University of Pittsburgh Finds DC-Optimized Inverter to Solve Solar Installation Challenges

The University of Pittsburgh at Bradford has been working to install a variety of solar arrays across the campus to increase energy efficiency and renewable power generation. The most recently operational solar project is the installation of a 108 kW rooftop solar system on the George B. Duke Engineering and Information Technologies Building. 

Solar installation. Image used courtesy of the University of Pittsburgh

 

This array is projected to generate 116,500 kWh of electrical power annually to offset around 40% of the building’s total electricity consumption. The installation is part of the University’s goal to achieve Leadership in Energy and Environmental Design (LEED) certification. It is using SolarEdge’s DC-optimized inverter solution to mitigate power-generation challenges and support this goal. 

 

Design Challenges

The Duke Building is a recent construction that houses engineering, computer, and energy studies. Unfortunately, the solar installation proved to be a technical challenge.

As seen in the image below, the roof of the building holds a sizeable mechanical penthouse, which significantly reduces the area where a solar array can be installed.

Bifacial rooftop array on the University of Pittsburgh’s Pitt-Bradford campus. Image used courtesy of the University of Pittsburgh

 

In addition to the reduced area, the walls of the penthouse are nine feet tall, which will cause shading over parts of the array at different times of the day. These challenges reduce the amount of sunlight exposure and the generation capacity of a solar array; a traditional solar string inverter system would have needed more power to meet University goals.

 

Inverter Solution

The solar array was completed by EIS Solar, who chose to use SolarEdge’s DC-optimized inverter to mitigate the technical challenges the roof presented. The SolarEdge DC-optimized inverter is designed to enhance power generation efficiency while reducing the overall cost of energy derived from photovoltaic systems. 

In a traditional solar PV system, the DC power generated by individual solar panels (photovoltaic modules) is combined into strings. Then, these strings are connected to a central inverter to convert DC power to AC power suitable for use in homes and businesses.

However, a DC-optimized inverter takes a more granular approach by managing the power conversion at the level of each solar panel or a small group of panels.

There are 200 bifacial modules installed on the Duke roof in two separate arrays. Each array has its own SolarEdge inverter and a SolarEdge Power Optimizer on each module pair. This setup allows each module to operate independently from others along the same string.

By utilizing the SolarEdge DC-optimized inverter, EIS Solar could position the modules along an east-west orientation – the ideal orientation for maximum generation and determined by the direction of the tilted face ‒ and in varying string lengths. This was crucial for increasing the number of modules that would fit on the roof.

Attaching power optimizers to each module pair further increased the energy output by reducing power losses from degradation or mismatch. Performance mismatch can be particularly prevalent in bifacial modules and arises from the diminished surface reflectance and variations in sunlight exposure on the modules’ rear surfaces due to their proximity to the roof.

Without the inverter solution, the Duke building would have been much more limited in its solar capacity and unlikely to meet the University’s renewable energy goals. The University aims to produce or procure 100 percent renewable electricity by 2037 across the University of Pittsburgh campuses.