Marine energy devices could conceivably generate as much electricity as is generated from all current sources. However, while even the most passionate advocates of marine energy agree the full potential of marine energy generation will be unlikely for some time, they insist that wave and tidal power can add more diversity to the mix of renewable energy sources in New Zealand.

Dr John Huckerby is one such advocate. He’s the head of the Aotearoa Wave and Tidal Energy Association (AWATEA), and a participant in Wave Energy Technology – New Zealand (WET-NZ), a research venture that is about to launch its first wave device off the south coast of Wellington. He sees the potential generating capacity of wave and tidal power devices matching that of wind turbines, but not straight away.

“About three-and-a-half years ago a colleague of mine and I did a study for the Government on the potential for ocean energy for New Zealand and its likely development.

We concluded that there was about 8,500 megawatts of potentially developable wave and tidal current, of which the majority 8,000 megawatts was wave and the other 500 megawatts was tidal. The current generation capacity in New Zealand stands at about 8,600 megawatts.

“Up to 20 per cent of that potential capacity is realisable, roughly the same forecast as for wind.”

With demand for electricity still rising by about two per cent a year, and with a strong community feeling against more use of thermal plant, there is pressure to find other renewable sources.

Hydro currently accounts for 56 per cent of New Zealand’s electricity generation followed by gas alone on 19 per cent, geothermal with 10 per cent, with gas and coal combined on nine per cent. Wind and co-generation plants account for three per cent each. The potential for further large scale hydro development is limited – the best rivers already have big dams on them, and further developments would be expensive and controversial, even if they were technically feasible. Contact Energy is currently examining several options for the Clutha River, but is not committed to anything beyond investigation.

It’s also proving hard and costly to get resource consents for wind farms, particularly those that are close to human settlements or visible from them. Landscape values are also held to be important too. Meridian’s Project Hayes, which would have put wind turbines on the Lammermoor Range in Central Otago, has been abandoned altogether after extensive and expensive legal battles.

However, there have been several new geothermal projects consented or commissioned – Te Mihi and Tauraha II (Contact Energy), and Rotokana and Nga Awa Purua (Mighty River Power).

With a coastline of 15,134 kilometres and the sixth largest Exclusive Economic Zone in the world, it seems natural that New Zealand engineers and planners should look to the sea and seek to realise its potential for generating power.

The last Labour-led government set a goal of 90 per cent self sufficiency in renewable energy. The current National-led government doesn’t have the same priorities – National’s Energy Strategy published in August 2011, has limited actions for sectors other than oil and gas.

The New Zealand Government is a member of Ocean Energy Systems, a work programme organised under a framework established by the International Energy Agency in Paris. Dr Huckerby is the current Chairman of the programme, which has 19 member governments including those most active in ocean energy. Ocean Energy Systems recently published International Vision for Ocean Energy, which forecasts growth of up to 750 gigawatts of marine energy capacity by 2050.

Many Ocean Energy Systems member countries are moving to exploit the potential of their coastlines. In the United States, for example, the Ocean Renewable Energy Coalition unveiled the first United States Marine and Hydrokinetic (MHK) Technology Roadmap in November 2011. The roadmap describes the issues, challenges and opportunities facing the MHK industry and sets out a path to commercialise the technology. The Ocean Renewable Energy Coalition claims “technologies that capture energy from free-flowing waves, tides and currents [have] the potential to provide up to 10 per cent of US electricity consumption and continue to make advances and gain popularity in coastal communities around the world”.

Canada claims it is also well positioned to lead on marine energy technologies. It too published a Marine Renewable Energy Technology Roadmap in November 2011, which refers to “Canada’s collaborative efforts to advance the commercialisation of marine energy technologies while sharpening its global competitiveness”.

Electricity industry executive James Taylor, who chaired the taskforce that developed the roadmap, says Canada is already “the only country selling river current generators, supplying wave and current monitoring equipment worldwide. We have seen [energy company] Alstom develop a Canadian tidal technology to be the world’s first two-megawatt system”. One interesting initiative was the announcement that the government in Nova Scotia had “recently accepted applications for a number of projects under its community feed in tariff – a special price for community-controlled tidal projects to connect to their distribution grid”.

