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INTRODUCTION TO HYDRO ENERGYHydro energy is derived from flowing water in rivers, water streams in mountains or from

man-made installations where water flows from a high-level reservoir down through a

tunnel and away from the dam. Energy from flowing water (or kinetic energy) has been

used for centuries to turn water wheels attached to grinding wheels for grinding corn orflour or other machinery in mills and factories, specifically in Mesopotamia as early as 3000

BC. During the 18th century the application of waterwheels spread further into industry,

driving a vast range of machines for every conceivable purpose, notably textile production.A century later there were over 20,000 waterwheels operating in Engalnd alone.Water wheel technology was largely replaced by steam power or fossil fuel energy in theIndustrial Revolution.

Hydro energy is now mostly used to generate electrical energy on large scale by collecting

water in large reservoirs or dams called hydroelectric power.Turbines placed within the flow of water extract its kinetic energy and convert it to

mechanical energy. This causes the turbines to rotate at high speed. The turbines drive agenerator that converts the mechanical energy into electrical energy. The amount of

hydroelectric power that can be generated is related to the water flow and the verticaldistance (known as head) through which the water has fallen.In the smallest hydroelectric schemes, the head of water can be a few metres; in larger

schemes, the power station that houses the turbines is often hundreds of metres below thereservoir.Hydroelectric systems can be connected to the main electricity grid, or can be part of astand-alone power system. In a grid-connected system, any electricity generated in excess

of consumption on site can be sold to electricity companies. In an off-grid hydroelectric

system, electricity can be supplied directly to the user or via a battery bank.There are three main types of hydroelectric schemes:

storage schemes run-of-river schemes pumped storage

In storage schemes, a dam impounds water in a reservoir that feeds the turbine andgenerator, usually located within the dam itself.Run-of-river schemes utilise the natural flow of a river, where the continuity of flow can beenhanced by a weir. Both storage and run-of-river schemes can be diversion schemes

where water is channelled from a river, lake or dammed reservoir to a remote powerhousecontaining the turbine and generator. A canal or low-pressure tunnel transports the water tothis end point and then back to the river or to another watercourse.Pumped storage incorporates two reservoirs. At times of low demand, generally at night,electricity is used to pump water from the lower to the upper basin. This water is thenreleased to create power at a time when demand, and therefore price, is high. Pumpedstorage is not a renewable application as it is reliant upon an electricity supply and energy

losses are always involved when pumping the water. However, by providing a rapid supply

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of electricity in response to sudden changes in demand, it does have value in aiding the

overall efficiency of the generation infrastructure.In order to utilise the locally available energy sources, more attention is now being given tosmall hydro energy systems. Efforts are also being made to revive the old water wheel

technologies which need minimal expertise. Smaller hydro energy systems fall in following

three types:Micro-hydropower systems are relatively small power sources that are appropriate forindividual users or groups of users who are independent of the electricity supply grid,

having a generating capacity of less than 100 kW.

Mini hydropower systems have an installation capacity of between 100 kW and 1000 kW

(1.0 MW).Small hydropower systems have a capacity of more than 1.0 MW and up to 10 MW.

Depending on the site, the following may be needed to develop a micro-hydropower

system: an intake or weir to divert stream flow from the water course a canal/pipeline to carry the water flow to the fore-bay from the intake a fore-bay tank and trash rack to filter debris and prevent it from being drawn into

the turbine at

the penstock pipe intake a penstock pipe to convey the water to the powerhouse a powerhouse, in which the turbine and generator convert the power of the water

into electricity

a tailrace through which the water is released back to the river or streamMany micro-hydropower systems operate from "run of river," which means only a fraction of

the available stream flow at a given time is used to generate power, and this has littleenvironmental impact. The amount of energy that can be captured depends on the amountof water flowing per second (the flow rate) and the height from which the water falls (thehead).