With global energy demand estimated to rise considerably and global warming accepted by the majority of scientists, the pressure to reduce fossil fuel usage is increasing. To this end, the UK government has set a target of generating 50% of
electricity from renewable energy sources by 2050. It can therefore be deduced that
decreasing the cost of renewable energy by increasing the energy capture is critical.
Oscillating Water Columns (OWCs) employing bidirectional turbines coupled with
generators can be used to capture energy from oceanic waves and convert it to electrical energy. This thesis includes a study to quantify the potential power smoothing
that can be achieved from a wave farm of ideal OWC devices and from auxiliary
hardware such as flywheel energy storage systems. Also detailed are the upgrades to
the OWC test facility at Cranfield University, including the world-first capability to
simulate polychromatic waves. This test facility has been employed to validate turbine characteristics derived from Computational Fluid Dynamic (CFD) numerical
results.
This thesis contains a literature review of the existing control strategies for OWCs
that concludes that the optimization of power capture from individual components
in the energy chain forces system-level compromises. This conclusion drove the
development of an unique energy-based model of the complete wave-to-wire system utilizing port-Hamiltonian mechanics which mandated two modifications to the
port-Hamiltonian framework. The first modification to the port-Hamiltonian framework resulted in a new generalized means of modeling systems where the potential
energy is dependent on the momentum variables. The second modification expands
the port-Hamiltonian framework to allow the modeling of ow source systems in
addition to effort source systems. The port-Hamiltonian wave-to-wire OWC model
enables the future development of a control approach that optimizes power capture
at a system level. As a first step to achieving this goal an Injection Damping Assignment (IDA) Passivity Based Control (PBC) strategy was successfully applied
to an OWC system and an energy storage flywheel system. These strategies pave
the way for future developments utilizing optimization techniques, such as the use
of cost functions to identify the peak efficiency operating condition.Engineering and Physical Sciences (EPSRC)PhD in Energy and Powe