1. History

Hydro-power is derived from the energy of falling water and running water. Since ancient times, hydro-power has been used for irrigation and the operation of various mechanical devices, such as watermills, textile mills, sawmills and so on.

Since the early 20th century, the term has been used almost exclusively in conjunction with the modern development of hydro-electric power.

Hydro-electricity is the term referring to the use of the gravitational force of falling or flowing water to produce electricity. It is the most widely used form of renewable energy, accounting for 16 percent of global electricity generation and is expected to increase between 2.5-3.0 % each year for the next 10 years.

Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer with around 17 percent of domestic electricity use.

Hydro-electricity can be produced in many ways: through conventional dams, run-of-river hydro- electric stations, pumped water storage and the use of large tidal movements of water. Most hydro-electric power is produced by conventional water dams because they have the largest capacity.

Pumped storage is used to supply high peak demands by moving water between reservoirs at different elevations. At times of low energy demand, excess generation capacity is used to pump water in the higher reservoir. When there is higher peak demand water is released back into the lower reservoir through a turbine. Pumped water provides a useful way of storing grid-energy.

Run-of-the-river hydroelectric stations are those with small or no reservoir capacity, so that the water coming from upstream must be used for generation at that moment.

Large hydro-electric facilities (large dams) can generate as much as 10 GW (10.000 MW). Smaller hydro facilities may be built when local conditions are favorable. Small units provide electricity up to 10 MW. Micro-hydro facilities are mostly run-of-river projects delivering local electricity to small communities with capacities of up to 100 KW.

2. Economics

The cost of hydro-electricity is relatively low, making it a competitive source of renewable electricity. The average cost of electricity from a hydro plant larger than 10 MW is 3 to 5 U.S. cents per kilowatt-hour. Hydro is also a flexible source of electricity since plants can be ramped up and down very quickly to adapt to changing energy demands.

3. Advantages and Disadvantages

There are significant disadvantages of building large dams. Damming interrupts the flow of rivers and can harm local ecosystems, and building large dams and reservoirs often involves displacing people and wildlife.

When the river flow is reduced due to lack of rain, the capacity may be reduced. Therefore hydro projects are subject to frequent capacity constraints.  Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of the CO2) than fossil fuel powered energy plants.

4. Hydro-electricity future

Hydro-electricity accounts for approximately 16% of global electricity demand.


As can be seen from the graph above the share of the hydro-electricity of total global energy production is fairly stable.

5. Summary and conclusion

As shown in the above graph, the percentage of electricity production from fossil fuels such as coal, natural gas and oil is still rising, despite the many efforts to create awareness concerning global warming, pollution of air in cities and the rising cost of fossil fuels.

Access to hydro-electric energy is limited because the local geography has to allow for it. The low hanging fruit has been tapped.

Hydro-electricity is a useful contributor to the production of clean renewable energy. on a global scale. However hydro-electricity has no potential to replace fossil fuels in the long run. Clearly new clean and efficient energy technologies are required to replace fossil fuels.