Page 437 - A Comprehensive Guide to Solar Energy Systems

Chapter 23 • Materials: Abundance, Purification, and the Energy Cost 449

Table 23.1 General Comparison of Metal Content in Different PV Technologies
c-Si CIGS CdTe a-Si
AI x
Cu x x
ln x
Fe x
Pb x
Ni x
Ag x
Zn x x
Adapted from [6]. Note that this is not a comprehensive list and many secondary materials are not represented here.

more versatile forms. A breakdown of the current composition of global PV capacity by
technology is illustrated in Fig. 23.1 and annual production of PV capacity by technol-
ogy in Fig. 23.2. Currently, c-Si accounts for about 90% of the current PV deployment
by capacity and 66% is comprised of poly-Si. Although poly-Si does not have the high
efficiency of mono-Si, it is more cost effective for most applications; however, mono-Si
has recently experienced an increase in development. Thin films comprise around 9% of
the total deployment by capacity to date and around 6% of total 2016 PV development.
Among the thin films, CdTe is the most popular due to its higher efficiencies and low cost
of production; CIGS can also become relatively cheap to produce, and a-Si suffer from
the lowest performance but can be printed onto flexible surfaces.
As can be understood from Table 23.1 and Figs. 23.1 and 23.2, materials for c-Si solar
cells such as Ag and for thin films such as In and Te are very important to the PV industry.
This is especially true moving forward into the future with the kind of growth expected
from these technologies. Table 23.2 provides the most up to date values for the amounts
of certain metals required based on capacity output for the PV industry as a whole. Even
within PV technologies, there are ranges of material requirements due to differences in
production pathways, countries of origin, and technological developments over time [37].
Each metal is more thoroughly discussed in terms of its part in specific PV technologies in
later sections of the chapter, which is summarized in Table 23.2.

23.3.1 Mining and Refining Materials for PV

mining the Earth for materials is something humans have been doing for thousands of
years. Today mining is done mostly by heavy machinery, but it is still integral to industry
and can be the backbone of a nation’s economy. There are thousands of mines on earth
today, ranging from small family-size operations to large-scale mountain top removal. It is
important to remember that every ore deposit is different, and so is every mine.
mining includes searching for, extracting and beneficiating (separating commercially
useful ore and mineral content from surrounding materials) from the Earth. There are seven
distinct main steps in any mining operation: (1) exploration, (2) design, (3) construction,