Feature

Tidal power: an update


Elizabeth Block

Compared to wind and solar, tidal power is still regarded as a renewable energy technology that remains unviable on a large scale. But throw together climate change, political will in the UK and the US, entrepreneurial enthusiasm and academic research - with some significant investment - and a new mood of optimism is starting to pervade the sector.

Tidal current power, sometimes called tidal stream power, is the process of converting the kinetic energy of the tide – whether in tidal rivers (think London's Thames or New York's East River), streams or ocean waters, into useable power in the form of electricity.

The process typically involves an underwater turbine, and a plethora of devices are being developed – some in rivers or streams and others offshore. While a few technologies are past the testing stage and now feeding the grid, no company in the world has actually reached the commercial stage, delivering “proven technology”.

And the stakes are high. According to some estimates, tidal power could provide around 20% of Britain's needs – and comparable levels in countries like Chile, Canada, the USA and Australia.

So why does it seem to be taking so long for tidal energy to be recognised, when as far back as June 2003 Time magazine was saluting tidal pioneer Richard Ayre for discovering the untapped force of the tide back in 1997 (not to mention the potential for electric power) while placing information buoys in a marine park in Pembrokeshire, UK. Ayre went on to set up Tidal Hydraulic Generators and is now at Tidal Energy Ltd., where he led the development of the DeltaStream turbine, a 1MW unit that sits on the seabed (DeltaStream has undergone trials and full production is planned by summer 2009).

Some cynics argue tidal technologies will never have a place at the table of the large-scale power-generating technologies, but experts believe that far from “taking a long time to emerge”, tidal power is simply at the beginning of a journey, with major (but surmountable) challenges to overcome. “The sites of potential energy extraction are the ones normally avoided by mariners and for good reason”, says Neil Kermode, managing director of the European Marine Energy Centre (EMEC) in Orkney, Scotland: “it is exceedingly difficult to put devices in the water and to keep them there. The conditions are harsh and unforgiving and the technologies new and unproven.”

2008 – tidal scale up continues

Despite the difficulties though, tidal technology needs to ultimately provide power on a large scale if it is to succeed commercially. And there are plenty of positives to indicate that more and more organisations believe this will ultimately happen:

  • Big money from companies like nPower, E.ON, EDF, Morgan Stanley and others;
  • Increased Government commitment on both a national and regional/state basis;
  • Wider full-scale testing;
  • Ambitious plans for big tidal farms;
  • Talent being attracted into the industry (one example being Mike Smith, an oil and gas veteran who joined Singapore based Atlantis Resources as COO in September 2008).

As EMEC's Kermode adds, “there has been an explosion of effort recently. Partly as a result of the Government's determination to bring this energy source online and partly buoyed up by the recent successes of various developers.”

Despite criticism for its lack of leadership in renewable energy, the UK Government, for example has made considerable support available for tidal power and other marine technologies, in light of the fact that the UK has one of the best marine resources in the world:

  • The Marine Renewables Deployment Fund (MRDF) was set up in August 2004, with a modest budget of £50M;
  • As recently as October 2008, a new UK Department for Energy and Climate Change was established, which should be even more pro-active towards marine power development;
  • There is already speculation that the rebanding of the UK Renewables Obligation support scheme will favour marine technologies as we move forward. The RO works by awarding certificates (ROCs) for power generated by renewable technologies. In future, it is likely that more ROCs will be awarded per MWh of tidal power generated than, say, for onshore wind power which is more mature, in an effort to encourage tidal development;
  • The Scottish Government too is likely to increase funding for wave and tidal energy technology following proposed changes to the Renewables Obligation in Scotland. In fact the Scottish Government, which is opposed to nuclear energy unlike the UK Government, has plans to use transferable skills from Dounray nuclear power station (which is being de-commissioned), for tidal power projects.

This activity has driven the tidal industry forward, and many are now competing to “go commercial”. According to John Aldersey-Williams, principal of Redfield Consulting, who regularly reviews more than 100 emerging wave and tidal stream technologies for the consultancy's Review of Marine Renewables, horizontal axis longitudinal turbines, set in seabed mounted housings, are the leading technology.

Redfield rates tidal technologies on dimensions of technical and commercial feasibility, working only on data available in the public domain. Its technologies of choice all use the horizontal axis model:

The barriers

But before proceeding with progress made, we should look at the barriers that have kept tidal power in the development stage so long.

The tide is a powerful force. Although highly reliable and predictable, converting it into useful electrical power is not easy.

Developers of tidal energy must calculate the force of the tide, and must factor in technological development, construction of components, environmental assessments and monitoring, planning permission, and finance – all before actual prototype deployment and testing.

Not surprisingly, deployment is heavily-dependent on the weather, and there is much planning – and waiting – for the “weather window” – the slack tide, to say nothing of availability of the appropriate tugs and barges.

