Ocean power in New Zealand
Encyclopedia
New Zealand
has large ocean energy resources but does not yet generate any power from them. TVNZ reported in 2007 that over 20 wave
and tidal power
projects are currently under development. However, not a lot of public information is available about these projects. The Aotearoa Wave and Tidal Energy Association
was established in 2006 to "promote the uptake of marine energy in New Zealand". According to their 10 February 2008 newsletter, they have 59 members. However, the association doesn't list its members.
From 2008 to 2011, the government Energy Efficiency and Conservation Authority
is allocating $2 million each year from a Marine Energy Deployment Fund, set up to encourage the utilisation of this resource.
The greater Cook Strait
and Kaipara Harbour
seem to offer the most promising sites for using underwater turbines. Two resource consents have been granted for pilot projects in Cook Strait itself and in the Tory Channel
, and consent is being sought for a project sites at the entrance to the Kaipara. Other potential locations include the Manukau
and Hokianga Harbours, and French Pass
. The harbours produce currents up to 6 knots with tidal flows up to 100,000 cubic metres a second. These tidal volumes are 12 times greater than the flows in the largest New Zealand rivers.
or dam like structures (barrages
), used to hold the tide back, or turbines anchored within the tidal stream.
By world standards, New Zealand's tides are, for the most part, moderate. The tide usually ranges between one and two metres. Tidal currents are usually around two kilometres per hour (one knot). Some exception are in and around Cook Strait
, where tidal currents can be much stronger, and at the entrance to some harbours, particularly Kaipara Harbour
. Headlands and constrictions like these focus the currents, giving energy levels reaching 750 W per square metre.
s are controlled mainly by the gravitational pull of the moon. About once a day the moon rotates about the earth, attracting as it travels the bulge of water called the high tide
that also travels round the earth. There are actually two high tides, because the earth and moon, as a system, both rotate about a common centre of mass. This centre is two-thirds from the centre of the earth, and not at the centre of the earth. The effect of the earth spinning about this centre is that it behaves as a centrifuge, resulting in a second high tide bulge in the ocean most distant from the moon.
A second influence on the tides occurs because of gravitation from the sun. Gravitation from the sun has less influence than the moon, because it is so much further from earth. However, the sun influences the tidal range
. When the sun, earth and moon are aligned in a straight line (at new
and full moon
), their gravities combine, producing the particularly high and low tides called spring tides. When the sun is at right angles to the moon, their gravities are partially cancelled, producing the small tides called neap tides.
New Zealand has a relatively small tidal range, usually less than two metres. However, some of the larger harbours on the west coast of the North Island, in particular the Kaipara
, experience significant currents as the tides rise and fall.
Altogether there are 62 natural influences on the tides. The gravitation of the moon and sun are the most important.
A third influence occurs because the moon revolves at an angle to the equator. This means that if one of the bulges travelling around the earth is above the equator, then the other bulge is below the equator. It also follows that some places will have one daily diurnal
tide, while other places will have semi-diurnal tides twice a day. For example, there is a diurnal tide in the Ross Sea
near Antarctica every 24.84 hours. The height of this tide dwindles to almost zero in a cycle which takes 13.66 days. New Zealand's tides are semi-diurnal. The primary cause, the lunar tide, is labelled the M2. The M stands for the moon and the 2 stands for twice a day.
A fourth influence occurs because the orbit the moon moves around the earth and the orbit the earth moves around the sun are more elliptical than circular. The effect of this is that the time between high tides changes a little from day to day. The moon takes about 24.8 hours to rotate about the earth, so it takes half this time, 12.4 hours, for the M2 tides to occur. The tides can be predicted far in advance, because the moon and earth have orbits that are predictable. The National Institute of Water and Atmospheric Research
(NIWA) run a tidal computer model specific to New Zealand.
