[ExI] Global solar photovoltaic industry is likely now a net energy producer, Stanford researchers find

[Eugen Leitl]

Why the net energy decay is a problem -- you need energy input
for heavy infrastructure work. In absence of cheap energy,
rapid EROEI is more important than high EROEI.

http://news.stanford.edu/news/2013/april/pv-net-energy-040213.html

Global solar photovoltaic industry is likely now a net energy producer,
Stanford researchers find
 
The construction of the photovoltaic power industry since 2000 has required
an enormous amount of energy, mostly from fossil fuels. The good news is that
the clean electricity from all the installed solar panels has likely just
surpassed the energy going into the industry's continued growth, Stanford
researchers find.

By Mark Golden

Video by Mark Shwartz 

Despite its rapid growth rate, the photovoltaic power industry is producing -
or is on the cusp of producing - a net energy benefit for society, Stanford
researchers say. 

The rapid growth of the solar power industry over the past decade may have
exacerbated the global warming situation it was meant to soothe, simply
because most of the energy used to manufacture the millions of solar panels
came from burning fossil fuels. That irony, according to Stanford University
researchers, is coming to an end.
 
For the first time since the boom started, the electricity generated by all
of the world's installed solar photovoltaic (PV) panels last year probably
surpassed the amount of energy going into fabricating more modules, according
to Michael Dale, a postdoctoral fellow at Stanford's Global Climate & Energy
Project (GCEP). With continued technological advances, the global PV industry
is poised to pay off its debt of energy as early as 2015, and no later than
2020.
 
"This analysis shows that the industry is making positive strides," said
Dale, who developed a novel way of assessing the industry's progress globally
in a study published in the current edition of Environmental Science &
Technology. "Despite its fantastically fast growth rate, PV is producing – or
just about to start producing – a net energy benefit to society."
 
The achievement is largely due to steadily declining energy inputs required
to manufacture and install PV systems, according to co-author Sally Benson,
GCEP's director. The new study, Benson said, indicates that the amount of
energy going into the industry should continue to decline, while the issue
remains an important focus of research.
 
 "GCEP is focused on developing game-changing energy technologies that can be
deployed broadly. If we can continue to drive down the energy inputs, we will
derive greater benefits from PV," she said. "Developing new technologies with
lower energy requirements will allow us to grow the industry at a faster
rate."
 
The energy used to produce solar panels is intense. The initial step in
producing the silicon at the heart of most panels is to melt silica rock at
3,000 degrees Fahrenheit using electricity, commonly from coal-fired power
plants.
 
Mark Shwartz 

To be considered a success, PV panels must ultimately pay back all the energy
that went into them, said Michael Dale, a postdoctoral fellow at Stanford's
Global Climate & Energy Project.
 
As investment and technological development have risen sharply with the
number of installed panels, the energetic costs of new PV modules have
declined. Thinner silicon wafers are now used to make solar cells, less
highly refined materials are now used as the silicon feedstock, and less of
the costly material is lost in the manufacturing process. Increasingly, the
efficiency of solar cells using thin film technologies that rely on
earth-abundant materials such as copper, zinc, tin and carbon have the
potential for even greater improvements.
 
To be considered a success – or simply a positive energy technology – PV
panels must ultimately pay back all the energy that went into them, said
Dale. The PV industry ran an energy deficit from 2000 to now, consuming 75
percent more energy than it produced just five years ago. The researchers
expect this energy debt to be paid off as early as 2015, thanks to declining
energy inputs, more durable panels and more efficient conversion of sunlight
into electricity.
 
Strategic implications
 
If current rapid growth rates persist, by 2020 about 10 percent of the
world's electricity could be produced by PV systems. At today's energy
payback rate, producing and installing the new PV modules would consume
around 9 percent of global electricity. However, if the energy intensity of
PV systems continues to drop at its current learning rate, then by 2020 less
than 2 percent of global electricity will be needed to sustain growth of the
industry.
 
This may not happen if special attention is not given to reducing energy
inputs. The PV industry's energetic costs can differ significantly from its
financial costs. For example, installation and the components outside the
solar cells, like wiring and inverters, as well as soft costs like
permitting, account for a third of the financial cost of a system, but only
13 percent of the energy inputs. The industry is focused primarily on
reducing financial costs.
 
Continued reduction of the energetic costs of producing PV panels can be
accomplished in a variety of ways, such as using less materials or switching
to producing panels that have much lower energy costs than technologies based
on silicon. The study's data covers the various silicon-based technologies as
well as newer ones using cadmium telluride and copper indium gallium
diselenide as semiconductors. Together, these types of PV panels account for
99 percent of installed panels.
 
The energy payback time can also be reduced by installing PV panels in
locations with high quality solar resources, like the desert Southwest in the
United States and the Middle East. "At the moment, Germany makes up about 40
percent of the installed market, but sunshine in Germany isn't that great,"
Dale said. "So from a system perspective, it may be better to deploy PV
systems where there is more sunshine."
 
This accounting of energetic costs and benefits, say the researchers, should
be applied to any new energy-producing technology, as well as to energy
conservation strategies that have large upfront energetic costs, such as
retrofitting buildings.  GCEP researchers have begun applying the analysis to
energy storage and wind power.
 
Mark Golden works in communications at the Precourt Energy Efficiency Center
at Stanford University.

Media Contact
 
Mark Golden, Precourt Institute for Energy: (650) 724-1629,
mark.golden at stanford.edu
 
Dan Stober, Stanford News Service, (650) 721-6965