• Energy Research
• 12. Responsible consumption close
• IN close
• AU close
• BE close
• Energy Conversion and Management close

Abstract Many countries committed themselves in the Kyoto protocol to reduce greenhouse gas (GHG) emissions. Some of these targeted emission reductions could result from a switch from coal-fired to gas-fired electricity generation. The focus in this work lies on Western Europe, with the presence of the European Union Emission Trading Scheme (EU ETS). For the switching to occur, several conditions have to be fulfilled. First, an economical incentive must be present, i.e. a sufficiently high European Union Allowance (EUA) price together with a sufficiently low natural gas price. Second, the physical potential for switching must exist, i.e. at a given load, there must remain enough power plants not running to make switching possible. This paper investigates what possibilities exist for switching coal-fired plants for gas-fired plants, dependent on the load level (the latter condition above). A fixed allowance cost and a variable natural gas price are assumed. The method to address GHG emission reduction potentials is first illustrated in a methodological case. Next, the GHG emission reduction potentials are addressed for several Western European countries together with a relative positioning of their electricity generation. GHG emission reduction potentials are also compared with simulation results. GHG emission reduction potentials tend to be significant. The Netherlands have a very widespread switching zone, so GHG emission reduction is practically independent of electricity generation. Other counties, like Germany, Spain and Italy could reduce GHG emissions significantly by switching. With an allowance cost following the switch level of a 50% efficient gas-fired plant and a 40% efficient coal-fired plant in the summer season (like in 2005), the global GHG emission reduction (in the electricity generating sector) for the eight modeled zones could amount to 19%.

Abstract Many countries committed themselves in the Kyoto protocol to reduce greenhouse gas (GHG) emissions. Some of these targeted emission reductions could result from a switch from coal-fired to gas-fired electricity generation. The focus in this work lies on Western Europe, with the presence of the European Union Emission Trading Scheme (EU ETS). For the switching to occur, several conditions have to be fulfilled. First, an economical incentive must be present, i.e. a sufficiently high European Union Allowance (EUA) price together with a sufficiently low natural gas price. Second, the physical potential for switching must exist, i.e. at a given load, there must remain enough power plants not running to make switching possible. This paper investigates what possibilities exist for switching coal-fired plants for gas-fired plants, dependent on the load level (the latter condition above). A fixed allowance cost and a variable natural gas price are assumed. The method to address GHG emission reduction potentials is first illustrated in a methodological case. Next, the GHG emission reduction potentials are addressed for several Western European countries together with a relative positioning of their electricity generation. GHG emission reduction potentials are also compared with simulation results. GHG emission reduction potentials tend to be significant. The Netherlands have a very widespread switching zone, so GHG emission reduction is practically independent of electricity generation. Other counties, like Germany, Spain and Italy could reduce GHG emissions significantly by switching. With an allowance cost following the switch level of a 50% efficient gas-fired plant and a 40% efficient coal-fired plant in the summer season (like in 2005), the global GHG emission reduction (in the electricity generating sector) for the eight modeled zones could amount to 19%.

Abstract Combined absorption cooling device and humidification-dehumidification desalination component is newly proposed to be an alternative system to substitute the existing individual conventional arrangement for the betterment of energy usage. Specifically, among many waste heat recovery technologies, the combination of cooling and humidification-dehumidification processes is an innovative thought to implement a new thermodynamic system for improving the overall system performance. To be successful implementation of this innovation concept, in this study, both the above systems are combined to produce simultaneously 150 kW cooling effect and 0.1 kg s−1 freshwater production. This combined system also improves the effective use of waste heat. A parametric study of the proposed system is carried out to determine the optimum operational effect by varying different design constants based on the energy, exergy, and economic analyses. A multi-objective optimization model is also developed using the non-dominated storing genetic algorithm (NSGA-II) to obtain the minimum operating cost. In the optimization study, the total exergy efficiency is considered to be a maximization function and the total product cost is treated as a minimization objective. The results obtained from the exergy and economic studies reveal that the cooling assembly is the primary source for the irreversibility production with the exergy destruction rate of 17.0415 kW. Also, the exergoeconomic factor of humidifier is the lowest one (0.94%). From the multi-objective optimization, the total exergy efficiency and the total product cost are calculated as 0.5014 and 68.1680 $ GJ−1, respectively. At the optimum operating condition, calculated values of the gained output ratio (GOR) and coefficient of performance (COP) are 2.0181 and 1.2474, respectively. Furthermore, the present combined system is compared with the traditional humidification-dehumidification desalination system. This comparison highlights that the GOR of the proposed system is about 140% higher than the traditional system. Therefore, there is no doubt to be arising in mind that the operation of the proposed system produces more beneficial thermal aspects in comparison to the existing system.

