Concentrating Solar to Reach 18 Gigawatts by 2020

The main reason for his doubt is the ability to build large solar-thermal projects.

The debate about whether large fields of PV panels or solar-thermal equipment make more sense is not a new one (see Solar Desert Debate Heats Up and Large PV Gets Big Boost). But while some advocates contemplate that so-called "very large-scale" PV could one day include projects with capacities in the gigawatts, planned solar-panel parks today are not as large as some of the solar-thermal projects already underway.

"[Concentrating solar-thermal] is just more scaleable than PV; it’s just more easily scaled to 500 megawatts," Wilder said. "That would be an eye-popping big flat-panel plant. Using flat panels at utility levels is being done in Europe, but to a flat-panel solar farm, 100 megawatts is enormous. By contrast, it’s really no sweat to plan a 200 megawatt solar-thermal plant."

The largest solar-panel installation today is a 23-megawatt park in Spain, according to PV Resources, while Florida Power and Light is building a 300-megawatt solar-thermal plant using technology from Ausra (see FPL and PG&E Back Solar-Thermal and Ausra to Build 177-Megawatt Solar-Thermal Plant).

"It’s mainly a function of economics," Wilder said. "It would be bloody expensive to produce [that much] electricity using flat panels. It’s hard to say when and if that’ll happen."

Speed of Cost Fall Uncertain

The truth is, because concentrating solar power is still at such an early stage, with only a handful of examples online, it’s difficult to predict how quickly costs will fall, Bradford said.

"It’s a little easier to know what the costs of PV will be because it is already at scale, and some of these other technologies aren’t," he said. "PV is going to get cheaper than it is today, in line with our forecast in normal experience curves that we all understand. The degree to which CSP will be competitive with that will determine whether it can meet or exceed those cost improvements in PV."

Bradford said he thinks concentrating solar power will do well in the sunniest climates, as well as in applications where heat, as well as electricity, is needed. While the ability to store heat is an advantage today, the amount of that advantage will vary depending upon whether good electricity-storage technologies -- such as better batteries -- also emerge, he said.

"It’s kind of a race for that utility-scale market," he said. "There are advantages and disadvantages to each of the technologies, and one might be better than the others in particular types of locations."

But the key factor in determining which technology will dominate utility-scale installations will be cost, he said.

"The question about [solar-thermal] will be the dominant technology for utility-scale solar applications depends solely on its ability to get cheaper faster than PV, and that will be somewhat a function of how quickly it will be deployed and scaled up," he said. "CSP doesn’t just have to get cheaper than it is today, which it will, it has to also get cheaper than PV gets cheaper if it wants to continue to grow in market share."