The M2 tides sweep continuously anticlockwise around New Zealand, as can be seen in the computer model link at the right. When it is high tide on the west coast, it is low tide on the east coast, and vica versa. These currents are most noticeable in strait
s such as Cook Strait and in Foveaux Strait. A notable example is French Pass
, just off the greater Cook Strait, where, despite the low tidal range, tidal streams can reach nearly eight knots.
has tidal flows amongst the strongest in the world, even though it has a smaller tidal range than most places in New Zealand. This is because the main M2 lunar tide component which circulates anti-clockwise around New Zealand is out of phase at each end of the strait. On the Pacific Ocean side the high tide occurs five hours before it occurs at the Tasman Sea side. On one side is high tide and on the other is low tide. The difference in sea level can drive tidal currents up to 2.5 metres per second (5 knots) across Cook Strait as well as into the Tory Channel.
A further consequence of these opposed tides is that there is almost zero tidal height change at the centre of the strait. Although the tidal surge should flow in one direction for six hours and then the reverse direction for six hours, a particular surge might last eight or ten hours with the reverse surge enfeebled. In especially boisterous weather conditions the reverse surge can be negated, and the flow can remain in the same direction through three surge periods and longer. This is indicated on marine charts for the region.
There are numerous computer model representations of the tidal flow through Cook Strait. While the tidal components are readily realizable, the residual flow is more difficult to model.
In April 2008, a resource consent was granted to Neptune Power for the installation of an experimental underwater tidal stream turbine
in the strait. The turbine has been designed in Britain and will be built in New Zealand at a cost $10 million. Fourteen metres in diameter and constructed of carbon fibre, it will be capable of producing one megawatt. It will be placed in eighty metres of water, 4.5 kilometres due south of Sinclair Head, in waters known as the “Karori rip”. Power from the turbine will be brought ashore at Vector's
Island Bay substation. The turbine is a pilot, and will be sited in slower tides for testing. Neptune hopes to generate power from the unit by 2010. The company claims there is enough tidal movement in Cook Strait to generate 12 GW of power, more than one-and-a-half times New Zealand's current requirements. In practice, only some of this energy could be harnessed.
On the other side of the strait, Energy Pacifica has talked for some time about applying for resource consent to install up to ten marine turbines, each able to produce up to 1.2 MW, near the Cook Strait entrance to Tory Channel
. They claim Tory Channel has tidal flows of 3.6 metres per second with good bathymetry
and access to the electricity network. No application had been lodged by March 2011.
The power generated by tidal marine turbines varies as the cube of the tidal speed. Because the tidal speed doubles, eight times more tidal power can be produced at spring tides than at neap tides.
, one of the largest harbours in the world, is a channel to the Tasman Sea
. It narrows to a width of 6 kilometres (3.7 mi), and is over 50 metres (164 ft) deep in parts. On average, Kaipara tides rise and fall 2.1 metres (6.9 ft). At high tide, nearly 1000 square kilometres are flooded. Spring tidal flows reach 9 km/h (5 knots) in the entrance channel and move 1,990 million cubic meters per tidal movement or 7,960 million cubic meters daily.
In 2011, Crest Energy, a power company, received resource consent
to install about 200 underwater tidal turbines for the Kaipara Tidal Power Station
, which would use the substantial tidal flows moving in and out every day near the harbour mouth to produce electricity for approximately 250,000 homes.
Crest plans to place the turbines at least 30 metres deep along a ten kilometre stretch of the main channel. Historical charts show this stretch of the channel has changed little over 150 years. The output of the turbines will cycle twice daily with the predictable rise and fall of the tide. Each turbine will have a maximum output of 1.2 MW, and is expected to generate 0.75 MW averaged over time.
The peak level of generation for the combined turbines is about 200 MW. This exceeds the projected peak electricity needs of Northland. It would have environmental benefits in offsetting annual carbon emissions from a thermal-based, gas turbine generator of 575,000 tonnes of carbon. The project is costed at about $600 million and to be economic would have to be scaled up rapidly to near full capacity.
However, while the Department of Conservation has approved the project, and has made substantial environmental monitoring conditions part of the consent, the project also has objectors on the grounds of claimed influences on the local ecosystem
s and charter fishing. Appeals before the Environment Court were concluded in 2010, with a favourable decision released in February 2011.
involves converting the energy in ocean surface wave
s into electricity using devices either fixed to the shore, the seabed or floating out at sea. Wave energy varies with time, depending on when and where the winds and storms that drive the waves occur. Tidal energy is more regular and predictable.
