Energy Solutions to Air Pollution and Global Warming - Air Pollution and Global Warming: History, Science, and Solutions - page 330

the prospects of cadmium telluride (CdTe) and copper
indium gallium selenide (CIGS) thin-film cells.
The power production of silicon PV technologies is
limited not by crystalline silicon (because silicon is
widely abundant) but by silver, which is used as an
electrode. Reducing the use of silver as an electrode
would allow virtually limitless production of silicon-
based solar cells.
Formultijunction concentrator cells, the limiting
material is germanium (Ge); however, substitution of
gallium (Ga), which is more abundant, would allow ter-
awatt expansion. Overall, it is unlikely that the devel-
opment of a large global PV system will be limited by
the scarcity or cost of raw materials.

Table 13.5. Estimated resource by country for
Nd 2 O 3 (s), as of 2009 (Tg)

Country Resource

United States 2.1

CIS 3.8

India 0.2

Australia 1.0

China 16.0

Other 4.1

WORLD LAND TOTAL 27.3

CIS, Commonwealth of Independent States.
Sources: Jacobson and Delucchi (2011); U.S. Geological
Survey (2011).

13.6.3. Materials for Concentrated
Solar Power
CSP plants consist primarily of mirrors, receivers, and
thermal storage fluid. Mirrors are generally glass mir-
rors with a reflective silver layer on the back of the glass.
Receivers are stainless steel tubes with a surface that
selectively absorbs solar radiation and is surrounded
by an antireflective glass tube. The receiver heats the
thermal storage fluid circulating through the receiver
inner tube. Materials shortages are not expected to limit
the large-scale production of CSP, particularly because
many alternate mirror types, receivers, and thermal stor-
age fluids are possible.

An element used in wind turbine generator permanent
magnets is neodymium (Nd). Nd is one of seventeen
rare earth elements (REEs) . REEs are not actually
rare because they comprise a significant fraction of the
Earth's crust. For example, Nd comprises 38 mg kg − 1 of
the crust. REEs were named as they were because they
were initially found distributed rather than concentrated
in economically extractable deposits. However, more
deposits have been discovered over time.
Building 3.8 million turbines would require about
3.8 million metric tonnes of Nd, or about 4.4 mil-
lion metric tonnes of neodymium oxide [Nd 2 O 3 (s)].
Table 13.5 indicates that the estimated world resource
of Nd 2 O 3 (s) is about 27.3 million tonnes. The resource
of a material is defined as the “concentration of naturally
occurring solid, liquid, or gaseous material in or on the
Earth's crust in such form and amount that economic
extraction of a commodity from the concentration is
currently or potentially feasible” (U.S. Geological Sur-
vey, 2011). Thus, Nd should not be a limiting factor
in worldwide wind power development, although recy-
cling may be needed.

13.6.4. Materials for Electric Vehicles
Forelectric vehicles, two types of materials are of most
concern: Nd for electric motors and lithium for lithium
ion batteries. Some permanent magnet alternating cur-
rent motors, such as those used in the Toyota Prius
hybrid electric vehicle, use Nd. However, the amount
required per vehicle is about an order of magnitude less
than that required per wind turbine, and Nd is not a
limiting factor in wind turbine production (Table 13.5).
Furthermore, numerous electric motors do not use Nd.
Table 13.6 shows recent estimates of worldwide
lithium resources; however, it does not include the
recently discovered, potentially large lithium resources
in Afghanistan. More than one-fourth of the estimated
global lithium resources in 2011 were in Bolivia (Figure
13.15). However, Bolivia to date has produced lit-
tle lithium, and Chile is currently the world's leading
producer.
At 10 kg per vehicle, the current estimated world
lithium resource could supply 3.3 billion vehicles, far

13.6.2. Materials for Solar Photovoltaics
Solar PVs are made of amorphous, polycrystalline,
and microcrystalline silicon; cadmium telluride; copper
indium selenide/sulfide; and other materials. Because
many alternative types of PV systems are available, it
is unlikely that the growth of PV will be constrained
by one or a few materials. For example, for thin-film
PVs, substituting ZnO electrodes for indium thin oxide
allows multiterawatt production of PV cells. The limited
availability of tellurium (Te) and indium (In) reduces