were achieved (by 48% and 72%) in small and large-scale experiments, respectively. Considering only the harvest cycle, the highest mean productivity was achieved in the longer cycles, triennial for small-scale experiments and biennial and triennial for large-scale experimental and commercial plantations. Studies conducted using small-scale experiments still play a very important role in the initial phase of studies on the yield-generating factors under analysis and enable their verification in multiple combinations. Meanwhile, farmers and researchers, as well as national policy-making institutions, value data from commercial plantations. However, there have been few papers published so far on the productivity of such plantations in Poland, particularly those describing studies conducted in similar soil conditions in successive harvest cycles. Moreover, studies should be conducted at sites with poor quality soil, i.e. intended for growing energy crops, where the yield is usually smaller than on good soils used in agriculture for the production of food and fodders. Graphical abstract fx1 Highlights • Studies of the productivity of willow were conducted in Poland for over 20 years. • Various clones and cultivars were tested in 1-, 2-, 3-, 4- and 5-year cycles. • The mean yield of willow in small-scale experiments was 11.4 ± 6.0 Mg ha−1 y−1 d.m. • The highest yield was achieved in 3-year harvest cycles. • The mean yield in large-scale experiments was smaller by 50% than in small-scale. [ABSTRACT FROM AUTHOR]

Abstract Microgrids for rural electrification are expected to play a key role in achieving global energy access goals. However, the high cost of stand-alone microgrids intended to serve generally poor communities remains a key barrier to their deployment, while design and operation is challenging, given generally low diversity of loads and generators, and often high penetrations of variable renewable generation. Current practices for providing electricity access still often focus on the supply side with an emphasis on ensuring the reliability, affordability and security of electricity supply to meet user demand. This supply focus misses some key opportunities on the demand-side for providing low cost and reliable energy service delivery. In particular, rural communities may place very different relative values on various energy services, while there may be considerable flexibility in terms of when some of these energy services are delivered; due to inherent energy storage in the end-use equipment, or user willingness to shift the energy service itself. This paper presents a novel characterisation framework for energy services based on their relative flexibility and consumer prioritisation. Detailed survey data from 154 households across five microgrid sites in Nepal is used to test this framework, and assess the potential insights that it can provide for microgrid designers and operators seeking to reduce costs and improve reliability when serving poor rural communities. The five microgrids represent very different energy services and microgrid technology contexts, yet all would appear to have demand-side management opportunities that can trade-off cost and reliability and prioritise loads according to user preferences. Highlights • A new energy service characterisation framework has been developed, based on end-users' prioritisation and flexibility. • The framework will form the basis for improved demand-side management strategies for standalone microgrids. • 154 end-users' key energy service needs from five microgrids have been categorised using the framework, forming a useful basis for modelling these microgrids. [ABSTRACT FROM AUTHOR]

Abstract Biomass is a potential energy source for the diversification of the Brazilian energy matrix. In this context, the biogas produced from the anaerobic digestion of residues is a relevant renewable resource that plays a significant role in the mitigation of environmental problems and the local generation of electric energy. This review presents the scenario of the biogas production and electricity distributed generation within the Brazilian context. Firstly, it presents an overview of the electric energy generation from biogas and the Brazilian plants that compose this electric matrix. Secondly, the main technologies to produce biogas and the possibilities of its use, followed by the comparison of technologies for distributed generation of electric energy from biogas in the Brazilian market. To illustrate the application of biogas technology, this paper presents a case study of a biogas plant operation and its connectivity to the grid, the Colombari Farm. The information presented here aims to enhance and to foment the recovering of biomass residues to produce biogas via anaerobic digestion and its utilization to generate electricity. Although the case study considers a specific plant in Brazil, the information and results presented can be applied to others areas of the country or regions of the world, so contributing to promote the expansion of biogas plants to generate electricity. Finally, a future perspectives section describes the practical implications of the biogas production and electricity generation in rural and urban areas and its contribution to the implementation of Brazilian environmental and social policies. This review also is useful to support the research development of biogas for electricity production. Graphical abstract fx1 Highlights • Biogas applied Distributed Generation in the Brazilian Market. • Different types of biodigesters and its biogas production. • Technologies for biogas production and electric power generation. • Study of the first biogas generation plant: Colombari Farm at Parana, Brazil. [ABSTRACT FROM AUTHOR]

Abstract Long-time search for green energy as a replacement of the depleting conventional sources to the eternal power demand still remains as an unanswered question. But the steady growth in the contribution of solar energy towards the electrical power generation for the past three decades have persuaded many researchers to consider it as a viable option. However, the power harnessed from solar PV is low due to its less conversion efficiency. Therefore, it is necessary to perform some critical analysis on the factors improving the efficiency of the solar PV system. In this paper, an attempt is made in performing a detailed comprehensive review on the factors affecting the efficiency of solar cell. A detailed review is carried out on basic material used for solar cells, Maximum Power Point Tracking (MPPT) Techniques and the DC-DC converters used for power conversion. Highlights • Efficiency of PV system depending on materials used for manufacturing. • Efficiency of PV system depending on Maximum power point tracking techniques. • Comparative analysis of MPPT techniques on various factors. • Efficiency of PV system depending on Converter topologies employed. [ABSTRACT FROM AUTHOR]

