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| Thanks to this wafer-thin technology (AP Photo/Mike Groll) |
by
Phil McKenna, Quartz:
http://qz.com/386261/solar-power-will-soon-be-as-cheap-as-coal/
This post originally appeared at Ensia. 
Inside
a sprawling single-story office building in Bedford, Massachusetts, in a
secret room known as the Growth Hall, the future of solar power is
cooking at more than 2,500 °F.
Behind closed doors and downturned
blinds, custom-built ovens with ambitious names like “Fearless” and
“Intrepid” are helping to perfect a new technique of making silicon
wafers, the workhorse of today’s solar panels. If all goes well, the new
method could cut the cost of solar power by more than 20% in the next
few years.
“This
humble wafer will allow solar to be as cheap as coal and will
drastically change the way we consume energy,” says Frank van Mierlo,
CEO
of 1366 Technologies, the company behind the new method of wafer fabrication
.
Secret
rooms or not, these are exciting times in the world of renewable
energy. Thanks to technological advances and a ramp-up in production
over the decade, grid parity - the point at which sources of renewable
energy such as solar and wind cost the same as electricity derived from
burning fossil fuels - is quickly approaching.
In some cases it has
already been achieved, and additional innovations waiting in the wings
hold huge promise for driving costs even lower, ushering in an entirely
new era for renewables.
Solar surprise
In Jan. 2015, Saudi Arabian
company ACWA Power surprised
industry analysts when it won a bid to build a 200-megawatt solar power
plant in Dubai that will be able to produce electricity for
6 cents per kilowatt-hour.
The price was less than the cost of electricity from natural gas or
coal power plants, a first for a solar installation. Electricity from
new natural gas and coal plants would cost an estimated 6.4 cents and
9.6 cents per kilowatt-hour, respectively, according to the US Energy
Information Agency.
Technological
advances, including photovoltaics that can convert higher percentages
of sunlight into energy, have made solar panels more efficient. At the
same time economies of scale have driven down their costs.
For
much of the early 2000s, the price of a solar panel or module hovered
around $4 per watt. At the time Martin Green, one of the world’s leading
photovoltaic researchers, calculated the cost of every component,
including the polycrystalline silicon ingots used in making silicon
wafers, the protective glass on the outside of the module, and the
silver used in the module’s wiring.
Green famously declared that so long
as we rely on crystalline silicon for solar power, the price would
likely never drop below $1/watt.
The
future, Green and nearly everyone else in the field believed, was with
thin films, solar modules that relied on materials other than silicon
that required a fraction of the raw materials.
Then, from 2007 to 2014, the price of crystalline silicon modules dropped from
$4 per watt to $0.50 per watt, all but ending the development of thin films.
The dramatic reduction in cost came from a wide number of incremental gains, says Mark Barineau, a solar analyst
with Lux Research.
Factors include a new, low-cost process for making polycrystalline
silicon; thinner silicon wafers; thinner wires on the front of the
module that block less sunlight and use less silver; less-expensive
plastics instead of glass; and greater automation in manufacturing.
“There
is a tenth of a percent of an efficiency gain here and cost reductions
there that have added up to make solar very competitive,” Barineau says.
25 cents per watt
“Getting below $1 [per watt] has exceeded my expectations,” Green says. “But now, I think it can get even lower.”
One
likely candidate to get it there is 1366’s new method of wafer
fabrication. The silicon wafers behind today’s solar panels are cut from
large ingots of polycrystalline silicon.
The process is extremely
inefficient, turning as much as half of the initial ingot into sawdust.
1366 takes a different approach, melting the silicon in specially built
ovens and recasting it into thin wafers for less than half the cost per
wafer or a 20% drop in the overall cost of a crystalline silicon module.
1366 hopes to begin mass production in 2016, according to van Mierlo.
Meanwhile,
thin films, once thought to be the future of solar power, then crushed
by low-cost crystalline silicon, could experience a renaissance. The
recent record-setting low-cost bid for solar power in Dubai harnesses
thin-film cadmium telluride solar modules made by US
manufacturer First Solar.
