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96-534: The Tiwai Point Aluminium Smelter is an aluminium smelter owned by Rio Tinto Group (79.36%) and the Sumitomo Group (20.64%), via a joint venture called New Zealand Aluminium Smelters (NZAS) Limited. The facility, New Zealand's only aluminium smelter, is at Tiwai Point , near Bluff . It imports alumina and processes it into primary aluminium. The plant's alumina is supplied from refineries in Queensland and

192-476: A state-owned enterprise , although some lines are owned by local distribution companies and leased to Transpower. In total, the national grid contains 11,803 kilometres (7,334 mi) of high-voltage lines and 178 substations . Much of New Zealand’s electricity generation is hydroelectric , the majority of which is from power stations on lakes and rivers in the lower half of the South Island , while most of

288-474: A batch process, with the aluminium deposited at the bottom of the pots and periodically siphoned off. Particularly in Australia these smelters are used to control electrical network demand, and as a result power is supplied to the smelter at a very low price. However power must not be interrupted for more than 4–5 hours, since the pots have to be repaired at significant cost if the liquid metal solidifies. Aluminium

384-424: A by-product. The basic reaction is Al 2 O 3 → 2Al + 3"O". Oxygen equivalents react at the red-hot carbon anode, forming a mixture of carbon monoxide (that subsequently becomes carbon dioxide) and carbon dioxide. For one tonne of aluminium, 1.55 tonnes of CO result, becoming 2.4 tonnes of CO 2 . However, if all the oxygen were instead directly converted to CO 2 , then only 1.56 tonnes of CO 2 would result. At

480-481: A ceramic matrix of nickel ferrite. Unfortunately, as the number of anode components increases , the structure of the anode becomes more unstable. As a result. cermet anodes also suffer from corrosion issues during reduction. Aluminium smelting is highly energy intensive, and in some countries is economical only if there are inexpensive sources of electricity. In some countries, smelters are given exemptions to energy policy like renewable energy targets . To reduce

576-698: A connection between the North and South Island grids. The HVDC link connects to the South Island 220 kV grid at Benmore Power Station in South Canterbury . The power is transmitted via overhead transmission lines over 535 kilometres (332 mi) to Fighting Bay in Marlborough . From here, it crosses the Cook Strait via submarine power cables for 40 km to Oteranga Bay, west of Wellington . At Oteranga Bay,

672-461: A contract for electricity supply with Meridian Energy for the continuous supply of 572 megawatts for the period 2013 to 2030. The price it pays for electricity was renegotiated in 2015 and 2021. The 2021 agreement was reported to have reduced the price from 5.5 to 3.5c per kWh, with the smelter scheduled to close in 2024. Aluminium smelting via the Hall–Héroult process produces carbon dioxide as

768-496: A melting temperature of 1010 °C, and it forms a eutectic with 11% alumina at 960 °C. In industrial cells the cryolite ratio is kept between 2 and 3 to decrease its melting temperature to 940–980 °C. Cathode: Carbon cathodes are essentially made of anthracite, graphite and petroleum coke, which are calcined at around 1200 °C and crushed and sieved prior to being used in cathode manufacturing. Aggregates are mixed with coal-tar pitch, formed, and baked. Carbon purity

864-487: A mixture of CO and CO 2 is produced. Thus the idealised overall reactions may be written as By increasing the current density up to 1 A/cm , the proportion of CO 2 increases and carbon consumption decreases. As three electrons are needed to produce each atom of aluminium, the process consumes a large amount of electricity. For this reason aluminium smelters are sited close to sources of inexpensive electricity, such as hydroelectric . Electrolyte: The electrolyte

960-580: A new 220 kV cross-harbour underground cable link between Pakuranga, Penrose , Hobson Street ( Auckland CBD ), Wairau Road ( North Shore City ), and Albany . The route crosses the Waitematā Harbour in a special cableway installed underneath the Auckland Harbour Bridge . The Wairakei ring is a set of transmission lines north of Lake Taupō linking Wairakei with Whakamaru . These lines connect several hydro and geothermal power stations into

1056-703: A news release in January 2012, the Commerce Commission reported that Transpower was planning to invest $ 5 billion over the next 10 years in upgrades of critical infrastructure. Initial use of electricity in New Zealand was associated with mining. The first industrial hydro-electric power plant was established at Bullendale in Otago in 1885, to provide power for a 20 stamp battery at the Phoenix mine. The plant used water from

