Vast tidal power schemes have been proposed in Russia and China and large industrial prototype modules are undergoing sea tests in Australia. Development and practical applications are what is needed now.
Tidal, esturial flow and wave projects in Russia, China and Australasia over the last 20 years have generally been characterised by larger and more ambitious pilot projects than those in Europe, Scandinavia and the Americas, and contemporary reports from China indicate that several tidal barrage projects of up to 400 MW output are in the offing. Tidal Electric, which has bases in London and North America, reported in October 2004 that,
following a meeting in at the Yale Club in New York with governor Zhand Wenyue of Liaoning Province and the mayors from four cities close to the project site, together with consenting authorities, foreign trade officials and other key officials, ‘The Chinese government has expressed its enthusiastic support of Tidal Electric’s ambitious 300 MW offshore tidal lagoon in the waters of the Yalu River by signing an agreement pledging to co-operate with the development.’
Tidal Electric was represented by chairman Peter Ullman, director Gregory Bonenberger, and Michael Ashburn, who heads up Tidal Electric’s affiliate company Tai Yang Dian Li (‘Clear World’). Detailed discussion were held in New York and included a contingent of local officials who pledged their support and agreed to provide Tidal Electric with environmental data, tidal data, and liaison services.
Tidal Electric chairman Peter Ullman had travelled to China in August when he toured the sites and quarries, met with candidate Design Institutes and conducted a day-long workshop in Beijing describing the offshore tidal technology and fielding questions from government officials, oceanographers, environmental specialists, and engineers along with GE Hydro Asia based in Hangzhou.
Progress in China
China has been among the first to develop wave and tidal energy conversion systems as part of a major industrial effort. According to the World Energy Council’s 2001 Survey of Energy Resources, since the beginning of the 1980s China’s wave energy research has concentrated mainly on fixed and floating oscillating water column (OWC) devices and also a pendulum device. By 1995, the Guangzhou Institute of Energy Conversion (GIEC) of the Chinese Academy of Sciences had successfully developed a symmetrical turbine wave power generation for navigation buoys (60 W). Over 650 units were deployed along the Chinese coast.
There were three main projects then supported by China’s State Science and Technology Committee aiming to develop onshore wave power stations:
• A shoreline coastal OWC undertaken by GIEC in Guangdong province. After problems encountered in planning a device on Nan’ao Island, construction proceeded on a two-chambered machine with a total width of 20 m, rated at 100 kWe at Shanwei. Power generation was scheduled for 2000/2001.
• A shoreline pivoting flap device (‘Pendulor’) developed by Tianjin Institute of Ocean Technology of the State Oceanic Administration rated at 0.05 MW situated on Daguan Island in Shandong province.
• An experimental 3 kW shoreline OWC measuring some 4m wide was installed on Dawanshan Island in the Pearl River estuary in water 10 m deep and supplied electricity to the island community. Following a period of good performance it was upgraded with a 20 kW turbine addition. However, following a three month test run 1990, technical problems forced the closure of the power station.
There have also been reports of a substantial tidal power project in Jiangxia and a number of small tidal projects as well a large tidal lagoon project on the mouth of the Yalu River.
High tide in Korea
In the Republic of Korea a potential 480 MW tidal energy site in Garolim Bay, where the mean tidal range is reported to be some 4.7 m, and another at Cheonsu in the Gulf of Asam with a mean tidal range of 4.5 m, have been investigated by KORDI – the Korean Ocean Research and Development Institute. Some parts of the west coast of Korea have mean tidal ranges of up to 6 m.
KORDI commissioned three British engineering firms to pursue tidal power studies in 1986. Engineering & Power Development Ltd in association with Binnie & Partners and Sir Robert McAlpine investigated the west coast barrage project in Garolim Bay and a pre-feasibility assessment was also mooted on the harnessing of tidal current in the Usuyong channel between Chindo Island and the mainland.
In September 2004 the Korean Ministry of Maritime Affairs and Fisheries (MMAF) announced the construction of ‘the world’s largest tidal power plant’ a 260 MW tidal barrage at Ansan City’s Shihwa lake in Gyeonggi Province (Figure 1) about 20 km SW of Seoul. Further south in the Uldol-mok strait, Jin-do island, off the southern tip of Korea, construction on an experimental tidal current plant got underway, in 2005, in the Uldol-mok strait. It is due to be in operation by 2007. The strait is described as a 300m wide bottleneck with a maximum water speed of 6.5 m/s and is one of three prospective sites in the Jin-do island area with a combined potential of 3.5 GW.
