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The implementation of monitoring tools and energy management systems (EnMSs) supports companies in their long-term energy efficiency strategies, and they are essential to analyse the effectiveness of energy performance improvement actions (EPIAs). The first fundamental step towards increasing energy efficiency is the development of energy audits (EAs). EAs provide comprehensive information about the energy usage in a specific facility, identifying and quantifying cost-effective EPIAs. The crucial role of these tools in clean energy transition is remarked by the European Energy Efficiency Directive (EED), which promotes the implementation of EAs and EnMS programmes. The purpose of this work is to better understand the link between EnMSs (specifically ISO 50001) and EAs in the EED Article 8 implementation in two industrial and two tertiary sectors in Italy. Moreover, the impact of company size, energy monitoring systems, and EnMSs on planned and/or implemented EPIAs is analysed. Our findings show that, albeit the complexity of the variables involved in energy efficiency gap, the “energy savings/company” and “EPIA/site” ratios are higher in enterprises with an EnMS and monitoring system. Thus, a correct energy audit must always be accompanied by a specific monitoring plan if it is to be effective and useful to the company decision maker.
Carlos Herce; Enrico Biele; Chiara Martini; Marcello Salvio; Claudia Toro. Impact of Energy Monitoring and Management Systems on the Implementation and Planning of Energy Performance Improved Actions: An Empirical Analysis Based on Energy Audits in Italy. Energies 2021, 14, 4723 .
AMA StyleCarlos Herce, Enrico Biele, Chiara Martini, Marcello Salvio, Claudia Toro. Impact of Energy Monitoring and Management Systems on the Implementation and Planning of Energy Performance Improved Actions: An Empirical Analysis Based on Energy Audits in Italy. Energies. 2021; 14 (16):4723.
Chicago/Turabian StyleCarlos Herce; Enrico Biele; Chiara Martini; Marcello Salvio; Claudia Toro. 2021. "Impact of Energy Monitoring and Management Systems on the Implementation and Planning of Energy Performance Improved Actions: An Empirical Analysis Based on Energy Audits in Italy." Energies 14, no. 16: 4723.
Within a broader national project aimed at the hybridization of a standard city car (the 998 cc Mitsubishi-derived gasoline engine of the Smart W451), our team tackled the problem of improving the supercharger performance and response. The originally conceived design innovation was that of eliminating the mechanical connection between the compressor and the turbine. In the course of the study, it turned out that it is also possible to modify both components to extract extra power from the engine and to use it to recharge the battery pack. This required a redesign of both compressor and turbine. First, the initial configuration was analyzed on the basis of the design data provided by the manufacturer. Then, a preliminary performance assessment of the turbocharged engine allowed us to identify three “typical” operating points that could be used to properly redesign the turbomachinery. It was decided to maintain the radial configuration for both turbine and compressor, but to redesign the latter by adding an inducer. For the turbine, only minor modifications to the nozzle guide vanes (NGV) and rotor blades shape were deemed necessary, while a more substantial modification was in order for the compressor. Fully 3-D computational fluid dynamics simulations of the rotating machines were performed to assess their performance at three operating points: the kick-in point of the original turbo (2000 rpm), the maximum power regime (5500 rpm), and an intermediate point (3500 rpm) close to the minimum specific fuel consumption for the original engine. The results presented in this paper demonstrate that the efficiency of the compressor is noticeably improved for steady operation at all three operating points, and that its choking characteristics have been improved, while its surge line has not been appreciably affected. The net energy recovery was also calculated and demonstrated interesting returns in terms of storable energy in the battery pack.
Nicolò Cuturi; Enrico Sciubba. Design of a Tandem Compressor for the Electrically-Driven Turbocharger of a Hybrid City Car. Energies 2021, 14, 2890 .
AMA StyleNicolò Cuturi, Enrico Sciubba. Design of a Tandem Compressor for the Electrically-Driven Turbocharger of a Hybrid City Car. Energies. 2021; 14 (10):2890.
Chicago/Turabian StyleNicolò Cuturi; Enrico Sciubba. 2021. "Design of a Tandem Compressor for the Electrically-Driven Turbocharger of a Hybrid City Car." Energies 14, no. 10: 2890.
In recent years, many studies have been published on the applications of exergy analyses to complex systems, including entire countries. Oddly, the results, although consistent, appear to lead to divergent conclusions. The underlying problem is that in a “pure” thermodynamic analysis, the so-called “externalities”, i.e., labor, capital, and environmental costs, are often neglected or only approximately included in the picture. In 1998, an extension of the theory that included the exergy content of the externalities was introduced, called “extended exergy accounting” (EEA). Its novelty consisted of the explicit inclusion of the exergy embodied in the externalities. The aim of this work is to use the results of the extended exergy accounting to obtain an indicator that can be used to assess the sustainable development of a country. First, a novel methodological approach to the theory is presented, based on the exploitation of a very large dataset obtained from several national and European statistical institutions. After a brief discussion of the theory, an application to the case of Italy is developed over a 5 years time window (2013–2017). The paper includes a comparison with the concurrent evolution of other sustainability indicators and of the gross domestic product (GDP) indicator. The results show a consistent trend for EE as compared with those of other indicators, and also convincingly proves that this trend is incompatible with that of the GDP. The EE indicator is called the exergy footprint, which also displays a remarkable sensitivity to both environmental and economic factors.
