Comparative Assessment of Possible Topologies of Offshore Transmission Network in the North Sea

Abstract

TenneT’s vision of the North Sea Infrastructure (NSI) creates a basis for a joint European approach up to 2050 which focuses specifically on developing the North Sea as a source and distribution hub for Europe’s energy transition. High wind speed, central location and shallow water qualify the Dogger Bank as the location of the central hub.
For further development of the NSI, more detailed research is needed.
The research gap is recognized that there is not sufficient research on proposing new HVDC grids in the North Sea considering optimization (e.g. following a cost-related objective) of different topology structures within a scope of six surrounding countries (BE, DE, DK, GB, NL and NO), with sensitivity tests regarding uncertainties (e.g. in meteorological condition, load, or industry development).
Therefore, the main research objective of this thesis project is to evaluate CAPEX, overall OPEX of participating countries and other operational performances (e.g. energy mix, nodal price, EENS) of possible topologies of HVDC network in the North Sea, including NSI (with a central North Sea Wind Power Hub at the Dogger Bank) and other two competitive topologies, considering uncertainties in green energy technology development, European coordination, load and meteorological condition (e.g. wind speed, solar radiation and hydrology).
Three specific research questions were studied in order to achieve the aforementioned research objective: How to define 3 topologies of the North Sea HVDC network with different feasible structures? What are the criteria to optimize each topology and to compare the topologies? What are the implications of each topology, when evaluated against a wide range of uncertainties, on the overall CAPEX and OPEX of countries involved?
The simulation considers the scenario in the year 2030. Software PowerGAMA and PowerGIM were used for operation simulation and topology optimization. When calculating OPEX throughout the lifetime of the equipment (assuming 30 years), the year 2030 is taken as a representative year and the 30-year OPEX is obtained by multiplying OPEX in 2030 by an annuity factor.
In short, 3 topologies of the North Sea HVDC grid, with hub-and-spoke structure (for the NSI), point-to-point structure and meshed (without central energy hub) structure, respectively, are defined. They are then optimized towards and compared for the lowest overall cost (i.e. the sum of CAPEX and OPEX including CO2 prices) throughout the lifetime.
Simulating under different uncertainties/selected critical scenarios (4 Visions from ENTSO-E’s Ten Year Network Development Plan which reflect different RES share target and European coordination level, and extreme RES inflow and load conditions), the optimized NSI design stays most socio-economically preferable (with lowest overall cost) topology.
It is also recognized that NSI is able to realize its expected functions, namely transmission of renewable energy, enhancement of system security and price convergence. On the other hand, launching of NSI brings in challenges such as grid congestion and benefit asymmetry.
Main contributions of this thesis include:
• Creation of the baseline model/dataset for European power system in 2030 as a background/environment for the North Sea HVDC grid planning;
• Design and optimization of the North Sea HVDC grid topologies in three different feasible structures;
• Verification of NSI’s advantage in cost saving, compared to two competitors, in 4 Visions reflecting different green energy transition and European coordination level, and under extreme RES inflow and load conditions;
• Verification of NSI’s function in improving energy sustainability, affordability and security;
• Realization of Non-Homogeneous Markov Chain algorithm in Excel to generate wind power inflow time series.