As Stephen Wilson, director of wind and marine energy at NaREC, the UK's New and Renewable Energy Centre in Northumberland, says: “it's not just about capturing the tide. It's about putting a reliable power system in a wet environment that can guarantee your payback.”

Pointing out the long lapse before onshore wind went offshore, Wilson says, “it's difficult to get the balance right.” In his view not a single tidal technology is yet at Level 9 of technology readiness, i.e. “mission ready”.

Which technologies have made it to the grid?

Connection to the grid may be viewed as the last step before actually going to the market. A world first can be claimed by the Norwegian company, Hammerfest Strøm AS, which connected a 300kv Lànstrøm tidal turbine to the town of Hammerfest in 2003. This three-bladed device was rated at 300 kW, supplying 700 MWh per year, providing electricity to 35 Norwegian homes. The submerged structure weighs 120 tonnes and has gravity footings of 200 tonnes.

And in 2006 Atlantis Resources began exporting to the grid at San Remo near Melbourne, Australia, with its Nereus turbine.

Very significantly, this year saw two more tidal companies connecting to the grid, with more planning to do so in the near term. In May 2008, for example, Open Hydro, an Irish company, after 18 months of testing, connected its 250kW Open-Centre Turbine to the UK grid off Orkney, Scotland, at the European Marine Energy Centre (EMEC).

OpenHydro also intends to install tidal turbines in sites across the globe, including the Bay of Fundy in Nova Scotia. The Bay of Fundy claims to have the highest vertical tidal range in the world.

A few months earlier, in March 2008, Marine Current Turbines (MCT) put its SeaGen marine turbine into the water near the mouth of Strangford Lough, Northern Ireland, and connected to the grid in July. SeaGen has a capacity of 1.2 MW, four times the power of an earlier prototype, the SeaFlow, which was installed in the ocean off Lynmouth in Devon in 2003.

SeaGen is claimed as the world's first commercial-scale tidal turbine. The tidal current turbine initially generated 150kW of power onto the grid but once fully operational will generate 1.2 MW of power, supplying electricity to the equivalent of 1000 homes. MCT also has a power purchase agreement in place with ESB Independent Energy. ESB International, an Irish utility, is an investor and shareholder of MCT.

And in addition, in partnership with nPower Renewables (now part of RWE Innogy), MCT is working on the Anglesey Skerries tidal farm project in Wales, where the water is about 25 metres deep. This would be one of the world's first commercial-scale tidal stream projects. A new company, SeaGen Wales, will aim to get a large tidal farm commissioned by 2011 or 2012, subject to planning consent and financing, to generate 10.5 MW of tidal power. This will involve 7, 1.5 MW SeaGen turbines, each about 9m above sea level.

According to Martin Wright, managing director, MCT, “the involvement of nPower Renewables highlights the very real potential of decentralised tidal energy in the UK energy mix.”

Testing, testing…

Take a step back from the grid, and a large number of companies are active at the testing stage.

Pulse Tidal, based in Yorkshire, and Aquamarine Power, based in Edinburgh, is among the UK companies moving forward. Aquamarine, which claims to be the only marine energy company in Scotland developing both wave and tidal power devices, plans to test its Neptune tidal device at EMEC within the next three years, and Ocean Flow Energy has started testing a 1/10th scale model of its floating tethered tidal generator Evopod in Strangford Narrows, Northern Ireland. Lunar Energy, based in East Yorkshire does not yet have a unit in the water, but plans to start testing next year.

Meanwhile, Lunar is working with E.ON to develop a major underwater tidal stream power project off the Welsh coast. If given the go-ahead, it would be the world's largest, consisting of a field of 60-foot Rotech Tidal Turbines situated on the sea floor, capable of generating enough electricity to power up to 5,000 homes.

Lunar is also working with South Korea, having signed a £500m deal with the Korean Midland Power Company (KOMIPO) in March 2008 to create a giant 300-turbine field in the Wando Hoenggan Water Way off the South Korean coast. The plant is expected to provide 300 MW of renewable energy to KOMIPO by December 2015.

Tidal power is highly collaborative with regard to R&D, and many universities are working on tidal devices or are affiliated with tidal companies:

  • The Energy Systems Research Unit (ESRU) at Strathclyde University is conducting short tests of a single small prototype turbine in two separate locations in the west of Scotland;
  • Ocean Flow Energy is working with Queen's University Belfast and other institutions;
  • Oxford University researchers have designed a turbine called THAWT (Transverse Horizontal Axis Water Turbine) to intersect the largest possible area of current, regardless of the depth of water in which it is situated.

Scotland – huge potential

Scotland is causing much excitement in the marine sector. The UK's Crown Estate recently outlined the application and consent procedure for wave and tidal energy projects in the Pentland Firth (strait) – the first UK marine power site to be opened up for commercial-scale development – with the aim of generating more than 700 MW of energy by 2020 (MCT is one of the tidal companies with the Pentland Firth in its sights, and has said it will seek a licence).