Alfonso Biondi; Enrico Sciubba. Extended Exergy Analysis (EEA) of Italy, 2013–2017. Energies 2021, 14, 2767 .
AMA StyleAlfonso Biondi, Enrico Sciubba. Extended Exergy Analysis (EEA) of Italy, 2013–2017. Energies. 2021; 14 (10):2767.
Chicago/Turabian StyleAlfonso Biondi; Enrico Sciubba. 2021. "Extended Exergy Analysis (EEA) of Italy, 2013–2017." Energies 14, no. 10: 2767.
Ceramic tile production is an industrial process where energy efficiency management is crucial, given the high amount of energy (electrical and thermal) required by the production cycle. This study presents the preliminary results of a research project aimed at defining the benefits of using combined heat and power (CHP) systems in the ceramic sector. Data collected from ten CHP installations allowed us to outline the average characteristics of prime movers, and to quantify the contribution of CHP thermal energy supporting the dryer process. The electric size of the installed CHP units resulted in being between 3.4 MW and 4.9 MW, with an average value of 4 MW. Data revealed that when the goal is to maximize the generation of electricity for self-consumption, internal combustion engines are the preferred choice due to higher conversion efficiency. In contrast, gas turbines allowed us to minimize the consumption of natural gas input to the spray dryer. Indeed, the fraction of the dryer thermal demand (between 600–950 kcal/kgH2O), covered by CHP discharged heat, is strictly dependent on the type of prime mover installed: lower values, in the range of 30–45%, are characteristic of combustion engines, whereas the use of gas turbines can contribute up to 77% of the process’s total consumption.
Lisa Branchini; Maria Bignozzi; Benedetta Ferrari; Barbara Mazzanti; Saverio Ottaviano; Marcello Salvio; Claudia Toro; Fabrizio Martini; Andrea Canetti. Cogeneration Supporting the Energy Transition in the Italian Ceramic Tile Industry. Sustainability 2021, 13, 4006 .
AMA StyleLisa Branchini, Maria Bignozzi, Benedetta Ferrari, Barbara Mazzanti, Saverio Ottaviano, Marcello Salvio, Claudia Toro, Fabrizio Martini, Andrea Canetti. Cogeneration Supporting the Energy Transition in the Italian Ceramic Tile Industry. Sustainability. 2021; 13 (7):4006.
Chicago/Turabian StyleLisa Branchini; Maria Bignozzi; Benedetta Ferrari; Barbara Mazzanti; Saverio Ottaviano; Marcello Salvio; Claudia Toro; Fabrizio Martini; Andrea Canetti. 2021. "Cogeneration Supporting the Energy Transition in the Italian Ceramic Tile Industry." Sustainability 13, no. 7: 4006.
Within a broader national project aimed at the hybridization of a standard city car (the 998 cc Mitsubishi-derived gasoline engine of the Smart W451), our team tackled the problem of improving the supercharger performance and response. The design concept is that of eliminating the mechanical connection between the compressor and the turbine. It turned out that it is also possible to modify both components to extract extra power from the engine and to use it to recharge the battery pack. First, the initial configuration was analyzed on the basis of the design data provided by the manufacturer. Then, a preliminary performance assessment of the turbocharged engine allowed us to identify three “typical” operating points that could be used to properly redesign the turbomachinery. It was decided to maintain the radial configuration for both turbine and compressor, but to redesign the latter by adding an inducer. For the turbine, only minor modifications to the NGV and rotor blades shape were deemed necessary. Fully 3-D CFD simulations of the rotating machines were performed to assess their performance at three operating points: the kick-in point of the original turbo (2000 rpm), the maximum power regime (5500 rpm) and an intermediate point (3500 rpm) close to the minimum specific fuel consumption (SFC) for the original engine. The results presented in this paper demonstrate that the efficiency of the compressor is noticeably improved for steady operation at all three operating points, and that its choking characteristics have been improved, while its surge line has not been appreciably affected. The net energy recovery was also calculated, and demonstrated interesting returns in terms of storable energy in the battery pack.
Nicolò Cuturi; Enrico Sciubba. Design of a Tandem Compressor for the Electrically-Driven Turbocharger of a Hybrid City Car. Proceedings 2020, 58, 24 .
AMA StyleNicolò Cuturi, Enrico Sciubba. Design of a Tandem Compressor for the Electrically-Driven Turbocharger of a Hybrid City Car. Proceedings. 2020; 58 (1):24.
Chicago/Turabian StyleNicolò Cuturi; Enrico Sciubba. 2020. "Design of a Tandem Compressor for the Electrically-Driven Turbocharger of a Hybrid City Car." Proceedings 58, no. 1: 24.
