The tidal energy potential of the Manukau Harbour, New Zealand

A renewable source of electricity generated near the demand in Auckland might help defer investment in grid infrastructure, avoid grid transmission losses and help achieve the target for renewable energy mix in New Zealand. The tidal energy at both ends of the entrance channel to the Manukau Harbour is calculated based on navigation chart current speed data. Calculation is done using the kinetic energy flux method, and a farm method calculation is used for comparison purposes.The peak current speeds are modest: 1.35 and 1.80 m/s. These give estimated extracted electricity results of 7.2 and 7.9 GW h/year for flux method and 13.3 and 11.2 GW h/year for farm method. This electricity could supply about 900–1400 New Zealand homes and is similar to the generation output of a small wind farm. Factors affecting feasibility for a future tidal energy project in the Manukau Harbour include New Zealand electricity demand changes, technology maturity, and environmental effects – especially on rare dolphins. The study concludes that the resource is sufficient to support a small-scale distributed generation project after technology costs reduce. A strong case is made for investment in another more detailed study in 2017.