LONDON — A planned tidal energy project off the coast of Washington state in the US has come under fire over the lack of a standard defining how close such projects can be to existing underwater cables.
The project’s developer, the Snohomish County Public Utility District (SNOPUD), says it will feature two six-metre open centre turbines from Irish company OpenHydro which will be mounted on submerged gravity foundations and connected to the grid on nearby Whidbey Island. Other facilities will include a subsea transmission cable, a cable termination vault and a power conditioning and control building, SNOPUD said. The project, named the Admiralty Inlet Pilot Tidal Project, is expected to generate 1 MW during peak times.
SNOPUD is seeking approval from the Federal Energy Regulatory Commission (FERC) for the project. But Pacific Crossing, the company that owns a high-capacity fibre optic cable linking Japan and California that lies near the proposed site, has raised concerns, saying the turbines would be located “dangerously close” to the cable. SNOPUD says it plans to place the turbines 175 and 235 metres from the cable.
“This project appears to be going forward yet there is no research available to back up the claim that the degree of separation between the cable and the proposed turbine is safe,” Pacific Crossing said in a statement. “If this project is approved as-is, the decision may undermine any future safe tidal energy distance standards” and “create significant issues for the telecommunications industry.”
There is currently no U.S. standard for the distance tidal energy projects need to be from other subsea installations. The Federal Communications Commission has stated that neither it nor FERC has the expert guidance necessary to make an informed decision about what a safe separation distance would be. The FCC has charged an advisory committee, the Communications Security, Reliability and Interoperability Council (CSRIC), to work with the industry to develop guidance, delegating a special submarine cable working group to address the issue.
Distance guidelines do exist for offshore wind turbines in the U.S. The FCC and industry groups have suggested that these standards, which require 500 metres between offshore wind turbines and submarine cables, should be used in this case.
In its comment to the FERC, Pacific Crossing invoked a UK guideline, Subsea Cables UK Guideline number 6, which recommends proximity limits of 200-400 metres from an existing subsea structure for marine energy development. The North American Submarine Cable Association has urged U.S. regulatory agencies to apply the UK guidelines to all U.S. marine energy projects, including tidal energy projects.
But the UK study which produced Guideline number 6 also said it would be inappropriate to predefine separation distances, “as the range of issues at any particular location are varied and particular to site-specific circumstances.” It recommended that proximity situations “are best dealt with through the mechanism of commercial agreement” and offered examples of common proximity and crossing agreements within the offshore industry.
In an interview with local newspaper the Whidbey News-Times, Craig Collar, the SCPUD’s senior manager of energy resource development, said Pacific Crossing has only leased a patch of land six inches wide from the state for the cable. Given this, “what we are proposing doesn’t pose a problem or we wouldn’t have proposed it,” he told the paper.
The project previously encountered opposition when environmental groups such as the Whidbey Environmental Action Network raised concerns about its impact on marine life, specifically the potential effects on native plants near the shoreline where it would connect to the grid. Pacific Crossing has also said the turbine will cause problems for cable maintenance, and that the installation process may damage the cable.
Lead image: Preparing an open centre turbine for installation, via OpenHydro