The solar receiver is a critical component of concentrated solar power technology; it works as a heat exchanger, transforming the concentrated solar radiation into high-temperature heat. Volumetric receiver technologies, using air as a heat transfer fluid, are designed to reach higher temperatures than the current receiver technology, which is limited by material resistance and fluid instability. The higher temperature, up to 1200 K, could be used in high-temperature industrial processes or a high-temperature thermodynamic cycle. A correct radiation propagation is essential to develop their performances, reducing reflection and emission losses and promote the heat transfer to the fluid. In this study, the optical behaviour of a hierarchical volumetric receiver (HVR) developed in Bruno Kessler Foundation (FBK) has been studied using Monte Carlo ray tracing (MCRT) simulations. The simulations have been validated in an experimental setup that evaluates the light transmissivity of the HVR porous structure. Two different HVR structures are evaluated with MCRT simulations that use a real solar dish geometry to configure a complete concentrated solar power (CSP) plant. Results show that frontal and rear losses are, respectively, 12% and 3% of the incoming concentrated radiation. Inside the HVR, 15% of the incoming power is propagated trough the lateral void spaces. Therefore, the power spreading avoids the overconcentration of the centre of the focalized area. The HVR optical behaviour has been investigated, showing an optical efficiency of 85%.
Luca Pratticò; Ruben Bartali; Luigi Crema; Enrico Sciubba. Analysis of Radiation Propagation inside a Hierarchical Solar Volumetric Absorber. Proceedings 2020, 58, 27 .
AMA StyleLuca Pratticò, Ruben Bartali, Luigi Crema, Enrico Sciubba. Analysis of Radiation Propagation inside a Hierarchical Solar Volumetric Absorber. Proceedings. 2020; 58 (1):27.
Chicago/Turabian StyleLuca Pratticò; Ruben Bartali; Luigi Crema; Enrico Sciubba. 2020. "Analysis of Radiation Propagation inside a Hierarchical Solar Volumetric Absorber." Proceedings 58, no. 1: 27.
This paper presents a critical and analytical description of an ongoing research program aimed at the implementation of an expert system capable of monitoring, through an Intelligent Health Control procedure, the instantaneous performance of a cogeneration plant. The expert system is implemented in the CLIPS environment and is denominated PROMISA as the acronym for Prognostic Module for Intelligent System Analysis. It generates, in real time and in a form directly useful to the plant manager, information on the existence and severity of faults, forecasts on the future time history of both detected and likely faults, and suggestions on how to control the problem. The expert procedure, working where and if necessary with the support of a process simulator, derives from the available real-time data a list of selected performance indicators for each plant component. For a set of faults, pre-defined with the help of the plant operator (Domain Expert), proper rules are defined in order to establish whether the component is working correctly; in several instances, since one single failure (symptom) can originate from more than one fault (cause), complex sets of rules expressing the combination of multiple indices have been introduced in the knowledge base as well. Creeping faults are detected by analyzing the trend of the variation of an indicator over a pre-assigned interval of time. Whenever the value of this ‘‘discrete time derivative’’ becomes ‘‘high’’ with respect to a specified limit value, a ‘‘latent creeping fault’’ condition is prognosticated. The expert system architecture is based on an object-oriented paradigm. The knowledge base (facts and rules) is clustered—the chunks of knowledge pertain to individual components. A graphic user interface (GUI) allows the user to interrogate PROMISA about its rules, procedures, classes and objects, and about its inference path. The paper also presents the results of some simulation tests.
Roberto Melli; Enrico Sciubba. Diagnostics and Prognostics of Energy Conversion Processes via Knowledge-Based Systems. Proceedings 2020, 58, 1 .
AMA StyleRoberto Melli, Enrico Sciubba. Diagnostics and Prognostics of Energy Conversion Processes via Knowledge-Based Systems. Proceedings. 2020; 58 (1):1.
Chicago/Turabian StyleRoberto Melli; Enrico Sciubba. 2020. "Diagnostics and Prognostics of Energy Conversion Processes via Knowledge-Based Systems." Proceedings 58, no. 1: 1.
In the recent past, several examples of the application of Exergy Analysis (ExA) to Very Large Complex Systems, including entire countries, have been published, and it can be fairly said that—while the goals of the individual authors were completely consistent—the results, the conclusions and the recommendations diverge. There are several contingent reasons for this, but the underlying problem is that a purely thermodynamic analysis cannot reproduce the complex influence that monetary, social, political and technological factors have on the purely “material” or “energetic” streams. Clearly, ExA represents a substantial improvement with respect to the “Material and Energy Balance Reports” published annually by most industrialized countries, because the exergy flow diagram unequivocally demonstrates how and at what penalty the primary exergy inflow (fossil fuels, renewables, ores, harvested food and other primary goods) is transformed into final energy, such as diesel fuel, electricity or other commodities. The issue here is, though, that the so-called Externalities (Capital, Labor and Environmental Effects) are, in spite of some opinion to the contrary, completely left out of the picture. It turns out though that ExA can be extended by including the exergy equivalents of the externalities. The theory is called Extended Exergy Accounting (EEA) as a reminder of the inclusion of monetary, labor and environmental “exergy costs” in the global budget. The scope of the study presented in this paper is twofold: First, the introduction of a novel approach based on the exploitation of a very disaggregated dataset, in order to perform the EEA of a whole country; second, the analysis of the results of the application of the method to the Italian society, over a five-year (2013–2017) window of observation, to extract new insights that could be useful to critically assess the trend of the exergy destruction of Italy vs. that of the GDP.
