DNV calls for US states to build out offshore transmission network

April 11, 2024
Joint industry project issues recommendations, timeline to help create offshore HVDC transmission network.

Offshore staff

KATY, Texas – DNV has issued a set of recommendations and a timeline to help support the construction of a “fully functional” offshore HVDC transmission network to support US offshore wind power goals.

As the first phase of a joint industry project (JIP) exploring the feasibility of incorporating HVDC (high voltage direct current) transmission into the US grid concludes, DNV says that these guidelines have emerge from extensive collaboration across the sector, incorporating insights from a multitude of stakeholders. 

An offshore HVDC transmission system will enable the reliable delivery of offshore wind energy to onshore markets and will help ensure that developers and investors achieve a secure return on their investments. 

Most imperative is an urgent need for states to focus on procuring 320 kV HVDC symmetric monopoles without AC or DC interlinks, says DNV. Leveraging mature technology and a larger fleet of vessels for offshore converter station transportation and installation, this approach minimizes risks, providing immediate benefits to existing and upcoming offshore wind projects. 

The study also recommends a step-by-step build-up of infrastructure that takes into account the global HVDC equipment market and recent procurements and partnerships in Europe that are driving the market. The phased approach to procuring and installing an HVDC transmission network is intended to overcome current barriers and create a clear pathway to an offshore transmission network. 

Participants in the JIP laid out short-, mid-, and long-term milestones for building a HVDC transmission network, starting with symmetric monopoles at 320kV, leading to a fully functional, 525 kV HVDC network with DC interlinks. Ultimately, the creation of a fully functional HVDC transmission network will maximize public benefits by increasing energy deliverability and enabling intra- and inter-regional power transfers, DNV says.

Specific recommendations from the JIP include: 

  • Establishing a task force with industry and state participants to review the feasibility of AC mesh solutions given the significant supply chain constraints that have emerged since AC mesh solutions were first envisioned. 
  • Enabling the connection of 525 kV HVDC bipole circuits from the Northeast through the Mid-Atlantic
  • Investigating options to reduce the size and weight requirements of offshore platforms for 525 kV HVDC bipoles
  • Defining the planning, operational, and functional performance expectations for DC interlinks between 525 kV HVDC bipoles
  • Identify any points of interconnection and/or navigable channels that should be reserved for 525 kV HVDC bipoles.

In September 2023, the US Department of Energy awarded DNV the role of coordinating offshore wind and transmission developers, utilities, regional transmission operators, equipment manufacturers, and other key stakeholders to identify gaps in US HVDC standards.