National Minerals Information Center

Minor Metals and Renewable Energy—Diversifying America’s Energy Sources

Solar photovoltaic (PV) and wind turbine technologies are 

projected to make up an increasing proportion of electricity generation 

capacity in the United States in the coming decades. By 2050, they 

will account for 36 percent (or 566 gigawatts) of capacity compared 

with about 11 percent (or 118 gigawatts) in 2016 (fig. 1; EIA, 2017).

There are several different types of commercial solar PV and wind 

turbine technologies, and each type makes use of different minor 

metals. “Minor metal” is the term used for metals for which world 

production is small compared with the more widely produced base 

metals, and they are often produced as byproducts of the mining or 

processing of base metals. Minor metals used in renewable energy 

technologies often have complex supply chains, are often produced 

primarily outside of the United States, and are also used in many other 

applications. A larger amount of minor metals will be needed in the 

future to support the projected increases in solar PV and wind energy 

production capacity (Nassar and others, 2016).

84 GW

979 GW 1,009 GW 34 GW

192 GW

374 GW

2016 2050

Figure 1. U.S. electricity generation capacity, in gigawatts (GW), for 

wind, solar photovoltaic (PV), and all other sources (fossil fuels, nuclear, 

hydroelectric, and so forth) for 2016, with projections for 2050 (EIA, 2017).

Solar Photovoltaic

Solar PV technologies (fig. 2) can be generally 

classified as either wafer or thin-film. Wafer-based 

solar cells, currently the dominant technology, are made mostly 

of crystalline silicon and use a conductive paste made of silver. 

Thin-film-based solar cells are named for the material in their 

light-absorbing layer that consists of cadmium telluride, copperindium-gallium-(di)selenide, or amorphous silicon germanium. 

Thin-film-based solar cells may become more economically competitive in the future as their cost decreases and their electrical 

conversion efficiency increases. It is not yet clear, which, if any, 

of the three types of thin-film-based solar cells will eventually 

dominate the market.

A supply chain consists of the manufacturers, suppliers, 

technologies, information, and activities involved in creating 

and distributing products. For the minor metals used in solar 

PV technologies, the supply chain is complicated for several 

reasons. For instance, the minor metals are present in only trace 

amounts in the deposits from which they are recovered, so, for 

economic reasons, they are usually obtained as byproducts from 

the processing of ore minerals such as bauxite, chalcopyrite, gold, 

and sphalerite (fig. 2). The availability of these minor metals is 

therefore dependent on the supply of and demand for the main ore 

mineral(s) in the deposit. Additionally, these minor metals are also 

used in many other technology applications (such as batteries, 

electronics, fiber optics, flat-panel displays, integrated circuits, 

metallurgy, and thermoelectronics), so producers of solar PV cells 

may need to compete with others for the supply of these metals. 

Lastly, the United States is highly net import reliant—defined as 

imports minus exports plus adjustments for stock changes (Fortier 

and others, 2015)—on many of these minor metals, meaning that 

it relies on other countries for its overall supply of these commodities. The United States obtains more than one-half of its raw 

material consumption of gallium, germanium, indium, silver, and 

tellurium as imports from other countries, such as Canada, China, 

and Mexico, so the supply could be restricted if trade is disrupted 

for any reason.

Ag Cd Te In Ga Se Ge

Silver Cadmium Tellurium Indium Gallium Selenium Germanium

c-Si CdTe CIGS α-SiGe

Wafer Thin-film

Gold

Chalcopyrite

Sphalerite

Bauxite

Source ore minerals

67% <25% <75% 100% 100% 0% 85%

EXPLANATION

67%

Ag

Silver

2016 U.S. net import 

reliance

Element abbreviation

Element name

Primary competing use

Competing use

Electronics

Batteries

Thermoelectronics

Flat-panel displays

Integrated circuits

Metallurgy

Fiber optics

Figure 2. Minor metals used in wafer and three types of thin-film 

solar photovoltaic technologies, along with their source ore minerals, 

percentage of U.S. net import reliance in 2016, and major competing 

uses. α-SiGe, amorphous silicon germanium; CdTe, cadmium telluride; 

CIGS, copper-indium-gallium-(di)selenide; c-Si, crystalline silicon.

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2017–3061

August 2017
Wind Turbine

Modern wind turbine technologies can generally be 

classified into three categories: (1) induction, (2) hybrid 

drive, and (3) direct drive (fig. 3). These designs vary by the 

absence or presence of a gearbox, which, among other things, 

determines the frequency with which the turbines require 

maintenance, as well as the quantity of minor metals required 

for them to function. Direct drive turbines, which have no 

gearboxes, and hybrid versions, which contain only a simple 

gearbox, use generators with neodymium-iron-boron (Nd-Fe-B) 

permanent magnets (PMs) to function. These two designs 

require different sized PMs: about 200 kilograms per megawatt 

(kg/MW) for hybrid drive turbines and 500 to 600 kg/MW for 

direct drive turbines (Constantinides, 2016). Several rareearth elements (REEs)—including dysprosium, neodymium, 

praseodymium, and terbium—are used in the PMs because of 

the various properties they impart.

