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This review article addresses the status of research within the application of renewable energy sources. It focuses on the status of renewable technologies, the role of renewable energy sources in meeting sustainable development goals, the status of the research into the sustainability of the renewable energy systems, and finally on the integration of renewable energy technologies in low carbon energy systems. Regarding renewable resources and technologies, wind and wave power resource assessment, heating and cooling, solar energy, renewable energy fuels, and integrated energy systems are reviewed and summarized. The article takes a starting point in work presented at the conference series on Sustainable Development of Energy, Water and Environmental Systems (SDEWES), published in the Renewable Energy journal and puts this work into a broader context. [ABSTRACT FROM AUTHOR]

This article presents some of the main findings from the SDEWES conferences of 2021 within the field of renewable energy. More specifically, results are summarized and contextualised within solar energy and thermal comfort, wind power resource assessment, and biogas and biomass resources and technology. The two last sections deal more broadly with energy systems and energy systems transition issues; the systems analyses used to design complex renewable energy systems and the investment strategies and barriers associated with the transition. [ABSTRACT FROM AUTHOR]

This article present a review of the status of research within the exploitation of renewable energy sources with a focus on the status of technologies exploiting renewable energy sources, a status of the assessment of the availability of renewable energy sources and the status on the research into the types of systems, that can integrate renewable energy sources. In terms of technologies and resources, wind and wave power resources, wind technology, geothermal energy, solar heating, cooling and electricity and salinity gradient technologies are reviewed. Lastly, system integration, impacts and environmental performance of energy systems are assessed. The review takes a starting point in work presented at the conference series on Sustainable Development of Energy, Water and Environmental Systems (SDEWES), published in Special Issues in various journals and puts this work into a wider context. • Review of recent developments in renewable energy technology. • Unexploited potentials for renewable energy exploitation identified. • Systems analyses indicate good prospects for transforming energy systems. [ABSTRACT FROM AUTHOR]

This article examines some of the latest findings in the exploitation of renewable energy sources (RES) for sustainable development. It outlines some of the latest findings at the system level – e.g., local systems, community systems, and assemblies of buildings – as well as some of the main components in future renewable energy systems. This includes solar technologies, where particular attention is given to the cooling of photovoltaic panels to improve conversion efficiency. Hydrogen – in one way or the other – will play a role as a storage medium or as a means of electrifying otherwise hard-to-electrify sectors. Bioenergy is a valuable but restricted source in the energy system, hence different processes are investigated to optimize the use of different biomass waste streams. Lastly, wind power is addressed as one of the key constituents of future renewable energy-based energy systems. In this special issue, the focus, however, is on the end-of-life handling of turbine blades. [ABSTRACT FROM AUTHOR]

The environmental impact of the energy sector and the security and economics of energy supply and utilisation have been raising increasing concerns, stimulating the search for innovative solutions for a sustainable use of resources. This article provides an overview of published research in this area, with a focus on papers contributed in special issues of leading journals dedicated to the series of Conferences on Sustainable Development of Energy, Water and Environment Systems (SDEWES), including the articles in the current special issue. Based on this review, research trends are identified and achievements supporting the energy transition are highlighted. The studies that focused on regional or urban energy planning have aimed at (a) increasing penetration of renewable energy sources, (b) optimizing the mix of centralized and distributed technologies (c) introducing additional flexibility in the power sector and (d) identifying solutions for sustainable heating. Conversely, researches focused on single plants or users have targeted the development of technologies for efficient energy use in industry and buildings, with emphasis on multi-generation and waste heat utilisation. The review highlights that future scenarios based on sustainable energy systems are viable, although their implementation will require further efforts by researchers and investors and active involvement of consumers. • Research trends on energy transition and the associated technologies are reviewed. • Literature review examined the Special Issues of journals dedicated to SDEWES Conferences. • Challenges posed by increased share of renewables are solvable by cost-efficient solutions. • Power-to-heat and district heating are key-technologies for sustainable energy supply. • Energy saving in the building and industrial sectors contributes to sustainability of energy sector. [ABSTRACT FROM AUTHOR]

This editorial gives an introduction to the important relationship between Smart Energy Systems and 4th Generation District Heating and presents a number of selected papers from the 1st International Conference on the topic. All of the papers elaborate on or otherwise contribute to the theoretical scientific understanding on how we can design and implement a suitable and least-cost transformation into a sustainable energy future. The concept of Smart Energy Systems emphasizes the importance of being coherent and cross-sectoral when the best solutions are to be found and how this also calls for the active inclusion of the heating and cooling sectors. The concept of 4th Generation District Heating emphasizes that district heating and cooling are both important elements but also technologies that have to be developed further into a 4th generation version to be able to fulfil their roles in future sustainable energy systems. The conclusion is that further development of such theoretical scientific understanding is essential for the implementation of political goals related to future sustainable energy solutions. [ABSTRACT FROM AUTHOR]

