Tidal power rides wave of popularity 

The government is being urged to give more support to the development of wave and tidal power after a study found it is greener than other forms of renewable energy.

Despite the rush to build wind farms around the country, two Auckland University students say tidal power is superior.

Hydro electricity is the backbone of the nation's energy system but when the students looked at whether it was more sustainable than wind, geothermal or tidal power, they got a surprise.

"We were sort of expecting hydro generation to be the winner, but as it turned out tidal came out first," says student Zeb Worth.

Tidal power doesn't exist in New Zealand yet, but there are at least 24 wave and tidal power projects under development.

"Wave pattern and tidal energy probably have less impact in terms of visual pollution, noise, and competition with other human uses," says John Huckerby, Wave and Tidal Energy Association.

Tidal power projects leave their renewable rivals for dead when it comes to carbon footprint, because geothermal plants use stacks of stainless steel, and hydro dams involve huge amounts of energy intensive concrete and steel.

"Steel and concrete have a lot of carbon emissions associated with their manufacture and construction," says Worth.

The findings have been welcomed by crest energy, which wants to create the world's largest tidal power plant in the Kaipara Harbour.

They hope their low carbon footprint will help the resource consent process.

"As people get more and more familiar with these kind of concepts of full life costs in terms of carbon, it can only be a good thing," says Anthony Hopkins, Crest Energy.

The government has created an $8 million marine energy deployment fund to encourage projects, and the first project could be up and running within five years.

"The government could play a greater part there. The fund's a great start, we probably need more capital grants in future," says Huckerby.

But while tidal power may be the greenest of the green energy options, the technology is still mostly unproved and expensive, which means investors will need deep pockets to harness the deep blue sea.