ARİF HEBBAŞLI Arif Hepbasli_afyon 17-1-2014

8/18/2019 ARİF HEBBAŞLI Arif Hepbasli_afyon 17-1-2014

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Exergy Analysis of Renewable EnergySystems

17 January 2015Afyon

Arif Hepbasli

Department of Energy Systems Engineering

Yasar University, Izmir, Turkey

Outline(61 slides)

1. Objective2. Introduction3. Historical Development of Exergy Concept4. What is exergy ?

5. Why exergy ?6. Dead State7. Driving Force8. Exergy efficiency

9. Sankey and Grassmann diagrams10. Modeling11. An Illustrative Example12. Conclusions

LET US COME TO AN AGREEMENT!!!

My speech will not be on the pure technical basis.

1. Objective

A Sketch Showing the Meaning of RESs

RESs are money mints .

2. Introduction

ENERGY EXERGY

Unit energy price - Unit exergy price

Specific energy production - Specific exergyproduction

Energy analysis - Exergy analysis

Energy efficiency – Exergy efficiency

Energy management – Exergy management

Energy consultant - Exergy consultant

Specific moisture extraction - Specific moistureexergeticrate (SMER) index (SMEI)

Number of publications ???????

Footprints…

Carbon footprint

Water footprint

h-index

Impact-Citations-Exergy (ICEx)Fractionalized exergy for evaluating research performance (X)

Source: Prathap, G. JOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, 62(11):2294 – 2295, 2011

By fractionalcounting we meanthat instead ofcounting eachcitation as unity, weconsider it asweighted

(fractionated) interms of thenumber ofreferences in thecitingarticle.

Exergy Consulting Services

Dr. Wall (in

Sweden):www.exergy.se

Dr. Cornelissen

(Holland):www.exergy.nl

Engineers and scientists dealing with the design andoperation of an energy conversion plant want to improveor optimize it by maximizing efficiency and minimizing (a) product cost and (b) environmental impact associated with this plant.

In order to effectively deal with these problems, wemust understand the real mechanisms according towhich thermodynamic inefficiencies, costs, and

environmental impacts are formed.

Source: G. Tsatsaroni s9

In the improvement phase , the following questions arise:

Where do real thermodynamic inefficiencies occur, howhigh are they, and what causes them ?(Exergy analysis )

● What measures or what alternative designs would

improve the efficiency of the overall plant ?(Exergy analysis, but a conventional one isusually not sufficient )

● How high are the total investment and the equipmentcosts of the major plant components ?

(Economic analysis )

Source: G. Tsatsaronis10

● How high are the cost and the environmental impactassociated with thermodynamic inefficiencies ?

(Exergoeconomic and exergoenvironmental analyses )

●How high are (a) the environmental impacts associatedwith the major plant components, and (b) the

overall environmental impact ?

(LCA and exergoenvironmental analysis )

A conventional exergetic , conventional exergoeconomic

and conventional exergoenvironmental analysis doesnot evaluate the mutual interdependencies among thesystem components nor the potential for improving acomponent.

These issues are considered in advanced analyses , inwhich the exergy destruction, capital investment costand construction-of-component-related environmentalimpact in each component are split into:● endogenous and exogenous parts,● unavoidable and avoidable parts, and● the resulting combined parts.

12Advanced (or enhanced) analyses

Nicolas Léonard Sadi Carnot : Sadi CarnotIn his only publication, the 1824 monograph Reflections on theMotive Power of Fire , Carnot gave the first successful theoryof the maximum efficiency of heat engines .Source:http://en.wikipedia.org/wiki/Nicolas_L%C3%A9onard_Sadi_Carnot , Access date: 17 January 2015.1824’de ısı makinaları üzerine çalışmasını yayınladı.

What is his birthday ? Doğum yılı nedir ?

What is the magic of number 28 ? “28” sayısı nin sihiri nedir ?

Kaynak: Yantovski, E.

Five Equations That Changed the World

http://en.wikipedia.org/wiki/Five_Equations_That_Changed_the_World

Comparison and evaluation of the energy systemsEnergy analysisExergy analysisEconomic analysis

Life cycle assessment

Exergo economic analysis

Exergo environmental analysisExergetic life cycle assessment

Advanced exergy analysis

Advanced exergo economic analysisAdvanced exergo environmental analysis

17Our understanding

Energy analysis Conventional exergetic analysis

Sensitivity analysis Advanced exergetic analysis

3. Historical Development of Exergy Concept

In 1824, Carnot started that the extractable work of aheat engine is proportional to the temperaturedifference, which later led to the definition of thesecond law of thermodynamics.

