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The sustainability of the second-generation biofuels requests to confirm that the energy produced from lignocellulosic biomass is significantly greater than the energy consumed in the process. As lignocellulosic biomass does not affect the food supply, sugarcane bagasse was analyzed as a raw material for second-generation biofuels production. Exergy analysis serves as a unified and effective tool to evaluate the global process efficiency. Exergy analysis evaluates the performance of sugarcane bagasse and its sustainability in the bioethanol production process. In this work, four ethanol production topologies using the typical daily amount of residual biomass produced by the sugar industry were compared. The exergy...
Norway has administered its petroleum resources using three distinct government bodies: a national oil company engaged in commercial hydrocarbon operations; a government ministry to direct policy; and a regulatory body to provide oversight and technical expertise. Norway's relative success in managing its hydrocarbons has prompted development institutions to consider whether this “Norwegian Model” of separated government functions should be recommended to other oil-producing countries. By studying ten countries that have used widely different approaches in administering their hydrocarbon sectors, we conclude that separation of functions is not a prerequisite to successful oil sector development. Countries where...
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,...
This study deals with modeling and analyzing the performance of greenhouses from the power plant through the heating system to the greenhouse envelope using exergy analysis method, the so-called low exergy or LowEx approach, which has been and still being successfully used in sustainable buildings design, for the first time to the best of the author’s knowledge. For the heating applications, three options are studied with (i) a solar assisted vertical ground-source heat pump greenhouse heating system, (ii) a wood biomass boiler, and (iii) a natural gas boiler, which are driven by renewable and non-renewable energy sources. In this regard, two various greenhouses, the so-called small greenhouse and large greenhouse,...
This study analyses three feasible regulation methods of an in-service cogeneration plant. The main task is to study the potential energy savings, CO2 reduction and the increase in profitability compatible with the lowest transformation costs. The cogeneration system is composed of two General Electric LM2500 gas turbines and a heat recovery steam generator (HRSG). Two plant localizations in Spain have been considered; San Fernando (Cádiz) where the current plant is located, and Burgos. The latter has been taken into account to analyze the effect of cooler weather on the regulation methods. The paper has been divided into three parts. First, a revision of the current legislation regarding cogeneration in Spain is...
We propose a model for an exhausted upper continental crust. The Crepuscular Earth represents a degraded planet where all resources have been extracted and dispersed, and all fossil fuels have been burned. The starting point of the model of crepuscular crust is the composition given by the geochemist Grigor’ev, which is constrained by the conservation of mass statement between the chemical composition of the crust in terms of elements and in terms of minerals. Additionally, the model is given geological consistence, by introducing a series of assumptions based on geological observations. As a result, the obtained crepuscular crust is composed of the 294 most abundant minerals. Together with the model of exhausted...
The concept of probability density frequency, which is successfully used for analyses of wind speed and outdoor temperature distributions, is now modified and proposed for estimating solar radiation distributions for design and analysis of solar energy systems. In this study, global solar radiation distribution is comprehensively analyzed for photovoltaic (PV) panel and thermal collector systems. In this regard, a case study is conducted with actual global solar irradiation data of the last 15 years recorded by the Turkish State Meteorological Service. It is found that intensity of global solar irradiance greatly affects energy and exergy efficiencies and hence the performance of collectors.
The concept of probability density frequency, which is successfully used for analyses of wind speed and outdoor temperature distributions, is now modified and proposed for estimating solar radiation distributions for design and analysis of solar energy systems. In this study, global solar radiation distribution is comprehensively analyzed for photovoltaic (PV) panel and thermal collector systems. In this regard, a case study is conducted with actual global solar irradiation data of the last 15 years recorded by the Turkish State Meteorological Service. It is found that intensity of global solar irradiance greatly affects energy and exergy efficiencies and hence the performance of collectors.
The analysis framework introduced in this paper utilizes the recognition that exergy is a form of environmental free energy to provide a fundamental basis for valuing environmental interactions independent from their secondary impacts (e.g., global warming, photochemical smog). In order to extend exergy to analyze environmental interactions, modifications are required to the traditional representation of the environment and definition of the dead state used in technical exergy analysis. These are accomplished through a combination of logical extensions and use of non-equilibrium thermodynamic principles. The framework is comprised of two separate components: (1) environmental exergy analysis and (2) anthropocentric...
The status of computer simulation models from around the world for evaluating the possible ecological, environmental, and societal consequences of global change is presented in this paper. In addition, a brief synopsis of the state of the science of these impacts is included. Issues considered include future changes in climate and patterns of land use for societal needs, Models dis cussed relate to vegetation (e.g, crop), soil, bio-geochemistry, water, and wildlife responses to conventional, forecasted changes in temperature and precipitation. Also described are models of these responses, alone and interactively, to increased CO2, other air pollutants and UV-B radiation, as the state of the science allows. Further,...
In order to identify approaches for integrated gasification combined cycle (IGCC) plant optimization it is necessary to analyse where and why the losses in the process occur. Therefore a structured exergy analysis of an IGCC with carbon capture was performed to identify losses on a plant, subsystem and individual component level. The investigation of the IGCC base case revealed an exergetic efficiency of 40%. Thus, 60% of the whole fuel exergy is lost in the process. On the subsystem level it was found that the major loss contributor is the combined cycle followed by the gas treatment section and the gasification island. Furthermore, it was demonstrated that the significance of the losses is higher in upstream processes...
Norway has administered its petroleum resources using three distinct government bodies: a national oil company engaged in commercial hydrocarbon operations; a government ministry to direct policy; and a regulatory body to provide oversight and technical expertise. Norway's relative success in managing its hydrocarbons has prompted development institutions to consider whether this “Norwegian Model” of separated government functions should be recommended to other oil-producing countries. By studying ten countries that have used widely different approaches in administering their hydrocarbon sectors, we conclude that separation of functions is not a prerequisite to successful oil sector development. Countries where...
The status of computer simulation models from around the world for evaluating the possible ecological, environmental, and societal consequences of global change is presented in this paper. In addition, a brief synopsis of the state of the science of these impacts is included. Issues considered include future changes in climate and patterns of land use for societal needs, Models dis cussed relate to vegetation (e.g, crop), soil, bio-geochemistry, water, and wildlife responses to conventional, forecasted changes in temperature and precipitation. Also described are models of these responses, alone and interactively, to increased CO2, other air pollutants and UV-B radiation, as the state of the science allows. Further,...
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,...
Norway has administered its petroleum resources using three distinct government bodies: a national oil company engaged in commercial hydrocarbon operations; a government ministry to direct policy; and a regulatory body to provide oversight and technical expertise. Norway's relative success in managing its hydrocarbons has prompted development institutions to consider whether this “Norwegian Model” of separated government functions should be recommended to other oil-producing countries. By studying ten countries that have used widely different approaches in administering their hydrocarbon sectors, we conclude that separation of functions is not a prerequisite to successful oil sector development. Countries where...