Global energy security is greatly undermined by broad reliance on burning finite fossil fuels. Total and per capita energy consumption has been going upward throughout the last few decades and overall demand is only expected to burgeon along with human population growth. Many countries across the world have started recognizing the dire need for sustainable energy, thereby developing policies to encourage investments in renewable technologies. Over 30% of global energy consumption is currently being met by green sources. It is expected that about 85% of energy production will derive from clean energy within the coming two decades. According to the International Energy Agency, marine energy alone is sufficient to meet entire global electricity needs. If it grows by 33% a year, we could achieve a net-zero world by 2050.
The Intergovernmental Panel on Climate Change (IPCC) has identified six renewable energy sources that carry global potential. These include bioenergy, direct solar energy, geothermal energy, hydropower, ocean energy, and wind energy. The last two have marine environment component that carries extensive potential in renewables. Wind technology, covering both onshore and offshore options, is far advanced so far compared to marine energy. However, the latter has been emphasized recently as its theoretical potential is far greater than the human requirements to be met.
Types of Marine Energy
Marine energy includes a diverse range of technologies used to extract renewable energy from waves, tidal ranges, tidal currents, and ocean currents as well as ocean thermal energy conversion and salinity gradients. Marine energy is not only created in oceans but also in rivers, lakes, streams, estuaries, and more.
Wave Energy
Waves are repetitive in nature as well as consistent within a specific season. They also have the highest energy density compared to other renewable sources like wind, solar, biomass, and geothermal. These features turn waves into a particularly valuable renewable energy source. Kinetic energy from wave movements can be captured by wave energy devices.
Mutriku wave power plant is the world’s first commercial wave power plant that is connected to the grid. It first became operational in 2011 and carries a capacity of 300 kW. The plant capitalizes on oscillating water column technology. Air pressure changes created by waves drive turbines to generate electricity.
Tidal Energy
Tidal energy is produced by the constantly changing gravitational pull of the moon and sun on the world’s oceans. Tides never stop as water constantly flows in and out generating kinetic energy that can be captured. Since the relative positions of the sun and moon can be determined with high accuracy, resultant tides are also easily predictable. Both wave and tidal energy devices are used to convert the kinetic energy of the ocean into electricity.
MeyGen in the Pentland Firth, Scotland, was the world’s first commercial tidal site. It currently has four turbines that produce energy into the grid. Since the initial deployment, Maygen has generated millions of kilowatt-hours of electricity and is still expanding. It has demonstrated the ability of large-scale tidal energy projects to contribute to the grid reliably.
Offshore Wind
Offshore wind turbines are the most successful and efficient marine energy technology, owing to the strength and regularity of the wind at sea. It is also the most developed of the renewable energies. There are two types of offshore wind technologies – land-based wind turbines that rest on the seabed and floating wind turbines. The key advantage of offshore wind farms compared to those on land is that there are no obstacles to reducing wind speed. Therefore, more of the resources can be harnessed.
The Hornsea Project in the UK is the largest offshore wind farm across the globe. Its first phase has an installed capacity of 1.2 GW which is enough to power over one million homes. The second phase is still under development. Hornsea has been a dramatic milestone for the offshore wind industry. It has proved the scalability of offshore wind farms and driven innovation in turbine technology.
Ocean Thermal Energy Conversion (OTEC)
Modern technologies are able to harness the difference in temperature that exists between the ocean surface waters and deeper waters. This difference is known as the ocean thermal gradient. Conversion requires a temperature over 20ºC. Therefore, the regions close to the equator and the subtropics are the most adequate for capturing this type of energy.
Although small in scale, the Natural Energy Laboratory of Hawaii Authority (NELHA) OTEC plant has been an indispensable research and demonstration facility. It has provided precious data on the performance and efficiency of OTEC systems. What’s more, this project has showcased the potential for island nations to use OTEC for renewable energy, desalination, and even aquaculture.
Saline Gradient
This technology obtains energy from the difference between salt concentration in ocean water and river water. When fresh water is mixed with salt water, the energy is released. Capturing this energy is possible in theory, however, costs are yet excessively high, and processes require robust refinement.
Osmotic Pressure Energy
Osmotic pressure energy relies on osmosis by yielding energy from the difference in pressure between fresh and salt water. The Norwegian State Energy group Statkraft inaugurated the world’s first prototype in the Oslo fjord. It utilized pressure-retarded osmosis to generate electricity, showcasing the technology’s potential. However, this project eventually got suspended due to challenges with costs.
Challenges with Marine Energy Transition
It is not surprising that the transition to marine energy comes with its drawbacks. First and foremost are the high costs associated with building and operating marine energy infrastructure. On another side come cables, turbines, and other infrastructure that could negatively impact aqua life.
As the majority of marine power plants are situated in coastal locations, they might not necessarily be able to support all populations. Even more so if they are in remote locations making the connection to the central grid challenging. Furthermore, technological advancements need to keep up the pace given that most of the structures are still in early development or commercialization stages.
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