Exergy tools

Wall, Göran

doi:10.1243/09576500360611399

Cited by 71 publications

(33 citation statements)

References 7 publications

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“…As Gaggioli and Wepfer [49] state, exergy "is synonymous with what the layman calls 'energy'. It is exergy, not energy, that is the resource of value, and it this commodity, that 'fuels' processes, which the layman is willing to pay for" (for further details on exergy see Wall [50][51][52], Kanoglu et al [53], Dincer [54], Rosen [55,56], Sciubba and Wall [57]). Nonetheless, it is important to acknowledge that exergy does not account for certain aspects of energy quality that are important for economic purposes (e.g., capacity for storage, cleanliness, transportability, density, and so on) [17,43].…”

Section: Accounting For Energy Qualitymentioning

confidence: 99%

Developing an Input-Output Based Method to Estimate a National-Level Energy Return on Investment (EROI)

et al. 2017

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Abstract:Concerns have been raised that declining energy return on energy investment (EROI) from fossil fuels, and low levels of EROI for alternative energy sources, could constrain the ability of national economies to continue to deliver economic growth and improvements in social wellbeing while undertaking a low-carbon transition. However, in order to test these concerns on a national scale, there is a conceptual and methodological gap in relation to calculating a national-level EROI and analysing its policy implications. We address this by developing a novel application of an Input-Output methodology to calculate a national-level indirect energy investment, one of the components needed for calculating a national-level EROI. This is a mixed physical and monetary approach using Multi-Regional Input-Output data and an energy extension. We discuss some conceptual and methodological issues relating to defining EROI for a national economy, and describe in detail the methodology and data requirements for the approach. We obtain initial results for the UK for the period 1997-2012, which show that the country's EROI has been declining since the beginning of the 21st Century. We discuss the policy relevance of measuring national-level EROI and propose avenues for future research.

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Section: Accounting For Energy Qualitymentioning

confidence: 99%

Developing an Input-Output Based Method to Estimate a National-Level Energy Return on Investment (EROI)

et al. 2017

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“…It is based on the principle of conservation of energy applied to the system. For a general steady state, steady-flow process, the four balance equations (mass, energy, entropy) are applied to find the work and heat interactions, the rate of irreversibility, the energy and power efficiencies [9] [10] [13] [14].…”

Section: Parametric Study For Power Analysismentioning

confidence: 99%

“…The energy balance for these spools per unit air mass flow rate is given by following relations [14]:…”

Section: High and Low Pressure Turbine (Hpt And Lpt)mentioning

confidence: 99%

Power System Analysis of an Aero-Engine

Turan¹,

Aydın²

2015

JPEE

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The aim of this study is analyzed in detail for better understanding of energy and power of an aero-engine. In this regard, this study presents energy equations were applied to the turbofan engine components. The engine has a thrust range of 82 to 109 kN. It consists of fan, axial low pressure compressor (LPC), axial high pressure compressor (HPC), an annular combustion chamber, high-pressure turbine (HPT) and low pressure turbine (LPT). The results show that power of the engine flow approaches a maximum value to be 82.85 MW in the combustor outlet, while minimum power is observed at LPC inlet with the value of 1.37 MW. Furthermore, important parameters of the engine are also analyzed from reverse-engineering method. It is expected that results of this study will be beneficial of power, cogeneration and aero-propulsive generation systems in similar environment.

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“…Although the phenomena produced in the electric arc at the terminals of the circuit-breaker are complicated and not completely explained, the concept of exergy is useful for understanding the physical phenomena [17][18][19][20][21][22]. Investigations of electrics show that the limits between the microscopic and macroscopic phenomena are fragile and certain phenomena could be studied in related frames of work.…”

Section: Exergy Analysis Of Electric Arc In Generator Circuit-breakermentioning

confidence: 99%

Approaching the Processes in the Generator Circuit Breaker at Disconnection through Sustainability Concepts

et al. 2013

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Nowadays, the electric connection circuits of power plants (based on fossil fuels as well as renewable sources) entail generator circuit-breakers (GCBs) at the generator terminals, since the presence of that electric equipment offers many advantages related to the sustainability of a power plant. In an alternating current (a.c.) circuit the interruption of a short circuit is performed by the circuit-breaker at the natural passing through zero of the short-circuit current. During the current interruption, an electric arc is generated between the opened contacts of the circuit-breaker. This arc must be cooled and extinguished in a controlled way. Since the synchronous generator stator can flow via highly asymmetrical short-circuit currents, the phenomena which occur in the case of short-circuit currents interruption determine the main stresses of the generator circuit-breaker; the current interruption requirements of a GCB are significantly higher than for the distribution network circuit breakers. For shedding light on the proper moment when the generator circuit-breaker must operate, using the space phasor of the short-circuit currents, the time expression to the first zero passing of the short-circuit current is determined. Here, the manner is investigated OPEN ACCESSSustainability 2013, 5 1162 in which various factors influence the delay of the zero passing of the short-circuit current. It is shown that the delay time is influenced by the synchronous machine parameters and by the load conditions which precede the short-circuit. Numerical simulations were conducted of the asymmetrical currents in the case of the sudden three-phase short circuit at the terminals of synchronous generators. Further in this study it is emphasized that although the phenomena produced in the electric arc at the terminals of the circuit-breaker are complicated and not completely explained, the concept of exergy is useful in understanding the physical phenomena. The article points out that just after the short-circuit current interruption by the generator the circuit-breaker (when the GCB has been subjected at the metal contact terminals to the high temperature of a plasma arc, up to 50,000 K) between its opened contacts, there arises the transient recovery voltage (TRV) which constitutes the most important dielectric stress after the electric arc extinction. Since the magnitude and shape of the TRV occurring across the generator circuit-breaker are critical parameters in the recovering gap after the current zero, in this paper, we model, for the case of the faults fed by the main step-up transformer, the equivalent configurations, with operational impedances, for the TRV calculation, taking into account the main transformer parameters, on the basis of the symmetrical components method.

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Exergy tools

Cited by 71 publications

References 7 publications

Developing an Input-Output Based Method to Estimate a National-Level Energy Return on Investment (EROI)

Developing an Input-Output Based Method to Estimate a National-Level Energy Return on Investment (EROI)

Power System Analysis of an Aero-Engine

Approaching the Processes in the Generator Circuit Breaker at Disconnection through Sustainability Concepts

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