Alfonso Biondi; Enrico Sciubba. New Insights from Econometric Data: An Extended Exergy Analysis (EEA) of the Italian System, 2013–2017. Proceedings 2020, 58, 3 .
AMA StyleAlfonso Biondi, Enrico Sciubba. New Insights from Econometric Data: An Extended Exergy Analysis (EEA) of the Italian System, 2013–2017. Proceedings. 2020; 58 (1):3.
Chicago/Turabian StyleAlfonso Biondi; Enrico Sciubba. 2020. "New Insights from Econometric Data: An Extended Exergy Analysis (EEA) of the Italian System, 2013–2017." Proceedings 58, no. 1: 3.
The continuous quest for improving the performance of heat exchangers, together with evermore stringent volume and weight constraints, especially in enclosed applications (engines, electronic devices), stimulates the search for compact, high-performance units. One of the shapes that emerged from a vast body of research is the disc-shaped heat exchanger, in which the fluid to be heated/cooled flows through radial, often bifurcated, channels inside of a metallic disc. The disc, in turn, exchanges heat with the heat/cold source (the environment or another body). Several studies have been devoted to the identification of an “optimal shape” of the channels: Most of them are based on prime principles, though numerical simulations abound as well. The present paper demonstrates that, for all engineering purposes, there is only one correct design procedure for such a heat exchanger, and that this procedure depends solely on the technical specifications (exchanged thermal power, materials, surface quality): The design, in fact, reduces to a zero-degree of freedom problem! The argument is described in detail, and it is shown that a proper application of the constraints completely identifies the shape, size and similarity indices of both the disc and the internal channels. The goal of this study is not that of “inventing” a novel heat exchanger design procedure, but that of demonstrating that -in this as in many similar cases- a straightforward application of prime principles and of diligent engineering rules may generate “optimal” designs. Of course, the resulting configurations may be a posteriori tested as to their performance, their irreversibility rates, their compliance with one or the other “techno-economical optimization methods”, but it is important to realize that they enjoy a sort of “embedded” optimality.
Enrico Sciubba. A Note on the “Optimal” Design of Disc-Shaped Heat Exchangers. Proceedings 2020, 58, 8 .
AMA StyleEnrico Sciubba. A Note on the “Optimal” Design of Disc-Shaped Heat Exchangers. Proceedings. 2020; 58 (1):8.
Chicago/Turabian StyleEnrico Sciubba. 2020. "A Note on the “Optimal” Design of Disc-Shaped Heat Exchangers." Proceedings 58, no. 1: 8.
Bifurcated flows are ubiquitous in nature. Their being such a common feature of many natural “structures” has prompted a multitude of investigations in diverse scientific branches: botanists, neurophysicians, biologists and chemists have attempted to find a “structural plan” on which to build a general model of the formation and evolution of bifurcations. Not incidentally, the engineering side of the issue is also extremely interesting: from heat exchangers to pipelines to district heating networks, the existence of a “general geometric model” would much facilitate a designer’s life. The study reported in this paper is based on a straightforward application of the exergy cost theory to the development and self-sustenance of natural bifurcated structures and leads to the conclusion that the shape, connectivity and evolution of a dycotomic depend on several factors that are irreducibly case dependent. This result is of great importance for engineered bifurcations, for which the same impossibility to generalize is again demonstrated: here though, since the “design goals” are formulated as rather simple constraints (simpler than in nature!), a somewhat larger degree of (albeit always application-dependent) generality is found. The exergy cost method is valid for any virtual or real system, and assigns a “resource cost” to its products: it consists in evaluating the exergy inflows (in W) and in keeping an accurate bookkeeping of the embodied exergy (in W/kg or W/m3) into the system, to calculate an average (instantaneous or lifetime-based) exergy input. The cost is then obtained by dividing this “cumulative input” by the exergy flux of the “products” in the same time window. In natural processes, this cost is called the Exergy Footprint, because it represents the actual primary resource consumption necessary to generate the outputs. In engineered artifacts, an additional procedure can be used to internalize the externalities (Labour, Capital and Environmental Remediation cost) so that the total equivalent primary exergy consumption needed to generate a unit of “product” can be again applied as a cost indicator. The novelty of the method and of the results discussed in this paper is twofold: first, the two most popular bifurcation models (Fractal and Constructal) are critically re-evaluated to show that neither one succeeds in generating credible predictive correlations. Second, it is demonstrated that the exergy costing paradigm provides a feasible and rigorous method for identifying the optimal bifurcation geometry for practical engineering applications. To express the results in a concise sentence: it is indeed possible to accurately and rigorously predict the optimal shape of a bifurcated structure once its function is known, but at the loss of generality. Neither in nature nor in engineering sciences bifurcated flows can be optimized by a universally valid allometric rule.