Two wind zones affect New Zealand. South-east trade wind
s dominate in the north, enlivened an occasional cyclone from the tropics. The rest of the country is dominated by the roaring forties
, a broad band of westerly winds that span the middle latitudes of the southern hemisphere. The roaring forties extend over most of the southern part of the Tasman Sea
and the Southern Ocean
. These winds produce some of the stormiest seas in the world, with maximum wave heights regularly exceed 4 metres.
On average, ocean waves in New Zealand deliver about 25 kW to each metre of coastline. The west and south-west coasts have the country’s most energetic waves. Even on windless days, swells that were generated in the Southern Ocean still arrive. Less wave energy arrives at the north-east coast, because it is sheltered from the south-west waves (click the link on the right for a diagram). The amount of energy in a wave is proportional to the square of its height, so a two metre wave contains four times the energy of a one metre wave.
Wave Energy Technology - New Zealand (WET-NZ) is a Government-funded research and development collaboration programme between Industrial Research Limited
, a Crown Research Institute, and Power Projects Limited, a privately-owned Wellington-based company. The programme seeks to develop a wave energy device that generates electricity from both the kinetic and potential energy available in open ocean waves. In 2010 WET-NZ received resource consent for half-scale prototype testing at two test sites.
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
has large ocean energy resources but does not yet generate any power from them. TVNZ reported in 2007 that over 20 wave
Wave power
Wave power is the transport of energy by ocean surface waves, and the capture of that energy to do useful work — for example, electricity generation, water desalination, or the pumping of water...
and tidal power
Tidal power
Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity....
projects are currently under development. However, not a lot of public information is available about these projects. The Aotearoa Wave and Tidal Energy Association
Aotearoa Wave and Tidal Energy Association
The Aotearoa Wave and Tidal Energy Association is a New Zealand organisation established in 2006 to promote renewable energy from marine sources. This includes energy from tides, waves and ocean currents....
was established in 2006 to "promote the uptake of marine energy in New Zealand". According to their 10 February 2008 newsletter, they have 59 members. However, the association doesn't list its members.
From 2008 to 2011, the government Energy Efficiency and Conservation Authority
Energy Efficiency and Conservation Authority
Energy Efficiency and Conservation Authority is a New Zealand government/crown agency responsible for promoting energy efficiency and conservation....
is allocating $2 million each year from a Marine Energy Deployment Fund, set up to encourage the utilisation of this resource.
The greater Cook Strait
Cook Strait
Cook Strait is the strait between the North and South Islands of New Zealand. It connects the Tasman Sea on the west with the South Pacific Ocean on the east....
and Kaipara Harbour
Kaipara Harbour
Kaipara Harbour is a large enclosed harbour estuary complex on the north western side of the North Island of New Zealand. The northern part of the harbour is administered by the Kaipara District and the southern part is administered by the Rodney District...
seem to offer the most promising sites for using underwater turbines. Two resource consents have been granted for pilot projects in Cook Strait itself and in the Tory Channel
Tory Channel
Tory Channel is one of the drowned valleys that form the Marlborough Sounds in New Zealand.Tory Channel is named after the "Tory", a pioneer ship that brought British colonists to Wellington in 1840. It lies to the south of Arapawa Island, separating it from the mainland. At its western end it...
, and consent is being sought for a project sites at the entrance to the Kaipara. Other potential locations include the Manukau
Manukau Harbour
Manukau Harbour is the second largest natural harbour in New Zealand by area. It is located to the southwest of the Auckland isthmus, and is an arm of the Tasman Sea.-Geography:...
and Hokianga Harbours, and French Pass
French Pass
French Pass is a narrow and treacherous stretch of water that separates D'Urville Island, at the north end of the South Island of New Zealand, from the mainland coast. At one end is Tasman Bay, and at the other end the outer Pelorus Sound leads out to Cook Strait.French Pass has the fastest tidal...
. The harbours produce currents up to 6 knots with tidal flows up to 100,000 cubic metres a second. These tidal volumes are 12 times greater than the flows in the largest New Zealand rivers.
