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Abstract The combination of biomass gasification with fuel cells, especially high temperature Solid Oxide Fuel Cells (SOFCs) promises sustainable and highly efficient (decentralized and modular) energy conversion systems. This review encompasses the components of biomass integrated gasification–SOFC technology including biomass characteristics, the thermochemical conversion in gasifiers and the factors affecting the gasification process, the cleaning technologies for raw producer gas and its conditioning and finally the integration of gasifier with SOFCs. The influence of impurities present in biomass producer gas such as particulates, tar, H 2 S, HCl and alkali compounds based on recent experimental studies and their tolerance limits towards SOFCs are presented. Even though analysis based on the probable tolerance limits of impurities towards SOFCs and a comprehensive overview of the cleaning technologies for producer gas impurities indicate that producer gas cleaning at various temperatures using current technologies to meet SOFC requirements is possible, more experimental studies are still needed to acquire the detailed information on the tolerance limits of impurities for SOFCs. The recent theoretical modeling and experimental studies of biomass integrated gasification–SOFC systems are also presented.

In this study, a comprehensive exergy analysis was applied to a solar power system (SPS) located in the city of Van, Turkey. Van was always known as a sun city throughout history with the name of TUSBA. It has an average of 300 sunny days a year, an altitude of 1727 m, and an average daily temperature of 9.85°C. Considering how the need for sustainable and renewable energy sources - and knowledge over them - constantly increases, this SPS was built to reveal the true solar potential of the campus area of Yuzuncu Yil University of the city of Van, hopefully as a precursor for further large-scale SPS constructions in the region. A daily analysis considering energy production and global radiation was applied to the system in 2013 for 365 days. It was found that the yearly exergy efficiency of the system was 10% and total electrical energy production was 31,038.95 kWh, averaging 1763.5 kWh/kWp yearly.

Beyond the anticipated experience associated with tourism destinations, the United Nations World Tourism Organization (UNWTO) has further tasked (especially the destination countries) on the importance of tourism to achieving the 2030 Sustainable Development Goals (SDGs). From this dimension, this study employed the ecological footprint of the 10 most visited countries (France, Spain, United States, China, Italy, Mexico, United Kingdom, Turkey, Germany, and Thailand) over the period 1995-2016. Specifically, the study employed an econometric approach and found that increase in tourism arrivals and globalization is detrimental to the attainment of sustainable environmental quality in a long term. Precisely, a 1% increase in international arrivals and globalization is responsible for a 0.18 and 0.89% increase in ecological footprint in the long-run. These impacts of tourism activities and globalization are detrimental to the environmental quality of the destination countries. Meanwhile, the real income per capita and biocapacity in the destination countries improve the environmental quality of the panel of destination countries in the long-run. In addition, the study found significant evidence of Granger causality from tourism and real income to ecological footprint without feedback, the globalization-ecological footprint Granger causality nexus is with feedback. Moreover, potentially effective policies for government and other stakeholders especially toward attaining Global goals were proffered in the study.

Renewable energy has become more popular since it is cost-effective and more efficient than conventional energy sources. Biomass-based renewable energy is primarily used in emerging economies to ensure environmental sustainability. This study examines the asymmetric correlation between biomass energy consumption and CO2 emissions in the top-10 biomass energy consumer countries (Brazil, Canada, Thailand, China, Italy, India, Germany, USA, UK, and Japan). A new approach "Quantile-onQuantile (QQ)" is employed by utilizing the data from 1991 to 2018. Biomass energy consumption, with the exception of Thailand, significantly mitigates CO2 emissions at various quantiles in selected countries. As a robustness check, we used the quantile regression test, whose findings are consistent with the outcomes from the quantile-on-quantile method. However, the degree of asymmetry in the biomass energy-CO2 nexus varies by country, necessitating extra attention and government vigilance when developing biomass energy and environmental policies.

The aim of this study was to examine the risk of heavy metal, ammonia and sulfate transition from underground coal gasification (UCG) chars and process water of Malkara lignite to the groundwater around the UCG cavity. The residues were collected during laboratory-scale underground coal gasification studies of Malkara lignite in ex situ gasification simulator. In order to compare gasification with combustion in terms of water pollution, ash samples were obtained by combustion of Malkara lignite. To determine the leaching behavior of the char and ash samples, two leaching tests (EPA TCLP and EN 12457-2 methods) were applied. The concentration of heavy metals in char, ash and process water samples was determined by ICP-OES. Additionally, ammonia and sulfate analyses were conducted for process water. Based on the results of this study, it has been found that the concentration of some elements, such as B, Sb and Al in char and ash eluates exceeded the maximum level of drinking water standards. However, there is no landfill concern about char samples according to EU Landfill Directive. A significant increase in B concentration was observed in ash samples. Considering B and some other elements combustion residues were identified with much higher water contamination ability, compared to gasification residues. Ammonia concentration was observed extremely high in process water of the gasification tests. UCG technique may be more environmentally applicable technology compared to combustion for Malkara lignite reserves. However, further detailed studies are necessary in the early stage of the UCG field test design and application.

