Obvious differences aside, what has set the business models for oil and gas and renewables apart is the attitude toward cost. When the oil price is up, the long-established oil and gas sector has traditionally adopted a high-spend approach to exploration, development and extraction.

As more of a challenger industry, this is a luxury that the renewable sector has not been able to enjoy. Striving to enhance its competitiveness and in anticipation of the end of subsidy regimes in the long term, the focus on driving down costs has been embedded in offshore wind from its very inception.

So it is perhaps not surprising that with a prolonged slump in the price per barrel, oil and gas operators are looking at the renewables sector as a potential source of cost savings. Equally, in its constant search for cost-effective innovation, the renewables sector has been eyeing possible solutions from its oil and gas counterparts.

The idea that there could be some technology-driven convergence between oil and gas on one hand and renewables on the other is not as outlandish as it might have seemed only a few years ago, so much so that certain oil and gas operators that had previously exited the renewables sector are now considering a reentry, with some already taking the plunge.

Nowhere is this convergence more obvious than in the area of offshore energy generation, where technologies used by the North Sea oil and gas community are being considered by offshore wind operators and innovations developed for wind and tidal generation are being considered by oil and gas operators.

Higher voltage, lower costs

The first area of interest is that of high-voltage cabling developed for offshore wind generation that also can be used in the oil and gas sector as a cost-competitive solution for driving large amounts of power across the seabed.

For example, new so-called “wet design” 66-kV cabling significantly steps up the voltage from the 33-kV inter-array standard cable voltage capacity and is being adopted by a number of new wind development projects this year. The advantage of this type of cabling is that it enables power to be transmitted to and from larger turbines that are installed farther offshore, essential as the industry starts to look beyond shallower waters to build its wind farms.

The wet-design cable ensures long-term operations without the need for a metallic barrier layer such as an extruded circular lead sheath that, until now, has typically been a large cost component of high-voltage power cables at 66 kV. With the removal of the lead sheath barrier layer the cable is also much lighter, allowing the capital costs associated with installation to be reduced and further enabling operators to deliver more power for the same amount of copper. Although the cable itself requires a small increase in outside diameter over standard 33-kV alternatives, it can deliver double the amount of power through the same conductor size with much less than double the overall cable capital cost.

The cable was initially developed to support expansion of offshore wind turbine capacity to higher power generation, enabling developers to exploit more offshore wind resources including locations farther away from shore. But those high-power deeper water characteristics also make it a suitable technology for offshore oil and gas applications. What’s more, the 66-kV technology allows a cable to run from the shore to field, where a distribution hub and subsea transformer can be configured to distribute power on the seabed at typically 11 kV to suit subsea consumers such as pumps, compressors and other subsea processing equipment.

Some examples already being seen are of a hub-style power distribution system off the coast of Cornwall in the U.K., this time for wave energy. An export power cable runs underneath the beach in the village of St. Ives and travels 25 km (15.5 miles) out into the Bristol Channel to a hub, where a number of smaller cables split off to connect different wave-energy devices, test them and enable them to transmit power back into the grid.

This kind of subsea power distribution system and the technologies that support it also present great opportunities to oil and gas operators for subsea power consumption rather than generation. Interestingly, it may be possible to combine energy generation with energy consumption on the seabed, enabling oil and gas infrastructure to be powered by future tidal energy devices.

Dynamic opportunities

In return, the possibilities offered by deepwater operations give the offshore wind industry plenty of opportunity to consider the technologies and expertise residing in the oil and gas sector. There is a growing drive toward floating structures for offshore wind as a means of reducing the construction costs associated with building an offshore wind farm in harsh environments and difficult weather conditions and to create more efficient and effective maintenance operations.

With the Norwegian Continental Shelf dropping away, floating systems are going to be a very interesting development in the North Sea, offering significant growth potential. When Statoil presented its view of offshore wind up to 2030, it claimed that about 105 GWh of installed capacity, about 20% to 25% of the total, would be floating offshore wind.

Naturally, managing floating structures is something the oil and gas sector has been doing for decades. And with savings in capex and opex on offer, the offshore wind industry is looking for ways of replicating its success— in particular, by deploying more dynamic power cables that can be hooked onto floating structures and FPSO vessels. These cables have to be capable of installation and dynamic operation underneath a floating structure and withstand all the fatigue loads and various environmental conditions throughout the cable life.

With static applications the cable design often has a single layer of armoring, with a roved protective outer layer comprising a series of polypropylene strings to protect the cable. For the design of dynamic systems, cable design is more complex, ensuring that the cable remains torque-neutral under high tensile loads and that the outer protective layers can withstand the arduous external environment. The cable design has to minimize twist and to ensure the dynamic cable stays in place and responds appropriately to the motion of the vessel and the platform to safeguard its longevity and long-term performance.

Collaboration and convergence

Many of the underlying differences come down to cost. Static cables for current offshore wind farms tend to be a highly cost-efficient design optimized for a range of subsea locations and often either buried or protected by additional cable protection conduits.

Cables for dynamic systems are a highly engineered product that is more bespoke and can sometimes be fine-tuned to suit the specific dynamic conditions prevalent at the offshore location and precise water depth.

There are plenty of opportunities for renewables and oil and gas to learn from each other. The gap between the two industries seems likely to become narrower as those lessons are embedded in technology development. The collaborative future goes beyond the essential support technologies like cabling. Engineers are looking at the possibility of reusing oil and gas infrastructure itself for some offshore wind projects as well as combining new infrastructure.

The future will increasingly be about knowledge-sharing and integration. Driving down the costs of offshore operations will mean that the distinction between offshore renewable and offshore oil will diminish. Soon the conversation and the innovation will simply be about offshore energy and reducing the offshore costs for the benefit of developers and operators alike.