ZJU develops electricity-generating turbine using ocean current energy

The ocean is teeming with energy and it is inexhaustible. It plays a crucial role in the sustainable development of mankind.

Three gigantic electricity-generating platforms using ocean current energy are in smooth operation near Zhairuoshan Island, Zhoushan.

Over the past month, Guodian United Power Technology Co. Ltd. has developed an electro-hydraulic variable-pitch turbine with a capacity of 300 kW, based on a sample device designed by ZJU. The turbine has successfully produced electricity at the ZJU Experimental Base for Ocean Current Energy Electricity Generation on the Zhairuoshan Marine Technology Demonstration Island.

“This turbine is a sample unit on an industrial scale and is expected to become China’s first well-formed facility for electricity generation using ocean current energy,” says LI Wei, vice director of ZJU Ocean Academy.

Ocean current power is a form of marine energy derived from the harnessing of the kinetic energy of marine currents. It is theorized that the annual average power of ocean current energy amounts to approximately 1.4×107 kW in China, one of the regions with the highest power density in the world. The average power density in the waters adjacent to Zhoushan Archipelago hits 20kW/m². Thus, these waters have enormous promise for electricity generation.

Equipment is key to obtaining kinetic energy from ocean water and converting it to electrical energy. It is therefore essential that the three hard nuts be cracked in three dimensions—the efficiency of energy machinery, the reliability of marine facilities and the stability of intermittent power supply units.

“It is perfectly possible to overcome one of the afore-mentioned difficulties. To measure up to these requirements, Zhejiang University has developed a set of ocean current energy turbines, featured by a high length-to-diameter ratio, a semi-direct drive system and a high-performance horizontal axis,” says LI Wei. ZJU has contrived a holistic approach and developed a new type of turbine. 

There are primarily three types of ocean current turbines: the horizontal-axis turbine, the vertical-axis turbine and the vibration-axis turbine. The turbine developed by ZJU rotates around a horizontal axis. “In comparison with the other two types, the horizontal-axis turbine is most efficient. When water flows by, virtually half of the current energy can be extracted,” explains LI Wei.

How can a horizontal axis be made? What is the sophisticated technological line? After meticulous analysis, LI Wei et al. found out that conventional medium- and large-sized horizontal-axis devices have their limitations, such as low efficiency, poor reliability, weak temperature control and deterioration of sealing material.

In response to these flaws, LI Wei et al. pioneered in developing an optimal turbine with a high length-to-diameter ratio and a semi-direct drive system. It indicates that the higher the length-to-diameter ratio, the better the turbine performs.

Meanwhile, LI Wei et al. also incorporated innovativeness into the making of two key components in variable pitch and sealing. On the one hand, they invented a hydraulic pitch-controlled device marked by its exceptional propulsion. On the other hand, they developed dynamic sealing technology on the basis of differential pressure and a three-layer sealing structure, thereby elevating the turbine’s underwater operation time to the top-notch level.

This turbine has produced a far-reaching impact both at home and abroad.