Subsea cables – a key component of the global energy system

Cables laid undersea connect different regions with each other and form the basis of our global energy system. They also enable offshore energy production by transferring electricity between power grids and offshore energy source, such as offshore wind farms.

By connecting regions and countries, subsea cables enable an efficient global energy network, facilitating trade and optimizing energy distribution. This enhances system security and stability by balancing production and demand variations while increasing the flexibility and resilience of the electricity supply.

High efficiency and stable solutions with HVDC

In long-distance transmission, especially over oceans, high-voltage direct current (HVDC) cables are preferred over alternating current (AC) cables. HVDC technology reduces energy losses over long distances, allowing for more efficient electricity transmission. Unlike AC, which incurs higher losses in long-distance transmission, HVDC provides an efficient solution for subsea cables between countries and continents. This makes HVDC the primary technology for ensuring both high efficiency and stability in the global energy grid.

When planning for an HVDC solution, there are several aspects to take into account. What we look at are for example:

• choosing the right technology and converter location, as both Line Commutated Converter (LCC) and Voltage Source Converter (VSC) technologies have different advantages and applications.
• cable routing is also a critical part, with detailed seabed surveys to avoid obstacles and minimize environmental impact.
• installation and maintenance is also a world of its own, where specialist cable vessels are used to lay the heavy, long cables in sometimes challenging marine and weather conditions.
• risk assessments for technical, environmental and security to mitigate and hopefully also avoid any damage to the environment and the cables themselves.

What’s lurking in the seabed

In a world where climate change and global crises continuously challenge energy security, maintaining system stability and the ability to recover quickly from disruptions is crucial. Subsea cables play a central role in ensuring efficient energy transfer between regions.

By connecting countries and areas, they help strengthen the flexibility and resilience of the energy system in several key ways. One of the key benefits is the ability to efficiently link with different regions and diversify the supply and routes. By laying the cables in the seabed, they’re also more protected from extreme weather conditions.

The risk landscape is, however, increasing. This means that any future cable projects, whether it be data or energy related, need to take into account various new threats for example from climate change or even sabotage.

In addition to natural threats, such as earthquakes or rising sea levels that can damage cable structures, human threats like sabotage and geopolitical tensions also pose significant risks. Fishing activities and other human actions can also cause physical damage to cables.

Addressing these risks requires the use of surveillance technologies, such as sensor networks and underwater drones, to quickly detect and mitigate potential threats. Strong international cooperation is essential to ensure the protection and sustainable maintenance of subsea cables.

AFRY's expertise

AFRY has extensive experience in subsea cable projects, both in Sweden and internationally. We offer comprehensive consulting services that span the entire project lifecycle, from initial planning and detailed engineering design to project management, installation, and maintenance.

Our expertise includes feasibility studies, environmental impact assessments, route optimization, and dynamic analysis of underwater structures.

We specialize in interconnectors (HVDC/HVAC) and offshore wind farms, both fixed and floating, where subsea cables are essential for transferring electricity between power grids and offshore energy sources. To ensure robust and resilient networks, AFRY also provides advanced expertise in monitoring and troubleshooting, from network components such as relays to specific on-site issues.

By integrating innovative solutions and sustainable practices, AFRY plays a key role in the development of efficient, flexible energy systems, supporting the transition to renewable energy sources and strengthening global energy security.