Chapter 4
Dreams and Realities
Sites are numerous around the world where tidal power could be harnessed. Many have been the locale of tide mills. More have become potential locations as a con- sequence of the development of low) and ultra-low head turbines. Thorough stud- ies have been conducted in prime areas: Argentina, Australia, Korea, Japan, India, England, Wales. Except for Wales, plans have been laid to rest: Argentina is short of the needed funds, Australia lacks sufficient customers, Korea locked into a political furore with France, the potential builder; however, it is again considering building a TPP, this time as an wholly “national” undertaking (Table 4.1).
Table 4.1 Non-comprehensive list of tidal power generation devices
Device Characteristics
Tide mill Ancestral scheme including a retaining basin, sluices, wheel, occasionally Sea mill using run of river in an estuary, mostly up and down movement due to tide Most derelict or dismantled. Some reconstructed and resumed activity as tourist attraction or as part of a “working museum”.
Tidal Power Plant[TPP]
Single or multiple basins system. Single or double (ebb and flood) effect.
With or without pumping mode. Requires a barrage or dam. A model with “removable” dam has been designed. Uses bulb, straflo, or even other turbines.
Tidal stream Tide current
Uses the tide current (horizontal movement) instead of up-and-down tidal movement. Avoid the need of a dam. Some operate in shallow waters, other schemes in deep fast moving channels.
Pulse stream Developers BMT and IT. Converter uses pair of hydrofoils oscillating across tidal flow, permitting extraction of tidal energy from shallow water. Currently building 100 kW prototype.
Gorlov Aleksandr Gorlov (Northeastern University, Boston) has developed a tidal power scheme with a helicoidal turbine. Needs no dam. Support from US Dept of Energy.
E.ON & 8 MW project on UK west coast. Uses Rotech Tidal Turbines Lunar Energy horizontal-axis turbines mounted offshore on sea-bed. Tide current system to be tested in 1 MW version at European Marine Energy Center (Orkney).
[EMEC]. Minimal environmental impact (Robert Gordon University).
Time frame: 2008–2010.
Neptune underwater generator converting tide current energy for feeding into the grid. A central tower is anchored to seabed, it has 2 arms each supporting a 3-blade rotor. Time frame 2007–2008.
Open hydro US company associated with Alderney Renewable Energy Holdings. 250 kW device to be tested at EMEC.
SeaFlow Property of Marine Current Turbines. Single rotor 300 kW device tried out (2003) off Devonshire coast. Forerunner of SeaGen.
SeaGen 2 rotor device generating 3 times as much power as SeaFlow. (1 MW) Cooperative undertaking EDF, UK Gov., Marine Current Turbines. Time frame 2007–2008. Site: No. Ireland.
Lynmouth 10 MW tidal farm in Bristol Channel. An array of 12 SeaGen-s.
SeaGen Arrays Environmental impacts currently under scrutiny. Considered currently at research stage only
Tidel Twin turbo device floating in the tide current, able to turn as the tide itself turns, enabling it to face the flow. Needs no support structure and offering easy installation and maintenance as it is simply moored to the seafloor. Time frame: 2008-2010 for a 1 MW for a pilot trial. Current trials held at NaRec (New and Renewable Research Centre, Newcastle)
Other rivers have also been considered such as the Mersey. Strong pleas continue to be made, particularly in Great Britain, for harnessing tidal power and the gov- ernment has implemented various incentive plans towards that end. Details about British past plans can be found in works by Shaw and in Charlier (1982) mentioned in the General Bibliography.
4.1.2 Japan
Japan once considered a Kyusyu-sited plant, and currently studies are being con- ducted at the Tokyo Institute of Technology for sites in Ariake Bay and tidal current schemes in the Kuroshyo. Tides in Ariake Bay reach 4.56 m with a mean range of 3.18 m. Mean depth of water is 21 m and maximum depth is 40 m. A barrage built to span the bay would be 13.6 km long. The output with 100 generators (com- pared with the Rance’s 24) would be 500 MW. Annual electricity generated would be 68.4×108kWh. The price tag, in the seventies, for such a plant was estimated to exceed 2,5×1010Yen, around US$2,500 million.
4.1.3 South Asia, Egypt
Studies have been pursued in Bangladesh (Salequzzaman and Newman 2001) while Singapore examined four locations to tap the energies of tides: the Lighthouse, Pasir Panjang, Sembawang, and Tanjong Fagar (Gupta et al. 2001). A design for a TPP in Egypt on the Red Sea has been submitted by Fahmy (2001) at the Fifth International Conference on Electrical Machines and Systems held in Shenyang (PR China) in 2001. As in China, the locations for the proposed plants are remote, hence these would provide small quantities of power, ranging from 1 to 10 MW.