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1152-459: A paste with a doughy consistency. This material is most often vibro-compacted but in some plants pressed. The green anode is then sintered at 1100–1200 °C for 300–400 hours, without graphitization , to increase its strength through decomposition and carbonization of the binder. Higher baking temperatures increase the mechanical properties and thermal conductivity, and decrease the air and CO 2 reactivity. The specific electrical resistance of

1248-405: A quantity of fluoride waste: perfluorocarbons and hydrogen fluoride as gases, and sodium and aluminium fluorides and unused cryolite as particulates. This can be as small as 0.5 kg per tonne of aluminium in the best plants in 2007, up to 4 kg per tonne of aluminium in older designs in 1974. Unless carefully controlled, hydrogen fluorides tend to be very toxic to vegetation around

1344-530: A resource consent application to the Taupō District Council to build a series reactor on the Wairakei to Whakamaru A line at Ātiamuri . The reactor will re-balance the electricity flow between the A and C lines to allow an extra 500 MW to be transmitted towards Whakamaru, especially with the construction of Tauhara Power Station (152 MW) and Harapaki Wind Farm (176 MW). Transmission in

1440-541: A result, the Government announced it would subsidise Rio Tinto to keep the Tiwai Point smelter operating in the short term, garnering criticism from business commentators and opposition politicians. However, on 2 April 2013, John Key said Rio Tinto had rejected the Government's offer, preferring a "longer-term deal than the Government was prepared to offer". John Key stated that if the smelter couldn't sustain itself financially,

1536-406: A seven-hour outage of the inner city, and an October 2009 incident where a forklift accidentally knocked out power to northern Auckland and the whole of Northland. In 2008, Transpower turned its attention to the need for replacement and refurbishment of the aging grid assets. A new strategy was developed that focussed on advancing investment proposals to increase the capacity of the grid. Some of

1632-423: A specific situation in aluminium smelting and depending on the type of anode, aluminium smelting is divided in two different technologies; “Soderberg” and “prebaked” anodes. Anodes are also made of petroleum coke, mixed with coal-tar-pitch, followed by forming and baking at elevated temperatures. The quality of anode affects technological, economical and environmental aspects of aluminium production. Energy efficiency

1728-413: A strategy known internally as “the glide path”, and minimised spending on the grid and renewing assets. The rationale for this strategy was based on the expectation that there would be widespread installation of distributed generation (electricity generated close to where it is used), and that this would significantly reduce the need to expand and renew the grid. However, by 2003, it had become clear that

1824-405: Is a molten bath of cryolite (Na 3 AlF 6 ) and dissolved alumina. Cryolite is a good solvent for alumina with low melting point, satisfactory viscosity, and low vapour pressure. Its density is also lower than that of liquid aluminium (2 vs 2.3 g/cm ), which allows natural separation of the product from the salt at the bottom of the cell. The cryolite ratio (NaF/AlF 3 ) in pure cryolite is 3, with

1920-637: Is not as stringent as for anode, because metal contamination from cathode is not significant. Carbon cathode must have adequate strength, good electrical conductivity and high resistance to wear and sodium penetration. Anthracite cathodes have higher wear resistance and slower creep with lower amplitude [15] than graphitic and graphitized petroleum coke cathodes. Instead, dense cathodes with more graphitic order have higher electrical conductivity, lower energy consumption [14], and lower swelling due to sodium penetration. Swelling results in early and non-uniform deterioration of cathode blocks. Anode: Carbon anodes have

2016-408: Is now required to give at least two years notice of closure, and there are penalty payments of at least $ 180 million for early closure. The new contracts also include requirements for the smelter to provide a demand response capability to reduce demand by up to 185   MW during times when the electricity system is under stress. The supply new contracts were expected to provide greater certainty for

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2112-425: Is produced by electrolytic reduction of aluminium oxide dissolved in molten cryolite . At the same time the carbon electrode is oxidised, initially to carbon monoxide Although the formation of carbon monoxide (CO) is thermodynamically favoured at the reaction temperature, the presence of considerable overvoltage (difference between reversible and polarization potentials) changes the thermodynamic equilibrium and

2208-430: Is related to the nature of anode materials, as well as the porosity of baked anodes. Around 10% of cell power is consumed to overcome the electrical resistance of prebaked anode (50–60 μΩm). Carbon is consumed more than theoretical value due to a low current efficiency and non-electrolytic consumption. Inhomogeneous anode quality due to the variation in raw materials and production parameters also affects its performance and

2304-615: The Northern Territory of Australia . Around 90 per cent of the aluminium produced at NZAS is exported, mainly to Japan. The smelter was opened in 1971 following the construction of the Manapouri Power Station by the New Zealand government to supply it with electricity. It uses 13 percent of New Zealand's electricity, and is reported to account for 10 percent of the Southland region's economy. Rio Tinto has threatened to close

