Client Sisters of Saint Francis
Location Rochester, Minnesota
Scope 150 kW Solar Project

Assisi Heights Solar Project

Project Details

Westwood’s Role

  • Electrical Engineering
  • Civil Engineering
  • Surveying

Overview

Assisi Heights is home to the Sisters of St. Francis retirement and healthcare center and their administration offices. The building sits on hilly land and is surrounded by mature trees. These features make it a beautiful location, but they can make siting and designing a solar array a challenge, with shading a major obstacle to quality energy production. After visiting the site, Westwood proposed unique design features and engineering techniques to mitigate shading on the site and was subsequently awarded the contract to engineer the 150 kW Assisi Heights solar project. The challenges presented by the site gave Westwood the opportunity to put to use some high-tech solutions, making a success out of a difficult location for a solar installation.

High-Tech Solar Design on a Shady Site

The project site is far from typical for a solar project: elevation changes from the hills and sloping grades demanded precise placement of each rack to prevent modules from shading one another, while mature trees surrounding the project made the design even more complex. To help solve these problems, Westwood used a high-end AutoCAD-based program called Helios 3D to calculate and optimize the placement of each solar rack based on the terrain and tree shading present. Westwood was one of only a handful of firms in the nation utilizing the Helios software at the time of this project and it was a leading factor in its success.

New Technology Maximizes Output

Typically in a project this size, all the panels feed to a single power inverter. For this project, that configuration would have compromised energy production: as individual panels are shaded by surrounding trees, their decrease in output causes a decrease in the efficiency of the system as a whole. Westwood’s solution was to use DC-DC optimizers, a newer technology just starting to gain mainstream usage, mounted on the back of each module. These optimizers allow each module to operate independently, meaning they don’t affect the production of nearby modules if they are shaded. The optimizers, in turn, feed power to eight smaller inverters, which are distributed across the site. This system lets the project operate at a higher efficiency than standard solar equipment would have allowed.

“The Assisi Heights project was a fun one,” said project manager Jack Hays. “We love the opportunity to work with new technologies and designs. Smaller projects like this are always great, because you get to work one-on-one with motivated and engaged clients who are genuinely excited about the project and its results.”