The REEs used in these technologies are often present 

in only trace amounts in the deposits from which they are 

recovered, making mining of them dependent on the economics 

of the primary products in the deposits. In addition to wind turbines, many other products, such as hard disc drives and motors 

for electric vehicles, use magnets containing these REEs, and 

the REEs are also used in other technological applications, 

such as phosphors for various display and lighting applications. 

Demand for these REEs in other applications can affect their 

availability for wind power. Since 2016, the United States has 

had no domestic REE mines in operation and remains entirely 

reliant on imports from foreign sources, mainly China, for its 

supply of dysprosium, neodymium, praseodymium, and terbium, and for goods, such as magnets, that contain them.

High-speed generator 

(contains no PMs)

Multistage 

gearbox

1- or 2-stage gearbox

Medium-speed generator 

(about 200 kg/MW Nd-Fe-B PMs)

Low-speed generator 

(500 to 600 kg/MW Nd-Fe-B PMs)

EXPLANATION

Magnets Phosphors

Induction

Hybrid

drive

Direct

drive

Minor metals in PMs

Dy

Dysprosium

85%

Pr

Praseodymium

100%

Tb

Terbium

0%

Nd

Neodymium

100%

Figure 3. Wind turbine technologies and the minor metals required for hybrid 

and direct drive turbines, along with percentage of U.S. net import reliance in 

2016 and major competing uses for these minor metals. The direct drive design, 

which contains no gearbox, has fewer maintenance requirements than the 

other designs but uses the largest neodymium-iron-boron (Nd-Fe-B) permanent 

magnets (PMs) and thus requires the largest amount of rare-earth elements to 

produce. kg/MW, kilogram per megawatt.

Key Points

Electricity generation capacity in the future is projected to 

increase to meet increased demand by homes, businesses, and 

industries. An increasingly larger proportion of the electricity 

supply is projected to come from solar PV and wind power—

technologies that use a number of minor metals. In the future, 

more of these minor metals will be required, with the exact amount 

depending largely on which technology becomes dominant (Nassar 

and others, 2016). The future supply of and demand for these 

minor metals is uncertain because they are often produced as 

byproducts of other nonfuel mineral commodities, they are used in 

numerous competing applications, and the United States is heavily 

reliant on imports of these metals from other countries, especially 

Canada, China, and Mexico.

The U.S. Geological Survey (USGS) National Minerals Information Center tracks domestic and world production, domestic 

consumption, and trade data for minor metals as well as many 

other nonfuel mineral commodities. By analyzing these data, forecasting future trends in industry, and publishing regular updates, 

the USGS provides information to policymakers and members of 

industry to help them anticipate and react to changes in mineral 

commodity supply chains, thus helping to ensure a steady supply 

of these necessary mineral commodities.

References Cited

Constantinides, Steve, 2016, Permanent magnets in a changing world market: 

Magnetics Business and Technology, February 14, accessed May 23, 2017, at 

http://www.magneticsmagazine.com/main/articles/permanent-magnets-in-achanging-world-market/.

Fortier, S.M., DeYoung, J.H., Jr., Sangine, E.S., and Schnebele, E.K., 2015, Comparison 

of U.S. net import reliance for nonfuel mineral commodities—A 60-year retrospective 

(1954–1984–2014): U.S. Geological Survey Fact Sheet 2015–3082, 4 p. [Also available at https://doi.org/10.3133/fs20153082.]

Nassar, N.T., Wilburn, D.R., and Goonan, T.G., 2016, Byproduct metal requirements for 

U.S. wind and solar photovoltaic electricity generation up to year 2040 under various 

Clean Power Plan scenarios: Applied Energy, v. 183, 1206–1226. 

U.S. Energy Information Administration (EIA), 2017, Annual energy outlook 2017: 

Washington, D.C., U.S. Department of Energy, tables 9 and 16, accessed 

May 23, 2017, at https://www.eia.gov/outlooks/aeo/.

For more information, contact:

Director, National Minerals Information Center 

U.S. Geological Survey 

12201 Sunrise Valley Drive 

988 National Center 

Reston, VA 20192

Email: nmicrecordsmgt@usgs.gov

Or visit the USGS National Minerals Information 

Center website at 

https://minerals.usgs.gov/minerals/

By Sheryl A. Singerling and Nedal T. Nassar

ISSN 2327-6916 (print) ISSN 2327-6932 (online)

https://doi.org/10.3133/fs20173061