IRENA predicts all marine technologies will supply about 4% of the world’s electricity by 2050

According to the International Renewable Energy Agency (IRENA), of the current marine energy deployed, 97% is from tidal barrages and the remaining 3% from four emerging technologies: tidal stream, ocean wave, ocean thermal energy conversion and salinity gradient.

IRENA estimated that in 2020, despite the pandemic, developers deployed more marine power from tidal streams and ocean wave energy. The agency is forecasting exponential growth in the coming decade. Most of this will be tidal stream energy, with much of the rest being wave energy. IRENA further predicts that all marine technologies (excluding hydroelectric power) will supply about 4% of the world’s electricity by 2050.

Tidal Barrages Tidal energy is considered the most reliable form of renewable energy, as tides are constant and predictable. Significant research is taking place to develop tidal power into cost-efficient electricity.

The world’s two largest tidal research centers are in Nova Scotia’s Bay of Fundy and Scotland’s Orkney Islands, both of which have some of the most powerful tides on the planet. Despite their long-proven capability to generate electricity, there are only about 20 operational tidal power plants in the world, with numerous others proposed.

The largest two are in France and South Korea. The thirdlargest, and the only one in North America, is in the Bay of Fundy in Nova Scotia. These three plants are all tidal barrages and are relatively old, built in 1966 (France), 1984 (Canada), and 2011 (South Korea). Tidal barrages have been criticized for their threat to fish, wildlife and land erosion.

Tidal Stream

The world’s first two operational tidal current arrays were installed in 2016 off the coast of Scotland. More tidal energy installations are in the pipeline, including projects planned in China, Scotland, the Faroe Islands, and a hybrid project on Ushant Island off the coast of Brittany that will incorporate wind, solar, tidal and energy storage.

Tidal Energy Challenges:  Reducing costs to be competitive with other forms of renewable energy. Tidal energy will not maximize cost savings until enough of these systems are being installed to realize new cost-cutting opportunities, as has occurred with wind and solar energy.  Project developers continue to have difficulty attracting investors, who still view tidal energy systems as experimental.

Some tidal turbines have been badly damaged by strong underwater forces, with maintenance and repairs both difficult and costly.  Years long development and approval hurdles, combined with high costs with no revenues, have resulted in some large industry players exiting the market and one recently declaring bankruptcy.  Public opposition persists because of potential harm to fish and other marine wildlife

Wave Energy

Ocean wave (hydrokinetic) energy has the potential to be the world’s largest source of renewable energy for electricity generation, but it is the least developed. Prior to the pandemic, the global market for wave power energy was forecast to grow at an annual rate of 10.2% between 2017 and 2023. This industry is still evolving, with numerous Wave Energy Converter (WEC) technologies being tested and no clear winner. This has been one deterrent to attracting private investment. The European Marine Energy Centre lists 255 different WEC devices and their developers, most from Europe, the U.S. and Australia. One reason for the wide variety is that the device is designed to optimize the location and wave conditions where it will be deployed.

The most common types of WECs are:  Point absorbers (capture 40% of wave energy)  Attenuators (capture 23% of wave energy)  Oscillating wave surge converters (capture 19% of wave energy)

Wave Energy Trends

Hybrid systems are being developed that include other types of renewable energy.  A wave energy system in Gibraltar is adding solar panels to its floaters A project in Scotland will combine both wave and wind energy on a floating platform  A project being developed in Western Australia will incorporate wave energy, a solar farm and a battery storage system. Oscillating body power converters are a new type of WEC designed to resist damage from being constantly battered by powerful ocean waves. 

Salinity Gradient Power (“Blue Energy”) There are currently two technologies used in salinity gradient projects, both require membranes:  Pressure Retarded Osmosis  Reversed Electrodialysis These can be used to generate electricity for a standalone power plant in the right location or another area with high salt concentrations in water, such as brine from a desalination water plant. There are two new pilot projects in Europe, one in the Netherlands and the other in Denmark.

France also is looking into using a salinity gradient energy converter for desalination plants. PRO research has focused on improving the membranes, as polymer membranes proved too expensive and clogged with salt. One possibility being considered is carbon nanotube membranes.

Other research is under way experimenting with artificial salt solutions so the technology can be used in landlocked countries with no saltwater access. Blue energy, like tidal power, is a constant and predictable source of renewable energy. Still in the development phase, it is expected to become an important energy source if it can become cost competitive with solar and wind power.

Ocean Thermal Energy Conversion

Ocean Thermal Energy Conversion is a technology for continuous electricity generation based on the temperature difference between warm water on the ocean’s surface and cold seawater at depths below 2,600 feet. The world’s largest operational OTEC power plant is in Hawaii, with annual generating capacity to power 120 homes. It is onshore at the Ocean Energy Research Center, part of the Natural Energy Laboratory of Hawaii Authority. France’s Naval Group has installed an onshore OTEC prototype in its territory of La Réunion, an island in the Indian Ocean. Another OTEC pilot plant was built in 2015 in South Korea.