Abstract Combined absorption cooling device and humidification-dehumidification desalination component is newly proposed to be an alternative system to substitute the existing individual conventional arrangement for the betterment of energy usage. Specifically, among many waste heat recovery technologies, the combination of cooling and humidification-dehumidification processes is an innovative thought to implement a new thermodynamic system for improving the overall system performance. To be successful implementation of this innovation concept, in this study, both the above systems are combined to produce simultaneously 150 kW cooling effect and 0.1 kg s−1 freshwater production. This combined system also improves the effective use of waste heat. A parametric study of the proposed system is carried out to determine the optimum operational effect by varying different design constants based on the energy, exergy, and economic analyses. A multi-objective optimization model is also developed using the non-dominated storing genetic algorithm (NSGA-II) to obtain the minimum operating cost. In the optimization study, the total exergy efficiency is considered to be a maximization function and the total product cost is treated as a minimization objective. The results obtained from the exergy and economic studies reveal that the cooling assembly is the primary source for the irreversibility production with the exergy destruction rate of 17.0415 kW. Also, the exergoeconomic factor of humidifier is the lowest one (0.94%). From the multi-objective optimization, the total exergy efficiency and the total product cost are calculated as 0.5014 and 68.1680 $ GJ−1, respectively. At the optimum operating condition, calculated values of the gained output ratio (GOR) and coefficient of performance (COP) are 2.0181 and 1.2474, respectively. Furthermore, the present combined system is compared with the traditional humidification-dehumidification desalination system. This comparison highlights that the GOR of the proposed system is about 140% higher than the traditional system. Therefore, there is no doubt to be arising in mind that the operation of the proposed system produces more beneficial thermal aspects in comparison to the existing system.

Abstract Efficient energy utilization from renewable energy sources can resolve multidimensional problems of environmental pollution, energy security and reduction in conventional fossil fuel reserves. In this circumstance, biomass-based energy systems can play an important role. In this study, modeling and analysis of an advanced integrated co-generation system comprising of a biomass gasifier, a solid oxide fuel cell module and a heat recovery steam generator have been carried out for generating power and process heat. The proposed system has been evaluated through exergetic and economic methods. Furthermore, response surface methodology has been applied for the multi-objective optimization of the system. Current density, pressure ratio of the secondary air compressor and saturation pressure of steam at the heat recovery steam generator are considered as the inputs for predicting the optimum performance parameters i.e., exergy efficiency, levelized cost of energy and levelized cost of exergy. Regression models, generated from the analysis of variance tool, are found to have a very high degree of accuracy for the exergy efficiency, levelized cost of energy and levelized cost of exergy. The optimal levels of the current density, pressure ratio and saturation pressure of steam are found to be 5101.01 A/m2, 4 and 12 bar, respectively. At this optimum condition, exergy efficiency, levelized cost of energy and levelized cost of exergy of the cogeneration system are 46.58%, 0.0454 $/kWh and 0.0657$/kWh, respectively. Composite desirability is found to be on the higher side (around 0.90), which indicate that the setting seems to attain favorable results for all the responses as a whole.

Abstract Efficient energy utilization from renewable energy sources can resolve multidimensional problems of environmental pollution, energy security and reduction in conventional fossil fuel reserves. In this circumstance, biomass-based energy systems can play an important role. In this study, modeling and analysis of an advanced integrated co-generation system comprising of a biomass gasifier, a solid oxide fuel cell module and a heat recovery steam generator have been carried out for generating power and process heat. The proposed system has been evaluated through exergetic and economic methods. Furthermore, response surface methodology has been applied for the multi-objective optimization of the system. Current density, pressure ratio of the secondary air compressor and saturation pressure of steam at the heat recovery steam generator are considered as the inputs for predicting the optimum performance parameters i.e., exergy efficiency, levelized cost of energy and levelized cost of exergy. Regression models, generated from the analysis of variance tool, are found to have a very high degree of accuracy for the exergy efficiency, levelized cost of energy and levelized cost of exergy. The optimal levels of the current density, pressure ratio and saturation pressure of steam are found to be 5101.01 A/m2, 4 and 12 bar, respectively. At this optimum condition, exergy efficiency, levelized cost of energy and levelized cost of exergy of the cogeneration system are 46.58%, 0.0454 $/kWh and 0.0657$/kWh, respectively. Composite desirability is found to be on the higher side (around 0.90), which indicate that the setting seems to attain favorable results for all the responses as a whole.

