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Conversion efficiencies of the best research solar cells worldwide from 1976 through 2011 for various photovoltaic technologies; efficiencies determined by certified agencies/laboratories. Credit: NREL.

The steady march to grid parity for solar energy devices continues: A Santa Clara, Calif., maker of gallium arsenide photovoltaic panels, Alta Devices, announced Tuesday that the NREL verified that its top-line panels operate at 23.5% efficiency. The ability to deliver an entire high-efficiency panel is a big step forward for the company’s business, which last year achieved verified record-setting efficiencies as high as 28.2% with a single, single-junction PV cell.

This looks to be a record efficiency-level for PV panels. Although, as the chart above indicates, NREL has verified higher efficiencies in other PV arrangements, these have been for a single or small sets of PV cells, not full panels. (It should probably be noted that Sanyo asserts that its in-production silicon heterostructure (HIT) panels come near to the numbers achieved by Alta, but this has not been verified by NREL.)

In a news release, Alta Devices explains a little bit about its interest in GaAs-based devices. The company says, “Alta chose to focus on GaAs because of its intrinsic efficiency advantages as well as its ability to generate electricity at high temperatures and in low light. This means that Alta’s panels have substantially higher energy density than other technologies, generating more kilowatt–hours of energy over the course of a year in real life conditions.”

Some investors have been cautious about GaAs-based solar technologies because they generally have appeared to require higher-priced materials than, for example, silicon. But the company says, “though GaAs is known for being expensive to produce, Alta has invented a manufacturing technique that enables extremely thin layers of GaAs that are a fraction of the thickness of earlier GaAs solar cells. Alta’s cells are about one micron thick… In utilizing very thin devices that have the highest energy density possible, the cost of the material needed in Alta panels remains low and the potential costs of an entire solar energy system based on Alta’s technology could be dramatically reduced.”

Alta deposits the GaAs on a thin, flexible film substrate. By focusing on this form factor, Alta says its film “has the potential to be integrated in wholly unique ways and into a variety of applications, including roof and building materials, and numerous military, consumer and transportation products.”

The company was cofounded by two well known California scientists engaged in academic-based energy research, CalTech’s Harry Atwater and University of California at Berkeley’s Eli Yablonovitch. Atwater is director of the Energy Frontier Research Center on Light-Matter Interactions and director of the Resnick Institute for Science, Energy and Sustainability, and Yablonovitch is director of the NSF Center for Energy Efficient Electronics Science, at their respective schools. Alta has received venture capital funding from high profile groups, such as August Capital and Kleiner Perkins Caufield & Byers.

In a recent story on the Lawrence Berkeley National Lab website, Yablonovitch offered a fundamental defense of GaAs. He said, “Gallium arsenide absorbs photons 10,000 times more strongly than silicon for a given thickness but is not 10,000 times more expensive,” says Yablonovitch. “Based on performance, it is the ideal material for making solar cells.”

But the trick is to extract the high efficiency from GaAs. In a June 2011 release, Yablonovitch explained, “Up until now it was understood that to increase the current from our best solar materials, we had to find ways to get the material to absorb more light. But, the voltage is a different story. It was not recognized that to maximize the voltage, we needed the material to generate more photons inside the solar cell. Counterintuitively, efficient light emission is the key for these high efficiencies.”

How are these efficiencies and energy density being achieved? For one thing, it required some open-mindedness. The LBL story describes that a leap in logic had to occur: “Past efforts to boost the conversion efficiency of solar cells focused on increasing the number of photons that a cell absorbs. Absorbed sunlight in a solar cell produces electrons that must be extracted from the cell as electricity. Those electrons that are not extracted fast enough, decay and release their energy. If that energy is released as heat, it reduces the solar cell’s power output. [LBL's Owen Miller] calculated that if this released energy exits the cell as external fluorescence, it would boost the cell’s output voltage. ‘This is the central counter-intuitive result that permitted efficiency records to be broken,’ Yablonovitch says.”

“In the open-circuit condition of a solar cell, electrons have no place to go so they build up in density and, ideally, emit external fluorescence that exactly balances the incoming sunlight. As an indicator of low internal optical losses, efficient external fluorescence is a necessity for approaching the [theoretical efficiency] limit,” Miller said.

In other words, the Alta Devices PV panels achieve high efficiency by emitting certain light while converting solar energy, instead of allowing excess electron energy to build up internal heat.

On the processing side of things, the company says it “is making substantial progress on the build-out of its pilot manufacturing line, which uses mostly off–the–shelf equipment with some proprietary optimizations unique to Alta’s process. Moreover, Alta is starting to plan for full–scale production, with activities such as building strategic manufacturing partnerships and selecting its first large, commercial manufacturing site.”

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Screenshot from NREL interactive atlas for renewable energy showing energy intensities for solar photovoltaic energy (yellow) and biomass residue (green). Credit: NREL.