4.1.4 Down Under
What has occasionally been hailed as the largest electrical power potential in Aus- tralasia remains untapped. One site, some 250 km north of Broome (State of Western Australia), was already considered as a “source of electricity” nearly 90 years ago.2 It was also discussed in a thesis in 1950 (Raynor) that dealt with tidal power in general. Since then and through the 1970s, the matter periodically received some publicity and the area was the subject of an in-depth study3. The latter dates from the mid 1960s and is the subject of SOGREAH reports published both in Perth and in Grenoble (France).4Of 50 sites examined along 1,700 km of coast, half were
2Easton, W.R., 1921, Report on North Kimberley District: Perth (West. Austr.), Northwest De- partment Government.
3Lewis, J.G., 1963, The tidal power resources of the Kimberleys: J. Inst. Eng.Austral. 35, 12, 333–345; Maunsell et al.,1976, Kimberley tidal power: Perth (W.A.), The State Energy Commis- sion of Western Australia; Saunders, D.W., 1974, Kimberley tidal power revisited: The Inst. Eng.
Austral., Conf. [Proc. Techn. Conf.] Melbourne (Vict.) 47, 11, 44–51. 47–55; Saunders, D.W., 1976, Kimberley tidal power: Proc. Cong. Austr. New Z. Assoc. Adv. Sci; Scott, W.E., 1976, Aus- tralia takes a new look at tidal energy: Ener. Int. 13, 9, 41–43.
4SOGREAH=Soci´et´e Grenobloise d’Applications et d’Etudes Hydrauliques (constructors of the Rance TPP for the French electricity company).
found technically (but obviously not economically) suitable, with Secure Bay, Wal- cott Inlet, George Water and St George’s Basin as the preferred ones.
4.1.5 Much Power, No Users
At several Australian sites, tidal ranges exceed that of the Rance, running from 9 to 12 m. TPP locations exist also on the east coast, e.g. on Broad Sound. The feasibility study, while mentioning several big problems—that however “can be overcome”—
points out that once a plant is constructed, it would be rather simple to expand the scheme to satisfy additional demand. The SOGREAH recommendation foresaw 30 bulb-turbines, inclusion of islands to cut down cost of the dam, two sluiceways, single generation, and an awesome ten-year construction window. There would be cofferdams—no longer considered necessary, as explained in Maunsell’s study—
and a kilowatt would still be considerably more expensive than one generated from fossil fuel. However, Lewis considering a rapidly amortized loan (for construction) by a sinking fund, predicted produced power below the cost of that from a nu- clear plant.
There have been no developments on the Australian tidal power horizon for some decades. Possibilities were also examined for New Zealand, but these are dwarfed by Australian potential.5The problem is that there is plenty of power available, and harnessable, but there is a lack of potential close-by customers in this region of Australia, and is similar to the one in Northwest America where energy is for the taking, but customers are too few; it is what has torpedoed any plans to implant a TPP on the Turnagain Inlet.6
4.1.6 India
There have been new statements of interest made by Indian laboratories, but no actual plan is being “pushed”. Of the several locations once retained, the Gulf of Kutch is the principal one. The 600 MW installed capacity plant would have neces- sitated three barriers, a 3 km one across Hansthal Creek. The help of the Electricit´e de France would have been called in. The Rann of Katchchh was ultimately se- lected for a feasibility study. As in France, proponents envisioned a road atop the barrage that would encompass no less than four barriers. The scheme would be a single-basin, single-effect facility taking advantage of an 8 m local tide range.
But some drawbacks were obvious: the vicinity of the ports of Navlakhi and Kandia, the lack of a solid firm rock foundation to within 15 m of the site with a clayey soil as foundation, aeolean sediments and a highly saturated marine littoral,
5Keough, Mc., 1959, Tidal power: NZ Elec. J. 32, 3, 82–83.
6See details, e.g. in Charlier, 1982, Tidal energy: New York, Van Nostrand-Reinhold.
conspicuous sedimentation, an uneven topography, seasonal variations.7On the pos- itive side substantial socio-economic advantages would accrue and the absence of natural impact has been underscored. Optimists had seen the plant “at work” by 1997, but more than ten years later not even the first stone has been laid.