Primary, Final & Useful Energies Sankey Diagrams Class # 3

Apresentação em tema: "Primary, Final & Useful Energies Sankey Diagrams Class # 3"— Transcrição da apresentação:

1 Primary, Final & Useful Energies Sankey Diagrams Class # 3
Energy Management: 2013/2014 Primary, Final & Useful Energies Sankey Diagrams Class # 3 Prof. Tânia Sousa

2 Energy Units and Scales
How much energy should we ingest daily? How much energy do you spend per hour using an electric heater?

3 Energy Units and Scales
IAASA – Global Energy Assessment 2012

4 Energy Units and Scales
Activities (kJ) IAASA – Global Energy Assessment 2012

5 Energy Units and Scales
IAASA – Global Energy Assessment 2012

6 Energy Units and Scales
Activities (MJ-GJ or kWh=3.6MJ) IAASA – Global Energy Assessment 2012

7 Energy Units and Scales
IAASA – Global Energy Assessment 2012

8 Energy Units and Scales
Activities (GJ-TJ or toe=41.87GJ) IAASA – Global Energy Assessment 2012

9 Energy Units and Scales
Activities (GJ-TJ or toe=41.87GJ) In early agricultural societies 10-20 GJ/capita/year 2/3 for food and feed 1/3 for cooking, heating and early industrial activities In UK in the mid-19th century 100 GJ/capita/year In Portugal in 2010 108 GJ/capita/year

10 Energy Units and Scales
IAASA – Global Energy Assessment 2012

11 Energy Units and Scales
IAASA – Global Energy Assessment 2012

12 Energy Units and Scales
IAASA – Global Energy Assessment 2012

13 Energy Units and Scales
IAASA – Global Energy Assessment 2012

14 Energy Units and Scales
IAASA – Global Energy Assessment 2012

15 Forms of Energy - Primary energy

16 Forms of Energy - Final energy

17 Forms of Energy – Useful Energy

18 Forms of Energy Primary energy – embodied in resources as it is found in nature (coal, oil, natural gas in the ground) Final energy – sold to final consumers such as households or firms (electricity, diesel, processed natural gas) Useful energy – in the form that is used: light, heat, cooling and mechanical power (stationary or transport) Productive energy – the fraction of useful energy that we actually use

19 From Primary Energy to Energy Services

20 From Primary Energy to Energy Services
Energy Supply energy flows driven by resource availability and conversion technologies IAASA - Global Energy Assessment 2012

21 From Primary Energy to Energy Services
The energy supply sector dealing with primary energy is referred as “upstream” activities IAASA - Global Energy Assessment 2012

22 From Primary Energy to Energy Services
The energy supply sector dealing with secondary energy is referred as “downstream” activities IAASA - Global Energy Assessment 2012

23 From Primary Energy to Energy Services
Energy Demand Energy system is service driven IAASA - Global Energy Assessment 2012

24 From Primary Energy to Energy Services
Quality and cost of energy services IAASA - Global Energy Assessment 2012

25 Energetic Balance Where are the primary and final energies in the energetic balance? BALANÇO ENERGÉTICO tep Total de Carvão Total de Petróleo Gás Natural (*) Gases o Outros Derivados Total de Eectricidade Calor Resíduos Industriais Renováveis Sem Hídrica TOTAL GERAL 2008 4 = 1 a 3 22= 23 30 = 24 a 29 36 = 31 a 35 37 38 46 = 39 a 45 47= IMPORTAÇÕES 1. PRODUÇÃO DOMÉSTICA 2. 39 800 VARIAÇÃO DE "STOCKS" 3. 5 960 - 837 97 193 SAÍDAS 4. 24 949 17 634 CONSUMO DE ENERGIA PRIMÁRIA 5. PARA NOVAS FORMAS DE ENERGIA 6. 1 120 CONSUMO DO SECTOR ENERGÉTICO 7. 56 103 3 CONSUMO COMO MATÉRIA PRIMA DISPONÍVEL PARA CONSUMO FINAL 8. 81 170 38 680 ACERTOS 9. 9 851 12 279 CONSUMO FINAL 10. 71 319 AGRICULTURA E PESCAS 10.1 3 359 87 218 2 366 21 INDÚSTRIAS EXTRACTIVAS 10.2 66 103 8 444 49 882 30 844 4 INDÚSTRIAS TRANSFORMADORAS 10.3 CONSTRUÇÃO E OBRAS PÚBLICAS 10.4 5 063 50 490 TRANSPORTES 10.5 6 659 46 677 3 452 SECTOR DOMÉSTICO 10.6 SERVIÇOS 10.7 14 211 6 579