People in the renewable and alternative energy business talk about an “energy portfolio,” where the electricity deposited on the local grid will be generated from a mix of what the local natural resources offer (solar, wind, wave power, geothermal) and power plants that can be built anywhere (nuclear, coal).

Like all natural resources, the distribution of energy resources varies. The National Renewable Energy Laboratory in Golden, Colo., recently released an interactive tool, the RE Atlas, that maps the locations of potential renewable energy resources in the US.

In the press release, Dan Getman, whose NREL team developed the tool says, “Ease of use and breadth of data make RE Atlas an excellent tool for policymakers, planners, energy developers, and others who need to better understand the renewable resources available in the United States. RE Atlas is an important addition to NREL’s suite of geospatial tools, because it brings together so many renewable energy datasets in one easy-to-use tool.”

Those datasets include a rich collection NREL maps of energy resources, geographic data and maps, EPA site information, links to research and much more. The energy resources that the atlas maps are

• Hydro (existing small projects)
• Geothermal (potential hydrothermal sites)
• Biomass residue
• Geothermal (enhanced geothermal system)
• Concentrated solar power
• Solar photovoltaic
• Wind speed - offshore
• Wind power class - onshore
• Wave power density.

Renewable energy resources are distributed as one would expect across the country, and it is interesting to see how broad the swaths of intensity are. For example, solar photovoltaic is most intense in the most southern regions of the Southwest, but it is decently intense in the entire southwestern quadrant of the US. Biomass, too, which would seem to be region-independent, is most intense across the Midwest from the Dakotas down through Missouri.

The intensities of each energy resource are not given in a common energy unit like joules or BTU, but according to the units used to quantify that energy type, which makes it difficult to compare magnitudes of energy available unless you are familiar with the unit conversions. For example, the units for solar photovoltaic energy are kWh/m²/day, biomass is expressed in thousand tons/year, geothermal is categorized into ranges (class 1-5), etc.

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Pyreheliometers are pointed toward the sun for their yearly calibrationat NREL. Accurate measurement of solar energy is needed for due diligence of photovoltaic installations. Credit: NREL.

If you have one, you probably were at the 16th annual convening of the NREL Pyrheliometer Comparisons in October in Golden, Colo.

If you don’t have one, it helps to know that a pyrheliometer is a type of radiometer for measuring the sun’s solar energy, and like all instruments, it needs to be calibrated regularly in order for its measurements to be valuable.

And, valuable they are. Solar energy measurements are used by almost anyone in the sunshine business: researchers, universities, the solar industry, and the bankers, venture capitalists and financiers who invest in them.

Calibrations are done against standards, and the international standard for solar energy is kept in Davos, Switzerland, at the World Radiation Center. Every five years instruments are calibrated against it in Davos. NREL is the only facility in the world that holds an annual event for intermediate recalibrations. According to the website, the goal of the gathering is to “transfer the World Radiometric Reference to international, national, and regional researchers.”

In the news release, NREL group manager Tom Stoffel says, “It’s all about traceability.” He continues, “This is all part of due diligence. … [if] you’re proposing a $30 million concentrating-solar-power plant, exactly how much direct sun are you going to get?”

The due diligence requirements have become very demanding since the 1980s. Twenty-five years ago, daily updates on the sun’s intensity in a few zones across the country were typical. Fifteen years ago, hourly reports became available. Now, according to the news release, “The gold standard is once-a-second updates at the exact spot where the solar installation is envisioned.”

NREL keeps a solar calendar that dates back to 1981 with data on the sun’s radiation starting at sunrise. DOE, through its Climate Research Facility in Lamont, Okla., maintains radiometers at 25 sites, three of which are internationally based and two that are mobile (and currently deployed overseas). The CRF, through its Atmosphereic Radiation Measurement program, has 20 years of solar and atmospheric radiation data. These days, data is taken every 60 seconds.

CRF electronic technician, Craig Webb was one of the participants at this year’s calibration event. In the news story, he sums up, “They want everybody to be tied to the same base so we can measure accurately the watts from the sun. That’s why we’re here every year.”

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Credit: NREL.

About a week ago, Boulder Wind Power, a maker of a direct-drive system with what’s been described as a low-speed permanent magnet generator for utility-scale wind turbines, announced that it had received $35 million in investment venture capital firm NEA and rare-earth producer Molycorp.

Molycorp’s involvement, presumably, is based on its insights to rare-earth markets and what they think will be the long-term role that rare earths will play in permanent magnets. The company had previously said it wants the company to be organized around a “mines-to-magnets” strategy. BWP’s news release says the investment “positions Molycorp to become the ‘preferred provider’ of rare earth magnets and/or alloys for wind generators using Boulder Wind Power’s innovative drivetrain technology.”

