General methodology for exergy balance in ProSimPlus® process simulator

This paper presents a general methodology for exergy balance in chemical and thermal processes integrated in ProSimPlus® as a well-adopted process simulator for energy efficiency analysis. In this work, as well as using the general expressions for heat and work streams, all of exergy balance is presented within only one software in order to fully automate exergy analysis. In addition, after exergy balance, the essential elements such as source of irreversibility for exergy analysis are presented to help the user for modifications on either process or utility system. The applicability of the proposed methodology in ProSimPlus® is shown through a simple scheme of Natural Gas Liquids (NGL) recovery process and its steam utility system. The methodology does not only provide the user with necessary exergetic criteria to pinpoint the source of exergy losses, it also helps the user to find the way to reduce the exergy losses. These features of the proposed exergy calculator make it preferable for its implementation in ProSimPlus® to define the most realistic and profitable retrofit projects on the existing chemical and thermal plants

Exergy analysis of a solar photovoltaic module

PV energy is the direct conversion of solar radiation into electricity. In this paper, an analysis of the influence of parameters such as global irradiance or temperature in the performance of a PV installation has been carried out. A PV module was installed in a building at the University of Málaga, and these parameters were experimentally determined for different days and different conditions of irradiance and temperature. Moreover, IV curves were obtained under these conditions to know the open-circuit voltage and the short-circuit current of the module. With this information, and using the first law of thermodynamics, an energy analysis was performed to determine the energy efficiency of the installation. Similarly, using the second law of thermodynamics, an exergy analysis is used to obtain the exergy efficiency. The results show that the energy efficiency varies between 10% and 12% and the exergy efficiency between 14% and 17%. It was concluded that the exergy analysis is more suitable for studying the performance, and that only electric exergy must be considered as useful exergy. This exergy efficiency can be improved if heat is removed from the PV module surface, and an optimal temperature is reached.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Exergy analysis of a PWR nuclear steam supply system – Part I, general theoretical model

The paper provides an alternative, novel methodology to perform the exergetic analysis of a Pressurized Nuclear Reactor (PWR) based on the strictest definition of fission temperature to get to a careful evaluation of Exergy Destruction and exergetic Efficiency of the component. Up today, the exegetic analyses of Nuclear Power Plants (NPP) have been based on the assumption that Fission Exergy and Fission Energy are almost the same having assumed Carnot Factor almost equal to 1 as Tfiss >>T0. This assumption is based on some simplified hypotheses concerning fission temperature as applied in the definition of the Fission Exergy itself, whose value, to the best knowledge of the authors, was never modeled. On the contrary, in the first part of the paper, the authors present the results of an ongoing research, just aimed at evaluating the Exergy efficiency of the heat exchange in a PWR reactor, whose first results were already presented in [1], based on the most detailed modeling of Tfiss. The modeling, referring to a steady-state operational mode of the Reactor, takes into account all heat transfer phenomena between nuclear fuel UO2, its Zircaloy clad, cooling water, vessel material and the external environment. In the second part of the paper, the Exergy analysis is extended to all main Reactor Cooling System components (Vertical recirculating type Steam Generator, primary coolant pump and piping) with the aim to compare the Exergy Destructions and exergetic Efficiencies of the RPV with those of the other components of the Nuclear Steam Supply System, NSSS. In the Part II of the same paper,, "Exergy Analysis of a PWR Nuclear Steam Supply System - II part: a case study ", a test case is exemplified with the aim to compare the results obtained applying the methodology in question with those obtained applying the most established methodology adopted by other authors

Advanced Exergy Analysis in the Dynamic Framework for Assessing Building Thermal Systems

This work applies the Dynamic Advanced Exergy Analysis (DAEA) to a heating and domestic hot water (DHW) facility supplied by a Stirling engine and a condensing boiler. For the first time, an advanced exergy analysis using dynamic conditions is applied to a building energy system. DAEA provides insights on the components’ exergy destruction (ED) by distinguishing the inefficiencies that can be prevented by improving the quality (avoidable ED) and the ones constrained because of technical limitations (unavoidable ED). ED is related to the inherent inefficiencies of the considered element (endogenous ED) and those coming from the interconnections (exogenous ED). That information cannot be obtained by any other approach. A dynamic calculation within the experimental facility has been performed after a component characterization driven by a new grey-box modelling technique, through TRNSYS and MATLAB. Novel solutions and terms of ED are assessed for the rational implementation of the DAEA in building energy installations. The influence of each component and their interconnections are valuated in terms of exergy destruction for further diagnosis and optimization purposes.BMWi, 03ET1218B, Anwendung exergiebasierter Methoden zur Verbesserung von Gebäudeenergiesysteme

