Renewable Technologies Research Articles

Improved Clamped Z-Source Converter with Optimized Maximum Power Point Tracker for Hybrid Renewable Energy Systems Based Energy Management System

In light of the intermittent and seasonal nature of wind and solar energy, electrical systems are becoming more problematic to operate. The purpose of the work is to establish an energy storage system that helps to minimize such operational challenges, which are essential to improve grid stability and reliability. The tasks solved in the article to achieve the given goal are the following: incorporating an energy management system with the aid of improved converter and optimized maximum power point (MPPT) for (Photovoltaic) PV and PMSG (permanent magnet synchronous generator) based wind system. On comparing with conventional Z-source converters, a novel improved clamped Z-source converter, which is utilized in this work has high efficiency with low THD and it has the capacity to protect electrical circuits against damage caused by short circuits, overcurrent and overvoltage. The Pulse Width Modulation (PWM) rectifier is implemented to convert AC-DC supply obtained from the PMSG wind system. Firefly optimization with an aid of Radial Basis Function Neural Network (RBFNN) technique is employed as an MPPT system for extracting optimal power from photovoltaic system. The excess energy obtained from the hybrid sources are stored in the battery and it is controlled by the recurrent neural network (RNN) with the bidirectional converter. The overall developed system is executed in MATLAB software and the most important outcomes are demonstrated in terms of high efficiency with 91.2%, high tracking efficiency of 98.54% and reduced THD of 2.45% respectively. The significance of results obtained in this research lies in the advancement of renewable energy integration technologies. By overcoming the challenges associated with intermittent energy sources, the developed system contributes to the improvement of grid stability and reliability.

Research and development of a new combination of piezo-thermoelectric energy harvester systems from roadways

Due to the problems associated with fossil fuels, scientists and governments are investigating alternative energy sources. In recent decades, there has been an increase in interest in initiatives involving the collection of clean, limitless energy. This paper focuses on two renewable energy harvesting combination technologies: mechanical vibration utilizing piezoelectric technology and thermal sources utilizing thermoelectric technology. Existing scientific literature proposes various techniques for producing and modeling each system individually. This study proposes a novel piezo-thermoelectric pavement model with piezo-thermoelectric coupling. Due to the lack of typical experimentation in the scientific literature, a new laboratory experimental prototype proposes to reproduce artificially and simultaneously heat harvesting on the artificial road surface and mechanical vibration caused by passing vehicles. Testing the laboratory-developed prototype has determined the efficacy of the piezo-thermoelectric coupling electronic model. This study demonstrated that a hybrid piezo-thermoelectric system is more suitable for road pavement applications than a piezo-thermoelectric coupling system. A hybrid combination system can continue to produce energy even if one of the energy sources is unavailable or malfunctioning, whereas a coupling combination system cannot. In laboratory testing, the combined piezo-thermoelectric harvester proposed could generate up to 1.75 μW without optimizing the materials or power generation. This innovative study demonstrates the feasibility and applicability of combining thermoelectric and piezoelectric technology to harvest energy from road surfaces.

Electrochemical-induced hydrofunctionalizations of alkenes and alkynes

The hydrofunctionalizations of readily available alkenes and alkynes are one of the most effective and useful routes to afford diverse value-added compounds. Although traditional hydrofunctionalization strategies catalyzed by metal catalysts present convenient approaches, they are also accompanied by resource consumption and environmental crisis. Electrosynthesis, as a renewable and sustainable technology, has become a cost- and atom-efficient and useful synthetic route. In this review, the electrochemical-induced hydrofunctionalizations of alkenes and alkynes are summarized and presented. In each section, the electrochemical synthetic strategy to access hydrogenation and other hydrofunctionalization (hydroboration, hydrosilylation, hydroalkylation, hydroalkoxylation, hydrocyanation, hydrocarboxylation, etc. ) products are elaborated in detail separately. Finally, the current challenges and prospects for electrochemical hydrofunctionalizations of unsaturated carbon‒carbon (C‒C) bonds are also discussed briefly.

Hybrid Technologies for Water Heating Applications: A Review

The over-reliance on fossil resources necessitates the development of a sustainable energy system. Renewable energy and efficient hybrid water heating technologies are viable net-zero energy options. The economic benefits of these hybrid technologies offer a promising prospect for widespread adoption in developing countries as a means of increasing the hot water production. These hybrid technologies are becoming increasingly popular for domestic thermal applications in remote areas to compensate for energy shortages. This paper provides an overview of hybrid renewable water heating technologies with a focus on hybrid configurations, optimization techniques, mono-particle, and hybrid nanofluids and modelling. This paper also highlights the prospects for increasing the economic attractiveness and public acceptance of such systems.

