Driving towards Port Augusta, a luminous white light appears on a concrete shaft to the side of the highway.

The giant light is a receiver; it sits among a sea of mirrors which beam the sun onto it, producing intense heat that creates steam, turns a turbine, and makes electricity. It's known as concentrating solar thermal, a new breed of energy.

Nearby, a chimney is visible in the distance across the salt pans.

Looking across the saltpan to the old power plant's tower. ( ABC News: Carl Saville )

It's a remnant of the Northern Power Station, one of two defunct coal-fired plants here that used to supply more than a third of South Australia's electricity. Its boilers were detonated last December.

"In 2015 when they announced the closure of the [Northern] coal-fired power station, I said that Port Augusta would become the renewables capital of Australia," Sam Johnson, the mayor of Port Augusta, said.

"Three years on, I think we have."

Or soon will be.

That white light on the outskirts of town is a mere taste of the technology coming to Port Augusta on a far grander scale.

Renewables boom boosts Port Augusta

Thirteen renewable energy projects are underway or under consideration — from wind farms and pumped hydro-electric power to solar with storage that can shift electricity made when the sun's shining to meet peak demand in the evening.

"The one great resource we have here in Port Augusta and the upper Spencer Gulf is this wonderful natural resource called the sun," Mr Johnson said.

"It's no different to having a massive uranium deposit, a massive gold deposit, a massive copper deposit."

In a country drenched in sun, this natural resource is particularly abundant in the arid landscape around Port Augusta, and there are also plenty of flat expanses on which to build the facilities needed to exploit it.

Framed by the Flinders Ranges, stage one of the Bungala solar farm stretches over 300 hectares of land owned by the Bungala Aboriginal Corporation about 10 kilometres north-east of town.

Bungala uses a solar photovoltaic technology, with panels mounted on a tilting axis that can follow the sun's path from east to west, maximising output and efficiency.

The Bungala solar power plant currently stretches over 300 hectares of land. ( ABC News: Carl Saville )

"It's not only the largest solar project in Australia," Mr Johnson said. "It's also the largest in the southern hemisphere. And it's only half complete."

When stage two is complete, the entire 300 megawatt project will cover more than 800 hectares — an expanse nearly as big as the Melbourne CBD — and generate enough electricity to power about 82,000 households, according to its owners, Italian multinational Enel Green Power and the Dutch Infrastructure Fund.

"The solar plant will only operate when the sun is shining, but when you start to incorporate battery storage and solar thermal, you then build in the energy security," Mr Johnson said.

Solar that releases energy even when the sun doesn't shine

The Aurora project about 30 kilometres north-west of Port Augusta addresses the criticism often levelled at renewable energy — that when the sun doesn't shine, and the wind doesn't blow, the power doesn't flow.

Construction is due to start soon on the concentrated solar thermal power station. It will able to store a massive 1,100 megawatt-hours of electricity, according to the project proponent, SolarReserve.

When it is built, an impressive sight will greet observers: a tower full of molten salt standing about 250 metres high, surrounded by more than 10,000 heliostats — movable mirrors, the size of billboards, algorithmically programmed to track the sun.

Those thousands of mirrors will reflect and concentrate sunlight, beaming it onto a receiver straddling the top of the tower.

During the day, molten salt will flow through the receiver and be heated to temperatures as high as 566 degrees Celsius, then stored in tanks overnight.

The energy will be dispatchable as electricity when needed — after dark in the evening peaks, or in the morning, hours after it was generated. It will be enough energy to power 90,000 homes, according to SolarReserve, which wants to build six of these plants in South Australia.

The Crescent Dunes solar power plant in Nevada is the same type of facility as Aurora will be. ( Supplied: SolarReserve )

Crescent Dunes in the Nevada desert uses an identical technology.

There is one key difference: the price of the power.

"Pricing has come down dramatically, as it has throughout the renewable energy industry," Kevin Smith, the chief executive of SolarReserve, said.