2400-648: The Resource Management Act to "call in" Transpower's proposal, because of its national significance. He established a Board of Inquiry to consider the designations and resource consents required for the project. The Board of Inquiry gave its final approval for the project in September 2009. A further grid upgrade project was completed to increase supply security to central Auckland, the North Shore, and further afield to Northland . This project involved building

2496-512: The national grid is about 570  MW . Most of the energy for the smelter is supplied from the Manapouri hydroelectric power station, via two double circuit 220 kV transmission lines. The facility is the largest electricity consumer in New Zealand. It uses about one third of the total electricity consumed in the South Island and 13% of the total electricity nationwide, equivalent to around 680,000 households. New Zealand Aluminium Smelters had

2592-567: The 220 kV grid, and also connect smaller power stations to the grid. Auckland's power grid has suffered several famous blackouts , such as the 5-week long 1998 Auckland power crisis caused by failure of cables in the Mercury Energy distribution network. Because of the location of the major load centres in Auckland city, the geography of the Auckland isthmus , and the historical development of

2688-715: The Arapuni system stretched from the Hibiscus Coast in the north to Ōtorohanga and Rotorua in the south and Ōpōtiki in the east; the Mangahao-Waikaremoana system stretched from Wellington north to Gisborne and west to Wanganui ; and the Coleridge system stretched along coastal Canterbury from Rangiora to Oamaru . During the Depression years, the Arapuni and Mangahao-Waikaremoana systems were connected via Taranaki and

2784-486: The Clutha and Upper Waitaki area to enable more northwards power transmission in this region. The decision to start the remaining projects was in response to speculation about the possible closure of the Tiwai Point smelter. The projects were to be funded by agreements with Contact Energy and Meridian Energy. The purpose was to ensure that if the smelter closed, there was sufficient transmission capacity to ensure that energy from

2880-477: The Government to preserve the smelter in some way. On 14 January, Rio Tinto and Meridian Energy agreed to continue Tiwai Point's operations until December 2024, with 100   MW of its baseline power to be supplied by Contact Energy . The price reduction was later reported to have been from 5.5c to 3.5c per kWh, but with no change to transmission fees. In July 2022, NZ Aluminium Smelters announced that it would seek new power supplies to try and remain open beyond

2976-406: The Government would make no further contribution to support it, which he reiterated in 2015 following speculation that Rio Tinto was seeking to sell the smelter. In 2016, an analyst at First New Zealand Capital (FCNZ) utilities said that the smelter was thought to be breaking even, helped by favourable currency rates and low alumina prices. In October 2019, Rio Tinto announced a strategic review of

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3072-601: The HVDC line converts back to overhead lines to cover the last 35 km, with the line terminating and connecting to the North Island's 220 kV grid at Haywards in Lower Hutt . The main reason for a power system connection between the two islands is due to New Zealand's geography and demographics. The South Island has a large number of rivers suitable for hydroelectricity generation, however 75% of New Zealand's population lives in

3168-580: The Lower South Island within the next few years. The proposal aimed to facilitate competition in the generation market, supporting renewable generation and improve the security of supply to the lower South Island region. The proposal was approved in April 2010. Transpower’s proposal was to upgrade five transmission lines between Roxburgh and the Waitaki Valley namely: In November 2011, Transpower reviewed

3264-552: The Manapouri Power Station attracted controversy for its environmental effects, with over 264,000 New Zealanders signing the Save Manapouri petition. With a supply of electricity to be available, ConZinc built the Tiwai Point smelter, opening in 1971. The original ownership was 50% Comalco , 25% Sumitomo Chemical Company and 25% Showa Denko KK. Tiwai Point is the only aluminium smelter in New Zealand. In December 1980,

3360-546: The North Island was constructed in 1913-14, connecting the Horahora hydro station to Waikino to meet the power requirements of the stamp battery 5 miles (8.0 km) further on at the Waihi gold mine. The line length between Horahora and Waikino was 45 miles (72 km), and the transmission voltage was 50 kV, which was to set a precedent for North Island transmission voltage for many years. The first major transmission line in

3456-605: The North Island. HVDC was chosen for the inter-island connection because it is a more practical and economical solution for long distance transmission, particularly where significant lengths of cable are required. In May 2008, Transpower submitted a Grid Upgrade Plan proposal to the Electricity Commission for a major project to upgrade the HVDC system including: On 25 September 2008, the Commission issued its final approval for