Abstract This paper proposes and analyses a novel energy management system for buildings connected in a micro-grid, by considering electric vehicles as active components of such energy scheme. Renewable energy sources, PV, energy storage systems and bidirectional electricity exchange with the buildings and the grid are taken into account. The considered energy scheme, Building to Vehicle to Building, is analysed by including both buildings and mobility consumptions in the energy balance. Three different management system scenarios, designed to analyse the role of electric vehicles as electricity vector among buildings integrating PV panels and electrical storages, are analysed through a case study analysis. To this aim, a dynamic simulation model, implemented in MatLab, is suitably developed for the assessment of the energy demands and loads of the building, as a function of the considered electric vehicles energy use patterns. Simulation results show that the proposed energy management systems improves the building grid reliance and the grid electricity consumption is remarkably reduced up to 45% and 77% depending on the proposed scenarios. Their energy exchange options also enhanced the energy-matching indexes. The economic analysis highlights the economic viability of the system, as well as the need of suitable funding policies to support the development of such micro-grid systems. Highlights • Modelling the impact of EVs toward the NZEB goal at micro-grid level. • Investigating the electricity transfer among multiple buildings by the EV battery. • Development of a dynamic simulation model of the proposed novel V2B energy scheme. • Development of a case study analysis based on 3 generation and storage scenarios. • Encouraging energy and economic performance of the proposed scheme are obtained. [ABSTRACT FROM AUTHOR]

Abstract The analysis of power systems with a significant share of renewable generation using probabilistic tools is essential to appropriately consider the impact that the variability and intermittency of the renewable generation has on the grid. This paper provides a critical assessment and classification of the available probabilistic computational methods that have been applied to power system stability assessment (including small and large disturbance angular stability, voltage and frequency stability). A probabilistic analysis framework with a state-of-the-art review of the existing literature in the area is presented comprising of a review of (i) input variable modelling, (ii) computational methods and (iii) presentation techniques for the output/results. The most widely used probabilistic methods in power system studies are presented with their specific application areas, advantages, and disadvantages. The purpose of this overview, classification, and assessment of the existing methods is to identify the most appropriate probabilistic methods to be used in their current forms, or suitably modified, for different types of stability studies of power systems containing renewable generation. Highlights • Uncertainty modelling techniques for independent variables. • Uncertainty modelling techniques for correlated variables. • Probabilistic techniques applied to power system stability. • Identification of efficient computational techniques. • Future research needs in this area. [ABSTRACT FROM AUTHOR]

Abstract The study presents an effort to classify the territories of a specific area, according to similarities in the estimated potential of their renewable sources, considering also their economic and sociodemographic structure and their geographic features. Specifically, the paper focuses on the area of EU28 and Switzerland and uses as basis for the analysis, data estimating the potential of renewable energy sources collected and elaborated in the framework of the project HotMaps (Horizon 2020). The method used to group the territorial units is cluster analysis, and specifically the k-means algorithm. The data present some interesting patterns and the territories of EU28 and Switzerland at NUTS3 level are classified into 17 clusters. The analysis shows the presence of heterogeneity within national borders and among territories comprised in the macro regions target of specific EU programmes, specifically the Adriatic-Ionian region, the Alpine region, the Baltic Sea region and the Danube region. The results of this research are meant to be used by European policy makers in developing more focused transnational renewable energy policies and strategies. Highlights • Spatial patterns in the distribution of renewable energy potential in EU28 exist. • EU28 regions can be grouped into 17 clusters. • Renewable energy potential is distributed heterogeneously within countries. • There are cross-border similarities in the distribution of renewable energy potential. • Policy recommendations on renewable energy planning can be drawn from the findings. [ABSTRACT FROM AUTHOR]

Abstract The recycling of carbon dioxide (CO 2) into synthetic fuels via Power-to-Gas (PtG) could represent an important instrument for achieving the complete decarbonization of the energy sector. To address such issue, this paper calculates the investments in PtG units, grid reinforcements and renewable installations that allow the almost complete recycling of the CO 2 emissions of a countrywide electric power system. Furthermore, this work evaluates the feasibility of gas and electric operations in the new system configuration. The analysis is enabled by coupled gas and electric network modelling. The necessary PtG station installations and overhead line reinforcements are identified via scenario-based cost optimization. Hourly operations of electric power plants are scheduled as a sequence of day-head security-constrained unit commitment problems. A transient gas flow model assesses the capability of the gas network to act as short- and long-term storage of synthetic gas. The developed framework is applied to the electric and gas transmission networks of Great Britain, whose investments and operations are investigated for increasing renewable capacity levels based on the 2030 Gone Green case. Results show that almost complete CO 2 recycling is achieved if the installed renewable capacity is approximately three times as large as the 2030 Gone Green estimates. The investments comprise 114 GW of PtG capacity and the construction of 23 electric parallel lines. Remarkably, gas network operations do not represent a limit to the storage of large amount of synthetic methane. Moreover, PtG stations are preferentially installed at locations with large RES capacity and foster large renewable penetration; only small curtailments occur even for large renewable capacity levels. These results support decision makers by quantifying the techno-economic implications of the presented extensive CO 2 recycling strategy. Highlights • We investigate the techno-economic implications of extensive CO 2 recycling. • Complete CO 2 recycling is achievable via PtG if enough RES power is available. • CO 2 recycling in the British system requires 114 GW of PtG and 23 new power lines. • Gas network operations do not limit the injection of synthetic methane. • The gas infrastructure can serve as long-term energy storage of RES. [ABSTRACT FROM AUTHOR]

