Turning the ‘tides’

While solar and wind power have become the dominant renewable energy sources, there are other sources such as wave and tidal energy, which can be exploited in coastal areas. While wave and tidal energy have been used in some form or another since hundreds of years, the modern applications can be traced back to 1960s. In particular, the Japanese Naval Commander Yoshio Masuda may be regarded as the father of modern wave energy. In 1947, he invented the Oscillating Water Column (OWC), which is basically a navigation buoy fitted with a small air turbine. As a wave or a tide pushes water into the OWC, air is displaced and pushed through the air turbine, which creates electricity.

Wave and tidal power can also be tapped by Tapchans (or Tapered Channels, which raise the wave length of waves by tapering a channel, which feeds into a reservoir) and pendular devices (which is a rectangular box, with one end open to the sea with a flap attached. The waves create a pendular motion in the flap which powers a hydraulic pump and a generator).

Wave and tidal power devices can be onshore and offshore. Among the offshore devices, these could be either floating devices or fixed devices (fixed to the ocean floor with a chord or rope). These devices are collectively known as wave energy converters or tidal energy converters.

Untapped potential

Wave and tidal energy have the same disadvantage as wind energy, i.e. variability with the source of energy. Wave and tidal energy vary with the size of the waves, which, in turn vary with time of the day, location in the sea and time of the year. The UK, Norway and Scotland were the early experimenters in wave energy. With the European Commission launching a wave energy atlas called WERATLAS in the mid-1990s, many European countries began taking interest. In other parts of the world, many initiatives have been taken in Asia (Japan, Korea, Australia, New Zealand), USA, Canada and South America (Brazil, Chile, Mexico).

The total installed capacity of wave and tidal energy in the world was 527 Megawatts in 2023. However, the potential of tidal energy at 3,000 Gigawatts and that of wave energy at 2,000 Gigawatts is far higher. This translates to 29,500 Terawatt hours per year for waves and 26,000 Terawatt hours per year for tides.

Among the large wave energy projects in the world are:

• Perth Wave: This is the first wave farm connected to the grid and consists of a submerged buoy connected to a pump fixed on the sea bed. It has a peak capacity of 5 MW. The plant also produces desalinated water.
• Mutriku Wave: This is located in the Bay of Biscay in Basque Country in Spain and has an installed capacity of 296 KW.
• CalWave: This was a pilot project to harness ocean waves in San Diego, California, which was a success. A single xWave device of CalWAVE can generate 45KW of power. The plan is to install 500 units of wave energy converters to benefit many remote islands in the Pacific.

Many other wave power projects such as CorPower in Sweden and StingRAY of C-Power in Virginia, USA, are in the experiment stage and are expected to provide grid-connected wave power in the next 5-10 years.

Tidal energy is mostly harnessed through the construction of barrages or dams across the tidal estuary, with underwater turbines installed in the channels. The three large tidal power projects are:

• Sihwa Lake (South Korea, 254 MW, operating since 2011).
• La Rance River (France, 240 MW, operating since 1966) and Annapolis Royal (Nova Scotia, 20 MW, operated from 1984 to 2019).
• Minesto’s Dragon 12, in the Faroe Islands, supplying electricity generated from the ocean to the UK’s national grid. The 1.2-MW utility-scale power plant with a 28-ton, 12-meter subsea kite tied to the seabed produces electricity by converting kinetic energy from ocean currents and tidal streams.
• Magallanes Renovables, Spain: It has developed a vessel called ATIR, which has blades attached to harness wave power. This company proposes to set up wave energy plants in North Wales and in the European Marine Energy Centre in Scotland.

Many other tidal energy projects are also being planned across the world such as the River Mersey project in Liverpool, the UK , Swansea Bay, the UK and Incheon, Korea.

Conclusion

According to a Fortune Business Insights report of October, 2024, the global potential of wind and tidal energy in 2023 was USD 1 billion and will rise to about USD 20 billion by 2032. Many wave and tidal projects are being planned and the pilots have shown encouraging results. However, the complex technology and the high capital costs along with the limited geography where it can be harnessed are the main constraints.

The writer is Additional Chief Secretary, Department of Mass Education Extension and Library Services and Department of Cooperation, Government of West Bengal