Postgraduate Research Student
School of Civil Engineering, Room 360
Research project - An Investigation into a Power Maximising Control System for a Bottom Hinged Wave Energy Converter
Supervisor: Prof John Patterson
Associate Supervisor: Dr Tim Finnigan
Renewable energy sources are increasingly attractive in this time of diminishing oil reserves and human induced climate change. Ocean wave energy is one potential alternative. However, it is proving difficult to exploit this vast resource economically.
To be economic a wave energy converter (WEC) must produce a good ratio of power output for size in average sea conditions and it must be able to survive storm conditions without being hugely over-engineered in normal conditions.
One promising class of WEC is the bottom hinged oscillating body point absorber. Point absorbers are much smaller than the wavelengths of the waves that drive them and they have the characteristic that they can effectively interact with, and extract energy from, a greater volume of water than their physical dimensions would suggest. Bottom hinged devices also have the ability to lie flat on the bottom to ride out storms.
Oscillating body WECs perform best near resonance. Unfortunately, point absorbers have a narrower resonant response compared with larger WEC types which means, in variable conditions, without some form of active control, they will operate well below their optimum for much of the time.
A bottom hinged WEC has two parameters that can be controlled – the power take off (PTO) loading and the volume of ballast water the device carries.
My project will theoretically analyse the dynamics of bottom hinged WECs to identify some useful control strategies for these parameters. These strategies will then be tested practically in the School of Civil Engineering’s 30m wave flume using a vertical cylinder as the oscillating body.
An electric motor with computer controlled torque output will be used to simulate PTO as this offers greater versatility more simply than a hydraulic system typical in real WECs.