PHILADELPHIA, Aug. 21, 2012 — With enough sunlight falling on home roofs to supply at least half of America's electricity, scientists today described advances toward the less-expensive solar energy technology needed to roof many of those homes with shingles that generate electricity.
Shingles that generate electricity from the sun, and can be installed like traditional roofing, already are a commercial reality. But the advance ― a new world performance record for solar cells made with "earth-abundant" materials ― could make them more affordable and ease the integration of photovoltaics into other parts of buildings, the scientists said.
Their report was part of a symposium on sustainability at the 244th National Meeting & Exposition of the American Chemical Society, the world's largest scientific society, being held here this week. Abstracts of other presentations appear below.
"Sustainability involves developing technology that can be productive over the long-term, using resources in ways that meet today's needs without jeopardizing the ability of future generations to meet their needs," said Harry A. Atwater, Ph.D., one of the speakers. "That's exactly what we are doing with these new solar-energy conversion devices."
The new photovoltaic technology uses abundant, less-expensive materials like copper and zinc ― "earth-abundant materials" ― instead of indium, gallium and other so-called "rare earth" elements. These substances not only are scarce, but are supplied largely by foreign countries, with China mining more than 90 percent of the rare earths needed for batteries in hybrid cars, magnets, electronics and other high-tech products. Atwater and James C. Stevens, Ph.D., described successful efforts to replace rare earth and other costly metals in photovoltaic devices with materials that are less-expensive and more sustainable.
Atwater, a physicist at the California Institute of Technology, and Stevens, a chemist with The Dow Chemical Company, lead a partnership between their institutions to develop new electronic materials suitable for use in solar-energy-conversion devices.
Atwater and Stevens described development and testing of new devices made with zinc phosphide and copper oxide that broke records for both electrical current and voltage achieved by existing so-called thin-film solar energy conversion devices made with zinc and copper. The advance adds to evidence that materials like zinc phosphide and copper oxide should be capable of achieving very high efficiencies, producing electricity at a cost approaching that of coal-fired power plants. That milestone could come within 20 years, Atwater said.
Stevens helped develop Dow's PowerHouse Solar Shingle, introduced in October 2011, which generates electricity and nevertheless can be installed like traditional roofing. The shingles use copper indium gallium diselenide photovoltaic technology. His team now is eyeing incorporation of sustainable earth-abundant materials into PowerHouse shingles, making them more widely available.
"The United States alone has about 69 billion square feet of appropriate residential rooftops that could be generating electricity from the sun," Stevens said. "The sunlight falling on those roofs could generate at least 50 percent of the nation's electricity, and some estimates put that number closer to 100 percent. With earth-abundant technology, that energy could be harvested, at an enormous benefit to consumers and the environment."
Other presentations at the symposium included:
- Efforts by the mining company Molycorp to expand and modernize its Mountain Pass, Colo. facilities to increase United States production of rare earth elements with greener and less costly technology.
- An overview of the challenges to maintaining a sustainable supply of critical materials ranging from rare earth elements to more abundant metals like copper.
- A new material for recovering rare metals from the 800 billion gallons of wastewater produced by mining and oil and gas drilling every year.
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Abstracts
Finding alternatives to critical materials in photovoltaics and catalysis - Part II: Industrial perspective
James C. Stevens1, The Dow Chemical Company, Core R&D, 2301 N. Brazosport Blvd., B-1814, Freeport, TX, 77541, United States , 979-238-2943, JCStevens@dow.com
Extension of photovoltaics technology to the terawatt scale demands that the materials utilized in solar cells be abundant in the earth's crust and amenable to formation of efficient photovoltaic devices. For this symposium on critical materials and their possible replacement with Earth abundant materials, we will focus on two key areas – photovoltaics and catalysis. We will present new results on Zn3P2 PV devices with improved open circuit voltages and short circuit current densities over previous records for solar cells based on p-Zn3P2/Mg Schottky diodes, as well as advances in Cu2O-based devices. Potential applications will be described, including uses in Building-Integrated PV.
