Generating and storing sustainable energy is the holy grail

Transmission lines have fallout. Battery farms are expensive. Repeating Snowy II is out of the question.  But there is a simple solution to generating and storing sustainable energy for overnight electricity. And country businesses are taking it on themselves to prove its powerful potential. 

“All transitions happen at a steady pace,” says Dominic Zaal, Director of the CSIRO’s Australian Solar Thermal Research Institute (ASTRI).

“People start with the easy things, the cheapest things – the obvious things. And, of course, for regional Australia and remote towns, that will always be photovoltaic (PV) panels. And batteries make PV even better because you can store excess power and use it when you get home from work to fire up the oven and turn on the air conditioner.”

Australia’s energy balance is at a tipping point, says Zaal. And what we do now can topple us into a lucrative new industry – or out of contention on global markets.

The heat is on

“Wind farms are great,” says Zaal. “They’re an important part of any energy mix. But you can never rely on them alone. Sometimes the wind doesn’t blow.’

And not only are lithium-ion batteries far too expensive to cover demand for an overnight stretch. They must also be replaced every 10-15 years and even sooner in hot, dry locations. 

Zaal says there are three available alternatives.

One is pumped hydro – where excess solar electricity is used to push water uphill to flow back down again at night (over electrical turbines, of course).

“Australia doesn’t have large amounts of available water. We also don’t have that many tall mountains – and making them will probably be too carbon intensive,” he quips. 

Another pathway is hydrogen. Renewable energy powers electrolysis machines to split water atoms into their component parts. The hydrogen can be burnt to produce steam.

“But hydrogen is very expensive to produce. It’s even more expensive to move around,” says Zaal. “I think Australia can produce and export more hydrogen than any other country in the world because of our richness in sunlight. But in terms of domestic use, moving large amounts around will only be economically viable for heavy industries.”

The third is solar thermal heat storage.

“It’s not rocket science. But people often think it is”.

And Zaal says it could tilt the cost-benefit balance back in favour of rural and regional communities.

“The reality is that industry will move to wherever the energy is cheapest,” he told Cosmos. “Guess what – it ain’t going to be cheapest in the middle of Melbourne where you’ve got limited space and therefore no solar generation potential. So you will see a migration of industries that need heat and power to regional Australia. And that’s a great thing, right? Well, solar thermal means they’ll also be able to work 24-7!”

Lean, green sustainable energy machines

At the heart of this technology is heat. And the engineering behind applying heat to water to generate steam to drive a turbine has been around since 1712 – ironically invented to pump water out of coal mines.

Coal-powered power plants use heat to generate steam to run a turbine to generate power. As do thermal gas plants and nuclear reactors.

Solar thermal is just another way to generate heat. And this heat can be stored in a suitable container – usually salt, oil, water or a solid material like graphite. Once the sun goes down, that heat generates steam – and you know the rest.

It’s a proven technology. The first operational facilities were built in the US in the early 1980s. And it is 100 per cent renewable.

“People go, well, if it’s that simple – why hasn’t it been deployed yet?” says Zaal. “Well, it hasn’t been deployed because we haven’t needed it. Coal-fired power stations provide most of our cheap overnight power, so the imperative for a renewable alternative hasn’t been there. But all of our coal-fired power stations are retiring in the next 10-15 years, so very soon, we will need an alternative”.

Now the concept’s being put to the test at a Wodonga, Victoria, Mars Petcare manufacturing facility.

In June, Graphite Energy installed a shipping container-sized heat storage system at the plant. It gets heated to 650C during the day by the cheapest available solar-generated electricity. And that heat is extracted at night to generate steam to cook pet food – reducing the plant’s demand for expensive natural gas.

“We call them electric Thermal Energy Storage systems or e-TES for short,” says Zaal. “They’re graphite blocks in an insulated shipping container. And they’re a no-brainer. There’s no pressure. No risk of explosion. It’s just graphite – like in your pencil!”.

Powering change

“Everyone said displacing steam boilers with renewable heat technologies couldn’t be done commercially,” Zaal says. “But once we bring industry leaders to Mars, show them the system and get them to talk to the operators – the next minute they’re wanting to know how to get one for themselves!’”

The 8-megawatt-hour Graphite Energy TES container, built at Lake Cargelligo in Central NSW, has been operating 24-7 for the past five months without a hiccup. If heated by on-site solar collectors, it could pay for itself within five years. That increases to 10 years if solar electricity is sourced from the general power grid.

Mars Wodonga is also contemplating the next level of this technology – a Concentrated Solar Thermal (CST) system. This uses a mirrored parabolic trough collector of about 5.5m in diameter. The trough follows the sun – focusing its rays on a metal pipe receiver running its length. And this heat gets stored.

“They don’t replace PV or batteries,” Zaal explains. “They complement them. Your PV panels provide power during the day. Your PV-charged batteries get you over the two-hour evening peak. And then, about 8 in the evening, the solar thermal storage kicks in to get you through until dawn.”

Solar panels also help kick these low-profile reflector units over the finishing line. Smaller parabolic trough systems operate at about 400C. But PV panels can power a traditional thermostat in the heat tank to boost it up to 550C. That’s the temperature needed to produce superheated steam for a 30-40 megawatt generator.

Zaal says these hybrid solar panel / solar thermal / heat tank facilities are relatively easy to build at the 50 to 100-megawatt scale with 12 to 18 hours of storage. “And that’s what’s needed to provide remote districts and centres with 100 per cent renewable electricity 24/7,” he says. “The technology is also being refined into smaller units suitable for remote communities and outlying mines.”

Our time in the sun?

“If any nation can benefit from this technology, it will be Australia,” Zaal says. “We soak up more solar radiation than any other. However, despite having all this land and renewable energy potential, we continue to be very slow at using this to our competitive advantage.”

But some progress is being made.

The mining hub of Mount Isa in the Gulf Country region of Queensland is a case study. 

It’s not connected to the national grid. It must generate its own power. And most of that is currently supplied by burning natural gas extracted from local reserves. 

“It’s a classic challenge because not only do you have a township that requires energy during the day, you’ve also got a large mine site that must be powered 24-7,” Zaal explains.

A new constant power supply is needed. Urgently.

“Vast Solar – which is building a CST plant at Port Augusta – has designed a 15-hour solar thermal power facility as part of a proposed new power supply mix for Mount Isa,” says Zaal. “It’s potentially ready to go”.

Its future now rests in government hands.

As does Australia’s, says Zaal.

“My advice is that whoever gets there first in the smartest way will benefit the most because carbon pricing is coming,” he warns. “Whether we like it or not, green countries will get sick of subsidising less green countries. So they’re going to start penalising them by imposing tariffs.”

Australia has a lot of heavy lifting to do. And little time left in which to do it.

“I’m sick and tired of people telling me solar thermal with storage can’t be done in Australia,” he says. “So we are working with several companies on building parabolic trough systems within the next 12 months. And then we will then take ministers, industry and energy planners to these sites to show them an operational system that is taking energy from the sun to provide renewable steam power … I hope then they can see its ability to do the same for any regional centre and any industry that wants to relocate for cheap energy.”