News

(Portland, Ore.) May 6, 2009 — A team of researchers at Portland State University (PSU) has received over $600,000 to study the integration of solar panels and eco-roofs on rooftops to assess how combining these green technologies might boost overall photovoltaic energy production and green roof function.

The researchers want to know if shading provided by the solar panels might benefit green roof vegetation, which often suffers during hot, dry months. The shading might also enable the use of plants that increase carbon sequestration, while the plants below could help cool the solar panels, which lose efficiency as temperatures rise.

“People tend to think of solar panels and green roofs as ‘either/or’ when it comes to installation, but they might be mutually beneficial, so people could do both,” said Carl Wamser, a professor of chemistry at PSU with expertise in solar energy production and artificial photosynthesis. “Nobody else that I know of is doing this.”

Principal investigators include Carl Wamser; David Sailor, professor of mechanical engineering with expertise in green building, eco-roof performance modeling and the urban heat island effect; and Todd Rosenstiel, assistant professor of biology, with expertise in plant physiology, including metabolism of carbon dioxide. All three are member faculty of the statewide Oregon Built Environment and Sustainable Technologies Center (Oregon BEST), which is helping fund the project.

Researchers and students will study how combining green roof and photovoltaic systems affects building energy consumption, solar energy production, urban heat island effect, carbon sequestration, water runoff and other factors. By comparing performance of commercially available solar panels in both conventional and green roof settings, the PSU researchers hope to better inform construction and development practices.

A set of solar arrays will be installed over a series of 12-by-15 foot stainless steel trays simulating green roof conditions. The test project will be housed on a third-floor patio of Science Building 2 (1719 S.W. 10th Ave., Portland, Ore.).

Each set of solar panels installed above the green roof trays will have a corresponding set installed in a separate array on the regular roof of Science Building 2, as part of PSU’s 11 kilowatt (kW) Photovoltaic Test Facility, a separate but related project showcasing nine different arrays. SolarWorld, a manufacturer of photovoltaic cells and modules with a manufacturing site in Hillsboro, Ore., has donated a set of panels to be included for testing in the standard roof arrays for comparison with panels used in the green roofs arrays.

Installation for both projects is tentatively set for early summer 2009.

The three-year project, “Integrating Green Roofs and Photovoltaic Arrays for Energy Management and Optimization of Multiple Functionalities,” will test several hypotheses about the potential benefits of combining these green building technologies:
• Whether increased rates of green roof evapotranspiration (how water moves from soil and plants to the atmosphere) will enhance photovoltaic energy production;
• Whether shading from solar arrays will enhance green roof ecosystem viability and carbon gain;
• Whether solar panels and green roofs will reduce winter heating demand in the building and reduce summer peak and total electricity load through reductions in air conditioning demand;
• And, whether the installation of solar panels with green roofs will result in a net cooling of the urban environment that offsets the warming effect of solar panels.

The project will also incorporate plants less typical of eco-roofs—but more in keeping with plants native to the Pacific Northwest. Real-time data capture will allow for additional scientific inquiry for researchers and industry partners, and with plans underway to in corporate some data in a renewable energy exhibit at Oregon Museum of Science and Industry (OMSI).

Major funding for the project comes from a three-year, $300,000 grant by the National Science Foundation. Additional support comes from a variety of public, private and government sources:
• Oregon Built Environment & Sustainable Technologies Center (Oregon BEST), through its proposal matching program: $36,400;
• Portland General Electric, through purchase of solar array equipment: ~$45,000;
• City of Portland Bureau of Environmental Services, including green roof materials, and assistance from Tom Liptan, a renowned green roof expert: ~$20,000;
• PSU Center for Sustainable Processes and Practices, via an allocation from the James F. and Marion L. Miller Foundation fund in support of sustainability programs: $83,442;
• PSU Office of Graduate Studies and Research, through waivers of indirect cost charges and tuition waivers for student researchers: ~$120,000;
• SolarWorld, through contribution of solar panels to the project;
• Silicon Chemical Corporation, through support of Carl Wamser's solar energy research, $25,000;
• E C Company, primary contractor for both projects, led by Cliff Schrock.

Additional resources:
PSU Green Building Research Lab: www.greenbuilding.pdx.edu
Oregon BEST: www.oregonbest.org

For Immediate Release (#09-017)

By:
David Santen, Office of University Communications, Portland State University
santend@pdx.edu | 503-725-8765

Source:
Carl Wamser, Department of Chemistry, Portland State University
wamserc@pdx.edu | 503-725-4261