New marine renewable technologies that extract energy from ocean tides and waves are hoped to increase the nation’s future electricity supply.
Renewable energy harnessed from naturally replenished sources such as wind, sun, rain, geothermal heat, tides and waves, is the fastest growing energy source in the world.
In Australia it accounts for 15 per cent of the country’s total energy generation, with hydro power the primary source of renewable energy, followed by wind and then solar.
Tasmanian scientists, and emerging company Wave Swell Energy, hope to add tidal and wave energy to this mix, and are working on projects to see this goal come to fruition.
The first is at the Bank Straight in Tasmania’s north-east, which is earmarked as a promising site for tidal energy and is part of a major national research project.
The second is Tasmania’s first wave energy project to be installed near King Island by Wave Swell Energy in 2019, with the support of Hydro Tasmania.
Australian Maritime College associate professor of mathematics and hydrodynamics Irene Penesis is a researcher of tidal and wave technologies and lead investigator of AUSTEn – a $6 million tidal energy project supported by the Commonwealth’s Australian Renewable Energy Agency (ARENA).
Associate professor Penesis said AUSTEn conducts feasibility studies on two high potential locations where commercial tidal energy is possible – one of them being the Bank Straight in Tasmania.
“Australia has some of the largest tides in the world, with 11.8 metre tidal ranges...we only have tidal ranges of three metres in Tasmania but the tidal streams through our channels are very strong,” she said.
Associate professor Penesis said Banks Straight tidal stream was also very suitable for tidal energy and its proximity to Musselroe Bay and Woolnorth wind farm was advantageous, enabling the energy devices to convert to electricity directly on the grid.
“The Banks Straight is about 15 kilometres wide and its channel is shallow. The flow of water accelerates through this small and narrow channel and has the capacity to generate about three terrawatt hours of tidal energy per year,” she said.
“We estimate that this one channel, with installed tidal technologies, could generate around 300 megawatts of electricity per year, which would provide electricity for a quarter of Tasmania’s population.”
She explained that if the average person’s electricity consumption was 5000 kWh per year, just one tidal turbine with a one megawatt capacity could generate power to more than 600 homes. AUSTEn research will locate the best area of the Bank Straight to install tidal technologies and estimate the size and layout of any future potential tidal farms, taking into account factors such as sea-bed and sediment characteristics and water currents.
Associate professor Penesis said an environmental assessment will also look at things such as water temperatures, salinity, and flora and fauna.
The impact on commercial operations such as fishing and shipping routes would also be considered.
“We are very mindful of the environmental footprint,” she said.
“For instance if we see whales moving through the Bank Straight, what impact would tidal technologies have on their migratory paths? And there is a lot of international research looking to understand the environmental impacts from tidal energy technologies.”
AMC has already conducted tidal turbine tests in the Tamar River near Batman Bridge for its industry partner Mako Tidal Turbines. This horizontal turbine has three to five blades about 20 metres in diameter and looks similar to a wind turbine but operates underwater “where the density is 832 times that of air, so you are generating a lot more power”.
“We were testing the device at full scale in an operating environment, assessing its performance, the anchoring and mooring systems, environmental aspects and the power performance in that tidal stream,” associate professor Penesis said.
She said supporting local companies in the development of renewable technologies would ensure they remain competitive in the international market.
“We believe there is an opportunity for commercial development to happen in Australia. I would like to see tidal energy projects being developed within the next five to ten years, grid connected or micro-grids,” associate professor Penesis said.
“Tasmania could effectively become a battery of the nation by being 100 per cent renewable but also by exporting renewable energy to other parts of Australia, and maybe exporting to the world.”
Wave Swell Energy has international markets in its sights, but is currently testing its wave energy technologies in Tasmania, with the hope of gaining future commercial momentum.
Its rigorously designed units capture energy from the ocean’s waves and convert it into electricity, with associate professor Penesis and AMC being involved in hydrodynamic and structural integrity experiments for the units.
In 2019 it will launch an $8 million project planned for King Island, where a full-scale prototype of its unit will be installed and its energy generation assessed, with construction of the unit likely to take place in Launceston.
The unit consists of a large concrete chamber that contains a narrow opening at its top, connected to a turbine that sits above water, and is designed to work like a blow-hole.
Chief executive Tom Denniss said the success of the trial would hopefully lead to future wave energy farms in Tasmania, such as on the state’s west coast.
“The advantages of waves over traditional renewables such as wind and solar is that it is much more reliable and predictable,” he said.
He said winds may drop suddenly or clouds can hide the sun, but waves can be monitored and predicted days ahead of time.
“Waves can travel thousands of kilometres without using very much energy at all, so when you have a storm coming in computer modelling can predict to a few percent what the wave heights will be at a particular location at a particular time,” he said.
“We are not advocating that waves will power the whole world but we would hope to see a meaningful proportion of the world’s power being derived from waves.”
CSIRO scientist Mark Hemer said a national marine energy network would add security to the nation’s
“The variability (complentary) load needs to be taken up by something else other than solar and wind,” he said.
“One way you can do that is to have a diverse feed of renewables – solar, wind, wave and tide – that together form a distributed network. Energy would come from a range of spatial locations across the country and having these different stores would lead to more steady supply of power,” he said.