Alternative Energy

Nuclear Power

  1. Nuclear Fission: unstable radioactive element splits into two particles suddenly (U-235)

    • releases heat and radioactivity

    • U-235 and an extra neutron which causes fission, and 3 more neutrons are released to trigger other U-235 atoms

    • must be controlled and regulated to that the rate of fission generates enough heat, but not enough to cause a melt down (controls rods absorb neutrons)

    • 99% of U238 is not available for fission, 0.72% of U is U-235 can be used for fission

    • need 3% of U-235 for a generator, 90% U-235 for a weapon

Step to Uranium Processing

  1. Mine U ore

  2. Ore is milled to yellowcake

  3. Yellowcake is oxidized and F is added

  4. Gas is enriched to increased U-235

  5. Gas turned back in to a solid, made into pellet rods

  6. Pellets used for fuel energy to general heat , 1 pellet = 3 barrels of oil (high efficiency, much lower carbon footprint)

Risks

Nuclear Radiation: alpha, beta, and gamma rays are released during fission

  • alpha is weak (paper), but beta (al) and gamma (pb) is hazardous

Nuclear Waste: leftover nuclear material from fission can be reprocessed or stored at nuclear waste

  • in USA waste is stored in local facilities

  • Yuka mountain was proposed to be the national repository for nuclear waste (NV)


Wind Power

  1. Advantages: wind is a renewable resources

    • no air or water emissions

    • farmers are paid

    • wind is directly turning a turbine

  2. Challenges: wind is unreliable

    • turbines generable 10-40% of max potential output

    • storage isses

    • killing birds/bats


Solar Power

  1. Active

    a) concentrated solar thermal plant- mirrors or lenses focus sunlight onto a receiver, which heats liquid to steam

    b) photovoltaic solar panel (PV)- converts light into electricity

    • not turbine/generator

    • only suns rays to displace material which moves electrons to start electricity

    • about 15-20% efficient

  2. Advantages: renewable source

  3. Challenges: no use at night or during storms, needs to store electricity when not in use batteries


Hydroelectric Power

Comes from damned rivers and uses the water flow to turn a turbine

  1. Advantages: after construction, no carbon footprint, no mining involved

  2. Disadvantages: large construction cost ad carbon footprint during construction

    • disrupts local ecosystems (aquatic life)

    • displaces people

    • changes the velocity of the river (decreased before dam, increased after dam)

    • creates reservoirs that floods areas, can generate greenhouses gases as vegetation is flood


Geothermal Power

Wells extract hot water and gases to turn a stream turbine, used in volcanic areas (heat source close to the surface) (Greenland)

Advantages: constant electric output, low emissions

Challenges: start up cost is expensive (deep well drilling), operation can cool the subsurfaces, suitable sites are limited


Other sources: biofuel (wood, ethanal, peat), Tidal and waves (low/high tide to turn a turbine, depends on coastal configuration)