Tidal power
Tidal power is generated by capturing some of the energy in the tides as they cycle forth and back, twice each day. Tidal devices can be weirWeir
A weir is a small overflow dam used to alter the flow characteristics of a river or stream. In most cases weirs take the form of a barrier across the river that causes water to pool behind the structure , but allows water to flow over the top...
or dam like structures (barrages
Barrage (tidal)
A barrage is an artificial obstruction at the mouth of a tidal watercourse.-Purpose:The common primary functions of a barrage are:* Increase the depth of a river * Maintain a separation between fresh and salt water...
), used to hold the tide back, or turbines anchored within the tidal stream.
By world standards, New Zealand's tides are, for the most part, moderate. The tide usually ranges between one and two metres. Tidal currents are usually around two kilometres per hour (one knot). Some exception are in and around Cook Strait
Cook Strait
Cook Strait is the strait between the North and South Islands of New Zealand. It connects the Tasman Sea on the west with the South Pacific Ocean on the east....
, where tidal currents can be much stronger, and at the entrance to some harbours, particularly Kaipara Harbour
Kaipara Harbour
Kaipara Harbour is a large enclosed harbour estuary complex on the north western side of the North Island of New Zealand. The northern part of the harbour is administered by the Kaipara District and the southern part is administered by the Rodney District...
. Headlands and constrictions like these focus the currents, giving energy levels reaching 750 W per square metre.
Tides
TideTide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
s are controlled mainly by the gravitational pull of the moon. About once a day the moon rotates about the earth, attracting as it travels the bulge of water called the high tide
High Tide
High Tide was a band formed in 1969 by Tony Hill , Simon House , Peter Pavli and Roger Hadden .-History:...
that also travels round the earth. There are actually two high tides, because the earth and moon, as a system, both rotate about a common centre of mass. This centre is two-thirds from the centre of the earth, and not at the centre of the earth. The effect of the earth spinning about this centre is that it behaves as a centrifuge, resulting in a second high tide bulge in the ocean most distant from the moon.
A second influence on the tides occurs because of gravitation from the sun. Gravitation from the sun has less influence than the moon, because it is so much further from earth. However, the sun influences the tidal range
Tidal range
The tidal range is the vertical difference between the high tide and the succeeding low tide. Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth...
. When the sun, earth and moon are aligned in a straight line (at new
New moon
In astronomical terminology, the new moon is the lunar phase that occurs when the Moon, in its monthly orbital motion around Earth, lies between Earth and the Sun, and is therefore in conjunction with the Sun as seen from Earth...
and full moon
Full moon
Full moon lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.Lunar eclipses can only occur at...
), their gravities combine, producing the particularly high and low tides called spring tides. When the sun is at right angles to the moon, their gravities are partially cancelled, producing the small tides called neap tides.
New Zealand has a relatively small tidal range, usually less than two metres. However, some of the larger harbours on the west coast of the North Island, in particular the Kaipara
Kaipara Harbour
Kaipara Harbour is a large enclosed harbour estuary complex on the north western side of the North Island of New Zealand. The northern part of the harbour is administered by the Kaipara District and the southern part is administered by the Rodney District...
, experience significant currents as the tides rise and fall.
Altogether there are 62 natural influences on the tides. The gravitation of the moon and sun are the most important.
A third influence occurs because the moon revolves at an angle to the equator. This means that if one of the bulges travelling around the earth is above the equator, then the other bulge is below the equator. It also follows that some places will have one daily diurnal
Day
A day is a unit of time, commonly defined as an interval equal to 24 hours. It also can mean that portion of the full day during which a location is illuminated by the light of the sun...
tide, while other places will have semi-diurnal tides twice a day. For example, there is a diurnal tide in the Ross Sea
Ross Sea
The Ross Sea is a deep bay of the Southern Ocean in Antarctica between Victoria Land and Marie Byrd Land.-Description:The Ross Sea was discovered by James Ross in 1841. In the west of the Ross Sea is Ross Island with the Mt. Erebus volcano, in the east Roosevelt Island. The southern part is covered...
near Antarctica every 24.84 hours. The height of this tide dwindles to almost zero in a cycle which takes 13.66 days. New Zealand's tides are semi-diurnal. The primary cause, the lunar tide, is labelled the M2. The M stands for the moon and the 2 stands for twice a day.
