This time we will be sharing more about the conversion of moving water to electricity!
In the hydroelectric dam, the water stored at a higher elevation is a source of potential energy. When released, it runs through a pipe called a penstock, and is delivered to the turbine. The potential energy is then converted to kinetic energy in the turbines and then to electrical energy. Generally more than 90% of the potential energy of the water can be converted into electrical energy, which means that the Power-Work efficiency is 90%.
In order to generate electricity from the kinetic energy in moving water, the water has to be moving with sufficient speed and volume to turn a generator, which explains why the water is stored at a higher elevation. One gallon of water per second falling one hundred feet can generate approximately one kilowatt of electrical power.
The key factors that maximise the amount of energy produce are the volume of water and the height difference between the intake and the outflow of water. This height difference is called the head. Thus to produce maximum power, it is best to locate the hydroelectric plant at the maximum elevation. The height difference is proportionate to the speed of the water and the water pressure in the penstock. Therefore, these factors can be placed aside.
The energy produced is determined by the mass of the water, the gravitional acceleration which is a constant and the height where the water is released. This is derived from the potential energy formula, E = mgh. Whereas the power is given by a function of rate of fluid flow or the head. This is because, power equals to energy produced over time, E/t = m/t(g)(h) and m/t is the rate of fluid flow. The rate of fluid flow is proportionate to the head. Therefore, to obtain maximum energy and power, there must be maximum height difference and volume of water.
Citations:
- Union of concerned scientists. (16/11/07). Clean energy. USA, retrieved 1/4/08, from http://www.ucsusa.org/clean_energy/renewable_energy_basics/how-hydroelectric-energy-works.html
- Barry Gilman. (2008). How it works: Hydropower. Southern California Edison, retrieved 13/4/08, from http://www.sce.com/Feature/Archive/hydropowerfeature.htm
- K.S.Sidhu. Hydropower. India,Punjab state electricity board, retrived 5/5/08, from http://www.indiacore.com/bulletin/papers-gp5/k-s-sidhu-hydro-power.pdf
Signing off,
Hydroelectricians:D
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