Experts believe that the Pentland Firth alone contains enough tidal energy to meet a third of Scotland's power requirements. And Scotland's First Minister Alex Salmond has himself boasted about Scotland's “marine energy resource, which is unrivalled in Europe [with] an estimated 25% of Europe's tidal resource and 10% of its wave potential”.

Recently in late September 2008, in the midst of the global financial crisis, Scottish Power Renewables, part of Scottish Power, announced a plan to build the world's first tidal farms (within three years) on three sites in Scotland and Ireland. These would have a combined output of 60 MW. If permission is granted, these would be the first commercial underwater tidal turbine farms anywhere.

All three projects are expected to deploy the Lànstrøm tidal turbine developed by Hammerfest Strøm AS – which is jointly owned by ScottishPower Renewables, StatoilHydro and Hammerfest Energi. Lànstrøm is an underwater wind turbine, but with much shorter blades that turn more slowly. The units are mounted on the sea bed and aligned to the tidal flow. Each device generates around 1MW of output. Future arrays of multiple devices are anticipated which could generate 50 MW to 100 MW each.

ScottishPower Renewables is part of the Iberdrola Group, the largest renewable energy provider in the world. Iberdrola has committed to investing €1.2billion in the development of renewables in the UK between 2008–2010.

Tidal developments in North America

In New York City, where the law mandates local generation, Verdant Power has ambitious plans. In late 2006, in the glare of massive local publicity, Verdant put five Free Flow system turbines on underwater piles off Roosevelt Island in the East River – with power going to the local grid – and a sixth turbine performing analytical tasks. However, the company had to twice go back to the drawing board when the tide first ripped off the blades, and then the bolt connection to the hub.

Despite the difficulties, two newly-design turbines were launched in early September 2008.

To date, Verdant has generated 50 MW of electricity – at the cost of US$12 million, including US$2 million on high-tech fish monitoring equipment as specified by the Environmental Protection Agency. The company, which has funding from the New York State Energy Research & Development Authority (NYSERDA), the US Navy, and the Government of Ontario, among others, plans for commercial delivery of energy in 2010. The company is also applying for a license from FERC – the Federal Energy Regulatory Commission – to deploy 30 turbines in New York's East River.

Elsewhere in the USA, Ocean Renewable Power Company in Maine plans to test a commercial design of its proprietary turbine-generator unit (TGU) in both a tidal and river application starting in summer 2009.

According to Christopher R. Sauer, president and ceo, a commercial model is planned for 2010. “The first full prototype of our ocean current generation (OCGen) module, a much larger submersible power generation platform for tidal and deep water ocean current applications, will be deployed in 2010, with commercial availability planned for 2012,” he said.

Meanwhile in September 2008, Atlantis Resources acquired Current Resources, owned by Morgan Stanley, which remains the largest shareholder to this day. Mike Smith of Current Resources then became coo of Atlantis. Smith, who earlier formed a partnership with GE Wind, is convinced that much can be learned from offshore wind. “The cost of deployment at a tidal test site is high,” he said, “higher than wind, and it's more technically challenging”.

Nevertheless, he believes that the potential for tidal to offset the cost of diesel power generation, especially in Asia, is excellent. Atlantis is currently sounding out interest in its 1 MW shallow water Nereus turbine in South Korea, China, Japan and the Philippines.

Canada, Australia, Norway and New Zealand are among other countries with significant tidal resource and active tidal power companies. In the developing world, the Scottish Government recently sent a delegation to Chile to discuss tidal resources.

Finance for tidal

Many of the tidal developers around the world have progressed their prototypes with private money, along with a mixture of national and regional grants, university support, some funds from mainstream investors and increasingly, from private equity houses. It is thus very difficult to arrive at an estimate of total investment in this still fragmented sector.

While venture capital firms have been largely put off by the huge development costs of tidal power, the tide may be turning. For example, Triodos Investment Banking, a so-called ethical bank, considers itself a pioneer in investment in renewable energy, financing small scale wind farms since the mid 1980s. Gareth Zahir-Bill, investment manager, venture capital, at Triodos, said, “we are keen on tidal technologies. The behaviour of the resource is accurately predictable, and therefore it is possible to set out precisely what the power generation pattern of a particular tidal farm will be for the entire life of the farm. This makes it extremely attractive to project developers who can more accurately forecast their return on investment.”

Triodos invested in MCT in 2007. So far that is the bank's sole investment in the marine sector but Zahir-Bill says that the door is open.

Looking at the overall prospects for VC investment in renewable energy, Eric Wesoff, senior analyst at Greentech Media, said of 2008, “early stage financing is still alive. VCs and angel investors are still investing in new innovative technologies. Not as much as in 2005 to 2007, but angel and Round A financings are still represented.”

Going forward, it is likely that many other areas will show new enthusiasm for tidal power – or begin to act on plans formulated long before.

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