One year ago, a report from the U.S.
Department of Energy (DOE) on the global supply of essential PV module
materials predicted possible disruptions for thin-film manufacturing.
Now,
the DOE has released the latest edition of its Critical Materials
Strategy. Have the worries over thin-film PV materials supply eased?
According to the DOE, the general supply-demand picture for indium,
gallium and tellurium has “improved slightly,” but the situation is not
entirely reassuring. The three metals are still highlighted (alongside
neodymium and dysprosium) as clean-energy materials that face a
“significant risk of supply chain bottlenecks in the next two decades.”
The
report attributes the slight improvement primarily to decreased demand
for the three thin-film materials: Although PV deployment is expected to
grow, the requirements of the materials per module are expected to
shrink.
For copper indium gallium
diselenide (CIGS) modules, manufacturers are shifting to compositions
with higher proportions of gallium and lower concentrations of indium,
the DOE says. The result is a “partial trade-off in the potential for
supply risk between the two elements.” At the same time, CIGS’ market
share assumption has been reduced under the DOE’s new calculations,
lowering projected demand for both indium and gallium.
Cadmium
telluride (CdTe) thin-film modules currently account for approximately
10% of the PV market, according to the report. Declining silicon prices
may threaten this slice of the market, but high tellurium costs and the
increasing need for CdTe manufacturers to compete for supply with non-PV
companies requiring tellurium continue to cause supply headaches.
“The
cost of tellurium is a critical issue for CdTe solar cell makers, and
the industry is working to lower material use and increasing recovery of
new scrap to reduce reliance on primary tellurium,” the DOE says in the
report.
Although short-term supply
of tellurium appears adequate, future capacity increases may be
insufficient to supply both CdTe manufacturing and the multitude of
other manufacturing sectors that use tellurium. Under one scenario
modeled in the report, tellurium supply would need to increase 50% more
than its projected 2015 total in order to meet expected demand.
Indium
and gallium have also experienced increased popularity in non-PV
manufacturing uses, such as semiconductor applications, flat-panel
displays, and coatings for smartphones and tablet computers. The DOE
forecasts that as a result, supplies may run short by 2015 unless
production of these materials is increased – or non-PV demand lessens.
Of
the two metals, gallium poses more cause for concern, as the DOE has
adjusted its assumptions of future gallium use under CIGS manufacturers’
expected manufacturing modifications.
“These
higher estimates [of gallium requirements] are driven largely by the
assumption that gallium will increasingly be substituted for indium in
CIGS composition,” the DOE explains. This change points to the benefits
of reducing material intensity in other aspects of PV manufacturing,
such as reducing cell thickness and improving processing efficiency.
Overall,
indium, gallium and tellurium all receive moderate scores (2 or 3 on a
scale of 1 to 4) from the DOE with regard to both their importance to
clean energy and short- and medium-term supply risk.
In
order to help mitigate possible supply disruptions that could threaten
the manufacturing and deployment of PV, as well as other types of clean
energy, the agency has developed a three-pronged approach.
“First,
diversified global supply chains are essential,” the DOE stresses in
the report. “To manage supply risk, multiple sources of materials are
required. This means taking steps to facilitate extraction, processing
and manufacturing here in the United States, as well as encouraging
other nations to expedite alternative supplies.”
The
second strategy relies on developing alternatives to materials whose
supply may be constrained. For PV, one DOE research program focuses on
advancements in thin-film formulations such as copper-zinc-tin and
sulfide-selenide. Another initiative funds research and development into
PV inks based on earth-abundant materials such as zinc, sulfur and
copper.
“Several projects also seek
to use iron pyrite – also known as fool’s gold – to develop prototype
solar cells,” the DOE notes in the report. “Pyrite is non-toxic,
inexpensive, and is the most abundant sulfide mineral in the Earth’s
crust.”
Finally, improving recycling
and reuse mechanisms can reduce demand for new materials, the DOE says,
adding that these strategies also can help improve the sustainability of
manufacturing processes.
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