Internationally there are several examples of ocean energy plants. A 240-megawatt tidal barrage station on the Rance River in Northern France at St Malo was the world’s first tidal station.

It has been operating since 1966 with an annual output of 600 gigawatt hours. In late 2011 Korea commissioned the 254-megawatt Sihwa Lake tidal barrage about 40 kilometres south of Seoul.

A commercial 300-kilowatt wave power plant, consisting of 16- by 18-kilowatt turbines and housed within a breakwater, has just been commissioned at the port of Mutriku in the Basque Country of Spain. In New Zealand, Mike Underhill, Chief Executive of the Energy Efficiency and Conservation Authority (EECA), argues that renewable energy is one of New Zealand’s global strategic advantages.

He says New Zealand actually has the highest per capita renewable potential in the world, and believes marine energy will be an important part of future development.

Research from the EECA (which works to implement New Zealand government strategies for energy efficiency, conservation and renewable energy in the private and public sectors) has found there is good public support for marine energy, despite a poor understanding of the technologies involved.

Dr Huckerby lists seven types of ocean energy: waves, tidal currents, ocean currents, tidal rise and fall, salinity gradients, ocean thermal energy, and submarine geothermal energy (the latter is a long way from development). Wave and tidal energy have the most potential for New Zealand, although Dr Huckerby acknowledges there are still technical issues to overcome. More government support would help and more private investment capital would also make a difference. Both have shrunk since the global financial crisis.

In 2011 the Electricity Authority issued a policy statement on renewable energy. In a section on marine energy it states, “As marine energy is on the rise worldwide and the pace of the domestic marine energy activity has picked up over the last few years, it seems reasonable to look at this particular technology”.

On its website the Electricity Authority says that wave energy was more likely than tidal sources to contribute to generation. It has identified six potential projects that might generate up to 857 megawatts a year in total, but none has a forecast starting date before 2027.

The four wave sites are in Port Waikato, Taranaki, Westport and Southland, and the two tidal sites in Foveaux and Cook Straits.

As Dr Huckerby says, “Anywhere on a west or south coast from Cape Reinga all the way down to Tiwai Point, you could probably develop a wave project off shore”.

The last Labour-led government established a Marine Energy Development Fund (MEDF) to assist in getting early developments started so New Zealand engineers could learn about the technology and accelerate opportunities for exports to the growing international markets.

One of the first projects partially funded by the MEDF was the WET-NZ project, which is also supported by funding from the Foundation for Research, Science and Technology.

The project seeks to develop a wave energy device that maximises engineering efficiency through the novel use of direct-drive and adaptive response to changes in wave motion. The majority of the device is submerged but floating and is designed to operate in transitional/deepwater waves of between 20 to 100 metres. Several other New Zealand marine energy projects have been assisted through MEDF funding. Of the active projects, three are wave device deployments and four are tidal energy device projects. Only one, WET-NZ, is developing domestic technology.

A proposal to establish a marine energy centre in New Zealand was put to the Government by AWATEA and the Heavy Engineering Research Association in August last year. A syndicate of members is currently working on a business plan for the centre. Small scale wave and tidal power devices may be particularly useful in remote areas where power from normal sources is difficult to access.

Places with remote emergency backup and the Third World are all potential niche markets. Engineering consultant Cliff Turner says, “The economics become more attractive because the cost of alternatives is also high and the convenience of having power at all is valued”.

The efforts being made in the Chatham Islands (where a wave device project is currently underway) are an example here.

However, marine energy development in New Zealand is still seen as a mid to long term project. There are technical issues to overcome, although costs are expected to fall from better design and higher production volumes. Maintaining political will and access to funding are important issues for this fledgling industry.

“The Ministry of Science and Innovation has published a request for proposals at the end of 2011 on energy and minerals but it did not include marine energy. There’s been no new research funding for three years,” Dr Huckerby says. “We need to get some projects up and running to demonstrate to everyone that wave and tidal power can work in this country. There are no mature technologies for wave. There are some that are close, and there are a number under development ranging from R&D [research and development] to early prototypes to one or two pre-commercial prototypes.”