The company not only hung on as the vast majority of thin film
companies folded, but has consistently produced some of the least
expensive modules by increasing the efficiency of their solar cells
while scaling up production. The company now says it can manufacture
solar modules for
less than 40 cents per watt and anticipates further price reductions in coming years.
Ten
years from now we could easily see the cost of solar modules dropping
to 25 cents per watt, or roughly half their current cost, Green says. To
reduce costs beyond that, the conversion efficiency of sunlight into
electricity will have to increase substantially. To get there, other
semiconducting materials will have to be stacked on top of existing
solar cells to convert a wider spectrum of sunlight into electricity.
“If you can stack something on top of a silicon wafer it will be pretty much unbeatable,” Green says. Green
and colleagues set a record for crystalline silicon solar module
efficiency at 22.9% in 1996 that still holds today. Green doubts the
efficiency of crystalline silicon alone will ever get much higher. With
cell stacking, however, he says “the sky is the limit.”
A matter of size
While
solar power is just starting to reach grid parity, wind energy is
already there. In 2014, the average worldwide price of onshore wind
energy was the same as electricity from natural gas, according to
Bloomberg New Energy Finance.
As
with solar, the credit goes to technological advances and volume
increases. For wind, however, innovation has mainly been a matter of
size. From 1981 to 2015 the average length of a wind turbine rotor blade
has
increased more than sixfold, from 9 meters to 60 meters, as the cost of wind energy has
dropped by a factor of 10.
“Increasing
the rotor size means you are capturing more energy, and that is the
single most import driver in reducing the cost of wind energy,” says D.
Todd Griffith of
Sandia National Laboratories in Albuquerque, New Mexico.
Griffith
recently oversaw the design and testing of several 100-meter-long blade
models at Sandia. His group didn’t actually build the blades, but
created detailed designs that they subsequently tested in computer
models.
When the project started in 2009, the biggest blades in
commercial operation were 60 meters long. Griffith and his colleagues
wanted to see how far they could push the trend of ever-increasing
blades before they ran into material limitations.
Their
first design was an all-fiberglass blade that used a similar shape and
materials as those found in relatively smaller commercial blades at the
time. The result was a prohibitively heavy 126-ton blade that was so
thin and long it would be susceptible to vibration in strong winds and
gravitational strain.
The
group made two subsequent designs employing stronger, lighter carbon
fiber and a blade shape that was flat-backed instead of sharp-edged. The
resulting 100-meter blade design was 60% lighter than the initial
model.
Since
the project began in 2009 the largest blades used in commercial
offshore wind turbines have grown from 60 meters to roughly 80 meters
with larger commercial prototypes now under development. “I fully expect
to see 100 meter blades and beyond,” Griffith says.
As
blades grow longer, the towers that elevate them are getting taller to
catch more consistent, higher speed wind. And as towers grow taller,
transportation costs are growing increasingly expensive. To counter the
increased costs
GE recently debuted
a “space frame” tower, a steel lattice tower wrapped in fabric.
The new
towers use roughly 30% less steel than conventional tube towers of the
same height and can be delivered entirely in standard-size shipping
containers for on-site assembly. The company recently received a $3.7
million grant from the US Department of Energy to develop similar space
frame blades.
Offshore innovation
Like
crystalline silicon solar panels, however, existing wind technology
will eventually run up against material limits. Another innovation on
the horizon for wind is related instead to location. Wind farms are
moving offshore in pursuit of greater wind resources and less land use
conflict.
The farther offshore they go, the deeper the water, making the
current method of fixing turbines to the seafloor prohibitively
expensive. If the industry moves instead to floating support structures,
today’s top-heavy wind turbine design will likely prove too unwieldy.
One
potential solution is a vertical axis turbine, one where the main rotor
shaft is set vertically, like a merry go round, rather than
horizontally like a conventional wind turbine. The generator for such a
turbine could be placed at sea level, giving the device a much lower
center of gravity.
“There
is a very good chance that some other type of turbine technology, very
well vertical axis, will be the most cost effective in deep water,”
Griffith says.
The
past decade has yielded remarkable innovations in solar and wind
technology, bringing improvements in efficiency and cost that in some
cases have exceeded the most optimistic expectations. What the coming
decade will bring remains unclear, but if history is any guide, the
future of renewables looks extremely positive.