3552-594: The RenewAl brand, which according to NZAS guarantees that less than four tonnes of CO 2 is emitted for every tonne of aluminium produced. Significant amounts of hazardous waste have been stored at the site, mainly spent cell liner (also known as spent pot lining) containing compounds including fluoride and cyanide. Estimates of the waste stockpiled at the site range up to a quarter of million tonnes. It has been described as uncontrolled, unconsented and untreated in complete absence of any regulatory oversight or recognition, being

3648-611: The South Island was constructed by the government as part of the Coleridge hydro station development and was commissioned in 1914. Two transmission lines operating at 66 kV carried the power from Coleridge over a distance of 65 miles (105 km) to Addington in Christchurch . Following World War I, regional networks began to develop using 110 kV transmission lines to connect towns and cities with remote hydroelectric schemes. By 1930, there were three major transmission networks:

3744-577: The South Island with Haywards in the North Island. The original link used mercury arc valve converters and was rated at 600 MW. It was the first HVDC link to be commissioned in the Southern Hemisphere. In 1978, the Electricity Division of the Ministry of Energy was established to integrate the state-owned electricity generation and transmission business with the oil, gas and coal businesses of

3840-666: The Statistical Review of Comalco's New Zealand Activities, page 22 of the 1993 Annual Report. The smelter production is in tonnes of saleable metal, the aluminium price is the average London Metal Exchange 3 month in US$ /tonne, the Nett Profit/Loss is after tax and NZ$ . The employee count includes contract employees and the full-time equivalent of part-time employees. Comalco-CHH Aluminium employees are not included from 1990; 425 were employed in 1993. The smelter's power demand from

3936-675: The Tiwai Point Aluminium Smelter, including a wide range of issues associated with closure. The NZAS chief executive Stew Hamilton said that they had been losing money for the previous 12 months, and that options ranged from operating at the status quo, which would require cheaper power, to closure of the plant. During New Zealand's lockdown for the Covid-19 pandemic , the smelter was deemed an essential service and exempt from restrictions. On 31 March 2020, Rio Tinto announced that it would close potline four, to ensure it could cope with

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4032-408: The alumina recovered from the bauxite into aluminium. In 1960, ConZinc reached an agreement with the government for it to build a smelter and power station using the hydroelectric capacity of Lake Manapouri and Lake Te Anau. In 1963, ConZinc decided not to build the power station, and following that decision the government decided to construct it, with power first being generated in 1969. Construction of

4128-507: The cell stability. Prebaked consumable carbon anodes are divided into graphitized and coke types. For manufacturing of the graphitized anodes, anthracite and petroleum coke are calcined and classified. They are then mixed with coal-tar pitch and pressed. The pressed green anode is then baked at 1200 °C and graphitized. Coke anodes are made of calcined petroleum coke, recycled anode butts, and coal-tar pitch (binder). The anodes are manufactured by mixing aggregates with coal tar pitch to form

4224-537: The circuits from the existing switchyard to the new GIS switchyard, to improve network resilience. The project was approved in August 2007. On 30 October 2009 at around 8:00am, power was cut to the whole of Northland and most of the northern half of Auckland, affecting 280,000 consumers (14.5% of the country). A forklift carrying a shipping container accidentally hit one of the Otahuhu to Henderson 220 kV circuits while

4320-472: The city indirectly. On 11 December 2006, the Electricity Commission (NZ) received an application from Transpower for the establishment of a new 220 kV gas insulated switchgear (GIS) facility adjacent to but geographically separate from the existing outdoor 220 kV switchyard at Otahuhu. This project was described as the Otahuhu substation diversity project, and included transferring approximately half of

4416-479: The closure, and 1600 jobs indirectly connected to the smelter would also be under threat. The decision followed a 25% decrease in aluminium prices over the prior 18 months, and increasing power costs. At that time, Rio Tinto said it intended to close the smelter in August 2021. The smelter featured in the 2020 general election , with many parties pledging to keep – or try to keep – the smelter running for at least some time. The National Party announced that, if it won

4512-571: The coke-type anodes is higher than that of the graphitized ones, but they have higher compressive strength and lower porosity. Soderberg electrodes (in-situ baking), used for the first time in 1923 in Norway, are composed of a steel shell and a carbonaceous mass which is baked by the heat being escaped from the electrolysis cell. Soderberg Carbon-based materials such as coke and anthracite are crushed, heat-treated, and classified. These aggregates are mixed with pitch or oil as binder, briquetted and loaded into

