IES Seminar Series - Dr Tom Bruce | School of Engineering

Date:

Friday, March 20, 2015 - 13:00 to 14:00

Speaker: Dr. Tom Bruce

Senior Lecturer in the Institute for Energy Systems

Title: Oscillating Water Column (OWC) Wave Energy Converters – Large scale Tests at GWK

Abstract:

Morale within wave energy is not at its highest at present, with costs remaining stubbornly, off-puttingly high due to issues spanning uncertainty in design for survivability, device performance and reliability. While offshore, near-shore and coastal wave energy converters face these challenges which all result in high costs, integrating a WEC, most likely an oscillating water column (OWC), into a port/harbour development offers some possibility for cost-sharing between the coastal protection and energy generation functions. In the future, it may become significant in terms of lifecycle assessment too.

In common with all WECs (and indeed almost any emerging technology), the journey of OWC plant from concept to deployment has seen highs and lows. Notable successes have included LIMPET being the world’s first grid-connected wave power station and, for the final three years of its service, its offering availabilities in excess of 90%. Notable lows have been energy captures far below design (LIMPET again), and much more seriously but less-reported, the catastrophic damage caused to the Mutriku plant (in Basque province) due to a major storm during its construction. The lows point to a need for yet-better modelling of loadings on the structure, and on performance in the field.

OWCs have been developed by a combination of numerical and physical modelling, but with physical modelling restricted to small-scale laboratory tests. But the OWC is a highly complex (and intriguing!) device to model because of an array of challenges in scaling / scale effects, involving (at least) Froude, Mach/Cauchy and Reynolds scaling when moving from the incident wave to the captured energy. If we start to consider wave impacts on the front face, or slamming within the chamber, we really are into the most challenging situations for physical modelling. (And all of this is before we consider model effects, e.g. the representation of the PTO, but we won’t go there…).

In an attempt to shed some light on scale effects in OWCs, Tom and his PhD student, William Allsop (a.k.a Prof Allsop, Technical Director, HR Wallingford), supported by colleagues from Queens Belfast, East Anglia and Naples II, applied for and were successful in gaining access to the Grosse Wellenkanal (GWK = Large Wave Channel) in Hannover, Germany, under the EC FP7 “Hydralab III” project. As a result, they ran an extensive set of large-scale (c. 1:9) tests over a 5-week period in March/April 2014.

This seminar will describe the design and operation of the GWK tests, present some of the findings of early analysis, and take a look forward to the next stages in this research.

Bio:

Dr Tom Bruce is Senior Lecturer in the Institute for Energy Systems. Tom’s early research work was in the then-emerging field of Particle Image Velocimetry (PIV), work which led him into the company of coastal engineers and scientists, as a very junior partner in the EC “PROVERBS” project (1996-1999) where he focussed on wave impact forces on vertical breakwaters. From there, together with William, he led the UK “VOWS” project on violent wave overtopping at seawalls, which in turn led to his being a partner in the EC FP5 “CLASH” project, which made detailed field-laboratory comparisons of overtopping. Results from “VOWS” and “CLASH” found their way into European guidance on wave overtopping – the “EurOtop” manual – downloaded .c 8300 times from 89 countries – on which Tom is a chapter lead author.

While Tom continues to work on wave overtopping (including work with Claudio on direct hazard to people from overtopping), and on EurOtop II), he has become increasingly involved in wave and tidal energy projects, mostly based upon physical modelling (not too far from his comfort zone!)