Gestão de Energia: 2013/2014
Introduction
&
Review of Thermodynamics
Class # 1
Prof. Tânia Sousa
taniasousa@ist.utl.pt
Docentes
• Tânia Sousa
– taniasousa@ist.utl.pt
• Carla Silva
– carla.silva@ist.utl.pt
• Carlos Silva
– carlos.santos.silva@ist.utl.pt
• André Pina
– andre.pina@ist.utl.pt
Avaliação
• Exame (50%) com nota mínima 9.5 val.
• Avaliação Contínua (50%)
– Trabalhos feitos por grupos de 2/3 alunos
– Os trabalhos começam nas aulas e são para terminar
em casa
– A avaliação é feita nas aulas e com os trabalhos
• Trazer um portátil por grupo para as aulas
práticas
Objectivo
1. Compreender e modelar os fluxos energéticos
à escala do país, em sistemas industriais, em
edifícios ou equipamentos complexos.
2. Definir acções que permitam racionalizar o
uso da energia, quantificando os benefícios
económicos e ambientais destas acções.
Gestão de Energia: Conteúdo
Semana
Teóricas
21-02-2014 Apresentação. Revisões Termodinâmica
4ª feira à
tarde
Práticas
28-02-2014 Balanço Energético Português
Energia Primária Final e e Útil. Diagramas de Sankey
07-03-2014 Transições Energéticas. Análise da Eficiência de
Sistemas Energéticos
Modelos analíticos para a análise energética de sistemas:
14-03-2014
diagramas de blocos
Eficiência Energética na Indústria. Regulamento da
21-03-2014
eficiência energética na indústria (SGCIE).
Eficiência Energética nos edifícios.
28-03-2014
Regulamentos de eficiência energética nos edifícios.
04-04-2014 Modelos Input-Output
Energia e Economia
11-04-2014
Métodos de contabilização da electricidade primária.
18-04-2014 FÉRIAS
25-04-2014 FERIADO
Exercícios
02-05-2014 Análise Ciclo de Vida
Eficiência energética nos Transportes. Regulamento da
09-05-2014
eficiência energética nos Transportes
Exercícios
14-05-2014 Auditorias Energéticas
Trabalho V (Tranportes)
4ª feira manhã e à tarde
Trabalho I (B.E.N)
Trabalho II (Sankey)
Exercícios
Trabalho III
Exercícios
Trabalho IV (Input-Output)
FÉRIAS
FERIADO
Exercícios
23-05-2014 Modelação Oferta e Procura de Energia
Visita a um Laboratório Tagus Park
30-05-2014 Revisões.
Exercícios
Course Contents
Thermodynamics
• Energy and Entropy Balances for Closed &
Open Systems
• Thermodynamic Cycles: power cycle,
heat pump & refrigerator cycle
• 1st Pratical Class (exercises)
• Bibliography
– “Fundamental of Engineering Thermodynamics”
Shapiro & Moran
Course Contents – T2
• The Portuguese Energetic Balance:
– Supply, Conversion & Demand
– Energy Carriers
BALANÇO ENERGÉTICO
tep
Total de Carvão Total de Petróleo
2008
IMPORTAÇÕES
PRODUÇÃO DOMÉSTICA
VARIAÇÃO DE "STOCKS"
SAÍDAS
CONSUMO DE ENERGIA
PRIMÁRIA
PARA NOVAS FORMAS DE
ENERGIA
CONSUMO DO SECTOR
ENERGÉTICO
4=1a3
Total de
Eectricidade
Calor
Resíduos
Industriais
Renováveis
Sem Hídrica
TOTAL GERAL
23
30 = 24 a 29
36 = 31 a 35
37
38
46 = 39 a 45
47=4+22+23+30+36+37
+38+46
2 327 219
- 223 603
24 949
315 673
3 680 661
5 960
5.
2 525 873
12 612 050
4 157 207
1 953 404
6.
2 444 703
1 079 137
2 597 143
-2 810 996
-1 472 450
475 376
56 103
605 301
270 736
7.
16 608 384
Gases o
Outros
Derivados
1.
2.
3.
4.
CONSUMO COMO MATÉRIA PRIMA
DISPONÍVEL PARA CONSUMO
FINAL
ACERTOS
CONSUMO FINAL
AGRICULTURA E PESCAS
INDÚSTRIAS EXTRACTIVAS
INDÚSTRIAS
TRANSFORMADORAS
CONSTRUÇÃO E OBRAS
PÚBLICAS
TRANSPORTES
SECTOR DOMÉSTICO
SERVIÇOS
22= 15 + 21
Gás Natural
(*)
4 163 167
923 984
1 142 338
39 800
3 190 679
- 837
17 634
24 022 754
4 372 817
97 193
3 836 162
39 800
3 173 882
24 462 216
1 120
1 367 391
3 206 048
3
1 407 519
112 918
1 275 842
1 275 842
8.
81 170
9 781 695
1 503 961
4 159 099
1 201 714
38 680
1 806 488
18 572 807
9.
10.
10.1
10.2
9 851
71 319
- 47 340
9 829 035
358 801
66 103
- 1 382
1 505 343
3 359
8 444
12
4 159 087
87 218
49 882
1 201 714
2 366
30 844
38 680
279
1 806 209
21
4
- 38 580
18 611 387
451 765
155 277
10.3
71 319
1 085 788
1 027 157
1 340 009
1 154 293
38 680
615 382
5 332 628
10.4
576 210
5 063
50 490
21
631 784
10.5
10.6
10.7
6 680 176
552 680
509 277
6 659
300 190
154 471
46 677
1 157 672
1 427 139
3 452
1 180 750
6 579
6 736 964
3 191 292
2 111 677
14 211
Course Contents – T2
• 2nd Pratical Class & 1st assignment
– Each group analyses the PEB for a specific year and
compares it with 2012 (bring the computer)
• Learning Outcomes:
– Be able to retrieve information from the Energetic
Balance of a country/region
– Compute electricity production efficiencies and
other 1st law efficiencies for the country level
• Bibliography:
– Chap. 2 “Balanço Energético Nacional Metodologia de Elaboração, Evolução da Estrutura e
do Consumo Energético Primário”, Ramos, A.
