Developers of solar thermal technologies might like this to be the story of the tortoise and the hare.
The promoters of parabolic trough, power towers and linear Fresnel technologies were poised to dominate the solar market just a few years ago, before a series of grand projects were mothballed because solar PV suddenly offered a much cheaper alternative.
Now the solar thermal companies are plotting their revenge, or at least their return to the front line of solar developments. And storage, says eSolar CEO John van Scoter, will be the key.
US company eSolar is typical of the solar thermal companies that have found themselves effectively sidelined by the dramatic cost fall in solar PV technologies, but are now looking for a revival through their ability to provide dispatchable power by integrating storage into their solar tower power plants.
“One of the big challenges is grid stability, and the intermittency of renewables and the fact that they are not matching the demand profile throughout the day,” van Scoter told RenewEconomy soon after a visit to the Sierra SunTower facility, the company’s 5MW demonstration solar tower project near the Californian city of Lancaster.
“With molten salt, we can collect more energy through the day, it’s like a large thermal capacitor and it can continue to run after the sun comes down.
“There may be room for non-storage based solar, but I believe that with more and more renewables added to the grid, the value of storage will go up non linearly.”
“What we need to do is to make solar energy competitive with fossil fuel sources with no subsidies. And we want to compete with PV on cost, and have storage as a differentiating factor.”
That’s a view shared by the likes of SolarReserve, another Californian company that is building the 110MW Crescent Dunes facility in Nevada, which will be the largest solar tower system with integrated storage. (We will be running their story over the next few days).
Van Scoter, however, has a different strategy to other solar tower technology developers such as SolarReserve and Brightsource Energy, which are looking to build large-scale power plants of between 100MW and 400MW, centred around individual units of more than 100MW each, with large towers soaring between 150m and 200m high.
eSolar, he says, is favouring a “modular” strategy, which means an array of 46MW, for instance, would have up to 12 smaller towers of 65m high. This is not to say that it can’t create a single large plant of 500MW or more, it means that it can also service smaller demand profiles.
The Lancaster demonstration plant, which van Scoter says is effectively to the scale that would be deployed, did not have storage attached, and neither did the 2.5MW facility built in Rajasthan. But eSolar recently completed a molten storage integration study funded by the Department of Energy, and it is certain that this is the future.
eSolar though, is still in the throes of a fund raising process. It says it has received $22 million in commitments so far, but has not revealed how much it is seeking, or how much it needs. “We haven’t made a formal press release about that,” van Scoter says. Current shareholders include Google, NRG, GE and IdeaLab.
For the moment, however, van Scoter sees the biggest opportunities outside of the US, and in other applications such as enhanced oil recovery and industrial processes – both large markets that require a lot of steam.
The biggest users of steam for industrial processes are in Saudi Arabia and the UAE, and in Oman and Kuwait for enhanced oil recovery. “They have a very compelling solar resource, and very compelling economics. If they take those (petro) dollars to invest in solar, they will come out way ahead. That really is the biggest market we can see in short to medium term.”
Like SolarReserve, eSolar also sees opportunities in Australia in the mining space, and van Scoter says the company is in talks with several parties. In 2009, it was an unsuccessful bidder in the Solar Flagships tender.
“We were disappointed that we did not get into that. Our interest in Australia remains high.”
The US market, he says, is hampered by falling demand, which is providing an incentive to the market to stay with existing technologies. And there is no federal renewable energy target.
“Some state targets have teeth, others don’t,” he says. A unified renewable portfolio standard, or a unified carbon tax would change the picture dramatically. There is still not a real appreciation of the carbon impact here. Until that changes, we will have limited opportunities.
Van Scoter believes the sweet spot is in modular projects around a similar size, which can then be scaled up. That would mean a 100MW solar facility with his technology would have a dozen or more solar towers. It remains to be seen how that competes on costs with the likes of his rival technology providers.
But van Scoter sees advantages in that the technology could equally be applied to projects with smaller demand requirements. And it could be tailored to meet the local requirements. Around 5 hours storage was logical for many applications, but where power 24/7 was required, then more storage would be added.
“It’s important to realise that we really are early on in this whole technology revolution. It takes a long time to penetrate the energy space,” van Scoter says. “Companies with the eye for the long term will have the focus on costs and storage. That will be lion’s share of the market in the future.”