• Energy Research

Benchmarking the performance of cities across aspects that relate to the sustainable development of energy, water and environment systems requires an integrated approach. This paper benchmarks a sample of 12 Southeast European cities based on a composite indicator that consists of 7 dimensions and 35 main indicators. The composite indicator is namely the Sustainable Development of Energy, Water and Environment Systems (SDEWES) City Sustainability Index. The first three dimensions are energy consumption and climate, penetration of energy and carbon dioxide saving measures, and renewable energy potential and utilization. The last four dimensions are water and environmental quality, carbon dioxide emissions and industrial profile, city planning and social welfare, and research, development, innovation, and sustainability policy. The data collection process for the 12 cities integrates data from Sustainable Energy Action Plans and other sources. Data entries are normalized based on the Min–Max method and aggregated for a final ranking. Zagreb, Bucharest (District 1), and Ohrid are the top three cities. An average city receives a composite score of 2.69. Best practices are identified to allow cities to adopt well-rounded efforts to improve future performance. The SDEWES Index is useful to trigger learning, action, and collaboration among cities to transition to a more sustainable future.

This paper analyzes the case study of an interdisciplinary course in Energy Economy that was developed at the Energy Engineering Graduate Program at Başkent University. The course integrated several unique pedagogical features to satisfy the aim of developing a working knowledge in energy economy with an energy systems perspective. The novel aspects of the course thematically led to a capstone research project where 5 teams of 17 course participants analyzed their prioritized solutions towards improving the energy self-sufficiency of the campus based on the practice of energy economy. The results of the teams’ solutions towards a net-zero energy/exergy campus included electric buses for city-campus transport, poly-generation for the new Arts Center, LED/OLED lighting for campus lighting, dynamo driven/piezoelectric sports center, biofuels from the university-owned dairy products farm, and an energy efficient technology incubation center. This unique course with participatory learning is compared with others before concluding that the case study is a useful international example for energy economy.

Abstract The realization of net-zero exergy districts can be supported by urbanization options for district density and building characteristics. This research work formulates an urbanization algorithm to minimize the carbon dioxide emissions responsibility of districts based on energy usage and aspects of embodied energy to tackle multiple drivers of urban emissions. The combined method is implemented to scenarios that contribute to a net-zero exergy district target with 6 options for district density and the selection of building materials. Based on a comparison of scenarios for a case study in the province of Ankara, Turkey, the scenario in which on-site exergy production is about 9.5% of the annual exergy consumption will be responsible for about 13,731 ktonnes of carbon dioxide emissions in a timeframe of 30 years. Conversely, a near net-zero exergy district in which on-site exergy production is 75% of the annual exergy consumption will have about 2967 ktonnes of carbon dioxide emissions during the same timeframe, including embodied energy in buildings. The sensitivity analysis with 9 different combinations provides differences in trade-offs based on timeframes and scenarios. The research work has ramifications for local decision-making to avoid locking-in of carbon dioxide emissions by prioritizing an integrated approach to urban energy solutions on the supply and demand sides, district density, and building materials while reaching net-zero targets in the future.

The integration of sectors for more sustainable systems and processes provide a multi- disciplinary research domain to which researchers are contributing with intense motivation in the context of urgency for addressing global climate change. The 26 papers in the current special issue of the 12th Conference on Sustainable Development of Energy, Water and Environment Systems represent a pursuit of excellence for leading related advancements. This editorial contains a review of these advances with a focus on the themes of effective valorisation of bioenergy resources, energy-water nexus in wastewater treatment processes, optimized local energy supply for efficient and clean systems, solar energy technologies for the energy transition, and technologies for efficient combustion and electric transport. Other themes are alternative and cross-cutting technologies for the energy system in addition to analyses of thermal energy recovery and heat transfer. Significant contributions under these themes relate to biomass residues and biogas upgrading processes, novel renewable energy and performance comparisons in the wastewater sector, efficient micro-cogeneration, polygeneration and load- sharing approaches, clustering techniques in district heating networks as well as hybrid and concentrated solar power systems. Control strategies for latent energy storage, aging processes in battery packs, engine knock occurrence and coupled numerical engine modelling, fuel blends with nanoparticle additives, utilization of flue gas, soot formation in plastic waste pyrolysis, high altitude wind energy systems as well as exergy analyses for heat and cold recovery and reverse electrodialysis are other key contributions. The advances are expected to enable more sustainable energy conversion and management processes in a time when an integrated approach is nothing less than essential to maintain a coherent and liveable Planet.