Enrico Sciubba. Shape from function: The exergy cost of viscous flow in bifurcated diabatic tubes. Energy 2020, 213, 118663 .
AMA StyleEnrico Sciubba. Shape from function: The exergy cost of viscous flow in bifurcated diabatic tubes. Energy. 2020; 213 ():118663.
Chicago/Turabian StyleEnrico Sciubba. 2020. "Shape from function: The exergy cost of viscous flow in bifurcated diabatic tubes." Energy 213, no. : 118663.
In the last few years, waste-energy recovery systems based on the Organic Rankine Cycle (ORC) have gained increased attention in the global energy market as a versatile and sustainable technology for thermo-electric energy conversion from low-to-medium temperature sources, up to 350 °C. For a long time, water has been the only working fluid commercially adopted in powerplants: axial and, for smaller machines, radial inflow turbines have been the preferred expanders since their gulp capacity matches the ρ-T curve of water steam. The density of most organic compounds displays extremely large variations during the expansion (and the volume flow rate correspondingly increases along the machine channels), so that Radial Outflow Turbines (ROTs) have been recently considered instead of traditional solutions. This work proposes a two-dimensional inviscid model for the stage optimization of a counter-rotating ROT, known as the Ljungström turbine. The study starts by considering five different working fluids that satisfy both the gulp requirements of the turbine and the hot source characteristics. On the basis of a limited number of geometric assumptions and for a fixed set of operating conditions, different kinematic parameters are optimized to obtain the most efficient cascade configuration. Moreover, as shown in the conclusions, the most efficient blade profile leads to higher friction losses, making further investigation regarding the best configuration necessary.
Umberto Coronetta; Enrico Sciubba. Optimal Design of a Ljungström Turbine for ORC Power Plants: From a 2D model to a 3D CFD Validation. International Journal of Turbomachinery, Propulsion and Power 2020, 5, 19 .
AMA StyleUmberto Coronetta, Enrico Sciubba. Optimal Design of a Ljungström Turbine for ORC Power Plants: From a 2D model to a 3D CFD Validation. International Journal of Turbomachinery, Propulsion and Power. 2020; 5 (3):19.
Chicago/Turabian StyleUmberto Coronetta; Enrico Sciubba. 2020. "Optimal Design of a Ljungström Turbine for ORC Power Plants: From a 2D model to a 3D CFD Validation." International Journal of Turbomachinery, Propulsion and Power 5, no. 3: 19.
Modern gas turbine firing temperatures (1500–2000 K) are well beyond the maximum allowable blade material temperatures. Continuous safe operation is made possible by cooling the HP turbine first stages, nozzle vanes and rotor blades, with a portion of the compressor discharge air, a practice that induces a penalty on the thermal efficiency cycle. Therefore, a current issue is to investigate the real advantage, technical and economical, of raising maximum temperatures much further beyond current values. In this paper, process simulations of a gas turbine are performed to assess HP turbine first-stage cooling effects on cycle performance. A new simplified and properly streamlined model is proposed for the non-adiabatic expansion of the hot gas mixed with the cooling air within the blade passage, which allows for a comparison of several cycle configurations at different turbine inlet temperatures (TIT) and total turbine expansion ratio (PR) with a realistically acceptable degree of approximation. The calculations suggest that, at a given PR, the TIT can be increased in order to reach a higher cycle efficiency up to a limit imposed by the required amount and temperature of the cooling air. Beyond this limit, no significant gains in thermal efficiency are obtained by adopting higher PR and/or increasing the TIT, so that it is convenient in terms of cycle performance to design at a lower rather than higher PR. The small penalty on cycle efficiency is compensated by the lower plant cost. The results of our model agree with those of some previous and much more complex and computationally expensive studies, so that the novelty of this paper lies in the original method adopted on which the proposed model is based, and in the fast, accurate, and low resource intensity of the corresponding numerical procedure, all advantages that can be crucial for industry needs. The presented analysis is purely thermodynamic and it includes no investigation on the effects of the different configurations on plant costs. Therefore, performing a thermo-economic analysis of the air-cooled gas turbine power plant is the next logical step.
Roberta Masci; Enrico Sciubba. A Gas Turbine Cooled-Stage Expansion Model for the Simulation of Blade Cooling Effects on Cycle Performance. International Journal of Turbomachinery, Propulsion and Power 2019, 4, 36 .
