Water power sources is an interesting source of energy. It is available freely in nature. The constant flow of water can guarantee the availability of energy. Water power take it sources of energy from the motion of water. The motion of water is happening in river, sea and water fall. This movement can be derived from two resources:
1. Flows of water streams, this is attracted by earth gravity force
2. Tides which are the rise and fall of sea level by moon and sun gravity force
It is known that the solar energy output for the lifting of water steam against earth gravity is a only a small fraction. The absolute amount of energy that is theoretically recoverable as a result of the streams is enormous and massive but its quantity is still unknown. Of this amount of potential energy, only a small portion is suitable for to be explored and converted to energy.
The contribution of water power facilities and installations to the nation’s power supply and consumption at the beginning of World War II was approximately 30 percent. While the production of hydroelectric plant power has grown ever since, the contribution to total energy was estimated at around 15 percent and dropping since. This is due to steam-electric plants have grown at a much more rapid rate than new hydro plants installation.
The Energy Information Agency of the Department of Energy estimates that by the end of 2003 a total developed water capacity of water power installation is about 100,000 MW. Nonetheless, this figure does not include a number of potential sites in the future that need to be considered. Theoretically, the Energy Information Agency estimates the possibility of maximum potential of 188,000 MW. There are some of the undeveloped water power sites are located in the Pacific Northwest and Alaska. Only some fraction of that will be developed through a variety of reasons. The most attractive sites have already been utilized.
Hydroelectric plants have some disadvantages due to their high initial costs and usually located in long distances from the major load centers. Economically hydroelectric plants need to compete with large and efficient, fuel stations, and the burgeoning, economically, large power plants. Large dam sites should normally justified not only on the value of performance, but also the benefits of flood control, irrigation and recreation. Problems with the migration of fish, conservation and preservation of aesthetic values are also considered to be the decision factors. Then again, hydroelectric plant, have more flexibility in meeting with emergency and peak loads. The economies of low head sites are improved by the new, efficient, axial-flow turbines of the tubular type.
Pumped Storage Hydroelectric Plant
There is another operation way to generate electric power, by pumping water from a stream or lake to a reservoir at a higher elevation. This operation mode is how pumped storage hydroelectric plant systems works. Pumping up to a storage reservoir is most commonly done by reversing the hydraulic turbine and generator. The generator becomes a motor driving the turbine as a pump. For the purpose of pumping water, power is drawn on weekends or night where power demand is at the lowest level. It is impractical to shutdown large, high temperatures steam stations for a few hours in the night or even during a weekend.
Since they need to continue running, the cost of pumping energy is low, while the energy produced by pumping during the peak storage is valuable. Moreover, the pumping system provides for transferring of energy responsively in an emergency condition, such as during the failure of a large unit of steam or nuclear power. The process of power generation in a pumped storage hydroelectric plant system is immediate. It can be changed over starting from pumping until generation of power just in 3 to 5 minutes.
Tidal Power
Tidal power is a part of kinetic energy of rotation of the earth as in the form of ocean tides. It has been estimated that the mean tide of the oceans as 2 feet (or 0.6 m) and the mean power resulted as 5.4 × 1010 horse power (or 40 TW). This outcome a massive the equivalent of 3.6 × 103 kWh (or 4 × 1019 Joules ) on an annual basis
But, only a minute amount of this can be harnessed and used. To stem the tide sufficiently in engineering point of view, the fall would be at least 15 feet (or 4.5 m). Unfortunately, only few such falls existed, and some of these are in remote areas.
The Passamaquoddy site, is the only superpower of tidal power in the U.S. It has the potential power output 1800 MW (on peak load). Nevertheless, engineers do not believe their power to compete economically with other source of power.
Another major obstacle to tidal power as source of energy is that with a simple, single-basin installation, power generation is only available if there is a sea level difference (in several feet) between sea and the basin. Moreover, the time for tidal power to generate power is in accordance with the tides season, not necessarily when the power is needed.
One major tidal power plant in operation is located near the mouth of the Rance River in Normandy, France. It consists of twenty-four 10-MW turbine generator. The system embodies a reservoir into which sea water is pumped during off-peak hours. Turbines are then run as pumps, power being drawn from the French electrical grid. The plant produces 5 × 108 kWh (1.8 × 1015 J) annually, including a significant amount of firm power.
Tidal power is an attracting and dramatic technique, and some other large plants may be constructed. Still, the amount contribution of the tides to the world’s energy supply will be small portion.
Silting as Hydro Plants Operation Problem
There is some problem that stir up the longevity of hydro plants operational. The capacity of hydro plants can not be counted, for perpetuity. This is due to the gradual filling of sedimentary deposits. This is serious consequences not only for hydro plants but flood control , for irrigation, and navigation as well. But then again, even if a lake behind a power dam is completely filled with silt, still electric power can be generated by the flow of river, while the output production would depend much on the stream flow. (Photo:foxpar4)
