NREL is the biggest US success story since the solar cell was invented by
Bell Labs in 1954.
http://www.nrel.gov/continuum/leading_solar.cfm
Spring 2011 | Issue 1, Vol. 1
Leading Solar Expertise-A Launch Pad to the Future - Spring 2011 | Issue 1,
Vol. 1
NREL is speeding solar devices from the lab to utility-scale operation.
Before a rocket blasts off into the atmosphere, the stratosphere, and
eventually to orbit and payload stage, it must first be earthbound,
supported within a strong framework, and perched on a rock-solid foundation.
When it comes to solar research, NREL's trajectory has had the benefit of a
solid foundation in fundamental science and has followed a successful
"flight plan"-a well-tuned strategy. Consequently, the lab has entered its
own "payload stage" in commercialization and deployment of solar
technologies.
The solar industry provides tens of thousands of jobs across the country
and is projected to grow for years to come.
NREL's 30-year history and unique leadership make it especially suited to
lead the effort in speeding solar devices from the lab to utility-scale
operation.
Since its inception in 1977, NREL has focused on increasing solar
efficiency, reducing the costs of producing those technologies, and helping
to bring them to market. NREL's successes in the solar realm are legion-from
the dozens of times it has broken the record for solar efficiencies, to a
host of patents and licenses on solar devices, to hundreds of U.S. companies
that have collaborated with the lab and adopted the resulting technological
breakthroughs.
Another stellar achievement is the number of R&D 100 Awards that the NREL
solar research teams have garnered-21 since 1984 (see sidebar). The awards
are given out by R&D Magazine and identify each technology as one of the top
100 technological innovations of the award year.
These accomplishments are the direct results of a strategy that NREL is
using to bring about the vision of creating a national, sustainable energy
system by 2050 that is carbon-neutral, highly efficient, affordable,
reliable, and that supports high-value domestic jobs. At the utility-scale
level, the laboratory has made great progress in two solar technology areas:
photovoltaics (PV) and concentrating solar power (CSP).
Photovoltaics
The first viable PV cells were developed in 1954 by Bell Laboratories. In
the 1970s the global oil crisis demonstrated the need for alternative
energy. It was then that the Solar Energy Research Institute (which later
became NREL) began managing many research subcontracts involving crystalline
silicon materials. The contracts were for R&D that successfully reduced the
amount of silicon required in PV devices, and hence their cost. These
activities played an instrumental role in helping the solar silicon industry
evolve and led to NREL's leadership in solar cell research.
Since 1996, PV research has been performed at the National Center for
Photovoltaics (NCPV), which is based at NREL and funded by the U.S.
Department of Energy (DOE). The NCPV is charged with accelerating PV as a
viable energy option in the United States. It focuses on innovations in PV
technology that drive industry growth in U.S. PV manufacturing. DOE has
directed the center to use the resources and capabilities of the national
labs and universities to serve the U.S. PV industry. The NCPV enhances
communication and catalyzes strategic partnerships between these entities
and also functions as a source for knowledge and research facilities within
the DOE system.
Bob Hawsey, NREL Associate Lab Director for Renewable Electricity and End
Use Systems, recognizes NREL's unique leadership contributions, "The NCPV is
truly without peer when it comes to PV research and development and is
currently the envy of the wider international PV community," he says. "We
are most recognized for tremendous basic science and technology research
that is enabling photovoltaic systems to make a real difference in the
everyday lives of citizens of our nation, and around the world."
Within the PV research sphere, NREL has concentrated on two areas: thin-film
and high-efficiency solar cells.
Thin-Film Solar Cells
Enlarge image
Before the turn of the century, NREL worked on some of the world's first
solar power towers-Solar One and Solar Two, shown here.
Thin-film solar cells use less than 1% of the raw material of silicon
wafer-based solar cells, leading to significant cost advantages. These cells
can also be applied to flexible materials such as metal foil or even plastic
film, expanding their use.
Thin-film research at NREL gained notice in 1980 by scientists worldwide
when efficiencies passed 10%. NREL collaborated with Boeing in 1984 for the
first solar cell to pass 10% efficiency, using films thinner than a human
hair. The cell was made from copper indium diselenide (CIS). In the early
1990s, the group worked with Golden Photon to create the first large-area
device made from cadmium telluride (CdTe).
NREL made rapid progress in 1994 by surpassing 15% efficiency and then
reaching 17.7% in 1996 for copper indium gallium diselenide (CIGS). One of
the more popular thin-film solar cells to be developed with NREL
participation in the last 30 years is the Uni-Solar triple-junction
amorphous-silicon solar module, which resembles a traditional roof shingle.
In 2003, NREL co-developed, with First Solar, a new method for producing
CdTe modules. In 2004, NREL joined with Global Solar to develop a new
lightweight, flexible, CIGS module. For 16 years, NREL held the world record
for conversion efficiency. Today, CIGS cell efficiencies at NREL are at 20%.
