1 exergy and possible applications zhang lixiao email:[email protected] 11/14/2015
TRANSCRIPT
2
Questions?
What is real resource or wealthy ?
-Available energy
How to interpret the concept of scarcity ?
-Irreversibility
3
Let there be a series of thermal reservoirs. WR is the reversible (maximum) obtainable work
between any two temperatures.
Past Memory
Temperature T*
T1
T2
WR
QH
QC
4
Maximum attainable work
HR QW max
H
CHR T
TQW 1
5
The general concept of exergy In 1953 the term exergy was suggested by Z. Rant to denote “techni
cal working capacity”.
A complete definition was given by H.D.Baehr in 1965-
Exergy is that part of energy that is convertible into all other forms of
energy.
Exergy is a measurement of how far a certain system deviates from
a state of equilibrium with its environment (Wall,1977).
According to Szargut et al. (1988) "exergy is the amount of work obt
ainable when some matter is brought to a state of thermodynamic e
quilibrium with the common components of the natural surrounding
s’’.
6
Some remarks
Contrast is the source of action and depletion of contrast is tContrast is the source of action and depletion of contrast is t
he creator of time. Exergy is the physical value of contrast.he creator of time. Exergy is the physical value of contrast.
Contrast is everywhere: Dark/Light, Cold/Hot, Woman/Man,Contrast is everywhere: Dark/Light, Cold/Hot, Woman/Man,
Yin/Yang, Mother Earth/Father Sun, Good/Evil, God/Satan, Yin/Yang, Mother Earth/Father Sun, Good/Evil, God/Satan,
Life/Death, ... Life/Death, ...
Energy and matter cannot be created, destroyed, produced oEnergy and matter cannot be created, destroyed, produced o
r consumed.r consumed.
7
Possible applications
Bufferingcapacity
Resource
Exergy
Environ-mentalimpact
Exergy as the trinity of resource, buffering capacity and environmental impact
8
Second Law analysis of a real process
9
10
Resource accounting-wall School On global scale
-G. Wall & M. Gong(2000), "On Exergetics, Economics and Desalination", Ency
clopedia of Desalination and Water Resources (DESWARE), EOLSS Publisher
s, Oxford
-CHEN, G. Q.(2005). Exergy consumption of the earth. Ecological Modelling18
4(2-4), 363-380.
-HERMANN, W. A.(2006). Quantifying global exergy resources. Energy31(12),
1685-1702.
11
Exergy budget of the earth
12
On state scale
County Associated years Authors and published year Methodology
USA 1970 (Reisad, 1975) Reistad’s approach
Sweden 1980 (Wall, 1987) Wall’s approach
Japan 1985 (Wall, 1990) Wall’s approach
Italy 1990 (Wall et al., 1994) Wall’s approach
Norway 1995 (Ertesvag & Mielnik, 2000) Wall’s approach
China 1993 (Chen & Chen, 2006) Wall’s approach
13
On sectoral scale
County Associated years Authors and published year Sectors
Saudi Arabia 1990-2001 (Dincer et al., 2004) public and private sector
Saudi Arabia 1990-2001 (Dincer et al., 2005) agricultural sector
Saudi Arabia 1990-2001 (Dincer et al., 2004) transportation sector
Turkey 1990-2001 (Utlu & Hepbasli, 2006) agricultural sector
Turkey 2000-2020 (Utlu & Hepbasli, 2005) residential–commercial
sector
China 1978-2002 (Ji & Chen, 2006) transportation sector
14
Exergy as ecological indicator-Jorgenson School
The biggest asset of ecosystem exergy analysis is that it can measure the increase in disorder in ecosystems associated with human environmental impact.
Wagendorp et al. (2001) proposed to use the ecosystem exergy concept as the theoretical basis for selecting indicators of the land use impact category in Life Cycle Assessment (LCA).
15
Ecosystem exergy concept
Four key elements: Ecosystems are open systems that receive external exergy
fluxes (mainly solar exergy);
Ecosystems use part of that external exergy to increase their
internal exergy level in terms of biomass, structure and
information (order from disorder)
Ecosystems increase and maintain their capability to build
up order through a process of learning and memorizing by
genetic selection and transfer (order from order)
Ecosystems with high exergy level are more successful in
dissipating external exergy flows; it means that they are
better buffered and thus have higher stability
16
Exergy analysis of waste emissions- Rosen School
17
How to calculate the exergy?
Is not so important compared to how to define a syst
em boundary!
Not very difficulty but very complicated!
Vast references can help you finish your work once y
ou catch the philosophy of exergy!
18
Thanks for your attentions!