Today we discussed on how are we going to carry out our research and the list of different things we want to research on for our topic,

Water Generating Electricity (Hydroelectric dam)

List of things to research on:
-Hydroelectric dam
-Hydraulic power
-Physics involved
-Cons and pros of hydroelectric power

HOW THE HYDROELECTRIC DAM WORKS(by Ruth)

The hydroelectric power plant works in a similar way as coal-fired power plants. For both power plants, a power source is used to turn a propeller-like piece called a turbine, which then turns turns a metal shaft in an electric generator, which then produces electricity. The only difference between the two, is that the coal-fired power plants use steam to turn the blades of the turbines while falling water is used to turn the turbine in the hydroelectric dam.





A hydroelectric dam has to be built on a large river that has a large drop in elevation. Behind the dam, a large amount of water is stored in a reservoir. The intake of water is located near the bottom of the dam so that with the help of gravity, the water enters penstock in the dam. The penstock is a large pipe that raises the potential energy in the water for higher electricity produced. As the water then continues to flow through the turbine, the shaft from the turbine then turns up to the generator, which produces the power. Power lines that are connected to the generator then transports the electricity to where it is needed. The water continues past the propeller through the tailrace into the river past the dam.


Kinetic energy from the flowing water is converted into mechanical energy by the hydraulic turbine. The generator then converts this mechanical energy into electricity. This is based on the discovery of a man called Faraday. He discovered that when a magnet is moved past a conductor, electricity flows through it.

In a generator, field poles are mounted on the perimeter of the rotor. Field poles are electromagnets made by circulating direct current through loops of wire wound around stacks of magnetic steel laminations. The rotor rotates at a fixed speed according to the turbine. When the rotor rotates, the field poles are rubbed against the conductors fixed on the stator. Thus, electricity is generated and a voltage develops at the generator output terminals.

HYDRAULIC POWER/HYDROPOWER(by Chun Mei)

The "hydro" in hydropower suggests that the term has something to do with water. It is the force or energy of moving water, which is the kinetic energy of water.

Hydraulic power can be present in water wheels, watermills, not just in hydroelectric dams.

PHYSICS INVOLVED(by Chun Mei)

A hydropower resource can be measured according to the amount of available power, or energy per unit time. In large reservoirs, the available power is generally only a function of the hydraulic head and rate of fluid flow. In a reservoir, the head is the height of water in the reservoir relative to its height after discharge. Each unit of water can do an amount of work equal to its weight times the head.

The amount of energy released by lowering an object of mass by a height in a gravitational field is

where is the acceleration due to gravity which is about 10m/s.

The energy available to hydroelectric dams is the energy that can be liberated by lowering water in a controlled way. In these situations, the power is related to the mass flow rate.

Substituting for and expressing in terms of the volume of liquid moved per unit time (the rate of fluid flow ) and the density of water, we arrive at the usual form of this expression:

For in watts, is measured in kg/m³, is measured in m³/s, (gee) is measured in m/s², and is measured in metres.

Some hydropower systems such as water wheels can draw power from the flow of a body of water without necessarily changing its height. In this case, the available power is the kinetic energy of the flowing water.

where is the velocity of the water,

or with where A is the area through which the water passes, also

Over-shot water wheels can efficiently capture both types of energy.

taken from http://en.wikipedia.org/wiki/Hydropower

Cons and Pros of using Hydroelectric Power (by Pei Jia)

Advantages:
-reduces the amount of greenhouse gases emitted
-fossil fuels are not burnt therefore there is little or no pollution
-water that runs the dam is free, provided by nature
-low costs (operation/maintenance)
-water is renewable, so the fuel is always present
-proven as a reliable method

Disadvantages:
-high costs (investment)
-loss/modification of aquatic (fish) habitat
-fish passage restriction
-need lots of land and water