4. Power Plant Machinery - 2. Hydro Electric Power Plant

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Hydro Electric Power Plant


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Water is a chemical substance that iscomposed of hydrogen and oxygenand is essential for all forms of life.

And it covers 71% of earths surface.


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Hydroelectricity is electricity generated byhydropower, the production of powerthrough use of the gravitational force offalling or flowing water. It is the most widelyused form of renewable energy. Once a

hydroelectric complex is constructed, theproject produces no direct waste, and hasa considerably lower output level of the

greenhouse gases such as carbon dioxide(CO 2) than fossil fuel powered energyplants.


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Hydroelectric power plants are plants thatproduce energy through the use of water.


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Parts of the Plant


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Dam - A dam is a barrier that impounds water orunderground streams. Dams generally serve theprimary purpose of retaining water.


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A penstock is a sluice or gate or intakestructure that controls water flow,
http://en.wikipedia.org/wiki/File:Ohakuri_Dam_Blue_Penstocks.jpg


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A turbine is a rotary engine that extractsenergy from a fluid or air flow and convertit into useful work.

An electrical generator is a device thatconverts mechanical energy to electrical

energy, generally using electromagneticinduction.


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Electrical Generator
http://en.wikipedia.org/wiki/File:Water_turbine.jpg


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How it works:

Most hydroelectric power comes from the

potential energy of dammed water drivinga water turbine and generator. In this casethe energy extracted from the waterdepends on the volume and on thedifference in height between the sourceand the water's outflow. This heightdifference is called the head. The amountof potential energy in water is proportionalto the head. To obtain very high head,water for a hydraulic turbine may be runthrough a large pipe called a penstock.


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Pumped storage hydroelectricity produceselectricity to supply high peak demands by

moving water reservoirs at differentelevations. At times of low electricaldemand, excess generation capacity isused to pump water into the higher

reservoir. When there is higher demand,water is released back into the lowerreservoir through a turbine.


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Advantages:

Economics

The major advantage of hydroelectricityis elimination of the cost of fuel. The costof operating a hydroelectric plant isnearly immune to increases in the costof fossil fuels such as oil, natural gas orcoal, and no imports are needed .


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Hydroelectric plants also tend to havelonger economic life than fuel-firedgeneration, with some plants now inservice which were built 50 to 100 yearsago. Operating labor cost is also usuallylow, as plants are automated and havefew personnel on site during normaloperation.


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Greenhouse gas emissions

Since hydroelectric dams do not burnfossil fuels, they do not directly producecarbon dioxide(a greenhouse gas).While some carbon dioxide is producedduring manufacture and construction ofthe project, this is a tiny fraction of theoperating emissions of equivalent fossil-fuel electricity generation.


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Disadvantages:

Very Hazardous

Dam failures have been some of the largestman-made disasters in history. Also, gooddesign and construction are not anadequate guarantee of safety. Dams aretempting industrial targets for wartime

attack, sabotage and terrorism.


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Limited Service Life

Almost all rivers convey silt. Dams on those rivers willretain silt in their catchments, because by slowing thewater, and reducing turbulence, the silt will fall to thebottom. Siltation reduces a dam's water storage so that

water from a wet season cannot be stored for use in adry season. Often at or slightly after that point, the dambecomes uneconomic. Near the end of the siltation, thebasins of dams fill to the top of the lowest spillway, and

even storage from a storm to the end of dry weather willfail. Some especially poor dams can fail from siltation inas little as 20 years.


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Environmental damage

Hydroelectric projects can be disruptiveto surrounding aquatic ecosystemsboth upstream and downstream of theplant site.


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Population relocation

Another disadvantage of hydroelectricdams is the need to relocate the peopleliving where the reservoirs are planned.In February 2008, it was estimated that40-80 million people worldwide hadbeen physically displaced as a directresult of dam construction


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Hydroelectricity eliminates the flue gasemissions from fossil fuel combustion, including

pollutants such as sulfur dioxide, nitric oxide,carbon monoxide, dust, and mercury in thecoal. Hydroelectricity also avoids the hazards ofcoal mining and the indirect health effects ofcoal emissions. Compared to nuclear power,hydroelectricity generates no nuclear waste,has none of the dangers associated withuranium mining, nor nuclear leaks. Unlikeuranium, hydroelectricity is also a renewableenergy source.


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Compared to wind farms, hydroelectricity power

plants have a more predictable load factor. Ifthe project has a storage reservoir, it can bedispatched to generate power when needed.Hydroelectric plants can be easily regulated to

follow variations in power demand.Unlike fossil-fueled combustion turbines,construction of a hydroelectric plant requires a

long lead-time for site studies, hydrologicalstudies, and environmental impact assessment.


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http://upload.wikimedia.org/wikipedia/commons/7/7c/Dreischluchtendamm_hauptwall_2006.jpg


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4. Power Plant Machinery - 2. Hydro Electric Power Plant

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