Page 434 - A Comprehensive Guide to Solar Energy Systems

446 A COmPREhEnSIVE GuIdE TO SOlAR EnERGy SySTEmS

the technology continues to be heavily evaluated, the energy cost of developing PV is just
starting to come to light for certain systems (see Chapter 27). The implications of rapid
up-scaling in PV technology deployment to the materials industry, including the energy
costs of developing materials necessary for a variety of PV technologies, however, is just
beginning to be widely discussed [6].
Our current modern economies are dependent on growth; thus, the same technological
and resource dependence that has allowed us to experience a wealth of materials defines
our vulnerability within the system. disruptions in the complex network of global resource
chains and industrial development can lead to serious degradation of productivity and
where energy production is concerned, even a decrease in social well-being. Recent rapid
development of PV energy throughout the world has led to questions of material con-
straints on it, especially given other profitable industries competing for resources.

23.2 Critical Metals

material constraints are those that arise due to limited amounts of critical metals required
for rapid PV production [7,8]. Critical metals are those that are vulnerable to supply dis-
ruptions, where such disruptions would have significant impact to the industry and have
a high likelihood of occurrence [9–11]. metals critical to the rapid upscale of the PV indus-
try are such typically due to the required rapid rates of development, not to any inherent
properties of the material itself. material constraints apply to both primary ores (those
extracted from the earth to obtain metal) and secondary ores (those that are derived from
primary ores). For example, tellurium (Te)—a secondary ore—is obtained from the impu-
rities of copper (Cu) refinement—Cu being the primary ore. This is not to be confused with
secondary production (Cu production from recycling products containing Cu). Another
important distinction is that between “resources” and “reserves.” “Known resources”
refers to the crustal abundance of an elemental material. It is the total of that material
which exists on Earth and typically does not change over time. “Known reserves” or the
“reserve base” refers to the subset of resources that can be economically used given cur-
rent technologies of extraction and processing. historically, the reserve base of a given
material tends to increase over time as new technologies are developed to access deposits
more difficult to process. Technology can also increase extraction efficiency. Consumption
acts to decrease geologic reserves. Assessing the criticality of a metal toward PV produc-
tion requires a good understanding of the metal resources, reserves, and supply dynamics;
however, the reserves and resources of secondary ores are very uncertain today [12].
Ever since hubbert predicted, in 1956, a future peak in crude oil production in the
united States (uS) [13], similar efforts have been made to predict the peak of other non-
renewable resources. It has been suggested that Canada and the united States have al-
ready passed peak Cu production [14,15] and that zinc (Zn) might also be approaching
global production peak [7,16]. Cu is a primary metal necessary for PV production, and
like Zn so are its secondary products. like the criticality of a material, peak production
refers not to the amount of material in reserves, but primarily the rate at which it can be