Project Summary
This project aims to assess the potential for implementing novel high-temperature superconductor (HTS) technology on National Grid's overhead line (OHL) assets. Meeting Net Zero goals requires £21.7 billion for 94 onshore network reinforcement projects by 2030, with additional build-out by 2050 (NOA 2021/22 Refresh). However, the required pace of network expansion is unprecedented and regulatory processes and public resistance can slow deployment, especially for new OHL routes which have high visual impact.
Overhead superconducting technology could improve system robustness by increasing the power transfer capability of existing transmission corridors, reducing network constraints and allowing for significantly increased flexibility in our energy mix and ability to meet demand from all available generation sources. The ability to rebuild or add lines within existing corridors and transmit more power in smaller corridors shortens the time to construct and energize new transmission capacity. Expediting the upgrading and expansion of the network in this way offers greater certainty about connection timeframes and development costs and quickens our ability to cut carbon emissions through the ability to connect more renewable generation and limit its curtailment due to network constraints. The resulting guarantee of the unconstrained availability of generated power significantly increases network resilience and robustness.
SCOHLs are currently at TRL 4 as the novel cryogenic cooling system with superconducting conductors have been operated as a raised overhead system in a lab environment and detailed simulation models of the system and its components have been verified. A SIF-funded project provides an opportunity to increase this TRL; in the discovery phase, an appropriate methodology for increasing the TRL will be developed through scanning for potential applications on NGET's assets, investigating technical limitations and financial benefits and identifying an adoption into BAU roadmap. The alpha and beta phases will subsequently progress towards to use of prototype demonstrators at live testing sites.
Project partners:
*National Grid Electricity Transmission (NGET) as a transmission network owner and transmission licensee with access to required testing facilities and OHL assets
*VEIR as the developers of the cooling technology that will enable SCOHL rollout
*University of Strathclyde as experts in power system analysis
HTS-enabled SCOHLs could be used by TNOs and DNOs across GB and potentially beyond. This project will identify the specific benefits and abilities of SCOHLs, where they can be used successfully, and their operational limitations so that users can be guided on the optimal route for adoption into BAU.
Innovation Justification
The GB network has several highly constrained boundaries which have caused two problems:
-Limited power capacity meaning power flow increase is reliant on building additional major civil infrastructure.
-Significant power system losses.
Superconductors may present a solution to these issues. However, traditional superconducting lines are buried underground and rely on heavy closed-loop, mechanical cooling systems to keep conductors below the critical temperature. Another SIF-funded project led by NGET, entitled SCADENT, focuses on these underground superconducting lines. Despite its success, mechanical cooling is a barrier to deploying superconductors in overhead applications due weight and size limitations.
A novel cooling approach can bring high-efficiency, superconducting electric transmission lines to market at scale. VEIR's technology uses an open-loop system that evaporates a portion of liquid nitrogen at points along the line. This eliminates the need for mechanical cooling and relieves constraints on locations and length. VEIR's approach also shrinks the cryostat; for the first time enabling superconducting transmission lines to deploy overhead, as with conventional lines.
Unlocking superconducting technology for broader grid application increases options for grid planners - transmission lines could be rebuilt in existing corridors to increase capacity five- to tenfold, or new, lower-voltage lines could be built under existing ones. Alternatively, new corridors could carry high amounts of power within the same rights-of-way and with smaller towers. Line retrofit capability will also be explored. Across new and existing corridors, superconducting lines could provide low-sag options that consistently carry power despite ambient temperature change -- eliminating the need to dynamically rate lines. This will become increasingly important due to climate change induced temperature increases.
However, deploying first-of-a-kind technology on the grid is challenging. To be successful, utilities and regulators need to confirm that overhead superconducting lines can be reliably and cost-effectively deployed with installation and maintenance techniques akin to those used today.
The SCOHL project will review technical limitations to deployment, operations and maintenance of overhead superconducting lines, such as the availability of equipment to integrate 3,000-5,000 amp lines or any factors limiting installation and repair practices; outline applications that most benefit grid resilience and provide customer savings; and roadmap efficient routes to market.
Funding support for these activities is critical as overhead superconducting lines have never been deployed commercially before. Though HTS technology is proven and could become a strategic tool for decarbonizing the energy system reliably, further work is needed to test and gain confidence in overhead applications.
Project Benefits
The project scope includes a benefits analysis that will provide an initial estimate of direct and indirect CO2 and financial savings as well as a summary of technical considerations for deploying overhead superconducting lines in GB. These techno-economic analyses will be based on high-level application scenarios selected based on an initial brainstorming of opportunity by team members. In particular, University of Strathclyde with support from other partners will identify high-value applications such as lines with very large predicted power flows over the coming years (e.g., Harker-Hutton 400 kV double circuit); strategically important lines facing deployment delays or constraints (e.g., the 11 reinforcement projects identified by National Grid ESO in its July 2022 Pathway to 2030 report which are required by 2030 but anticipated to be delivered late); or lines that if built with higher capacity could avoid smaller-capacity projects.
University of Strathclyde, with support from VEIR and National Grid, will review the application of VEIR's product and identify any technical challenges with integrating the technology. The team will also confirm an approach to estimating potential benefits of reduced losses. Frazer-Nash will help National Grid provide a range of CO2 savings estimates using the initial loss estimates and a blended average emissions rate. National Grid will also work with Frazer-Nash to estimate first-order material and civil works savings, with the counterfactual being the resources used to deploy a conventional line. The University of Strathclyde will review VEIR's estimates for capacity in a given installation and estimate first-order total congestion reduction with added capacity. For a given application type, National Grid, with Frazer-Nash, will estimate a range of potential congestion and electrical loss cost reductions. For example, if the "Leading the Way" FES is followed up to 2030/31, losses in the particularly heavily loaded Harker-Hutton and Legacy-Shrewsbury/Ironbridge 400 kV double circuits could reach a combined value of 516 TWh per year. If resistance in these lines was reduced by half, this would save consumers £12.9m annually at £50/MWh, for a total of £258m over a 20-year asset lifespan. Similarly, in the 12 months from 01/04/21 to 31/03/22, 3850 TWh of energy were constrained due to thermal constraints in the GB network at an average cost of £341/MWh for a total cost of more than £1bn. These are only indicative numbers, with true savings dependent on the results of the more detailed analyses which will take place in the discovery phase.
