The University of Arizona Alumnus / Winter 2009
Deep in the Heart of Solar
by Dan HuffJacob Chinn photos
Sometimes I feel like doing astronomy these days is almost like playing in the band on the Titanic. Beautiful music, but you know…,” Roger Angel’s voice trails off in what appears to be a moment of dark contemplation.
A University of Arizona Regents’ Professor of astronomy, one of the world’s foremost designers of space- and earth-based telescopes, and the recipient of a prestigious MacArthur “genius grant,” Angel is explaining why, several years ago, he suddenly switched his focus from the stars to the problem of global warming.
His wife, Ellinor, asked if he could do something about what they both consider to be a major environmental threat, and Angel had an epiphany of sorts. First, he looked at the idea of cooling the planet with sunshades orbiting the sun so as to shadow the Earth. Then he realized it would be more practical to capture light from our sun to make carbon-free electrical energy. He could take his decades of experience designing and building unique steel structures, motor drives, and advanced optics, and put them to use to capture the faintest sunlight.
The design Angel eventually settled on uses mirrors to concentrate sunshine onto clusters of germanium cells that transform light directly into electricity in a pollution-free photovoltaic process (PV). Angel wants to do this on such a large scale that PV plants in Arizona could power much of the United States.
He’s far from being a lone dreamer. Arizona Rising Enthusiasm for Arizona solar power is also found at the Arizona Research Institute for Solar Energy (AzRISE). The UA-based institute promotes development of various forms of solar technology, including PV, and works with all three state universities.
“Most people who’ve done economic analyses talk about solar being about equivalent in cost to other sources of electricity by 2012 to 2015,” says Joseph
Simmons, AzRISE co-director and head of the UA materials science department. Personally, I expect it to happen by 2011 or even 2010. Human ingenuity is incredible, and since people have already determined solar to be a major player in the future of electricity, new things have developed. It’s truly amazing.”
Simmons and his AzRISE associates are so confident of Arizona’s role in a solar-powered future that the institute’s co-director, Ardeth Barnhart, organized a major economic summit on the subject, held in January 2009, in Phoenix. The pow-wow featured thinkers from the state’s three universities and outlined precise steps Arizona government and business officials could take to dominate this rising national industry.
The Arizona Board of Regents and private entities funded AzRISE to the tune of $1.2 million during its start-up in 2007. A healthy chunk of that money already has been awarded to 14 of the state’s academic researchers, including Angel, who says that in the coming year he will begin field-testing concepts that could lead to the massive PV facility he envisions.
Arizona Powers America
Angel estimates that a generating plant covering roughly 10,000 square miles — 100-by-100 miles — of Arizona desert could produce enough energy to replace the coal, oil, and natural gas systems now yielding roughly 450 million kilowatts of generating capacity. By some estimates, the U.S. consumes one terawatt of electricity — or one billion kilowatts — each year. Arizona could produce nearly half of the power the U.S. needs per year.
(A project of that size is not inconceivable — Arizona, the nation’s sixth-largest state, covers 114,006 square miles, with only 364 of those square miles under water.)
The cost for such a plant, Angel estimates, would be about $1 trillion.
For that investment, America would be getting a system based on existing PV chips, plus engineering and materials. Angel would concentrate sunlight on PV chips, attach chip clusters to a heat-dissipating ceramic base, and hit those clusters with sunlight focused by a UA-designed mirror. The dish-like, motor-driven mirror-and-chip assembly would be secured in lightweight steel supports and computer-directed to aim at the sun.
If the solar chip’s efficiency could be increased from 36 percent to 50 percent — a real possibility in the coming years, Angel says — the profit margin for this type of installation would go up dramatically.
Imagine millions of Angel’s solar units gleaming under the vast Arizona sky as you cruise for more than an hour through the PV-generating facility in your hybrid-electric car, and you might have a good picture of America’s renewable energy future.
The trick has been to balance all aspects of the design to come up with the cheapest possible device with the maximum bang for the buck. “It’s really more of a problem of the cost of glass and steel than the photovoltaics,” Angel says. But then, that’s always been the underlying challenge when he and his UA associates have designed big telescopes, like the Large Binocular Telescope. The largest in the world, the telescope operates atop 10,700-foot Mount Graham in the Pinaleño Mountains of southeastern Arizona.
The Global Energy Revolution
Arizona’s clear skies have attracted the world’s top astronomers for years. As a consequence, the UA astronomy department has become one of the best in the world.