Now the 260 MW Shihwa Lake Tidal Plant has received the go ahead and construction contracts are already being signed. Daewoo, the leader of the Korean joint venture with KOWACO (Korean Water Resources Corporation) the government water authority of South Korea serves as the project developer and owner. Daewoo will lead the Korean joint venture along with other civil engineering companies. The total project cost is put at $250 million.
Daewoo has placed contracts with VA Tech Hydro to carry out the detailed design and equipment supply for the turbine generator equipment as technology provider as well as supplying electromechanical equipment and services. There will be ten 26 MW unidirectional bulb type turbines with directly driven generators.
The unidirectional flow of some 60 billion tonne of sea water into Shihwa Lake will also purify the water in the lake from pollution by industrial process water discharges. The predicted power output is said to match the total demand of Ansan City’s 500 000 population.
Some 20 years ago in the August 1985 issue of Modern Power Systems we reported plans to install massive tidal power projects on the Russian north western sea coast, and a 400 kW tidal plant planned in Murmansk might have shown the way.
Tidal power development has been under way in Russia at least since the 1930’s, not so much in eastern Russia as transarctic russian Lapland. A pilot plant generating some 400 kW from 5m high waves was constructed at Kislogubsk in Kislaya Bay on the White Sea about 10 km from Murmansk and commissioned in 1968. The reinforced concrete structure was 36m long, 18.3 m wide, 15.35m high. A floating powerhouse was constructed to be towed to the site and sunk in a gap in the already built dam.
According to Novosti the plant was mothballed due to a lack of funds for modernisation in the mid-1990’s but recently commissioned again after “a hiatus of almost a decade”. A new fixed blade rotor was installed which was developed at the Sevmash nuclear submarine facility and built at Sevmash. This initiative was successful enough to stimulate a number of design studies for much larger tidal plants at sites in the north and east of the country: Lumbov (67 MW) and Mezen Bay (15 000 MW) in the White Sea, Penzhinsk Bay (87 400 MW) and Tugur Bay (6 800 MW) in the Sea of Okhotsk where according to Novosti tides reach 17 m.
The Mezenskaya Tidal Power Plant in the White Sea would have a 92.7 km long dam enclosing 15 000 km2 of water carrying an average head of 9m. This would have had a generating capacity of 15 000 MWe and would produce as much as 50 million MW/a. The Mezen Dam, much of which would span quite shallow water, would be formed by detonating a string of explosive charges buried in the sea bed to throw up a wall of debris.
Kembla operates down under
The Energetech company was founded by Dr Tom Dennis in Sydney, Australia in 1997. Installation of the first wave plant using the Energetech technology commenced at Port Kembla in New South Wales, Australia. The turbine unit and its associated equipment was lifted by a 250 ton crane on to the main wave energy structure and attached on 10 June 2005 at the roll-on/roll-off berth inPort Kembla Harbour.
During July 2005 Energetech reported that the wave energy device, shown in Figure 2, was installed and operated at Port Kembla and power delivered to Australian based utility Integral Energy during a planned test period in June. ‘Tests were run and valuable data was logged indicating that the primary system worked as designed. While the incident waves during the deployment period were low, there was clear confirmation of the amplification of the waves due to the parabolic wall. The air velocities past the turbine and the overall system efficiency indicators exceeded expectations. ‘During further testing, the wave energy unit regenerated power into the local grid. Final installation in the near future will now incorporate the technical improvements during this initial test phase.’
As currently designed, the modules constitute four legged structures mounted on pads on the ocean floor, with the main body located above water level and anchored with stabilising cables moored to the sea bed. Two curved walls concentrate the waves into a central hollow chamber with substantial Bernoulli acceleration to drive an oscillating column, in which the up and down wave motion impels compressed air through a bi-directional flow turbine.
Seapower Pacific Pty Ltd of Perth, Western Australia has built another sea bed OWC prototype of massive proportions backed by venture capitalist Carnegie Corporation Ltd which holds an equity stake in their Renewable (Wave) Energy Project known by the acronym CETO. Deployment of this self-contained 20 m long by 10 m wide by 4.85 m high seabed mounted device, (shown in figure 3) will carried out in Perth with the full support of the Freemantle Port Authority.