26 Energetic Balance Where are the primary and final energies in the energetic balance? BALANÇO ENERGÉTICO tep Total de Carvão Total de Petróleo Gás Natural (*) Gases o Outros Derivados Total de Eectricidade Calor Resíduos Industriais Renováveis Sem Hídrica TOTAL GERAL 2008 4 = 1 a 3 22= 23 30 = 24 a 29 36 = 31 a 35 37 38 46 = 39 a 45 47= IMPORTAÇÕES 1. PRODUÇÃO DOMÉSTICA 2. 39 800 VARIAÇÃO DE "STOCKS" 3. 5 960 - 837 97 193 SAÍDAS 4. 24 949 17 634 CONSUMO DE ENERGIA PRIMÁRIA 5. PARA NOVAS FORMAS DE ENERGIA 6. 1 120 CONSUMO DO SECTOR ENERGÉTICO 7. 56 103 3 CONSUMO COMO MATÉRIA PRIMA DISPONÍVEL PARA CONSUMO FINAL 8. 81 170 38 680 ACERTOS 9. 9 851 12 279 CONSUMO FINAL 10. 71 319 AGRICULTURA E PESCAS 10.1 3 359 87 218 2 366 21 INDÚSTRIAS EXTRACTIVAS 10.2 66 103 8 444 49 882 30 844 4 INDÚSTRIAS TRANSFORMADORAS 10.3 CONSTRUÇÃO E OBRAS PÚBLICAS 10.4 5 063 50 490 TRANSPORTES 10.5 6 659 46 677 3 452 SECTOR DOMÉSTICO 10.6 SERVIÇOS 10.7 14 211 6 579

27 Energetic Balance Where is the useful energy in the energetic balance?
BALANÇO ENERGÉTICO tep Total de Carvão Total de Petróleo Gás Natural (*) Gases o Outros Derivados Total de Eectricidade Calor Resíduos Industriais Renováveis Sem Hídrica TOTAL GERAL 2008 4 = 1 a 3 22= 23 30 = 24 a 29 36 = 31 a 35 37 38 46 = 39 a 45 47= IMPORTAÇÕES 1. PRODUÇÃO DOMÉSTICA 2. 39 800 VARIAÇÃO DE "STOCKS" 3. 5 960 - 837 97 193 SAÍDAS 4. 24 949 17 634 CONSUMO DE ENERGIA PRIMÁRIA 5. PARA NOVAS FORMAS DE ENERGIA 6. 1 120 CONSUMO DO SECTOR ENERGÉTICO 7. 56 103 3 CONSUMO COMO MATÉRIA PRIMA DISPONÍVEL PARA CONSUMO FINAL 8. 81 170 38 680 ACERTOS 9. 9 851 12 279 CONSUMO FINAL 10. 71 319 AGRICULTURA E PESCAS 10.1 3 359 87 218 2 366 21 INDÚSTRIAS EXTRACTIVAS 10.2 66 103 8 444 49 882 30 844 4 INDÚSTRIAS TRANSFORMADORAS 10.3 CONSTRUÇÃO E OBRAS PÚBLICAS 10.4 5 063 50 490 TRANSPORTES 10.5 6 659 46 677 3 452 SECTOR DOMÉSTICO 10.6 SERVIÇOS 10.7 14 211 6 579

