Intelligent Energy

Magnifying solar electricity's future

Magnifying solar electricity's future

Posting in Energy

Don't just convert it. Intensify your sunlight before turning it into electricity. Concentrated photovoltaics may soon shine bright, a new report declares.

We've all heard of the kid who zaps ants under a magnifying glass. The image strikes us for the cruelty, but also, for the undeniable power of combining the sun and optics.

Take the nastiness out of the picture, and it could also represent the future of solar electricity, as companies advance techniques for focusing and intensifying sunlight onto a solar cell. The technology goes by the name concentrated photovoltaics, and, of course, it comes with an acronym: CPV.

Not to be confused with the eponymous concentrated solar thermal electricity, in which the sun heats a piped liquid that ultimately drives a turbine, CPV works directly on solar cells, no turbine necessary. Unlike the solar cells in your rooftop panels, which take whatever light they can from whatever the sun casts their way, CPV intensifies that light with a lens or mirror before it hits the cell. Magnification can hit a staggering factor of 1,200 times, such as with a system under development at Tuscon, Ariz.-based REhnu, where the company's fancy gear has melted a hole in steel.

One of CPVs great promises is that it slashes the number of solar cells in a panel, since each cell produces a lot more electricity than a solar cell that doesn't benefit from focused light. CPV can therefore reduce the land and real estate required for utility scale projects. Leading commercial vendors include California's Amonix Inc. and SolFocus Inc., as well as France's Soitec Group, through its acquisition of Germany's Concentrix Solar GmbH.

CPV is not new, but for several reasons it has failed to gain much market share. That could now be changing.

According to a report released this week by Greentech Media (GTM), after decades of R&D, the concentrating photovoltaics (CPV) industry is finally breaking into the utility-scale solar market. GTM Research forecasts new CPV installations to grow from under 5 MW in 2010 to more than 1,000 MW globally by 2015.

Okay, 1,000 megawatts is still miniscule. That's a gigawatt, which is the normal size of a single nuclear power station. It's barely an ant, if you will, on the global energy scene. Even in the world of solar power, it's, er, a small fry. The figures still pale in comparison to the annual installation of traditional non-concentrating PV, which was over 13,000 (megawatts, or 13 gigawatts) 2010 alone, states GTM's report, Concentrating Photovoltaics 2011: Technology, Costs and Markets.

What GTM likes about CPV is that, according to report co-author Brett Prior, it is low-cost compared to other forms of solar. The key driver enabling CPV to win projects in high solar resource locations is CPV's ability to provide developers with superior economics, as CPV has a lower levelized cost of electricity (LCOE) versus the non-concentrating PV alternatives, the report notes. Prior says the LCOE is around $0.12 per kilowatt-hour.

That might surprise CPV detractors, who say CPV costs are the bubble under the carpet- push it down on one end and it pops up on the other. CPV may cut the number of solar cells, but the cost of mirrors, lenses and other contraptions that help intensify and track the sun can more than offset those savings.

On top of that, high-magnification CPV manufacturers typically deploy costly non-standard solar cells, called triple junction gallium arsenide cells. Triple junctions are used in space on satellite-mounted solar panels, but they can exceed earthly budgets.

GTM likes the chances that the cost of triple junction cells will decline. The forecast is predicated upon CPV companies successfully achieving their cost reduction roadmaps, and bringing the installed cost of a CPV system down by more than 30 percent over the next four years, the report states. Where will that price reduction come from? One place will be from the solar cell suppliers like Solar Junction, Cyrium, Semprius, Soitec, and JDSU that have made advances in the triple-junction cell that lies at the heart of the CPV system.

One factor holding back CPV, notes Prior, is that the technology is unproven, which in turn makes it difficult to finance and insure CPV projects.

"You need bankers and equity guys to put money in, but they don't want to if they're worried it's going to break down," Prior told me when I spoke with him earlier this year. Power providers who use CPV equipment will almost certainly insist that CPV vendors buy warranty insurance to cover against breakdown. In a possible turning point last October, German insurance giant Munich Re last October backed SolFocus.

One of the beauties of CPV, but equally, one factor that rattles financiers, is that there are no real standards. Every system is different. REhnu's 1200-times technology uses large reflectors, fancy ball lenses and optics inspired by founder Roger Angel, a University of Arizona professor of astronomy and optical science who is now applying his prize-winning work on telescopes towards CPV. Low and medium-magnification systems, such as those from Santa Barbara, Calif.-based HyperSolar Inc., Fremont, Calif-based Solaria Corp., and Mountain View-based Skyline Solar, use conventional crystalline solar cells rather than triple junction chips - but each applies different techniques.

As positive sign, GTM notes that utility scale projects are stating to take hold. In March, Soitec won a 150-megawatt deployment from energy company Tenaska Solar Ventures, to provide electricity to San Diego Gas & Electric. Amonix is deploying a 30-megawatt plant near Alamosa Colorado, for power generation company Cogentrix Energy LLC, contracted to the Public Service Company of Colorado.

It sounds like the story of concentrated photovoltaics will mirror the technology itself, and magnify in the coming years.

Photo: REhnu

Author's note: Watch for my upcoming blog on University of Arizona professor Roger Angel, the founder of REhnu who's swapping his prize-winning career in astrophysics for a fresh start in renewable energy.

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Mark Halper

Contributing Editor

Mark Halper has written for TIME, Fortune, Financial Times, the UK's Independent on Sunday, Forbes, New York Times, Wired, Variety and The Guardian. He is based in Bristol, U.K. Follow him on Twitter. Disclosure