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Exergy is a thermodynamic concept that ponders the quality of energy. It evaluates the irreversibilities of a machine, demonstrating its capacity to perform work associated with energy conversion. This article focuses on directing public policies and vehicle development toward their most proper usage worldwide. In the urban mobility scenario, there is an obvious demand to decrease greenhouse gas (GHG) emissions. In addition, the internal combustion engine (ICE) experiences considerable energy losses through heat exchange through the radiator and exhaust flow gases, which are not considerable in battery electric vehicles (BEVs) since there are no exhaust gases subsequent to combustion, nor combustion itself. This work presents longitudinal dynamics simulations of passenger vehicles to understand the magnitude of exergy destruction in ICEVs and BEVs, considering the Brazilian and European Union electric energy mix. Overall, the method can be applied to any other country. The simulation and model parameters were configured to match production road vehicles commercialized in the Brazilian market based on different versions of the same model. Two vehicle dynamic duty cycles were used, one relating to urban usage and another to highway usage, resulting in an overall exergy efficiency of around 50–51% for BEVs considering the exergy destruction in power plants. In contrast, ICE has an average efficiency of 20% in the urban cycle and around 30% in the highway cycle. By comparing the overall equivalent CO2 emissions, it is possible to conclude that EVs in the European energy matrix produce more GHG than ICE vehicles running on ethanol in Brazil. Nevertheless, there are increasing uses of coal, natural gas, and oil thermal electric power plants, raising the question of how the transition may occur with a general increase in electrification since there is an increasing electric expenditure in all sectors of society, and the renewable energy plants may not meet all of the demand. [ABSTRACT FROM AUTHOR]

Exergy is the maximum useful work that can be obtained from a system in a specific state and environment. Exergy research has focused on energy fuels, although wastewater systems have not been studied in depth. This review explores the study and exergy use for wastewater systems in Latin America over the last 20 years. Chronological production, authors, citations, geographic origin, topic and purpose of publishing were examined through a documentary and bibliometric analysis. Exergy has started its development in Latin America, and it is led by a single school, there is evidence of a single author with 30% of citations and 25% of publications. Brazil, Colombia and Mexico produced 81% of publications, their main purpose is evaluating processes and by-products. The review concluded an incipient exergy development in wastewater systems in the region and exposed the need to stimulate research as a strategy to achieve the SDGs. [ABSTRACT FROM AUTHOR]

A mixed cabin solar dryer was designed and tested in Brazil in the spring equinox, for the drying of corn grains. The key advantage of the current design is its ability to work even in locations with no electricity because a photovoltaic module is used to power an electrical heater and fans. The analysis of the drying process was performed based on the first and second laws of thermodynamics. For average solar radiation and ambient temperature of 710 W/m2 and 30 °C, respectively, the average thermal efficiency obtained was 21% and the exergy efficiency ranged between 10% and 66%, with an average value of 23%. It was observed that the corn grains reached the desired moisture content of 13% in 8.5 h, while a similar sample subjected to natural sun drying failed to reach this moisture content in 24 h. The PV module was also used to preheat the drying air, allowing an average increase in the airflow temperature of 14 °C, reaching a maximum of 27 °C. • This study used a mixed cabin solar dryer to dry corn grains. • Energetic and exergetic analyses of the dryer system are investigated. • Average increase of the air temperature through the PV module was 14 °C. • Average drying efficiency was 6.1%. • Exergetic efficiency varied between 10 and 66%. [ABSTRACT FROM AUTHOR]

