Sandia researchers have developed a new system to monitor how clouds affect large-scale solar photovoltaic (PV) power plants. By observing cloud shape, size, and movement, the system provides a way for utility companies to predict and prepare for fluctuations in power output due to changes in weather. The resulting models will provide utility companies with valuable data to assess potential power plant locations, ramp rates, and power output.
WARD BOWER (6364) is part of a Sandia team that is studying the effects of cloud cover on large photovoltaic installations on the island of Lana’i in the Hawaiian Islands. Here, he checks out a field of PV collectors on the sparsely populated 141-square-mile island.
Sandia researchers’ work is currently focused on the 1.2-megawatt La Ola Solar Farm on the Hawaiian island of Lana’i. La Ola is the state’s largest solar power system, and can produce enough power to supply up to 30 percent of the peak electric demand, one of the highest rates of PV power penetration in the world. Understanding variability of such a large plant is critical to ensuring that power output is reliable and that output ramp rates remain manageable.
“As solar power continues to develop and take up a large percentage of grids nationwide, being able to forecast power production is going to become more and more critical,” says Chris Lovvorn, director of alternative energy of Castle & Cooke Resorts, LLC, a Los Angeles-based food and real estate development company that owns 98 percent of the 141-square-mile island. “Sandia’s involvement and insight have been invaluable in our efforts to meet 100 percent of the island’s energy needs with renewable resources.”
The effects of clouds on small PV arrays are well-documented, but there is little research on how large-scale arrays interact and function under cloud cover. A small system can be completely covered by a cloud, which drastically reduces its power output, but what’s less well understood is what happens when only part of a large system is covered by a moving cloud shadow, while the rest stays in sunlight.
“Our goal is to get to the point where we can predict what’s going to happen at larger-scale plants as they go toward hundreds of megawatts. To do that, you need the data, and the opportunity was available at La Ola,” Sandian Scott Kuszmaul (6352) says.
The high penetration of PV power on Lana’i, combined with the sun and cloud mix at the 10-acre La Ola plant, provides an optimal environment for prediction and modeling research. Research could not interfere with the ongoing operations of the plant, which currently sells power to Maui Electric Company (MECO), so Sandia engineers connected 24 small, nonintrusive sensors to the plant’s PV panels and used a radio-frequency network to transmit data. The sensors took readings at one-second intervals to provide researchers with unprecedented detail about cloud direction and coverage activity.
A radio-frequency transmission system has the added benefit of being portable. “Currently, a utility company that wants to build a large solar PV power plant might have a lot of questions about the plant’s output and variability at a proposed site. Work being done at the La Ola plant is leading to new methods that eventually can be used to answer these questions,” says Josh Stein (6352). “These techniques will allow a developer to place a sensor network at a proposed site, make measurements for a period of time, and use that to predict plant output variability.”
La Ola was commissioned in December 2008 by Castle & Cooke and SunPower Corp., a manufacturer of high-efficiency solar cells. The project uses SunPower’s Tracker technology. Panels rotate on a single axis to follow the sun, which increases energy capture by up to 25 percent. Since February, Sandia has held a cooperative research and development agreement (CRADA) with SunPower to conduct research on integrating large-scale PV systems into the grid. The CRADA is funded with about $1 million of combined DOE and SunPower funding and is expected to achieve significant results, which will be disseminated through joint publications over the next two years.For more information about Sandia’s photovoltaic work, visit www.sandia.gov/pv. -- Stephanie Hobby
By Patti Koning
When John Goldsmith (8131) looks back on his 30-year career at Sandia, he’s incredibly proud of his work on a Raman lidar (light detection and ranging) system that has been deployed and operating continuously at the Atmospheric Radiation Measurement (ARM) program’s Oklahoma site for the past 15 years. This year, he’s had the chance to recreate that project.
BEEN THERE, DONE THAT — John Goldsmith aligning the optics in the Oklahoma Raman lidar in 1996 (left) and the Darwin, Australia, Raman lidar in 2010 (right).
