INFO AT A GLANCE:
1-litre camo-painted Sistema in the same vicinity as the original cache, containing a logbook and laminated cache note. You will need to bring your own pen. Access from Ashton Fitchett Drive. Gates open 8am-5pm in winter, 8am-8pm in summer. Good views, historical site, bring camera, 30 second walk to cache from wind turbine parking.
| A panorama taken from the Brooklyn Wind Turbine carpark in the late afternoon, looking out toward Rongatai and Eastbourne. |
Brooklyn Blades
Here at the summit of the Brooklyn Hills, along the fenceline of the Karori Wildlife Sanctuary, is an interesting site with fantastic views in every direction. At this site in March 1993, the Electricity Corporation of New Zealand installed the first commercial wind turbine in New Zealand, the Brooklyn Wind Turbine on Pol Hill, as part of a research project into wind power generation, specifically how wind turbines perform in New Zealand conditions and wind turbines compare to other forms of generation. The Brooklyn site was chosen for the wind evaluation project because of Wellington’s strong winds and since it was installed, the turbine has set international generation records for turbines of its size. In 1999, Meridian Energy inherited the single turbine when the company was formed in 1999.
The turbine, while at the time was a modern cost-effective choice, is now dwarfed by much larger turbines both nationally and internationally. The turbine is a 22.8 tonne Danish-designed and built Vestas V27 turbine, which is 31 metres tall and has fiberglass-reinforced polyester blades which are 13.5 metres long, with which it has a capacity of 225 kilowatts (0.225MW), very small by modern standards. Nearby, to the west, and visible from the Brooklyn Wind Turbine is Project West Wind – this set of 62 turbines are Siemens 2.3 turbines, which stand 67 metres tall with a blade length of 40 metres, larger than the Brooklyn Wind Turbine alone, and each generate 2.3 MW each (2,300 kilowatts) – over 10 times the capacity of the Brooklyn Wind Turbine.
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| Out towards Makara on the western Hills, the 62 turbines of Project West Wind can be seen. |
The tallest turbines in New Zealand are located at the TrustPower commissioned Mahinerangi Wind Farm, 70km west of Dunedin. Each 3MW capacity turbine is 80 metres high and the blades 44 metres long. Even these pale in comparison to the largest turbine in production, the German Enercon E126, which proudly stands 135 metres high, and has a whopping 63 metre blade length – which is actually so large that each blade has to be composed of 2 blade segments and structurally joined together.
The Brooklyn Wind Turbine, with its panoramic views from the Hutt Valley all the way around to Makara, operates with an average generation capacity of about 45%, setting an exceptional nominal generation benchmark which is nearly unsurpassed around the world – internationally turbines operate between 25%-30% of potential generation capacity, this is due to New Zealand having one of the most consistent wind energy resources in the world, because of our location right in the path of the roaring forties.
All of the above factors combined allow the Brooklyn Wind Turbine to produce roughly 1,000 megawatt•hours (1000 MW•h) of electricity each year – enough to constantly supply 60-80 homes for the same amount of time. The energy produced is then fed into the local network for distribution in Wellington. A megawatt•hour is a measure of accumulated power produced or expended over time, while a megawatt is a unit of the amount of constant power produced or expended. For example, a heater rated at 1 kilowatt will use 1 kilowatt•hour of electricity in an hour and 2 kilowatt•hours of electricity in 2 hours – while using 1 kilowatt of power constantly. Likewise, the Brooklyn Wind Turbine will (theoretically) produce 225kW (kilowatts) of electricity at a constant rate, which after an hour of generation is equal to 225kW•h, and after a day is equal to 5,400kW•h (24 hours x 225kW). This will never occur however as this requires the wind to blow at optimum speed constantly, which never happens. When the turbine is not running, it is producing no electricity.
The Brooklyn Wind Turbine has a cut in speed (the speed that it starts generating electricity) of 13 km/h. Between this speed and 23km/h, the blades sweep clockwise around the nacelle at 33 RPM, rising to 43 RPM above 23km/h. The turbine achieves its maximum generating capacity of 225kW when winds are between 50km/h and 80km/h, the cut out speed. Above this, the built in sensors and microcomputer automatically shut the turbine down by pitching the nacelle slightly out of the wind with a disc brake back up present. The turbine itself can survive gusts approaching 193km/h.
| A comaparison of the Brooklyn Wind Turbine, Project West Wind - to the west of here, a Mahinerangi turbine, the largest in New Zealand, and the Enercon E126 - the largest turbine in the world. |
Since its March 1993 installation, it has become a popular Wellington landmark, attracting thousands of visitors every year – and it operated reliably for 17 years before any major repairs were required. In 2010, while the turbine was out of commission for several months while waiting for repairs, Meridian asked Wellingtonians what should happen to the turbine, and an overwhelming 85% of respondents said they wanted a turbine operating at the site.
