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1 Τμήμα Μηχανολόγων Μηχανικών Ειδικά κεφάλαια παραγωγής ενέργειας Ενότητα 5: HYDROGEN & FUEL CELLS Αν. Καθηγητής Γεώργιος Μαρνέλλος (Γραφείο 208) Τηλ.: , Τμήμα Μηχανολόγων Μηχανικών

2 Άδειες Χρήσης Το παρόν εκπαιδευτικό υλικό υπόκειται σε άδειες χρήσης Creative Commons. Για εκπαιδευτικό υλικό, όπως εικόνες, που υπόκειται σε άλλου τύπου άδειας χρήσης, η άδεια χρήσης αναφέρεται ρητώς. 2

3 Χρηματοδότηση Το παρόν εκπαιδευτικό υλικό έχει αναπτυχθεί στα πλαίσια του εκπαιδευτικού έργου του διδάσκοντα. Το έργο «Ανοικτά Ψηφιακά Μαθήματα στο Πανεπιστήμιο Δυτικής Μακεδονίας» έχει χρηματοδοτήσει μόνο τη αναδιαμόρφωση του εκπαιδευτικού υλικού. Το έργο υλοποιείται στο πλαίσιο του Επιχειρησιακού Προγράμματος «Εκπαίδευση και Δια Βίου Μάθηση» και συγχρηματοδοτείται από την Ευρωπαϊκή Ένωση (Ευρωπαϊκό Κοινωνικό Ταμείο) και από εθνικούς πόρους. 3

4 HYDROGEN & FUEL CELLS 4

5 A Vision of a Hydrogen Future "I believe that water will one day be employed as fuel, that hydrogen and oxygen which constitute it, used singly or together, will furnish an inexhaustible source of heat and light, of an intensity of which coal is not capable. I believe then that when the deposits of coal are exhausted, we shall heat and warm ourselves with water. Water will be the coal of the future." Jules Vernes (1870) L île mystérieuse 5

6 Hydrogen Economy Schematic 6

7 Hydrogen Η2 7

8 Energy Content of selected Fuels 8

9 The Ideal Hydrogen Energy Cycle 9

10 Hydrogen Economy Cycle 10

11 Operating the Hydrogen Economy 11

12 Advantages of a Hydrogen Economy 12

13 Disadvantages of Hydrogen Low energy densities. Difficulty in handling, storage, transport. Requires an entirely new infrastructure. Creates CO 2 if made from fossil fuels. Low net energy yields: Much energy needed to create hydrogen. 13

14 Issues with Hydrogen Not widely available on planet earth. Usually chemically combined in water or fossil fuels (must be separated). Fossil fuel sources contribute to pollution and greenhouse gases. Electrolysis requires prodigious amounts of energy. 14

15 Hydrogen Uses 15

16 Hydrogen Energy & Air Liquide 16

17 Hydrogen Pathways (1/2) 17

18 Current Hydrogen Production Current hydrogen production. 48% natural gas. 30% oil. 18% coal. 4% electrolysis. Global Production: 50 million tonnes / yr. Growing 10% / yr. 18

19 Hydrogen Production 19

20 Hydrogen Pathways (2/2) 20

21 How is Hydrogen Produced? Reforming fossil fuels: Heat hydrocarbons with steam. Produce H 2 and CO. Electrolysis of water: Use electricity to split water into O 2 and H 2. High Temperature Electrolysis: Experimental. Biological processes: Very common in nature. Experimental in laboratories. 21

22 Hydrogen Production from fossil fuels 22

23 Steam Reforming (1/2) 23

24 Hydrogen from natural gas reforming (1/4) 24

25 Hydrogen from natural gas reforming (2/4) 25

26 Steam Reforming (2/2) 26

27 Hydrogen from natural gas reforming (3/4) 27

28 Autothermal Reformer 28

29 Steam Reforming Plants 29

30 Hydrogen from natural gas reforming (4/4) 30

31 Steam Reforming Techno-Economic Data 31

32 Integrated gasification coal combustion (IGCC) 32

33 Biomass to H2 Routes 33

34 Hydrogen Production from Biomass (1/3) 34

35 Hydrogen Production from Biomass (2/3) 35

36 Hydrogen Production from Biomass (3/3) 36

37 Hydrogen from Biomass 37

38 Hydrogen Production by Electrolysis 38

39 Electrolysis of Water (H 2 O) 39

40 Electrolysis of Water 40

41 High Temperature Electrolysis 41

42 Electrolysis Techno-Economic Data 42

43 Renewable Hydrogen Pathways 43

44 Solar Hydrogen: the Hydrosol process 44

45 Hydrosol technology evolution 45

46 Biological Hydrogen Creation Nature has very simple methods to split water. Scientists are working to mimic these processes in the lab; then commercially. Crabtree et al., The Hydrogen Economy, Physics Today, Dec

47 Hydrogen Storage Storage a major difficulty with hydrogen. H 2 has low energy density per volume: Requires large tanks to store. H 2 can be compressed to reduce volume: Requires heavy, strong tanks. H 2 can be liquefied to reduce volume: Boils at -423 F (cryogenic). Requires heavily insulated, expensive tanks. Both compression and liquefaction require a lot of energy. 47

