The University of Adelaide has worked with final-year students to develop a prototype marine current turbine since 2009, when a group of students successfully designed, built and tested a simplified scale model that optimised diffuser configuration.
The 2009 team conducted preliminary investigations into developing a Sustainable Marine Current Energy (SMCE) turbine and proposed an initial design concept, and investigated a number of different models to enhance free stream flow through critical assessment of a nozzle, diffuser and slotted diffuser.
In 2011, the project’s focus turned to optimising a state-of-the art blade configuration incorporating tubercles based on the concept of pectoral fins on a Humpback Whale. This was achieved via computational fluid dynamics analysis and scale model testing in the University of Adelaide’s civil engineering testing facilities. The blades were then matched with a generator to extrapolate power output data. Results were encouraging, with energy production continuing in a broader range of current flows where traditional blades began to stall.
The team behind the 2012 version of the SMCE project is designing, optimising, building and field-testing a larger-scale axial flow marine current turbine incorporating both a slotted channelling device and tubercles, based on evidence from previous years that optimisation of a scale model marine current turbine occurred when these key design features are included. Both technologies aim to control the local flow through and over the turbine blades, providing for greater energy extraction in a wider range of ocean currents.Article continues below…
Several concepts have been generated and analysed using computational fluid dynamics and finite element analysis numerical modelling software to verify and select the optimum design. In the coming months, the turbine will be manufactured and tested in a marine environment with Dr Brian Kirke, Adjunct Senior Research Fellow at the Sustainable Energy Centre in the University of South Australia. It is expected that the results will stimulate increased investor confidence in the SMCE, allowing its developers to pursue commercialisation of the technology.
The team of participants in the project include Rosemary Hallam, Joshua Harley-Hill, Ben Murphy, Ashraf Salha, Philippa Williams and Melissa Wong, led by Dr Antoni Blazewicz in conjunction with Associate Professor Richard Kelso, Dr Zhao Tian and Dr Kirke.
The achievement of the team’s commercialisation goal is largely dependent on the attainment of sufficient funding. Current sponsors of the research project include VEHTEC Pty Ltd and Santos.
Tidal energy in economic context
Project participant Joshua Harley-Hill notes that marine tidal energy has been shown to provide a promising and predictable source of capturing energy, as ocean conditions have been studied for centuries to increase the reliability of shipping.
“Unlike waves, which are partially reliant on wind and other factors, marine currents are primarily caused by gravitational effects of the earth, moon, and sun, making it possible to predict their flows centuries in advance,” Mr Harley-Hill says.
“An advantage of marine currents over other renewable energy sources is its increased power density. On average, typical marine current power density available in ocean water is approximately three times greater than typical wind turbine power density, and approximately four times greater than typical solar power density.”
Despite this, the commercial deployment of marine current energy is still primarily initiated by start-up companies tied closely to their individual technology, so it represents a significant untapped energy resource. Mr Harley-Hill says that optimisation of the marine current turbine’s operational efficiency is a key driver in increasing investor support for the marine current industry.
Current barriers to commercialisation primarily surround the cost efficiency of the turbines, as well as difficulties in maintenance and installation. Environmental effects of marine turbines are relatively minor when compared to other renewable resources. Noise effects, strike risk and sediment disturbance with a technology such as SMCE are minimal after installation, due to low rotational speeds.
Charting a course for SMCE
Mr Harley-Hill says that a commercialised version of the SMCE would involve securing the final product to either the ocean floor or a pile structure.
“Our device will be tested in both the University’s wind tunnel and in open water, being towed behind and underneath a catamaran,” he says.
“The expected capacity of the turbine is highly dependent on the flow speed; to allow for effective comparison with published data, the turbine will be operated at flow speeds allowing for rated power of 0.6 kilowatts (kW).
“However, the prototype – when matched with a suitable generator and in flow speeds of 3.5 m per second – has the potential to generate as much as 21 kW.”
Average tidal flow speeds in promising Australian areas average 2 m per second, at which the SMCE prototype would be expected to generate 3.9 kW.
“A commercial-scale turbine would be much larger than our prototype, and hence would generate much higher power output,” Mr Harley-Hill adds. “As an example, a 5 m diameter turbine in 2 m per second would be rated at approximately 160 kW.”
The SMCE team has assessed that the most promising areas for its deployment would be the north-western coast of Western Australia and the western coast of the Northern Territory. Other suitable locations would include the Bass Strait, particularly near King Island and Flinders Island in addition to Backstairs Passage between Kangaroo Island and Cape Jarvis.
“The technology required for this turbine is currently available and so there is no inherent time delay in commercialising SMCE,” explains Mr Harley-Hill. “Optimisation will still be possible after this year’s extensive research, so an estimate of time from optimisation to commercialisation and then to implementation would be approximately three to five years.”