28 Energetic Balance How do you go from final to useful energy for household electricity consumption? BALANÇO ENERGÉTICO tep Total de Carvão Total de Petróleo Gás Natural (*) Gases o Outros Derivados Total de Eectricidade Calor Resíduos Industriais Renováveis Sem Hídrica TOTAL GERAL 2008 4 = 1 a 3 22= 23 30 = 24 a 29 36 = 31 a 35 37 38 46 = 39 a 45 47= IMPORTAÇÕES 1. PRODUÇÃO DOMÉSTICA 2. 39 800 VARIAÇÃO DE "STOCKS" 3. 5 960 - 837 97 193 SAÍDAS 4. 24 949 17 634 CONSUMO DE ENERGIA PRIMÁRIA 5. PARA NOVAS FORMAS DE ENERGIA 6. 1 120 CONSUMO DO SECTOR ENERGÉTICO 7. 56 103 3 CONSUMO COMO MATÉRIA PRIMA DISPONÍVEL PARA CONSUMO FINAL 8. 81 170 38 680 ACERTOS 9. 9 851 12 279 CONSUMO FINAL 10. 71 319 AGRICULTURA E PESCAS 10.1 3 359 87 218 2 366 21 INDÚSTRIAS EXTRACTIVAS 10.2 66 103 8 444 49 882 30 844 4 INDÚSTRIAS TRANSFORMADORAS 10.3 CONSTRUÇÃO E OBRAS PÚBLICAS 10.4 5 063 50 490 TRANSPORTES 10.5 6 659 46 677 3 452 SECTOR DOMÉSTICO 10.6 SERVIÇOS 10.7 14 211 6 579

29 Useful Energy How do you go from final to useful energy for household electricity consumption? Electrical resistance 100% Electrical motor 90% Fluorescent lamp 50% Refrigerator 200% Heat pump 250%

30 Sankey diagrams Schematic representation of the energy flow
Miguel Águas (2009)

31 Sankey Diagram for Portugal for 2010
BALANÇO ENERGÉTICO tep Total de Carvão Total de Petróleo Gás Natural Total de Eletricidade Renováveis Sem Eletricidade TOTAL GERAL 2010 4 = 1 a 3 22= 23 36 = 31 a 35 46 = 39 a 45 47= CONSUMO DE ENERGIA PRIMÁRIA 5. PARA NOVAS FORMAS DE ENERGIA 6. Produtos de Petróleo 6.3 Eletricidade 6.6 Cogeração 6.7 CONSUMO DO SECTOR ENERGÉTICO 7. 10 Consumo Próprio da Refinação 7.1 45 829 Perdas da Refinação 7.2 58 915 58 925 Centrais Eléctricas 7.4 3 035 Bombagem Hidroeléctrica 7.5 44 032 Perdas de Transporte e Distribuição 7.8 13 716 DISPONÍVEL PARA CONSUMO FINAL 8. 59 330 ACERTOS 9. 9 130 4 999 4 761 - 132 14 762 CONSUMO FINAL 10. 50 200 AGRICULTURA E PESCAS 10.1 3 511 88 164 65 INDÚSTRIAS EXTRATIVAS 10.2 62 582 7 951 47 271 91 INDÚSTRIAS TRANSFORMADORAS 10.3 CONSTRUÇÃO E OBRAS PÚBLICAS 10.4 9 218 52 436 TRANSPORTES 10.5 12 581 40 857 4 233 SECTOR DOMÉSTICO 10.6 SERVIÇOS 10.7 29 776

32 Sankey diagram for Portugal 2010

33 World Sankey Diagram in 2005
IAASA – Global Energy Assessment 2012

34 World Sankey Diagram in 2005
IAASA – Global Energy Assessment 2012

35 World Sankey Diagram in 2005
IAASA – Global Energy Assessment 2012

36 World Sankey Diagram in 2005
IAASA – Global Energy Assessment 2012

37 World Sankey Diagram in 2005
IAASA – Global Energy Assessment 2012

38 World Sankey Diagram in 2005
IAASA – Global Energy Assessment 2012

39 World Sankey Diagram in 2005
IAASA – Global Energy Assessment 2012

40 Regional Energy Use in 2005

41 World Sankey Diagram in 2005
Overall 1st law efficiency in converting primary to final energy? ? ? US – 94 EJ Portugal – 1.1 EJ IAASA – Global Energy Assessment 2012

42 World Sankey Diagram in 2005
Overall 1st law efficiency in converting primary to final energy? 66% ? ? US – 94 EJ Portugal – 1.1 EJ IAASA – Global Energy Assessment 2012

43 World Sankey Diagram in 2005
Overall 1st law efficiency in converting primary to useful energy? ? ? US – 94 EJ Portugal – 1.1 EJ IAASA – Global Energy Assessment 2012

44 World Sankey Diagram in 2005
Overall 1st law efficiency in converting primary to useful energy? 34% ? ? US – 94 EJ Portugal – 1.1 EJ IAASA – Global Energy Assessment 2012

