Shades of Solar

Sept. 1, 2008

Facilities in Brighton, MA, Oberlin, OH, and Eugene, OR, use photovoltaics to harvest energy.

By C.C. Sullivan

With rising energy costs posing a long-term threat to global economies and security, business leaders, policy makers, and sustainable advocates are embracing the idea of renewable resources.

Technology has transformed the discussion from futuristic questions of "can we" to present-day answers of "we can."

"In fact, we can start right now using solar power, wind power, and geothermal power to make electricity," former Vice President Al Gore said in July in a speech at Washington's Constitution Hall.

The rooftop PV array, which does not penetrate the roof structure, will be surrounded by a green roof element at the new PBS studio complex in Boston.  (larger image) COURTESY SOLAR DESIGN ASSOCIATES INC.

The national leaders in the use of green power tend to be long-term building owners such as institutions, universities, and municipal and federal agencies. "Five years ago we had two clients interested in being green, and now every single client is, particularly at the universities," says Richard Olcott, design partner with Polshek Partnership, New York City, a firm well known for work with educational and cultural groups. "It becomes very obvious to people, and as solar technology evolves, more people will do it, and the price will come down." 

Public Broadcaster Goes Green
One of Olcott's recent clients is the Public Broadcasting System affiliate in Boston: WGBH, which boasts the first solar-powered network TV station. Completed in 2006, the two-building complex in Brighton, MA, consists of a new 130,000-square-foot broadcast studio facility connected to an existing 150,000-square-foot speculative office building by a "bridge" of new office space over a major thoroughfare. The LEED-certified building, visible from the highway, advertises WGBH's commitment to quality programming with a giant LED "digital mural." Unseen, however, is evidence of the group's commitment to having a light environmental footprint, such as its rooftop solar electric arrays surrounded by a roof garden.

"We consume an awful lot of energy in this business, so anything you can supplement with free energy is better," says Chris Pullman, WGBH vice president for branding and visual communications. "So we have quite large solar arrays—one on the second floor of the southernmost building and one on the sixth floor—which combine to produce about 100 kilowatts (kW). Still that's a drop in the bucket for what we consume—it's roughly what it takes to run the digital mural." (In fact, because the facility's energy consumption is so high, the project received no LEED points for the solar array.) However, Pullman explains, the solar array is just as significant a statement as the mural: It's a reminder to visitors and employees of a commitment to a greener future.

Solar Design Associates (SDA), Harvard, MA, consulted on the photovoltaic (PV) system, recommending a non-penetrating ballasted mounting system with no bolts or collars into the roof structure. "Penetrating systems add cost and complexity and cause more work downstream because the solar system will outlast roof application," says SDA President Steven J. Strong. "So when the roof has to be replaced, the modular PV arrays can be disassembled and stockpiled."

According to Pullman, the project team initially planned to use a "tracking solar" system, which would adjust the position of the cells following the sun's movement to optimize energy draw. "It seemed better suited to the climate in the Northeast, but we ended up with a silicon-based passive system"—less costly to acquire and install and much easier to maintain. A custom data-acquisition system is mounted in the building's lobby to monitor the PV electrical system and also to remind visitors of the broadcaster's commitment to sustainability.

Upstairs, an outdoor dining terrace overlooks the expansive rooftop array, which is wrapped with the green roof—two features that were partially offset by state grants. Yet they are hardly the only green features of the project. Constructed of 90 percent recycled steel, the facilities feature motion-sensitive office lighting, ultraviolet light-filtering glass, motorized sunshades, and water-conservation systems that cut consumption by as much as 30 percent. "Even better, our client was smart enough to save energy, material, and money by adapting an existing building," says Olcott. "People forget the greenest thing you can do is not build at all."

Oberlin College staff and designers used every advance they could to make their Lewis Center a proving ground for the rest of the college. (larger image) COURTESY OBERLIN COLLEGE

A Carbon-neutral Campus
Another green option is to become carbon-neutral, meaning that the facilities send no net greenhouse-gas emissions into the atmosphere. That's what officials at Oberlin College in Oberlin, OH, were working toward when they built a zero-energy academic facility and solar parking pavilion. Led by David Orr, professor of environmental studies, the team sought every possible efficiency advance and renewable technology to make their Lewis Center a model and proving ground for the rest of the campus. According to Orr, the goal was "to power civilization on contemporary sunlight, eliminate toxic materials, purify wastewater, protect biological diversity, increase efficiency in the use of energy and materials, and grow food sustainably. These challenges are built into the architecture, technology, and landscaping of the Lewis Center."

Oberlin College professionals are working toward carbon-neutral facilities. (larger image) BARNEY TAXEL, COURTESY WILLIAM MCDONOUGH + PARTNERS

Working with venerable green architect William McDonough and consultants including SDA's Strong, the team developed a highly integrated strategy for making the Lewis Center a net energy exporter. "You can't get there from here if you just throw a solar array on a tobacco barn. Every design decision needs to be driven by efficiency," says Strong. "There's one overriding criterion, from the biggest decisions to the smallest details: Does it advance our winning in terms of reducing energy use?"

At the heart of the Lewis Center's strategy is a 59-kW photovoltaic array covering about 3,500 square feet of the main building's roof and an 8,800-square-foot, 100-kW array set atop a newer parking pavilion adjacent to the academic facility. Each of the arrays employs crystalline silicon solar cells that use the largest practical module size for a glass-laminated system. For the 330 panels atop the parking pavilion, modules are approximately 4 feet by 6 feet, the largest produced industrially. The arrays are tied into the facility's electrical distribution system, which is integrated into the city's electrical grid.

