Energy Systems and Technologies for the Coming Century ...

Of the 17 rare earth elements, there are several which are considered ‘the magnet metals’[5]:PraseodymiumNeodymiumTerbiumDysprosiumRare Earth Oxide Demand [kt]302520151050Fig. 2 Estimated demand of rare earth elements by industry in 2008 [6]. It should be noted that theweight fraction of Nd in Nd 2 O 3 is 0.86, which indicates that the magnets would demand in the order of22360 tons if it was only based on Nd.Of particular interest to this industry is neodymium, which is integral to neodymium ironboron Nd 2 Fe 14 B (NdFeB) magnets. These magnets have become the industry standardfor permanent magnet machines. Their use is conducive to motors and generators withhigh power density and high efficiency. Perhaps the most well-known hybrid car, theToyota Prius, is estimated to require 1kg of neodymium per unit [7], [8]. A similar trendis taking place in the wind turbine industry. As a rule of thumb, modern wind turbinesusing permanent magnet generators require approximately 800 kg permanent magnetsper rated megawatt [9]. Terbium and dysprosium are also utilized to improve theperformance of NdFeB magnets with regards to the Curie temperature and increasing thecoercivity. Neodymium is a so-called ‘light’ rare earth element, while dysprosium andterbium are ‘heavy’ rare earth elements, which are currently in shorter supply. Withoutthe addition of these heavy REEs, the performance of NdFeB magnets deterioratessignificantly with increasing temperatures.In nature, mineral deposits containing rare earth elements contain all of them, in somedistribution [10]. While they are not actually rare in nature, it is very difficult to separatethem, due to their similar chemical structure. This is what makes the individual rare earthmetals effectively rare in the marketplace. It is extremely expensive and time consumingto go from a mining operation to production of a useable rare earth material. While thevalues of most commodities are dictated by supply and demand, the case of rare earthmetals is more complicated due to the state of the rare earth mining industry.2.1 Mining and productionCurrently, almost all rare earth mining and production takes place in China. This was notthe case prior to 2002, before which the USA was self-sufficient in rare earth metals. Atthat time Chinese rare earths became cheaper, and this made the US rare earth miningoperation uneconomical. China has since been the world’s supplier of rare earth metals.Moving from 2010 and onward, Chinese demand for rare earths is expected to approachits supply. This realization, along with the current lack of rare earth production outside ofRisø International Energy Conference 2011 Proceedings Page 229