In addition, a broad perspective on the use of critical materials, especially platinum group metals (PGM's) as catalysis in industry will be reviewed. The chemical industry, in general, is extremely efficient in the use of PGM's and other scarce materials in catalysis. It is important to recognize that various catalyst key performance criteria are much more economically significant than the cost of the PGM, and that many chemical processes have evolved from originally using low-cost metals such as Co to much scarcer metals such as Ir and Rh because the high cost of separations and plant capital overwhelm the difference in the price of the metal. Opportunities may exist for further work in the areas of emissions catalysis, hydrosilylation, hydroformylation, and enantioselective catalysis. In addition, supply chain issues relevant to PGM's in catalysis will be discussed.
Finding alternatives to critical materials in photovoltaics and catalysis - Part I: Academic perspective
Harry A. Atwater1, The California Institute of Technology, Thomas J. Watson Laboratory of Applied Physics, MS 128-95, Pasadena, CA, 91125, United States , 626-395-2197, haa@caltech.edu
Extension of photovoltaics technology to the terawatt scale demands that the materials utilized in solar cells be abundant in the earth's crust and amenable to formation of efficient photovoltaic devices. For this symposium on critical materials and their possible replacement with Earth abundant materials, we will focus on two key areas – photovoltaics and catalysis. We will present new results on Zn3P2 PV devices with improved open circuit voltages and short circuit current densities over previous records for solar cells based on p-Zn3P2/Mg Schottky diodes, as well as advances in Cu2O-based devices. Potential applications will be described, including uses in Building-Integrated PV.
In addition, a broad perspective on the use of critical materials, especially platinum group metals (PGM's) as catalysis in industry will be reviewed. The chemical industry, in general, is extremely efficient in the use of PGM's and other scarce materials in catalysis. It is important to recognize that various catalyst key performance criteria are much more economically significant than the cost of the PGM, and that many chemical processes have evolved from originally using low-cost metals such as Co to much scarcer metals such as Ir and Rh because the high cost of separations and plant capital overwhelm the difference in the price of the metal. Opportunities may exist for further work in the areas of emissions catalysis, hydrosilylation, hydroformylation, and enantioselective catalysis. In addition, supply chain issues relevant to PGM's in catalysis will be discussed.
Sustainable supply of critical materials: Addressing the fundamental challenges in separation science and engineering
Mamadou Diallo1 , California Institute of Technology, Director of Molecular Environmental Technology, Materials and Process Simulation Center, Mail Stop 139-74, Pasadena, CA, 91125, United States , (626) 395-8133, diallo@wag.caltech.edu
Recent stresses in the global market of rare-earth elements (REEs) have brought the sustainable supply of critical metals to the forefront in the United States and other industrialized countries. In addition to REEs (e.g., europium, cerium, neodymium, gadolinium, and terbium), significant amounts of copper, silver, gold, manganese, lithium, titanium, gallium and platinum group metals (e.g., platinum, palladium, and ruthenium) will be needed to build the sustainable products, processes, and industries of the 21st century. This overview will highlight some key challenges in separation science and engineering associated with the sustainable supply of critical materials.
Meeting the global rare earth challenge: Molycorp from mine-to-magnets
Andy Davis1 , Molycorp, Manager of Public Affairs, 5619 Denver Tech Center Pkwy, Greenwood, CO, 80111, United States , 571-431-8386, Andy.Davis@molycorp.com
Less than two years since its initial public offering, Molycorp has taken enormous strides towards eliminating the U.S.'s rare earths and critical materials capability gap and broadening global supply diversity. Molycorp will report on the modernization and expansion of its Mountain Pass facilities, which will return the company to high volume rare earth oxide production by the end of the third quarter this year, and it will outline the technologies it has integrated to dramatically advance the company's environmental performance and cost-competitiveness. Additionally, in pursuit of its "mine-to-magnets" strategy, Molycorp has acquired downstream manufacturing capabilities in metal and alloy production and established a joint venture to manufacture sintered neodymium-iron-boron (NdFeB) magnets. With its recently announced agreement to acquire Neo Material Technologies, it is poised to add high purity processing, bonded NdFeB magnet production, and an expanded rare metal portfolio to its suite of capabilities. The company will discuss its continued progress and welcomes your participation.
