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Darren's Diaries for Water Power

Diary 2 - Wednesday 17 June 2009

Field Trip Name: Water Power Field Trip Place: Waitaki Diary number of total: 2 of 4 Weather: A very cold start (minus 5 degrees Celsius!) but warmed up during the day Where's Darren: Benmore Hydro station

Hi everyone, Darren here. The view from the lookout point above the Benmore Dam wall. Image: Heurisko Ltd. It was certainly an icy start to the day for us in . The temperature was well below freezing as we carefully drove to Meridian's offices at their Control Centre just out of town. We were met there by our expert for the week, Hydro Maintenance Manager, Paul Lloyd. After collecting protective overalls to go with our hard hats, steel capped boots and safety glasses we jumped into Paul's truck for the 40 minute drive to Benmore Hydro Station. We didn't need the safety gear because of Paul's driving, it was because maintenance work is being carried out at Benmore and so everyone who visits must wear the gear.

Approaching the power station the wall of the Benmore Dam doesn't look that big. As you get closer though you suddenly The powerhouse at Benmore Hydro Station. Image: Heurisko Ltd. realise how massive it is. At 110m high and over 800m wide at the crest it was the largest solid earth dam in the Southern Hemisphere when it was built. Check out the panorama image.

Paul took us up onto the top of the dam wall and across to a lookout point to get an overview of the power station. Watch the video where Paul explains what bits make up Benmore Hydro Station. Soon after it was time for an audioconference with students from Broadfield School. We quickly drove from Canterbury to along the road that runs across the top of the dam wall. You see, the that the dam is built across marks the boundary between the two provinces. We held the audioconference from above the dam wall looking down on Inside the machine hall. The green box is above a generator that is spinning below the floor. Image: . Heurisko Ltd.

Once the students' questions had been answered we drove down to the powerhouse. After signing in we headed into the massive machine hall. This huge room is where the electrical energy is generated. The tops of the generating units peek above the floor with most of the unit being below. The ceiling is so high because a lot of room is needed to lift out the units for maintenance and repair. Paul told us in a video about what bits make up each unit. Basically at the bottom there is a turbine (like a large propellor) turned by water and the turbine is connected by a shaft to a generator at the top. Here magnets spin near coils of copper wire. This movement makes electrical energy in the copper wire. A brand new Francis turbine. It has a mass of 40 Each of the six generating units in the machine hall can produce tonnes and will be spinning at nearly three times a 90MW of electrical energy (enough for over 36 000 homes). second once it is in place. Image: Heurisko Ltd.

Another audioconference was held with students from Westmount School. We used a quiet office near to the machine

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hall for this. Usually the machine hall is fairly quiet but maintenance work meant it was a bit noisy at times.

We then went back into the machine hall and headed down below the main floor into what is known as the turbine pit. Here you can get close to spinning turbines and generators. The turbines have to be made to turn at nearly three times a second by the water rushing through the power station so that electrical energy can be made for us. This must involve a lot of force as each turbine is 40 tonnes. It is a very efficient way of making electrical energy as 90% of the kinetic energy of the water is converted into electrical energy. Watch the video where Paul Ye olde electricity meter. Today Benmore is run remotely from Tiwzel. In the past it was run from a explains why the turbines are so efficient. control room on site that had meters like this to tell you how much electrical energy each generator Webster wanted to get a closer look at the penstocks that bring was producing. Check out all the cogs and dials. Image: Heurisko Ltd. the water from high above the powerhouse so we popped outside the machine hall to see them. These giant concrete pipes bring the water from the dam nearly a hundred metres above the powerhouse down to the turbines. A series of paddles, called wicket gates, direct the water onto the turbines. These wicket gates can also control the force which the water exerts on the turbine by controlling how much water flows through. The turbines always turn at the same speed but to get more electrical energy from the generator the strength of the magnets in it are increased and so a greater force is needed to turn the turbine. All these adjustments are made remotely from a control centre in Twizel. This is a small auxillary generator at Benmore that generates electrical energy for the power station The water that goes through the power station leaves through itself. The blocks attached to the blue spokes are the tailrace into the Waitaki River. It will then pass through two magnets and they spin inside copper wires that are around the outside. Image: Heurisko Ltd. more power stations, Aviemore and Waitaki, on its way to the sea. We visited those power stations last year so take a look at that field trip to learn about them.

Tomorrow we'll head upstream to see the Ohau Hydro Stations (A, B and C) along with the canals that link them.

Today's competition clues

1. I am 110m high

2. I am over 800m wide at my crest

3. I am made of solid earth The penstocks are giant concrete tubes that bring the water from the dam 92m down into the powerhouse to the turbines below. Image: The competition prize is a Navir Physics Frenzy Kit (23 Heurisko Ltd. experiments to explore magnetism, electricity, light and colour, force and power) for your class courtesy of Meridian. Remember you will also need the clues from Thursday and Friday.

See you in the morning.

Darren the LEARNZ Field Trip Teacher (and Webster)

Darren auditions for the Village People (ask your teacher who they are) inside a section of penstock. Image: Heurisko Ltd.

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Webster on top of a wicket gate. These paddles direct and control the water flowing onto the turbine. Image: Heurisko Ltd.

Transformers and the tailrace. This is where both the electrical energy and water leave the power station. Image: Heurisko Ltd.

The LEARNZ programme is provided by Heurisko Ltd Level 2, Spark House, 5 Durham St, Box 8577, Riccarton, 8440, New Top Zealand. Ph: +64 3 353-7360, Fax: +64 3 366-5488, NZ Teachers' FreePhone: 0800 CALL LEARNZ or 0800 22 55 53 [email protected] © Crown Copyright 2009

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