Session 3 energy carriers and fuels

T. Ferguson, University of Minnesota, Duluth, 2008

Session 3 – Energy Carriers and Fuels

• Text, Chapter 2• Some additional units and concepts• Human energy• Photosynthesis• Primary energy and energy carriers• Conversion efficiency• Primary fuels compared• Reserves and depletion


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


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

= 350 BTUs/hour(A 70,000 BTU furnace = 200 people)

McDonald’s Big Mac

540 CaloriesSource: McDonald’s Website and American Heart Association


Potential Impact of Cutting BackTotal 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%)


Photosynthesis

6 CO2 + 6 H2O → C6H12O6 + 6 O2

ΔH = +2800 kJ• 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%

1Sienko, M.J. and R.A.Plane, 1974. Chemical Principles and Properties, Second Edition. New York: McGraw-Hill.2At 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


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


Conversion/Delivery Efficiency(based on Figure 2.1 in text)

Fuel=coal

100%

Power Plant

35% efficient

High VoltageTransmission96% efficient

DistributionFeeders98% efficient

Load (incan.Light)5% efficient


Primary Fuels Compared

Five primary fuels, in order of global merit:

1. Petroleum

2. Natural gas

3. Coal

4. Uranium

5. Renewables


Petroleum

• 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 GroupsOPEC (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


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


Coal

• Most carbon intensive – 94 E6 cal/kg-mole of CO2

– Methane: 211 E6 cal/kg-mole of CO2

– Propane: 175 E6 cal/kg-mole of CO2

• 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)


Uranium

• 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


Renewables

• 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, non-

dispatchable• Geothermal: due to interior radioactive decay


Fossil Fuel Reserves and Depletion

• Two views:– Classic: fixed stock; presumes we will run out– Non-classic: new technology will leave reserves in the ground

• 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

Session 3 energy carriers and fuels

Technology

Transcript of Session 3 energy carriers and fuels