Setting the stage for sustainability
Catherine T. Hunt1, The Dow Chemical Company, R&D Director, Innovation Sourcing & Sustainable Technologies, 727 Norristown Road, Midland, MI, 19477-0904, United States , 215-619-5289, catherinehunt@dow.com
How do we define sustainability? And more to the point of today's session, the sustainability of critical materials. Today will be dedicated to setting the stage for sustainability - from defining terms and understanding challenges, to discussing options and identifying opportunities. Join us in setting a course for the future, a course where chemists and engineers are center stage.
Moderated panel: Rethinking the role of separation science and engineering - Reduce, reuse, repurpose!
1. Catherine T. Hunt1 , The Dow Chemical Company, R&D Director, Innovation Sourcing & Sustainable Technologies, 727 Norristown Road, Spring House, PA, 19477-0904, United States , 215-619-5289, catherinehunt@dow.com
A moderated panel discussion to synthesize the ideas of the day, highlight exciting developments, and surface unmet needs. This is a chance for us to actively participate in making a difference, a sustainable difference.
New tools in the water treatment technology toolbox: Swellable organosilica materials for reversible extractions of dissolved organics and metals
Paul L Edmiston1,2 , Professor, College of Wooster, Department of Chemistry, 943 College Mall, Wooster, Ohio, 44691, United States , 330-263-2113, pedmiston@wooster.edu
Swellable organosilica (tradename: Osorb®) is has the unusual characteristic of instantaneously absorbing eight times its weight in organic liquids. The volumetric changes on absorption lead to a concomitant generation of force (>500N/g) due to mechanical relaxation of a collapsed nanoscale architecture. Matrix relaxation can be used as a new mechanism for the absorption of dissolved organics in a reversible manner. The materials can be tailored to include functional groups or embedded metals for expanded applications. Swellable organosilicas are being tested for the treatment of produced water, a term used for the water co-extracted with oil and gas. Produced water represents the largest volume aqueous waste stream with an estimated volume of 800 billion gallons/year. Extraction of dissolved petroleum hydrocarbons and metals is described in a manner by which such components are recovered. In this manner, important chemicals are mined as value-added commodities (fuel, rare metals) rather than being discarded.
Ionic liquids and strategic metals: Challenges and opportunities
Robin D. Rogers1 , Prof., The University of Alabama, Center for Green Manufacturing and Department of Chemistry, Box 870336, Tuscaloosa, AL, 35487, United States , 205-348-4323, 205-348-0823, rdrogers@as.ua.edu
The depletion of easily accessible reserves of nonrenewable resources, especially metals, has forced people to turn to recycling and the use of historically nonviable sources to get these resources. The main hinderance to exploiting these nontraditional resources is the lack of energetically and chemically efficient separations methods. Given the need for new solvents that are tunable, robust, and environmentally benign, it is no surprise that separations have become one of the chief applications of ionic liquids (ILs). ILs are salts with low melting points that frequently have wide liquid ranges, low volatility, good thermal, chemical, and electrochemical stability, and tunable physicochemical properties. This overview will cover the application of ILs to the recovery of resources from nontraditional sources including recovery of uranium from seawater, extraction of rare earth elements and precious metals from spent nuclear fuel, and the processing of metal ores.