Electrochemical Nitrate-to-Ammonia Conversion Enabled by Carbon-Decoration of Ni─GaOOH Synthesized via Plasma-Assisted CO2 Reduction.

The release of nitrates into the environment leads to contaminated soil and waterthat poses a health risk to humans and animals. Due to thetransition to renewable energy-based technologies, an electrochemical approach is an emerging option that can selectively produce valuable ammonia from nitrate sources. However, traditional metal-based electrocatalysts often suffer from low nitrate adsorption that reduces NH3production rates. Here, aNi-GaOOH-C/Ga electrocatalyst for electrochemical nitrate conversion into NH3 is synthesized via a low energy atmospheric-pressure plasma process that reduces CO2into highly dispersed activated carbon on dispersed Ni─GaOOH particles produced from a liquid metal Ga─Ni alloy precursor. Nitrate conversionrates of up to 26.3µgh-1mg-1 catareachieved with good stability of up to 20h. Critically, the presence of carbon centers is central to improved performance whereboth Ni─C and NiO─C interfaces act as NO3-adsorption and reduction centers during thereaction. Density functional theory (DFT) calculations indicate that the NiO─C and Ni─C reaction sites reduce the Gibbs free energy required for NO3-reduction to NH3compared to NiO and Ni. Importantly, catalysts without carbon centers do not produce NH3, emphasizing the unique effects of incorporating carbon nanoparticles into the electrocatalyst.

Enhanced energy storage and temperature-stable dielectric properties in (1-x)[(Na0.4K0.1Bi0.5)0.94Ba0.06TiO3]-xLa0.2Sr0.7TiO3 lead-free relaxor ceramics

With the continuous growth in sustainable and renewable technologies, ceramic capacitors are emerging as a promising energy storage device. Lead-free (1-x)[(Na0.4K0.1Bi0.5)0.94Ba0.06TiO3]-xLa0.2Sr0.7TiO3 (0 ≤ x ≤ 0.40) ceramics were prepared using the solid-state reaction technique for obtaining relaxor characteristics with improved energy storage density, efficiency, and temperature stability of dielectric permittivity. A high recoverable energy density (Wr) ∼ 2.39 J/cm3 with a good efficiency (η) of ∼ 75.21% was obtained for x = 0.30 composition under 220 kV/cm applied field. The specimen x = 0.30 exhibited excellent fatigue resistance during 105 cycles and good temperature stability of energy storage characteristics (Wr > 0.87 J/cm3, η > 74%) in the temperature range of 25–180 °C under 100 kV/cm. In addition, the temperature range in which the dielectric permittivity variation was less than ±15% was very wide (204 °C (63–267 °C) and 275 °C (39–314 °C) for x = 0.30 and 0.20 specimens, respectively). Significant improvements in material performance were attributed to A-site engineering, which resulted in a mixture of P4bm and R3c polar nano regions (PNRs), leading to reduced hysteresis loss and temperature-stable dielectric permittivity. Additionally, the size of PNRs ranged between 3 and 6 nm, with the P4bm phase dominating in the x = 0.30 specimen, leading to a large maximum polarization under an applied electric field. Therefore, (1-x)[(Na0.4K0.1Bi0.5)0.94Ba0.06TiO3]-xLa0.2Sr0.7TiO3 relaxor ceramics are promising for high energy density materials and electronic applications requiring high permittivity stability over a wide temperature range.

Tingkat emisi (CO) dan upaya penurunan emisi gas rumah kaca pada sektor transportasi di Kabupaten Semarang, Jawa Tengah

Background: Greenhouse gases are gases present in the atmosphere that are beneficial in trapping solar radiation, thereby maintaining the Earth's temperature stability. However, if the concentration of greenhouse gases increases, it can lead to global warming, which impacts climate change. This research aims to present estimates of greenhouse gas emissions originating from the transportation sector in Semarang District. This is necessary to plan strategies to reduce greenhouse gas emissions. Methods: The data used are secondary data obtained from various literature studies. The data were analyzed using emission strength formulas (Q). Finding: The results of this study show that the number of motor vehicles in Semarang District in 2021 reached 559,805 with emissions produced amounting to 348,230 tons/hour. The highest percentage of emissions is from passenger cars at 42%. Conclusion: Various efforts are being made to reduce greenhouse gas emissions, including implementing environmental taxes and reducing the use of oil-fueled vehicles by switching to renewable technologies, such as electric vehicles.