45 Typical values of 1st law efficiencies
1st Law efficiencies from primary to final energy 1st Law efficiencies from final to useful energy

46 Sankey Diagram for an Energy Service
Example?

47 Sankey Diagram for an Energy Service
Example?

48 Sankey Diagram for an Energy Service
Schematic representation of the energy flow (natural gas electricity light reading) What is the aggregate efficiency? 20% 50%

49 Sankey Diagram for an Energy Service
Schematic representation of the energy flow (natural gas electricity light reading) What is the aggregate efficiency? 20% 50%

50 Are there 1st law efficiencies > 1?
What is the 1st Law efficiency in a heat pump?

51 Are there 1st law efficiencies > 1?
What is the 1st Law efficiency in a heat pump? Typical values of  between 3 – 5 What is the Sankey diagram like?

52 Are there 1st law efficiencies > 1?
What is the 1st Law efficiency in a heat pump? Typical values of  between 3 – 5 What is the Sankey diagram like?

53 Sankey Diagram A coal thermal power plant has an efficiency of 40%. The combustion of coal releases 7000kcal/kg. The energy consumption associated with extraction, transport and grinding represent 500 kcal/kg. Draw the Sankey Diagram

54 Sankey Diagram A coal thermal power plant has an efficiency of 40%. The combustion of coal releases 7000kcal/kg. The energy consumption associated with extraction, transport and grinding represent 500 kcal/kg. Draw the Sankey Diagram What is the overall efficiency? 40% 93% Coal Mine Coal at the Power Plant Electricity Coal at the coal mine 1 Mcal = MJ 1 toe = MJ 7% Coal at the Power Plant 60% Electricity at the Power Plant

55 Sankey Diagram A coal thermal power plant has an efficiency of 40%. The combustion of coal releases 7000kcal/kg. The energy consumption associated with extraction, transport and grinding represent 500 kcal/kg. Draw the Sankey Diagram What is the overall efficiency? What is the coefficient of conversion between final and primary energy in MWhe/TOE? 40% 93% Coal Mine Coal at the Power Plant Electricity Coal at the coal mine 1 Mcal = MJ 1 toe = MJ 7% Coal at the Power Plant 60% Electricity at the Power Plant Eficiency = 2800/7500 = 37%

56 Sankey Diagram A coal thermal power plant has an efficiency of 40%. The combustion of coal releases 7000kcal/kg. The energy consumption associated with extraction, transport and grinding represent 500 kcal/kg. Draw the Sankey Diagram What is the overall efficiency? What is the coefficient of conversion between final and primary energy in MWhe/TOE? 40% 93% Coal Mine Coal at the Power Plant Electricity 1 Mcal = MJ 1 toe = MJ

57 Conversion between F.E and P.E
Conversion coefficients are efficiencies and not direct conversions From coal (P.E) to electricity (F.E) Direct conversion What about the conversion coefficient from natural gas to electricity?

58 Are first law efficiencies enough?
Heating of a house can be done by one of the following methods: Electrical heating using the Joule effect Central heating Heating using a heat pump

59 Are first law efficiencies enough?
Heating of a house can be done by one of the following methods: Electrical heating using the Joule effect Central heating (burning natural gas in a furnace with a 90% efficiency) Heating using a heat pump (COP=3). Suppose that electricity has a production efficiency of 45% and costs 0.12 euros per kWh, natural gas is transported with a 99% efficiency, and costs euros per kWh. Compare the alternatives in terms of primary energy, final energy and cost for 1 kWh of thermal energy. Draw the Sankey Diagrams Discuss the investment associated with each solution.

60 Are first law efficiencies enough?
Heating of a house can be done by one of the following methods: Electrical heating using the Joule effect Central heating (burning natural gas in a furnace with a 90% efficiency) Heating using a heat pump (COP=3). Suppose that electricity has a production efficiency of 45% and costs 0.12 euros per kWh, natural gas is transported with a 99% efficiency, and costs euros per kWh. Compare the alternatives in terms of primary energy, final energy and cost for 1 kWh of thermal energy. Draw the Sankey Diagrams Discuss the investment associated with each solution. Electrical Resistance Central Heating Heat Pump Primary (kWh) 1/0.45=2.22 (1/0.90)/0.99=1.12 (1/3)/0.45=0.74 Final (kWh) 1 1/0.90=1.11 1/3=0.33 Useful (kWh) Cost (euros) 1*0.12 ((1/0.9))*0.0708 1/3*0.12