AMA StyleRoberta Masci, Enrico Sciubba. A Gas Turbine Cooled-Stage Expansion Model for the Simulation of Blade Cooling Effects on Cycle Performance. International Journal of Turbomachinery, Propulsion and Power. 2019; 4 (4):36.
Chicago/Turabian StyleRoberta Masci; Enrico Sciubba. 2019. "A Gas Turbine Cooled-Stage Expansion Model for the Simulation of Blade Cooling Effects on Cycle Performance." International Journal of Turbomachinery, Propulsion and Power 4, no. 4: 36.
A thermodynamic analysis of population dynamics and of sustainability provides rigor to many important issues. In this work, the “system society” is analysed in connection with the “system environment” using an exergy metric, and the method includes an internalization of the externalities (capital, labour, environmental effects) conducted on the basis of a “system + environment” balance. In this perspective, this study investigates the Late Pleistocene extinction of the Homo neanderthalensis, which took place in a geologically short time and in the presence of a competing species, the Homo sapiens. The case in study is not trivial, and its choice not casual: in those times, the only factor that could lead to an advantage of one group over the other was their respective resource use intensity. A specific indicator, the exergy footprint (EF), is here applied to measure the total amount of primary resources required to produce a certain (material or immaterial) commodity, including the resources needed for the physical survival of the individuals. On the basis of the available data, the results of a steady-state analysis show that the EF of the Neanderthal was higher than that of the Sapiens, and that with both species sharing the same ecological niche in a time of dwindling resources, the less frugal of the two was also more fragile in an evolutionary sense.
Enrico Sciubba. The Exergy Footprint as a Sustainability Indicator: An Application to the Neanderthal–Sapiens Competition in the Late Pleistocene. Sustainability 2019, 11, 4913 .
AMA StyleEnrico Sciubba. The Exergy Footprint as a Sustainability Indicator: An Application to the Neanderthal–Sapiens Competition in the Late Pleistocene. Sustainability. 2019; 11 (18):4913.
Chicago/Turabian StyleEnrico Sciubba. 2019. "The Exergy Footprint as a Sustainability Indicator: An Application to the Neanderthal–Sapiens Competition in the Late Pleistocene." Sustainability 11, no. 18: 4913.
I would like to take the occasion of writing this newsletter to draw a sort of summary of our publishing activities at Energies and of the results and perspectives
Enrico Sciubba. A Letter from the Editor-in-Chief to Our Readers. Energies 2019, 12, 2542 .
AMA StyleEnrico Sciubba. A Letter from the Editor-in-Chief to Our Readers. Energies. 2019; 12 (13):2542.
Chicago/Turabian StyleEnrico Sciubba. 2019. "A Letter from the Editor-in-Chief to Our Readers." Energies 12, no. 13: 2542.
Modern gas turbines firing temperatures (1500-2000K) are well beyond the maximum allowable blade material temperatures. Continuous safe operation is made possible by cooling the HP turbine first stages -nozzle vanes and rotor blades- with a portion of the compressor discharge air, a practice that induces a penalty on the cycle thermal efficiency. Therefore, a current issue is to investigate the real advantage, technical and economical, of raising maximum temperatures much further beyond current values. In this paper, process simulations of a gas turbine are performed to assess HP turbine first-stage cooling effects on cycle performance. A new simplified and properly streamlined model is proposed for the non-adiabatic expansion of the hot gas mixed with the cooling air within the blade passage, which allows for a comparison of several cycle configurations at different TIT (turbine inlet temperature) and max (total turbine expansion ratio) with a realistically acceptable degree of approximation.. The calculations suggest that, at a given max, the TIT can be increased in order to reach higher cycle efficiency up to a limit imposed by the required amount and temperature of the cooling air. Beyond this limit, no significant gains in thermal efficiency are obtained by adopting higher max and/or increasing the TIT, so that it is convenient in terms of cycle performance to design at lower rather than higher max. The small penalty on cycle efficiency is compensated by lower plant cost. The results of our model agree with those of some previous much more complex and computationally expensive studies, so that the novelty of this paper lies in the original method adopted on which the proposed model is based, and in the fast, accurate and low resource intensity of the corresponding numerical procedure: all advantages that can be crucial for industry needs. The presented analysis is purely thermodynamic, with no investigation on the effects of the different configurations on plant costs, so that future work addressing a thermo-economic analysis of the air-cooled gas turbine power plant is the next logical step.
Roberta Masci; Enrico Sciubba. A gas turbine cooled-stage expansion model for the simulation of blade cooling effects on cycle performance. 2019, 1 .
AMA StyleRoberta Masci, Enrico Sciubba. A gas turbine cooled-stage expansion model for the simulation of blade cooling effects on cycle performance. . 2019; ():1.
Chicago/Turabian StyleRoberta Masci; Enrico Sciubba. 2019. "A gas turbine cooled-stage expansion model for the simulation of blade cooling effects on cycle performance." , no. : 1.