Proposing a life cycle land use impact calculation methodology

The Life Cycle Assessment (LCA) community is yet to come to a consensus on a methodology to incorporate land use in LCA, still struggling with what exactly should be assessed and which indicators should be used. To solve this problem we start from concepts and models describing how ecosystems function and sustain, in order to understand how land use affects them. Earlier our research group presented a methodology based on the ecosystem exergy concept. This concept as based on the hypothesis that ecosystems develop towards more effective degradation of exergy fluxes passing through the system and is derived from two axioms: the principles of (i) maximum exergy storage and the (ii) maximum exergy dissipation. This concept aiming at the area of protection natural environment is different from conventional exergy analysis in LCA focusing on natural resources. To prevent confusion, the ecosystem exergy concept is further referred to as the MAximum Storage and Dissipation concept (MASD concept). In this paper we present how this concept identifies end-point impacts, mid-point impacts and mid-point indicators. The identified end-point impacts to assess are Ecosystem Structural Quality (ESQ) and Ecosystem Functional Quality (EFQ). In order to quantify these end-point impacts a dynamic multi-indicator set is proposed for quantifying the mid-point impacts on soil fertility, biodiversity and biomass production (quantifying the ESQ) and soil structure, vegetation structure and on-site water balance (quantifying the EFQ). Further we present an impact calculation method suitable for different environmental assessment tools and demonstrate the incorporation of the methodology in LCA

Methodology for Energy and Energy Analysis of Steam Boilers

This paper presents a framework of thermodynamic, energy and exergy, analyses of industrial steam boilers. Mass, energy, and exergy analysis were used to develop a methodology for evaluating thermodynamic properties, energy and exergy input and output resources in industrial steam boilers. Determined methods make available an analytic procedure for exergetic analysis on steam boilers for appropriate applications. Chemical exergy of the material streams was considered to offer a more comprehensive detail on energy and exergy resource allocation and losses of the processes in a steam boiler. Keywords: exergy, energy, steam boilers, chemical exergy, exergy destructio

“Exergy based analysis of economic sustainability”

Exergy is presented here as the physical prime-mover of economic systems, and an exergy based concept of value is proposed in this paper. The main exergy fluxes are identified as those carried by raw exergy (primary sources), raw materials, usable exergy and exergy embodied in manufactured commodities. It is shown how efficiency of exergy use is the physical basis for competitiveness and how exergy content (value)can be assigned to skillfulness and expertise. Sustainability of economic systems is analyzed in the light of competitiveness and ability to take extra exergy taken from markets. It is also shown that in competitive economies the ratio (raw exergy)/(total value) tends to decrease, therefore indicating extra exergy from the markets, and this trend is illustrated with the case of the US economy. Finally, the average electricity price in the markets was proposed as a provisional correspondence between exergy content and price of commodities

The comparison of various gas turbine inlet aircooling methods for various ambient condition trough energy and exergy analysis

The strong influence of climate conditions on gas turbine behavior is well known. During the summer season the output of gas turbines falls to a value that is less than the rated output under high temperature conditions. Cooling the turbine inlet air can increase output power considerably, because cooled air is dense, giving the turbine a higher mass flow rate and resulting in increased turbine output and efficiency. This study is to use the energy and exergy analysis method to evaluate the air cooling method used for enhancing the gas turbine power plant. In addition, the effect of inlet air cooling method on the output power, exergy efficiency and exergy destruction have been analyzed. Also at the end of the paper the comparison of two mentioned methods has been investigated

Evaluating the Rationale for Folding Wing Tips Comparing the Exergy and Breguet Approaches

The design and development processes for future aircraft aims to address the environmental and efficiency challenges needed to facilitate the engineering of concepts that are far more integrated and require a multidisciplinary approach. This study investigates the benefit of incorporating span extension wing tips onto future aircraft configurations as a method of providing improved aerodynamic efficiency, whilst allowing the extension to fold on the ground to meet airport gate size constraints. Although the actuated wing tips are not studied in detail, the focus of this study is to compare two different methods of analysis that can be used to identify the benefit and limitations of adding such devices. The two methods considered are a quasi-steady implicit energy analysis based on the Breguet Range Equation and an explicit energy analysis based on the first and second laws of thermodynamics known as Exergy Analysis. It has been found that both methods provide agreeable results and have individual merits. The Breguet Range Equation can provide quick results in early design, whilst the Exergy Analysis has been found to be far more extensive and allows the complete dynamic behaviour of the aircraft to be assessed through a single metric. Hence, allowing comparison of losses from multiple subsystems