# Energy & Its Impact on Global Society Jerome K. Williams, Ph.D. Saint Leo University Dept. Mathematics & Sciences.

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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

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

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 D 2 x v 3 (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 (19 th 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

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 WheelOvershoot Wheel

Hydroelectric Energy Systems Pelton TurbineFrancis Turbine

Problems 11, 15, 19

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