Urban areas have key roles in climate mitigation, including increasing renewable energy penetration in smart energy systems. The potential of urban areas in limiting global warming, however, is not quantified. This research work develops a new framework to analyse urban emissions and land use efficiency scenarios with coupling to the transient climate response to cumulative carbon dioxide emissions. Two new parameters that quantify contributions to and avoidance of increments of global warming from urban areas are formulated and applied to twelve scenario combinations. The results for 465 urban areas indicate that a green-growth scenario with lower ambition in reducing urban emissions can lead up to a 0.13 °C additional increment of global warming in 2050 based on the best estimate of the transient climate response to cumulative carbon dioxide emissions. Those of the most ambitious urban emissions scenario with green-growth and renewable energy are limited to 0.06 °C. When combined with the most ambitious land use efficiency scenario for 135 urban areas, it is possible to avoid more than double or 2.09 times additional increments of global warming in comparison to other integrated urban scenarios. The mean and 5–95th percentile range of the results are compared based on 10,000 Monte Carlo simulations. Informing on the urgency to ensure ambitious mitigation action in urban areas can support a climate future that remains within critical thresholds and tipping elements of the planet.

Abstract Urban areas provide strategic settings for attaining more sustainable urban systems. This paper provides fivefold contributions to the literature based on the Sustainable Development of Energy, Water and Environment Systems City Index. A comprehensive benchmarking of 120 cities is undertaken of which the first three cities are found to be Copenhagen, Stockholm, and Helsinki. Uncertainty and sensitivity analyses are conducted by comparing the original ranking with those based on Monte Carlo simulations and three aggregation schemes with and without the use of the geometric mean. The ranking of cities that take place in the 95% confidence interval and strong coefficients of correlation are found to suggest aspects of index robustness. As the third contribution, a scenario that represents the cross-sectoral strategy of utilizing residual energy in the urban vicinity from the industry, thermal power generation, wastewater, and urban biowaste is applied to 60 cities. The integration of data from the Pan-European Thermal Atlas provides additional practical value to local decision-makers who can assess possible improvements in city performance through such an approach. Fourth, 13 city pairs of 3 or more cities with the same above or below average performances across the dimensions of the index are identified as another means of supporting policy-learning opportunities. The fifth contribution synthesizes the original results of the research work to discuss the need for integrated urban transitions and proposes a vision for cities to envision the sustainable development of urban energy, water and environment systems. The research work provides analytical support to cities in a time when local actors are tasked with a mission that is nothing less than leading the transition to net-zero emissions by mid-century.

Integrated approaches across energy, water and environment systems can accelerate the process of mitigating climate change through urgent action. New scientific advances that extend multiple opportunities in this direction have emanated from the 2nd Latin American, 1st Asia Pacific, 4th South East European and 15th Conferences on Sustainable Development of Energy, Water and Environment Systems as represented in this editorial. The review of recent scientific advances connects the 27 research articles in this special issue with those of other researchers based on eight main themes. The first two themes relate to system flexibility for renewable energy penetration and urban solutions in the energy transition. The foci of these themes include enabling energy system flexibility, climate neutral islands, electrification solutions, optimizing urban energy systems, spatiotemporal modelling of heat demand and smart energy hubs. The next three themes relate to solar energy technologies, hydrokinetic, wind and osmotic innovations as well as bioenergy and combustion modelling. These themes include new advances for predicting and monitoring photovoltaic module performance, thermochemical energy storage for concentrated solar options, artificial intelligence for wind energy, micro- cogeneration, and wastewater utilization. The last three themes relate to batteries and hydrogen energy advances, including sector coupling opportunities, optimizing heat exchangers and networks as well as solutions for redesigning sectors and repurposing post- mining reservoirs for energy storage. There are multi-disciplinary interrelations among these themes and each contribution will support the wide-ranging opportunities for realizing the European Climate Law and any other similar targets around the world for sustaining planetary life-support systems on which sustainable development depends.

Operating within safe and just Earth system boundaries requires mobilizing key actors across scale to set targets and take actions accordingly. Robust, transparent and fair cross-scale translation methods are essential to help navigate through the multiple steps of scientific and normative judgements in translation, with clear awareness of associated assumptions, bias and uncertainties. Here, through literature review and expert elicitation, we identify commonly used sharing approaches, illustrate ten principles of translation and present a protocol involving key building blocks and control steps in translation. We pay particular attention to businesses and cities, two understudied but critical actors to bring on board.