Page 450 - A Comprehensive Guide to Solar Energy Systems

462 A COmPREhEnSIVE GuIdE TO SOlAR EnERGy SySTEmS

study to another. For 2014, the global metal mining industry represented about 14.5% of
total primary energy finally consumed and about 28% of the energy consumed in total
mining [56,61,62]. A summary of the estimated energy cost per elemental material is avail-
able in Table 23.4. As illustrated, the highest energy cost among metals produced in 2014
was for Al by far. Al is also the most widely recycled metal on Earth.
Just as primary ore energy costs tend to be higher than that for secondary ores, primary
materials can also have a much higher energy cost than secondary, or recycled, materi-
als. In general, it is accepted that to increase life cycle efficiency and lower energy costs
for PV systems, a serious effort is going to have to be made for the recycling of electronics
sometime in the future. In fact, from 1900 to 2010, global human-made material stocks
accumulating in buildings, infrastructure, and machinery increased 23 fold and required
half of all the annual global resource use to be improved, maintained, or operated [63].
despite efforts to improve recycling rates, only 12% of materials inflows to stocks are from
secondary sources. There are avenues for hope in this regard but the situation is complex.
The impact of recycling PV panels and electronics to the energy costs of PV production
is already beginning to be studied. This work could inform material and design choices in
the future to minimize life cycle energy costs and maximize material throughput. Pathways
for recycling PV and manufacturing waste have been studied for some time [64] and pre-
liminary results show that exhaustive recovery of PV materials has the potential to reduce
energy costs by more than half for mature c-Si and thin-film technologies [65]. however,
although intuition would suggest that cheaper low-efficiency modules be discarded and
expensive energy intense modules recycled, the complex materials might be too costly to
disassemble and so there may be no incentive for producers to use them. Also, although Al
frames are easily recyclable, they also increase energy intensity and must be disassembled.
ultimately, producer take-back, if not mandated will continue to be dictated by econom-
ics, but when regulated may provide incentives for design efforts that ease recycling.
Currently, of the most important metals utilized in the PV industry, only Al and Cu
experience any significant recycling efforts from industry or the public [46]. no second-
ary ores are recycled in any great quantities. Although there is plenty of room for much
needed improvement in these rates, especially from an energy consumption point of view,
recycling rates are not yet increasing significantly. Other metals that are expected to re-
quire significant secondary recovery and could be called critical include In, Te, and Ag.
Economic factors that influence extraction and processing have led to significant wast-
age in the PV industry and it is becoming important to consider mine wastes as a major
contributor to future supplies. Possibly, the immense and potentially growing amounts
of pollution due to the mining required for materials extraction will lead to the public
demanding their clean up [66,67]. Perhaps this would provide incentive for recovery from
waste. It is possible that with concerted efforts to recycle and employ secondary recovery
technology and policy that In supplies might last well into the twenty-first century [35]. To
avoid the issue of critical metals, at some point at least, the PV industry will have to either
encourage public recycling or find incentives to improve material recovery and secondary
production on their own [30].