Findings and opportunities from the 2012 NSF SusChEM workshop
Susannah L Scott1 , PhD, University of California, Department of Chemistry & Biochemistry, 3325 Engineering 2, Santa Barbara, CA, 93106-9510, United States , 805-893-5606, sscott@engineering.ucsb.edu
In January, 2012, the first SusChEM (Sustainable Chemistry, Engineering and Materials) workshop was held in Arlington, VA. Co-sponsored by CHE, CBET and DMR divisions at NSF, the workshop was charged with exploring fundamental research and educational needs to advance the goal of increasing the sustainability of chemical processing and manufacturing. Strategies to reduce or eliminate the use of rare elements and other scarce materials, minimize the use of freshwater and energy, and increase the efficiency of recovery/recycling, were discussed, as well as the need for a systems-level perspective and more interdisciplinary training to appreciate the interdependence of science, technology, economics and societal impact.
Challenges for extracting and purifying critical materials
Bruce A. Moyer1 , Group Leader, PhD, Oak Ridge National Laboratory, Chemical Sciences Division, P.O. Box 2008, 1 Bethel Valley Rd., Oak Ridge, TN, 37831-6119, United States , 865-574-6718, moyerba@ornl.gov
While the current crisis in the supply of rare earth elements (REEs) resolves itself, balancing the supply and demand for materials needed for economic sustainability has been, and will remain, a fundamental societal concern. Indeed, as archeological evidence shows, even the first hunter-gatherers had to grapple with maintaining the supply of raw materials for stone implements! Lessons from recent decades of shortages of various critical materials show that the solution lies on both the supply and demand sides: seeking new sources, higher efficiencies in production and utilization, avenues for recycling, and opportunities for material substitutions. This presentation examines the example problem of the supply of REEs and the role that R&D can play to assure greater sustainability. Given that the cost of extraction and purification of REEs is significant, more efficient separation technologies will have an impact in the medium to long term, and challenges therein will be discussed.
Separation science for a sustainable future
Matthew Platz1 , National Science Foundation, Director, Division of Chemistry, 4201 Wilson Blvd, Arlington, VA, 22230, United States , (703) 292-2665, mplatz@nsf.gov
A recent NSF sponsored workshop in sustainable chemistry, engineering and materials has identified new research in separation science as a key priority. Thus, the NSF Division of Chemistry (CHE) and Division of Chemical, Bioengineering, Environmental, and Transport Systems (CBET) are co-sponsoring this symposium aimed at communicating the immediate needs for resource separation and recovery to the separation community. We hope through this symposium the separation community will discuss and brainstorm the basic science and engineering needed to economically recycle chemicals that cannot be replaced such as phosphorus and the rare earth elements, and devise environmentally friendly separation processes that require significantly less energy, water and organic solvents than current practices.
Developments in alternatives to critical materials for energy applications
Mark Johnson1 , Department of Energy, Advanced Research Projects Agency – Energy, 1000 Independence Avenue, S.W., Washington, DC, 20585, United States , 919-513-2480, mark.johnson2@hq.doe.gov
Motivated by recent volatility in the supply of rare-earth element based materials, the development of alternative technologies for critical materials has become a priority in emerging energy fields. Critical materials are key enabling materials that are also subject to potential supply chain variability. Developing a diversity of technical approaches to meeting the functional requirements of a critical material is essential to the development of new technologies. For example, rare-earth elements are used as alloying constituents to high energy permanent magnets such as SmCo and NdFeB. The partially filled f-shell orbital exhibit high spin anisotropy, thereby inducing a high magnetic coercivity in permanent magnet alloys. High energy density permanent magnets are essential for coupling electricity to mechanical motion in emerging energy applications such as permanent magnet motors for electric vehicles and generators for direct drive wind turbines. At the Advanced Research Projects Agency – Energy (ARPA-E), we have initiated a program for the development of alternatives to critical rare-earth based magnets. Looking forward, the ability there is a need for new technologies which can effectively expand the availability of critical materials from available resources: whether from geological reserves or recycling. A key enabling technology is the need to efficiently separate critical materials from available resources. In addition to the rare-earth elements, we will survey the periodic table and highlight research areas that are ripe for new research into separation and extraction of critical materials