The opportunity of producing power in space seems to be attractive considering the exponential growth of the human population and the renewed interest in space missions. Space Solar Dynamic Systems promise to be a better alternative to PVs by eliminating the need for batteries, offering lower drag problems and high efficiencies taking advantage of the lower temperature of space. In this paper the modeling, simulation and exergy analysis of a Closed Brayton Cycle (CBC) for power generation in space driven by a solar parabolic collector is presented. The main objective has been the investigation of a “reduced weight” configuration, to reduce the launch costs, one of the most critical issues for the system feasibility. The investigation of a “reduced weight” configuration has been performed identifying the key process parameters: the compressor inlet temperature and its pressure ratio and the receiver diameter. Starting from the NASA Freedom data, the results have shown a weight reduction of 21% and an exergy efficiency increase of 7.4%. A comparison with a CBC driven by nuclear power has been then performed, showing the thermodynamic conditions for which the solar dynamic systems could get the recommended specific weight of 30 kg/kW.
Alfonso Biondi; Claudia Toro. Closed Brayton Cycles for Power Generation in Space: Modeling, simulation and exergy analysis. Energy 2019, 181, 793 -802.
AMA StyleAlfonso Biondi, Claudia Toro. Closed Brayton Cycles for Power Generation in Space: Modeling, simulation and exergy analysis. Energy. 2019; 181 ():793-802.
Chicago/Turabian StyleAlfonso Biondi; Claudia Toro. 2019. "Closed Brayton Cycles for Power Generation in Space: Modeling, simulation and exergy analysis." Energy 181, no. : 793-802.
The paper addresses the problem of the evolution of systems that are initially in a state of non-equilibrium. The model we propose leads to an equation of motion that starts from a rephrasing of the classical non-equilibrium Ginzburg-Landau equation by reinterpreting in the sense of an exergy evolution paradigm. This paper may be considered as a logical corollary to -and at the same time as an e conceptual extension of- the solution to the problem of the existence and quantification of a non-equilibrium exergy presented in previous articles by the present Authors. In previous papers it was shown that, if both energy and exergy are considered a priori concepts, the evolution of the exergy of a solid body subject to a sufficiently smooth relaxation process can be calculated for arbitrary initial temperature or concentration distributions with an accuracy that depends only on the information about the initial distribution of the system properties at the initial time and on the availability of proper material relations. It was shown that the non-equilibrium exergy, i.e., the extra ideal work that can be extracted from the body, relaxes to zero as the system tends to its equilibrium state, so that the total exergy content (given by the sum of non-equilibrium and equilibrium exergy) attains the value given by its classical definition. The evolution history depends of course on the imposed b.c. and on the “gradient” that drives the relaxation. In this paper, we formalize the dependence of the non-equilibrium exergy on its possible drivers (pressure, temperature or concentration gradients) and derive a general “equation of motion” that links the former to the latter. The solution is analytical, and therefore there is no need to postulate local equilibrium, as long as we are dealing with a continuum (scales sufficiently removed from the atomic ones). A few applications to ideal and real processes are presented and discussed, while the application of the method to more complex and industrially relevant cases is left for later studies. The paradigm is theoretically simple and the resulting model of relatively easy implementation: we therefore hope that applications of the proposed framework may be systematically developed in the fields of engineering and natural science, to gain a better insight into real non-equilibrium processes.
Enrico Sciubba; Federico Zullo. A general model for the evolution of non-equilibrium systems. Energy 2019, 182, 483 -492.
AMA StyleEnrico Sciubba, Federico Zullo. A general model for the evolution of non-equilibrium systems. Energy. 2019; 182 ():483-492.
Chicago/Turabian StyleEnrico Sciubba; Federico Zullo. 2019. "A general model for the evolution of non-equilibrium systems." Energy 182, no. : 483-492.
An optimization model based on the use of Neural Network surrogate models for the multi-objective optimization of small scale Organic Rankine Cycles is presented, which couples the optimal selection of the thermodynamic parameters of the cycle with the main design parameters of In-Flow Radial turbines. The proposed approach proved well suited in the resolution of the highly non-linear constrained optimization problems, typical of the design of energy systems. Indeed the use of a surrogate model allows to adopt gradient based methods that are computationally more efficient and accurate than conventional derivative-free optimization algorithms. The intensive numerical experiments demonstrate that assuming a constant efficiency for the In-Flow Radial turbine leads to an error in the evaluation of the performance of the system of up to 50% and that the optimization approach proposed improves the accuracy of the solution and it reduces the computational time required to reach it by two orders of magnitude. An holistic approach in which the turbine and the thermodynamic cycle are designed simultaneously and the use of multi-objective optimization proved to be essential for the design of Organic Rankine cycles that satisfy both size and performance criteria.
Laura Palagi; Enrico Sciubba; Lorenzo Tocci. A neural network approach to the combined multi-objective optimization of the thermodynamic cycle and the radial inflow turbine for Organic Rankine cycle applications. Applied Energy 2019, 237, 210 -226.