4608-527: The company. Prime Minister and Labour leader Jacinda Ardern initially said that a Government project to widen the Homer Tunnel would provide some local jobs, but that no one industry could offset the job losses. Later, Labour announced that it would negotiate to extend the life of the smelter by three to five years if elected, seeking to protect jobs in the short term to provide time for the community to consider alternative options. Local politicians also lobbied

4704-570: The construction of a new 220/400 kV transmission line between Whakamaru and Pakuranga . Transpower submitted its initial investment proposal for the project in May 2005. The regulatory process for investment approval for the project created significant tension between Transpower and the Electricity Commission, and led to political pressure for progress, to ensure the security of electricity supply to Auckland. There were strong protests against

4800-469: The delivery schedule of this project in the absence of significant new generation being committed in the lower South Island. From that review it was confirmed that the Roxburgh to Clyde and Aviemore to Livingstone sections of work would proceed as planned but that other sections would be the subject of a further review on or before June 2013. In 2019, Transpower restarted the remaining upgrade work on lines in

4896-422: The desirable properties of both; the electrical conductivity and toughness of the metal and stability of the ceramic. These anodes often consist of a combination of the above metal and ceramic materials. In industry, Alcoa and Rio Tinto have formed a joint venture, Elysis, to commercialize inert anode technology developed by Alcoa. The inert anode is a cermet material, a metallic dispersion of copper alloy in

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4992-435: The election, it would keep the smelter running for at least five years and would facilitate negotiations between Rio Tinto, power companies and Transpower to achieve a more cost-competitive environment. New Zealand First leader Winston Peters said that keeping the smelter open would be a bottom line in any coalition negotiations, and that he had a 20-year plan for the smelter. The Government ruled out any further bailouts of

5088-581: The electricity demand is in the North Island , in particular, the Auckland region . Consequently, large amounts of electricity need to be transmitted long distances from power stations to electricity users, including transmission across Cook Strait through the HVDC Inter-Island link. Investments in new transmission are regulated by the Electricity Commission and the Commerce Commission . In

5184-461: The electricity sector as a whole, and lead to new generation proposals going ahead. 46°35′21″S 168°23′02″E  /  46.589184°S 168.384022°E  / -46.589184; 168.384022 Aluminium smelting This is an electrolytic process, so an aluminium smelter uses huge amounts of electric power; smelters tend to be located close to large power stations, often hydro-electric ones, in order to hold down costs and reduce

5280-474: The electrolyte, and are therefore not consumed during the reduction process. Because the anode does not contain carbon, carbon dioxide is not produced. Through a review of literature, Haradlsson et al. found that inert anodes reduced the green house gas emissions of the aluminum smelting process by approximately 2 tonnes CO2eq/ tonne Al. Ceramic anode materials include Ni-Fe, Sn, and Ni-Li based oxides. These anodes show promise as they are extremely stable during

5376-500: The energy cost of aluminum reduction up to 30% by lowering the voltage needed for reduction to occur. Applying these two technologies at the same times allows the anode-cathode distance to be minimized which decreases restive losses. National Grid (New Zealand) The National Grid is the nationwide system of electric power transmission in New Zealand . The grid is owned, operated and maintained by Transpower New Zealand ,

5472-540: The energy cost of the smelting process, alternative electrolytes such as Na3AlF6 are being investigated that can operate at a lower temperature. However, changing the electrolyte changes the kinetics of the liberated oxygen from the Al 2 O 3 ore. This change in bubble formation can alter the rate the anode reacts with Oxygen or the electrolyte and effectively change the efficiency of the reduction process. Inert anodes, used in tandem with vertical electrode cells, can also reduce

5568-614: The first South Island 220 kV line was commissioned between Roxburgh and Islington in July 1956. In 1958 the State Hydro-electric Department was changed into the NZ Electricity Department (NZED), reflecting the development of thermal generation to supplement the hydro-electric schemes. The electricity systems of the two islands were joined together by the HVDC Inter-Island link in 1965, connecting Benmore in

5664-496: The glide path strategy was unsustainable. Many of the grid assets were approaching the end of their useful life, and at the same time had to carry higher loads than previously experienced to meet the demands of a growing economy and population. Transpower identified that the grid backbone was nearing its capacity and that investment was needed in many other parts of the grid. The transmission lines into and around Auckland were of particular concern, having remained largely unmodified since

5760-581: The government announced a project that would build a second smelter at Aramoana , but opposition from the public, changes in the aluminium market, and the loss of a commercial partner meant the project did not go ahead. The smelter uses the Hall–Héroult process to convert alumina (aluminium oxide) to elemental aluminium. Bauxite is mined in Australia and refined into alumina before being shipped to New Zealand. The smelter consists of three lines of P69 technology cells, with 208 cells each (i.e. 624 total), and one line of 48 CD200 technology cells. The third P69 Line

