While wind and solar power projects can be unpredictable because of variations in output, tidal power has long been mooted as one of the few renewable energy technologies that can be used to provide a base load for national power systems. Tides certainly can be predicted but although developers have been slow to turn scientific promise into commercial reality, significant breakthroughs are now being made. A combination of companies specialising in tidal energy, large power corporations and governments keen on promoting energy security and tackling climate change are providing the investment that should turn hypothetical potential into low carbon power production

Two trends can be discerned. Most projects involve the deployment of small numbers of relatively small scale turbines that have already been tested over several years and which could later be deployed in their hundreds to generate large amounts of electricity at many different locations. A handful of schemes, most notably in South Korea, are being developed that involve the installation of large turbines and hundreds of megawatts of generating capacity in the first instance, utilising technology that has been specifically designed for the project in question.

South Korea is a prime example of a country that promotes tidal power in an effort to boost energy security. With very little oil, gas or coal of its own, Seoul has long relied on imported feedstock and a burgeoning nuclear sector to supply the electricity that powers the thriving economy. Although liquefied natural gas (LNG) prices have fallen markedly in East Asia in the past six months, South Korea remains eager to reduce its dependence on energy imports through a two pronged strategy of new nuclear reactors and substantial investment in renewable energy schemes.

Under Seoul’s Second Basic Plan for New & Renewable Energy Technology Development and Dissemination, the proportion of renewables in the generation mix is scheduled to increase from just 1.4% in 2003 to 5% by 2011 and 10% by 2020. While solar power will make some contribution towards achieving this target, large scale tidal power projects will account for the lion’s share. A tidal power park is being created on the Wando Hoenggan Water Way, where new tidal technologies will be tested at the same time as selling the electricity they produce.

Korean Midland Power Company and British firm Lunar Energy have already tested their 1MW, 11.5m turbine in the area and are currently undertaking a feasibility study into the construction of a 300MW tidal scheme at the park, which will require the installation of 300 turbines by 2015. The turbines will be manufactured by Rotech Engineering and Hyundai Heavy Industries and the chairman of Lunar Energy, William Law, says that the joint venture “will combine the subsea engineering skills of Rotech with the known fabrication expertise of Hyundai.”

Another major investor in Wando Hoenggan is voith-siemens Hydro Power Generation, which has taken a 51% stake in Korea Current Power Joint Venture, alongside partners Korea Hydro & Nuclear Power Company (KHNP), renewable power company Renetec, the government of Jeonnan Province and South Korean conglomerate Posco. The joint venture plans to test tidal power equipment at the site.

However, it is the Sihwa Tidal Power Plant close to Ansan City on Inchon Bay in Gyeonggi Province, which is the country’s best known tidal power project. Developer Daewoo Engineering & Construction for Korea Water Resources Corporation (KWater) expects the project to come on stream as planned by the end of this year, when it will become the world’s biggest tidal scheme with generating capacity of 254MW, ahead of the 240MW La Rance plant in France. The total generating capacity is important but it is the sheer size of the turbines involved that could allow Sihwa to change the face of the global tidal power sector. Its ten bulb type 25.4MW turbines are being supplied by andritz Hydro as part of a €75M (US$99.5M) contract that also includes electromechanical equipment and engineering services.

Despite the progress that has been made with tidal power technology in recent years, it is unlikely that the Sihwa scheme would be economically viable if it were not for $250M of government support and the obvious environmental benefits of the project. In 1994, a 12.4km wall was built to separate Sihwa Lake from the sea but this has allowed waste from industrial operations on the lake to build up over the past 15 years. By allowing 60 billion tonnes of sea water to enter and then leave the lake each year as part of the tidal energy scheme, it is therefore hoped that pollution will be removed. The ten turbines will be located on the sea wall and will be powered by the movement of the water between the sea and the lake, using the head between the high tide and reservoir levels.

Yet the South Korean national and provincial authorities remain committed to exploiting the country’s tidal power potential, even where such environmental benefits are not apparent. Incheon municipal authority hopes to develop a much bigger power scheme by constructing 7.8km of barriers between four islands close to its city. It is estimated that this could support 600MW of generating capacity but Incheon does not benefit from existing sea walls, so total construction costs are expected to be in excess of $2B. A development consortium has yet to be created to pursue the proposed project and it seems likely that Incheon council will wish to see the successful operation of Sihwa before it commits its own funds.

French connection

Although La Rance came on stream in 1966, France made relatively little progress on expanding its tidal power sector for several decades. However, French interest in renewable energy seems to have exploded over the past year, and ambitious plans for new wind, solar, geothermal and tidal power projects have been drawn up. According to French firm Electricité de France (edf), about 80% of all European tidal power potential is located around the UK and France, so it is not surprising that France is the second biggest centre for tidal power investment in Europe after the UK.

