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Exergy and Possible Applications

Exergy and Possible Applications. Zhang Lixiao Email:zhanglixiao@bnu.edu.cn 7/16/2014. Questions?. What is real resource or wealthy ? -Available energy How to interpret the concept of scarcity ? -Irreversibility. Q H. T*. Temperature. W R. T 1. Q C. T 2. Past Memory.

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Exergy and Possible Applications

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  1. Exergy and Possible Applications Zhang Lixiao Email:zhanglixiao@bnu.edu.cn 7/16/2014

  2. Questions? • What is realresource or wealthy ? -Available energy • How to interpret the concept of scarcity ? -Irreversibility

  3. QH T* Temperature WR T1 QC T2 Past Memory • Let there be a series of thermal reservoirs. • WR is the reversible (maximum) obtainable work between any two temperatures.

  4. Maximum attainable work

  5. The general concept of exergy • In 1953 the term exergy was suggested by Z. Rant to denote “technical 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 obtainable when some matter is brought to a state of thermodynamic equilibrium with the common components of the natural surroundings’’.

  6. Some remarks • Contrast is the source of action and depletion of contrast is the creator of time. Exergy is the physical value of contrast. • Contrast is everywhere: Dark/Light, Cold/Hot, Woman/Man, Yin/Yang, Mother Earth/Father Sun, Good/Evil, God/Satan, Life/Death, ... • Energy and matter cannot be created, destroyed, produced or consumed.

  7. Possible applications Resource Exergy Environ- mental impact Buffering capacity Exergy as the trinity of resource, buffering capacity and environmental impact

  8. Second Law analysis of a real process

  9. Resource accounting-wall School • On global scale -G. Wall & M. Gong(2000), "On Exergetics, Economics and Desalination", Encyclopedia of Desalination and Water Resources (DESWARE), EOLSS Publishers, Oxford -CHEN, G. Q.(2005). Exergy consumption of the earth. Ecological Modelling184(2-4), 363-380. -HERMANN, W. A.(2006). Quantifying global exergy resources. Energy31(12), 1685-1702.

  10. Exergy budget of the earth

  11. On state scale

  12. On sectoral scale

  13. 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).

  14. 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

  15. Exergy analysis of waste emissions- Rosen School

  16. How to calculate the exergy? • Is not so important compared to how to define a system boundary! • Not very difficulty but very complicated! • Vast references can help you finish your work once you catch the philosophy of exergy!

  17. Thanks for your attentions!

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