It's a sunny day in the city and travellers on board a Sydney ferry are enjoying the sights, smells and sounds that surround them.
"Well, if this is public transport, it's probably the best in the world," said New Zealand tourist Greg Seaward-Searle.
But for others, the roar of diesel engines is something they'd rather live without.
"It would be good to see something that's very cutting edge and responding to the new energy technologies," said commuter Fiona Pacey, as she heads to a meeting in the city.
With a state election fast approaching in New South Wales, both sides of politics are being urged to commit to replacing the city's ageing RiverCat ferries with electric-powered vessels.
That’s looking more and more likely — recently, the government abandoned a $43 million tender process to build seven new diesel-powered craft.
Transport for NSW said it will now "gauge market interest in a new process," though it won’t say if electric ferries could be in the running.
According to Dr Gail Broadbent, who researches electric vehicle policy at UNSW, it's not an impossible dream.
“We could sign contracts this year if that was what the government wanted to do," Dr Broadbent said.
On the ferry, one elderly man leaning on a cane trod carefully but sure-footedly as he came aboard.
"I'm a retired ferry master," he said, casting an experienced eye over the vessel and her crew.
As someone long-familiar with the waterways of Sydney and the vessels that ply them, he has questions about calls to electrify the city's ferry fleet.
"I think the cost is everything. How long are they going to last? How many trips are they going to get out of an electric ferry?” he said.
“I can't see it being cost effective. Not at this point."
But Dr Gail Broadbent said those doubts are misplaced, and that when existing fleets are upgraded, the old diesel-powered craft are replaced with cleaner technology.
"It is true that they're more expensive to buy up front, but these cost savings can be made from the fuel savings over a period of about six years,” she said.
“So it is economical. The ferries generally last a lot longer than six years."
Innovation in materials and charging stations
Like electric cars, one of the biggest obstacles is the recharging facilities that provide electric ferries with sufficient range.
But Dr Broadbent points out that other countries have come up with a solution.
"In Norway and Denmark and Sweden at the moment, they are running these short haul ferries of about one hour's duration for each trip because they can put the charging mechanism at either end of the trip, so that when you load / unload, that's when the recharging takes place.
Tim Burnell, the CEO of INCAT Tasmania, a company that makes light-weight catamarans, agrees the biggest challenge is probably shore-side infrastructure.
“That's where we see the big problems, getting the power into the ports or to the berths where the vessels are going to need to charge and then having enough capacity so they can charge without causing other issues in the grid."
One solution could be to install bigger batteries on new electric ferries, but that means weight becomes an issue.
To counter that, boat manufacturers are developing innovative ways to keep weight to a minimum.
Right now, INCAT Tasmania is developing a massive 2,000-passenger battery-powered car ferry for a South American customer.
Tim Burnell said light-weight aluminium will be used to build the boat, rather than heavier steel.
"When it comes to electricity or batteries, it is all about weight,” he said.
“The same as a car, the lighter you can build something, the less energy you need to propel that.”
EV Maritime designs and builds electric ferries, with two under construction for the city of Auckland in New Zealand.
It builds vessels from carbon fibre.
"If you make the boat lighter, you can use smaller motors and you can use less energy, and so you can put smaller batteries in them, which makes it lighter," EV Maritime CEO Michael Eaglen said.
"(So) although you're spending a lot more money to build a carbon fibre structure than an aluminium one, you save so much in the systems that you put into it.
“And through the efficiency that comes as a result of that, you can end up with a boat that costs you the same amount and spends a lot less time charging."
Revolutionising boat design
Dr Saul Griffith, a Sydney-born engineer and founder of Rewiring America and Rewiring Australia, said we need to completely revolutionise the way we travel by boat.
"If you think about traditional boats, they were all very long and skinny (which) uses the least energy to get through the water," Dr Griffith said.
"Once we invented fossil fuels, we made all of our boats short and fat because we didn't really care how much energy they used.
“I think there's this extraordinary opportunity to redesign boats. They'll look more like they used to. They'll look more like big, long, sleek canoes.
“And that's how we'll get the energy efficiency. That's how it will make the batteries go further."
Proponents argue this change needs to happen today if Australia wants to become a global leader in technology and manufacturing.
"In some respects, the biggest obstacles aren't really technical ones. The technology is there to be able to do it,” Mr Eaglen said.
“The challenge is that it's quite a different commercial model, in that electric ferries, like electric cars, cost a lot more to buy, a lot more to build, but they cost a lot less to run.
"But doing that then in the public sector, especially when you've then got existing public transport contracts in place and budgets and all the rest of it, it can take a bit to drive that through the system."
Saul Griffith argues Australian governments need to seize the moment.
"There's every reason to be a first mover, not a follower,” he said.
“If Australia develops the capacity to design and build these boats for the rest of the world, then that will be an export industry for us.
“If we don't do it, China will do it. And we'll be buying lower quality ferries from them."
But Tim Burnell believes the future is bright for Australia’s ferry industry.
"I think our routes, certainly Sydney Harbour, even Port Phillip Bay, Brisbane, even Hobart, (those places have) got the perfect geographies to support electric ferries.
“And I'm looking forward to see where we go."
