Powered by the Sun: Rooftop Solar

The large, south-facing roof of the new residence hall offers an ideal location for solar collectors.

This array of 114 photovoltaic (PV) panels will generate electricity to meet just over 15% of the building’s energy needs: at 50 kW. The solar potential in central Kentucky is strong, at 4.5 to 5.0 kWh/m2/Day, so Berea may add more panels in the future.

This rooftop system utilizes a series of PV panels connected as a grid (or array) to a solar inverter and utility meter inside the building. The slope of the residence hall’s roof is close to latitude for Berea, KY and yet high enough to avoid shading by trees on the south side of the building. These panels attach to the standing-seam metal roof using an “S-5” clamp – making them easy to install and remove as necessary. Comment: We are not storing energy via batteries.

HOW IT WORKS

Converting sunlight into electricity is a pretty simple process. It begins with solar cells, comprised of semiconductor materials, as the building blocks of a PV system. In our case, we’re using monocrystalline material – a traditional type made from silicon that’s very efficient and long-lasting. As these cells absorb sunlight, the energy converts light (photons) to electricity (voltage); this is known as the “photoelectric effect.”

To boost energy production, solar cells then combine into modules (of up to 40 cells). One or more PV modules are assembled into a pre-wired, field-installable panel. Several panels wired together into a series and/or parallel make up an array to deliver the required voltage for the system. This modular design also allows systems to grow as needs change. Finally, the entire configuration is mounted on the roof at a fixed angle facing south or on a tracking system that follows the sun.

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