5856-662: The government owned energy sector. In 1987, the Electricity Corporation of New Zealand (ECNZ) was established as a State Owned Enterprise , and in 1988, the transmission business was established as a subsidiary within ECNZ, taking the name Transpower New Zealand . The late 1980s and early 1990s saw the completion of the 220 kV backbone, with the last line connecting Stratford in Taranaki to Huntly in Waikato. The HVDC Inter-Island

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5952-564: The government was not interested in keeping it open long-term. Much media commentary in April 2013 focused on the impact of closure on both domestic power prices and share prices when the State-owned enterprise and electricity generator Mighty River Power would be partially sold off to private investors. NZAS produced a report which claimed that if the smelter closed, there would be a permanent loss to Southland's GDP of about 7-8 percent and that 2-3 percent of Southland's population could move out of

6048-447: The grid, all but one of the transmission lines from the south converge on Otahuhu substation creating limited redundancy in the network. A major transmission failure occurred at Otahuhu substation on 12 June 2006, leading to the 2006 Auckland Blackout . It started at 8:30 am local time, with most areas of Auckland regaining power by 2:45 pm local time. It affected some 230,000 customers directly and at least 700,000 people in and around

6144-596: The largest stockpile of hazardous waste in Australasia and posing an estimated $ NZ300 million liability. Rio Tinto has committed $ NZ4 million towards the removal of all aluminium dross and ouvea premix. 8,000 tonnes of aluminium dross from the smelter were stored without consent in Mataura from 2015 until 2021. If flooded by the nearby Mataura river, this "ouvea premix" would have released ammonia gas. The New Zealand government subsidised New Zealand Aluminium Smelters to remove

6240-529: The last regions to join the national grid system when a transmission line between Inangahua and Stoke was completed in 1956. The construction of the 220 kV network began in the early 1950s, initially connecting Auckland and Wellington to the Waikato River dams, and Christchurch to Roxburgh Dam . The first North Island 220 kV line was commissioned between Maraetai and Whakamaru in October 1952, and

6336-479: The late 1970s while the city's population has doubled. The aging and near-capacity infrastructure has caused several high profile failures, including the 1998 Auckland power crisis , where aging cables caused a cascading failure and blacking out the CBD for five weeks (strictly speaking, this was a distribution system failure, not a transmission failure); the 2006 Auckland Blackout , where a corroded shackle broke and caused

6432-419: The main grid upgrade projects are described in the following section. The backbone of New Zealand's national grid is the network of 220 kV transmission lines in each of the North and South Islands, which links the major power stations and the country's major cities. Supplementing this are 110 kV, 66 kV and 50 kV transmission lines, which supply provincial towns and cities with electricity from

6528-435: The national grid, enabling their power to be exported to the major centres of electricity demand. A number of new geothermal power stations are being built or are planned for the area, and a higher capacity line is needed to transport their power to market. In December 2008, Transpower submitted a Grid Upgrade proposal to the Electricity Commission to build a new double circuit 220 kV line, Wairakei to Whakamaru C, to replace

6624-645: The nearby Skippers Creek, a tributary of the Shotover River . There was a two-mile-long (3.2 km) transmission line from the generating station to the stamping battery. The first transmission line constructed by the government was associated with the Okere Falls Power Station near Rotorua. Electricity was transmitted at 3.3 kV over a 13-mile (21 km) route to Rotorua, and was used to drive sewage pumps, and some public buildings including five thermal baths. The first major transmission line in

6720-520: The other circuit was out for maintenance, leaving the region supplied by four low capacity 110 kV circuits. Power was restored to the entire region around 11:00am. The North Island Grid Upgrade (NIGU) between the southern Waikato region and central Auckland was a large and controversial transmission project. This project involved a 220 kV switching station at Drury, upgrading the existing 220 kV Otahuhu to Whakamaru C line, new capacitors at Otahuhu, Penrose, and Hepburn Road substations, and

6816-400: The overall carbon footprint . Smelters are often located near ports, since many smelters use imported alumina. The Hall-Héroult electrolysis process is the major production route for primary aluminium. An electrolytic cell is made of a steel shell with a series of insulating linings of refractory materials. The cell consists of a brick-lined outer steel shell as a container and support. Inside

6912-642: The plants. The Soderberg process which bakes the Anthracite/pitch mix as the anode is consumed, produces significant emissions of polycyclic aromatic hydrocarbons as the pitch is consumed in the smelter. The linings of the pots end up contaminated with cyanide-forming materials; Alcoa has a process for converting spent linings into aluminium fluoride for reuse and synthetic sand usable for building purposes and inert waste. Inert anodes are non-carbon based alternatives to traditional anodes used during aluminum reduction. These anodes do not chemically react with