Predictive analytics in climate finance: Assessing risks and opportunities for investors

Predictive analytics is increasingly recognized as a pivotal tool in climate finance, offering investors invaluable insights into both the risks posed by climate change and the opportunities for sustainable investment. This Review delves into the burgeoning field of predictive analytics within climate finance, emphasizing its significance in aiding investors to navigate the multifaceted landscape of climate-related risks and opportunities. By leveraging advanced data analytics techniques, predictive analytics empowers investors to anticipate and mitigate climate-related risks, ranging from physical risks such as extreme weather events and sea-level rise to transition risks associated with regulatory changes and technological shifts. Moreover, predictive analytics enables investors to identify emerging opportunities in sectors poised for sustainable growth, such as renewable energy, clean technology, and climate resilient infrastructure. This Review also sheds light on the methodologies and data sources utilized in predictive analytics for climate finance, encompassing climate models, satellite imagery, socioeconomic indicators, and financial data. Through the analysis of historical trends and future projections, predictive analytics provides investors with actionable insights to inform their investment decisions and align their portfolios with climate-related goals and mandates. Despite its potential benefits, the adoption of predictive analytics in climate finance is not without challenges. This Review examines the hurdles associated with data quality, model uncertainty, regulatory complexities, and the integration of climate-related factors into financial decision-making processes. Addressing these challenges necessitates interdisciplinary collaboration, robust risk assessment frameworks, and ongoing innovation in predictive analytics methodologies. In conclusion, this Review underscores the critical role of predictive analytics in climate finance and its transformative potential in enhancing the resilience and sustainability of investment portfolios. By harnessing the power of data-driven insights, investors can proactively manage climate-related risks, capitalize on sustainable investment opportunities, and contribute to the transition towards a low-carbon economy. As climate change continues to exert profound impacts on financial markets, the integration of predictive analytics represents a strategic imperative for investors seeking to navigate the evolving landscape of climate finance effectively.

Europe’s independence from Russian natural gas — Effects of import restrictions on energy system development

With the Russian invasion on Ukraine in 2022 and the following disruption of Russian natural gas imports, Europe’s energy reliance on Russia has become more apparent than ever. To tackle the resulting challenges of a limited supply of fossil fuels from Russia and especially its effects on energy system development, short and long-term effects need to be investigated thoroughly. This paper aims to quantitatively analyze the impact of reduced natural gas availability from Russia on the European energy system, both in the coming years, as well as in the future. Using the Global Energy System Model (GENeSYS-MOD), three scenarios with varying amounts of Russian natural gas and further impacts of reduced fossil fuel imports from Russia are calculated. Results show that strong effects are mostly observed in the short to medium-term, but an overall earlier phase-out of fossil fuels can be achieved in the long-term. The reduction of natural gas imports is tackled by an increase in LNG imports and domestic natural gas production to overcome the supply gap. Strong reactions are seen in the levelized costs of electricity generation between 2022 and 2025, with higher costs in scenarios with restrictions on Russian natural gas imports, but with a negligible difference in the long-term. Most importantly, lower emissions in scenarios with reduced natural gas supply from Russia highlight the positive effect of an early reduction in fossil fuels and investment in renewable technologies, resulting in a near 100% emission-free energy system by 2045, 5 years before the Base scenario with unrestricted Russian gas imports. The results find that a limitation of Russian fossil imports does not pose a long-term threat to the European energy system or its required transition away from fossil fuels, but can rather accelerate its decarbonization and energy demand reductions.

Renewable Energy Systems 2023

In the last few years, the adoption of renewable technologies and energy efficiency strategies has become increasingly pivotal for reaching the ambitious target of an 80–95% reduction in greenhouse gas emissions by 2050 [...]

