The Cable Nobody Talks About
Offshore wind has become a centerpiece of clean energy planning in Europe, the United States, and Asia. Billions of dollars are committed, turbines are growing larger, and installation vessels are booked years in advance. But a CleanTechnica analysis highlights a critical vulnerability in the offshore wind supply chain that receives far less attention than turbine manufacturing or permitting delays: the high-voltage direct current export cables that carry electricity from offshore substations to the onshore grid.
These cables are not interchangeable components. Each one is custom-engineered for the specific distance, water depth, voltage requirements, and seabed conditions of the project it serves. A single export cable for a large offshore wind farm can run 50 to 100 kilometers or more, cost hundreds of millions of dollars, and take 18 to 24 months to manufacture and install. There are only a handful of companies globally capable of producing them at scale.
Why HVDC Is Necessary
The physics of long-distance underwater power transmission drives the choice of direct current over alternating current. AC power transmission loses significant energy over long underwater cable runs due to capacitive charging effects — essentially, the cable itself acts as a giant capacitor that absorbs reactive power rather than transmitting useful electricity. Beyond roughly 50 to 80 kilometers, AC submarine cables become impractical for bulk power transfer.
HVDC cables solve this problem by converting offshore AC power to DC before transmission, then converting it back to AC at the onshore converter station. The conversion equipment is expensive and complex, but the physics of DC transmission make it far more efficient over long distances. As offshore wind development moves further from shore into deeper water and stronger wind resources, HVDC becomes not an optional enhancement but a technical requirement.
The Supply Chain Bottleneck
The global manufacturing capacity for HVDC submarine cables is concentrated among a small number of companies: Prysmian, Nexans, NKT, and a few others. These firms operate specialized cable-laying vessels alongside their manufacturing operations — vessels that are similarly in short supply and must be pre-booked years ahead of project installation windows.
This concentration creates a bottleneck that is already being felt. Project developers report multi-year lead times for cable procurement, and delays in cable delivery have cascaded into broader construction delays on multiple high-profile projects. Unlike delays in turbine supply or installation weather windows, cable delays are extremely difficult to work around — you cannot install an offshore wind farm without its export cable.
Vulnerability to Physical Damage
The risks are not purely commercial. Submarine cables are physically vulnerable in ways that overhead transmission lines are not. Anchor strikes from ships represent the most common cause of cable damage, and the increase in offshore wind construction has dramatically increased cable traffic in already congested shipping lanes. A single anchor drag incident can sever a cable that took two years to manufacture and install.
Beyond accidental damage, there is growing concern about deliberate attacks on undersea infrastructure. The 2022 sabotage of the Nord Stream gas pipelines demonstrated that undersea infrastructure is vulnerable to targeted interference, and NATO and European governments have since elevated protection of submarine cables as a security priority. Offshore wind export cables represent energy infrastructure that, if disrupted, would eliminate the output of entire wind farms.
What the Industry Needs
Solutions exist but require deliberate action. Diversifying the cable manufacturing supply chain — including incentivizing new entrants and expanding existing capacity — is a long-term investment that governments and utilities have been slow to make. Cable routing studies that avoid high-traffic anchorage areas can reduce accidental damage risk. Redundant cable configurations, while expensive, provide resilience against both failure and attack. The offshore wind industry has made enormous progress on turbine reliability and cost reduction over the past decade. The export cable supply chain represents a dependency that has not received proportionate investment, and whose constraints may ultimately pace the entire clean energy buildout.
This article is based on reporting by CleanTechnica. Read the original article.