EDF has asked potential investors to submit bids for tidal schemes that will receive priority connection to the national grid. OpenHydro of Ireland was unveiled as the first successful investor in October and will test its Open Centre turbines, with generating capacity of 2-4MW each, in the Paimpol-Brehat region off the coast of Brittany. The company hopes that its technology will overcome a great deal of the opposition to tidal power projects from environmental groups because they are mounted on the sea bed and so do not affect sea views and allow ships to pass overhead. EDF plans to test its own 3-6MW turbines in the same area from 2011, following an assessment of the tidal potential of sites along the coast of Brittany.

OpenHydro is also interested in developing tidal power projects in the nearby Channel Islands, where interest in tidal power is even greater. Although British crown dependencies, the islands of Jersey, Guernsey, Sark and Alderney lie much closer to France and so are ideally placed to export electricity to the European mainland, if and when tidal power schemes are developed in their waters.

In November, the Irish company bought a 20% stake in Alderney Renewable Energy (ARE), which has a 65-year licence to develop tidal power projects around the island. OpenHydro has drawn up plans for a 284MW scheme but ARE suggests that there is 3GW of tidal power generating potential in total. Brendan Gilmore, the chairman of OpenHydro, said: “Alderney’s waters contain one of the world’s largest resources of marine energy. We are delighted to invest in Alderney Renewable Energy Ltd and to provide our technology to harness this unique resource. This resource will deliver security of energy supply and further economic benefits for the residents of Alderney, and will provide Europe with long term carbon free renewable tidal energy.”

The plans are not without controversy, particularly as the island’s legislature, the States of Alderney, has voted to shelve a planned two year pilot scheme in favour of moving on to the 284MW phase more quickly. Given the lack of commercial track record for the technology in question, this certainly seems a bold move. However, Gordon Fitton, the chairman of the Alderney Commission for Renewable Energy (ACRE), says that the pilot project is not needed because of thorough testing at the European Marine Energy Centre.

Competition between the various islands, which are all governed separately, seems to be driving enthusiasm for tidal power. Guernsey Electricity is a shareholder, alongside EDF and Triodos Bank, in Marine Current Turbines, which has already tested its 1.2MW SeaGen turbine in Strangford Lough in Northern Ireland. The company is undertaking a thorough survey of tidal flows around the Bailiwick of Guernsey, which a UK government report has already concluded has some of the most attractive tidal resources in Europe. The Guernsey company certainly seems to have a bright future: it was named the leading marine power developer in Europe in a survey by Library House and The Guardian in September.

Jersey is keen to follow its neighbours’ lead. In December, the Jersey States’ tidal power steering group concluded that tidal energy could make “a real contribution” to the island’s energy security, as well as providing a new source of income by exporting electricity. New legislation and an environmental impact assessment on likely projects are now expected. The steering group’s chairman, Dan Murphy, commented: “We believe that Jersey’s waters offer an opportunity for us to harness significant amounts of renewable energy both for Jersey but also potentially for export to European markets.” The island is keen to hold talks with the other Channel Islands regarding cooperation on exporting electricity from tidal power schemes and indeed it would make commercial sense to develop a shared interconnection with the French grid.

British leadership

While the Channel Islands boast some of the best tidal power potential in Europe, there are numerous other sites around the UK that have the potential to turn the country into the world leader in such technologies. Indeed, both London and the Scottish government appear to have grasped the potential of tidal and wave power, both to provide low carbon, high security generating capacity and to create a new hi-tech sector and much needed employment. In the early 1980s, the UK had the potential to lead the way on wind power technology but government support was withdrawn, enabling German and Danish firms to dominate the industry. London is keen not to make the same mistake again and is providing a range of financial incentives to tidal power investors.

Scotland’s tidal power potential has long been discussed but it has taken rather too long to move from optimistic academic research to developing commercially viable projects. However, the Scottish government has steadily provided more financial support and a string of projects are now under development. All are on a small scale but most are being designed with rapid expansion in mind. Estimates published by the Scottish government suggest that there is more than 20GW of tidal power potential along its west coast and around the islands, from the Shetland Islands and Orkney, down the west coast to Kintyre and Galloway.

A development agency, Highlands and Islands Enterprise (HIE), is funding a study by Aquaterra to survey the tidal potential around Orkney and in the Pentland Firth, and applications for tidal projects have already been invited. A 2MW turbine is being tested in the Pentland Firth by Atlantis Resources Corporation of Hong Kong. In December, the company announced that it had signed a memorandum of understanding with CLP Group of China to develop tidal power turbines for commercial projects, although no financial details of the deal were revealed. Atlantis and HIE also plan to set up a central tidal data centre in Caithness to provide technical information.

