Wave power generator in Islay Island (UK) and Vizihinjam (India) used wound type induction generator with resister controls. Hellers generator is the same to use wound type induction generator, but control is different. Resister, capacitor and reactor are used for control to connect to power grid. Figure 22 shows efficiency of Hellers generator by control method. When it is controlled with resister, efficiency is 60 percent. When it is controlled with resister and capacitor, efficiency is 75 percent. When it is controlled with resister, capacitor and reactor, efficiency is 90 percent.

　

　

　

BBDB with box duct (Fig.23) was standard shape, but BBDB with cylinder duct (Fig.24) is an improved shape. Comparison between both shapes is shown in Figure 25 in order to improve economy of wave power in low wave areas such as Japan, BBDB with cylinder duct was adopted. BBDB with box duct (B Buoy) and BBDB with cylinder duct (C Buoy) are compared in specific pressure (Air pressure / Wave height). As shown in Figure 25, Cylinder duct (Fig.24) has higher air pressure than box duct (Fig.23) and air output is 170% higher in peak, with 30% higher in average for single float BBDB. The reason of this output difference is the difference between the surface areas of the inner duct. The cylinder duct has a smaller inner surface and movement loss of inner water will be at a minimum.

　

　

　

　

　

Based on the three floats terminator of Figure 10, two other designs of the terminator were developed (box duct, Fig.26, and cylinder duct, Fig.27) for 25 times scale up from the model 1,183 mm long, 510 mm wide.

　

The three floats terminator with box duct (Fig.26) has 12 ducts, each duct is 3,187 mm wide, 4,433 mm high and 14.36 square meter per duct times four ducts provide 56.52 square meter/one air turbine, three turbines and twelve ducts with total duct area of 169 square meters including horizontal duct of 29.5 meters long and vertical duct of 7.6 meters high.

　

　

　

Preparing the Terminator BBDB with cylinder ducts (Fig.27) has six cylinder ducts that are 6 meters in diameter. It has 28.36 square meters per one cylinder duct and total of 170 square meters and three turbines. Steel needed for Terminator BBDB (three floats) with box duct is 12 mm by 6,774.1 square meters of steel plate weighing and 650.3 tons. Terminator BBDB with cylinder duct needs 5,266.4 square meters, 505.6 ton of steel weight. Can be decreased by 23% of steel weight, and ship hull construction needed 505.6 ton x 30,0000=151,680,000 yen.

　

Twenty-five times scale up is suitable size for low wave power area such as Japan Sea, but for high sea such as Ireland, 36 times scale up is better and 1,350 tons of buoy weight is necessary, and construction cost of ship-hull is 1,350 x 300,000=405,000,000 yen.

　

　

(For high wave area such as Ireland)

Ship hull construction for Box duct---1,359 tons x 300,000 yen/t=405,000,000 yen

　

　

Year cost---0.13 x 795,000,000 yen=103,350,000 yen per year

　

When prototype BBDB model is scale up 36 times. Air output increases to 36 to the power of 3.5(36=279,936) which is equal to 2.2 watts x 279,936 = 616 KW. Average air output is estimated at 2.2 watts x 279,936 = 616KW per one float, and 1,848 KW by three floats terminator, and electric output 0.5 of it. In this high sea area, no wave climate is 5%, and three floats terminator generates 616 KW x 3 x 24 h/d x 365 x 0.95 x 0.5 = 8,094.240 KW-h/y. In this estimation, efficiency of 0.5 is consisted of generator efficiency of 0.9 and turbine efficiency 0.6 and others.

　

Power Cost---103,350,000 yen/y/8,094,240 KW-h/y = 12.7yen/KWh = 10.9 Cent Euro/KWh

　

Similar calculation was reported in Lewis (2000), using a single float BBDB (16 m wide, 40 m long), in Atlantic Wave Condition. Power Cost was reported 9.3 Cent Euro/KWh.

　

For low wave area such as Japan and Hawaii: three floats terminator BBDB (25 times scale up) with cylinder duct is adopted, 172 KW x 3 x 1.3=760.5 KW---1,3 is cylinder duct effort. Year Electric output is 760.5 KW x 24 h/d x 365 d/y x 0.75 x 0.6 x 0.8 =2,698,101 KWh/y In it. No wave time/y is 0.25 in Japan sea. Turbine efficiency=0.6. Generator efficiency 0.9.

　

　

Year cost 0.13 x 391,680,000 yen = 50,918,400 yen/y

Power cost=50,918.400yen/2,698,102KWh= 18yen/KWH=16Cent Euro/KWh

　

Since, low wave area has a merit in operation and maintenance than high wave area, and economical wave power use in low wave area become too practical but to do so, scale up ratio must be changed from 36 to 25. Terminator BBDB can generate higher output by using wave power in wide width of wave front (Masuda et al., 2002; Article, 2001; Masuda et al., 2002). Terminator will be the best way to get high and smooth electric output. Nielsen (2002) compared various kinds Wave Power devices, and BBDB was selected as the most economical wave power system in Wave Power Devices studied in Denmark.

　

　

Article. 2001. Terminator BBDB (Backward Bent Duct Buoy) MAREC Conference pp.219-P226. New Castle, UK.

　

Lewis, Tony. 2002. The Performance of Backward Bent Duct Device B2D2 in Atlantic Wave C condition. Fourth European Wave Energy Conference. pp.185-193.

　

Masuda, Y., Y. Kuboki, A. Takker, T. Lewis, X. Liang. 2002. Prospect of Economical Wave Power Electric Generator by the Terminator Backward Bent Duct Buoy (BBDB) ISOPE 2002 Kitakyushu, Japan.

　

Masuda, Y., T. Kuboki, T. Setoguchi, X. Liang. 2002. Development of Terminator type BBDB (Backward Bent Duct Buoy) Fourth European Wave Energy Conference. p.E12.

　

Nielsen, Kim. 2002. The Danish Wave Energy Program Second Year Status (SWAN DK 3) in Atlantic Wave Condition. Fourth European Wave Energy Conference, pp.312-P324.