Abstract Blockchains or distributed ledgers are an emerging technology that has drawn considerable interest from energy supply firms, startups, technology developers, financial institutions, national governments and the academic community. Numerous sources coming from these backgrounds identify blockchains as having the potential to bring significant benefits and innovation. Blockchains promise transparent, tamper-proof and secure systems that can enable novel business solutions, especially when combined with smart contracts. This work provides a comprehensive overview of fundamental principles that underpin blockchain technologies, such as system architectures and distributed consensus algorithms. Next, we focus on blockchain solutions for the energy industry and inform the state-of-the-art by thoroughly reviewing the literature and current business cases. To our knowledge, this is one of the first academic, peer-reviewed works to provide a systematic review of blockchain activities and initiatives in the energy sector. Our study reviews 140 blockchain research projects and startups from which we construct a map of the potential and relevance of blockchains for energy applications. These initiatives were systematically classified into different groups according to the field of activity, implementation platform and consensus strategy used. 1 1 A summary of the research projects reviewed in this study can be found in the Appendix A. Opportunities, potential challenges and limitations for a number of use cases are discussed, ranging from emerging peer-to-peer (P2P) energy trading and Internet of Things (IoT) applications, to decentralised marketplaces, electric vehicle charging and e-mobility. For each of these use cases, our contribution is twofold: first, in identifying the technical challenges that blockchain technology can solve for that application as well as its potential drawbacks, and second in briefly presenting the research and industrial projects and startups that are currently applying blockchain technology to that area. The paper ends with a discussion of challenges and market barriers the technology needs to overcome to get past the hype phase, prove its commercial viability and finally be adopted in the mainstream. Highlights • One of the first systematic reviews of blockchains in the energy sector. • Overview of key principles of distributed ledger technologies. • Detailed review of energy applications and use cases such as P2P energy trading. • Discussion on benefits and limitations of blockchains for energy applications. • Review & classification of around 140 blockchain commercial and research initiatives. [ABSTRACT FROM AUTHOR]

Abstract The use of renewable energies in the heating and cooling sector in Spanish households is a key strategy to improve the final energy consumption of the country. The main goal of this paper is to identify end-users' decision making factors when making choices about heating and cooling systems, which is essential to deploy renewable energy technologies. Besides, this research analyses empirically the households' awareness, perception and willingness to pay for renewable heating and cooling systems in Spain. To this aim, a survey was conducted and the responses were crossed with a set of socio-demographic parameters of the sampling, showing the influence of different population groups on them. Nowadays, 63% of respondents are familiarised with renewable energy technologies for heating and cooling uses in the Spanish residential sector. More than a half of those respondents who know any renewable energy technologies would pay more for them; the preferred technology is solar thermal energy, followed by biomass. To the best of our knowledge this is the first research in Spain with these characteristics and it provides a better understanding about how to deploy renewable technologies in the Spanish market and can be used for sectoral agents and policy planning purposes. Highlights • Spanish households: a survey analysing the keys to choose heating & cooling systems. • Analysis of awareness, perception and willingness to pay for renewable technologies. • High influence of socio-demographic features of sample in decision-making process. • Election of thermal systems based on comfort and economic criteria – savings & cost. • 63% of population know renewables for thermal uses and 50% would pay more for them. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a literature review on the selected applications of renewable resource and power forecasting models to facilitate the optimal integration of renewable energy (RE) in power systems. This review is drafted on the basis of the selected high quality research publications from the past decade. Although the development of forecast models for RE generation, i.e., wind and solar energy, is a well-researched area, however, the performance of these models is usually evaluated using statistical error metrics. With regard to application, determining the optimality of accurate forecasts in terms of system economics and major planning aspects is an emerging phenomenon, that chalks out the main subject area of this survey. Specifically, the application domains include: 1) optimal power system dispatch (unit commitment, generation scheduling, economic dispatch), 2) optimal sizing of energy storage system, 3) energy market policies and profit maximization of market participants, 4) reliability assessment, and 5) optimal reserve size determination in power systems. The application-oriented review on these vital areas can be used by the power sector for familiarization with the recent trends and for analyzing the impact of forecasting improvement on optimal power system design and operation. Highlights • An application-focused literature review on the role of forecasting models in renewable power system planning and operation. • The study of forecasting in unit commitment, generation scheduling and economic dispatch problems. • Investigation of the impact of forecasting uncertainties in energy market operations. • Study of the application of forecasting in sizing problems, reserve estimation and power system reliability. • The review is drafted on the basis of the high-quality research publications from the past decade. [ABSTRACT FROM AUTHOR]

Abstract Virtual Power Plant combines a wide variety of distributed generation resources and operates them as a unified resource on the energy markets. It gives an economic opportunity to renewable energy-based distributed generation, such as photovoltaic, small hydro or wind, as it can build a bridge to the integration of renewable resources in the wholesale electricity market. In this market, changes in the offers of portfolio electricity technologies affect wholesale electricity prices, since marginal generation costs are transmitted through to the wholesale market. This paper investigates the impact of energy-based distributed generation technologies composition on wholesale electricity prices variations of different EU energy markets by using a Maximum Entropy Econometric estimation procedure. To know how much each unit of electricity produced by each technology can alter the electricity price could be very useful to develop optimal strategies in an electricity technologies portfolio decision. Highlights • Virtual Power Plant (VPP) combines distributed generation resources (DG). • To know the effect of DG on electricity prices is useful to develop VPP strategies. • The impact of renewable DG on European wholesale electricity markets is quantified. • The Maximum Entropy Econometric approach is used. • Wind brings the most widespread market impacts across countries. [ABSTRACT FROM AUTHOR]

