Setbacks Are No Setback for Marine Energy Development

A U.S. Submarine Cable Analysis

Dec. 13, 2019

The ocean may very well be the next frontier, and two major industries—telecommunications and marine renewable energy—are already employing and exploring this vital asset.

Vital to both telecom and marine renewable energy development is careful planning to accommodate their respective operations, as well as those of other users of the ocean. The telecom industry relies on the submarine cables that crisscross the vast ocean floor, transmitting data around the world, whether a voice on one end of a phone call or a blog post published online. For marine renewable energy, which encompasses devices that generate power from waves, tides, and currents, as well as wind turbines installed offshore, the locations of these telecom cables should, ideally, be considered when planning marine energy systems.

Finding the balance between these seemingly competing spatial demands is critical, as 95% of the world’s intercontinental, data, and voice traffic rely on the integrity of these cables. Additionally, the production of marine renewable energy is key to complementing U.S. renewable energy output, particularly during periods of high demand off densely-populated coastal areas. Thanks to recent research, finding this balance isn’t as challenging as it might seem.

Planning to Coexist

In their technical report, Submarine Cable Analysis for U.S. Marine Renewable Energy Development, National Renewable Energy Laboratory (NREL) researcher Dr. Levi Kilcher and colleague Ben Best evaluated the potential overlap between the likely areas for marine renewable energy resource development and existing telecom submarine cables.

Though the current law only mandates 100 feet allowances on either side of telecom cables, submarine cable operators have advocated for larger spatial allowances so they may safely access these cables for repairs and maintenance. Referred to as “setbacks” by the cable industry, the larger spatial allowances on either side of the cables are a generally advised practice—exceptions to the rules exist to accommodate cables that must cross one another.

Drilling Into Deep Ocean Data

Using publicly accessible data sets, researchers identified 100,000 kilometers (km) of submarine cable currently installed within the 200-nautical mile (370 kilometers from the coastline) U.S. exclusive economic zone (EEZ). They then applied both the Code of Federal Regulation’s 100-foot (ft) allowance on either side of the cable, as well as the cable industry’s suggested setback guidance for maintenance and repair—a maximum of 500 meters (m), or three times the bottom depth (referred to as 3z). The narrow 100-ft setback allowance covered only .05% of the U.S. EEZ; the 3z setback covered 1.3 million square kilometers (km2), or 11% of the U.S. EEZ.

Utilizing NREL’s Wind Prospector and Marine Energy Atlas tools, the researchers pinpointed areas where marine energy resources are most energetic (i.e., where marine energy production is considered most promising or feasible). They found that the feasible offshore wind and wave energy resource areas occupied 3.9% and 3.2% of U.S. EEZ, respectively. The viable tidal energy resource area was found to be .014% of the U.S. EEZ.

Researchers then applied a “percent area” approach in their analysis, meaning that they looked at the percent of viable renewable energy resource areas in km2 that overlaps with existing cables and the recommended setback distances surrounding them.

Across all resource types, nationally, this overlap of cable setbacks with viable energy resources was less than or equal to 4% of the U.S. EEZ.

The researchers found that the areas of greatest overlap are concentrated in pockets, highly dependent on region and resource type. For example, Hawaii’s offshore wind exhibits 14% overlap due to the deep cables with wide setbacks employed there. The West Coast of the United States was home to the greatest overlap of cables and tidal energy sites at 21%, due to cable placement on the bottom of narrow channels, such as in the Puget Sound. The largest degree of overlap of cables and viable wave energy sites was also found on the West Coast, due to potential wide setback margins.

Reach Out Early and Often

While overlaps between telecom and viable marine renewable energy resources exist, researchers found they are few and far between.

The cable maps included throughout the report provide potential marine energy developers with a better understanding of the locations where cables are present. Developers of possible energy sites can mitigate risks to both cables and energy projects by reaching out to cable operators, as a point of practice, early in the design process.

Ultimately, the research suggests that submarine telecom and renewable energy projects are not mutually exclusive and can peaceably coexist. There is plenty of ocean space available for the development of viable marine energy projects that do not overlap with the routes of existing cables.

Learn more about NREL’s water research.