Cost Effective Expansion Planning Mathematical optimization models to support large scale offshore wind deployment

Name: Stephen Hardy

Prof. dr. ir. P. Wollants, chair
Prof. dr. ir. D. Van Hertem, supervisor
Dr. dipl.-ing. H. Ergun, supervisor
Prof. dr. ir. R. Sabariego
Prof. dr. ir. J. Meyers
Prof. dr. ir. L. Meeus (KUL/Florence School
of regulation)
Prof. dr. ir. B. Kazemtabrizi
(Durham University)
Prof. dr. ir. E. Prieto-Araujo
(Universitat Politècnica de Catalunya (UPC))
Kristof Van Brusselen
(Parkwind)

Effective long term planning of offshore generation and transmission infrastructure
in the North Sea is key for the efficient development of Europe’s offshore
wind resources, an essential component to reach our climate commitments. Planning
approaches have been proposed within industry and academia. These
approaches are generally grouped into either generation expansion planning or
transmission network expansion planning. In Europe’s liberalized energy markets,
the responsibility for generation expansion lies with private industry, while
regulated entities oversee transmission system expansion. One of the challenges
in this context is the possible conflict of objectives between these entities, with
private investors prioritizing profit maximization and regulated entities responsible
for ensuring the reliability and affordability of the electricity supply. As
such, to consider either generation or transmission expansion planning in isolation
from the other can be problematic. Rather, an integrated approach is
more appropriate, one that can simultaneously consider the objectives of all
stakeholders involved. Such modelling in the context of offshore wind expansion
planning is still lacking and is a principle focus of the work in this thesis.

The rapid pace at which offshore wind technology has evolved further complicates
offshore planning. Planning models have failed to keep pace. Over the last thirty
years, the capacity of offshore wind farms has increased by orders of magnitude,
multiple concessions are placed side by side, and locations farther out to sea
are utilized. Still, planning approaches at the power plant scale have tended
to focus heavily on collection circuit topology optimization while assuming a
radial transmission connection to shore. These planning models have not tended
to consider the possibility of a transmission system design based on multiple
neighboring concessions. The high level offshore expansion planning models
have largely missed this scale as well, rather focusing on trans-national network
expansion such as the planning of HVDC interconnectors. The gap in between
these two scales is of particular interest when considering an integrated approach
as it is the transitional piece that links models suited for low level collection
circuit optimization with those for high level trans-national grid planning.

This thesis proposes a comprehensive planning methodology that addresses the
integration of offshore wind generation and the interconnection of energy markets.
The methodology covers a broad range of planning levels, including medium
voltage collection circuits up to HVDC interconnectors. This approach allows
the incorporation of various energy market models to investigate their impact on
offshore generation and expansion planning. At the highest transmission capacity
level, the proposed methodology employs a step-wise, least regret generation and
transmission network expansion formulation that considers hybrid offshore assets
and market design. At the medium capacity transmission level, the methodology
includes a mathematical framework that describes the combinatorial search space
of the problem, classical and heuristic based approaches to efficiently traverse
the search space, a machine learning clustering approach for handling very large
offshore development regions, and a candidate offshore substation placement
methodology that considers spatial constraints. Finally, the methodology reviews
state-of-the-art classical and heuristic optimization techniques at the collection
circuit level, with a particular focus on the integration of the medium voltage
network with the proposed high voltage network optimization.

In summary, this thesis presents a novel and comprehensive approach to offshore
wind expansion planning that addresses the challenges of integrating different
energy market models and considers the objectives of all stakeholders involved,
from private investors to regulated entities. The proposed methodology fills a
critical gap in the existing planning models and provides a valuable tool for the
effective long-term planning of offshore generation and transmission infrastructure
in the North Sea, which is key for the efficient development of Europe’s
offshore wind resources and the achievement of our climate commitments.