"We calculated the size of the array needed to make it a net energy exporter, and now we're operating 10 percent to 30 percent over our energy budget for building," says Orr. He adds that the total production of electricity from the solar arrays would be sufficient to power 15 single-family homes.

The project illustrates one of the key issues related to solar technology integration in architectural projects, says Strong: ensuring enough area is available for the PV array. To improve the prospects for a solar-powered project, Strong advised the Lewis Center project team to consider their total "roof aperture"—the net area on the roof available for a PV array—and then plan early on to keep that real estate free of vents, skylights, and the like. "We always encourage integrating solar planning from the beginning because it's painful to go back and remove all that stuff on the roof to make room," says Strong. "It doesn't cost you that much more from the beginning to be solar-friendly."

The four-story atrium inside the University of Oregon Lillis facility serves as the visual centerpiece of the building. (larger image) COURTESY SOLAR DESIGN ASSOCIATES INC.The BIPV Business School

Where the roof aperture is inadequate, however, another strategy is to employ building integrated PV (BIPV) systems, which are becoming more commonly available for roofs, claddings, and other architectural applications.

"There are ways you can harness more energy from the sun, such as from flat panel systems, but they are not generally visible. With BIPV, the buildings literally become a billboard for sustainability," says Hussain Mirza, principal with Portland, OR-based SRG Partnership, which designed the recently finished Lillis Complex at the University of Oregon's business school. The Lillis facility, which has flat panel arrays, also features an ornamental BIPV curtain wall, skylights with solar cells, and a standing-seam metal roof with peel-and-stick PV.

The LEED Silver project consists of a new, four-story complex that added 145,000 square feet of space to the business school and connects three existing buildings. The visual centerpiece is a four-story, 65-foot-high atrium treated as part indoor, part outdoor space, clad with the BIPV curtain wall in one of the largest vertical applications of electric glass in the United States. The five-story BIPV curtain wall was designed with a varying density of solar cells to limit unwanted solar glare and gain in the upper areas while preserving transparency at the floor level—an effect that was originally conceived with fritted glass panels, says Mirza. According to Strong, the custom PV modules were produced in Germany to the team's design requirements to match the detailing and glass dimensions of the insulated curtain wall. The glazing sandwich has a clear glass layer and the solar cell laminated between its second and third glass panels. The "packing density" of the wall's solar cells was varied to modulate the light transmission into the rotunda—a kind of "active" ornamentation.

"From a distance, the curtain wall looks like architectural patterning that is quite handsome, that gets more dense as it goes higher up the façade, and it has an iridescent color to it," says Mirza. "It's very compelling and calls a lot of attention to it—people pass by and wonder, ‘What is this?'"

Left: The photovoltaic curtain wall at Lillis adds aesthetics and environmental sensitivity. (larger image) SR6 PARTNERSHIP
Above: The Lillis solar electric curtain wall is one of the largest vertical applications of electric glass in the United States. (larger image) COURTESY OF SOLAR DESIGN ASSOCIATES INC.
Below Left: Building integrated photovoltaic systems, such as the one at the University of Oregon, help showcase clean solar electric generation as a design element. (larger image) PHOTO BY LARA SWIMMER
Below: This close-up of the school's PV curtain wall shows details from the inside out. (larger image) COURTESY SOLAR DESIGN ASSOCIATES INC.

Other solar features of the Lillis Complex are less noticeable, such as sawtooth skylights set at 31 degrees—the optimal angle for sunlight harvesting at the university's latitude. The rooftop penthouses sport a novel appliqué of PV peel-and-stick modules running the length of the standing-seam sections on the south-facing rooftops and connected to the campus electrical distribution system. To literally top it all off, flat-panel arrays cover all of the available roof area.

Mirza notes that the BIPV systems are merely one of myriad energy-efficient and sustainable features. Other key elements of the building concept include positioning and daylighting of classrooms to minimize the use of electric lighting as well as external shades and light shelves to regulate temperature thermal loading from the sun. Automatically dimmed lighting adjusts to daylight levels, with occupancy sensors for regulating energy systems in each room. In addition, many of the building materials for the new facility were salvaged from previous campus buildings.

Thanks to these and other efforts by the University of Oregon, the school was recently included in a list of 11 institutions in The Princeton Review's first "Green Rating Honor Roll."

Left: The "packing density" of solar cells at Lillis was varied to modulate light transmission into the rotunda. (larger image) PHOTO BY LARA SWIMMER Right: The Lillis building includes a PV skylight to capture solar energy. (larger image) COURTESY SOLAR DESIGN ASSOCIATES INC.

"Sustainability is in the DNA of the University of Oregon," says the school's president, Dave Frohnmayer. "Maybe it's because we live in a beautiful environment, maybe it's because we've learned to treasure the gorgeous world we live in, that we've become more conscious of the need to take care of it."

In either case, Strong is not surprised that architects are vital protagonists in such efforts. "The architect, by nature, has to become more involved in the technology integration, as traditionally he or she is the leader of the design discipline and sets the goals and direction," he says. "People ask me, ‘What's the most important thing you can do to increase energy efficiency?' The answer is, ‘Hire the right architect.'"

C.C. Sullivan ([email protected]) is an author and marketing consultant specializing in architecture, interiors, and construction technology.

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