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

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