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Energy in Context
Overview
• Magnitude of Energy Use- Implications to human living- Implications to global climate change
• Technological Cycles– Impact of human practices on energy use
Magnitude of Energy Use
Energy Required to raise 100 kg a distance of 1 m.
~1000 Joules
Energy required for 60 Watt light bulb operating 1 hours
~216,000 Joules
Energy required to heat 5 kg pan of water to boiling temperature
~1,670,000 Joules
Energy required to process 1 kg wood products
~2,000,000 Joules
Energy required to process 1 kg of plastic products
~100,000,000
Energy required to mine/smelt 1 kg aluminum
~220,000,000 Joules
Energy required to drive an SUV 25 miles
~200,000,000 Joules
Implications for how we live?
Connection to ‘Global ClimateChange’
(gCO2 per 3,600,000 Joules)
Energy Source Coal Oil Gas Hydro Nuclear Solar PV
Current technology 972 684 684 18 21.6 126
Next generation technology
288 504 504 18 10.8 28.8
Energy Efficiency of Industrialized Economy
• Est. 1-3%
• Why so low?
Product Life Cycle
Consider life cycle energy impact of a 1 kg of aluminum being used in an aluminum wheel of a Ford Excursion over a 150,000mile life.
Case A – No Recycling
Oildiesel
aluminum ore
Smelting process
coal nat. gas
Casting process
nat. gas
product
materials stage manuf. stage use stage
landfill
Life Cycle
StageTotal Energy
Input from Fuel (typical)
Energy efficiency (typical), %,
Minumum energy
required if 100% efficient
Mining 10 MJ/kg 30 3.33 MJ/kg
Materials Processing
220 MJ/kg 60 132 MJ/kg
Manufacturing - Casting
20 MJ/kg 60 12 MJ/kg
Use[1] 375 MJ/kg-al 15 56.75 MJ/kg
Total 625 MJ/kg 32.6 204
[1] Ford Excursion = 3000 kg, 15 mpg, 150,000 miles/life…Useful energy from I.C. engine overcomes rolling resistance, inertia, drag. 75% of this is dependent upon weight. Therefore the mass consumed in the burning of gasoline over life due to the 1 kg mass on the vehicle is:(150,000 miles/life)/(15 miles/gallon) x (3 kg-fuel/gallon) / 3000 kg-al x 0.75 = 7.5 kg – fuel/kg-alEnergy consumed = 7.5 kg-fuel/kg-al x ( 50 MJ/kg-fuel) = 375 MJ/kg-al
Nylon 120.2 32.1$2.50/kg
MaterialVirgin MJ/kg
Recycled MJ/kg
Cost[1]
Aluminum 220 20$1.50/kg
Polyethylene
98 56$0.80/kg
PVC 65 29$1.20/kg
Steel 40 18$0.45/kg
Glass 30 13$0.20/kg
Copper 200 10$5.00/kg
[1] Source: American Metals, amm.com
Case B – Recycling r% of the aluminum
Oildiesel
aluminum ore
Smelting process
coal nat. gas
Casting process
nat. gas, Eng
product
materials stage manuf. stage use stage
landfill
separate
r
Eprocessing
1-r
Same energy use as in Case A except that the mining energy and material processing energy are reduced by:
r(Emining + Ematerials)
where r is the fraction of recycled aluminum going into the making of a new wheel
Life Cycle Stage
Total Energy Input from Fuel
(typical) MJ/kg-al
Energy efficiency (typical), %,
Minumum energy
required if 100% efficient
MJ/kg-al
Mining (1-r) 10 30 (1-r) 3.33
Materials Processing
(1-r) 220 60 (1-r) 132
Manufacturing
20 60 12
Use[1] 375 15 56.75
Total 395+(1-r)230 …. 68.75 +(1-r)135.33
[1] Ford Excursion = 3000 kg, 15 mpg, 150,000 miles/life…Useful exergy from I.C. engine overcomes rolling resistance, inertia, drag. 75% of this is dependent upon weight. Therefore the mass consumed in the burning of gasoline over life due to the 1 kg mass on the vehicle is:(150,000 miles/life)/(15 miles/gallon) x (3 kg/gallon) x 0.75 / 3000 = 7.5 kg – fuelExergy consumed = 7.5 kg-fuel x ( 50 MJ/kg-fuel) = 375 MJ/kg-al
Comparison
0
200
400
600
800
0 0.5 1
recycle fraction
NR
G/k
g-a
l
0
10
20
30
40
0 0.5 1
recycle fraction
ove
rall
effi
cien
cy (
%)
Cost Comparision
If 100% recycle and given a cost of
$0.10 / (3.6 MJ), a 230 MJ reduction in energy yields a
$6.30 savings per kg
Note: This is 4 times more expensive than it would seem because aluminum companies have been given cheap access to hydroelectric energy!!!!!
Energy Generation Efficiency
Process Efficiency
CoalElectricity transmission
20%
Natural gas electricity transmission
25%
Fuel Cell 40% (70-80%) if heat used
Solar PV 20% typical
Wind 30%
