By D.A. Barber
There could be a struggle to meet the solar energy targets many countries have set because the current global supply of rare metals needed to produce PVs is unlikely to meet demand, according to a November 2011 study reported in Resources, Conservation and Recycling.
The study, “Considerations of Resource Availability in Technology Development Strategies: The Case of Photovoltaics,” looked at the four main PV technologies: crystalline silicon (c-Si), amorphous silicon (a-Si), cadmium tellurium (CdTe) and copper indium gallium diselenide (CIGS). Some of the critical materials are silver, tellurium and indium, while neither cadmium nor copper were found to be seriously limited. For example, researches found thatthe predicted demand for tellurium could be between 30 and 180 times higher than today’s production rate, depending on the scenario used.
While calculations based on available appropriate land, global irradiance and conversions of solar energy to electricity demonstrate that technically, solar energy could provide 7.5 to 9 times the expected electricity demand in 2050, since several PV technologies employ rare metals the disruption in supply could limit the actually capacity achieved for electricity generation.
Though the report singles out silver at not being at risk, the annual report released in July 2011 by The Silver Institute reported that annual industrial demand for silver will grow from about 487.4 million ounces in 2010 to 665.9 million ounces in 2015. That report indicates that the highest end users of silver in 2010 were the thick film photovoltaic industry, followed by the automobile and computer industries.
Use of Rare Earth Minerals
Rare earth metals are critical for clean energy technologies, such as PVs, as well as hybrid and electric vehicles, high-efficiency wind turbines, smart grid technologies, and even compact fluorescent lights that are targeted to replace energy-wasting incandescent bulbs in the United States.Other high-tech uses include: fiber optics, lasers and hard disk drives; defense guidance and control systems; global positioning systems; and advanced industrial, military and outdoor recreation water treatment technology.
While rare earth metals aren’t all that rare, the mining operations for them are. Today roughly 95 to 97 percent of the world’s rare earth metals come from China where the government drastically reduced export quotas in 2010-11 to keep more of the metals for its own wind, solar, and battery manufacturers, who then export their finished products. These same rare earth elements are also highlighted in the British Geological Survey’s 2011 list of “economically important metals which are at risk of supply disruption” due to human factors “such as geopolitics, resource nationalism, along with events such as strikes and accidents.”
In January 2012, the U.S. Department of Energy(DOE) expressed increasing concern about rare earth shortages slowing the rapid adoption of clean energy technologies and announced a strategy to try to avert rare earth mineral shortages that is supported by $20 million in Congressional funding. The three-pronged strategy DOE has developed over the past year to attack the problem includes a diversify of supply, finding more available substitutes, and recycling electronic equipment that currently uses rare earth materials.
The DOE’s “2011 Critical Materials Strategy,” released in December 2011, finds that “many clean energy technologies depend on raw materials with potential supply risks” and assessed the 16 elements considered most critical. On the short-term critical supply list are dysprosium and neodymium, needed for magnets and motors in wind turbine-generators and electric vehicles, and terbium, europium and yttrium, which supply phosphors for high-efficiency compact fluorescent light bulbs. In the medium term, lithium, used in many EV batteries, and tellurium, used in thin-film PVs, are of concern for the coming years, but not yet critical. The DOE study also looked at gallium and indium, used in advanced PV panels, but found that the supply was currently at a low risk.
The shortages rare earth minerals has meant that the proces of some have spiked to global highs, in some cases 10 to 20 times higher than 2010 prices. DOE says more plans are emerging for extracting the materials outside China and government researchers were able to identify about two dozen locations where mines for various rare earths may open in coming years, starting with Molycorp's Mountain Pass, California.
Short-Term Risk, Present–2015 (DOE)
In February 2012, Molycorp, Inc. announced the start-up of their new Project Phoenix rare earth manufacturing facility located at its flagship Mountain Pass mine in California – at one time the world's largest rare earth mine. The company says its Project Phoenix is currently producing 2,800 short tons of fresh rare earth ore per day and expects to reach full production by April 2012.
Meanwhile, there continues to be a push to find rare earth alternatives: In May 2011, DOE's Advanced Research Projects-Energy (ARPA-E) announced it was making $30 million available for early stage technology alternatives that reduce or eliminate the dependence on rare earth materials by developing substitutes that focus on two key industries: EV motors and wind generators.
CIGS Demand and Silicon Shortages
The researchers of the November 2011 “Resource Availability” study assumed that by the year 2040 the two silicon-based technologies, the use of CdTe, and the use of CIGS, would each have roughly 25 percent of the solar energy generating market. This is because even though using crystalline silicon for PVs currently dominates 81 percent of the solar industry, the move towards more use of thin-film PVs using rare earth materials is already well underway. The researchers used a “neutral” scenario where all PV technologies would increase in efficiency combined with 2008 mining production numbers to determine that the needed tons per year of rare earth materials for CIGS alone would surpass production at the rate of 7.3 times for gallium, and indium at a factor of 2.8. In fact, even at their most “optimistic future scenario” where high efficiency rates would require less material, the researchers concluded demand for gallium would still overtake production by factor of 3.9 and indium at 1.5.
The research results were not that great for silicon either. Despite it being the Earth’s second most common element, silicon used for both the PV and electronics industries needs to be of extremely high purity. Without even factoring in the electronics industry, researchers concluded that PV manufacturers need to see an increase of pure silicon produced at a rate 15 times higher in their projected “neutral” scenario. Interestingly, when researchers looked at the use of the amorphous silicon technology for utility-scale power plants they determined that by 2040 the cumulative demand would only account for 20 percent of even the current production rate.
Better Refining Techniques Needed
The researchers did have another take on their results: While the solar energy goals for 2040 highly anticipate the increased use of rare earth materials, it will not necessarily be the supply of these materials but rather the limits on production and processing that slow the rate of growth in the industry. The researchers conclude that “better refining techniques, increased exploitation of deposits, and strategic planning of technological shifts” will be needed to assure the ability to meet this demand for rare PV earth materials. One reason is the fact that supplies of the most important rare earth materials like tellurium, indium, gallium, selenium, and cadmium are mostly by-products of the mining operations of other minerals and are very rarely mined independently. The report notes that any new production and mining methods are “likely to take up to 10 years to develop,” a fact that puts pressure on both the mining and processing industry to start looking into new techniques now in order to meet the future demands.
A shortage of rare earth minerals has the potential to delay adoption of clean technologies, such as high-efficiency PVs, EV motors, wind turbines, and smart grid technologies. Prices for some of these rare earth metals have already jumped 300-700 percent because of a limited global supply. Some have blamed China, the world's supplier of about 97 percent of rare earth minerals, for their 2011 announced of severe cuts in rare earth exports.
But while the Resources, Conservation and Recyclingstudy concludes that production rates need to be drastically improved, the report also notes that as the rapid growth rate of new PV installations slows and recycling of end-of-life PV materials increases, the need for new raw rare earth materials could be drastically reduce. Another aspect of PV development the researchers said they
were not included in their scenarios and projections was the potential of current research, such as nano-material technologies, that are expected to dramatically increase PV cell efficiency.