SolarReserve chases even hotter molten salt

SolarReserve, the solar thermal power plant developer, intends to dramatically increase the temperature of molten salt storage with a grant from the SunShot Initiative. Photo credit: Crescent Dunes, SolarReserve

SolarReserve, the solar thermal power plant developer, intends to dramatically increase the temperature of molten salt storage with a grant from the SunShot Initiative. Photo credit: Crescent Dunes, SolarReserve

By Jason Deign

SolarReserve, the solar thermal plant developer, is going after molten salt storage systems of more than 700ºC with a USD$2.4m award from the US government.

The award, announced last Wednesday, comes from the US Department of Energy SunShot Initiative’s Concentrating Solar Power: Advanced Projects Offering Low LCOE Opportunities (CSP: APOLLO) programme.

It will be used with matching funds from SolarReserve and other commercial partners to develop a new form of high-temperature ceramic receiver, according to Tim Connor, SolarReserve’s vice president of engineering and technology.

This “breaks through current temperature and performance barriers, while meaningfully increasing efficiency, energy storage capabilities and lowering capital cost,” Connor said in a press release.

The receiver technology should raise operating temperatures in molten salt power tower solar thermal plants by some 300ºC from a current maximum of around 565ºC.

Molten salt power tower plants

SolarReserve will be working with Trex Enterprises Advanced Materials Group and the University of California, San Diego, on the project.

Kevin Smith, SolarReserve’s CEO, told Energy Storage Report that the work should take three years, with up to another couple of years for commercialisation.

The project will result in “a significant increase in the efficiency of the plant and storage,” he said.

In the meantime, however, SolarReserve is also working on refinements to its existing receiver design. This mainly involves increasing the size of the receiver so it can deliver a greater output, albeit at the same temperature.

At the same time the company is aiming to cut the cost of new heliostat fields significantly compared to that of its first completed project, Crescent Dunes.

Up to 40% less cost for heliostats

“The heliostat field in Crescent Dunes is 40 to 50% of the [plant] cost and we are seeing 30 to 40% less cost for heliostats,” Smith said. “Everything else is moving forward as well.”

Taking these advances into account, Smith reckons SolarReserve can already shave up to 30% off the cost of a new CSP plant.

Within three to five years, meanwhile, he predicts cutting the levelised cost of energy (LCOE) for CSP by up to 40%, “well into the single digits per kilowatt-hour.”

This is welcome news for an industry that appears to have lost its way in recent years.

The long lead times and high capital costs associated with grid-scale solar thermal plants put the technology at a disadvantage compared to PV towards the end of the 2000s.

A valuable asset for off-takers

And by the time CSP developers realised that molten salt storage could be a valuable asset for off-takers, the world had already become engrossed in integrating lower-LCOE wind and PV generation into the grid.

Storage is now more than ever seen as the key for CSP’s survival.

But in an industry that has always been dominated by a small number of major players, SolarReserve is increasingly looking like the only company that can make a go of it.

Only three firms can currently be said to be really active in grid-scale CSP plant development, and two of those face question marks at the moment.

BrightSource Energy, developer of the iconic Ivanpah power tower project in California, is exploring opportunities in China but has yet to develop a plant with storage; Ashalim, in Israel, will be its first.

Looking to employ molten salt

Meanwhile Abengoa Solar, a Spanish company, has developed storage systems for its Solana plant in the US and is looking to employ molten salt in a second American project, Palen.

In July Abengoa Solar’s US director of sales and marketing, Amparo Pazos Cousillas, revealed the company was planning to commercialise molten salt as a standalone storage asset, without CSP, for US utilities.

Since then, however, Abengoa Solar’s parent company has sailed into stormy waters. It’s asset-holding subsidiary, Abengoa Yield, has been trounced by a wider investor backlash against yieldcos, losing around 47% in value in a year.

And even though some analysts maintain a ‘buy’ recommendation on the yieldco shares, Abengoa itself is in deep trouble over a likely debt default. The outlook for the business seems uncertain.

That pretty much leaves SolarReserve as the flag bearer for grid-scale solar thermal plus storage.

Developing and selling PV plants

So far the company has been able to satisfy the financial appetites of its private equity backers by developing and selling off PV plants.

And its strategy is nothing if not pragmatic, mixing and matching CSP with PV to suit the needs of markets such as Chile or South Africa.

Smith said SolarReserve has, like Abengoa, been studying the deployment of standalone molten salt storage “for several years” but that it only sees a need in “very specific applications.”

But in markets like the US, where attitudes towards solar thermal have soured following bird deaths around plants, those very specific applications might be the best on offer.

“It’s hard to deny that the CSP market isn’t as large as people expected four or five years ago,” Smith admitted.

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