Following the 2015 Paris Agreement and other agreements which have been signed after, sustainable energy development is becoming the major goal in many countries. EU have set the targets to reduce the annual greenhouse gas emission by 40% in 2030 and 80% for 2050 compared with 1990 levels. For achieving this ambitious energy policy, three major technological changes are available: energy savings on the demand side, efficiency improvements in the energy production, and replacement of fossil fuels by various sources of renewable energy. Also, for realization cited three major technological changes the support of the multi-disciplinary scientific knowledge is needed. Therefore, from the beginning of the 21st century, since 2002, a series of Sustainable Development of Energy, Water and Environment Systems (SDEWES) Conferences were founded. This paper presents an overview of published researches in special issues of leading journals dedicated to the series SDEWES Conferences, including also the papers in current special issue. The focus is on five main fields: (1) energy policy and analysis of smart energy systems; (2) energy savings in the building sector; (3) co/polygeneration - integrated heating, cooling and electricity systems and district heating; (4) biomass for energy; and (5) measurement of energo-environmental sustainability of processes and systems. Researchers are focused on the development of methods, policies and technologies for both efficient production of energy, mainly from renewable sources, and consumption in industry, buildings and transport. Undoubtedly, the researches presented in the papers in this special issue as well as in previous ones, dedicated to SDEWES conferences, will contribute to the promotion of sustainable development and thus to the achievement of the goals of the Paris Agreement. [ABSTRACT FROM AUTHOR]

Abstract: Increase of the global energy demand and environmental problems relating to fossil energy utilization request the new energy sources to replace the traditional fossil fuels. With respect to energy production, most of the islands in European Union and in the other parts of the world, depend on importation, mainly from oil and its related products. The global development of renewable energy technologies can assure sustainable supply of power for islands. To overcome the limitation of the sources of renewable energy, hydrogen is utilized as a storage medium integrated with intermittent renewable energy sources such as wind and solar. This paper introduces the programme of “Renewislands—Renewable Energy Solutions for Islands”, the work tasks, details of the design of the activities to develop solutions integrating intermittent renewable energy supply (RES), fuel cell (FC) and hydrogen infrastructure to promote RES and innovative decentralized power systems penetration in islands; main results achieved in each work packages are presented; in addition, the development of intermittent renewable energy penetration in specific European Islands are reviewed briefly. [Copyright &y& Elsevier]

Abstract This paper provides a perspective on the development of future district heating systems and technologies and their role in future smart energy systems. The reviewed papers elaborate on or otherwise contribute to the theoretical scientific understanding of how we can design and implement a suitable and least-cost transformation into a sustainable energy future. Focus is on the important role of the next generation of district heating and cooling technologies. The status of the scientific contributions demonstrates a high level of understanding of how to deal with the technical aspects. The primary current challenge seems to be the understanding of the implementation of these. Highlights • A transformation into low-temperature becomes essential for future district heating. • High level of understanding of how to deal with the technical aspects. • Primary current challenge seems to be the understanding of the implementation. [ABSTRACT FROM AUTHOR]

Island communities require in-detail mapping of resources available for exploitation for energy purposes, since infrastructure and connections to the mainland present, in most cases, a weak point of the island energy supply. As the present energy supply on Croatian islands relies mostly on fossil fuels and electricity from the mainland, it becomes obvious that exploitation of renewable energy sources is the only solution that leads towards self-sufficiency and sustainable development. In order to design a self-sufficient and sustainable island, three major technological changes are needed: integration of renewable energy sources alongside with energy savings and improvements in energy efficiency in the energy production. Analyses for several other Croatian islands have been performed using Renewislands/ADEG methodology in order to assess all possible outcomes. The scenarios in these cases have shown that islands can become self-sufficient through combining renewable technologies and energy storage systems. Energy storage systems will be crucial for achieving desired objectives in terms of energy independence from the mainland and in general import of fossil fuels. The analysis conducted for the island of Hvar will result in creation of several scenarios which will clearly point out the favorable solutions for improvement of both security of energy supply and covering the majority of energy demand with renewable energy sources and storage technologies. Also, when talking about implementation of renewable technologies on island of Hvar, an optimal mix of technologies must be applied in order to avoid excess costs and to achieve minimal impact on environment in terms of visual pollution. [ABSTRACT FROM AUTHOR]