Abstract Conventional room air conditioners consume a significant amount of energy, and thereby negatively affect the environment. In this perspective, passive air conditioning systems using phase change material (PCM) are very promising and widely investigated recently. In this study, influence of a PCM-based passive air conditioner on temperature distribution was experimentally studied in a test room under the local tropical climatic conditions. Coconut oil and water were used for latent heat storage and sensible heat storage, respectively. A storage panel was constructed with two openings—an outlet for conditioned air and an inlet for indoor air, then filled with coconut oil or water to create an additional internal thermal mass (ITM) in the room. The storage material was discharged at night in the indoor or outdoor, and stratum air circulation was utilized to provide the conditioned air into the room during diurnal period. Temperature measurements were conducted at five vertical and five horizontal points. The gained results showed that employing ITM heat storage panel in the room reduced peak temperatures and enhanced the thermal environment. Coconut oil ITM provided 0.5 °C lower peak temperature in the occupant zone while greater temperature reductions were observed in the upper zone compared to the reference case. In addition, ITM panel significantly decreased the observed temperature fluctuations throughout a day. This study revealed that ITM-based stratum air circulation can be a profound solution to the existing high energy consumption problem of conventional air conditioners used in the small urban houses under tropical climate.

Abstract In this paper, energy and exergy analyses of the geothermal-based hydrogen production via thermochemical water decomposition using a new, four-step copper–chlorine (Cu–Cl) cycle are conducted, and the respective cycle energy and exergy efficiencies are examined. Also, a parametric study is performed to investigate how each step of the cycle and its overall cycle performance are affected by reference environment temperatures, reaction temperatures, as well as energy efficiency of the geothermal power plant itself. As a result, overall energy and exergy efficiencies of the cycle are found to be 21.67% and 19.35%, respectively, for a reference case.

Abstract Hydrogen is considered a potential game changer for world energy systems and a solution to climate change concerns, as it generates zero waste and it is suited for power generation and transportation. Despite its several advantages, there are significant technical challenges in deploying a stable hydrogen economy including improving its process efficiencies, lowering production costs, maintaining cost-effective transmission and distribution, and exploiting inexpensive and sustainable feedstocks. In this context, a detailed study was conducted to analyze the production sources, technologies, storage and transport systems, and global potential exportable feedstocks to produce hydrogen. A comprehensive analysis of current hydrogen production technologies with their energy efficiencies and hydrogen selling prices was reported in this study. Various hydrogen production technologies with their capital investments and CO2 emissions were also presented. Potential feedstocks for hydrogen production were identified and analyzed through a product space model, which characterizes a network of global exportable products based on their similarities and productive knowledge. It was established that the hydrogen production feedstocks and sources currently used are primarily available in six countries: the United States of America, France, Russia, Sweden, the Netherlands, and Spain. Broadly, the results revealed that the United States of America and Russia shared the highest hydrogen feedstock exports, indicating a higher probability of hydrogen production in these countries. Except for Russia, all the studied countries fell in the most desired quadrant, indicating that they can move in all product space directions to exploit unexplored hydrogen feedstocks for better sustainable economic growth.

Abstract This paper examines the effects of foreign trade and foreign direct investment (FDI) on CO 2 emissions in Turkey. We consider linear and nonlinear ARDL models and find significant asymmetric effects of exports, imports and FDI on CO 2 emissions per capita. However, FDI has no statistically significant long-run effects. In the long run, decreases in exports reduce CO 2 emissions per capita but increases in exports have no statistically significant effects. Increases in imports push up CO 2 emissions per capita, while decreases in imports have no long-run effects. On the other hand, CO 2 intensity, which measures CO 2 emissions per unit of energy, is not influenced by exports and imports, nor by FDI. Instead, it is affected positively by financial development and urbanization. Also, we find that an environmental Kuznets curve is present for both CO 2 measures so that increases in real GDP per capita have led to reductions in CO 2 emissions for at least the most recent decade, controlling for other confounding factors. Furthermore, the sectoral shares of CO 2 emissions in total CO 2 emissions change asymmetrically with foreign trade for two of four sectors, with export increases leading to lower CO 2 shares and imports having the opposite effect.