Tira Ora's main source of electrical energy is a hydroelectric system.  Water is diverted from our main stream into a reservoir dug into a natural shelf in the hills.  A penstock (pressure pipe) carries the water down the valley to the generator in the power house, after which it is returned to the stream.  Depending on rainfall, and therefore the flow available in the river, we generate between three and six kilowatts.

Almost all our lighting utilises low-energy compact fluorescent lamps or LEDs.  Together with efficient modern freezers and washing machines, and prudent load management, this means that the hydro plant provides ample power for the Lodge and all its guests.  There is usually excess power available for some water and space heating.

The hydro system was installed in 1989.  In 1993, it was the winner of the "eta" Award, Category 1 (businesses with fewer than 15 employees), from the Electricity Supply Association of New Zealand.  The awards scheme is for energy efficiency and productivity in industry, and recognises and rewards companies which have significantly improved their performance by adopting an electrical process or service.

Q & A

How much water does the reservoir hold?

600,000 litres.

What are the dimensions of the penstock?

150mm diameter; 600m long.

How is the electricity generated?

The water falls 60 metres vertically in the penstock under the force of gravity, gaining momentum in the process.  The penstock holds over 10 tonnes of water, travelling at over 3km per hour.  But as the water exits the jets and strikes the turbine, it is travelling at 110km/h.  When the moving water strikes the steel buckets of the turbine, its energy is efficiently transferred to the rotor of the generator.  

The rotor revolves at 3000rpm, creating a strong electromagnetic field which causes electrical current to flow in the coiled wires surrounding it.  That current is fed to the fifteen buildings on the estate with 300m of overhead wires.