A fourth influence occurs because the orbit the moon moves around the earth and the orbit the earth moves around the sun are more elliptical than circular. The effect of this is that the time between high tides changes a little from day to day. The moon takes about 24.8 hours to rotate about the earth, so it takes half this time, 12.4 hours, for the M2 tides to occur. The tides can be predicted far in advance, because the moon and earth have orbits that are predictable. The National Institute of Water and Atmospheric Research
National Institute of Water and Atmospheric Research
The National Institute of Water and Atmospheric Research or NIWA , is a Crown Research Institute of New Zealand. Established in 1992, NIWA conducts commercial and non-commercial research across a broad range of disciplines in the environmental sciences...
(NIWA) run a tidal computer model specific to New Zealand.
The M2 tides sweep continuously anticlockwise around New Zealand, as can be seen in the computer model link at the right. When it is high tide on the west coast, it is low tide on the east coast, and vica versa. These currents are most noticeable in strait
Strait
A strait or straits is a narrow, typically navigable channel of water that connects two larger, navigable bodies of water. It most commonly refers to a channel of water that lies between two land masses, but it may also refer to a navigable channel through a body of water that is otherwise not...
s such as Cook Strait and in Foveaux Strait. A notable example is French Pass
French Pass
French Pass is a narrow and treacherous stretch of water that separates D'Urville Island, at the north end of the South Island of New Zealand, from the mainland coast. At one end is Tasman Bay, and at the other end the outer Pelorus Sound leads out to Cook Strait.French Pass has the fastest tidal...
, just off the greater Cook Strait, where, despite the low tidal range, tidal streams can reach nearly eight knots.
Cook Strait
Cook StraitCook Strait
Cook Strait is the strait between the North and South Islands of New Zealand. It connects the Tasman Sea on the west with the South Pacific Ocean on the east....
has tidal flows amongst the strongest in the world, even though it has a smaller tidal range than most places in New Zealand. This is because the main M2 lunar tide component which circulates anti-clockwise around New Zealand is out of phase at each end of the strait. On the Pacific Ocean side the high tide occurs five hours before it occurs at the Tasman Sea side. On one side is high tide and on the other is low tide. The difference in sea level can drive tidal currents up to 2.5 metres per second (5 knots) across Cook Strait as well as into the Tory Channel.
A further consequence of these opposed tides is that there is almost zero tidal height change at the centre of the strait. Although the tidal surge should flow in one direction for six hours and then the reverse direction for six hours, a particular surge might last eight or ten hours with the reverse surge enfeebled. In especially boisterous weather conditions the reverse surge can be negated, and the flow can remain in the same direction through three surge periods and longer. This is indicated on marine charts for the region.
There are numerous computer model representations of the tidal flow through Cook Strait. While the tidal components are readily realizable, the residual flow is more difficult to model.
In April 2008, a resource consent was granted to Neptune Power for the installation of an experimental underwater tidal stream turbine
Tidal stream generator
A tidal stream generator, often referred to as a tidal energy converter is a machine that extracts energy from moving masses of water, in particular tides, although the term is often used in reference to machines designed to extract energy from run of river or tidal estuarine sites...
in the strait. The turbine has been designed in Britain and will be built in New Zealand at a cost $10 million. Fourteen metres in diameter and constructed of carbon fibre, it will be capable of producing one megawatt. It will be placed in eighty metres of water, 4.5 kilometres due south of Sinclair Head, in waters known as the “Karori rip”. Power from the turbine will be brought ashore at Vector's
Vector Limited
Vector Limited is a multi-network infrastructure company in New Zealand. It is the national number one provider of electricity distribution, number one provider of gas transmission and distribution, number one provider of electricity and gas metering, number two wholesaler of LPG and number three...
Island Bay substation. The turbine is a pilot, and will be sited in slower tides for testing. Neptune hopes to generate power from the unit by 2010. The company claims there is enough tidal movement in Cook Strait to generate 12 GW of power, more than one-and-a-half times New Zealand's current requirements. In practice, only some of this energy could be harnessed.
