News and commentary about ecodesign, geothermal heatstorage, PAH seasonal storage, urban farming, rainwater harvesting, grey water recycling, natural ventilation, passive summer cooling, energy autonomy, off grid solar comfort, as well as refined prototypes i am currently building.
Thin Epitaxial Silicon Solar Cell Milestone Completed
Crystal Solar has completed a U.S. Department of Energy (DOE) funded
Incubator project regarding technology development and manufacturing
cost-effectiveness of epitaxial solar cells and modules. Thin epitaxial
silicon solar cell technology has the capability to improve the way
silicon is made by eliminating many steps in the current process flow
while retaining the high efficiency of mono-crystalline silicon.
They
estimate this could result in reduction of module costs by
approximately 50% from today's levels to ~$0.40/W, enabling the cost of
solar power to become comparable to existing energy costs in most parts
of the world.
During the eighteen month period of this project,
Crystal Solar demonstrated multiple cell architectures which allow
high-efficiency solar panels, developed and productized industrial grade
production tools for the manufacture of cost-effective Epi Thin Silicon
technology, and completed detailed blue prints for a 100 MW factory.
Scientists from DOE's National Renewable Energy Laboratory (NREL) worked
with Crystal Solar in providing overall guidance, assisting with
advanced processing and metrology, and verifying the efficiency and
reliability of the prototype solar panels. Crystal Solar also
collaborated with Georgia Institute of Technology in the silicon solar
cell processing during this project.
Crystal Solar is currently
commercializing this Epi Thin-Silicon technology and plans to complete
pilot production in 2013, followed by high volume manufacturing in
2014.
Initially, customers generating power in the city will receive 17
cents a kilowatt-hour, a price that gradually will decline for later
projects to 14 cents; projects in Owens Valley, also home to DWP
ratepayers, will receive 14 cents a kilowatt-hour. Single-family homes
probably won't be able to participate because most aren't large enough.
"We've acknowledged we're paying a slightly higher incentive to make
absolute certain we get major players here," Nichols said. "We're
starting a pioneering program. We didn't want to put out a price, hold a
party and nobody comes."
Jim Jenal, founder and chief executive of rooftop solar company Run
on Sun in Pasadena, said he worries the program will leave the city's
nonprofits in the lurch.
Clean L.A. Solar carved out four megawatts for smaller projects, such
as the North Hollywood apartment building. These can generate anywhere
between 30 and 150 kilowatts per hour. The remaining 16 megawatts in the
first portion of the program were reserved for large projects that can
generate 150 kilowatts to 3 megawatts per hour.
Jenal said it's hard for small entities to carry the financial burden
of installing and maintaining solar projects. Nonprofits are ineligible
for the tax breaks that most large commercial entities use to increase
the return they see off their green endeavors.
Jenal said that could hamstring a key objective of the solar program: familiarizing the public with alternative energy sources.
"What the LADWP did right is to see this as a way to get solar
throughout a lot of different places in the city. It demystifies the
whole concept," Jenal said. "From the stated goal, there is no place
better than nonprofits — places where people come to congregate, come to
learn — for them to learn about the value of sustainable energy."
Leslie of the LABC said residents and smaller organizations that
can't shoulder the cost of a full solar installation can still invest as
shareholders in nearby projects, and would see a return once these
projects become profitable.
"We didn't want a program that would only be for a select part of the
city," Leslie said. "We want to make sure that solar is diverse."
"We have sunshine over 300 days a year. The sun's free," she said,
"so the better we get at harnessing it, the better off we're going to
be."
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Rice University lab combines graphene nanoribbons with tin oxide for improved anodes
HOUSTON – (June 13, 2013) – Researchers at Rice University have come
up with a new way to boost the efficiency of the ubiquitous lithium ion (LI) battery by employing ribbons of graphene that start as carbon nanotubes.
Proof-of-concept anodes — the part of the battery that stores lithium
ions — built with graphene nanoribbons (GNRs) and tin oxide showed an
initial capacity better than the theoretical capacity of tin oxide
alone, according to Rice chemist James Tour. After 50 charge-discharge
cycles, the test units retained a capacity that was still more than
double that of the graphite currently used for LI battery anodes.