So how far away is a commercial operation? Dr Huckerby says that question is very difficult to answer. “In 2004 I said that it would be by 2010, and at that time I did think that would be the case. Now my answer is the same – in roughly five years’ time.”

Globally, Cliff Turner sees huge momentum and commercial deployment taking place. “In New Zealand we have alternative options. Wind and geothermal are the competition. Large scale wave technologies are not quite ready yet. We will keep working on it because it will happen. Wave energy will soon come into its own.”

New Zealand has six active projects in various stages of development. The three most active projects are Crest Energy’s tidal power project in the Kaipara Harbour and two wave device projects: the Chatham Islands Marine Energy project and the WET-NZ device development.

Crest Energy obtained resource consents for a 200-megawatt tidal power station in the outer part of the Kaipara Harbour in March 2011, after five years of much local controversy, consultation, hearings and appeals. The company says, “The project comprises up to 200 completely submerged marine tidal turbines with a maximum generating ca- pacity of around 200 megawatts, located invisibly underwater”.

Crest estimates harnessing tidal energy would provide enough generation to power the roughly 75,000 homes between Albany and Cape Reinga. Todd Energy took a 30 per cent stake in the company in July 2009 and has since increased that to 54 per cent.

That company says the project has the potential to lead the world in the commercialisation of tidal power, which is “clean, silent and sustainable, and will make a substantial contribution to the nation’s electricity needs”.

Crest spokesman Anthony Hopkins says although the company has consents and could proceed with its tidal generation plans, it will first undertake two years of environmental monitoring “given the strength of feeling that the project has aroused locally”.

“We need to get everything lined up, and it isn’t at the moment,” he says. WET-NZ, which is a collaboration

between Power Projects Ltd and Industrial Research Ltd, has developed a point absorber wave energy converter.

“The first 1:5 scale device was deployed from 2006 to 2008. The second 1:4 scale version was deployed from 2009 to June 2011. The third 1:2 scale version was trialled off the Akaroa Heads between September and December 2011.

It was towed to Wellington in early December and, following refurbishment, it will be deployed at a consented site two kilometres south of Moa Point, which is the southern end of the airport runway.

“This one worked. The first two generated two kilowatts, the third 20 kilowatts, and the ultimate aim is to get to individual units of about 500 kilowatts.

When that would be I don’t know because we don’t have funding to build a commercial scale device.”

New Zealand company Neptune Power Ltd is also looking ahead, and plans to place a tidal stream turbine 80 metres

underwater at Karori Rip, which is a part of Cook Strait immediately outside Wellington harbour known for strong tidal currents. In New Zealand the company obtained resource consent for a single prototype device in April 2008 and has to use it by April 2013.

In addition, a $2.2 million grant from the Marine Energy Development Fund in July 2010 was provided to Chatham Islands, and it was granted resource consents in August that year for its Point Durham Wave Power Project. It plans to utilise a twin-turbine 220-kilowatt version of the Voith Hydro Wavegen device. The original version of this device has been operating at Islay in south west Scotland since 2001 (the second version was commissioned at Mutriku in the Basque Country).

Besides these, Tangaroa Energy Rakaia Amps Ltd has signed an agreement with a Norwegian company, Langlee Wave Power, which has developed a surge device. This has four posts with flaps, which move backwards and forwards in the waves, and extract what’s called the surge energy. Langlee has developed a device which was tested extensively in Norway and Denmark, and it is planning to install a 22-kilowatt prototype off Oban in Stewart Island. The company applied for resource consent in June 2011.

In a more locally-based project, Community Leisure Management Ltd received $203,000 to partially fund the installation of three small vertical axis turbines under the Tamaki Drive Bridge east of Auckland city centre. The electricity generated will be used to pump and re-circulate water in the nearby Parnell Baths.

Another company, Energy Pacifica Ltd, is proposing to install 50 large marine turbines, purchased from overseas, with a total generating capacity of 75 megawatts at the entrance to Tory channel. This project is being driven by the company’s founder Dr Anthony Bellvé.

Given the interest, the future for marine energy in New Zealand looks bright. The first device will be in the water for an extended period by the middle of this year and other projects are moving to deployment.