But BWP isn’t the only direct-drive startup, so I wondered, why is Molycorp interested in it?

For example Danotek, a high-speed permanent magnet innovator, also has been highly touted and nearly the same time BWP was getting its new investments, Danotek also was receiving a nice venture funding package from GE Energy Services, CMEA Capital, Khosla Ventures and Statoil Hydro.

A story over at the American Wind Energy Association’s blog perhaps provides some explanation about Molycorp’s involvement and how other investors are formulating their bets. The AWEA post contains comments from people involved with both start-ups, including Sandy Butterfield, BWP’s CEO and once the chief engineer for the Wind Technology section of the National Renewable Energy Lab. The payoff paragraphs in the AWEA story are

One of the most distinguishing characteristics of the BWP PMG design is that its magnets are part of an axial flux air core machine which operates at relatively low temperatures and are made with a rare-earth metal called neodymium. More commonly, PMG magnets are part of iron core radial flux machines like Danotek’s, operate at relatively high temperatures and require a rare earth metal called dysprosium.

In very round numbers, Butterfield said, dysprosium sells - in today’s very constrained market dominated by China’s hoarding of its unique rare earth metal supply - for around $1,000 to $2,000 per kilo; neodymium sells for about $100 per kilo and is relatively more common.

…

Rare earth metal processing techniques used in China, Butterfield said, “are pretty environmentally detrimental. But, he said, “Molycorp has developed a closed loop system that is both efficient and environmentally friendly. Nothing comes out of it and their yield is much better.”

This assures BWP a secure domestic supply of neodymium while other PMG system makers must continue to pursue supplies of dysprosium, which, Butterfield said, “drives the price of high temperature magnets.”

Indeed, Molycorp is pretty overt in how it sizes up its business plans. On its website, the company notes

“While the US currently has no capacity whatsoever for production of NdFeB magnets and intermediate magnet materials (metals and magnet alloys), it does control one of the world’ s largest and richest rare earth deposits at the Mountain Pass, Calif., facility. … [P]lans are in place to bring the facility back into full production over the next couple of years. In addition, with appropriate federal assistance for research and development and capital costs, [Molycorp Minerals] is prepared to move forward to reestablish domestic manufacturing capacity for both intermediate magnet materials and finished NdFeB magnets on an expedited basis.

Butterfield predicts its costs of generating electricity could drop to $0.04 per kilowatt-hour with a PM generator system.

BWP and Danotek aren’t the only players in this field. For example, Siemens offers a low-speed PM system and  ABB has a high-speed PM system and claims on its website, “Our global, long-term supply agreements for magnet material secures capacity, availability and cost control.”

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For the first time that I am aware of, it General Electric seems to have jumped on the Sach’s Law bandwagon and decided that solar power very soon will be competitive with fossil fuel and nuclear energy sources. In a recent interview with Bloomberg News, GE’s global research director, Mark M. Little, asserts that parity will arrive in three to five years.

From a business point of view, it should be noted that Little is glossing over a least one crucial distinction, namely that one has to differentiate between the a discussion about the wholesale cost (less costly per kilowatt-hour) of energy or the retail cost (more costly). But, you get the idea: GE sees a big change coming.

Little tells Bloomberg, “If we can get solar at 15 cents a kilowatt-hour or lower, which I’m hopeful that we will do, you’re going to have a lot of people that are going to want to have solar at home.”

GE also still has a significant footprint in the natural gas and wind turbine-generation business, so in a sense it is covering several scenarios. But the company has been putting some serious investments into thin-film solar R&D that are starting to pay off.

For one thing, GE became a major investor in 2007 in PrimeStar Solar, a maker of cadmium telluride thin-film panels, which just two months ago set the record (12.8 percent) efficiency for CdTe thin films. GE now fully owns PrimeStar and said in an April DOE blog post that it intended to soon build a 400-megawatt CdTe manufacturing facility. The company will be competing with CdTe panel maker First Solar, a company that has been singled out by market researchers, such as Lux, for its ability to continually reduce its manufacturing costs.

Little reiterated these manufacturing plans in the Bloomberg interview and says the facility will open in 2013. He notes that GE is developing many Smart Grid products and services. He specifically mentions its Nucleus consumer-grade power monitor product, announced in 2010, that integrates with personal computers and smart phones. The company is also working on complimentary metering devices.

The PrimeStar–GE relationship is a positive example of how government research can pay off in the commercial sector. The CdTe approach they use, according to the DOE, was developed at the National Renewable Energy Lab by a group led by Xuanzhi Wu. PrimeStar was launched in 2006 to commercialize Wu’s innovations.

I expect some of GE’s plans will be discussed later this summer at ACerS’ Ceramic Leadership Summit, where Krishan L. Luthra, technology leader in ceramics & metallurgy for GE Global Research, will be doing a presentation on emerging applications and challenges at GE

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