The research appeared this week in the American Chemical Society journal ACS Nano.
Better batteries are greatly desired by everyone who carries a
cellphone or computer or drives an electric car. The Rice team sees the
potential for GNRs to contribute to their development.
Tour and his colleagues developed a method for unzipping nanotubes
into GNRs, revealed in a 2009 cover story in Nature. Since then, the
researchers have figured out how to make graphene nanoribbons in bulk
and are moving toward commercial applications. One area ripe for
improvement is the humble battery. In an increasingly mobile world,
battery capacity is becoming a bottleneck that generally limits devices
to less than a day’s worth of use.
In the new experiments, the Rice lab mixed graphene nanoribbons and
tin oxide particles about 10 nanometers wide in a slurry with a cellulose gum binder
and a bit of water, spread it on a current collector and encased it in a
button-style battery. GNRs are a single atom thick and thousands of
times longer than they are wide. The GNRs not only separate and support
the tin oxide but also help deliver lithium ions to the nanoparticles.
Lab tests showed initial charge capacities of more than 1,520
milliamp hours per gram (mAh/g). Over repeated charge-discharge cycles,
the material settled into a solid 825 mAh/g. “It took about two months
to go through 50 cycles,” said lead author Jian Lin, a postdoctoral
researcher at Rice, who believes it could handle many more without
losing significant capacity.
GNRs could also help overcome a prime difficulty with LI battery
development. Lithium ions tend to expand the material they inhabit, and
the material contracts when they’re pulled away. Over time, materials
like silicon, which shows extraordinary capacity for lithium, break down
and lose their ability to store ions. Other labs at Rice
have made breakthroughs that help solve the expansion problem by
breaking treated silicon into a powder, achieving great capacity and
many cycles.
GNRs take a different approach by giving batteries a degree of
flexibility, Tour said. “Graphene nanoribbons make a terrific framework
that keeps the tin oxide nanoparticles dispersed and keeps them from
fragmenting during cycling,” he said. “Since the tin oxide particles are
only a few nanometers in size and permitted to remain that way by being
dispersed on GNR surfaces, the volume changes in the nanoparticles are
not dramatic. GNRs also provide a lightweight, conductive framework,
with their high aspect ratios and extreme thinness.”
The researchers pointed out the work is a “starting point for
exploring the composites made from GNRs and other transition metal
oxides for lithium storage applications.” Lin said the lab plans to
build batteries with other metallic nanoparticles to test their cycling
and storage capacities.
Co-authors of the paper are Rice graduate students Zhiwei Peng,
Changsheng Xiang, Gedeng Ruan and Zheng Yan and Douglas Natelson, a Rice
professor of physics and astronomy and of electrical and computer
engineering. Tour is the T.T. and W.F. Chao Chair in Chemistry as well
as a professor of mechanical engineering and materials science and of
computer science at Rice.
Boeing, the Air Force Office of Scientific Research, Sandia National
Laboratory and the Office of Naval Research supported the research.
The ‘unstoppable’ renewable grid | SmartPlanet
As I’ve detailed in previous columns, renewables have begun pushing
nuclear and coal off the grid in regions where renewables provide a
significant fraction of grid power. This is primarily because their
priority dispatch on the grid and their generation at times of peak
demand are destroying the economics of traditional “baseload” generation.
But gas is a natural complement to the variable output of wind and
solar, because gas-fired “peaking” plants are able to ramp up and down
quickly to fill in when renewable generation fluctuates.
In order to have a grid mostly powered by renewables, it will be
important for gas prices to remain competitive with coal and nuclear. At
the same time, the cost of unsubsidized renewable power must continue
to fall until it is competitive with fossil fuels. Several new reports
find that it will reach that point in key areas by 2020.
Citigroup study
A new report by Citigroup, nicely summarized by Giles Parkinson for Renew Economy,
forecasts that solar will be competitive with fossil-fueled grid power
in much of the world by the end of the decade, and that “the perception
of renewables as an expensive source of electricity is largely
obsolete.”