The mechanical energy generated in this case is transported to the electrical generators and/or reverse osmosis desalination system, or other utilities by high pressure sea water at up to 1000 psi (7000 kPa) through small bore pipe driven by specialised steam pumping technology. This is a concept on which another Carnegie backed company – Pursuit Dynamics – has spent some $A20 million. Renewable Energy Holdings plc of Douglas, Isle of Man, UK also has an interest in this project. Seapower Pacific Pty Ltd is owned by the London listed company Renewable Energy Holdings plc, of which Australian companies Pacific Hydro Ltd and Carnegie Corporation are substantial shareholders.
CETO is a sea bed mounted device, allegedly safe from storms and ocean forces, which has been under development since 1999 with in-sea testing originally scheduled to commence in 2004. Construction started in December 2003. It took some 12 months to manufacture and install followed by a 3 month dry testing period. The CETO unit was reportedly launched on 21 March 2005 and then kept at the quayside for ‘testing, concrete ballasting and installation of computer software’.
On 4 May 2005 the device was towed out to sea and sunk onto the demarcated area on the sea bed and 250 m3 of water pumped into its ballast tanks. Following the Australian winter the unit was flooded with water inside as a security measure while pipeline connections were installed. A 125 mm ID water pipeline was connected to the pumps as well as two airlines and a fibre optic cable for control and measurement purposes.
On 19 July the unit was pumped out, and after internal inspection the interior was sealed and then pressurised. The underlying principles of the device were reported to have been quickly proven in the first few hours of operation. Testing continues.
In the late 1990s Tidal Energy Australia, a Western Australian company, proposed a combination double basin/double flow design for Doctor’s Creek, on King Sound near the Kimberley town of Derby. The advantage of their scheme was that it could provide around-the-clock power. One basin retains a high water level and the other a low level. A channel cut between the two holds the turbines used for power generation.
At high tide, water is let into the high basin, and at low tide, is let out of the low basin. The plant, with a capacity of 48 MW, would have been the second largest tidal power station in the world and the only one providing continuous power output. This capacity would fully supply the needs of the region (for both residential purposes and exploitation of the Kimberley’s abundant mineral resources), but after much debate, the tidal plant was rejected. On as smaller scale a delayed current device installed by Hydro Venturi in the U.K. is already up and operating on a small river close to the original Derby and selling electricity into the grid profitably. In this case some of the flow in the river is diverted through a large pipeline containing a Venturi restriction to discharge back into the river further downstream.
Air is drawn into the low pressure region of the Venturi stream through a pipe connecting to an air turbine-generator unit. The equipment is simplicity itself and maintenance is minimal, carried out in open air on dry land.
Woodhead Technologies of Melbourne, working along with the SMEC group of companies and energy storage specialists Lloyd Energy Systems are working on a far grander prospect using sea flow restricted or constrained by a peninsula or isthmus (Figure 4) and they have found a prospective site in Java. Its characteristic variable power generation is used to create heat for storage in high purity carbon, then utilised to generate electricity on demand. Technical and commercial evaluations have reportedly been carried out by RMIT University (Australia) and LEK Consulting and the system has now been patented in Australia, the UK and the USA.
The three companies were planning to team up with British concerns including Pennant Wind, JWG Consulting and Rushbrook Designs to develop pilot plant sites on the coasts of Scotland and/or Wales before construction of commercial systems for outputs of 1 to 5 MW in 2006/2007.
Sixty years of experiments
Research into wave energy began in Japan with experiments in the 1940s and became significant with the late 1970’s. Commander Yoshio Masuda’s wave powered navigation buoys using the resonant oscillating water column principal which was further developed in Norway by Kvaerner Brug.
Since then extensive research has been undertaken with particular emphasis on the construction and deployment of prototype OWC devices:
Developed by Japanese ministry of Transport’s Port and Harbour Research Institute, a 20 m wide five-chambered OWC built as part of the harbour infrastructure of the Port of Sakata became operational in 1989. The structure was built into the end of the port’s second caisson breakwater. After tests just three of the 3 m wide air chambers were used for energy production. A turbine-generator module of 60 kW was used as a power generator unit for demonstration and monitoring purposes. The 16 bladed turbine measure some 1.34 m diameter. This was due to be replaced later by a larger and more powerful turbine of some 130 kW.
In 1983, a 40 kW steel and concrete OWC deployed on the shoreline structure at Sanze functioned for several years after which it was examined to investigate its resistance to corrosion and fatigue. The 17m wide structure operated in a mere 3m depth of water.
