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How does a hydro plant work?

Types of hydro plants

Hydro plants range in size from the very small (providing a few kilowatts to a home or farm) to the very large (supplyingthousands of megawatts to large urban areas).

Many hydro plants use large dams to store water supply. They are sometimes called storage hydroplants. But hydropower

doesnt necessarily require dams or falling water. Run-of-the-river facilities use little, if any, stored water and produce powerby diverting fast-flowing rivers through a turbine set in the river or off to the side. Of the 450 hydro stations in Canada, morethan 125 are run-of-the-river.

Both dam plants and run-of-the-river are considered conventional plants, because they use one-way water flow to generateelectricity.

In contrast, pumped storage plants use a two-way water flow. After water is processed to produce electricity, the water flowsinto a lower reservoir below the dam. Some of this water is then pumped back into an upper reservoir to be reused laterduring periods of increased demand.

Hydropowe r depends on two factors

The amount of electricity a hydro plant produces depends on two factors:

quantity of water moving through a turbine (volume of water flow)height from which the water falls (the greater the height, the greater the potential energy source). This is called thehead

Generally, the greater the flow and head, the more electricity can be produced.

Hydro pr ovides flexibility

Hydro plants are unique among energy sources for their operational flexibility. If there is an increased electricity demand,plant operators release more water from the dam. On the other hand, when demand is slow, they store water for futureneeds.

The flow of rivers varies from season to season. Usually, rivers have the highest flows in spring or early summer. For thatreason, hydro plants often store surplus water during high flow periods for use during low flow periods. This allows generatorsto control their electrical output over the year.

How is electricity delivered?

After electricity is generated, it has to be moved to customers that use the electricity. This involves two basic steps:transmission (moving electricity at high voltages from generating plants to local communities) and distribution (moving powerto individual customers).

Transmission

The transmission system carries electricity from the power plant to local communities, often over long distances.

Electricity does not travel easily. Transmission lines have some resistance to the flow of electricity (this is similar to thefriction caused by the flow of water in a pipe). This causes them to lose a portion of the electricity they transport.

Early in the history of electricity transmission systems, energy developers discovered that the higher the voltage in electricitylines, the less resistance and, therefore, the less wasted electricity. Thats why when electricity travels long distances, it isbetter to have it at higher voltages.

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Generators produce electricity at lower voltages (25,000 volts or less). So before the electricity leaves the plant, it goes to atransformer that boosts it to higher voltages (typical voltages for long-distance transmission are 138,000 to 500,000 volts).This equipment is called a step-up transformer.

High voltage transmission lines, supported by large steel towers, then carry the electricity long distances to substations incommunities.

Distribution

The distribution system takes power from the substation (part of the transmission system) and delivers it to homes andbusinesses. The distribution systems network of wires can be overhead, with wires strung from poles, or underground, usingburied cables.

In the distribution system, transformers first reduce or step down the high voltage electricity to distribution voltages (typicallyless than 10,000 volts). From these substations, electricity is used at different power levels to run factories, mass transit andstreetlights.

Substations also send electricity to residential neighborhoods. Another small transformer on the street or in the neighborhoodfurther reduces the voltage to 120 volts for lights and 240 volts for larger appliances, such as stoves and clothes dryers.

When it arrives at our homes or businesses, the amount of electricity we use is metered and we are charged according towhat we use.

Did you know ?

there are more than 160,000 kilometres of transmission lines in Canadain Quebec, power is transmitted from James Bay at 735,000 volts one of the highest transmission voltages in theworld