In 1873, Gibbs introduced the nation of available work,including the diffusion term.

In 1953, Keenan interpreted exergy as “available” energy.

In 1953, Rant suggested the term exergy to denote“technical working capacity” .

Wall and Gong has reported the historical

development of the concept “exergy” as follow s:

In 1961, Tribus linked classical thermodynamicswith information theory, through the entropy andthe exergy concepts.

At a conference in Rome in 1987, it was agreedamong the participants to encourage strongly theuse of exergy for the general concept of the

potential to cause change,in lieu of terms such as

availability, available energy, essergy, utilizableenergy, work potential, available work,convertible energy, etc .

The quality of energyThe capacity of energy to cause change

The maximum work that can be obtained from agiven form of energy using the environmentalparameters as the reference state

A measure of the departure of the state of thesystem from the state of the environment

Sources:Leskinen, M. Low Exergy Sources for Heating and Cooling & IEA Annex 37Tsatsaronis, G and Cziesla, F. Thermoeconomics, 2003.

4. What is Exergy ?

Where is Exergy ?

It is in my pocket.

What happens when we squeeze the toothpaste tube ?

Could we put the paste back in the tube again

after coming out ?

The entropy of a systemincreases when exergy is lost.

Source: http://www.holon.se/folke/kurs/Distans/Ekofys/fysbas/exergy/exergybasics.shtml

To more easily understand the concept of exergy , you canconsider the previous picture as an analogy: You buy is the(toothpaste) tube, but have to squeeze it to get at what

you really need, the toothpaste. When the tube is emptyof paste (exergy) the tube is still there, the same amountas when you bought it.In these circumstances, the word entropy often comes up.In the picture this is represented as the depression in thetube . The depression increases as the amount of pastediminishes, but the depression is not a negative paste (Youcan not take the depression and un brush your teeth !).

Entropy is not negative exergy, but another description ofthe system. Furthermore, it is not defined in far-from-equilibrium systems , as living systems and other organisedsystems.

26Source: http://www.holon.se/folke/kurs/Distans/Ekofys/fysbas/LOT/LOT.shtml , Access date: 13 Feb. 2011.

Differences between Energy and ExergyAnalysis

Source: LOWEX Guidbook

Source: Helga Ferket, Ben Laenen & Peter Van Tong eren. Low-exergy applications of low-enthalpygeothermal prospects . 12 Oct . 2009.

Symbols for exergy and exergetic efficiency used intextbooks [initially compiled by Noam Lior]

exergy[J] the specific

exergyfunction [J/kg]

exergydestruction exergetic

efficiency Textbookreference

b Irreversibility Keenan

Λ Φ, b I Hatsopoulos &Keenan, 1965 Kotas, 1985

E E d Moran and

Shapiro E x for opensystems, Ξ for closed

b for opensystems, a forclosed

W lost η I I

(contnd ) Symbols for exergy and exergetic efficiency used in textbooks [initially

(contnd.) Symbols for exergy and exergetic efficiency used in textbooks [initiallycompiled by Noam Lior]

exergy[J]

the specific exergyfunction [J/kg]

exergydestruction

exergeticefficiency

Textbookreference

Bejan, Tsatsaronis,and Moran

B δb η B , η p Szargut et al.

X I , Xdestro yed η I I

Cengel and Boles

Ψ, ф η2nd Anderson

Ψ, Ω ε Gyftopoulos andBeretta

E Bosnjakovic

η II Sussman

ф I η2nd law Sontag,Borgnakke, vanWylen

Ė (onlyfor

streams)

Ė V Baehr

Exergy and Anergy

Exergy= “Useful”

energy= Q [1-(T 0 /T h)]

Anergy= “Useless” energy = Q (T 0 /T h)

Given: an amount of material with temperature T h Energy content = Q

QEnergy = Exergy + Anergy

5. Why Exergy ? An effective method using the conservation of mass andconservation of energy principles together with the SLT forthe design and analysis of energy systems.

A primary tool in best addressing the impact of energyresource utilization on the environment.

A suitable technique for furthering the goal of more

efficient energy-resource use.

A crucial key for determining the locations, types, and truemagnitudes of wastes and losses.