Abstract Islands' energy systems present a challenge in energy planning due to a limited amount of resources which could be used to make islands self-sufficient and sustainable. This paper presents a novel approach for defining energy system of a carbon neutral island which utilizes only intermittent renewable energy sources in combination with vehicle-to-grid concept as a demand response technology, where marine transportation has also been taken into account. Integration of power, heating, cooling and transport sectors has been modelled by using EnergyPLAN tool, i.e. its updated November 2017 version which is capable of simulating vehicle-to-grid operation in mentioned conditions. Power supply capacities have been selected not by using scenario analysis but by implementing an optimization procedure based on series of simulations in EnergyPLAN tool. In order to choose the most suitable power supply system configuration, two boundary conditions have been defined. Firstly, only solar and wind capacities must be utilized. Secondly, total electricity import and export must be balanced, i.e. the island has to be CO 2 neutral. In order to validate the approach, Croatian Island of Korčula has been used as the case study. 2011 has been selected as the base year for which final energy consumption has been calculated. The final simulation year was set to 2030 in which optimal capacities are installed. It has been shown that configuration with 40 MW of wind and 6 MW of installed solar capacities presents the least cost solution, while 22 MW of wind in combination with 30 MW of installed solar capacities provides the lowest amount of total electricity import and export. Analysis of the vehicle-to-grid share reduction has shown increase in total import and export in both cases, while transmission peak loads have not been influenced. Highlights • Optimization of supply capacities in order to achieve carbon neutrality. • Vehicle-to-grid with 100% share, including the ferry line. • Case study of Island of Korčula in Croatia. [ABSTRACT FROM AUTHOR]

Abstract This paper presents the steps taken by the Korea Electric Power Corporation (KEPCO), the nation's only utility, to overcome limitations involved in increasing renewable energy penetration in an effort to support the government's movement for renewable energy expansion. While the government proposes reducing carbon dioxide emissions by 37% of the Business As Usual (BAU) value by 2030, which is about 315 million tonnes, it has improved energy policies for developing and deploying renewable energy technologies. To facilitate the integration of renewable energy into the future Korean power system, the government has announced a guaranteed interconnection policy for renewable energy sources under 1 MW. Based on this movement, the following measures have been enacted. First, examination of the hosting capacity of the current power system has been initiated to streamline the interconnection process for the distributed renewable energy sources and to reinforce the transmission and distribution network in a proactive manner. Second, to comply with reliability performance standards, an efficient planning procedure has been established for determining the optimal location and size of a renewable complex. To proceed with interconnection requests without delay, a prototype of a Renewable Energy Map (REM) based on PSS/e and Python has been developed. This tool facilitates more practical impact studies by incorporating capacity factors of renewable sources. In addition, it automates the screening process for determining suitable interconnection buses and feasible options for grid reinforcement. This tool is a step toward realizing the twin visions of "G-Platform" and "Carbon Zero" projects in Jeju Island." These efforts, which have been initiated in response to the Paris Climate Change Accord of 2015 and the 23rd Conference of the Parties 2017, aim to increase renewable energy from 7% to 20% of the total generated energy in Korea by 2030. Highlights • The movement of the Korea government in improving support policy, interconnection procedure, and investments for renewable energy expansion. • The movement of Korea Electric Power Corporation (KEPCO) in fully understanding current hosting capacity of the power system for enabling 'Guaranteed interconnection of renewable energy sources under 1 MW'. • The movement of KEPCO and associated universities for developing renewable energy map (REM) for establishing foundation of predicting efficient installation of renewable energy aggregation without violating reliability standard. • Current projects regarding renewable energy expansion. [ABSTRACT FROM AUTHOR]

Abstract The Renewable energy power generation capacity has been rapidly increasing in China recently. Meanwhile, the contradiction between power supply and demand is becoming increasingly more prominent due to the intermittence of renewable energies. On the other hand, on the mitigation of carbon dioxide (CO 2) emissions in China needs immediate attention. Power-to-Gas (PtG), a chemical energy storage technology, can convert surplus electricity into combustible gases. Subsurface energy storage can meet the requirements of long term storage with its large capacity. This paper provides a discussion of the entire PtG energy storage technology process and the current research progress. Based on the comparative study of different geological storage schemes for synthetic methane, their respective research progress and limitations are noted. In addition, a full investigation of the distribution and implementation of global PtG and CO 2 capture and storage (CCS) demonstration projects is performed. Subsequently, the opportunities and challenges of the development of this technology in China are discussed based on techno-economic and ecological effects analysis. While PtG is expected to be a revolutionary technology that will replace traditional power systems, the main issues of site selection, energy efficiency and the economy still need to be adequately addressed. Additionally, based on the comprehensive discussion of the results of the analysis, power-to-gas and subsurface energy storage implementation strategies, as well as outlook in China are presented. Graphical abstract fx1 Highlights • The entire process of power-to-gas (PtG) and subsurface energy storage is reviewed in detail. • A comparative analysis of gas storage in the same or different formations. • Opportunities and challenges for China based on techno-economic and ecological effects analysis. • Power-to-gas implementation strategies and outlook for China. [ABSTRACT FROM AUTHOR]

