Shane Moloney, global energy expert and MD of Rockboro Project Management
Whereas oil and gas were the most traded energy commodities in the 20th century, electricity will join them as a globally traded energy source in the 21st century. Electricity interconnectors are the technology driving this change. Like electricity pipelines, they allow large power volumes to be efficiently transported over great distances, and these distances continue to grow. While it is now possible to deliver electricity across hundreds of kilometres, soon it will be possible to accomplish this over thousands of kilometres, over land and most importantly, across oceans. As interconnector capacity increases, it has been identified as a powerful tooltofacilitate the global energy transition.
Understanding the technology
The type of electricity interconnectors used are high-voltage, direct current (HVDC) systems. The high operating voltage and the use of direct current increase the efficiency to a point where it is feasible to transmit gigawatts of power over hundreds of kilometres. For example, the Viking Link project linking Denmark to the United Kingdom is the longest land and subsea HVDC interconnector in the world, with a total route length of 765 kilometres and is capable of delivering 1.4 gigawatts of power.
The electricity we use in our homes, offices and factories uses alternating current, so these HVDC systems use converters to change the electricity from alternating current into direct current for transmission along cables and then back again to alternating current for delivery to the electricity grid.
The system comprises highly specialised cables, particularly those designed to be installed underwater, and convertor stations, which change the electricity from alternating current into direct current and back again.
The cables are designed to operate at up to 600,000 volts and in water depths of up to 3000 meters. They must also resist substantial internal and external forces for a design life of up to 40 years. They have conductors made from copper or aluminium, covered in layers of insulation and protective sheaths. The cables are then covered in armour wire layers to protect them during installation and operation on the seabed.
Why connect electricity grids across countries?
One reason is that it can enhance supply security by providing alternative options in case of system failure or supply shortages. Differences in supply and demand patterns across countries, such as time zones, can be used to achieve more efficient electricity use through regional electricity trade.
However, the primary benefit is that cross-border collaboration is crucial in integrating renewable energy sources. Differences in demand peaks and renewable energy production patterns, such as wind and solar availability, across countries help balance the intermittent nature of renewables over broader regions, enabling a higher proportion of renewable energy in the electricity grid. Interconnectors also allow renewable energy generated in remote areas to be efficiently delivered to the population centres where it is needed most.
A great example of how electricity interconnectors can aid in the fight against climate change is the planned Xlinks project, which will supply the UK with 3.6 gigawatts of electricity from a solar, wind, and battery facility in Morocco transported via 4,000km of subsea cable. It’s estimated that this project would reduce the UK’s sector CO2 emissions by 9.9% in its first year of operation. Projects like this push the boundaries of what is possible, but challenges remain.
Material and design challenges
Electricity interconnectors must overcome technical challenges to unlock their full environmental potential. The greater the distances over which electricity is transported, the greater the losses. The key to overcoming this is increasing the voltages at which these systems operate beyond the 600,000-volt mark. Higher voltage means greater efficiency, but cable insulation technology needs to advance to achieve this.
We need to be able to install cables in deeper waters to cross greater distances. To lay cables from a ship in deep water, the cable must be strong enough to support its weight as thousands of meters hang from the vessel to the seabed. The cable materials that carry this load must be strong but light, and the cable industry is borrowing from the aerospace industry, working with composite materials instead of traditional materials such as steel.
These challenges are substantial, but the industry is busy solving them, with new cable types in development to overcome these voltage and water depth challenges.
Government support
For boundary-expanding projects to be considered, let alone approved, governments play a critical role in creating a supportive environment. Regulatory and policy frameworks are crucial factors in the feasibility and operation of interconnector systems. These frameworks establish the rules, standards, and market structures that govern cross-border electricity trading, grid connectivity, and system reliability requirements. They address issues such as tariff structures, market access, and the harmonisation of technical standards between countries, ensuring that electricity can flow seamlessly across borders.
Additionally, supportive policies and incentives can drive investment by mitigating risks and creating a stable environment for system developers. Conversely, misaligned or restrictive regulatory regimes can hinder progress by introducing uncertainty or making projects economically unviable. As such, the successful implementation of interconnector projects relies heavily on navigating and influencing these frameworks to align with the project’s technical, economic, and environmental goals.
The One World, One Sun, One Grid (OSOWOG) initiative is an example of governments backing ambitious and paradigm-shifting projects. The OSOWOG initiative aims to connect different regional grids through a common grid that will be used to transfer renewable energy power and, thus, realise the potential of renewable energy sources, especially solar energy. Indian Prime Minister Narendra Modi proposed the OSOWOG initiative in the first assembly of the International Solar Alliance (ISA) in October 2018. The project has proposed three phases. In the first phase, the Middle East, South Asia, and Southeast Asia grids will be integrated. In the second phase, the Asian grid will be connected with the African grid. In the final phase, the grid will be the global grid.
Big thinking, technological developments, and supportive governments are required to overcome the challenges, but the prize is an electricity grid powered by renewable energy that extends worldwide.
