Graduation of Stefan Gerrits

04 October 2017 13:00 - Location: Room F, faculty of Civil Engineering and Geosciences

“Feasibility Study of the Hub and Spoke Concept in the North Sea: Developing a Site Selection Model to Determine the Optimal Location”| Professor of graduation: Prof.ir. T. Vellinga , supervisors: Ing. C. Kuiper (TU Delft), Ir. P. Quist (TU Delft), Ir. E.J. Van Druten (Witteveen+Bos)

The European energy system is changing. In order to meet the climate goals, fossil fuels are being replaced by renewable energy sources  and this resulted in an exponential growth of offshore wind farms in the North Sea over the last two decades. Technological developments go very rapid and cause the cost of offshore wind energy to decrease, but there is also a trend of installing offshore wind farms at greater water depths and further from shore. There is only limited space available along the coastlines and this latter development counteracts the cost reductions achieved by the industry. 

The greater share of renewable energy sources is however also causing the production of electricity to become more volatile. More production capacity becomes dependent on prevailing local conditions and is generated irrespective of consumer demand, thereby creating higher production peaks which are destabilizing the energy system. There are several methods to mitigate these production peaks which are necessary for the successful integration of large shares renewable energy sources. The European Commission is entirely focused on strengthening the electricity grid by installing interconnectors between countries. Europe will be acting more as a single market in which increased trade will flatten the generation peaks and enables the integration of renewable energy sources.

In June 2016, Dutch transmission system operator TenneT proposed the Hub and Spoke concept to be developed on Dogger Bank. The infrastructure of offshore wind farms and subsea interconnectors is mainly overlapping and combining these two structures probably leads to synergies. The construction of an island in the middle of the North Sea would make it possible for offshore wind farms to be constructed far out at sea, but with advantageous near shore conditions. Distance to shore becomes much less relevant. Jackets are made obsolete, structures does no longer have to comply with strict offshore regulations, structures are much easier to access by personnel and expensive offshore operations are no longer needed. Furthermore, the infrastructure can be used much more efficiently. Utilisation of offshore wind farms far out at sea is currently around 40%, because the wind conditions are not always optimal and time is needed to perform maintenance and repairs. The island however also functions as a hub for electricity trade with connections to multiple countries. The utilisation of cables thereby increases from roughly 40% towards 100% and additional revenues can be generated.

According to TenneT the biggest constraint to the project comes from opposing environmental organisations. The Hub and Spoke concept is envisioned to be realised on Dogger Bank due to its shallow water conditions and central location in the North Sea, although its unique characteristics also make the location rich in biodiversity and the area is therefore appointed Natura 2000 territory. The feasibility of the Hub and Spoke concept has however never been quantified and it is not even certain that Dogger Bank is the optimal location. In my master thesis I will investigate the optimal location by creating a site selection model, which determines the feasibility of the Hub and Spoke concept for the entire the North Sea.