The report offered two charts showing the natural gas prices at which
wind and utility-scale solar are competitive with gas-fired power
generation.
The wind chart plots “capacity factors” against gas prices. A
capacity factor indicates the actual output of a wind farm, expressed as
a percentage of the output it would have if it were running full time
at full “nameplate” capacity. So, a 1 MW wind farm with a 32 percent
capacity factor would produce 2,803 MWh of power per year (1 MW x 8760
hours in a year x 0.32).
EIA offers an average capacity factor for U.S. wind of 33 percent,
while recent (2010-2012) estimates compiled by the National Renewable
Energy Laboratory (NREL) give a median capacity factor of 38 percent for onshore wind and 39 percent for offshore wind.
In the Citi chart, wind at a 32 percent capacity factor was
competitive with natural gas at about $7.50/MMBtu in 2012, and will be
competitive with gas at about $6.50 by 2020. In very windy locations
with capacity factors of 40 percent, wind is already competitive with
gas priced below $6, and would be competitive with gas at $5 by 2020.
Put another way, both onshore and offshore wind would be cheaper than
gas-fired power in the United States at a gas price of $6/MMBtu or
more. Natural gas at $6 would make most of the U.S. shale gas industry
profitable, and seems like a good bet for 2020, if not sooner.
For utility-scale solar, Citi cites various solar insolation factors
(kWh/kW/year). Insolation factors reflect how sunny a given region is.
An insolation factor of 2100 would correspond to a capacity factor of 24
percent (2100 ÷ 8,760 hours in a year). For U.S. solar PV, EIA (which
skews a bit to the high side) gives an average capacity factor of 25 percent, while recent estimates compiled by NREL range from 20 to 28 percent.
Solar Kettle allows for boiling water off the grid
Phys.org) —A company called Contemporary Energy has unveiled a new
device it calls the Solar Kettle. It looks very much like a normal
coffee thermos, but has flaps on one side that open to allow for
collecting solar energy, thus heating whatever is held inside. The
company will be marketing the device to campers and others that need a
way to boil water when electricity is not available.
The Solar Kettle looks very much like a normal thermos when
not in use, though it's heavier—2.6 pounds when empty, compared to about
a half pound for a normal thermos. It looks markedly different however
when heating a liquid. The flaps open and direct the sun's energy to the
vacuum sealed thermos. The device comes with a stand as well to allow
for unattended heating. It typically takes about two hours to heat cold water
to boiling. The Kettle can also be used to brew tea, melt snow or to
boil water to make it safe to drink. And if the need arises, it can even
be used to desalinate seawater.
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Devices that can make tainted water safe to drink have become increasingly popular as world health authorities
have spread the word about the risks posed to people around the world
who don't have access to clean drinking water. While the Solar Kettle is
not directed towards such end users, it's clear it could very easily be
used for that purpose. The device holds 17 ounces of liquid, which is
enough to make three cups of tea. That means it's capable of providing
enough safe drinking water for one person, indefinitely. Of course that
only applies on days when the sun is shining.
Reps for the new device point out that their Solar Kettle can also be used to heat soup, or even to boil eggs.
That makes it ideal, they say, for hikers, campers or anyone else who
wants to boil water without going to the trouble of setting up a
campfire. They note also that the exterior of the device remains cool to
the touch during heating, preventing users from getting burned—and
because it's heavily insulated, water once heated, will remain that way
for several hours.
Executives at companies that inspect Chinese factories on behalf of
developers and financiers said that over the last 18 months they have
found that even the most reputable companies are substituting cheaper,
untested materials. Other brand-name manufacturers, they said, have shut
down production lines and subcontracted the assembly of modules to
smaller makers.
“We have inspectors in a lot of factories, and it’s not rare to see some
big brands being produced in those smaller workshops where they have no
control over quality,” said Thibaut Lemoine, general manager of STS Certified,
a French-owned testing service. When STS evaluated 215,000 photovoltaic
modules at its Shanghai laboratory in 2011 and 2012, it found the
defect rate had jumped from 7.8 percent to 13 percent.
In one case, an entire batch of modules from one brand-name manufacturer
listed on the New York Stock Exchange proved defective, Mr. Lemoine
said. He declined to identify the manufacturer, citing confidentiality
agreements.
