An efficient energy transition can only be achieved with a European approach to grid planning, according to a new study released by German TSO TransnetBW. The intent of the study was to initially focus solely on Germany but the authors quickly realised the critical nature of the pan-European dimension.
Werner Gotz, the CEO of TransnetBW told a Brussels event in June:
“Now is the time to think more European,” Götz said. “There is no single state, no single company, no single technology that can do this transition on its own. We have to work together, we need an integrated Europe, we need an integrated approach…And we have to start now.”
The study recognised the changing dynamics and requirements of a renewables-based energy system:
“Due to the increasing distances between the sources of renewable generation and future load centres…To meet this need in an efficient and targeted manner, we see interconnected and power flow optimising European HVDC overlay grid as the best solution.”
The growing importance, advantages and requirements of the offshore space were also recognised:
“The interconnection of offshore wind farms, regardless of national borders, offers greater potential for efficiently increasing offshore wind integration to meet long distance transmission needs.”
Offshore wind and an overlay Supergrid will be critical to Europe’s energy ambitions. It has become increasingly difficult to construct large scale onshore infrastructure projects like wind turbines and overhead transmission lines due to public opposition. This is much less of an issue in the offshore space which also offers stronger and more consistent wind speeds. The coordination of Europe’s offshore basins via a meshed offshore grid should be the first step in a pan-European Supergrid.
There is significant momentum building for this concept, no more notable than the Esbjerg Declaration signed in May 2022. The Prime Ministers of the North Sea adjacent countries Belgium, Denmark, Germany and the Netherlands along with the President of the European Commission pledged to expand their collective offshore wind to 65GW by 2030 and 150GW by 2050. Their intention is for the North Sea to become the ‘Green Power Plant of Europe’.
This Supergrid momentum also indicates momentum for the deeper interconnection between nations, with targets of at least 15% now set by the EU. The progress made here is positive but interconnection alone will not be enough. An interconnected overlay grid must also be meshed, providing multiple routes to multiple markets. Most current interconnections and those that are planned for the near future are point-to-point. This is insufficient for a truly pan-European grid powered by renewables as the existing AC grid, designed and sized for a carbon based energy system, becomes a debilitating bottleneck for the large power flows required.
Technical Drawbacks of the Study
Where the study does fall down, is in its assessment of the long term transmission technology that will be needed for this pan-European grid. The study performs no evaluation of the power flows that will be needed in the long term and thereafter assess the transmission gap. Instead there is simply an acceptance that we should use the next generation of already established grid technology. This is a common incrementalistic mistake.
The study assumes copper-based HVDC cables with a rating of 800kV will be technically feasible before 2050 which would increase the capacity of HVDC links to 3.5GW and be capable of fulfilling the grid’s high capacity power flow requirements. There are a number of problems with this assumption.
The first problem is that running underground transmission cables at this level of voltage (800kV) requires extremely large and expensive transformers and offshore platforms. China does currently run Ultra-High Voltage DC lines in their own version of a Supergrid, most notably the Changji-Guquan line. This is an overhead line which operates at 1,100kV and can transfer 12GW of electricity 3,293km from the west of China to its eastern coastal region.
The pylons required for this line are enormous and the project is a result of a combination of an engineering and political will that simply does not exist in many countries outside of China. Europe’s geographic and political paradigms prevent this scale of infrastructure development from occurring. Europe’s own Supergrid must be primarily built underground and offshore, where there is less public opposition.
The second problem is HVDC cables based on copper are too capacity constrained for a future based on renewables. Europe already has plans for state-of-the-art 525kV HVDC cables capable of carrying up to 2GW (SuedLink, Germany) and the 800kV cables predicted for 2050 extend that capacity up to 3.5GW. But these capacities are not compatible with an efficient and cost-effective European Energy system based on renewables. We need new innovative cable technologies that extend the range beyond 3.5GW. The levels of renewable electricity that will be produced from the offshore wind farms and solar farms of the future require cable technology capable of transferring capacities of 4GW, 6GW, 8GW and even up to 10GW over long distances from resource to demand centre.
The TransnetBW study comes to the right conclusion on the overall approach to grid planning but overlooks the limitations of established transmission technology. A pan-European overlay grid, as proposed by TransnetBW, cannot be achieved cost-effectively without new innovative cable technology, appropriately designed and sized for the transmission links of a renewables powered energy system.
Superconductor Cables are the solution
Superconductor cables are that new innovative cable technology that can be the final piece to the complex puzzle that is the Supergrid. Superconductor cables have a very high power density and so can transfer extremely high levels of power, up to 10GW and at lower voltages than traditional conductors. The Best Paths Superconducting demo project operated a 6.4GW line at 320kV, which is already an established DC cable voltage.
The use of lower voltages reduces the need for larger footprints and more expensive infrastructure like converters, transformers and offshore platforms. Superconductor cables require much less space, material and infrastructure than conventional cable technology and can transfer power with zero electrical losses. This means superconductor cables facilitate the required level of power flows for a renewables powered system, while increasing efficiency, decreasing costs, and overall having a much smaller environmental footprint.
SuperNode’s superconductor cables will be the key to unlocking a pan-European weather-based energy system..
The TransnetBW Study can be found here.