ALBUQUERQUE, N.M. – Engineers at Sandia National Laboratories, along
with partner institutions Georgia Tech, Bucknell University, King Saud
University and the German Aerospace Center (DLR), are using a falling
particle receiver to more efficiently convert the sun’s energy to
electricity in large-scale, concentrating solar power plants.
Falling particle receiver technology is attractive because it can
cost-effectively capture and store heat at higher temperatures without
breaking down, which is an issue for conventional molten salts. The
falling particle receiver developed at Sandia drops sand-like ceramic
particles through a beam of concentrated sunlight, and captures and
stores the heated particles in an insulated container below. The
technique enables operating temperatures of nearly 1,000 degrees
Celsius. Such high temperatures translate into greater availability of
energy and cheaper storage costs because at higher temperatures, less
heat-transfer material is needed.
Central receiver systems use mirrors to concentrate sunlight on a
target, typically a fluid, to generate heat, which powers a turbine and
generator to produce electricity. Currently, such systems offer about 40
percent thermal-to-electric efficiency. The falling particle receiver
enables higher temperatures and can work with higher-temperature power
cycles that can achieve efficiencies of 50 percent or more.
“Our goal is to develop a prototype falling particle receiver to
demonstrate the potential for greater than 90 percent thermal
efficiency, achieve particle temperatures of at least 700 degrees
Celsius, and be cost competitive,” said the project’s principal
investigator, Sandia engineer Cliff Ho. “The combination of these
factors would dramatically improve the system performance and lower the
cost of energy storage for large-scale electricity production.”
The project is funded up to $4 million by the Department of Energy’s SunShot Initiative,
which aims to drive down solar energy production costs and pave the way
to widespread use of concentrating solar power and photovoltaics.
Sandia Concentrating Solar Power at SolarPACES Conference – Cliff Ho, principal investigator of the Falling Particle Receiver project, will be available to discuss his work at the 2013 SolarPACES conference in Las Vegas on Tuesday, Sept. 17-Friday, Sept. 20. Ho recently earned a R&D 100 Award for his Solar Glare Hazard Analysis Tool.
Several Sandia researchers, including Chuck Andraka (large-scale
optical metrology and modeling) and David Gill (thermal energy storage)
will also be available to discuss other Sandia innovations in concentrating solar power and ongoing work at the newly renovated National Solar Thermal Test Facility (NSTTF). Members of the media who desire interviews should contact Stephanie Holinka, slholin@sandia.gov or 505-284-9227.
Falling particle receiver technology was originally studied in the
1980s, and Sandia researchers are working to address challenges that
hindered greater acceptance of the concept. Among the issues are
mitigating particle loss, maintaining the stability of falling
particles, increasing the residence time of the particles in the
concentrated beam and reducing heat losses within the receiver cavity.
Ho and his colleagues at Sandia have been working to address these
issues by studying the effect of an added air curtain, created by a
series of blower nozzles, to help particles fall in a stable pattern and
reduce convective losses. Adjusting the particle size and how sand is
dropped has also helped, ensuring more of the sand gets heated in a pass
and makes it to the collection bin at the bottom. Researchers are also
investigating the benefits of using an elevator to recirculate particles
through the aperture a second time to increase their temperature.
“Given our unique facilities at the National Solar Thermal Test Facility,
we have the capability of developing prototype hardware and testing the
concepts we’ve simulated, which include innovations such as air
recirculation and particle recirculation. Advanced computing lets us do
complex simulations of the falling particle receiver to understand the
critical processes and behavior,” Ho said. “We’re very encouraged by our
progress and look forward to further developing this enabling
technology.”
Falling particle receiver technology is expected to lead to
power-tower systems capable of generating up to 100 megawatts of
electricity. The project is in its first of three years, and a
test-ready design is expected in 2015.
Sandia National Laboratories is a multi-program laboratory operated
by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin
company, for the U.S. Department of Energy’s National Nuclear Security
Administration. With main facilities in Albuquerque, N.M., and
Livermore, Calif., Sandia has major R&D responsibilities in national
security, energy and environmental technologies and economic
competitiveness.
http://cleantechnica.com/2013/09/20/sandia-harnessing-solar-energy-tiny-particles/
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