ZS Peak: A Brief History of More Space in Less Time

We like to think our products make solar installation easy, but it takes rigorous work on the development end to make it look and feel that way to the customer.  ZS Peak, unveiled earlier this month, is the culmination of a three-year odyssey to address some of the more intractable challenges of commercial solar installation. Many are familiar with SolarCity’s Zep product line based on the success of its “snap together”, groove-framed residential system, but few know we have been working on the commercial solution almost as long. Many of the Zep team started as installers and we’ve always approached product development through that prism. We start by thinking about installer problems—transporting the panels to a roof, mounting the panels in a way that minimizes penetrations and looks good, wiring the panels together safely and reliably, grounding the metal parts and routing the wires back off the roof—before we create the solutions.

Soon after we developed our residential mounting system, we knew the architecture would deliver similar benefits for commercial buildings. Residential and commercial rooftops present different challenges, however. Primarily due to space and weight considerations, commercial rooftop systems typically offset less than half the building’s load. Thus any system that can increase the number of panels on a commercial rooftop is particularly valuable.

Our first attempt was a row connector system with legs for the solar panels that snapped onto the row connectors. The entire panel mounting system was tool-free, and once installed, every row of modules and components were automatically grounded to each other.  The system (internally referred to by our code name, Doobie Brothers) was very fast to install, but in the end rapidly falling prices in the market at that time forced us to discontinue the product after the first year of sales.

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Zep Solar’s first commercial flat roof solution..

Informed by the Doobie Brothers experience, the initial focus with our second generation commercial system (aka James Brown) was to bring the array closer to the roof to improve panel density and aerodynamics. After numerous iterations, we landed on an excellent, low-cost design.  The system dramatically simplified installation by only requiring four parts and by utilizing tool-free fasteners made from a single stamped, sheet metal part. Eureka, or so we thought. Unfortunately, James Brown failed a critical internal thermal expansion test prior to launch, so we had to shelve the concept and start over.

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Testing James Brown on the Zep Solar HQ roof.

We developed and tested roughly a half dozen more prototypes, but continued to run into two problems. Typical south-facing orientations had to be spaced sufficiently to prevent the panels from shading one another, which meant fewer panels on the roof and lower offset. Furthermore, a significant portion of commercial rooftops simply can’t support much additional weight. Ultimately we landed on a concept (referred to internally as U2) that harkened back to our residential design– a snap-together system of tubes and grooves that framed the panels in east and west-facing pairs arranged in rows that look like a stretched out accordion.

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Uplift load testing U2 to determine the system’s stiffness.

The system (now publicly referred to as ZS Peak) has numerous technical advantages over conventional flat roof systems. The dense, east-west orientation makes it possible to install 20 percent more panels on standard roofs, and the lightweight, aerodynamic design can allow installers to place up to 50 percent more panels on some warehouses and other roofs that aren’t designed to support much weight. ZS Peak’s east-west orientation also allows it to extend peak power production over a longer period of the day, and make more efficient use of inverters.  By lengthening power production time and eliminating the typical mid-day spike of standard solar systems, SolarCity can make more efficient use of solar inverters to further reduce costs for customers. ZS Peak has so significantly improved on the aerodynamics of conventional systems that it can be installed as a lightweight, non-penetrating system on many roofs that would otherwise require the solar panels to be bolted down.

At the end of the day, these benefits make it easier and more affordable for companies, cities, schools and other organizations to go solar. Our original mission when founding Zep was to advance the proliferation of solar energy with our products, and we’re excited to hand this solution over to SolarCity and achieve the same impact on the commercial space as we have on residential.

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Sun rising over the first completed U2 pilot.

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