Abstract Owing to the wind and photovoltaic (PV) potential in Brazil, the country has recently seen increased exploration into the construction of wind-PV hybrid plants. However, as specific criteria for contracting this type of project have not yet been developed, this paper presents a model to assist the government in contracting projects that maximize the socioeconomic well-being of the Brazilian electricity sector. For this, multiobjective programming is used to simultaneously handle two objective functions—maximally reducing emission density and minimizing the levelized cost of electricity (LCOE)—with the aid of the mixture arrangement technique. In this respect, the optimization method called normal boundary intersection (NBI) is applied to solve the multiobjective problem and construct the Pareto frontier. Additionally, a metric based on the ratio between entropy and the global percentage error (GPE) is used to identify the optimal Pareto solution. The model was applied to determine optimal configurations for wind-PV powerplants in twelve Brazilian cities, and the results obtained reveal the capacity of the model to indicate the optimum configuration according to the wind and PV potential of each city. Highlights • The use of renewable energy sources has been encouraged in Brazil. • The construction of PV-wind hybrid plants has been recently explored. • Normal Boundary Intersection is used to simultaneously handle two objective functions. • Reduced emission density and LCOE were optimized in twelve Brazilian cities. • Results reveal the capacity of the model to indicate the plants optimum configuration. [ABSTRACT FROM AUTHOR]

Abstract Nowadays, due to the need for clean energy and sustainable electricity production, hydropower plays a central role in satisfying the energy demand. Particularly, use of low head micro hydropower plants is spreading worldwide, due to their low payback periods and good environmental sustainability. Gravity water wheels are micro hydropower converters typically used in sites with heads less than 6 m and discharges of a few cubic meters per second. Although water wheels were scientifically investigated as far back as the eighteenth century, they were largely ignored throughout the twentieth century, and only in the last two decades has there been a renewed interest in their use among the scientific community. In this paper a review on gravity water wheels is presented, distinguishing between undershot, breastshot and overshot water wheels. Water wheels technology is discussed focusing on geometric and hydraulic design; data and engineering equations found in historic books of the nineteenth century are also presented. Water wheels' performance is described examining experimental results, and modern theoretical models for efficiency estimation are presented. Finally, results achieved through experiments and numerical simulations were discussed with the aim of optimizing the performance of gravity water wheels. The results showed that maximum efficiency of overshot and undershot water wheels was around 85%, while that of breastshot water wheels ranged from 75% to 80%, depending on inflow configuration. Maximum efficiency of modern water wheels can be maintained at such high values over a wider range of flow rates and hydraulic conditions with respect to older installations. Hence well designed water wheels can be considered as efficient and cost-effective micro hydropower converters. Highlights • Water wheels are cost-effective hydropower converters, especially in rural areas. • Water wheels are low head hydropower machines with 85% maximum efficiency. • Modern results should be used for their design to support old empirical equations. • Their performance can be optimized and their operation made more flexible. [ABSTRACT FROM AUTHOR]

Abstract Power systems with a high share of renewable energy sources face new challenges with respect to reliability management. Scientific literature argues that a paradigm shift is needed in terms of reliability management to efficiently integrate a large amount of renewable energy sources and the required flexibility services. Reliability management involves the use of indicators to support system operation and to assess its performance. Many indicators (proposed to be) used in power system reliability management are presented in technical and scientific literature. To coordinate the development, selection and use of indicators in power systems with a high share of renewable energy sources, this paper presents a structured and consistent overview of the characteristics and the scope of indicators currently in use and available in the literature. A transparent way to characterize indicators is proposed. Available indicators are analyzed in terms of the generic properties of an adequate indicator: relevance in the context of evolving reliability management, ease of use, data availability and reliability determined by the data accuracy. Based on this analysis, missing indicators, shortcomings of existing indicators and directions for future work in a practical and scientific context are identified. Highlights • Overview of available indicators (proposed to be) used in power system reliability management. • Structured and coherent characterization and classification of indicators. • Probabilistic, security and socio-economic indicators have not been used in practice. • Availability and accuracy of data is a challenge for probabilistic and socio-economic indicators. [ABSTRACT FROM AUTHOR]

Abstract A hydrogen fuel cell has many advantages, such as no pollution, high efficiency, low noise and continuous operation. Therefore, it has the potential to be widely applied in both the power propulsion and power supply of a ship. However, the consequent hydrogen safety and leakage issues have attracted much attention and become key issues that need to be resolved urgently. In this paper, based on the component transportation and chemical reaction modules in Fluent software, a ferry is selected as the research object, and a diffusion model of the high pressure hydrogen leakage in a cabin is established. The hydrogen concentration distributions at different leakage positions after the leakage occurs are obtained by making transient numerical calculations of the hydrogen leakage diffusion at the corresponding leakage positions in the cabin. At the same time, the effects of different ventilation conditions on the diffusion trend of hydrogen are analyzed. The simulation results have ascertained the optimal positions for hydrogen sensors and ventilations and it is hoped that these results can provide guidance for the design of a fuel cell ship that uses high pressure gaseous hydrogen. Highlights • The safety of hydrogen fuel cell ship is researched by a CFD simulation. • The corners of fuel cell cabins are the areas with a higher concentration of hydrogen. • Reasonable ventilation is the most effective solution to hydrogen safety in cabin. [ABSTRACT FROM AUTHOR]