As industrial air compressors are the most energy intensive, a comprehensive energy and exergy analysis, reducing energy usage by various energy savings measures are highly important to reduce their energy consumption and emission for the sustainable future growth. A comprehensive analysis on energy performance, exergy efficiency, CO 2 emission, sustainability, and the associated economic implications were studied in a typical industrial air compressor system of a TiO 2 manufacturing industry, located in Bahia, Brazil. Necessary input data were taken from this industry to analyze energy, exergy, emission, economic, and sustainability performance of the air compressor. The predicted overall exergy efficiency of the compressors varies from to 5.27%–21.94%. Sustainability indicators like Sustainability Index (SI), Depletion Number (DN), Waste Exergy Ratio (WER), & Environmental Effect Factor (EEF) were analyzed and the evaluated sustainability index found to vary from 1.05 to 1.28. Waste exergy ratio is estimated to be 0.95 and environmental effect factor is found to be 17.95 for compressor A. Discharge pressure reduction, power factor improvement, waste heat recoveries are the main areas where improvement have been identified. Reducing discharge pressure can save annually 3515.180 MWh of electricity leading to a reduction of 347.7 ton of CO 2 emission per year. It is also noted that the reduced discharge pressure lead to an increased exergetic efficiency. Among various options, reducing discharge pressure came out to be the most cost effective measure with lesser internal rate of return. The industry could save a total of 5634.2 MWh of electricity and reduce CO 2 emission by 557 ton per annum with an investment of US$ 570,000. The return on investment for the investment is estimated to be 9 months. • Overall exergy efficiency of the compressors varies from 21.94% to 5.27%. • Sustainability indexes found to vary from 1.05 to 1.28. • Waste exergy ratio is 0.95 and environmental effect factor is 17.95 for Compressor A. • Reducing discharge pressure can save annually 3515.180 MWh of electricity. • Investment of US$ 570000 can save 5634.2 MWh of electricity & reduce 557 ton CO 2. [ABSTRACT FROM AUTHOR]

This paper presents a technical (based on the exergy amount) and environmental analysis concerning an existing 50 MWe steam power plant located in the south of the Santa Catarina state - Brazil, designed to operate with pulverized coal and modified to operate in co-firing process with coal-biomass. In addition to the power plant, the study considered an extended boundary that involves the processes related to the obtaining, transportation, and handling of both coal and biomass. The exergy analysis was focused in the second law of thermodynamics, while the environmental analysis followed the Life Cycle Assessment (LCA) methodology, taking into account 1 MWh as functional unit and the global warming impact category, following the IPCC GWP index, over 100 years. For both cases (only coal and co-firing), the exergetic analysis indicated that the power plant is responsible for over 95 % of the exergy consumption. Results indicated that for the case of operating only with coal, 1,230 kg of CO2-eq per MWh are emitted, whereas for operation in co-firing, with a share of 10% of biomass on energy basis, this amount changes to 1,103 kg CO2-eq per MWh. [ABSTRACT FROM AUTHOR]

Abstract: Many works have shown the potential of the Brazilian sugarcane industry as an electricity supplier. However, few studies have studied how this potential could be achieved without jeopardizing the production of sugar and ethanol. Also, the impact of modifications in the cogeneration plant on the costs of production of sugar and ethanol has not been evaluated. This paper presents an approach to the problem of exergy optimization of cogeneration systems in sugarcane mills. A general model to the sugar and ethanol production processes is developed based on data supplied by a real plant, and an exergy analysis is performed. A discussion is made about the variables that most affect the performance of the processes. Then, a procedure is presented to evaluate modifications in the cogeneration system and in the process, and their impact on the production costs of sugar, ethanol and electricity. Furthermore, a discussion on the renewability of processes is made based on an exergy index of renewability. As a general conclusion, besides adding a new revenue to the mill, the generation of excess electricity improves the exergo-environmental performance of the mill as a whole. [Copyright &y& Elsevier]

Abstract: An assessment is made of the atmospheric emissions from the life cycle of fuel ethanol coupled with the cogeneration of electricity from sugarcane in Brazil. The total exergy loss from the most quantitative relevant atmospheric emission substances produced by the life cycle of fuel ethanol is 3.26E+05kJ/t of C2H5OH. Compared with the chemical exergy of 1t of ethanol (calculated as 34.56E+06kJ), the exergy loss from the life cycle''s atmospheric emission represents 1.11% of the product''s exergy. The activity that most contributes to atmospheric emission chemical exergy losses is the harvesting of sugarcane through the methane emitted in burning. Suggestions for improved environmental quality and greater efficiency of the life cycle of fuel ethanol with cogenerated energy are: harvesting the sugarcane without burning, renewable fuels should be used in tractors, trucks and buses instead of fossil fuel and the transportation of products and input should be logistically optimized. [Copyright &y& Elsevier]