“The Raman lidar system was one of the most satisfying projects of my career,” he says. “Nothing else I’ve worked on has had this kind of lasting impact on something as important as climate change. So the chance to build a second system was really exciting.”
Raman lidar is an active, laser remote-sensing instrument used to measure atmospheric water vapor, a measurement important in studying climate change, as well as temperature, clouds, and aerosol particles. The instrument identifies water vapor by pulsing laser light for billionths of a second, then recording the light scattered back, some of it slightly shifted in wavelength by the molecules of water and nitrogen in the atmosphere.
The raw data is analyzed by automated value-added procedures (VAPs) developed by the ARM program and then made available to scientists across the globe. By comparing the ratio of the water vapor signal to the nitrogen signal, the software is able to strip away variables that would otherwise make the data difficult to interpret.
This data is critical to creating accurate general circulation models for climate study. “Climate scientists need good atmospheric data to initialize and validate these complex computer codes,” John says. “The amount of water vapor in the atmosphere and its distribution in terms of space and time is crucial. Much of the dynamics of climate is related to interactions with water in the form of vapor and clouds.”
Lidar system launched
The original Raman lidar system was launched in 1995, early in Sandia’s involvement in DOE’s ARM program, and was expected to operate for 10 years. The system is entering its 16th year of operation, running over 90 percent of the time with very little operator attention. In fact, John says, the most significant maintenance task is cleaning the window.
With the success of the original system, there has been significant interest in updating and expanding the capabilities of the Tropical Western Pacific ARM Climate Research User Facility (ACRF) in Darwin, Australia. Recently, the DOE Office of Science allocated funds to Sandia for the capital upgrade of ACRF data collection sites in Oklahoma and Alaska. Sandia also was asked to add Raman lidar to the suite of instruments at the Darwin site (Lab News, Aug. 28, 2009).
John describes the system as a “laser lab in a box,” housed in a standard shipping container with a window at the top for the laser beam to exit and a telescope and associated optics to measure backscatter radiation. The new system is essentially a carbon copy of the current Oklahoma system, including the many upgrades and improvements that were made over the past 16 years.
“When I was told we needed to get this instrument built and operational in Darwin by the end of this year, I knew it would be a challenge,” says John. Fortunately, he was able to work with many of the same players that contributed to the original Raman lidar system.
Sixteen years ago, Orca Photonics Systems Inc., a small company in Redmond, Wash., built the shipping container laboratory. “The company is still there, even the same guys who built the original container,” John says. “They are scientists and they know lidar. They understood exactly what I needed, sometimes better than I did.”
For the Darwin system, Orca separated the equipment into two shipping enclosures, one for the lidar and the other for the utilities. The new laser came from the same company, Continuum of Santa Clara, Calif., that supplied the Oklahoma system. For the electronics, John went to Berlin-based Licel GmbH, which he used for an upgrade of the Oklahoma system about eight years ago.
He also credits Lupe Martinez (8514) and others in the project engineering and facilities departments with keeping the project on track. “They’ve done a tremendous job supporting this project from start to finish,” he says. “Getting the right kind of power to run the system while it was here on site was tricky, since Australia runs on 415 volts/50 hertz.”
Australia presented a few other challenges. In Oklahoma, the sun is always to the south and thus never directly overhead. Darwin is located in Australia’s Northern Territory and sits north of the Tropic of Capricorn, so at certain times of the year the sun is directly overhead.
“If the telescope points directly at the sun, the collected sunlight will do a great deal of damage,” says John. “We had to develop a protection system to ensure that the telescope is always covered unless actively opened.” A sliding hatch covers the window on top of the container and a second shade is gravity loaded so that it will close automatically if power is lost.
In terms of risks, John says he’s most worried about the laser arriving safely in Darwin. It left on Sept. 13 on what he describes as “the slow boat to Australia” and will arrive in mid-November. “If you’ve been to a port and seen shipping containers, you know it’s not done in the gentlest fashion,” he explains. “So we put a lot of thought into packing the system to withstanding bumps and bangs.”