Abstract Offshore wind farm operations and maintenance costs currently total 6 m€/year, or 25–28% of total costs. For wave and tidal energy converters, this cost is projected to be twice that of offshore wind, but has high levels of uncertainty. As the wave and tidal energy industries mature, decreasing O&M costs through reliability-based design optimization is critical to increasing feasibility and competitiveness with other energy technologies. In this paper, we will synthesize existing information on reliability-based optimization in systems analogous to offshore renewable energy systems. We will conclude by highlighting opportunities for future work in this field. Highlights • Explores state-of-the-art optimization for reliability in offshore renewable energy systems. • Operations and Maintenance costs for offshore renewable energy systems are very high. • Reliability-based design optimization increases the longevity of these systems, reducing costs. • Not accounting for reliability can lead to inviable designs or higher probabilities of failure. • RBDO methods accelerate convergence, improve reliability, and enhance market competitiveness. [ABSTRACT FROM AUTHOR]

Abstract Despite a major, policy-driven increase in research on the food – energy – water (FEW) nexus in recent years, research addressing the required changes in policy structures and processes for an effective, integrated governance of FEW nexus resources is still in its infancy. This paper adapts the Institutional Analysis and Development Framework to the requirements and challenges of FEW nexus governance and sets a special focus on action situations, actors, and institutions. The analysis thus contributes to the debate about the practicality and benefits of a comprehensive FEW nexus policy approach. Two different conceptual FEW nexus frameworks are developed, which span the spectrum of possible integration options. The first one describes a holistic integration framework that defines the FEW nexus as a single, fully integrated system. The second one represents vertical policy integration and is largely based on existing structures and a reframing of the present institutional setting. After their theoretical derivation, the two hypothetical frameworks are analyzed with respect to their strengths and weaknesses in governing the FEW nexus using two sample cases of integrated FEW nexus governance in Germany. The results show that effective FEW nexus governance requires a combination of both integration options. Highlights • Two novel FEW nexus governance frameworks are developed. • The holistic FEW nexus framework represents horizontal policy integration. • The FEW nexus cooperation framework represents vertical policy integration. • In Germany, both frameworks are used in current policy measures. • Successful FEW nexus governance requires instruments from both frameworks. [ABSTRACT FROM AUTHOR]

Abstract The focus of this paper is to analyse the determinants of wind energy development in the United States and how procedural and regulatory frameworks influence the deployment of wind power facilities. The empirical analysis uses statistical regression models integrating geospatial, macroeconomic and socio-environmental control variables. Using wind penetration as well as wind capacity additions as dependent variable permits a more differentiated analysis of both absolute and relative growth factors. This enables a precise assessment of state-to-state variations in permitting, zoning and siting procedures that wind developers have to clear before being authorised to start construction. Quantifying the number of state-level financial support measures and various permitting and regulatory process stages allowed for a more comprehensive assessment of administrative barriers to wind energy development than prior research studies. The results indicate a partial reversal of previous findings that showed that a high quantity of state-level regulations negatively affects wind capacity additions. Exogenous factors such as the ratio of in-state federal lands, population density, and especially wind energy potential, as well as federal statutes and incentives remain the main drivers of wind capacity additions and overall wind energy penetration. Contrasting prior literature, the influence of localised financial incentives or regulatory approval procedures appears to be minor; therefore streamlining national policies and incentives at the federal level might prove more effective than promoting wind development at the state level. We point out that future research should also examine the role of quality of state-level regulations in addition to quantity. Highlights • Most up-to-date United States state-level study using recent data sets from 2010 to 2016. • Number of financial incentives & regulatory measures are weak growth indicators. • Overall wind potential is the strongest driver of wind development. • Novel dependent variable for wind penetration enables relative growth analysis. • Quantity of environmental regulations did not influence energy growth. [ABSTRACT FROM AUTHOR]

Abstract District heating (DH) has been widely acknowledged as the future for urban heating, as concerns of sustainability and greenhouse gas emissions are pushing, to revamp the heating sector. Although not a new technology, DH has evolved over four different generations, and is now capable of incorporating low temperature distributed renewable heat sources. The ongoing advancements and typical characteristics of a complete grid are researched upon in this paper. The research is extended to link up these characteristics with some of the most interesting DH networks in the world. The technical configurations of these DH grids along with their regulations and policies are explored upon, to understand their evolution and uniqueness. A basic overview of the economics and social aspects are presented as well. The overall trends and results of this study show that, as fossil fuel prices fluctuate and are depleting, there is a unified effort to promote DH, especially for residential heating purposes. The characteristics of modern DH are evolving to cater for distributed renewable technologies with the aim of making the entire system carbon free and sustainable. Highlights • Trends in generation, transmission, distribution and operation of DH are outlined. • Distributed renewable heat sources coupled with latent heat storage are promising. • Smart fourth generation grids are at the forefront of research and development. • The Danish grid is considered the most sustainable and developed in the world. • Unified reforms and policies favoring DH are emerging globally. [ABSTRACT FROM AUTHOR]

Abstract Life cycle assessment (LCA) is a comprehensive method used to investigate the environmental impacts and energy use of a product throughout its entire life cycle. For solar photovoltaic (PV) technologies, LCA studies need to be conducted to address environmental and energy issues and foster the development of PV technologies in a sustainable manner. This paper reviews and analyzes LCA studies on solar PV technologies, such as silicon, thin film, dye-sensitized solar cell, perovskite solar cell, and quantum dot-sensitized solar cell. The PV life cycle assumes a cradle-to-grave mechanism, starting from the extraction of raw materials until the disposal or recycling of the solar PV. Three impact assessment methods in LCA were reviewed and summarized, namely, cumulative energy demand (CED), energy payback time (EPBT), and GHG emission rate, based on data and information published in the literature. LCA results show that mono-crystalline silicon PV technology has the highest energy consumption, longest EPBT, and highest greenhouse gas emissions rate compared with other solar PV technologies. Highlights • Mono-Si indicated the highest energy, longer EPBT and excessive GHG emissions contribution. • DSSC shows the lowest energy requirement and shorter EPBT among other PV technologies. • EPBT depends on solar irradiation, module efficiency and lifetime, and type of technology. • Differences in GHG emissions rates were caused by energy mix for each countries, solar irradiations and lifetime of PV technologies. [ABSTRACT FROM AUTHOR]