An efficient technique revealing whether or not and by howmuch it is possible to design more efficient energy systemsby reducing the inefficiencies.

A key component in obtaining sustainable development.Source: I. Dincer

Exergy analysis of the thermal systems allows thedesigner to:

a) assess the influence of every process (component)of the system on the overall efficiency;

b) eliminate the major processes (components) of thesystem that diminish its performance;

c) definite the maximum value of the systemefficiency with respect to the best performance ofthe assumed process (component); and

d) identify methods for improving the effectivenessof a power plant.

Source: I. Dincer

E d E Fl Di

Energy and Exergy Flow Diagrams

Source: Wall, G; Zvolinschi, A.

6. Dead (Reference) State DefinitionIt should be noticed that exergy is always evaluated withrespect to a reference environment (i.e. dead state).When a system is in equilibrium with the environment, the stateof the system is called the dead state due to the fact that theexergy is zero. At the dead state, the conditions of mechanical,thermal, and chemical equilibrium between the system and theenvironment are satisfied: the pressure, temperature, and

chemical potentials of the system equal those of theenvironment, respectively.

In addition, the system has no motion or elevation relative tocoordinates in the environment. Under these conditions, there isneither possibility of a spontaneous change within the system orthe environment nor an interaction between them. The value ofexergy is zero..

Dead (Reference) State Definition (Cont’d)Another type of equilibrium between the system andenvironment can be identified. This is a restricted form of

equilibrium, where only the conditions of mechanical andthermal equilibrium (thermomechanical equilibrium) must besatisfied. Such state is called the restricted dead state.At the restricted dead state, the fixed quantity of matterunder consideration is imagined to be sealed in an envelope

impervious to mass flow, at zero velocity and elevationrelative to coordinates in the environment, and at thetemperature T 0 and pressure P 0 taken often as 25 oC and 1atm.The selection of dead state conditions is arbitrary, but

depends on some criteria.Please note that we will call only the dead state throughoutthis lecture.

Source: Moran MJ. Availability analysis: a guide to efficiency energy use. Englewood Cliffs,NJ: Prentice-Hall; 1982. 37

7. Driving ForceThe impetus, power, or energy behind something inmotion, as in He was clearly the driving force in the new

administration . This term transfers the force that sets inmotion an engine or vehicle to other enterprises. RalphWaldo Emerson was among the first to use it figuratively(English Traits , 1856): “The ability of its journals is thedriving force .”

Source: http://dictionary.reference.com/browse/driving+force

What is the driving force for the heat transfer, electriccurrent and fluid flow ?

7. Driving Force

8. Exergy Efficiency

Exergy Efficiency = Product/Fuel

Exergy Efficiency = Desired Effect/Fuel

Exergy Efficiency = Benefit /Fuel

Exergy Efficiency = Product /Source

http://upload.wikimedia.org/wikipedia/commons/1/10/JIE_Sankey_V5_Fig1.png

The firstSankeydiagram

9. Sankey and Grassmann diagrams

http://www.sei.ie/uploadedfiles/CHP/Sankey%20diagram2.png

In this diagram, called a Sankey Diagram, we can see that of 72 kW of powerfrom the fuel, only 9 kW are used in actually driving a car along a road. Therest is lost as low grade heat.

http://www.antonine-education.co.uk/Physics_A2/Options/Module_7/Topic_5/Sankey.gif

Exergy balance diagram

(Grassmann diagram)

Mass balance equation:

General energy balance:

General exergy balance:

Other balance equations ???

Exergy efficiency:

10. Modelling

Total exergy of a system:

Exsys= ExPH+ ExKN+ ExPT + ExCH

Total specific exergy on a mass basis:

ex sys= exPH+ exKN+ exPT + exCH

11. An Illustrative Example

12. Conclusions

Exergy analysis is an effective method, using theconservation of mass and conservation of energy principlestogether with the SLT, that can be employed for thedesign and analysis of thermal systems.It is therefore an efficient technique revealing whetheror not and by how much it is possible to design more

efficient thermal systems by reducing the inefficiencies.Illustrative example is presented to highlight theimportance of understanding and considering exergy as apotential tool.The potential usefulness of exergy analysis in addressingand solving environmental problems is substantial.

THANK YOUVERY MUCHFOR YOUR

STAYING HERE

TILL THE END

QUESTIONS ???

HEPBASL

QUESTIONS ???

ARİF HEBBAŞLI Arif Hepbasli_afyon 17-1-2014

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