Efficient and selective conversion of xylose to furfural over carbon-based solid acid catalyst in water-γ-valerolactone

Hydrothermal liquefication of biomass to produce high-quality chemicals and liquid fuels is considered as a renewable and sustainable technology. Herein, a one-step hydrothermal method was used to prepare microcrystalline cellulose supported carbon-based catalyst PTA-BC with the activation factor of phosphotungstic acid. It was demonstrated by Py-FTIR, NH3-TPD and XPS that PTA-BC is not only rich in functional groups but also contains Brønsted acid sites (hydroxyl groups) and Lewis acid sites (CC, carboxyl groups). After experimental optimization, the optimum yield of furfural obtained from xylose catalyzed by PTA-BC was 81.02% at the reaction temperature of 180 °C and the reaction time of 20 min. The results show that PTA-BC contains –COOH, –OH and CC as catalytic sites and that the synergistic effect of these functional groups. The nature of the reaction solvent, appropriate reaction temperature and residence time are the main reasons for the good catalytic performance. This work provides a promising way for the synthesis of solid acid catalyst, which has a wide application prospect for the production of furfural.

Sustainable green remodeling strategies for public nursery school in South Korea: A simplified model

Existing buildings necessitate conversion to green buildings through remodeling. In early stages of this green remodeling project, it is crucial to establish a clear objective or strategy, because this determines the energy efficiency improvement rate of existing buildings. In this study, a local public nursery school was taken as the case study, where three objectives were determined: zero energy building (ZEB), greenhouse gas emissions (GHG), and energy saving cost (ESC), and an efficient strategy for green remodeling according to each objective was provided. In addition, this study introduced a function called multi-objective energy efficiency ratio (MO-EER) to allow consumers to establish an optimal strategy by setting weights for each objective. The results of the study demostrated that both passive and renewable technologies were important in zero energy buildings. To achieve ZEB, it was advantageous to apply passive and renewable energy technologies that greatly reduces primary energy consumptions. In terms of GHG emissions, the more green remodeling technology, the better the building energy efficiency. In case of ESC, it was advantageous to apply a technology that greatly reduces secondary energy consumptions.

RENEWABLE ENERGY TECHNOLOGIES IN ENGINEERING: A REVIEW OF CURRENT DEVELOPMENTS AND FUTURE PROSPECTS

This comprehensive review examines the current state of renewable energy technologies within the field of engineering, analyzing recent developments and outlining future prospects. As the global demand for sustainable energy solutions continues to rise, understanding the advancements in renewable technologies becomes crucial for the engineering community. The review encompasses a diverse range of renewable sources, including solar, wind, hydropower, biomass, and geothermal energy. The solar energy sector has witnessed remarkable progress, with innovations in photovoltaic materials, energy storage, and efficiency enhancements. Advancements in wind energy technologies focus on improving turbine designs, optimizing energy conversion, and exploring offshore wind farms. Hydropower developments emphasize sustainable and eco-friendly dam designs, while biomass technologies explore novel methods for efficient biofuel production. Geothermal energy, often overlooked, is gaining momentum with advancements in enhanced geothermal systems and innovative drilling techniques. The review also delves into the integration of renewable energy sources into smart grids, promoting efficient energy distribution and storage. Additionally, it addresses the role of artificial intelligence and machine learning in optimizing renewable energy systems, enhancing predictability, and maximizing energy output. Furthermore, the review emphasizes the importance of policy frameworks and financial incentives in driving renewable energy adoption. The ongoing transition towards decentralized energy systems and the exploration of novel materials for energy capture and storage are highlighted as key areas for future research. The potential of emerging technologies such as perovskite solar cells and floating offshore wind farms is also discussed. This review provides a holistic overview of the current landscape of renewable energy technologies in engineering, offering valuable insights into the advancements made thus far and outlining the promising prospects for a sustainable energy future. Engineers and researchers will find this review instrumental in navigating the evolving field of renewable energy and contributing to the ongoing global efforts towards a greener and more sustainable energy landscape.
 Keywords: Renewable Energy, Energy, Climate Change, Development, Engineering, Review.

The Role of the Green Economy in Economic Growth in Indonesia Based on an Islamic Economic Perspective

Over the past few years, the concept of a green economy has been recognized as a vital mechanism for achieving economic progress in both developed and emerging nations. This study aims to analyze the role of the green economy in Indonesia's economic expansion based on an Islamic economic perspective. The research methodology employs library analysis and content assessment. The data sources utilized in this study were gathered from previous research, articles, regulations, and reference literature pertaining to green economics, economic growth, and Islamic economics. The results denote that the green economy bears tremendous potential to support economic advancement in Indonesia under an Islamic economic lens. By applying key tenets such as the obligation to safeguard nature and the judicious utilization of resources, Indonesia can cultivate a development paradigm that is sustainable and beneficial across all societal strata. This research recommends that private and public sector entities continue endorsing and integrating green economy principles moving forward. Specifically, Islamic financial instruments can be directed toward eco-friendly investments like renewable energy, sustainable agriculture, green technologies, and environmentally-conscious infrastructure. Such participations from Islamic economics in "greening" the economy signify promising trajectories aligning ethical and sustainable finance. As the world grapples with urgent ecological crises, policy frameworks in Indonesia should incentivize collective societal and commercial transitions toward greener fiscal practices. Islamic finance with its underlying moral philosophy can potentially transform finance itself into an apparatus upholding both economic and environmental welfare.