Abstract Electricity, heating, and cooling are the three main components constituting the tripod of energy consumption in residential, commercial, and public buildings all around the world. Their separate generation causes higher fuel consumption, at a time where energy demands and fuel costs are continuously rising. Combined cooling, heating, and power (CCHP) or trigeneration could be a solution for such challenge yielding an efficient, reliable, flexible, competitive, and less pollutant alternative. A variety of trigeneration technologies are available and their proper choice is influenced by the employed energy system conditions and preferences. In this paper, different types of trigeneration systems are classified according to the prime mover, size and energy sequence usage. A leveled selection procedure is subsequently listed in the consecutive sections. The first level contains the applied prime mover technologies which are considered to be the heart of any CCHP system. The second level comprises the heat recovery equipment (heating and cooling) of which suitable selection should be compatible with the used prime mover. The third level includes the thermal energy storage system and heat transfer fluid to be employed. For each section of the paper, a survey of conducted studies with CHP/CCHP implementation is presented. A comprehensive table of evaluation criteria for such systems based on energy, exergy, economy, and environment measures is performed, along with a survey of the methods used in their design, optimization, and decision-making. Moreover, a classification diagram of the main CHP/CCHP system components is summarized. A general selection approach of the appropriate CCHP system according to specific needs is finally suggested. In almost all reviewed works, CCHP systems are found to have positive technical and performance impacts.

Abstract Electricity, heating, and cooling are the three main components constituting the tripod of energy consumption in residential, commercial, and public buildings all around the world. Their separate generation causes higher fuel consumption, at a time where energy demands and fuel costs are continuously rising. Combined cooling, heating, and power (CCHP) or trigeneration could be a solution for such challenge yielding an efficient, reliable, flexible, competitive, and less pollutant alternative. A variety of trigeneration technologies are available and their proper choice is influenced by the employed energy system conditions and preferences. In this paper, different types of trigeneration systems are classified according to the prime mover, size and energy sequence usage. A leveled selection procedure is subsequently listed in the consecutive sections. The first level contains the applied prime mover technologies which are considered to be the heart of any CCHP system. The second level comprises the heat recovery equipment (heating and cooling) of which suitable selection should be compatible with the used prime mover. The third level includes the thermal energy storage system and heat transfer fluid to be employed. For each section of the paper, a survey of conducted studies with CHP/CCHP implementation is presented. A comprehensive table of evaluation criteria for such systems based on energy, exergy, economy, and environment measures is performed, along with a survey of the methods used in their design, optimization, and decision-making. Moreover, a classification diagram of the main CHP/CCHP system components is summarized. A general selection approach of the appropriate CCHP system according to specific needs is finally suggested. In almost all reviewed works, CCHP systems are found to have positive technical and performance impacts.

Abstract Carbon derived from waste biomass has emerged as a promising candidate towards the synthesis of catalyst or catalyst support for chemical and enzymatic reactions. Excellent surface properties like large specific surface area and high porosity make carbon an exceptional contender for catalyst support. Moreover, appreciable electron conductivity and relative chemical inertness enrich its applicability in chemical processes. The biomass-derived carbon catalysts are environmentally benign for reducing carbon footprint and cost competitive to other heterogeneous catalysts available for biodiesel production. Carbons functionalized with different alkali metals, SO3H group, alkoxides, enzymes and transition metals enhance the catalytic activity in the transesterification of triglycerides to alkyl esters. Biodiesel, a promising alternative to the conventional petro-diesel is studied globally in the modern era. The cost-effective process for the biodiesel synthesis involves heterogeneous catalysis employing various catalyst supports. The traditional process of biodiesel synthesis is expensive on the indus trial scale; hence, heterogeneous catalysis plays a vital role in minimizing the cost of the final product due to high stability, efficient activity, and noticeable reusability. For the success of biorefinery concept in the present day and sustainable development towards future, there is a need for the design of a new generation of multifunctional catalysts perhaps consisting of carbon as a support derived from waste biomass. This, in turn, will enhance the selective transformation of non-conventional sources into biodiesel as a sustainable source of energy. Henceforth, the present review offers a broad synopsis on the synthesis of evolving carbonaceous catalysts such as activated carbon, graphene, carbon nanotubes, carbon monoliths and carbon nanohorns for their use in biodiesel production.