On the other side of the strait, Energy Pacifica has talked for some time about applying for resource consent to install up to ten marine turbines, each able to produce up to 1.2 MW, near the Cook Strait entrance to Tory Channel
Tory Channel
Tory Channel is one of the drowned valleys that form the Marlborough Sounds in New Zealand.Tory Channel is named after the "Tory", a pioneer ship that brought British colonists to Wellington in 1840. It lies to the south of Arapawa Island, separating it from the mainland. At its western end it...
. They claim Tory Channel has tidal flows of 3.6 metres per second with good bathymetry
Bathymetry
Bathymetry is the study of underwater depth of lake or ocean floors. In other words, bathymetry is the underwater equivalent to hypsometry. The name comes from Greek βαθύς , "deep", and μέτρον , "measure"...
and access to the electricity network. No application had been lodged by March 2011.
The power generated by tidal marine turbines varies as the cube of the tidal speed. Because the tidal speed doubles, eight times more tidal power can be produced at spring tides than at neap tides.
Kaipara Harbour
The entrance to Kaipara HarbourKaipara Harbour
Kaipara Harbour is a large enclosed harbour estuary complex on the north western side of the North Island of New Zealand. The northern part of the harbour is administered by the Kaipara District and the southern part is administered by the Rodney District...
, one of the largest harbours in the world, is a channel to the Tasman Sea
Tasman Sea
The Tasman Sea is the large body of water between Australia and New Zealand, approximately across. It extends 2,800 km from north to south. It is a south-western segment of the South Pacific Ocean. The sea was named after the Dutch explorer Abel Janszoon Tasman, the first recorded European...
. It narrows to a width of 6 kilometres (3.7 mi), and is over 50 metres (164 ft) deep in parts. On average, Kaipara tides rise and fall 2.1 metres (6.9 ft). At high tide, nearly 1000 square kilometres are flooded. Spring tidal flows reach 9 km/h (5 knots) in the entrance channel and move 1,990 million cubic meters per tidal movement or 7,960 million cubic meters daily.
In 2011, Crest Energy, a power company, received resource consent
Resource consent
A resource consent is the authorisation given to certain activities or uses of natural and physical resources required under the New Zealand Resource Management Act . Some activities may either be specifically authorised by the RMA or be permitted activities authorised by rules in plans...
to install about 200 underwater tidal turbines for the Kaipara Tidal Power Station
Kaipara Tidal Power Station
The Kaipara tidal power station is a proposed tidal power project to be located in the Kaipara Harbour. The project is being developed by Crest Energy, with an ultimate size of 200MW at a cost of $700 million....
, which would use the substantial tidal flows moving in and out every day near the harbour mouth to produce electricity for approximately 250,000 homes.
Crest plans to place the turbines at least 30 metres deep along a ten kilometre stretch of the main channel. Historical charts show this stretch of the channel has changed little over 150 years. The output of the turbines will cycle twice daily with the predictable rise and fall of the tide. Each turbine will have a maximum output of 1.2 MW, and is expected to generate 0.75 MW averaged over time.
The peak level of generation for the combined turbines is about 200 MW. This exceeds the projected peak electricity needs of Northland. It would have environmental benefits in offsetting annual carbon emissions from a thermal-based, gas turbine generator of 575,000 tonnes of carbon. The project is costed at about $600 million and to be economic would have to be scaled up rapidly to near full capacity.
However, while the Department of Conservation has approved the project, and has made substantial environmental monitoring conditions part of the consent, the project also has objectors on the grounds of claimed influences on the local ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
s and charter fishing. Appeals before the Environment Court were concluded in 2010, with a favourable decision released in February 2011.
Wave power
Wave powerWave power
Wave power is the transport of energy by ocean surface waves, and the capture of that energy to do useful work — for example, electricity generation, water desalination, or the pumping of water...
involves converting the energy in ocean surface wave
Ocean surface wave
In fluid dynamics, wind waves or, more precisely, wind-generated waves are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They usually result from the wind blowing over a vast enough stretch of fluid surface. Waves in the...
s into electricity using devices either fixed to the shore, the seabed or floating out at sea. Wave energy varies with time, depending on when and where the winds and storms that drive the waves occur. Tidal energy is more regular and predictable.