AMA StyleLaura Palagi, Enrico Sciubba, Lorenzo Tocci. A neural network approach to the combined multi-objective optimization of the thermodynamic cycle and the radial inflow turbine for Organic Rankine cycle applications. Applied Energy. 2019; 237 ():210-226.
Chicago/Turabian StyleLaura Palagi; Enrico Sciubba; Lorenzo Tocci. 2019. "A neural network approach to the combined multi-objective optimization of the thermodynamic cycle and the radial inflow turbine for Organic Rankine cycle applications." Applied Energy 237, no. : 210-226.
This paper presents a summary of the conceptual development and the practical applications of exergy-based Environmental Indicators. After a brief historical introduction, the two most popular methods are presented and discussed: the Exergo-Environmental Analysis (here TEA, as a memento of Jan Szargut's original denomination “Thermo-Ecological Analysis”, currently adopted also by Valero's school) and the Extended Exergy Accounting (EEA). Both emerged from Szargut's idea of the existence of a consumption index, the Cumulative Exergy Consumption (CExC), which can be used to quantify the consumption of primary resources “embodied” in a final product or service. The extension introduced by both methods with respect to CExC consists in the explicit inclusion in the exergy budget of one or more of the Externalities, lumped in the original CExC formulation into the exergetic material contents of the single commodities. The differences between the three formulations are obviously reflected in the numerical values of the resulting indicators. The Thermo-Ecological Cost (TEC) and the CExC differ because of the inclusion in the former of the exergetic resources that reflect the “penalty” in the use of primary non-renewable consumption caused by the anthropic intervention. The CExC index and the Extended Exergy Cost EEC differ because the latter explicitly includes in the calculation a “Labour and Capital equivalent exergy consumption” that allows for the survival of the individuals in a given region according to the respective life standards (variable in space and time). Another difference is the way the Environmental Externality is computed: while TEA takes an ex-post assessment, EEA introduces a calculation of the -ideal or real-remediation costs.
Enrico Sciubba. Exergy-based ecological indicators: From Thermo-Economics to cumulative exergy consumption to Thermo-Ecological Cost and Extended Exergy Accounting. Energy 2018, 168, 462 -476.
AMA StyleEnrico Sciubba. Exergy-based ecological indicators: From Thermo-Economics to cumulative exergy consumption to Thermo-Ecological Cost and Extended Exergy Accounting. Energy. 2018; 168 ():462-476.
Chicago/Turabian StyleEnrico Sciubba. 2018. "Exergy-based ecological indicators: From Thermo-Economics to cumulative exergy consumption to Thermo-Ecological Cost and Extended Exergy Accounting." Energy 168, no. : 462-476.
Plants are open, irreversible and non-equilibrium systems that live via mass- and energy exchanges with the environment, and therefore, are amenable to a thermodynamic treatment: in fact, they may be considered “energy converters”, because their metabolism is nothing else than a controlled ability to transform energy from one form (solar) into another (chemical energy suitable to cell metabolism) and to activate and maintain reactions at cellular- and molecular level -promoting the plant growth. This paper presents an original model based on mass conservation and on the First- and Second Law of Thermodynamics, which results in a set of equations that allow for the calculation of the Primary Productivity (NPP) and consequently lead to a measure of the plant growth. The model is lumped, steady-state and totally deterministic, because no primary process is modelled in detail: the control volume is a portion of the universe that contains the plant and its immediate surroundings (atmosphere and the relevant portion of the soil), and the solution is strongly depending on the imposed boundary conditions. In such a formulation, the tree is considered as a non-equilibrium system evolving at a steady rate, and the only implicit assumption is the local equilibrium hypothesis. The general evolution equations are derived, and their steady-state form is analysed in detail. The approach is based on the calculation of the exergy in- and outflows from the control volume. Based on reasonably accurate empirical data, the exergy budget shows that the overall exergy conversion efficiency is quite low in plants and is very sensitive to even small changes in the environmental condition and to the adopted evapotranspiration model, as it would have been expected. The model is applied to a mature specimen of Pinus sylvestris and the results are compared with some literature data: despite neglecting the real chemo-physical details, the model reproduces the most salient characters of the tree growth. The sensitivity of the results to the tree age as well to the main model parameters is also calculated. The application of the same model to different species may reveal asymmetries in the “adaptability” of certain genotypes to different environments. On the more specific engineering side, the model may see an immediate application in the estimate of CO2 capture by plants.
F. Attorre; E. Sciubba; M. Vitale. A thermodynamic model for plant growth, validated with Pinus sylvestris data. Ecological Modelling 2018, 391, 53 -62.
AMA StyleF. Attorre, E. Sciubba, M. Vitale. A thermodynamic model for plant growth, validated with Pinus sylvestris data. Ecological Modelling. 2018; 391 ():53-62.
Chicago/Turabian StyleF. Attorre; E. Sciubba; M. Vitale. 2018. "A thermodynamic model for plant growth, validated with Pinus sylvestris data." Ecological Modelling 391, no. : 53-62.