Energy & Its Impact on Global Society Jerome K. Williams, Ph.D. Saint Leo University Dept. Mathematics & Sciences
Dec 14, 2015
Energy & Its Impact on Global Society
Jerome K. Williams, Ph.D.Saint Leo University
Dept. Mathematics & Sciences
Chapter 12: Wind and Water
• Harnessing the Wind• Windmills: NIMBY• Wind Energy Systems• Wind Energy Storage & Economics• Hydropower: Using Water for Energy• Hydroelectric Energy Systems
Harnessing the Wind
• One of first natural energy sources used: windmills used to pump water, grind grain
• Extraction of energy from wind is enjoying a renewal in interest
• Fastest growing form of energy today (30-40% in many areas)
Harnessing the Wind
Harnessing the Wind
• Advantages
– Non-polluting– Short construction times– Small, easily scaled to specific needs & locations– Very good complement to solar energy
Harnessing the Wind
• Top Wind-Energy Markets (Table 12.2)
– China– US– Germany– Spain– India
Windmills: NIMBY
• Drawbacks?
– Visual Pollution (Lower Property Values)– Noise, Communication Interference– Bird Fatalities
• NIMBY = Not in My Back Yard
Windmills: NIMBY
• Solution to NIMBY Faction?
– Wind farms where population density very low– Offshore Wind Farms
• Higher costs (construction & maintenance)• More energy harvested (higher wind speed over open
water and less turbulence)
Windmills: NIMBY
Wind Energy System
Wind Energy System
• Power extracted from wind is proportional to the cube of wind’s velocity and area swept out by blades
• Power = 2.36 x 10-6 x D2 x v3 (Units: kW)– Equation allows calculation max. power output– Blade diameter (D) in feet– Wind velocity (v) in miles per hour (mph)
Wind Energy System
• Support Tower for turbine must be as high as possible since wind speed increases with distance from ground
• Generators with fewer blades more efficient than mutivane rotors which function better at low wind speeds
Wind Energy System
• Wind Turbine classified by orientation of rotor shaft and are of two varieties:
– Horizontal axis (vertical blades): most common– Vertical axis (horizontal blades):
Wind Energy System
Wind Energy Storage & Economics
• Present cost for at home wind generator system: around $4000 for 100 kWh monthly output
• Still less expensive to buy electricity from local utility
Wind Energy Storage & Economics
• Large wind-farm units are where demand lies
• 36 states have “large wind-farms” (Table 12.4)
– Incentives reduce installed costs to $1000 kWh– Electricity costs: 4 – 6 cents/kWh; dirt cheap– Landowners paid royalty by Uncle Sam to use land
(up to $6000 /yr/turbine). PIMBY PLEASE !!!
Hydropower: Using Water for Energy
• Hydropower used for many centuries to control water to do useful work (e.g., grind grain, saw lumber)
• Water & wind: Only sources of mechanical energy until steam engine (19th century)
Hydropower: Using Water for Energy
• How does hydropower work?
– Recall from chapter three that one can convert potential energy to kinetic energy by changing elevation of water
• Electricity Production (water) is not expensive; construction of new dams is very costly
Hydropower: Using Water for Energy
• Table 12.5 lists hydropower output by country (China, US, Brazil, Canada, Russia, India)
• 7% electricity in US is from hydropower• 21% world’s electricity comes from water
Hydropower: Using Water for Energy
• Advantages– Plentiful supply of water– Non-polluting, renewable energy source– Economic potential for developing world (Africa)
• Drawback– Affect environment (flooding large land area)– Trapping pollutants in water from human activity
Hydroelectric Energy Systems
• Water flow to power plant from dam is through large pipe (penstock), where it drives a reaction or impulse turbine.
• Output is function of both “head” and rate of water flow. The “head” is vertical distance from highest water level in dam and turbine.
Hydroelectric Energy Systems
Hydroelectric Energy Systems
• Kinds of Waterwheels– Undershot wheel– Breast wheel – Overshoot wheel
• Water Turbines (Two Kinds)– Impulse or Pelton Turbine – Reaction or Francis Turbine
Hydroelectric Energy Systems
Breast Wheel Overshoot Wheel
Hydroelectric Energy Systems
Pelton Turbine Francis Turbine
Problems
• 11, 15, 19