When the system arrives in Darwin, John plans to be the first one to open the container. If all the equipment makes it safely, he’ll only have to worry about the saltwater (estuarine) crocodiles commonplace at Kakadu National Park, about 100 miles from Darwin. Not coincidentally, that’s where the Crocodile Dundee movies were filmed. -- Patti Koning
By Iris AboytesAnthony Medina (2500) and Angel Urbina (1544) will receive Hispanic Engineer National Achievements Awards Corp. (HENAAC) awards on Oct. 8 in ceremonies held at the annual HENAAC Awards conference at Disney’s Coronado Springs Resort in Lake Buena Vista, Fla. Anthony is this year’s Luminary Award winner and Angel will receive the Most Promising Engineer/Scientist, Graduate Degree Award.
HENAAC is a nonprofit organization promoting careers in science, technology, engineering, and mathematics (STEM).
Anthony began his career in 1983 as a member of the technical staff in the Firing Sets Department, where he was codeveloper of a novel electronic safing, arming, and firing technology adopted by DoD for conventional weapons. He spent 17 years in Sandia’s Monitoring Systems & Technology Center 5700 as a manager, senior manager, and director. Anthony was instrumental in the research, development, production, and launch of more than 50 satellite sensor payloads and one Sandia-produced satellite.
Currently Anthony is the director of Energetic Component Realization Center 2500, where he manages the research, development, design, and production of critical nuclear weapon components. The center also leads metrology science for the entire nuclear weapons complex.
“It is a great honor to receive this recognition from HENAAC,” Anthony says. “I owe much of my success to Sandia for giving me the opportunity to work on interesting, important, and rewarding programs throughout my career.”
Anthony grew up in Taos, N.M., but spent much of his time working on his family’s cattle ranch in Black Lake, six miles south of Angel Fire. Ranch life meant hard physical work and long days.
Anthony’s parents, Felipe and Anita, stressed the importance of education first. Each of them was the first child in their respective families to receive a college education. Anthony and his five siblings all earned college degrees.
Anthony received his Bachelor of Science in electrical engineering from New Mexico State University, and his Master of Science in electrical engineering from Stanford University through Sandia’s One Year on Campus program.
Angel has spent 12 years at Sandia developing methods for modeling physical phenomena using various modeling approaches, such as artificial neural networks and nonphenomenological models. He has developed and implemented methodology for uncertainty quantification and model validation of complex systems.
”I am honored to be recognized by this prestigious HENAAC award,” Angel says. “It is truly a team award and is shared by all who have been my inspiration and support.
Born in El Paso, Texas, Angel was raised by his mother, Rosa, his grandmother Ana, and grandfather Angel. Angel describes his family as having very humble beginnings but a hard-working nature. Angel’s grandfather assumed the role of a father figure for him. “My ‘father’ always spoke calmly, never raised his voice, but always commanded respect,” says Angel. “He taught me by example.”
Ana is the pillar of strength and the driving force behind Angel’s education. Raised in a family of 11 and living in poverty, Ana’s strong personality was necessary for survival as she strived for a better life. She believed that education and perseverance were the only ways to reach greatness.
With the help of Sandia, Angel recently received his doctorate. His 85-year-old grandmother was present to witness his PhD ceremony. “Her belief in the power of education to change lives and her trips to my high school teachers so long ago paid off,” Angel says.
Both honorees are involved in helping students. Anthony works with the NMSU Alliance for Minority Participation to help recruit minority students into pursuing a technical education. Anthony has also hosted a Hispanic Roundtable Forum for new hires and serves as Sandia’s campus executive to NMSU.
Angel is involved in teaching schoolchildren the joys of math and science through his participation in the New Mexico MESA Program (Math, Engineering and Science Achievement) and Sandia’s MANOS program. This year Angel added a new module to the program, earthquake engineering. He hopes it becomes a standing module for the next 10 years. - Iris Aboytes