Between 1987 and 1997 a scheme comprising 10 OWCs installed in front of an existing breakwater at Kujukuri beach, Chiba Prefecture, directed air emitted from each of the units into a pressurised reservoir to drive a 40 kW turbine.
During 1996 a prototype 130 kW OWC was mounted in a breakwater serving the Haramachi coal-fired power station in Fukushima Prefecture. This used rectifying valves to control the flow of air to and from the turbine in order to produce a steady power output. Experimental operation proceeded 1996 and 1998. The floating OWC, designated the ‘Backward Bent Duct Buoy’, was similar to a conventional OWC but with the opening facING towards the shoreline.
Also, a Pendulor wave energy device has been under investigation for over 15 years by the Muroran Institute of Technology. Wave action causes oscillation of the plate and the Pendulor compresses fluid in a hydraulic power take-off. A second generation prototype was said to use active control for efficient energy conversion.
The “Mighty Whale”, a 50 m long, 30 m wide, 12 m deep prototype shown in figures 5 and 6, was under development by the Japan Marine Science and Technology Centre (JAMSTEC) from 1987 to 2002. As the world’s largest floating OWC, with a displacement of 4380 tonne it was inaugurated in July 1998 at its mooring position just outside the mouth of Gokasho Bay off Mie Prefecture. Six mooring chains were used to restrain the structure some 1.5 km offshore in about 40 m depth of water in a region which experienced major typhoons.
The overall rated power capacity was set at 110 kW and it was planned to test the device for a period of approximately two years. The Whale also served Nansei Town as a wave breaker: an area of calm water behind it was intended to be beneficial to fisheries and other forms of marine activities. Larger assemblies of such modules could be used to form a sea wall or barrage.
The structure contained three air chambers to absorb wave energy distributed breadthwise to face the predominant wave direction. Each chamber house a tandem type Wells turbine and generator.
The total output recorded from August 1998 to December 2001 was 136.2 MWh generated at an overall efficiency varying from 12 to 15%. Jamstec’s performance report indicates that it operated at an average power output of 5.85 kW. The device ceased operating in March 2002, when the project term expired, and was dismantled, but not before it had produced what Jamstec characterised as valuable data for the optimisation of future floating wave designs.
India initiated a wave energy programme in1983 at the Indian Institute of Technology (IIT) under the sponsorship of the Department of Ocean Development beginning with three types of device: double float system, single float vertical system and the oscillating water column. It was reportedly found that the OWC was the most suitable for Indian conditions.
A 150 kW pilot OWC was built onto the breakwater of the Vizhinjam Fisheries Harbour, near Trivandrum (Kerala), with commissioning in October 1991. The scheme operated successfully and an improved power module was installed at Vizhinjam in April 1996 that in turn led to the production of new designs for a breakwater comprised of 10 caissons with a total capacity of 1.1 MWe. The caissons were designed to be spaced at an optimum distance apart, in order to increase their overall capture efficiency to above that of a single caisson.
The slipformed concrete caissons measured some 23 m x 17 m x 15 m high with a chamber entrance 10 m wide by 6 m wide. The completed caisson, with a draft of some 10 m, was towed to its location and lowered onto a prepared stone bed by flooding and then filled with 3000 te of sand ballast. A sea bed slope of 1 in 50 before the caisson met a wave resource of 20 kW/m average monsoon input. The single 10 m wide chamber fed two eight bladed turbines
Wave and tidal power does not necessarily need to generate electricity to be commercially viable. In some parts of the world desalination of sea water is a more urgent requirement as well as being an easier and more natural application using hydraulic accumulators and reverse osmosis. Many forms of energy storage have already been tried and tested including pumped storage, delayed tidal systems and high purity carbon heat storage.
Existing experience is not entirely new and unproved, but waves and tides are quite ubiquitous. With water levels rising owing to greenhouse effects, ever increasing floods and tsunami disasters in divers places, perhaps we need a specialist, possiblya United Nations, agency to speed up development, reduce duplication of effort and deal with the international implications.
Figure 1. Location of the 260 MWe
Shihwa Lake tidal barrage in South Korea. Figure 2. The Energetech seabed mounted wave generation module in action at Kembla. Figure 3. Sketch showing the salient features of Seapower’s seabed mounted CETO. Figure 4. A suitable tidal barrage site in Java. Figure 5. Artist’s impression of Japan’s “Mighty Whale” and its working principle Figure 6. The Mighty Whale takes to the sea. (Both photographs courtesy of JAMSTEC)