Soaking up the sun on a vast scale at Ivanpah

IT LOOKS like a planetary tattoo designed to be seen from space, a vast set of concentric circles inscribed in the skin of southern California's desert. Ground was broken on the Ivanpah power plant, which is to be one of the biggest solar installations in the world, last October. Already, some of the rings of mirrors which will eventually concentrate acres-worth of desert sunshine on to collectors perched atop 140-metre-high towers are in place. And as of this week, so is the financing.

BrightSource, based in Oakland, California, announced on April 11th that it had finalised $1.6 billion in loans for Ivanpah from America's government. At the same time it announced that Google had taken a $168m stake in the project.

Ivanpah needs all this money because BrightSource's technology requires it to be vast compared with other types of solar installation. Most solar power comes from photovoltaic cells that turn sunlight directly into electricity: installations of this type can be any size. BrightSource's system, like other “solar thermal” technologies, concentrates the sun's heat to drive turbines; and the high-performance steam turbines it relies on are big. The three to be installed at Ivanpah will together have a greater capacity than all the “utility scale” photovoltaic plants yet built in America.

It was once thought that photovoltaic installations might attain a similar size as they spread across America's West (a prospect viewed with alarm by some environmentalists). There are now indications that this won't happen. Nathaniel Bullard of Bloomberg New Energy Finance has been looking at photovoltaic projects registered with California ISO, the state's grid operator, since 2007. Their median size started off close to 100MW; now it is around 20MW. Not all these projects will be completed—but it seems a reasonable assumption that bigger ones may be more likely to fall by the wayside. If so, the average size will drop even more dramatically.

Mr Bullard thinks the photovoltaic business is learning that small, if not exactly beautiful, is easier to get past environmental controls and planning consents, and handier if you want to feed into existing grids. “Brownfield” industrial sites near towns beat desert skies.

This is not to say that big photovoltaic projects are finished. The day after the Department of Energy bestowed its beneficence on Ivanpah, it offered a conditional loan of $1.2 billion to SunPower, a maker of high-efficiency photovoltaic cells, for a 250MW project, the California Valley Solar Ranch near San Luis Obispo. SunPower will build and operate the plant; NRG Solar, a subsidiary of NRG Energy of New Jersey, will own it. (NRG Solar is also investing up to $300m in Ivanpah.)

Such big projects make sense for large solar-cell producers like SunPower and Arizona-based First Solar, since they provide reliable demand with which to keep their manufacturing plants running at peak efficiency. Tom Werner, SunPower's chief executive, says that although the Solar Ranch project is “on the large side”, there is a role for photovoltaic plants of all sizes, and his company has plenty more of similar scale in the pipeline. As experience grows, he hopes to find banks, rather than governments, to finance them.

Whereas being extremely big remains optional for photovoltaics, for thermal-solar companies such as BrightSource it is a must. BrightSource hopes that in time its technology will prove sufficiently efficient and reliable to overcome the disadvantage of having to raise so much capital. If so, Ivanpah will be the ground on which it makes its case.