Indoor comfort management and energy consumption in Arctic buildings: Occupant perceptions in an indigenous community of Canada

Arctic and subarctic communities currently face major and unique energy and housing challenges. However, the perceptions, needs, and adaptive strategies of occupants related to energy consumption and comfort in their dwellings are not well known. In this study, 16 semi-structured interviews were conducted in the Inuit community of Quaqtaq (Nunavik, Quebec, Canada) to investigate occupants’ experiences, observations, and perceptions on these topics. The topics covered comfort, window opening, use of curtains, and usage of thermostats, water, and lighting. Furthermore, awareness of energy consumption and renewable technologies was investigated, and occupants shared their vision of the ideal home. It was found that windows and thermostats are often used simultaneously to regulate temperature and that non-uniform temperature distribution and cold floors were often noted by occupants. Due to the limited amount of water available, coordination with neighbors was needed for activities requiring water. Awareness and interest in energy savings and renewable energy varied significantly among participants. Participants mentioned that their ideal home would have better insulation, larger water tanks, and more storage space. These results help to understand occupant behavior, energy consumption patterns, and well-being in houses of northern communities and can guide the development of future housing units.

Екотрансформація енергетичного сектора України

The research has been focused on analyzing the stages of formation of Ukraine’s energy sector and its transformation in the context of full-scale military aggression from Russia. Considering the significance of energy for national security and economic growth, the article is emphasized the perspectives for green development during wartime. Specifically, it is examined the readiness of the energy sector to implement renewable energy sources and green technologies in the context of global challenges and the need to reduce dependence on traditional energy sources. The research is highlighted the interrelation between consumer-conscious development and stimulating innova­tion in the energy sector during crises. The relevance of the research is driven by global trends, climate changes, and the necessity for reforms in the energy sector. The hypothesis is suggested that the war may serve as a catalyst for implementing green development strategies and transitioning to renewable energy sources. The methodology is included an analysis of the stages of formation and the current state of the energy sector during military actions, as well as its preparedness for the implementation of environmentally friendly technologies. The re­sults of the research are confirmed that the conscious development of consumers, focused on supporting green initiatives, it can be a key factor in the development of the renewable energy sector in the conditions of geopolitical uncertainty.

How does trade policy uncertainty affect green innovation in the USA and China? A nonlinear perspective.

Green innovations are the most critical factor in promoting environmental sustainability worldwide. Trade can speed up the adoption of green innovations by facilitating the transfer of information, skills, and technology. However, trade policy uncertainty can create significant challenges for businesses investing in eco-innovations, leading to increased risk, reduced investment, and slower progress toward sustainable technologies. Recently, a growing number of researchers have shown their interest in finding the factors that can impact green innovations, but none have investigated the influence of trade policy uncertainty on green innovations in the USA and China. In addition, none of the past studies has relied on the nonlinear assumption. This analysis fills these gaps by examining the nonlinear impacts of trade policy uncertainty on eco-innovations in China and the USA over 2000Q1-2021Q4 by employing a nonlinear ARDL model. The finding reveals that a positive shock in trade policy uncertainty results in a decrease in green innovation in the USA and China, while a negative shock in trade policy uncertainty leads to an increase in green innovation in the USA over the long run. The nonlinear models also indicate that a positive shock in trade policy uncertainty harms green innovation in both the USA and China in the short run. The robustness of these results is confirmed by the NQARDL model, which confirms that an upsurge in trade policy uncertainty lowers green innovation in most quantiles in the USA and China in the short and long run. Conversely, negative shocks in trade policy uncertainty stimulate green innovation at most quantiles in both China and the USA, in the short and long run. Thus, policymakers need to consider the potential impact of trade policies on eco-innovations and work to create stable and predictable trade environments that support the growth of renewable technologies and other sustainable solutions.

