“I’m going to quote Marisa Tomei in My Cousin Vinny,” said Ryne Raffaelle, a researcher at the U.S. Department of Energy’s prestigious National Renewable Energy Laboratory. “'It’s a bullshit question.'”

Raffaelle was responding to two questions posed by the moderator of the “Which Technology Will Emerge Dominant in the Market?” panel at Solar Power International 2010, the U.S.’s biggest yearly gathering of solar businesses.

Following a detailed presentation of the competing technologies and the scientific strengths and challenges of each, the panelists were asked to say which was most likely to be first to achieve unsubsidized grid parity and which would be dominant when solar is producing twenty percent of U.S. power.

Johanna P. Schmidtke of Lux Research was first to field the questions. She said it would only be possible to answer the grid parity question by first knowing where the solar was installed and what kind of installation it was. “Crystalline silicon,” she pointed out, “is relatively close to grid parity in some areas like parts of California” where the sun is abundant and retail electricity rates are high. “For large-scale applications, in the long term,” Schmidtke said, concentrating PV, though it has challenges like complexity of materials and overall system performance and has not been conclusively demonstrated, “does have some significant value, just not quite yet.”

Not exactly a ringing endorsement, is it?

“The technology not only needs to reach grid parity but also needs to be produced at scale,” said Simone M.P. Arizzi of DuPont Photovoltaic Solutions. “I see no reason why, certainly, crystalline silicon and also the thin film technologies and amorphous silicon should not be able to reach, in a reasonable amount of time, certainly less than a decade, grid parity at a large scale.”

It takes a scientist to predict that?

As to which will be dominant, Arizzi said, “The question of who’s going to be the number-one horse almost implies that all the other horses are going to somehow fall off.” A strength of the solar industry, he said, is the fact that contrary to what happens in many other industries, “whenever there is a technology barrier, the other can be the supply” and the barrier can be overcome because there are “so many technology options when one thinks about third-generation technologies” like multijunction cells, organic photovoltaics and quantum dots.

“It’s going to be really, really difficult to displace silicon,” Chris Constantine of Oerlikon Solar said. “It’s tough to not bet on silicon.” As for grid parity, Constantine pointed out, “it’s clearly regional, it’s clearly policy-driven, it’s clearly something that’s a lot more complex than an easy answer.” But, he said, “80 percent of everything being put up facing the sky is silicon.”

As to the future, Constantine said, “we’ve got two different PV systems. There’s the crystalline silicon,” he went on, “and  clearly, that system has come a long way. There’s also the thin film approach. Put in there what you want, whether it’s CdTe, whether it’s CIGS, whether it’s amorphous silicon or microcrystalline silicon.” But, he said, these materials may well come together. “And you know what? They really do, based on the science, at least, go together rather nicely.”

In other words, like Arizzi, Constantine says the answer is 'all of the above.'

That’s when Raffaelle chimed in with the Marisa Tomei answer. There are many places, he said, “where PV is already below grid parity. And there are places where it’s CPV and there are places where it’s silicon and there are places where it’s thin film. And some places, all three of them can do it. [The question] also assumes that 'grid parity' means something. You’re assuming that the coal industry isn’t subsidized. That the nuclear industry isn’t subsidized.”

Raffaelle then turned to the question of which technology will emerge. “To sit here today and say what will the technology be when we hit twenty percent of penetration -- it’s not going to be what we’re looking at right now, it’s going to evolve.”

He obviously doesn’t know, either.

Jim Armour of Spectrolab brought the discussion to a close by going back to the panel’s most consistent theme. “The sun is a diffuse resource and it’s not a uniform resource,” he said. “To think that one size is going to fit all, from a PV standpoint, is just ridiculous.” He went on: “CPV works in certain areas very well. It’s more than cost-competitive, it’s cost efficient. And in other areas, it absolutely does not work at all. And there are thin films that work very well in those areas. In fact, there are places where the best way to use the solar resource is to put up a windmill.”

Didn’t see that one coming.

Tags: amorphous silicon, cadmium telluride, cdte, cigs, concentrating photovoltaic, concentrating pv, copper indium gallium diselenide, cpv, grid parity, microscrystalline silicon, multijunction cells, organic pv, quantum dots, solar technology, thin film