Offshore substations — whether AC, DC, mesh-ready, collector or any derivative — are the heart of the offshore wind generation system. No substation, no power transmission, and hence no revenue. Will offshore substations become a bottleneck?

The U.S. has just 14 MW of offshore wind power today and is aiming for 30 GW by 2030 and 110 GW by 2050. Europe is further along, with roughly 28 GW currently installed and aiming for 150 GW of offshore wind capacity by 2030 and 300 GW by 2050. Every day new and increasing gigawatt targets seem to appear, so what do those numbers mean for offshore substations in general and offshore wind in the U.S. in particular?

Start with some basic calculations. An alternating current (AC) cable has a rule-of-thumb maximum capacity of 450 MW. Dividing 30 GW by 450 MW would equate to nearly 70 cables/circuits. Then there are the configurations to think about: Will there be one, two or three AC circuits per platform? How about direct current (DC)? Will projects utilize DC with direct 66-kV array connected or DC with AC collector substations? Conversations in the U.S. now are all about mesh-ready, modular integration plans, offshore transmission networks, and power building blocks — all of which will affect substation composition. There are numerous variables.

The National Renewable Energy Laboratory (NREL), together with the University of Delaware’s Special Initiative in Offshore Wind (SIOW), predicted 53 substations would be required to support 30 GW of installed capacity in the U.S. Regardless of the number calculated — 53, 70, slightly more or slightly less — the 30 GW goal for 2030 clearly requires a lot of offshore substations. When you fast-forward to 2050, the number likely grows to 200-plus. Where will they come from?

Notwithstanding the U.S. fabrication work being done for the South Fork Wind Farm located off the coast of Long Island, the first-mover offshore substations are largely depending on the European supply chain. But as the numbers above imply, the EU will be quite busy servicing local market needs. It’s worth noting that the target for the Baltic Sea recently increased from 2.5 GW to 19.6 GW by 2030 — that’s potentially another 30 or so offshore substations. This will certainly have significant implications for the EU supply chain and the availability of steel fabrication from Eastern Europe. To secure U.S. targets, it is essential to establish a U.S. supply chain for offshore substation engineering, procurement and construction.

Recognizing Relevant Experience

While an offshore substation often is viewed as a single item, it consists of a number of significant parts, including the high-voltage primary electrical system, the supporting structure, the foundation, the auxiliary systems such as fire protection and HVAC, as well as offshore safety components. Each requires specialized design knowledge and delivery capability.

Although the U.S. market does not have an extensive resume of offshore substations, it can still boast of both offshore structures and onshore substation capabilities. The U.S. has ample experience with designing and building onshore substations, and the same can be said for oil and gas platform topsides and substructures.

As an example of what it might take to help the U.S. reach its offshore wind generation targets and address global supply chain challenges for the industry, Burns & McDonnell and Bay Ltd. have recently teamed up to provide U.S.-based engineering, procurement, fabrication and construction of offshore substations, with Kent appointed to provide offshore structural and safety engineering.

Products, Not Projects

To hit the numbers that will be necessary, it helps to look at offshore substations as products, not just projects.

The industry needs to develop standard building blocks that can be reused with minimal tweaks required per project. In the U.K., the earliest offshore substation projects had bespoke designs and dedicated engineering teams, but more recent efforts have featured single teams delivering multiple projects. This design-once mindset and strategy improved volume and quality while reducing cost and schedule.

Collaborations like the one among Burns & McDonnell, Bay Ltd. and Kent will benefit from leveraging a combination of extensive practical experience and a standardized approach as they work to meet this growing demand.


Learn more about how Burns & McDonnell, Bay Ltd. and Kent plan to work together to strengthen the U.S. offshore wind supply chain.

Read the News Release

Mark Rogers is the offshore substation engineering manager at Burns & McDonnell. He has more than 35 years of experience in offshore and onshore electrical transmission and power generation.