Marine Current Turbines, which was mentioned earlier in relation to Guernsey Electricity, is confident that its SeaGen turbine will be ready for widespread distribution in the near future. In December, the turbine, which produces electricity for up to 22 hours a day, operated at its maximum capacity of 1.2MW for the first time at the Strangford Lough site, which the company claims is “the highest power so far produced by a tidal stream system anywhere in the world”.

The managing director of Marine Current Turbines, Martin Wright, commented: “Generating at full power is an important milestone for the company and in particular our in-house engineering team. It demonstrates, for the first time, the commercial potential of tidal energy as a viable alternative source of renewable energy. SeaGen is now running exactly as we said it would, but testing will continue to be carried out, not only to check SeaGen’s performance over extended periods of operation but also to evaluate how components are standing up to the harsh conditions and to determine how the design might be improved.”

While most interest in British tidal energy is concentrated on western coasts, some investment is being made on the North Sea coast. Experimental units are being tested near Immingham in the Humber Estuary by Pulse Tidal that could generate electricity in areas not generally considered suitable for tidal schemes. In a statement, the company argued: “Much of the tidal resource in UK waters and elsewhere is less than 20m deep and is not suitable for technologies based on rotating turbines. Shallow sites tend to be closer to shore where installation, connection and maintenance become more straightforward than in remote locations.”

Yet like South Korea, the UK has its own ambitions for jumbo tidal power projects. The most high profile potential site is the Severn Estuary, which has the second highest tidal range in the world. A 16km barrier across the entire estuary has been mooted that would cost £19.6B-22.2B (US$27.6B-31.2B) and provide generating capacity of up to 8.6GW, making it by far the biggest tidal energy scheme in the world.

However, it is feared that such a structure would have a detrimental environmental impact over a wide area of the estuary and the Severn Basin. Opponents argue that a more modest scheme based on a series of lagoons around the estuary to be filled at high tide would be more economical than a single barrier. The government appointed engineering firm Parsons Brinckerhoff to help assess the various designs and a shortlist of the five most attractive schemes was published at the end of January (see news story p5). A three month public consultation on the five designs is currently underway.

Further afield

Elsewhere in the world, tidal power is playing a more modest role in the dash for renewables, but there are great hopes for alternative tidal power technology in Italy. A 500kW unit is being tested by Fri-El Green Power in the Straits of Messina, which separates Sicily from mainland Italy. When developed on a commercial scale, each unit will comprise a floating platform that is attached to the sea bed and which has four cables connected to it. Each cable is kept on the surface of the sea by five buoys and has five 4m turbines attached to it that provide 1.2MW generating capacity on each cable. A spokesperson for the company said: “These tidal power plants are an economical way of producing electricity. The system is comparatively inexpensive to build and also to maintain, not least because it is based on modules, which can also be easily transported.”

Water speeds in the test area reach 2.5m a second and change direction every six hours but the turbines have been designed to allow the blades to move 180 degrees to capture energy in both directions. The company hopes that its technology can be deployed on a large scale to provide base load energy, while in the longer term it expects that it can be deployed far out to sea. At present, it has proved uneconomical to locate such devices more than 100km from the coast but Fri-El Green Power aims to use electrolysis to turn the energy produced into hydrogen, which could then be collected by tanker to be shipped to the mainland.

The Canadian province of Nova Scotia is reputed to have the highest tides in the world and so it is not surprising that it will be home to Canada’s first commercial tidal power venture. Three companies, Nova Scotia Power, Minas Basin Pulp and Power Company, and Clean Current Power Systems are to each invest $10-15M in testing their own turbines in the Bay of Fundy. The chief executive of Clean Current Power Systems, Glen Darou, commented: “Tides are better the farther you are from the equator, so Canada is in a good position. Tidal energy really has some special features because the tides are cyclical, which gives you predictability. When it comes to energy, that is very attractive.” The government of British Colombia is also assessing its tidal potential on the opposite side of the country, on the Pacific coast.

It is clear from the wide range of investors and new projects under development that tidal power is coming of age. It remains to be seen whether the industry will become a mainstream element in the generation mix of any country but technological advances are bringing production costs down at a time when governments are becoming increasingly concerned about energy security and fluctuating oil and gas prices. Yet while power production costs could be competitive with thermal power plants on highly prospective sites such as the Severn Estuary, the environmental implications of such major projects will need careful assessment. Smaller scale ventures, particularly those that do not require barriers overcome this obstacle but generate electricity at a far higher cost. The real challenge for the industry will be to demonstrate, as the wind power sector has done, that mass production of a range of different technologies can bring down production costs to a more sustainable level.