Sectoral Energy and Exergy Analysis

Mostafa Ghadamyari

Advanced Thermodynamics Course

Mechanical Engineering Department – Energy Conversion

Tarbiat Modares University

Spring 2014

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”German theoretical physicist who pioneered developments in atomic and quantum physics

Thermodynamics definition

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Energy, Entropy and Exergy concepts stem from thermodynamics and are applicable to all fields of science and engineering.

Introduction

Energy, Exergy & Entropy

o Entropy and Exergy are also used in other fields (such as statisticsand information theory), and Therefore they’re not subsets of energy.

o Some forms of Energy (such as shaft work) are entropy-free, and thus entropy subtends only part of energy.

o Likewise, Exergy subtends only part of the energy field since some systems (such as air at atmospheric conditions) possess energy but no exergy.

Energy, Exergy & Entropy

o Most thermodynamic systems (such as steam in a power plant) possess energy, entropy and exergy, and thus appear at the intersection of these three fields.

o So we can have Energy Analysis, Exergy Analysis & Entropy Analysis according to system

Applying Exergy Analysis to MacroSystems

• Exergy is the ‘fuel’ of dissipative systems, i.e., systems that are sustained by converting energy and materials.• Examples include a living cell, an organism, an

ecosystem, and the earth’s surface with its material cycles.

• Societies are also dissipative systems, and can therefore be assessed with exergy analysis.

Exergy Analysis helps us to:

• Improving the efficiency of energy resource utilization.

• Assessing the locations, types and true magnitudes of wastes and losses.

• Distinguishing between high- and low-quality energy resources and services, and better matching the quality of energy required for a service with the quality of the energy supplied.

• High Temperature Resource -> High Temperature application

• Determining whether or not and by how much it is possible to design more efficient energy systems by reducing inefficiencies.

• Reducing the impact of energy resource utilization on the environment.

Energy Loss

Energy flow model for a country

• First introduced in a landmark paper by Reistad (1975), who applied it to the U.S.

• Since then, several other countriesbeen examined using modifiedversions of this approach:

• Canada (Rosen,1992)

• Japan, Finland and Sweden (Wall, 1990, 1991)Italy (Wall et al., 1994)

• Turkey (Ozdogan and Arikol, 1995; Rosen and Dincer, 1997b)

• …

Backgrounds

• Relations:

• 𝜼 =𝑬𝒏𝒆𝒓𝒈𝒚 𝒊𝒏 𝒑𝒓𝒐𝒅𝒖𝒄𝒕𝒔

𝑻𝒐𝒕𝒂𝒍 𝒆𝒏𝒆𝒓𝒈𝒚 𝒊𝒏𝒑𝒖𝒕

• 𝚿 =𝑬𝒙𝒆𝒓𝒈𝒚 𝒊𝒏 𝒑𝒓𝒐𝒅𝒖𝒄𝒕𝒔

𝑻𝒐𝒕𝒂𝒍 𝒆𝒙𝒆𝒓𝒈𝒚 𝒊𝒏𝒑𝒖𝒕

• Heating:

• Electrical:

• 𝜼𝒉,𝒆 = 𝑸𝒑/𝑾𝒆

• 𝝍𝒉,𝒆 = 𝟏 −𝑻𝟎

𝑻𝒑

𝑸𝒑

𝑾𝒆= 𝟏 −

𝑻𝟎

𝑻𝒑𝜼𝒉,𝒆

• Fuel:• 𝜼𝒉,𝒇 = 𝑸𝒑/𝒎𝒇𝑯𝒇

• 𝝍𝒉,𝒇 ≅ 𝟏 −𝑻𝟎

𝑻𝒑𝜼𝒉,𝒇

• Work production:

• Electrical:

• 𝜼𝒎,𝒆 = 𝑾/𝑾𝒆

• 𝝍𝒎,𝒆 = 𝜼𝒎,𝒆

• 𝑃𝑒𝑛𝑣 = 1𝑎𝑡𝑚

• 𝑇𝑒𝑛𝑣 = 25𝐶

Analysis of the residential/commercialsector

Case study: Turkey (Utlu 2005)

Energy usage in Iran vs Turkey

Turkey Iran

Population 76M 77M

Energy usage in Turkey

Industrial42%

Residental31%

Transportation19%

Agricultural5%

Non-energy3%

TURKEY 2003 ENERGY USE

Residential/Commercial sector model

Residential Commercial

space heating 45% 42%

water heating 27% 30%

cooking 9% 11%

electrical

appliances

19% 17%

Share of Primary Energy Usage:

Utilization of Energy in Turkish Residential Sector

• Turkey Residential energy consumption:• 41.5% Renewable

• 38.7% Fuel

• 19.8% Electricity

• Wood: Sustainable & Renewable Energy Source

Wood - Multi-Fuel & Boiler Stoves

• Output to room: 2.8 kW

• Output to water: 9 kW

• No. of radiators in average installation: 3-4• Based on Double Panel Radiators

1m*0.6m

• Dimensions: 0.5m 0.5m 0.5m

• Weight: 95kg

• Price: ~1700$ (Include VAT, DELIVERY

Energy utilization values of TRCS

• We need fraction of energy use in each application• Source:

• Utlu Z. Analysis of Turkey’s Sectoral Energy and Exergy Utilization Efficiency by 2023. Ph.D. thesis in Solar Energy Institute (Advisor: A.Hepbasli ), Graduate School of Natural andApplied Sciences, EgeUniversity, Izmir, Turkey; 2003 [in Turkish].