Macedonian energy sector is the main emitter of greenhouse gases with share of about 70% in the total annual emissions. Also, 70%-75% of emissions are associated with the electricity generation due to the predominant role of the lignite fuelled power plants. Recently, the government has adopted a strategy for the use of renewable energy sources (RES) which identifies a target of 21% of final energy consumption from RES by 2020. In this paper, analyses are conducted in order to investigate to which extent and in which way the absorption capacity of the power system for RES electricity can be improved. For this purpose, combining various conventional and RES technologies, including pump storage hydro power plant and revitalisation of the existing lignite power plants six scenarios for the power system expansion are developed by making use of EnergyPLAN model. Critical excess of electricity analyses are conducted in order to identify the maximal penetration of wind electricity. The results have shown that in the exiting capacities maximal penetration of wind electricity in 2020 is 13% of total electricity consumption. The revitalization of the existing lignite power plants and building of pump storage power plant would increase the wind penetration. Furthermore, the developed scenarios are comparatively assessed in terms of the associated greenhouse gases emissions and import of electricity. [ABSTRACT FROM AUTHOR]

Geothermal energy is a widely available renewable energy source. In Croatia geological data have been indicating promising potential, especially in the North-Eastern part of the country with a geothermal gradient higher than 49 °C/km and terrestrial heat flux of 76 mW/m 2 . Nonetheless, despite this potential, this resource is not highly exploited to date. Efficient use of geothermal energy can contribute on reducing Croatia’s energy dependence. In this paper, a methodology of a possible integration of geothermal energy within residential, commercial and industrial systems was attempted. Pinch analysis was used to find the best ways to fulfil the energy system requirements in an efficient, clean and cost-effective way. The used approach gives a good overall picture of energy targets for process, site and utility levels. The recommendation for cost-effective integration of geothermal energy into regional energy network is considered by use of Pinch Analysis. Additional attention was paid to geothermal energy utilisation in low enthalpy sedimentary environments. The obtained results can be used for integration of geothermal energy in different cases and “countries”. It gives general recommendation for geothermal sources placement as well as for energy planning and regional sustainability. [ABSTRACT FROM AUTHOR]

Due to the stochastic nature and variability of renewable energy sources (RES), it is necessary to integrate still expensive storage capacities into an energy system with a high share of RES and to model appropriate energy market. The study presented here considers all energy carriers, however, only the electricity carrier is modeled in detail, with notion taken for the heating demand that is covered but without proper modeling of storage. A proposed two-level approach with multi-objective optimization on the global level, was used to design a Croatian Energy System (CES), where electric vehicles (EVs) are integrated to serve as battery storage in Vehicle-to-Grid (V2G) mode, for a scenario between 2015 and 2050. In addition, case study includes nine aggregated hydro power plants, one for each river basin in Croatia. Also, case study includes solar and wind power plants modeled for six locations in Croatia: Osijek, Zagreb, Rijeka, Sibenik, Split and Dubrovnik. The resulting Pareto front suggests that with assumed future costs of fuels and technology certain level of conventional energy sources will have to remain in the energy system to take into the account unfavourable weather conditions and to cover heating demand, which also results in significantly lower load factors for those power plants. Also, variants with more RES share have lower total energy system load factor and significantly higher installed capacity. [ABSTRACT FROM AUTHOR]

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

This short paper gives some perspectives on the recent development in the concept of Smart Energy Systems while introducing the contents of selected papers from the 5th International Conference on Smart Energy Systems, 4th Generation District Heating, Electrification, Electrofuels and Energy Efficiency – SESAAU2019. All of the papers elaborate on or contribute to the theoretical scientific understanding on how to design and implement an energy efficient green transition with an emphasis on system integration and sector-coupling. Low-temperature 4th generation district heating and its possibilities of providing flexible demand is particularly emphasized in the papers presented. However, in order to reach 100% renewability in the energy system, further research is required particularly on the transformation of the transport and industrial sectors. Methods for accommodating increased levels of renewable energy sources, while maintaining proper load-balancing capability and security of supply, should also be further investigated – an area where smart energy systems play an important role. • Recent studies related to the development of Smart Energy Systems are presented. • Studies are divided in 6 categories, each contributing to the green transition. • The overall development is discussed, and perspectives on this research is presented. [ABSTRACT FROM AUTHOR]