The Northland Regional Council in New Zealand received an application last week from Crest Energy, Ltd., to build a 200-megawatt tidal power plant just north of the country's largest city, Auckland. The proposed project, situated in the mouth of Kaipara Harbour, calls for two 20-mile DC cables that run across the harbor -- and the construction of a DC-AC converter and substation on land at the Hoteo River.

Once completed in 2011, the $400 million project is expected to generate about 4% of New Zealand's annual energy supply. According to Anthony Hopkins, director of Crest Energy, the Kaipara Harbour has a number of factors that make it suited to marine turbines. The harbor is about 40 miles long and an immense volume of water passes through a fairly narrow channel around four times a day. The lack of commercial shipping in the vicinity is also important, added Hopkins, allowing turbines to be sited about 16 feet under the low tide point. "The relatively low labor rates and a commitment to sustainable energy make the idea of placing marine turbines for power generation in the mouth of a natural harbor not as unrealistic as it might seem in other countries. New Zealand produces over 60% of its electricity from renewable energy, primarily from hydroelectric and geothermal sources," said Hopkins. The Kaipara Harbour is a delicate marine environment, with many large mammals including whales, dolphins, orcas and sealions -- along with huge numbers of wading and diving birds that feed in the harbor. To minimize possible impacts on the environment the cables will follow a longer but safer route and will be buried at least four feet under the harbor floor, said Hopkins. High voltage DC is the choice for technical reasons but also because DC radiates about 5% of AC (sharks, skates and rays can be disrupted by electrical radiation). "Tidal power is predictable, sustainable, silent and invisible -- these advantages need to remain the focus, rather than the eight hours a day when tidal turbines produce little or no power. Tidal power complements other energy sources and will, eventually, be of importance to maritime countries," said Hopkins. The application process is expected to be completed by mid 2007. Assuming a positive outcome, Crest Energy plans to raise capital through a public offering of shares, and to proceed with the three key elements -- construction of the 200 marine turbines, the DC cables across the harbor, and the DC-AC converters and substation on land. The Northland Regional Council in New Zealand is accepting comments on the proposed project through January 12th, 2007.