7008-406: The principal formulation and the fundamental reactions occurring on their surface are the same. An aluminium smelter consists of a large number of cells (pots) in which the electrolysis takes place. A typical smelter contains anywhere from 300 to 720 pots, each of which produces about a ton of aluminium a day, though the largest proposed smelters are up to five times that capacity. Smelting is run as

7104-483: The proposed transmission line during the initial planning and regulatory approval process from those most directly affected. Many individuals and communities living near the proposed route expressed concerns about the visual impact of the line, possible health effects, and the devaluation of their properties. A particular point of concern was that the proposed transmission towers were to be up to 70 metres (230 ft) in height. Cabinet Minister Pete Hodgson used powers under

7200-407: The reduction process at normal operating temperatures (~1000 °C), ensuring that the Al is not contaminated. The stability of these anodes also allows them to be used with a range of electrolytes. However, ceramic anodes suffer from poor electrical conductivity and low mechanical strength. Alternatively metal anodes boast high mechanical strength and conductivity but tend to corrode easily during

7296-430: The reduction process. Some material systems that are used in inert metal anodes include Al-Cu, Ni-Cu, and Fe-Ni-Cu systems. Additional additives such as Sn, Ag, V, Nb, Ir, Ru can be included in these systems to form non reactive oxides on the anode surface, but this significantly increases the cost and embodied energy of the anode. Cermet anodes are the combination of a metal and ceramic anode, and aim to take advantage of

7392-421: The region is a mix of core grid (220  kV) and smaller (110  kV) lines. The 220  kV grid supplies major loads at Dunedin , Invercargill and Tiwai Point , from generation at Roxburgh and Manapouri . The 110  kV lines supply smaller load centres throughout the region including some larger industrial loads (Brydone fibreboard plant and Edendale dairy factory). Power transfer into and out of

7488-490: The region is primarily through the two Invercargill–Roxburgh circuits. There are two issues in this region: The 220  kV and 110 kV circuits were also not inter-connected at Gore . A Lower South Island transmission reliability investment proposal was approved by the Electricity Commission in September 2010. The project has a maximum approved cost of $ 62.4m, and was originally scheduled to be completed by 2016. The scope includes: The new interconnection at Gore

7584-417: The region. Invercargill mayor Tim Shadbolt said it was a myth that closing the smelter would result in lower power prices for others, and vowed to keep it open. In August 2013, the New Zealand government agreed to make a $ 30 million payment to NZAS as a deal to support the smelter and to save jobs, in exchange for agreeing the smelter could be closed before January 2017. Finance Minister Bill English said

7680-418: The restrictions at the plant that are needed because of the coronavirus pandemic . Potline 4 originally opened in 1996 but was turned off for six years between 2012 and 2018 before reopening as a result of an uptick in aluminium prices and a new deal with power supplier Meridian. Potline four is smaller than the smelter's other three potlines, producing about 31,000 tonnes of aluminium a year, about 9 per cent of

7776-409: The scheduled 2024 closure date, this time suggesting a new strategy of seeking power from suppliers other than Meridian Energy. After two years of negotiations, new supply contracts were agreed in May 2024 between the smelter and three electricity suppliers: Mercury, Contact Energy and Meridian Energy. The contracts are for a twenty year term, and include some changes in contract conditions. The smelter

7872-418: The shell, cathode blocks are cemented together by ramming paste. The top lining is in contact with the molten metal and acts as the cathode. The molten electrolyte is maintained at high temperature inside the cell. The prebaked anode is also made of carbon in the form of large sintered blocks suspended in the electrolyte. A single Soderberg electrode or a number of prebaked carbon blocks are used as anode, while

7968-437: The shell. Temperature increases bottom to the top of the column and in-situ baking takes place as the anode is lowered into the bath. Significant amount of hydrocarbons are emitted during baking which is a disadvantage of this type of electrodes. Most of the modern smelters use prebaked anodes since the process control is easier and a slightly better energy efficiency is achieved, compared to Soderberg anodes. The process produces

8064-417: The single circuit Wairakei to Whakamaru B line. that was intended to help facilitate the connection of up to 1000 MW of new generation expected in the region over the next 5–7 years. The Commission announced their intention to approve the investment on 20 February 2009. Transpower completed the project in mid-2013. The estimated cost of the project was $ 141 million. In October 2021, Transpower submitted