– Chap. 2 “Energy Economics”, Bhattacharyya.
Course Contents - T3
• From Primary Energy to Energy Services at
different scales
IAASA - Global Energy Assessment 2012
Course Contents - T3
• World and national patterns of energy use
• Energy Transitions
Energy Transition
Grubler, A. “Energy Transitions” biomass to coal
Energy Transition
coal to oil
Course Contents - T3
• Sankey diagrams for different scales
• 1st and 2nd Law
Efficiencies
Course Contents – T3
• 2nd Pratical Class & 1st assignment
– Each group draws the Sankey diagram using e-Sankey
for the PEB for a specific year for Portugal
• Learning outcomes:
–
–
–
–
Understand concepts of primary, final & useful energy
Historical perspective on world energy use & transitions
Use Sankey diagrams to analyse energy systems
Understand 1st and 2nd law efficiencies
• Bibliography:
– Cap. 2 da sebenta “Gestão de Energia”, Águas, M.
– Chapter 1 & 16 GEA, IAASA
– Cullen and Alwood “The efficient use of energy:
Tracing the global flow of energy”, Energy Policy 2010.
Course Contents – T4
• Block Diagrams Energy Analysis
• 3th Practical Class
– Exercises
• Learning Outcomes
– Compute the energy intensity of a product or service,
i.e., the total energy required to produce it
– Compute the impact of efficiency measures on the
specific energy consumption
• Bibliography:
– Cap. 5 da sebenta “Gestão de Energia”, Águas, M.
Course Contents – T5
• Energy use in industry
• SGCIE: Energy efficiency
in industry
• 4th Practical Class & 3rd assignment
– Each group chooses a case study (e.g. the Secil),
finds the correct data and describes the production
process and computes the specific consumption
Course Contents – T5
• Learning Outcomes
– Apply & understand the SGCIE legislation
• Bibliography:
– DL n.º 71/2008; Despachos nº 17449/2008 &
17313/2008
– Chap. 6 “Energy Efficiency and the Demand for
Energy Services” Danny Harvey
Course Contents – T6
• Energy use in Buildings
– Factors controlling energy use in buildings
– Techniques to reduce energy use:
Course Contents – T6
• RCCTE & RSECE: Energy efficiency in buildings
• 5th Practical Class
– Exercises
• Learning Outcomes
– Learn about strategies to reduce energy use in buildings
and their impact
– Apply & understand the RCCTE & RSECE
• Bibliography:
– Chap. 4 “Energy Efficiency and the Demand for Energy
Services” Danny Harvey
– Decreto-lei n.º 118/2013
Course Contents - T7
• IO Analysis at the Macroeconomic scale
• Computation of Direct and Indirect Effects of
changes in Demand
• 6th Pratical Class & 4th assignment
– Each group computes energy demand scenarios for a
country for 2 & 5 & 10 years based on changes in the
economic structure & compares with reality
• Application of this methodology to Block
Diagrams Analysis
• Bibliography:
– Chap. 5 “Ecological Economics”, Common & Stagl.
Course Contents – T8
• Methods to compute primary energy for
renewable electricity
• EROI
Course Contents – T8
• Learning Outcomes
– Critically evaluate statistics and political goals on
the weight of renewables on primary energy mixes
at the country level.
– Understand & apply the concept of EROI
• Bibliography
Chapter. 14 & 15 from “Energy and the Wealth of
Nations”,Hall, C. & Klitgaard, K..
• 7th Practical Class
– Exercises
Course Contents – T8
• Energy & Economic Growth & Environment
Course Contents – T8
• Learning Outcomes
– Identify the interactions between energy use,
economic growth and environmental quality
• Bibliography:
– Chap. 2 & 6 “Energy at the Crossroads” Smil, V.
Course Contents – T9
• Life Cycle Assessment
Bioethanol Life Cycle
CO2
Bioethanol
DDG
• 8th Practical Class
– Exercises
• Bibliography:
Course Contents – T10
• Energy use in Transports
Course Contents – T10
• Legislation
• 9th Practical Class
– Exercises
• Learning Outcomes
– Learn about factors that influence energy use in
transports and strategies & technologies that reduce
the energy use in and their environmental impact
– Apply & understand the legislation on transports
• Bibliography:
– Chap. 5 “Energy Efficiency and the Demand for
Energy Services” Danny Harvey
Course Contents – T11
• Energy Audits
– Measurements
– Mass and Energy Balances
– Equipments
• 10th Practical Class
– Visita de Estudo (no Tagus Park)
Course Contents – T12
• Tools to Model the Supply and Demand of
Energy
• 11th Practical Class
– Exercises
• Learning Outcomes
– Learn about the energy modeling softwares & their
usefulness
Energy Balance in Closed Systems
Energy Change = Heat + Work
dE d U  E p  Ec 

