KEY CONCEPTS
• A new study complements a 2015 U.S. Department of Energy study on offshore wind power.
• Concern about the availability of rare earth metals in general and neodymium in particular led the study to develop what-if scenarios for its use in wind turbines through 2050.
• Researchers used a materials flow analysis to evaluate the supply and demand for neodymium. 

Wind power continues to offer a potential alternative approach for generating electricity that is more environmentally friendly. But the severe operating conditions placed on the lubricant in gearboxes needed to convert low-speed wind energy to high-speed energy in the wind turbine have decreased the ability for operating at an optimum level for a long period of time. 

This factor is particularly critical because wind turbines are in remote locations making it very difficult and costly to maintain them. The potential use of wind turbines in offshore farms has a much higher potential for generating electricity than on land but faces greater challenges. One of the operational issues has been the premature failure of gearboxes. In the U.S., only one offshore wind farm has been commercialized off the coast of the state of Rhode Island (see Figure 2). 


Figure 2. A new study discusses scenarios for the use of the rare earth metal neodymium in offshore wind turbines built in the U.S. during the next 30 years. (Figure courtesy of Yale University.)

In a previous TLT article (1), researchers determined that placement of a wind farm in the North Atlantic Ocean would produce a higher electricity output than wind farms of a comparable size on land in a state such as Kansas. The key parameter is the kinetic energy extraction rate, which measures the amount of wind energy available for turbines. The kinetic energy extraction rate is four times higher in the North Atlantic Ocean than on land. 

Dr. Tomer Fishman, a former post-doctoral associate at the Yale University School of Forestry & Environmental Studies in New Haven, Conn., and currently a lecturer at the Interdisciplinary Center IDC Herzliya in Herzliya, Israel, says, “The U.S. Department of Energy (DOE) published a 2015 study (2) that developed scenarios for producing over 80 gigawatts of offshore wind power by 2050. This study envisioned that the U.S. will be able to not only boost wind power but potentially create a domestic industry that would include the potential production of turbines.”

Several factors not covered in the DOE study may reduce the potential for utilizing wind energy particularly off shore. One of these issues is directly related to the challenges faced in using gearboxes in wind turbines. Fishman says, “Operational difficulties with using gearboxes in offshore wind turbines led the wind power industry to evaluate the use of direct drive systems. This technology initially was more expensive and heavier than gearboxes, but ongoing developments have led to reductions in cost and weight.”

Fishman and his co-author, Thomas Graedel, professor emeritus at the Yale University School of Forestry & Environmental Studies, have now conducted a study to complement DOE’s vision of offshore wind energy and demonstrate that other factors must be considered to predict the future use of wind turbines in the U.S.

Neodymium
The focus of the study conducted by Fishman and Graedel deals with the fact that DOE did not factor in the availability and use of the rare earth metal neodymium in its 2015 study. Fishman says, “Rare earth metals in general are considered to be critical raw materials necessary for the long-term growth of the U.S. economy. The concern about them is their long-term supply because there is only one country processing most of the rare earth metals, China.”

Fishman explained that rare earth metals are less economically available and are needed for critical applications such as computers and electric vehicles. The permanent magnet systems used in direct drive systems are based on neodymium, iron and boron because they demonstrate the most efficient generation of electricity and enable wind turbines to be designed that are lighter and more compact. 

Nearly all of the world’s neodymium is mined in China according to Fishman. He adds, “The supply chain for producing the wind turbines off the Rhode Island coast were prepared from a vulnerable and complex supply chain that started in China and then went through Japan and France before ending up in the U.S.”

Fishman continues, “The purpose of our study was to develop what-if scenarios regarding the use of neodymium in wind turbines over the next 30 years until 2050. Approximately 15,500 metric tons of neodymium are predicted to be required during this time. We believe that 20% of this usage could be avoided through the development of recycling techniques and more effective magnets.”

The U.S. was divided into five distinct regions (Northeast, Mid-Atlantic, Pacific, Great Lakes and Gulf) because demand for wind power will not be uniform. Fishman says, “Each of these regions has its own requirements for wind energy which will impact the demand for neodymium.”

The researchers used a materials flow analysis to evaluate the supply and demand for neodymium. Fishman says, “This approach represents a framework to account for the demand, supply and use of neodymium. It is similar to how a company will assess earnings, losses and profitability through accounting practices.”

A second rare earth metal, dysprosium, also is used in neodymium, iron and boron permanent magnets to a smaller extent and will face the same supply situation. Fishman says,” We expressed similar concerns about dysprosium, which enables the permanent magnetic to perform under more severe conditions such as higher stress and higher temperatures.”

The researchers hope that by factoring in the supply and demand for rare earth metals, the U.S. will be able to develop a successful wind energy program. Additional information on this study can be found in a recent article (3) or by contacting Fishman at Tomer.fishman@idc.ac.il. 

REFERENCES
1. Canter, N. (2018), “Open ocean wind farms,” TLT, 74 (3), pp. 18-20.
2. Please go to the following link for the executive summary of the DOE study here.
3. Fishman, T. and Graedel, T. (2019), “Impact of the establishment of US offshore wind power on neodymium flows,” Nature Sustainability,” 2, pp. 332-338.