Hydropower industry is the sphere of human domestic and economic activity, aggregate of large natural and man-made subsystems that serve to transform the water flow energy into electric power. Most often, the power of falling water is harnessed in its hydropower plants.
Advantages:
• use of renewable energy;
• very low-cost electric power;
• its generation related work is not attended by emissions of harmful substances into the atmosphere;
• quick (in comparison with combined heat and power plants/thermal power plants) starting operation in the operating power generation mode after running the hydropower plant.
Disadvantages:
• flooding irrigated lands;
• hydropower plants are built where the are great water energy stores;
• it is dangerous to built hydropower plants on mountain rivers because of high seismicity in such areas;
• reduced and uncontrolled water releases from reservoirs for 10-15 days cause unique floodplain ecosystems along the entire river channel to restructure and, as a consequence, leads to contamination of rivers, shortening of trophic (food) chains, decrease in fish population, elimination of invertebrate aquatic animals, rise of the aggression of blood-sucking insects (midges) components because of they do not eat enough during their larval stage, extinction of breeding grounds of many types of migrating birds, insufficient moistening of floodplain soil, negative plant succession (depletion of phytomass), and decrease in the biogenic substances inflow to oceans.
Conventional (dams)
Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. The power extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This height difference is called the head. A large pipe (the "penstock") delivers water from the reservoir to the turbine.
Pumped-storage
This method produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, the excess generation capacity is used to pump water into the higher reservoir, thus providing demand side response. Pumped storage is not an energy source, and appears as a negative number in listings.
Run-of-the-river
Run-of-the-river hydroelectric stations are those with small or no reservoir capacity, so that only the water coming from upstream is available for generation at that moment, and any oversupply must pass unused. A constant supply of water from a lake or existing reservoir upstream is a significant advantage in choosing sites for run-of-the-river.
Tide
A tidal power station makes use of the daily rise and fall of ocean water due to tides; such sources are highly predictable, and if conditions permit construction of reservoirs, can also be dispatchable to generate power during high demand periods. Less common types of hydro schemes use water's kinetic energy or undammed sources such as undershot water wheels. Tidal power is viable in a relatively small number of locations around the world.
Conduit
Conduit hydroelectricity stations use mechanical energy of water as part of the water delivery system through man-made conduits to generate electricity. Generally, the conduits are existing water pipelines such as in public water supply. Some definitions expand the definition of conduits to be existing tunnels, canals, or aqueducts that are used primarily for other water delivery purposes than electricity generation.