“Based on our testing, some manufacturers are absolutely swapping in
cheap Chinese materials to save money,” Jenya Meydbray, chief executive
of PV Evolution Labs, a Berkeley, Calif., testing service.
SolarBuyer, a
company based in Marlborough, Mass., discovered defect rates of 5.5
percent to 22 percent during audits of 50 Chinese factories over the
last 18 months, said Ian Gregory, the company’s senior marketing
director.
Some Chinese manufacturers acknowledge that quality has become a problem
“There are a lot of shortcuts being taken, and unfortunately it’s by
some of the more reputable companies and there’s also been lot of new
companies starting up in recent years without the same standards we’ve
had at Suntech,” said Stuart Wenham, the chief technology officer of
Suntech, which is based in Jiangsu Province in eastern China.
When asked about quality standards, Trina Solar,
one of the largest Chinese manufacturers, said in an e-mailed response,
“For Trina, quality will not be compromised in our cost-reduction
efforts.”
The heart of a solar panel is a photovoltaic cell that generates
electricity when struck by sunlight. Among the most critical components
are a thin film that protects the cell from moisture, and the
encapsulant that seals the cell between layers of glass.
Mr. Gregory said repeat inspections of factories found some
manufacturers had been constantly switching to cheaper materials,
including some whose use-by date had expired.
“If the materials aren’t good or haven’t been thoroughly tested, they
won’t stick together and the solar module will eventually fall apart in
the field,” he said.
That’s what happened in 2011 at a year-old Australian solar plant, Mr.
Meydbray of PV Evolution said. Testing confirmed that substandard
materials were causing the Chinese-made modules’ protective coating to
degrade, he said. The power plant operator declined to be identified.
“I think quality is increasingly a concern, but it’s not a major issue yet,” said Rhone Resch, chief executive of the Solar Energy Industries Association, a trade group. “As companies race to cut their costs, some who are on the edge may take short cuts.”
The Energy Department’s National Renewable Energy Laboratory
has studied the performance of solar panels up to 2010, according to
Sarah Kurtz, a scientist who manages the laboratory’s photovoltaic
reliability group.
“The question is whether things are deteriorating rapidly or whether
it’s a few isolated companies not doing so well on their quality
control,” she said. “I hear a lot of angst, but I haven’t seen a lot of
solid information.”
All solar panels degrade and gradually generate less electricity over
time. But a review of 30,000 installations in Europe by the German solar
monitoring firm Meteocontrol found 80 percent were underperforming. Testing of six manufacturers’ solar panels at two Spanish power plants by Enertis Solar in 2010 found defect rates as high as 34.5 percent.
Enfinity
operates solar installations in Europe and the United States. Bob
Hopper, Enfinity’s chief development officer, said his company had
stopped buying Chinese modules because of quality concerns. “Even a
small amount of unforecasted degradation in electricity production can
have significant economic impact on us,” he said.
Other solar developers and installers said they had not experienced quality problems.
“The systems we installed in 2012 had the best performing year yet,” said Lyndon Rive, chief executive of SolarCity, the largest residential solar installer in the United States and a buyer of panels from China’s Yingli Solar and Trina.
Non-Chinese manufacturers have had quality problems as well. The
defective panels installed on the Los Angeles area warehouse, for
instance, were made by an American manufacturer. A reporter was granted
access to the project on the condition that the parties’ identities not
be disclosed because of a confidential legal settlement.
First Solar, one of the United States’ biggest manufacturers, has set aside $271.2 million to cover the costs of replacing defective modules it made in 2008 and 2009.
Nor are all solar developers shunning Chinese manufacturers. The United
States subsidiary of Yingli, the world’s largest solar panel maker since
2012, won a contract last year to supply solar panels for a California
power plant.
“The one thing I can tell you is that Yingli does not cut corners,” said
Brian Grenko, vice president for operations at Yingli Americas, adding
that only 15 defective modules had been returned to the company out of
2.8 million shipped to the United States since 2009.
Still, Yingli executives acknowledge that quality has become a competitive issue.