Abstract: This study is to modify the ecological footprint methodology by incorporating non-renewable or abiotic resources as an additional category. The use of abiotic resources can be quantified as global hectare by using thermodynamic approaches. A detailed case study on various countries including Australia, Belgium, Brazil, Canada, Japan, USA, and Vietnam shows the advantage of using the new modified ecological footprint (EF) as an indicator for sustainable development. The modified EF includes not only biotic resources, but also the abiotic resources. The case study indicates that the modified EF differs from the traditional EF up to 123% in the case of Belgium, and 90% in the case of Australia. For developing countries such as Brazil and Vietnam, the differences are relatively smaller (21% for Brazil and 9.4% for Vietnam). The estimated total ecological footprint of the world using the new method implies more serious problems associated with over consumption than using results from the original ecological footprint method. [Copyright &y& Elsevier]

Due to the major role played by fossil fuels in the current hydrogen production scenario, environmentally friendly pathways are being considered. These pathways can use a wide variety of raw materials, providing flexibility for hydrogen production regardless of geographical, economic and political aspects. However, the choice for a given process and feedstock must ensure its environmental viability, which can be evaluated through several indicators such as carbon, land and water footprints. In this study, one of the most promising hydrogen production processes, namely steam reforming, was assessed for the Brazilian scenario from a water consumption point of view. The systems were computationally simulated using Aspen HYSYS V11™ software for hydrogen production from natural gas, bioethanol and glycerol – all of which are readily available for use in Brazil, and an exergy analysis was applied alongside known and estimated water footprint indicators. Steam methane reforming (SMR) presented the lowest water footprint per kg of H 2 (0.257 m³/kgH 2), followed by glycerol (0.768 m³/kgH 2) and bioethanol reforming (9.651 m³/kgH 2). The exergoenvironmental analysis shows that the main bottlenecks identified are related to exergy destruction in the burners (52.46–57.32%), reformers (2.48–21.72%) and heat exchangers (19.45–32.61%), but globally, exergoenvironmental indicators showed that steam reforming of the presented feedstock can be an alternative to be explored in the context of water resources preservation. [Display omitted] • Three steam reforming pathways for H 2 production were computationally assessed. • Energy/exergy analysis was carried out to identify major irreversibilities. • Water footprint indicator was applied to estimate the final water consumption of H 2. • Methane led to the lowest water consumption, followed by glycerol and bioethanol. • High water usage of sugarcane crops was decisive for high ethanol water footprint. [ABSTRACT FROM AUTHOR]

The transportation sector in Brazil is a significant consumer of energy. This consumption progressed at a regular speed, even though vehicles individually become more efficient. The exergy analysis of societies conventionally consists of a single efficiency value applied to extended periods, and this value is essentially a reproduction of an instant. In this study, the exergy efficiencies are calculated for the Brazilian passenger vehicle fleet from 1970 to 2020 based on a definition of efficiency (ratio of the transport service needed to the fuel exergy consumed), which differs from traditional input/output analysis. To calculate efficiencies, some key vehicle parameters were analyzed, and their evolution was measured over time. Exergy efficiencies were low in the period, between 3.4% and 8.3%, with a recent improvement tendency. Transportation service required fell steadily until around 2010 when the trend was reversed. This formulation of efficiency should improve conventional exergy analysis applied to societies and help understand the administration of vehicle improvement and consumer choice, improving policy motivations for better resource use in the future. • Method can be replicated to improve comparisons and traditional exergy analysis applied to societies. • Exergy efficiencies were calculated for 50 years for hundreds of vehicles and did not improve substantially. • Efficiencies were low, between 3.8% and 8.3%. • Transportation service can be useful to assess the state of technology and consumer preferences. [ABSTRACT FROM AUTHOR]