 Q W
dt
dt
Energy change in the system
Flows at the boundaries
• 1st Law: Energy Conservation
• U, Ec and Ep
• Energy transfer by Heat
• Energy transfer by Work
• Sign of heat and work fluxes
• Steady state vs. Transient
heat
work
Energy Balance in Closed Systems
• Choosing the boundaries
– Flows, Thermodynamic System, Steady vs.
Transient state – flows at the boundaries?
Energy Balance in Closed Systems
• Choosing the boundaries
– Flows, Thermodynamic System, Steady vs.
Transient state
Energy Balance in Closed Systems
• Exercise:
Energy Balance in Closed Systems
• Thermodynamic Cycles • 1st Law efficiencies
Power Cycle
Refrigerator &
Heat Pump Cycles
– Power Cycle

Wcycle
Qin
– Heat Pump

Qout
Wcycle
– Refrigerator

Qin
Wcycle
Energy Balance in Closed Systems
• Exercise (Homework)
W    Fdx    P. Adx    P.dV
– If P is constant then W   P V f  Vi 
Vf
– If PV is constant then W   PV
i i ln
Vi
Energy Balance in Closed Systems
• Exercise (Homework)
• Exercise:
– Why is it possible that   1 ?
– How much does the electricity of your fridge costs
in a month?
Energy Balance in Open Systems
Mass Change =  Mass Flows
dm
  min,i   mout , j
dt
i
j
Energy Change = Heat + Work + Energy in Mass Flow


v j2


vi 2
dE
 Q  W   min ,i  hi 
 gzi    mout , j  h j 
 gz j 


dt
2
2
i

 j


Enthalpy of component j
hi  ui  pi vi
Flows at the boundaries
Energy Balance in Open Systems
• Exercises
–
–
–
–
1º Write the energy balance eq.
2º Identify energy flows
3º Simplify the eq.
For incompressible liquids at
constant pressure:
h  c  T 
c  water at 50ºC   4.182 kJ/kg.K
Energy Balance in Open Systems
• Turbines:
– Produce work as a result of gas or liquid passing
through a set of blades attached to a shaft free to
rotate


v j2


vi 2
dE
 Q  W   min ,i  hi 
 gzi    mout , j  h j 
 gz j 


dt
2
2
i

 j


Electricity from Epot of the water
Electricity from Ekin of the wind
Wmec from Ekin of the wind
Hydraulic Turbine
Wind Mill
Wind Turbine
Energy Balance in Open Systems
• Turbines:
– Produce work as a result of gas or liquid passing
through a set of blades attached to a shaft free to
rotate


