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Waunakee Community High School Photovoltaic System

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Project Concept: This project will incorporate a study of photovoltaic systems into an energy education program at the Waunakee High School. Installation of a rooftop photovoltaic (PV) system will provide utility bill energy and coincidental demand savings in addition to providing hands-on experience for students.

Educational Tie-Ins:  Each year, students can explore PV module options, perform an economic assessment, make PV equipment selections, and assist with the installation. A meaningful performance evaluation can be made with separate measurements of system parameters for each annual PV array addition. These measurements can be made and recorded with a datalogger, linked directly to classrooms.

576 x 316 pixels, 30 KB The photo enlargement is a view (building's south face) of the new school addition. The area highlighted by a white bounding box indicates the most promising location for siting a PV system.

Planning a rooftop PV system Initially, the PV array will be configured as a small system (about 2 kW) that can be increased in size annually to a maximum of about 20 kW. Power output from most PV modules is DC (direct current). The power conditioning equipment (inverter that converts DC to AC power output) is matched to the size of the PV array for maximum efficiency in the conversion process. As the Waunakee High School PV system is expanded, additional (or larger) inverters will be needed.

Site assessment The unshaded roof of the new school addition was chosen as a preferred PV system location in part because it was located over science classrooms. The roof composition is ballast stone over EPDM rubber membrane. The location is accessible for occasional tours by students and others via the penthouse.

576 x 389 pixels, 39 KB Photo showing preferred PV array site.

Planning for roof loads and electrical interconnection The PV system can easily be connected to the electrical distribution panels located in the penthouse (yellow area). Architectural and electrical system drawings were provided for planning purposes. The Waunakee High School Director of Facilities and Director of Maintenance participated in the site assessment. Both preferred a ballasted PV structural support system that did not require any roof penetrations and would not jeopardize the roof warranty. Existing roof ballast stone may be placed inside the PV support structure trays, thereby, eliminating the additional dead load of ballast necessary for weighting down the PV support trays. School roofs are usually more robust than those found on typical commercial structures. In this case, the deadload of the modeled PV modules and empty ballast trays would be approximately 8.7 lbs./ft2, -- less than the architect's recommended limitation of 10 to 15 lbs./ft2. By spacing the PV array modules and supports further apart, loading on the roof structure can also be reduced. The spacial and loading characteristics of additional types of PV modules were examined, so students could have a full range of PV choices in the future.

576 x 432 pixels, 9KB The drawing is a spacial layout, showing the area required for the maximum anticipated PV system size of 20 kW.The available area has dimensions of approximately 120 x 68 feet. The PV module and support structure used for modeling purposes is commonly used on ballasted EPDM rubber membrane roofs.

576 x 224 pixels, 36 KB Close-up of ballast pan support structure for PV modules

Funding for the project The Waunakee PV system project is funded by numerous sources: Curriculum - Wisconsin Enviromental Education Board Planning, Site Assessment, Demonstration Funds - Energy Center of Wisconsin PV System WPPI (Wisconsin Public Power Inc.) "Green Power" Program Support (over a 10 year period) Waunakee Utilities Wisconsin Energy Bureau (Wisconsin Dept. of Administration) Association of Energy Engineers Waunakee Area Education Foundation Other Wisconsin Utilities (contribution for tour access) School Energy Savings School District Staff (in kind)

576 x 432 pixels, 44 KB First PV array increment installed, October 1999

Credits Curriculum: Steve Bower, Waunakee Faculty Planning: Energy Center of Wisconsin PV site and planning assessment: L & S Associates Extended financial support: WPPI, Waunakee Utilities Installer, initial PV 2 kW increment: Great Northern Solar

576 x 504 pixels, 44 KB Power conditioning and PV array power disconnect equipment located in the penthouse.

Link to Waunakee High School Website