• Usually published by Institute of statistics

Step 1: Estimate end-use energy efficiency

• Step 1: Energy efficiencies (First law efficiencies) are estimated.• Source:

• Utlu Z. Analysis of Turkey’s Sectoral Energy and Exergy Utilization Efficiency by 2023. Ph.D. thesis in Solar Energy Institute (Advisor: A.Hepbasli ), Graduate School of Natural andApplied Sciences, EgeUniversity, Izmir, Turkey; 2003 [in Turkish].

Step 2: Calculate Exergy Efficiency

Example: Cooking

Energy efficiency:

𝜀1,𝑐𝑜𝑜𝑘𝑖𝑛𝑔 = 50%

Cooking temperature: 120C

Ambient temperature: 20C

𝜀2,𝑐𝑜𝑜𝑘𝑖𝑛𝑔 = 50% × 1 −273+20

273+120= 12.7%

Exergy efficiencies

• Exergy efficiencies are

calculated as shown in

the table.

Step 3 : Overall Application efficiency

• Overall energy efficiency:• 𝜀1𝑜 = (𝑎1𝜀1𝑐+ 𝑎2𝜀2𝑐+…+𝑎2𝜀2𝑐)/100

• Overall exergy efficiency:• 𝜀2𝑜 = (𝑎1𝜀2𝑐+ 𝑎2𝜀2𝑐+…+𝑎3𝜀2𝑐)/100

Step 3 : Overall Application efficiency

• Cooking:

• 𝜀1𝑜 =91.7∗50+7.5∗50+0.3∗80+0.3∗22

100= 49.9

• 𝜀2𝑜 =91.7∗10.7+7.5∗10.8+0.3∗17.2+0.3∗4.5

100= 10.68

Overall Energy and Exergy efficiency

• Overall application Energy & Exergy efficiencies are calculated as shown in the table.

• Overall Sector Energy & Exergy efficiencies:• 𝜀1𝑜 = (𝜀1𝑒𝑒𝑟𝑐 + 𝜀1𝑓𝑓𝑟𝑐 + 𝜀1𝑟𝑟𝑟𝑐)/(𝑒𝑟𝑐 + 𝑓𝑟𝑐 + 𝑟𝑟𝑐)

• 𝜀2𝑜 = (𝜀2𝑒𝑒𝑟𝑐 + 𝜀2𝑓𝑓𝑟𝑐 + 𝜀2𝑟𝑟𝑟𝑐)/(𝑒𝑟𝑐 + 𝑓𝑟𝑐 + 𝑟𝑟𝑐)

Step 4 : Overall sector efficiency

• Residential-Commercial Efficiency:• Space Heating: 45%

• Water Heating: 27%

• Cooking: 9%

• Electrical: 18%

• 𝜀1𝑜 =50.32∗45+60.43∗27+40.32∗9+80.98∗18

100= 57.16

• 𝜀2𝑜 =2.65∗45+3.95∗27+10.30∗9+22.17∗18

100= 7.17

Overall Sector Efficiency

• Summary:• 1- Estimate Energy Efficiency

• 2- Estimate Product temperature

• 3- Calculate Exergy Efficiency

• 4- Calculate Overall Energy & Exergy Efficiency by using:

• Energy consumption of each application

Conclusion

• The residential/commercial sector have great potential for energy savings, because large disparities exist between the overall energy and exergyefficiencies

• Space heating & Water heating have more inefficiencies rather than cooking.

Analysis of the Industrial sector

Case study: Turkey (Utlu 2005)

Introduction

• Exergy analysis provides more realistic picture considering the irreversibilities and potential optimization of the process• A review on exergy analysis of industrial sector [2013 Renewable and Sustainable Energy Reviews]

• Energy consumption in industrial sectors varies between 30% to 70%• Slovenia: 30%, Jordan: 31%, Turkey: 35%, South Africa: 44%, China: 70%• Iran:

• 25% of total energy in 2011• 34.6% electrical energy in 2011

• Exergy analysis of industrial sector divides to:• 1. Exergy analysis of industrial sector of different countries• 2. Exergy analysis of different industries• 3. Exergy analysis of industrial devices

Energy Flow in Turkish industrial sector

Exergy analysis of Industrial sector

• First, The most energy consuming units are chosen (e.g. for Turkey: iron–steel, chemical–petrochemical, petrochemical–feedstock, cement, fertilizer, sugar, non-metal industry, Covers ~95% of energy usage)

• Energy usage in industrial sector can be devided into four different categories:

• 1.Process Heating : 66%

• 2.Mechanical Process : 15%

• 3.Lightning

• 4.Air Condioning

• Characteristic of some fuels are shown :

5% - 18%

82% - 95%

Exergy analysis of Industrial sector

• Heating processes for each industry are grouped into low, medium, and high temperature categories

• H.L. Brown, B.B. Hamel, B.A. Hedman, Energy Analysis of 108 Industrial Processes. Fairmount press, Lilburn, GA, 1996

Energy Analysis of 108 Industrial Processes

Example process

Exergy analysis of Industrial sector

Energy Annual Report

Hidrocarburi Annual Report

Summary

• Energy, Exergy & Entropy analysis are applicable to systems which contain them

• Energy & Exergy analysis procedure of Residential/Commercial sector was introduced

• Energy & Exergy analysis procedure of Industrial sector was introduced

• Some Iranian data source were introduced: Hidrocarburi, Energy

Thank you!