energy carriers and fuels

1. Session 3 – Energy Carriers and
Fuels
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Text, Chapter 2
Some additional units and concepts
Human energy
Photosynthesis
Primary energy and energy carriers
Conversion efficiency
Primary fuels compared
Reserves and depletion
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2. Additional Units and Concepts
• Accuracy: abbreviations, leading zero, signage
• Bbls, Mcf, tonnes, tons, 1000 Btus/SCF of gas
• 3413 Btu/kWh, 746 W/hp (useful for heating,
pumps
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3. Human Energy
1 food Calorie = 1000 calories
1 calorie = 4.2 Joules
Mean U.S. daily intake = 2146 Calories
= 0.025 Calories per second
= 25 calories/s
= 105 Joules/s = 105 Watts
McDonald’s Big Mac
= 350 BTUs/hour
(A 70,000 BTU furnace = 200 people)
540 Calories
Source: McDonald’s Website and American
Heart Association
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4. Potential Impact of Cutting Back
Total US Caloric intake in 2003:
1.2 X 1015 BTUs
Total US Energy Consumed to Produce:
1.8 X 1015 BTUs (plus transportation)
If 25% of US population cut back by 200 Calories
per day,
Energy Savings = 5.4 X 1013 BTUs annually
= 15.9 million MWh
Or . . . One 2137 MW Coal-fired Power
Plant! (Capacity factor = 85%)
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5. Photosynthesis
6 CO2 + 6 H2O → C6H12O6 + 6 O2
ΔH = +2800 kJ
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Each block of 2800 kJ yields 1 mol of Glucose (180g)
Net primary production average over earth’s surface estimated at
320 g/m2 (dry grams of green plant/yr)1
Or, 1.6 E17 g/yr over the earth
Energy required = (1.6 E17 g/yr) / (180 g/mol) X (2800 kJ/mol)
= 2.49 E18 kJ/yr =
2349 Quads/yr
Energy from sun = 3,301,887 Quads/yr2
Photosynthesis uses 7 E-4 of Sun’s incident energy, or 7/100 of 1%
Sienko, M.J. and R.A.Plane, 1974. Chemical Principles and Properties, Second Edition. New York: McGraw-Hill.
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At earth, we receive 5.4 E24 J/Yr, but 35% is reflected, leaving 3.5 E24 J/yr at the surface. 1 Quad = 1.06 E18 J
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6. Primary Energy and Energy
Carriers
• Carriers: Electricity and Hydrogen
• Primary Forms: Solar, gravitational,
radioactive
• Transport/transmission may require carrier
• Efficiency: Storage and Conversion
– Storage: power density, energy density
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7. Conversion/Delivery Efficiency
(based on Figure 2.1 in text)
Fuel=coal
100%
Power Plant
35% efficient
High Voltage
Transmission
96% efficient
Distribution
Feeders
98% efficient
Load (incan.
Light)
5% efficient
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8. Primary Fuels Compared
Five primary fuels, in order of global merit:
1.
2.
3.
4.
5.
Petroleum
Natural gas
Coal
Uranium
Renewables
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9. Petroleum
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World’s most important –
flexible, transportable
• Easy to produce with
minimal impact, large int’l
market
• Production has
intermediate carbon
intensity
• Reserves to production rate
= decades
Petroleum Producing Groups
OPEC (Organization of Petroleum Exporting Countries)
– 11 countries, 40% of world oil production, 2/3 of
proven reserves
• Algeria
• Indonesia
• Iran*
• Iraq*
• Kuwait*
• Libya
• Nigeria
• Qatar
• Saudi Arabia*
• UAE
• Venezuela*
• Original member; founded in 1960
Non-OPEC, Non-US, Non-former USSR
• Mexico
• China
• Canada
• Norway
• United Kingdom
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10. Natural Gas (methane)
• Abundant, but difficult to transport from remote sites
• Transport: gas in pipelines, liquid in ships, etc.
• Preferred fossil fuel: lowest carbon intensity, least
impact in production and consumption
• Barriers: costs of pipelines and LNG terminals (hard on
poorest)
• US relies heavily on Canada, who is 2nd to Russia as
exporter
• Reserves/production = 1 decade
• Combined cycle gas plants: preferred elect gen
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11. Coal
• Most carbon intensive
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94 E6 cal/kg-mole of CO2
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Methane: 211 E6 cal/kg-mole of CO2
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Propane: 175 E6 cal/kg-mole of CO 2
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Used primarily for electricity production
Substantial air pollution w/o controls
Reserves/production = 240 years
Major producers: US, Russia, China, India,
Australia
• Deposits remote from loads (transport issues)
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12. Uranium
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Primary mineral used in nuclear fission
Deposits in many countries; only a few produce
Historically low, stable prices
Most US needs are imported
Reserves = century
Easily transported – high energy density
Increased use = reserves shrink to decades
Breeder reactors
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13. Renewables
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Solar, geothermal, gravitational
Regeneration of fuel over short time scales
Free fuel, costly equipment
Enormous reserves
Biomass: solar to biofuel at 1-2% efficiency
Biomass use can cause desertification
Hydro is largest of sources, storage is natural
Wind is solar; both are variable, nondispatchable
• Geothermal: due to interior radioactive decay
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14. Fossil Fuel Reserves and Depletion
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Two views:
– Classic: fixed stock; presumes we will run out
– Non-classic: new technology will leave reserves in the ground
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Latter supported by: more, not less, reserves; stable prices
Hubbert curves = classic theory
Reserves vs. resources (hi/lo confidence)
Which is greater concern: scarcity or global warming?
Reduction of fossil fuels = higher costs
Public supports war subsidy above energy self reliance
Renewables must be cost competitive with fossils
Some want externalities figured in
Transportation tougher to de-carbonize than electricity
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