What is hydro energy?

Hydro energy uses a natural element, water, to create power.

How is electricity generated from hydro energy?

Hydro power schemes generate electricity from water, or hydro energy. They usually have four main components: dam, penstock, power station and trailrace.

Dam (or intake area): A dam collects large volumes of water for storage in a reservoir. The higher the water level in a reservoir, the more potential energy there is available for generation in future. A generator can be used to divert water from nearby streams, rivers and lakes to fi ll the dam.

Penstock: A penstock is the pipe which carries water from the reservoir to the power station.

Power station: In a power station, a turbine and a generator convert water into electricity. When water enters the turbine, the force and weight of the water turns the turbine blades. This rotates the generator and produces electricity. A hydro power scheme can have more than one power station. The Tongariro Power Scheme has two power stations.

Trailrace: A trailrace releases water from the power station back into a river, stream, or lake. It is a channel designed to remove surplus energy from the water and calm it down.

How much energy is created depends on the rate at which water fl ows and the height it falls from. The greater the height and the faster the fl ow of water, the more energy the turbine blades generate.

What are the advantages of hydro energy?

Hydro energy is a renewable form of power generation and is a very e�ective method of converting energy into electricity. Hydro energy produces little or no greenhouse gas emissions and the water is free.

What are the disadvantages of hydro energy?

Because hydro schemes use waterways to generate energy, building and operating these schemes can disrupt natural waterways and aquatic eco-systems.

The e�ects of damming rivers both upstream and downstream, e.g., the Clutha River and the Wanganui River, have signifi cant impacts.

When rainfall is limited, hydro generation is a�ected. Continuity of supply is an issue with hydro energy which means we can’t be entirely reliant on it.

How is hydro energy used in New Zealand?

Hydro energy generation is well established and is the most common way to produce electricity in New Zealand because of our many waterways and mountains. In the North Island, three hydro power schemes

HYDRO

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WHAT IS HYDRO ENERGY?Hydro power stations use the energy released when water falls due to gravity. They convert this energy into electricity.

HOW IS ELECTRICITY GENERATED FROM HYDRO ENERGY? As water falls from the top of a hydro dam, it picks up speed. The kinetic energy from this fall is used to turn the turbine and drive the generator of the power station. Hydro power schemes usually have four main components: dam, penstock, power station and trailrace (or spillway).

DamA dam holds back a large volume of water and stores it in a lake or reservoir. The higher the water level in a reservoir, the more potential energy is available for electricity generation. Water may also be diverted from nearby streams, rivers and lakes to �ll the reservoir.

PenstockA penstock is the pipe through which the water falls from the reservoir to the power station.

Power stationIn the power station, a turbine and a generator convert the kinetic energy of the water into electricity. The fast-�owing water hitting the turbine blades turns the turbine, and this turns the rotor of the generator, producing electricity. A hydro power scheme may have more than one power station; for example, the Tongariro Power Scheme has two power stations, one at Rangipo and one at Tokaanu.

Trailrace (or spillway)A trailrace releases water from the power station back into a river, stream or lake. It is a channel designed to slow the water back to its normal speed.

The rate at which energy is generated depends on the height that the water falls and the rate at which it �ows through the power station. The greater the height and the faster the �ow, the greater the power output.

WHAT ARE THE ADVANTAGES OF HYDRO ENERGY?Hydro energy is a renewable form of electricity generation and is a very e�ective method of converting mechanical energy into electricity. Hydro energy produces few or no greenhouse gas emissions and the water is free.

HYDRO POWER SCHEME AT TOKAANU, NEW ZEALAND. SOURCE: GENESIS ENERGY

(Tongariro, Waikaremoana, and Kourarau) produce a total of 499MW of power annually. New Zealand’s total hydro-electricity capacity is approximately 65% of the total power generation.

ACTIVITIES

ACTIVITY ONE

Research one of the current or proposed hydro power schemes in your region. What are the costs and benefi ts or advantages and risks of the scheme? Consider social, economic, environmental and cultural factors.

ACTIVITY TWO

Selecting one of the following topics, write a brief newspaper article or letter to the editor:

gnidulcni ,noitareneg ygrene ordyh etomorp •the benefi ts of this type of energy source

nac ygrene ordyh hcihw ni syaw ebircsed •a�ect the environment

tsom eht si ygrene ordyh yhw nialpxe •common form of energy generation in New Zealand.

ACTIVITY THREEBUILD A MODEL WIND TURBINE

Divide the class into four groups. Assign

scheme (dam, penstock, power station, and trailrace). Have the groups draw and label their component.

Teacher display the components of the hydro power scheme together on the wall. As a class, discuss how electricity is generated from hydro energy.

ACTIVITY FOURRESEARCH PROJECT

What impact is climate change in New Zealand predicted to have on hydro energy generation?

SUPPORTING RESOURCESzn.tvog.acee.www :ytirohtuA noitavresnoC dna ycneic fifE ygrenE -

zn.tvog.dem.www :tnempoleveD cimonocE fo yrtsiniM - :ygrenE siseneG - www.genesisenergy.co.nz

WHAT ARE THE DISADVANTAGES OF HYDRO ENERGY?Because hydro schemes need dams on existing lakes or rivers, land must be �ooded for the dams to be built. This may mean farmland is lost and people need to be put into new homes. It may also cause disruption to animal, plant and aquatic ecosystems.

When rainfall is limited, for example, during periods of drought, hydro generation is reduced. Continuity of supply may therefore be a problem, which means we should not rely entirely on hydro energy.

HOW IS HYDRO ENERGY USED IN NEW ZEALAND?The generation of electricity from hydro energy is well established in both the North and South Islands of New Zealand. It is the most common way to produce electricity in New Zealand because of our many waterways and mountains. In 2009, New Zealand’s total hydro capacity was 5400 MW: approximately 3500 MW in the South Island and 1900 MW in the North Island.

A transmission line has been constructed from Benmore, in the Mackenzie country, to Haywards, just north of Wellington, to transfer energy to the North Island. In 2009, hydro energy accounted for 57% of New Zealand’s electricity-generating capacity.

ACTIVITIESACTIVITY ONEResearch one of the current or proposed hydro power schemes in your region. What are the costs and bene�ts or advantages and risks of the scheme? Consider social, economic, environmental and cultural factors.

ACTIVITY TWOSelecting one of the following topics, write a brief newspaper article or letter to the editor.

ACTIVITY THREEDesign your own hydro schemeDivide the class into four groups. Assign each group a component of a hydro power scheme (dam, penstock, power station or trailrace). Have the groups draw and label their component.The teacher displays the components of the hydro power scheme together on the wall. As a class, discuss how electricity is generated from hydro energy.

ACTIVITY FOURResearch projectWhat impact is climate change in New Zealand predicted to have on hydro energy generation?

Promote hydro energy generation, including the bene�ts of this type of energy source.

Describe ways in which hydro energy can a�ect the environment.

Explain why hydro energy is the most common form of energy generation in New Zealand.