Karāpiro Power Station facts for kids
Quick facts for kids Karāpiro Power Station |
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Part of the Karāpiro Dam
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 Location of Karāpiro Power Station in New Zealand
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| Country | New Zealand |
| Location | Near Cambridge, Waikato |
| Coordinates | 37°55′26″S 175°32′21″E / 37.92389°S 175.53917°E |
| Status | Operational |
| Construction began | 1940 |
| Opening date | May 1948 |
| Owner(s) | Mercury Energy |
| Dam and spillways | |
| Type of dam | Arch dam |
| Impounds | Waikato River |
| Height | 52.4 m (172 ft) |
| Length | 335 m (1,099 ft) |
| Width (crest) | 2.4 m (7 ft 10 in) |
| Width (base) | 15.2 m (50 ft) |
| Spillways | Four |
| Reservoir | |
| Creates | Lake Karapiro |
| Surface area | 7.7 km2 (3.0 sq mi) |
| Maximum water depth | 30.5 m (100 ft) |
| Power station | |
| Type | Conventional |
| Hydraulic head | 30 m (98 ft) |
| Turbines | 3 × Kaplan |
| Installed capacity | 112.5 MW |
| Annual generation | 537 GWh |
The Karāpiro Power Station is a big power plant in New Zealand's North Island. It uses the power of water from Lake Karapiro to make electricity. It's the last of eight power stations along the Waikato River. You can find it about 30 kilometres (19 mi) south-east of Hamilton and 9 kilometres (5.6 mi) from Cambridge.
Karāpiro is a 'baseload' power station. This means it needs to keep running to make sure there's always enough water flowing in the Waikato River below the dam. It runs even when there's not much water coming into the lake or when people don't need much electricity. Usually, at least 148 cubic metres per second (5,200 cu ft/s) of water must flow out of the station. Two of its three turbines usually run to keep the river flowing. The third turbine is ready for when more power is needed or when one of the others is being fixed.
Like all the power stations on the Waikato River, Karāpiro is run by an electricity company called Mercury Energy.
Contents
History of Karāpiro Power Station
Karāpiro was the second power station built as part of the Waikato River power plan. The first was Arapuni. Building the dam and power station started in 1940. But because of World War II, there weren't enough materials or workers. This made the building process very slow. The station was finally finished in 1947, which was four years later than planned.
When Lake Karapiro was created behind the new dam, it flooded an older power station. This older station was called the Horahora Power Station. It was the very first power station ever built on the Waikato River.
The first machine that makes electricity, called a generator, started working on April 10, 1947. This was just six days after the Horahora station was flooded. However, there were some problems, so it didn't start making full power until April 21, 1947. The second generator began working on September 21, 1947. In its first year, the station made a lot of electricity. It produced over 20 percent of all the electricity needed in the North Island.
The third and last generator was ready to go in May 1948.
There's a bridge over the spillway, which is the only road to get to the turbine hall. The first bridge had a support pole in the middle. But a huge flood washed that bridge away. The new bridge you see today doesn't have that middle support.
To the left of the four spillway gates, there are three siphon tubes. These were meant to control the lake level during normal river flow. The spillway gates were only supposed to be used in very big floods. But the siphon tubes didn't work quite right. They were supposed to stop the water flow with a blast of air, but this never happened properly. So, the spillway gates ended up being used more often to control the lake level.
In 2019, Mercury Energy announced a big plan to make the power station better. Between 2022 and 2025, they replaced all three original turbines and generators. This upgrade increased the power station's ability to make electricity. It went from 96 megawatts (MW) to 112.5 MW. This means it can now produce more electricity each year. The average yearly production is expected to go up from 505 gigawatt-hours (GWh) to 537 GWh.
How Karāpiro Makes Electricity
The main building where electricity is made, called the powerhouse, is on the northern side of the river. There's also a special tunnel and a spillway on this side. The river is held back by a strong concrete arch dam behind the powerhouse. The electricity substation, which helps send the power out, is on the southern side of the river.
Water from Lake Karapiro flows down through large pipes called penstocks. This water then spins three special machines called Kaplan turbines. Each turbine is connected to a generator. Each generator can make up to 37.5 megawatts of power at 11,000 volts. To make just 1 megawatt of power, about 3,770 litres (830 imp gal; 1,000 US gal) of water must flow through the turbines every second!
Karāpiro Power Station is controlled from far away. It's managed by Mercury Energy's Waikato River control room in Hamilton.
Sending the Power Out
When the power station was built, a special power line was also put in place. This line carries 110,000 volts of electricity from Karāpiro to a substation in Hamilton. This line started working on March 29, 1947. It's still used today to connect Karāpiro to New Zealand's main electricity network.
There are also other 110,000-volt lines that connect Karāpiro to substations in Te Awamutu and Hinuera. These power lines are owned and managed by a company called Transpower. Transpower is in charge of New Zealand's national electricity grid.
See also
- Electricity sector in New Zealand
- List of power stations in New Zealand
