Technology Progress in Tidal Energy

The key technology for tidal power station includes tidal-powered generation sets, hydraulic structure, and operation of power station and marine environment. The technology employed to the tidal power station built in 1960s and 1970s was under-developed. But Langce power station in France, Andeboriece power station in Canada and Jiangxia power station in China were constructed with riper technologies.

In tidal power station, the investment on turbine generation sets covers 50% of the total, and the manufacturing and installation of the sets should be firmly controlled during the period of construction. Bulb passing-through type generation sets adopted in Langce power station belong to the first generation of model, with the individual capacity of 10MW. The whole passing through type generation sets adopted in Andeboriece power station in Canada are the second generation of model with the individual capacity of 20MW. Jiangxia power station was designed with the individual capacity in the region of 0.5 to 0.7MW, in accordance with Langce power station and combined with the actual condition of Jiangxia, which can compete with Langce power station. The whole passing-through type of generation sets has also been developed in China with the individual capacity of 0.14MW, which was supported in the major project to tackle by the former national science commission in the period of ¡°the Eighth of Five years¡±. This generation sets were commissioned in low water head power station in Mei county of Guangdong.

The production cost of whole passing through type can be 15%-20% lessen than that of bulb passing through type. Generally speaking, the technology of tidal-powered generation sets tends to be well developed. Langce power station has been put in operation smoothly for over 30 years, while Jiangxia also nearly 20 years. But they were all manufactured on the grounds of the technologies in 1960s to 1970s.

It has great potential for improvement of tidal-powered generation sets, in particular to mitigate the cost and to upgrade the efficiency, designed by state-of-the-art technology in the field of manufacturing, material, control and as well as fluid power.

The cost for hydraulic structure covers 45% of the total in a tidal power station, which is also one of important aspect in cutting down the cost. The traditional method was to construct by the local material for dam or reinforced concrete through gravity structure, which was heavy in engineering and expensive in cost. Gicelaya power station in former Soviet Union adopted pre-cast reinforced concrete caisson for buoy transport, which mitigated the engineering and cost. This technology was also applied to some of tidal power stations in China to construct part of the facilities for the power station, i.e. the penstock, which received the same effect.

The operation of tidal power station is to be of high intelligence. Phase difference between the level in open sea and reservoir must be skillfully made use of to effectively increase the output power of the station.

Langce power station firstly adopted the technology called Pump Technique, which resulted in the increment of 10% of annual net generating capacity for the power station. In single-reservoir and dual functional power station, the technology is utilized to expand the dual direction pumping capability, which can be realized by bringing the generator sets with dual function, that is generation or pumping, or by adding dual directional pumps. Its working process is to lower down 1m of the water level of the reservoir by pump shortly after the generation in the ebb tide, so as to expand the water head for generation in the flood tide. Since the technology is utilized to proceed in very low water head, and the following generation should be proceeded in higher water head, the generation capacity resulted by the increasing of water head is therefore far larger than the generating consumption for pumping, which may bring greater net energy benefits.

Issue of marine environment on tidal power station has been a complex question for study, mainly comprising of two aspects, one of which is the environmental impact in the construction of power station, for example, water temperature, water flowing, salinity layer and the seashore immersed by water. This variety will impact on the growth of plankton and organic subsistence and fishes in this area. Research on the complex relationship between the ecology and nature still remains to be conducted. Another impact of marine environment on the power station is about the accumulating of mud, which has related to the sand content in local water, local topography, as well as tidal and current. For example, Jiangxia, Shashang and Haishang power stations are all locating at Leqing Bay of Zhejiang province, in particular Jiangxia and Shashang power stations are very close, which the sand content are similar, but Jiangxia is not accumulated with mud, while Shashang happened the accumulation of mud in premier stage. Another example is regarding the Baishakou power station in Shangdong province, where the mud is accumulated light in the reservoir, but heavy in inlet and outlet channel of power station. The reason is related to the incorrect arrangement on the position of inlet and outlet channel. In a word, the environment issue on tidal power station is much more complex, and detail analysis should be made for different power stations.