61 Are first law efficiencies enough?
Providing 1 kWh of heat at 30ºC to a building with an outside temperature of 4ºC First law efficiencies do not provide information on how much you can improve your efficiency Electrical Resistance Central Heating Heat Pump Ideal Heat Pump Final (kWh) 1 1/0.90 1/3 1/12 Useful (kWh) First Law  100% 90% 300% 1200%

62 Second law efficiencies
Ratio between 1st law real and best efficiencies Providing 1 kWh of heat at 30ºC to a building with an outside temperature of 4ºC Second law efficiencies provide information on how much you can improve your efficiency Electrical Resistance Central Heating Heat Pump Ideal Heat Pump Final (kWh) 1 1/0.90 1/3 1/12 Useful (kWh) First Law  100% 90% 300% 1200% Second Law  8.3% 7.5% 25%

63 Typical values of 2nd law efficiencies
IAASA - Global Energy Assessment 2012 Overall 2nd law efficiency in converting primary to final is 76% and primary to useful energy is 10%

64 Primary Energy Use 1800-2000 Grubler, A. “Energy Transitions”
Population (lines) Primary energy use (bars) industrialized countries (white squares and bars) developing countries (gray triangles and bars) Energy use data includes estimates of noncommercial energy use Grubler, A. “Energy Transitions”

65 Primary Energy Use Population (lines) Primary energy use (bars) industrialized countries (white squares and bars) developing countries (gray triangles and bars) Energy use data includes estimates of noncommercial energy use Primary energy use increased more than 20-fold in 200 years Heterogeneity in per capita primary energy use: In industrialized countries population increased linearly while primary energy use increased exponentially until recently In developing countries energy use increased proportionally to population until recently Primary Energy Mix ? Grubler, A. “Energy Transitions”

66 Primary Energy Mix 1850-2010 Grubler, A. “Energy Transitions”
IAASA – Global Energy Assessment 2012

67 Primary Energy Mix 1850-2010 Mostly biomass in 1850
Increasing diversification of energy vectors Grubler, A. “Energy Transitions” IAASA – Global Energy Assessment 2012

68 Primary Energy Mix Grubler, A. “Energy Transitions”

69 Primary Energy Mix Energy Transition: The switch from an economic system dependent on one or a series of energy sources and technologies to another (Fouquet & Pearson, 2012)

70 Primary Energy Mix Energy Transition: The switch from an economic system dependent on one or a series of energy sources and technologies to another (Fouquet & Pearson, 2012) Energy Transition biomass to coal

71 Primary Energy Mix Energy Transition: The switch from an economic system dependent on one or a series of energy sources and technologies to another (Fouquet & Pearson, 2012) Energy Transition biomass to coal Energy Transition coal to oil

72 Primary Energy Mix Energy Transition: The switch from an economic system dependent on one or a series of energy sources and technologies to another (Fouquet & Pearson, 2012) Energy Transition biomass to coal Energy Transition coal to oil Stabilization

73 Energy Eras and Transitions
Energy Transformations before industrial civilization:

74 Energy Eras and Transitions
Energy Transformations before industrial civilization: Solar radiation – food & feed, light and heat Animate labor from humans and work animals (levers, inclined planes, pulleys) – mechanical work & transport Kinetic energies of water & wind – mechanical work & transport Biomass fuels (wood, charcoal, crop residues, dung) –residential & industrial heat and light

75 Energy Eras and Transitions
Energy Transformations before industrial civilization: Dominant in the western world until the 2nd half of the 19th century Dominant for most of humankind until middlle of the 20th century Annual per capita primary energy consumption  20 GJ

76 Energy Eras and Transitions
Energy Transformations that came with industrial civilization: Fossil fuels – heat & mechanical work & transport (steam engines, internal combustion engines and steam turbines)

77 Energy Transitions An aggregated transition to other energy source(s) includes numerous services and sectors

78 Energy Transitions 16th century (tall narrow chimneys and suitable grates ) 17th century (coal gets even cheaper) The switch from an economic system dependent on one or a series of energy sources and technologies to another (Fouquet & Pearson, 2012)