Abstract In the recent decades, researchers have been focussing more and more on renewable energy because of the known climate crisis that will occur in the near future. One possible solution is the use of fuel cells that generate clean energy. Regarding fuel cell technologies, polymer electrolyte fuel cells (PEFCs) are widely used for portable, stationary or automotive applications as well as backup systems for emergency situations. To build a full PEFC stack, a single cell is used, which is then stacked with more similar cells (the number of cells depends on the electrical power required) and are then integrated into the final product. In a cell, there are two parts that deserve special attention: membrane electrode assembly (MEA) and bipolar plates (BPs). This paper is dedicated to carry out detailed review of processes involved in these two parts, describing the catalyst deposition techniques and BPs manufacturing methods. Finally, a discussion of how to assemble the cells to build a stack of suitable power is included. The review shows the different techniques in chronological order to be able to understand where the fuel cells technology started, and all of the new developments that have been made over time. Each of the techniques has been studied separately in order to provide a comprehensive analysis of the various possible methods found in the scientific literature. After a description and analysis of each technique, a comparative evaluation has been carried out to highlight the most important characteristics of each technique. The review also shows that for fuel cells manufacturing technology to achieve good rates of accuracy, mass production and homogeneity, research should be aimed at achieving less restrictive manufacturing and environmental conditions, and equipment is required with lower costs. Highlights • Chronological review. • Description of catalyst deposition techniques. • Description of Bipolar plates manufacturing methods. • How to assemble the cells to build the stack of suitable power. [ABSTRACT FROM AUTHOR]

Abstract As for other renewable energy sources in Germany like wind or photovoltaics, biogas has rapidly expanded in the past fifteen years. The installed electricity capacity for German biogas plants increased from 0.2 GW el in 2001 up to about 4.2 GW el by the end of the year 2016. This expansion has been supported in particular by the Renewable Energy Sources Act (EEG) through electricity Feed-In-Tariffs (FITs). However, major uncertainties are linked to the future capacity expansion in particular due to volatile electricity and energy crops prices. Taking into account this situation this paper analyzes possible future developments of the German biogas plant capacity up to 2030. For this purpose, a regional optimization model is employed, with the objective of determining the optimal economic development of the future biogas plants under different legal framework conditions. The base scenario with a constant energy crops cost evolution shows that the EEG 2012 framework -if maintained- would have fostered the development of agricultural plants, especially co-digestion plants valorizing energy crops and manure. The new EEG 2014 stops the expansion of energy crops mono-digestion plants, which will no longer be built due to an unprofitable situation. The German biogas market will thus face a paradigm shift and move towards the increase of biowaste and small-scale manure plants. Further scenarios quantify the impact of a strong variation of three main fundamental drivers, namely the energy crop costs, the EPEX-Peak electricity price and the biowaste valorization revenues, on future capacity developments. Based on the model results recommendations in direction of plant operators and policy-makers are formulated aiming at a more sustainable electricity production from biogas. Further work should consist in integrating the present analysis in national bioenergy models under the EEG 2017 legal framework. [ABSTRACT FROM AUTHOR]

The energy demand in Chile arises mostly from mining, its largest industry that accounts for about 35% of total electricity consumption. Energy generation to satisfy this demand depends completely on imported fossil fuels. As a result, the mining industry faces several energy related challenges. In particular, the cost and environmental impact of fuel sources are threatening the competitiveness of the industry and urge for new developments. In that regard, the importance of using clean and cost-competitive renewable energy sources has increased significantly in Chile and several government policies helped to increase the investment in them. The impact has been particularly large in the development of solar energy in the northern part of the country, where almost all mines are located. In fact, the country has become one of the largest solar markets in Latin America thanks to its abundant solar resources, favorable market conditions, and successful policy reforms. Solar energy then, could play a significant role as an alternative to satisfy the mining industry's energy demand offering a broad range of technological solutions. This study examines the key issues -barriers and drivers- influencing the adoption of solar technologies in the Chilean mining industry from the perspective of mining actors. As a result of the analysis the paper also provides a scope for appropriate policy interventions. [ABSTRACT FROM AUTHOR]

Among all the available solutions to the current high energy demand and consequent economic and environmental problems, solar energy, without any doubt, is one of the most promising and widespread solutions. However, conventional solar systems face some intractable challenges affecting their technical performance and economic feasibility. To overcome these challenges, increasing attention has been drawn towards the utilization of heat pipes, as an efficient heat transfer technology, in conventional solar systems. To the authors’ knowledge, despite many valuable studies on heat pipe solar collectors (mainly during the last decade), a comprehensive review which surveys and summarizes those studies and identifies the research gaps in this field has not been published to date. This review paper provides an overview of the recent studies on heat pipe solar collectors (HPSCs), their utilization in different domestic, industrial, and innovative applications, challenges, and future research potentials. The concept and principles of HPSCs are first introduced and a review of the previous studies to improve both energy efficiency and cost effectiveness of these collectors is presented. Moreover, a concise section is dedicated to mathematical modeling to demonstrate suitable methods for simulating the performance of HPSCs. Also, the latest applications of HPSCs in water heating, desalination, space heating, and electricity generation systems are reviewed, and finally, some recommendations for future research directions, regarding both development and new applications, are made. [ABSTRACT FROM AUTHOR]