• Thermoeconomic model to assess the feasibility of ORC cogeneration systems was made; • Case based on the energy demands of an laboratory university building was analyzed; • Two mode simple (S) and combined (C) of the Organic Rankine cycle (ORC) were analyzed; • ORC-C allowed increases of 33.6% in power production and 34.5% energy efficiency; • ORC-S and ORC-C mode achieve up to 24.5 and 37.5% of the electricity demand, respectively; • Specific cost of hot water has a strong influence on the total cost of the products; This paper proposes a cogeneration system to achieve the partial electric and thermal demands of a building in the public University. This proposed system comprises an Internal Combustion Engine (ICE), an organic Rankine cycle (ORC), and equipment that will operate as a sink. For the latter, two types of equipment were selected: a cooling tower and an Absorption Refrigeration System (ARS). The building selected to propose the cogeneration system is the Institute of Sustainable Energies (IES), located at the Federal University of Paraíba (UFPB), in the Northeast of Brazil. The performance of the system based on energetic and exergetic points of view operating under two distinct modes; ORC Simple (ORC-S) and ORC Combined (ORC-C), was compared. Both modes are based on the energy availability of the ICE exhaust gases. The thermodynamic models for both modes were developed based on the first and second laws of thermodynamic considering input parameters, such as inlet temperature, pressure ratio, and outlet temperature of the expander and the cold-water storage tank. For the exergoeconomic technique, the SPECO Method (Specific Exergy Costing) was used and implemented along with the Thermodynamic model. The ORC system studied uses a scroll expander and operates with R-134a as the working fluid and water/ammonia pair for the single-effect ARS. The results showed that the ORC-C mode can meet from 18.9% to 37.5% of the IES electricity demand, while the ORC-S mode can meet from 12.4% to 24.5%. The thermodynamic analysis reported that the ORC-C allowed a 33.6% increase in mechanical power production, an increase from approximately 4.5% to 34.5% in energy efficiency as well as exergy efficiencies around 40% and reduction of the total destroyed exergy. From the exergoeconomic point of view, the specific cost of the chilled water has a slight influence on the total cost of the products, while the specific cost of hot water has a strong influence on the total cost of the products (a variation of approximately 46% for a distinct heat source). [ABSTRACT FROM AUTHOR]

This article proposes the utilization of the concepts of destroyed exergy and exergy efficiency for equipment and process performance indicators that are related to the current energy planning scenario in Brazil, more specifically with energy-efficiency labelling. Several indicators associated with these concepts are discussed, including one national program that is based on labeling the energy efficiency of several residential, commercial and industrial appliances. The grades are indicated in the equipment using values from A to G. This labeling system is useful for discriminating similar technologies used for the same function; nevertheless produced by different enterprises. For this complementary analysis, two types of refrigeration methods were compared, absorption and vapor compression; however, these energy indexes alone are not sufficient parameters to select among these two technologies, because their performance indexes definition are different. To address this, our research considers the second law of thermodynamics through exergy analysis as a proper sub-index to obtain a systematic comparison between these various indicators. It is significant to highlight that seldom research studies addressed to this problem so explicitly, in an actual governmental working solution, aiming at discussing to the society the advantage of the usage of the "quality of the energy" as a complementary index to governmental and personal choices. Results indicate that it is possible to use the destroyed exergy and exergy efficiency to help select the technology that better utilizes natural resources, considering the energy matrix of the country. Appliances for water heating and air conditioning were compared from energy and exergy viewpoint, where the last gave additional information about the quality of energy conversion process, giving a completely different trend from the energy analysis alone, without the necessity to think about the energy matrix. Later this issue is addressed from both points of view. Future studies may suggest an exergy based index. The energy efficiency suggests that electrical shower (values higher than 95%) are better than gas water heaters (83%) in using natural resources, whereas the exergy efficiency shares similar magnitudes (about 3%). A related pattern is shown for the theoretical air conditioning systems. The vapor compression systems have an energy index higher than 3, and absorption systems lower than 1. For these circumstances, the exergy efficiency shows figures nearby 30%. [ABSTRACT FROM AUTHOR]