The ocean forms one of the largest yet least explored renewable energy sources on earth. Ocean energy has the potential for providing a substantial amount of new renewable and reliable energy around the world.
The oceans represent a major source of renewable energy. Different technologies employ different strategies for harvesting that energy. The main sources of ocean energy are:
- Tidal streams
- Ocean currents
- Tidal range (rise and fall)
- Ocean thermal energy
- Salinity gradients
Minesto's Deep Green technology is developed to efficiently harvests the energy in tidal streams and ocean currents.
Tidal streams and ocean currents offer safe, reliable and locally produced renewable energy. They have several significant advantages over other renewable energy sources:
- Predictable and reliable. Unlike wind, solar and other ocean energy sources such as wave power, tides and ocean currents are almost 100 percent predictable. The endless flows create reliability of the future energy availability.
- Global: Tidal streams and ocean currents are available on all continents.
- Energy-rich: Moving water is 832 times denser than moving air, creating conditions for efficient energy conversion.
- Minimal use of land and no visual impact: In many regions, land is a scarce resource. Therefore, on-shore solutions such as wind and solar compete with other users. Subsea ocean energy technologies such as Minesto’s Deep Green are hidden in the depth of the ocean, out of sight and does not compete for land space.
The large resource of tidal streams and ocean currents can be also exploited with relatively small environmental interaction, thereby offering one of the most lenient methods for large-scale electricity generation.
Tidal streams: closing in on commercialisation
Tides are generated by the gravitational forces between the earth, the moon and the sun. This relative motion creates tidal currents that contain a tremendous amount of energy. Since the positions of the sun and moon can be predicted with complete accuracy, so is the tide’s movement and stream speed.
Together with the fact that tides are not affected by weather or climate makes tidal energy a reliable, predictable source of clean energy, with all prerequisites to become a significant part of the future renewable energy mix.
The tidal stream industry is on the brink of commercialisation, with hundreds of megawatts announced for installation or under development. For the last years, major breakthroughs have been made as several MW turbines has been successfully commissioned.
Ocean currents: renewable base-load power
Ocean currents are created by regional differences in temperature and salinity and the Coriolis effect due to the rotation of the earth. Ocean currents exist in open oceans and flow continuously in the same direction with low variability. This means ocean current energy represents a completely reliable non-intermittent energy source.
In addition to the earlier mentioned benefits of tidal and ocean currents, the characteristics of the latter brings further advantages such as:
- High load factors. Since ocean currents are continuous, they enable capacity factors of 70 to 95 percent, which doubles the energy output per installed megawatt and therefore lowers the cost of energy.
- Renewable base-load power. The continuous streams mean feasibility for providing sustainable, renewable base-load power to the grid.
According to the Intergovernmental Panel on Climate Change (IPCC), given the scale of open ocean currents, there is a promise of significant project scale when technologies harness lower-velocity currents.
Minesto expands the ocean energy potential
Common to both tidal streams and ocean currents is that the vast majority of the resources consists of relatively slow-flowing currents. First-generation tidal technologies require strong tidal flows with mean peak stream velocities of at least 2.5 m/s and an installation depth between 25 and 50 meters in order to be commercially viable. Research has shown that technologies such as Minesto’s Deep Green, which can operate in conditions with mean peak velocities from about 1.5 m/s at depths exceeding 50 meters, increase the potential for extracting energy from tidal streams by a factor of 35*.
Global market potential
A summary of available data that Minesto has analysed shows that the technically exploitable potential of tidal streams and ocean currents for Minesto is more than 600 GW installed capacity. This is comparable to the fact that there is currently just under 400 GW of nuclear power capacity installed globally.
The above-mentioned market potential is largely comprised of tidal flow installations. The potential of ocean currents is less studied as there have been few initiatives to approach this resource so far. Only in the Gulf Stream, the US Energy Department estimates that the theoretical recoverable capacity is equivalent to 75 GW, and in Taiwan estimates have been made that 1 percent of the Kuroshio current would equal half of the country's electricity consumption.