Eleven years on since the United Nations' Intergovernmental Panel on Climate Change was awarded the Nobel Peace Prize in recognition of its efforts in combating climate change, fossil fuels remain the most dominant global energy source. As the total replacement of fossil fuel energy is not expected to take place immediately in the near future, the International Energy Agency has repeatedly declared carbon capture and sequestration (CCS) as a key technology for mitigating climate change. However, CCS lacks the scale required for substantial reduction in carbon dioxide emissions from fossil fuel power generation. Even though CCS is one of the key technologies for mitigating climate change, why has this technology not had an international breakthrough? To shed light on this question, this paper employs a simple model of energy generation, scrutinizes the economic drivers of CCS based on the analytical results, and discusses the possible obstacles that can prevent a widespread rollout of the technology. This is followed by a state-of-the-art in literature pertaining to the economics of CCS, and a discussion that points to a dichotomy between the economic theory and reality. The study concludes with some policy suggestions and directions for future research. [ABSTRACT FROM AUTHOR]

The Sun is the primary energy source for all life on Earth. Solar energy is clean and is available all over the world. The total energy produced, in 2016, was 7236 MWh, while the total consumed was 6660 MWh. The average photovoltaic energy generated was 255 MWh, which accounts for 3.5% of the total production and 8.2% of the RES (3096 MWh). Investments in renewable energy in Romania began in late 2008, when Green Certificates were granted by Law no. 220. In this paper, we review the photovoltaic system development in Romania, from 2011, when the market began to develop, to the present day. The climate change and air pollution have to be slowed down and reduced by implementing renewable and sustainable solutions in order to generate electricity. The photovoltaic industry has an important role in Romania's development, both economically and environmentally and by having the “unlimited resource” advantage, it is a good alternative to fossil fuels. Now, the largest solar park in Romania, with 332,000 operational PV units, located in Ucea de Sus, Brasov County and commissioned in 2013, has an installed capacity of 82 MW, and covers a land surface of 200 ha. 178 years ago, French physicist Edmond Becquerel discovered the photoelectric effect, in 1839. At the moment, the typical power of solar PV modules is less than 500 W, depending on efficiency and temperature sensitivity. Currently, long-term research on photovoltaic cells focus on increasing the power output, increasing the efficiency and reducing the temperature sensitivity. [ABSTRACT FROM AUTHOR]

This paper presents a review on the application of neural networks for the estimation, forecasting, monitoring, and classification of exogenous environmental variables that affect the performance, salubrity, and security of cities, buildings, and infrastructures. The forecast of these variables allows to explore renewable energy and water resources, to prevent potentially hazardous construction locations, and to find the healthiest places, thus promoting a more sustainable future. Five research themes are covered—solar, atmospheric, hydrologic, geologic, and climate change. The solar section comprises solar radiation, direct and diffuse radiation, infrared and ultraviolet radiation, clearness index, and sky luminance and luminous efficacy. The atmospheric section reviews wind, temperature, humidity, cloud classification, and storm prediction. The hydrologic section focuses on precipitation, rainfall-runoff, hail, snow, drought, flood, tides, water levels, and other variables. The geologic section covers works on landslides, earthquakes, liquefaction, erosion, soil classification, soil mechanics, and other properties. Finally, climate change forecasting and downscaling of climate models are reviewed. This work demonstrates the wide range of applications of these methods in different research fields. Some research gaps and interdisciplinary research opportunities are identified for future development of comprehensive forecast and evaluation approaches regarding the estimation of renewable energy and built environment-related variables. [ABSTRACT FROM AUTHOR]

Malaysia's framework for energy development was established in the early 1970s. Henceforth, many successive policies were introduced as potential resources for electricity generation and utilization. Currently, as a signatory to the United Nations Framework Convention on Climate Change, Malaysia is sparing a number of effort to comply with the policy to meet the challenges of mitigating over-dependence on fossil fuels, reducing carbon levels, and achieving sustainable national development. This paper reviews the baseline studies on electrical energy policies and the measurement indicators used in Malaysia's electric power system. This research involves a comprehensive survey of electrical energy policies in Malaysia that focus on issues pertaining to energy supply, utilization, its environmental impact and considerations, renewable energy (RE) policies, production and consumption, energy efficiency, and feed-in tariffs. Fourteen energy indicators for sustainable development in Malaysia were investigated through the identification of energy policies in significant areas, such as reliability, safety, adequacy and cost-effectiveness of energy supply; increasing energy efficiency; minimizing environmental impact; and enhancing quality of life in terms of social well-being. The policies and the indicators are classified into different sustainable dimensions and summarized in tables along with the corresponding key references. In this study, future energy planning and options, especially in nuclear and RE programs, as well as the conflict between them, are illustrated through the overall performance relative to targets and benchmarks for past and future projections up to the year 2030. This review seeks to examine the past, present, and future policies and indicators to provide a sufficient overview of Malaysian energy policies for optimizing sustainable development. The goal is for this review to lead to increased efforts to accommodate the increasing demand for the management and utilization of RE, promote energy efficiency, and improve performance in achieving sustainable national development. [ABSTRACT FROM AUTHOR]