The general consensus among parents is that the 2003 Pixar flick Finding Nemo was OK the first couple of times they sat through it but, given the opportunity, they may not be willing to watch it again.
All of them, however, will credit the movie for educating them about the East Australian Current, which carries hero dad Marlin all the way down the coast to Sydney, where he eventually finds his son, Nemo.
Kids grow up to learn that fish can’t talk, like they do in the film, but the East Australian Current is real. And like the wind that rattles our shoreline and hilltops and the sun that blazes above us, its energy can be harnessed. But how?
It’s a problem Chris Drake was attracted to when he saw the prizes on offer at open data hackathon GovHack2018 for finding hidden value in ocean data. With a background in computational fluid design and particle form optimisation, and an interest in optimisation of turbine blades, he decided to work on a way to generate electricity using the East Australian Current (EAC).
The peak flow of the EAC, Drake says, is just off the tip of Fraser Island, “where all the waters are squeezed off the continental shelf on their way down south”. Drake is located on the Sunshine Coast, not far south of Fraser and near the EAC. “We’re perfectly located to reach the ideal point in the East Australian Current for putting some marine turbines out there.”
Beneath the waves
The EAC moves between 1 and 3 knots, about a brisk walking pace, but because there is around 800 times more energy in moving water than there is in moving air this amounts to “gargantuan amounts of energy,” Drake says. “More than double what the entire Sunshine Coast uses.”
Ocean Hydro’s plan is for an array of underwater turbine generators off the coast feeding a central power cable that delivers the energy to shore. “Kind of like an underwater wind farm, with big turbines that sit below the surface.” The units would be about 24 metres in diameter and rotate far more slowly than wind turbines, he says, to manage the very high torque.
Marine turbines used in tidal applications won’t fit the role, he says, and ocean current turbines that have recently come to the market are untested and expensive.
“We can either build our own or we can buy someone else’s,” he says. “At the moment we’re planning a hybrid; some development of our own technology while sourcing theirs for trials.”
Like wind blades, marine blades are shaped to be lifted by the current – like the wings of an aircraft. “We’re planning to make ours from a soft material, around a hard structure,” he says, to minimise the chance of the slow-moving blades hurting sea creatures.
The tips will be moving about 12 knots and a decision is yet to be made about the number of blades per unit. The tips will not reach within 16 metres of the surface, to avoid ships’ hulls. Each turbine will produce 200kW and a 400kV DC power cable will bring the electricity 88km to shore.
Sounds massive, but Drake is going to start small with a trial using two 350-watt generators with counter-rotating blades that will produce enough energy to power a house, about 6,000kWh a year, he says. The units will be anchored in a shallow location and connected to a buoy. “You need to have something that spins in both directions, so it doesn’t twist.”
The test generator units, developed for unmanned deep sea vehicles, cost $98 each. “It’s quite phenomenal. Hopefully we can scale that up for the larger ones.”
The trial will be much closer to shore, and closer to the surface. “The tidal flow in the Noosa River is roughly the same as the East Australian Current, so we can test there.”
To power the 25,000 homes of the Noosa Shire, Drake expects he’ll need a 15MW installation of about 75 turbines.
“We’re hoping we can get our 15MW installed for less than $350 million,” Drake says.
Energex has confirmed a local substation can accept 15MW and Noosa Council has given its permission for a trenched submarine cable to the substation. Battery storage or generator back-up may be included to satisfy the network’s concerns about supply “if the current slows down”.
Out of sight, out of mind
Measuring the energy resource below the surface of the sea is no trivial task. Most of the data available on ocean currents is not empirical but generated by computer modelling. Buoys and underwater gliders are deployed in oceans around the world to collect data on salinity, current and temperature, etc, and every so often one will be sucked down the EAC. In Australia, the CSIRO collects data from buoys off the coast near Brisbane. There is a lot to learn about conditions below the surface.
Hiding a generation fleet over the horizon and beneath the waves will please most clean energy sceptics, but the invisible nature of marine turbines also means they are hard to access when work needs to be done. “The big problem with doing anything in the ocean is maintenance.”
Without investors Drake admits work on the prototype is a hobby – and there is far more to it than applying his expertise in fluid dynamics and blade profile design.
“The opportunity for this to be an incredibly significant contributor to green energy and reversing carbon emissions in our vicinity is so huge that I think it’s more sensible to find people who are willing to help in the other parts of the business to give me time to design turbines,” he says, “and hopefully some investors willing to [take part in] an incredible new business.”
There are a hundred different coastlines around the world with similar currents flowing past them, he says. “If it works, there is enormous global potential.”
So far, Drake has discovered it will cost “several hundred thousand dollars to get the right kind of professionals” to produce the academic research and mathematical calculations required to satisfy an investment community that is fixated on a required rate of return.
“It would be nice to get an investor who is happy to spend small amounts of money proving it, rather than an investor who wants to get some guarantee of return at the end of it.”
New tech, it seems, has to beat old tech, and solar is the benchmark in the investment community. It’s a shame, says Drake, because solar generates nothing for 70% of the time.
Chris Drake spoke at the National Clean Technologies Conference and Exhibition in Caloundra, Queensland, in May.