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The assignment for the first class of the Practice School of Sustainability is to design a cogeneration system that combines a solar photovoltaic array with water cooling.

By Lew Serviss
October 28, 2009

One by one, the eight students climbed an iron ladder to the highest part of the roof of the Harshbarger Building. They produced tape measures and cameras and set to work. They frowned at mysterious vents and stacks that cast odd shadows across the flat roof. They had a mission.

The students are the first participants in a College of Engineering senior design project known as the Practice School for Sustainability. The concept behind the practice school, said Glenn Schrader, associate dean for research of the College of Engineering, is to have the students conceptualize and design "projects that work, that make a difference and save energy or water or whatever."

The assignment for the first class is to design a cogeneration system that combines a solar photovoltaic array with water cooling that keeps the PV operating efficiently and yields a byproduct of hot water or steam.

Schrader said it is believed no one has tried to create such a system in Arizona. Solar PV panels can lose as much as 20 percent efficiency when they get too hot. The conventional idea is for wind to cool them off. "The idea that we're pursuing here is that can you actually water cool these panels and then use the heat to heat the water for hot water or maybe it's going to be high enough temperatures we can actually make steam, which would go directly into the university energy generation system," said Schrader. "So it's a real win-win."

The 50 students in the class have split into eight teams and one student working individually. The groups will each submit designs for an installation to go on the Harshbarger roof. The design phase will culminate in a short "power sales pitch" by each group, said Paul Blowers, associate professor in chemical and environmental engineering, who is teaching the class.

"This is the first hands-on real project our students have done in, I think, 10 years," Blowers said. The class began to take shape when Lon Huber, a solar policy program associate of AzRISE, the Arizona Research Institute for Solar Energy, approached Schrader with an idea about a sustainability program.  

"We have a grass roots thing going on here," said Huber, who is also the manager of the Sage Fund, the funding arm of the ASUA's Sustainability Committee,. "It's like, Hey, let's put some of our expertise to work here to make our world a little bit more sustainable – and our world being where we live right now, the university campus."

The Sage Fund will pay contractors to build the eventual design. Scott Logan of Facilities Management is collaborating on the project, as is the Solar Store.

Next semester, three teams will "do a more rigorous re-evaluation of this," said Blowers. "And they're probably going to be actually crawling through places that we haven't gone yet. And they're going to be asking even more specific questions – what can I drill into on this wall and what can't I. Exactly how much weight can this roof hold? What are the other alternatives?"

Early in the second semester, they'll provide more specific data, including economic models, and work with the Solar Store and Huber to actually build it. "I doubt Facilities Management lets students construct permanent parts of buildings," said Blowers. "We might be out there measuring and testing and evaluating, but they're not going to be putting down the bricks and mortar."

Huber said he likes the practicality of the project, and its portability as something that could be duplicated across campus.

"Let's do something that's manageable and it's also more realistic, too, to have it on a building like this," he said. "There are a lot of older buildings like this that we would need to retrofit, instead of a newer dorm, let's say."

As the students inspected the rooftop, they confronted shadows and strange utility boxes that would complicate their project: the sorts of things not visible in the classroom.

"On paper they can do anything," said Huber, "but this is cold, hard reality." Logan, leading a contingent from Facilities Management that oversaw the inspection tour, was enthusiastic about challenging the students, but curious how they would overcome the eccentricities of a building dating to 1939. He cautioned the students that the installation needed to be eight feet from the edge of the unguarded rooftop.

The students tucked away their cameras and tape measures to hear Charlie Boas of the Solar Store explain how to find the best location with a solar pathfinder, a combination chart,  level and compass. As he explained how the pathfinder determines the amount of sun available at various times of day throughout the year, an air processor on the roof, sounding like a pair of motorcycles, fired up.

"What I would do by seeing that that stack shades right here," Boas said, "is I would move. I'd say this spot is not very good. I'd start moving this way. I would move over to here, set up my pathfinder again and now I can see that the stack is really at 9 in the morning, just in February and October."

Schrader said he expects the practice school will have a bigger focus at the masters level in the future. More advanced students can design an integrated system, tackling more complicated questions about materials and construction, and spend more time on it, he said. The undergrads will put the two systems together, determining where to locate the PV, what angles to place them, whether to generate steam or hot water. But they simply don't have the time and flexibility to focus as deeply, he said.

"I think sustainability is our biggest challenge," said Blowers. "There's no problem that the world faces that isn't going to need engineers to solve it. If the engineers aren't thinking cleverly, we're going to make really bad decisions."