RETRACTED: Hydrogen role in energy transition: A comparative review

This comparative review explores the pivotal role of hydrogen in the global energy transition towards a low-carbon future. The study provides an exhaustive analysis of hydrogen as an energy carrier, including its production, storage, distribution, and utilization, and compares its advantages and challenges with other renewable energy sources. The study emphasizes the potential of hydrogen, produced via electrolysis powered by conventional and renewables, as a promising solution for abate sectors such as heavy industries, transport, and heating applications. Despite its potential, the study recognizes significant obstacles, such as high production costs, lack of adequate infrastructure for transport and storage, and the need for supportive policies and regulatory frameworks. A key insight is that hydrogen is not in competition with other renewable technologies, but rather, is a vital complement, especially for addressing renewable intermittency and energy storage issues. A regional analysis shows varied levels of readiness and adoption, with Europe, United States and, East Asia leading in policy support and infrastructure development. The study concludes with the broader social and economic implications of a hydrogen economy, including regional development opportunities. The review study underscores the substantial role of hydrogen in the energy transition, while acknowledging the challenges that need to be addressed through technology advancements, policy support, and international collaboration.

Effect of bandgap tunability on the physical attributes of potassium-based K2CuBiX6 (X = I, Br, Cl) double perovskites for green technologies

Potassium-based perovskites hold significant potential to revolutionize renewable technology by enabling more cost-effective and sustainable energy devices. The DFT incorporated in the Wein2K interface is used to provide an extensive investigation of the structural, mechanical, electrical, optical, and thermoelectric behavior of double perovskites K2CuBiX6 (X = I, Br, Cl). Structural stability is confirmed through optimization curves, tolerance factor and octahedral tilting. Mechanical properties support the ductile character of K2CuBiX6 (X = I, Br, Cl). Electronic band structures reveal that perovskite K2CuBiI6 initially possesses a bandgap of 0.6 eV. This bandgap is increased to 0.97 eV when (I) atom is replaced with (Br) atom. Furthermore, a prominent shift in the bandgap value occurs when the bromine (Br) atom is replaced with a chlorine (Cl) atom, resulting in a bandgap of 1.3 eV. The Kramer-Kronig equations are used to evaluate the optical characteristic, which shows significant absorption in the visible range for all structures, allowing them to be utilized in optoelectronics. Numerous thermoelectric characteristics are calculated using the Boltzmann semi-classical theory. The perovskites exhibit substantial potential for renewable energy applications, as they demonstrate significant ZT values, along with elevated Seebeck coefficients and electrical conductivities, which enhance their suitability for utilization in clean energy technologies.

Dynamic nonlinear CO2 emission effects of urbanization routes in the eight most populous countries.

A dynamic STIRPAT model used in the current study is based on panel data from the eight most populous countries from 1975 to 2020, revealing the nonlinear effects of urbanization routes (percentage of total urbanization, percentage of small cities and percentage of large cities) on carbon dioxide (CO2) emissions. Using "Dynamic Display Unrelated Regression (DSUR)" and "Fully Modified Ordinary Least Squares (FMOLS)" regressions, the outcomes reflect that percentage of total urbanization and percentage of small cities have an incremental influence on carbon dioxide emissions. However, square percentage of small cities and square percentage of total urbanization have significant adverse effects on carbon dioxide (CO2) emissions. The positive relationship between the percentage of small cities, percentage of total urbanization and CO2 emissions and the negative relationship between the square percentage of small cities, square percentage of total urbanization and CO2 emissions legitimize the inverted U-shaped EKC hypothesis. The impact of the percentage of large cities on carbon dioxide emissions is significantly negative, while the impact of the square percentage of large cities on carbon dioxide emissions is significantly positive, validating a U-shaped EKC hypothesis. The incremental effect of percentage of small cities and percentage of total urbanization on long-term environmental degradation can provide support for ecological modernization theory. Energy intensity, Gross Domestic Product (GDP), industrial growth and transport infrastructure stimulate long-term CO2 emissions. Country-level findings from the AMG estimator support a U-shaped link between the percentage of small cities and CO2 emissions for each country in the entire panel except the United States. In addition, the Dumitrescu and Hulin causality tests yield a two-way causality between emission of carbon dioxide and squared percentage of total urbanization, between the percentage of the large cities and emission of carbon dioxide, and between energy intensity and emission of carbon dioxide. This study proposes renewable energy options and green city-friendly technologies to improve the environmental quality of urban areas.