The turbine is not the only reason sightseers visit the spot – present at the site is an information board about the turbine, but also truly spectacular views of Wellington region and the South Island even. To the north, Kaukau, and then sweeping around one can see very prominently the Wellington fault as it cuts through the west side of the Hutt and the harbour, with Westpac Stadium and the wharf visible in the foreground. Somes Island, a very small Mount Victoria, Rongatai Isthmus with the airport to the south and Ward Island just visible behind it, and then out to the Cook Strait across the harbour entrance is Baring Head, the southern bays, and then rotate a bit more and there is Hawkins Hill and the radar dome on top of it. Keep circling clockwise and you will see the large Project West Wind out to Makara, with rare peeks at the South Island, before arriving back and having come full circle.
The area is also littered with mountain bike trails, walking tracks and other reserves. Pol Hill Reserve is one of these, and most notably, the Karori Wildlife Sanctuary – the fenceline and loop track of which are a few metres away.
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| Looking northeast towards the turbine and Wellington from above the sanctuary fenceline track |
Wind Power - Mathematics
There are a few basic relational equations and theories which act a bit like economies of scale in wind turbine design. The first is that energy in wind is not linear. Double the wind speed and the energy does not double, but actually increases by a factor of 8. Easily stated as “As wind speed increases, the power increased by a cube factor”.
Secondly, blade size influences the idea of “swept area”. Swept area is the invisible circle the blades rotate in to gather power and is a crucial calculation in wind turbine design. The larger the swept area, the more power can be collected. Think of a blade length as the radius of that invisible circle – you can find the area of that circle through the calculation: pi * radius2. So, as you double the blade length, the swept area quadruples.
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| Swept Area (sq. metres) = pi * radius2 |
The final equation is the main wind power calculation. The potential, theoretical power of a wind turbine can be found using the equation:
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| Power = 0.5 * Swept Area (pi * blade length2) * 1.23kg/m3 (Air Density) * Wind Speed3 (m/s) |
This however, is the theoretical capacity potential, and can never be achieved nor realized – once one factors in the turbine’s efficiency (usually 25%), and a few other energy losses, the maximum rated output can be found.
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| Looking directly up to the turbine nacelle and blades |
Wind Power - History
Wind power is one of the newer, more modern forms of electricity generation – and it falls under the broad category of renewable energy, sitting with solar, tidal, wave, hydroelectric, and geothermal along with a few others. And while the idea has been around for centuries, with the first rudimentary windmills in modern-day Iran appearing in the 7th century, it wasn’t until the 19th century that the Danish really started using windmills to pump water to clear large tracts of land for agricultural use; the delta works, as they are called.
By 2011, the worldwide capacity of wind power had reached 197 gigawatts (GW), generating about 2.5% of the worldwide electricity use. Despite this, wind power is still a relatively new and unused technology with very little market infiltration, although this is expanding rapidly. New Zealand currently has 16 wind farms with 456 turbines, with a capacity of 622.8 MW, generating about 4% of our country’s electricity, a rather meager amount considering our abundant wind resources.
A few countries around the world have achieved higher levels of wind power usage, Nordic & European countries especially. Denmark supplied 21.9% of its electricity usage through wind in 2010. Germany has over 21,000 wind turbines with a capacity of 27.2 GW. At 2.15am on 31 October 2010, wind power supplied an instantaneous 75% of Portugal’s electricity consumption, a world record. Sweden is harnessing its large ocean area to build mammoth offshore wind farms away from the coast, with successively larger and larger turbines. Europe doesn’t have a monopoly on wind power however. Surprisingly, the historically conservative right-wing red state of Texas is the leader in the U.S. on wind power, where large expansive low-cost wind farms sited on agricultural land are regularly forcing coal and nuclear plants to dump their energy on the grid at a loss at certain times of the day.
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| Global Wind Power; cumulative installed capacity in gigawatts. |
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| Looking northeast from the turbine out to Somes Island and Mount Victoria |
Cache
Oh that’s right, the cache. There was a cache here, and it was one of the more historical ones – the 15th oldest in Wellington as -gonefishing- mentioned to us, being placed in April 2003, before over 4 years later it was muggled archived after people didn't search hard enough. Why let such an awesome spot go to waste? It’s only appropriate we reuse the same name as the last one (Brooklyn Blades) and that we either keep the cache size the same or make it larger.
Access is very easy, simply follow the numerous ‘wind turbine’ signs scattered around Brooklyn – or alternatively head for Ashton Fitchett Drive at the top of Brooklyn, follow the street until you turn off to an unmarked road uphill towards the Brooklyn Battery and the wind turbine. You can park right beside the wind turbine and the cache is only a 30 second stroll from there. Please note however that the unmarked road is controlled by automatic gates which are open between the hours of 8.00am-5.00pm in winter and 8.00am-8.00pm during summer. If you are visiting outside these hours, you will need to park at the gates and walk up the track or road to the turbine – which is a fair distance away.
The cache is a 1.2L translucent Sistema hidden in roughly the same location as the last one was, hopefully this one will also survive – but this is a very popular spot, so it is absolutely imperative that you rehide and cover the cache up well. Not only that, but also be very stealthy and aware whilst searching for and handling the cache.
When placed it contained a logbook with a pencil in a logbag, a geocaching notice, a small prize for the FTF, and a few (about 5) travel bugs. Enjoy the view and bring a camera.
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| An isometric upwards view of the turbine. |