Strategic: U.S. has world’s largest known reserves, 30% of world
total
Limits: For transportation, must be “gasified” which requires
more energy than using petroleum directly
Biomass
Uses biological sources of carbon
Biodiesel - old cooking oil
Ethanol
From crops
From “cellulosic” source - grasses, trees, and other
materials that are being harvested anyway
Costs
Economic: currently competitive with petroleum
Health: alcohol burns cleaner than petroleum, so less air pollution
Environmental: can be carbon-neutral (cellulosic), carbon-negative (biodiesel),
or carbon-positive (ethanol)
Strategic: all U.S. made. Brazil has already switched to largely an
ethanol economy
Nuclear Power
Fission
Large molecules split, releasing energy and particles
Radioactive waste
Currently in operation in commercial reactors
Fusion
Small molecules stuck together
Waste products are clean
Currently requires more energy to generate reaction than it yields
How does a reactor work?
Naturally occurring uranium is not concentrated enough to keep reaction
running, so uranium must be enriched first
Control rods that absorb neutrons are slide into uranium fuel rods to
stop reaction
Whole assembly is in water to cool system
Another water system is heated by circulating past reactor
Hot water turns turbine, makes electricity
Summary of costs of nuclear
Economic: currently economic viable. BUT coast of electricity generated
by nuclear power does NOT include cost of either permanent disposal of
fuel or of decommissioning of old reactors
Health: risk from accident. Original estimated total deaths from Chernobyl
- about 10,000. But so far these have not appeared - no increased cancer
rates. Deaths of uranium workers. Total risk unknown
Chernobyl: Reactor used graphite as combination control mechanism
and insulation (instead of water)
April 25, 1986
Reactor safety systems were shut down for a test of the turbines
A power surge caused the reactor to overheat, melting the fuel
rods
The reactor exploded and the graphite ignited, sending radioactive
particles high into the atmosphere
25% of Belorus contaminated, also Ukraine and Russia
Environmental: contamination in accident (so far no serious impacts
of Chernobyl), uranium mining, low CO2, waste disposal
Yucca Mountain: inside Nevada Atomic Test Site
Requirements for permanent disposal of high level nuclear waste
(spent fuel rods):
10,000 years of isolation from: Groundwater, Earthquakes, Volcanoes,
Accidents, Terrorists
Reasonable transportation
US DOE originally considered three sites. Two were removed from
list by their Senators. Only Nevada was left
Impermeable volcanic layers, above water table
Spent fuel embedded in glass, put in canisters, stored in tunnels
Issues at Yucca Mountain
More groundwater motion than originally thought
Potentially seismically active
Volcanics younger than originally thought
Transportation issues
Fierce local opposition
Strategic: US has large reserves of uranium, but waste is a terrorist
risk
Limited amounts of U-235. Must develop breeder reactors (use U-238)
or fusion for long run
Solar Power
Passive Solar
Using design features of home to use sunlight in winter and shade from
it in summer
Already widely used; some cities require it
Active solar
Systems that actively collect solar energy either for heating or electricity
Heating systems: sunlight warms water or oil that is circulated past
fans
Solar electric: either
sun heats a liquid to turn a turbine
Photovoltaics: solar panel directly generates electricity
Summary of Solar Costs
Economic: currently very expensive
Health: Risk to workers.
Environmental: carbon-free, low polluting except for manufacture of
panels
Strategic: US has many high intensity sun areas
Limits: requires back-up system
Geothermal
Energy from hot water in ground
The Geysers, Napa: largest producing field in the world
Hot dry rock: uses difference in temperature between surface and deep
rock
Household systems now available
Summary of geothermal costs:
Economic: inexpensive: between coal and petroleum
Health: risk primarily to workers
Environmental:open systems can vent sulphur. Modern systems are all
closed to maintain steam pressure
Strategic: does not require contributions from other countries
Limits: for electricity, requires very hot systems near young volcanoes
(Cal., Hawaii, Yellowstone)
Wind
Requires high, constant wind
Windfarms in California in Altamont, Suisun, Mojave
California - about 1.5% of energy supply, with goal of 4%
Summary of costs:
Economic: inexpensive, and price is dropping
Health: risk to workers, transportation
Environmental: almost carbon-free, clean, bird kills (raptors), eyesore
Strategic: depends on where turbines are manufactured
Limits: only viable in a few areas, moving the electricity is inefficient,
needs back-up