79 Energy Transitions 1709 (coke) 18th century (efficiency improvments) The switch from an economic system dependent on one or a series of energy sources and technologies to another (Fouquet & Pearson, 2012)

80 Energy Transitions 1804 (1st steam locomotive) The switch from an economic system dependent on one or a series of energy sources and technologies to another (Fouquet & Pearson, 2012)

81 Why do energy transitions occur?
Main Drivers/Catalyst for adoption of a new energy carrier: Price of energy Better/Different Service Technological change and innovation Efficiency improvments

82 Decarbonization of Energy Systems
Decreasing trend in CO2 emitted per GJ from 1850 to 2000 2010: GJ/capita/year 7600 kg CO2/capita/year

83 Decarbonization of Energy Systems
Historically energy related biomass burning has not been carbon-neutral (maximum estimated value of 38%)

84 Decarbonization of Energy Systems
Why a slight increasing trend in the last 10 years?

85 Power generation 1990-2010 Non-hydro renewables Hydro
Share of coal-based electricity Despite an increasing contribution across two decades, the share of non-fossil generation has failed to keep pace with the growth in generation from fossil fuels. Share of non-fossil electricity Non-hydro renewables Electricity generation (TWh) Hydro Share of electricity (%) Nuclear Coal has also satisfied the major growth in power generation over the past decade. The figure speaks for itself. Note the declining share of non-fossil fuels to generate electricity. IEA - Energy Technology Perspectives 2012 © OECD/IEA 2012

86 Final Energy from World final energy use by consumers. Solids (such as coal and biomass, brown), Liquids (such as oil, red) and fuels delivered via dedicated Grids (such as natural gas and electricity, green). Grubler, A. “Energy Transitions”

87 Final Energy from World final energy use by consumers. Solids (such as coal and biomass, brown), Liquids (such as oil, red) and fuels delivered via dedicated Grids (such as natural gas and electricity, green). “With rising incomes, consumers pay increasing attention to convenience and cleanliness, favoring liquids and grid-delivered energy forms” Grubler, A. “Energy Transitions”

88 Final Energy from World final energy use by consumers. Solids (such as coal and biomass, brown), Liquids (such as oil, red) and fuels delivered via dedicated Grids (such as natural gas and electricity, green). Developing countries OECD (squares) Grubler, A. “Energy Transitions”

89 Final Energy from World final energy use by consumers. Solids (such as coal and biomass, brown), Liquids (such as oil, red) and fuels delivered via dedicated Grids (such as natural gas and electricity, green). Heterogeneity in final energy quality Grubler, A. “Energy Transitions”

90 Final Energy per capita in 2010
Heterogeneity in Final Energy Use per capita: IAASA – Global Energy Assessment 2012

91 What is Final Energy used for?
UK IAASA – Global Energy Assessment 2012

92 What is Final Energy used for?
Regular expansion of energy services in 19th dominated by heat and transport High volatility due to political and economic events Moderated growth after 1950 Decline in industrial energy services compensated by strong growth in transport Saturated at a level of 6 EJ or 100 GJ/capita What about energy services? IAASA – Global Energy Assessment 2012

93 From Final Energy to Energy Services
UK IAASA – Global Energy Assessment 2012

94 From Final Energy to Energy Services
UK Increasing efficiencies in converting final energy to energy services Ranges between a factor of 5 for transportation and 600 for lighting IAASA – Global Energy Assessment 2012

95 From Final Energy to Energy Services
UK Lower prices of energy services Ranges between a factor of 10 for heating and 70 for lighting IAASA – Global Energy Assessment 2012

96 Energy Services 2005 Energy services cannot be expressed in common units Transport 13 km/day/per capita 1 ton 20 km/day/per capita Industry 9 ton/year/per capita (steel + fertilizers + construction materials + plastics … Buldings Heating/cooling to 20m2/per capita Useful energy minimizes distortions among different energy service categories, as it most closely measures the actual energy service provided.

97 World Sankey Diagram in 2005

98 Second law efficiencies
Second law efficiencies provide information on the destruction of exergy What is exergy? Δz = 0m Δz = 120m Power = 0 W Power = 150 kW

99 Energy vs. Exergy environment 20ºC 160ºC 25ºC Energy = 105 MJ
Potential Work = 34 MJ Potential Work = 1.8 MJ Exergy = 34 MJ Exergy = 1.8 MJ environment 20ºC