High-Efficiency Solar Cells
In the late 1980s, NREL experimented with a new type of solar cell made by
using multiple solar cell junctions of differing materials: gallium indium
phosphide and gallium arsenide. The resulting "tandem" solar cell led to
record efficiencies. The technology was licensed for space applications in
the early 1990s to Spectrolab and EMCORE corporations and has since become
the industry standard for powering Earth-orbiting satellites.
The technology came back to earth quickly, however, when NREL stimulated
interest in high-efficiency solar cells. In 2002, the lab organized the
first international conference on solar concentrators using high-efficiency
solar cells. Solar concentrators use lenses or mirrors to concentrate the
sun's energy several hundred times, increasing the electricity generated by
super-efficient solar cells by the same factor.
In May 2005, NREL announced that it had confirmed a new solar cell record
efficiency of 37.9%. A month later, Spectrolab, Inc., the lab's industry
research partner, announced an even higher record with a 39%-efficient cell.
NREL built on that success in a partnership with Amonix to develop the
Amonix 7700 Solar Power Generator, which uses Fresnel lenses to focus the
sun's rays onto ultrahigh-efficiency solar cells. This bulk power generator
produces 40% more energy than conventional fixed PV panels and is
well-matched to utility-scale solar energy projects, especially in dry,
sunny climates. In 2010, NREL and Amonix received an R&D 100 Award for this
technology.
According to the Solar Energy Industries Association, as of January 2011 a
total of 2.1 GW of PV capacity was installed in the United States with more
than 16 GW under construction or in the development stage.
The DOE Solar Program recently announced the SunShot Initiative (see
sidebar), which is dedicated to expanding the market for solar technologies
by helping solar energy reach cost parity with other baseload electricity
generation sources across the United States
Concentrating Solar Power
Enlarge image
The Amonix 7700 Solar Power Generator is an example of a concentrating PV
system that is well-matched to utility-scale projects. Thirteen of these
generators have been installed at the Solar Technology Acceleration Center
in Aurora, Colorado.
CSP systems produce electricity by using mirrors to concentrate the sun's
energy to heat a working fluid to drive conventional turbines that convert
heat to electricity. By using thermal storage, such as molten salt, or by
supplementing the solar plant with natural gas, CSP systems can deliver
electricity when utilities need it most, which is typically at times of high
demand in late afternoon or early evening. This "dispatchability" adds
significantly to the value of power delivered by utility-scale solar power
plants.
NREL's roots in CSP go back to the 1970s with the development of the
High-Flux Solar Furnace. Since the early 1990s, NREL has added many more CSP
research capabilities, including laboratories dedicated to optical materials
and thermal storage. These capabilities have allowed NREL to make solid
gains in developing CSP technology for utility-scale use, including
scientific advances in materials and processes used in parabolic trough
systems and power towers.
Parabolic Trough Systems
A parabolic trough system consists of arrays of parabolic mirrors that
collect heat from the sun and focus it on receiver tubes that contain a
heat-transfer fluid. The hot fluid is sent through a series of heat
exchangers, which release the heat to generate high pressure steam. That
steam is then fed to steam turbines that generate electricity.
In the mid-1980s to early 1990s, nine commercial parabolic trough power
plants were constructed at three locations in the Mojave Desert in
California for a combined capacity of 354 MW-and they are still operating
today. In an effort to make parabolic trough plants cost-effective in
southwest markets and without incentives, NREL established the USA Trough
Initiative, a partnership with U.S. industry. The effort helped expand U.S.
industry involvement and competitiveness in worldwide trough development
activities and helped advance U.S. knowledge of this technology.
Today, NREL uses state-of-the-art facilities to characterize collectors and
receivers. The laboratory's work in this area falls primarily within the
following: determining optical efficiency, measuring heat loss, developing
and testing concentrators, and advancing optical characterization. NREL also
enables the CSP industry by developing and testing advanced mirrors and
receiver tube coatings.
One such effort involved collaboration with SkyFuel, Inc., a small company
headquartered in Arvada, Colorado, and earned an R&D 100 Award for the
SkyTrough parabolic trough. The result of more than a dozen years of
collaboration, SkyTrough is unique in that its mirrors are made of
lightweight aluminum sheets covered with ReflecTech mirror film, the
component that NREL helped develop. Lighter and less expensive to
manufacture than glass mirrors, ReflecTech is also much easier to transport
and install, and less prone to break.
These types of scientific advances at NREL have helped bring about
reductions in operation, maintenance, and system costs, which in turn have
led to a significant decrease in the cost of parabolic trough-generated
electricity. The costs have fallen from more than $ 0.28 per kilowatt-hour
(kWh) in the 1980s (in 2009 dollars) to costs approaching $ 0.18/kWh today,
which is approaching current costs in intermediate load markets.
