Hydropower

Hydropower or water power is power derived from the energy of falling water or flowing water, which may be harnessed for useful purposes.

Hydroelectricity is the term referring to electricity generated by hydropower

It is the most widely used form of renewable energy, accounting for 16 percent of global electricity consumption

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

Paraguay produces 100% of its electricity from hydroelectric dams, and exports 90% of its production to Brazil and to Argentina.

Types of generating methods

Conventional (Dams)

Pumped-storage

Run-of-the-river

Conventional (Dams)

Most hydroelectric power comes from

the potential energy of dammed

water driving a water turbine and

generator.

This height difference is called the

head.

The amount of potential energy in

water is proportional to the head.

A large pipe (the "penstock") delivers

water to the turbine.

Cross section of a Conventional

Hydroelectric Dam.

Run-of-the-river

Run-of-the-river hydroelectric stations

are those with small or no reservoir

capacity

So water coming from upstream must

be used for generation at that

moment.

Micro-hydro

Micro-hydro: the basics "Run of the river" systems do not require

a dam or storage facility to be constructed.

Instead they divert water from the stream or river and is channelled through a settling basin

The water then flows into the ForebayTank where it is directed downhill through a pipe called a penstock.

When the water reaches the bottom, it drives a specially designed turbine to produce the electricity.

Advantages of Hydropower

Renewable, indigenous, non-polluting resource

Flexibility

◦ Can be ramped up and down very quickly to adapt to changing

energy demands

Low power costs

◦ Not effected by increases in the cost of fossil fuels

◦ No imports are needed.

◦ Have long economic lives (50–100 years)

◦ Operating labour cost is also usually low, as plants are

automated and have few personnel on site during normal

operation.

◦ Dam serves multiple purposes, providing a useful revenue stream

to offset the costs of dam operation.

Reduced CO₂ Emissions

◦ Do not burn fossil fuels, they do not produce greenhouse gases

Produces no direct waste

Disadvantages

Loss of land – for construction of Large reservoirs leading to submersion, destroying biologically rich and productive lowland and riverine valley forests.

Ecosystem damage- Is disruptive to surrounding aquatic ecosystems both upstream and downstream of the plant site.

Relocation- Relocate the people living where the reservoirs are planned.

Failure Risks – because hold back large volumes of water, a failure due to poor construction, natural disasters or sabotage can be catastrophic to downriver settlements and infrastructure.

Flow shortage-Lower river flows will reduce the amount of hydroelectricity, power shortages in areas that depend heavily on hydroelectric power.

Siltation-Negative effect on dams and subsequently their power stations. Siltation can fill a reservoir and reduce its capacity to control floods .

Methane emissions from reservoirs - power plants in tropical regions