Page 446 - A Comprehensive Guide to Solar Energy Systems

458 A COmPREhEnSIVE GuIdE TO SOlAR EnERGy SySTEmS

and development, and also by Fizaine and Court [56] who developed a model for estimat-
ing the impacts of material depletion on renewable energy in general.
As can be understood from this chapter so far, Cu is integral to the future of the
PV industry because it is required in PV systems themselves and in the infrastructure
required to transport and consume the energy produced. It also has a useful amount
of scientific information associated with it given its history and prevalence in industry.
As is the case for most resource extractions, as Cu is mined, the grade of the ore tends
to decline overtime [53–60]. The economic rationale is to first produce metals from the
most profitable, easily accessible and thus less costly deposits. These tend to be of higher
concentration and closer to the surface. As the best resources are consumed first, the
operation tends toward moving deeper into the ground to lower grade materials. There-
fore, it is observed that as one depletes a metal deposit, it reduces in concentration and
thus the more material must be handled and the more energy must be expended per
unit of metal obtained [54]. This relation was recently observed and updated for Cu by
Koppelaar and Kopelaar [55] and 34 metals by Court and Fizaine [56]. The opposing fac-
tor to increasing energy costs given ore degradation is process efficiency, or improved
technology in general.
As discussed it is very difficult to generate good data for mining metals, as no two mines
are the same. differences include those in the deposits, both in quantity and quality of the
ore, the geography, and even the technology at hand. A time-series industry-wide view can
therefore be very useful. It is important to observe how the energy costs associated with
mining and metal extraction and production relate to the rest of the economy over time.
Fig. 23.3 illustrates the growth in energy consumption of the industry as it relates to the
energy consumption of the total economy.
Global mining and quarrying includes all upstream activities pertaining to mineral
extraction and beneficiation applied to metals and nonmetals, excluding fossil fuels.
Energy consumption for nonmetallic minerals, nonferrous metals, and iron and steel refer
to downstream activities, including final energy consumption, which refers to the entire
global economy. We can see that, especially in the twenty-first century, the energy con-
sumption for the materials industry is growing faster than that for the global economy as a
whole. This is especially true for upstream activity (mining and quarrying), which is sensi-
tive to ore grades and where the most material is handled. One reason for this increase is
the extraction and processing of increasing volumes of ore. Another reason is the increas-
ing energy required to obtain more remote and less concentrated deposits. In other words,
there could be an increase in quantity and decrease in quality.
In the united States, during the year 2000, 92% of metals obtained were through surface
mining [56]. Of the energy consumed approximately 35% was electrical, 32% fuel oil, and
33% coal, gas, and gasoline [40]. Electricity is mostly used for ventilation, water pump-
ing, crushing, and grinding. diesel fuel is used mostly in hauling and transportation in
general. Typically, electricity is the major source of energy consumed in an underground
mine due to the ventilation needs, where surface mining uses mostly diesel fuel for dig-
ging and hauling. It is estimated that on average two-thirds of the energy consumption in