Two wind zones affect New Zealand. South-east trade wind
Trade wind
The trade winds are the prevailing pattern of easterly surface winds found in the tropics, within the lower portion of the Earth's atmosphere, in the lower section of the troposphere near the Earth's equator...
s dominate in the north, enlivened an occasional cyclone from the tropics. The rest of the country is dominated by the roaring forties
Roaring Forties
The Roaring Forties is the name given to strong westerly winds found in the Southern Hemisphere, generally between the latitudes of 40 and 49 degrees. Air displaced from the Equator towards the South Pole, which travels close to the surface between the latitudes of 30 and 60 degrees south, combines...
, a broad band of westerly winds that span the middle latitudes of the southern hemisphere. The roaring forties extend over most of the southern part of the Tasman Sea
Tasman Sea
The Tasman Sea is the large body of water between Australia and New Zealand, approximately across. It extends 2,800 km from north to south. It is a south-western segment of the South Pacific Ocean. The sea was named after the Dutch explorer Abel Janszoon Tasman, the first recorded European...
and the Southern Ocean
Southern Ocean
The Southern Ocean comprises the southernmost waters of the World Ocean, generally taken to be south of 60°S latitude and encircling Antarctica. It is usually regarded as the fourth-largest of the five principal oceanic divisions...
. These winds produce some of the stormiest seas in the world, with maximum wave heights regularly exceed 4 metres.
On average, ocean waves in New Zealand deliver about 25 kW to each metre of coastline. The west and south-west coasts have the country’s most energetic waves. Even on windless days, swells that were generated in the Southern Ocean still arrive. Less wave energy arrives at the north-east coast, because it is sheltered from the south-west waves (click the link on the right for a diagram). The amount of energy in a wave is proportional to the square of its height, so a two metre wave contains four times the energy of a one metre wave.
Wave Energy Technology - New Zealand (WET-NZ) is a Government-funded research and development collaboration programme between Industrial Research Limited
Industrial Research Limited
Industrial Research Limited is a Crown Research Institute of New Zealand. IRL provides research, development and commercialisation services aim at fostering industry development, economic growth and business expansion...
, a Crown Research Institute, and Power Projects Limited, a privately-owned Wellington-based company. The programme seeks to develop a wave energy device that generates electricity from both the kinetic and potential energy available in open ocean waves. In 2010 WET-NZ received resource consent for half-scale prototype testing at two test sites.
Timeline
- 1966: The world's first tidal barrageRance tidal power plantThe Rance Tidal Power Station is the world's first tidal power station and also the world's second biggest tidal power station. The facility is located on the estuary of the Rance River, in Brittany, France. Opened on the 26th November 1966, it is currently operated by Électricité de France, and is...
project goes online at La Rance, France, with a capacity of 240 MW.
- 2003: Seaflow, the world's first underwater turbine prototype, goes on stream off north DevonDevonDevon is a large county in southwestern England. The county is sometimes referred to as Devonshire, although the term is rarely used inside the county itself as the county has never been officially "shired", it often indicates a traditional or historical context.The county shares borders with...
with a peak capacity of 300 KW.
- 2008: The world's first commercial wave farmWave farmA wave farm or wave power farm is a collection of machines in the same location and used for the generation of wave power electricity.-Portugal:...
goes on line in Portugal. It uses PelamisPelamis wave energy converterThe Pelamis Wave Energy Converter is a technology that uses the motion of ocean surface waves to create electricity. The machine is made up of connected sections which flex and bend as waves pass; it is this motion which is used to generate electricity....
devices and has a peak capacity of 2.25 MW.
- 2008: SeaGen, the world’s first commercial scale tidal stream energy generator, goes on stream in Strangford LoughStrangford LoughStrangford Lough, sometimes Strangford Loch, is a large sea loch or inlet in County Down, Northern Ireland. It is separated from the Irish Sea by the Ards Peninsula. The name Strangford is derived ; describing the fast-flowing narrows at its mouth...
, Northern Ireland with a peak capacity of 1.2 MW.
- 2008: Crest Energy Kaipara Limited applies for resource consentResource consentA resource consent is the authorisation given to certain activities or uses of natural and physical resources required under the New Zealand Resource Management Act . Some activities may either be specifically authorised by the RMA or be permitted activities authorised by rules in plans...
to sink 200 marine turbines near the entrance of Kaipara HarbourKaipara HarbourKaipara Harbour is a large enclosed harbour estuary complex on the north western side of the North Island of New Zealand. The northern part of the harbour is administered by the Kaipara District and the southern part is administered by the Rodney District...