8160-453: The smelter is most dependent on prices for electricity, alumina and the finished aluminium as well as the New Zealand dollar. Between 2008 and 2013, aluminium prices fell by more than 30 percent. Rio Tinto threatened to close the Tiwai Point smelter if it could not get a cheaper deal for electricity from retailer Meridian , or the Government failed to give it a substantial subsidy to cover losses. In 2013, Rio Tinto again threatened to shut down

8256-583: The smelter several times, for example in 2013 and 2020, but to date closure has been deferred after renegotiation of the price it pays for electricity. As of January 2021, Rio Tinto announced that it had reached an agreement with its power supplier Meridian Energy to pay a lower price in return for keeping the smelter running until December 2024. In July 2022, NZAS signalled that it would once again offer to remain open if it could secure new power agreements on favourable terms. In May 2024, new twenty year electricity contracts were agreed with three suppliers, allowing

8352-485: The smelter to remain open until 2044. There are concerns regarding the environmental legacy of waste stockpiled at the site, near to an eroding beachline. In 1955, a geologist working for Consolidated Zinc Proprietary Ltd (ConZinc) identified a commercial deposit of bauxite in Australia on the west coast of Cape York Peninsula . The company investigated sources of large quantities of cheap electricity needed to reduce

8448-472: The smelter unless it was able to continue re-negotiating favourable electricity prices with Meridian Energy. Meridian was one of several state-owned enterprises which at the time were proposed for privatisation by the John Key National Government. The government wanted to get the maximum possible sale price, which would potentially conflict with Rio Tinto's desire for low electricity prices. As

8544-461: The smelter's total output, and consumes about 50 MW of electricity. On 9 July 2020, Rio Tinto again announced that it would close the smelter. The company said that it would wind down operations and end New Zealand Aluminium Smelters Limited after a strategic review that "showed the business is no longer viable given high energy costs and a challenging outlook for the aluminium industry". The company stated that 1000 jobs would be directly lost from

8640-493: The southern hydro-electric generating stations could be transmitted north. The restarted projects included tower strengthening and the installation of duplex conductor on the Roxburgh - Livingstone circuits during the summers of 2020-2021 and 2021-2022. The new work also included upgrade of the Cromwell-Twizel circuits. The HVDC Inter-Island link is New Zealand's only high voltage direct current (HVDC) system, and provides

8736-414: The stated rate of 1.97 tonnes of carbon dioxide per tonne of aluminium, the production of 272,000 tonnes of aluminium in a year would emit 535,000 tonnes of carbon dioxide. In 2007, Tom Campbell, the chief executive of majority owner Rio Tinto Aluminium NZ, said that the smelter was among the top 5% of the world's 250 aluminium smelters in terms of low emissions. Metal produced by Tiwai Point is marketed under

8832-489: The system extended north to Whangārei . The Coleridge system extended south to link with Dunedin 's Waipori system and Southland's Monowai system, inland from Oamaru to the Waitaki Dam , and west over Arthur's Pass to Greymouth . The State Hydro-electric Department was established in 1946 to oversee the development of electricity generation and transmission to meet rapidly growing demand. Nelson and Marlborough were

8928-405: The toxic waste, which was achieved by July 2021. NZAS reports that the facility employs 800 full-time employees and contractors and indirectly creates jobs for 3,000 people. The smelter is reported to account for 10 percent of the Southland region's economy. Tiwai Point has frequently operated at a loss, such as in 2012 when it lost $ 548 million. Analysts have commented that the profitability of

9024-426: Was also upgraded by increasing the operating voltage of the lines, replacing the original Cook Strait submarine cables and installing a new thyristor pole in parallel to the existing mercury arc valve converter equipment to double its capacity to 1240 MW. In 1994, Transpower was separated from Electricity Corporation of New Zealand to become a State-Owned Enterprise in its own right. In 1997, Transpower adopted

9120-456: Was built in the early 1980s as part of the Muldoon government 's " Think Big " projects. The smelter produces the world's purest aluminium – 99.98 percent pure – and is one of two smelters in the world producing ultrahigh purity aluminium. In 2011 the smelter produced 354,030 saleable tonnes of aluminium, which was its highest ever output at the time. In 2015, it produced 335,290 tonnes. Taken from

9216-408: Was constructed during 2017-2018 On 30 November 2009, Transpower submitted Part V of the 2009 Grid Upgrade Plan (2009 GUP), Lower South Island Renewables Investment Proposal, with approval sought for up to $ 197 million. It was an economic, rather than a reliability investment proposal. At the time of submission, it was expected that a large amount of new renewable generation would be commissioned in

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