Concentrated solar power?
This idea has always been attractive and exciting but it has been around now for long enough for us to assess its practicality. And the one certain thing about it is that is trouble-prone and often fails. You can imagine how dicey anything is going to be that relies on moving molten salt round at at 550 degrees C. The one thing it is good at is eating up goverment subsidies
The best-known such project is the Ivanpah installation in California. See below for some history of it:
Concentrated solar power (CSP) uses mirrors to focus heat from the Sun to drive a steam turbine and generate electricity.
While CSP was once the great hope for replacing coal and gas-fired generation, it's now generally considered to have been eclipsed by cheaper forms of renewable generation, like solar panels and wind turbines.
Recently, however, it's been making a quiet comeback.
The reason for this boils down to three words that describe one of the major challenges of decarbonising the grid: overnight energy storage.
The CSIRO's Renewable Energy Storage Roadmap, released last week, predicts that by 2050, CSP will be the cheapest way to store energy for 8–24 hours.
Developing this "medium-duration" storage is a necessary step to switching off coal- and gas-fired generators that produce most of the power we use at night.
For this reason, CSP projects are starting to gather momentum.
The Australian Renewable Energy Agency (ARENA) recently approved $65 million in funding for a Sydney-based company, Vast Solar, to build the country's first commercial-scale CSP plant in Port Augusta, South Australia.
So how does CSP work?
And what role will CSP play in a net-zero Australia?
A technology that once rivalled solar panels
The idea of CSP is so simple that the technology hasn't changed much in decades.
Italy built the first CSP plant in 1968, and California installed the first commercial-scale array in 1981.
At the time, solar panels were expensive and mostly used in consumer electronics, whereas CSP relied on familiar technologies, such as steam turbines.
CSP plants also looked impressive: The popular "power tower" design featured a circular field of thousands of mirrors, focusing their light on the crown of a central tower, which in some cases soared taller than 200 metres.
But then, more efficient panels and larger factories drove down the price of photovoltaics (PV), while CSP plants ran into problems with leaking fluids and dirty mirrors.
In 2019, South Australia scrapped a $650 million project to build Australia's first commercial-scale CSP after the company behind the project revealed it could not raise funding.
"It's been a bit of a tale of woe in Australia," said Keith Lovegrove, director of the Australian Solar Thermal Energy Association. "We've actually managed to snatch defeat from the jaws of victory a couple of times."
As of 2021, the global installed capacity of CSP was 6.8 gigawatts, which was many hundreds of times less than the figure for photovoltaics.
But CSP is not dead. Spain, Morocco, South Africa, Israel and other countries are using CSP in their grids, while China has dozens of projects underway.
"China is the most active place at this, at this very moment," Dr Lovegrove said.
CSP cannot generate daytime electricity as cheaply as solar PV, but it has one advantage: built-in storage.
The heat from the Sun is stored in a medium such as molten salt. When the Sun goes down, this stored heat can be tapped to drive the turbine and generate electricity.
This combination of generation and storage makes CSP "dispatchable", meaning the power can be sent to the grid when it's needed. "The whole point about CSP is that it's dispatchable renewable generation," Dr Lovegrove said.
"It's generation you can have when you need it at night, or peak periods. It comes at a higher price because it's got this added value and complexity."