48 Liquifaction Energy vs. Intrinsic Energy Bossel et al., The Future of the Hydrogen Economy: Bright or Bleak?, Oct 28,

49 Energy Densities for Various Fuels 49

50 Hydrogen Storage Densities 50

51 H 2 and Energy Density for Various Fuels 51

52 Ammonia Storage H 2 can be stored as ammonia (NH 3 ). Exceptionally high hydrogen densities. Ammonia very common chemical. Large infrastructure already exists. Easily reformed to produce hydrogen. No harmful waste. BUT: Ammonia production is energy intensive. Ammonia is a toxic gas. 52

53 Metal Hydride Storage Metal hydrides can carry hydrogen: Boron, lithium, sodium. Good energy density, but worse than gas. Volumes much larger than gasoline: Three times more volume. Four times heavier. Hydrides can react violently with water. Leading contenders: Sodium Borohydride. Lithium Aluminum Hydride. Ammonia Borane. 53

54 Alkali Prod. Energy vs. Intrinsic Energy 54

55 Transporting Hydrogen 55

56 Hydrogen Fueling Station 56

57 Environmental Concerns 48% of hydrogen made from natural gas: Creates CO 2 a greenhouse gas. Hydrogen H 2 inevitably leaks from containers: Creates free radicals (H) in stratosphere due to ultraviolet radiation. Could act as catalysts for ozone depletion. 57

58 Elemental Hydrogen Economy 58

59 Synthetic Liquid Hydrocarbon Economy 59

60 UNIDO-ICHET Projection 60

61 The Iceland Example Iceland committed to be the first hydrogen economy goal. Will use geothermal resources to create hydrogen. Power autos, buses, and fishing fleet with hydrogen. 61

62 Fuel Cell... A brief history The 1 st fuel cell was constructed by Sir William Grove in Before 60's there was no any practical application. However, fuel cell technology was selected instead of nuclear or solar energy to implemented in the Apollo Space Mission. 62

63 Fuel Cells vs Thermal Engines Fuel cells are electrochemical devices that directly convert the chemical energy of a fuel to electricity at higher efficiencies compared to conventional thermal engines. 63

64 Comparative Efficiency... 64

65 Electrolysis How is related with Fuel Cells? 65

66 Fuel Cell Operating principle Reverse Electrolysis 66

67 Fuel Cell Operation and Performance (1/3) 67

68 Fuel Cell Operation and Performance (2/3) 68

69 SOFC operation 69

70 H 2 + ½ O 2 H 2 O. Fuel Cell Performance 1.17 Volts (@ no current). Voltage losses. Fuel cross-over. Reaction kinetics. Electrolyte resistance. Slow mass diffusion. Power = I*V. Peak efficiency at low I. Peak power at mid I. 70

71 Fuel Cell Operation and Performance (3/3) 71

72 Fuel Cells Thermodynamics (1/3) 72

73 Fuel Cells Thermodynamics (2/3) Enthalpy Change of the Chemical Reaction: ΔH=ΔH reaction =ΣH products ΣH reactants = (1mol)( kj/ mol ) (0)= kj Entropy Change of the Chemical Reaction: ΔS = ΔS reaction = ΣS products ΣS reactants = [(1mol)(69.91 J/mol K)] [(1mol)( J/mol K)+ (½mol)( J/mol K)]= J/ K Heat of the System: ΔQ= TΔS= (298K)( J/ K )= kj 73

74 Fuel Cells Thermodynamics (3/3) 74

75 Fuel & reactions in fuel cells 75

76 Fuel Cell: Principle of Operation 76

77 Principle of Operation... 77

78 Animation of PEMFC 78

79 What are the main components of a Fuel Cell... 79

80 Components: Fuel Cell Components Electrolyte (Membrane): Transport ions. Block electrons, gases. Electrodes: Catalyze reactions. Transport: Ions, electrons, gases. May be a composite: (electro)catalyst +. Conductors +. Pore former. 80

81 Fuel Cell Types (1/2) 81

82 Fuel Cell Types (2/2) 82

83 Fuel Cell Choices Temperature sets operational parameters & fuel choice. Ambient Temperature: Rapid start-up. H 2 or CH 3 OH as fuels. Catalysts easily poisoned. Applications: Portable power. Many on/off cycles. Small size. High Temperature: Fuel flexible. Very high efficiencies. Long start-up. Applications: Stationary power. Auxiliary power in portable systems. 83

84 Types of Fuel cells & Process Complexity 84

85 Conventional Method Additional cost for fuel treatment. Complexity. Thermal Integration. 85

86 Direct use of fuels Simple and auto-thermal process Lower cost 86

87 Direct Utilization of Hydrocarbons 87

88 Overview of Anodic Processes The fuel can react in the gas-phase (flow channels & anode pores). Pyrolysis fragments and the fuel can catalytically decomposed. Thermal and catalytic decomposition fragments can be oxidized by O 2- The CO 2 and H 2 O products allow dry/steam reforming of fuel species. Water-gas shift reaction. Carbon formation due to pyrolysis and Boudouard reactions. 88

89 Alkaline Fuel Cells 89

90 Molten Carbonate Fuel Cells (MCFC) 90

91 Phosphoric Acid Fuel Cell (PAFC) 91

92 Proton Exchange Membrane Fuel Cell (PEMFC) (1/2) 92

93 Proton Exchange Membrane Fuel Cell (PEMFC) (2/2) 93

94 Solid Oxide Fuel Cell (SOFC) (1/2) 94

95 Solid Oxide Fuel Cell (SOFC) (2/2) 95

96 Applications 96

97 Estimated Costs (1/3) 97

98 Estimated Costs (2/3) 98

99 Estimated Costs (3/3) 99

100 Τέλος Ενότητας 100

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