Hydro Turbine

Net exploitable hydropower resources

Advantages No Pollution No waste heat High efficiency Plants have decades long lifetimes and low maintenance costs Good response to changing electricity demands Damming of rivers can serve other purposes: flood control, irrigation, drinking water supply

Limitations About 50% of the US capacity for Hydro is developed Limited lifetimes for certain reservoirs-as the fill with silt, they become less useful for water storage. But the dam must be maintained long term, if it fails, communities downstream are in danger from the tremendous volume of silt that would be released. Loss of free flowing streams due to damming and the loss of the lands flooded by damming a river-environmental impacts – Salmon population in the Nothwest has been impacted Flood risk due to dam failures – Currently hundreds thousands of people in danger if dam failures occur

Fish Ladders Solution to the salmon problem - have not been very effective

Wind power Not subject to day night cycles Direct result of solar heating of the Earth’s atmosphere Use of wind for energy first noticed by sailors the old sailing ships could extract the equivalent of 10,000 hp from the wind! Windmills were prevalent in Europe in the 19 th century Several million were pumping water in the US in the early 1900s

WHAT YOU’RE PROBABLY THINKING OF….

Power in a windmill The power in the wind can be calculated by P/m 2 =6.1 X v 3 This gives the power in kilowatts per meter squared, where the cross sectional area is oriented perpendicular to the wind direction. This is the total power, of course not all of it can be extracted. According to Betz’s Law, developed in 1919 by German physicist Albert Betz, no turbine can capture more than 59.3 percent of the potential energy in wind. However, the total amount of economically extractable power available from the wind is considerably more than present human power use from all sources!

Extracting the energy: The turbine The world's first automatically operated wind turbine was built in Cleveland in 1888 by Charles F. Brush. It was 60 feet tall, weighed four tons and had 12kW turbine.

Turbine types: 2 types, based on the direction of the axis that the turbine rotates about. Horizontal axis wind turbines (HAWT) -the turbine rotates around an axis that is horizontal. Vertical Axis Wind Turbines (VAWT) –the turbine rotates around a vertical axis

HAWT Horizontal Axis Wind Turbines main rotor shaft and electrical generator are locate at at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a servo motor. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator.

HAWT the turbine is usually pointed upwind of the tower since it creates turbulence behind it. Turbine blades are made stiff to prevent the blades from being pushed into the tower by high winds. The blades are placed a considerable distance in front of the tower and are sometimes tilted up a small amount.