Project summary

Through a comprehensive environmental research project, we’ve assessed the carbon impact of high voltage direct current (HVDC) transmission systems through their entire lifecycle. The insight it’s given us will help inform our sustainability considerations and decision making for future HVDC projects.

Background

The offshore infrastructure we’re developing will play a crucial role in the UK’s decarbonisation ambitions. The infrastructure involves high voltage direct current (HVDC) transmission systems. These are generally considered to have lower emissions compared to traditional alternating current (AC) systems, as they can transmit power over longer distances with less energy loss.

As part of The Great Grid Upgrade, we have a growing number of HVDC link projects, each able to move enough low carbon power for two million homes. Eastern Green Link 2, one of our Great Grid Upgrade projects, will be the longest HVDC cable in the UK.

There is additional equipment required though, such as converters and transformers, and these can produce emissions during their manufacturing and operation. We need to accurately quantify and understand the carbon footprint of our HVDC projects, so we can assess their overall environmental impact.

Through this project, we calculated the total carbon emissions of an example HVDC link – comprising two converter stations connected by an HVDC cable – over a full 40-year life.  

The main source of emissions we found were the supply of raw materials operating the link (both around 44%) . For example, the seven single phase transformers each weigh some 220 tonnes, comprising steel, copper, iron ore, and other materials. These and materials used for cable protection and construction, for example, all contribute to emissions. 
 

Who did we work with? 

We partnered with DNV, an expert body in assurance and risk management, to conduct a study to understand the carbon footprint of our new HVDC transmission systems. DNV recommended ten specific areas to focus on in our efforts to reduce emissions – ranging from using low-carbon copper through to making sure the overall system is operating at maximum efficiency. 

Among DNV’s recommendations were measures to reduce the emissions from raw material supply – a significant carbon hotspot. DNV recommended we focus on:  

• Equipment efficiency, so we can reduce electricity losses
• Decarbonising materials, such as the concrete used in construction
• Reducing the amount of virgin aggregate needed for our works
   

Benefits for energy consumers

By adopting DNV’s recommendations, we could reduce emissions by more than 15% or the equivalent of 113,000 tons CO2 total emissions of an HVDC link. In our case we considered 40 years lifetime of the HVDC link.

For example, diesel powers plant used in the construction and decommissioning of the site. By switching to biofuel or HVO, we could reduce emissions by nearly 10,400  tonnes of CO2 over the construction and later decommissioning of the sites.

We’re now putting these recommendations into practice by challenging our contractor to find solutions for construction materials, and to use the Sustainability Innovation Fund on our first two Eastern Green link projects to cover premium costs. 

Overall, we’re integrating the findings from this research into our HVDC framework, so the insight we’ve gained informs our project planning and supply chain processes. 
The work is also feeding into wider improvements we’re aiming to make in carbon management.
 

Muhammad Shaban, Lead Innovation Engineer:

This initiative shows how we’re leading the way in sustainable energy transmission, working towards a low carbon future.