, with a peak capacity of 200MW.
- 2008: Neptune Power given resource consent to build a pilot turbine off Sinclair Head in Cook StraitCook StraitCook Strait is the strait between the North and South Islands of New Zealand. It connects the Tasman Sea on the west with the South Pacific Ocean on the east....
.
- 2008: Energy Pacifica applies for resource consent to install up to 10 marine turbines, each able to produce up to 1.2 MW, near the Cook Strait entrance to Tory ChannelTory ChannelTory Channel is one of the drowned valleys that form the Marlborough Sounds in New Zealand.Tory Channel is named after the "Tory", a pioneer ship that brought British colonists to Wellington in 1840. It lies to the south of Arapawa Island, separating it from the mainland. At its western end it...
.
See also
- Renewable energy in New ZealandRenewable energy in New ZealandRenewable energy in New Zealand is primarily from hydropower. In 2010, 74% of the electricity generated in New Zealand came from renewable sources, a ratio that has been falling for decades while load growth has been met primarily by natural gas-fired power stations...
- Capacity factorCapacity factorThe net capacity factor or load factor of a power plant is the ratio of the actual output of a power plant over a period of time and its potential output if it had operated at full nameplate capacity the entire time...
- Marine current powerMarine current powerMarine current power is a form of marine energy obtained from harnessing of the kinetic energy of marine currents, such as the Gulf stream. Although not widely used at present, marine current power has an important potential for future electricity generation...
- Ocean thermal energy conversionOcean thermal energy conversionOcean Thermal Energy Conversion uses the difference between cooler deep and warmer shallow or surface ocean waters to run a heat engine and produce useful work, usually in the form of electricity....
- Pelamis Wave Energy ConverterPelamis wave energy converterThe Pelamis Wave Energy Converter is a technology that uses the motion of ocean surface waves to create electricity. The machine is made up of connected sections which flex and bend as waves pass; it is this motion which is used to generate electricity....
- Salinity gradient power
- Tidal powerTidal powerTidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity....
- Wave farmWave farmA wave farm or wave power farm is a collection of machines in the same location and used for the generation of wave power electricity.-Portugal:...
- Wave powerWave powerWave power is the transport of energy by ocean surface waves, and the capture of that energy to do useful work — for example, electricity generation, water desalination, or the pumping of water...
- Wind wave
- Intermittent power sourceIntermittent power sourceAn intermittent energy source is any source of energy that is not continuously available due to some factor outside direct control. The intermittent source may be quite predictable, for example, tidal power, but cannot be dispatched to meet the demand of a power system. Examples of intermittent...
Further reading
- Marine energy in NZ report - 2008 Prepared for the Energy Efficiency and Conservation AuthorityEnergy Efficiency and Conservation AuthorityEnergy Efficiency and Conservation Authority is a New Zealand government/crown agency responsible for promoting energy efficiency and conservation....
- Marine energy fact sheet Prepared for the Energy Efficiency and Conservation Authority.
- Rickard, Graham and Hadfield, Mark (2004) Forecasting ocean "weather" Water & Atmosphere, Vol.12, No.4 - December
- Bowen M, Richardson K, Pinkerton M, Korpela A and Uddstrom M (2004) Squeezing information from an elusive ocean: surface currents from satellite imagery Water & Atmosphere, Vol.12, No.4
- Stevens, Craig (2007) Harnessing the Oceans? The Gamma Series, Royal Society of New Zealand.
- Tidal Power | Kaipara Harbour
- Tidal power rides wave of popularity
- Why Marine> – BWEA
- NZ: Chance to turn the tide of power supply Anthony Bellve, 2005.
- Harnessing the Tides: Marine Power Update 2009
External links
- Ocean Energy Review 2008
- A Beautiful Source of Energy
- Video: Chasing currents (NIWA)
- Electricity Generation from Tidal Power In New Zealand
- Oceanography: waves – J Floor Anthoni, 2000.
- WET-NZ (Wave Energy Technology - New Zealand)
- Power Projects Limited Publications