Crescent Dunes, the first plant of its kind, began operating in 2014.

Construction was aided by a concessional loan of $US737 million ($1,040 million) from the US Department of Energy. Despite that subsidy, it was contracted to supply electricity to Nevada at $190 a megawatt hour. Not cheap.

The Aurora project is receiving a much smaller concessional loan from the Australian Government — about $110 million — but will supply energy at a fraction of the price.

SolarReserve is cagey about the precise figure (the contractual conditions are complex) but Mr Smith agreed with reports that put the cost at about $78 a megawatt hour.

At current exchange rates, that is well under half the price of electricity from its inaugural plant in the US — and far cheaper than new coal-fired power.

"In terms of cents per kilowatt hour, we can supply electricity 30 to 40 per cent cheaper than new-build coal," Mr Smith maintained.

A town blanketed in ash

Coal used to be Port Augusta's lifeblood.

From the middle of last century, generations of Port Augustans worked in the coal-fired plants. They burnt lignite, the lowest rank of coal, mined at Leigh Creek about 250 kilometres away.

Port Augusta was, until recently, home to two coal-fired power stations. ( ABC News: Carl Saville )

The jobs buoyed the town but came at a cost: air pollution which blanketed the town, putting its citizens at risk of respiratory diseases from asthma to lung cancer.

"For 60 years the coal-fired power stations were dumping ash over the city," Lisa Lumsden, a community activist and city councillor, said. "At times in the early years up to 15 tonnes of ash a day.

"People's health suffered; asthma, respiratory disease was commonplace."

For years, no one assessed the toll the pollution was taking, but when a study finally examined lung cancer rates in Port Augusta, it found a cluster double the average rate.

Though particulate matter and other carcinogens released by burning coal is a known cause of lung cancer, the government tried to blame it on smoking.

The ABC met Lisa Lumsden in the town square by a statue of her mentor, Joy Baluch, mayor of Port Augusta for 29 years until she died in 2013.

A statue commemorates former Port Augusta mayor Joy Baluch, who died of cancer, as did her husband. ( ABC News: Carl Saville )

Ms Baluch took to politics because of her son's severe asthma. For decades, she battled to cut the city's air pollution.

Her husband worked in the power stations. He died of lung cancer 16 years before her, though he did not smoke.

Ms Baluch campaigned for solar thermal technology to replace the ageing coal-fired electricity generators.

Through the community group Repower Port Augusta, Ms Lumsden took on the mantle.

"[In] 2011 we started the campaign — well before the power station announced its closure," she said.

"The community could see that there was a short future. We could see that it was likely that in a world of climate change and dirty coal ash and a 60-year-old power station, change was going to come.

"We researched and found that solar thermal technology was exactly suited to the environment here, started a local campaign, then a state campaign, then a national campaign, and we won."

Ms Lumsden acknowledged the closure of the coal plants had been tough for locals.

"We lost 200 jobs. It brought huge stability to our community — great, secure, well paid jobs — but it was no longer economically viable," she said.

"We had to embrace the options we have.

"We have incredible geography. We have everything we need to become the renewables capital of the world."

An exaggeration? Maybe, but it's not far off the mark.

The arid-zone landscape of the upper Spencer Gulf has solar resources ideally suited for concentrating solar thermal power, wind in abundance at speeds well suited for turbines, and a coastal location that opens the possibility of pumped hydro energy using seawater.

What you won't find are fields of fruit and vegetables — but where there's a will, there's a way.

Sundrop Farm on the outskirts of Port Augusta, which uses solar energy to desalinate water and grow tomatoes. ( ABC News: Carl Saville )

That white beacon of light on the edge of town? It's a solar thermal power plant that runs a massive greenhouse that grows truss tomatoes.

Sundrop Farm is using the solar thermal electricity to desalinate water, create electricity to power the operation, and pump heat through 60 kilometres of pipe around the vines.

It's a testament to human ingenuity, like much of what's happening in the renewal of Port Augusta.