For astronomers and physicists who like to build devices such as spectrometers and inferometers — devices that measure light and other electromagnetic waves in the far reaches of the universe — “The University of Arizona is about the greatest home you can have,” Angel says. “I used to build stuff at Columbia, in New York City, but I found myself coming out west to use the telescopes. And then the attraction was to be here, on the spot, to develop new things. That’s a direct consequence of the asset we have, which is a major university in a high-quality observing area with major telescopes available.”
AzRISE’s Simmons seeks to capitalize on that UA expertise, as well as the talent at the state’s two other universities, including ASU’s recently formed solar power laboratory and its Arizona Institute for Renewable Energy (AIRE), which has a mission broader than solar. His goal is to give Arizona a big lead in the coming global energy revolution.
Surprisingly, Simmons sees a truly spectacular opportunity coming not just from what the state’s scientists and engineers do with sunlight, but from what they might eventually make of Arizona’s massive underground salt deposits.
Down to the Salt Mines
“As you know, solar energy is intermittent and variable and doesn’t exist at night, which means storage is critical,” Simmons says. “So we’ve been looking at a method called underground compressed air storage, which has extremely high promise.” The method uses available energy — from solar or wind, for example — to compress air and store it underground. Then, when there’s no energy available, the compressed air is heated slightly and released, producing electricity via turbines, with “reasonably high efficiency,” according to Simmons.
“It’s a very promising method, and it turns out that the best underground storage locations are salt caverns,” he says, “and the state of Arizona is blessed with a large number of salt deposits.”
He’s got his eye on the Holbrook Salt Basin in northeastern Arizona, where, he notes, “there’s enough salt that we could store sufficient energy to run the entire United States for more than 30 days.” Of course the deposits would have to be hollowed out, a task Simmons says is possible through a process called solution mining, which involves attacking salt with water jets to carve out storage caverns.
Oddly, one of the biggest questions a series of successful AzRISE programs might trigger one day is, “Where do we put all the salt?” Because not only is Simmons talking up the idea of creating salt caverns for compressed air storage in Arizona, he’s focusing on a project to marry solar power with desalination along America’s coastlines. Those plants could produce potable water and electricity simultaneously.
“That’s our future,” he says confidently of the possibility that humankind could head off its two looming shortages, in power and water, in one brilliant move. “We have big plans. At AzRISE we’re very forward-looking.”
Slowing Global Warming
Before Angel came up with his solar concentrator technology, he designed a “last-ditch plan” to prevent the earth from overheating. Wired magazine called it “an umbrella big enough to cool the world.” Angel’s backup plan called for launching 16-trillion self-stabilizing transparent discs, each about two feet wide, into stationary orbit above the earth, where they would deflect about 2 percent of the sunlight that reaches the earth.
This solar umbrella likely would be far less harmful to earth’s fragile web of life than the effects we’re on track to get from global warming, he says, noting that even the “tiniest wisp of cloud blocks 2 percent of the sunlight.”
But Angel has moved beyond the umbrella idea now, partly because it would have cost an estimated $5 trillion and taken 20 to 30 years to implement, but mostly because, he says, “It would just be a much better expenditure of money to do alternative energy.” The time to start building PV and other solar power systems is now, he declares.
AzRISE is working with the state’s big utilities, on the assumption that Arizona will need large central generating facilities of the kind Angel is proposing for roughly 70 percent of its power. But Simmons adds that 30 percent of the state’s solar power could also come from “distributed” sources — “substation” generating facilities serving small, rural communities and isolated areas, as well as rooftop solar power units for individual homes.
“If you’re going to put solar power on your home, you still want to stay connected to the grid,” he says, “because there are times when there are clouds over your house.” And given the expected population growth in Arizona, and the fact that power demand is rising, all of these methods can work together, Simmons says.
Dramatic price drops in recent years are making both “central” and “distributed” solar plants much more attractive, he says.
Timing Matters
Angel views the situation as urgent, even dire.
“There are several important time constraints involved here,” he warns. “One is that it takes 3,000 years for the carbon dioxide we’re putting into the atmosphere to dissipate naturally.
Another is that when you build a coal-fired electrical plant — and China is now building two a month — the lifetime of those plants is 40 years. It’s unlikely we could persuade China to walk away from the investment they’re making in those plants, so getting anything to happen on a time scale of less than four decades is going to be hard.”
What Angel is most afraid of “is that you get runaway warming and the planet’s permafrost melts, and that dumps even more carbon dioxide into the atmosphere, which creates more warming. The earth could become like it was 200 million years ago, when it was temperate at the poles and 90 percent of all species were lost.”
