October 5

Energy-- Chemical Resources

Desirable features of energy source--

• high energy density
• portable, transportable
• low cost
• efficient, safe way to use
• Needed for
  • heating (houses, hot water, stores, factories)
  • industrial energy (cement plants, Al foundries)
  • conversion to electrical energy
    • fire, boiler, steam turbine, generator
    • (lighting, motors, heating)
  • mechanical motion (engines)
    • transportation

• Electrical System as we know it
  • began circa 1880's with Edison lamp
  • Edison knew lamps alone wouldn't sell
    • he built generators, distribution, system
  • Motors existed, but were very inefficient
    • worth improving if power was available

(Think system rather than a key invention)

• Factory in 1890-- One steam engine / water wheel
  • overhead shafts, belts and pulleys
  • one engine drives each lathe, loom, saw
• now-- all power is electrical
  • individual motors where required

Edison's Electrical Meter

• If you pass electrical current through a chemical solution
  • Can cause chemical reaction
  • Need one species that wants electrons
    • electrical power is a supply of electrons
    • Ag⁺ ion + 1 electron ---> Ag (metal)
    • can "reduce" metal ion to elemental metal
• But electrons can't build up
  • container would become electrically charged (negative.)
  • Need no net change of electrons:
  • Need a second reaction
    • 2H₂O ----> H₂ + 2OH^- +2e
    • we say we oxidize the Hydrogen
      • hint: for oxidation, think rusting of iron
      • iron Fe ----> Fe⁺³ (as in Fe₂O₃, rust) + 3 e^-
      • after 40+ years, that's how I remember it; not as oxidation produces electrons and reduction uses them, but as a short story with very typical case history
• Back to Edison Meter
  • had two silver rods in a silver solution
  • caused one rod to oxidize (lose wt)
  • caused other rod to reduce Ag+ from solution (gains wt)
    • also the way to electroplate an object
  • meter man came by with a balance and weighed the silver, computed the electricity ("moles of electrons" from molece of chemical change) and sent a bill

Energy density is important

• comparisons
• how much energy can you get from...
  • a pound of fuel or a pound of batteries
  • a storage tank of a given size
• may be as important as cost or the energy
• electricity is a loser in this model
  • ordinary storage batteries can add 1000 lbs to weight of a car
  • volume larger than gas tank of a car
  • fully charged, may provide 50-100 miles
  • charging likely to need burning of same amount of fuel elsewhere

Hybrid Vehicles

• "can't be done" said Detroit
• been done in Diesel Locomotives since 1930's
  • a. Power comes from burning oil or gasoline
  • b. Engine powers a generator
  • c. Actual drive is by electrical motors
    • efficiency-- fueled engines run most efficiently at constant speed
    • electrical motors work well at varying speed
• automobile-- starting = largest, brief power requirement
  • build big engine
  • inefficient operation 95% of the time

• alternative-- use engine to maintain battery charge (steady)
  • rely on battery power for acceleration
  • (use braking as way to recharge batteries)

• honda hybrid
• toyota hybrid
• alternative fuel and alternative vehicles: directory of web sites

Public Policy and Energy Efficiency

• There are a number of federal laws relating to energy conservation
  • a. several types of light bulbs were outlawed
    • (low energy efficiency)
  • b. automobile mfr. were required to meet
    • tougher mile/gal standards
    • fleet average over all cars produced
    • loophole (SUV's and pickups weren't covered and overall fuel efficiency of passenger vehicles has gotten worse)
  • rules got frozen about 10 years ago so no push to improve design (may be changing)
  • c. water heaters, A/C, refrigerators, furnaces were required to either meet
    • efficiency standards
    • label products with energy efficiency data

Electricity can obviously come from a variety of energy sources

• solar panels, water power( turbine), wind turbine, nuclear
• geothermal heat (all of Iceland is heated and electrified this way)
• but mostly by burning fossil fuel

• There is a loss due to efficiency
  • some loss of energy in flame, boiler, turbine,
  • generator, transformers, power lines,
  • electrical heaters or motors
    • e.g., electrical heating of a house consumes more energy than a gas furnace in the same house.
    • it also costs more (more steps, each with a cost) unless the power plant's energy source is cheaper
      • Iceland, the promise of Nuclear Plants and Wind

• one advantage--
  • large systems usually more efficient
    • it's a more important factor in design
    • an emergency power generator may be expensive to run, but most cost is purchase and maintain (idle)
• from previous chapter
  • it's a lot cheaper to treat emissions from one
  • large source than from 100,000 tiny sources.
    • (SO₂, NOx, CO)
  • Still, all fossil fuel consumption leads to increased CO₂ levels

Element of the day page: CARBON