Progress in research and application of oscillating water column wave power generation devices

More successful in recent years has been the floating wave power plant developed by the Irish company Ocean Energy in 2006. The device has been in good operation after more than 20,000 hours of live sea tests, and the worst sea conditions recorded were wind speeds of 25-30 m/s and wave heights of 8.2 m[35]. FIG. 4 shows the test scene of the device under harsh sea conditions.

Oceanlinx, an Australian company, also developed a floating OWC wave energy conversion device - MK3 Floating OWC wave energy generation device [36]. The device, which is about one-third the size of a 2.5MW wave power plant, was installed in May 2010 off Kemblan Harbour, Australia, and serves as a floating breakwater on the west side. The unit is connected to the grid and sends electricity to the local Intergal Energy grid company.

(4) OWC type breakwater. With the deepening of research and development, small OWC wave power generation devices have been successfully commercialized, while large onshore and floating OWC wave power generation devices have been in the experimental stage due to high cost, low economic efficiency, and some technologies are not mature enough. The combination of the OWC with the breakwater increases the possibility of the device being widely used.

In the summer of 2011, Voith Company built the world's first OWC type breakwater that successfully supplied power to land in Mutriku, northern Spain [37], as shown in Figure 5. The plant generates about 300 kW of electricity, which can meet the electricity needs of 250 households. The unit equipment includes 16 Wells turbines with a power of 18.5 kW, and also makes full use of existing infrastructure such as the power grid, providing a good platform for the research and maintenance of OWC wave energy generation plants.

Voith is currently planning to build a shore-connected OWC breakwater unit off the north-west coast of the Isle of Lewis, Scotland, consisting of 15 OWC units, each connected to two turbine generators with a capacity of 132 kW and rated to produce up to 4 MW. The project will be the first newly built OWC breakwater power plant, the output of which will benefit many people, considering that the completion of the project will have a huge impact on the local grid, a series of other relevant factors such as power storage, control, etc. will be planned within the project. In addition, several Portuguese ports are planning to convert their original breakwaters to OWC breakwaters. [38]

3.2 Application progress of OWC devices in China

Compared with Western countries, the research and application of OWC devices in China started relatively late. In the mid-1980s, China developed 10 W OWC beacon lights, and later developed 60, 100 W OWC beacon lights. Among them, 10 W OWC beacon light was put into production in 2003, which is widely used in China's coastal areas and exported to many countries [32]. The development of a 3 kW onshore OWC wave power generation unit began in 1987 and was completed two years later on Dawansan Island. It has been proved that the shaft power of the turbine is much greater than 3 kW and the power generation efficiency is higher.

From 1992 to 1996, China built a 20 kW onshore OWC wave power generation device [39]. The device was an attempt to connect with a diesel generator in parallel, and was eventually terminated because the electrical energy could not be stably output. However, through the test of actual sea conditions, we know that the device has very good hydrodynamic performance.

In the same period, China also developed a kilowatt-class floating wave power generation device for the first time - the 5 kW rear-bent OWC wave power generation ship [40]. The device was tested at sea for 18 days with a maximum power of about 1.8kW, but the test had to be stopped due to a broken anchor chain [32]. From 1997 to 2002, China developed a grid-connected onshore OWC wave power station with a power of up to 100 kW[41]. After 2002, the research and development of oscillating water column in China basically stopped, and most scholars began to turn to the research and development of other wave energy power generation devices.