More likely, at least in the short run, we’ll see a rise in ocean levels, Angel says.
“We know exactly how carbon dioxide and the earth’s sea level have behaved during the past 600,000 years.” When carbon dioxide is at the low end, “sea level is about 120 meters lower than it is now — that’s when people crossed the Bering Straits.” But atmospheric CO2 is now the highest it’s ever been. “We’re already in a situation now where the issue seems to be not if we’ll melt all that ice, but when.”
Now is not a good time to be fooling around with the planet, Angel warns. But it’s definitely shaping up as a good time for Arizona to invest in solar power.
Student Solar Decathlon
A multidisciplinary UA team working on a solar-house design is one of 20 university teams selected to compete in the fourth U.S. Solar Decathlon.
UA students from the College of Architecture and Landscape Architecture and the College of Engineering will design, build, and operate an energy-efficient, fully solar-powered home for the competition.
Scheduled to be held on the National Mall in Washington, D.C., in 2009, the Solar Decathlon is a project of the U.S. Department of Energy. It will bring together teams from the U.S., Canada, and Germany.
Using energy-efficient technology, the students will demonstrate that homes powered entirely by the sun do not have to sacrifice the modern comforts and aesthetics Americans are used to. Each Solar Decathlon house must produce enough electricity to power lights and electronics, and enough hot water for cooking, washing clothes, and doing dishes. The home also must produce enough surplus energy to power an electric car.
The UA’s team is led by faculty advisors Dale Clifford and Jason Vollen, assistant professors in the College of Architecture and Landscape Architecture, and Joseph Simmons, head of the Department of Materials Science and Engineering in the College of Engineering. Students from architecture, materials science, and biosystems engineering also will serve as project leaders.
“We saw this as an opportunity to develop a collaborative effort between emerging materials technologies, urban design, materials science, and the College of Agriculture and Life Sciences,” Clifford says. “We hope it will redefine the process of design from the ground up.”
Students began working on the project in an architectural studio class during the spring 2008 semester. More than 20 courses over the next two years will feature a Solar Decathlon element, with students asked to help design, develop, market, and construct the house.
Each Solar Decathlon team, including the UA, receives $100,000 from the U.S. Department of Energy for development expenses. The Arizona Research Institute for Solar Energy, AzRISE, has matched the contribution to the UA team.
Sun and Fun for the Student Solar Racing Team
The 2008 UA solar racing team finished in 10th place in a 2,400-mile race from Plano, Texas, to Calgary, Alberta, Canada. The car was fueled only by the sunlight it gathered with its photovoltaic cells.
The UA finished the final stretch of the race against 15 teams, racing 180 miles from Medicine Hat, Alberta, to the finish line in Calgary. The previous leg — 299 miles from Regina, Saskatchewan, to Medicine Hat — was the longest of the race and truly tested the team and the car, Drifter 2.0.
The weather forecast was mostly sunny for the last leg of the race. Team member and honors student Arshed Al-Obeidi was upbeat about the team’s performance. “We decided to take advantage of the ideal conditions and run hard and fast.”
Nevertheless, as member Wei-Ren Ng wrote in the team blog, “Our battery pack could not hold its potential in the extreme terrain going up the Rockies toward Medicine Hat.”
More than 30,000 solar race fans gathered to welcome the teams at the finish line.
Twenty-four solar teams hoped to race, but the UA was one of only 15 teams that qualified to compete after passing a series of inspections.
To watch a video about solar car racing at the UA, visit http://uanews.org/node/20417.
UA Professors and Students Set Up
PV Monitoring in TEP’s Solar
Research Test Yard
Alex Cronin, UA associate professor of physics, the College of Optical Sciences, and Tucson Electric Power (TEP), have established a computer-controlled data logging system at TEP’s solar test yard. Results from data analysis will be used to inform utility companies, homeowners, photovoltaic (PV) panel installers, and other researchers about the performance of PV systems in the Arizona environment. More than 600 PV modules, from 20 different manufacturers, are operating at the TEP solar test yard, with 23 inverters in strings similar to residential systems. Cronin is working with students to install sensors for DC current, DC voltage, and AC power produced by each string of panels. The temperature of each type of panel, the air temperature, wind velocity, direct and diffuse solar irradiation, and the spectral content of the irradiation are being measured.
The UA team, including Cronin and professors Bill Conant and Ray Kostuk, is coordinated by the Arizona Research Institute for Solar Energy (AzRISE).
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