Growing technology diversification illustrates how the CSP industry is targeting greater efficiency and maximising its investments. Expect more to come.

By Jason Deign in Barcelona

 Developers are trying their hands at new CSP technologies: witness Sener-owned Torresol Energy’s foray into power towers after building a reputation in parabolic troughs, or SkyFuel’s grant-funded work on a linear power tower concept alongside its SkyTrough technology.

And some CSP companies are going even further. Solar Millennium and Ferrostaal’s joint venture, Solar Trust of America, last month struck a deal with SolarHybrid to develop photovoltaic (PV) plants. SolarReserve is also adding PV capacity to its existing CSP portfolio.

Why is the industry developing a taste for variety all of a sudden? There are a couple of reasons. At Torresol, the decision to move into power towers with the opening of the Gemasolar plant in Fuentes de Andalucia, Seville, Spain, essentially reflects the evolution of technology.

Towering in the future

“Tower technology offers many advantages over parabolic trough but there are not yet any commercial plants in operation,” Sener’s solar business director Miguel Domingo explained in a company newsletter article last autumn.

“Therefore, finding financing for tower plants was much more difficult than for parabolic trough plants. Parabolic trough plants was what the market demanded and could be financed much more easily by the banks.”

Sener spokesperson Oihana Casas tells CSP Today: “They are complementary technologies. Our technicians believe the solar tower is better, but it is more innovative, so it is much easier to sell parabolic trough plants... we have made 17.”

However, she adds: “Torresol is betting on solar towers with Gemasolar. According to the studies we have done, the efficiency is much greater. It has 15 hours of storage compared to seven for parabolic trough plants.

“Torresol has yet to decide on future investments but right now it wants to build more tower plants.”

Brett Prior, senior analyst at GTM Research, backs this strategy: “Trough is about the same price now as tower, but I forecast tower is going to have faster cost improvements over the next decade.

“So trough at the moment makes sense, but it makes sense to look to tower in the future. Tower is the new, better model. Operating at higher temperatures, it has better potential to incorporate storage and should provide a lower LCOE [levelised cost of energy].”

As a result, he expects trough technology to be overtaken by towers in around 2014. Dish Stirling plants may also start to gain market share thereafter but other technologies, such as micro-CSP or Compact Linear Fresnel Reflector, are not predicted to enter the mainstream.

Solar hybrids

And where does PV fit in? Solar Millennium’s chief executive Dr Christoph Wolff says the advantage of branching into PV is that: "For CSP you need flat surfaces, but often sites are partly flat and partly hilly, so it is good to offer a mixed product.

“In terms of financial models, there is a higher cycle time for PV, so you ca build it faster, which confers an advantage on the overall investment budget. In terms of demand characteristics, CSP offers storage, whereas PV is a peaker.”

Tom Georgis, senior vice president of development at SolarReserve, adds: “Both have merits given our approach to focus on smaller-scale PV projects and larger solar thermal projects. 

“Our joint venture with GCL on the PV side will allow us to be extremely competitive in price and our CSP molten salt systems will provide the operating capabilities required to meet peak demand and transmission system stability and reliability."

Prior points out: “SolarReserve have already hired a whole team to find sites. They have probably found a lot of good sites which were too small for CSP but would be good for PV, so instead of doing all that legwork and throwing it all away they could just develop PV plants.”

A GTM Research analysis shows that concentrated PV (CPV), in particular, compares favourably with other solar options, CSP included, on a number of measures, including LCOE, modularity, water use, capacity factors, solar-to-electric efficiency and land use.

What remains to be seen is whether CSP developers could benefit from bolting CPV onto their existing plants.

Georgis says SolarReserve is looking into this, but Prior thinks: “From a technological point of view I am not sure there is any benefit from having those two things located next to each other. 

“What you want to do is have bring in one set of contractors who know how to build one kind of plant. It is difficult to see why you would want to build half PV and half CSP. The economies would be no good.”

To respond to this article, please write to the Editor:

Rikki Stancich: This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

Image credit: Abengoa's PS10, world's first commercial power tower plant

If you found any of these articles useful, you might find these upcoming events of interest:

5th Annual Concentrated Solar Power Summit US
29-30 June, Las Vegas, USA
Contact: Belen Gallego

CSP Plant Optimization US
7-8 September, San Francisco, USA
Contact: Jack Ahearne