Plugging into tidal power
A single tidal turbine 10 metres in diameter in the Cook Strait’s Tory Channel could generate enough electricity to
power 12 homes, says National Institute of Water & Atmospheric Research (NIWA) scientist Derek Goring.
NIWA has calculated the tidal currents in Tory Channel from 2001 to 2100 and used this to work out the average power and
daily energy outputs for a single generator in the Channel, says the latest Climate–Energy Matters newsletter released
today.
‘Tidal power could be one way to help solve our power shortage, says Dr Goring. ‘New Zealand has many good tidal power
locations, including several parts of Cook Strait and harbour mouths.’
Tidal flows from harbour mouths are huge, says Dr Goring. ‘The tidal flow at the mouths of the Manukau, Kaipara, and
Hokianga Harbours oscillates by plus or minus100 000 cubic metres per second each tidal cycle. That’s 12 times larger
than the largest flow in any New Zealand river – and it happens twice every day.’
‘Tidal currents are a natural and renewable source of energy that’s reliable and predictable. We can predict the tide
hundreds of years ahead because it’s controlled by astronomical forces, and there’s no problem with lack of wind or rain
or with fluctuations in El Nino or La Nina cycles.’
The turbines, submerged well below the ocean’s surface, would be invisible except for onshore cables. Dr Goring says the
turbines are unlikely to have a significant effect on marine life because they rotate very slowly at 20 revolutions per
minute.
‘The huge quantities of sediment which are moved across harbour mouths by tidal flows do pose a significant engineering
challenge to harnessing the power, but the amount of available energy is so large that we should investigate it
further.’