Taking advantage of wave energy in Trường Sa Islands

Posted at: WEDnesday - 12/09/2012 14:28 - post name: Phan Trọng Quỳnh

 
Taking advantage of wave energy in Trường Sa Islands

Recently, a research team of scientists from the Institute of Applied Mechanics and the University of Natural Sciences has conducted the project named “Research and Evaluation on Major Potential Marine Energy Sources and Proposal on Exploiting Solutions” in the Trường Sa Islands and make a detailed calculation of the total annual average wave energy in the study area. On the basis of the obtained results, along with the economic, social, and environment impact assessments, the research team had selected the suitable device to convert wave energy into electric energy for the Trường Sa Islands.

The research team placed 4 survey spots the Southeast, Northeast, Southwest, and Northwest around the Trường Sa Island. Based on the calculated results of wave mode and wave energy at 4 survey spots and results of wave energy of the entire East Sea, it could be seen that the wave energy of the Trường Sa Island in particular and of the Trường Sa Islands in general is the strongest one in the coastal areas and offshore areas of Vietnam's territory. The wave energy significantly depends on the two seasons of northeast monsoon and southwest monsoon, of which in the northeast monsoon season, due to the strong and stable wind speed and huge wave momentum, so that the wave energy reaches the peak of the year. This demonstrates that the potential of wave energy in the Trường Sa Islands is very significant.

According to the survey results, the Northeast of the island is the most suitable place to install equipment to convert wave energy into electricity. This is the place with the largest energy among the 4 survey spots. The energy difference between the strongest and weakest months is still within the limits of the device. In addition, this place is located in the minimum slope and depth compared to the others (about 25m in depth). Therefore, the slope and depth conditions of the place will help the process of construction and equipment maintenance easier.

After surveying the area around the island to find the location to place the wave-energy conversion device, the scientists needed to select a suitable device.

Among the popular types of wave-energy conversion device of the world, the researchers selected the improved Powerbuoy device of the Uppsala University, Sweden. This device proved to be best suited to the Hoàng Sa Islands. The preeminence of this device is the new energy conversion principle, which largely differs from the existing principles. Instead of changing the standard generators so that they could be correspond to the rotational speed of the wave motion, a completely new type of generator was invented at the Uppsala University.

These generators are designed for “standard” of the wave. The installation option is also improved – the generator is placed on the seabed. Another accessory is a wire connecting the generator up to a buoy on the sea surface. The generator consists of a piston moving up and down in the stator. Hence, the generator does not rotate itself, but creates movement of the direct piston from the buoy on the sea surface through a cable. This is the preeminence of the system. The generator located at the bottom of the sea is protected from the extreme weather conditions and human destruction. Even in the case the buoy is broken due to the extreme stormy conditions, the buoy and wires will be drifted into the shore and the damage will be negligible. The generator is designed as the direct-driven linear generator with the slow rotation speed, which means that it could convert the energy of the small waves. Moreover, this type of generator is made from the very simple mechanical devices – buoys and wires. This reduces the design cost and increases the efficiency of investment. The calculations show that the option to use this system could raise the trade competitiveness without long-term subsidies.

Translated by Nga Nguyen

 

Author: MSc. Nguyễn Thanh Điệp (Faculty of Maritime – Vietnam Naval Academy) -
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