Reflected glory

The latest electricity generation technology du jour got a run in the press today, with reports of a $600m solar thermal hybrid plant being planned for Mt Isa. As is often the case there is currently less than meets the eye – the developer, Vast Solar – appears to be merely in talks with large users at this stage. But given that dispatchable zero emissions technology has long been the holy grail of emissions reduction for the power sector, the proposal will attract more interest than a run-of-the-mill solar PV or wind plant.

Back in the days when the federal government had an interest in climate policy, there were endless modelling runs to determine the optimal low carbon generation mix. Given the geographic and political limitations on building a lot of new hydro capacity (pumped storage notwithstanding), the modelling always included a substantial contribution from one or more of the following dispatchable technologies:

  • Nuclear – still illegal;
  • Carbon capture and storage (CCS) – for power generation, not progressed beyond a couple of flagship projects in North America;
  • Geothermal – hot rocks proved too deep to be economical in Australia; and/or
  • Concentrated Solar thermal power (CSP) with thermal (usually molten salt) storage – still waiting…

This is why the policy settings have been “taken by surprise” that we seem to be doing it all with variable renewables and storage instead. So, an economically viable solar thermal solution would be a real boon.

We have of course been here before. A 150MW concentrated solar thermal plant was planned for Port Augusta back in 2017 by an American company, SolarReserve. The state government, desperate at the time for dispatchable power following the closure of Northern and Playford power stations, seemed happy to underwrite it. But it never got built. SolarReserve’s only operational plant, in Nevada, has been mired in controversy over its reliability and the company went bankrupt. More successful is BrightSource with its Ivanpah plant in California, the world’s largest “power tower” CSP plant (although it has no storage component). However, BrightSource are struggling to capitalise on this with only one further project completed, in Israel.

SolarReserve, Vast and BrightSource have all utilised power tower technology where the mirrors, otherwise known as heliostats, are arranged around a central tower and focus the sun’s energies on fluid in the tower. The other main type of CSP is a parabolic trough, where curved mirrors are arranged along a line in order to focus sunlight onto a tube containing a fluid. The heated fluid can be used to drive an electric turbine. Spain has the largest installed capacity of parabolic trough plants, with around 2GW. Intriguingly these were all built in a few years around 2008-13, under a generous feed-in-tariff regime. The lack of new plants since then suggests developers have struggled to make the technology cost competitive in the market. A few have been built elsewhere, since, but the technology is yet to breakthrough to widespread deployment.

Vast’s track record is a successfully operating pilot plant of around 1MW capacity in Jemalong, NSW. Now it will need to show that it can scale up and has added a degree of difficulty by proposing a hybrid complex of CSP with thermal storage, gas turbine, solar PV and a battery. This will shore up the reliability of overall output, which given the remote location proposed (Mt Isa) will reassure potential offtakers.

A pilot plant is no guarantee of success of course; Australia has seen operational pilots of geothermal, wave and CCS in the last decade with none of these technologies progressing to widespread deployment. Meanwhile, solar, wind and batteries continue their march down the cost curve, helped by their modular nature, making it harder for other technologies to get a look-in.  even if it gets built and is operationally successful, the Mt Isa plant may not by a stepping stone to widespread grid deployment of CSP. Remoter areas with good sun, where reliability/dispatchability carried a bigger premium may turn out to be its niche.