v j2


vi 2
dE
 Q  W   min ,i  hi 
 gzi    mout , j  h j 
 gz j 


dt
2
2
i

 j


Electricity from Epot of the water
Electricity from Ekin of the wind
Wmec from Ekin of the wind
Hydraulic Turbine
Wind Mill
Wind Turbine
Energy Balance in Open Systems
• Exercises
– Write the energy
balance eq.
– Identify energy flows
– Simplify the eq.
Castelo de Bode dam
•3 turbines
• medium water fall 80 m
•Installed power: 159 MW
•Medium annual electricity
production: 390 GWh
• What is the energy conversion taking place?
Energy Balance in Open Systems
• Exercises
– Write the energy
balance eq.
– Identify energy flows
– Simplify the eq.
Castelo de Bode dam
•3 turbines
• medium water fall 80 m
•Installed power: 159 MW
•Medium annual electricity
production: 390 GWh
• Potential energy is converted into electricity and kinetical
energy
Energy Balance in Open Systems
• Compressors (gas) & Pumps (liquids):
Reciprocating
Compressor
– Used in aircraft engines, water pumping, natural gas
transport, etc
– Increase the pressure of a gas (compressor) or move fluids or
Increase in pressure of gas
slurries (pumps) using work
obtainned from decreasing
volume (obtainned with work)


v j2


vi 2
dE
 Q  W   min ,i  hi 
 gzi    mout , j  h j 
 gz j 


dt
2
2
i

 j


Pump water using work
Pump water using human work
Treadle Pump
Pumps
Energy Balance in Open Systems
• Compressors (gas) & Pumps (liquids):
Reciprocating
Compressor
– Used in aircraft engines, water pumping, natural gas
transport, etc
– Increase the pressure of a gas (compressor) or move fluids or
Increase in pressure of gas
slurries (pumps) using work
obtainned from decreasing
volume (obtainned with work)


v j2


vi 2
dE
 Q  W   min ,i  hi 
 gzi    mout , j  h j 
 gz j 


dt
2
2
i

 j


Pump water using work
Pump water using human work
Treadle Pump
Pumps
Energy Balance in Open Systems
• Exercises
–
–
–
–
1º Write the energy balance eq.
2º Identify energy flows
3º Simplify the eq.
Ideal gas model:
Underground storing of natural gas in Carriço
Storing Pressure: 180 bar
Storing capacity: 2 155 GWh
PV  NRT
u  u (T )
h  c  T 
c  CH 4   2.226 kJ/kg.K
– The need to cool after compression
Energy Balance in Open Systems
• Heat Exchangers:
– Used in power plants, air conditioners, fridges,
liquefication of natural gas, etc
– Transfer energy between fluids at different
temperatures


v j2


vi 2
dE
 Q  W   min ,i  hi 
 gzi    mout , j  h j 
 gz j 


dt
2
2
i

 j


Direct Contact Heat
Exchanger
Counter-flow Heat
exchanger
Direct Flow Heat
Exchanger
Energy Balance in Open Systems
• Heat Exchangers:
– Used in power plants, air conditioners, fridges,
liquefication of natural gas, etc
– Transfer energy between fluids at different
temperatures


v j2


vi 2
dE
 Q  W   min ,i  hi 
 gzi    mout , j  h j 
 gz j 


dt
2
2
i

 j


Direct Contact Heat
Exchanger
Counter-flow Heat
exchanger
Direct Flow Heat
Exchanger
Energy Balance in Open Systems
• Exercises (homework)
– 1º Write the energy balance eq.
– 2º Identify energy flows
– 3º Simplify the eq.
Liquefaction of natural gas
T=-162ºC
Decrease in volume: 1/600
• Discuss boundaries
Power cycle revisited
• Coal power plant:
Power Cycle
Refrigerator
The state variable: Entropy
• Entropy is the state variable that gives
unidirectionality to time in physical processes
ocurring in isolated & adiabatic systems.
– Hot coffee in a cold room gets colder and not hotter
– Radiating energy is received by the Earth from the
sun and by outer space from the earth and not the
other way around.
– If the valve of the tyre is opened, air gets out and
not in
Entropy Balance in Closed Systems
Entropy Change = Entropy transfer in the form of
heat + entropy production Not relevant for entropy balance
It is not a flow at the boundary
dS Q
 
dt T
Flows at the boundaries
work
Entropy change in the system
• Meaning of 
• 2st Law:
• >0
• In adiabatic systems…
• Entropy transfer by Heat & sign
• Steady state vs. Transient
heat
Entropy Balance in Closed Systems
• 2nd Law: In an adiabatic system the entropy
must not decrease
• Suppose the system is adiabatic and that T2>T1
dS
  0
dt
dS dS1 dS 2 Q Q


  0
dt
dt
dt T1 T2
T2
dS
  0
dt
dS dS1 dS2
Q Q


  00
dt
dt
dt
T1 T2
T1
• 2nd Law: the arrow of time
T2
T1