Today's PV market is a tremendous success story, with compound
annual growth of more than 30% over the last 10 years,
sales climbing to tens of billions of dollars, and the prospect of
further growth fueled by a developing perfect storm of market
forces - as long as the industry continues to achieve lower
costs for solar-generated electricity.
PV now uses as much or more of the silicon feedstock supply
as other electronic devices, contributing to the runup of prices
for supplies of polysilicon and the scramble for long-term contracts.
Today's best silicon PV modules deliver more than 20%
conversion efficiency - a testament to engineering prowess and
quality control and to the technology's maturity.
Silicon is one of the world's most studied materials, but the
physics of the indirect band-gap absorber trumps any engineering.
Roughly half of the cost of a photovoltaic module today is
the cost of the silicon, and only incremental reductions at the
shallow end of the learning curve are likely.
Researchers foresee a future where nearly ideal PV devices
can be assembled molecule by molecule at the nanoscale. Copper
indium gallium selenide (CIGS), an available and proven
material, can spontaneously nanostructure itself through phase
separation into the desired absorber and percolation network
arrangement when manufactured properly.
Don't Hold The Mayo
CIGS is one example of the
many potential advantages of "electronic mayonnaise" materials
that we are now beginning to recognize and exploit. Somewhere
between colloids and "hard" matter, they contain different phases
of similar materials. Their electronic properties may depend
as much on the spatial arrangement and electronic states of
these phases as their proportions.
Working with these materials is as much metallurgy as chemistry.
Compound semiconductors such as CIGS have several
bonds and many ionic interactions that are very different from
traditional silicon devices. Many of the old rules of thumb do not
apply. Where variations in composition of one part per billion
may render a silicon device inoperative, CIGS devices can vary by
several percent and still function well, if the right nanostructures
form within them. In fact, they may be the first widely deployed
and profitable commercialization of nanotechnology.
Just as small-area integrated circuits opened up huge markets
that couldn't be reached with discrete components and
pc-board technology, large-area, high-efficiency, and low-cost
PV integrated circuits will pave the way for a new energy mass
market. Frost and Sullivan analysts recently estimated that
thin-film PV could achieve a 25% market share by 2010.
This post-2010 PV market will make today's market pale by
comparison. Despite all of its incredible growth, PV as an industry
today is only where air conditioning was in the 1940s. Back
then, if you were a well-heeled early adopter and wanted air
conditioning for your home, you purchased a window unit
designed for retrofit onto existing construction.
Up on the Roof
By 1960, few buildings and homes
were designed without central air. Soon, mass-market central air
conditioning dwarfed the sales of window units.
Today's PV system of discrete components retrofitted onto
an existing roof is equivalent to the window unit of the 1940s,
while tomorrow's building-integrated solutions will let buildings
generate much of their own electric power through large-scale,
high-efficiency electronic components that are part of the
building envelope.
Making photovoltaic layers part of roofing materials or facades
can eliminate the marginal cost of installation. Roofs could alternate
areas of plantings and photovoltaics. Curtain wall systems
could include opaque photovoltaic spandrels to use the large
surface area of tall buildings to gather power. These components
could be installed by roofers and glaziers and interconnected by
electricians in the normal course of construction.
In the U.S., especially in the Sun Belt where much of today's
construction is taking place, most homes and buildings could
generate at least half of their electrical energy needs from PV
components incorporated as roofing and cladding, avoiding
spending billions of dollars every year to burn fossil fuels.
And, the potential growth for large-area thin-film electronics
isn't limited to PV. Many other applications are emerging for
displays, sensors, electrodes for batteries, fuel cells, capacitors,
flexible electronics, and perhaps even high-temperature
superconductors. There is a lot of electronic mayonnaise to
spread around.