Run-off river plant:
This type of hydropower is usually built in the perennial river (flow in river available throughout the year). Water retaining structure such as dam is constructed of small heights to increase the head of flow and not for the storage purposes to be used during the flow slack time. So the power to be generated is the function of the discharge of the river and maximum during the excess flow period and decreases during the dry period. Due to the small nature of the structures to be constructed than that of the storage projects this type of projects is not much cost and could be built within the relatively short period of time compared.
In case of wide rivers at the plain area and of perennial type, where gain in head is difficult to achieve due to the topographical condition but sufficient discharge is available, power should be generated through the low head plants embodied with the dam spanning inside the river.
As it is known fact that flow of river during the dry season is the minimum stage and due to that energy production is also curtailed. As the power demand is not much varying during the dry period, there will be chances of energy shortage during the dry season. In order to cope this problem, water is needed to be stored when there is excess low in the river. In order to store the water, necessary is to build some storage pond and utilized it during the needy period. For construction of storage pond retaining structures like dam is required.
Accumulation type: (pumped storage plant)
This type of projects is usually constructed in the countries where there is storage of water throughout the period or places where there is availability of two reservoirs naturally. The water stored shall be used again and again in a cyclic manner during scarcity of flowing water. It could be termed as the plant for the indirect storage of surplus energy generated by other plants. As the generated electricity is not possible to be stored, so it has to be instantly used while being generated. So the electricity generated from any source of plants (hydroelectric, thermal or nuclear) could be utilized to pump the water to upstream reservoir and then utilized it when required. Commercially, such projects are very much suitable when there is much variation of energy demand at day and the nighttime where the energy rate is different during this period. During night time cheap energy could be purchased to pump the water to upper reservoir and at the day time much expensive energy could be produced for selling. Most of all the best feature of this type project is reversible use of water.
Tidal hydro project:
Hydropower could also be generated through the tidal rise in the sea and is termed as the tidal power. The suitable location for such purposes is the bay where relatively short dam could divide the bay with the sea. Due to action of the sun and moon, tides get rise at the sea and the rise of potential water head, thus developed potential head could be utilized for the power generation. Depending upon the geographical location, depth of water and wind speed, rise in the water level could be from one meter up to 15 meter. Low head turbines equipments and sluice holes are embodied inside the dam body. When the tidal rises the turbines openings are shut and sluice holes are opened to fill the bay. After the maximum level of the water at eh bay is raised, sluice holes are shut down and turbines are run for the power generation.