Power Towers
R&D 100 Awards for NREL Solar Program Technologies
1984 - CIS Solar Cell
1991 - Tandem Solar Cell
1991 - CdTe Solar Cell
1992 - Solar Detoxification of Contaminated Groundwater
1993 - Silicon Defect Mapping System
1994 - Transpired Solar Collector
1997 - PV Optics Software
1998 - Solar Roof Shingle
1999 - CIS Solar Module
2001 - Triple-Junction Solar Cell
2002 - PowerViewT Module Smart Glass
2003 - High-Rate Module Process
2004 - Flexible CIGS Module
2005 - Sinton Silicon Evaluation System
2007 - HEMM Concentrator Solar Cell
2008 - IMM Solar Cell
Hybrid CIGS
2009 - SkyTroughT Parabolic Trough
Ultra-Accelerated Weathering System
2010 - Black Silicon Wet-Chemical Etch
Amonix 7700 Solar Power Generator
See a complete list of NREL's R&D 100 Awards.
A power tower system uses a large field of flat, sun-tracking mirrors called
heliostats to focus and concentrate sunlight onto a receiver on the top of a
tower. The receiver contains heat-transfer fluid that becomes hot enough to
convert water into steam, which is then used in a conventional turbine
generator to produce electricity.
In the 1980s and early 1990s, NREL worked with Sandia National Laboratories
on some of the world's first solar power towers-Solar One and Solar Two.
Solar One used water/steam as the heat-transfer fluid. The plant was later
converted into Solar Two, which used molten nitrate salt because of its
superior heat-transfer and energy-storage capabilities.
Today, NREL continues to improve power tower technology by supporting the
U.S. industry with the development of advanced system performance models,
conducting research on advanced thermal energy storage materials and design
concepts, and investigating advanced high-temperature thermodynamic cycles.
NREL is also researching ways to improve the thermal characteristics of
currently available storage materials and developing and characterizing
advanced nanofluids and phase-change materials for future thermal storage
applications.
A Proven, Working Technology
According to the Solar Energy Industries Association, as of February 2011,
508 MW of CSP utility-scale projects were operating in the United States,
399 MW were under construction, and 9,146 MW were under development, for a
total of more than 10 GW.
For more information on this technology, view the CSP 101 video on the DOE
website.
Rock-Solid Launch Pad + Well-Aimed Flight Plan = Direct Hit
Using tools such as cooperative research and development agreements,
licensing, and technology partnerships, NREL has helped stimulate the market
for solar technologies and assisted the growth of solar start-ups, such as
Abound Solar, Amonix, First Solar, Global Solar, and SkyFuel.
Companies such as these exist across the country and create jobs as they
grow. The National Solar Jobs Census was compiled in August 2010 by The
Solar Foundation (a nonprofit organization), Green LMI Consulting, Cornell
University, and others. The census identified 93,502 solar workers in the
United States, roughly double the number estimated for 2009. In addition,
employers from all of the studied subsectors expected significant employment
growth well into 2011.
A 30-year history of excellence in solar R&D and a well-honed strategy have
combined to make NREL the pre-eminent laboratory to lead solar technologies
to the utility-scale level. In this way, NREL is enabling solar energy to
help protect the environment, achieve U.S. energy security, reduce petroleum
dependence, create new jobs, and boost the nation's economy.
Learn more about solar energy research at NREL.
Shooting for the Sun
When Energy Secretary Steven Chu announced the SunShot Initiative on
February 15, 2011, it harkened back to President Kennedy's famous "moon
shot" speech delivered to Congress on May 25, 1961. The goals Kennedy
outlined set the United States on a path to regain the lead in the space
race and land an American safely on the moon by the end of that decade.
Similarly, the goal of SunShot is to restore America's once-dominant
position in the global market for solar photovoltaics (PV) and concentrating
solar power (CSP).
Analysis from NREL indicates that at an installed cost for utility-scale
solar electricity of roughly 6 cents per kilowatt hour without subsidies,
solar energy would reach cost parity with other baseload electricity
generation sources across the United States. At this level, rapid,
large-scale adoption of solar electricity across the United States would be
possible.
Dana Christensen, NREL's deputy director for science and technology, calls
it a "Herculean challenge" to bring solar energy to the marketplace at grid
parity, but one that would pay enormous dividends. "The organization, the
country that makes it happen first is going to control the market. This is a
big jobs opportunity. It's a technology opportunity that is truly leveraging
what is really good about our country-and that's innovating things into the
marketplace quickly," he said.
The goals of the initiative underscore solar energy's benefits to the United
States and will have multiple benefits for the country: reaching cost parity
with baseload energy rates, increasing solar PV market share, boosting dom
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